Does meniscus removal affect ACL-deficient knee laxity? An in vivo study.

PURPOSE: The purpose of the present study was to determine, in vivo, the effect of different types of meniscectomy on an ACL-deficient knee. METHODS: Using a computer-assisted navigation system, 56 consecutive patients (45 men and 11 women) were subjected to a biomechanical testing with Lachman test (AP30), drawer test (AP90), internal/external rotation test, varus/valgus rotation test and pivot-shift test. The patients were divided into three groups according to the status of the medial meniscus. Group BH, 8 patients with bucket-handle tear of medial meniscus underwent a subtotal meniscectomy; Group PHB, 19 patients with posterior horn body of medial meniscus tear underwent a partial meniscectomy; and Group CG with isolated ACL rupture, as a control group, with 29 patients. RESULTS: A significant difference in anterior tibial translation was seen at 30 grades and in 90 grades between BH and PHB groups compared to the CG. In response to pivot-shift test, no significant differences in terms of AREA and POSTERIOR ACC were found among the three groups (n.s). Concerning the anterior displacement of the pivot shift a statistically significant differences among the three tested groups was found. CONCLUSION: The present study shows that meniscal defects significantly affect the kinematics of an ACL-deficient knee in terms of anterior tibial translation under static and dynamic testing.

The adductor tubercle as an important landmark to determine the joint line level in total knee arthroplasty: from radiographs to surgical theatre.

PURPOSE: The restoration of the normal joint line (JL) is important both in primary and revision total knee arthroplasty (TKA). However, the assessment of the femoro-tibial JL is still controversial. A strong correlation between femoral width (FW) and distance from adductor tubercle (AT) to JL was found on radiographs, with a ratio of 0.54. The hypothesis was that this ratio was applicable also in the surgical theatre by using measurements obtained intra-operatively with a caliper. METHODS: Femoral width, AT to JL distance and the RATIO between AT to JL distance and FW of 40 patients who underwent TKA were measured on radiograph and intra-operatively. Bland-Altman agreement tests with repeated measurements and linear regression analysis were used. The ratio was used to estimate the distance between JL and AT. RESULTS: The AT to JL distance/FW ratio calculated with linear regression resulted 0.54 for radiographic measurements and 0.53 for intra-operative measurements. There was no difference (0.009 ± 0.03) between the calculated ratios on radiographic and intra-operative measurements, and the correlation between intra-operative and radiographic measurements was 0.5 (p = 0.0016). CONCLUSIONS: This study shows that the validity of the radiographic method which uses an AT to JL distance/FW ratio to determine the level of the JL is confirmed also when using intra-operatively acquired measurements. Thus, this ratio represents a reliable tool to determine the JL level even in challenging prosthetic revision cases when the anatomical JL is missing. LEVEL OF EVIDENCE: Case series, Level IV.