From the American Society for Dermatologie Surgery Troubles With Power Punches in Hair Transplantations
BERNARD J. BENDL, M.D. d e v e l o p m e n t of the powered punch represents a significant advancement in hair transplantation surgery. In order for the powered cutting tool to be used to good advantage, however, punches must be sharp and must operate without vibration or wobble. While most instru ment suppliers have solved the problem of producing sufficiently sharp punches, it is the author’s belief that many power punches do not produce high quality plugs because they possess mechanical and geometric flaws. Occasionally, wobbling or vibration may occur as a result of movement of the motor of the power tool within its housing. This is most likely to occur after extensive use, particularly if the motor housing is made of plastic. More commonly, problems arise as the result of defects within the punch itself. The most common flaws are demonstrated in Fig. 1. Left to right: (a) a slight bend is present in the shaft of the punch (usually seen in resharpened instruments); (b) the shaft is placed eccen trically on the hub of the punch; (c) the shaft is placed centrally but not perpendicularly to the hub of the punch. The last figure on the right (d) represents a punch that is free of defects. The defects schematized in (a), (b), and (c) of Fig. 1 result in a wobbling of punches in those manners defective and cause coning and injury to or destruction of follicles at the periphery of donor grafts (Fig. 2). Before a power punch is used an effort should be made to determine whether or not it will rotate without wobble or vibration. If the power tool has a variable speed control, the motor can be slowed to a point where the punch is barely turning. If the punch is then observed end-on (Fig. 3) wobble will be detected if the punch is defective. If the punch turns true, a high quality plug will be obtained. Unfortunately, some units rotate so rapidly, even at their lowest speeds, that wobble and vibration cannot be detected with the naked eye. When an instrument that cannot be read for wobble is used, the first donor plugs obtained should be examined carefully for evidence of coning or peripheral damage. If coned or peripherally damaged plugs are cut in spite of
Dr. Bendl is in private practice (dermatology). Address reprint requests to Dr. Bendl, 3195 Granville St., Suite 206, Vancouver, B.C. V6H 3K2, Canada.
J. Dermatol. Surg. Oncol. 3:6 November/December 1977
FIGURE 1. (a) Slight bow in shaft o f power punch; (b) Shaft attached eccentrically to hub o f power punch; (c) Shaft attached centrally on hub o f power punch , but perpendicularly to it; (d) Shaft properly set.
plug site caused by a wobbly power punch.
FIGURE 3. To detect a wobble, the power punch is observed on end with the punch barely rotating.
proper technique on the part of the operator, the punch should be discarded. It has been the author’s finding that one out of three power punches wobble and that two out of three resharpened punches are similarly defective.