Perfusion magnetic resonance imaging correlates with the duration of stages and lateral pillar class in Legg-Calvé-Perthes disease

Abstract

Background: Legg-Calvé-Perthes disease (LCPD) progresses through 4 stages characterized by unique radiographic features, and stage duration is recognized as an important prognostic factor. Newer perfusion magnetic resonance imaging (pMRI) allows for the evaluation of vascularity early in the disease process. This study aims to describe the relationship between global and regional perfusion patterns on early pMRI and the duration of Waldenström stages. A secondary aim was to verify the relationship between hypoperfusion and subsequent lateral pillar class.

Methods: Through a prospectively collected multicenter international cohort, patients with early LCPD (Waldenström Stage I) and pMRI were followed with serial radiographs at 3-month intervals for a minimum of 2 years. Epiphyseal hypoperfusion was quantified by HipVasc Software for the entire epiphysis and regional thirds of the femoral head. Waldenström stages and lateral pillar class were determined by mode assessments from 3 pediatric orthopedic surgeons. Duration of the stage was defined as the interval between the first radiograph demonstrating features of stage IIa and stage IIIa for fragmentation and between IIIa and IV for reossification.

Results: One-hundred and seven patients (88.8% male, median age 8.0 years) met the study criteria. The average global hypoperfusion was 73.7%. Poorer global perfusion was predictive of a longer duration of fragmentation (rho = 0.34, P < .001) and of reossification (rho = 0.38, P = .003). The average regional hypoperfusion of the medial, central, and lateral third of the femoral head was 65.3%, 83.7%, and 61.3% respectively, and was similarly related to the duration of fragmentation (rho = 0.26, 0.24, and 0.31, respectively) and of reossification (rho = 0.31, 0.43, and 0.39, respectively) (P < .05 for all). Similar to previous studies, we found a significant positive association between hypoperfusion in the lateral third of the femoral head and lateral pillar class (P = .037).

Conclusions: The degree of both global and regional hypoperfusion correlated with the duration of fragmentation and reossification stages in LCPD. Lateral epiphyseal hypoperfusion is predictive of lateral pillar class. Taken together, the information provided by perfusion magnetic resonance imaging can provide crucial prognostic information for children with LCPD.

Key concepts: 1.Amount of hypoperfusion both globally and regionally on perfusion MRI correlates with the duration of fragmentation and reossification stages in LCPD.2.Lateral epiphyseal hypoperfusion correlates with lateral pillar class.3.Perfusion information offered by contrast MRI can offer crucial prognostic information in children with LCP.

Level of evidence: II Prognostic Study.

Keywords: Duration; Legg-Calve-Perthes; Perfusion MRI; Perthes.

Figure 1

a. Perfusion MRI in a 9 + 4 month old male demonstrates 50.5% global hypoperfusion of the right hip based on HipVasc analysis (Lat: 52.4%, Central: 75.8%, Medial: 35.8%). b. Anteroposterior (AP) radiograph of the right hip at initial visit demonstrates Waldenström Stage 1B. c. Immediate postoperative AP hip radiograph after varus femoral osteotomy demonstrates Waldenström stage 2A (early fragmentation). d. AP hip radiograph at approximately 3-month follow-up demonstrates early healing stage (Waldenström stage 3A). The duration of fragmentation was therefore deemed to be 63 days. e. AP hip radiograph at Waldenström stage 4 indicates that the duration of the healing stage was approximately 550 days.

Figure 2

a. Perfusion MRI in a 7 + 11-month-old male demonstrates 83.9% global hypoperfusion of the right hip based on hipVasc analysis. (Lat: 65.6%, Central: 94.4%, Medial: 87.2%). b. AP radiograph of the right hip at the initial visit demonstrates Waldenstrom Stage 1B. c. AP hip radiograph at 3-month follow-up after varus femoral osteotomy demonstrates Waldenstrom stage 2A. d. AP hip radiograph demonstrates healing (Waldenstrom 3A) after 259 days of fragmentation. E. AP hip radiograph at Waldenstrom stage 4 indicates that the duration of the healing stage was approximately 665 days.

Figure 3

Global and Regional Hypoperfusion Percent of Total Sample* and by Lateral Pillar Class. * Except those who bypassed fragmentation (N = 3).