Differentiating Spinal Deformity Versus Leg Length Discrepancy in Patients With Pelvic Obliquity : Systematic Review of Diagnostic Methods, Imaging, and Clinical Management

Systematic review, PROSPERO ID: (CRD42023112392). We aim to provide physicians with an evidence-based stepwise approach to distinguishing the primary cause of plane pelvic obliquity (PO) to guide treatment. PO is a frequent clinical finding in both spinal deformity (SD) and leg length discrepancy (LLD) but distinguishing between these etiologies remains challenging due to overlapping clinical and radiographic features and potential multifactorial origins. Misdiagnosis may delay care and worsen patient outcomes. PubMed, Embase, Scopus, and Web of Science were searched from inception to July 2025 for English-language studies evaluating coronal PO in the context of LLD and/or SD that explicitly compared or differentiated limb-origin from spine-origin obliquity using radiographic, advanced imaging, or validated clinical assessments and reported diagnostic accuracy, discriminative features, or management impact. Two reviewers independently screened studies, extracted data, and performed ROBINS-I risk assessment and Newcastle-Ottawa Scale quality assessment. Owing to marked heterogeneity in populations, measurement protocols, and thresholds, findings were synthesized qualitatively with stratification by age group where possible. Of 436 records, 24 cohort studies met the inclusion criteria. Standing anteroposterior (AP) radiographs reliably quantified both LLD and PO, while advanced imaging provided high reproducibility for subtle or ambiguous cases. Radiographic block or shoe lift correction tests distinguished limb-origin and spine-origin PO through immediate postural correction. Key discriminators included a lumbar curve or PO resolving with block/lift correction suggesting LLD, versus persistent deformity despite correction suggesting spinal etiology. Difficulty remains in diagnosing and treating mixed etiology patients. Accurate differentiation of spinal versus limb-driven PO begins with a structured diagnostic approach. AP radiographs, followed by functional block tests, and advanced imaging, may increase diagnostic confidence and decrease unnecessary interventions. Particularly in patients with both LLD and coronal plane SD, prospective studies are required to standardize measurement protocols and improve long-term outcomes. Level IV.