Transverse stress fractures of the humerus occur in the proximal and middle portions of the humerus and are rare, with very few case reports existing in the literature. Transverse stress fractures of the humerus are common in weight lifting with the injury being reported in a body builder [20] and in a competitive weight lifter [21]. Flat bench press seems to exacerbate the symptoms with the most pain being felt during this exercise. During the bench press exercise, the humerus effectively proceeds through an arc of shoulder extension, followed by shoulder flexion—with virtually no rotation of the humerus. Thus the rotational actions of the pectoralis major muscle must be countered by the other muscles of the shoulder girdle, including the deltoid and rotator cuff muscles [22]. The muscular tissues are able to dynamically redistribute the forces across the supporting skeleton, allowing the bone to effectively endure more load or stress, a phenomenon known as stress shielding [21]. A transverse stress fracture can occur with increased bending load across the bone, which is often the sequela of muscle fatigue that leads to the compromise of stress shielding [21, 22].

In the reported cases, presentation involved significant pain localized to the proximal, anterior aspect of the affected arm, occurring during bench press and persisting for hours after the exercise. These symptoms were present for at least 4–6 weeks prior to diagnosis [20, 22]. Each patient tried a period of rest from bench press and other aggravating activities such as incline press, pectoral fly, biceps, and overhead exercises [20, 21]. Inevitably after the period of rest in which the pain subsided, ranging 1–6 weeks, a flare of the same pain occurred on their return to flat bench or other previously mentioned activities. One weight lifter progressed to a complete fracture and experienced an audible snap, with his arm giving way, on the second set of his normal weight lifting routine [22]. All of the patients denied the use of anabolic steroids.

In most cases, the physical examination revealed tenderness to palpation in the region between the bony insertions of pectoralis major and anterior deltoid [20, 21]. There can be mild pain on manual resistance of shoulder movements, especially internal rotation and abduction [20]. Strength and range of motion of the shoulder and elbow usually does not show any deficits. Plain radiographs can show a transversely oriented radiolucency with surrounding periosteal reaction and sclerosis. Bone scans can confirm the diagnosis of stress fracture by showing abnormal focal increased uptake in the cortex of the affected mid-humerus.

A period of 6–8 weeks free from all weight lifting activities involving the upper extremities, followed by gradual resumption of training is usually the first course of treatment for a transverse humeral stress fracture [20, 21]. If displacement or complete fracture has occurred, ORIF can be performed. Usually no bracing or immobilization is necessary.

These fractures typically respond quite favorably to a period of rest and a return to previous levels of competition can be expected once the fracture is completely healed, usually by 4 months. Progressing to full activities too quickly can lead to minor relapses in symptoms [20, 21]. If surgery is performed, return to sport can be unpredictable.

These fractures present with dull aching and localized tenderness around the olecranon, worsened with activity, usually without recall of an acute injury [27, 28]. Symptoms evolve over a variable time frame which can be anywhere from a few weeks up to a year. These injuries are common in throwing athletes who will describe posteromedial elbow pain during the acceleration and follow-through phases of throwing [23, 24]. Very few athletes report pain at rest or while performing daily activities [29]. Clinically, tip fractures are more likely to present with a painful elbow after a particularly strong throw, whereas other stress fractures in the olecranon are more likely to present with a longer history of pain that lessens with rest and recurs when they resume throwing [28].

Physical examination often reveals decreased arc of motion at the elbow, with flexion contractures that are common in the throwing population often present [30–33]. There is marked tenderness to palpation along the posteromedial aspect of the olecranon. In certain cases a milking maneuver may be positive, which could indicate a concomitant MCL injury [30]. The diagnostic modalities for each are similar, with plain radiographs often missing the diagnosis of stress fracture early in the process. Thus for the most accurate diagnosis to be made, bone scan or MRI must be considered [24, 27, 29]. The mechanisms, specific imaging findings, treatment, and prognosis will be discussed separately for each stress fracture in the remainder of this section.

Stress fractures of the ulna have been reported in a variety of athletes, including tennis players [47–51], baseball and softball pitchers [52–55], weight lifters [56–58], a body builder [59], riflemen [60], a volleyball player [54], a baton twirler [61], a cheerleader [62], an honor guard participant [63], a bowler [64], a golfer [65], a polo player [66], and a kendo player [67]. Though there are reports of stress fractures occurring proximally [52, 54, 64], distally [47, 50, 65], and even in the ulnar styloid [67], the middle one-third of the ulna has the smallest cross-sectional area as well as the most triangular (least circular) shape, making it the least resistant to torsional stress. The majority of cases described involve the middle one-third of the shaft [48, 49, 51, 53, 55–63, 66]. The torsional stress in the diaphysis of the ulna usually occurs between the origin of the flexor digitorum profundus and the outcropping muscles [49].

