Thomas J. Noonan

Muscle strain injury: diagnosis and treatment.

Muscle strain is a very common injury. Muscles that are frequently involved cross two joints, act mainly in an eccentric fashion, and contain a high percentage of fast-twitch fibers. Muscle strain usually causes acute pain and occurs during strenuous activity. In most cases, the diagnosis can be made on the basis of the history and physical examination. Magnetic resonance imaging is recommended only when radiologic evaluation is necessary for diagnosis. Initial treatment consists of rest, ice, compression, and nonsteroidal anti-inflammatory drug therapy. As pain and swelling subside, physical therapy should be initiated to restore flexibility and strength. Avoiding excessive fatigue and performing adequate warm-up before intense exercise may help to prevent muscle strain injury. The long-term outcome after muscle strain injury is usually excellent, and complications are few.

Thermal effects on skeletal muscle tensile behavior

The effect of temperature on the mechanical failure properties of rabbit skeletal muscle (tibialis anterior and extensor digitorum longus) was examined. For all tests, one leg was maintained at 25°C and the contralateral leg at 40°C. Muscles were pulled to failure according to assignment into one of three groups: 1) passive failure at 10 cm/sec, 2) passive failure at 1 cm/sec, or 3) active (muscle is stimulated to contract as it is pulled) failure at 10 cm/sec. Load to failure was higher in the cold muscle for all groups tested. Total deformation was the same except in Group 1, when the warm muscle had a greater deformation. Energy absorbed before failure was greater in the cold muscle in Groups 2 and 3. Stiffness was higher in cold muscles for all muscles except the extensor digitorum longus in Group 1. In this study, temperature had a significant effect on the tensile properties; these thermal effects were de pendent on both loading rate and contractile state. Comparing loading rates, warm muscle tested at 10 cm/sec had higher failure loads than that tested at 1 cm/sec. Comparing stimulated versus unstimulated muscle (Group 1 versus Group 3), the stimulated tibialis anterior muscle absorbed more energy than unstimu lated ones. Stimulated extensor digitorum longus mus cles had higher failure loads, absorbed more energy, and were stiffer than nonstimulated muscles. This study offers experimental data to support the theory that warming muscles can aid in injury prevention and im provement in athletic performance.

Preseason Shoulder Strength Measurements in Professional Baseball Pitchers Identifying Players at Risk for Injury

Background: The ability to identify pitchers at risk for injury could be valuable to a professional baseball organization. To our knowledge, there have been no prior studies examining the predictive value of preseason strength measurements. Hypothesis: Preseason weakness of shoulder external rotators is associated with increased risk of in-season throwing-related injury in professional baseball pitchers. Study Design: Cohort study (prognosis); Level of evidence, 2. Methods: Preseason shoulder strength was measured for all pitchers in a professional baseball organization over a 5-year period (2001-2005). Prone internal rotation (IR), prone external rotation (PER), seated external rotation (SER), and supraspinatus (SS) strength were tested during spring training before each season. The players were then prospectively followed throughout the season for incidence of throwing-related injury. Injuries were categorized on an ordinal scale, with no injury, injury treated conservatively, and injury resulting in surgery delineated 0, 1, and 2, respectively. Subset analyses of shoulder injuries and of players with prior surgery were also performed. The association between strength measurements and injury was analyzed using Spearman rank correlation. Results: A statistically significant association was observed for PER strength (P = .003), SER strength (P = .048), and SS strength (P = .006) with throwing-related injury requiring surgical intervention. Supraspinatus strength was also significantly associated with incidence of any shoulder injury (P = .031). There was an association between the ratio of PER/IR strength and incidence of shoulder injury (P = .037) and some evidence for an association with overall incidence of throwing-related injury (P = .051). No associations were noted in the subgroup of players with prior surgery. Conclusion: Preseason weakness of external rotation and SS strength is associated with in-season throwing-related injury resulting in surgical intervention in professional baseball pitchers. Thus, preseason strength data may help identify players at risk for injury and formulate strengthening plans for prevention.

