Beyond the incision: Does release extent matter in congenital muscular torticollis? A systematic review

To compare clinical outcomes after unipolar versus bipolar sternocleidomastoid (SCM) release for congenital muscular torticollis (CMT), and to describe how patient age, chronicity, and postoperative rehabilitation varied across studies and may have contributed to between study differences.

Following PRISMA guidelines, 17 observational studies were included, comprising 382 surgical procedures (unipolar 228; bipolar 154). The primary outcome was achievement of a global good-excellent clinical result using validated composite scoring systems (Lee, Cheng-Tang, Tanabe, or Lee-Kang). Secondary outcomes were recurrence and complications. Comparative quantitative synthesis was restricted to studies reporting both techniques within the same cohort and extractable technique-specific data. For recurrence, comparative quantitative synthesis was feasible in two cohorts. For global good-excellent outcome, head-to-head data were too sparse and confounded for a robust pooled comparison, and evidence remained descriptive. Heterogeneity was assessed using I².

Only a small number of studies provided extractable head-to-head comparisons. In these cohorts, no statistically significant difference was observed between unipolar and bipolar release in achieving a good-excellent global clinical outcome, and recurrence rates did not differ significantly between techniques, although confidence intervals were wide and events were sparse. Across single-arm cohorts, both techniques were associated with high rates of good-excellent outcomes and low recurrence, with greater variability observed in bipolar cohorts that more frequently included older or neglected cases. Complications were uncommon overall and were predominantly minor; technique-stratified reporting suggested a higher frequency of minor complications following bipolar release. Where reported, cervical alignment and range of motion improved substantially after both procedures, with no consistent radiographic advantage of one technique over the other. Across studies, postoperative rehabilitation intensity and patient chronicity appeared to influence durability of correction at least as much as release extent.

Within the limits of available observational evidence, unipolar and bipolar SCM release yield comparable global clinical outcomes with low recurrence and complication rates. No consistent comparative advantage of greater release extent was demonstrated. Between-study differences may also reflect variation in patient age, deformity chronicity, and postoperative rehabilitation. Comparative certainty remains limited by small head-to-head cohorts, heterogeneous outcome definitions, and incomplete arm-level reporting.