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Patient-Specific Instrumentation for Medial Opening Wedge High Tibial Osteotomies in the Management of Medial Compartment Osteoarthritis Yield High Accuracy and Low Complication Rates: A Systematic Review
Corresponding Author Department of Orthopaedic Surgery Rush University Medical Center 1611 W. Harrison St, Suite 300 Chicago, IL, USA Phone Number: (303)931-1921 Investigation performed at the Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA
There has been growing interest in the use of patient-specific instrumentation (PSI) to maximize accuracy and minimize the risk of major complications for medial opening-wedge high tibial osteotomies (MOW-HTO). Numerous studies have reported the efficacy and safety of implementing this technology into clinical practice, yet no systematic review summarizing the clinical literature on PSI for MOW-HTO has been performed to date.
Aim
The aim of this investigation was to perform a systematic review summarizing the evidence surrounding the use of PSI for MOW-HTO in the management of medial compartment osteoarthritis (OA).
Evidence Review
PubMed, Scopus, and the Cochrane Library were queried in October 2021 for studies that used PSI for MOW-HTO when managing medial compartment knee OA. Primary outcomes included accuracy in coronal plane correction (mechanical medial proximal tibial angle [mMPTA]), sagittal plane correction (posterior tibial slope [PTS]), and mechanical axis correction (hip-knee-ankle angle [HKA], mechanical femorotibial angle [mFTA], weight-bearing line [WBL]). Accuracy was defined as error between post-operative measurements relative to the planned pre-operative correction. A secondary outcome was the incidence of major complications.
Findings
This review included 8 different techniques among the 14 included studies. There was a weighted mean error of 0.5° (range: 0.1°-1.3°) for mMPTA, 0.6° (range: 0.3°-2.7°) for PTS, and 0.8° (range: 0.1°-1.0°) for HKA. Four studies compared correctional error of the mechanical axis between conventional techniques and PSI techniques. The comparative difference between the two techniques favored the use of PSI for MOW-HTO (Standardized Mean Difference = 0.52; 95% CI, 0.16 to 0.87; p = 0.004). Among the 14 studies evaluated, four studies explicitly reported no major complications, while five studies reported a non-zero incidence of major complications. Among these nine studies, the weighted mean major complication rate was 7.1% (range: 0.0-13.0%).
Conclusions and Relevance
The findings of this present systematic review suggest that the use of PSI for MOW-HTOs leads to high accuracy relative to the planned corrections in the coronal plane, sagittal plane, and mechanical axis. Furthermore, these findings would suggest there is a low risk of major complications when implementing PSI for MOW-HTO.
two dimensional, MINORS, Methodology Index for Non-Randomized Studies
aPPTA
anatomic posterior proximal tibial angle
PRISMA
Preferred Reporting Items for Systematic Reviews and Meta-analyses
IV
inverse-variance
All authors have fulfilled the following ICJME requirements for authorship: Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND Drafting the work or revising it critically for important intellectual content; AND Final approval of the version to be published; AND Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
What is already known.
•
1º of malalignment in the coronal plane can result in an additional 12% more body weight distributed to the medial compartment. Consequently, pre-operative planning and accurate, precise intraoperative correction are critical for satisfactory HTO outcomes.
•
The utilization of PSI in MOW-HTO has since been proposed as a solution to improve accuracy, precision, and safety of the procedure as it allows for the implementation of 3D preoperative planning as well as intraoperative guidance while performing the procedure
•
Clinical studies have also demonstrated several benefits related to PSI, including decreased operative times, reduced fluoroscopy exposure, fast learning curves, and decreased risk of major complications such as hinge fractures and non-unions.
What are the new Findings.
•
Four studies compared correctional error of the mechanical axis between conventional techniques and PSI techniques which showed that a comparative difference between the two techniques favored the use of PSI for MOW-HTO (Standardized Mean Difference = 0.52; 95% CI, 0.16 to 0.87; p = 0.004).
•
Operative error relative to preoperative planning in the HKA measurement was reported in eight studies (279 patients). The weighted mean of HKA angle error was 0.8° (range: 0.1°-1.0°).
•
In nine of the included studies (253 patients), there were 18 total major complications and a 7.1% (range: 0-13.0%) major complication rate.
Introduction
Medial opening wedge high tibial osteotomies (MOW-HTOs) are effective procedures for redistributing load within the knee away from the medial compartment to offload articular cartilage and minimize pain associated with medial compartmental osteoarthritis (OA) [
]. While effective, high tibial osteotomies (HTOs) can be challenging due to a relatively high published rate of complications, including excessive unintended tibial slope changes, hinge fractures, infections, delayed union, and nonunion [
3D-Printed Patient-Specific Instrumentation Technique Vs. Conventional Technique in Medial Open Wedge High Tibial Osteotomy: A Prospective Comparative Study.
]. For patients to have successful HTO outcomes, achieving proper mechanical alignment is crucial given the substantial changes in load distribution with even modest coronal corrections [
]. For example, a study by Hsu et al. demonstrated that just 1º of malalignment in the coronal plane can result in an additional 12% more body weight distributed to the medial compartment [
]. Consequently, pre-operative planning and accurate, precise intraoperative correction are critical for satisfactory HTO outcomes.
