Abstract
Introduction
The pelvis moves in the sagittal plane during functional activity. These movements can have a detrimental effect on functional cup orientation. The authors previously reported that 17% of total hip replacement (THR) patients have excessive pelvic rotation preoperatively. This increased pelvic rotation could be a risk factor for instability and edge-loading in both flexion and/or extension. The aim of this study was to investigate how gender, age and lumbar spine stiffness affects the number of patients at risk of excessive sagittal pelvic rotation.
Method
Pre-operatively, 3428 patients had their pelvic tilt (PT) and lumbar lordotic angle (LLA) measured in three positions; supine, standing and flexed-seated, as part of routine planning for THR. The pelvic rotation from supine-to-standing and from supine-to-seated was determined from the difference in pelvic tilt measurements between positions. Lumbar flexion was determined as the difference between LLA standing and LLA when flexed-seated. Patients were stratified into groups based upon age, gender and lumbar flexion. The percentage of patients in each group with excessive pelvic rotation, defined by rotation ≥13° in a detrimental direction, was determined.
Results
Posterior pelvic rotation from supine-to-stand increased with age and decreasing lumbar flexion. This was more pronounced in females. Similarly, anterior pelvic rotation from supine-to-seated increased with age and decreasing lumbar flexion. This was more pronounced in males. Notably, 30% of elderly females had excessive pelvic rotation. Furthermore, 38% of patients with lumbar flexion <20° had excessive pelvic rotation.
Conclusions
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Excessive pelvic rotation was more common in older patients and in patients with limited lumbar flexion. This might be a factor in the increased dislocation rate in the elderly population.
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A more stable articulation might be a consideration in patients with limited lumbar flexion (<20°). This constitutes 5% of the THR population.
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The large range of pelvic rotation in each group supports individual analysis on all patients undergoing THR.
