The Effect of Wrist Guards on Bone Strain in the Distal Forearm
Abstract & commentary
Synopsis: Dorsal and volar distal radius bone strain was reduced significantly with both types of wrist guards and they also aided in increased energy absorption.
Source: Staebler MP, et al. The effect of wrist guards on bone strain in the distal forearm. Am J Sports Med 1999;27(4): 500-506.
There are significant epidemiological data that suggest that wrist guards are effective in preventing wrist injuries, but there are few biomechanical data available. Staebler and associates have successfully studied how wrist guards function in the realm of load-sharing and subfailure loading levels. Bone strain was measured in the distal radius, distal ulna, and midshaft of the radius in cadaveric forearms, with and without two types of commercially available wrist guards. Stiffness was also measured during the testing, as was energy absorption. Staebler et al found that dorsal and volar distal radius bone strain was reduced significantly with both types of wrist guards and that they also aided in increased energy absorption. There was also a reduction in the dorsal and distal ulnar bone strain, but only with the wrist guard that had a nonconforming volar plate that was elevated off the palm pad. It appeared to be, in many cases, more effective. During the testing, the bone strain did not increase at the radial midshaft when using the guards.
These findings give a better explanation as to the functional load-sharing capacity of these braces, as well as their ability to absorb impact energy during a fall. Staebler et al used six cadaveric specimens, all from elderly people that compromised the study slightly, but with their internal design they were able to overcome this variable. Strain gauges were used to record the various measurements. The results with guard A with a nonconforming volar plate appeared to be better in many of the parameters tested. Bone strains were reduced 61% and 44% in the midshaft volar radius; however, the results for guard B were not statistically significant. Both of these guards reduced the distal radius bone strain: with guard A it was 46% lower, and with guard B it was 23% lower.
Most of the data in Staebler et al’s study appear to be in concert with other epidemiological studies except that of Giacobetti et al1 who, however, tested forearms to failure, while the current study concentrated on the response to lower loads. There have been some reports on midshaft fractures by Cheng et al, hypothesizing that these injuries were analogous to "boot-top" tibial shaft fractures seen in Alpine skiers.2 Cheng et al hypothesized that the stress riser occurs at the proximal end of the guard. With guard A, there was a significant reduction in volar midshaft bone strain, while with guard B, there were insignificant increases. Cheng et al hypothesized that this may not be as much of an issue when the nonconforming volar plate is used. Staebler et al conclude that it is impossible to directly extrapolate the findings to the multivariable clinical setting of a fall onto an outstretched hand, but this study does provide further support for the effectiveness of wrist guards in preventing injuries. Staebler et al also state that more studies are needed to further delineate the functional properties and effectiveness of these particular protective devices.
Comment by James P. Tasto, MD
Snowboarding and in-line skating are common recreational sports; speeds in excess of 20 mph are easily achieved, and upper extremity injuries are quite common. The wrist injuries that we see are distal radius fractures, carpal fractures, and ligament tears, and they are among the most common injuries occurring in athletes.3,4,5 The majority of these injuries (35-46%) are distal forearm or wrist fractures.
Most wrist guards maintain the wrist in approximately 30° of extension, are either wrapped around or slipped over the wrist, and generally occupy the distal third of the forearm and wrist.
There is one study that shows that in-line skaters have up to a 10 times greater incidence of wrist fractures when not wearing the guard.6 There have also been a number of studies that reported increased fracture rates in the upper extremities in skateboarders, roller skaters, and snowboarders.
It has been postulated that the wrist guards protect the wrist from injury by three different mechanisms: 1) the prevention of extreme dorsiflexion of the wrist; 2) energy absorption; and 3) the reduction of impact forces by allowing the skater to slide forward on the guard’s firm volar plate.
This article has validated the use of wrist guards for common recreational sports, which obviously comprise a large number of common sports medicine injuries. The article also seems to point out that not having a conforming volar plate (the palm pad has some freedom from direct contact with the plate) appears to have at least some theoretical advantages.
Just as with shoulder pads, football helmets, cycling helmets, and now such protective devices as wrist guards, we have come a long way in the prevention of injuries instead of just waiting for them to occur. Validation is going to be important now and in the future in order for third-party payers, as well as high schools and universities, to be able to fund these preventive bracing measures. A certain amount of responsibility, however, will have to go back to the patient and his/her family, as the health care system will not be able to afford the supply and demand needs of the population for all of its recreational activities. In this case, the education of parents, as well as participants, is extremely important and plays a significant role for those of us interested in the subspecialty of sports medicine.
References
1. Giacobetti FB, et al. Biomechanical analysis of the effectiveness of in-line skating wrist guards for preventing wrist fractures. Am J Sports Med 1997;25: 223-225.
2. Cheng SL, et al. "Splint-top" fracture of the forearm: A description of an in-line skating injury associated with the use of protective wrist splints. J Trauma 1995; 39:1194-1197.
3. Abu-Laban RB. Snowboarding injuries: An analysis and comparison with alpine skiing injuries. CMAJ 1991;145:1097-1103.
4. Callé SC, Evans JT. Snowboarding trauma. J Pediatr Surg 1995;30:791-794.
5. Chong AL, et al. Wrist guards in in-line and conventional roller-skating injuries [letter]. Med J Aust 1995; 162:444.
6. Schieber RA, et al. Risk factors for injuries from in-line skating and the effectiveness of safety gear. N Engl J Med 1996;335:1630-1635.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content