Historically, surgeons utilized two-dimensional (2D) radiographic planning to calculate the required correction needed to satisfactorily redistribute load. These views were an anteroposterior view of the knee, weightbearing posteroanterior view (Rosenberg / skiers view), a lateral view of the knee, an axial view of the patellofemoral joint, and a weightbearing alignment view of both lower extremity limbs from hip to ankle [
]. Calculating the degrees of correction using traditional methods is intrinsically challenging as the surgeon must use 2D planning for complex three-dimensional (3D) anatomy. For example, a study by Kawakami et al. reported significant differences in measured mechanical femorotibial angle (mFTA) and hip-knee-ankle (HKA) angle with slight changes in the axial rotation of the limb [
]. This has led to the implementation of computer assisted navigation (CAN) and patient specific instrumentation (PSI) in an attempt to minimize intraoperative error when performing a MOW-HTO.
CAN has been used to enhance the precision and accuracy of osteotomy cuts. It utilizes real-time feedback of correction angles in multiple planes at the time of surgery in order to aid the surgeon [
]. A major benefit of this technology is that it facilitates 3D evaluation and allows the surgeon to assess rotational components that are often overlooked when using traditional 2D planning [
]. While effective, CAN still has limitations and can often lead to unintended changes of the mechanical medial proximal tibial angle (mMPTA) in the coronal plane or posterior tibial slope (PTS) in the sagittal plane during the procedure [
The utilization of PSI in MOW-HTO has since been proposed as a solution to improve accuracy, precision, and safety of the procedure as it allows for the implementation of 3D preoperative planning as well as intraoperative guidance while performing the procedure. This theoretically minimizes challenges associated with conventional and CAN techniques. Initial results examining the use of PSI technology in MOW-HTO have been promising [
3D-Printed Patient-Specific Instrumentation Technique Vs. Conventional Technique in Medial Open Wedge High Tibial Osteotomy: A Prospective Comparative Study.
Is patient-specific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?.
Orthopaedics & Traumatology: Surgery & Research.2020; 106 (Supplement): S231-S236
Patient-specific high-tibial osteotomy’s ‘cutting-guides’ decrease operating time and the number of fluoroscopic images taken after a Brief Learning Curve.
]. These clinical studies have also demonstrated several other benefits related to PSI, including decreased operative times, reduced fluoroscopy exposure, fast learning curves, and decreased risk of major complications such as hinge fractures and non-unions.
Despite the growing evidence supporting the efficacy of PSI for MOW-HTO, there has not been a systematic review that summarizes the clinical literature regarding the implementation of this technology. Therefore, the purpose of this study was to 1) systematically summarize the current clinical literature regarding PSI for MOW-HTO and approximate the correctional accuracy of this technique in the coronal plane, sagittal plane, and mechanical axis, and 2) assess the published major complication rate of this technique. The authors hypothesized that the implementation of PSI will lead to accuracy within 1° of preoperative planning for all primary outcome measures and lead to low complication rates.
Methods
Article Identification and Selection
This systematic review was conducted in accordance with the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [
]. A search was performed in October of 2021 using PubMed, Scopus, and the Cochrane Library. The following search terms were used: “opening wedge high tibial osteotomy,” “opening wedge proximal tibial osteotomy,” and “patient specific tibial osteotomy.” The inclusion criteria were as follows: utilized patient specific instrumentation, medial opening wedge high tibial osteotomy, primarily managing medial compartment OA with a varus axis, clinical study. Exclusion criteria were as follows: distal femoral osteotomy, medial tibial closing wedge osteotomy, management of lateral compartment or valgus/varus deformity without OA, studies with fewer than four patients, any cadaveric/animal/in vitro study, any editorial article, any survey, any letter to the editor, any special topics, and any expert reviews. Two independent reviewers (R.F. and A.W.) performed a review of the abstracts from all identified articles. For studies that were included based on abstracts, a full-text review was performed. Any disagreements were discussed until a consensus decision could be made.
Data Extraction
Data was extracted in a standardized fashion into a customized spreadsheet. Data that was extracted for each study included first author, year, study design, total number of patients, number of male patients, number of female patients, average age in years at time of surgery, average final follow-up in months, primary indication for surgery, patient specific surgical planning system/technique, plate used, use of grafting, error of correction (HKA angle, weightbearing line [WBL], mFTA, mMPTA, PTS), and major complications such as hinge fracture, nonunion, deep wound infection, or as defined by the respective authors. For studies that included data from patients who received osteotomies other than a MOW-HTO, only data related to the MOW-HTO was extracted.
Studies were designated a level of evidence by the classification system described by Wright et al [
]. Bias analysis was performed by a single author (A.A.W.) on studies included for data extraction. The Methodology Index for Non-Randomized Studies (MINORS) score was utilized [
]. The MINORS criterion is a validated scoring tool used for nonrandomized studies. It involves 12 items to assess quality, four of which are only applicable to comparative studies. This creates a 16-point scale for noncomparative studies and a 24-point scale for comparative studies. Each item is scored 0 to 2 as follows: 0, not reported; 1, reported but poorly done and/or inadequate; and 2, reported well and adequately done. In order to best represent the data, weighted means with a range were utilized to summarize the accuracy and complication rate of the included studies. This was calculated using IBM SPSS Statistics for Macintosh (Version 28.0. Armonk, NY: IBM Corp).
