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Original Article
- Proximal screw number and neck-shaft angle after locking plate fixation of proximal humerus fractures at a single center in Korea: a retrospective cohort study
- Dong Uk Jin, Se Ho Kang, Yeong Chan Kim, Kyu-Hak Jung, Sang-Pil So
- J Musculoskelet Trauma 2026;39(4):365-373. Published online October 20, 2026
- DOI: https://doi.org/10.12671/jmt.2026.00276
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Abstract
PDF - Background
The neck-shaft angle (NSA) may decrease between the immediate postoperative assessment and radiographic union after locking plate fixation of proximal humerus fractures. However, the relationship between the number of proximal humeral head screws and postoperative NSA remains unclear. This study compared postoperative NSA and the change in NSA (ΔNSA) among groups defined by the number of proximal screws.
Methods
This retrospective cohort study included consecutive patients who underwent locking plate fixation of a proximal humerus fracture between August 2025 and June 2026. Patients were classified into three groups according to the number of proximal screws: ≤7, 8, or 9. NSA was measured preoperatively, immediately postoperatively, and at radiographic union, hereafter referred to as the final assessment. Final NSA, ΔNSA, the proportions of patients with varus malalignment (final NSA <120°) and angular loss of reduction (ΔNSA ≤−10°), and complication rates were compared among groups. Trends across increasing screw numbers were also assessed.
Results
Nineteen patients were evaluated: nine in the ≤7-screw group, four in the 8-screw group, and six in the 9-screw group. Immediate postoperative NSA was 140.1°±5.7°, 136.2°±11.8°, and 134.0°±6.2° in the three groups, respectively; final NSA was 131.6°±9.2°, 129.5°±16.1°, and 130.2°±8.3°; and ΔNSA was −8.6°±8.8°, −6.8°±4.6°, and −3.8°±5.2°. None of these outcomes differed significantly among groups (all P>0.05). Varus malalignment occurred in 22.2%, 25.0%, and 16.7% of patients, respectively (P=0.944). Angular loss of reduction occurred in 44.4%, 25.0%, and 0%, respectively; neither the overall group difference (P=0.159) nor the trend across groups (P=0.056) reached statistical significance. Complication rates also did not differ significantly among groups.
Conclusions
In this small retrospective cohort, the number of proximal screws was not significantly associated with final NSA or ΔNSA. Although the proportion of patients with angular loss of reduction decreased numerically as the screw number increased, this trend was not statistically significant and should be regarded as exploratory. Level of evidence: III.
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