Response to Letter to the Editor on “Effects of Sagittal Spinal Alignment on Postural Pelvic Mobility in Total Hip Arthroplasty Candidates”

Abstract

To the Editor Considerable attention was given to the study by Buckland et al [1] on postural changes in the pelvis based on pelvic incidence (PI)e lumbar lordosis (LL), which are as follows: >10 (flat back), À10 to 10 (balanced sagittal alignment), and <À10 (hyperlordosis). They concluded that patients with hyperlordosis likely utilize their spines, whereas patients with flat back use their hips. Definitions of "physiological" and "nonphysiological" spinopelvic conditions should be considered. Physiological states are defined based on the anatomical parameters of PI and anatomical acetabular anteversion angle (AAA) [2]. A small PI and high anatomical AAA are associated with a low LL and small sagittal pelvic range of motion during sitting or squatting, making patients use more of each hip's cone of mobility (physiological hip users) [2]. However, patients with a large PI and small anatomical AAA are likely to have a high LL and large sagittal pelvic range of motion using more of the flexible spine during postural changes (physiological spine users) [2]. Therefore, as shown by Buckland et al [1], balanced sagittal alignment may be "physiological states." Considering the lumbopelvic complex, nonphysiological states are determined through positional parameters: LL and positional AAA [3]. Patients having very small PI and acetabular undercoverage are considered to have a "pathoanatomy" and are likely to have a fixed flexion deformity of the hip resulting in decreased positional AAA [4]; therefore, pelvic anteversion and its associated increased LL (nonphysiological spine users) are required. In patients with high PI and stiff degenerated spine, decreased LL and its associated pelvic retroversion are noted, resulting in high positional AAA (nonphysiological hip users) [3]. Therefore, as described by Buckland et al [1], the spine users with hyperlordosis and hip users due to flat back may be in "nonphysiological states." In conclusion, future research should focus not only on sagittal spinopelvic kinematics but also on AAA to further understand hip anatomy and its relation to the development of hip osteoarthritis.

The Accuracy of Patient-Specific Instrumentation with Laser Guidance in a Dynamic Total Hip Arthroplasty: A Radiological Evaluation

“…The component positioning and dynamic function are being extensively studied as significant factors in THA stability and survival [ 9 , 19 , 23 , 24 ]. The current literature focuses on understanding individual lumbopelvic sagittal kinematics and the relationship with functional cup alignment during daily life activities [ 13 , 25 , 26 , 27 ].…”