Anatomical study for the treatment of proximal humeral fracture through the medial approach.

BACKGROUND: The treatment of complex 3- and 4-part proximal humeral fractures has been controversial due to numerous postoperative complications. With the further study of medial support and blood supply of humeral head, new techniques and conception are developing. The study aims to illustrate the medial approach of the proximal humeral fracture through cadaver autopsy. METHOD: Upper limbs from 19 cadavers have been dissected to expose the shoulder joint. We selected the coracoid process as the bony reference. Vernier caliper will be used to measure the following data, including distance from coracoid process to circumflex brachial artery, distance between anterior humeral circumflex artery (ACHA) and posterior circumflex brachial artery (PCHA) and their diameters. Assessment included the characteristics of the vascular supply around the humeral head, identification of the structures at risk, quality of exposure of the bony structures, and feasibility of fixation. RESULTS: The medial approach is appropriate in 86.84% anatomical patterns. Between the lower part of the shoulder capsule and the insertion of conjoined tendon, the bony surface exposed was limited by the interval between ACHA and PCHA. An interval of 2 to 3 cm (24.29 ± 3.42 mm) was available for medial plate. ACHA (49.35 ± 8.13 mm, 35.14-68.53 mm) and PCHA (49.62 ± 7.82 mm, 37.67-66.76 mm) were about 5 cm away from the coracoid process. Risk structures including ACHA and PCHA originate in common, PCHA originated from the deep brachial artery (DBA), the presence of perforator vessels, musculocutaneous nerve intersects with ACHA, the diameter of PCHA: ACHA < 1.5. In 13.15% anatomical patterns, this risk structure should be taken seriously. CONCLUSION: The medial approach opens a new perspective in the optimal management of complex fractures of proximal humerus. Anatomical research proves that the medial approach is feasible. The interval between ACHA and PCHA is suitable for placement. Anatomical pattern and indication have been discussed, and we hypothesized that ACHA has been destroyed in complex PHFs. With further studies on the anatomy and mechanism of injury, the development of more clinical cases will be an important work of our institution in the future.

Biomechanical properties of a novel fixation system for intra-articular distal humerus fractures: a finite element analysis.

BACKGROUND: The traditional strategy for fixing intra-articular distal humerus fractures is double plating placed in an orthogonal configuration, based on posterior approach. With a combined medial and lateral approach, a novel configuration of plating (combined anteromedial and anterolateral plating) has been used. In this study, we investigated the biomechanical properties of the novel plating by comparing it with some traditional strategies. METHODS: Based on the 3D morphology of a healthy subject's humerus, models of three types of intra-articular distal humeral fractures were established using a variety of different internal fixation methods: (a) treatment of a simple intra-articular fracture of the distal humerus with the novel double plate and a traditional orthogonal plate; (b) treatment of a comminuted fracture of the lower distal humerus with the novel double plate, a traditional orthogonal plate and a traditional orthogonal plate combined with distally extended tension screws; (c) treatment of a coronal shear fracture of the distal humerus with the novel double plate, a traditional orthogonal plate and the intra-articular placement of three screws. The material properties of all plates and screws were isotropic and linearly elastic. The Poisson ratio of the implant and bone was 0.3, and the elastic modulus of the implant was 114,000 MPa. The axial loading is 200 N, the bending loading is 30 N and varus rotation is 7.5 Nm in the longitudinal direction. RESULTS: A simple model of intra-articular fracture of the distal humerus (AO C1 type) was established. Under all experimental conditions, the novel double plate showed greater stiffness than the orthogonal double plate. The axial straightening, bending compression and varus torsion increased by 18.00%, 16.00% and 44.00%, respectively. In the model of comminuted fracture of the lower distal humerus, the novel double plate showed the best stiffness under three experimental conditions (163.93 N/mm, 37.97 N/mm, 2697.84 N mm/°), and the stiffness of the traditional orthogonal plate combined with the distally extended tension screws was similar to that of the traditional orthogonal plate (121.21 N/mm, 32.61 N/mm, 1968.50 N mm/°). In the model of coronal shear fracture of the distal humerus, the novel double plate showed the best stiffness under all test conditions (194.17 N/mm, 38.46 N/mm, 2929.69 N mm/°), followed by the traditional plate (153.85 N/mm, 33.33 N/mm, 2650.18 N mm/°), while the stiffness of the three screws was the smallest (115.61 N/mm, 28.30 N/mm, 2180.23 N mm/°). CONCLUSIONS: In terms of biomechanics, compared with other internal fixation methods, the novel combined anteromedial and anterolateral anatomical locking double-plate showed less stress, less displacement and greater stiffness. The novel double-plate method can be used to treat not only simple intra-articular fractures of the humerus but also complex comminuted fractures of the lower distal humerus and coronal shear fractures of the distal humerus, with a better effect than current traditional internal fixation methods.

