Hugh L. Jones

The acetabular labrum regulates fluid circulation of the hip joint during functional activities.

Background: An assessment of the effect of surgical repair or reconstruction on the function of the hip labrum is critical to the advancement of hip preservation surgery; however, validated models of the hip that allow the quantification of labral function in functional joint positions have yet to be developed. Purpose: To evaluate (1) whether intra-articular pressures within the hip are regulated by fluid transport between the labrum and femoral head and (2) whether the sealing capacity of the labrum varies with joint posture. Study Design: Descriptive laboratory study. Methods: The sealing ability of the hip labrum was measured during fluid infusion into the central compartments of 8 cadaveric specimens. Additionally, the pathway of fluid transfer from the central to the peripheral compartment was assessed via direct visualization in 3 specimens. The effect of joint posture on the sealing capacity of the labrum was determined by placing all 8 specimens in 10 functional postures. The relationship between pressure resistance and 3-dimensional motion of the femoral head within the acetabulum was quantified using motion analysis and computer modeling. Results: Resistance to fluid transport from the central compartment of the hip was directly controlled by the labrum during loading. Maximum pressure resistance was affected by joint posture (P = .001). Specifically, positions that increased external rotation of the joint (pivoting) provided an improved seal, while positions that increased flexion combined with internal rotation (stooping) augmented the ease of fluid transport from the central to the peripheral compartment. Maximum pressure resistance was associated with the distance between the labrum and femoral head during pivoting. Conclusion: This study demonstrated that the transfer of fluid from the central compartment of the hip occurs at the junction of the labrum and femoral head. Joint position was shown to strongly affect the sealing function of the labrum and was attributable to the distance between the labrum and femoral head in certain positions. Clinical Relevance: Altering the relationship between the labrum and femoral head may disrupt the sealing ability of the labrum, potentially leaving the joint at risk for pathological changes with time.

Does high knee flexion cause separation of meniscal repairs

Background: Previous clinical studies comparing nonrestrictive and restrictive protocols after meniscal repair have shown no difference in outcomes; however, some surgeons still limit range of motion out of concern that it will place undue stress on the repair. Hypothesis: Large acute medial meniscal tears will gap during simulated open chain exercises at high flexion angles, and a repaired construct with vertical mattress sutures will not gap. Study Design: Controlled laboratory study. Methods: Tantalum beads were implanted in the medial menisci of 6 fresh-frozen cadaveric knees via an open posteromedial approach. Each knee underwent 10 simulated open chain flexion cycles with loading of the quadriceps and hamstrings. Testing was performed on 3 different states of the meniscus: intact, torn, and repaired. Biplanar radiographs were taken of the loaded knee in 90°, 110°, and 135° of flexion for each state. A 2.5-cm tear was created in the posteromedial meniscus and repaired with inside-out vertical mattress sutures. Displacement of pairs of beads spanning the tear was measured in all planes by use of radiostereometric analysis (RSA) with an accuracy of better than 80 μm. Results: With a longitudinal tear, compression rather than gapping occurred in all 3 regions of the posterior horn of the meniscus (mean ± standard deviation for medial collateral ligament [MCL], –321 ± 320 μm; midposterior, –487 ± 256 μm; root, –318 ± 150 μm) with knee flexion. After repair, meniscal displacement returned part way to intact values in both the MCL (+55 ± 250 μm) and root region (–170 ± 123 μm) but not the midposterior region, where further compression was seen (–661 ± 278 μm). Conclusions: Acute posteromedial meniscal tears and repairs with vertical mattress sutures do not gap, but rather compress in the transverse plane at higher flexion angles when subjected to physiologic loads consistent with active, open kinetic chain range of motion rehabilitation exercises. The kinematics of the repaired meniscus more closely resemble that of the intact meniscus than that of the torn meniscus in regions adjacent to the MCL and the root but not in the midposterior region, where meniscal repair led to increased compression across the tear plane. Clinical Relevance: This study supports the idea that nonrestrictive unresisted open chain range of motion protocols do not place undue stress on meniscal repairs.

