Much of the Ryan Braun's past two seasons have been marred by a peculiar and recurring hand injury that has robbed him of much of his prodigious power. Typically described as a right thumb injury, it is an inflamed nerve in the 'webbing between his right thumb and index finger that runs up the base of the thumb' that is the actual source of Braun's issues. Secondary to this matter are the blisters in the area as a result to gripping the bat too tightly due to the injury causing numbness of the thumb.
While a number of resolutions have been presented—increased padding of the thumb to relieve pressure and even surgery that would completely resolve the issue at the cost of sensation in the thumb—all have had deficits of one form or another, resulting in a pair of disappointing seasons which have found him hitting at an ISO of .200 and .208 in 2013 and 2014, respectively, both well under his career average of .247.
Before we begin our discussion, some anatomical sleuthing is necessary, as the exact nerve causing Braun's troubles has never been directly identified. However, with the general area mentioned in the above quote from Milwaukee Journal Sentinel's Tom Haudricourt and some other considerations, we have a great idea as to which nerve is the culprit. Since Braun has no issue gripping a bat and it's is solely a matter of a sensory nerve wreaking havoc on his swing, our list of suspects is cut down precipitously.
Three nerves supply innervation to the hand to various degrees: the median, radial, and ulnar nerves. Knowing the area of concern is around the thumb and the webbing between the thumb and index finger and that it is sensory in nature, we can be fairly confident that it is a branch of the median nerve that is problematic—a palmar digital cutaneous branch. There is a non zero percentage of anatomic variation that must be taken into consideration, but overall, the sensory side of the median is at the root of this injury.
With the sensory aspects of Braun's injury considered and with the understanding that a permanent resolution to the nerve aggravation is still up in the air, let's now turn to the motor and biomechanical aspects of his swing and consider some of the effects the lack of sensation has on these components. The act of gripping an object has been studied for many years and has been broken down into two basic types—a power grip and a precision grip (or handling)—with handling and swinging a bat being a power grip. Further refinement of the grip type used shows that a bat grip to be similar to a hammer grip, with the muscles of the forearm and hand interacting and firing in a dynamic fashion.
With respect to the muscles involved, one study of the intrinsic and extrinsic muscle control of grips found the interossei of the fingers assist in the rotation of the fingers as they wrap around the bat, while the flexor digitorum superficialis, an extrinsic flexor muscle, comes into play as the need for increased force in flexion of the fingers is required and can be thought of as a reserve muscle.
A number of other extrinsic muscles—muscles arising from the forearm that assist in movement at the hand at wrist—provide the lion's share of gripping power seen in the power grip. Intrinsic muscles—muscles that are fully contained within the hand—also play a large role in the generation of grip force, with the thenar muscles of the thumb and the fourth lumbrical muscle being the primary intrinsic components to the power grip of a bat, with the thenars at greatest risk for injury and aggravation in Braun's case of reduced sensation of his right thumb.
From a hitting perspective, the top hand is what provides the power of the swing and is also the hand that essentially delivers the bat to the right spot for contact with a pitch, accelerating the bat to the point of contact and in the process, allowing for the shortest swing path. With Braun's thumb injury arising from the right hand (the top hand for a right-handed hitter), it isn't any surprise that while his contact rates are in line with career averages, his chase rates are higher than usual—2014 sees him at a 10.9% swinging strike rate—coinciding with his power numbers all but sapped.
Looking at his slugging trends between 2012 (a healthy season) as well as his injury-hampered 2013 and 2014, this notion is amplified:
In particular, Braun has had problems with generating any power from inside pitches, with a lack of proprioceptive input from the top hand thumb playing a large role in this. Given the sensory issues, Braun's default action is to squeeze too hard on the bat, with the aforementioned intrinsic muscles overtaxed and the thenar eminence of the right thumb subjected to excessive forces that have led to blistering. This over-tight grip on the bat has also hindered his usually quick, smooth, compact swing path to all pitches, but is especially apparent on those on the inside half of the plate. As such, what contact he makes with inside offerings will be hit to the opposite field, with little power put behind the swing; a propensity to roll over balls he pulls can also be seen when the injury is at peak aggravation. The graphic below highlights the shift in Braun's spray chart across 2012-2014 and the move in his overall hit field:
In many ways, Braun's thumb issue puts him in a position where he is constantly at risk of jamming himself, especially when over-gripping the bat with the top hand. This also can lead to slower bat speed and erratic swing path, making the swing longer than desired. This is highlighted in Braun's ability to put bat to ball on good fastballs (here considered to be pitches thrown 95+ MPH), where he has seen his whiff rates go from 11.4 percent in 2012 to 16.9 and 13.4 percent in 2013 and 2014, respectively.
The data does show Braun having some improvement in his production as of late, with some of the therapies and protective approaches employed by the Brewers medical staff providing some relief of his symptoms and allowing for him to remain fairly productive at the plate. This is particularly reflected in his 2014 data, which does show a return to some of the hitting tendencies seen in his healthier 2012 season, hitting to all fields. That said, it appears that Braun's issue is chronic, with rest being the only effective treatment. Aside from a procedure to cut the nerve, thereby leaving Braun with no sensation to the afflicted area, there are few other medical options.
A less common approach to treating the injury—something along the lines of a superficial sensory radial nerve entrapment procedure—is possible, but would more than likely be something that is infrequently performed and also rife with the usual caveats that going under the knife entail. From a behavioral perspective, assisting Braun with various strategies to endure the sensory deficits that occur when the injury flares up, such as occupational therapy approaches or even a change to a different style of bat handle, batting gloves with marks on them that prompt him to line up his hands with the proper amount of grip strength, even if he cannot quite feel his thumb fully, are all other possibilities that could help Braun endure and overcome the thumb numbness.
With surgery more than likely out of consideration due to the potential for permanent loss of sensory function, a durable and long term resolution to Braun's nerve injury remains a tricky proposition; one that will allow Braun to fully return to his slugging ways remains even more elusive.
Intrinsic-extrinsic muscle control of the hand in power grip and precision handling. An electromyographic study. The Journal of bone and joint surgery. American volume, Vol. 52, No. 5. (July 1970), pp. 853-867 by C. Long, P. W. Conrad, E. A. Hall, S. L. Furler