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ACL graft selection: state of the art

      Despite recent developments in anterior cruciate ligament (ACL) reconstruction techniques, there are still several intraoperative factors affecting clinical outcomes that remain widely debated. Among such factors, graft selection might be the most critical yet controversial question for surgeons. As the primary factor influencing a patient's choice for the ACL graft is surgeon recommendation, surgeons have to consider several factors to select the best graft for each patient. Graft options currently include autograft, allograft or synthetic grafts. In terms of autograft, there are three main options: hamstring tendon, bone-patellar tendon-bone (BPTB) and quadriceps tendon, the two most commonly used being hamstring tendon and BPTB. Limited evidence is available to select the one best graft for every individual patient. Graft selection should be based on the reported rate of graft failure/revision and be individualised according to multiple factors such as gender, age, activity level and type of activity, complications and other patient needs and demands. Furthermore, surgeons should be familiar with a variety of grafts, their specific associated surgical procedures and the advantages and disadvantages of each, with the aim of offering the best graft selection for each individual patient.

      Introduction

      Anterior cruciate ligament (ACL) injury is one of the most commonly seen injuries in orthopaedics, especially among young athletes. If athletes suffer from recurrent knee instability, it is difficult for them to return to preinjury activity level. Therefore, ACL reconstruction has been developed to restore knee stability as well as to restore preinjury activity levels. Recent short-term knee stability and patient-reported functional outcomes of ACL reconstruction have been good to excellent in most cases. However, failure rates can be up to 30% in young athletes, return to sport can take as long as 18 months and the development of post-traumatic osteoarthritis (OA) following reconstruction continues to be an unsolved issue.
      While many of these issues surround the biological impact of the injury and the ongoing deficits in neuromuscular conditioning, there are still several intraoperative factors affecting clinical outcomes that remain widely debated. These include graft selection, tunnel position, graft fixation angle, initial graft tension, native tissue remnant preservation and concomitant ligament/meniscus/ cartilage injuries. Among them, graft selection might be the most critical but controversial question for surgeons that can be addressed at the time of surgery. As the primary factor influencing a patient's choice for the ACL graft is surgeon recommendation,
      • Cohen SB
      • Yucha DT
      • Ciccotti MC
      • et al.
      Factors affecting patient selection of graft type in anterior cruciate ligament reconstruction.
      surgeons have to consider several factors to facilitate an informed choice. These include rate of graft failure/revision, rate of return to preinjury activity level, donor site morbidity, risk of future OA, surgical time, cost effectiveness, associated complications and also surgeons' familiarity with the graft in order to make this critical decision. Currently available grafts can be categorised into autograft, allograft or synthetics. In terms of autograft, there are three main options: hamstring tendon, bone-patellar tendon-bone (BPTB) and quadriceps tendon, with the two most commonly used being hamstring and BPTB. There are many studies comparing these two autografts, with more recent meta-analyses and systematic reviews having summarised high-quality randomised controlled trials, prospective comparative cohorts and large national registries.
      • Poehling-Monaghan KL
      • Salem H
      • Ross KE
      • et al.
      Long-term outcomes in anterior cruciate ligament reconstruction: a systematic review of patellar tendon versus hamstring autografts.
      ,
      • Gabler CM
      • Jacobs CA
      • Howard JS
      • et al.
      Comparison of graft failure rate between autografts placed via an anatomic anterior cruciate ligament reconstruction technique: a systematic review, meta-analysis, and meta-regression.
      ,
      • Samuelsen BT
      • Webster KE
      • Johnson NR
      • et al.
      Hamstring autograft versus patellar tendon autograft for acl reconstruction: Is there a difference in graft failure rate? A meta-analysis of 47,613 patients.
      ,
      • Xie X
      • Xiao Z
      • Li Q
      • et al.
      Increased incidence of osteoarthritis of knee joint after ACL reconstruction with bone-patellar tendon-bone autografts than hamstring autografts: a meta-analysis of 1,443 patients at a minimum of 5 years.
      ,
      • Xie X
      • Liu X
      • Chen Z
      • et al.
      A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      However, conclusions from these studies are still controversial. Allografts are also commonly used in some parts of the world with theoretical advantages in elimination of donor site morbidity and shorter surgical time. Several studies have compared autografts and allografts as well as the source and preparation of allografts. Synthetic grafts had been less commonly used because of the high risk of complications such as mechanical failure, infection, tunnel osteolysis and massive effusions. But even this option is making a comeback with the introduction of newer generation devices. The purpose of this article is to summarise the current literature and discuss the current state of the art of graft selection in the treatment of ACL injury.
      Key articles on anterior cruciate ligament graft selection
      • 1.
        Poehling-Monaghan KL, Salem H, Ross KE, et al. Long-term outcomes in anterior cruciate ligament reconstruction: A systematic review of patellar tendon versus hamstring autografts. Orthop J Sports Med 2017;5:2325967117709735.
      • 2.
        Samuelsen BT, Webster KE, Johnson NR, et al. Hamstring autograft versus patellar tendon autograft for ACL reconstruction: Is there a difference in graft failure rate? A meta-analysis of 47,613 patients. Clin Orthop Relat Res 2017.
      • 3.
        Gabler CM, Jacobs CA, Howard JS, et al. Comparison of graft failure rate between autografts placed via an anatomic anterior cruciate ligament reconstruction technique: A systematic review, meta-analysis, and meta-regression. Am J Sports Med 2016;44:1069–79.
      • 4.
        Gifstad T, Foss OA, Engebretsen L, et al. Lower risk of revision with patellar tendon autografts compared with hamstring autografts: a registry study based on 45 998 primary ACL reconstructions in Scandinavia. Am J Sports Med 2014;42:2319–28.
      • 5.
        Xie X, Liu X, Chen Z, et al. A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction. Knee 2015;22:100–10.
      • 6.
        Xie X, Xiao Z, Li Q, et al. Increased incidence of osteoarthritis of knee joint after ACL reconstruction with bone-patellar tendon-bone autografts than hamstring autografts: a meta-analysis of 1443 patients at a minimum of 5 years. European journal of orthopaedic surgery & traumatology: orthopedie traumatologie 2015;25:149–59.
      • 7.
        Slone HS, Romine SE, Premkumar A, et al. Quadriceps tendon autograft for anterior cruciate ligament reconstruction: a comprehensive review of current literature and systematic review of clinical results. Arthroscopy 2015;31:541–54.
      • 8.
        Maletis GB, Inacio MC, Reynolds S, et al. Incidence of postoperative anterior cruciate ligament reconstruction infections: graft choice makes a difference. Am J Sports Med 2013;41:1780–5.
      • 9.
        Tejwani SG, Chen J, Funahashi TT, et al. Revision risk after allograft anterior cruciate ligament reconstruction: Association with graft processing techniques, patient characteristics, and graft type. Am J Sports Med 2015;43:2696–705.
      • 10.
        Batty LM, Norsworthy CJ, Lash NJ, et al. Synthetic devices for reconstructive surgery of the cruciate ligaments: a systematic review. Arthroscopy 2015;31:957–68.

      Current state of the art: graft selection

      Graft selection should be individualised as it can be affected by factors such as gender, age, patient's activity level and other needs and demands such as employment. The following is a thorough review of current popular graft options.

