Constant Caroline, Zderic Ivan, Arens Daniel, Pugliese Brenna, Gehweiler Dominic, Gueorguiev-Rüegg Boyko, Zeiter Stephan
AO Research Institute Davos, Davos, Switzerland.
Vet Surg. 2022 May;51(4):576-591. doi: 10.1111/vsu.13797. Epub 2022 Mar 18.
To determine the influence of screw head diameter on equine condylar fracture fixation with 5.5 mm cortical screws.
Ex vivo, biomechanical study, blinded, matched-pair design.
Fifteen pairs of equine third metacarpal (MC3) bones.
Lateral condylar fractures were simulated by parasagittal osteotomies and repaired pairwise by 2 × 5.5 mm cortical screws of 8 mm (standard) or 10 mm (modified) head diameter. Interfragmentary compression at maximum screw insertion torque was measured. The instrumented specimens were pairwise stratified for biomechanical testing under the following modalities (n = 5): (1) screw insertion torque to failure, (2) quasi-static axial load to failure, and (3) cyclic axial load to 2 mm displacement followed by failure. Tests (1) and (2) were analyzed for yield, maximum, and failure torque/angle and load/displacement, respectively. Number of cycles to 2 mm displacement and failure was assessed from test (3).
Maximum insertion torque was greater, and failure angle smaller, when constructs repaired with modified screws were tested (8.1 ± 0.5 vs. 7.4 ± 0.5 Nm; P = .0047 and 550 ± 104 vs. 1130 ± 230; P = .008). Axial yield (7118 ± 707 vs. 5740 ± 2267 N; P = .043) and failure load (12 347 ± 3359 vs. 8695 ± 2277 N; P = .043) were greater for specimens repaired with modified screws. No difference was detected between constructs in the number of cycles to 2 mm displacement.
Condylar MC3 osteotomies repaired with modified 5.5 mm cortical screws sustained greater maximal hand torque insertion, smaller insertion failure angle and 1.4 fold greater quasi-static failure forces than constructs repaired with standard 5.5 mm screws.
Use of modified screws with larger heads may improve the fixation of condylar fractures in horses. These results provide evidence to justify clinical evaluation in horses undergoing fracture repair.
确定螺钉头直径对使用5.5毫米皮质骨螺钉固定马髁突骨折的影响。
离体生物力学研究，双盲配对设计。
15对马第三掌骨（MC3）。
通过矢状旁截骨模拟外侧髁突骨折，并用2枚头部直径为8毫米（标准）或10毫米（改良）的5.5毫米皮质骨螺钉成对修复。测量最大螺钉插入扭矩时的骨折块间压缩力。将仪器化标本成对分层，进行以下方式的生物力学测试（n = 5）：（1）螺钉插入至失效的扭矩，（2）准静态轴向加载至失效，（3）循环轴向加载至2毫米位移后失效。分别对测试（1）和（2）的屈服、最大和失效扭矩/角度以及载荷/位移进行分析。从测试（3）评估达到2毫米位移和失效的循环次数。
测试使用改良螺钉修复的结构时，最大插入扭矩更大，失效角度更小（8.1±0.5对7.4±0.5牛米；P = 0.0047，550±104对1130±230；P = 0.008）。使用改良螺钉修复的标本轴向屈服载荷（7118±707对5740±2267牛；P = 0.043）和失效载荷（12347±3359对8695±2277牛；P = 0.043）更大。在达到2毫米位移的循环次数方面，两种结构之间未检测到差异。
与使用标准5.5毫米螺钉修复的结构相比，使用改良的5.5毫米皮质骨螺钉修复髁突MC3截骨时，能承受更大的最大手动扭矩插入力、更小的插入失效角度以及1.4倍的准静态失效力。
使用头部较大改良螺钉可能改善马髁突骨折的固定。这些结果为对接受骨折修复的马进行临床评估提供了依据。
