Gradual ulnar lengthening in Masada type I/IIb deformity in patients with hereditary multiple osteochondromas: a retrospective study with a mean follow-up of 4.2 years

Li et al. Journal of Orthopaedic Surgery and Research https://doi.org/10.1186/s13018-020-02137-z (2020) 15:594 RESEARCH ARTICLE Open Access Gradual ulnar lengthening in Masada type I/IIb deformity in patients with hereditary multiple osteochondromas: a retrospective study with a mean follow-up of 4.2 years Yuchan Li*† , Zhigang Wang†, Mu Chen and Haoqi Cai Abstract Background: Gradual ulnar lengthening is the most commonly used procedure in the treatment of Masada type I/ II deformity in patients with hereditary multiple osteochondromas. However, the treatment remains controversial for the recurrence of deformity in growing children. This study aims to evaluate the clinical and radiological outcomes of ulnar gradual lengthening in our clinic. Methods: We retrospectively reviewed patients who underwent ulnar lengthening by distraction osteogenesis from June 2008 to October 2017. The carrying angle (CA) and range of motion (ROM) of the forearm and elbow were clinically assessed, and the radial articular angle (RAA) and ulnar shortening (US) were radiologically assessed before lengthening, 2 months after external frame removal, and at the last follow-up. Results: The current study included 15 patients (17 forearms) with a mean age of 9.4 ± 2.3 years at the index surgery. The mean follow-up period was 4.2 ± 2.4 years. There were 9 patients (10 forearms) with Masada type I deformity and 6 patients (7 forearms) with Masada type IIb deformity. The mean amount of ulnar lengthening was 4.2 ± 1.2 cm. The mean RAA improved from 37 ± 8 to 30 ± 7° initially (p = 0.005) and relapsed to 34 ± 8° at the last follow-up (p = 0.255). There was a minimal deterioration of US yet significant improvement at the last follow-up compared to pre-op (p < 0.001). At the last follow-up, the mean forearm pronation and elbow flexion increased significantly (p < 0.001 and p = 0.013, respectively), and the mean carrying angle also improved significantly (p < 0.001). No patient with type IIb deformity achieved a concentric radial head reduction. Conclusions: Gradual ulnar lengthening significantly reduces cosmetic deformity and improves function in patients with Masada type I/IIb deformity. Our results supported early ulnar lengthening for patients with a tendency of dislocation of the radial head. Keywords: Gradual ulnar lengthening, Forearm deformity, Radial head dislocation, Recurrence, Hereditary multiple osteochondromas * Correspondence: † Yuchan Li and Zhigang Wang contributed equally to this work and should be considered as co-first authors. Department of Pediatric Orthopedics, Shanghai Children’s Medical Center, Shanghai Jiao Tong University School of Medicine, 1678 Dongfang Road, Shanghai 200127, People’s Republic of China © The Author(s). 2020 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/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. (2020) 15:594 Page 2 of 8 Background Hereditary multiple osteochondromas (HMO) is an autosomal dominant condition characterized by multiple benign cartilage-capped tumors, which typically occur at the juxta-epiphyseal region of the tubular bones. Forearm deformities resulting from tumorinduced growth disturbances of the proximal and distal radial and the distal portion of the ulna are common, with a prevalence of 40–74% of HMO patients [1]. Masada et al. classified forearm deformities into three types [2]. In type I, the main osteochondroma is located in the distal ulna and results in ulnar shortening and ulnar deviation at the wrist, with a secondary bowing radius often observed. Type II is ulnar shortening with a dislocated radial head; this type can be further divided into two subgroups: type IIa (proximal radial osteochondroma involved) and type IIb (no proximal radial osteochondroma involved). In type III, the main osteochondroma involves the distal part of the radius with a relative shortening of the radius. Because of the crosssectional diameter of the distal ulnar physis being smaller than the radius, the ulna is more vulnerable to growth impairment [2], and therefore, type I and type II are more common. A shorter proportional ulnar length is associated with a diminished range of motion of the forearm in type I, while in type II, the deformities result in the restriction of both elbow movement and forearm rotation [1, 2]. Gradual ulnar lengthening has been widely used with successful reported results in managing forearm deformity [3–7]. However, the treatment remains controversial. The current study aims to evaluate our mid-term clinical and radiological outcomes of gradual ulnar lengthening for Masada type I/II deformity, and we hypothesized that simple gradual ulnar lengthening would effectively improve the cosmetic problems and forearm function for Masada type I/II deformity. radiological assessment included the radial articular angle (RAA) [8], as measured on the anteroposterior (AP) radiograph, and ulnar shortening (US), as measured on the lateral radiograph (Fig. 1); these data were recorded before lengthening, 2 months after the external frame removal, and at the last follow-up. The concentric reduction was defined as a line drawn through the center of the radial neck and should extend directly through the center of the capitellum both on the AP and lateral radiographs. The operative procedure included gradual ulnar lengthening with an external fixator and/or excision of the distal ulnar osteochondroma. The lengthening began 10 days after the surgery with distraction at a rate of 0.75 mm/day. The anticipated lengthening should meet the two following criteria. Proximally, the radial head should pull the trochlear notch of the ulna, while distally, the positive ulnar variance should be obtained by overlengthening at 5–10 mm. The obtained lengthening was measured and recorded on a lateral film on the last day of lengthening. The parametric Kolmogorov-Smirnov test was used to check for normal distribution of the data. A one-way analysis of variance was used to compare the continuous variabl (...truncated)