Four-dimensional micro-building blocks.

Four-dimensional (4D) printing relies on multimaterial printing, reinforcement patterns, or micro/nanofibrous additives as programmable tools to achieve desired shape reconfigurations. However, existing programming approaches still follow the so-called origami design principle to generate reconfigurable structures by self-folding stacked 2D materials, particularly at small scales. Here, we propose a programmable modular design that directly constructs 3D reconfigurable microstructures capable of sophisticated 3D-to-3D shape transformations by assembling 4D micro-building blocks. 4D direct laser writing is used to print two-photon polymerizable, stimuli-responsive hydrogels to construct building blocks at micrometer scales. Denavit-Hartenberg (DH) parameters, used to define robotic arm kinematics, are introduced as guidelines for how to assemble the micro-building blocks and plan the 3D motion of assembled chain blocks. Last, a 3D-printed microscaled transformer capable of changing its shape from a race car to a humanoid robot is devised and fabricated using the DH parameters to guide the motion of various assembled compartments.

[Application of three-dimensional printing personalized acetabular wing-plate in treatment of complex acetabular fractures via lateral-rectus approach].

Objective: To investigate reduction and fixation of complex acetabular fractures using three-dimensional (3D) printing technique and personalized acetabular wing-plate via lateral-rectus approach. Methods: From March to July 2016, 8 patients with complex acetabular fractures were surgically managed through 3D printing personalized acetabular wing-plate via lateral-rectus approach at Department of Orthopedics, the Third Affiliated Hospital of Southern Medical University. There were 4 male patients and 4 female patients, with an average age of 57 years (ranging from 31 to 76 years). According to Letournel-Judet classification, there were 2 anterior+ posterior hemitransverse fractures and 6 both-column fractures, without posterior wall fracture or contralateral pelvic fracture. The CT data files of acetabular fracture were imported into the computer and 3D printing technique was used to print the fractures models after reduction by digital orthopedic technique. The acetabular wing-plate was designed and printed with titanium. All fractures were treated via the lateral-rectus approach in a horizontal position after general anesthesia. The anterior column and the quadrilateral surface fractures were fixed by 3D printing personalized acetabular wing-plate, and the posterior column fractures were reduction and fixed by antegrade lag screws under direct vision. Results: All the 8 cases underwent the operation successfully. Postoperative X-ray and CT examination showed excellent or good reduction of anterior and posterior column, without any operation complications. Only 1 case with 75 years old was found screw loosening in the pubic bone with osteoporosis after 1 month's follow-up, who didn't accept any treatment because the patient didn't feel discomfort. According to the Matta radiological evaluation, the reduction of the acetabular fracture was rated as excellent in 3 cases, good in 4 cases and fair in 1 case. All patients were followed up for 3 to 6 months and all patients had achieved bone union. According to the modified Merle D'Aubigné and Postel scoring system, 5 cases were excellent, 2 cases were good, 1 case was fair. Conclusions: Surgical management of complex acetabular fracture via lateral-rectus approach combine with 3D printing personalized acetabular wing-plate can effectively improve reduction quality and fixation effect. It will be truly accurate, personalized and minimally invasive.

[Anatomical study of reconstruction of vertebral artery with neighboring non-trunk arteries].

OBJECTIVE: To study the anatomical basis for reconstruction of vertebral artery with neighboring non-trunk arteries. METHODS: Twenty preserved adult cadavers were used in this study to observe the morphology of superior thyroid artery, inferior thyroid artery, transverse cervical artery, thyrocervical trunk and extracerebral portion of vertebral artery, and reconstruction of vertebral artery with these arteries was simulated in two preserved cadavers. RESULTS: The calibers of superior or inferior thyroid artery, or transverse cervical artery were more than 2 mm in diameter, and the arteries had suitable free length for end-to-side anastomosis with vertebral artery. Thyrocervical artery had similar caliber to vertebral artery so that end-to-end anastomosis could be carried out between them, but only 38.5% of this artery had adequate artery trunk (more than 10 mm). It was proved from the simulated procedures that the reconstruction of vertebral artery with these neighboring non-trunk arteries was possible. CONCLUSION: Reconstruction of vertebral artery with neighboring non-trunk arteries has anatomical basis and can be used clinically for treatment of the lesion affecting the first or second portion of vertebral artery.

Partial purification and osteoinductive activity of swine bone morphogenetic protein.

Bone morphogenetic protein (BMP) was isolated from the bone matrix of swine and partially purified by means of differential precipitation and molecular sieve chromatography. The molecular weight of BMP estimated by SDS-gel electrophoresis was 19,000 dalton. Bioassay by implanting two milligrams of BMP fraction into thigh muscles of mice resulted in bone formation in 100% of the experimental animals.

[Bone matrix gelatin. Clinical application in 38 cases].

Bone matrix gelatin (BMG) was prepared and used clinically as graft-stuff in 38 patients. It was used to fill the bone defects resulted from excision of benign bone tumors (22 patients) and debridement of chronic osteomyelitis (3), to treat delayed union of fractures (5), and to make posterior spinal fusion (8). Fourty-five days after operation, speckles or flakes of dense shadow appeared in the film at the original defects and fields. In 2 to 6 months, bony union took place in 36 patients (95%). Failure was noted in 2 patients with chronic osteomyelitis. Because of its excellent osteo-inductive property and nonantigenic treat, BMG has been proved to be an ideal substitute for bone graft. It is easy to prepare, safe for storage at room temperature and sound for transportation.