      Hamstring tendon autograft

      The use of hamstring tendons was first reported in 1982.
      • Lipscomb AB
      • Johnston RK
      • Snyder RB
      • et al.
      Evaluation of hamstring strength following use of semitendinosus and gracilis tendons to reconstruct the anterior cruciate ligament.
      After criticism of poor strength and stiffness in 2-strand hamstring tendon grafts, 4-strand hamstring tendon constructs were introduced showing comparable strength to BPTB grafts.
      • Wilson TW
      • Zafuta MP
      • Zobitz M
      A biomechanical analysis of matched bone-patellar tendon-bone and double-looped semitendinosus and gracilis tendon grafts.
      Subsequently, there has been an increased popularity of hamstring tendons in recent years.
      The semitendinosus tendon with or without gracilis tendon is harvested and can be fashioned into multistrand graft(s) to be used to reconstruct the ACL either with single-bundle (SB) or double-bundle (DB) technique (figure 1). The native ACL does not function as a SB and can be anatomically divided into two bundles: the anteromedial bundle (AMB) and posterolateral bundle (PLB). Anatomically, DB technique, which replicates both the AMB and the PLB of the native ligament, better reproduces native ACL anatomy. Recent biomechanical studies have revealed that DB ACL reconstruction restores more normal knee biomechanics than traditional SB reconstructions, especially in response to rotatory loading.
      • Woo SL
      • Kanamori A
      • Zeminski J
      • et al.
      The effectiveness of reconstruction of the anterior cruciate ligament with hamstrings and patellar tendon. A cadaveric study comparing anterior tibial and rotational loads.
      ,
      • Yagi M
      • Wong EK
      • Kanamori A
      • et al.
      Biomechanical analysis of an anatomic anterior cruciate ligament reconstruction.
      A recent meta-analysis has revealed that DB reconstruction has some clinical advantages in objective measurements of knee stability and protection against repeat ACL rupture or a new meniscal injury.
      • Tiamklang T
      • Sumanont S
      • Foocharoen T
      • et al.
      Double-bundle versus single-bundle reconstruction for anterior cruciate ligament rupture in adults.
      In addition, more recent studies comparing only anatomic SB versus DB reconstructions further have revealed that DB reconstruction is better in terms of restoration of knee kinematics as well as reduced risk of revision surgery.
      • Svantesson E
      • Sundemo D
      • Hamrin Senorski E
      • et al.
      Double-bundle anterior cruciate ligament reconstruction is superior to single-bundle reconstruction in terms of revision frequency: a study of 22,460 patients from the Swedish National Knee Ligament Register.
      ,
      • Desai N
      • Björnsson H
      • Musahl V
      • et al.
      Anatomic single- versus double-bundle ACL reconstruction: a meta-analysis.
      In terms of graft fixation, extracortical suspensory fixation such as EndoButton (Smith & Nephew Endoscopy, Andover, Massachusetts, USA) is usually used for the femoral side, whereas various devices are used for the tibial side. It has been reported that use of cortical suspensory fixation causes tunnel widening mainly because of an increased distance between the location of fixation and ACL natural insertion. Therefore, other femoral fixation devices such as cross-pin fixation have been developed to shorten the fixation distance. However, a recent meta-analysis showed that there were no differences in clinical and functional outcomes between cortical button fixation and cross-pin fixation.
      • Jiang H
      • Ma G
      • Li Q
      • et al.
      Cortical button versus cross-pin femoral fixation for hamstring anterior cruciate ligament reconstruction: A meta-analysis of randomized controlled trials.
      However, it is expected that longer graft incorporation will be observed with the use of hamstring tendon grafts compared with BPTB grafts, as the former is based on tendon-to-bone healing inside the tunnels. Furthermore, without bone, the normal bone-ligament junction can never be restored.
      Figure thumbnail gr1
      Figure 1Anatomic double-bundle ACL reconstruction using hamstring tendon graft. (A) Femoral tunnels for AMB (blue suture) and PLB (white suture). (B) Reconstructed ACL. The grafts are covered with preserved remnant tissues. (C,D) Postoperative 3D-CT of the femur (C) and tibia (D). ACL, anterior cruciate ligament; AMB, anteromedial bundle; PLB, posterolateral bundle.
      Hamstrings tendon grafts gained popularity mainly because of lower donor site morbidity, such as kneeling pain and anterior knee pain that is reported with BPTB graft.
      • Poehling-Monaghan KL
      • Salem H
      • Ross KE
      • et al.
      Long-term outcomes in anterior cruciate ligament reconstruction: a systematic review of patellar tendon versus hamstring autografts.
      ,
      • Xie X
      • Liu X
      • Chen Z
      • et al.
      A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      On the other hand, knee flexor strength deficits after hamstring tendon harvest is a common complaint.
      • Spindler KP
      • Kuhn JE
      • Freedman KB
      • et al.
      Anterior cruciate ligament reconstruction autograft choice: bone-tendon-bone versus hamstring: does it really matter? A systematic review.
      ,
      • Gifstad T
      • Sole A
      • Strand T
      • et al.
      Long-term follow-up of patellar tendon grafts or hamstring tendon grafts in endoscopic ACL reconstructions.
      In this regard, this morbidity could be greater if additional gracilis tendon is harvested in addition to semitendinosus tendon. As such, some surgeons recommended that gracilis tendon should be preserved if possible.
      • Ardern CL
      • Webster KE
      Knee flexor strength recovery following hamstring tendon harvest for anterior cruciate ligament reconstruction: a systematic review.
      ,
      • Yosmaoglu HB
      • Baltaci G
      • Ozer H
      • et al.
      Effects of additional gracilis tendon harvest on muscle torque, motor coordination, and knee laxity in ACL reconstruction.
      ,
      • Sharma A
      • Flanigan DC
      • Randall K
      • et al.
      Does gracilis preservation matter in anterior cruciate ligament reconstruction? A systematic review.
      Even DB ACL reconstruction can be performed using only semitendinosus tendon in most cases, although in some cases with thin and/or short semitendinosus tendon, additional gracilis tendon harvest is necessary.

