Measurement and clinical significance of lumbar pedicle CT imaging parameters / 中国组织工程研究

BACKGROUND: Although more and more accurate and personalized detection and assistive tools are used in the field of orthopedics with the development of technology, the preoperative CT is still the first-line examination choice of many orthopedic surgeons. Therefore, to master the lumbar spine CT imaging performance is not only the basis of spine surgeons, but also the cornerstone of spinal nail surgery. OBJECTIVE: Through CT imaging technique, we measured the parameters of lumbar pedicle imaging, and understood its internal structure as the basis for the choice of screws, in order to improve the safety and accuracy of nail surgery. METHODS: Totally 36 cases without lumbar vertebrae-related disease undergoing lumbar vertebra and abdominal cavity CT scan were randomly selected, including 20 males and 16 females at the age of (43.3±12.3) years. PACS was used to reconstruct lumbar vertebrae, and the related imaging parameters were measured. RESULTS AND CONCLUSION: (1) There was no significant difference between the left and right sides of the pedicle for paired t-test (P >0.05). (2) Pedicle sagittal angle had downward trend, the level of change was small; L4increased relative to L3; L5level was minimum at the average of -1.3°. Pedicle transverse angle had gradually increased trend, and maximum at L5; the average was 25.4°. (3) The length of the pedicle channel increased first and then decreased in the lumbar segment; the longest average was 52.2 mm in the L2segment, the shortest at L5, with an average of 47.4 mm. (4) The pedicle height was slightly narrowed at L1-L3levels; the smallest was 15.4 mm (L3mean), and reached the maximum in the L5at 22.7 mm (L5mean). Cancellous bone height also showed the same trend, the minimum in the L3at 10.2 mm, the maximum in the L5at 17.9 mm. (5) Lumbar pedicle width showed an upward trend, L1minimum of 7.7 mm, L5maximum of 12.5 mm. Cancellous bone width also became a similar upward trend; the narrowest L1, averagely 4.9 mm; the maximum L5, averagely 8.5 mm. (6) Overall, the upper lumbar pedicle channel was slender, while the lower lumbar spine was slightly short. (7) The parameters of the pedicle can be used as the basis for selecting the appropriate screw. At the same time, lumbar pedicle morphology has a certain difference, and there is a certain law. Accurately grasping its structure and image characteristics of pedicle screw fixation is the basis of surgery. The preoperative imaging data collection and assessment, combined with the general situation of patients, and the development of personalized programming, will help in improving the safety and accuracy of screw placement.

Finite element analysis on relationship between wearing high-heeled shoes and stresses in intermetatarsal region of foot / 医用生物力学

Objective To study stress changes in forefoot intermetatarsal region when wearing high-heeled shoes, so as to provide references for quantitative analysis on inducement mechanism of intermetatarsal neuroma and corresponding treatment strategy. Methods Based on the validated foot-ankle-shoe finite element platform, changes of stress levels and tendency in intermetatarsal region were analyzed for both in balanced standing when wearing 0-3 inch (0, 2.54, 5.08, 7.62 cm) high-heeled shoes and walking when wearing 5.08 cm high-heeled shoes in a gait cycle. Results With the increase of heel height, the stresses in intermetatarsal region were significantly increased, and the stress in the third web space of toes when wearing 7.62 cm high-heeled shoes reached 312% of that when wearing flat shoes (0 cm high-heeled shoes). When walking with 5.08 cm high-heeled shoes, the third web space of toes at push-off instance had the largest stress, reaching 90 kPa, which agreed with the most commonly pathogenic site of intermetatarsal neuroma in clinic. Conclusions Wearing high-heeled shoes can obviously increase the stress in intermetatarsal region. Squeezing by upper extrusion of shoes can result in the largest stresses in the third web space of toes region, which is most likely to cause the development of intermetatarsal neuroma.

