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Use of Hybrid Technique in Knee Arthroplasty Not as Effective as Cemented Implant

The use of cementless total knee arthroplasties (TKAs) is appealing because of the many advantages, however, cementless approaches also have some drawbacks, including a higher rate of loosening that will require revision surgery later on. In the late 1980s, surgeons tried to combine the advantages of both cemented and uncemented TKAs with a hybrid TKA; the femoral, or thigh bone, part was cementless while the tibial, or shin bone, part was cemented. Unfortunately, despite early reports of success, longer term follow up is finding that the hybrid TKAs have a higher than acceptable failure rate.

The authors of this study studied the records of 57 patients who had, in total, 65 TKAs with the hybrid approach. The average age of the patients was 60 years, ranging from 27 to 83 years. The diagnoses for the knees were primary osteoarthritis (46), posttraumatic arthritis (8), rheumatoid arthritis (6), osteonecrosis (2),and other causes (3). One criteria to participate in this study was the patients' bones had to still have good quality of the femur. The patients were followed for an average of 15 years.

Patient function was measured with the Knee Society Scores, out of 100, with 100 being the best score possible. Before surgery, the average functional score was 38. This increased to an average of 86 at the last follow-up. When the patients were asked to rate their pain as mild, moderate, or severe, 18 percent said it was mild before surgery, 40 percent moderate, and 42 percent severe. At the latest follow-up, 54 percent rated the pain as mild, 34 percent moderate, and 12 percent severe. When doing stairs, after surgery at
latest follow-up, 92 percent of the patients were able to climb stairs and 91 percent could get out of a chair without difficulty.

Revision surgery was needed in 27 percent (18 knees). Eleven of these were related to the femur: five for failure of the bone to grown into the implant, four due to loosening and osteolysis from wear, and two because the femoral components had fractured. On the patellofemoral side, four revisions were done. Three other revisions were performed because of wear to the implant and destruction of the bone.

The statistics showed that the overall implant survival was an estimated average of 89 percent at 5 years, 82 percent at 10 years, 64 percent at 15 years, and 58 percent at 17.5 years. This, the authors say, is an unacceptably high rate of failure, leading their institution to stop performing the procedure.


Gavan P. Duffy, MD, Barbara E. Murray, B.S., and Robert R. Trousdale, MD. Hybrid Total Knee Arthroplasty. In The Journal of Athroplasty. December 2007. Vol. 22. No. 8. Pp. 1112-1115.


12/20/2007

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