Markers of muscle damage for comparing soft tissue injury following proximal femur nail and dynamic hip screw operations for intertrochanteric hip fractures.

Background: Femoral neck fractures are the most common fractures among the elderly. The two operative approaches used for the treatment of AO/OTA 31 intertrochanteric fractures include an intramedullary device (proximal femoral nail [PFN]) or an extramedullary device (sliding/dynamic hip screw [DHS]). The aim of this study was to provide objective evidence of local soft tissue injury by measuring serum creatine phosphokinase (CPK), a biochemical marker, to quantify muscle damage and inflammation in patients treated by the two approaches.

Patients And Methods: Medical data of 359 patients operated for intertrochanteric fractures with PFN (156 patients) or DHS (193 patients) were retrospectively reviewed. The fractures were classified according to AO/OTA classification. Perioperative and radiographic data were collected to ensure cohorts with similar characteristics. Serum CPK and serum hemoglobin (Hb) levels were measured preoperatively and on postoperative day 1 (POD1). Independent predictors of elevation in the levels of markers of inflammation and muscle damage were determined by a multivariate linear regression model.

Results: The demographics were similar for the two groups. Our study population included 64.2% female patients. Preoperative serum CPK levels were available for 89 patients and POD1 serum CPK levels were available for all patients. One-hundred and thirteen of the 193 DHS patients (58%) and 14 of the 156 PFN patients (9%) had a stable fracture (AO/OTA 31A1, p<0.0001). The DHS patients had a greater increase between pre- and postoperative CPK levels compared to the PFN patients (DHS, δ=368 versus PFN, δ=65, p<0.0002). The PFN patients had a greater decrease in both the pre- and postoperative Hb levels compared to the DHS patients (Diff_Hb 0.27g/dl). The older the patient, the greater decreases in Diff_CPK compared to the younger ones.

Conclusions: Implementation of POD1 CPK blood levels as a biochemical marker of soft tissue injury provided quantitative evidence that patients whose intertrochanteric fracture was stabilized by a DHS suffered greater soft tissue injury compared to patients whose fracture was stabilized by a PFN.