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Despite its current widespread use, evidence to support the indications for hip arthroscopy lags behind: a review of current literature

      Importance

      Hip arthroscopy is commonly used for diagnostic purposes and for treatment of a variety of hip pathologies. Despite its current widespread use, evidence to support the indications for its application may lag behind.

      Objective

      Review the body of evidence for commonly accepted indications (ie, femoroacetabular impingement (FAI), labral tear, septic hip, loose bodies, extra-articular lesions, mild/moderate osteoarthritis, extra-articular impingement, abductor tendon tears and labral reconstruction) for hip arthroscopy based on recent systematic reviews.

      Evidence review

      A literature review was performed (in August 2015) using the PubMed database. The search results were filtered to include only the most recent (past 4 years 2012–2015) systematic reviews. Only articles that were selected for inclusion by these systematic reviews were included in this review of indications. Articles were then combined by indication and sorted by level of evidence and assigned a Grade of Recommendation.

      Findings

      Fair evidence exists to support the arthroscopic repair of acetabular labral tears and for the treatment of symptomatic FAI. Poor-quality evidence exists to support the use of hip arthroscopy in the treatment of extra-articular impingement, septic arthritis, mild/moderate osteoarthritis, abductor tendon tears and labral reconstruction. No recommendation could be made on the use of hip arthroscopy for ischiofemoral impingement, greater trochanter pelvic impingement and treatment for asymptomatic FAI.

      Conclusions and relevance

      There has been a large increase in published studies on hip arthroscopy; however, the studies published hitherto are generally of lesser quality and as such do not provide a higher Grade of Recommendation for most hip arthroscopy procedures.
      What is already known
      • The common indications for hip arthroscopy may be derived from the different pathologies that may cause pain around the hip joint.
      • Despite the current widespread use of hip arthroscopy, evidence to support the indications for its application may lag behind.
      What are the new findings
      • Fair evidence exists to support the arthroscopic repair of acetabular labral tears and for the treatment of symptomatic femoroacetabular impingement (FAI).
      • Poor-quality evidence exists to support the use of hip arthroscopy in the treatment of extra-articular impingement, septic arthritis, mild/moderate osteoarthritis, abductor tendon tears and labral reconstruction.
      • No recommendation could be made on the use of hip arthroscopy for ischiofemoral impingement, greater trochanter pelvic impingement and treatment for asymptomatic FAI.

      Introduction

      Hip arthroscopy has become a more prevalent procedure used for diagnosis and treatments of a variety of hip pathologies. The indications for the use of hip arthroscopy have not been widely discussed throughout the literature.
      • Tibor LM
      • Sekiya JK
      Differential diagnosis of pain around the hip joint.
      In 2010, Stevens et al
      • Stevens MS
      • Legay DA
      • Glazebrook MA
      • et al.
      The evidence for hip arthroscopy: grading the current indications.
      published the first systematic review to grade the indications for hip arthroscopy. The authors reviewed the common indications for hip arthroscopy including femoroacetabular impingement (FAI), labral tear, septic hip, loose bodies, extra-articular lesions, and mild-to-moderate osteoarthritis (OA). Since the aforementioned review, further indications for hip arthroscopy have been published such as treatment of extra-articular impingement syndromes (psoas impingement (PI),
      • Domb BG
      • Shindle MK
      • McArthur B
      • et al.
      Iliopsoas impingement: a newly identified cause of labral pathology in the hip.
      subspine impingement (SSI)
      • Hetsroni I
      • Larson CM
      • Dela Torre K
      • et al.
      Anterior inferior iliac spine deformity as an extra-articular source for hip impingement: a series of 10 patients treated with arthroscopic decompression.
      ), deep gluteal syndrome (DGS),
      • Martin HD
      • Shears SA
      • Johnson JC
      • et al.
      The endoscopic treatment of sciatic nerve entrapment/deep gluteal syndrome.
      abductor tendon tears (ATT)
      • Voos JE
      • Shindle MK
      • Pruett A
      • et al.
      Endoscopic repair of gluteus medius tendon tears of the hip.
      and labral reconstruction.
      • Matsuda DK
      • Burchette RJ
      Arthroscopic hip labral reconstruction with a gracilis autograft versus labral refixation: 2-year minimum outcomes.
      Despite the current widespread use of hip arthroscopy, evidence to support the indications for its application may lag behind.
      This paper will review the body of evidence for commonly accepted indications for hip arthroscopy, classify the level of evidence for individual papers and assign the Grade of Recommendation for the aforementioned indications based on recent systematic reviews.

