The Dorr Type and Cortical Thickness Index of the Proximal Femur for Predicting Peri-Operative Complications during Hemiarthroplasty

Abstract

Purpose. To assess the Dorr proximal femoral types and the cortical thickness index for predicting peri-operative complications during hemiarthroplasty. Methods. Records of 53 male and 147 female elderly who underwent cemented or uncemented monopolar hemiarthroplasty for displaced intracapsular femoral neck fractures were reviewed. Any intra-operative fracture and postoperative dislocation within 30 days was recorded. The cortical thickness index was defined as the ratio of cortical width minus endosteal width to cortical width at a level of 100 mm below the tip of the lesser trochanter. Higher values indicated thicker cortices. The Dorr proximal femur morphology was classified into types A, B, and C. Results. 28 patients were excluded. The proximal femurs of the remaining 172 patients (mean age, 85 years) were categorised as Dorr type A (n=29), type B (n=75), and type C (n=68). The respective mean cortical thickness indices were 1.10, 0.79, and 0.65. Lower cortical thickness indices correlated with worse Dorr types (p<0.05). There were 18 intra-operative fractures; 8 and 10 occurred in Dorr types B and C femurs versus none in Dorr type A femurs (p=0.046). There were 5 postoperative dislocations; 3 and 2 occurred in Dorr types B and C femurs versus none in Dorr type A femurs (p=0.591). The mean cortical thickness index was significantly lower in those with a fracture (n=18) than those without a fracture (n=154) [0.59 vs. 0.81, p=0.0003]. Conclusion. Dorr types B and C proximal femurs were at greater risk of intra-operative fracture.