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.