      Methods

      This is a review of the indications for hip arthroscopy based on the last systematic review that graded the indications for hip arthroscopy in 2010.
      • Stevens MS
      • Legay DA
      • Glazebrook MA
      • et al.
      The evidence for hip arthroscopy: grading the current indications.
      A literature review was conducted on 1 August 2015 using PubMed for the same indications for hip arthroscopy that were graded in the aforementioned systematic review along with the key words ‘hip’ and ‘arthroscopy’. An additional search, including indications that were not included in the review that graded the indications (SSI, PI, DGS, repair of hamstring tear, repair of ATT, and labral reconstruction), along with the key words ‘hip’ and ‘arthroscopy’, was also conducted. This review is based only on the most recent (past 4 years 2012–2015) systematic reviews written in English. A total of 11 systematic reviews with listed indications of symptomatic and asymptomatic FAI, labral tear, labral reconstruction, adductor tendon tear, septic hip, OA and extra-articular impingement syndromes were found. Only articles that were selected for inclusion by these systematic reviews were included in this review of indications.
      Articles were then combined by indication and sorted by level of evidence using criteria by Wright et al
      • Wright JG
      • Swiontkowski MF
      • Heckman JD
      Introducing levels of evidence to the journal.
      (table 1). The evidence for each indication was graded using the grades of recommendation scale of Wright et al
      • Wright JG
      • Einhorn TA
      • Heckman JD
      Grades of recommendation.
      (table 2). A subscale proposed by Stevens et al
      • Stevens MS
      • Legay DA
      • Glazebrook MA
      • et al.
      The evidence for hip arthroscopy: grading the current indications.
      was adopted to further differentiate the evidence for indications (table 2). Assigning the Grade of Recommendation based on the level of evidence was done by three authors (EA, IHW and MAG) independently with 100% agreement.
      Table 1Levels of evidence for therapeutic studies
      Therapeutic studies investigating results of treatment
      Level I
      • 1.
        Randomised controlled trial that shows either a significant difference or no significant difference but had narrow CIs.
      • 2.
        Systematic review of randomised controlled trials (studies were homogeneous)
      Level II
      • 1.
        Prospective comparative studies
      • 2.
        Randomised controlled trial of lesser quality
      • 3.
        Systematic review of level II studies
or systematic review of non-homogeneous level I studies
      Level III
      • 1.
        Case–control study
      • 2.
        Retrospective comparative study
      • 3.
        Systematic review of level III studies
      Level IVCase series with a historical or no control group
      Level VExpert opinion
      Level of evidence according to Wright et al.
      • Wright JG
      • Swiontkowski MF
      • Heckman JD
      Introducing levels of evidence to the journal.
      Table 2Grades of recommendation for summaries or reviews of orthopaedic surgical studies and a subscale differentiating evidence for indications receiving Grade of Recommendation of C
      GradeDescription
      AGood evidence (level I studies with consistent findings) for or against recommending intervention
      BFair evidence (level II or III studies with consistent findings) for or against recommending intervention
      CConflicting or poor-quality evidence (level IV or V studies) not allowing a recommendation for or against intervention
      IThere is insufficient evidence to make a recommendation
      Subscale
      CfRepresenting literature ‘for,‘ or in support of, a surgical intervention
      CaRepresenting literature ‘against’, or not in support of, a surgical intervention
      CcRepresenting conflicting literature, some of which is in support of a surgical intervention and some of which is not in support of a surgical intervention
      Grade of indication according to Wright et al.
      • Wright JG
      • Einhorn TA
      • Heckman JD
      Grades of recommendation.
      Subscale according to Stevens et al.
      • Stevens MS
      • Legay DA
      • Glazebrook MA
      • et al.
      The evidence for hip arthroscopy: grading the current indications.

