Z. B. Friedenberg

Bioelectric Potentials in Bone

Bioelectric phemiomenia have been intensively studied in plamit arid animal tissue. Most. of this research has concentrated on rapidly evoked potentials of short duratiomi, w’hile the study of steady, direct current potentials of lomig duratiomi has proceeded more slowly. Steady, resting potentials, ranging from microvolts to more than one hundred millivolts, have been recorded in biological systems. Single cells, extracellular collagemi and crystallites, membranes, skin, amid whole organs have beeni

Stimulation of Fracture Healing by Direct Current in the Rabbit Fibula

An undisplaced fracture of each fibula in a rabbit was permitted to heal for eighteen days. The fracture in one fibula of each animal was subjected to a ten microampere galvanic current, the electrodes being placed in various positions relative to the fracture. Leads were placed in the opposite (control) fibula but did not deliver any current.nnEach fibular fracture was studied by roentgenogram, stressed for rigidity, and evaluated microscopically. The evidence strongly suggests that a cathodal current of this intensity placed within the fracture site stimulates fracture healing.

The Response of Non-traumatized Bone to Direct Current

A direct constant-current cathode caused bone to form at a site remote from any bone trauma in the medullary cavity of a rabbit tibia. The osteogenic response was current-dependent and the greatest bone respoose developed around cathodes delivering twenty microamperes of current. Excessive current (thirty microamperes or more) caused osteonecrosis. EIevation of voltage also caused bone destruction.

Direct-current stimulation of non-union and congenital pseudarthrosis. Exploration of its clinical application

Based on the response of bone to electrical current in previous studies, an exploratory clinical study of the effect of electrical current on non-union and congenital pseudarthrosis was performed. Constant direct current of ten to twenty microamperes was applied to twenty-four non-unions and five congenital pseudarthroses. Complete union occurred in fifteen non-unions and in one congenital pseudarthrosis. A single cathode delivering ten microamperes seemed sufficient to heal non-union in small bones, but multiple cathodes each delivering twenty microamperes appeared to be required to heal non-union in the tibia and femur. As the technique was refined, the percentage of successes increased. While these preliminary results appear promising, further laboratory and clinical experiments are required to define the true role of electrical stimulation in clinical practice.

Treatment of nonunion with constant direct current.

Laboratory experiments show the following relationships between electricity and bone: (1) stressed bone exhibits electronegativity in areas of compression, (2) living, nonstressed bone exhibits electronegativity in areas of bone growth and healing, and (3) the application of low magnitude direct current to bone induces osteogenesis at the negative electrode or cathode. Based on the above principles, a clinical study was performed in which 10-20 microamperes of constant direct current was used in treating nonunion in 57 patients. The results suggest that specific electrical parameters are required for successful osteogenic stimulation in patients. When these electrical parameters are met, a successful healing rate of 70 per cent can be achieved in treating nonunion with direct current. As experience is gained with this new technique in the treatment of nonunion, the results should improve even further. Basic studies exploring the mechanism(s) whereby electricity induces osteogenesis are opening new vistas into our understanding of bone growth and repair. The extension of these basic studies has far-reaching clinical implications.

Cathodic oxygen consumption and electrically induced osteogenesis.

Small amounts of electric current stimulate bone formation in the region of a cathode. The purpose of this experiment is to compare changes in oxygen and hydroxyl ion concentration that occur at the cathode at current levels known to be capable of inducing osteogenesis (10-20 muamps) with those changes that occur at current levels known to be toxic to bone (100 muamps). An oxygen consumption chamber containing an oxygen electrode is fitted with two stainless steel electrodes which are connected to a constant current source. At the cathode, with a current of 100 muamps, oxygen is consumed at nearly stoichiometric rates. At higher current (100 muamps) levels, cathodic oxygen consumption gives way to hydrogen evolution. Cathodic hydroxyl ion production is directly proportional to current. It is concluded from these in vitro experiments that at 10-20 muamps the oxygen tension in the vicinity of the cathode is lowered and the pH is moderately increased. At 100 muamps the oxygen tension is not lowered, but the pH is increased dramatically. If these same changes occur in the vicinity of a cathode in vivo, then lowering the local tissue oxygen tension and raising the local pH may be mechanisms operative in electrically induced bone formation.

The cellular origin of bioelectric potentials in bone.