      Bone-patellar tendon-bone (BPTB) autograft

      BPTB graft had been the gold standard until the 1980s because of high strength and stiffness, consistency of the size of the graft and faster graft incorporation with solid fixation using interference screws.
      • Papageorgiou CD
      • Ma CB
      • Abramowitch SD
      • et al.
      A multidisciplinary study of the healing of an intraarticular anterior cruciate ligament graft in a goat model.
      ,
      • Kurosaka M
      • Yoshiya S
      • Andrish JT
      A biomechanical comparison of different surgical techniques of graft fixation in anterior cruciate ligament reconstruction.
      However, there are several complications associated with the use of BPTB grafts mainly due to donor site morbidity, such as anterior knee pain, kneeling pain, extensor strength deficit, patellar fracture, patellar tendon rupture and postoperative OA.
      • Xie X
      • Xiao Z
      • Li Q
      • et al.
      Increased incidence of osteoarthritis of knee joint after ACL reconstruction with bone-patellar tendon-bone autografts than hamstring autografts: a meta-analysis of 1,443 patients at a minimum of 5 years.
      ,
      • Xie X
      • Liu X
      • Chen Z
      • et al.
      A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      ,
      • Busam ML
      • Provencher MT
      • Bach BR
      Complications of anterior cruciate ligament reconstruction with bone-patellar tendon-bone constructs: care and prevention.
      ,
      • Mohtadi NG
      • Chan DS
      • Dainty KN
      • et al.
      Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults.
      Therefore, hamstring tendon grafts became more popular in the 1990s. However, a more recent swing back to BPTB grafts seems to be occurring after more recent large national registry studies showed that BPTB grafts had lower risk of revision compared with hamstring tendon grafts.
      • Gifstad T
      • Foss OA
      • Engebretsen L
      • et al.
      Lower risk of revision with patellar tendon autografts compared with hamstring autografts: a registry study based on 45,998 primary ACL reconstructions in Scandinavia.
      ,
      • Persson A
      • Fjeldsgaard K
      • Gjertsen JE
      • et al.
      Increased risk of revision with hamstring tendon grafts compared with patellar tendon grafts after anterior cruciate ligament reconstruction: a study of 12,643 patients from the Norwegian Cruciate Ligament Registry, 2004-2012.
      ,
      • Rahr-Wagner L
      • Thillemann TM
      • Pedersen AB
      • et al.
      Comparison of hamstring tendon and patellar tendon grafts in anterior cruciate ligament reconstruction in a nationwide population-based cohort study: results from the danish registry of knee ligament reconstruction.
      Recently, the concept of anatomic reconstruction has also been applied to BPTB grafts, with the anatomic rectangular tunnel reconstruction to mimic natural ACL fibre arrangement (figure 2).
      • Shino K
      • Nakata K
      • Nakamura N
      • et al.
      Anatomically oriented anterior cruciate ligament reconstruction with a bone-patellar tendon-bone graft via rectangular socket and tunnel: a snug-fit and impingement-free grafting technique.
      This technique has some theoretical advantages such as to mimic fibre orientation of the native ACL, to maximise the graft-tunnel contact area, to keep tunnel apertures inside the ACL attachment areas and to preserve the notch anatomy. A recent biomechanical study also showed that using BPTB graft, the ACL-reconstructed knee with a rectangular femoral tunnel more closely resembled the normal knee in biomechanical behaviour than that with a round femoral tunnel.
      • Suzuki T
      • Shino K
      • Otsubo H
      • et al.
      Biomechanical comparison between the rectangular-tunnel and the round-tunnel anterior cruciate ligament reconstruction procedures with a bone-patellar tendon-bone graft.
      Figure thumbnail gr2
      Figure 2Anatomic rectangular tunnel reconstruction using BPTB graft. (A) Femoral rectangular tunnel. (B) Reconstructed ACL. (C, D) Postoperative 3D-CT of the femur (C) and tibia (D). ACL, anterior cruciate ligament; BPTB, bone-patellar tendon-bone.

      Hamstring versus BPTB: comparative studies

      There are numerous studies comparing hamstring tendon and BPTB grafts for ACL reconstruction. Several past meta-analyses comparing hamstring tendon and BPTB included multiple (2–5) strand grafts and the results of 4-strand graft were not analysed separately.
      • Mohtadi NG
      • Chan DS
      • Dainty KN
      • et al.
      Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults.
      ,
      • Biau DJ
      • Katsahian S
      • Kartus J
      • et al.
      Patellar tendon versus hamstring tendon autografts for reconstructing the anterior cruciate ligament: a meta-analysis based on individual patient data.
      ,
      • Li S
      • Chen Y
      • Lin Z
      • et al.
      A systematic review of randomized controlled clinical trials comparing hamstring autografts versus bone-patellar tendon-bone autografts for the reconstruction of the anterior cruciate ligament.
      Recent meta-analyses compared BPTB graft with 4-strand hamstring tendon graft, although they still did not separately analyse SB and DB.
      • Gabler CM
      • Jacobs CA
      • Howard JS
      • et al.
      Comparison of graft failure rate between autografts placed via an anatomic anterior cruciate ligament reconstruction technique: a systematic review, meta-analysis, and meta-regression.
      ,
      • Samuelsen BT
      • Webster KE
      • Johnson NR
      • et al.
      Hamstring autograft versus patellar tendon autograft for acl reconstruction: Is there a difference in graft failure rate? A meta-analysis of 47,613 patients.
      ,
      • Mohtadi NG
      • Chan DS
      • Dainty KN
      • et al.
      Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults.
      In this regard, a most recent randomised controlled trial with large population compared BPTB, SB and DB hamstring tendon grafts.
      • Mohtadi N
      • Chan D
      • Barber R
      • et al.
      Reruptures, Reinjuries, and Revisions at a minimum 2-year follow-up: a randomized clinical trial comparing 3 graft types for ACL reconstruction.

      Graft failure/revision

      There is still no consensus regarding risk of graft failure/revision between Hamstring tendon and BPTB, whereas recent large registry studies from both Scandinavian registries
      • Gifstad T
      • Foss OA
      • Engebretsen L
      • et al.
      Lower risk of revision with patellar tendon autografts compared with hamstring autografts: a registry study based on 45,998 primary ACL reconstructions in Scandinavia.
      ,
      • Persson A
      • Fjeldsgaard K
      • Gjertsen JE
      • et al.
      Increased risk of revision with hamstring tendon grafts compared with patellar tendon grafts after anterior cruciate ligament reconstruction: a study of 12,643 patients from the Norwegian Cruciate Ligament Registry, 2004-2012.
      ,
      • Rahr-Wagner L
      • Thillemann TM
      • Pedersen AB
      • et al.
      Comparison of hamstring tendon and patellar tendon grafts in anterior cruciate ligament reconstruction in a nationwide population-based cohort study: results from the danish registry of knee ligament reconstruction.
      and Kaiser Permanente registry
      • Maletis GB
      • Inacio MC
      • Funahashi TT
      Risk factors associated with revision and contralateral anterior cruciate ligament reconstructions in the Kaiser Permanente ACLR registry.
      showed that hamstring tendon grafts had higher revision rates than BPTB grafts. In addition, a recent randomised controlled trial with large population comparing BPTB, SB and DB hamstring tendon grafts showed that more traumatic reinjuries occurred with SB and DB hamstring grafts compared with BPTB. However, no recent systematic reviews or meta-analyses of randomised or prospective studies showed any difference in the revision rate between hamstrings and BPTB grafts,
      • Poehling-Monaghan KL
      • Salem H
      • Ross KE
      • et al.
      Long-term outcomes in anterior cruciate ligament reconstruction: a systematic review of patellar tendon versus hamstring autografts.
      ,
      • Gabler CM
      • Jacobs CA
      • Howard JS
      • et al.
      Comparison of graft failure rate between autografts placed via an anatomic anterior cruciate ligament reconstruction technique: a systematic review, meta-analysis, and meta-regression.
      ,
      • Xie X
      • Liu X
      • Chen Z
      • et al.
      A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      except one most recent meta-analysis showing that hamstring tendon graft failed at a higher rate than BPTB graft.
      • Samuelsen BT
      • Webster KE
      • Johnson NR
      • et al.
      Hamstring autograft versus patellar tendon autograft for acl reconstruction: Is there a difference in graft failure rate? A meta-analysis of 47,613 patients.
      One large limitation of this study is, however, that most of the patients included in this study came from the Scandinavian registry study with the lowest Modified Coleman Methodology Score and those results factor heavily into the results (79.1%). In any case, failure rates in both grafts were quite low and almost equivalent, and the small difference in failure rate should be just one part of a larger conversation with each individual patient regarding optimal graft selection.

