Ulnar lengthening in multiple hereditary exostosis with forearm deformity-A long-term follow-up study

Bing Zeng¹Han Xiao²An Yan²Kun Liu²Mi Zhou^3*Haibo Mei^2*

• ¹The First Affiliated Hospital of Jinan University, Guangzhou, China
• ²Hunan Children's Hospital, Changsha, China
• ³The First People's Hospital of Changde City, Changde, China

Purpose: Ulnar lengthening surgery for multiple hereditary exostosis (MHE) with radial head dislocation can achieve satisfactory reduction in the short term, its long-term efficacy remains controversial. We aim to investigate the long-term effects of ulnar lengthening on forearm deformity, functional improvement, and radial head dislocation in pediatric patients. Methods: We conducted a retrospective study of patients with MHE who underwent ulnar lengthening procedures at Hunan children's hospital between 2010 and 2020. The radial articular angle (RAA), ulnar variance (UV), radial variance (RV) and range of motion of the affected forearm and elbow were clinically assessed before surgery and at the last follow-up. The total ulna lengthening distance (LD) and radiographic outcome were also recorded. Results: There were six girls and six boys with 12 forearms involved. The average age was 7.6 ± 2.9 years. The average follow-up time was 63.8 ± 15 months. The mean LD was 2.5 ± 0.7 cm, while the duration of distraction was 141 ± 62.5 days. At the last follow-up, the ulnar length percent, UV, RV, and RB were improved statistically significant. The pre-ulnar length percent was 0.91 ± 0.05, while the postulnar length percent was 1.0 ± 0.08 (p < 0.001). The pre-UV was -1.1 ± 0.5, while the post-UV was -0.4 ± 0.5 (p < 0.001). The pre-RB was 8.8 ± 1.2, while the post-RB was 7.6 ± 1.4 (p < 0.001). The pre-RV was 0.7 ± 0.6, while the post-RV was 0.4 ± 0.8 (p = 0.02). Postoperative assessment revealed improved forearm supination and elbow pronation mobility to varying extents after ulnar lengthening procedure. The pre-supination was 56° ± 10.0°, while the post-supination was 67° ± 9.4° (p < 0.001). The pre-pronation was 54° ± 9.3°, while the post-pronation was 65° ± 7.8° (p = 0.003). One pin-track infection was recorded. Conclusions:Early ulnar lengthening surgery remains a reliable treatment option for patients with MHE who develop severe forearm shortening secondary to ulnar involvement.