中华肩肘外科电子杂志
中華肩肘外科電子雜誌
중화견주외과전자잡지
Chinese Journal of Shoulder and Elbow (Electronic Edition)
2015年
2期
7-13
,共7页
白露%张洪雷%陈鹏%李伟%江长青%张文涛
白露%張洪雷%陳鵬%李偉%江長青%張文濤
백로%장홍뢰%진붕%리위%강장청%장문도
肱骨骨折 ,近端%肱骨头%内翻畸形%锁定钢板
肱骨骨摺 ,近耑%肱骨頭%內翻畸形%鎖定鋼闆
굉골골절 ,근단%굉골두%내번기형%쇄정강판
Humral fracture,proximal%Humral head%Inversion deformity%Locking plate
目的：探讨肱骨头内翻状态下锁定钢板固定肱骨近端骨折内固定失败的生物力学原因。方法采用防腐处理肱骨标本6对，经肱骨外科颈截骨制作肱骨近端骨折模型。根据不同临床情况分为力线正常组和肱骨头内翻组。通过循环轴向压缩试验（5000次）和静态轴向压缩破坏试验对两组骨折内固定模型进行生物力学测试。结果在循环轴向压缩试验早期，肱骨头内翻组骨折块间隙移位与力线正常组差异无统计学意义（ P ＞0．05）。在循环压缩3000次后，肱骨头内翻组骨折端移位明显高于力线正常组。在破坏力学实验中，肱骨头内翻组内固定失败所需载荷明显小于力线正常组（ t ＝3．812，P ＝0．003）。内固定失败轴向最大移位，力线正常组明显高于肱骨头内翻组（ t ＝2．994， P ＝0．013）。结论肱骨头内翻畸形显著降低了肱骨近端骨折锁定钢板内固定系统的稳定效能。
目的：探討肱骨頭內翻狀態下鎖定鋼闆固定肱骨近耑骨摺內固定失敗的生物力學原因。方法採用防腐處理肱骨標本6對，經肱骨外科頸截骨製作肱骨近耑骨摺模型。根據不同臨床情況分為力線正常組和肱骨頭內翻組。通過循環軸嚮壓縮試驗（5000次）和靜態軸嚮壓縮破壞試驗對兩組骨摺內固定模型進行生物力學測試。結果在循環軸嚮壓縮試驗早期，肱骨頭內翻組骨摺塊間隙移位與力線正常組差異無統計學意義（ P ＞0．05）。在循環壓縮3000次後，肱骨頭內翻組骨摺耑移位明顯高于力線正常組。在破壞力學實驗中，肱骨頭內翻組內固定失敗所需載荷明顯小于力線正常組（ t ＝3．812，P ＝0．003）。內固定失敗軸嚮最大移位，力線正常組明顯高于肱骨頭內翻組（ t ＝2．994， P ＝0．013）。結論肱骨頭內翻畸形顯著降低瞭肱骨近耑骨摺鎖定鋼闆內固定繫統的穩定效能。
목적：탐토굉골두내번상태하쇄정강판고정굉골근단골절내고정실패적생물역학원인。방법채용방부처리굉골표본6대，경굉골외과경절골제작굉골근단골절모형。근거불동림상정황분위력선정상조화굉골두내번조。통과순배축향압축시험（5000차）화정태축향압축파배시험대량조골절내고정모형진행생물역학측시。결과재순배축향압축시험조기，굉골두내번조골절괴간극이위여력선정상조차이무통계학의의（ P ＞0．05）。재순배압축3000차후，굉골두내번조골절단이위명현고우력선정상조。재파배역학실험중，굉골두내번조내고정실패소수재하명현소우력선정상조（ t ＝3．812，P ＝0．003）。내고정실패축향최대이위，력선정상조명현고우굉골두내번조（ t ＝2．994， P ＝0．013）。결론굉골두내번기형현저강저료굉골근단골절쇄정강판내고정계통적은정효능。
Background Proximal humerus fracture (PHF ) is a common disease in the traumatic orthopedics due to decreased density of bone in the proximal humerus with age .It occurs more often in the medium‐and old‐age people ,accounting for 5% of fractures .With the process of aging population ,the incidence of PHF tends to increase .In recent 20 years ,the surgery methods of unstable PHF change greatly from the percutaneous fixation and common plate for fractures to locking plate fixation with "internal fixator" as mainstay .As the locking plate is widely used for PHF ,some medium‐and long‐term clinical follow‐up data indicated loss of reduction of fracture ,varus deformity of humeral head ,and secondary internal fixation failure were found in PHF cases with two or three sites of defective medial cortex .These complications are characterized by defective medial cortex and varus deformity of humeral head .Over time ,it causes varus and prolapsed of humeral head ,breakage of screws or plate .From biomechanics ,the loss of support for proximal humerus by the medial cortex is an unstable factor .But not all cases with defective medial cortex develop internal fixation failure .The types of internal fixation failure vary in patients .Is the varus deformity of humerus head another risk factor for internal fixation failure? This study investigated the relationship between the varus deformity of humeral head and the internal fixation failures after locking plate treatment for PHF from the biomechanics .Methods Sample treatment and establishment of fracture model:6 pairs of adult humeral samples with antiseptic treatment were obtained from the anatomy department of the Shenzhen University‐affiliated Medical School .The pathological symptoms such as bone disease and chronic fracture were excluded by radiograph .The samples were stored at -20 ℃ before biomechanical study and thawed at room temperature (18 ℃) for 8 h when the biomechanical study was about to start .During thawing ,samples were sprayed with normal saline to prevent drying .Either right or left side of the samples was randomly assigned to the varus deformity group and normal alignment group to establish the fracture model .The fracture model was established on the X‐Y workbench .First ,20 cm was removed from the proximal ends of all samples .The osteotomy was performed in parallel with the vertex tangent of the humeral head at the surgical neck on the junction between humeral metaphysis and the humeral head using oscillating saw .The cortex of the lateral greater tuberosity in proximal humerus was reserved at an amount accounting for 1/3 of the perimeter ,which helped to insert the PHILOS plate .The fracture gap between the osteotomy surfaces was 10 mm .The varus deformity of humeral head was prepared using the method described by Voigt et al .The varus of humeral head by 20° was measured using gauge on the X‐Y workbench .All fractures were fixed using 5‐hole Synthesis PHILOS locking plate .According to recommendation by the AO Organization ,the plate