A predictive method for subsequent avascular necrosis of the femoral head (AVNFH) by observation of bleeding from the cannulated screw used for fixation of intracapsular femoral neck fractures.

OBJECTIVES

To examine the validity of bleeding from the drill holes used for cannulated screw placement as a method for predicting any subsequent avascular necrosis of the femoral head (AVNFH) after the fixation of intracapsular femoral neck fractures.

DESIGN

Retrospective study.

SETTING

University hospital.

PARTICIPANTS

Forty-four patients (mean age, 51 years; range, 18-76 years) whose femoral neck fractures had been fixed with cannulated screws from March 1999 to January 2001 were enrolled in this study. The fractures were classified according to Garden and included 11 type I, 5 type II, 17 type III, and 11 type IV. The average delay between injury and surgery was 52 hours (< or =24 hours, 26; > or =24 hours, 18; range 7 to 504 hours). The follow-up period was more than 25 months (range, 25-57 months).

INTERVENTION: 7.0 mm cannulated screws were used for fracture fixation. Three and 4 screws were used for fixation in 35 and 9 cases, respectively.

MAIN OUTCOME MEASUREMENTS: The presence or absence of blood drainage from the holes of the proximal cannulated screws was determined by an independent observer and defined as bleeding or no bleeding throughout a 5 minute observation period. According to those findings, patients were classified into 2 groups: the bleeding group (38 cases), and the nonbleeding group (6 cases). The validity of the relationship between the 2 groups and the development of AVNFH was evaluated according to the sensitivity, specificity, positive predictive value, and negative predictive value. A chi test was used for univariate analysis of the relationship between the related factors with the development of AVNFH.

RESULTS

The mean follow-up was 39 months (range, 25-57 months). AVNFH developed in 7 cases (16%). One patient of 38 in the bleeding group (2.6%) and all 6 patients in the nonbleeding group (100%) developed AVNFH. The sensitivity was 86%, specificity 100%, positive predictive value 100%, and negative predictive value 97%. Age (P < 0.734), sex (P < 0.587), the type of the fracture (P < 0.356), procedure interval (P < 0.398), the reduction status of the fracture site (P < 0.3849), the positions of the fixed screws (P < 0.2137), and the existence of osteoporosis (P < 0.4347) were not related to the development of AVNFH.

CONCLUSION

It seems that bleeding from the holes of proximal cannulated screws is a simple and accurate perfusion assessment technique for predicting the development of AVNFH after a femoral neck fracture. Given that assumption, primary arthroplasty might be an appropriate choice as a treatment method in a nonbleeding-group patient whose treatment choice is ambivalent or who might not be able to undergo additional surgery should he or she develop a subsequent AVNFH after internal fixation of femoral neck fracture.