Osteochondral Allograft Donor-Host Matching by the Femoral Condyle Radius of Curvature

Background: Conventional osteochondral allograft (OCA) matching, requiring orthotopic, size-matched condyles, and narrow surgical time windows often prohibit timely transplantation. Hypothesis: The femoral condyle radius of curvature (RoC) is an appropriate, isolated criterion for donor-host matching in fresh OCAs, potentially enhancing matching efficiency when compared with conventional matching techniques. Study Design: Descriptive laboratory study. Methods: In part 1 of this study, 3-dimensional digital reconstructions of 14 randomly selected, cadaveric distal femoral hemicondyles were performed. Each condyle was divided into anterior, middle, and posterior zones. A virtual best-fit grid was applied to each, and each zone’s sagittal- and coronal-plane RoCs were determined. Seven nonorthotopic OCA transplantations were performed based on RoC matching with 1-mm tolerance, and the preoperative and postoperative surface geometry were quantified to assess the accuracy of articular surface restoration. Of note, each donor-host pair did not match by the conventional method. In part 2 of this study, 12 cadaveric distal femora were categorized by size and digitized in the aforementioned manner. Simulated circular defects measuring 20, 25, and 30 mm in diameter were introduced into each zone. OCA matches were determined based on donor and host RoCs, and the total number of potential matches (of 71 total comparisons) was recorded as a percentage for each simulated defect. Finally, the results of RoC matching were compared with the conventional method for simulated defects in all zones of both the medial and lateral femoral condyles. Results: Part 1: The mean surface deviation after OCA transplantation was −0.09 mm, with a mean maximum protrusion at any point of 0.59 mm. Part 2: Using the RoC, 20-mm defects had a 100% chance of being matched. Defects of 25 and 30 mm had a 91% and 64% chance of being matched, respectively. Compared with the conventional method, the RoC method yielded a 3.2-fold greater match rate for lesions of the medial and lateral femoral condyles (P = .02). Conclusion: This investigation shows that femoral condyle RoCs in the sagittal and coronal planes may be useful, alternative matching criteria, expanding on current standards. Clinical Relevance: These matching criteria may increase the number of available matches, reduce wait times for patients, and reduce the number of wasted grafts.

Comparison of Kinematics and Tibiofemoral Contact Pressures for Native and Transplanted Lateral Menisci

Background: Lateral meniscus transplantation is a proven treatment option for the meniscus-deficient knee, yet little is known about meniscal kinematics, strain, and tibiofemoral contact pressure changes after transplantation or the effect of altered root position in lateral meniscus transplantation. Purpose: To compare the native lateral meniscal kinematics, strain, and tibiofemoral contact pressures to a best-case scenario meniscus transplant with perfectly matched size and position and to determine how sensitive these factors are to subtle changes in shape and position by using a nonanatomic meniscus transplant position. Study Design: Controlled laboratory study. Methods: The lateral menisci of 8 cadaveric knees were circumferentially implanted with radiopaque spherical markers. They were mounted to a testing apparatus applying muscle and ground-reaction forces. The meniscus was evaluated at 0°, 30°, 90°, and 115° of knee flexion using Roentgen stereophotogrammetric analysis (RSA), with a pressure sensor affixed to the lateral tibial plateau. Measurements were recorded for 3 states: the native lateral meniscus, an anatomic autograft transplant, and a nonanatomic autograft transplant with an anteriorized posterior root position. Results: After transplantation, there was less posterior displacement in both the anatomic and nonanatomic transplant states compared with the native meniscus, but this was not significant. The largest lateral translation in the native state was 2.38 ± 1.58 mm at the anterolateral region from 0° to 90°, which was increased to 3.28 ± 1.39 mm (P = .25) and 3.12 ± 1.18 mm (P = .30) in the anatomic and nonanatomic transplant states, respectively. Internal deformations of the transplant states were more constrained, suggesting less compliance. The native meniscus distributed load over 223 mm2, while both the anatomic (160 mm2) and nonanatomic (102 mm2) states concentrated pressure anteriorly to the tibial plateau centroid. Conclusion: This study is the first to characterize kinematics in the native lateral meniscus compared with a transplanted state utilizing RSA. Results demonstrate increased meniscal constraint and pressure concentrations even after an ideal size and position matched transplantation, which further increased with a nonanatomic posterior root position. Clinical Relevance: The results show that kinematics are similar in both transplanted states when compared with the native meniscus at various flexion angles. Because both transplanted states were more constrained with less deformation compared with the native state, this should allow for relatively safe postoperative range of motion. However, in the transplanted states, peak pressures were distributed over a smaller area and shifted anteriorly. This pattern was exacerbated in the nonanatomic state compared with anatomic. This could have detrimental effects with regard to articular cartilage degeneration, and ultimately result in a failed transplantation.