Data Analysis
Accuracy of PSI was defined as the difference in degrees between post-operative measurements relative to the planned pre-operative correction. For this study, this was addressed with three primary outcomes. It was measured in the coronal plane as the mMPTA. In the sagittal plane, accuracy was measured using the PTS. Finally, overall alignment was measured with the hip-knee-ankle (HKA) angle. The primary alignment outcome measures for this study are depicted in Figure 1.
Figure 1. Weight bearing radiographs (A-C) and lateral radiograph (D) demonstrating primary outcome measures for this systematic review. Panels A-C demonstrate the weight bearing line (WBL), the hip-knee-ankle angle (HKA), and the medial mechanical proximal tibial angle (MPTA). Panel D depicts the posterior tibial slope angle (PTSA) and the anatomic posterior proximal tibial angle (aPPTA).
Four studies examined the error in mechanical axis correction relative to preoperative planning and compared this outcome between conventional techniques and 3D printed PSI techniques [
3D-Printed Patient-Specific Instrumentation Technique Vs. Conventional Technique in Medial Open Wedge High Tibial Osteotomy: A Prospective Comparative Study.
Is patient-specific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?.
Orthopaedics & Traumatology: Surgery & Research.2020; 106 (Supplement): S231-S236
]. For this outcome, a pooled estimate of the effect size was calculated and a standardized mean difference (SMD) with a 95% confidence interval (CI) was used to compare correctional error between the two groups. The magnitude of the SMD was assessed according to Cohen’s d estimate, where <0.5, 0.5-0.8, and >0.8 correspond to small, medium, or large effect sizes respectively [
]. For one study, values were reported as a mean with a range so the method described by Hozo et al. was utilized to estimate the standard deviation for their mechanical axis error outcomes [
]. An inverse-variance random effects model was implemented. The variance in the true effect value (T2) and the percentage of variance from sampling error was determined using I-squared tests (I2). Statistical analysis was performed using Review Manager 5 (The Nordic Cochrane Center; Copenhagen, Denmark).
Results
Study Characteristics
The database query yielded a total of 1025 studies after duplicates were removed (Figure 2). Fourteen studies satisfied all prespecified inclusion criteria. Study characteristics of these included studies are presented in Table 1. Five studies had a LoE of II, one study had an LoE of III, and eight studies had a LoE of IV. A total of 382 patients were included in this systematic review with a weighted age of 46.2 years (range: 44.0 to 67.2 years).
Figure 2Preferred Reporting Items for Systematic Reviews and Meta-analyses Flow Diagram
Figure 2. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) flow diagram representing search and screening process of studies implementing patient specific instrumentation for medial opening wedge high tibial osteotomies.
Patient-specific high-tibial osteotomy’s ‘cutting-guides’ decrease operating time and the number of fluoroscopic images taken after a Brief Learning Curve.
3D-Printed Patient-Specific Instrumentation Technique Vs. Conventional Technique in Medial Open Wedge High Tibial Osteotomy: A Prospective Comparative Study.
Is patient-specific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?.
Orthopaedics & Traumatology: Surgery & Research.2020; 106 (Supplement): S231-S236
Yang, J.C.-S., et al., Clinical Experience Using a 3D-Printed Patient-Specific Instrument for Medial Opening Wedge High Tibial Osteotomy. BioMed Research International, 2018. 2018: p. 9246529.
A bias analysis was performed for all 14 included studies utilizing the Methodology Index for Non-Randomized Studies (MINORS) score to evaluate the quality level. Four included studies were comparative and had an average MINORS score of 18.3 (range: 16 to 20). The remaining 12 studies were noncomparative. These included noncomparative studies had a mean score of 12.2 (range: 7 to 16). The results of this bias analysis are summarized in Table 1 and presented in greater detail in Supplementary Table 1.
Patient Specific Instrumentation Surgical Techniques
When summarizing surgical technique based on the planning software, eight different techniques were described among the 14 included studies. These are summarized in Table 2. Bone graft augmentation was used in eight studies, while injectable cement was used in three studies. The two most commonly used plates were the TomoFix plate (Synthes GmbH, Solothurn, Switzerland) and the Activmotion plate (Newclip Technics, Haute-Goulaine, France). These plates were used in six and five studies, respectively.
Table 2Summary of Patient Specific Instrumentation Surgical Techniques for Medial Opening Wedge High Tibial Osteotomies.
Author (Year)
Planning Software
Plate Type
Concomitant Procedures
Graft Augmentation
Radiographic Outcome Measures
Clinical Outcome Measures
Surgical Technique Description
Chaouche (2019)
Newclip Technics, (Haute-Goulaine, France)
Activmotion HTO plate
None
Femoral head wedge allograft or injectable phosphocalcic cement
HKA; mMPTA; PPTA
KOOS
PSCG secured to the bone with two pins (fluoroscopy was used to confirm orientation of the osteotomy cut). Eight holes for the plate were pre-drilled prior to performing the osteotomy. The saw blade was guided by a specific slotted capture of the PSCG, then the proximal portion of the modular cutting guide was removed to finish the osteotomy in a single plane or two planes. The osteotomy was opened/distracted with a lamina-spreader until the pre-drilled screw holes were aligned with the holes in the plate. The plate was secured using eight pre-sized screws.
