The throw and its modifications are integral components of many sports. This study correlates case histories of acute injuries in throwing with a biomechanical analysis of the throwing mechanism. Comparisons are made with a similar analysis of the kick analyzed by the same film technique and computer program. Just prior to ball release, the pitching arm extends through an arc of about 73 degress in 40 msec, beginning with the elbow flexed at 80 degrees. This produces an axial load on the humerus and coincides with a pulse of external torque at the shoulder. This acts as stress protection to the humerus which is developing an internal torque of 14,000 inch-lb prior to ball release. The change in angular velocity, or the angular acceleration, during the throw is acquired in a much shorter time than in the kick. Torque is directly proportional to angular acceleration. This necessitates the development of substantially higher torques in the humerus during the throw than about the knee during a kick. The kinetic energy in the arm is 27,000 inch-lb during the throw. This is much higher than the kinetic energy in the kicking leg because the kinetic energy varies proportionally with the square of the angular velocity of the extremity. The angular velocity of the arm is about twice that of the leg. Thus, the pitching arm contains about four times as much kinetic energy as the kicking leg. These severe overloading conditions predispose the upper extremity to injury in the throwing mechanism.
t Organized soccer is enjoying an almost exponential growth on the community, interscholastic, and professional level in the United States.' It is a year-round game played by both sexes, and with its expansion comes a population of injured participants. The kick is the basic play of the game, and many injuries result from the violent collision of players and their extremities. The sports of football and rugby also involve kicking the ball as an important element. The admixture of bony and soft tissue injuries suggests high energy mechanisms, and studies were done to explore the biomechanical factors involved. The objectives of this study were to (1) describe the motion of the lower extremity in the act of kicking a ball, (2) to define the magnitude and types of loads transmitted by the soft and hard structures about the knee, and (3) to obtain an appreciation of the potential for injury during such activity. The results of this study were correlated with the several case histories. CASE HISTORIESCase 1: This 30-year-old male kicked a soccer ball at the same time an opponent kicked the ball in the opposite direction. The patient had immediate pain over the anterior calf and was unable to finish the game. On physical examination 17 hr later, the patient was unable to dorsiflex the foot, and the anterior compartment of the calf was tense to palpation. The tissue pressure in the anterior tibial compartment measured 95 mm Hg, while the other compartments in the calf had normal pressures.Fasciotomy was done immediately and the muscle appeared viable. With delayed wound closure the leg healed uneventfully, and some motor function returned quickly. Three months later, persisting mild weakness in dorsiflexion prevented the patient's return to sports, but did not interfere with his ambulation. , Case 2: This 18-year-old male was kicking a soccer ball and collided with an opponent who was attempting to block the kick bodily. The patient was struck on the medial aspect of the leg at the same moment he kicked the ball. In the emergency room the patient presented with a recurvatum of the knee, a swollen lateral joint line, and posterolateral rotatory instability. The x-rays disclosed widening of the lateral compartment of the knee, as shown in Figure 1. At surgery the iliotibial band was torn at its insertion on the tibia, and the biceps femoris tendon and fibular collateral ligament were avulsed. The posterior lateral joint capsule was shredded, and the lateral geniculate artery was disrupted. The patient had an anatomical repair
Myositis ossificans is a benign condition resulting from severe muscular contusion manifested by heterotrophic bone formation. The process is common in the anterior thigh but the literature dealing with myositis ossificans in the upper arm is limited. Ten cases of the condition in the upper arm were seen in our practice. All 10 were the result of football injuries and exhibited one or more of the triad of local pain, a hard palpable mass in the muscle, and a flexion contracture of the elbow. Seven of the cases (70%) were asymptomatic or signficantly improved in less than 3 months with conservative nonoperative management. Three patients (30%) underwent surgery because the painful mass persisted. In two (66%) of the surgically managed cases, there was clinical and radiographic evidence of recurrence postoperatively in spite of delaying excision until radiographic parameters of maturation were present.
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