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Editorial Commentary: Anatomical Vandalism of the Hip? Hip Capsular Repair Seems a Sound Adjunct to Hip Arthroscopic Surgery

      Abstract

      The study “Contribution of the Pubofemoral Ligament to Hip Stability: A Biomechanical Study” by Martin, Khoury, Schröder, Johnson, Gómez-Hoyos, Campos, and Palmer found that cutting the hip capsular ligament allowed a large increase in femoral internal rotation, particularly in the flexed hip, causing subluxation to occur. In addition to providing new data on the role of the pubofemoral ligament, it raises the question of whether hip joint surgeons should repair the capsule—what are the likely consequences?—and whether any beneficial effects persist in long-term clinical follow-ups. For now, hip capsular repair seems a sound adjunct to hip arthroscopic surgery.
      The hip joint capsule, with its intertwined ligaments, completely encases the hip joint and femoral neck and, rather inconveniently, must be cut during joint preserving surgery. Although joint preserving surgery has promising short-term results,
      • Levy D.M.
      • Kuhns B.D.
      • Chahal J.
      • Philippon M.J.
      • Kelly B.T.
      • Nho S.J.
      Hip arthroscopy outcomes with respect to patient acceptable symptomatic state and minimal clinically important difference.
      • Frank R.M.
      • Lee S.
      • Bush-Joseph C.A.
      • Salata M.J.
      • Mather III, R.C.
      • Nho S.J.
      Outcomes for hip arthroscopy according to sex and age: A comparative matched-group analysis.
      questions remain: what to do about the capsule? Where should it be incised? Are there therapeutic benefits or iatrogenic consequences of releasing it? When/how does it need to be repaired? Is repair a waste of surgical time?
      The research titled “Contribution of the Pubofemoral Ligament to Hip Stability: A Biomechanical Study” by Martin, Khoury, Schröder, Johnson, Gómez-Hoyos, Campos, and Palmer
      • Martin H.D.
      • Khoury A.N.
      • Schröder R.
      • et al.
      Contribution of the pubofemoral ligament to hip stability: A biomechanical study.
      used a cadaveric model to investigate the function of a capsular ligament to help surgeons make an informed decision about the consequences of releasing it. The paper complements the authors' previous work detailing a quantitative description of the function of all 3 hip capsular ligaments in low flexion/extension
      • Martin H.
      • Savage A.
      • Braly B.
      • Palmer I.
      • Beall D.
      • Kelly B.
      The function of the hip capsular ligaments: A quantitative report.
      and the ligamentum teres.
      • Martin H.D.
      • Hatem M.A.
      • Kivlan B.R.
      • Martin R.L.
      Function of the ligamentum teres in limiting hip rotation: A cadaveric study.
      Their main finding, that the pubofemoral ligament provides internal rotational restraint in high/deep flexion with abduction,
      • Martin H.D.
      • Khoury A.N.
      • Schröder R.
      • et al.
      Contribution of the pubofemoral ligament to hip stability: A biomechanical study.
      is in agreement with our own findings,
      • van Arkel R.J.
      • Amis A.A.
      • Cobb J.P.
      • Jeffers J.R.T.
      The capsular ligaments provide more hip rotational restraint than the acetabular labrum and the ligamentum teres: An experimental study.
      • van Arkel R.J.
      • Amis A.A.
      • Jeffers J.R.
      The envelope of passive motion allowed by the capsular ligaments of the hip.
      and many aspects of their methods are commendable. They tested a large number of specimens and used computed tomography to screen them for pathology and to quantify their morphology. They have also previously quantified their minimum detectable difference and intraclass correlation coefficient for their methodology.
      • Martin H.D.
      • Hatem M.A.
      • Kivlan B.R.
      • Martin R.L.
      Function of the ligamentum teres in limiting hip rotation: A cadaveric study.
