The pronounced side sway is not passive, but constitutes 10% of the total work of lifting and accelerating the CoM. The work on the CoM per unit mass and distance (mechanical cost of transport) is higher than that in humans, but lower than that in bipedally walking monkeys and gibbons. This variability is probably related to the poor phasic coordination of energy fluctuations in these facultatively bipedal animals. Despite the pendular nature of chimpanzee bipedalism, energy recoveries from exchanges of kinetic and potential energies are low on average and highly variable. The mediolateral oscillations of the CoM are more pronounced relative to stature than in human walking when compared at the same Froude speed. Maximum height is achieved during single support and minimum height during double support. Despite being a bent-hip, bent-knee (BHBK) gait, chimpanzee walking uses pendulum-like motion with vertical oscillations of the CoM that are similar in pattern and relative magnitude to those of humans. Full-stride ground reaction forces were recorded as well as kinematic data to synchronize force to gait events and to determine speed. In addition, histologic evidence supports the hypothesis that anorganic bovine bone is replaced by vital bone.Center of mass (CoM) oscillations were documented for 81 bipedal walking strides of three chimpanzees. These results demonstrate that sinus grafting with anorganic bovine bone maintains radiographic evidence of density and height stability of 1.5 years. The bovine Type I collagen matrix vital bone percentage at 7.5 months was 34 +/- 21%. With the anorganic bovine bone treatment, the percentage of vital bone area increased from 62 +/- 3% to 70 +/- 7% and the percentage of natural bone mineral area decreased from 19 +/- 14% to 6 +/- 3%.
Lateral wall biopsy specimens at 7.5 months were compared to those at 18 months. On average, the grafts were found to have a height of 14 mm. The radiographic vertical height was maintained between the 6.5- and 18-month time points. Radiographic analysis of computed tomographic scans taken at 1.5 years revealed an average BMD of 658 mg/mL, which was not significantly different from the values found at 6.5 months. The purpose of this in vivo study was to determine the bone mineral density (BMD) of the sinus grafts, the vertical height stability, the vital bone area, and the extent of anorganic bovine bone replacement 18 months postoperatively in 4 maxillary sinuses from 4 different animals.
We have previously shown by histomorphometric and radiographic analysis that the percentage of vital bone area, the vertical height, and the density of new bone in the maxillary sinus was significantly greater with anorganic bovine bone compared to bovine Type I collagen matrix. The short-term histologic and radiographic healing following sinus grafting with natural bone mineral (Bio-Oss) in the chimpanzee has been evaluated. Maxillary sinus grafting procedures are currently the treatment of choice when the alveolar crest of the posterior maxilla is in close approximation to the maxillary sinus.
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