Posteromedial vertical capsulotomy selectively increases the extension gap in posterior stabilized total knee arthroplasty.

PURPOSE: In total knee arthroplasty (TKA), it is important to obtain an appropriate flexion-extension gap. The extension gap is expanded by posteromedial vertical capsulotomy (PMVC). This study aimed to evaluate the increase in the extension gap by PMVC using a navigation system. METHODS: In posterior stabilized (PS)-type TKA, PMVC was performed in 37 knees. The medial extension gap at 0° and flexion gap at 90° flexion of the knee joint using the navigation system before and after PMVC were measured. RESULTS: The extension gap before the PMVC was 5.3 ± 2.9 mm. After PMVC, the extension gap had significantly increased to 8.0 ± 2.8 mm (p < 0.001). In addition, the flexion gap was 8.1 ± 2.7 mm before the PMVC, but it was 8.7 ± 2.8 mm after the PMVC, and the flexion gap was not enlarged (n.s.). CONCLUSION: In PS-type TKA, it is possible to obtain selective expansion of about 2.7 mm of the extension gap by PMVC. Therefore, gap balance can be acquired by soft-tissue treatment while preserving the bone. The PMVC was a useful method for acquiring gap balance and preserving the bone stock. LEVEL OF EVIDENCE: IV.

The accuracy of a newly developed guide system in medial meniscus posterior root repair: a comparison between two aiming guides

PURPOSE@#Posterior root repair of the medial meniscus (MM) can prevent rapid progression of knee osteoarthritis in patients with a MM posterior root tear (MMPRT). The anatomic reattachment of the MM posterior root is considered to be critical in a transtibial pullout repair. However, tibial tunnel creation at the anatomic attachment is technically difficult. We hypothesized that a newly developed point-contact aiming guide [Unicorn Meniscal Root (UMR) guide] can create the tibial tunnel at a better position rather than a previously designed MMPRT guide. The aim of this study was to compare the position of the created tibial tunnel between the two meniscal root repair guides.@*MATERIALS AND METHODS@#Thirty-eight patients underwent transtibial pullout repairs. Tibial tunnel creation was performed using the UMR guide (19 cases) or MMPRT guide (19 cases). Three-dimensional computed tomography images of the tibial surface were evaluated using the Tsukada's measurement method postoperatively. The expected anatomic center of the MM posterior root attachment was defined as the center of three tangential lines referring to three anatomic bony landmarks (anterior border of the posterior cruciate ligament, lateral margin of the medial tibial plateau, and retro-eminence ridge). The expected anatomic center and tibial tunnel center were evaluated using the percentage-based posterolateral location on the tibial surface. The distance between the anatomic center and tunnel center was calculated.@*RESULTS@#The anatomic center of the MM posterior root footprint was located at a position of 79.2% posterior and 39.5% lateral. The mean of the tunnel center in the UMR guide was similar to that in the MMPRT guide (posterior direction, P = 0.096; lateral direction, P = 0.280). The mean distances between the tunnel center and the anatomic center were 4.06 and 3.99mm in the UMR and MMPRT guide group, respectively (P = 0.455).@*CONCLUSIONS@#The UMR guide, as well as the MMPRT guide, is a useful device to create favorable tibial tunnels at the MM posterior root attachment for pullout repairs in patients with MMPRTs.LEVEL OF EVIDENCE: IV

Time-Dependent Increase in Medial Meniscus Extrusion after Medial Meniscus Posterior Root Tear Analyzed by Using Magnetic Resonance Imaging

PURPOSE: Medial meniscus posterior root tear (MMPRT) causes progression of medial meniscus extrusion (MME). This study aims to calculate the progression rate of MME based on findings in two preoperative magnetic resonance imaging (MRI) scans and determine the associated factors. MATERIALS AND METHODS: We retrospectively reviewed 33 patients (27 females and 6 males; mean age, 60 years) who underwent MRI twice, at a mean interval of 48 days. We measured the medial meniscus body width, medial joint space width (MJSW), and MME. The MME progression rate was derived from regression analysis of the increase in MME (ΔMME) between the two MRI scans. In addition, the correlations of the MME increase rate with age, body mass index, femorotibial angle, and MJSW were evaluated. RESULTS: The mean MME increased from 3.4 mm to 4.5 mm (p<0.001). A good correlation was observed between ΔMME and the interval of MRI scans (R²=0.621), and the MME progression rate was 0.020 mm per day. A moderate correlation was observed between the MME increase rate and the MJSW (R²=0.432). CONCLUSIONS: The MME progression rate was rapid in MMPRT and narrowing of the MJSW was associated with the progression of MME. LEVEL OF EVIDENCE: V, Cross-sectional study