Short versus long thread cannulated cancellous screws for intracapsular hip fractures: a randomised trial of 432 patients.

It is unclear which length of thread may be most advantageous for the internal fixation of an intracapsular fracture with cancellous screws. We have compared the 16 mm versus the 32 mm threads on cancellous screws within a randomised trial for 432 patients. All fractures were fixed with three screws and patients followed-up for a minimum of one year from injury. The characteristics of the patients in the two groups were similar with a mean age of 76 years. 23% were male. The most common complication encountered was non-union of the fracture which for undisplaced fractures occurred in 7/107 (6.5%) of short threaded screws versus 11/133 (8.3%) of long threaded screws. For displaced fractures the figures were 29/104 (27.9%) versus 24/89 (27.0%). Other complications for the short versus long threaded group were avascular necrosis (two cases versus five cases) and fracture below the implant (two cases in each group). Elective removal of the screws for discomfort was undertaken in five and three cases, respectively. None of these differences between groups was statistically significant. In summary there is no difference in fracture healing complications related to the length of the screw threads.