To investigate the effects of augmentation with bone cement on the biomechanics of the dynamic hip screw (DHS) fixation in the intertrochanteric fracture specimen that has a normal bone density.MethodsTwentyfour matched pairs of the embalmed male upper femora (48sides) were used to make the specimens of the intertrochanteric fracture of Type A2. All the specimens were fixed with DHS. The right femur specimen from each pair was fixed by augmentation with DHS (the augmentation group) and the left femur specimen was fixed with the conventional fixation (the control group). Thebiomechanical tests on the bending stiffness and the torsional stiffness were performed with the servohydraulic testing machine in the two groups.ResultsThe maximum load and the maximum torque were 3 852.160 2±143.603 1 N and 15.5±2.6 Nm in the augmentation group and 3 702.966 7±133.860 1 N and 14.7±3.4 Nm in the control group. There was no significant difference in the biomechanical effects between the two groups (P＞0.05). Conclusion The augmenting fixation with bone cement in the intertrochanteric fracture specimen with a normal bone density has no significant effect on the strength of the DHS augmentation or on the overall stability of the fractured bone.
Objective To simulate anterosuperior instabil ity of the shoulder by a combination of massive irreparable rotator cuff tears and coracoacromial arch disruption in cadaveric specimens, use proximally based conjoined tendon transfer forcoracoacromial l igament (CAL) reconstruction to restrain against superior humeral subluxation, and investigate its feasibility and biomechanics property. Methods Nine donated male-adult and fresh-frozen cadaveric glenohumeral joints were applied to mimic a massive irreparable rotator cuff tear in each shoulder. The integrity of the rotator cuff tendons and morphology of the CAL were visually inspected in the course of specimen preparation. Cal ipers were used to measure the length of the CAL’s length of the medial and the lateral bands, the width of coracoid process and the acromion attachment, and the thickness in the middle, as well as the length, width and thickness of the conjoined tendon and the lateral half of the removed conjoined tendon. The glenohumeral joints were positioned in a combination of 30° extension, 0° abduction and 30° external rotation. The value of anterosuperior humeral head translation was measured after the appl ication of a 50 N axial compressive load to the humeral shaft under 4 sequential scenarios: intact CAL, subperiosteal CAL release, CAL anatomic reattachment, entire CAL excision after lateral half of the proximally based conjoined tendon transfer for CAL reconstruction. Results All specimens had an intact rotator cuff on gross inspection. CAL morphology revealed 1 Y-shaped, 4 quadrangular, and 4 broad l igaments. The length of the medial and lateral bands of the CAL was (28.91 ± 5.56) mm and (31.90 ± 4.21) mm, respectively; the width of coracoid process and acromion attachment of the CAL was (26.80 ± 10.24) mm and (15.86 ± 2.28) mm, respectively; and the thickness of middle part of the CAL was (1.61 ± 0.36) mm. The length, width, and thickness of the proximal part of the proximally based conjoined tendon was (84.91 ± 9.42), (19.74 ± 1.77), and (2.09 ± 0.45) mm, respectively. The length and width of the removed lateral half of the proximally conjoined tendon was (42.67 ± 3.10) mm and (9.89 ± 0.93) mm, respectively. The anterosuperior humeral head translation was intact CAL (8.13 ± 1.99) mm, subperiosteal CAL release (9.68 ± 1.97) mm, CAL anatomic reattachment (8.57 ± 1.97) mm, and the lateral half of the proximally conjoined tendon transfer for CAL reconstruction (8.59 ± 2.06) mm. A significant increase in anterosuperior migration was found after subperiosteal CAL release was compared with intact CAL (P lt; 0.05). The translation after CAL anatomic reattachment and lateral half of the proximally conjoined tendon transfer for CAL reconstruction increased over intact CAL, though no significance was found (P gt; 0.05); when they were compared with subperiosteal CAL release, the migration decreased significantly (P lt; 0.05). The translation of lateral half of the proximally conjoined tendon transfer for CAL reconstruction increased over CAL anatomic reattachment, but no significance was evident (P gt; 0.05). Conclusion The CAL should be preserved or reconstructed as far as possible during subacromial decompression, rotator cuff tears repair, and hemiarthroplasty for patients with massive rotator cuff deficiency. If preservation or the insertion reattachment after subperiosteal release from acromion of the CAL of the CAL is impossible, or CAL is entirely resected becauseof previous operation, the use of the lateral half of the proximally based conjoined tendon transfer for CAL reconstruction isfeasible.