Fucentese (2020)
CASPA (Balgrist CARD AG, Zurich, Switzerland)
Tomofix Medial High Tibial Plate (Depuy-Synthes Oberdorf, Switzerland)
None
None
HKA; PTS
None
Basic guide placed and reference pins for orientation of PSCG inserted. Screw positions of the TomoFix Medial High Tibial Plate were pre-drilled using the integrated drill sleeves. The osteotomy guide was then placed and the HTO was performed using predefined osteotomy-plane position and orientation and cutting depth. Using the reduction guide, predefined reduction was performed, and the TomoFix Medial High Tibial Plate could be placed over the pre-drilled screw holes. The screws were then inserted. Fluoroscopy was used to confirm osteotomy and positioning of the implants.
Gao (2021)
Mimics 25.0
Metal plate
None
Bone grafting (not specified)
WBL, mMPTA, HKA, PTS
None
Double-plane osteotomy was performed along the direction of the proximal osteotomy guide plate. The calibration connecting rod was installed and expanded to the preoperative design angle. Once the calibration connecting rod was connected to the proximal osteotomy guide and the distal calibration guide, then the second X-ray fluoroscopy was performed. After the correction was satisfactory, a steel plate was implanted and fixed with screws. During the operation, if the distance between the medial side was more than 1 cm, bone grafting was performed.
Jacquet (2020)
Newclip Technics, (Haute-Goulaine, France)
Activmotion HTO plate
None
Quickset, Graftys®, (Aix-en-Provence, France)
HKA, PPTA, mMPTA
KOOS
PSCG was positioned on the tibia and secured by using two k-wires (final position confirmed with fluoroscopy). Screw holes were pre-drilled using the jig and dedicated pins were inserted to secure the position of the jig on the tibia. Using the dedicated slot of the jig, the saw blade was guided during the cut. The upper part of the PSCG was then removed to finalize the cut and another slot of the jig was used to guide the bi-planar anterior cut below the tibial tuberosity. The osteotomy cut was then slowly opened and distracted until the plate holes aligned with predrilled tibial holes. The osteotomy gap was filled with an injectable phosphocalcic cement.
Kim (2019)
3D Slicer software (Brigham and Women’s Hospital, Boston, MA, USA)
Allogenic bone chips + autologous bone marrow from ASIS
PTS, mFTA
None
Biplanar osteotomy was performed after initial dissection. Then, the posteromedial tibial osteotomy site was opened using a chisel and bone spreader, the osteotomy site was spread, and the printed 3D model was inserted in the gap. The locking plate was fixed, and the 3D printed model was removed. Graft augmentation was placed into the gap.
Kim (2018)
3D Slicer software (Brigham and Women’s Hospital, Boston, MA, USA)
Diagnostic knee arthroscopy prior to HTO to assess the condition of the articular surface and meniscus, followed by debridement or meniscectomy if needed. After the pes anserinus was completely separated and the superficial MCL was elevated from the periosteum, the patient underwent a biplanar osteotomy behind the tibial tuberosity. The posteromedial tibial osteotomy site was opened using a chisel and bone spreader, and the osteotomy site was spread. In the method using radiographic images, the gap was measured with a ruler and maintained using a bone spreader. Then, the TomoFix locking plate was fixed. In the technique using the 3D printed model, the printed 3D model was inserted in the osteotomy gap. Then the OhtoFix locking plate (Ohtomedical Co. Ltd., Goyang, Korea) was fixed, and the 3D printed model removed. Allogeneic bone chips mixed with an autologous bone marrow were harvested from the ipsilateral ASIS and grafted into the osteotomy gap.
Mao (2020)
OsteoMaster
Metal locking plate
ACLR, Meniscectomy
Autogenous or allogenic bone graft
mFTA, mMPTA
IKDC, Lysholm score
For PSI technique, a 10-cm vertical medial tibial skin incision was made below the tibial articular surface. After dissection, osseous landmarks were made for the PSI cutting guide model positioning and fixed by pins. The two-planar osteotomy was performed by a saw through the cutting grooves of the guide model. The wedge shape gap was widened with steel rulers and fixed at a predetermined angle via a metal bar stabilizer, and the PSI guide model was removed. A curved HTO plate was attached to the medial surface of the tibia, and the locking plate was fixed by screws. Autogenous or allogenic bones were implanted if the lateral border of the osteotomy opening was larger than 10 mm. For conventional HTO, under fluoroscopic guidance, osteotomy sites were determined visually by free hand of the senior surgeon.
Munier (2016)
NewclipTechnics®, (Haute-Goulaine, France)
Activmotion plate
None
Quickset, Graftys®, (Aix-en-Provence, France)
HKA, mMPTA, PTS
None
PSCGs were secured to the bone with two pins and fluoroscopy done to confirm the orientation of the osteotomy cut. The six holes needed for the plate were drilled prior to osteotomy. The osteotomy was performed with the PSI guide in place. The saw blade was guided by a specific portion of the PSI and then the proximal portion of the guide was removed to finish the osteotomy. The lateral cortex was weakened with a drill bit to preserve the lateral hinge and then the osteotomy cut was gradually opened with a lamina-spreader until the pre-drilled screw holes were aligned with the holes in the Activmotion plate. The plate was secured using six screws of the size chosen during the pre-operative planning and then the bone defect filled with injectable calcium phosphate cement.
