Skeletal Radiol (2002) 31:362–365 DOI 10.1007/s00256-002-0497-9
A. Lalaji H. Umans R. Schneider D. Mintz M.S. Liebling N. Haramati
Received: 16 November 2001 Revised: 18 January 2002 Accepted: 12 February 2002 Published online: 23 March 2002 © ISS 2002 A. Lalaji · H. Umans (✉) · M.S. Liebling N. Haramati Department of Radiology, Albert Einstein College of Medicine and Montefiore Medical Center, 111 East 210th Street, Bronx, NY 10467, USA e-mail:
[email protected] Tel.: +1-718-9202916 Fax: +1-718-7987983
C A S E R E P O RT
MRI features of confirmed “pre-slip” capital femoral epiphysis: a report of two cases
Abstract We describe the morphologic and signal changes detected about the proximal femoral growth plate in two patients with hip pain preceding the progression to slipped capital femoral epiphysis using magnetic resonance imaging.
Keywords Slipped capital femoral epiphysis · “Pre-slip” · Metaphyseal · Physeal · Growth plate · Magnetic resonance imaging
R. Schneider · D. Mintz Department of Radiology, The Hospital for Special Surgery, 525 East 71st Street, New York, NY 10021, USA
Introduction We define pre-slip of the capital femoral epiphysis as hip pain without radiographic evidence of slipped capital femoral epiphysis (SCFE) in a child who, left untreated, would progress to SCFE. Conventional radiographs may reveal only subtle indistinctness of the proximal femoral physis that might precede SCFE and indicate “pre-slip” or impending SCFE. Although not recommended for routine screening of SCFE, magnetic resonance imaging (MRI) may be useful to evaluate radiographically occult causes of hip pain, including: pre-slip, early avascular necrosis, infectious or inflammatory synovitis, myotendinous injury or neoplasm. We have previously reported the MRI features of SCFE, including one case of presumed pre-slip [1]. The patient with presumed pre-slip was prophylactically pinned; therefore, morphologic and signal alterations about the proximal femoral physis, pre-
sumably related to pre-slip, remained of unproven clinical relevance. Without a sensitive diagnostic imaging test that could detect abnormality prior to the development of SCFE, pre-slip would remain a retrospective diagnosis of no clinical or surgical consequence. We present two cases of proven pre-slip which progressed to SCFE prior to pinning. In both cases MRI demonstrated distortion of the physis and/or peri-physeal bone marrow edema before the development of radiographically detectable SCFE.
Case reports Case 1 An 11-year-old female presented with limping and pain on movement of her left hip which persisted for 2 weeks following a fall onto her left side. Physical examination revealed painful restric-
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Fig. 1A–E Case 1. A Anteroposterior radiograph of both hips of an 11-year-old female who presented with left-sided hip pain and limping 2 weeks after a fall onto her left side demonstrates subtle left-sided slipped capital femoral epiphysis (SCFE) with associated widening of the growth plate (arrowheads). B The frog lateral view of the right hip appears normal. C Spin echo coronal T1weighted MR image demonstrates globular widening of the physis bilaterally. Due to the tomographic nature of MRI, this single coronal image does not illustrate slippage of the left femoral capital epiphysis. D Short tau inversion recovery (STIR) coronal MR image demonstrates bilateral synovial effusions of both hip joints. E Frog lateral preoperative radiograph of the right hip obtained 12 weeks following the MRI examination demonstrates a new moderate right-sided SCFE. Corresponding radiographs of the left hip (not shown) revealed a moderate interval increase in the severity of the left-sided SCFE tion of the left hip with limited abduction and external rotation. The right hip was initially normal. Radiographs of the left hip (unavailable for review at the time of imaging) were initially misinterpreted as normal. In retrospect, the radiographs confirmed minimal left-sided SCFE (Fig. 1A). The corresponding frog lateral projection of the right hip was normal (Fig. 1B). One month following presentation, MRI (GE Signa 5.3, GE Medical Systems, Milwaukee, Wis.) of the symptomatic left hip was performed. The patient was recalled for imaging to in-
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Fig. 2A–D Case 2. A Anteroposterior radiograph of both hips in a 15-year-old female with a previously pinned left-sided SCFE who presented with chronic right-sided hip pain, exacerbated by playing lacrosse. The right hip appears normal. Note the apparent shortening of the left femoral capital epiphysis due to posterior and medial slippage of the femoral head. B STIR coronal MR image demonstrates marrow edema about the medial right proximal femoral metaphysis and growth plate (arrow). Note that the contralateral hip cannot serve as a normal comparison due to the pinned left-sided SCFE, with hardware artifact around the cannulated screw resulting in signal drop-out. C Fast spin echo proton density weighted axial MR image at the level of both hip joints demonstrates irregular widening of the right-sided proximal femoral growth plate, indicative of pre-slip of the femoral capital epiphysis (arrowheads). D Follow-up anteroposterior radiograph 4 months later reveals a new mild right-sided SCFE
clude the contralateral hip, which is routine at our institution. Imaging confirmed left-sided SCFE. Bone marrow edema within the right proximal femoral metaphysis, and globular widening of the physis without slippage of the capital femoral epiphysis, was interpreted as right-sided pre-slip (Fig. 1C, D). Within days of the repeat MRI, the patient complained of new-onset right hip pain. Due to non-medical delays, surgery was not performed until 12 weeks later. In the interim, preoperative radiographs demonstrated progression of the left-sided SCFE, and new development of right-sided SCFE (Fig. 1E).
