Potential of the non-weight-bearing tunnel view in diagnosing medial meniscus posterior root tear: a pilot study of X-ray characteristics

PURPOSE: Early detection of medial meniscus posterior root tear (MMPRT) is important in preventing the rapid onset and progression of degenerative knee disease. Diagnosis is facilitated by the availability of non-weight-bearing X-ray view, but information on the X-ray characteristics of MMPRT is scarce. Here, we conducted a pilot study of the X-ray characteristics of MMPRT on non-weight-bearing tunnel view. METHODS: We retrospectively reviewed 43 consecutive patients treated in the outpatient department for medial knee pain or popliteal pain. Patients were divided into MMPRT (21 knees) and non-MMPRT groups (22 knees). We investigated X-ray characteristics and magnetic resonance imaging findings. Femorotibial angle, posterior tibial slope, medial tibial eminence (MTE)–medial femoral condyle (MFC) distance (contralateral and affected sides, and difference between the two), medial tibiofemoral joint (MTFJ) width (contralateral and affected sides, and difference between the two), and meniscus radial dislocation between the groups were evaluated using the Mann–Whitney U test. The association between X-ray characteristics and MMPRT was determined using univariate and multivariate logistic regression analyses. RESULTS: A highly significant difference between the affected and contralateral sides was seen in MTFJ width and MTE–MFC distance on non-weight-bearing tunnel view between the MMPRT and non-MMPRT groups. Moreover, a difference in MTFJ width of <−0.575 mm and in MTE–MFC distance of >0.665 mm between the affected and contralateral sides was useful in predicting MMPRT. CONCLUSIONS: The non-weight-bearing tunnel view is useful for the initial diagnosis of MMPRT. Prospective evaluation in a larger population is warranted.