      Stability

      Laxity in ACL-injured knees can be described in two ways: anterior and rotatory laxity. Anterior laxity is manually assessed by Lachman test, which has been shown to be a non-invasive test with high specificity and high sensitivity.
      • Berruto M
      • Uboldi F
      • Gala L
      • et al.
      Is triaxial accelerometer reliable in the evaluation and grading of knee pivot-shift phenomenon?.
      In addition, anterior laxity can be semiquantitatively evaluated by an instrument such as the KT-1000 arthrometer (MEDmetric, San Diego, California, USA), again with high inter-rater reliability.
      • Kocher MS
      • Steadman JR
      • Briggs KK
      • et al.
      Relationships between objective assessment of ligament stability and subjective assessment of symptoms and function after anterior cruciate ligament reconstruction.
      ,
      • Daniel DM
      • Malcom LL
      • Losse G
      • et al.
      Instrumented measurement of anterior laxity of the knee.
      On the other hand, rotatory laxity in ACL-injured knees is commonly represented by the pivot shift test. It has been shown to be superior to anterior laxity tests such as Lachman and KT-1000 measurement when it comes to predicting patient-reported instability. It has shown to be correlated with poor subjective and objective outcome scores
      • Kocher MS
      • Steadman JR
      • Briggs KK
      • et al.
      Relationships between objective assessment of ligament stability and subjective assessment of symptoms and function after anterior cruciate ligament reconstruction.
      as well as osteoarthritis after ACL reconstruction;
      • Jonsson H
      • Riklund-Ahlström K
      • Lind J
      Positive pivot shift after ACL reconstruction predicts later osteoarthrosis: 63 patients followed 5-9 years after surgery.
      however, the pivot shift test is subjective with low interobserver reliability.
      • Noyes FR
      • Grood ES
      • Cummings JF
      • et al.
      An analysis of the pivot shift phenomenon. The knee motions and subluxations induced by different examiners.
      ,
      • Lopomo N
      • Zaffagnini S
      • Amis AA
      Quantifying the pivot shift test: a systematic review.
      It has also been reported that there are no correlations between anterior and rotatory laxities.
      • Nakamura K
      • Koga H
      • Sekiya I
      • et al.
      Evaluation of pivot shift phenomenon while awake and under anaesthesia by different manoeuvres using triaxial accelerometer.
      ,
      • Hoshino Y
      • Kuroda R
      • Nagamune K
      • et al.
      In vivo measurement of the pivot-shift test in the anterior cruciate ligament-deficient knee using an electromagnetic device.
      Recent meta-analyses and systematic reviews have shown that there are no differences in regards to anterior laxity, as represented by the Lachman test and instrumented laxity measurements, between the two grafts.
      • Poehling-Monaghan KL
      • Salem H
      • Ross KE
      • et al.
      Long-term outcomes in anterior cruciate ligament reconstruction: a systematic review of patellar tendon versus hamstring autografts.
      ,
      • Samuelsen BT
      • Webster KE
      • Johnson NR
      • et al.
      Hamstring autograft versus patellar tendon autograft for acl reconstruction: Is there a difference in graft failure rate? A meta-analysis of 47,613 patients.
      ,
      • Xie X
      • Liu X
      • Chen Z
      • et al.
      A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      In terms of the pivot shift test, some studies have shown no difference between the two grafts,
      • Poehling-Monaghan KL
      • Salem H
      • Ross KE
      • et al.
      Long-term outcomes in anterior cruciate ligament reconstruction: a systematic review of patellar tendon versus hamstring autografts.
      ,
      • Samuelsen BT
      • Webster KE
      • Johnson NR
      • et al.
      Hamstring autograft versus patellar tendon autograft for acl reconstruction: Is there a difference in graft failure rate? A meta-analysis of 47,613 patients.
      whereas one meta-analysis showed that BPTB had lower rate of positive pivot shift after excluding one heterogeneous study.
      • Xie X
      • Liu X
      • Chen Z
      • et al.
      A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      Actually this excluded study compared the outcomes of DB hamstring tendon reconstruction versus SB BPTB reconstruction, favouring hamstring tendon.
      • Sadoghi P
      • Müller PE
      • Jansson V
      • et al.
      Reconstruction of the anterior cruciate ligament: a clinical comparison of bone-patellar tendon-bone single bundle versus semitendinosus and gracilis double bundle technique.
      It has been shown that DB reconstruction has some clinical advantages in knee stability and graft failure. Therefore, further comparative studies should focus on comparison of anatomic DB hamstring tendon reconstruction and anatomic BPTB reconstruction. The recent randomised controlled trial comparing BPTB, SB and DB hamstring tendon grafts showed that BPTB was better than both SB and DB hamstring tendon in static anterior laxity, although there were no differences in other outcomes.
      • Mohtadi N
      • Chan D
      • Barber R
      • et al.
      A randomized clinical trial comparing patellar tendon, hamstring tendon, and double-bundle ACL reconstructions: patient-reported and clinical outcomes at a minimal 2-year follow-up.
      On the other hand, a most recent study comparing anatomic DB hamstring tendon reconstruction and anatomic rectangular tunnel BPTB reconstruction showed that there were no difference in any of objective and subjective outcome measures at 2 year follow-up.
      • Sasaki S
      • Tsuda E
      • Hiraga Y
      • et al.
      Prospective randomized study of objective and subjective clinical results between double-bundle and single-bundle anterior cruciate ligament reconstruction.

      Muscle strength

      Many studies have evaluated muscle strength after ACL reconstruction with either hamstring tendon or BPTB grafts. The location of the donor site has an influence on the muscle deficit. Recent meta-analysis and systematic review studies showed that patients with BPTB grafts showed a greater deficit in extensor muscle strength and lower deficit in flexor muscle strength compared with hamstring tendon graft, and these deficits appear to be unresolved up to 2–5 years after ACL reconstruction.
      • Xergia SA
      • McClelland JA
      • Kvist J
      • et al.
      The influence of graft choice on isokinetic muscle strength 4-24 months after anterior cruciate ligament reconstruction.
      Therefore, rehabilitation protocols after ACL reconstruction should focus on the specific graft used, especially in terms of muscle strength training. With regard to hamstring tendon graft, the residual hamstrings deficits were related to the number of tendons harvested, and this flexor muscle strength deficit is more emphasised in deep flexion angle.
      • Ardern CL
      • Webster KE
      Knee flexor strength recovery following hamstring tendon harvest for anterior cruciate ligament reconstruction: a systematic review.
      ,
      • Yosmaoglu HB
      • Baltaci G
      • Ozer H
      • et al.
      Effects of additional gracilis tendon harvest on muscle torque, motor coordination, and knee laxity in ACL reconstruction.
      ,
      • Sharma A
      • Flanigan DC
      • Randall K
      • et al.
      Does gracilis preservation matter in anterior cruciate ligament reconstruction? A systematic review.
      Therefore, it is suggested that the gracilis tendon could be preserved if possible in hamstring tendon graft reconstruction, and in some specific sports needing deep flexion (eg, ballet, judo and so on), use of hamstring tendon graft should be avoided.

