Sports Update

This month we will review a few issues that have been reviewed in past articles. However, we now have new research support and information. Here are the questions of the month:

• What effect does helmet removal have on cervical spine alignment?
• How "protective" are functional ACL braces?
• What are injury rates and mechanisms for upper-extremity snowboarding injuries?

In September of 1999 (Sports Research Update; Part I) I included a review of an article on helmet removal in football and its effect on cervical spine alignment.¹ Generally, there was no difference in cervical alignment between subjects that wore no padding or helmets, and those wearing both the helmets and padding. However, with those subjects that had the helmets removed and shoulder padding left on, there was a statistically significant increase in cervical lordosis (extension), especially in the upper cervical area. Following is a recent similar article, however, addressing the same issues in hockey players.

LaPrade RF, Schnetzler KA, Broxterman RJ, et al. Cervical spine alignment in the immobilized ice hockey player: A computed tomographic analysis of the effects of helmet removal. Am J Sports Med 2000;28(6):800-803.

This study used CT lateral scout scans to evaluate the effects on cervical spine lordosis in three situations (1) no equipment (control), (2) helmet and shoulder pads, and (3) shoulder pads only (helmet removed) on patients placed supine on a spine board. With the helmet removed, however, the shoulder pads remaining, there was a significant increase in the C2-C7 lordosis when compared to the other two conditions. The area with the most increased lordosis was C6-C7. The recommendation is not to remove the helmet from injured players unless there is a life-threatening scenario.

How Protective are Functional ACL Braces?

It really depends on which brace you talk about; what functional element you test; whether the patient has had ACL reconstruction or not; and the specific sport activity (e.g., football versus skiing). Past DC articles (e.g. December, 1997, August, 1998, and November, 2000) have addressed issues such as electromyographic activity with a functional brace used in skiing and other activities, the effects of performance limitations, and the role of functional bracing on injury rates. Some articles have measured strain loads in cadavers; however, very few articles have addressed the issue of strain load on the ACL in live subjects during weightbearing and non-weightbearing.

Fleming BC, Renstrom PA, Beynnon BR, et al. The influence of functional knee bracing on the anterior cruciate ligament strain biomechanics in weightbearing and nonweightbearing knees. Am J Sports Med 2000;28(6):815-824.

Subjects were tested under local anesthesia. All subjects had intact ACLs. An externally applied load was used with a strain gauge (differential variable-reduction transducer) measuring ACL tension. Loads were applied to braced and unbraced knees during weightbearing and non-weightbearing scenarios with (1) anterior-posterior shear forces, (2) internal-external torques, and (3) varus-valgus moments. For anterior shear loads (up to 130 N) there was a significant reduction in strain values in braced knees when compared to unbraced knees, in both weightbearing and non-weightbearing scenarios. For internal torque applications, there was a significant decrease in strain in the braced knee compared to the unbraced knee but only when non-weightbearing. There were no reductions in strain for external torques or varus-valgus moments in weightbearing and non-weightbearing knees. The brace used was a Legend (dj Orthopaedics, LLC, Vista, CA). It is a fairly typical "off-the-shelf" type of functional knee brace. Therefore, the data probably cannot be extrapolated to more custom-fitted braces and, perhaps, to some degree, other off-the-shelf braces.

What are Injury Rates and Mechanisms for Upper-Extremity Snowboarding Injuries?

In a DC article earlier this year (Winter Sports Update, February, 2000) I reviewed a review article on snowboarding injuries.² The statistics were fairly alarming regarding the numbers of injuries. The types of injuries were also separated into upper and lower extremity injuries and the fracture rate and region were discussed. Below is a recent article confirming these findings and adding more information with regards to the snowboarder at risk.

Idzikowski JR, James PC, Abbott PJ. Upper extremity snowboarding injuries: Two-year results from the Colorado Snowboard Injury Survey. Am J Sports Med 2000;28(6):825-832.

This study surveyed snowboarders over a 10-year period (1988-1998). A total of 7430 injuries were reported. Following are some of the more interesting statistics:

• Falling was the most common cause of upper extremity injuries.

   

• 74% of injuries occurred in men (26% in women).

   

• 39% of those injured were beginners (61% injury rate for intermediate to expert).

   

• 49% of injuries were upper extremity with the following break-down:

  1. 56% were fractures.
  2. 27% sprains.
  3. 10% dislocations.

   

• The most common injury site was the wrist (22% of all snowboarding injuries).
• Wrist fractures were more common in beginners, women, and younger age groups.

   

• Hand, elbow, and shoulder injuries (and more severe injuries) were more likely in intermediate and expert men.

   

• Snowboarders who used protective wrist guards were half as likely to sustain wrist injury compared to those not wearing a wrist guard.

1. Swenson T, Lauerman WC, Blanc RO, et al. Cervical Spine Alignment in the Immobilized Football Player: Radiographic analysis Before and After Helmet Removal. American Journal of Sports Medicine. 25(2):1997;226.

    

2. Binder S, Geiger KM. The Downside of Snowboarding: Common Injuries in Novices and Those Seeking "hospital air". Postgraduate Medicine 1999;105