Pérez-Mañanez (2016)
Meshmixer 2.4
TomoFix (Synthes GmbH, Solothurn, Switzerland)
None
Iliac crest autogenous bone graft
Executional accuracy (HKA), final valgus
None
After the medial approach was completed, K-wires were inserted through the cannulated cylinders to the lateral cortex. Correct orientation and positioning was assessed fluoroscopically. The osteotomy positioning guide was removed, keeping the K-wires in their position, and the osteotomy was performed by sliding an oscillating saw over the proximal aspect of the wires. More than a centimeter of the lateral metaphysis was preserved for opening the gap by osteoclasia, preserving lateral cortical bone. Progressive distraction of the osteotomy allowed the insertion of two ABS spacer wedges. The third printed wedge was used as a model for carving the angulation and height of the wedged graft. The graft was then inserted into the osteotomy space, which was fixed with a locked conformed plate.
Predescu (2021)
Newclip Technics®, Haute (Goulaine, France)
Activmotion plate
None
Autologous distal femur bone graft (used in 3 cases)
HKA, mMPTA, PPTA
None
PSI is secured to the bone with two pins, fluoroscopy is used to confirm the orientation of the osteotomy cut. The six holes needed for the plate are pre-drilled prior to performing the osteotomy. The osteotomy is then performed with the PSI in place. The saw blade is guided by a specific cut of the PSI, then the proximal portion of the modular cutting guide is removed to finish the osteotomy in a biplanar mode. The osteotomy is distracted by inserting wedges of increasing sizes until the planned size is in position and the pre-drilled screw holes are aligned with the holes in the plate.
Tardy (2020)
Newclip Technics®, Haute (Goulaine, France)
Activmotion plate
None
Bone allograft or autograft
HKA, mMPTA,
None
Patients were allocated to 3 groups according to surgical technique: conventional, navigation, and PSI. Preoperative planning determined the target angular correction and HKA value. The decision between medial opening wedge or lateral closing wedge HTO and choice of planning between conventional techniques, navigation or PSI were at the surgeon’s discretion. Exact surgical technique was not described.
Van Genechten (2020)
3-matic (Materialise, Heverlee, Belgium)
TomoFix (Synthes GmbH, Solothurn, Switzerland)
Meniscectomy (one patient)
Structural bone allograft (half femoral head)
mMPTA, mFTA, mMDFA
None
Two parallel K-wires were introduced horizontally at 3 cm below the medial tibial joint line on the medial cortex and the wires were aimed laterally, proximally of the tibiofibular joint and 1 cm below to the lateral joint line. A horizontal osteotomy was made with a sawblade distally. Then, an oblique step osteotomy was performed at the level of the tibial tubercle, as planned earlier on the 3D virtual model. Next, the lateral cortex was perforated to reduce the risk for lateral hinge fractures. The horizontal osteotomy was gently opened. While applying valgus stress, the 3D PSI printed wedge was introduced in the gap. To verify limb alignment, the electrocautery cord was used under fluoroscopy representing the WBL. The bone graft was trimmed in a triangular shape and inserted accordingly. All osteotomies were fixed with a TomoFix locking plate.
Victor (2013)
Mimics®(Materialise N.V. Leuven, Belgium)
TomoFix (Synthes GmbH, Solothurn, Switzerland)
None
None
HKA, mFTA
None
For tibial osteotomies, a medial approach used for patients that underwent valgus correction (one patient underwent varus correction/lateral approach). The guide was fixed with K-wires and the screw holes drilled through the cylinders on the guide, checked fluoroscopically. The osteotomy was performed via the captured cut slot and was initiated with the oscillating saw. The guide was removed, and the osteotomy completed with double-edged osteotomes. For the uniplanar and biplanar corrections, the osteotome stopped at a planned distance from the opposite cortex to retain a physical hinge of residual bone. The osteotomy is carefully and slowly wedged open until the drill holes match the screw holes in the plate The plate was inserted and fixed with locking screws.
A 4-cm incision was made in the proximal and anteromedial portion of the tibia, then dissection of the pes anserinus and superficial MCL was performed. The PSI guide was attached, and K-wires were drilled to fix the guide. Using the cutting slot and guiding plane, a biplanar cut was performed to create the desired hinge. After two wedges had been created, the guide was separated into proximal and distal parts from the cutting slot. An osteotome was inserted until the planned length reached the sawing depth. This was followed by insertion of another osteotome for distraction. A spreader was used to hold the distracted wedge. The distal K-wires were removed before taking the radiographs. Finally, the TomoFix plate and locking screws were used to fix the osteotomized tibia.
The technique described using the Newclip Technics patient-specific cutting guide system (Haute-Goulaine, France) and corresponding Activmotion plate was the most common and implemented in five studies (Figure 3) [
Is patient-specific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?.
Orthopaedics & Traumatology: Surgery & Research.2020; 106 (Supplement): S231-S236
Patient-specific high-tibial osteotomy’s ‘cutting-guides’ decrease operating time and the number of fluoroscopic images taken after a Brief Learning Curve.
