Do increasingly unstable balance devices provide a graded challenge to bipedal stance in total hip arthroplasty patients?

Background: Progressive balance exercises are critical to early functional rehabilitation after total hip arthro-plasty (THA) but little is known regarding the challenge imposed by common balance devices. Research question: Do progressively unstable balance devices provide a graded challenge to bipedal stance during early functional rehabilitation in THA patients?Methods: Postural control was evaluated in 42 patients (age, 63.7 +/- 9.6 years; height, 1.72 +/- 0.08 m and body mass, 78.9 +/- 14.6 kg) approximately 3 weeks (23 +/- 6 days) following unilateral primary THA. Patients were divided into two groups, based on their ability to complete a 20-second unipedal stance test (UPST) on the operated limb. A lumbar mounted inertial sensor monitored center of mass (COM) displacement during bipedal balance conditions involving three balance pads of progressive stiffness and an oscillatory platform, used in isolation and in combination with the most stable balance pad. COM displacement was normalised to bipedal stance on a hard surface. Differences between conditions and patient groups were assessed using a mixed-model analysis of variance.Results: Twenty patients (48%) were able to complete the UPST on their operated limb. There was a significant effect of balance condition on COM displacement during bipedal stance (F4,160 = 82.6, p < .01). COM displacement was lowest for the oscillatory platform but increased non-linearly across the three balance pads (p < .05). There was no significant difference in COM displacement between THA patients able and unable to complete the UPST.Significance: Increasingly compliant balance pads provided a progressive, though nonlinear, challenge to bipedal balance control in THA patients that was greater than that of an oscillating platform and independent of the ability to stand independently on the operated limb. These findings serve as a guide for the design of progressive training programs that enhance balance in THA patients.