Abstract
Purpose: We report the results at more than five years of a consecutive series of total knee arthroplasties (TKAs) implanted without cement and with preservation of the posterior cruciate ligament (PCL).
Material and methods: This series included 98 patients who underwent 109 primary TKAs between 1994 and 1998. Mean patient age was 67.7 years. The press-fit Interax prosthesis has a macroporous hydroxyapatite coating since 1996. The patella was resurfaced in 92% of the cases with a cemented polyethylene button. Ligament balance and joint space were controlled by progressive release of the ligaments with a tensor derby. Clinical assessment was based on the KSS. Radiological assessment included the femorotibial axis, the position of the implants, and the bone-implant interfaces.
Results: Seven (6.4%) of the patients were lost to follow-up. Fifteen (13.4%) died or were demented and two (1.8%) developed late infection and were not included in the primary analysis. Thus, 85 patients (77.9%) were retained for analysis at a mean 5.2 years follow-up. The KSS improved from 33.4 preoperatively to 79.4 at last follow-up. The KSS function score improved from 55.1 to 82.4. Knee flexion was 124.5° preoperatively and 113.1° at last follow-up. Anteroposterior laxity greater than 5 mm was observed in 4.8% at last follow-up. Radiologically, the mechanical femorotibial axis changed from 184.4° to 180.6°. Alpha 95.6°, geta 89.1°, omega 4.77°, gamma 3.8°, sigma 89.4°. Patellar height was 0.84 preoperatively and 0.65 at last follow-up. Lucent lines were observed 3.5 times less frequently with hydroxyapatite coated implants. Patellar loosening and femorotibial loosening were observed in one patient each. Revision procedures were necessary for three prostheses for bipolar loosening, painful stiff knee, and anteroposterior instability. Non-infectious survival rate was 94.1% at 5.2 years.
Discussion: These mid-term clinical results are comparable with those reported in the literature for cemented or non-cemented implants with or without preservation of the posterior cruciate ligament. Longer follow-up is however necessary to assess the anteroposterior stability. The radiographic measurements provide a good demonstration of the operative precision and proper ligament balance. Hydroxyapatite coating improves bony fixation of the implants and provides a fixation comparable with cemented implants.
Conclusion: This series confirms the mid-term reliability of the non-cemented Interax THA with preservation of the posterior cruciate ligament.
The abstracts were prepared by Docteur Jean Barthas. Correspondence should be addressed to him at Secrétariat de la Société S.O.F.C.O.T., 56 rue Boissonade, 75014 Paris.
