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Friday, March 2, 2001

Similar range of motion in mobile- or fixed-bearing

Patients with a mobile- or fixed-bearing posterior cruciate substituting total knee arthroplasty have similar passive and weight bearing range of motion, say researchers in scientific exhibit 29. Also, they say that the addition of polyethylene bearing mobility did not enhance flexion.

The maximum flexion following total knee arthroplasty is more dependent on articular geometry than bearing mobility, they report in their study of 40 subjects using video fluoroscopy. Twenty patients had a mobile-bearing posterior cruciate substituting total knee arthroplasty and 20 subjects had fixed-bearing posterior cruciate substituting total knee arthroplasty. Under weight-bearing conditions, each subject performed successive deep knee bends to maximum flexion. Then, under passive nonbearing conditions, the subjects stood on one leg and passively flexed their knee to maximum flexion.

The preoperative flexion (nonweight bearing) for the implanted knee groups was 97.4 degrees and 111.8 degrees for the subjects having a mobile-bearing posterior cruciate substituting total knee arthroplasty. Under weight-bearing conditions, range of motion decreased for both groups, with the average range of motion of 108.8 degrees for the mobile-bearing group and 115.4 degrees for subjects in the fixed-bearing group.

Previous weight-bearing vs. passive nonweight bearing range of motion studies have determined that subjects having posterior cruciate substituting total knee arthroplasty have statistically similar passive range of motion compared to subjects having a posterior cruciate retaining total knee arthroplasy. However, under weight-bearing conditions subjects having a posterior cruciate substituting total knee arthroplasty experience statistically greater range of motion.

The results of this study determined that subjects having a mobile- or fixed-bearing posterior cruciate substituting total knee arthroplasty experience a similar passive and weight-bearing range of motion.

The researchers, all of the Rocky Mountain Musculoskeletal research Laboratory, Denver, Colo.,are Douglas A. Dennis; Brian Haas, MD; Richard D. Komistek, PhD, president and executive director; Jamey T. Brunley, MS; and Travis Dennis,

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2001 Academy News March 2 Index C

Last modified 15/February/2001 by IS