This study was performed to identify the mechanoreceptors in the tibial remnants of ruptured human anterior cruciate ligaments (ACL) by immunohistochemical staining. Thirty-six specimens of tibial ACL remnants were obtained from patients with ACL ruptures during arthroscopic ACL reconstruction. As control, two normal ACL specimens were taken from healthy knee amputated at thigh level due to trauma. The specimen was serially sectioned at 40 mum. In control group, the average number of sections per specimen was 132, and a total of 264 slices were available. In remnant group, the average number of sections per specimen was 90, and a total of 3,251 slices were available. Immunohistochemical staining was performed to detect the neural element of mechanoreceptors. Histologic examinations were performed under a light microscope and interpreted by a pathologist. Nineteen (8 Ruffini, 11 Golgi) mechanoreceptors were identified in the two normal ACLs, which were evenly distributed at both tibial and femoral attachments. In the remnant group, mechanoreceptors were observed in 12 out of 36 cases (33%), and a total of 17 (6 Ruffini and 11 Golgi) mechanoreceptors observed. No significant differences in the harvest volume, number of sections, age, or time between injury to surgery was observed between the 12 mechanoreceptor-present and the 24 mechanoreceptor-absent ones. The presence of mechanoreceptor at the tibial remnants of torn ACLs was verified. The immunohistochemical staining methodology proved useful, but requires further refinement. Although the mechanoreceptors were detected relatively less frequently than expected, the authors consider that it does not negate the necessity of remnant-preserving ACL reconstruction.

The purpose of this study was to retrospectively compare clinical results, including proprioceptive function, after anterior cruciate ligament (ACL) reconstruction between 2 groups using techniques that preserve and eliminate the tibial remnant. Forty-eight patients who were followed for at least 24 months after ACL reconstruction with 4-strand hamstring tendon autografts were enrolled in this study. They were then divided into 2 groups: the remnant-preserving group (group A, 26 patients), in whom more than 7 mm of the remnant tibial stump (approximately 20% of the mean length of the ACL) was preserved; and the remnant-eliminating group (group B, 22 patients), in whom the tibial remnant was eliminated during ACL reconstruction. The average duration of follow-up was 25.5 months. At last follow-up, patients were evaluated using the International Knee Documentation Committee scale, Hospital for Special Surgery score, Lachman test, arthrometer, reproduction of passive positioning (RPP) test, threshold to detection of passive motion (TTDPM) test, one-leg hop test, and single-limb standing test. The clinical results between the 2 groups were statistically compared. Group A showed significantly better results on the RPP test at 15° ( P =.040) and 30° ( P =.010), one-leg hop test ( P =.017), and single-limb standing test ( P =.007) compared with group B. The other results showed no significant differences. The remnant-preserving technique in ACL reconstruction yields better proprioceptive and functional outcomes and may help achieve postoperative patient satisfaction. [ Orthopedics . 2020;43(4):e231–e236.]

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Discoid medial meniscus is very rare and bilateral discoid medial meniscus is extremely rare. We report symptomatic bilateral discoid meniscus with abnormal attachment to anterior cruciate ligament (ACL) in three patients and we think that our report is a combination of very rare conditions. The patients had symptoms in both sides and we performed magnetic resonance imaging (MRI) and operated five knees. The operation methods were different by the condition of menisci.

Intra-articular synovial lipoma is rare and clinically manifested mostly by mass effect and occasionally by torsion of the stalk. Patellar dislocation rarely occurs owing to a mass effect of intra-articular tumor of the knee joint. The authors present a case of large intra-articular synovial lipoma at the lateral gutter of the knee joint, which presents as patellar dislocation. A 19-year-old man visited our clinic due to pain and limitation of motion owing to mass at his left knee. MRI revealed an intra-articular soft tissue mass at the lateral gutter of the knee joint with considerable mass effect displacing patella from the trochlear groove. Excisional biopsy confirmed the diagnosis of lipoma, and the final diagnosis was intra-articular synovial lipoma with clinical information. The final radiograph showed well-aligned patella on the trochlear groove. After marginal excision, there was no recurrence or tumor-related morbidity.