ObjectiveTo evaluate the biomechanical characteristics and effectiveness of repairing anteroinferior tibiofibular ligament and fixing the posterior malleolar fracture in reconstructing syndesmotic stability after ankle fracture of pronation-external rotation type (PER) stage IV. MethodsTwenty-four normal lower extremity cadaver specimens were collected and made into intact ankle specimens. A MTS Bionix 858 test system was used to measure the maximum rotation of the foot under a static axial load of 150 N, internal rotation torque to the tibia at a rate of 1°/second and 4 N·m torque. Then a fracture of PER stage IV model was established in each specimen. Internal fixation of lower tibiofibular ligament union was performed by screws in group A, fixation of posterior malleolar fractures in group B, fixing posterior malleolar fracture combined with repairing anteroinferior tibiofibular ligament in group C (8 specimens each group). Then the maximum rotation of the foot was measured under the same condition, and the syndesmotic stability was calculated. Between July 2009 and September 2012, 32 patients with ankle fracture of PER stage IV were treated. There were 19 males and 13 females with an average age of 35 years (range, 20-63 years). The locations were the left ankle in 14 cases and the right ankle in 18 cases. The time from injury to admission was 3.5 hours on average (range, 1-72 hours). Open reduction and plate compression internal fixation were performed in fibula, and medial malleolus was fixed by conpression screws, then anteroinferior tibiofibular ligament was mended and posterior malleolar fracture was fixed by screws. ResultsThe preservation rates of syndesmotic stability after repair were 46.2%±12.3%, 62.6%±10.7%,and 66.5%±12.6% in groups A, B,and C, respectively; groups B and C were significantly superior to group A (P<0.05),but no significant difference was found between groups B and C (P>0.05). All patients achieved wound healing by first intention, and were followed up 12-24 months (mean,15 months). All fractures healed,with an average healing time of 11.2 weeks (range, 10-14 weeks) on the X-ray films. No seperation of inferior tibiofibular syndesmosis was observed during the follow-up period. American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score was 88.4 on average (range, 61-98) at last follow-up; the results were excellent in 13 cases,good in 15 cases, and fair in 4 cases, with an excellent and good rate of 87.5%. ConclusionIn patients with ankle fracture of PER stage IV, a combination of fixing the posterior malleolar fracture and repairing anteroinferior tibiofibular ligament can reconstruct syndesmotic stability effectively.
Objective To investigate the influence of collagen on the biomechanics strength of tissue engineering tendon. Methods All of 75 nude mice were madethe defect models of calcaneous tendons, and were divided into 5 groups randomly. Five different materials including human hair, carbon fibre (CF), polyglycolic acid (PGA), human hair and PGA, and CF and PGA with exogenous collagen were cocultured with exogenous tenocytes to construct the tissue engineering tendons.These tendons were implanted to repair defect of calcaneous tendons of right hind limb in nude mice as experimental groups, while the materials without collagenwere implanted to repair the contralateral calcaneous tendons as control groups. In the 2nd, 4th, 6th, 8th and 12th weeks after implantation, the biomechanicalcharacteristics of the tissue engineering tendon was measured, meanwhile, the changes of the biomechanics strength were observed and compared. Results From the 2nd week to the 4th week after implantation, the experimental groups were ber than the control groups in biomechanics, there was statistically significantdifference (Plt;0.05). From the 6th to 12th weeks, there was no statisticallysignificant difference between the experiment and control groups (Pgt;0.05). Positivecorrelation existed between time and intensity, there was statistically significant difference (Plt;0.05). The strength of materials was good in human hair,followed by CF, and PGA was poor. Conclusion Exogenous collagen can enhance the mechanics strength of tissue engineering tendon, and is of a certain effect on affected limb rehabilitation in early repair stages.
This article aims to compare and analyze the biomechanical differences between wing-shaped titanium plates and traditional titanium plates in fixing acetabular anterior column and posterior hemi-transverse (ACPHT) fracture under multiple working conditions using the finite element method. Firstly, four sets of internal fixation models for acetabular ACPHT fractures were established, and the hip joint stress under standing, sitting, forward extension, and abduction conditions was calculated through analysis software. Then, the stress of screws and titanium plates, as well as the stress and displacement of the fracture end face, were analyzed. Research has found that when using wing-shaped titanium plates to fix acetabular ACPHT fractures, the peak stress of screws decreases under all working conditions, while the peak stress of wing-shaped titanium plates decreases under standing and sitting conditions and increases under forward and outward extension conditions. The relative displacement and mean stress of the fracture end face decrease under all working conditions, but the values are higher under forward and outward extension conditions. Wing-shaped titanium plates can reduce the probability of screw fatigue failure when fixing acetabular ACPHT fractures and can bear greater loads under forward and outward extension conditions, improving the mechanical stability of the pelvis. Moreover, the stress on the fracture end surface is more conducive to stimulating fracture healing and promoting bone tissue growth. However, premature forward and outward extension rehabilitation exercises should not be performed.
