Ulnar lengthening for forearm deformities in hereditary multiple exostoses: a systematic review and meta-analysis (2015–2025)

Hamza Journal of Orthopaedic Surgery and Research https://doi.org/10.1186/s13018-026-06888-z (2026) 21:313 S YS T E M AT I C R E V I E W Journal of Orthopaedic Surgery and Research Open Access Ulnar lengthening for forearm deformities in hereditary multiple exostoses: a systematic review and meta-analysis (2015–2025) Mohamed Safwat Hamza1* Abstract Background Hereditary multiple exostoses (HME) is an autosomal dominant skeletal disorder frequently associated with progressive forearm deformities, including ulnar shortening, radial bowing, and radial head dislocation. Ulnar lengthening using distraction osteogenesis has become the principal surgical strategy; however, outcomes, techniques, and complication profiles vary across studies. This systematic review and meta-analysis synthesize contemporary evidence on radiographic correction, functional outcomes, and complications following ulnar lengthening for HME-related forearm deformities. Methods A systematic search of SciSpace, PubMed, and Google Scholar was performed to identify studies published between January 2015 and December 2025 evaluating ulnar lengthening in patients with HME. Observational studies reporting radiographic, functional, or complication outcomes were included. Data were extracted on patient characteristics, surgical techniques, radiographic parameters, functional outcomes, and complications. Study quality was assessed using the Newcastle–Ottawa Scale. Random-effects meta-analyses were conducted, with heterogeneity assessed using the I2 statistic. Results Thirty observational studies comprising 350 patients and 380 forearms were included, with a mean follow-up of 38.6 months. The pooled mean ulnar lengthening achieved was 33.8 mm (95% CI: 28.4–39.2; I2 = 68%). Significant improvements were observed in radial articular angle (mean difference − 6.3°, 95% CI: − 8.7 to − 3.9; I2 = 52%) and ulnar variance (mean difference − 15.4 mm, 95% CI: − 18.2 to − 12.6; I2 = 58%). Radial head reduction was achieved in 76% of affected forearms. Functional outcomes improved significantly, with DASH scores decreasing by a pooled mean of 12.7 points (p < 0.001). The overall complication rate was 18.1%, with most complications being minor and manageable. Conclusions Ulnar lengthening via distraction osteogenesis provides effective radiographic correction and meaningful functional improvement in patients with HME-related forearm deformities, with acceptable complication rates. Monolateral external fixation is the most commonly employed technique and yields reliable outcomes. Despite encouraging results, the evidence base is limited to observational studies with heterogeneous reporting, underscoring the need for prospective studies with standardized outcome measures and longer follow-up. *Correspondence: Mohamed Safwat Hamza Full list of author information is available at the end of the article © The Author(s) 2026. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Hamza Journal of Orthopaedic Surgery and Research (2026) 21:313 Page 2 of 15 Keywords Distraction osteogenesis, Forearm deformity, Hereditary multiple exostoses, Meta-analysis, Pediatric orthopedics, Radial head dislocation, Ulnar lengthening Introduction Hereditary multiple exostoses (HME), also known as hereditary multiple osteochondromas, is an autosomal dominant skeletal disorder characterized by the development of multiple cartilage-capped bony outgrowths arising from the metaphyseal regions of long bones during growth [1, 2]. The condition is most commonly caused by mutations in the EXT1 and EXT2 genes, which disrupt heparan sulfate biosynthesis and result in abnormal endochondral ossification [3]. Although many osteochondromas remain asymptomatic, their presence can lead to progressive skeletal deformities, limb length discrepancies, neurovascular compression, pain, and functional impairment, particularly during childhood and adolescence [4]. The forearm is among the most frequently and severely affected anatomical regions in patients with HME, with deformities reported in approximately 30–60% of cases [4–6]. The pathophysiology of forearm deformity is multifactorial and is primarily driven by differential growth inhibition of the ulna relative to the radius due to metaphyseal osteochondromas. Progressive ulnar shortening results in compensatory radial bowing, increased radial articular angle, distal radioulnar joint incongruity, and, in more advanced cases, radial head subluxation or dislocation [6–8]. These deformities can significantly impair forearm rotation, grip strength, and upper limb function, while also producing cosmetic deformity and, occasionally, chronic pain [7, 8]. The Masada classification system is widely used to categorize forearm deformities in HME based on the degree of ulnar shortening and the position of the radial head [9]. Type I deformities involve ulnar shortening without radial head displacement, whereas Type IIa and IIb deformities are associated with radial head subluxation and complete dislocation, respectively. This classification has important clinical implications, as increasing severity is associated with greater functional impairment, more complex surgical management, and a lower likelihood of spontaneous correction with growth [10, 11]. Historically, surgical management of HME-related forearm deformities focused on isolated osteochondroma excision, radial corrective osteotomy, or radial head excision. However, these approaches often failed to address the underlying ulnar shortening and were associated with high rates of persistent deformity, recurrent symptoms, and unsatisfactory functional outcomes [12–15]. Recognition of ulnar shortening as the primary driver of forearm deformity led to a paradigm shift toward ulnar lengthening as the cornerstone of surgical treatment. The introduction of distraction osteogenesis techniques, based on the principles described by Ilizarov, enabled gradual ulnar lengthening while allowing adaptive remodeling of bone and surrounding soft tissues [13]. Over the past two decades, ulnar lengthening using external fixation has become the preferred surgical strategy for symptomatic forearm def (...truncated)