Session V - Femur

High-Energy Femoral Neck Fractures: Sliding Hip Screw or Cannulated Screw Fixation?

James J. Yue, MD; Lisa Cannada, MD; Andrew R. Burgess, MD; John H. Wilber, MD; J. Mark Scarboro, MD, Shock Trauma Center, Baltimore, MD

Purpose: The purpose of the present study was to evaluate the use of a sliding hip screw combined with a derotation screw versus multiple cannulated screws in the treatment of high-energy femoral neck fractures with a significant vertical shear component.

Methods: Between 1993 and 1997, 32 adult patients (average age, 40) with high-energy femoral neck fractures were treated at two separate Level I trauma centers. Of these 32 patients, 5 patients were lost to follow-up, 1 patient died shortly after admission, and 1 patient was excluded because of underlying medical conditions, leaving 25 patients for final analysis at a minimum of 1 year postinjury. A retrospective chart review was performed on all patients. In addition, 23 patients (88%) were available for functional assessment telephone interviews and/or physical examination. Fractures were classified by the OTA as well as the Garden and Pauwels classification. All parameters (i.e., age, mechanism of injury, open versus closed reduction, time to surgery, time to union, AVN and nonunion rates, and secondary procedures) were determined for fractures treated with a sliding hip screw and those treated with multiple cannulated screws. Plain radiographs were obtained on all patients available for follow-up. Functional outcome was assessed with the Harris Hip Score and the SF-36 health survey. A Student's t-test or z-test of ratios assuming both equal and unequal variances was performed for statistical analysis as indicated.

Results: At institution A, there were 11 patients treated with sliding hip screws combined with a derotation screw and 1 with multiple cannulated screws. At institution B, there were 13 patients treated with multiple cannulated screws. There were equal numbers of males (9) and females (A-3 and B-4) at both centers and among both treatment groups. The ages were also similar between the two treatment groups (42 yo for sliding screw and 37 yo for cannulated screws). The median Injury Severity Score was 16 and 15 at institution A and B, respectively. The predominant mechanisms of injury were 10 falls (A-4 and B-6) and 9 MVAs (A-5 and B-4). Eighty-seven percent had a significant vertical shear component. Three fractures treated with a sliding hip screw required open reduction, and 2 fractures treated with cannulated screws required open reduction. The average follow-up was 14 and 16 months at center A and B, respectively.

Nonunion occurred in 9% and 28.6% for the sliding hip screw and multiple cannulated screw groups, respectively (p>0.05). AVN occurred in 9% and 0% for the sliding hip screw and multiple cannulated screw groups, respectively (p>0.05). Three Pauwel's valgus osteotomies were performed and 1 osteotomy is pending among the cannulated screw group. Of these three patients, one had a delayed (>24h) reduction and fixation of the femoral neck fracture. There was one failure of fixation in the cannulated screw group which was recognized early and converted to a sliding hip screw. Two total hip arthroplasties were performed on the sliding hip screw patients, both in patients who had delayed reduction and fixation of the femoral neck fracture (>24h). Of the 6 patients who developed either AVN (1 sliding hip screw) or a nonunion (2 sliding hip screw, 3 cannulated screws), 4 had a vertical shear component to the fracture line and 3 were delayed reduction and fixation (>24h).

The average Harris hip score was 75 for both treatment groups. The average SF-36 score was 96 for the cannulated group and 101 for the sliding hip screw group.

Discussion: Previous studies (Swiontkowski et al., JBJS 66A:837-846; Askin and Bryan, CORR 114:259-264) have examined femoral neck fractures in young adults. However, to the best of our knowledge, a study which has examined specifically high-energy femoral neck fractures in young adults with respect to treatment methods has not been performed.

Conclusions: 1) Based on our results, equivalent rates of union and AVN can be obtained with either multiple cannulated screws or the sliding hip screw combined with a derotation screw in the treatment of high-energy femoral neck fractures with a vertical shear component. The use of a sliding hip screw, however, may offer superior results in terms of rates of union (9% versus 28%). 2) The combination of a displaced vertical shear fracture with a delayed reduction and fixation produces the worse outcome in either treatment method. 3) Nonunion rates of 9% to 28% can be expected in patients with high-energy femoral neck fractures. 4) Good to excellent clinical outcomes can be expected in patients with high-energy femoral neck fractures successfully treated with either sliding hip screws or cannulated screws.