]. A 2020 case series by Fucentese et al. implemented CASPA pre-operative planning software (Balgrist CARD AG, Zurich, Switzerland) to design PSI for MOW-HTO [
]. They utilized the TomoFix Medial High Tibial Plate. The authors used a computer algorithm that they described in detail through a prior publication to calculate the optimal correction plane. A 2020 study by Mao et al. reconstructed an intact model with an osteotomy simulation software (OsteoMaster) that allowed them to generate a virtual 3D model [
3D-Printed Patient-Specific Instrumentation Technique Vs. Conventional Technique in Medial Open Wedge High Tibial Osteotomy: A Prospective Comparative Study.
]. Using this model, the authors were able to optimize the sagittal and coronal correction angles as well as the depth, width, height, slope, and position of the osteotomy before printing a custom-made cutting guide. A 2018 case series by Yang et al. used MatLab software (MathWorks Inc., Natick, MA, USA) to calculate the correction angle and utilized 3D models constructed from CT scans using Amira 4.0 software (Mercury Computer Systems, Inc., Berlin, Germany) and SolidWorks Ed. 2015 software (SolidWorks Corporation, Concord, MA, USA) [
Yang, J.C.-S., et al., Clinical Experience Using a 3D-Printed Patient-Specific Instrument for Medial Opening Wedge High Tibial Osteotomy. BioMed Research International, 2018. 2018: p. 9246529.
]. The authors shifted the weightbearing line to Fujisawa’s point and achieved fixation utilizing the TomoFix system. Gao et al. used Mimics software (Materialise, Leuven, Belgium) and implemented a calibrated connecting rod that was designed to expand and open the wedge based on preoperative planning [
]. In two separate studies, Kim et al. implemented 3D slicer software (Brigham and Women’s Hospital, Boston, MA, USA) to create a wedge that would open and hold the osteotomy at the ideal angle until the OhtoFix locking plate (Ohtomedical Co. Ltd., Goyang, Korea) was used for fixation [
]. Similar to the Newclip Technics technique, the osteotomy was wedged open until the pre-drilled holes match the screw holes on the fixation plate. Pérez-Mañanes et al. implemented a patient specific 3D printed osteotomy guide as well as wedges; the authors utilized Meshmixer 2.4 software for their planning [
Figure 3. Medial opening wedge high tibial osteotomy (MOW-HTO) using the NewClip Technics (Haute-Goulaine, France) patient specific instrumentation (PSI) system. Panel A depicts the patient specific cutting guide fitting against the anteromedial cortex. Panel B depicts the cutting guide held in place by 2 unicortical pins proximal to the slotted capture and 2 bicortical pins distal to the slotted capture; the cut pin, an additional guide pin, and the hinge pin are also placed. Panel C depicts the HTO plate being secured with a proximal and distal locking screw, while the osteotomy is wedged open to the optimal correction angle. Panel D depicts the final construct for the MOW-HTO using the NewClip Technics (Haute-Goulaine, France) PSI system.
Five studies (213 patients) reported mMPTA and the associated correctional error (Table 3). For the included studies, the weighted mean of mMPTA correction error was 0.5° (range: 0.1°-1.3°). For PTS, seven studies (242 patients) reported on the accuracy in this plane (Table 3). The weighted mean error in PTS for PSI in MOW-HTO was 0.6° (range: 0.3°-2.7°). Finally, for alignment accuracy, the HKA angle was evaluated (Table 3). Operative error relative to preoperative planning in the HKA measurement was reported in eight studies (279 patients). The weighted mean of HKA angle error was 0.8° (range: 0.1°-1.0°).
Table 3Correctional Error for the Hip-Knee-Ankle Angle, Mechanical Medial Proximal Angle, Posterior Tibial Slope, and Rate of Major Complications.
First Author (Year)
Error in correction of Hip-Knee-Ankle Angle (in Degrees)
Error in Correction of Mechanical Medial Proximal Tibial Angle (in Degrees)
Error in Correction of Posterior Tibial Slope (in Degrees)
Four studies compared the error in correction of the mechanical axis of the traditional 2D planning techniques against the implementation of 3D printed PSI (Figure 4) [
3D-Printed Patient-Specific Instrumentation Technique Vs. Conventional Technique in Medial Open Wedge High Tibial Osteotomy: A Prospective Comparative Study.
Is patient-specific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?.
Orthopaedics & Traumatology: Surgery & Research.2020; 106 (Supplement): S231-S236
]. All four studies reported on error of the mechanical axis correction relative to the planned correction for both techniques. More specifically, two studies reported mechanical axis correction using the HKA measurement, one utilized the error in correction of the weightbearing line (WBL) to Fujisawa’s point in millimeters, and one utilized mFTA as an additional measure. The pooled SMD suggested that there is a medium effect that favored the use of PSI to maximize accuracy and minimize error when correcting a patient’s mechanical axis using a MOW-HTO (SMD = 0.52; 95% CI, 0.16 to 0.87; p = 0.004). For this set of data, the variance of true effects (T2) was 0.04, and the I2 was 32%, indicating that there is little heterogeneity in estimates of the effect sizes. The standard deviation of true effects (T) was 0.2, and the resulting prediction interval was 0.12 to 0.92. This would suggest that 95% of patients sampled would have a more accurate correction of their mechanical axis if PSI were implemented at the time of their MOW-HTO procedure instead of traditional (non-PSI) osteotomy techniques.