      Results

      A summary of the grades of recommendation for or against the indications for hip arthroscopy based on the analysis of these current systematic reviews is presented in table 3. Fair evidence (grade B) exists to support the arthroscopic repair of acetabular labral tears and for the treatment of FAI. Poor-quality evidence based on the literature (grade Cf) exists to support a recommendation for the use of hip arthroscopy in the treatment of extra-articular impingement, septic arthritis, mild-to-moderate OA, ATT and labral reconstruction. No recommendation (grade I) could be made on the use of hip arthroscopy for ischiofemoral impingement (IFI), greater trochanter pelvic impingement (GTPI) and arthroscopic treatment for asymptomatic FAI.
      Table 3Summary of Grade of Recommendation for or against current generally accepted indications for hip arthroscopy based on recent systematic reviews
      IndicationYear of systematic reviewLevel ILevel IILevel IIILevel IVLevel VTotal number of patientsTotal number of articlesGrade
      Symptomatic FAI
      • Ayeni OR
      • Wong I
      • Chien T
      • et al.
      Surgical indications for arthroscopic management of femoroacetabular impingement.
      ,
      • Wall PD
      • Brown JS
      • Parsons N
      • et al.
      Surgery for treating hip impingement (femoroacetabular impingement).
      ,
      • Nwachukwu BU
      • Rebolledo BJ
      • McCormick F
      • et al.
      Arthroscopic versus open treatment of femoroacetabular impingement: a systematic review of medium- to long-term outcomes.
      2012–20151421275227B
      Labral tear
      • Ayeni OR
      • Adamich J
      • Farrokhyar F
      • et al.
      Surgical management of labral tears during femoroacetabular impingement surgery: a systematic review.
      2014154906B
      Labral reconstruction
      • Ayeni OR
      • Alradwan H
      • de Sa D
      • et al.
      The hip labrum reconstruction: indications and outcomes—a systematic review.
      20141131285Cf
      ATT
      • Alpaugh K
      • Chilelli BJ
      • Xu S
      • et al.
      Outcomes after primary open or endoscopic abductor tendon repair in the hip: a systematic review of the literature.
      201581358Cf
      Septic hip
      • de SA D
      • Cargnelli S
      • Catapano M
      • et al.
      Efficacy of hip arthroscopy for the management of septic arthritis: a systematic review.
      20151916511Cf
      Osteoarthritis
      • Domb BG
      • Gui C
      • Lodhia P
      How much arthritis is too much for hip arthroscopy: a systematic review.
      • Kemp JL
      • MacDonald D
      • Collins NJ
      • et al.
      Hip arthroscopy in the setting of hip osteoarthritis: systematic review of outcomes and progression to hip arthroplasty.
      2015323289626Cf
      Extra-articular
      • de Sa D
      • Alradwan H
      • Cargnelli S
      • et al.
      Extra-articular hip impingement: a systematic review examining operative treatment of psoas, subspine, ischiofemoral, and greater trochanteric/pelvic impingement.
       PI20142512Cf
       SSI2014521817Cf
       IFI20140I
       GTPI20140I
      Asymptomatic FAI
      • Collins JA
      • Ward JP
      • Youm T
      Is prophylactic surgery for femoroacetabular impingement indicated? A systematic review.
      201400I
      ATT, abductor tendon tear; FAI, femoroacetabular impingement; GTPI, greater trochanter pelvic impingement; IFI, ischiofemoral impingement; PI, psoas impingement; SSI, subspine impingement.

      Symptomatic FAI

      Three systematic reviews concerning arthroscopic treatment of FAI were reviewed.
      • Ayeni OR
      • Wong I
      • Chien T
      • et al.
      Surgical indications for arthroscopic management of femoroacetabular impingement.
      ,
      • Wall PD
      • Brown JS
      • Parsons N
      • et al.
      Surgery for treating hip impingement (femoroacetabular impingement).
      ,
      • Nwachukwu BU
      • Rebolledo BJ
      • McCormick F
      • et al.
      Arthroscopic versus open treatment of femoroacetabular impingement: a systematic review of medium- to long-term outcomes.
      Ayeni et al
      • Ayeni OR
      • Wong I
      • Chien T
      • et al.
      Surgical indications for arthroscopic management of femoroacetabular impingement.
      reviewed the indications for the arthroscopic treatment of FAI. The inclusion criteria included studies of human patients of all ages and genders with FAI, a minimum of 6-month follow-up, and studies reporting clinical outcome data. The authors found 20 papers suitable for review, of which 17 were level IV studies, two were level III and one was level II. The total number of patients was 1368. The authors concluded that an inconsistency exists between the reported clinical and radiographic indications for arthroscopic management of FAI. The only level II study identified in this systematic review by Brunner et al
      • Brunner A
      • Horisberger M
      • Herzog RF
      Evaluation of a computed tomography-based navigation system prototype for hip arthroscopy in the treatment of femoroacetabular cam impingement.
      prospectively evaluated 50 patients who underwent arthroscopic offset restoration for cam type FAI. Range of motion, a visual analogue scale, and non-arthritic hip scores (NAHS) significantly improved in all subgroups. Statistical analysis showed no significant difference regarding the clinical outcome between patients with sufficient and insufficient correction of the α angle. The first level III study identified by the systematic review by Bardakos and Villar
      • Bardakos NV
      • Villar RN
      Predictors of progression of osteoarthritis in femoroacetabular impingement: a radiological study with a minimum of ten years follow-up.
      compared two groups of patients with cam-type FAI. Both groups underwent arthroscopic debridement and one group underwent additional excision of their impingement lesion. The group that had arthroscopic excision of their impingement lesion in addition to arthroscopic debridement had a good or excellent outcome rate of 83% as compared with a 60% good or excellent outcome rate in the group that had arthroscopic debridement alone.
      The second level III identified by the systematic review was a retrospective comparative study by Larson and Giveans
      • Larson CM
      • Giveans MR
      Arthroscopic debridement versus refixation of the acetabular labrum associated with femoroacetabular impingement.
      where the arthroscopic treatment of FAI involving labral debridement and acetabular rim trimming with labral refixation and acetabular rim trimming were compared. The labral refixation group had a good or excellent outcome rate of 89.7% compared with a good or excellent outcome rate of 66.7% in the group that underwent labral debridement and acetabular rim trimming.
      A Cochrane review by Wall et al
      • Wall PD
      • Brown JS
      • Parsons N
      • et al.
      Surgery for treating hip impingement (femoroacetabular impingement).
      applied the following inclusion criteria: FAI diagnosis made on the basis of symptoms of hip or groin pain, or both; restricted range of motion and a positive anterior impingement test; and the presence of abnormal hip shape morphology and abnormalities of the adjacent labrum and cartilage on imaging. After reviewing 351 eligible studies, none met the inclusion criteria. The conclusion was that there is no evidence to either support or discourage the use of surgical interventions for FAI. Furthermore, no studies on the efficacy of FAI surgery compared with non-surgical or sham treatments were identified.
      In a systematic review in 2015, Nwachukwu et al
      • Nwachukwu BU
      • Rebolledo BJ
      • McCormick F
      • et al.
      Arthroscopic versus open treatment of femoroacetabular impingement: a systematic review of medium- to long-term outcomes.
      compared arthroscopic and open surgery for FAI. Sixteen studies were identified, of which seven included medium-term to long-term outcomes after arthroscopic treatment for FAI. The systematic review's inclusion criteria were therapeutic clinical outcome studies, primary treatment of FAI, and minimum mean follow-up of 3 years. The literature search yielded two level III studies where the remaining five studies were level IV. The authors found that both hip arthroscopy and open surgical hip dislocation showed excellent (over 90%) and equivalent hip survival rates at medium-term follow-up. Moreover, hip arthroscopy was shown to have superior results regarding general health-related quality of life in comparison to open treatment.
      • Skendzel JG
      • Philippon MJ
      • Briggs KK
      • et al.
      The effect of joint space on midterm outcomes after arthroscopic hip surgery for femoroacetabular impingement.
      • Larson CM
      • Giveans MR
      • Stone RM
      Arthroscopic debridement versus refixation of the acetabular labrum associated with femoroacetabular impingement: mean 3.5-year follow-up.
      Grade of Recommendation: On the basis of the consistent findings reported in the literature in support of this surgical technique including one level II study and four level III studies, a grade B recommendation was given in support of the arthroscopic treatment of FAI.