Correlation of Torque and Elbow Injury in Professional Baseball Pitchers

Background: During the pitching motion, velocity is generated by the upper extremity kinetic chain on internal rotation of the shoulder and trunk translational/rotational motion. This generation of power places significant forces and torques on the elbow and shoulder. Elbow valgus torque and shoulder rotational torque are theoretically linked to elbow injury. Hypothesis: Pitchers experiencing higher levels of elbow valgus torque and shoulder external rotation torque throughout the pitching motion are more likely to suffer elbow injury than pitchers with lower levels of torque. Study Design: Cohort study; Level of evidence, 3. Methods: With an established biomechanical analysis model, 23 professional baseball pitchers were videotaped during spring training games and followed prospectively for the next 3 seasons for elbow injury. A mixed statistical model using differences of least squares means and analysis of variance was used to analyze the association between elbow injury and torque levels throughout the pitching motion as well as at each major event within the pitching motion. Results: There were overall statistical trends relating elbow injury with both higher elbow valgus torque (P = .0547) and higher shoulder external rotation torque (P = .0548) throughout the entire pitching motion. More importantly, there was an individual significant correlation of elbow injury with both higher elbow valgus torque (P = .0130) and higher shoulder external rotation torque (P = .0018) at the late cocking phase (pitching event of maximum external rotation of the shoulder). Conclusion: This study provides information that supports existing theories about how and why certain injuries occur during the throwing motion in baseball. The late cocking phase appears to be the critical point in the pitching motion, where higher levels of torque at the shoulder and elbow can result in increased risk of injury. Manipulation of pitching mechanics to alter these torque levels or using these measures to identify pitchers at risk may help decrease injury rates.

Injury Patterns and Biomechanics of the Athlete's Shoulder

Although shoulder injury patterns vary by sport and position, overhead sports, such as baseball, swimming, tennis, and volleyball, share a common dependence on the integrity of the kinetic chain. Disruption of this critical mechanism predisposes to injury and deserves attention as the most important of the biomechanical principles required to help evaluate and manage problems of the athletes shoulder.

Association of Maximum Pitch Velocity and Elbow Injury in Professional Baseball Pitchers

Background Recent literature has explored the association of upper extremity injury in baseball players with various aspects of the pitching motion. To our knowledge, no study has directly evaluated the connection between maximum pitch velocity and elbow injury in professional baseball pitchers. Hypothesis Professional pitchers throwing at higher maximum ball velocity will have a higher risk of elbow injury. Study Design Cohort study; Level of evidence, 3. Methods Twenty-three professional pitchers were analyzed during spring training games and the ball velocity of the fastest pitch thrown for a strike (maximum pitch velocity) was recorded. This group was then followed prospectively over the following 3 seasons for elbow injury significant enough to warrant inclusion on the disabled list and/or require surgery. The association between maximum pitch velocity and elbow injury was then analyzed using an unpaired Student t test. Results There were 9 players with elbow injuries in the group of pitchers studied, including 4 pitchers with an elbow muscle strain and/or joint inflammation and 5 pitchers with an ulnar collateral ligament sprain or tear. Three of the ulnar collateral ligament injuries required surgery. For the 14 pitchers in the noninjured group, the mean pitch velocity was 38.09 m/s (±1.45) or 85.22 mph (±3.24). For the 9 players in the injured group, the mean pitch velocity was 39.88 m/s (±2.39) or 89.22 mph (±5.36). There was a statistically significant association between maximum ball velocity and elbow injury (P = .0354). The injured group had a longer average career length (9.7 years) than the noninjured group (6.5 years; P = .0248). The 3 pitchers with the highest maximum ball velocity had the injuries requiring surgery. Conclusion A statistically significant association between maximum pitch velocity and elbow injury was noted in this study, providing further support of existing theories about injury in baseball.

Identification of a Threshold for Skeletal Muscle Injury

This study was designed to detect the first evidence of injury to muscle induced by passive stretching. Rabbit extensor digitorum longus and tibialis anterior skeletal muscles were subjected to passive stretching at set force levels of 20% or 30% of load to failure. Both tibialis anterior and extensor digitorum longus muscles that were stretched to 30% exhibited no difference in the three tensile parameters when compared with their con tralateral control specimens. Maximum contractile force was decreased after stretching. Tibialis anterior and ex tensor digitorum muscles that were stretched to 20% of control failure force showed no decrement in the tensile parameters or maximum contractile force. Histology of the extensor digitorum longus muscles stretched to 30% of failure force showed small focal areas of muscle fiber rupture and hemorrhage near the distal myoten dinous junction. Tibialis anterior and extensor digitorum longus muscle-tendon units stretched to 30% of failure force suffered functional injury as their contractile ability decreased after stretching. In contrast, muscle-tendon units stretched to 20% of failure force suffered no dec rement in contractile ability; therefore, a threshold for passive muscle stretch injury has been found. Further more, changes in contractile properties and histologic assessment appear to be more sensitive predictors of injury than measurement of structural failure properties.

