The Kinetic Relationship between Sitting & Standing Posture & Pelvic Inclination. A. Stephens, S. Munir, S. Shah, W.L Walter The Specialist Orthopaedic Group, Sydney Australia ISOC Mexico City 2014

I declare that in the past three years I have: held shares in: N/A received royalties from: Stryker done consulting work for: Stryker/ Ceramtec/ Depuy/ Matortho given paid presentations for: Ceramtec received institutional support from: Depuy, Stryker Signed: A/P Bill Walter

Chair rising

dislocation

loading patch

Consequences of edge loading Ceramic-ceramicMetal-metalpolyethylene Squeaking +++- Wear Rim breakage +-+ Late dislocation --++

Edge loading

Case 1: High Metal Wear Max depth 90  m, Volume 66 mm 3

Fatigue failures of retrieved highly crosslinked UHMWPE acetabular liners Furmanski, Pruitt et al., AAOS 2008

56 Trident cups 28mm MoP 2 to 5 years Linear head penetration rate from AP X-ray 40% increase in linear poly wear in cups > 45deg inclination

Study Design Measurements: Clinical Hip flexion /Fixed flexion Hip flexion on XR Anterior pelvic plane on lateral radiographs Lower lumbar lordosis cobb angle Demographics N=60 30 male / 30 female Mean Age 63.2 (37 – 93)years Hip osteoarthritis Exclusion criteria Previous fractures Revision THA Long spinal fusion Patients without preoperative sitting and standing films

Posterior tilt No tilt Anterior tilt

Cobb angle change

Introduction Safe Zone of Lewinnek 40 inclination/ 20 anteversion of cup Individual differences to pelvic tilt in sitting and standing Influence acetabular version Aim To describe the influence of sitting and standing posture on sagittal pelvic inclination

Posterior tilt No tilt Anterior tilt

Pelvis motion standing to sitting -40° -20° 0° 20° 40°

Pelvis motion standing to sitting -40° -20° 0° 20° 40°

Results lordosis degrees < Standing Anterior tilt Posterior tilt lordosis < > 100 degrees Sitting

CONCLUSION Pelvic orientation changes from standing to sitting Stiff hips tend to tilt the pelvis posteriorly from standing to sitting The degree of tilt may be measured on lateral sitting and standing films This has implications for cup version during total hip arthroplasty Hip flexion Hip flexion range degree Anterior tilt Posterior tilt

Next questions. What happens after hip replacement? Does the pelvic motion change?