Failure of hydroxyapatite-coated acetabular cups. Ten-year follow-up of 85 Landos Atoll arthroplasties.

Between March 1990 and May 1991 we performed 85 primary total hip replacements in 74 patients using the Landos Atoll hydroxyapatite (HA)-coated cup and the Corail HA-coated stem. The patients were followed up for a mean of ten years. Of the 85 cups, 26 (31%) have already been revised and a further six are radiologically unstable and awaiting revision. Two femoral stems have been revised for infection without loosening. The retrieved acetabular cups were studied by SEM and image-processing techniques to quantify the amount of residual HA on the cup. This was correlated with the clinical variables and modes of failure. The residual HA (as a percentage of the surface) on the loose cups correlated negatively with the duration of implantation (r = -0.732, p < 0.001). Six cups were stable at revision and had more residual HA coating than those which were loose (p < 0.01). The rate of failure of the Landos Atoll HA-coated, smooth hemispherical cup with screw fixation is unacceptably high. Resorption of the HA coating is markedly increased in loose cups compared with stable cups. HA coating cannot substitute for stable mechanical fixation.

Effects of a functional electrical stimulation-assisted leg-cycling wheelchair on reducing spasticity of patients after stroke.

OBJECTIVE: To determine whether short-term propulsion of a functional electrical stimulation-assisted leg-cycling wheelchair (FES-LW) in patients with stroke can reduce spasticity of the affected leg and whether FES has additional effects on reducing spasticity. DESIGN: Within-subject comparison. SUBJECTS: A total of 17 patients after stroke were recruited from the university hospital. METHODS: Subjects propelled 2 leg-cycling wheelchairs (the FES-LW and the LW) and a manual wheelchair along an oval pathway. The Modified Ashworth Scale (MAS), H reflex/maximal M response (H/M ratio) and relaxation index were used to evaluate the immediate effects on leg spasticity. The changes in MAS, H/M and relaxation index were used to evaluate the effect of FES in comparing 2 leg-cycling wheelchairs. RESULTS: The MAS and H/M ratio were significantly decreased and the relaxation index significantly increased by FES-LW and LW usage. For subjects with higher muscle tone, significant lowering of the changes in MAS, H/M ratio and higher relaxation index were found for FES-LW usage compared with LW usage. CONCLUSION: Leg spasticity is reduced after short-term propulsion of the FES-LW and LW. The application of FES has an additional effect on reducing spasticity in subjects with higher muscle tone.