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Bracelet burn—An unusual electric burn
Bracelet B u r n - - A n Unusual Electric Burn--Benjamin K. Fisher and Israel Dvoretzky
BRACELET BURN--AN UNUSUAL ELECTRIC BURN
B E N J A M I N K. F I S H E R and I S R A E L D V O R E T Z K Y , Tel-Hashomer, Israel SUMMARY A car mechanic sustained a deep partial thickness burn of the wrist when his metal watch strap short circuited the battery of a car upon which he was working. CASE REPORT
A twenty-eight year old car mechanic was seen in the skin clinic of the Chaim Sheba Medical Centre on January 30th, 1975 with a burn of the left wrist sustained four days previously. He had been handling the engine of a vehicle which had two 12 volt batteries connected in series (i.e. a 24 volt unit) and two supporting iron rods connecting the back of the engine frame to its front. Inadvertently the patient's stainless steel watch strap touched both the positive pole of one battery and the adjacent iron rod causing a short circuit through the watch strap (Fig. 1). The patient experienced pain but was unable to pull away his hand for several seconds until the heat generated caused melting of the watch strap which broke and freed his hand. The patient immediately noticed a linear bracelet-like black burn involving the strap area of the watch but sparing the area under the watch itself. The burn seemed worse on the sides of the wrist than on the volar aspect where the metal clip was located.
Fig. 1. Car battery, short-circuited through patient's stainless-steel watch-strap, which touched battery's pole and a supporting iron rod above it. Patient demonstrates accident. Israel Dvoretzky, M.D., Department of Dermatology, The Chaim Sheba Medical Centre, Tel-Hashomer, Israel. 158
The H a n d - - V o l . 8
No. 2
1976
Bracelet B a r n - - A n Unusual Electric Burn--Beniamin K. Fisher and Israel Dvoretzky
Fig. 2. Left wrist. Burn with sharp borders extends to dorsum of hand. Notice fiat blister on margins of lesion. On the side is the damaged watch-strap which melted in several spots. Examination revealed a healthy man with a burned wrist. The hand and fingers were slightly swollen and there was a linear bracelet-like burn involving the volar and lateral sides of the wrist extending to the base of the thenar area, but sparing the areas corresponding to the watch and the clip. The lateral sides were the worst areas (Fig. 2). A punch biopsy confirmed that th~ burn was of deep partial thickness. T r e a t m e n t with antibiotics, systemic steroids and local dressings resulted in spontaneous healing which was complete by the seventh week, leaving a fiat scar. COMMENT
To confirm that car batteries could indeed cause such a burn a similar watch strap was connected to a 24 volt source and within seconds was too hot to hold. The current was measured and found to be approximately 50 amps. The resistance of the strap was 0.5 Ohms and one can, therefore, calculate that the power produced in the strap was approximately 1250 volts. The heat generated in the strap must have been high for the melting point of stainless steel used in watch straps is 1400-1500°C. The patient sustained a deep partial thickness burn which always leaves a scar and m a y be complicated by infection or hypertrophic or keloid scarring. In the wrist area, acute carpal tunnel syndrome secondary to infection m a y be a serious complication (Williams and Greer, 1963). DISCUSSION
It is accepted that handling car batteries requires no special precautions. However, if the battery is short circuited by a metal watch strap or ring the energy produced can cause local burns and even melting of the metal very rapidly. Welding of the strap to the battery terminal trapped our patient's hand. The Hand--Vol. 8
No. 2
1976
159
Bracelet B u r n - - A n Unusual Electric Burn--Benjamin K. Fisher and Israel Dvoretzky
The significance of this injury is clear. Batteries should not be handled while wearing rings or metal watch straps. Although we could find no similar case report in the English literature, these accidents are probably not rare and we know of other cases which were not reported. We would, therefore, like to emphasise the dangers which can be caused by car batteries in certain circumstances. ACKNOWLEDGEMENT
This study was supported by Canadian Friends of Hospital Tel-Hashomer, Calgary, Alberta, Canada. REFERENCE
WILLIAMS, L. F. and GREER, T. (1963) Acute Carpal Tunnel Syndrome Secondary to Pyogenic Infection of the Forearm. Journal of the American Medical Association, 185: 409-410.
