DOES REPLICATION OF NATIVE ACETABULAR ANATOMY SATISFY HIP-SPINE ALGORITHM PLANS FOR CUP ORIENTATION?

Patient-specific planning algorithms accounting for the hip-spine interaction are available for surgeons to use to minimize impingement- and dislocation- risk. Whether replicating native anatomy, such as the Transverse-Acetabular-Ligament (TAL), leads to satisfactory cup orientation is unknown. This study aims to assess whether replication of native anatomy, particularly TAL, would lead to cup orientation in line with hip-spine recommendations in patients, with and without adverse spinopelvic characteristics. 100 patients, pre-THA, that underwent detailed spinopelvic assessment [pre-op CT pelvis/femurs, spinopelvic radiographs (supine, standing and deep-seated)] was studied. The cohort comprised of 50 patients without any adverse spinopelvic characteristics and 50 patients with adverse characteristics [spinopelvic imbalance (PI-LL>20) & high PTstanding (>19°) & and lumbar stiffness (segmented to determine native acetabular anatomy, including TAL version, relative to the horizontal (Functional-version) and Anterior-Pelvic-Plane (Morphological-version). Native anatomy was compared to pre-operative plans as per 1. Patient-Specific-Instrumentation (PSI) planning considering impingement and edge-loading algorithms-; 2) Optimum-Combined-Sagittal-Index (CSIstanding: 205–245°). Native morphological anatomy was similar between groups for inclination (51°±8 vs. 50°±8; p=0.4) and version (19°±6 vs. 18°±8; p=0.7). However, functional version was different (15°±6 vs. 21°±7; p higher by 12°±5 (p non-adverse group (7°±7). Aiming for replication of TAL version and 40° radiographic inclination, satisfied CSIstanding in 98% of cases for both groups. Replication of TAL version and radiographic inclination of 40° would lead to satisfactory orientation in almost all patients, including those with adverse spinopelvic characteristics. Tools to improve accuracy and precision (consistency in achieving target) are necessary as visual aids such as TAL are not always clearly visible and might be erroneously interpreted intra-operatively.