In throwing athletes, an ulnar shaft stress fracture may occur more proximally in the diaphysis as the mechanism is similar to that described for humeral stress fractures. During the acceleration phase there is internal humeral rotation and rapid extension of the elbow, which generates tremendous valgus forces about the medial aspect of the elbow joint and valgus extension forces posteriorly [4]. These stresses are transmitted primarily to the medial collateral ligament complex of the elbow, the flexor carpi ulnaris, and the medial flexor-pronator muscles, and thus load the proximal ulnar diaphysis [52, 54].

Across each sport, presentation was very similar. Athletes presented with an insidious onset of pain in the ulnar shaft exacerbated by activity. The time before presentation ranged from weeks to months. In many cases, a recent increase in the length, intensity, or demands of training was noted [48–50, 54, 57, 58, 60–62, 66, 68]. Some athletes tried symptomatic treatment, which included anti-inflammatories, physiotherapy, and ice, none of which was significantly helpful. Rest from the offending activity tended to lessen the pain, with a classic flare on return to sport noted [51, 56–59, 62]. The location of the pain was reported anywhere from the proximal ulna into the elbow, down to the distal ulna into the wrist, and corresponded well with the location of the stress fracture.

There is tenderness to palpation in the area of the stress fracture. Often resisted wrist flexion and extension or resisted pronation and supination of the forearm can reproduce the pain [48, 50, 54, 55, 57, 64, 66, 67]. Plain radiographs are often negative if performed within the first few weeks of injury. MRI or bone scan should be performed if radiographs are negative or equivocal.

Ulnar shaft stress fractures should be managed non-operatively. Immobilization can be used for comfort, with immediate and total cessation from the offending activity. Often a 4–8 week period of rest from sport and/or immobilization is needed. Upon radiographic evidence of healing, or subsidence of symptoms, therapy can be begun if needed [47, 58, 65]. Most athletes are able to return to a pre-injury level of activity by 6–8 weeks after the initiation of conservative therapy.

Stress fractures of the radius in athletes have been described primarily in gymnasts [69–73], though case reports also exist in racquet sport athletes [74, 75], a basketball player [76], a pool player [77], an adolescent cyclist performing “wheelies” [78], and a field gun runner [79]. The epiphysis of the radius is the least resistant portion of the bone to shear and torsional forces [80], and this portion of the bone is particularly vulnerable when at its thickest, as seen during the growth spurt [81, 82]—placing adolescent athletes at higher risk. In all cases, repetitive torsional or axial loading forces on the radius eventually lead to the development of a stress fracture. The vast majority of these fractures occur in the distal one-third of the radius.

Tumbling and vaulting in gymnastics tends to produce an impact angle of 60–90° to the wrist which places increased stress on the radius [71]. In twisting (Tsukahara) vaults, one wrist is removed from the ground first, leaving the remaining (fulcral) wrist to suffer much of the twisting. This explains why in many gymnasts with radius stress fractures the injury usually occurs in their fulcral wrist [71]. The use of very soft mats also exaggerates the amount of dorsiflexion of the wrist again placing increased stress on the radius [73]. In beam and tumbling workouts, the hands may be fixed in a particular position while the forearms are undergoing torsion in the direction of pronation and supination. These torsional forces may, with time and repetition, affect the epiphysis of the radius [73].

Stress fractures of the radius in a tennis [75] and badminton player [74] have similarly been reported in the adolescent population. In the case of the basketball player, the stress associated with “dunking” of a basketball repeatedly (with striking of the forearms on the metal rim of the basket) was believed to have contributed to the injury [76]. In the case of the pool player, putting excessive “English” (side spin) on the ball generated repetitive torsional forces to the radius that eventually lead to a stress fracture [77]. In the case of the adolescent cyclist performing “wheelies,” the terminal motion of coming back down to the ground with a hard, jarring force to the forearm seemed to be the offending motion [78]. This patient’s stress fracture was closer to the mid-distal one-third diaphyseal junction of the radius. Lastly, in the case of the field gun runner, repeated unaccustomed heavy loading of the 900 lbs. muzzle of the gun barrel to his forearms was believed to have incited the stress fracture [79].