PROSPECTIVE-STUDY OF POSTOPERATIVE ANTERI OR KNEE LAXITY AFTER ANTERIOR-CRUCIATE-LIGAMENT RECONSTRUCTION USING 2 DIFFERENT PATELLAR TENDON GRAFTS

Purpose of the study The aim of this study was to evaluate postoperati ve evolution of anterior laxity, in order to know at what time the elo ngation of the reconstructed anterior cruciate ligament (ACL) begins t o develop after surgery, and if there were any correlations with recup eration of knee flexion or extension. The second purpose of this study was to compare two series of patients operated on by two different pr ocedures for a long standing ACL rupture, Material and methods Two ser ies of patients were compared: group I (60 cases), had an ACL reconstr uction using a free autologous patellar tendon graft with a bone-to-bo ne fixation, supplemented by an external extra-articular plasty with a strip of quadricipital tendon as a direct prolongation of the graft o f the patellar tendon and patella itself. ''Mac InJones'', and group I I (50 cases), had a reconstruction with a similar transplant, but stil l attached on the tibia and with a fibrous fixation through the femora l condyle and the Gerdy's tubercule (modified ''Marshall-Mac Intosh'') . Anterior laxity was measured using two instrumented methods; first, Medmetric knee arthrometer (KT-1000)(TM), before and after operation, then each month later during the first 6 months and yearly. On the oth er hand, a personnal stress X-ray protocol (at 200 of flexion and with application of a 9 kg load at the distal part of the thigh), was made before operation, 6 months later, and yearly during 8 years. The laxi ty of both medial and lateral compartments of the knee were separative ly measured. Laxity was studied in parallel with the recuperation of k nee flexion and extension during a reabilitation program without any l imitation in both directions. Results During a period of 3 months, the laxity was arthrometricaly inferior to the normal knee in the two gro ups, and appeared progressively. Laxity was independant from early rec uperation of full range of flexion and extension. The elongation of th e reconstructed ligament was showed to develop during the first 6 mont hs and less during the following 6 months. Better results were found f or group I during the earliest period with the Medmetric arthrometer, buth there was no difference beetwen both groups after 1 year and 2 ye ars. With dynamic radiography, laxity was higher than indicated by KT- 1000, and results were better for group I. Laxity was stabilized after one year and the results were still good after 8 years. Discussion KT -1000 showed a great interest for measurement of the compliance index (difference beetwen laxity at 89 newtons and 69 newtons of traction), and can be used without any inconvenient for patients. Stress radiogra phs may be used for yearly controls. The radiographic method had bette r accuracy than KT-1000 and gave precise laxity measurements of the me dial and lateral compartments of the knee. The laxity of the medial co mpartment showed to have a good pronostic value. Conclusion Evolution of laxity is more favourable in group I with bone-to-bone ligament fix ation. Recovering early and complete flexion and extension is not prej udicial for the ligament. Laxity developed beetwen 3 and 6 months and less beetwen 6 and 12 months. KT-1000 is able to detect laxity during early postoperative period. Dynamic radiographs are more precise to co ntrol laxity year after year. Informations concerning the two compartm ents of the knee are of great interest to compare different procedures and to improve new surgical techniques.