Variability in Acetabular Component Position in Patients Undergoing Direct Anterior Approach Total Hip Arthroplasty Who Have Concomitant Spine Pathology.

BACKGROUND

Hip instability following total hip arthroplasty (THA) can be a major cause of revision surgery. Physiological patient position impacts acetabular anteversion and abduction, and influences the functional component positioning. Osteoarthritis of the spine leads to abnormal spinopelvic biomechanics and motion, but there is no consensus on the degree of component variability for THAs performed by anterior approach. Therefore, we sought to present guidelines for changes in acetabular component positioning between supine and standing positions for patients undergoing primary THA by a uniform anterior approach.

METHODS

Perioperative patient radiographs of the pelvis and lumbar spine were collected. Images were used to determine acetabular component positioning and degree of coexisting spinal pathology, categorized as a Lane Grade (LG). Final analysis of variance was performed on a sample size of 643 anterior primary THAs.

RESULTS

From supine to standing position, as the severity of lumbar pathology increased the change in anteversion also increased (LG:0 = -0.11° ± 4.65°, LG:1 = 2.02° ± 4.09°, LG:2-3 = 5.78° ± 5.72°, P < .001). The mean supine anteversion in patients with absent lumbar pathology was 19.72° ± 5.05° and was lower in patients with worsening lumbar pathology (LG:1 = 18.25° ± 4.81°, LG:2-3 = 16.73° ± 5.28°, P < .001).

CONCLUSION

Patients undergoing primary THA by anterior approach with worsening spinal pathology have larger increases in component anteversion when transitioning from supine to standing positions. Consideration should be given to this expected variability when placing the patient's acetabular component.