Case 2 A 15-year-old female sought medical attention following 6 weeks of left-sided hip pain. A radiographically confirmed left-sided SCFE was promptly pinned. The patient subsequently complained of chronic right-sided hip pain that lasted approximately 1 year and worsened while playing lacrosse. Conventional radiographs of the right hip all remained normal (Fig. 2A). Seven months after the onset of right-sided hip pain, MRI (GE Signa 5.3) was performed. Comparison could not be made with the contralateral hip, as it had been previously pinned. Bone marrow edema was present in the right proximal femoral metaphysis, accompanied by physeal widening and synovitis (Fig. 2B, C). These subtle findings were not recognized by the orthopedist as an indication for surgical stabilization. Symptoms were attributed to Lyme arthritis, suspected on the basis of a positive Lyme titer. Despite treatment with doxycycline, right-sided hip pain worsened. One month later, radiographs confirmed a new right-sided SCFE (Fig. 2D), which was pinned.
Discussion SCFE is a well-recognized, potentially crippling but easily treated cause of hip pain affecting approximately 2 per 100,000 children in pre-adolescence, with a male to female ratio of 2.5:1 [2]. Recognized risk factors include previous unilateral SCFE, obesity, trauma and endocrinopathy [3]. Prompt stabilization by percutaneous
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pinning may prevent more severe slippage of the femoral head, which can be complicated by avascular necrosis, chondrolysis and osteoarthritis [3]. Patients present with dull hip pain that may radiate to the ipsilateral knee or thigh. Physical examination reveals diminished internal rotation of the hip, and external rotation of the thigh on flexion [2]. Both hips may be affected, with the reported incidence of bilateral SCFE ranging widely, from 25% to 61% [4]. Although the contralateral hip may become symptomatic within 1–5 years following unilateral SCFE, up to 50% of cases are bilateral at initial presentation [5]. It is therefore essential to evaluate the contralateral hip. Conventional anteroposterior and frog-lateral hip radiographs are typically diagnostic for SCFE, demonstrating posterior and medial slippage of the femoral capital epiphysis. Remodeling with beaking of the femoral neck metaphysis may be seen in more advanced cases. Although computed tomography (CT) can quantify even subtle degrees of epiphyseal slippage, its role in detection of pre-slip has not been studied. Anecdotally, imaging using CT for the single case of presumed pre-slip which we previously reported, was prospectively interpreted as normal. In retrospect, it demonstrated only subtle peri-physeal sclerosis. By contrast, all cases of SCFE we imaged using CT revealed sclerosis, accompanied by irregular physeal widening, some with metaphyseal beaking [1]. MRI performed using standard pulse sequences (T1weighted spin echo, fat-suppressed T2-weighted fast spin echo, and STIR) demonstrates morphologic distor-
tion of the physis and bone marrow edema in the adjacent metaphysis and epiphysis, both in SCFE and in these two reported cases of pre-slip. Coronal and axial planes are most useful for detection of these findings, and permit direct side-by-side comparison of the two hips. As in our second case of a previously pinned unilateral SCFE, direct comparison of the hips may be impossible. For that reason, marrow edema surrounding globular widening of the physis must be recognized as abnormal, and diagnostic of either pre-slip or SCFE, depending on the presence or absence of femoral head displacement. Conclusion MRI findings in pre-slip are identical to those for SCFE, but are not accompanied by slippage of the femoral capital epiphysis. The high incidence of synchronous bilateral SCFE emphasizes the importance of including both hips in the field of view if MRI is deemed necessary for evaluation. Conventional radiographs must remain the mainstay for routine screening of SCFE. MRI should be reserved for the child with continued, radiographically occult causes of hip pain, since it is sensitive and diagnostic for distinguishing between pre-slip, synovitis, early-stage avascular necrosis, myotendinous injury and neoplasm. If MRI is to be clinically useful in this setting, the findings we describe must be recognized by the radiologist and accepted by the orthopedist.
References 1. Umans H, Liebling MS, Moy L, Haramati N, Pritzker H. Slipped capital femoral epiphysis: a physeal lesion diagnosed by MRI, with radiographic and CT correlation. Skeletal Radiol 1998; 27:139–144.
2. Busch MT, Morissey RT. Slipped capital femoral epiphysis. Orthop Clin North Am 1987; 18:637–647. 3. Wilcox PG, Weiner DS. Maturation factors in slipped capital femoral epiphysis. J Pediatr Orthop 1988; 8:196–200. 4. Hurley J, Betz R. Slipped capital femoral epiphysis: the prevalence of the late contralateral slip. J Bone Joint Surg Am 1996; 78:226–228.
5. Loder RT, Aronson DD, Greenfield ML. The epidemiology of bilateral slipped capital epiphysis. J Bone Joint Surg Am 1993; 75:1141–1147.