      Return to preinjury activity level

      ACL injuries occur mostly in young athletes, and for those athletes, one of the most important clinical outcomes after ACL reconstruction is return to preinjury activity level or even higher level. There are plenty of factors affecting ability to return to preinjury activity level; however, it still remains unclear how graft selection affects return to preinjury level. A recent meta-analysis showed a statistical difference in favour of BPTB grafts compared with hamstring tendon grafts.
      • Xie X
      • Liu X
      • Chen Z
      • et al.
      A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      On the other hand, other systematic review and meta-analyses have shown that there are no differences in return to preinjury activity level or Tegner activity scale.
      • Poehling-Monaghan KL
      • Salem H
      • Ross KE
      • et al.
      Long-term outcomes in anterior cruciate ligament reconstruction: a systematic review of patellar tendon versus hamstring autografts.
      ,
      • Mohtadi NG
      • Chan DS
      • Dainty KN
      • et al.
      Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults.

      Other clinical evaluation scores

      International Knee Documentation Committee (IKDC) score and patient-reported Lysholm score have been widely used to evaluate postoperative ACL reconstruction outcomes. Several meta-analysis and systematic review papers have shown that there are no differences in IKDC score and Lysholm score between hamstring tendon and BPTB grafts.
      • Poehling-Monaghan KL
      • Salem H
      • Ross KE
      • et al.
      Long-term outcomes in anterior cruciate ligament reconstruction: a systematic review of patellar tendon versus hamstring autografts.
      ,
      • Xie X
      • Liu X
      • Chen Z
      • et al.
      A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      ,
      • Spindler KP
      • Kuhn JE
      • Freedman KB
      • et al.
      Anterior cruciate ligament reconstruction autograft choice: bone-tendon-bone versus hamstring: does it really matter? A systematic review.
      Recently, the importance of a patient-reported outcome score such as the Knee injury and Osteoarthritis Outcome Score (KOOS) has gained attention. Inadequate knee function detected by the KOOS has also been reported to be associated with future ACL-reconstruction graft failure.
      • Granan LP
      • Baste V
      • Engebretsen L
      • et al.
      Associations between inadequate knee function detected by KOOS and prospective graft failure in an anterior cruciate ligament-reconstructed knee.
      Several comparative studies have shown that there are no differences in the KOOS between hamstring tendon graft and BPTB;
      • Gifstad T
      • Sole A
      • Strand T
      • et al.
      Long-term follow-up of patellar tendon grafts or hamstring tendon grafts in endoscopic ACL reconstructions.
      ,
      • Sasaki S
      • Tsuda E
      • Hiraga Y
      • et al.
      Prospective randomized study of objective and subjective clinical results between double-bundle and single-bundle anterior cruciate ligament reconstruction.
      however, there has been no meta-analysis study comparing the KOOS between the two grafts.

      Osteoarthritis

      Prevention of OA after ACL injuries is also one the most important goals after ACL reconstruction, as the ACL-injured knee is at significant risk of developing post-traumatic OA.
      • Lohmander LS
      • Englund PM
      • Dahl LL
      • et al.
      The long-term consequence of anterior cruciate ligament and meniscus injuries: osteoarthritis.
      However, OA has been reported in up to 40% of patients at long-term follow-up after ACL reconstruction.
      • Øiestad BE
      • Engebretsen L
      • Storheim K
      • et al.
      Knee osteoarthritis after anterior cruciate ligament injury: a systematic review.
      Reported factors associated with the risk of OA include meniscus status, meniscus treatment, cartilage injury, age and obesity.
      • Jones MH
      • Spindler KP
      Risk factors for radiographic joint space narrowing and patient reported outcomes of post-traumatic osteoarthritis after ACL reconstruction: Data from the MOON cohort.
      ,
      • Li RT
      • Lorenz S
      • Xu Y
      • et al.
      Predictors of radiographic knee osteoarthritis after anterior cruciate ligament reconstruction.
      Graft selection has also been shown to be another associated factor for OA. Recent meta-analysis and systematic review papers revealed that BPTB graft resulted in an increased incidence of OA in both the patellofemoral joint and tibiofemoral joint compared with hamstring tendon graft.
      • Poehling-Monaghan KL
      • Salem H
      • Ross KE
      • et al.
      Long-term outcomes in anterior cruciate ligament reconstruction: a systematic review of patellar tendon versus hamstring autografts.
      ,
      • Xie X
      • Xiao Z
      • Li Q
      • et al.
      Increased incidence of osteoarthritis of knee joint after ACL reconstruction with bone-patellar tendon-bone autografts than hamstring autografts: a meta-analysis of 1,443 patients at a minimum of 5 years.
      ,
      • Magnussen RA
      • Carey JL
      • Spindler KP
      Does autograft choice determine intermediate-term outcome of ACL reconstruction?.
      On the other hand, in a large cohort study, graft selection itself was not a significant predictor for OA.
      • Jones MH
      • Spindler KP
      Risk factors for radiographic joint space narrowing and patient reported outcomes of post-traumatic osteoarthritis after ACL reconstruction: Data from the MOON cohort.
      There are many confounding variables on this topic; therefore, more evidence is needed with future studies aiming to determine the effects of graft selection on risk of OA in anatomic ACL reconstruction.

      Pain

      Anterior knee pain and kneeling pain are common complications after ACL reconstruction, especially using BPTB grafts. Several meta-analyses and systematic reviews have shown that the occurrence of anterior knee pain and kneeling pain were significantly higher in BPTB graft than hamstring tendon grafts after ACL reconstruction.
      • Poehling-Monaghan KL
      • Salem H
      • Ross KE
      • et al.
      Long-term outcomes in anterior cruciate ligament reconstruction: a systematic review of patellar tendon versus hamstring autografts.
      ,
      • Xie X
      • Liu X
      • Chen Z
      • et al.
      A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      ,
      • Spindler KP
      • Kuhn JE
      • Freedman KB
      • et al.
      Anterior cruciate ligament reconstruction autograft choice: bone-tendon-bone versus hamstring: does it really matter? A systematic review.
      ,
      • Li S
      • Chen Y
      • Lin Z
      • et al.
      A systematic review of randomized controlled clinical trials comparing hamstring autografts versus bone-patellar tendon-bone autografts for the reconstruction of the anterior cruciate ligament.
      ,
      • Poolman RW
      • Abouali JA
      • Conter HJ
      • et al.
      Overlapping systematic reviews of anterior cruciate ligament reconstruction comparing hamstring autograft with bone-patellar tendon-bone autograft: why are they different?.
      This donor site morbidity after ACL reconstruction with BPTB grafts, as well as extensor muscle strength deficits, is a significant concern for both patients and surgeons, particularly for those who have strict requirements for kneeling, such as for employment and sporting purposes or for praying as is the case in many countries. In these circumstances, BPTB grafts should be avoided.

