[Single-compartment "Lotus" type knee prosthesis in the treatment of lateralized gonarthrosis: results in 135 cases with a mean follow-up of 4.6 years].

Controversy exists on the indications and results of unicompartmental arthroplasty in the treatment of unicompartmental knee arthritis. This led us to study 135 Lotus prostheses implanted from December 1974 to February 1990. The follow-up lower than 1 year for 14 knees (11 were lost to follow-up, 3 were reoperated). One hundred and twenty-one knees were clinically evaluated with an average follow-up of 4 years and 6 months using both the GUEPAR and the Knee society grading systems. 71.9 per cent of the knees were rated good, 28.1 per cent were rated poor (19 per cent were revised). This important rate of poor results was due to poor technique (11 knees) and to poor indications (7 knees). Polyethylene wear, and radiolucent line especially when it was evolutive were significantly correlated to failures and poor results. Failures were seldom unifactorial but often multifactorial. Over or undercorrection of coronal deformity, absence or lengthening of the anterior cruciate ligament were the failure factors most often found. Decrease of good results with time, and polyethylene wear of unicompartmental arthroplasties are factors which lead us to carefully consider osteotomy for patients under 65 years. The failure rate may decrease with good indications and a better technique allowing unicompartmental arthroplasty to be a good choice for unicompartmental arthritis.