A Review Paper Hand Blisters in Major League Baseball Pitchers: Current Concepts and Management Andrew R. McNamara, MD, Scott Ensell, MS, ATC, and Timothy D. Farley, MD Abstract Friction blisters are a common sequela of spent time on the DL due to blisters. More- many athletic activities. Their significance can over, there have been several documented range from minor annoyance to major per- and publicized instances of professional formance disruptions. The latter is particularly baseball pitchers suffering blisters that did true in baseball pitchers, who sustain repeat- not require placement on the DL but did ed trauma between the baseball seams and result in injury time and missed starts. the fingers of the pitching hand, predominate- The purpose of this article is to review ly at the tips of the index and long fingers. the etiology and pathophysiology of friction Since 2010, 6 Major League Baseball blisters with particular reference to baseball (MLB) players accounted for 7 stints on the pitchers; provide an overview of past and disabled list (DL) due to blisters. These inju- current prevention methods; and discuss ries resulted in a total of 151 days spent on our experience in treating friction blisters the DL. Since 2012, 8 minor league players in MLB pitchers. riction blisters result from repetitive friction of rubbing (erythroderma). This is followed by a and strain forces that develop between the pale, narrow demarcation, which forms around the F skin and various objects. Blisters form in reddened region. Subsequently, this pale area fills areas where the stratum corneum and stratum in toward the center to occupy the entire affected granulosum are sufficiently robust (Figure), such area, which becomes the blister lesion.1,2 as the palmar and plantar surfaces of the hand and Hydrostatic pressure then causes blister fluid feet. Thus, these layers are capable of transmit- to accumulate within 1 to 2 hours following the ting the surface forces to the underlying layer, trauma. Compared to plasma, the blister fluid has a the stratum spinosum. In areas without strong lower protein level and similar electrolyte content.3,4 stratum corneum and stratum granulosum layers, Cells in the blister cavity continue to degrade for an abrasion forms instead.1 about 4 hours following the injury, with resumption It has been shown that the transmitted frictional of cellular activity beginning at 6 hours. Mitotic forces disrupt the stratum spinosum, with the blis- activity is increased after 24 to 30 hours, and at 48 ter roof being composed of the 2 upper epidermal hours, a new granular layer is present. By 120 hours layers as well as prickle cells of the traumatically post-injury, a new stratum corneum is formed.5,6 disrupted stratum spinosum. The basal cell layer A number of factors have been found to affect typically shows little damage and the dermal-epi- blister formation. Frictional force magnitude and dermal junction remains intact.1 number of cycles play the most obvious role. There Early experimental studies in humans using is an inverse relationship between the two: as the repeatedly cycled probes demonstrated the patho- frictional force increases, fewer cycles are required logic sequence of events in blister formation. First, for blister formation.7 This is likely the reason there is slight exfoliation of the stratum corneum blisters occur most commonly in areas where the layer, accompanied by a reddened area in the zone fingertips are in contact with a seam, as opposed Authors’ Disclosure Statement: The authors report no actual or potential conflict of interest in relation to this article. 134 The American Journal of Orthopedics ® March/April 2016 www.amjorthopedics.com to the smoother surface of a baseball. bags of rice, and superglue.14,15 Superglue, surgical Many authors have examined moisture’s effect glue, or any other foreign substance is not allowed on frictional forces, and found that very dry and during a game on the finger or hands of pitchers very wet skin produce low frictional forces, by Major League Baseball rules. Other anecdotal whereas moist skin produces the highest frictional options include the use of compounded medicines force.1,2,8-10 In the case of dry skin, this is thought that are marketed as creams and sprays designed to be due to exfoliation and sloughing of cells from to toughen skin. the stratum corneum, which produces a dry lubri- As with other injuries, it is important to recog- cation similar to graphite. Very wet skin has a fluid nize any predisposing factors and ways to avoid layer that lubricates the 2 surfaces. In the case of them. Dampness and temperature (>104°F) have moist skin, however, it is hypothesized that surface been identified as chief factors that substantially tension impedes the movement of squamous cells, increase the friction coefficient and increase blister increasing