      Infection

      Infections after ACL reconstruction can be a devastating complication requiring further surgeries, antibiotics and sometimes graft removal depending on the extension of the infection, causal bacteria and type of graft (biological vs synthetic). Several meta-analyses and large nationwide registry studies were conducted and revealed that there is an increased risk of infections with hamstring tendon compared with BPTB grafts.
      • Maletis GB
      • Inacio MC
      • Reynolds S
      • et al.
      Incidence of postoperative anterior cruciate ligament reconstruction infections: graft choice makes a difference.
      ,
      • Brophy RH
      • Wright RW
      • Huston LJ
      • et al.
      Factors associated with infection following anterior cruciate ligament reconstruction.
      ,
      • Bansal A
      • Lamplot JD
      • VandenBerg J
      • et al.
      Meta-analysis of the risk of infections after anterior cruciate ligament reconstruction by graft type.
      Although the overall infection rate is low with both graft types, the significantly higher rate of infection after hamstring tendon graft reconstruction should be a consideration when discussing graft selection for ACL reconstruction.

      Tunnel enlargement

      The majority of studies that have assessed radiographic tunnel enlargement have shown that hamstring tendon grafts cause greater tunnel enlargement than BPTB grafts in both femoral and tibial tunnels.
      • Hersekli MA
      • Akpinar S
      • Ozalay M
      • et al.
      Tunnel enlargement after arthroscopic anterior cruciate ligament reconstruction: comparison of bone-patellar tendon-bone and hamstring autografts.
      ,
      • Samuelsson K
      • Andersson D
      • Karlsson J
      Treatment of anterior cruciate ligament injuries with special reference to graft type and surgical technique: an assessment of randomized controlled trials.
      However, it seems that the tunnel enlargement does not correlate with clinical outcomes including knee laxity and functional knee scores.
      • Samuelsson K
      • Andersson D
      • Karlsson J
      Treatment of anterior cruciate ligament injuries with special reference to graft type and surgical technique: an assessment of randomized controlled trials.
      However, these results suggest that femoral tunnels should be created at a somewhat more posterior position to the native ACL attachment site, especially when using a hamstring tendon graft, as the femoral tunnel enlargement occurs anteriorly.
      • Shimizu R
      • Adachi N
      • Ishifuro M
      • et al.
      Bone tunnel change develops within two weeks of double-bundle anterior cruciate ligament reconstruction using hamstring autograft: a comparison of different postoperative immobilization periods using computed tomography.
      By doing so, the risk of decrease in knee joint stability caused by anterior deviation of the graft could be reduced.

      Quadriceps tendon autograft

      Although the quadriceps tendon is the least studied and least used autograft for ACL reconstruction, interest in and use of the quadriceps tendon seem to be increasing. Quadriceps tendon grafts have been reported to have comparable strength and stiffness to BPTB grafts
      • Harris NL
      • Smith DA
      • Lamoreaux L
      • et al.
      Central quadriceps tendon for anterior cruciate ligament reconstruction. Part I: Morphometric and biomechanical evaluation.
      and have several theoretical advantages such as smaller incision, less morbidity in regards to anterior knee pain and kneeling pain, less knee flexor muscle strength deficit than hamstring tendon grafts and still its bone block on one end would allow for bone-to-bone healing.
      • Slone HS
      • Romine SE
      • Premkumar A
      • et al.
      Quadriceps tendon autograft for anterior cruciate ligament reconstruction: a comprehensive review of current literature and systematic review of clinical results.
      ,
      • Lee JK
      • Lee S
      • Lee MC
      Outcomes of anatomic anterior cruciate ligament reconstruction: Bone-quadriceps tendon graft versus double-bundle hamstring tendon graft.
      Recently, several papers comparing the clinical results after ACL reconstruction using quadriceps tendon graft and either hamstring tendon
      • Lee JK
      • Lee S
      • Lee MC
      Outcomes of anatomic anterior cruciate ligament reconstruction: Bone-quadriceps tendon graft versus double-bundle hamstring tendon graft.
      ,
      • Cavaignac E
      • Coulin B
      • Tscholl P
      • et al.
      Is quadriceps tendon autograft a better choice than hamstring autograft for anterior cruciate ligament reconstruction? A comparative study with a mean follow-up of 3.6 years.
      or BPTB grafts
      • Slone HS
      • Romine SE
      • Premkumar A
      • et al.
      Quadriceps tendon autograft for anterior cruciate ligament reconstruction: a comprehensive review of current literature and systematic review of clinical results.
      ,
      • Lund B
      • Nielsen T
      • Faunø P
      • et al.
      Is quadriceps tendon a better graft choice than patellar tendon? A prospective randomized study.
      ,
      • Runer A
      • Wierer G
      • Herbst E
      • et al.
      There is no difference between quadriceps- and hamstring tendon autografts in primary anterior cruciate ligament reconstruction: a 2-year patient-reported outcome study.
      have been published.
      When quadriceps tendon and hamstring tendon were compared, a cadaveric study showed that there were no biomechanical differences between SB ACL reconstruction with quadriceps-bone graft and that with 4-strand hamstring tendon graft.
      • Sasaki N
      • Farraro KF
      • Kim KE
      • et al.
      Biomechanical evaluation of the quadriceps tendon autograft for anterior cruciate ligament reconstruction: a cadaveric study.
      Clinical studies have also shown that ACL reconstruction using a quadriceps tendon graft leads to equal or better knee laxity measurements and patient-reported outcomes and less flexor muscle strength deficit than that using hamstring tendon grafts.
      • Lee JK
      • Lee S
      • Lee MC
      Outcomes of anatomic anterior cruciate ligament reconstruction: Bone-quadriceps tendon graft versus double-bundle hamstring tendon graft.
      ,
      • Cavaignac E
      • Coulin B
      • Tscholl P
      • et al.
      Is quadriceps tendon autograft a better choice than hamstring autograft for anterior cruciate ligament reconstruction? A comparative study with a mean follow-up of 3.6 years.
      A recent systematic review comparing quadriceps tendon and BPTB grafts showed that knee stability, functional outcomes, overall patient satisfaction, range of motion and complications were similar between the two grafts, with less donor-site morbidity such as anterior knee pain and kneeling pain.
      • Slone HS
      • Romine SE
      • Premkumar A
      • et al.
      Quadriceps tendon autograft for anterior cruciate ligament reconstruction: a comprehensive review of current literature and systematic review of clinical results.
      These morbidities can be further decreased if the quadriceps tendon is harvested without a bone block.
      • DeAngelis JP
      • Fulkerson JP
      Quadriceps tendon–a reliable alternative for reconstruction of the anterior cruciate ligament.
      These data suggest that quadriceps tendon grafts may be the least morbid of the currently used ACL autograft reconstruction alternatives; however, complications after quadriceps graft harvest such as quadriceps muscle strength deficits and retraction of the rectus femoris muscle should be noted, especially for many surgeons who are unfamiliar with quadriceps tendon harvest technique.

