The influence of femoral head size following total hip replacement and hip resurfacing on hip biomechanics during walking, stair use and sit-to-stand

Ewen, Alistair (2013) The influence of femoral head size following total hip replacement and hip resurfacing on hip biomechanics during walking, stair use and sit-to-stand. Doctoral thesis, Northumbria University.

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Abstract

Due to geometrical features, it is claimed that larger femoral heads in total hip replacement (THR) are superior in achieving normal biomechanics than smaller ones; and that hip resurfacing (RSF) is superior to THR. This has not been conclusively proven. Most studies have investigated level walking, which may not be demanding enough to highlight what could be small biomechanical differences between implants. Few biomechanical studies have compared more demanding tasks and not with patients with different femoral head sizes or RSF.

This thesis aimed to address these omissions by investigating level walking, stair descent and sit-to-stand (STS) biomechanics between three groups (32mm THR, 36mm THR and RSF). Twenty-six osteoarthritis patients were recruited and tested pre-operatively, then three and twelve months post-operatively. Demographic differences between groups were expected due to patient considerations for different implants, so a study was performed to determine whether level walking biomechanics alter progressively during the aging process with a group of 63 healthy participants. Three matched sub-groups were extracted from this group as controls.

There was no suggestion that gait deteriorates progressively with age. Hip reconstruction, irrespective of head size, can allow patients to return to the biomechanical levels of controls during level walking. Stair descent differences remained 12 months post-operatively in cadence (p=0.042) and peak hip power generated (p<0.001) compared to controls. The 32mm group exhibited vertical ground reaction force (vGRF) asymmetry pre-operatively (p<0.001) and 3 months post-operatively (p=0.013); and impulse asymmetry (p<0.001) pre-operatively during STS. The 36mm group exhibited impulse asymmetry (p=0.05)three months post-operatively.

This thesis is the first biomechanical analysis of stair descent and STS of two THR groups and a RSF group. It has demonstrated stair descent differences at 12 months post-operatively and overloading of the healthy limb in some THR patients. The latter could be problematic for the healthy limb.

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