In-Vivo Bone Strain Telemetry in Monkeys (M. Nemestrina)

Abstract

A new method for collecting in-vivo bone strain data in monkeys has been developed and tested. The method includes a system which consists of a new design of implantable strain transducer and its companion telemetry package. The transducer fits into a hole drilled in a monkey tibia and is threaded for subsequent bone ingrowth. The transducers and telemetry package are biocompatible for over 503 days. The telemetry package uses Pulse Interval Ratio Modulation (PIRM) to transmit strain information to receiving equipment located outside the animal housing cage.

Letters to the Editor: Load Bearing in the Equine Metacarpal

“…In addition, the assumption of isotropic properties of bone leads to erroneous conclusions. In sharp contrast, an earlier publication (2) reported strains as high as 1060 μm/m in the posterior tibia of 10–12 kg active monkeys. As many as three to five events/s were recorded.…”

“…It is important to appreciate, as stated in the paper, that strain gauge attachment is achieved by applying significant pressure during the polymerization of the cyanoacry‐late. This technique leaves only an extremely thin film between the flimsy gauge and the bone (2, 3). That the bone matrix is orders of magnitude stiffer than either the glue or the gauge backing means that the deformation characteristics of the measurement system (gauge+glue) have negligible impact on the strains measured from the third metacarpal bone during activity.…”

“…While D.R. Young's own measurement methods provide some insight into the strain environment of the bone, it must be stressed that such a strategy also has clear limitations, not the least of which requires a stress defect in order to even make the measurement, which invariably would elevate local strains and must assume that the placement of the gauge represents a site of some functional significance, such as the site of greatest strain (9).…”

Radiographic evidence of disuse osteoporosis in the monkey (M. nemestrina)

“…In a prior report we examined the compressive strainstress history in the tibia of monkeys [14]. For causal walking and the shifting of weight from one leg to the other, typical strain values were in the range of 100-400 ~m/m.…”

A fully implantable telemetry system for the long-term measurement of habitual bone strain

“…To this day, the telemetric recording of bone strain in vivo is still a great challenge. Young et al (1977) succeeded in implanting a bone-strain transducer and its associated transmitter into a monkey hind leg. Their telemetry package collected tibial loads during various activities of the caged animal and transmitted these through pulse-interval ratio modulation.…”