SHOULDERING THE LOAD:  SHOULDER INJURIES AND THE VOLLEYBALL ATTACKER

By Donovan A. Shaw, master's degree student in biomechanics at the University of North Carolina at Greensboro, under Dr. Peter Vint, SMPC Biomechanics Team Leader

Introduction

In the explosive sport of volleyball, the incidence of shoulder injury ranks second only to that of the ankle. Approximately 85% occur as a result of overuse (Aagaard, Scavenius & Jorgensen, 1997). Common shoulder injuries will be discussed here, as will a more recently occurring injury to the upper rim of fibrocartilage in the shallow shoulder socket (the glenoid labrum). Called "SLAP lesions" (Superior Labrum Anterior to Posterior), these injuries are often misdiagnosed as anterior (frontal) shoulder instability.

Perhaps the most significant research in the area of shoulder and elbow joint movement during the volleyball spike is Chul Soo Chung's doctoral dissertation (Chung, 1988). Chung reported that rotation of the shoulder was the major contributor to ball speed. In volleyball, during repeated attack armswings, the shoulder joint is predisposed to impingement as a result of the upper arm reaching maximum elevation angles at ball contact while the shoulder rotates at its highest angular velocities (over 4000°/sec, maximum). When spiking in volleyball, a shorter follow-through is necessary to avoid contact with the net. This action, with rapid slowing of the arm provided by the biceps muscle, can also lead to injury. In addition, during the arm-cocking phase of the spike, the joint force by the head of the upper arm bone (the humerus) against the front of the shoulder joint can exceed 80 pounds. (Arroyo et al.,1997). The protecting group of four small Rotator Cuff muscles (the supraspinatus, infraspinatus, teres minor and subscapularis) experience great strain during the volleyball spike because of the shallowness of the shoulder socket along with the lack of bone and ligament support around the shoulder.

The primary goal of the Rotator Cuff is to provide stability to the shoulder joint through compressive force at the shoulder and to guide the humeral head inside the shallow shoulder socket. The Rotator Cuff is assisted by three ligaments on the front of the shoulder, which help resist excessive outward rotation and forward humeral head movement.

Injuries

Impingements

With the upper arm at 90° elevation, the large bony landmark (deltoid tubercle), on the humerus that serves as the site of attachment for the deltoid muscle, may be impinged against the arch of the shoulder blade unless the upper arm is outwardly rotated. Unless fatigue is a factor, which is often the case in volleyball attackers, the infraspinatus and teres minor (Rotator Cuff) muscles provide the outward rotation necessary to avoid impingement. Volleyball players may also have lowered playing shoulders, which causes a narrowed space between the body projection of the shoulder blade and the humeral head in the upright position, and can predispose them to impingement injuries (1996, Kugler et al.).

Instability

During the repeated overhead cocking phase of spiking, microtrauma can also occur in the shoulder joint, causing instability. The Rotator Cuff must compensate to keep the humeral head in place. If fatigue results, upward movement of the humeral head can occur, impinging it against the arch of the shoulder blade resulting in inflammation and tendonitis (Arroyo, 1997).

SLAP lesions

In 1990, Snyder et al. coined the term "SLAP lesions" to describe an increasingly common injury in the shoulder socket, which is a tearing away of the biceps origin or "anchor" and upper part of the glenoid labrum. In volleyball athletes SLAP lesions generally result from biceps overload injuries, since the biceps rapidly slows the armswing after ball impact (Morgan et al., 1998).

Recent research (Huber & Putz, cited in Morgan et al., 1998; Pal, Bhatt & Patel, 1991) describes a circular "basket" or "tension brace" system of fibers around the shoulder socket's glenoid rim, in the upper-rear section consisting of extended biceps fiber bundles, which is capable of withstanding humeral head movement in all directions. During the cocking phase of the volleyball spike, the arm is in extreme elevation and outward rotation, producing a twisting force at the biceps origin, possibly causing a "peeling-back" of the labrum (Burkhart & Morgan, 1998). This detachment or peeling-back of the upper-rear labrum causes a disabling secondary instability (1998, Morgan et al.). In volleyball attackers with a detached upper-rear labrum, repetitive upward movement of the humeral head also causes a high incidence of injury of the Rotator Cuff from inside the joint.

