The Hip Suction Seal, Part I: The Role of Acetabular Labral Height on Hip Distractive Stability

Abstract

Background: The acetabular labrum has been found to provide a significant contribution to the distractive stability of the hip. However, the influence of labral height on hip suction seal biomechanics is not known. Hypothesis: The smaller height of acetabular labrum is associated with decreased distractive stability. Study Design: Descriptive laboratory study. Methods: A total of 23 fresh-frozen cadaveric hemipelvises were used in this study. Hips with acetabular dysplasia or femoroacetabular impingement–related bony morphologic features, intra-articular pathology, or no measurable suction seal were excluded. Before testing, each specimen’s hip capsule was removed, a pressure sensor was placed intra-articularly, and the hip was fixed in a heated saline bath. Labral size was measured by use of a digital caliper. Maximum distraction force, distance to suction seal rupture, and peak negative pressure were recorded while the hip underwent distraction at a rate of 0.5 mm/s. Correlations between factors were analyzed using the Spearman rho, and differences between groups were detected using Mann-Whitney U test. Results: Of 23 hips, 12 satisfied inclusion criteria. The maximum distraction force and peak negative pressure were significantly correlated ( R = −0.83; P = .001). Labral height was largely correlated with all suction seal parameters (maximum distraction force, R = 0.69, P = .013; distance to suction seal rupture, R = 0.55, P = .063; peak negative pressure, R = −0.62, P = .031). Labral height less than 6 mm was observed in 5 hips, with a mean height of 6.48 mm (SD, 2.65 mm; range, 2.62-11.90 mm; 95% CI, 4.80-8.17 mm). Compared with the 7 hips with larger labra (>6 mm), the hips with smaller labra had significantly shorter distance to suction seal rupture (median, 2.3 vs 7.2 mm; P = .010) and significantly decreased peak negative pressure (median, −59.3 vs −66.9 kPa; P = .048). Conclusion: Smaller height (<6 mm) of the acetabular labrum was significantly associated with decreased distance to suction seal rupture and decreased peak negative pressure. A new strategy to increase the size of the labrum, such as labral augmentation, could be justified for patients with smaller labra in order to optimize the hip suction seal. Clinical Relevance: The height of the acetabular labrum is correlated with hip suction seal biomechanics. Further studies are required to identify the clinical effects of labral height on hip stability.

The Hip Suction Seal, Part II: The Effect of Rim Trimming, Chondrolabral Junction Separation, and Labral Repair/Refixation on Hip Distractive Stability

“…Each specimen was procured to include the pubic symphysis and sacrum and was devoid of reported hip injuries or surgeries. As described in Part I, 42 all hips were radiographically and arthroscopically screened to exclude hips with under- or overcoverage of the acetabulum (lateral center-edge angle <25° or >40°, respectively), large alpha angles (>55°), or labral or chondral pathologies. Specimens more than 65 years old, with body mass index greater than 35 kg/m 2 , or devoid of a ligamentum teres were also excluded, as were any specimens that did not have a measurable suction seal or negative pressure generation upon initial testing in the native state.…”

“…Specimens more than 65 years old, with body mass index greater than 35 kg/m 2 , or devoid of a ligamentum teres were also excluded, as were any specimens that did not have a measurable suction seal or negative pressure generation upon initial testing in the native state. 42 After screening, specimens were dissected free of all soft tissue to the level of the hip capsule, which was preserved for proper positioning before biomechanical testing.…”

“…For a full description of specimen preparation, please see the Specimen Preparation section of Part I. 42…”

Arthroscopic acetabular labral reconstruction: a review

“…While labral preservation with repair is the gold-standard treatment for labral tears [ 3 , 12–14 ], labral selective debridement has yielded favorable outcomes in some earlier hip arthroscopy series for FAI syndrome [ 10 , 15–18 ]. Selective debridement is defined as excision of only peripheral labral tearing that, when performed, will not compromise the labral sealing mechanism [ 19 ]. To accomplish this, the labrum must be of functional size after selective debridement and stable at its chondrolabral junction [ 17 , 20 ].…”

Autograft Versus Allograft: The Evidence in Hip Labral Reconstruction and Augmentation

“…20,22,27 Numerous investigations have supported the role of labral repair to preserve the function and stability of the hip joint 14,29 ; however, the labrum is not always able to be repaired. Extensive labral calcification, insufficient viable labral tissue (\6 mm), 2,33 irreparable tears, and iatrogenic labral insufficiency have all been described and are not amenable to repair. In this setting, multiple techniques have been described for labral reconstruction, when no viable native tissue remains, and for labral augmentation, when macroscopically normal, native circumferential labral tissue remains but is insufficient to provide a suction seal to the head-neck junction.…”