      However, one short sentence in the paper states that, after the pubofemoral ligament was released, if subluxation was noted, the specimen was deemed to have an internal rotation of 180°. This methodological detail goes on to influence the results—after ligament release, at 110° flexion, the average internal rotation is reported to be 180° or close to 180°. This position would allow you to rest your chin on your heel when sitting in a chair, which may be unlikely even for the more flexible among us. Setting the rotation to 180° will likely have had a strong influence on the reported percentage change in rotation and their statistical findings. This highlights a very important aspect of interpreting any in vitro work—have the results been influenced by sometimes subtle methodological details?
      The beauty of in vitro work, however, is that no 2 research groups adopt the same methodology and so the risk of bias can be reduced by comparing results from multiple laboratories. By considering Martin et al.'s in vitro work over the past decade
      • Martin H.D.
      • Khoury A.N.
      • Schröder R.
      • et al.
      Contribution of the pubofemoral ligament to hip stability: A biomechanical study.
      • Martin H.
      • Savage A.
      • Braly B.
      • Palmer I.
      • Beall D.
      • Kelly B.
      The function of the hip capsular ligaments: A quantitative report.
      • Martin H.D.
      • Hatem M.A.
      • Kivlan B.R.
      • Martin R.L.
      Function of the ligamentum teres in limiting hip rotation: A cadaveric study.
      • Martin R.
      • Palmer I.
      • Martin H.
      Ligamentum teres: A functional description and potential clinical relevance.
      • Kivlan B.
      • Richard Clemente F.
      • Martin R.
      • Martin H.
      Function of the ligamentum teres during multi-planar movement of the hip joint.
      alongside findings from others, we can paint a picture of how the hip joint capsule promotes healthy joint function. The hip capsule has complex anatomy,
      • Fuss F.K.
      • Bacher A.
      New aspects of the morphology and function of the human hip joint ligaments.
      which is commonly simplified to 3 ligaments to aid clinical interpretation.
      • Martin H.
      • Savage A.
      • Braly B.
      • Palmer I.
      • Beall D.
      • Kelly B.
      The function of the hip capsular ligaments: A quantitative report.
      • Telleria J.J.M.
      • Lindsey D.
      • Giori N.
      • Safran M.
      An anatomic arthroscopic description of the hip capsular ligaments for the hip arthroscopist.
      This fine-tuned anatomy enables a large range of motion with a large slack region where the hip is free to move under the action of muscles,
      • van Arkel R.J.
      • Amis A.A.
      • Jeffers J.R.
      The envelope of passive motion allowed by the capsular ligaments of the hip.
      whilst providing restraint at the limits of hip motion passively stabilizing the hip and helping to protect it against adverse loading conditions such as labral impingement, subluxation, and edge loading.
      • Martin H.
      • Savage A.
      • Braly B.
      • Palmer I.
      • Beall D.
      • Kelly B.
      The function of the hip capsular ligaments: A quantitative report.
      • van Arkel R.J.
      • Amis A.A.
      • Cobb J.P.
      • Jeffers J.R.T.
      The capsular ligaments provide more hip rotational restraint than the acetabular labrum and the ligamentum teres: An experimental study.
      • van Arkel R.J.
      • Amis A.A.
      • Jeffers J.R.
      The envelope of passive motion allowed by the capsular ligaments of the hip.
      • Safran M.
      • Lopomo N.
      • Zaffagnini S.
      • et al.
      In vitro analysis of peri-articular soft tissues passive constraining effect on hip kinematics and joint stability.
      • Smith M.V.
      • Costic R.S.
      • Allaire R.
      • Schilling P.L.
      • Sekiya J.K.
      A biomechanical analysis of the soft tissue and osseous constraints of the hip joint.
      • Ito H.
      • Song Y.
      • Lindsey D.
      • Safran M.
      • Giori N.
      The proximal hip joint capsule and the zona orbicularis contribute to hip joint stability in distraction.
      Biomechanical research also shows that capsulotomy inhibits this function, resulting in increased hip range of motion, whereas repair can restore passive restraint back to normal.
      • Myers C.A.
      • Register B.C.
      • Lertwanich P.
