The effect of triradiate cartilage injury on hip development / 中华骨科杂志

ABSTRACT

Objective To study the effect of premature physeal fusion of t ri radiate cartilage on hip development. Methods Ten rabbits aged 4 to 5 weeks were used by partial excision of triradiate physeal cartilage on the right hip of ea ch rabbit, and the opposite untreated hip served as control. Postoperative analy sis consisted of radiographic and histological studies. Radiographs of both hips were taken at 2 days and 3, 6, 9 and 12 weeks after surgery to evaluate the dev elopment and stability of hips. All rabbits were sacrificed at 12 weeks postoper atively. The gross and microscopic histological changes of the hip joints were s ubsequently assessed. The statistic analysis was performed by paired student’s t test worked out by SPSS software. Results On the operated hips, bone bridge fo rmed 3 weeks after operation at the site of triradiate cartilage. The medial ace tabular walls became thick, and the acetabula were shallow. At 6 and 9 weeks pos toperatively, the thickness of acetabular walls increased gradually, and irregul ar sclerosis appeared on the acetabular roof. The density of femoral head increa sed in 6 of 10 rabbits. At 12 weeks postoperatively, the acetabular cavity was m ore shallow, and the femoral head appeared flat. Subluxation of hip was observed in 5 rabbits. There was significant difference in approximate acetabular index (AAI), acetabular head index (AHI) and the thickness of acetabular wall between the operated and control hips. The mean value of AAI and AHI on the operated hip s at 12 weeks significantly decreased as compared to that at 2 days. Gross inspe ction confirmed that the acetabular cavity on the operated hips was characterist ically shallow with a marked increase thickness of medial wall. The femoral head became flattened, and the cartilage of both acetabulum and femoral head were th inned. Histological study showed thinning and partial loss of the joint cartilag e layer and irregularity of cartilage cells on the operated hip joints. There we re increased amounts of fibrovascular cells deep to the cartilaginous layer. In addition, the femoral head exhibited a zone of necrosis in its superior pole wit h thinning of the epiphyseal plate. On the control hips, structure of acetabulum and femoral head appeared normal congruity. Conclusion Acetabular triradiate ca rtilage injury might result in bony bar formation and premature fusion of physis . Its main pathologic changes are widening of the acetabular medial wall, shallo wness of the acetabular cavity, and subsequent hip dysplasia and dislocation.