Stress Fracture of the Ossification Center of the Scaphoid in a Skeletally Immature Gymnast.

An eleven-year-old male gymnast felt right wrist pain when performing handstands on the floor without any major traumas. Displaced scaphoid fracture was observed on the anteroposterior view of the radiograph. Both on the T1-weighted image from magnetic resonance imaging (MRI) and on the short TI inversion recovery (STIR) image from MRI, low intensity was detected at the middle of the ossification center of the scaphoid and the physis and the articular cartilage covering the scaphoid bone were preserved without any injury. The patient was diagnosed with stress fracture of the ossification center of the scaphoid and successfully treated conservatively.

Biomechanical Differences Between Japanese and American Professional Baseball Pitchers.

BACKGROUND: Although baseball injuries are common in both Japan and the United States, the majority of pitching injuries in Japanese players occur at the shoulder, whereas most pitching injuries in American players occur at the elbow. A biomechanical comparison between Japanese and American pitchers may help to identify the different injury mechanisms. HYPOTHESIS: Japanese pitchers produce greater shoulder kinetics whereas American pitchers generate greater elbow kinetics. Also, kinematic differences will be found between the 2 groups, including longer stride and greater lead knee flexion for Japanese pitchers. STUDY DESIGN: Descriptive laboratory study. METHODS: Biomechanical data for 19 Japanese professional baseball pitchers and an age-matched group of 19 American professional baseball pitchers were collected by use of a 3-dimensional, automated, high-speed optical motion capture system. Anthropometric, kinetic, and kinematic data for both groups were compared by use of t tests (P < .05). RESULTS: American pitchers were taller and heavier and generated greater ball velocity (38.1 ± 1.6 vs 34.7 ± 1.1 m/s; P < .001) than their Japanese counterparts. Most elbow and shoulder kinetic parameters, including elbow varus torque (99 ± 17 vs 86 ± 17 N·m; P = .018), were greater for American pitchers. However, when normalized by bodyweight and height, shoulder horizontal adduction torque was greater for Japanese pitchers (6.8% ± 1.0% vs 5.8% ± 1.1%; P = .005). Japanese pitchers had longer stride (86% ± 5% vs 82% ± 6% of height; P = .023), greater shoulder abduction at ball release (101° ± 8° vs 94° ± 9°; P = .014), and greater knee flexion after ball release (39° ± 18° vs 28° ± 14°; P = .039). Japanese pitchers also demonstrated greater shoulder internal rotation velocity, elbow flexion, and elbow extension velocity. CONCLUSION: Greater elbow varus torque may predispose American pitchers to greater risk of elbow injury. Japanese pitchers may have increased risk of shoulder injury due to greater normalized horizontal adduction torque and greater abduction angle. Japanese pitchers may be able to reduce their shoulder torque and risk of injury by shortening their stride, reducing their lead knee flexion, and decreasing their throwing arm abduction. CLINICAL RELEVANCE: Understanding anthropometric, kinetic, and kinematic differences between pitchers from the 2 countries may be of value to clinicians and coaches working to maximize performance of the pitchers while minimizing the risk of injury.

Do Mound Height and Pitching Distance Affect Youth Baseball Pitching Biomechanics?

BACKGROUND: Pitching injuries continue to be a serious problem, with adolescents now representing the group with the most injuries. Some have proposed that lowering or eliminating the pitching mound in youth baseball may reduce joint stress and subsequent injuries. Another potential risk factor is advancing from youth to adult pitching distance without an intermediate distance. HYPOTHESES: It was hypothesized that for a group of young pitchers, pitching kinetics and kinematics would change with mound height. It was also hypothesized that pitching kinetics and kinematics would change with pitching distance. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-one young (12.6 ± 0.5 years) baseball pitchers pitched 5 full-effort fastballs each from 5 different conditions, in random order: 14.02-, 16.46-, and 18.44-m distances from a 25 cm-high mound, 16.46-m distance from a 15 cm-high mound, and 16.46-m distance from flat ground. Pitching biomechanical values were collected with a 12-camera automated motion capture system. Ball velocity and 31 other parameters were computed for each pitch. Data were compared between the 3 mound heights at 16.46 m by use of repeated-measures analysis of variance and paired post hoc t tests ( P < .05). Similarly, data were compared between the 3 distances from the 25-cm mound via repeated-measures analysis of variance and paired post hoc t tests ( P < .05). RESULTS: No differences were found in ball velocity, shoulder kinetics, or elbow kinetics associated with mound height. Ten kinematic parameters differed with mound height, including 8 parameters at lead foot contact. Maximum shoulder horizontal adduction torque and maximum shoulder anterior force increased with pitching distance. Only 3 kinematic parameters showed significant differences with pitching distance. CONCLUSION: The hypothesis that shoulder and elbow kinetics would change with mound height was not supported by the data. Several kinematic differences were found, but the majority were at lead foot contact before the rapid, dynamic phases of pitching. Change in pitching distance was associated with slight increase in shoulder kinetics as well as a few kinematic differences. CLINICAL RELEVANCE: Lowering or eliminating pitching mounds in youth baseball would not significantly decrease joint stress and injury risk to young pitchers. However, when available, transition from 14.02-m to 16.46-m to 18.44-m pitching distance may reduce stress on the young throwing shoulder.