      Allograft

      Donor site morbidity, particularly in regard to BPTB grafts have led to the demand for the use of allograft, and classic animal studies,
      • Shino K
      • Kawasaki T
      • Hirose H
      • et al.
      Replacement of the anterior cruciate ligament by an allogeneic tendon graft. An experimental study in the dog.
      ,
      • Nikolaou PK
      • Seaber AV
      • Glisson RR
      • et al.
      Anterior cruciate ligament allograft transplantation. Long-term function, histology, revascularization, and operative technique.
      ,
      • Arnoczky SP
      • Warren RF
      • Ashlock MA
      Replacement of the anterior cruciate ligament using a patellar tendon allograft. An experimental study.
      followed by human clinical studies,
      • Shino K
      • Inoue M
      • Horibe S
      • et al.
      Maturation of allograft tendons transplanted into the knee. An arthroscopic and histological study.
      ,
      • Noyes FR
      • Barber SD
      • Mangine RE
      Bone-patellar ligament-bone and fascia lata allografts for reconstruction of the anterior cruciate ligament.
      ,
      • Noyes FR
      • Barber-Westin SD
      Reconstruction of the anterior cruciate ligament with human allograft. Comparison of early and later results.
      have justified use of allograft for ACL reconstruction.
      Lack of donor site morbidity, smaller incisions, availability of predictable graft sizes, shorter operative time and ease of use in multiple ligament and revision reconstructions are obvious advantages of allograft reconstruction. However, the use of allografts have been shown to have a higher risk of revision compared with autografts, especially in younger patients.
      • Pallis M
      • Svoboda SJ
      • Cameron KL
      • et al.
      Survival comparison of allograft and autograft anterior cruciate ligament reconstruction at the United States Military Academy.
      ,
      • Wasserstein D
      • Sheth U
      • Cabrera A
      • et al.
      A Systematic Review of Failed Anterior Cruciate Ligament Reconstruction With Autograft Compared With Allograft in Young Patients.
      Allografts have a longer and less complete course of incorporation and remodelling than autografts and are biomechanically inferior to autografts.
      • Jackson DW
      • Grood ES
      • Goldstein JD
      • et al.
      A comparison of patellar tendon autograft and allograft used for anterior cruciate ligament reconstruction in the goat model.
      Furthermore, the potential risk of immunogenic reaction and disease transmission along with increased cost for storage and preparation when compared with autograft are also matters of concern. However, the use of allograft does not seem to increase the risk of infection.
      • Maletis GB
      • Inacio MC
      • Reynolds S
      • et al.
      Incidence of postoperative anterior cruciate ligament reconstruction infections: graft choice makes a difference.
      ,
      • Barker JU
      • Drakos MC
      • Maak TG
      • et al.
      Effect of graft selection on the incidence of postoperative infection in anterior cruciate ligament reconstruction.
      Factors associated with a higher risk of allograft failure include graft irradiation greater than 1.8 Mrad, BioCleanse graft processing and the use of BPTB allograft.
      • Tejwani SG
      • Chen J
      • Funahashi TT
      • et al.
      Revision Risk After Allograft Anterior Cruciate Ligament Reconstruction: Association With Graft Processing Techniques, Patient Characteristics, and Graft Type.
      On the other hand, clinical results with non-irradiated and/or unprocessed allograft have been reported to be comparable to those with autograft.
      • Tejwani SG
      • Chen J
      • Funahashi TT
      • et al.
      Revision Risk After Allograft Anterior Cruciate Ligament Reconstruction: Association With Graft Processing Techniques, Patient Characteristics, and Graft Type.
      ,
      • Mascarenhas R
      • Erickson BJ
      • Sayegh ET
      • et al.
      Is there a higher failure rate of allografts compared with autografts in anterior cruciate ligament reconstruction: a systematic review of overlapping meta-analyses.
      ,
      • Sun K
      • Tian SQ
      • Zhang JH
      • et al.
      Anterior cruciate ligament reconstruction with bone-patellar tendon-bone autograft versus allograft.
      ,
      • Sun K
      • Zhang J
      • Wang Y
      • et al.
      Arthroscopic reconstruction of the anterior cruciate ligament with hamstring tendon autograft and fresh-frozen allograft: a prospective, randomized controlled study.
      ,
      • Noh JH
      • Yi SR
      • Song SJ
      • et al.
      Comparison between hamstring autograft and free tendon Achilles allograft: minimum 2-year follow-up after anterior cruciate ligament reconstruction using EndoButton and Intrafix.
      ,
      • Lawhorn KW
      • Howell SM
      • Traina SM
      • et al.
      The effect of graft tissue on anterior cruciate ligament outcomes: a multicenter, prospective, randomized controlled trial comparing autograft hamstrings with fresh-frozen anterior tibialis allograft.
      ,
      • Mariscalco MW
      • Magnussen RA
      • Mehta D
      • et al.
      Autograft versus nonirradiated allograft tissue for anterior cruciate ligament reconstruction: a systematic review.
      ,
      • Wei J
      • Yang HB
      • Qin JB
      • et al.
      A meta-analysis of anterior cruciate ligament reconstruction with autograft compared with nonirradiated allograft.
      However, a recent randomised controlled trial did demonstrate a higher failure rate of non-irradiated allograft ACL reconstructions compared with autograft in a young active military population.
      • Bottoni CR
      • Smith EL
      • Shaha J
      • et al.
      Autograft versus allograft anterior cruciate ligament reconstruction: a prospective, randomized clinical study with a minimum 10-year follow-up.
      Indications for allograft should therefore be limited to patients with shortage of autograft, low-demand elderly patients or patients who are reluctant to have autograft harvest.

      Synthetic grafts

      To overcome the concerns of both autograft (donor site morbidity) and allograft (higher failure rates and disease transmission), several kinds of synthetic grafts have been developed. They had gained in popularity because of easy availability, convenience, lack of disease transmission and donor site morbidity and the potential for dramatically accelerated rehabilitation with return to sport significantly earlier than autograft and allograft.
      However, earlier generations such as Dacron (Stryker, Kalamazoo, Michigan, USA), GORE-TEX (W.L. Gore and Associates, Flagstaff, Arizona, USA), Kennedy Ligament Augmentation Device (3M, St Paul, Minnesota, USA) and Leeds-Keio (Xiros, Leeds, England) have demonstrated high risk of complications including recurrent pain, mechanical failure, infection, tunnel osteolysis, massive effusions and OA.
      • Greis PE
      • Steadman JR
      Revision of failed prosthetic anterior cruciate ligament reconstruction.
      ,
      • Paulos LE
      • Rosenberg TD
      • Grewe SR
      • et al.
      The GORE-TEX anterior cruciate ligament prosthesis. A long-term followup.
      ,
      • Ventura A
      • Terzaghi C
      • Legnani C
      • et al.
      Synthetic grafts for anterior cruciate ligament rupture: 19-year outcome study.
      Patients with failed synthetic grafts often present with recurrent instability, pain, swelling and/or effusions, and these devices are not available for ACL reconstruction anymore.
      On the other hand, newer generation devices such as Ligament Augmentation and Reconstruction System (LARS; Surgical Implants and Devices, Arc-sur-Tille, France) have been reported with lower rates of failure, revision and sterile effusion/synovitis compared with other devices.
      • Batty LM
      • Norsworthy CJ
      • Lash NJ
      • et al.
      Synthetic devices for reconstructive surgery of the cruciate ligaments: a systematic review.
      While the results comparing LARS and autograft are controversial,
      • Liu ZT
      • Zhang XL
      • Jiang Y
      • et al.
      Four-strand hamstring tendon autograft versus LARS artificial ligament for anterior cruciate ligament reconstruction.
      ,
      • Pan X
      • Wen H
      • Wang L
      • et al.
      Bone-patellar tendon-bone autograft versus LARS artificial ligament for anterior cruciate ligament reconstruction.
      ,
      • Tiefenboeck TM
      • Thurmaier E
      • Tiefenboeck MM
      • et al.
      Clinical and functional outcome after anterior cruciate ligament reconstruction using the LARS™ system at a minimum follow-up of 10 years.
      more large cohort studies or high quality randomised control trials are necessary to justify the use of synthetic grafts.
      Validated outcome measures
      Primary outcomes:
      • Graft failure/revision rate.
      • Instrumented laxity measurement.
      • Lachman test.
      • Pivot shift test.
      Secondary outcomes:
      • Muscle strength.
      • Rate of return to preinjury activity level.
      • Tegner activity scale.
      • International Knee Documentation Committee Score.
      • Lysholm Score.
      • Knee injury and Osteoarthritis Outcome Score.
      • Rate of anterior knee pain.
      • Rate of kneeling pain.
      • Infection rate.
      Key issues for graft selection
      Graft failure/revision.
      Knee laxity:
      • Anterior laxity.
      • Anterolateral rotational laxity.
      Muscle strength:
      • Knee extensor muscle strength.
      • Knee flexor muscle strength.
      Return to preinjury activity level.
      Patient-reported clinical outcomes.
      Osteoarthritis.
      Pain:
      • Anterior knee pain.
      • Kneeling pain.
      Infection.
      Tunnel enlargement.

