Implications of Spinopelvic Mobility on Total Hip Arthroplasty: Review of Current Literature

Abstract

Understanding the impact of pathologic spinopelvic mobility on total hip arthroplasty instability requires an appreciation of the dynamic interplay between and the spine, hip and pelvis. This complex interdependent relationship changes with position, pathology and surgical intervention. Spinal pathology may prevent normal dynamic motion leading to spinopelvic stiffness and abnormal pelvic position. Patients at high risk for pathologic spinopelvic motion and subsequent total hip arthroplasty (THA) dislocation should be assessed with a functional imaging series with lateral standing, sitting and AP standing radiographs. Common patterns of stiffness and imbalance as well as proposed surgical treatment algorithms are presented and discussed in this review.

Keywords: Total hip arthroplasty; acetabular anteversion; adult spinal deformity; dislocation; flatback; pelvic tilt; spinopelvic mobility.

Figure 1.

Lateral standing (top row) and sitting (bottom row) spinopelvic radiographs showing the three classes of pelvic stiffness. Pelvic tilt (white arrows), sacral tilt (black arrows at L5–S1), and ante-inclination (black arrows measuring the cup angle) measured 9° posterior, 26°, and 39°, respectively, on the standing radiographs and 21° posterior, 12°, and 57° on the sitting radiographs of the patient with a stiff pelvis; 3° posterior, 35°, and 27° on the standing radiographs and 32° posterior, 3°, and 62° on the sitting radiographs of the patient with a normal range of pelvic tilt; and 14° anterior, 56°, and 27° on the standing radiographs and 32° posterior, 14°, and 73° on the sitting radiographs of the patients with a hypermobile pelvis.7#x201D; Permission from Kanawade, V., L.D. Dorr, and Z. Wan, Predictability of Acetabular Component Angular Change with Postural Shift from Standing to Sitting Position. J Bone Joint Surg Am, 2014. 96(12): p. 978–986.

Figure 2.

Standing lateral radiograph showing a surgical fusion in lordosis indicated by a sacral slope (SS) of 38°. Figure 2B Sitting lateral radiograph showing a fused spine with a sacral slope of 39o, which means that the pelvis is fixed in anterior tilt; an acetabular cup that does not open, with a cup ante-inclination (AI) of 32o in both positions; and a femur in relative hyperflexion, indicated by a pelvic-femoral angle (PFA) of 102°, to compensate for a pelvis that does not tilt posteriorly during sitting. The sitting combined sagittal index (CSI) is low (134°: 32° + 102°), which is predictive of anterior impingement.” Permission from Heckmann N, et al. Late Dislocation Following Total Hip Arthroplasty: Spinopelvic Imbalance as a Causative Factor. J Bone Joint Surg Am. 2018;100(21):1845–1853.

Figure 3.

Standing lateral radiograph showing loss of lumbar lordosis and a posterior position of the pelvis as indicated by a sacral slope (SS) of 14°. The femur is in hyperextension relative to the pelvis as indicated by a pelvic-femoral angle (PFA) of 215°. A standing combined sagittal index (CSI) of 249° (34° + 215°) is predictive of posterior impingement. Figure 3B Sitting lateral radiograph showing relative kyphosis of the spine indicated by a sacral slope of 3°. The sitting combined sagittal index is 188° (47° + 141°), which is within the normal range.” Permission from Heckmann N, et al, Late Dislocation Following Total Hip Arthroplasty: Spinopelvic Imbalance as a Causative Factor. J Bone Joint Surg Am. 2018;100(21):1845–1853.

Figure 4.

(A) Preoperative standing lateral image of a patient with severe posterior pelvic tilt (APP, yellow). (B) Templated cup position of 40° of inclination and 20° of anteversion relative to the APP (or traditional bony landmarks intraoperatively) leads to functional cup position of 45° of inclination and 38° of anteversion when the patient stands. (C) After accommodating for the patient's posterior pelvic tilt in the functional (standing) position, placement of the cup in 35° of inclination and 2° of anteversion relative to the APP will lead to a cup position of 40° of functional inclination and 20° of functional anteversion relative to the coronal plane when standing.” Permission from Luthringer TA, Vigdorchik JM. A Preoperative Workup of a “Hip-Spine” Total Hip Arthroplasty Patient: A Simplified Approach to a Complex Problem. J Arthroplasty. 2019.