Unthreaded Fixation of Slipped Capital Femoral Epiphysis Leads to Continued Growth of the Femoral Neck.

BACKGROUND

The optimal treatment for slipped capital femoral epiphysis (SCFE) remains controversial. In Sweden, the standard treatment is unthreaded fixation over the physis, with the purpose to permit continued growth of the femoral neck. The aim of the present study was to verify and quantify longitudinal growth of the femoral neck after in situ pinning with the Hansson hook-pin.

METHODS

We performed a retrospective study of 54 patients treated with the Hansson hook-pin for SCFE between 2001 and 2009. The immediate postoperative radiograph and the radiograph after physeal closure (mean interval, 34 mo) were analyzed. Because the smooth Hansson hook-pin only has a grip fixation in the epiphysis, the femoral neck growth was determined as the difference in nail protrusion from the lateral cortex between the 2 radiographs. The femoral neck offset was also measured in all radiographs.

RESULTS

Significant longitudinal growth occurred both in the slipped and the prophylactically treated contralateral hip by mean 7.1 mm (P<0.001) and 10.0 mm (P<0.001), respectively. There was no difference in growth between genders and no correlation between the amount of longitudinal growth and slip severity (range, 4.0 to 71,6 degrees; mean 27.3 degrees). Young patients (less than 11 y) grew more than older patients (more than 14 y), 12.1 vs. 4.2 mm, P=0.002. The femoral offset increased by mean 16% from mean 30.0 to 35.2 mm (P<0.001). The longitudinal growth of the femoral neck correlated with the increase in femoral offset (R=0.51, P<0.001).

CONCLUSIONS

Unthreaded fixation of SCFE with the Hansson hook-pin allows continued growth of the femoral neck. The remaining growth enables the patient to achieve an almost anatomic offset of the hip. This is essential to optimize the abduction forces that stabilize the pelvis during gait. Future studies need to establish whether the longitudinal growth also results in improved remodelling of the proximal femur.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.