      Labral tears

      A systematic review used for the review of the treatment of labral tear as an indication for hip arthroscopy was conducted by Ayeni et al
      • Ayeni OR
      • Adamich J
      • Farrokhyar F
      • et al.
      Surgical management of labral tears during femoroacetabular impingement surgery: a systematic review.
      to determine the optimal surgical management of labral tears during FAI surgery. The inclusion criteria were as follows: (1) comparative study (ie, case–control, cohort or randomised controlled trial) comparing labral repair versus debridement, (2) surgical treatment of FAI, and (3) study involving human patients. Only six studies met the inclusion criteria with a total of 490 patients. There was one level I study and five level III studies. The authors found that labral repairs resulted in superior outcomes when compared with labral debridement. The level I study by Krych et al
      • Krych AJ
      • Thompson M
      • Knutson Z
      • et al.
      Arthroscopic labral repair versus selective labral debridement in female patients with femoroacetabular impingement: a prospective randomized study.
      compared two groups of 18 patients who underwent labral tear repair versus focal debridement. Both groups demonstrated significant improvement in their Hip Outcome Score (HOS) for activities of daily living (ADL) and for sports from the preoperative to the final follow-up (p<0.05). The labral repair group had postoperative ADL and sports HOS that were significantly better compared with the debridement group.
      Grade of Recommendation: On the basis of the consistent findings reported in the literature in support of this surgical technique including one level I study and five level III studies, a grade B recommendation was given in support of the arthroscopic repair of labral tears.

