Total condylar knee prosthesis with posterior stability. A mid-term follow-up of 74 cases with severe deformity

The midterm results of 74 posterior stability total condylar prostheses were studied (average follow-up 3 1/2 years). The average age of the patients was 65 years with a predilection for females (73%). The most frequent diagnosis was osteoarthritis (70%) followed by rheumatoid arthritis (28%): in 20% of the cases previous operations had been performed. Most of the patients had severe deformity which was not susceptible to other surgical treatment. The most frequent deformity was varus (average 13 degrees), followed by valgus (average 25 degrees), and flexion contracture (average 37 degrees). Bone defect in the tibia requiring surgical treatment were present in 18% of the cases. The most frequent general complication was pulmonary embolism (5%), which was never fatal; minor complications related to wound healing were observed in 17.5% of the cases. The results, evaluated with a numerical recording form devised by the Hospital for Special Surgery (New York) were: excellent 72%, good 21%, fair 4%, poor 3%. Of the 4 fair results, one had lateral laxity following lysis for valgus knee, one had loosening of the tibial component, and one had painful patellar clicks. Painless, small patellar clicks were observed in 4 other patients. The two poor results were due to low-grade infection and detachment of both components. Seventy per cent of the knees had normal or almost normal function with maximum flexion averaging 100 degrees. In 78% of the cases a study of the cement-bone interface revealed either no radiotranslucent line or present in only one area of the tibia. Radiotranslucent lines around the femoral or patellar component was rare and of no clinical significance.