木村 優彌

PURPOSE: To evaluate the association between arthroscopically detected lateral meniscus (LM) hypermobility and popliteomeniscal fascicle (PMF) injuries in patients with varus knee osteoarthritis undergoing medial opening-wedge high tibial osteotomy (MOWHTO). METHODS: Patients with varus knee osteoarthritis who underwent MOWHTO were retrospectively reviewed. During arthroscopic observation before osteotomy, the presence of LM hypermobility and PMF tears was assessed. Tom's test was performed under standardized negative pressure using an arthroscopic suction system. LM hypermobility was defined as complete posterior translation of the LM beyond the midpoint of the lateral tibial plateau without major tear. The association between LM hypermobility and PMF tear was analyzed using logistic regression. RESULTS: LM hypermobility was detected in 72 of 136 knees. PMF tears were observed in 65 knees. LM hypermobility was significantly associated with PMF tears. Among the entire cohort, 33 knees had partial-type discoid lateral meniscus (DLM), and 3 knees had complete-type DLM. Among the hypermobile LM group, 21 knees presented with partial or complete DLM, whereas only 15 knees in the stable LM group had DLM. However, this difference was not statistically significant. Demographic characteristics including age, body mass index, preoperative mechanical axis, and Kellgren-Lawrence grade were comparable between the LM hypermobile and stable groups. No significant differences in clinical symptoms related to the lateral compartment were observed between groups. CONCLUSIONS: LM hypermobility is a frequent arthroscopic finding in patients undergoing MOWHTO and is significantly associated with PMF tears. Despite the absence of preoperative lateral symptoms, LM instability may represent a relevant intraoperative consideration. LEVEL OF EVIDENCE: Level IV, retrospective case series.

PURPOSE: To clarify the location of the popliteal artery (PA) is relative to the tibial osteotomy plane in patients with medial and lateral unicompartmental knee osteoarthritis (KOA) undergoing UKA. METHODS: Preoperative MRI and postoperative radiographs obtained from 50 patients with unicompartmental KOA who underwent fixed-bearing UKA were analyzed. The amount of tibial resection was determined from the surgical records, and a line was drawn parallel to the tibial posterior tilt angle on the sagittal MR image to create a virtual tibial cut line. The tibial resection width measured from the anteroposterior image of the postoperative radiograph was projected onto the transverse plane containing the intersection between the virtual tibial cut line and the posterior tibial cortex, after which a line was drawn parallel to the medial or lateral intercondylar ridge. We then determined whether the PA was within an extension of the osteotomy area. The shortest distance (Distance 1) between the posterior tibial cortex and the PA within the osteotomy area was measured. In addition, the shortest distance between the line extending the osteotomy posteriorly and the PA was measured (Distance 2). RESULTS: The medial UKA (group M) and lateral UKA (group L) group comprised 41 and 9 cases. The percentage of PA located behind the osteotomy plane was significantly higher in group L than in group M [6/9 knees (66.7%) vs. 2/41 knees (4.9%); P < 0.001]. The distance 1 was 12.6 (4.3) mm in group M and 7.9 (3.7) mm in group L (P = 0.004). The distance2 was 11.1 (4.9) mm in group M and 2.6 (3.5) mm in group L (P < 0.001). CONCLUSION: During lateral UKA, the PA was often located behind the tibial osteotomy plane and close to the posterior tibial cortex. Nearly 5% of medial UKAs, the artery was located behind the osteotomy plane. LEVEL OF EVIDENCE: Retrospective comparative LEVEL III study.

PURPOSE: To assess how intraoperative macroscopical anterior cruciate ligament (ACL) findings affect perioperative procedures, biomarkers, and postoperative anterior-posterior (AP) laxity and range of motion (ROM) after cruciate-retaining (CR) total knee arthroplasty (TKA) and to determine how chronic ACL deficiency may affect postoperative inflammatory biomarker, AP laxity, and ROM. METHODS: A total of 121 patients with varus knee osteoarthritis without a history of ACL injury who underwent ATTUNE® (DePuy Synthes, Warsaw, IN) CR TKA were analyzed. Intraoperative ACL findings were stratified into intact, damaged, and diminished, according to the tension by probing, synovial coverage, and vascularity. C-reactive protein (CRP) levels were examined at one, seven, and 14 days after surgery. Knee AP laxity measurements using Kneelax 3 (Monitored Rehab Systems, Haarlem, The Netherlands) and postoperative knee ROM were also compared. RESULTS: One-way ANOVA showed significant differences in CRP levels examined one day after surgery observed between the three groups (8.4 (3.8), 9.8 (4.3), and 13.2 (7.7) mg/dL, respectively; P = 0.018), with post hoc analysis showing that CRP levels one day after surgery were significantly greater in the diminished group than in the intact and damaged groups (P = 0.012 and 0.023, respectively). AP laxity in 30° of knee flexion was observed between the three groups (5.4 (2.3), 5.8 (2.5), and 7.1 (2.8) mm, respectively; P = 0.039), with post hoc analysis showing that AP laxity in 30° of knee flexion was significantly greater in the diminished group than in the intact group (P = 0.038). Knee ROM showed no significant differences. CONCLUSION: Intraoperative ACL diminishment was associated with higher CRP one day after surgery and midrange AP laxity one year after surgery.

BACKGROUND: Total knee arthroplasty (TKA) alleviates pain and improves daily living activities in individuals with end-stage osteoarthritis of the knee. However, up to 20% of patients have sub-optimal outcomes after TKA. OBJECTIVE: No studies have clarified the intraoperative factors that affect postoperative range of motion (ROM) after cruciate-retaining (CR) TKA. Thus, this study aims to clarify these factors. METHODS: Patients with knee osteoarthritis with varus knee deformity who underwent CR-TKA between May 2019 and December 2020 were included in this study. One year after surgery, patients were stratified into two groups based on knee flexion: Group F (over 120∘) and Group NF (below 120∘). Patient backgrounds including age, body mass index, hip knee angle, preoperative range of motion for both extension and flexion, intraoperative center joint-gap measurements of 0∘, 30∘, 45∘, 60∘, 90∘, and 120∘ of knee flexion using a tensor, intraoperative anterior-posterior (AP) laxity measurements of 30∘ and 90∘ of knee flexion using an instrumental laximeter were compared between the groups. Univariate analyses between the groups were used to construct the initial model. The receiver operating characteristic curve was also analyzed. The predictive variables included in the final model were selected by stepwise backward elimination. RESULTS: Intraoperative AP laxity with 30∘ of knee flexion smaller than 10.8 mm was a significant positive prognostic factor (OR: 1.39, 95% CI: 1.08-1.79, P= 0.011) of postoperative ROM over 120∘ of knee flexion one year after surgery. The sensitivity, specificity, PPV, and NPV were 70.9%, 82.4%, 92.9%, and 46.7%, respectively. CONCLUSION: Intraoperative AP laxity smaller than 10.8 mm was a significant positive predictive factor for obtaining knee flexion greater than 120∘ one year after surgery when using CR-TKA and its PPV was high up to 92.9%.