Effects of Capsular Reconstruction With an Iliotibial Band Allograft on Distractive Stability of the Hip Joint: A Biomechanical Study

Abstract

Background: The capsular ligaments and the labral suction seal cooperatively manage distractive stability of the hip. Capsular reconstruction using an iliotibial band (ITB) allograft aims to address capsular insufficiency and iatrogenic instability. However, the extent to which this procedure may restore hip distractive stability after a capsular defect is unknown. Purpose: To evaluate the biomechanical effects of capsular reconstruction on distractive stability of the hip joint. Study Design: Controlled laboratory study. Methods: Eight fresh-frozen cadaveric hip specimens were dissected to the level of the capsule and axially distracted in 3 testing states: intact capsule, partial capsular defect, and capsular reconstruction with an ITB allograft. Each femur was compressed with 500 N of force and then distracted 6 mm relative to the neutral position at 0.5 mm/s. Distractive force was continuously recorded, and the first peak delineating 2 phases of hip distractive stability in the force-displacement curve was analyzed. Results: The median force at maximum distraction in the capsular reconstruction state (156 N) was significantly greater than that in the capsular defect state (89 N; P = .036) but not significantly different from that in the intact state (218 N; P = .054). Median values for distractive force at first peak (60 N, 72 N, and 61 N, respectively; P = .607), distraction at first peak (2.3 mm, 2.3 mm, and 2.5 mm, respectively; P = .846), and percentage decrease in distractive force (35%, 78%, and 63%, respectively; P = .072) after the first peak were not significantly different between the intact, defect, and reconstruction states. Conclusion: Capsular reconstruction with an ITB allograft significantly increased the force required to distract the hip compared with a capsular defect in a cadaveric model. To our knowledge, this is the first study to report an initial peak distractive force and to propose 2 distinct phases of hip distractive stability. Clinical Relevance: The consequences of a capsular defect on distractive stability of the hip may be underappreciated among the orthopaedic community; with that said, capsular reconstruction using an ITB allograft provided significantly increased distractive stability and should be considered an effective treatment option for patients with symptomatic capsular deficiency.

Hip Joint Capsular Anatomy, Mechanics, and Surgical Management

“…In a similar stepwise resection study, van Arkel et al devised a custom joint tester and confirmed that the lateral iliofemoral ligament provided predominant external rotational restraint, whereas the pubofemoral ligament restrained external rotation and abduction during hip extension 43 . In similar studies, the labrum and the ligamentum teres acted as secondary restraints in wider external rotations [30][31][32]42,43 , whereas the structures of the capsule, labrum, and zona orbicularis were crucial for rotational and distraction stability 16,45 . These investigations examined hips without pathology from older donors, but were among the first laboratory studies to collectively provide important clinical insights as to which ligaments were responsible for rotational stability and which to potentially release or avoid during surgery.…”

“…They noted that the anterior capsule predominantly controlled rotation and displacement, suggesting that the iliofemoral ligaments should be carefully preserved using more conservative capsulotomies. For capsular defect cases, allograft can be a viable option to restore distraction stability 15,16 . On the other hand, Hebert et al compared the effects of hip effusion (simulated with an injection of 10 mL of saline solution) and capsular tears 13 .…”

“…It is essential to understand that capsular characteristics and mechanical properties of the hip with pathological conditions are different (i.e., a thicker, stiffer capsule) than a healthy joint 38,50,52 ; thus, the need for full capsular closure may depend on several other confounding factors (e.g., age, sex, osseous anatomy, and muscle function) [53][54][55] . More importantly, since unrepaired capsulotomies have been shown to heal within 24 weeks postoperatively 56 , and completely resecting the iliofemoral ligament does not destabilize the native hip 43 , there is evidence that not all capsulotomies need to be repaired after The findings of in vitro cadaveric studies on the effects of capsular conditions and surgical stages, outlining the contributions of the interportal capsulotomy 5,7,8,10,11,14,46 and T-capsulotomy 6,11,14,15,46 and the effects of instability 7,[11][12][13]16,47 , effusion arthroscopy, especially when capsular contracture may be part of the pathological process. It is still unclear what leads to inherent or iatrogenic instability; thus, if the native head size is not substantially reduced or altered, capsular repair in the setting of a small arthroscopic capsulotomy may not be necessary in the otherwise congruent and stable hip 4,54,56 .…”

“…More importantly, how the hip capsule is managed during surgical interventions (preservation and arthroplasty) and its effects on joint function are increasingly recognized [5][6][7][8] . Several recent laboratory studies have provided new insights into functional mobility and stability of the hip joint that should be carefully considered during surgery [9][10][11][12][13][14][15][16][17][18][19][20] . The purpose of this review was to provide a comprehensive summary of the functional anatomy and material characteristics of the hip capsule and the effects of different capsular management techniques during arthroscopic and arthroplasty procedures on joint function.…”

“…, and cam morphology15,16 . (For a detailed summary for each study's scope, methods, and observations, seeAppendix Tables II and III.…”