Cannulated screw unraveling: a case series and literature-based review of an under-recognized complication.

Partially threaded cannulated screws have enhanced the orthopedic surgeon's ability to fix periarticular fractures. There are many reports of complications and hardware failure during screw removal, but those during fracture fixation are under-reported and under-recognized in the literature. We describe a 21-year-old healthy man with a grade 1 open displaced medial epicondylar humerus fracture. Upon fracture fixation in the OR using a partially threaded cannulated screw over a Kirschner wire, the threads of the screw unraveled. The operating surgeon felt increased resistance and the unraveling was demonstrated on intra-operative fluoroscopy. The screw was removed by hand without hardware retention and a new K-wire and cannulated screw were used for definitive fixation. We found seven previous cases reporting a similar complication with mixed presentations and results. All occurred in young healthy patients, six of which were males. Six of the seven cases made no mention of a tactile change in resistance during fixation and only one of the seven pre-drilled the cortex prior to placement of the cannulated screw. We believe that screw unraveling is an under-reported complication of fracture fixation with cannulated screws that should be recognized by the orthopedic community. We found intra-operative fluoroscopy integral to the recognition of the problem in our case and recommend its use in fracture fixation with cannulated screws. We also suggest pre-drilling of cortices, especially when operating on young patients with strong bone.