Regeneration and functional recovery of rabbit knee joint after osteotomy under control of external artificial joint / 医用生物力学

Objective To discuss the possibility for regeneration of knee joint with normal function under bionics biomechanical environment. Methods Seven normal rabbits with two metal frames respectively mounted on their femur and tibia of single (right) side leg by two threading pins of 1.5 mm diameter were used. Then the external artificial joints, containing two four-bar-linkage inside and outside of the knee to simulate motion trajectory of the joint in sagital plane were connected with the two preset fixed frames before osteotomy. The arthro-cartilage of the knee joint, crucial ligaments, semi-lunar fibro-cartilages, and partial under-cartilage-osseous intra articular capsule were cut off during osteotomy, with the patella, sesamoid bones remained intact. Insertion sites of muscle tendons were not invaded as far as possible, and capsules with ligaments outside were kept complete when the incision wound was closed by suture. The rabbits could move freely after osteotomy. The range of motion (ROM) of the knees in sagital plane and bony gap between the femur and tibia were measured by X-Ray films during the fracture healing after osteotomy. Results External artificial knee joints were successfully installed on right legs of 6 rabbits among the seven. The rabbits moved freely after osteotomy under the control of minimal invasive external artificial joint in bionics trajectory. The average angles between femoral shaft and tibial shaft at the 1st week after osteotomy were from (144.7±15.62)° in extremely flexed position to (44.2±25.77)° in extremely extended position, with ROM of (100.5±29.03)°. At the 12th week, the average angles were from (139.4 ± 12.92)° in extremely flexed position to (40.4±22.04)° in extremely extended position, with ROM of (99.0±23.39)°. No significant differences were displayed in flexed/extended position and ROM between the 1st and 12th week, with the bony gaps of the knees still existed but decreased significantly from (4.03±1.84) mm at the 1st week to (2.32±1.05) mm at the 12th week. In contrast, bony gaps of the opposite knees were not changed significantly, which were (1.27±0.22) mm on average. At the end of 16th week after osteotomy, the external artificial joints were removed. Newly born cartilage, with white color and smooth surface, were covered at lower end of the femur and upper end of the tibia. Typical trochlear surface appeared at the front side of regenerated cartilage corresponding to the posterior surface of the patella. And the regenerated fibro-bundle linkage similar with ligament, which started from bony structure of regenerated lower end of the femur and inserted into regenerated upper end of the tibia, was observed in each rabbit. At the 25th week, the average angles between femoral shaft and tibial shaft were from (148.3 ± 4.75)° in extremely flexed position to (48.30±17.57)° in extremely extended position, with ROM of (100.0±20.80)°. In the opposite (left) leg, the average angles between femoral shaft and tibial shaft were from (148.3±7.5)° in extremely flexed position to (21.6±9.09)° in extremely extended position, with ROM of (126.7±6.88)°, and the average bony gap of the knees after osteotomy was (1.4±0.59) mm, while that of the opposite (left) knees was (0.92±0.35) mm. Conclusions The external artificial joint with bionics trajectory could reserve the space for regeneration of rabbit knee joint by providing motion modeling environment, and proved the stress adaption during fracture healing. The present results indicated that regeneration of the knee joint after intra-capsular osteotomy in bionics biomechanical environment was possible.

Revealing mechanical property of intact rabbit tibia in three-point bending test / 中国骨伤

<p><b>OBJECTIVE</b>To explore the mechanical property of intact long bone through three-point bending test of rabbit tibia according to mechanics of materials.</p><p><b>METHODS</b>Ten pairs of normal rabbits tibia were treated on three-point bending test with 80 mm supporting distance in order to corroborate the virtual loading test on bone model.</p><p><b>RESULTS</b>Bending stiffness and strength of 10 pairs of normal rabbit tibia were obtained. The maximum flexibility of the right and the left tibia was (2.737 +/- 0.262) mm and (2.739 +/- 0.233) mm respectively. The maximum load, which indicated the bending strength, of the right and the left tibia was (17.803 +/- 2.675) kg and (18.366 +/- 2.653) kg respectively. The area under the load-flexibility curve before fail of the right and the left tibia was (23.829 +/- 4.413) kg/mm and (24.725 +/- 4.101) kg x mm respectively. The slope of the load-flexibility curve which indicate the stiffness of the right and the left tibia was (7.545 +/- 1.310) kg/mm and (7.631 +/- 1.174) kg x mm respectively.</p><p><b>CONCLUSION</b>The discrepancy between different animal body is larger than conventionally required. It's suggested for performing three-point bending test of long bone of the body both sides in pair.</p>

Relationship between the gray level of X-ray photograph and the cortical thickness / 中国骨伤

<p><b>OBJECTIVE</b>In order to get three dimensional measurements simply an plain X-ray photographs.</p><p><b>METHODS</b>The multi-layers of bone pieces were made by use of bone saw, and piled up to spiral ladder, which was used as a calibrating module for to living bone in clinics. The relationship between the cortical thickness and gray level of the X-ray photographs was obtained.</p><p><b>RESULTS</b>The correlation can be described with a cubic regression curve, and it can be simplified to a linear regression equation when cortical thickness is small than 3.8 mm.</p><p><b>CONCLUSION</b>It can be realized to get three dimensional measures of the bone on plain X-ray photographs, by use of the bony spiral ladder described here.</p>