Figure 4Comparison of Error Relative to Pre-operative Planning of Mechanical Axis Correction
Figure 4: Forest plot demonstrating the standardized mean difference (SMD) for error in the correction of the mechanical axis relative to pre-operative planning. This includes a summary estimate (center of the diamond) and a 95% confidence interval (width of the diamond) for the standardized mean difference. The size of each square represents the relative weight given to each respective study.
Legend: Weightbearing Line (WBL); Mechanical Femorotibial Angle (mFTA); Hip-Knee-Ankle Angle (HKA); Inverse-Variance Model (IV); Confidence Interval (CI).
The final outcome extracted in this systematic review was the incidence of a major complication (Table 3). For this study, major complications were defined as non-unions, hinge factures, deep tissue infections, and those defined by the respective authors. For this systematic review, five studies reported a major complication, four studies explicitly reported no major complications had occurred, and five studies did not report the incidence of major complications. The five studies that did not explicitly state that there were zero complications were not included in this analysis of major complications. When examining the remaining nine studies (253 patients), there were 18 total major complications and a 7.1% (range: 0-13.0%) major complication rate.
Discussion
The findings from this systematic review support the implementation of PSI for MOW-HTO in clinical practice and demonstrated an average operative accuracy within 0.6º of the preoperative plan in both the coronal (mMPTA) and sagittal planes (PTS). Additionally, this study would suggest that there is a high degree of accuracy in correction of the mechanical axis with an average error that is within 0.8º of the planned correction in the HKA angle. The SMD would suggest that there is reduced error in correction of alignment when using PSI for MOW-HTO relative to techniques using conventional preoperative planning. Furthermore, when examining secondary outcomes, the use of PSI led to a low incidence of major complications (7.1%).
The largest included study in this systematic review was a prospective observational study by Chaouche et al. [
]. In this study, 100 patients were treated with a MOW-HTO using PSI. The authors noted excellent accuracy in all planes/axis of correction as well as a low rate of major complications (4%). Furthermore, they noted substantial clinical improvements in the Knee Injury and Osteoarthritis Outcome Score (KOOS) and UCLA outcome scores at two-year follow-up. A separate study by Jacquet et al. sought to evaluate the learning curve of implementing PSI into a surgeon’s practice [
Patient-specific high-tibial osteotomy’s ‘cutting-guides’ decrease operating time and the number of fluoroscopic images taken after a Brief Learning Curve.
]. The authors examined the use of PSI in 71 total cases performed by three separate surgeons. They noted a fast-learning curve: it took the surgeons 10 cases to optimize their operative time to a mean of 26.3 minutes per case. It took the surgeons eight cases to lessen their anxiety levels, and nine cases to decrease the number of fluoroscopic images utilized. Additionally, the authors noted highly accurate coronal plane, sagittal plane, and mechanical axis outcomes in all included cases, and the accuracy of the initial 10 cases was not affected by the learning curve for the procedure.
Four studies sought to directly compare PSI to conventional techniques. A 2020 study by Mao et al. sought to directly compare outcomes related to 19 patients treated with freehand conventional MOW-HTO to 18 patients treated with PSI MOW-HTO [
3D-Printed Patient-Specific Instrumentation Technique Vs. Conventional Technique in Medial Open Wedge High Tibial Osteotomy: A Prospective Comparative Study.
]. The authors noted significantly improved accuracy in the correction of the mFTA and mMPTA. The authors also noted significantly shorter operative times by approximately 16.8 minutes per case and significantly decreased radiation exposure for the PSI group. This led Mao et al. to conclude that PSI is readily implementable and has superior accuracy relative to conventional MOW-HTO techniques.
A separate 2020 multicenter non-randomized prospective study by Tardy et al. allocated 126 patients into three different treatment arms: conventional technique, CAN, and PSI [
Is patient-specific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?.
Orthopaedics & Traumatology: Surgery & Research.2020; 106 (Supplement): S231-S236
]. The authors performed preoperative planning and assessed the HKA angle accuracy relative to preoperative planning for all three groups. They reported an error of 1.1° in the conventional group, 2.1° in the CAN group, and 0.3° in the PSI group. In 2016, Pérez-Mañanes et al. compared error in HKA correction relative to preoperative planning and found a difference in 0.6° that favored the PSI group over the conventional group [
]. These results were further supported by a 2018 study by Kim et al. that reported increased accuracy in the correction of the weight-bearing line when using PSI relative to more conventional MOW-HTO techniques [
]. When these results were aggregated in the present systematic review, the SMD also suggested that the implementation of PSI in MOW-HTOs would lead to a reduced error in the mechanical axis correction relative to conventional osteotomy techniques. Thus, in the context of the current clinical literature, the results reported in this systematic review support the implementation of PSI for accurate, safe, and precise MOW-HTOs.
