Midterm Outcomes Following Hip Labral Augmentation

Objectives: Arthroscopic hip labral preservation techniques have evolved over the last decade. Arthroscopic hip labral augmentation with iliotibial band (ITB) autograft placed into a labral defect with viable circumferential fibers is a novel treatment option to restore the hip suction seal and improve functionality. The purpose of this study is to determine midterm (3-5 year follow up) outcomes of arthroscopic hip labral augmentation procedure. Methods: Patients who underwent arthroscopic hip labral augmentation from August 2011 to March 2017 were prospectively evaluated. Pre- and post-operative patient reported outcome scores were compared and included SF12 PCS, SF12 MCS, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Modified Harris Hip Score (mHHS), Hip Outcome Score (HOS) (Activities of Daily Living (ADL) and Sport). Post-operative Tegner Activity Scale and patient satisfaction (1 – 10) were also evaluated. Results: One hundred and six patients underwent arthroscopic hip labral augmentation with minimum 3-year follow-up. Mean follow-up was 5-year follow-up (range, 3 to 9.2 years). All patient reported outcomes improved after labral augmentation (SF12 PCS 39±8 vs. 50±10, p>0.01; mHHS 59±15 vs. 79±21, p<0.01; WOMAC 31±16 vs. 16±17, p<0.01; HOS ADL 64±17 vs. 84±21, p<0.01; HOS Sport 41±22 vs. 71±29, p<0.01). Median post-operative Tegner score was 4. Median post-operative patient satisfaction was 9 out of 10 (range, 1-10). In terms of survivorship, 12 patients (11%) required revision surgery and 6 (5.7%) converted to total hip arthroplasty (THA). Conclusions: Arthroscopic hip labral augmentation is a successful treatment option for patients that have viable circumferential fibers present at the time of arthroscopy. This technique continues to show improved patient reported outcomes and is another hip labral preservation technique that may help reestablish the intra-articular fluid suction seal.

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

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

Background: The acetabular labrum contains free nerve endings, and an unstable labrum can result in increased femoral head movement during hip motion. This can be caused by chondrolabral junction (CLJ) separation, especially in association with pincer-type femoroacetabular impingement, and may contribute to hip pain. Hypothesis: Rim resection alone has no effect on suction seal biomechanics. Further, separation of the CLJ changes hip suction seal biomechanics when compared with those of the native state, whereas repair and refixation with suture anchors restore these biomechanical parameters. Study Design: Controlled laboratory study. Methods: A total of 12 fresh-frozen human cadaveric hips were used in this study. Hips were mounted in a saline bath on a dynamic tensile testing machine and were distracted at a rate of 0.5 mm/s from neutral position. A total of 3 parameters (force, displacement, and intra-articular pressure) were measured throughout testing. Before testing, hips were randomly allocated to 1 of 2 groups: 1 that included the CLJ separation (CLJ Cut group) and 1 that did not (CLJ Intact group). Hips were tested in the following states: (1) native, (2) rim trimming, (3) separated CLJ (CLJ Cut group only), and (4) labral repair/refixation. For each group a linear mixed-effects model was used to compare biomechanical parameters between states. Results: Rim trimming did not affect any suction seal parameters relative to those of the native state. In the CLJ Cut group, no significant difference in distance to break the suction seal was observed for any states compared with that of the native state. In the CLJ Intact group, the distance to break the suction seal was significantly shorter in the labral refixation state (1.8 mm) than the native state (5.6 mm; P = .002). The maximum distraction force (62.1 ± 54.1 N) and the peak negative pressure (−36.6 ± 24.2 kPa) of the labral repair/refixation state were significantly lower than those of the native state in both groups (93.4 ± 41.7 N, P = .01; –60.7 ± 20.4 kPa, P = .02). Conclusion: Rim trimming did not change the biomechanical properties of the labral suction seal. Labral refixation resulted in a shorter distance to break the labral suction seal. This indicates that labral mobility is reduced by the labral refixation procedure, which could be beneficial in postoperative pain relief and labral healing. Clinical Relevance: The labral refixation reduced labral mobility, which could be beneficial for both pain relief and labral healing to the acetabulum after pincer-type femoroacetabular impingement resection.