Polydopamine coating with static magnetic field promotes the osteogenic differentiation of human bone-derived mesenchymal stem cells on three-dimensional printed porous titanium scaffolds by upregulation of the BMP-Smads signaling pathway.

Bone regeneration has always been a hot topic for orthopedic surgeons. The role of polydopamine coating in promoting bone regeneration has attracted much attention. Static magnetic field (SMF) is considered an effective and noninvasive treatment for enhancing bone regeneration. However, the effect of polydopamine combined with SMF on bone regeneration on scaffolds is not clear. The aim of this study was to investigate the effects and potential mechanism of polydopamine coating combined with SMF on bone regeneration in three-dimensional printed scaffolds. The polydopamine coating (pTi group) was applied onto porous Ti6Al4V scaffolds (Ti group). Surface characterization was performed by scanning electron microscopy. The 100 mT SMF environment (pTi-SMF group) was established to enhance osteogenic differentiation of human bone-derived mesenchymal stem cells (hBMSCs) on polydopamine coating scaffolds. The cell viability and proliferation were significantly enhanced in the SMF environment (pTi-SMF vs. Ti: P=0.005). Improved morphology (pTi-SMF vs. pTi: P=0.024, pTi-SMF vs. Ti: P=0.001) and adhesion (Ti: x̅±s=1.585±0.324; pTi: x̅±s=2.164±0.314; pTi-SMF: x̅±s=4.634±0.247, P<0.001) of hBMSCs were observed in the pTi-SMF group. The high expression of osteogenesis-related RNA and protein (ALP: Ti, x̅±s=1.249±0.218; pTi, x̅±s=2.503±0.209; pTi-SMF, x̅±s=2.810±0.246. OCN: Ti, x̅±s=1.483±0.304; pTi, x̅±s=3.636±0.322; pTi-SMF, x̅±s=4.641±0.278. Runx2: Ti, x̅±s=1.372±0.227; pTi, x̅±s=3.054±0.229; pTi-SMF, x̅±s=3.914±0.253) was found in the pTi-SMF group (pTi-SMF vs. Ti: P<0.001). Proteomics was applied to explore the osteogenic mechanism of polydopamine coating combined with SMF. A total of 147 different proteins were identified between the pTi-SMF and Ti group. The osteogenic effect might be associated with the BMP-Smads signaling pathway (pTi-SMF vs. Ti: BMPR1A, P=0.001; BMPR2, P<0.001; Smad4, P=0.001; Smad1/5/8, P=0.008). In conclusion, the osteogenic differentiation of hBMSCs on polydopamine coating scaffolds could be enhanced by SMF stimulation by upregulation of the BMP-Smads signaling pathway.

The upper brachial plexus defect model in rhesus monkeys: a cadaveric feasibility study.