      • et al.
      Role of the acetabular labrum and the iliofemoral ligament in hip stability: An in vitro biplane fluoroscopy study.
      • Jackson T.J.
      • Peterson A.B.
      • Akeda M.
      • et al.
      Biomechanical effects of capsular shift in the treatment of hip microinstability: Creation and testing of a novel hip instability model.
      • Wuerz T.H.
      • Song S.H.
      • Grzybowski J.S.
      • et al.
      Capsulotomy size affects hip joint kinematic stability.
      • Abrams G.D.
      • Hart M.A.
      • Takami K.
      • et al.
      Biomechanical evaluation of capsulotomy, capsulectomy, and capsular repair on hip rotation.
      In addition to this mechanical role, the capsule could also provide a proprioceptive role
      • Haversath M.
      • Hanke J.
      • Landgraeber S.
      • et al.
      The distribution of nociceptive innervation in the painful hip: A histological investigation.
      and contribute to synovial fluid circulation from central to peripheral compartments through the combined action of the zona orbicularis, labrum, and ligament teres.
      • Field R.
      • Rajakulendran K.
      The labro-acetabular complex.
      • Dwyer M.K.
      • Jones H.L.
      • Hogan M.G.
      • Field R.E.
      • McCarthy J.C.
      • Noble P.C.
      The acetabular labrum regulates fluid circulation of the hip joint during functional activities.
      • Bardakos N.V.
      • Villar R.N.
      The ligamentum teres of the adult hip.
      As might be expected, given these biomechanical findings, early clinical data also hint that capsular repair improves hip arthroscopy outcomes,
      • Domb B.G.
      • Stake C.E.
      • Finley Z.J.
      • Chen T.
      • Giordano B.D.
      Influence of capsular repair versus unrepaired capsulotomy on 2-year clinical outcomes after arthroscopic hip preservation surgery.
      with full repair superior to partial repair.
      • Frank R.M.
      • Lee S.
      • Bush-Joseph C.A.
      • Kelly B.T.
      • Salata M.J.
      • Nho S.J.
      Improved outcomes after hip arthroscopic surgery in patients undergoing T-capsulotomy with complete repair versus partial repair for femoroacetabular impingement: A comparative matched-pair analysis.
      Moreover, patients requiring revision hip arthroscopy have capsular defects
      • McCormick F.
      • Slikker III, W.
      • Harris J.
      • et al.
      Evidence of capsular defect following hip arthroscopy.
      whilst revision hip arthroscopy repairing the capsule improves outcomes for patients suffering instability following their index arthroscopy procedure.
      • Wylie J.D.
      • Beckmann J.T.
      • Maak T.G.
      • Aoki S.K.
      Arthroscopic capsular repair for symptomatic hip instability after previous hip arthroscopic surgery.
      Importantly, the data also suggest that a repaired capsule remains so in the short term: >90% capsular repairs have been reported to remain closed >1 year post-op.
      • Weber A.E.
      • Kuhns B.D.
      • Cvetanovich G.L.
      • et al.
      Does the hip capsule remain closed after hip arthroscopy with routine capsular closure for femoroacetabular impingement? A magnetic resonance imaging analysis in symptomatic postoperative patients.
      However, most of these recent clinical studies provide only a low level of evidence (4 Level IV, 1 Level III), and have very short-term follow-up making definitive conclusions hard to draw.
      Ultimately long-term follow-up will determine which hip arthroscopy procedures are truly joint preserving and if capsular repair is beneficial. Recent developments such as the British Hip Society Non-Arthroplasty Hip Register will no doubt help with this.
      However, until these data exist, biomechanical studies provide the best insight and suggest that perhaps the most cautious approach would be to appreciate nature for evolving a tissue with such lovely anatomy, and to repair the damage done to the capsule. A pessimist might say that at least an arthroplasty surgeon will thank you for leaving them something to work with in years to come.

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      1. The Non-Arthroplasty Hip Registry 2016 Annual Report. British Hip Society, London, England2016

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