      Labral reconstruction

      A systematic review was used to review the treatment of labral reconstruction as an indication for hip arthroscopy by Ayeni et al
      • Ayeni OR
      • Alradwan H
      • de Sa D
      • et al.
      The hip labrum reconstruction: indications and outcomes—a systematic review.
      and to determine the indication for labral reconstruction, the ideal graft and patient reported outcomes.
      Five studies met the systematic review's inclusion criteria with a total of 128 patients. There was one level II study, one level III study and three level IV studies. The inclusion criteria were as follows: (1) involved labral reconstruction by open surgery and/or arthroscopic means; (2) reported graft type and outcomes; and (3) involved human subjects. The authors found that the eligible candidate for labral reconstruction is a young, active individual with a minimum of 2 mm of joint space. Additionally, the authors found that the iliotibial band, ligamentum teres and gracilis have all been successfully utilised as a graft source. Finally, the authors concluded that hip labrum reconstruction is a new technique that showed short-term improvement in patient-reported outcomes and functional scores postoperatively, although definitive and long-term data are lacking. The level II study identified in the aforementioned systematic review by Sierra et al
      • Sierra RJ
      • Trousdale RT
      Labral reconstruction using the ligamentum teres capitis: report of a new technique.
      did not perform the labral reconstruction using an arthroscopic technique.
      The level III study identified in this systematic review by Matsuda and Burchette
      • Matsuda DK
      • Burchette RJ
      Arthroscopic hip labral reconstruction with a gracilis autograft versus labral refixation: 2-year minimum outcomes.
      was a retrospective comparative study with eight patients who underwent labral reconstruction and 46 patients who underwent labral refixation. At an average of a 30-month follow-up, 87.5% of the reconstruction group marked high satisfaction and 12.5% marked moderate satisfaction. Additionally, the NAHS in the reconstruction group improved by a mean of 50.5 points.
      Level of recommendation: The literature provides excellent outcomes for labral reconstruction procedures, but it is limited to only five studies with no long-term follow-up studies available. As a result, the arthroscopic labral reconstruction was given a grade Cf recommendation in support of the intervention.

      Abductor tendon tear

      A systematic review used for reviewing the treatment of ATT as an indication for hip arthroscopy by Alpaugh et al
      • Alpaugh K
      • Chilelli BJ
      • Xu S
      • et al.
      Outcomes after primary open or endoscopic abductor tendon repair in the hip: a systematic review of the literature.
      reviewed the outcomes after primary open or endoscopic abductor tendon repair in the hip. Studies were eligible for inclusion in the systematic review if they had identified tendon repair in a native hip as either open or endoscopic, and reported postoperative outcome scores. The review yielded eight level IV articles that met the inclusion criteria with a total number of 135 hips available for review. Four studies documented endoscopic abductor tendon repair with a total of 39 hips available for review. The authors concluded that both open and endoscopic techniques are viable surgical solutions with good to excellent functional results and reduced pain. Endoscopic repair appears to result in fewer postoperative complications including tendon retear.
      Grade of Recommendation: On the basis of the poor quality of evidence comprising only level IV studies, a grade Cf recommendation was given in support of the arthroscopic repair of ATTs.

      Septic hip

      In a recent systematic review conducted by de Sa et al,
      • de SA D
      • Cargnelli S
      • Catapano M
      • et al.
      Efficacy of hip arthroscopy for the management of septic arthritis: a systematic review.
      11 studies were found that examined arthroscopic treatment of septic arthritis of native hips. The systematic review's inclusion criteria included human studies and studies on arthroscopic surgical management of septic arthritis of the native hip joint. Studies of all levels of evidence that reported outcomes and/or complications were also included. The authors found one case–control study, eight case series and two case reports. The total number of patients reviewed in the systematic review was 65. Despite the variation between the study regarding diagnostic laboratory exams, contraindication, irrigation technique and surgical technique and causative agent, the authors found that all patients significantly improved after arthroscopic intervention. Furthermore, at documented follow-up time points, most patients were asymptomatic, with no fever, and without limitations in range of movement or ADL and with no arthroscopy-related complication, although no optimal follow-up period for these patients was established to determine outcomes and complications. The authors concluded that arthroscopic treatment of native septic hips comprises a safe and effective treatment.
      El-Sayed
      • El-Sayed AM
      Treatment of early septic arthritis of the hip in children: comparison of results of open arthrotomy versus arthroscopic drainage.
      published the only level III study identified in the systematic review,
      • de SA D
      • Cargnelli S
      • Catapano M
      • et al.
      Efficacy of hip arthroscopy for the management of septic arthritis: a systematic review.
      comparing the results of open arthrotomy versus arthroscopic drainage in treating septic arthritis of the hip in 20 children (10 in each group). There was no statistically significant difference between the arthrotomy and arthroscopy groups.
      Grade of Recommendation: The literature is consistent across both adult and paediatric studies and provides excellent outcomes for the procedure but is limited to one level III and several small level IV case series. As a result, the arthroscopic treatment of septic arthritis of the hip joint was given a grade Cf recommendation in support of the intervention.