At present, fatigue state monitoring of upper limb movement generally relies solely on surface electromyographic signal (sEMG) to identify and classify fatigue, resulting in unstable results and certain limitations. This paper introduces the sEMG signal recognition and motion capture technology into the fatigue state monitoring process and proposes a fatigue analysis method combining an improved EMG fatigue threshold algorithm and biomechanical analysis. In this study, the right upper limb load elbow flexion test was used to simultaneously collect the biceps brachii sEMG signal and upper limb motion capture data, and at the same time the Borg Fatigue Subjective and Self-awareness Scale were used to record the fatigue feelings of the subjects. Then, the fatigue analysis method combining the EMG fatigue threshold algorithm and the biomechanical analysis was combined with four single types: mean power frequency (MPF), spectral moments ratio (SMR), fuzzy approximate entropy (fApEn) and Lempel-Ziv complexity (LZC). The test results of the evaluation index fatigue evaluation method were compared. The test results show that the method in this paper has a recognition rate of 98.6% for the overall fatigue state and 97%, 100%, and 99% for the three states of ease, transition and fatigue, which are more advantageous than other methods. The research results of this paper prove that the method in this paper can effectively prevent secondary injury caused by overtraining during upper limb exercises, and is of great significance for fatigue monitoring.
ObjectiveTo study the biomechanical stability of neckwear-knot-loop-ligature fixation for tibial eminence avulsion fractures by comparing with cannulated screw fixation and suture anchor fixation. MethodsTwenty-four fresh porcine knee joints were selected. After the model of tibial eminence avulsion fracture (type Ⅲ) was made, 24 samples were randomly divided into 3 groups: neckwear-knot-loop-ligature group (group A), cannulated screw group (group B), and suture anchor group (group C), 8 samples in each group. The Universal electromagnetic and mechanical testing machines were used for the biomechanical tests. After 200 cyclic tests, pull-out test was done until fixation failure. The maximum failure load, yield load, stiffness, and displacement were measured. ResultsFailure mode: the displacement was beyond limit in 8 samples of group A; screws extraction (5 samples) and bone fragment re-fracture (3 samples) were observed in group B; and suture anchor extraction (4 samples), suture rupture (3 samples), and suture thread cutting (1 sample) were found in group C. Biomechanical test: From groups A to C, the maximum failure load and yield load showed significant decreasing tendency (P<0.05), but the displacements showed significant increasing tendency (P<0.05). The stiffness also gradually decreased, but differences was not significant (P>0.05). ConclusionCompared with cannulated screw and suture anchor, neckwear-knot-loop-ligature fixation for tibial eminence avulsion fracture has good biomechanical performance and the advantages of firm fixation and simple operation.
ObjectiveTo discuss the effect of three different ways of annulus fibrosus incision on the biomechanical strength of intervertebral disc. MethodsA total of 30 goats underwent intervertebral disc nucleus pulposus extraction at L3, 4 and L4, 5 by the working channel in group A (n=10), by circular incision in group B (n=10), and by square incision in group C (n=10). The body weight, male and female ratio, age, intraoperative blood loss, and wound healing time were recorded and compared among 3 groups. The survival rate and wound healing situation were observed after operation. At 24 weeks after operation, the goats were sacrificed, MRI images were taken to observe the signal intensity of nucleus pulposus. The disc height of L3, 4 and L4, 5 was measured to calculate the loss of disc height; biomechanical test was used to assess the strength of the disc and anulus. Histological staining was also conducted to observe the repair effect at L4, 5. ResultsThere was no significant difference in body weight, male to female ratio, age, intraoperative blood loss, and wound healing time among groups (P>0.05). All goats survived to the end of the experiment. MRI examination showed decreased signal intensity in 3 groups, indicating intervertebral disc degeneration. According to modified Thompson classification method, the degree of intervertebral disc degeneration of group A was significantly higher than that of groups B and C (P<0.05), but no significant difference was found between groups B and C (P>0.05). Difference was not significant in intervertebral space height before operation among 3 groups (P>0.05). But after 24 weeks, the intervertebral space height in group A was significantly higher than that in groups B and C (P<0.05), and the intervertebral space height loss in group A was significantly lower than that in groups B and C (P<0.05). The biomechanical strength in group A was also significantly higher than that in groups B and C (P<0.05), but no significant difference was found between group B and group C (P>0.05). HE and Masson staining showed good continuity of annulus fibrosus and clear layers in group A; poor continuity of annulus fibrosus and obvious scar tissues were observed in groups B and C. ConclusionApplication of working channel may have less destruction of annulus fibrosus, it plays a positive role in the maintenance of biomechanical strength and repair of annulus fibrosus.
