REVISION FOR DISLOCATION FOLLOWING PRIMARY THR: THE RELATIONSHIP BETWEEN SURGICAL APPROACH AND FEMORAL HEAD SIZE. A TEN-YEAR ANALYSIS FROM THE NEW ZEALAND JOINT REGISTRY

Background The New Zealand Joint Registry was started in 1999. An audit in 2009 showed 98% compliance. Ten year results were published in 2009. For Total Hip Replacement it showed that dislocation was the most common cause for revision (35%). Methods We reviewed the rate of revision for dislocation in the two most common diagnostic groups, Osteoarthritis (86%) and Acute Fracture NOF (3.6%) relative to the two most common surgical approaches, posterior and lateral. We also sought to analyse whether larger femoral head sizes decreased the dislocation rate. Results In Osteoarthritis there was a highly significant increase (p Conclusion This review confirms that the posterior approach has a significantly higher revision rate for dislocation over the lateral approach in osteoarthritis. The posterior approach shows a significant advantage for the 36mm head over 22 and 28mm, but the rate for the 36mm head posterior was virtually the same as for a 28mm head via the lateral approach. Larger diameter heads could lead to later revision from greater volumetric wear, increased frictional torque and thinner poyethylene liners and should be used with caution. To reduce dislocation in osteoarthritis the lateral approach should be considered.