A relationship between stem orientation and function following total hip arthroplasty.
A retrospective gait analysis of patients with cemented Charnley-Mueller total hip arthroplasties was conducted to determine if functional differences exist between patients with femoral stems placed in varus and valgus orientations. Twenty patients and ten normals were studied using gait analysis to quantify joint motion and moments during level walking. In addition, a radiographic analysis of stem placement and mechanics of the reconstructed hip was performed on the total hip patients. All patients selected for the study had excellent clinical results on the basis of a score of 95 or better on the Harris hip rating form. The patients were divided into two subgroupings on the basis of stem orientation. A valgus group was defined as having a valgus stem orientation relative to the femoral shaft, with the femoral head-shaft offset shortened by 5 mm or greater compared to the contralateral unoperated hip, while the varus group was defined on the basis of having a varus stem orientation relative to the femoral shaft, with the femoral head-shaft offset restored to normal or greater than normal. A difference in gait was found between the varus and valgus patient groupings. The varus group had abnormal gait characteristics in the range of hip motion, the flexion-extension moments at the hip, and stride length. The patients in the valgus group had statistically normal gait. The differences in the gait characteristics were interpreted as an attempt to alter forces on the hip joint for patients in the varus group. These alterations were possibly an early indication of a subtle adaptation in patients with varus-placed femoral stems since, historically, a greater percentage of the patients in this configuration, retrospectively, go on to mechanical failures.(ABSTRACT TRUNCATED AT 250 WORDS)
Hodge
W A
WA
Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston.
Andriacchi
T P
TP
Galante
J O
JO
D000368:Aged; D005260:Female; D005684:Gait / Q000502:physiology*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000502:physiology; D006622:Hip Prosthesis / Q000379:methods / Q000534:rehabilitation; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology; D012189:Retrospective Studies; D016138:Walking