Comparison of bone age delay and recovery in Meyer dysplasia and

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2 Department of Orthopedic Surgery, Rare Disease Institute, Korea University Guro Hospital, ... readily mistaken for Legg-Calvé-Perthes disease (LCPD).

J Orthop Sci (2010) 15:746–752 DOI 10.1007/s00776-010-1537-2

Original article Comparison of bone age delay and recovery in Meyer dysplasia and Legg-Calvé-Perthes disease: a pilot study XIAO-TANG SUN1, T.R. EASWAR2, BALCE CIELO2, SANG-HEON SONG2, SEUNG-JU KIM2, and HAE-RYONG SONG2 1 2

Department of Orthopaedic Surgery, Fuzhou General Hospital, Fuzhou, Fujian, China Department of Orthopedic Surgery, Rare Disease Institute, Korea University Guro Hospital, 80 Guro Dong, Guro Gu, Seoul 152-703, Korea

Abstract Background. Meyer dysplasia (MD) is a rare disease but readily mistaken for Legg-Calvé-Perthes disease (LCPD). Although most published studies on MD have characterized and differentiated it from LCPD radiologically and clinically, differences with regard to bone age delay and recovery have not been sought. We deemed it necessary to distinguish bone age delay and recovery patterns between the two entities for better differentiation, prognostication, and parental advice. Methods. Bone age delay and recovery of eight patients who were initially diagnosed with LCPD but were found to have MD were retrospectively reviewed and compared with those of age-matched patients with LCPD. Based on hand radiographs, the radius-ulna-short bones (RUSs) and carpal bone ages were determined using the Tanner and Whitehouse 3 (TW3) method. Minimum follow-up was 2 years (range 2–5 years). Differences in RUS and carpal bone ages and recovery patterns between the two entities were analyzed using trend lines in scatter plots. Results. The mean delay of RUS bone age was significantly less in MD (0.52 ± 0.87 years) than in LCPD (1.11 ± 0.99 years). However, the difference between the mean carpal bone age delay in MD (1.13 ± 1.28 years) and LCPD (1.47 ± 1.19 years) was not significant. Trend lines showed faster bone age recovery patterns in MD than in LCPD. Conclusions. Bone age was delayed in both MD and LCPD but was less delayed in the former. RUS bone age showed more significant differences than carpal bone age when comparing the two entities and hence might be more useful for differentiating the two. Earlier bone age recovery patterns may be anticipated in patients with MD.

Introduction Meyer dysplasia (MD),1 also known as dysplasia epiphysealis capitis femoris (DECF), is a rare condition and mainly affects children younger than 5 years, with a Offprint requests to: H.-R. Song Received: July 7, 2010 / Accepted: July 20, 2010

male/female ratio of 5:1.2.3 It resembles Legg-CalvéPerthes disease (LCPD) clinically and radiographically but usually has better prognosis without any intervention. Therefore, it is important to distinguish it from LCPD to avoid unnecessary or even invasive treatment due to misdiagnosis.4–6 Because of its rarity, or perhaps underdiagnosis, only a few documents describing MD could be retrieved. It has been clinically and radiographically differentiated from LCPD. Bone age delay in MD has been mentioned in the literature, but the data are limited by some confounding factors, such as sibling relationships.2–7 Also, it has not been interpreted in comparison with LCPD. Our previous study indicated delayed bone age in LCPD that is proportional to disease severity.8 Hence, along this trend, we hypothesized in this study that bone age is less delayed or even normal in MD compared to that in LCPD if we suppose MD is a milder condition than LCPD. Knowledge of the difference in bone age delay and recovery patterns between the two entities can add more detail to prognostication and provide us with a basis for parental advice and counseling regarding the skeletal maturation of their child.

Patients and methods The study was approved by our institutional review board, and informed consent was obtained from each patient. Among 178 patients diagnosed with LCPD in our hospital between 2004 and 2010, there were 8 who were initially diagnosed with LCPD but were later found to have MD (Table 1). They were all male. The right hip was affected in five patients, the left hip in two patients, and both hips in one patient (Fig. 1). The mean age at onset was 3.0 years (range 2.0–4.0 years), and the average follow-up was 3.8 years (range 2.1–5.0 years). Our diagnosis was based on the following criteria: (1) age

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