Conversion to total hip arthroplasty after failed proximal femoral nail antirotations or dynamic hip screw fixations for stable intertrochanteric femur fractures: a retrospective study with a minimum follow-up of 3 years

Background: Conversion to total hip arthroplasty (CTHA) is a relatively common procedure after a failed dynamic hip screw (DHS) or proximal femoral nail anti-rotation (PFNA) fixation of intertrochanteric fractures, but there have been far fewer reports specifically describing the long-term results of CTHA after failed treatments of stable intertrochanteric fractures with DHS or PFNA. The aim of the present study was to compare the clinical and radiological outcomes of CTHA after failed PFNA or DHS fixations of stable intertrochanteric fractures after a minimum follow-up of 3 years. Methods: Between January 2005 and April 2014, we retrospectively reviewed 142 active elderly patients treated at our institution (a single institution study). A total of 72 patients (72 hips; 41 women, 31 men; mean age 76.9 years old; range 60-92 years old) who underwent conversion of a failed PFNA to a THA were compared with 70 patients (70 hips; 36 women, 34 men; mean age 75.0 years old; range 60-90 years old) who underwent CTHA after a failed DHS fixation. The mean follow-up periods were 48 (range 43-52) and 48 (range 44-52) months for the DHS and PFNA groups, respectively. Clinical and radiologic evaluations were performed on all patients. The primary outcome was the Harris Hip Score (HHS). The secondary outcomes were the complication rates. Results: The Harris Hip Score (HHS) improved from 50.61 +/- 3.23 preoperatively to 85.28 +/- 4.45 at the last follow-up in the PFNA group and from 51.46 +/- 3.90 to 84.50 +/- 4.34 in the DHS group, with no significant differences noted between the groups at each follow-up (P > 0.05). However, the complication rate in the converted DHS patients was significantly higher (42.9%) than that in the converted PFNA patients (20.8%; P = 0.003). Thirty-seven PFFs (2.4%) occurred during a mean follow-up of 44.4 months. The incidence of periprosthetic fractures was found to be significantly higher (P = 0.021) for the DHS group (15.7%) than for the PFNA group (4.2%). Conclusions: CTHA after failed DHS fixations of stable intertrochanteric fractures might be associated with a significantly higher complication rate than CTHA after failed PFNA fixations. Therefore, PFNA patients with stable intertrochanteric fractures may be more suitable for CTHA.