BACKGROUND:
Stress fracture of the femoral neck (SFFN) is one of the severe complications of military training. Displaced SFFN may result in avascular necrosis of the femoral head (AVNFH). The purpose of this study was to evaluate the results of surgical treatment of the displaced SFFN.

METHODS:
Forty-two patients with displaced SFFN requiring internal fixation were treated with compression hip screw (17 cases) or multiple cancellous screws (25 cases). Forty-two patients were followed for an average of 5.6 years after operation. At the follow-up evaluation, routine radiographs were used to evaluate the fracture alignment and healing, and bone scan was used for fractures that were suspected of AVNFH. The functional assessments described by Arnold et al. were used to evaluate the functional results of surgical treatment.

RESULTS:
Seven (28%) of the 25 patients treated with multiple cancellous screws developed AVNFH during the period of follow-up. Of these seven patients, five were treated with prosthetic replacement and two treated with core decompression and bone graft. Three (17.6%) of the 17 patients treated with compression hip screw had AVNFH, and they were all treated with prosthetic replacement. The mean duration between fracture and surgery was significantly longer in patients with AVNFH (5.9 days) than in patients without AVNFH (1.9 days)( P< 0.05). Five (71.4%) of the seven patients who presented a varus alignment of the femoral neck developed AVNFH later, and only five (14.3%) of the 35 patients who presented with anatomic or valgus alignment of the femoral neck developed AVNFH during the period of follow-up. Of the 42 patients, 30 (71.4%) had good functional results, four (9.5%) had acceptable and eight (19%) had poor results at the end of evaluation.

CONCLUSION:
Delayed treatment and postoperative varus alignment were major factors contributing to AVNFH in our series. Early treatment and anatomical fixation of displaced SFFN are essential for diminishing the risk of AVNFH development.





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