A Biomechanical Comparison of Equine Third Metacarpal Condylar Bone Fragment Compression and Screw Pushout Strength between Headless Tapered Variable Pitch and AO Cortical Bone Screws

Abstract

The 6.5-mm tapered AP screw should provide ample holding strength but would provide less interfragmentary compression than 4.5-mm AO screws for repair of complete lateral condylar fractures in horses.

Arthrodesis of the Equine Proximal Interphalangeal Joint: A Biomechanical Comparison of Two Parallel Headless, Tapered, Variable‐Pitched, Titanium Compression Screws and Two Parallel 5.5 mm Stainless‐Steel Cortical Screws

“…From data supplied by the manufacturer, it has been previously reported that Acutrak-Plus s screws can provide a maximum of 2 mm of compression when inserted to their full length 13 and provided only 44% the compressive force and 65% the compressive pressure of 4.5 mm cortical screws. 14 These investigators found that the compressive force and pressure of Acutrak-Plus s screws compared with 4.5 mm cortical screws was substantially less and more variable (depending on fragment thickness-8, 12, or 20 mm) than in previous reports. 14 Results of this study indicated that compressive force and pressure were greatest in the 8mm-thick fragments owing to the engagement of the finer pitched proximal threads of the Acutrak-Plus s screw in the parent bone.…”

“…14 These investigators found that the compressive force and pressure of Acutrak-Plus s screws compared with 4.5 mm cortical screws was substantially less and more variable (depending on fragment thickness-8, 12, or 20 mm) than in previous reports. 14 Results of this study indicated that compressive force and pressure were greatest in the 8mm-thick fragments owing to the engagement of the finer pitched proximal threads of the Acutrak-Plus s screw in the parent bone. 31 Like previous studies, we did not remove the articular cartilage from either the distal articular surface of P1 or the proximal articular surface of P2.…”

“…1,2 Reported arthrodesis techniques include parallel screw techniques, 3 plate fixation techniques 4 , and plate-screw combination techniques 2,5 and several biomechanical comparisons have been performed. [6][7][8][9][10] Several different sizes of headless, tapered, titanium, variable-pitched compression screws have been used in both biomechanical evaluations [11][12][13][14][15] and clinical applications. 16,17 Advocates of the tapered screws would suggest that the increased biocompatibility, reduced need for implant removal (secondary to soft tissue irritation that is sometimes observed with headed screws) 18 , and possible increased fatigue resistance because of the increased bone-screw interface of tapered screws are advantages that tapered screws have over cortical screws.…”

Distal Interphalangeal Joint Arthrodesis in Seven Cattle Using the Acutrak Plus Screw

“…The headless design of the AP screw makes it ideal for DIPJ fusion because the entire screw can be successfully buried. Interfragmentary compression studies comparing the AP and 4.5 mm AO cortical bone screw in simulated lateral condylar fractures of equine 3rd metacarpal bone have shown that the AP achieves only 65% of the compressive pressure of the AO screw 11 . For DIPJ arthrodesis, the goal is not to achieve maximal compression, but rather to immobilize the joint (to decrease pain associated with severe degenerative joint disease) as well as to promote more rapid ankylosis; the AP screw accomplishes both objectives by immobilization of the DIPJ joint immediately after screw insertion.…”

Clinical Evaluation of a Titanium, Headless Variable‐Pitched Tapered Cannulated Compression Screw for Repair of Frontal Plane Slab Fractures of the Third Carpal Bone in Thoroughbred Racehorses

“…This is unlike traditional AO screws inserted in lag fashion where compression of the fracture relies completely on the screw head. The headless design allows the screw to be positioned beneath the outer cortex which prevents impingement on the overlying tendons, joint capsule, or periosteum and eliminates the need for countersinking in larger fracture fragments 8,14–17 . This design also decreases the likelihood of fragment splitting because there is no screw head applying compression to the fracture fragment 8,14 .…”