Femoral neck nonunion: new classification used in total hip arthroplasty in elderly patients

Introduction The risk of the femoral neck fracture nonunion is 48 % with avascular necrosis of the femoral head being reported in 42 % of cases. There are many classifications of acute intra-articular fractures of the proximal femur and there are no grading systems for femoral neck nonunions that would allow prediction of outcomes of total hip arthroplasty (THA). The objective was to evaluate mid-term results of THA in patients with femoral neck nonunion and develop a new classification of nonunions. Material and methods A prospective cohort single-center comparative study included 78 elderly patients with atrophic femoral neck nonunions treated with primary THA. The mean follow-up period was 24.2 months. Three prospective groups were identified. Separation criteria included shortening of the lower limb and femoral offset, changes in the Barnett-Nordin index, the Hounsfield bone density index, the presence of metal constructs and bone defects. Groups A and B were divided into 2 subgroups depending on the presence/absence of fixation metal constructs for a femoral neck fracture. Group C was divided into 2 subgroups: type C1, acetabular defect and type C2, proximal femur defect. Results Mean operating time was 81.1 minutes in group A, 102.9 minutes in group B and 145.2 minutes in group C. The minimum blood loss was recorded in group A measuring on average 429.25 mL in both subgroups. The maximum blood loss was seen in patients of groups B and C measuring 606.62 mL and 631.5 mL. Overall revision rate was 7.7 %. Conclusion A classification for femoral neck nonunions was developed suggesting grading patients into 3 types: type A, type B and type C which were further divided into 2 subtypes. The grading system was based on lower limb shortening and femoral offset, severity of osteoporosis, presence of metal constructs and acetabulum or proximal femur bone defect which prognostically affected the outcome of THA.