C. Andrew L. Bassett

Generation of Electric Potentials by Bone in Response to Mechanical Stress

The amplitude of electrical potentials generated in stressed bone is dependent upon the rate and magnitude of bony deformation, while polarity is determined by the direction of bending. Areas under compression develop negative potentials with respect to other areas. Similar results were obtained both in living and dead bone. Removal of the inorganic fraction from bone abolishes its ability to generate stress potentials. It is probable that these potentials influence the activity of osseous cells directly. Furthermore, it is conceivable that they may direct, in some manner, the aggregation pattern of the macromolecules of the extracellular matrix.

The effects of varying oxygen concentrations on osteogenesis and embryonic cartilage in vitro.

1. An improved method of organ culture, employing embryonic chick tibiae, demonstrated consistent patterns of osteogenesis. With all other factors constant, the amount of bone and collagen formed or destroyed could be controlled solely by altering the amount of oxygen available to the explants from the gaseous phase of the culture. 2. Maximum osteogenesis was observed with an oxygen concentration of 35 per cent. Collagen-fiber formation and osteogenesis were suppressed by lowering the oxygen concentration to 5 per cent and, to a lesser degree, by raising it to 95 per cent. High oxygen concentrations also appeared to cause osteoclasia. 3. Cartilage matrix and cells near the cut ends of explants also demonstrated significant alterations under various oxygen concentrations. High oxygen concentrations (95 per cent) caused extensive chondroclasia. Intermediate oxygen concentrations (20 to 65 per cent) produced numerous large collagen fibers in and about the lacunae of degenerating chondrocytes, while other chondrocytes, undergoing alterations of morphology, came to resemble osteoblasts. Metachromasia of cartilage matrix was lost. Low (5 per cent) and high (95 per cent) oxygen concentrations did not produce similar collagen fiber production, alterations of chondrocyte morphology, or loss of matrix metachromasia.

Peripheral nerve and spinal cord regeneration: Factors leading to success of a tubulation technique employing Millipore

Abstract Severed peripheral nerves and spinal cords have a strong regenerative potential when gaps in these structures are shielded within a porous cellulose acetate plastic tube, Millipore. Experiments, utilizing 1- to 2.5-cm gaps in the cats sciatic nerve demonstrated more successful results when a single sling stitch was used to unite the severed nerve ends within the tube. Addition of a preformed clot of cat plasma to the region of the gap did not significantly change the pattern of neural regeneration. The substitution of nonporous for standard porous Millipore tubes seemed to retard the progress of cell migration across the gap. The plastic filter material served as a satisfactory substrate for migration of cells of leptomeningeal origin across the gaps in spinal cords, while apparently meeting their nutritional requirements by passing adequate amounts of fluid from the tissue bed outside the tube. The following factors attributable to the physical properties of Millipore have been identified as favoring neural regeneration: (a) Millipore is inert in tissues; (b) a shield is provided which limits the regenerating tissue to a directed pathway and prevents invasion by extraneural tissue; (c) nutrition by exchange of extracellular fluids through the pores supplies the metabolic requirements of the early phases of neural regeneration; (d) a substrate for initial orientation of regenerating structures is offered by the inner walls of the tube.

Mechanical properties of hydrated cortical bone.

Abstract The elastic modulus and the viscous modulus of hydrated and airdried cortical bone were determined. All testing was done on highly organized specimens from the human femur with the same specimen loaded alternately in axial tension and compression. Sinusoidal strain rates in the physiologic range were employed. Specimens at 0. 30 and 45 to the long axis of femur were tested to demonstrate directional changes in the moduli. Both moduli showed no change of value in tensile and compressive loading modes.

Long-term pulsed electromagnetic field (PEMF) results in congenital pseudarthrosis.

SummaryNinety-one patients with congenital pseudarthrosis of the tibia have been treated with pulsed electromagnetic fields (PEMFs) since 1973 and all except 4 followed to puberty. Lesions were stratified by roentgenographic appearance. Type I and type II had gaps less than 5 mm in width. Type III were atrophic, spindled, and had gaps in excess of 5 mm. Overall success in type I and II lesions was 43 of 60 (72%). Of those 28 patients seen before operative repair had been attempted, 7 of 8 type I lesions healed (88%), whereas 16 of 20 type II lesions healed (80%) on PEMFs and immobilization alone. Only 19% (6 of 31) type III lesions united, only one of which did not require surgery. Sixteen of 91 limbs (18%) were ultimately amputated, most before treatment principles were fully defined in 1980. Fourteen of these 16 patients (88%) had type III lesions. Refracture occurred in 22 patients, most as the result of significant trauma, in the absence of external brace support. Twelve of the 19 refractures, retreated with PEMFs and casts, healed on this regime. Episodic use of PEMFs proved effective in controlling stress fractures in several patients until they reached puberty. PEMFs, which are associated with no known risk, appear to be an effective, conservative adjunct in the management of this therapeutically challenging, congenital lesions.