Thread Delamination in 4.5 mm AO Cannulated Screws: A Small Case Series in the Pediatric Trauma Population

Background: Thread delamination associated with cannulated screws have been reported but likely represent an under-recognized complication in the orthopaedic literature. The purpose of this study is to report the occurrence of repeated hardware failures through thread delamination in the setting of a commonly used orthopaedic cannulated screw implant in a small cohort involving pediatric fracture care at a single academic level I trauma center. Methods: Between August 2015 and December 2020, 9 cases of hardware failure associated with 4.5 mm arbeitsgemeinschaft fur osteosynthesefragen cannulated stainless-steel screws were identified within a pediatric orthopaedic division at a single academic level I trauma center. Three cases were excluded, and 6 cases of thread delamination were retrospectively reviewed. Results: Six cases of thread delamination comprised a cohort of patients with a mean age of 13.7 years (range: 12 to 15 y). All cases involved 4.5 mm arbeitsgemeinschaft fur osteosynthesefragen cannulated screws, including 5 partially threaded and 1 fully threaded screw. Five cases involved open reduction and internal fixation of incarcerated medial humeral epicondylar fragments and the other case was an open reduction and internal fixation of a displaced medial malleolar fracture. Five of these occurred within a recent 18-month period of time. There were 4 cases of partial, distal thread delamination, 1 case of partial proximal thread delamination and another case of complete thread delamination which had unwound into the tibiotalar joint and required an anterior ankle arthrotomy to retrieve the thread. None of the 5 patients in this series who currently harbor a retained thread have experienced symptoms because of this issue. Conclusions: Thread delamination associated with cannulated screw implantation likely represents an under-reported phenomenon in orthopaedic surgery. In cases where retained, delaminated threads exist, these do not appear to cause short-term concern.