BACKGROUND: Finite element method has become an important means for biomechanical study against sideways falls because of its unlimited sample size, small experimental error and good repeatability.OBJECTIVE: To establish three-dimensional normal pelvis and brace-covered pelvis models and then to analyze the stress, strain and displacement distribution during sideways fall and to verify the effectiveness of hip brace.METHODS: Digital human Abaqus 6.51 software was used to build three-dimensional normal pelvis and brace-covered pelvis models. The rigid constraint surface was fixed. The whole pelvic model was loaded with 2 m/s loading. The stress, strain and displacement variation with time and contours were detected prior to and after wearing the hip brace. RESULTS AND CONCLUSION: Compared with the normal model, the contact force between the pelvis and the ground, the maximal compression strain of the cancellous bone when the maximal contact force between the pelvis and the ground generated, the maximal strain of the greater trochanter and femoral neck, the maximal von-Mises stress of the greater trochanter and femoral neck, and the mean stress of the greater trochanter and femoral neck were significantly reduced in the brace-covered pelvis model during sideways falls. These findings indicate that the hip brace can play a protective role in the greater trochanter, and effectively reduce the incidence of intertrochanteric fractures during sideways fall.

BACKGROUND:Posttraumatic osteomyelitis is bone infection after surgery of open fractures or other joint, which leads to more secretions in antrum or bone exposed wounds, long treatment cycle, delayed healing of fracture, even disunion. The key link in the treatment is complete debridement, adequate drainage, and the use of external fixators with low interference and far away from lesions. ＜br> OBJECTIVE:To observe the clinical efficacy of external fixator combined vacuum sealing drainage (VSD) in the treatment of post-traumatic osteomyelitis, and compared with conventional catheter drainage. ＜br> METHODS:Since June 2010 to June 2013, 21 patients of post-traumatic chronic osteomyelitis were included in this study and divided into VSD group (n=11) and conventional catheter drainage group (n=10). Al patients in VSD groups underwent debridement and VSD was used to fil dead space, then the wounds were sutured. Cases appeared nonhealing fractures underwent external fixation, 10 cases using external fixators and 1 case retained original external fixator. Al patients achieved the closed wounds at the second phase, 9 cases were directly sutured, and 2 cases received skin flap transplantation. Among them, 1 case received autologous bone graft at the third phase because of bone defects. In the conventional catheter drainage group, al patients underwent debridement and conventional catheter drainage to rinse the wounds after surgery, 3 cases failing to close the wounds changed to receive ordinary dressing and skin flap transplantation at the second phase. Cases appeared nonhealing fractures underwent external fixation. Local swel ing, pain and fever were observed after treatment. The time of total hospitalization stay and fracture healing was recorded. ＜br> RESULTS AND CONCLUSION:The VSD group quickly control ed preoperative symptoms such as swel ing and pain and fever than the conventional catheter group (P＜0.05). The length of hospital stay showed no significant difference between the two groups (P>0.05). Al patients were obtained through clinic service and fol owed up for 24-36 months. The healing time in the VSD group was shorter than that in conventional catheter group (P＜0.05). Until the end of fol ow-up, no patients in the VSD group appeared infection recurrence, and two cases in the conventional catheter group had recurrent infection. The results suggest that VSD combined with external fixator can repair post-traumatic chronic osteomyelitis due to rapid control of infection, easy care, shortened treatment time, and reduced rate of postoperative recurrence. In addition, external fixator can be used as the final fixation for post-traumatic chronic osteomyelitis.