Laser-Assisted Thermal Capsulorrhaphy

PURPOSE The purpose of this study was to review the clinical results of laser-assisted thermal capsulorrhaphy in patients with glenohumeral instability. TYPE OF STUDY A case series of consecutive patients with shoulder instability treated with laser-assisted thermal capsulorrhaphy by one surgeon. METHODS From 1994 through 1997, 60 shoulders in 59 patients (27 men, 32 women) with no previous shoulder surgery underwent laser-assisted thermal capsulorrhaphy. The direction of instability was classified as anterior in 30, posterior in 7, anteroposterior in 4, and multidirectional (MDI) in 19. Patients were evaluated on the basis of pain, recurrent instability, function, and satisfaction. RESULTS Nine patients were lost to follow-up evaluation, and 9 patients underwent revision surgery (7 MDI, 1 anterior, I posterior). Of the remaining 42 patients, none underwent further surgery; the average follow-up time was 38.4 months (range, 24 to 66 months); and pain scores improved from 7.8 +/- 2.6 (1-10 scale) to 1.7 +/- 2.6. postoperatively. In addition, 86% of patients reported none or rare episodes of instability compared with 37% preoperatively. Painless overhead use of the shoulder improved from 12% to 73%. Scores based on the American Shoulder and Elbow Surgeons (ASES) rating system improved from 61.0 +/- 2.6 to 89.5 +/- 15.0 (P <.05). Patient satisfaction for the remaining 42 patients, on a 1 to 10 scale, averaged 8.0 +/- 2.8. CONCLUSIONS Based on these results, we conclude that laser-assisted thermal capsulorrhaphy is an effective adjunct in the treatment of anterior and posterior instability. Patients with MDI treated with this technique have high failure rates. We recommend caution when approaching MDI patients with this technique.

Electrothermal Arthroscopic Shoulder Capsulorrhaphy: A Minimum 2-Year Follow-Up

Background Few studies have documented the outcomes of thermal capsulorrhaphy for shoulder instability. Purpose To examine prospective evaluate outcomes of the first 100 patients with glenohumeral instability treated with thermal capsulorrhaphy. Study Design Case series; Level of evidence, 4. Methods Between 1997 and 1999, 85 of 100 patients treated with thermal capsulorrhaphy for glenohumeral instability were available for review at 2-year minimum follow-up (average, 4 years). Fifty-one patients suffered from anterior instability; 24 had an associated Bankart lesion. Ten patients demonstrated posterior instability; 1 had an associated reverse Bankart lesion. Seventeen patients had multidirectional instability; 8 had an associated Bankart lesion. Seven patients demonstrated anterior and posterior instability without an inferior component; 2 had an associated Bankart lesion. Failures were defined as shoulders requiring revision stabilization (14) or with recurrent instability (18), recalcitrant pain (3), or stiffness (2). Results Forty-eight of 85 procedures were successful, and 37 of 85 failed. For patients with anterior instability plus a Bankart lesion, 7 of 24 (26%) had failed results. For those with anterior instability without a Bankart lesion, 10 of 27 (33%) had failed results. The failure rates for posterior, multidirectional instability, and anteroposterior were 60% (6/10), 59% (10/17), and 57% (4/7), respectively. Of the 48 successes, mean preoperative American Shoulder and Elbow Surgeons score improved from 71 to 96 postoperatively, and patient satisfaction was 9.1 on a 10-point scale. Conclusion Because of the high failure rates, we now augment thermal capsulorrhaphy with capsular plication and/or rotator interval closure in cases of posterior and multidirectional instability and have lengthened the initial immobilization period to improve outcomes. Failure rates for thermal capsulorrhaphy, even with labral repairs, are high especially for shoulders with multidirectional instability and posterior instability. When procedures were successful, however, patients were very satisfied with significant improvements in American Shoulder and Elbow Surgeons scores.

Changes in passive range of motion and development of glenohumeral internal rotation deficit (GIRD) in the professional pitching shoulder between spring training in two consecutive years

BACKGROUND Pitching causes increased mechanical stress to the arm and is thought to result in alterations in range of motion (ROM) as a result of osseous and soft tissue adaptations. Understanding the factors that contribute to alterations in ROM will allow for improved understanding of the pitching shoulder. This study examined humeral torsion (HT) and shoulder mobility over 2 consecutive years. METHODS Bilateral shoulder mobility and HT were assessed in 33 asymptomatic professional pitchers over 2 spring trainings. A repeated-measures analysis of covariance was used to assess the change in motion of the dominant side/nondominant side across seasons while quantifying pre-existing HT. Prevalence of glenohumeral internal rotation deficit (GIRD) between seasons was compared with χ(2) analysis, and GIRD and non-GIRD pitchers were compared with the independent t test. RESULTS The dominant shoulder displayed increased external rotation (11.5° ± 0.1°, P = .02) and decreased internal rotation (-8.4° ± 11.0°, P = .03) and horizontal adduction (-17.6° ± 13.8°, P = .01). The nondominant shoulder remained the same. Mean HT was significantly different (P = .001) in the dominant (10° ± 11°) arm than in the nondominant arm (23° ± 11°). A significant number of pitchers had with GIRD (P < .01) at each assessment. CONCLUSIONS ROM was significantly altered between seasons of pitching. These changes likely resulted from soft tissue adaptations because we accounted for humeral retrotorsion. Pitchers who developed GIRD displayed a 7° increase in retrotorsion on the dominant shoulder. Changes in the pitching shoulder over time accounting for humeral retrotorsion may suggest pitching ROM is transient and should be monitored.