Biomechanical Characteristics of Labral Augmentation Versus Labral Reconstruction in a Hip Cadaver Model

Objectives: An integral component of hip stability is the negative pressure gradient created by the labral suction seal. No prior studies have quantitatively compared the integrity of the suction seal under normal, pathologic, and surgical conditions. The purpose of this study was to evaluate the biomechanical properties of the labral suction seal in the following four scenarios: intact labrum, labral tear, labral augmentation, and labral reconstruction. Methods: Eight fresh-frozen hemi-pelvises without osteoarthritis and with an intact labrum were dissected to the level of labrum and mounted for biomechanical testing. Each specimen was evaluated sequentially under four testing conditions: intact labrum, labral tear, labral augmentation, and labral reconstruction. Following testing of the intact labrum, the specimens were manipulated to create a labral tear from 12- to 3-o’clock. Labral augmentation was then performed with bone anchors and iliotibial band graft after debridement of only the peripheral half of the labral tear. Labral reconstruction was performed last with bone anchors and iliotibial band graft after removing the entire labral tear. In each condition the specimens were placed in the test machine to undergo pure distraction of the joint. First, the femur was compressed with 250 N of force and then distracted at 10 mm/s with force and displacement continuously recorded until the suction seal was disrupted. In each specimen, the tests were repeated for a total of three tests in each of the four conditions, and the average peak force was calculated. Data was normalized to the intact peak force for each specimen to account for gender and size differences. Statistical testing was performed via a repeated measures ANOVA with a post hoc Bonferroni correction for pairwise analysis. Results: Peak loads occurred early in displacement. The average peak force values (mean ± standard deviation) were as follows: intact (137.2 ± 40.7), labral tear (126.3 ± 43.5), labral augmentation (94.7 ± 59.7), labral reconstruction (78.9 ± 51.2). The average normalized peak force values relative to the intact condition were as follows: labral tear (91.1 ± 8.5), augmentation (66.1 ± 27.6), and reconstruction (55.6 ± 25.7). There was no statistically significant difference in peak force relative to the intact labrum for the labral tear (p = 0.34). Relative to the labral tear, there was no significant difference in peak force for the augmentation (p = 0.12), but there was a significant decrease in peak force for the reconstruction (p = 0.03). Conclusion: This model provides a new means of quantitatively evaluating the labral suction seal under various normal, pathologic, and surgical conditions. The results show that relative to the labral tear condition, labral augmentation may recreate the labral suction seal better than labral reconstruction. Clinically, these findings suggest augmentation may improve hip stability over labral reconstruction. [Figure: see text]

Proximal Over-Resection During Femoral Osteochondroplasty Negatively Affects the Distractive Stability of the Hip Joint

Objectives: Hip microinstability is an increasingly recognized source of hip pain and disability. Femoral osteochondroplasty is usually performed with direct visualization through the arthroscope, assisted with repeated fluoroscopic view for orientation and feedback. However, a two-dimensional representation of a three dimensional structure can be misleading compromising the precision of the planned osteochondroplasty. Sometimes the resection can extend proximally into the Femoral Head (FH) diminishing the surface area of the articular cartilage available to be in contact with the labrum, in order to create the suction effect (suction seal) that maintains the stability of the femoral head in the acetabulum. The purpose of the study is to evaluate the role of proximal over-resection of femoral osteochondroplasty in the rotational and distractive stability of the hip joint. We hypothesis that proximal over resection will result in decrease stability, specially at higher degrees of flexion and internal rotation where the contact between labrum and articular cartilage will be lost, and breaking the suction seal. Methods: Six hemi-pelvises were repeatedly tested in the following five conditions: (a) intact, (b) T-capsulotomy, (c) Osteochondroplasty to the level of the physeal scar, followed by a (d) 5mm and (e) 10mm proximal extension of the resection. The pelvis was secured to a metal plate and the distal portion of the femur was potted and attached to a multi-axial hip jig. (Fig.1) Specimens were axially distracted with a load from 0-150N followed by 5Nm of internal and external torque at 0 o, 15 o, 30 o, 60 o, 90o of flexion while the resultant displacement/rotation was recorded using a 3D motion tracking system. Repeated measures ANOVA was used with statistical significance set at p<0.05. Results: Proximal extension of the resection by 5mm and 10mm increased axial instability (decreased force required for hip distraction) at every angle of flexion tested, with the greatest increase observed at higher angles of flexion (60 deg and 90 deg), p<0.05. T-capsulotomy alone increased both internal and external rotation at all angles of flexion, p<0.05. (Fig. 2) Subsequent resection and extension of the resection did not significantly increase rotational instability compared to the capsulotomy state. Conclusion: Extending the osteochondroplasty proximally into the femoral head compromised the distractive stability of the hip joint. It is important to be precise when performing femoral osteochondroplasty to minimize proximal extension that can lead to iatrogenic instability of the hip joint and poor postoperative outcomes. [Figure: see text][Figure: see text]