the frictional forces.2,9 This moist envi- incidence.18 While temperature and perspiration ronment is most commonly produced by sweating. are impossible to avoid during competition, steps Other factors include skin temperature, which, can be taken to keep the pitcher’s hand dry on the when elevated, mildly predisposes the skin to blis- mound as well as between innings, such as a rosin ter formation. Some studies have shown tempera- bag, a dry towel, and a rice bucket. tures as high as 50°C in rubbing experiments2,7,8,11; Maintaining fingernail length plays an important however, it should be noted that friction blisters do role in preventing blister formation. The nail can not resemble second-degree burns, either histo- both protect the adjacent skin by decreasing the logically or clinically.12,13 frictional force on the skin as well as lead to the development of blisters on the other fingers by Blisters in Baseball Pitchers repetitive abrasion. Nail length and contour need to Blisters in baseball pitchers are a well-known and be tailored to each pitcher specifically. The length frequently publicized problem; however, there is of the nail can protect the finger pulp by minimally a paucity of literature describing the incidence or “elevating” the ball off of the finger itself. How- treatment of such blisters.14,15 The digital pulp expe- ever, too long of a nail may come at the cost of riences frictional forces from the baseball stiches abrading the abutting finger as the spin is imparted as well as from the distal margin of the nail plate onto the ball. The shape of the nail is generally kept during release of the ball. Forces are transmitted well contoured to avoid any sharp edges, which to the ball predominately through the thumb, can act as local irritants. In the instance of soft, index, and long fingers. While the thumb acts cracked, or torn nails, some pitchers have used mainly as a post, the index and long fingers impart acrylic nails. Maintaining proper fingernail shape the “action” on the ball. Not surprisingly, blisters and length is an essential preventive measure that form most commonly on these 2 fingers. While requires regular use of clippers and emery boards. relatively small in size and significance, the impact Callus care is also paramount in preventing of such a blister on a pitcher’s ability to maintain blister formation. It is believed that development of the fine control of his pitches cannot be over- a callus is inevitable with repetitive throwing and looked. Biomechanical studies have shown that likely protective of the underlying skin. The size maximum gripping strength is attained when the and shape of the callus, like that of the nail, needs fingers grasp a dynamometer handle at the level of the distal interphalangeal joint.16 Contact pressure mapping during gripping of a cylindrical object has shown that phalanges 2, 3, and 4 experience the highest forces in gripping and pulling activities.17 No study has specifically addressed phalangeal pressure generation in pitchers, however. Blister Prevention Blister prevention and treatment methods in base- ball pitchers are steeped in folklore and tradition. Methods for drying out blisters and hardening cal- luses have included the use of pickle juice, urine, Figure. Longitudinal section of the epidermis showing a friction blister. www.amjorthopedics.com March/April 2016 The American Journal of Orthopedics ® 135 Hand Blisters in MLB Pitchers: Current Concepts and Management to be carefully monitored. A callus that becomes References overly prominent can lead to increased friction 1. Sulzberger MB, Cortese TA, Fishman L, Wiley HS. Studies on with a baseball seam. This can lead to blister blisters produced by friction. I. Results of linear rubbing and twisting technics. J Invest Dermatol. 1966;47(5):456-465. development. A small, smooth callus without 2. Naylor PFD. Experimental friction blisters. Brit J Dermatol. edges or loose borders is the goal. The free edges 1955;67(10):327-342. of a callus can be trimmed with clean clippers. 3. Cortese TA, Mitchell W, Sulzberger MB. Studies on blisters Contouring is best performed with careful use of produced by friction. II. The blister fluid.J Invest Dermatol. 1968;50(1):47-53. an emery board. 4. Schmidt P. Quantification of specific proteins in blister fluid. J Invest Dermatol. 1970;55(4):244-248. Treatment of Finger Blisters 5. Epstein WL, Fukuyama K, Cortese TA. Autographic study Blister management is determined by the size of the of friction blisters. RNA, DNA, and protein synthesis. Arch Dermatol. 1969;99(1):94-106. blister as well as the integrity of the overlying callus. 6. Cortese TA Jr, Fukuyama K, Epstein W, Sulzberger MB. Small blisters with intact skin coverage can be Treatment of friction blisters. An experimental study. Arch sterilely drained with a needle or a No. 11 blade.6,19-21 Dermatol.