SUMMARY. Two patients sustained circumferential burns to the fingers associated with metal rings. In both cases the patients sustained a deep partial -thickness burn when their rings shorted the battery of a vehicle. Our treatment regimen was entirely on an out-patient basis and consisted of multiple daily washing, instruction in home physical therapy, and repeated clinical examinations.

Introduction
Electrical burns associated with rings are usually deep second-degree burns which may leave scars, cause loss of hair follicles and sweat glands, and leave permanent skin pigmentation. We believe this is not such an uncommon occupational electric burn as some authors have thought (1-5), and it has to be recognized by professional mechanics as well as by the medical community.

Case reports
Case 1
A 50-year-old auto mechanic was referred to hospital suffering from a circumferential electrical burn around his left ring-finger. The patient was working on a car electrical system with a metal spanner which touched the positive pole of the battery, the wedding band and the solenoid metal housing, causing a short circuit through the ring. The patient experienced mild pain to the left ring finger. He immediately washed his hand and sought medical attention. On examination, his left ring-finger was erythematous and swollen, with the ring still in place. The ring was cut and removed to reveal a circumferential burn at the proximal phalanx (Fig. 1).
No surgical procedure or hospitalization was needed. Our treatment consisted of daily washing, instruction in physical self-therapy and periodical clinical examination. The wound healed within 2 weeks, leaving a flat scar.

Case 2
A 32-year-old schoolteacher tried to help her husband start his car, which had a flat battery, by using her car battery and jump leads. She operated the starter and while she was adjusting the jump starting cables, her wedding ring shorted across the battery.

She presented to hospital a few . hours later. The ring was removed with a cutter, revealing a deep circumferential burn without vascular impairment (Fig. 2).
Digital sensation was normal at the finger tip. The bufn was treated conservatively with dressing and was fully healed within 3 weeks. Full function was obtained.

Fig. 2 Patient No. 2. Dorsal aspect of ring finger at I year.

Discussion
Both of these patients demonstrate the potential problem of wearing metal jewellery around electrical current. The perspiration underneath a wedding ring serves as an excellent conductor for the current. The three metals commonly used in rings are gold, platinum and silver. The thermal conductivity and resistivity of each metal is shown in Table 1. A gold ring, as can be seen, will conduct heat and electricity to a greater degree than a platinum ring since it has a higher thermal conductivity but lower resistivity.
DvoretAy and Silverman (2) reported similar cases. These authors were able to confirm that a car battery could indeed cause a severe burn. A gold ring was connected to a 24 V battery; within 1 to 2 seconds the temperature of the ring was above 1000 'C and it started to melt. The resistance of the whole electric circuit was 0. 1 ohm (the sum of the very low resistance of the ring, which was measured as 0.03 ohm, and the internal resistance of the battery, which in the case of a 24 V battery is typically about 0.02 ohm, plus the resistance of the contact points, which is around 0.05 ohm). With a battery of 24 V the current was around 240 amps, as can be calculated from Ohm's Law:

1 = V/R = 24 volts/0. 1 ohm = 240 amps

From this calculation, we can conclude that even a 12 V battery can cause the same hazard. If a car battery is short-circuited by a metal jewellery the energy produced can therefore cause a local deep second-degree burn. The significance of such a burn cannot be overemphasized as it may result in serious sequelae.

RESUME L'auteur décrit deux cas de patients qui ont subi des brélures circulaires associées A des anneaux de métal. Dans tons les deux cas les patients ont &é atteints d'une brOlure profonde de premier on de deuxi&me degré quand leurs anneaux ont court-circuité la batterie d'un véhicule. Les patients ont &é traités ambulatoirement avec lavage quotidien, instructions pour la thérapie physique chez soi, et des examens cliniques répétés.

1. Manstein C.M., Manstein M.E., Manstein G. et al.: Circumferential electric burns of the ring finger. J. Hand Surg. (Am.), 12: 808, 1987.
2. Dvoretzky 1. Silverman N.: Ring burn - an unusual electric burn. J. Am. Acad. Dermatol., 14: 855, 198é.
3. Fisher B.K., Dvoretzky I.: Bracelet burn - an unusual electric burn. J. Br. Soc. Surg. Hand, 8: 158, 1976.
4. Regan M.W., Moss L.H.: Circumferential burns to the fingers associated with gold and platinum rings. Burns, 12: 360, 1986.
5. Attala M.F., El-Ekiabi S., AI-Baker A.: Ring burn - electric contact? Burns, 16: 69-79, 1990.