Dynamic axial compressive strain promotes osteogenic differentiation of osteoblasts seeded in silk fibroin scaffolds / 医用生物力学

Objective To explore the effects of dynamic axial compressive strain on the mRNA expression of bone formation related-genes in osteoblasts seeded in 3D silk fibroin scaffolds. Methods In the experimental group, MC3T3-E1 cells were seeded in 3D scaffolds and then subjected to dynamic axial compressive strain (at amplitude of 5% and frequency of 1 Hz, 30 min/day for 20 days), while in the control group, MC3T3-E1 cells were cultured statically without any mechanical stimulation. The gene expression of alkaline phosphatase (ALP), collagenⅠ(COL-Ⅰ), runt-related transcription factor 2 (Runx2), osterix (Osx), osteocalcin (OCN) was detected by real-time PCR. Results Under cyclic axial compressive strain, the Runx2, Osx and COLⅠmRNA levels increased by 280%, 68.9% and 79.6%, respectively, while the ALP and OC mRNA levels also up-regulated by 10.7% and 26.9%, respectively. There were significant differences in mRNA expression of osteogenesis-related genes between the experimental group and control group (P＜0.05). Conclusions Under the stimulation of cyclic axial compressive strain, the osteogenic differentiation of osteoblasts seeded in the silk fibroin scaffolds is promoted, with a significant up-regulation in the mRNA expression of COLⅠ, Runx2, Osx and OCN, which suggests that the stimulation of compressive stress at physiologic magnitude could be one of important mechanisms in promoting fracture healing. This research finding will be important for the clinic application of mechanical stimuli-mediated cell therapy for bone defection.

Finite element analysis on transforaminal lumbar interbody fusion treatment / 医用生物力学

Objective To analyze the clinical feasibility of unilateral transforaminal lumbar interbody fusion (TLIF) for treating lumbar degenerative diseases by finite element method. Methods Based on CT scan data, three-dimensional (3D) finite element models of the normal L3-5 segments under physiological status (intact lumbar model), L4/5 with unilateral pedicle screw fixation plus interbody fusion (unilateral TLIF model) and L4/5 with bilateral pedicle screw fixation plus interbody fusion (bilateral TLIF model) were established by using Mimics, Pro/E, ANSYS software, respectively. Preload of 500 N and load of 10 N•m torque were applied on the superior surface of the L3 segment to simulate 5 physiological activities: body upright, flexion, extension, left lateral bending and right axial rotation. The deformation and stress distributions in vertebral body, vertebral discs, pedicle screw and cage under different loads were then recorded and analyzed to compare mechanical properties of the two fixation methods. Results The deformation of L3-5 segments fixed with unilateral TLIF or bilateral TLIF decreased as compared to the intact lumbar model; the stresses in cage reached the maximum in both unilateral TLIF model and bilateral TLIF model during back extension, meanwhile peak stresses on pedicle screws in unilateral TLIF were significantly higher than those on bilateral TILF model, with the peak stress of 463.39 MPa during back extension. ConclusionsUnilateral TLIF can be selected as a method for treating lumbar degenerative diseases; however, its stability was inferior to bilateral TLIF due to the higher peak stress. Therefore, less stretch exercises may be safe for patients during rehabilitation to avoid surgery failure or pedicle screw fracture.

Collagen membrane alleviates peritendinous adhesion in the rat Achilles tendon injury model / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Tendon adhesion is one of the most common causes of disability following tendon surgery. Therefore, prevention of peritendinous adhesion after surgical repair of tendon is a major challenge. The aim of this study was to explore the possible application of a collagen membrane for the prevention or attenuation of peritendinous adhesions.</p><p><b>METHODS</b>Sprague-Dawley (SD) rat Achilles tendon was cut and sutured by a modified Kessler's technique with or without the collagen membrane wrapped. Macroscopic, morphological and biomechanical evaluations were applied to examine the recovery of the injured tendon at 4 and 8 weeks after surgery.</p><p><b>RESULTS</b>The surgery group wrapped by collagen membranes had a better outcome than the group with surgery repair only. In the collagen membrane-treated group, less adhesion appeared, stronger tensile strength was detected, and more tendon fibers and collagen I expression were observed morphologically.</p><p><b>CONCLUSION</b>Wrapping the tendon with a collagen membrane may be an efficient approach for tendon repair and preventing tendon adhesion after its ruptures.</p>