clinical outcome, ligamentous stability and alignment after application of the various medial release techniques (capsular release and deep MCL, pie crust of superficial MCL, superficial MCL release on the tibial side, release of semimembranosus tendon) and to propose a rationale for their use.
In 255 of the 359 (71%) primary TKA’s, symmetrical gaps could be achieved by releasing the capsula and the deep MCL (group 0). In 87 cases (24%), an additional piecrust of the superficial MCL was necessary (group 1). In 55 cases out of these 87 an additional release of the insertion of the semimembranosus was performed. In 17 out of the 359 (5%), the medial tightness necessitated a distal release of the superficial MCL (group 2).
The mean preoperative mechanical femorotibial angle (MFTA) was 174.0, 172.1 and 169.5 and was corrected postoperatively to 179.1, 179.2 and 177.6 for group 0, 1 and 2 respectively. At 12 months, mediolateral stability was clinically evaluated as normal in 97% for group 0, 95% for group 1 and 83% for group 2. Three percent (3%), 5% and 17% has a mediolateral laxity ranging from 6–9 degrees for group 0,1 and 2, respectively.
Medial patello-femoral degenerative changes were found more frequently and these lesions were more pronounced: 20% had narrowing <
50% (IKDC C) and 4% had narrowing >
50% (IKDC D). Onset of medial patellofemoral osteoarthritis was correlated with medial femorotibial osteoarthritis (p<
0,001). Patellar height was statistically different between the operated and controlateral knee (CDI = 0.92 and 0.96, p<
0.001). Patella baja (CDI<
0.8, frequency 9.9%) was correlated with medial femoro-patellar osteoarthritis (<
0.001) and postoperative cast immobilisation (p=0.047).
Navigation was performed with dependant bone cuts, tibia first. The tibial trackers were implanted distally, while the femoral trackers were implanted medially close to the joint line, to prevent impingement with the stems. Bone morphing was performed on the surface of the ancient prosthesis. The system showed the difference between the level of the ideal joint line and the real bone cut, thus indicating the height that had to be reconstructed. The provisional tibial plateau was assembled with its stem and its metallic augments and the knee was balanced with the new tibial component and the ancient femoral component still in place. Femoral reconstruction was finally performed based on an ideal position that had memorized by the computer Bone reconstruction was required in 2 tibias (morselized allografts) and in one femur (structural femoral head allografts).