Purpose of the study: Recent studies have demonstrated that navigation systems provide highly accurate cuts for orthogonal alignment of the lower limb. The accuracy has not to our knowledge been assessed for rotation. Rotation of the femoral piece, which results from a strategy independent of the bone cut, is designed to «correct» for epiphyseal torsion of the distal femur and thus obtain a biepicondylar axis parallel to the «surgical» posterior bicondylar line described by Berger (line drawn between the medial sulcus and the lateral epicondyle), i.e. forming un angle of 2° with the anatomic biepicondylar line described by Yoshioka (line from the medial to lateral condyles). The purpose of this study was to access the precision of navigation rotation.

Material and methods: This prospective consecutive study included 40 osteoarthritic knees undergoing total knee arthroplasty (TKA). The anatomic angle of distal femoral torsion (Yoshioka angle: angle formed by the posterior bicondylar line and the biepicondylar line) was measured on the pre- and post(3 months)-operative scans. Navigation (Navitrack, Zimmer) used the rotation given by the preoperative scan to guide the femoral cut with the objective of achieving a residual Yoshioka angle of 2°, i.e. parallel to Berger’s surgical biepicondylar line. The postoperative HKA measured on the pangonogram in the standing position was 179.6±2° with 85% of patients between −2° and +2°, confirming the reliability of the navigation system.

Results: The mean preoperative epiphyseal rotation of the distal femur was 6.4±1.8°. The mean postoperative measurement was 1.1±2.4°. Eighty percent of patients were within ±2° of the objective.

Discussion: We demonstrated in previous work that navigation-based rotation using intraoperative data is satisfactory as long as the degree of rotation is based on the preoperative scan (and thus takes into account the wide rang of distal femur torsion). Navigation-based rotation is a progress compared with standardized rotation. The few errors observed were related to insufficient identification of the posterior bicondylar line during navigation or to difficulties in interpreting the postoperative scan.

Purpose of the study: Free patellar tendon plasty is the most common technique for repairing anterior knee laxity. Functional outcome can be compromised by invalidating knee pain. The purpose of this prospective randomized study was to compare the outcome of plasty procedures using hamstring tendon versus patellar tendon autografts.

Material and methods: From May 1998 through May 2001, 100 patients presenting an isolated grade I anterior cruciate ligament (ACL) tear were included. Exclusion criteria were: history of fracture, advanced-stage laxity (grade II or greater), and contralateral ACL tear. Randomization was performed in the operative theater using the closed envelop method. Two groups of 50 patients were designated: group A: arthroscopic free bone-tendon-bone patellar autograft; group B: arthroscopic free four-strand hamstring autograft. Two metallic interference screws were used for fixation in both groups. The two groups were comparable for demographic features and clinical, radiological, and instrumental laxity variables recorded before surgery. The position of the tunnels was noted according to Aglietti and was the same in the two groups. The same rehabilitation protocol in a dedicated center was used for both groups. All patients (none lost to follow-up) were assess using the IKDC 1993 criteria with objective instrumental measurement of residual laxity. The level of significance was set at 5%.

Results: There was no significant difference between the groups regarding: resumption of sports activity (level and delay), joint motion, ligament examination, the overall IKDC score, and radiological findings ate mean 40±13 months (range 13–69 months) follow-up. Pain at the harvesting site was observed in 34.78% of patients in group A at six months and in 39.5% of those in group B. Conversely, anterior pain was found in 8.5% of patients in group B at six months and 6.6% at one year (p< 0.05). This statistically significant difference disappeared at two years. Instrumental differential laxity was 0.57±1.3 mm in group A and 1.22±1.9 mm in group B (p=0.56, but with power < 80%). There were two cases of repeated traumatic tears in each group. Repeated meniscectomy was performed in one patient in group A and in three in group B (p=0.3074).

Conclusion: The results at 40 months follow-up of this prospective randomized study with no patients lost to follow-up confirmed the minimal morbidity observed at the harvesting site for hamstring plasty. There was no significant difference between the transplants (patellar tendon, hamstring). Anterior pain with the patellar tendon plasty attenuated after two years. Residual laxity was greater when using the hamstring method.

Purpose of the study: The purpose of rotating the femoral piece, using an indepenent cut strategy, is to «correct» for epiphyseal torsion of the distal femur and thus obtain a biepicondylar axis parallel to the posterior bicondylar axis. It is known however that epiphyseal torsion of the distal femur is highly variable from one individual to another. Intraoperative identification of the biepicondylar line enables appropriate rotation, as long as the data collected are reliable. The purpose of this study was to determine the reliability of intraoperative biepicondylar axis measurements made with navigation systems and to compare the results with the preoperative scan taken as the gold standard.

Material and methods: This prospective study included 60 degenerative knees undergoing total knee arthroplasty. The angle of epiphyesael rotation of the distal femur was measured on the preoperative computed tomography scan and intraoperatively with the navigation system which identified the biepicondylar line and the posterior bicondylar line. Statistical regression lines were determined.

Results: The rotation measured on the preoperative scan was 7.1±2.4° and by the intraoperative navigation system 3.2±4.3°. There was a very weak statistical correlation between the preoperative measurement and the intraoperative navigation measurement (p=0.234, R =0.320).

Discussion: Intraoperative identification of the biepicondylar axis is not reliable. Navigation does not enable an accurate assessment of the distal epiphyseal torsion of the femur and thus the proper rotation to give to the femoral piece. The only reliable measurement of the epiphyseal rotation of the distal femur is made on the preoperative computed tomography.