Abstract
Introduction
The prevalence of the various patterns of spinopelvic abnormalities that increase the risk for prosthetic impingement is unknown. While prior surgery or lumbar fusion are recognized as a risk factors for postoperative dislocation, many patients presenting for THA do not have obvious radiographic abnormalities. The purpose of this study is to determine the prevalence of large posterior pelvic tilt (PPT) when standing, stiff lumbar-spine (SLL) and spino-pelvic sagittal imbalance (SSI) in patients undergoing primary THA.
Methods
A consecutive series of 1592 patients (56% female) over 2 years underwent functional analysis of spinopelvic mobility using CT, standing, and flexed seated lateral radiographs as part of pre-operative THA planning. The average age was 65 (20–93). We investigated the prevalence of these 3 validated spinopelvic parameters known to increase the risk for impingent and correlated them to the patient's age and gender using Chi squared analysis. Finally, the risk of flexion and extension impingement was modeled for each patient at a default supine cup orientation (DSCO) of 40°/20° (±5°).
Results
Overall, 221 hips (14%) had at least 1 risk factor for impingement, while 64 (4%) had 2, and 18 (1 %) had all 3 risk factors. The most common risk factor was large PPT (10%) followed by SLL (4%) and SSI (4%). Female gender was not associated with increased spinopelvic abnormalities (p = 0.64), but age > 75 years increased the likelihood of at least having 1 risk factor (p<0.01) (Table-1). Placing the cup within the DSCO resulted in observed prosthetic impingement in 792 patients (50%) (Fig-1). 158 hips (20%) had at least 1 risk factor, while 56 (7%) had 2, and 16 (2 %) had all 3 risk factors for impingement. Posterior pelvic tilt was associated with extension impingement risk, while SLL and SSI increased flexion impingement risk.
Conclusion
Spinopelvic risk factors that increase impingement risk are not infrequent in THA patients. We observed 50% prosthetic impingement when a single target for acetabular orientation target was applied.
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