Biomechanics Research Of Internal Fixation Methods For Floating Shoulder Injury Treatment

Ⅰ,Back ground and PurposeFloating shoulder injury (FSI) is a serious unstable damage, refers to the fractures of ipsilateral collarbone and scapula neck, which caused the double damage of the superior suspensory shoulder complex results in shoulder joint weakness, unstable, floating. The superior suspensory shoulder complex (SSSC) is composed by bone and soft tissue (including glenoid cavity, coracoid, coracoclavicular ligament distal clavicle, acromioclavicular joint and acromion). The double damage of the superior suspensory shoulder complex expanded the scope of floating shoulder injury further. Acromioclavicular joint dislocation or distal clavicle fracture merger ipsilateral scapula neck fracture to be part of the generalized floating shoulder injury.Clavicle fractures and Acromioclavicular joint dislocation are common clinical type of injury, whose treatment currently has basically agreed. The scapula neck fractures formed two major part, including glenoid cavity block and scapula body block. Glenoid cavity fracture is composed by anatomic neck fracture and surgical neck fracture.Glenoid cavity block due to lost the direct support of scapula body block, as well as lack the indirect support of ligaments and muscles around, which prevent shoulder completely instability by surgery.The surgical neck block is connected directly to the collarbone through coracoclavicular ligament, acromion through coracoacromial ligament, and distal clavicle through acromioclavicular ligament. If these ligaments are ruptured, glenoid cavity block will lost connection with collarbone and human body axis bone, which must bone surgery in order to prevent shoulder instability. Abroad Willams, etc have biomechanical study of effect of collarbone,coracoclavicular ligament, coracoacromial ligament, and acromioclavicular ligament for the model of scapula neck fractures on cadavers. they thought distal clavicle cannot float without rupture of coracoacromial ligament and acromioclavicular ligament in the case of ipsilateral collarbone and scapula neck fractures. Is it necessary to cure surgical neck fracture by surgical inner fixation? Nomadays, there are many arguments on the treatment of FSI, which focus on whether need inner fixation or require single steel plate or double.Although there are arguments on the treatment of FSI of ipsilateral collarbone (or acromioclavicular joint dislocation) and scapula neck fractures, early surgery is dominant now.Reconstructione plates are applied for collarbone fractures. Clavicle hook plates are used for acromioclavicular joint dislocation.Though there are many clinical follow-up reports in the literature on single plate or double plates applied for scapula neck fractures, different fixations lack biomechanical data which could prove the effect on scapula neck fractures. The goal of this cadaver study evaluate the different fixations of FSI in the clinical treatment, and provide biomechanics basis for the choices of different fixations.Ⅱ,Mesthords1. Material PreparationPrepare 14 anti-corrosion specimen of upper limbs containing collarbone and scapula (left and right respective 7 cases), unlimit for gender, ages range 35-56 years old, average 48 years old, remove the skin, subcutaneous tissue and muscles around the brachial joints, detach glenohumeral joint, reserve collarbone, scapula, coracoclavicular ligament, coracoacromial ligament, and acromioclavicular ligament, fabricate man-made model of SSSC. All the specimens are taken X-ray, get rid of rheumatism, tuberculosis, cancer and have similar size and weight. All the specimens meet the requirements and are sealed by double package after spraying physiological saline, have a-20℃cryopreservation.Thaw the specimens 6 hours earlier before experiment at room temperature embed them according to normal human anatomical relation, sustain with polyethylene pipe between proximal collarbone and and scapula, make use of methyl methacrylate (self-congealing type, Shanghai dental material factory) to embed both as base. Then fix five screws in central and peripheral of the glenoid labrum, and embed them together. Specimens must be close to fixture, in case mobilization during testing. 2. Experimental designPrepare 7 anti-corrosion specimen of left upper limbs containing collarbone and scapula. The state of unfracture of collarbone and scapula neck is signed for normal specimens group (group A), as self-contrast. Bonesaw the middle clavicle and scapula surgery neck, namely man-made model of floating shoulder injury. Respectively for damage model do three different fixation:pure collarbone fixation (group B), clavicle fixation and scapula neck with single plate fixation (group C), clavicle fixation and scapula neck with double plate fixation (group D). Observe the ROM changes of four groups in six different directions and process biomechanical evaluation.Prepare 7 anti-corrosion specimen of right upper limbs containing collarbone and scapula. The state of uninjury of acromioclavicular joint and scapula neck is signed for normal specimens group (group A), as self-contrast. Sword the acromioclavicular ligament and Bonesaw the scapula surgery neck, namely man-made model of floating shoulder injury, which is signed for injury specimens group (group B), Fix injury model (Reconstructione plates for collarbone fractures, Clavicle hook plates for acromioclavicular joint dislocation), is signed for fixed specimens group (group C). Observe the changes of the ROM and the NZ of three groups in six different directions and process biomechanical evaluation.3. Fixed patternClavicle fractures