Bioelectric potentials were recorded from the unstressed tibia in the anesthetized rabbit by means of silver/silver chloride electrodes connected to saline bridges and a high impedence voltmeter. Potentials recorded from the anterior, medial, and lateral surfaces of the tibia indicated that the surface voltage was constant around the transverse axis of a bone but varied in relation to its long axis. Voltages were independent of bony landmarks and points of muscle attachment. The bioelectric potentials changed little after sciatic nerve denervation or ligation of the femoral artery. The potentials decreased dramatically thirty minutes following the intra-arterial administration of dinitrophenol or iodoacetamide. Also, the potentials fell sharply in a localized segment of tibia injured through the application of ultrasound energy. Animal death brought about a slow decay of potential commensurate with the gradual loss of bone cell viability. The experimental evidence from this study suggests that the steady state potentials observed from the surface of unstressed bone are not directly dependent on blood flow or nerve transmission. Rather, such potentials are dependent on a functioning bone cell population, and each recorded potential represents a summation of the electromotive forces from all cells in a localized area.RésuméDes potentiels électriques sont enregistrés au niveau du tibia, au repos, dun lapin anesthésié, et cela à laide délectrodes dargent/chlorure dargent, reliées à des ponts salins et un voltmètre à haute impédance. Les potentiels enregistrés à partir des surfaces antérieures, médianes et latérales du tibia indiquent que le voltage de surface est constant autour de laxe transversale de los, mais varie en rapport avec laxe longitudinal. Les voltages sont indépendants des limites osseuses et points dattaches musculaires. Ces potentiels bioélectriques varient peu après résection du nerf sciatique ou ligature de lartère fémorale. Les potentiels décroissent nettement trente minutes après administration intra-artérielle de dinitrophénol ou iodoacétamide. Les potentiels chutent nettement dans un segment localisé du tibia, endommagé par application dultra-sons. La mort de lanimal provoque une chute lente de potentiel en rapport avec la perte graduelle de viabilité des cellules osseuses. Il semble que les potentiels de repos, observés à la surface de los non stressé, ne sont pas directement liés à la circulation sanguine ou la transmission neurale. Ces potentiels semblent plutôt liés à lexistence dune population cellulaire osseuse active et chaque potentiel mesuré constitue la somme des forces électromotrices de toutes les cellules dune région localisée.ZusammenfassungAm anaesthesierten Kaninchen wurden die Biopotentiale der unbelasteten Tibia gemessen. Dazu wurden Silber/Silberchlorid-Elektroden benützt, welche über Salzbrücken an ein Voltmeter mit hohem Eingangswiderstand angeschlossen waren. Die an der vorderen, seitlichen und hinteren Tibia-Oberfläche gemessenen Potentiale zeigten, daß die Oberflächenspannung an der Querachse eines Knochens konstant ist, jedoch in bezug zur Längsachse variiert. Die Spannungen waren nicht beeinflußt durch knochentopographische und Muskelansatz-Punkte. Nach Sciaticus-Durchtrennung oder Ligatur der Arterie femoralis änderten sich die bioelektrischen Potentiale nur wenig. Ein eindrücklicher Abfall der Potentiale wurde jedoch 30 min nach intraarterieller Verabreichung von Dinitrophenol oder Jodacetamied beobachtet. Ebenso stark fielen die Potentiale in einem umgrenzten Tibia-Segment ab, das durch Ultraschallbehandlung lädiert worden war. Beim Tod der Tiere wurde ein langsamer Abfall der Potentiale, entsprechend dem allmählichen Verlust an lebenden Knochenzellen, beobachtet. Auf Grund der mit dieser Studie gewonnenen Resultate kann vermutet werden, daß die im Gleichgewicht bleibenden Potentiale der unbelasteten Knochenoberfläche nicht direkt von der Durchblutung oder der nervösen Reizleitung abhängig sind. Es scheint eher, daß dafür eine intakte Knochenzell-Population vorliegen muß, wobei jedes aufgezeichnete Potential eine Summierung der elektromotorischen Kräfte aller Zellen einer bestimmten Region darstellt.

Degenerative Changes in the Cervical Spine

Pain aimd disability of time Imead, neck, and upper extremity resulting fromim degenerative cimanges of time cervical spine are frequently encountered and often I)resent a timerapeutic enignma. Time literature dealing witim timis subject presents confused and often contradictory commcepts, not only of time patlmology, but also of time structural anatomy. Timere are certain ammatomical peculiarities of time cervical spine wimich must be considered in order to understand fully the cimanges which occur. The body of a typical cervical vertebra is broader from side to side than from before backward. Time sul)eriOr surface lmas two well marked lateral lips which render it concave fromn side to side, wimile time inferior surface is notcimed laterally and timus is convex fromtm side to side. Time posterior surface is squared, but the aimtenor surface is proloimged dowimward to formmm a distinct lip. Time lateral lips of time superior surfaces of time timird to seventim cervical vertebrae were described as eininentia costaria bvon Luscimka, jim 1858, vimo based imis observations omm Meckel’s suggestiomm timat timese projectiomms vestigial ribs of time cervical spine. Timis structure imas also l)een ternmed processes lunati by Giraudi. Ratimeke imoted timat timese lateral lips or ummcinate pm’ocesses develop during time second decade alm(1 timat, prior to timis, time superior surfaces of time bodies are fiat. These processes lie iim (lose relatiolmsimii) to time immtervem’tebral foramina ammd are in iimtinmate reiatiomm with the enmergimmg nerve roots. Bovill and Drazek foummd timat time lateral lips varied in size and extent ammd timat soimme of timese processes extended far eimougim posteriorly to present a barrier to l)Osterolateral disc 1)rotrusiomms into time spinal cammal. Frykimoim stated timat time ummcimmate pm’ocesses am e directly latem’al iim