Objective To explore the effectiveness of our self-designed 3D printing relay template in the treatment of malunion of irregular intra-articular ankle fractures.Methods From October 2013 to October 2015,our self-designed 3D printing relay template was used in 14 patients with severe malunion of intra-articular ankle fracture to assist their intra-articular osteotomy.They were 10 males and 4 females,with an average age of 40.5 years (from 34 to 59 years).Thin slice CT scan was preformed preoperatively for all the ankles involved.The computer fictitious tibial and fibular models for location and osteotomy navigation templates were acquired from the data of CT scan after processing,design and reconstruction by software.After the navigation templates which fit the size of solid ankle were printed by a 3D printer,they were sterilized and reserved.The guide plates were used in turn during operation.The irregular malunited bone blocks in the posterior malleolus were completely resected along the osteotomy template.After fracture reduction,the bone blocks were stabilized with internal fixation.Fracture union time was recorded.Scores of visual analogue scale (VAS),American Orthopaedic Foot and Ankle Society (AOFAS) and the short form-36 (SF-36),ankle ROM and complications were also recorded at the final follow-ups.Results The 14 patients obtained an average follow-up of 28.6 months (from 14 to 35 months).Bony union was achieved after an average of 3.7months (from 3 to 6 months).At the final follow-ups,on average,VAS score (2.2 ± O.8),AOFAS ankle and hindfoot score (81.1 ± 6.8),SF-36 score (82.5 ± 5.2),dorsal extension (27.5 ° ± 2.5°),and plantar flexion (24.2° ±6.3°) were significantly improved compared with the preoperative values (6.3 ± 1.8,43.1 ± 12.0,37.6 ± 9.9,14.1° ± 3.8° and 14.4° ± 3.9°,respectively) (P ＜ 0.05).No implant failure,soft tissue complications or post-traumatic arthritis occurred during the follow-up.Conclusion Since our self-designed 3D printing relay templates for osteotomy can accurately position the fracture lines of the distal tibia via limited incision and invasion,they help a lot in precise osteotomy and anatomical reduction of malunited intra-articular ankle fracture,preventing incidence of traumatic arthritis.

Aim To observe the effect of pyrimidine dithiocarbamate (PDTC) on the variance of disc morphology and the expressions of TNF-α, MMP-9 in the cervical disc in cervical dynamic equilibrium rat models, and to investigate the roles of PDTC in the process of intervertebral disc degeneration and the mechanism involved.Methods Fifty-four SD rats were divided into three groups randomly, then the dynamic equilibrium rat model was established by cutting the nuchal superficial and deep muscle of the rats.The dynamic equilibrium rats with PDTC solution intraperitoneal injection after operations were defined as PDTC group (group A), the models with saline intraperitoneal injection after operations as saline group (group B), the rats of fake operation with saline intraperitoneal injection as blank group (group C), and the animals were sacrificed in batches 10 weeks, 12 weeks, 16 weeks respectively after operation.The C5, C6 vertebrae and C5/6 discs were harvested, and the disc morphology was observed.TNF-α, MMP-9 mRNA expressions were detected by q-PCR and protein expression was observed by Western blot.Results Compared with the saline group, the morphology of disc in PDTC group was destructed slightly and fiber ring arranged orderly.TNF-α, MMP-9 gene and protein expressions had no obvious changes (P>0.05) in blank group (group C) at each time point.The expressions of IL-6, MMP-9 mRNA increased with time in group B, but the amount increased fast firstly, and slow lately, reaching peak in 12 weeks.The expression of TNF-α, MMP-9 protein became steady in group B from 10 weeks compared with other time points(P>0.05).TNF-α, MMP-9 genes and proteins expression decreased obviously in PDTC group (group A) compared with saline group (group B) (P<0.01) at each time point, but higher than blank group C(P<0.01) at each time point.Conclusions TNF-α and MMP-9 are important inflammatory factors involved in rat cervical disc degeneration, PDTC relieves the degeneration of rat cervical disc by reducing the expression of TNF-α and MMP-9 via disturbing the NF-κB signal pathway probably, and PDTC may become potential medicine for disc degeneration.

BACKGROUND:Human spine protector can protect human thoracic-lumbar vertebra segments against injury, and the design and development of a novel dynamic protector needs the verification of various experimental means.
OBJECTIVE:Using the three-dimensional finite element method, we evaluate the effect of spine protector and the biomechanical reaction of thoracic-lumbar vertebra under the axial loading.
METHODThe thoracic-lumbar vertebra were cut from the whole spine three-dimensional finite element model. Then the thoracic-lumbar vertebra models carrying spine protector were taken as experimental group, while the models without the protector served as control group. Al the specimens were evaluated, constrained, loaded and figured out by its properties. The results of equivalent stress and strain distribution were obtained from the data. RESULTS AND CONCLUSION:In both groups, the stress was distributed at axial and posterior column of L 2 when the load was applied in axial direction. According to the data obtained from the experiment, both the experimental group and the control group had achieved the maximum stress at 16 ms, 3.919 Mpa and 5.727 Mpa, respectively. The statistical analysis result showed that the stress varied significantly at T 12 and L 2 in two groups (both P<0.05). However, the stress distribution at T 11 and L 1 showed no significant difference between the two groups (both P>0.05). Experimental findings indicate that, spine protector can significantly reduce the vertical stress of the thoracic-lumbar vertebra when fal ing on the ground, and share the vertical load, which is protective to thoracic-lumbar vertebra.

e chain-link flap is the good way in the treatment of large areas of the lower leg soft tissue defects.