      Osteoarthritis

      Two recent systematic reviews concerning arthroscopic treatment of osteoarthritic hips were reviewed.
      • Domb BG
      • Gui C
      • Lodhia P
      How much arthritis is too much for hip arthroscopy: a systematic review.
      • Kemp JL
      • MacDonald D
      • Collins NJ
      • et al.
      Hip arthroscopy in the setting of hip osteoarthritis: systematic review of outcomes and progression to hip arthroplasty.
      The first systematic analysis was by Domb et al
      • Domb BG
      • Gui C
      • Lodhia P
      How much arthritis is too much for hip arthroscopy: a systematic review.
      who reviewed the current literature in an attempt to determine the extent of preoperative OA that precludes the benefit from hip arthroscopy and refines the indications for hip arthroscopy in the setting of OA. The systematic review's inclusion criteria included papers that commented on preoperative factors, parameters, physical examination, or diagnostic testing that may be evidence of cartilage damage and/or arthritis, papers that contained outcome data on patients undergoing hip arthroscopy and papers that had a sample size of at least 10 patients with arthritic changes in the hip. The authors identified 14 level IV studies and one level III study. The accumulated number of hip arthroscopies was 2051 with a mean patient age of 40.2 years (range 31–58.2 years). The mean follow-up period was 41.5 months. Conversion to total hip arthroplasty (THA) has been identified in a total of 345 patients with a mean time to conversion of 23 months (7–58.2). The authors therefore concluded that arthritic populations demonstrate lower postoperative scores than their non-arthritic counterparts. Additionally, current evidence is insufficient to define a cut-off that will serve as a contraindication for hip arthroscopy. However, the authors concluded that a Tönnis
      • Tonnis D
      • Heinecke A
      Acetabular and femoral anteversion: relationship with osteoarthritis of the hip.
      grade of 1 or greater or a joint space of 2 mm or less is less likely to benefit from hip arthroscopy and more likely to require conversion to THA.
      The only level III study identified in this systematic review was carried out by Skendzel et al
      • Skendzel JG
      • Philippon MJ
      • Briggs KK
      • et al.
      The effect of joint space on midterm outcomes after arthroscopic hip surgery for femoroacetabular impingement.
      in which 466 patients were evaluated with the mean age of 40.6 years. The authors found that patients with a joint space >2 mm demonstrated joint survival at the 5-year mark of 86% as opposed to 20% in the group of patients with a joint space <2 mm.
      The second systematic review by Kemp et al
      • Kemp JL
      • MacDonald D
      • Collins NJ
      • et al.
      Hip arthroscopy in the setting of hip osteoarthritis: systematic review of outcomes and progression to hip arthroplasty.
      reviewed the outcomes and progression to hip arthroplasty in patients undergoing hip arthroscopy in the setting of OA. The inclusion criteria were patients aged 17 years or older who had undergone hip arthroscopy as a primary intervention for hip OA and studies following patients for at least 3 months, using patient-reported outcome measures of pain and/or function, reporting a prevalence of THA, or time to THA. The authors reviewed 15 studies of which 13 were level IV studies and two were level III studies.
      The first level III study identified by this systematic review by Fontana et al
      • Fontana A
      • Bistolfi A
      • Crova M
      • et al.
      Arthroscopic treatment of hip chondral defects: autologous chondrocyte transplantation versus simple debridement—a pilot study.
      compared arthroscopic debridement versus arthroscopic autologous chondrocyte transplantation (ACT) for the treatment of hip chondral lesions in 30 patients (15 in each group). The authors demonstrated a significant difference in the improvement rate in favour of the ACT group as measured by the Harris Hip Score (HHS).
      The second level III study identified by this systematic review by McCormick et al
      • McCormick F
      • Nwachukwu BU
      • Alpaugh K
      • et al.
      Predictors of hip arthroscopy outcomes for labral tears at minimum 2-year follow-up: the influence of age and arthritis.
      retrospectively evaluated 176 patients using modified HHS and HOS to determine whether arthritis or age is predictive of outcomes after hip arthroscopy for labral pathology. The authors found that the presence of osteoarthritic changes at the time of arthroscopy (defined as Outerbridge 4) was predictive of worse outcome scores compared with the non-arthritic counterparts.
      Grade of Recommendation: The literature is consistent that the outcome inversely correlates with the level of OA, but it is limited to three level III studies and the remaining were level IV case series. As a result, the arthroscopic treatment of OA of the hip joint was given a grade Cf recommendation in support of the intervention for patients with mild-to-moderate OA.

      Extra-articular impingement syndromes

      Extra-articular hip impingement refers to disorders causing pain and limited function in young, patients without arthritis and includes PI, SSI, IFI and GTPI.
      • de Sa D
      • Alradwan H
      • Cargnelli S
      • et al.
      Extra-articular hip impingement: a systematic review examining operative treatment of psoas, subspine, ischiofemoral, and greater trochanteric/pelvic impingement.

