FAILURE OF COMPRESSION HIP SCREW: ANALYSIS OF THE FAILURE MECHANISM

Abstract

Compression hip screw is a well-accepted fixation device for peritrocahnteric fractures in old people. However, mechanical failures of the device were frequently reported, most of them condemned osteoporosis as the major cause of failure. Few reports discussed the pitfalls of the design of the device. We retrospectively reviewed 205 cases of peritrochanteric fracture treated in our institute with compression hip screw from 1998 to 2001. Fifteen patients (7.3%) had mechanical failure, where 14 of them (93.3%) were cutting out of the lag screw. Statistical analysis found that mechanical failures of the compression hip screw were more often in women than men (p < 0.05) and more often in unstable fractures (Boyd and Griffin types III and IV) than stable fractures (types I and II). The length of the lag screw (average 80.6 mm, range 75–95 mm) in the failure group was significantly shorter than that of the non-failure group (average 85.4 mm, range 75–100 mm) (p < 0.05). The Aesculap Compression hip screw used in our institute has a barrel length of 38 mm and a threaded part of the lag screw 24 mm in length. The average sliding capacity for the failure group was only 18.6 and was not enough for the fracture settling. Fourteen patients had the lag screw cut out of the femoral head at the end of sliding of the fixation device. We suggest application of a device with a shorter barrel and threaded part for patients with short femoral necks to gain more sliding distance in order to reduce the failure rate.