Using a modified Pauwels method to predict the outcome of femoral neck fracture in relatively young patients

Abstract

Background: Pauwels classification has long been used in femoral neck fracture to measure the inclination of the fracture line and is still widely used. In recent years, however, some studies have contested the reliability of this measurement method. This study investigates modified measurement method to assess the inclination angle with assisted parameters to evaluate the correlation between the different angles and the incidences of loss of reduction, nonunion and avascular necrosis.

Patients and methods: A retrospective study was conducted to analyse the clinical data of 209 relatively young patients (between 20 and 60 years old) with intracapsular femoral neck fracture fixed by inverted triangular screws between January 2004 and December 2010, including 111 males and 98 females, with an average age of 47.08±9.93 years. Using the modified measurement method, the pre-operative inclination angles of patients with intracapsular femoral neck fracture were analyzed. The measured angles were classified into three types: type I, <30 degrees; type II, 30-50 degrees; and type III, >50 degrees.

Results: With regard to loss of reduction, nonunion and avascular necrosis, there were no significant differences with respect to age, sex and fracture side. However, there were significant differences with respect to fracture type, reduction quality and different modified Pauwels types. In the multiple regression analysis, the factors associated with loss of reduction were the fracture type (odds ratio [OR]=7.22), reduction quality (anatomic vs unacceptable reduction, OR=0.11; acceptable vs unacceptable reduction, OR=0.23), and modified Pauwels type (type II vs type III, OR=0.36). The factors associated with fracture nonunion were the fracture type (OR=9.43), reduction quality (acceptable vs unacceptable reduction, OR=0.17) and modified Pauwels type (type II vs type III, OR=0.22). And the factors associated with avascular necrosis were the modified Pauwels type (type I vs type III, OR=0.15; type II vs type III, OR=0.36).

Conclusions: A displaced fracture, poor reduction quality and high modified Pauwels type are noted risk factors for loss of reduction and fracture nonunion in the post-operative follow up of intracapsular femoral neck fracture. The modified Pauwels type is also noted a risk factor for avascular necrosis. Thus, this modified method is a useful tool for correcting the deficiencies of traditional Pauwels classification and predicting the outcome of femoral neck fractures.

Keywords: Avascular necrosis; Femoral neck fracture; Loss of reduction; Modified Pauwels method; Nonunion.