Abstract
BackgroundRecent research has proposed a classification of spinopelvic stiffness according to pelvic spatial orientation for risk stratification in patients who undergo total hip arthroplasty (THA). However, the influence of global alignment was not investigated, and this study evaluated the effect of global balance (sagittal vertical axis [SVA]) on spinopelvic motion.MethodsWe conducted a retrospective review of consecutive primary THA patients. We measured SVA, spinopelvic parameters (pelvic tilt [PT], pelvic incidence, and sacral slope), thoracic kyphosis (TK), lumbar lordosis (LL), proximal femur angle (PFA), and cup version using functional radiographs of patients in the standing and upright sitting positions. Linear regression was performed to identify parameters related to global trunk alignment change (∆SVA). Spinopelvic stiffness was defined as PT position change < 10°, and a subset of patients with PT change < 0° was categorized into a paradoxical spinopelvic motion group.ResultsOne hundred twenty-four patients were analyzed (mean age: 65 years, 61% female). In univariate regression analysis, ∆TK, ∆LL, and ∆PFA were correlated to ∆SVA. In multivariate regression analysis, ΔLL (p < 0.001) and ΔPFA (p < 0.001) were found to be correlated to ΔSVA (ΔSVA = − 11.97 + 0.05ΔTK – 0.23ΔLL – 0.17ΔPFA; adjusted R2 = 0.558). Spinopelvic stiffness was observed in 40 patients (32%), including five (4%) with paradoxical motion (∆PT = − 3° ± 1°, p < 0.001) with characteristics of balanced standing global trunk alignment (standing SVA = − 1.0 ± 5.1 cm), similar stiffness of the lumbosacral spine (∆LL = − 7° ± 5°), higher hip motion (∆PFA = − 78° ± 6°, p = 0.017), and higher anterior trunk shift (∆SVA = 6.2 ± 2.0 cm, p = 0.003) from standing to sitting as compared to the stiffness group. Two of these five patients experienced dislocation events after THA.ConclusionsThe lumbosacral and hip motions were the major contributors to global alignment postural change. Paradoxical motion is a rare but dangerous clinical condition in THA that might be related to a disproportionally large trunk shift in the stiff lumbosacral spine causing excessive hip motion. In paradoxical motion, diminishing functional acetabular clearance during position change might pose the prosthesis at higher risk of impingement and instability than spinopelvic stiffness.
Highlights
Recent research has proposed a classification of spinopelvic stiffness according to pelvic spatial ori‐ entation for risk stratification in patients who undergo total hip arthroplasty (THA)
Recent studies have revealed that the Lewinnek safe zone [1] cannot effectively predict dislocation after total hip arthroplasty (THA) [2, 3]
Spinopelvic radiographs were taken in patients after THA, including films taken in standing and upright relaxed sitting positions, from the cranial base proximally to the proximal femur distally
Summary
Recent research has proposed a classification of spinopelvic stiffness according to pelvic spatial ori‐ entation for risk stratification in patients who undergo total hip arthroplasty (THA). Recent studies have revealed that the Lewinnek safe zone [1] cannot effectively predict dislocation after total hip arthroplasty (THA) [2, 3]. In normal spinopelvic motion (Fig. 1), switching from standing to a sitting position will result in the flattening of the lumbar-sacral complex [4, 6,7,8]. This motion includes flexion (kyphosis) of the lumbosacral spine (about 25°-30°) [9], which leads to approximately 20° pelvis retroversion and increases the acetabulum’s anteversion by approximately 14° [10]. This will affect global trunk balance, resulting in an anterior shift of the body’s center of gravity [11,12,13] to reach a stable upright sitting position
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
