title: Biomechanical Assessment of Hip Capsular Repair and Reconstruction Procedures Using a 6 Degrees of Freedom Robotic System.
abstract: BACKGROUND
  Although acetabular labral repair has been biomechanically validated to improve stability, capsular management of the hip remains a topic of growing interest and controversy.
  
  
  OBJECTIVE
  To biomechanically evaluate the effects of several arthroscopically relevant conditions of the capsule through a robotic, sequential sectioning study.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Ten human cadaveric unilateral hip specimens (mean age, 51.3 years [range, 38-65 years]) from full pelvises were used to test range of motion (ROM) for the intact capsule and for multiple capsular conditions including portal incisions, interportal capsulotomy, interportal capsulotomy repair, T-capsulotomy, T-capsulotomy repair, a large capsular defect, and capsular reconstruction. Hips were biomechanically tested using a 6 degrees of freedom robotic system to assess ROM with applied 5-N·m internal, external, abduction, and adduction rotation torques throughout hip flexion and extension.
  
  
  RESULTS
  All capsulotomy procedures (portals, interportal capsulotomy, and T-capsulotomy) created increases in external, internal, adduction, and abduction rotations compared with the intact state throughout the full tested ROM (-10° to 90° of flexion). Reconstruction significantly reduced rotation compared with the large capsular defect state for external rotation at 15° (difference, 1.4°) and 90° (difference, 1.3°) of flexion; internal rotation at -10° (difference, 0.4°), 60° (difference, 0.9°), and 90° (difference, 1.4°) of flexion; abduction rotation at -10° (difference, 0.5°), 15° (difference, 1.1°), 30° (difference, 1.2°), 60° (difference, 0.9°), and 90° (difference, 1.0°) of flexion; and adduction rotation at 0° (difference, 0.7°), 15° (difference, 0.8°), 30° (difference, 0.3°), and 90° (difference, 0.6°) of flexion. Repair of T-capsulotomy resulted in significant reductions in rotation compared with the T-capsulotomy condition for abduction rotation at -10° (difference, 0.3°), 15° (difference, 0.9°), 30° (difference, 1.3°), 60° (difference, 1.7°), and 90° (difference, 1.5°) of flexion and for internal rotation at -10° (difference, 0.9°), 60° (difference, 1.5°), and 90° (difference, 2.6°) of flexion. Similarly, repair of interportal capsulotomy resulted in significant reductions in abduction (difference, 0.9°) and internal (difference, 1.4°) rotations compared with interportal capsulotomy at 90° of flexion. In most cases, however, after the repair procedures, ROM was still increased in comparison with the intact state.
  
  
  CONCLUSIONS
  The results of this study suggest that common hip arthroscopic capsulotomy procedures can result in increases in external, internal, abduction, and adduction rotations throughout a full range (-10° to 90°) of hip flexion. However, capsular repair and reconstruction succeeded in partially reducing the increased rotational ROM caused by common capsulotomy procedures. Thus, consideration should be allotted toward capsular repair or reconstruction in cases with an increased risk of residual instability.
  
  
  CONCLUSIONS
  Although complete restoration of joint stability may not be fully achieved at time zero, capsular repair and reconstruction may lead to improved patient outcomes by bringing hip rotational movements nearer to normal values in the immediate postoperative period, especially in cases in which extensive capsulotomy is performed.
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.|The Steadman Clinic, Vail, Colorado, USA.
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Philippon
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Christiano A C
authors.initials: CAC
authors.lastname: Trindade
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Mary T
authors.initials: MT
authors.lastname: Goldsmith
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Rasmussen
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Adriana J
authors.initials: AJ
authors.lastname: Saroki
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Sverre
authors.initials: S
authors.lastname: Løken
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.|The Steadman Clinic, Vail, Colorado, USA.
authors.forename: Robert F
authors.initials: RF
authors.lastname: LaPrade
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002102:Cadaver; D006621:Hip Joint / Q000502:physiology / Q000601:surgery*; D006801:Humans; D017746:Joint Capsule / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures / Q000295:instrumentation / Q000379:methods*; D012371:Robotics
keywords: T-capsulotomy; capsular management; hip arthroscopic surgery; hip capsulotomy; hip instability