Design of custom-made navigational template of femoral head and pilot research in total hip resurfacing arthroplasty.

BACKGROUND: To develop a novel custom-made navigational template for accurate prosthesis implantation in total hip resurfacing arthroplasty (THRA) by computer-aided technology. METHODS: The template was produced based on data preoperatively acquired from computed tomography (CT) scan. The position of the drill guide was obtained according to the anatomical axis of the femoral neck which was defined by the point of the femoral head center and another point of the femoral neck center. The final direction of the drill guide was confirmed by a valgus angle. The surface of the template was constructed based on the inverse of the femoral neck surface. Then the template was made of acrylate resin by using rapid prototyping (RP) technique. Finally, all the templates were verified in 17 cadavers arranged for THRA and postoperative medical images were employed to evaluate the accuracy and validity of the template. RESULTS: The templates had achieved a high fitting with the femoral neck surface, and there were no guide failures. Postoperative evaluation revealed that the Kirschner-wires pass through the center of the femoral head and femoral neck, presenting a relative expected and acceptable valgus angle to the central axis of the femoral neck. The lateral offset showed the relative valgus angle achieved as expected, the horizontal offset showed that no obvious antero-posterior deviation occured. The comparison between the preoperative Neck-shaft angle (NSA) and the postoperative Stem-shaft angle (SSA) showed there is no significant difference(P > 0.05). CONCLUSION: The novel custom-made navigational template of femoral head can effectively assist surgeons for accurately implanting the femoral head components to the desired position in THRA.

Correlations between Microstructure Characteristics and Mechanical Properties in 5183 Aluminium Alloy Fabricated by Wire-Arc Additive Manufacturing with Different Arc Modes.

The effect of arc modes on the microstructure and tensile properties of 5183 aluminium alloy fabricated by cold metal transfer (CMT) processes has been thoroughly investigated. Heat inputs of CMT processes with three arc modes, i.e., CMT, CMT advance (CMT+A), and CMT pulse (CMT+P), were quantified, and their influence on the formation of pores were investigated. The highest tensile strength was found from samples built by the CMT+A process. This agrees well with their smallest average pore sizes. Average tensile strengths of CMT+A arc mode-built samples were 296.9 MPa and 291.8 MPa along the horizontal and vertical directions, respectively. The difference of tensile strength along the horizontal and vertical directions of the CMT+P and CMT samples was mainly caused by the pores at the interfaces between each deposited layer. The successfully built large 5183 aluminium parts by the CMT+A arc mode further proves that this arc mode is a suitable mode for manufacturing of 5183 aluminium alloy.

Microstructure Evolution and Mechanical Behavior of 2219 Aluminum Alloys Additively Fabricated by the Cold Metal Transfer Process.

In this research, four different welding arc modes including conventional cold metal transfer (CMT), CMT-Pulse (CMT-P), CMT-Advanced (CMT-ADV), and CMT pulse advanced (CMT-PADV) were used to deposit 2219-Al wire. The effects of different arc modes on porosity, pore size distribution, microstructure evolution, and mechanical properties were thoroughly investigated. The statistical analysis of the porosity and its size distribution indicated that the CMT-PADV process gave the smallest pore area percentage and pore aspect ratio, and had almost no larger pores. The results from optical microscopy, scanning electron microscopy, and fractographic morphology proved that uniform and fine equiaxed grains, evenly distributed Al2Cu second phase particles were formed during the CMT-PADV process. Furthermore, the X-ray diffraction test ascertained that the CMT-PADV sample had the smallest lattice parameter and the highest solute Cu content. Besides, the tensile strength could reach 283 MPa, the data scattering was the smallest, and the strength scattering of the sample in the horizontal direction was the shortest. In addition, the strength properties were nearly isotropic, with only 5 MPa difference in the vertical and horizontal directions. The above mentioned results indicated that the mechanical properties of 2219 aluminum alloy was improved using the CMT-PADV arc mode.

[ESTABLISHMENT AND TESTING OF RATING SCALE OF RAT ROTATOR CUFF FUNCTION].