BACKGROUND: Skidproof wrist protection devices can well protect the waist.OBJECTIVE: To analyze the efficacy of wrist protectors against fracture using three-dimensional finite element analysis.METHODS: Based on original data of Mechanical Virtual Human of China, three-dimensional finite element models of wrist with normal soft tissues and wrist wearing protectors were established using Abaqus6.51 software. The model was subjected to loading of 2 m/s. Stress-strain distribution of finite element model of the wrist before and after protectors wearing was compared, and maximum stress variation with time in the distal ulna was analyzed.RESULTS AND CONCLUSION: Compared with wrist not wearing protectors, the equivalent stress at soft tissues of hypothenar eminence, dorsal wrist, inferior segment of the radioulna, and distal radioulna was significantly decreased, which the stress at the second and fourth metacarpal bone, proximal segment of the index finger, and hamate bone was significantly increased, indicating the wrist protector can disperse, or transfer some stress from the distal radius and ulna to the wrist, palm or digital bone, thereby playing a positive role in preventing dital radial and ulnar fractures.

Objective To evaluate the advantage of 3D printing technique in treatment of complicated ace-tabula fracture,we compared the early clinical outcomes of surgical treatment for complex acetabula fracture with traditional surgery(group A)and that assisted by 3D printing technique(group B).Methods A prospective anal-ysis of 35 complicated acetabula fractures was performed at our department,13 patients cured assisted with 3D printing technique. The other 22 patients performed traditional surgery. Surgical trauma,systematic inflammation, immediate reduction effect were evaluated by Matta image assessment standard,and rehabilitation functional status evaluated by Harris score system and Merled' Aubigne and Postel Grading standard. Results There were signifi-cant differences between the two groups regarding intraoperative blood loss,postoperative drainage,operation time (P<0.05),and group B was superior to group A.C reactive protein,leucocyte and creatine kinase MM in periph-eral blood in group A were much higher than those in group B at 24 hours postoperatively(P<0.01).The result of reduction of fracture is poor in group A,but excellent rate of reduction is about 84% in group B. The result of Merled' Aubigne and Postel scores grading was superior in group B(P = 0.013). The excellent and good rate of Harris function score in B group was significantly higher than that in group A(P=0.027).Conclusion The treat-ment of complicated acetabula fracture assisted by 3D printing is excellent in short-term follow up,achieving good reduction with limited trauma,long-term prognosis needs to be further followed up.

Objective:To explore the role of virtual reduction and design of 3D printed guide template in assisting reduction and internal fixation of comminuted patellar fractures.Methods:A retrospective study was conducted of 12 patients who had been treated for closed patellar fractures from March 2016 to April 2019 at Department of Orthopaedics, Jiangxi Provincial People's Hospital. They were 8 males and 4 females with an average age of 35.4 years (from 22 to 51). All their fractures were type 34-C3 (more than 3 fragments) according to the AO/OTA classification. Their preoperative CT data were imported into software Mimics to print a full patella, upper and lower halves of the patella, and a guide template for reduction. During operation, bone fragments were first temporarily fixated with a fine Kirschner wire after combined together with the assistance of reduction templates for upper and lower hemi-patellas. Next, the whole patella was precisely reset and definitely fixated using patellar ring ligation and tension band wire with the assistance of the reduction guide template for full patellar. Recorded were operation time, fluoroscopic frequency, and visual analogue scale (VAS), knee range of motion (ROM) and knee function B?stman scores at the last follow-up.Results:In this group of patients, operation time averaged 90 minutes (from 75 to 120 minutes), fluoroscopic frequency 4.5 times (from 3 to 8 times), follow-up duration 19 weeks (from 16 to 22 weeks), and fracture healing time 14 weeks (from 11 to 17 weeks). At their last follow-up, X-ray showed good patellar morphology, fine internal fixation positions and an average VAS pain scores of 0.3 (from 0 to 1), their knee joints could be fully straightened, their knee ROM averaged 130°(from 100° to 138°), and their knee B?stman scores 28.8 points (from 21 to 30 points), giving 9 excellent and 3 good cases.Conclusion:3D printed reduction guide templates can significantly improve the efficiency and quality of surgical reduction in comminuted patella fractures, enhancing fixation strength and facilitating early and full range exercise of the knee joint to achieve excellent recovery.