ROENTGENOGRAPHIC AND MRI EVALUATION OF ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION USING A PATELLAR TENDON GRAFT - CORRELATIONS WITH PHYSICALFINDINGS

Introduction : the purpose of this study was to evaluate the influence of the graft positioning on the clinical outcome and MRI signal of th e graft as well, following ACL reconstruction using the central one-th ird of the patellar tendon. Material and methods : twenty one patients having a chronic anterior instability sustained a modified Marshall-M ac Intosh procedure, while 15 having a subacute torn ACL had an ACL re construction using a free bone-patellar tendon-bone graft. The patient s were retrospectively reviewed with a 1.8 year average follow-up (1-3 years). The clinical result was evaluated through the comparative ran ge of motion, the residual laxity as measured with the KT 1000 arthrom eter, and the pivot shift test. The roentgenographic analysis was perf ormed from AP and ML views, made first on one-leg standing with the kn ee at 30 degrees of flexion, and then in <<zero>> extension with activ e quadriceps contraction. Lines were drawn to visualise the location o f the tibial and femoral tunnels in relation to the tibial plateaus an d the roof of the intercondylar notch represented by the Blumensaat li ne. The analysis of the AP IRM views of the graft allowed to discrimin ate between homogenous and heterogenous graft signals. Results : on la teral roentgenograms of normal knees it was found that the Blumensaat line crossed the surface of the medial tibial plateau at its anterior third, at 30 +/- 9 per cent (20-40 per cent range), demonstrating the variability of the intercondylar roof inclination. The range of motion was normal in 22 patients (group 1), 8 patients had a flexion deficit (group II), and 6 exhibited an extension deficit (group III). The res idual laxity was similar in each group (p > 0.05). When comparing grou p III to group I, patients from group III had a tibial tunnel signific antly more anterior with regard to the Blumensaat line (p < 0.02). In group III, all patients exhibited an heterogenous MRI graft signal (p < 0.05), and the angle between the intraarticular part of the graft an d the tibial tunnel was higher (p < 0.001). These findings were not ob served in group II where the location only of the femoral tunnel seeme d to influence the flexion deficit (p > 0.05). Discussion and conclusi on : this study demonstrated that the location of the tibial tunnel wi th regard to the roof of the intercondylar notch, when the knee is in <<zero>> extension, was the most relevant parameter controling the ext ension deficit resulting from a graft impingement. No relation was fou nd between the tibial tunnel location with regard to the tibial platea us and the mobility deficit. Graft impingement also was always associa ted with an heterogenous graft MRI signal. Clinical relevance : when r econstructing the ACL care must be taken when inserting the K-wire aim ed to guide the tibial drill, to obtain a proper position with regard to the roof of the intercondylar notch. The K-wire location must be ch ecked in <<zero>> extension. Intra-operative X-rays may help.