LOW CONTACT STRESS MENISCAL BEARING UNICOMPARTMENTAL KNEE REPLACEMENT- LONG-TERM EVALUATION OF CEMENTED AND CEMENTLESS RESULTS

Cemented and cementless (Porocoat(R)) New Jersey low contact stress (L CS) meniscal bearing unicompartmental knee replacements were performed between September 1977 and April 1987. These implants were used inste ad of high tibial or distal femoral osteotomies in patients having min imal to no symptoms in the opposite tibio-femoral and patello-femoral compartments. In the cemented series, 36 knees were replaced: 33 for o steoarthritis (OA) and three for rheumatoid arthritis (RA). Follow-up ranged from 48 to 126 months, mean 80 months. Ages ranged from 52 to 8 3 years, mean 69.0 years. Good to excellent results were found in all 33 knees with OA and one of three knees with RA using both the New Jer sey Orthopaedic Hospital and the Hospital for Special Surgery scoring scales. Two cemented medial knee replacements failed in a 77-year-old, 88.9 kg, 1.49 m tall female who developed inflammatory arthritis of b oth knees resulting in poor results which required revision to total k nee replacements. In the cementless series, 44 knees were replaced: 41 for OA, and three for post traumatic arthritis (PTA). Follow-up range d from 26 to 86 months mean 63.6 months. Ages ranged from 40 to 87 yea rs, mean 63.4 years. Good to excellent results were noted in 40 of 41 knees with OA, and two out of three knees with PTA. One tibial compone nt loosened in a 56-year-old, 70.3 kg, 1.60 m tall, osteoporotic, post -traumatic female with a fixed-valgus deformity because of subsidence into poorly stabilized bone-grafts and required revision to a total kn ee replacement A second cementless failure involved a 78-year-old, 71. 7 kg, 1.55 m tall female with osteonecrosis who had an anterior crucia te ligament (ACL) deficiency and sustained twisting trauma 3 years pos t-operatively resulting in a rotary subluxation of the tibial componen t which also required revision to a total knee replacement. Overall, g ood to excellent results in cemented (94.4%) and cementless (95.5%) un icompartmental meniscal bearing knee replacement compares most favoura bly with the results of proximal tibial or distal femoral osteotomy fo r the treatment of arthritic unicompartmental disease of the knee. Thi s Food and Drug Administration (FDA) class III device is now approved for cementless use in the United States by means of successful complet ion of the Premarket Approval (PMA) application process.