Biomechanical And Clinical Study Of Fractures And Dislocaiton Of The Proximal Radius

The proximal radius articulates with the capitulum of humerus to form thehumeroradial joint, functioning as an important structure to maintain thestability of the lateral column of elbow. The alignment between the capitulumand the radial head is impaired when the radial neck is fractured and displacedor the radial head is dislocated. If the treatment for the proximal radial injuryis inappropiate and not able to restore the alignment of humeroradial joint,sequelae as instability, pain, valgus deformity, limited forearm rotation andtraumatic arthritis may will be inevitable. Researchers continuously makeefforts to improve clinical outcomes of proximal radial injuries includingradial head or neck fracture and radial head dislocation as in Monteggia’sfracture-dislocation. We also have made innovations in the fields of minimalinvasive fixation for radial neck fracture and fixation method for radial headdislocation. We have proposed a new technique used in the procedure ofpercutaneous reduction and intramedullary fixation for displaced radial neckfractures. The first two parts of this research aim to provide biomechanical andradiological and functional evidences to back up the clinical usage of this newtechnique. As regards radial head dislocation, we are the first to fix it with asteel-wire loop surrounding the radial neck. The third part of the research isdesigned to prove the effectiveness of this fixation method and find theappropriate manner to fix the steel-wire to the ulna.Part1Biomechanical study of the key technique for intramedullaryKirschner wire fixation of radial neck fractureObjective: To compare the rotational stability of intramedullary K-wirefixations using hammering technique versus drilling technique, to support theclinical adoptation of the hammering technique in the percutaneous reductionand intramedullary fixation procedure to treat displaced radial neck fracture. Methods: Using6pairs of formalin-fixed adult cadaveric radii,transverse fractures were created at the central level of radial neck, thenanatomically reduced and fixed with an intramedullary2.0mm K-wire.Drilling technique was adopted randomly for one side of a pair andhammering technique for its twin. All specimens were tested for torsionalrigidity and strength using Bose ElectroForce3520-AT mechanical testingmachine. Rigidity and strength data of the2groups were compared by pairedt-test.Results:. In this model, hammering technique showed an increase in bothtorsional ridigity (t=3.393, P=0.019) and strength (t=3.176, P=0.025) ascompared to drilling technique. The failure mode of all specimens was internalfixation loosening in the proximal fragment.Conclusion: Percutaneous reduction and intramedullary fixation usinghammering technique is a reliable alternative for radial neck fracture. Thehigher torsional stability of hammering technique may ensure earliermobilization and facilitate the recovery of elbow and forearm function.Part2Percutaneous reduction and intramedullary fixation technique fordisplaced pediatric radial neck fractureObjective: To investigate the outcomes of23cases of pediatric displacedradial neck fracture treated by percutaneous leverage reduction andintramedullary Kirschner wire fixation using hammering technique betweenFebruary2006and Augest2008.Methods: Between Feburary2006and August2008,23pediatric patientsaging8-14years with displaced radial neck fracture, classified as Judet grade3in15cases and grade4in8cases, were treated by percutaneous leveragereduction and intramedullary Kirschner wire fixation using hammeringtechnique. Adequate reduction was achieved using one or two K-wires. One2.0mm diameter K-wire was inserted into the medullary cavity and hammeredinto the proximal fragment to fix the fracture. Patients were followed up onradiological and functional outcomes. The intramedullary K-wires wereremoved8-10weeks after operation. Results:21patients were followed up for37months on average.Radiological follow-up ended on29months after operation, finding19caseshealed on8weeks and2cases on12weeks. Malunion was found in threepatients with an average residual angulation of7.3°. According to MayoElbow Performance Index, excellent outcome was achieved in15patients andgood in6. No heterotopic calcification and instability was detected.Conclusion: The minimal invasive percutaneous leverage reduction andintramedullary Kirschner wire fixation using the hammering technique canachieve adequate reduction and satisfying outcome and therefore is aneffective alternative to treat pediatric