title: An in vivo analysis of the effectiveness of the osteoarthritic knee brace during heel strike and midstance of gait.
abstract: Presently, there are multiple nonoperative techniques a surgeon can use to alleviate the pain of an osteoarthritic joint including: oral medications, physical therapy, injections and off-loading knee braces. The objective of this study was to analyze subjects under in vivo, dynamic conditions using fluoroscopy to determine if off-loading knee braces actually separate the femoral condyle from the tibial plateau during the mid-stance and heel-strike phases of gait. Forty subjects with substantial unicompartmental osteoarthritis were studied under fluoroscopic surveillance in the frontal plane while performing normal gait on a treadmill. The subjects were patients of one surgeon and were all clinically diagnosed to have marked unicompartimental degenerative joint space narrowing. Initially, each subject was asked to perform normal gait on a treadmill under fluoroscopic surveillance in the frontal plane. An offloading osteoarthritic knee brace was then fixated on the osteoarthritic knee joint. The subjects were then asked to walk on level ground while wearing the brace to rate the effectiveness of the brace in alleviating pain. The subjects were then asked to perform normal gait on a treadmill while wearing the brace. Successive fluoroscopic images of each patient at mid-stance and heel-strike (with and without a brace) were downloaded to a workstation computer. The captured fluoroscopic images were then analyzed using digitization. Thirty-four of forty subjects (85%) judged the osteoarthritic knee brace effective in reducing knee pain. Six of the subjects (15%) were not able to detect a change in knee pain. All of these subjects were overweight resulting in suboptimal brace fixation. Thirty-one of forty subjects (78%) demonstrated articular separation of the degenerative knee compartment at heel-strike and 28/40 (70%) at midstance. Thirty-one of forty subjects (78%) experienced an angular change at heel-strike, while 37/40 experienced an angular change at mid-stance. The average amount of change in condylar separation (A) was 1.7 mm (0.0-6.4) at heel-strike and 1.9 mm (0.0-7.9) at mid-stance. The average amount of change in angle ?S was 2.0 degrees (0.0-4.8 degrees) at heel-strike and 1.6 degrees (0.0-5.1) at mid-stance. Previous biomechanical studies have documented excessive loads in degenerative compartments of patients with unicompartmental arthrosis and associated angular deformities. Offloading braces have been developed to attempt to lessen loads in the degenerative compartment with subsequent reductions in knee pain. This present study demonstrates in vivo articular separation of degenerative knee compartments can be achieved with offloading braces with subsequent subjective relief of knee pain. These braces may have limited effectiveness in obese patients. Key words: osteoarthritis of the knee, a knee brace, conservative treatment.
authors.affiliation: Rocky Mountain Musculoskeletal Research Laboratory, Denver.
authors.forename: A D
authors.initials: AD
authors.lastname: Dennis
authors.forename: R D
authors.initials: RD
authors.lastname: Komistek