Impact of hyaluronic acid injection on the knee joint friction.

PURPOSE: The purpose of this in vitro study was to investigate whether or not hyaluronic acid supplementation improves knee joint friction during osteoarthritis progression under gait-like loading conditions. METHODS: Twelve human cadaveric knee joints were equally divided into mild and moderate osteoarthritic groups. After initial conservative preparation, a passive pendulum setup was used to test the whole joints under gait-like conditions before and after hyaluronic acid supplementation. The friction-related damping properties given by the coefficient of friction µ and the damping coefficient c (in kg m2/s) were calculated from the decaying flexion-extension motion of the knee. Subsequently, tibial and femoral cartilage and meniscus samples were extracted from the joints and tested in an established dynamic pin-on-plate tribometer using synthetic synovial fluid followed by synthetic synovial fluid supplemented with hyaluronic acid as lubricant. Friction was quantified by calculating the coefficient of friction. RESULTS: In the pendulum tests, the moderate OA group indicated significantly lower c0 values (p < 0.05) under stance phase conditions and significantly lower µ0 (p = 0.01) values under swing phase conditions. No degeneration-related statistical differences were found for µend or cend. Friction was not significantly different (p > 0.05) with regard to mild and moderate osteoarthritis in the pin-on-plate tests. Additionally, hyaluronic acid did not affect friction in both, the pendulum (p > 0.05) and pin-on-plate friction tests (p > 0.05). CONCLUSION: The results of this in vitro study suggested that the friction of cadaveric knee joint tissues does not increase with progressing degeneration. Moreover, hyaluronic acid viscosupplementation does not lead to an initial decrease in knee joint friction.

Are Knotted or Knotless Techniques Better for Reconstruction of Full-Thickness Tears of the Superior Portion of the Subscapularis Tendon? A Study in Cadavers.

BACKGROUND: Knotted and knotless single-anchor reconstruction techniques are frequently performed to reconstruct full-thickness tears of the upper portion of subscapularis tendon. However, it is unclear whether one technique is superior to the other. QUESTIONS/PURPOSES: (1) When comparing knotless and knotted single-anchor reconstruction techniques in full-thickness tears of the upper subscapularis tendon, is there a difference in stiffness under cyclic load? (2) Are there differences in cyclic gapping between knotless and knotted reconstructions? (3) Are there differences in the maximal stiffness, yield load, and ultimate load to failure? (4) What are the modes of failure of knotless and knotted reconstruction techniques? METHODS: Eight matched pairs of human cadaveric shoulders were dissected, and a full-thickness tear of the subscapularis tendon (Grade 3 according to the Fox and Romeo classification) was created. The cadavers all were male specimens, with a median (range) age of 69 years (61 to 75). Before biomechanical evaluation, the specimens were randomized into two equal reconstruction groups: knotless single anchor and knotted single anchor. All surgical procedures were performed by a single orthopaedic surgeon who subspecializes in sports orthopedics and shoulder surgery. With a customized set up that was integrated in a dynamic material testing machine, the humeri were consecutively loaded from 10 N to 60 N, from 10 N to 100 N, and from 10 N to 180 N for 50 cycles. Furthermore, the gapping behavior of the tear was analyzed using a video tracking system. Finally, the stiffness, gapping, maximal stiffness, yield loads, and maximum failure loads of both reconstruction groups were statistically analyzed. Failure was defined as retearing of the reconstructed gap threshold due to rupture of the tendon and/or failure of the knots or anchors. After biomechanical testing, bone quality was measured at the footprint of the subscapularis using microCT in all specimens. Bone quality was equal between both groups. To detect a minimum 0.15-mm difference in gap formation between the two repair techniques (with a 5% level of significance; α = 0.05), eight matched pairs (n = 16 in total) were calculated as necessary to achieve a power of at least 90%. RESULTS: The first study question can be answered as follows: for stiffness under cyclic load, there were no differences with the numbers available between the knotted and knotless groups at load stages of 10 N to 60 N (32.7 ± 3.5 N/mm versus 34.2 ± 5.6 N/mm, mean difference 1.5 N/mm [95% CI -6.43 to 3.33]; p = 0.55), 10 N to 100 N (45.0 ± 4.8 N/mm versus 45.2 ± 6.0 N/mm, mean difference 0.2 N/mm [95% CI -5.74 to 6.04]; p = 0.95), and 10 N to 180 N (58.2 ± 10.6 N/mm versus 55.2 ± 4.7 N/mm, mean difference 3 N/mm [95% CI -5.84 to 11.79]; p = 0.48). In relation to the second research question, the following results emerged: For cyclic gapping, there were no differences between the knotted and knotless groups at any load levels. The present study was able to show the following with regard to the third research question: Between knotted and knotless repairs, there were no differences in maximal load stiffness (45.3 ± 8.6 N/mm versus 43.5 ± 10.2 N/mm, mean difference 1.8 [95% CI -11.78 to 8.23]; p = 0.71), yield load (425.1 ± 251.4 N versus 379.0 ± 169.4 N, mean difference 46.1 [95% CI -276.02 to 183.72]; p = 0.67), and failure load (521.1 ± 266.2 N versus 475.8 ± 183.3 N, mean difference 45.3 [95% CI -290.42 to 199.79]; p = 0.69). Regarding the fourth question concerning the failure modes, in the knotted repairs, the anchor tore from the bone in 2 of 8, the suture tore from the tendon in 6 of 8, and no suture slipped from the eyelet; in the knotless repairs, the anchor tore from the bone in 2 of 8, the suture tore from the tendon in 3 of 8, and the threads slipped from the eyelet in 3 of 8. CONCLUSION: With the numbers available, we found no differences between single-anchor knotless and knotted reconstruction techniques used to repair full-thickness tears of the upper portion of subscapularis tendon. CLINICAL RELEVANCE: The reconstruction techniques we analyzed showed no differences in terms of their primary stability and biomechanical properties at the time of initial repair and with the numbers available. In view of these experimental results, it would be useful to conduct a clinical study in the future to verify the translationality of the experimental data of the present study.

