Static and gait finite element analysis on individualized titanium alloy pelvic prosthesis manufactured by 3D printing / 医用生物力学

Objective To evaluate the biomechanical properties of 3D printed individualized titanium alloy pelvic prosthesis in static and gait states by the method of finite element analysis. Methods Three patients with different types of pelvic tumors were treated by hemi-pelvic arthroplasty with resection of hemi-pelvis. CT and MRI were performed before the surgery, and the corresponding individualized titanium alloy pelvic prostheses were designed. The pelvic models were reconstructed with 3D reconstruction technique, and then assembled with the individualized pelvic prostheses. The human skeletal muscle model was established by AnyBody software to perform gait dynamics analysis. The stress distribution and stress concentration areas of 3 reconstructed pelvic models in static and gait states were obtained by ABAQUS. Results Under both static and gait conditions, the maximum stress of the 3 pelvic prostheses was smaller than the yield strength of the titanium alloy. The pelvic ring of the reconstructed pelvis could meet the rule of stress conduction. The patients’ daily life returned to normal condition after the surgery. Conclusions The effect of 3D prosthetic titanium prosthesis on recovery of pelvic ring is satisfactory, and its effectiveness and stability can meet the requirement of human biomechanics. The analytic results can provide references for clinicians and prosthesis designers.

Static and gait finite element analysis on individualized titanium alloy pelvic prosthesis manufactured by 3D printing / 医用生物力学

Objective To evaluate the biomechanical properties of 3 D printed individualized titanium alloy pelvicprosthesis in static and gait states by the method of finite element analysis.Methods Three patients with different types of pelvic tumors were treated by hemi-pelvic arthroplasty with resection of hemi-pelvis.CT and MRI were performed before the surgery,and the corresponding individualized titanium alloy pelvic prostheses were designed.The pelvic models were reconstructed with 3D reconstruction technique,and then assembled with the individualized pelvic prostheses.The human skeletal muscle model was established by AnyBody software to perform gait dynamics analysis.The stress distribution and stress concentration areas of 3 reconstructed pelvic models in static and gait states were obtained by ABAQUS.Results Under both static and gait conditions,the maximum stress of the 3 pelvic prostheses was smaller than the yield strength of the titanium alloy.The pelvic ring of the reconstructed pelvis could meet the rule of stress conduction.The patients' daily life returned to normal condition after the surgery.Conclusions The effect of 3D prosthetic titanium prosthesis on recovery of pelvic ring is satisfactory,and its effectiveness and stability can meet the requirement of human biomechanics.The analytic results can provide references for clinicians and prosthesis designers.

Bone cortex segmentation of CT images based on BP neural network / 医用生物力学

Objective To measure the bone mass, the shape of bones and the bone strength through segmentation of the bone cortex in CT images, and to calculate the corresponding parameters in histomorphometry. Methods CT images were first interpreted through the DCMTK to draw information of the corresponding images, then the OpenCV are used for preprocessing on the basis of ROI (range of interest), and the texture features of the image were extracted as the input vector. Results of the manual segmentation were used as the mentor signal to train BP neural network, which were then used for segmenting the bone cortex in a sequence of CT images. Results of the segmentation were further processed and displayed. Results The segmentation efficiency of the bone cortex in CT images through neural network met the needs of the practical application. The separation results showed an obvious shape of the bone cortex with easy distinguishing from the surrounding tissues, which could satisfy the demand of the clinical diagnosis. Conclusions When the texture features of the bone cortex are evident, this method can achieve a more satisfying segmentation effect with smooth contours, high segmentation accuracy and strong adaptability. With less artificial intervention in the process of the image segmentation, this method can be used for batch CT image segmentation of a complete set of the bone cortex. The inadequacy of the method lies in relatively longer training time demanded for the neural network training.

Design and clinical application of the drilling guide in the treatment of acromioclavicular joint dislocation with closed reduction and Kirschner fixation / 中国骨伤

<p><b>OBJECTIVE</b>To investigate a drilling guide in the treatment of acromioclavicular joint dislocation with closed reduction and Kirschner fixation and explore the therapeutic effect.</p><p><b>METHODS</b>From June 2008 to December 2009, 36 patients with acromioclavicular joint dislocation (Tossy III) were treated with closed reduction and Kirschner fixation using a self-designed drilling guide as well as percutaneous repair of acromioclavicular joint. Among the patients, 24 patients were male and 12 patients were female,ranging in age from 20 to 61 years, averaged 38.6 years. The duration from injury to operation ranged from 3.5 to 72 h,with a mean of 15.2 h. No clavicle fracture was found in all cases. The operative time, intra-operative bleeding and therapeutic effects were observed.</p><p><b>RESULTS</b>There were no complications including neurovascular problems. The mean operating time were 20 min,mean blood loss were about 10 ml. According to the observation of postoperative X-ray examination, all Kirschners in acromioclavicular joint were in place. All Kirschners were removed in 6 postoperative weeks. All the patients were followed up ranging from 2 to 26 months (averaged 14.3 months). According to the Karlsson standard,22 patients got an excellent result, 13 good and 1 poor.</p><p><b>CONCLUSION</b>This method has following advantages: easy operation and fixation; minimum injuries to articular surface; and which would be widely used in clinical practice.</p>

Clinical study of lumbar fusion by hybrid construct of stem cells technique and biodegradable material / 中华外科杂志