160
The H a n d - - V o l . 8
No. 2
1976
BRACELET BURN--AN UNUSUAL ELECTRIC BURN
B E N J A M I N K. F I S H E R and I S R A E L D V O R E T Z K Y , Tel-Hashomer, Israel SUMMARY A car mechanic sustained a deep partial thickness burn of the wrist when his metal watch strap short circuited the battery of a car upon which he was working. CASE REPORT
A twenty-eight year old car mechanic was seen in the skin clinic of the Chaim Sheba Medical Centre on January 30th, 1975 with a burn of the left wrist sustained four days previously. He had been handling the engine of a vehicle which had two 12 volt batteries connected in series (i.e. a 24 volt unit) and two supporting iron rods connecting the back of the engine frame to its front. Inadvertently the patient's stainless steel watch strap touched both the positive pole of one battery and the adjacent iron rod causing a short circuit through the watch strap (Fig. 1). The patient experienced pain but was unable to pull away his hand for several seconds until the heat generated caused melting of the watch strap which broke and freed his hand. The patient immediately noticed a linear bracelet-like black burn involving the strap area of the watch but sparing the area under the watch itself. The burn seemed worse on the sides of the wrist than on the volar aspect where the metal clip was located.
Fig. 1. Car battery, short-circuited through patient's stainless-steel watch-strap, which touched battery's pole and a supporting iron rod above it. Patient demonstrates accident. Israel Dvoretzky, M.D., Department of Dermatology, The Chaim Sheba Medical Centre, Tel-Hashomer, Israel. 158
The H a n d - - V o l . 8
No. 2
1976
Bracelet B a r n - - A n Unusual Electric Burn--Beniamin K. Fisher and Israel Dvoretzky
Fig. 2. Left wrist. Burn with sharp borders extends to dorsum of hand. Notice fiat blister on margins of lesion. On the side is the damaged watch-strap which melted in several spots. Examination revealed a healthy man with a burned wrist. The hand and fingers were slightly swollen and there was a linear bracelet-like burn involving the volar and lateral sides of the wrist extending to the base of the thenar area, but sparing the areas corresponding to the watch and the clip. The lateral sides were the worst areas (Fig. 2). A punch biopsy confirmed that th~ burn was of deep partial thickness. T r e a t m e n t with antibiotics, systemic steroids and local dressings resulted in spontaneous healing which was complete by the seventh week, leaving a fiat scar. COMMENT
To confirm that car batteries could indeed cause such a burn a similar watch strap was connected to a 24 volt source and within seconds was too hot to hold. The current was measured and found to be approximately 50 amps. The resistance of the strap was 0.5 Ohms and one can, therefore, calculate that the power produced in the strap was approximately 1250 volts. The heat generated in the strap must have been high for the melting point of stainless steel used in watch straps is 1400-1500°C. The patient sustained a deep partial thickness burn which always leaves a scar and m a y be complicated by infection or hypertrophic or keloid scarring. In the wrist area, acute carpal tunnel syndrome secondary to infection m a y be a serious complication (Williams and Greer, 1963). DISCUSSION
It is accepted that handling car batteries requires no special precautions. However, if the battery is short circuited by a metal watch strap or ring the energy produced can cause local burns and even melting of the metal very rapidly. Welding of the strap to the battery terminal trapped our patient's hand. The Hand--Vol. 8
No. 2
1976
159
Bracelet B u r n - - A n Unusual Electric Burn--Benjamin K. Fisher and Israel Dvoretzky
The significance of this injury is clear. Batteries should not be handled while wearing rings or metal watch straps. Although we could find no similar case report in the English literature, these accidents are probably not rare and we know of other cases which were not reported. We would, therefore, like to emphasise the dangers which can be caused by car batteries in certain circumstances. ACKNOWLEDGEMENT
This study was supported by Canadian Friends of Hospital Tel-Hashomer, Calgary, Alberta, Canada. REFERENCE
WILLIAMS, L. F. and GREER, T. (1963) Acute Carpal Tunnel Syndrome Secondary to Pyogenic Infection of the Forearm. Journal of the American Medical Association, 185: 409-410.
160
The H a n d - - V o l . 8
No. 2
1976