Abstract
The long-term results and problems of 20 knee joints in 19 cases with osteoarthritis (OA) with the Savastano's unicompartmental arthroplasty limited to a single compartment of the knee are reported. The average age at the time of surgery was 62.2 years. The diagnosis was medial compartment OA in 18 knees and lateral compartment OA in 2 knees. Of the 15 cases which were followed for 10 years on an average, about 80 % of the cases showed satisfactory results within 5 years, with knee function scores of more than 75 points. However, poor results were noted in 3 knees in the first 5 years, and in 2 knees thereafter. The long-term results of unicompartmental replacement in 15 knees, including 3 knees which required revision and arthrodesis, were rated as excellent in 4, good in 5, fair in 1 and poor in 5 (2 revision 1 arthrodesis and 2 with loosening) . The average postoperative functional score was 76.8.
Observation of radiographical findings showed that the average standing FTA was 186.3° (preoperatively) and 174.8° (postoperatively) in medial compartment knee OA. But some cases showed an increase of PTA, and a final angle of over 180° was noted in 6 knees. A clear zone appeared around the femoral and tibial components in 4 and 11 cases respectively. The clear zone expanded with passage of the time in 7 cases, and this tendency was marked in the knees with a 6 mm prosthesis. These cases ultimately developed loosened joints. Our results suggested that body weight, osteoporosis, stability of the tibial component, and setting of the prosthesis seemed to be related to loosening.
The prognosis 10 years after surgery was “good” in 9 knees, accounting for 60 % of all those treated. Therefore we believe that if the indicated cases are carefully chosen, unicompartmental arthroplasty can be one of the most useful surgical procedures for knee OA.
