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 (). Also noted were sclerotic changes in the acetabulum.
Seven-year-old female with mild right-sided limp. The AP pelvis x-ray demonstrates coxa magna with lateralization of the right femoral head. The acetabular roof and sourcil appear distorted.
A computerized tomography (CT) scan () that included three-dimensional reconstructed images () 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 (). 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.
Coronal (A) and sagittal (B) computed tomography images demonstrating a probable intra-articular osteochondroma of right hip.
Figure 3 AP (A, B and C) three-dimensional computed tomographic images of pelvis and hip demonstrating an intra-articular osteochondroma (solid arrows) within acetabulum (open arrow = anterior rim of acetabulum). Lateral images (D and E) showing osteochondroma (more ...)
Figure 4 Coronal MRI image demonstrates an intra-articular heterogeneous high-signal mass, which merges imperceptibly into the remainder of the ilium with anterolateral displacement of the femoral head and a small joint effusion. The reading suggested an intra-articular (more ...)
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 (). 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 (). 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 () to improve hip stability. Pathologic study demonstrated the lesion to be an osteochondroma ().
Pathologic specimen demonstrating cartilage cap with underlying bone consistent with a diagnosis of osteochondroma.
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 ().