Previously unreported failure of a Synthes 4.0mm diameter cannulated screw

Unwinding of a 4.5 mm partially threaded cannulated screw in an elderly patient: A case report

“…The mechanism of the screw unwinding has been thought to be due to weakness that develops at the self-cutting flute that propagates along the screw as the screw is inserted [3] . Previous case reports have cited catching on dense cortical bone which lead to the screw unwinding [1,4,5] .…”

Effect of different radial hole designs on pullout and structural strength of cannulated pedicle screws

“…However, screw fracture has been reported with the use of cannulated screws in trauma fixation. Levene and Templeton [17] reported cannulated screw failure during insertion -usually with the smaller diameter 4.0 mm AO SYNTHES screws. Similarly, Mooney and Simmons [18] reviewed three cases of distal screw breakage and indicated that the cannulated screw in combination with the self-taping design creates a potential area of weakness when used in hard bone.…”

Failure of asnis iii 5.0 mm cannulated screw: a case report

“…These included broken guidewires in the AO 3.5 mm system [ 1 ], and also many documentations of broken screws, including the AO 4.0 mm system [ 2 - 4 ]. There have been cases of screws unthreading in cancellous bone and one documentation of an AO 4.0 mm screw unthreading following contact with cortical bone, then breaking off in the elbow during cannulated screw fixation of a lateral epicondyle fracture [ 5 ]. All patients were young males and it has been hypothesized [ 2 ] and [ 5 ], that contact with dense bone caused the unravelling.…”

“…The exact aetiology of our screw failure is uncertain. In Levene's case [ 5 ], the surgeon experienced a tactile change informing him of the failure, but in all 3 of Mooney's cases [ 2 ], this did not occur. Likewise, in our case, there was no tactile feedback suggestive of the screw unthreading.…”

“…It had previously been suggested [ 5 ] that pre-drilling and tapping and real-time fluoroscopy during screw insertion may be helpful in reducing the incidence of unravelling. In our case, the proximal cortex was pre-drilled and tapped prior to screw insertion.…”