用于修复有或没有内侧皮质支撑的肱骨近端骨折的锁定钢板的生物力学

The biomechanics of locked plating for repairing proximal humerus fractures with or without medial cortical support.

作者信息

Lescheid Jon, Zdero Rad, Shah Suraj, Kuzyk Paul R T, Schemitsch Emil H

机构信息

Division of Orthopaedics, Department of Surgery, University of Toronto, Toronto, ON, Canada.

出版信息

J Trauma. 2010 Nov;69(5):1235-42. doi: 10.1097/TA.0b013e3181beed96.

DOI:10.1097/TA.0b013e3181beed96

PMID:20118814

Abstract

BACKGROUND

Comminuted proximal humerus fracture fixation is controversial. Locked plate complications have been addressed by anatomic reduction or medial cortical support. The relative mechanical contributions of varus malalignment and lack of medial cortical support are presently assessed.

METHODS

Forty synthetic humeri divided into three subgroups were osteotomized and fixed at 0 degrees, 10 degrees, and 20 degrees of varus malreduction with a locking proximal humerus plate (AxSOS, Global model; Stryker, Mahwah, NJ) to simulate mechanical medial support with cortical contact retained. Axial, torsional, and shear stiffness were measured. Half of the specimens in each of the three subgroups underwent a second osteotomy to create a segmental defect simulating loss of medial support with cortex removed. Axial, torsional, and shear stiffness tests were repeated, followed by shear load to failure in 20 degrees of abduction.

RESULTS

For isolated malreduction with cortical contact, the construct at 0 degrees showed statistically equivalent or higher axial, torsional, and shear stiffness than other subgroups examined. Subsequent removal of cortical support in half the specimens showed a drastic effect on axial, torsional, and shear stiffness at all varus angulations. Constructs with cortical contact at 0 degrees and 10 degrees yielded mean shear failure forces of 12965.4 N and 9341.1 N, respectively, being statistically higher (p < 0.05) compared with most other subgroups tested. Specimens failed primarily by plate bending as the humeral head was pushed down medially and distally.

CONCLUSIONS

Anatomic reduction with the medial cortical contact was the stiffest construct after a simulated two-part fracture. This study affirms the concept of medial cortical support by fixing proximal humeral fractures in varus, if absolutely necessary. This may be preferable to fixing the fracture in anatomic alignment when there is a medial fracture gap.

摘要

背景

肱骨近端粉碎性骨折的固定存在争议。锁定钢板的并发症可通过解剖复位或内侧皮质支撑来解决。目前评估了内翻畸形和内侧皮质支撑缺失的相对力学影响。

方法

将40个合成肱骨分为三个亚组，用锁定肱骨近端钢板（AxSOS，通用型；史赛克公司，美国新泽西州马霍瓦）在0°、10°和20°内翻畸形复位情况下进行截骨并固定，以模拟保留皮质接触的力学内侧支撑。测量轴向、扭转和剪切刚度。三个亚组中每组一半的标本进行第二次截骨，制造一个节段性缺损以模拟去除皮质后的内侧支撑缺失。重复进行轴向、扭转和剪切刚度测试，然后在20°外展位进行剪切载荷直至失效。

结果

对于保留皮质接触的单纯畸形复位，0°时的固定结构在轴向、扭转和剪切刚度方面显示出与其他测试亚组在统计学上相当或更高。随后在一半标本中去除皮质支撑对所有内翻角度的轴向、扭转和剪切刚度都产生了显著影响。0°和10°时保留皮质接触的固定结构平均剪切失效力分别为12965.4 N和9341.1 N，与大多数其他测试亚组相比在统计学上更高（p < 0.05）。标本主要因肱骨头向内侧和远端下压导致钢板弯曲而失效。