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ABSTRACT

This cohort study includes similar patients undergoing primary knee replacement, compares minimally invasive to traditional methods, and demonstrates the impact of patellar eversion on recovery. Between 2001 and 2003, 200 consecutive total knees were performed in patients with osteoarthritis. The first one hundred knees were done using traditional instruments through a standard surgical approach that included everting the extensor mechanism. The second one hundred knees were performed using the same implant system but with a minimally invasive surgical technique. In this technique, down-sized instruments were combined with an altered sequence of osteotomies and soft-tissue releases so that the operation could be completed without patellar eversion. All surgeries were done by the same surgeon using the same implant. A distal-cut-first technique was used, and gap management was standardized using the balancer method. Flexion and extension gaps were measured under 30 foot-pounds of tension. The clinical pathway was the same for both groups.

Hospital records, physical therapy records, and clinic visits were followed throughout the first year and were analyzed for operative times, length of stay, pain, range of motion, incision length, and the need for postoperative manipulations. Range of motion was quantified at 2 weeks, 6 weeks, 12weeks, 24 weeks, and one year. Lysholm and Knee Society scores were measured preoperatively and at one year. Radiographs were evaluated at 6 weeks, 6 months, and 12 months for component position.

Patients with rheumatoid arthritis, stiff knees, and previous open surgery were eliminated. This left 89 knees (73 patients) in the traditional group and 91 knees (81 patients) in the MIS group.

The traditional and (MIS) groups were similar in terms of age (64 and 63, t-test), and gender (Fisher’s exact test), weight, type of implant, diagnosis, preoperative Lysholm and Knee Society scores, and preoperative motion. Knees in the traditional group experienced early recovery similar to that reported in the literature with range of motion improving to their preoperative flexion at one year. The MIS group regained their preoperative flexion by three months. Fourteen per cent of the traditional group required manipulation compared to only 2% in the MIS group (p < .001) . The MIS group had smaller incisions (14 cm vs 20 cm), a shorter tourniquet time, a shorter length of stay (3.6 days vs 6.4 days), less pain at discharge, and significantly better motion at 2, 6, 12 , and 26 weeks (p < 0.01). There was no meaningful difference in component position between the two groups. Surgery times were somewhat less for the MIS group, and there was no difference in complication rates between the two groups. This study demonstrates superior early recovery in patients having MIS total knee replacement compared to traditional methods with no increase in complication rates and no component malpositioning. Patellar eversion during knee replacement may contribute to stiffness. Minimally invasive techniques eliminate patellar eversion, allow smaller incisions, and lead to improved motion with fewer manipulations.

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