Biomechanical and clinical study on screw hook fixation after direct repair of lumbar spondylolysis / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To evaluate the biomechanical effect and clinical results of hook screw fixation after direct repair of lumbar spondylous defects in the pars interarticularis.</p><p><b>METHODS</b>L(2)-L(6) spines of 8 fresh-frozen and thawed calf cadavers were used for mechanical testing. Bilateral spondylous defects were created in the L(4)vertebra. The intervertebral rotation ranges between L(4) and L(5) were scanned and computerized in various states of motion, such as flexion/extension, lateral bending and torsional loadings applied on the intact spine and the spondylous spine when the spondylous spine was fixed with modified Scott's fixation, hook screw fixation and Buck's fixation sequentially and respectively. Between July 2002 and February 2004, 14 young male patients (aged 15-31 years) suffering from symptomatic lumbar spondylolysis were treated with TSRH hook screw fixation after direct repair of the defects. MacNab criteria were used to assess their pre-and post-operative status.</p><p><b>RESULTS</b>Each fixation technique could significantly increase the intervertebral rotational stiffness and made the stiffness return to nearly the intact level. Hook screw technique provided more rotational stability than the others. Hook screw and Buck's techniques provided more flexion/extension stability than modified Scott's technique. Neither complication nor instrumental failure was observed in this study. The mean follow-up period was 21 months. All the patients except one acquired union during the follow-up period. Thirteen patients had a "good" or "excellent" result according to MacNab criteria.</p><p><b>CONCLUSIONS</b>Hook screw fixation shows biomechanical advantages and is safe and effective for young patients with lumbar spondylolysis.</p>

A new type of fusion apparatus of seaphoid-trapezium-trapezoid for limited interearpal arthrodesis / 中华创伤骨科杂志

Objective To develop a new type fusion apparatus for scaphoid-trapezium-trapezoid (STT) arthrodesis.Methods The apparatus was designed on the basis of the anatomic data of STT measured from Chinese cadaveric wrists.Simulated arthrodeses of STT joints were conducted to test the fixation performance of the apparatus made of titanium alloy on the STT joint specimens.Several modifications were made before the apparatus was made into a finished product.Results The fusion apparatus consists of a plate and screws.The fusion plate for STT arthrodesis is made into a taper one connected to a cylinder.On the plate are three screw holes through which the three carpal bones (STT) are fixed by three screws respectively.The hollow cylinder is designed for bone grafting,and its outer threads ensure a very tight contact between the fusion plate and the carpal bones.Auxiliary tools are also made.Conclusions As the novel design of the fusion apparatus improves the mechanical strength of fixation of STT and prevents the possible rotation and collapse of fused STT,the apparatus is a reliable internal fixation device for the limited intercarpal arthrodesis.