Objective To investigate the morphology and biomechanics of in vivo osteogensis after repairing rabbit skull defects with plastic engineered bone which was prefabricated with alginate gel, osteoblasts and bone granules. Methods Twenty-eight rabbits were divided into group A (n=16), group B(n=8) and group C(n=4).The bilateral skull defects of 1 cm in diameter were made. Left skull defects filled with alginate gel-osteoblasts-bone granules(group A1) and right skull defects filled withalginate gel-bone granules(group A2).The defects of group B was left, as blank control and group C had no defect as normal control. The morphological change and bone formation were observed by methods of gross, histology and biomechanics. Results In group A1, the skull defects were almost entirely repaired by hard tissue 12 weeks after operation. The alginate gel-osteoblasts-bone granule material had changed into bone tissue with fewbone granules and some residuary alginate gel. The percentage of bone formation area was 40.92%±19.36%. The maximum compression loading on repairing tissue ofdefects was 37.33±2.95 N/mm; the maximum strain was 1.05±0.20 mm; andloading/strain ratio was 35.82±6.48 N/mm. In group A2, the alginate and bone granules material partially changed into bone tissue 12 weeks after operation. The percentage of bone formation area was 18.51%±6.01%. The maximum compression loading was 30.59±4.65 N; the maximum strain was 1.35±0.44 mm; and the loading/strainratio was 24.95±12.40 N/mm. In group B, the skull defects were mainly repaired bymembrane-like soft tissue with only few bone in marginal area；the percentage of bone formation area was 12.72%±9.46%. The maximum compression loading was 29.5±2.05 N; the maximum strain was 1.57±0.31mm；and the loading/strainratio was 19.90±5.47 N/mm.In group C, the maximum compression loading was 41.55±2.52 N; the maximum strain was 095±017 mm; and the l oading/strain ratio was 47.57±11.22 N/mm. 〖 WTHZ〗Conclusion〓〖WTBZ〗The plastic engineered bone prefabricated with algina te gelosteoblastsbone granule may shape according to the bone defects and ha s good ability to form bone tissue, whose maximum compression loading can reach 89 % of normal skull and the hardness at 12 weeks after operation is similar to that of normal skull.
Objective To provide the anatomic evidences and the choice of tendon graft for anatomic reconstruction of posterolateral complex through the morphological and biomechanical study on posterolateral structures of the knee in normal adult cadavers. Methods Twenty-three fresh lower l imb specimens from voluntary donators and 9 lower l imbs soaked by Formal in were selected for anatomic study on the posterolateral complex of the knee. Six fresh specimens were appl ied to measure the maximum load, intensity of popl iteus tendon, lateral collateral l igament, and popl iteofibular l igament, which were key components of the posterolateral complex. Results Popl iteus musculotendinous junction was located at 7.02-11.52 mm beneath lateral tibial plateau and 8.22-13.94 mm medially to fibular styloid process. The distances from femoral insertion of popl iteus tendon to the lower border of femoral condyle and to posterior edge of femoral condyle were 10.52-14.38 mm and 14.24-26.18 mm, respectively. Popl iteofibular l igament originated from popl iteus musculotendinous junction and ended at fibular styloid process. Lateral collateral l igament was located at 10.54-16.48 mm inferior to fibular styloid process, and the distances from femoral insertion to the lower border of femoral condyle and to posterior edge of femoral condyle were 14.92-19.62 mm and 14.66-27.08 mm, respectively. The maximum load and intensity were 579.60-888.40 N and 20.50-43.70 MPa for popl iteus tendon, were 673.80-1 003.20 N and 24.30-56.40 MPa for lateral collateral l igament, and were 101.56-567.35 N and 8.94-36.16 MPa for popl iteofibular l igament, respectively. Conclusion During anatomical reconstruction of posterolateral complex, the bony tunnel of the key components should be located according to the insertion mentioned above. On the basis of this study, the maximum load and intensity of selectable grafts should exceed 833 N and 36 MPa.