Further, Morgan claims that the discovery of anterior instability in volleyball attackers is often mistreated with reconstruction surgery of the front of the shoulder. The correct way to fix instability in the front of the shoulder may be reconstruction of the SLAP injury usually present in the rear of the shoulder joint. Repair of the rear SLAP injury using suture anchors to pull the capsule against the socket surface usually eliminated the lower-front instability by restoring the circular "basket". In high-level athletes, posterior SLAP lesions repaired with suture anchors had 84% of patients returning to previous levels of play.

A Take Home Message To Coaches and Athletes

More volleyball players are incurring SLAP lesions (as well as other common shoulder injuries). Strength and flexibility of the shoulder (especially rear) are essential in avoiding them. Shoulder muscles need to be warm, loose and stretched before training or playing. Hitters must use a full follow through whenever possible to avoid rapid-deceleration injuries. During practice, alternate hitting drills with other less shoulder-intensive drills, to rest shoulders and help minimize overuse. Rear Shoulder Raises and Rotator Cuff Rotations (internal and external) should be included in strength training routines. Supraspinatus Raises should also be performed using a dumbbell: raise the straight arm at a 30° angle to the shoulder line, up to shoulder height, with the THUMB DOWN; squeezing shoulder blades together; for 2 sets of 10 reps, with LIGHT weights.

If a volleyball player's hitting shoulder looks lower or in any way different than the non-hitting shoulder, or if pain is experienced in the rear of the shoulder (or anywhere else in shoulder) have it checked by a Physical Therapist or Certified Athletic Trainer as soon as possible.

References

Aagaard, H., Scavenius, M., & Jorgensen, U. (1997). An epidemiological analysis of the injury pattern in indoor and in beach volleyball. International Journal of Sports Medicine, 18 (3), 217-221.

Arroyo, J.S., Hershon, S. J., & Bigliani, L.U. (1997). Special considerations in the athletic throwing shoulder. Orthopaedic Clinics of North America, 28 (1), 69-78.

Burkhart, S. S., & Morgan, C.D. (1998). The Peel-Back mechanism: It's role in producing and extending posterior type II SLAP lesions and it's effect on SLAP repair rehabilitation. Journal of Arthroscopic and Related Surgery, 14 (6), 637-640.

Chung, C.S. (1988). Three-dimensional analysis of the shoulder and elbow joints during the volleyball spike. Unpublished doctoral dissertation, Indiana University, Bloomington, IN.

Kugler, A., Kruger-Franke, M., Reininger, S., Trouillier, H.H., & Rosemeyer, B. (1996). Muscular imbalance and shoulder pain in volleyball attackers. British Journal of Sports Medicine, 30, 256-259.

Lee, S. B., Kim, K. J., & An, K. N. (1998, August). Vector analysis of GH joint force generated by the rotator cuff muscles. Poster session presented at the annual conference of the North American Congress on Biomechanics, Waterloo, Canada.

Morgan, C.D., Burkhart, S.S., Palmeri, M., & Gillespie, M. (1998). Type II SLAP lesions: Three subtypes and their relationships to superior instability and rotator cuff tears. Arthroscopy: The Journal of Arthroscopic and Related Surgery, 14 (6), 553-565.

Pal, G., Bhatt, R.H., & Patel, V.S. (1991). Relationship between the tendon of the long head of biceps brachii and the glenoidal labrum in humans. Anatomical Record, 229 (2), 278-280.

Snyder, S.J., Karzel, R.P., Del Pizzo, W., Ferkel, R.D., & Friedman, M.J. (1990). SLAP lesions of the shoulder. Arthroscopy, 6 (4), 274-279.