Increased Fracture Collapse after Intertrochanteric Fractures Treated by the Dynamic Hip Screw Adversely Affects Walking Ability but Not Survival

In osteoporotic hip fractures, fracture collapse is deliberately allowed by commonly used implants to improve dynamic contact and healing. The muscle lever arm is, however, compromised by shortening. We evaluated a cohort of 361 patients with AO/OTA 31.A1 or 31.A2 intertrochanteric fracture treated by the dynamic hip screw (DHS) who had a minimal follow-up of 3 months and an average follow-up of 14.6 months and long term survival data. The amount of fracture collapse and shortening due to sliding of the DHS was determined at the latest follow-up and graded as minimal (2 cm). With increased severity of collapse, more patients were unable to maintain their premorbid walking function (minimal collapse = 34.2%, moderate = 33.3%, severe = 62.8%, and p=0.028). Based on ordinal regression of risk factors, increased fracture collapse was significantly and independently related to increasing age (p=0.037), female sex (p=0.024), A2 fracture class (p=0.010), increased operative duration (p=0.011), poor reduction quality (p=0.000), and suboptimal tip-apex distance of >25 mm (p=0.050). Patients who had better outcome in terms of walking function were independently predicted by younger age (p=0.036), higher MMSE marks (p=0.000), higher MBI marks (p=0.010), better premorbid walking status (p=0.000), less fracture collapse (p=0.011), and optimal lag screw position in centre-centre or centre-inferior position (p=0.020). According to Kaplan-Meier analysis, fracture collapse had no association with mortality from 2.4 to 7.6 years after surgery. In conclusion, increased fracture collapse after fixation of geriatric intertrochanteric fractures adversely affected walking but not survival.