A recently published systematic review by Aman et al. demonstrated that PSI improves coronal correctional accuracy and minimizes complications for osteotomies around the knee [
]. Like our systematic review, their study supported the implementation of PSI; however, the authors did not assess sagittal accuracy and included opening and closing wedge HTOs as well as opening and closing wedge distal femoral osteotomies (DFOs). Our present study assessed coronal accuracy, sagittal accuracy, mechanical axis correction accuracy, and complication rate for MOW-HTOs using PSI when treating medial compartment osteoarthritis. It demonstrated a low complication rate and a high degree of accuracy for all included primary outcomes. Furthermore, direct comparison of PSI relative to a traditional (gold standard) technique for MOW-HTOs was feasible in our study by calculating relative effect sizes and a SMD. Our study suggested that 95% of included patients would have a more accurate mechanical axis correction if PSI were implemented for their MOW-HTO. Finally, given the chronological nature of systematic reviews, our study was able to include 14 studies examining PSI for MOW-HTO, while the study by Aman et al. included 14 total studies when combining opening/closing wedge HTOs and DFOs.
The improved accuracy outcomes with PSI noted in this study are clinically relevant given that error in either the coronal or sagittal planes can lead to subsequent suboptimal patient outcomes. Additionally, unintended changes in the sagittal plane can also lead to impaired knee kinematics, instability, and excessive strain on the cruciate ligaments [
]. This is relevant in the field of osteotomies given that LaPrade et al. demonstrated that a conventional MOW-HTO leads to an average unintended posterior tibial slope change of 2.9º when using a freehand technique [
]. The findings of the present systematic review suggest that such unintended changes in sagittal deformity could potentially be prevented through the use of PSI.
This study is not without limitations. First, analysis was limited by the overall currently available evidence on this topic, with substantial variations noted in PSI technique as well as planning software. Nevertheless, 14 studies were available for inclusion, with four studies available for calculation of SMD between PSI and traditional techniques. Second, the study was limited by variability in imaging outcome reporting as it relates to which coronal and sagittal measurements were provided in each study. Additionally, the definition of major/reported complications among the included studies varied on the basis of study design. Finally, long-term studies are needed to establish and quantify the clinical benefit of incremental increases in HTO osteotomies and define how they relate to long term patient reported outcomes and reoperation/arthroplasty rates. The above limitations highlight the need for future well-designed prospective, randomized clinical studies in order to better evaluate the true efficacy, safety, and benefits of PSI for MOW-HTO.
Conclusion
The findings of this present systematic review suggest that the use of PSI for MOW-HTOs leads to high accuracy relative to the planned corrections in the coronal plane, sagittal plane, and the mechanical axis. Furthermore, these findings would suggest there is a low risk of major complications when implementing PSI for MOW-HTO.
Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Appendix A. Supplementary data
The following is the Supplementary data to this article.
3D-Printed Patient-Specific Instrumentation Technique Vs. Conventional Technique in Medial Open Wedge High Tibial Osteotomy: A Prospective Comparative Study.
Is patient-specific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?.
Orthopaedics & Traumatology: Surgery & Research.2020; 106 (Supplement): S231-S236
Patient-specific high-tibial osteotomy’s ‘cutting-guides’ decrease operating time and the number of fluoroscopic images taken after a Brief Learning Curve.
Yang, J.C.-S., et al., Clinical Experience Using a 3D-Printed Patient-Specific Instrument for Medial Opening Wedge High Tibial Osteotomy. BioMed Research International, 2018. 2018: p. 9246529.
Suhas Dasari (Contribution: substantial conception/design of work, performed measurements, data collection, statistical analysis, interpretation of data, drafting the work, critically revising the work, manuscript preparation, approving final version for publication, and agreement for accountability of all aspects of work
Mario Hevesi (Contribution: substantial conception/design of work, performed measurements, data collection, statistical analysis, interpretation of data, drafting the work, critically revising the work, manuscript preparation, approving final version for publication, and agreement for accountability of all aspects of work.
Luc Fortier (Contribution: substantial conception/design of work, interpretation of data for work, revising of the work for important intellectual content, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Robert Ferrer-Rivero (Contribution: substantial conception/design of work, interpretation of data for work, revising of the work for important intellectual content, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Alec Warrier (Contribution: substantial conception/design of work, revising of the work for important intellectual content, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Bhargavi Maheshwer (Contribution: substantial conception/design of work, revising of the work for important intellectual content, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Garrett Jackson (Contribution: substantial conception/design of work, revising of the work for important intellectual content, manuscript preparation, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Harkirat Jawanda (Contribution: substantial conception/design of work, revising of the work for important intellectual content, manuscript preparation, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Enzo Mameri (Contribution: substantial conception/design of work, revising of the work for important intellectual content, manuscript preparation, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Zeeshan Khan (Contribution: substantial conception/design of work, revising of the work for important intellectual content, manuscript preparation, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Benjamin Kerzner (Contribution: substantial conception/design of work, revising of the work for important intellectual content, manuscript preparation, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Robert Browning (Contribution: substantial conception/design of work, revising of the work for important intellectual content, manuscript preparation, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Safa Gursoy (Contribution: substantial conception/design of work, revising of the work for important intellectual content, final approval of the version for publication, and agreement to accountability of all aspects of the work)
Jorge Chahla (Contribution: substantial conception/design of work, revising of the work for important intellectual content, manuscript preparation, final approval of the version for publication, and agreement to accountability of all aspects of the work)
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