To establish a model for nerve grafts and determine the anatomic characteristics of the brachial plexus in rhesus monkeys. Ten specimens of the brachial plexus were obtained from five rhesus monkey cadavers. Anatomic dissection of the brachial plexus was systemically performed. The length of each root, trunk, and each division was measured using a Vernier caliper proximodistally. The anatomic distributions of the suprascapular, axillary, and musculocutaneous nerve were documented. The brachial plexus of rhesus monkeys included the spinal nerves or roots of C5, C6, C7, C8, and T1 (80%, 8/10), with a small contribution from the C4 root (20%, 2/10) occasionally. The upper trunk was not measurable because of their irregular structures. The lower trunk had a mean length of 1.62 (range, 0.96-2.1 mm) and a mean diameter of 2.29 (range, 1.9-2.94 mm). For the upper trunk, the C5 and C6 roots either divided into two very short divisions or sent out very long divisions before they joined together. For the middle trunk, the C7 root had a straight course after leaving the foramen and blended imperceptibly into the middle trunk before dividing into the anterior and posterior divisions. The lower trunk was noted in almost all the specimens (80%, 8/10), which was formed by C8 and T1. The brachial plexus in rhesus monkeys varies from that of humans, and defects can be made at the level of C5 and C6 roots and the C7 root should also be cut off and ligated.

[Study on immune response after repair of nerve defect with acellular nerve xenograft laden with allogenic adipose-derived stem cells in rhesus monkey].

OBJECTIVE: To observe the systemic and local immune response after repair of nerve defect with acellular nerve xenograft laden with allogenic adipose-derived stem cells (ADSCs) in rhesus monkey so as to evaluate the safety of the proposed material for nerve reconstruction. METHODS: Bilateral tibial nerves were taken from a healthy adult male landrace (weighing 48 kg) to prepare acellular nerve xenograft by chemical extraction. ADSCs were isolated from a healthy adult male rhesus monkey (weighing 4.5 kg), and were seeded into the acellular nerve grafts. The radial nerve defect models with 25 mm in length were established in 10 healthy adult female rhesus monkeys (weighing 3-5 kg), and they were divided into cell-laden group (n = 5) and non-cell-laden group (n = 5) randomly. Defect was repaired with acellular nerve xenograft laden with allogenic ADSCs in cell-laden group, with acellular nerve xenograft only in non-cell-laden group. The blood samples were taken from peripheral vein preoperatively and at 14, 60, and 90 days after operation for lymphocyte analysis; at 5 months after operation, the grafts were harvested to perform histological examination for local immune response and nerve regeneration. The nerve autograft in rhesus monkey was used as control. RESULTS: In cell-laden group and non-cell-laden group, no significant difference was found in the count of lymphocytes and T lymphocytes, the percentage ofT lymphocytes, CD8+ T lymphocytes, as well as the ratio of CD4+ T lymphocytes to CD8+ T lymphocytes between pre- and post-operation (P > 0.05); in cell-laden group, the percentage of CD4+ T lymphocytes at 14 days was significantly lower than that at 60 and 90 days postoperatively (P < 0.05). The percentage of CD4+ T lymphocytes in cell-laden group was significantly lower than that in non-cell-laden group at 14 days (P < 0.05), but no significant difference was found in the other indexes at the other time between 2 groups (P > 0.05). At 5 months after operation, mild adhesion was found on the surface of nerve xenografts; the epineurium of nerve xenografts was thicker than that of nerve autografts; and neither necrosis nor fibrosis was found. CD3+, CD4+, CD8+, CD68+, and CD163+ T lymphocytes were scattered within the grafts, in which regenerative axons were revealed. CD3+, CD4+, CD8+, CD68+, and CD163+ T lymphocytes were comparable in cell-laden group, non-cell-laden group, and autograft group. CONCLUSION: Repair of nerve defect with acellular nerve xenograft elicits neither systemic nor local immune response in rhesus monkeys. Implantation of allogenic ADSCs might result in transient depression of CD4+ T lymphocytes proliferation early after surgery, no immune response can be found.