Influence of interlocking thread screws to repair simulated adult canine humeral condylar fractures

Abstract

Objective: To determine the influence of interlocking screw threads on the biomechanical properties of repaired canine humeral condylar fractures.Study Design: Ex vivo biomechanical study. Sample Population: Thirty-six humeral condyles.Methods: Simulated fractures of the lateral aspect of the humeral condyle were stabilized by a 3.5 mm interlocking thread screw (ITS) or 3.5 mm buttress thread screw placed in lag (BTS-L) or positional fashion (BTS-P) and axially loaded at a walk, trot, 2-mm displacement, and failure cycles. Compact flute drill bits (CFBs) were used for ITS constructs and standard flute drill bits (SFB) for BTS constructs. The effects of bit type on drilling parameters and screw type on screw insertion properties and fragment stability were assessed.Results: CFB produced a 6 C greater temperature increase (p = .042) and required 20 N higher torque (p = .003) than SFB. Insertional torque was greater for ITS than BTS-P (p = .001) and BTS-L (p = .001). Condylar fragment rotation at failure was lower in ITS (lsmean ± SE, 8.3 ± 1.9 ) than BTS-L constructs (14.5 ± 2.3 , p = .011). ITS resisted greater loads (1503 ± 105 N) than BTS-P (1189 ± 99 N, p = .038) but not BTS-L (1249 ± 123 N, p = .121) constructs. Conclusion:Biomechanical performance of constructs was improved with ITS rather than BTS fixation.Clinical Significance: ITS can be considered for stabilization of humeral condylar fractures in adult dogs.

Biomechanical comparison of compact versus standard flute drill bits, and interlocking versus buttress thread self‐tapping cortical bone screws in cadaveric equine third metacarpal condyle

“…Similar to the results of mechanical testing in canine humeral condyles, 4 ITS required significantly more torque for insertion than the BTS in equine metacarpal condylar bone. The interlocking thread has a larger surface area for contact with bone tissues than the buttress thread.…”

“…Both screw types have a positive rake angle and right-handed threads. However, the BTS has three right-handed cutting flutes, 4 whereas the ITS has two left-handed cutting flutes. has a larger helix angle than the standard flute drill bit (SFB; 315.25, DePuy Synthes).…”

“…In plating female geriatric bone, the ITS provided comparable stability to traditional locking screws 3 . Simulated canine humeral condylar fractures stabilized with ITS resisted greater loads compared to constructs stabilized with standard AO buttress thread screws 4 . The effect of interlocking thread geometry on the biomechanical performance of orthopedic screws in equine bone has not yet been investigated.…”

“…Both screw types have a positive rake angle and right‐handed threads. However, the BTS has three right‐handed cutting flutes, 4 whereas the ITS has two left‐handed cutting flutes.…”

Ex vivo biomechanical evaluation of a bone-screw-fastener for tibial plateau leveling osteotomy

“…To date, there is only one peer-reviewed publication reporting the use of bone-screw-fasteners in small animal orthopedic surgery (13). Because it is unknown how the new fasteners will perform mechanically in a TPLO construct, the objective of this study was to investigate the effect of screw type on stiffness and failure characteristics of a TPLO construct under cyclic loading conditions.…”