OBJECTIVE: To provides an objective tool to evaluate rotator cuff function in rats. METHODS: Sixty adult male Sprague Dawley rats, weighing (281.21 ± 20.12) g, were involved in this experiment. Botulinum toxin A (6 U/kg) was injected into the infraspinatus of 12 rats in Botox group. Infraspinatus tendons of 12 rats in tear group were cut by microinvasive method. Infraspinatus tendons of 12 rats in sham-operation group were exposed but not cut. No any treatment was performed on the 12 rats in normal control group. One shoulder joint of each rat was selected randomly as treatment side. After 7 days, cadence, rate of stand phase, support pressure, swing speed, stand speed, and stride length of rats in those 4 groups were measured. Treatment side and contralateral side ratio of each gait parameter was caculated. If parameters of Botox group and tear group both showed significant differences compared with those of normal control group and sham-operation group, the gait parameter was brought into rating scale as an item. Each item was assigned from 1 point to 5 points according to gait parameter. The chronic rotator cuff injury model was established in 12 rats of verification group and rating scale was used to evaluate rotator cuff function each week for 8 weeks after surgery. RESULTS: All gait parameters of tear group were significantly less than those of Botox group (P < 0.05), and Botox group was significantly less than sham-operation group and normal control group (P < 0.05), but no significant difference was found between sham-operation group and normal control group (P > 0.05). All gait parameters were brought into rating scale as items. All items were rated from 1 point to 5 points, so the total score was 30 points and the lowest score was 6 points. Thirty points meant normal function of infraspinatus (rotator cuff function was normal), and 6 points meant complete loss of infraspinatus function (rotator cuff function was severely damaged). Rotator cuff functional scores of rats in verification group were 27.00 ± 1.86, 23.75 ± 2.83, 21.33 ± 1.92, 18.17± 2.37, 13.17 ± 1.64, 11.67 ± 2.50, 8.17 ± 1.27, 6.50 ± 0.67 from the 1st week to the 8th week respectively. CONCLUSION: The rating scale of rat rotator cuff function may reflect the severity of rotator cuff injury and the functional status of rotator cuff to some extent in rats.

[Establishment of microinvasive modle of chronic rotator cuff injury in rats].

OBJECTIVE: To establish a model of chronic rotator cuff injury by inducing subacromial impingement syndrome in rats, so as to lay a foundation for further study on the mechanism and treatment of chronic rotator cuff injury. METHODS: The polyether-ether-ketone implants were designed and made with three-dimensional printing technique. In 48 male Sprague Dawley rats [weighing, (277.25 ± 22.03) g], one shoulder joint was selected randomly as the experimental group; in the experimental group, the implant was pierced into shoulder joint close to the acromion medial side and was pierced out under acromion close to the deltoid trailing edge; the penetrating part of implant was cut off after the implanting part was fixed with 4# braided silk suture. No any treatment was performed on the contralateral shoulder of 24 rats as control group; and the implants were immediately removed after they were pierced into the contralateral shoulder joint of the other 24 rats as sham- operation group. All the rats were exposed to 30 minutes of downhill running at 17 m/minute (-13.5°) every day at 4 days after operation and the general condition of rats was observed. At 2, 4, 6, and 8 weeks after operation, 12 rats were sacrificed to collect shoulder joint samples. The hard tissue slices was used for Van Gieson staining and histological observation of the supraspinatus tendon. RESULTS: All rats survived to the end of experiment, without infection. The rats suffered limp at 2-3 days after operation, and the gait of most rats returned to normal at 4 days after operation. The histological results showed that the supraspinatus tendon had smooth edge, without split layers or breakage in the control group and sham-operation group. In the experimental group, the implants were positioned accurately without dislocation; 4 kinds of typical pathological changes were observed. Partial-thickness tear on bursal side appeared at 2 weeks (5 rats) and 4 weeks (2 rats), showing no significant difference between at 2 and 4 weeks (P > 0.05); intratendinous gap formed mainly at 4 weeks (10 rats) and 6 weeks (11 rats), showing significant differences when compared with that at 2 weeks (2 rats) (P < 0.05) and 8 weeks (2 rats) (P < 0.05); partial-thickness tear on articular side mainly appeared at 6 weeks (8 rats), showing significant difference when compared with that at other time points (P < 0.05); full-thickness tear was found mainly at 8 weeks (10 rats), showing significant differences when compared with that at other time points (P < 0.05). CONCLUSION: A model of chronic rotator cuff injury is successfully established in rats through microinvasive implantation of subacromial impingement syndrome inducing implants and the pathological changes in this model are highly similar to the clinical pathological progress.