adopt 6 hole reconstruction plate placing the center of broken end, three screws on each side, then process stability testing. Scapula neck fractures in turn do single plate fixation (preflexed reconstruction plate of five holes lay longitudinally on the scapula neck-scapula lateral margins, neck:body= 1:4), double plate fixation (preflexed reconstruction plate of four holes lay latitudeiy on the scapula neck-basal parts of the scapula hummock. neck:body= 1:3; preflexed reconstruction plate of five holes lay longitudinally on the scapula neck-scapula lateral margins, neck:body=1:4), then process three-dimensional 6 DOF stability testing.Preflexed clavicle hook plates of five holes fix acromioclavicular joint dislocations. Scapula neck fractures double plate fixation (preflexed reconstruction plate of four holes lay latitudeiy on the scapula neck-basal parts of the scapula hummock. neck:body=1:3; preflexed reconstruction plate of five holes lay longitudinally on the scapula neck-scapula lateral margins, neck:body=1:4), then process three-dimensional 6 DOF stability testing.4. Testing procedureUsing spine three-dimensional motion analysis system (southern medical university, medical biomechanics key laboratory), refer to the study of Zhu Qing an, etc, and combine with time and again practical operation, simultaneously load 3Nm tension bilaterally, test the changes of three-dimensional 6 DOF under different states (Flexion/Extension, Left bending/Right bending, Left tortion/Right tortion).4.1 Scapula coronal displacement in up and downWhen load 3Nm tension on motion analysis device in left up and right down traction bow, scapula neck is maximum up displacement in the coronal (extension). then scan 3D images and preserve them. After that, remove bilateral loads, make the axis of motion analysis device and scapula neck coincidence, scan the 3D images of neutral position and preserve them. Next, When load 3Nm tension on motion analysis device in right up and left down traction bow, scapula neck is maximum down displacement in the coronal (flexion). then scan 3D images and preserve them. After that, remove bilateral loads, make the axis of motion analysis device and scapula neck coincidence again, scan the 3D images of neutral position and preserve them.4.2 Scapula coronal displacement in front and backWhen load 3Nm tension on motion analysis device in left up and right down traction bow, scapula neck is maximum forward displacement in the coronal (left bending). then scan 3D images and preserve them. After that, remove bilateral loads, make the axis of motion analysis device and scapula neck coincidence, scan the 3D images of neutral position and preserve them. Next, When load 3Nm tension on motion analysis device in right up and left down traction bow, scapula neck is maximum backward displacement in the coronal (right bending). then scan 3D images and preserve them. After that, remove bilateral loads, make the axis of motion analysis device and scapula neck coincidence again, scan the 3D images of neutral position and preserve them.4.3 Scapula coronal displacement in rotating shiftWhen load 3Nm tension on motion analysis device in left anterior and right posterior traction bow, scapula neck is maximum supination displacement in the coronal (Left tortion). then scan 3D images and preserve them. After that, remove bilateral loads, make the axis of motion analysis device and scapula neck coincidence, scan the 3D images of neutral position and preserve them. Next, When load 3Nm tension on motion analysis device in right anterior and left posterior traction bow, scapula neck is maximum pronation displacement in the coronal (right tortion). then scan 3D images and preserve them. After that, remove bilateral loads, make the axis of motion analysis device and scapula neck coincidence again, scan the 3D images of neutral position and preserve them.Import 3D scanning images into Geomagic Studio 8.0 reverse engineering software, and analyse the images, standard errora< 0.05. Summarize and preserve datas, then process the statistical analysis.5. Statistical analysisThe datas are analyzed by the statistical software SPSS 13.0, which are showed by mean±SD (x±s). Statistical method is repeated measurement ANOVA. First of all, all datas proceed double factors repeated measurement ANOVA.If the P value of Mauchly spherical inspection is more than 0.05, does not refuse to spherical hypothesis; if the P value is less than 0.05, use the Greenhouse-Geisser correction factor to correct the results. Calculate the F values and P value of the primary effect and the interaction effects. Then, different groups and statuses proceed single factor repeated measurement ANOVA. If the P value of Mauchly spherical inspection is more than 0.05, does not refuse to spherical hypothesis; if the P value is less than 0.05, use the Greenhouse-Geisser correction factor to correct the results. The level of significance is a=0.05 in all datas.6. AttentionFirst, maintain the normal length and position relation of clavicle and scapula; Secondly, standardize operation, minimize the defect error; Then, fix the screws into all the holes of the plate as far as possible, choose moderate screws to increase stability, and reduce the effects of the non-experimental factors; Finally, embed the specimen fully, avoid free cavity and gap.Ⅲ,ConclusionsThe collarbone (or acromioclavicular joint dislocation) and the scapula neck fixed simultaneously is an optimal fixation for the treatment of floating shoulder injury. In addition, the neck of scapula must adopt double steel plate fixation, which could avoid the instability of shoulder caused by malunion and get a satisfying effect.