      Graft selection in revision surgeries

      Graft selection in revision surgeries should also be individualised, as it could be affected by factors such as the graft used in the primary surgery, gender, age, patient's activity level and other patient needs and demands. The most likely factor is graft availability, which will clearly depend on what graft was used for the primary procedure. BPTB or quad autografts can be useful to fill larger bone tunnels or defects. If the tunnels are satisfactory, then a hamstring graft may be harvested from the ipsilateral or contralateral side. Similar to the primary ACL reconstruction, allograft may also be used. The major advantage in the revision scenario is the ability to fill larger bone defects in a single stage, as opposed to performing a two stage revision with initial tunnel bone grafting and subsequent second stage revision reconstruction. A DB technique with hamstring tendon graft can be used in patients after primary BPTB reconstruction, patients with failure of the primary hamstrings tendon reconstruction due to apparent technical errors and patients planning to participate in repetitive jumping. In these cases, if the primary surgery is hamstring tendon reconstruction, the graft for revision surgery is harvested from the contralateral side. On the other hand, indications for use of BPTB graft can be patients after primary hamstrings tendon reconstruction who do not want to have an incision in the healthy limb and those without apparent technical errors.
      From surgical technique's perspective, use of BPTB graft with rectangular tunnel creation has the advantage of avoiding tunnel encroachment, as reduced tunnel size with the rectangular aperture would be more suitable in revision surgery with previous improperly placed, enlarged tunnels.
      • Shino K
      • Mae T
      • Nakamura N
      Surgical technique: revision ACL reconstruction with a rectangular tunnel technique.

      Geographical differences

      In an epidemiologic study, 261 orthopaedic surgeons of 10 subspecialties from 57 countries (53% European, 23% North American, 7% Asian, 7% South American, 7% Middle East and 2% African) took part in a survey.
      • Chechik O
      • Amar E
      • Khashan M
      • et al.
      An international survey on anterior cruciate ligament reconstruction practices.
      The study documented that hamstring autograft was the most popular choice (63%), followed by BPTB (26%) and allograft (11%). Rate of allograft selection was 19%, 9% and 7% in North America, Europe and other countries, respectively. Another survey of 34 orthopaedic surgeons who attended an ACL conference in 2011 documented the preferred graft choice was hamstring tendon autograft (53.1%) followed by BPTB (22.8%) and allograft (13.5%).
      • Middleton KK
      • Hamilton T
      • Irrgang JJ
      • et al.
      Anatomic anterior cruciate ligament (ACL) reconstruction: a global perspective. Part 1.
      The rate of allograft selection seems to be higher in USA, as the community-based Kaiser Permanente Anterior Cruciate Ligament Reconstruction Registry of 15 101 primary ACLR patients by 244 surgeons in 48 medical centres within USA documented that allograft was used in 42.4%.
      • Maletis GB
      • Inacio MC
      • Funahashi TT
      Analysis of 16,192 anterior cruciate ligament reconstructions from a community-based registry.
      On the other hand, in Scandinavian countries, their national registries between 2004 and 2011 documented that majority of surgeons preferred hamstring tendon autograft (84.1%), followed by BPTB (14.6%) and less than 1.0% used allograft.
      • Gifstad T
      • Foss OA
      • Engebretsen L
      • et al.
      Lower risk of revision with patellar tendon autografts compared with hamstring autografts: a registry study based on 45,998 primary ACL reconstructions in Scandinavia.
      In addition, in some countries such as Japan the use of allografts is very limited. In these countries, only autografts are available. Graft selection is especially difficult in cases with multiple ligament injuries and multiple revision surgeries and all possible autografts should be considered. However, in very rare cases, use of synthetic graft can also be considered.
      Considerations for graft selection
      Graft selection should be individualised according to multiple factors as below and other patient needs and demands.
      • 1.
        Reported rate of graft failure/revision: Lower revision rate with autografts has been reported compared with allograft and synthetic graft, although revision rate among allografts seems to depend on processing and preparation methods. Among autografts, hamstring tendon graft seems to show higher revision rate than bone-patellar tendon-bone (BPTB), although results are still controversial.
      • 2.
        Age: In young active patients, use of allograft should be avoided as it has been reported to have higher revision rate than autografts. Use of BPTB might also have to be avoided in elderly patients with poor muscle strength.
      • 3.
        Patient' s activity level and type of activity: In active patients, use of allograft should be avoided as it has been reported to have higher revision rate than autografts. In patients with contact sports, use of BPTB could be recommended because of high strength and stiffness and faster graft incorporation with solid fixation.
      • 4.
        Complications: In patients with strict requirements for kneeling and females with low activity level, use of BPTB should be avoided to reduce the risk of anterior knee pain and kneeling pain. In patients with osteoarthritis (OA), use of BPTB might also have to be avoided, as it has higher risk of OA. In patients with high risk of infection, use of hamstring tendon might be avoided, as the significantly higher rate of infection after hamstring tendon graft reconstruction is reported.

      Conclusion

      Graft selection should be individualised as it is affected by factors such as reported rate of graft failure/revision, gender, age, activity level and type of activity, complications and other patient needs and demands. However, one of the most influencing factors seems to be surgeons' familiarity with the graft. Therefore, surgeons should be familiar with every kind of grafts available to offer the best graft selection for each patient. It is clear that more high level evidence is necessary, especially in terms of long-term clinical outcomes, graft failure rate and future risk of OA, before the true superiority of one graft over another can be ascertained.
      Future perspectives
      • 1.
        Graft selection should be individualised, and surgeons should be familiar with every kind of graft available to offer best graft selection for each patient.
      • 2.
        Graft failure rate should be just one part of a larger conversation with each individual patient regarding optimal graft selection; every factor such as gender, age, activity level and type of activity, complications and other patient needs and demands should be considered.
      • 3.
        Accumulating more evidence is necessary in order to select best graft for each patient.

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