<p><b>OBJECTIVE</b>To explorer the effectiveness of enriched bone marrow stem cells technique for lumbar fusion.</p><p><b>METHODS</b>With the randomization and control principles, 2 graft materials [Enrichment bone marrow mesenchymal stem cells hybridized with beta-tri calcium phosphate (composite graft group), autologous iliac crest bone graft (autograft group)] were compared in posterior lumbar fusion procedures. 56 patients with degenerative disc disease, lumbar instability or spinal stenosis, were included. The volume of cells suspension in pre- and post-enrichment and the number of nucleated cells (NCs) were identified. The number of osteoprogenitor cells was estimated by counting the colony-forming units which express alkaline phosphatase (CFUs/ALP+). Then the efficiency of the enrichment was evaluated. Clinical follow-up with roentgenogram and Oswestry scale scores was performed for outcome evaluation.</p><p><b>RESULTS</b>(249 +/- 31) ml bone marrow per patient from bilateral iliac crests was aspirated peri-operatively. About (43 +/- 11) ml enriched bone marrow was collected. The number of NCs was concentrated from (15.9 +/- 3.3) x 10(6)/ml to (44.1 +/- 10.8) x 10(6)/ml, CFUs/ALP+ was significantly increased from (118 +/- 86)/ml to(486 +/- 305)/ml. The follow-up was about (26.3 +/- 7.5) months. There was no significant differences in age, gender, disease and fusion segments between the two groups. The fusion rate was 93.3% and 96.2% for composite graft group and autograft group, respectively (chi2 = 0.2146, P = 0.6432). There was no difference in operation time between the two group (t = 0.5243, P = 0.6022), but blood loss in composite graft group was more than that in autograft group (t = 6.4664, P < 0.01). Cell salvage for auto-transfusion could transfuse back half of the blood loss during operation. No hematoma or chronic soreness in the bone marrow donor sites of composite graft group occurred, but a little exudation or moderate swelling in the wound happened in 4 cases which disappeared under medical treatment. Meanwhile, 15.4% patients had hematoma in the iliac bone donor site and 26.9% patients had chronic soreness, but no case had wound problem in autograft group. As for Oswestry scale scores, there was no significant difference between the two groups.</p><p><b>CONCLUSIONS</b>The enrichment technique of autologous bone marrow stem cells can greatly increase the concentration of MSCs. It is a rapid and safe method used peri-operatively. The composite material of enriched MSCs and porous beta-TCP is a good bone substitute in posterior spinal fusion.</p>

Total hip arthroplasty for Crowe type-IV development dysplasia of hip in adults / 中华外科杂志

<p><b>OBJECTIVE</b>To determine the operation procedure of total hip arthroplasty (THA) for Crowe type-IV developmental dysplasia of hip and its relationship with nerve injury.</p><p><b>METHODS</b>A consecutive series of 39 THAs was performed for Crowe type-IV developmental dysplasia of hip in 35 patients (all female). The mean age of the patients at the time of surgery was 46 years (range 36 - 56 years). Thirty-five hips in 31 patients were followed up. The average follow-up period of the whole series was 4 years (range 1 - 8 years). All procedures were carried out through a lateral-posterior approach. In 33 of 35 hips, the cup was inserted in the "true" acetabulum. All the prostheses used were cementless, except for 5 cemented femoral stems in 5 patients. Each patient was evaluated clinically and by radiographs before the operation and during the follow-up period, according to the Harris hip score (HHS).</p><p><b>RESULTS</b>None of the cups and stems were revised for aseptic loosening, dislocation or infection during the follow-up period. The mean preoperative HHS was 43 compared with the postoperative HHS of 87. The mean amount of postoperative leg lengthening was 5 cm (range 4 - 6 cm).</p><p><b>CONCLUSIONS</b>The reconstruction of the hip at the level of the "true" acetabulum through a lateral-posterior approach is a safe and effective procedure of THA for Crowe type-IV developmental dysplasia of hip in adults. Acute leg lengthening of less than 6 cm could not cause nerve injury.</p>

A prospective study of the anterior cruciate ligament reconstruction: allograft versus autograft / 中华外科杂志

<p><b>OBJECTIVE</b>To compare the clinical outcomes and differences of arthroscopic anterior cruciate ligament (ACL) reconstruction by using allografts and autografts.</p><p><b>METHODS</b>Fifty-three patients with grade III ACL injuries were divided randomly into 2 groups. Twenty-five cases of group A with autografts of patellar bone-tendon-bone (B-PT-B;n = 15) and 4 strands of semitendinosus/gracilis (n = 10); 28 patients of group B with allografts of B-PT-B (n = 18), 4 strands of semitendinosus/2 strands of gracilis tendons (n = 6) and double tibialis posterior (n = 4) as well as Achilles bone-tendon (n = 2). All procedures were performed endoscopically by some surgeons. All patients were followed up for 12 to 31 months, average 19 months.</p><p><b>RESULTS</b>There were statistically significant differences revealed in physical examination. IKDC and Lysholm-Tegner Score as well as KT-2000 testing was used preoperation and postoperation for both group, but there were no significant differences between the two groups except that group B had less time in operation and longer time in postoperative fever comparing with group A. (2-sample t test, P < 0.05). The KT-2000 side to side difference less than 3 mm were 88% and 86% and more than 5 mm were 4% and 7.1% respectively. The infection rates were 0% and 3.5% for the two groups.</p><p><b>CONCLUSION</b>The clinical outcomes of the allografts and autografts in ACL reconstruction is almost the same. Allografts are a reasonably alternative choice for ACL reconstruction in patients over middle ages and for multiple ligament surgery as well as revision procedures.</p>