Neuromapping of the Capsuloligamentous Knee Joint Structures.

PURPOSE: To investigate neuromuscular electromyographic response of the of the upper and lower leg muscles after the application of an intraoperative, isolated mechanical stimulus of the capsuloligamentous structures, including the anterior (ACL) and posterior cruciate ligaments (PCL), lateral (LM) and medial menisci (MM), plica mediopatellaris (PM), and Hoffa's fat pat (HFP). METHODS: The electromyographic response of the upper and lower leg muscles (M. rectus femoris; M. vastus medialis; M. semitendinosus; M. biceps femoris; M. gastrocnemius lateralis) of 15 male patients were measured after an isolated mechanical stimulus of the capsuloligamentous structures during an arthroscopic intervention using a customized intraoperative setup. Target parameters were the short (SLR; <30 milliseconds) and medium latency responses (MLR; >30 milliseconds) after the mechanically-induced trigger. RESULTS: The ACL, PCL, LM, and MM displayed high interindividual reproducibility of >76%. The MM was the only structure indicating both an SLR and MLR for all muscles. Although signals could be detected, there was no reproducibility in electromyographic signal activation for the HFP. The most rapid MLR was observed for the PM (quadriceps: 37 milliseconds). CONCLUSIONS: Each stimulated structure displayed an individual MLR response, which allowed us to create neuromapping combining the anatomical and quantitative representations of the individual muscular activation patterns after isolated mechanical stimulation of the capsuloligamentous knee joint structures, corroborating our hypothesis. LEVEL OF EVIDENCE: Diagnostic - Level II.

ACL double-bundle reconstruction with one tibial tunnel provides equal stability compared to two tibial tunnels.

PURPOSE: The purpose of this study was to investigate whether an anterior cruciate ligament (ACL) double-bundle reconstruction with one tibial tunnel displays the same in vitro stability as a conventional double-bundle reconstruction with two tibial tunnels when using the same tensioning protocol. METHODS: In 11 fresh-frozen cadaveric knees, ACL double-bundle reconstruction with one and two tibial tunnels was performed. The two grafts were tightened using 80 N in different flexion angles (anteromedial-bundle at 60° and posterolateral-bundle at 15°). Anterior tibial translation (134 N) and translation with combined rotatory and valgus loads (10 Nm valgus stress and 4 Nm internal tibial torque) were determined at 0°, 30°, 60° and 90° flexion. Measurements were taken in intact ACL, resected ACL, three-tunnel reconstruction and four-tunnel reconstruction. Additionally, the tension on the grafts was determined. Student's t test was performed for statistical analysis of the related samples. Significance was set at p < 0.017 according to Bonferroni correction. RESULTS: The two reconstructive techniques displayed no significant differences in comparison with the intact ACL in anterior tibial translation at 0°, 60° and 90° of flexion. The same results were obtained for the anterior tibial translation with a combined rotatory load at 60° and 90°. When directly comparing both reconstructive techniques, there were no significant differences for the anterior tibial translation and combined rotatory load at all flexion angles. The measured tension on grafts displayed similar load sharing between both bundles. Except at full extension, both grafts displayed a significantly different tension increase under anterior tibial translation for both techniques (p = 0.0086). CONCLUSIONS: Tightening both bundles in ACL double-bundle reconstruction with one or two tibial tunnels in different flexion angles achieved comparable restoration of stability, although there was different load sharing on the bundles. With regard to individualized ACL reconstruction, the double-bundle technique with one tibial tunnel offers a possibility to address small tibial insertion sites without compromising the advantages of a double-bundle procedure.