SLR - April 2022 - Katrin Heineman
Reference: Murawski C, Reddy R, Tisherman R, et al. Thread Delamination in 4.5 mm AO Cannulated Screws: A Small Case Series in the Pediatric Trauma Population. J Pediatr Orthop. 2022;42(3):e257-e261. doi:10.1097/BPO.0000000000002047Level of Evidence: Level IV
Scientific Literature Review
Reviewed By: Katrin Heineman, DPM
Residency Program: Temple University Hospital – Philadelphia, PA
Podiatric Relevance: Podiatric surgeons must be knowledgeable of the type of orthopedic hardware available for use in the operative room. Additionally, the surgeon must recognize possible complications associated with each hardware option. A common screw used in podiatric surgery is the 4.5 millimeter AO cannulated screw. Cannulated screw systems are self-drilling and self-tapping implants. Complications are relatively low with cannulated systems, however, there are documented case reports of a unique complication in the form of thread failure with screw unraveling (delamination). The authors assessed the occurrence of repeated hardware failures through thread delamination involving pediatric fractures.
Methods: The authors retrospectively reviewed six cases of 4.5 millimeter AO cannulated thread delamination in pediatric patients aged 12 to 15 years old between August 2015 and December 2020 at a level 1 trauma center. Each screw was inserted in standard surgical AO technique for a 4.5 millimeter stainless steel cannulated screw. Patient age, sex, as well as procedural details, including the type of procedure performed and screw type utilized, were collected. In addition, screw length, thread type, whether the thread was retained or removed, and the type of delamination that occurred, were also noted.
Results: Five cases utilized a partially threaded screw and one was a full threaded screw. Five cases involved ORIF of a medial humeral epicondylar fracture and one ORIF of a medial malleolus. There were four cases of partial, distal thread delamination, one case of partial proximal thread delamination and one case of complete thread delamination which had unwound into the tibiotalar joint and required an anterior ankle arthrotomy to retrieve the thread. All patients with retained threads have no symptoms.
Conclusions: The use of hardware in podiatric surgery is not without complications. There is a known delamination rate of one screw per month world-wide among around 6,500 similar screws. The authors are unsure if their rate of delamination may be due to changes or defects in the manufacturing process. Podiatric surgeons should be aware of potential complications of any hardware and use fluoroscopy to confirm final hardware placement. If thread delamination does occur, it does not appear to cause symptoms for patients.