Predictors of Cubitus Varus After Paediatric Supracondylar Humerus Fracture: A Structured Review of The Evidence

Abstract

Background: Cubitus varus is the commonest late complication of paediatric supracondylar humerus fracture (SCHF) and can cause late instability and ulnar neuropathy. Which factors predict it remains uncertain.

Methods: A structured review was conducted under PRISMA 2020 reporting principles. The Crossref and Europe PMC databases and the open web were searched for clinical studies and meta-analyses reporting cubitus varus, or its intermediate step, loss of reduction, by patient, fracture or treatment factor. Data were extracted from the abstracts and open-access full texts that could be retrieved. Odds ratios (OR) were calculated from 2 × 2 data where available. Findings were synthesised narratively by predictor following the SWiM guideline, and certainty was rated with GRADE for prognostic factors.

Results: Fifteen sources were included: twelve primary studies (three randomised trials and nine cohort studies; 985 children) and three meta-analyses of pin configuration. Reported incidence of cubitus varus ranged from 2.5% (2 of 79, mean follow-up more than 6 years) to 8.8% (3 of 34), and was about 2% in pooled pinning series. Severity of injury (Gartland grade), posteromedial (medial) displacement and medial column comminution were the most consistent fracture-related predictors. Posteromedial displacement was associated with greater carrying-angle loss (15° vs 8.8°, P = 0.019), and medial comminution with change in Baumann angle (adjusted OR 4.15, 95% CI 1.25–13.80). For Gartland type II fractures, casting rather than pinning was associated with more loss of reduction (OR 4.28, 95% CI 1.20–15.22), and in a matched cohort cubitus varus occurred only after casting (2 of 41 vs 0 of 38), although a larger cohort with short follow-up found similar rates of Baumann-angle malunion (13.5% vs 15.2%). In fractures with medial column impaction, casting left a smaller carrying angle than pinning (3.3° vs 11.9°). Pin configuration did not clearly affect cubitus varus (about 2% with either lateral or crossed pins), although crossed pins reduced loss of reduction in randomised trials (RR 0.70, 95% CI 0.52–0.94). Evidence for age, sex and side was sparse and inconsistent. Certainty was low to very low for every predictor.

Conclusion: Cubitus varus after SCHF appears to be driven mainly by fracture instability on the medial side and by failure to achieve or hold reduction, rather than by patient characteristics. Medial displacement and medial comminution should prompt stable fixation and careful checking of the Baumann angle. A definitive, registered meta-analysis of individual-level data using a standard definition of cubitus varus is needed.