Background: Despite the good and reliable results of the dynamic hip screw (DHS) for stable fracture patterns, complications of excessive sliding of the lag screw and inadequate bone anchorage occur frequently in elderly patients with unstable intertrochanteric fractures. Although polymethylmethacrylate (PMMA) bone cement has been widely used as a secondary fixation to facilitate fixation stability, there has been no prospective study on the clinical significance of PMMA cement to prevent these two complications in unstable fracture patterns.
Methods: A prospective study was conducted. The DHS was applied either with or without PMMA cement augmentation in 108 elderly patients. The Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association fracture classification was 31-A2 in 91 patients and 31-A3 in 17 patients. The average age of the patients was 81.9 years (range, 75-96 years). The average follow-up period was 13.9 months (range, 12-30 months). PMMA cement was injected precisely into the proximal fragment with an average amount of 13.7 mL (range, 10-19 mL) in 55 patients.
Results: All but six patients (5.6%) had eventual bone union, and the average time to union was 18.1 week (range, 12-36 weeks). Screw sliding, femoral shortening, and varus collapse of the proximal fragment were all significantly reduced in the cemented group at the 1-year follow-up (p < 0.001, p < 0.001, p < 0.001, respectively). The mean hip pain score was 1.9 (range, 1-4) in all 102 patients and was significantly lower in the cemented group (p = 0.008). One patient with a deep infection in the cemented group and five patients with lag screw penetration in the noncemented group received a total hip replacement. All 18 patients with malunion were in the noncemented group. Of these 18 patients, 14 patients (77.8%) had excessive sliding of the lag screw. The overall complication rate was significantly higher in the noncemented group (p < 0.001).
Conclusions: With the meticulous augmentation technique demonstrated in this study, the PMMA cemented DHS proved to have better outcome than a conventional DHS for unstable intertrochanteric fractures in elderly patients. Typical complications related to a conventional DHS device for the treatment of such fractures were successfully prevented.