      Psoas impingement

      A systematic review was conducted in order to establish the indication for surgical management, as well as the surgical options and outcomes of the surgical intervention.
      • de Sa D
      • Alradwan H
      • Cargnelli S
      • et al.
      Extra-articular hip impingement: a systematic review examining operative treatment of psoas, subspine, ischiofemoral, and greater trochanteric/pelvic impingement.
      The inclusion criteria were as follows: all levels of evidence on humans, studies on native hips of patients aged at least 12 years who were followed up for a minimum of 6 months and who underwent surgical treatment (open and/or arthroscopic) for PI. The authors excluded studies pertaining to PI after THA, or studies of patients with FAI or internal snapping hip syndrome. The authors found two papers that met the inclusion criteria with a total of 51 hips available for review. The authors concluded that surgical treatment of PI and its associated labral lesions resulted in improvements in subjective and objective clinical outcomes, with no major or moderate complications reported.
      • de Sa D
      • Alradwan H
      • Cargnelli S
      • et al.
      Extra-articular hip impingement: a systematic review examining operative treatment of psoas, subspine, ischiofemoral, and greater trochanteric/pelvic impingement.
      Grade of Recommendation: On the basis of the poor quality of evidence comprising only level IV studies, a grade Cf recommendation was given in support of the arthroscopic treatment of PI.

      Subspine impingement

      A systematic review used for reviewing the treatment of SSI as an indication for hip arthroscopy was conducted by de Sa et al.
      • de Sa D
      • Alradwan H
      • Cargnelli S
      • et al.
      Extra-articular hip impingement: a systematic review examining operative treatment of psoas, subspine, ischiofemoral, and greater trochanteric/pelvic impingement.
      The systematic review's inclusion criteria were quite broad and included studies on native human hips that underwent surgical treatment for SSI. The authors found seven papers (5 case reports and 2 case series) that met the inclusion criteria with a total of 180 hips available for review. The major reported indications for surgical treatment included persistent pain after intra-articular anaesthetic injection, either pain with palpation of the AIIS and/or imaging demonstrating a prominent AIIS. Improvement in the pain level was reported for all patients with no major complications.
      • de Sa D
      • Alradwan H
      • Cargnelli S
      • et al.
      Extra-articular hip impingement: a systematic review examining operative treatment of psoas, subspine, ischiofemoral, and greater trochanteric/pelvic impingement.
      Grade of Recommendation: On the basis of the poor quality of evidence comprising only level IV studies, a grade Cf recommendation was given in support of the arthroscopic treatment of SSI.

      Ischiofemoral impingement

      A systematic review published in 2014 was conducted to establish the indication for surgical management, as well as the surgical options and outcomes of the surgical intervention. The inclusion criteria were quite broad and included studies on native human hips that underwent surgical treatment for IFI. The authors found three papers (2 case reports and 1 case series) that met the inclusion criteria with a total of 16 hips available for review. None of the operations were performed endoscopically.
      • de Sa D
      • Alradwan H
      • Cargnelli S
      • et al.
      Extra-articular hip impingement: a systematic review examining operative treatment of psoas, subspine, ischiofemoral, and greater trochanteric/pelvic impingement.
      Grade of Recommendation: Since no studies reviewing arthroscopic treatment of IFI were found, a grade I recommendation was given to the arthroscopic treatment of IFI.

      Greater trochanteric pelvic impingement

      In a systematic review set to evaluate the surgical treatment for GTPI, the authors found two papers (case series) that met the inclusion criteria with a total of 40 hips. The inclusion criteria were quite broad and included studies on native human hips that underwent surgical treatment for GTPI. None of the operations were done endoscopically.
      • de Sa D
      • Alradwan H
      • Cargnelli S
      • et al.
      Extra-articular hip impingement: a systematic review examining operative treatment of psoas, subspine, ischiofemoral, and greater trochanteric/pelvic impingement.
      Grade of Recommendation: Since no studies reviewing arthroscopic treatment of GTPI were found, a grade I recommendation was given for the arthroscopic treatment of GTPI.

      Asymptomatic FAI

      A systematic review for the treatment of asymptomatic FAI as an indication for hip arthroscopy was conducted by Collins et al
      • Collins JA
      • Ward JP
      • Youm T
      Is prophylactic surgery for femoroacetabular impingement indicated? A systematic review.
      in an effort to answer the question, ‘Is prophylactic surgery for FAI indicated?‘.
      The systematic review's inclusion criteria were prospective or retrospective studies, studies in which the patients were asymptomatic, skeletally mature people with more than one radiographic finding consistent with cam or pincer impingement, studies that compared patients who underwent prophylactic hip surgery with non-operative management, studies in which the outcome measures must include radiological assessment of OA, patient development of pain, change in functional status, or further surgical intervention including THA and the follow-up period of a minimum of 2 years. The authors reviewed 840 abstracts with inclusion criteria and found no study that compared surgical results in asymptomatic versus symptomatic patients. The authors concluded that current evidence does not support prophylactic surgery for asymptomatic FAI in the vast majority of cases.
      Grade of Recommendation: Since no studies comparing surgical versus non-surgical treatment of asymptomatic FAI were found, a grade I recommendation was given for the arthroscopic treatment of asymptomatic FAI.

