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Dysplasia epiphysealis hemimelica (DEH), or Trevor's disease, is a rare disorder that most commonly affects the epiphysis of long bones in children. Rarely, major joints such as the hip can be involved. In this paper we describe a successfully treated case involving the acetabulum, documented with multiple imaging modalities, intraoperative photographs, histology, and follow-up radiographs.
Dysplasia epiphysealis hemimelica (DEH), or Trevor disease, is a rare disorder affecting the epiphysis of long bones in pediatric patients. Initially described in 1926 by Mouchet and Belot1 and subsequently in 1950 by Trevor2 in relation to the foot, Fairbank3 in 1956 provided its current name.
The disease is most commonly seen in male children under ten years of age1,2,3,4,5,6 although it has been described in adults up to age 45.4 The epiphyseal osteochondroma has a predilection for the lower extremity, typically involving the distal femur, distal tibia and talus. 1,2,3,4,5,6 It usually involves the medial side of the joint, but lateral involvement has also been described. Multiple sites on a single extremity are often involved. Azouz7 classified the process as localized (involving a single epiphysis), classic (involving more than one bone on a single limb) or generalized (involving the entire lower extremity from pelvis to foot).
We describe a case of localized dysplasia epiphysealis hemimelica involving the acetabulum that caused progressive hip dysplasia. This case is of special interest because of the extensive imaging studies used to document its severity, the complexity of surgery required for treatment, and the good result obtained.
A seven-year-old female presented to the orthopaedic clinic for evaluation of a mild limp and hip pain, which had been present for one year. She initially had fallen while rollerblading, without significant injury, and subsequently developed a limp which was worse at the end of each day. She also complained at that time of hip pain with walking or running over a distance.
The patient had a near-normal gait. Hip range of motion was limited, especially in external rotation (which lacked 35 degrees compared to the uninvolved hip) and abduction (which lacked 20 degrees). All other hip ranges were symmetric bilaterally. The other joints of the lower extremities appeared to be uninvolved with normal motion.
Radiographs of the pelvis and hips showed acetabular dysplasia with associated coxa magna (Figure 1). Also noted were sclerotic changes in the acetabulum.
A computerized tomography (CT) scan (Figure 2) that included three-dimensional reconstructed images (Figure 3) was ordered to further evaluate the hip for surgical planning. A magnetic resonance imaging (MRI) study was also ordered to evaluate the lesion and the articular cartilage of the acetabulum (Figure 4). Both studies showed the dysplasia to be caused by an intra-articular bony lesion involving the superior and posterior articular surface of the acetabulum, pushing the femoral head laterally.
At surgery, the hip was approached anteriorly and the hip capsule opened. The femoral head was then gently dislocated. A large intra-articular bony growth was noted within the acetabulum (Figure 5). After a varus derotational and shortening osteotomy of the femur was performed (through a separate lateral incision), the femoral head could be retracted distally, allowing better visualization of the hip joint. The joint was best inspected with the osteotomy performed but prior to blade plate fixation, because of free mobility of the head and neck.
The extent of the lesion was then better appreciated, involving the medial, superior and posterior portions of the acetabulum. Curved gouges were then used to carefully remove the osteochondroma (Figure 6). Although a substantial portion of the acetabular articular surface was also removed (having already been destroyed by the lesion), this approach was selected with the idea that the non-involved femoral head articular cartilage could mold the formation of fibrocartilage on the acetabular surface, as might occur in a cup arthroplasty.
The femoral head was then concentrically reduced into the acetabulum, but appeared poorly covered laterally. Therefore, a triple osteotomy of the pelvis was performed (Figure 7) to improve hip stability. Pathologic study demonstrated the lesion to be an osteochondroma (Figure 8).
Post-operatively, the patient was maintained in a hip spica cast for four weeks, at which time early motion of the hip was initiated. She was kept non-weight bearing for twelve weeks. Hardware was removed from the pelvis and femur one year postoperatively.
At most recent follow-up, three-and-one-half years after excision, she had no hip complaints and had returned to all activities. Her hip range of motion continued to be moderately decreased as compared to the uninvolved side, especially in relation to external rotation (lacking 30 degrees) and abduction (lacking 50 degrees). There had been no radiographic evidence for recurrence (Figure 7).
While other cases of DEH involving the acetabulum have been reported (with varying degrees of documentation), 8,9,10,11,12,13,14 the patient presented here represents the most complete case documentation to date. Our case clarifies how each type of imaging modality can contribute unique information that guides successful treatment.
Treatment of DEH is not clearly defined and must be specialized for each case encountered. Some authors recommend observation for lesions that are not causing pain, deformity or interference with function.15 Partial excision of the osteochondroma, while avoiding excessive damage to the articular surface, has been recommended for other cases.1,2,3,4,5 Others recommend avoiding the joint altogether, preferring to make compensatory osteotomies distant from the lesion itself in cases in which the joint surface remains intact.16 A final novel approach has recently been proposed involving cartilage wedge excision from the lesion itself.6
We felt that intra-articular excision would provide the best treatment in this case because allowing progressive femoral head extrusion would lead to inevitable painful hip arthritis. Only longer-term follow-up will define the ultimate outcome for our patient.
The other benefit of surgical excision is the ability to provide a definitive histological diagnosis. This allows a definitive prognosis to be relayed to the patient and family, since malignant degeneration of a DEH lesion has not been documented in the literature.17
In summary, dysplasia epiphysealis hemimelica of the hip joint in a child is a rare condition demanding complex planning and analysis. Careful surgical excision that includes acetabular and/or femoral osteotomies to ensure hip joint stability, would appear to provide the best treatment option.
Investigation performed at Children's Hospital San Diego and the University of California—San Diego
No author received financial support for this study.