Stress Fracture of the Ulna
Abstract & Commentary
Synopsis: This case report emphasizes the point that stress fractures can occur in the upper extremity as highlighted by a case of an ulnar stress fracture in an equestrian polo player.
Source: Clark RJ, et al. Am J Sports Med. 2002;30:130-132.
Clark and associates at Texas Tech University report an unusual case of ulnar stress fracture in a competitive male polo player from their university. They review his case history, and note that his stress fracture was related to a sudden increase in training, as is a common point identified in the history of players sustaining stress fractures. They highlight the fact that while most stress fractures occur "below the pelvis" that stress fractures of the upper extremity should be included in the differential diagnosis of upper extremity pain in the athlete. They also note the significant rate of injuries sustained in equestrian polo, as best can be obtained from the sparse literature on equestrian polo injuries.
Clark et al hypothesize that the etiology of this stress fracture was overuse of the flexor digitorum profundus (FDP). This hypothesis is based on the fact that the bone scan revealed abnormally bright activity at the origin of the FDP. They also note that the player had only been playing competitively for 2 years and had a tendency to hit the ball in such a way as to force the ball toward the ground, requiring greater strength to prevent the mallet from falling out of his hand and to drive the ball forward. This poor technique, they hypothesize, contributed to this injury. They also hypothesize that the patient’s use of prednisone for 20 months, including during the time he sustained the stress fracture, may have contributed to his sustaining the stress fracture. They performed a dexa scan 7 months after he stopped taking the steroids/sustained the injury. The scan revealed normal bone density.
The stress fracture healed with cessation of steroids and a period of immobilization followed by strengthening. He returned to polo at 7 weeks postdiagnosis.
Clark et al recommend consideration of stress fracture in the differential diagnosis in athletes who have forearm pain and use their upper extremity in sports. They also recommend the athlete’s technique be analyzed to rule out improper form as a contributing factor to result in increased stress to the musculoskeletal system resulting in injury.
Comment by Marc R. Safran, MD
Stress fractures of the ulna have been reported in many sports including tennis, softball, bowling, body building, and table tennis. In tennis, the nondominant arm is often affected, particularly in players with 2-handed backhand stokes, and in the dominant forearm of softball pitchers, table tennis players, and bowlers. One prevailing theory is that this overuse injury, often associated with sudden increase in activity, is due to repeated pronation of the forearm. It may not be the torsion, per se, but the muscular forces to cause the pronation, or more likely, the eccentric action to slow pronation. While polo players hit the ball in supination, the mechanics of hitting the ball include a sudden pronation of the mallet after ball contact. The effects of this sudden pronation are pronounced by the long lever arm of the end-weighted mallet.
The symptoms of ulnar stress fractures are often very subtle and may result in a significant delay in diagnosis. Thus, a high index of suspicion is needed in athletes, particularly unilateral arm dominant athletes, to be able to make this diagnosis. The player’s symptoms and clinical examination may be masked by the anti-inflammatory effects of corticosteroids. Corticosteroids are known to result in osteopenia and increase the risk of fractures. Bone scan is certainly a useful tool in making this diagnosis, although MRI has also been useful in this reviewer’s experience with ulnar stress fractures. Conservative management is the rule with ulnar stress fractures, as these heal with reduction in activity.
As with most overuse injuries, especially in athletes involved in repetitive mechanics sports, review of technique can be critically important in the treatment and prevention of future injury.
Dr. Safran, Co-Director, Sports Medicine, Associate Professor, UCSF Department of Orthopaedic Surgery, San Francisco, CA, is Associate Editor of Sports Medicine Reports.
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