      Discussion

      Hip arthroscopy is a surgical technique that holds promise of shorter recovery times, decreased hospital stays and reduced surgical morbidity.
      • El-Sayed AM
      Treatment of early septic arthritis of the hip in children: comparison of results of open arthrotomy versus arthroscopic drainage.
      • Botser IB
      • Smith Jr, TW
      • Nasser R
      • et al.
      Open surgical dislocation versus arthroscopy for femoroacetabular impingement: a comparison of clinical outcomes.
      Over the last decade, there has been a significant increase in the number of procedures performed and the number of surgeons performing hip arthroscopy in the USA.
      • Colvin AC
      • Harrast J
      • Harner C
      Trends in hip arthroscopy.
      • Montgomery SR
      • Ngo SS
      • Hobson T
      • et al.
      Trends and demographics in hip arthroscopy in the United States.
      The quality of evidence to support hip arthroscopy for commonly accepted indications, however, does not follow the same trend. Since the last systematic review that graded the evidence for the indications for hip arthroscopy in 2010,
      • Stevens MS
      • Legay DA
      • Glazebrook MA
      • et al.
      The evidence for hip arthroscopy: grading the current indications.
      there has been an ‘explosion’ in the number of studies pertaining to this subject. The authors' search in 2010 using the PubMed and Cochrane databases with key words ‘hip’ and ‘arthroscopy’ revealed 693 articles. A similar search using PubMed alone from 2010 until 2015 yielded 857 articles.
      Despite the increasing number of hip arthroscopy studies and expanding techniques for hip arthroscopy in recent years, the Grade of Recommendation assigned for each indication in this paper did not differ for the most part from the Grade of Recommendation made by Stevens et al.
      • Alpaugh K
      • Chilelli BJ
      • Xu S
      • et al.
      Outcomes after primary open or endoscopic abductor tendon repair in the hip: a systematic review of the literature.
      The fact that the Grade of Recommendation has not significantly changed in a 5-year span may imply that most of the aforementioned ‘explosion’ in the number of studies comprised lesser quality studies that do not contribute significantly to the body of evidence.
      Moreover, the indications for hip arthroscopy have broadened since the 2010 systematic review, and now may include labral reconstruction, extra-articular impingement syndromes, DGS, and repair of hamstring and ATTs. The increasing number of indications along with heterogeneity of patient populations, diagnostic measures, surgical techniques and outcome measures between different studies hinders the analysis and amalgamation of data rendering low quality of evidence. For example, our search of the evidence for arthroscopic treatment for FAI yielded three systematic reviews: one from 2012 by Ayeni et al,
      • Ayeni OR
      • Wong I
      • Chien T
      • et al.
      Surgical indications for arthroscopic management of femoroacetabular impingement.
      a Cochrane review from 2014 by Wall et al
      • Wall PD
      • Brown JS
      • Parsons N
      • et al.
      Surgery for treating hip impingement (femoroacetabular impingement).
      and a recent systematic review from 2015 by Nwachukwu et al.
      • Nwachukwu BU
      • Rebolledo BJ
      • McCormick F
      • et al.
      Arthroscopic versus open treatment of femoroacetabular impingement: a systematic review of medium- to long-term outcomes.
      While the systematic review by Ayeni et al
      • Ayeni OR
      • Wong I
      • Chien T
      • et al.
      Surgical indications for arthroscopic management of femoroacetabular impingement.
      identified 20 papers, a recent systematic review, conducted 3 years later by Nwachukwu et al,
      • Nwachukwu BU
      • Rebolledo BJ
      • McCormick F
      • et al.
      Arthroscopic versus open treatment of femoroacetabular impingement: a systematic review of medium- to long-term outcomes.
      identified only seven papers, of which the oldest was from 2010. The Cochrane review conducted in 2014 by Wall et al
      • Wall PD
      • Brown JS
      • Parsons N
      • et al.
      Surgery for treating hip impingement (femoroacetabular impingement).
      identified no paper that met the inclusion criteria. This demonstrates the heterogeneity of diagnosis as every systematic review defined FAI differently.

      Study limitations

      One of the limitations of this study stems from the methodology of this review. We did not perform our own search and analysis; rather, we relied on other systematic reviews. The fact that every systematic review utilised different inclusion and exclusion criteria may introduce bias to the grade assigned for each indication and may result in missed papers. Moreover, our search included only studies written in English and published in PubMed. This fact may limit the results of the search and may again result in omitted papers. Finally, no duplicate search, abstraction process and no agreement statistics on paper selection or recommendation rating was performed by the authors.

      Conclusions

      This literature update of indications for hip arthroscopy based on recent systematic reviews suggests that there has been a large increase in published studies on hip arthroscopy. However, the studies published hitherto are generally of lesser quality and as such do not provide a higher Grade of Recommendation for most hip arthroscopy procedures.

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