was placed on the greater tuberosity 5‐8 mm away from the intertubercular sulcus ,8‐10 mm away from the greater tuberosity tip .The PHILOS plate was fixed in holes A ,B ,C ,D and E .Three locking screws were used to fix the distal end .All screws were 3 .5 mm locking screws .Procedures of mechanical study :Fixation and testing of samples :The mechanics study was performed on the Instron 8874 (2 kN ,± 1% ) mechanical tester .The fracture model was fixed at the workbench of the tester .The axis of the humeral shaft was vertical to the pressure head of the mechanical tester .The pre‐moulding for mechanical pressure head in the axial compression was prepared using bone cement ,which was matched for the shape of humeral head to avoid damage of the surface of humeral head at the area with concentrating stress during compression .The circular axial compression experiment was performed under the following conditions :minimum pressure of 50 N , maximum pressure of 300 N ,permitted maximum displacement of 5 mm ,cycle number of 5 ,000 .The biomechanical curve was expressed by displacement‐load curve .Determination of internal fixation failure:In the axial compression experiment ,the sample was regarded as internal fixation failure if the variation of the data curve of each sample was within the range of the curve for flexible variables .In the damage mechanical experiment ,real‐time displacement of mechanical tester‐load curve was observed .In the damage mechanical experiment ,the presence of inflection point on the displacement‐load curve when the displacement curve tended to be zero indicated failure of internal fixation .The mechanical measurement was stopped after failure of internal fixation .The samples were removed for observation .The types of internal fixation were recorded .Statistical analysis :The statistical analysis was performed using PASW18 .0 (SPSSInc IBM Chicago ,USA) .The measurement data was expressed as ± s .The difference of maximum load to damage internal fixation in different groups was compared using student t test .The differences in the maximum and minimum displacement of circular mechanics between the varus group and alignment normal group were compared using Mann Whitney‐Wilcoxon . The independent‐sample test was performed for comparison of differences in maximum damage load and maximum displacement of the samples with internal fixation failure between groups .P < 0 .05 indicatedstatisticalsignificance.Results (1)Resultsofcircularmechanics:In5,000axial compressions ,6 pairs of samples did not show internal fixation failure .In measurement of the pressure during axial cycles ,the varus group had greater minimum and maximum displacements than the normal alignment group within 2 ,000 cycles of axial compression ,although no significant difference was found ( P >0 .05) .The mean maximum displacement in the varus group was 2 .37 mm (1 .01‐2 .78) at 3 ,000 cycles of axial compression ,significantly different from 1 .73 mm (0 .91‐2 .08) in the normal alignment group ( P = 0 .044) .After 4 ,000 cycles of axial compression ,the varus group had significantly higher minimum displacement ( P = 0 .039) and maximum displacement ( P = 0 .037) than the normal alignment group .After 5 ,000 cycles of axial compression ,the varus group had a mean minimum displacement of 0 .91 mm (0 .39‐1 .23) and a mean maximum displacement of 3 .08 mm (1 .78‐3 .67) .The normal alignment group had a mean minimum displacement of 0 .56 mm (0 .37‐0 .86) and a mean maximum displacement of 2 .32 mm (1 .58‐2 .94) .The normal alignment group had significantly lower mean minimum displacement ( P =0 .026) and mean maximum displacement ( P=0 .019) than the normal alignment group .(2) Results of damage mechanics:The damage mechanical experiment was performed immediately after the circular load experiment .The mean damage loads were 870 ± 104 N for the normal alignment group and 632 ± 111 N for the varus deformity group . There was significant difference between two groups ( t =3 .812 ,P =0 .003) .In cases with internal fixation failure ,the mean fracture gap displacements were 6 .72 ± 0 .71 mm for the normal alignment group and 5 .67 ± 0 .53 mm for the varus group .There was significant difference between the two groups ( t =2 .994 ,P =0 .013) .Conclusion The varus deformity of the humeral head significantly lowered the stabilization performance of the locking plate internal fixation system for the PHF .
