Background: Obstetric brachial plexus injury (OBPI) can cause long-term functional limitations due to muscle imbalance and progressive skeletal deformity. Secondary shoulder deformities such as internal rotation contracture, glenoid dysplasia, and humeral head subluxation are challenging to treat once bony remodeling occurs. The triangle tilt procedure reorients the distal acromioclavicular complex to allow improved glenohumeral congruency.

Aim: To evaluate the functional and radiographic outcomes of the triangle tilt procedure in pediatric patients with OBPI-related secondary shoulder deformities.

Materials and Methods: Fifty children (29 males, 21 females; mean age 7.2 years) with OBPI and documented glenohumeral dysplasia underwent the triangle tilt procedure between January 2021 and December 2023. Functional outcomes were assessed using the Mallet score preoperatively and at 12 months postoperatively. Radiographic parameters included glenoid version and percentage of humeral head anterior to the scapular line (PHHA), measured on CT or MRI scans. Statistical analysis was performed using paired t-tests with p < 0.05 considered significant.

Results: The mean Mallet score improved from 12.8 ± 1.4 preoperatively to 17.9 ± 1.2 postoperatively (p < 0.001). Mean glenoid version improved from −25.6° ± 5.2 to −15.3° ± 4.8 (p < 0.001), and PHHA improved from 29.4% ± 6.7 to 47.1% ± 7.2 (p < 0.001). No major complications such as infection, neurovascular injury, or re-dislocation were observed.

Conclusion: The triangle tilt procedure significantly improves both functional and radiographic parameters in children with OBPI-related secondary shoulder deformities. Early surgical correction after skeletal remodeling may prevent further degenerative changes and improve long-term upper limb function