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In Vitro Pullout Strength of Screws Inserted in Adult Equine Third Metacarpal Bone After Overdrilling a 4.5‐mm Threaded Insertion Hole
Author(s) -
SEDRISH STEVEN A.,
MOORE RUSTIN M.,
KELLY KEVIN,
MARTIN GEORGE S.,
BURBA DANIEL J.
Publication year - 1998
Publication title -
veterinary surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 79
eISSN - 1532-950X
pISSN - 0161-3499
DOI - 10.1111/j.1532-950x.1998.tb00111.x
Subject(s) - cancellous bone , cortical bone , medicine , diaphysis , metaphysis , cadaver , drill , ultimate tensile strength , anatomy , orthodontics , orthopedic surgery , materials science , surgery , composite material , metallurgy
Objective—To determine and compare the in vitro pullout strength of 5.5‐mm cortical versus 6.5‐mm cancellous bone screws inserted in the diaphysis and metaphysis of adult equine third metacarpal (MCIII) bones, in threaded 4.5‐mm cortical bone screw insertion holes that were then overdrilled with a 4.5‐mm drill bit to provide information relevant to the selection of a replacement screw if a 4.5‐mm cortical screw is stripped. Study Design— In vitro pullout tests of 5.5‐mm cortical and 6.5‐mm cancellous screws in equine MCIII bones. Sample Population—Two independent cadaver studies each consisting of 14 adult equine MCIII bones. Methods—Two 4.5‐mm cortical screws were placed either in the middiaphysis (study 1) or distal metaphysis (study 2) of MCIII bones. The holes were then overdrilled with a 4.5‐mm drill bit and had either a 5.5‐mm cortical or a 6.5‐mm cancellous screw inserted; screw pullout tests were performed at a rate of 0.04 mm/second until screw or bone failure occurred. Results—In diaphyseal bone, the screws failed in all tests. Tensile breaking strength for 5.5‐mm cortical screws (997.5 ± 49.3 kg) and 6.5‐mm cancellous screws (931.6 ± 19.5 kg) was not significantly different. In metaphyseal bone, the bone failed in all tests. The holding power for 6.5‐mm cancellous screws (39.1 ± 4.9 kg/mm) was significantly greater than 5.5‐mm cortical screws (23.5 ± 3.5 kg/mm) in the metaphysis. There was no difference in the tensile breaking strength of screws in the diaphysis between proximal and distal screw holes; however, the holding power was significantly greater in the distal, compared with the proximal, metaphyseal holes. Conclusions—Although tensile breaking strength was not different between 5.5‐mm cortical and 6.5‐mm cancellous screws in middiaphyseal cortical bone, holding power of 6.5‐mm cancellous screws was greater than 5.5‐mm cortical screws in metaphyseal bone of adult horses. Clinical Relevance—If a 4.5‐mm cortical bone screw strips in MCIII diaphyseal bone of adult horses, either a 5.5‐mm cortical or 6.5‐mm cancellous screw, however, would have equivalent pullout strengths. A 6.5‐mm cancellous screw, however, would provide greater holding power than a 5.5‐mm cortical screw in metaphyseal bone.