Three-dimensional kinematic analysis of throwing motion focusing on pelvic rotation at stride foot contact.

BACKGROUND: Because the throwing motion can be considered a kinetic chain, pelvic and trunk motion should be included in the analysis. Early pelvic rotation during the throwing sequence has been reported to be a factor leading to overloading of the shoulder and the elbow. A large pelvic rotation angle at the stride foot contact (SFC) was thought to indicate early pelvic opening. This study examined the kinematic features in each motion segment associated with increased pelvic rotation at SFC in pitchers of various ages and competition levels. MATERIALS AND METHODS: The study included 324 pitchers with various age/competition levels. Throwing motion was analyzed using an infrared-type motion capture system. In the assessment, pelvic rotation angle at SFC was adopted as a parameter for the timing of pelvic opening. Statistical analyses were performed for correlation between pelvic rotation and kinematic variables of other motion segments at the instant of SFC as well as the difference in kinematics between the groups of different levels. RESULTS: Most of the kinematic results were not significantly different among the 4 groups with different levels. The increase in the pelvic opening angle at SFC was significantly correlated with increased trunk bend to the nonthrowing arm side and decreased hip flexion angle on the throwing arm side. DISCUSSION AND CONCLUSION: Early pelvic rotation in the throwing motion sequence, as manifested by increased pelvic rotation at SFC, was correlated with changes in kinematic parameters at other motion segments such as increased trunk tilt and decreased hip flexion.

Stress fracture of the ulna in a softball pitcher.

BACKGROUND/AIMS: We present a rare case of stress fracture of the diaphysis of the ulna in a softball pitcher. CASE: A thirteen-year-old girl felt pain over the distal third of the right forearm during pitching. Stress fracture was detected as callus formation of the ulna before fracture displacement. When windmill pitching for softball, the pitcher rotates their arm around the shoulder joint and powerfully hits their forearm to their thigh, which is accompanied by simultaneous pronation of the forearm and flexion of the wrist. The ball is then released and this movement is known as "brushing". CONCLUSIONS: The typical throwing form in a softball pitcher can play an important role in stress fractures of the ulna.

Surgical treatment of posterior interosseous nerve paralysis in a tennis player.

We report a rare case of posterior interosseous nerve (PIN) paralysis in a tennis player. The PIN, a 2 cm section from a bifurcation point of the radial nerve, presented increased stiffness in the surgical findings and treated with free sural nerve grafting after excision of the degenerative portion of the PIN. We speculate that PIN paralysis associated with hourglass-like constriction can be caused and exacerbated by repetitive forearm pronation and supination in playing tennis.

Increased horizontal shoulder abduction is associated with an increase in shoulder joint load in baseball pitching.

BACKGROUND: Soft tissues of the shoulder undergoes substantial stresses due to humeral head movement, and this may contribute to throwing shoulder injuries in baseball pitchers. Prevention and management of throwing shoulder injuries critically rely on reduction of shear force at the shoulder joint. However, the amount and direction of the force applied to the shoulder during the throwing motion have not been clarified. The purpose of this study was to analyze forces applied to the shoulder during a baseball pitch. METHODS: We performed biomechanical analysis of 213 baseball pitchers of various ages and skill levels. Throwing motion was analyzed with a 3-dimensional motion capture system. The Euler angle sequence was adopted to describe angular values of the upper arm relative to the trunk for shoulder rotation, and inverse dynamics was used to estimate the resultant joint forces at the shoulder. RESULTS: There was a significant relation between horizontal abduction/adduction angle and resultant anterior/posterior force at the point of maximum external rotation (MER) (r = -0.63, P < .01), whereby increased horizontal abduction was associated with increased resultant anterior force. There was a significant but weak correlation between abduction/adduction angle and superior/inferior force at MER (r = 0.24, P < .01). Comparison among the groups with variable ages and skill levels showed larger horizontal abduction and smaller external rotation angles at MER in the adult amateur player group, whereas normalized compression force and internal rotation torque values at MER were smaller in the junior high school- and elementary school-aged groups. DISCUSSION: These results suggest that excessive horizontal abduction at MER increases anterior shear force in the shoulder and may lead to shoulder injuries. Focusing on reducing horizontal abduction at MER in the throwing motion may be key to preventing and managing shoulder injuries in baseball pitchers.

Localized naviculocuneiform arthrodesis combined with osteosynthesis of fracture nonunion of the tarsal navicular bone using a locked plating system.

AIMS: Navicular fracture is still challenging disorder to treat because there is a risk of nonunion, avascular necrosis and symptomatic osteoarthritis. PATIENTS METHODS AND RESULTS: A 40-year-old woman with an ununited fracture of the tarsal navicular bone was treated with localized naviculocuneiform arthrodesis (arthrodesis of the navicular, the middle cuneiform, and the lateral cuneiform). Fusion with the navicular, the middle cuneiform, and the lateral cuneiform as well as union of fracture of the navicular was confirmed on the radiographs. CONCLUSION: Localized naviculocuneiform arthrodesis using a locked plating system is one of the options to treat nonunion of the navicular bone.