displaced radial neck fracture.Part3Biomechanical study of the steel-wire loop fixation for treatingradial head dislocationObjective: To investigate the effectiveness of the steel-wire loop fixationwith4different ulnar tunnel manners through this biomechanical study usingadult cadaveric radial head dislocation model, with an aim to providescientific evidence for the clinical use of this fixation on adult traumatic radialhead dislocation cases.Methods: Four pairs of formalin-fixed adult cadaveric upper extremitieswere used for analysis. The specimens were disarticulated at the radiocarpallevel carefully preserving the distal radioulnar joint. Transverse osteotomieswere created at the junction of the distal and middle thirds of the humerus. Allsoft tissues were stripped off the bone except the capsule, annular ligamentand interosseous membrane. The distal ulna was connected to the motion unitof Bose ElectroForce3520-AT testing machine and the osteotomy end of thehumerus was rigidly attached to its fixed unit, with the elbow fully extendedand the forearm rotation axis passing through the torsional center of themachine. A torsion test, rotating the forearm from maximum supinationposition to maximum pronation position and then back to the initial position,was carried out while the humeroradial joint capsule, annular ligament andinterosseous membrane were intact. Then these three structures were allremoved to prepare the radial head dislocation model. We designed four type of ulnar tunnel through which the steel-wire loop was fixed:(1) single anteriortunnel,(2) single middle tunnel,(3) single posterior tunnel, and (4) anteriorand posterior tunnels. Same torsion tests were executed after each type ofsteel-wire loop fixation was applied to the models. The testing processes wererecorded by two high-resolution cameras on coronal plane and sagittal plane.The coronal and sagittal locations of the radial head were measured on thevideo images and calculated at every10degrees in the range available for allspecimens. Statistical analysis was performed using variance analysis of therandomized block design and SNK test.Results: The available range of rotation motion for all specimens wasfrom90°of supination to50°of pronation. During pronation, the coronallocations of radial head after middle tunnel, posterior tunnel and two tunnelfixations all varied following the normal trend and slight lateral translationwas detected under these three conditions (middle tunnel> posterior tunnel>two tunnel); whereas the coronal location of radial head after anterior tunnelfixation deviated medially as the forearm pronating; comparison with thenative case found significant difference only at90°of supination after middletunnel fixation(P<0.05). During supination, the radial head moved following atendency symmetric to that in the process of pronation; comparison of radialhead location between native case and the steel-wire loop fixation cases foundsignificant difference only at50°and40°of pronation with anterior tunnelfixation(P<0.05). During pronation, the sagittal locations of radial head aftermiddle, posterior and two tunnel fixations were very close to that of nativecase in the first half of the process and translate anteriorly in the second halfwith no significant difference from the native case(P>0.05); the anteriortranslation of radial head after anterior tunnel fixation was significant from80°of supination to50°of pronation(P<0.05). As the forearm supinating, theradial head remained steady in the native case but traveled posteriorly in allsteel-wire loop fixation cases; the anterior translation of radial head locationwas significant during the whole process after anterior tunnel fixation(P<0.05); significant posterior translation was found at80°and90°of supination after posterior tunnel fixation(P<0.05). In general, after steel-wireloop fixation, the change in sagittal location of radial head was greater thanthe change in its coronal location. Anterior tunnel fixation changed both thecoronal and sagittal location of radial head more than any other cases, with thetwo tunnel fixation being the opposite.Conclusions: Temporary steel-wire loop fixation after annular ligamentrepair of reconstruction for the treatment of adult traumatic radial headdislocation can ensure the stability of humeroradial joint, facilitating thehealing of repaired or reconstructed annular ligament. Fixation of the steelwire through anterior and posterior tunnels is the best method. Alternativesare fixations through single middle tunnel or single posterior tunnel. Singleanterior tunnel is not recommended.