Gains in relative cortical area during growth and their relationship to nutrition, body size, and physical activity.

OBJECTIVES: In studies of growth in the past, low percentage of cortical area (%CA) is commonly attributed to poor general health, due to factors including poor nutrition, low socioeconomic status, or other physiological stressors. What constitutes low relative cortical dimensions has not been established across a diverse range of human skeletal samples. This study examines %CA in a large immature skeletal sample to establish typical variation in humans with consideration of both body mass and subsistence strategy. MATERIALS AND METHODS: Percentage of cortical area was calculated at the midshaft of the humerus, femur, and tibia in seven skeletal samples. Age at death was estimated from dental development, and body mass from bone dimensions. Patterns of %CA with age and log-transformed body mass were examined in the pooled sample and compared among samples using LOESS regression, Welch's ANOVA, and Kruskal-Wallis tests. RESULTS: Across all samples, %CA displays a generally non-linear pattern, but variation in %CA with age was high, particularly in samples with lower levels of %CA. There was no relationship between %CA and age-adjusted body mass. DISCUSSION: The lack of a relationship between %CA and body mass suggests that %CA should not be used as an indicator of mechanical loading. The variation present across samples implies that appositional bone growth is affected by physiological stress in varying ways. Without a deeper understanding of what is "typical" for long bone development, it is impossible to draw conclusions about individual or population level health.

Age-related differences in glenohumeral internal rotation deficit, humeral retrotorsion angle, and posterior shoulder tightness in baseball players.

BACKGROUND: Glenohumeral internal rotation deficit is generally recognized as a risk factor for throwing disability in baseball players. However, the pathology, timing of onset, role in the onset of humeral retrotorsion angle (HTA) and soft tissue extensibility (STE), and the relationship with age remain unclear. Therefore, the purpose of this cross-sectional study was to investigate age-related glenohumeral internal rotation deficit, HTA, and STE in Japanese baseball players and determine whether these factors correlate with throwing disability. METHODS: Participants were 172 male baseball players divided into a symptomatic group (n = 68) and an asymptomatic group (n = 104). The mean age at examination was 15.4 ± 3.2 (range, 8-22) years. Measurement items were range of motion of bilateral internal and external rotation at 90° abduction (2ndIR and 2ndER, respectively), bilateral HTA, and posterior shoulder muscle elasticity. Correlations of age, symptom, and dominance with these measurements were investigated, and significant bilateral differences in HTA and STE by age and symptom were analyzed. RESULTS: HTA and 2ndER of the dominant side were significantly greater than those of the nondominant side in those over the age of 13 years in both the asymptomatic and symptomatic groups. In contrast, 2ndIR of the dominant side was significantly smaller than that of the nondominant side in those over the age of 13 years in both the asymptomatic and symptomatic groups. The difference in HTA between the dominant and nondominant sides increased and then plateaued at 12° after the age of 16 years. STE was observed only in the symptomatic group, and the value of STE was significantly greater in players aged >16 years compared with that in players aged <12 years (P = .001). Muscle elasticity did not differ significantly between sides and showed no correlation with STE. CONCLUSIONS: The difference in HTA between the dominant and nondominant sides increased with age until 16 years old regardless of symptoms. STE in the dominant side was observed only in symptomatic baseball players after the age of 13 years and increased with age, plateauing around the age of 16 years. Posterior shoulder muscle elasticity was not indicated as a cause of STE.

Effect of adduction during glenohumeral external rotation exercises in the scapulohumeral muscles / Efecto de la adducción durante ejercicios de rotación externa glenohumeral en los músculos escapulohumerales

SUMMARY: The effect of adduction during glenohumeral external rotation (ER) exercises on the scapulohumeral muscles is controversial. The aim of this study was to evaluate the effect of carrying out adduction during external rotation exercises in low and high shoulder positions on the electromyographic (EMG) activity of the infraspinatus (IS), middle deltoid (MD), and posterior deltoid (PD) muscles. EMG activity of the IS, MD, and PD muscles of 20 healthy participants was evaluated. Subjects performed 6 ER exercises that combined two factors: i) different adduction pressures according to biofeedback unit (0, 5 and 10 mmHg), and ii) low and high shoulder position. The pressure was controlled using a biofeedback unit. The low and high shoulder positions were 20? and 90? of abduction. In the low shoulder position, the activity of the IS muscle increased as the pressure on the biofeedback unit increased and the MD and PD muscles presented the highest activity at 10 mmHg. In the high shoulder position, the activity of the IS muscle was higher at 0 and 10 mmHg, the MD muscle presented higher activity at 5 mmHg, and PD muscle activity did not vary with the pressure. The addition of adduction at a pressure of 5 mmHg in the low shoulder position promotes is activity. Likewise, adduction at a pressure of 10 mmHg will promote activity of the IS, MD, and PD.

RESUMEN: El efecto de la aducción durante los ejercicios de rotación externa (RE) glenohumeral sobre los músculos escapulohumerales es controversial. El objetivo de este estudio fue evaluar el efecto de la realización de la aducción durante los ejercicios de rotación externa en posiciones bajas y altas del hombro sobre la actividad electromiográfica (EMG) delos músculos infraespinoso (IS), deltoides medio (DM) y deltoides posterior (DP). Se evaluó la actividad EMG de los músculos IS, MD y PD de 20 participantes sanos. Los sujetos realizaron 6 ejercicios de RE que combinaron dos factores: i) diferentes presiones de aducción de acuerdo con la unidad de biorretroalimentación (0, 5 y 10 mmHg), y ii) posición del hombro baja y alta. La presión se controló mediante una unidad de biorretroalimentación. Las posiciones del hombro baja y alta fueron de 20? y 90? de abducción. En la posición del hombro bajo, la actividad del músculo IS aumentó a medida que aumentaba la presión sobre la unidad de biorretroalimentación y los músculos MD y PD presentaron la actividad más alta a 10 mmHg. En la posición del hombro alto, la actividad del músculo IS fue mayor a 0 y 10 mmHg, el músculo MD presentó mayor actividad a 5 mmHg y la actividad del músculo PD no varió con la presión. La adición de aducción a una presión de 5 mmHg en la posición baja del hombro promueve la actividad del músculo IS. Asimismo, la aducción a una presión de 10 mmHg promoverá la actividad del IS, MD y PD.

Evaluation of glenohumeral range of motion and humeral retroversion at ages after major change and differences in wrestlers.

PURPOSE: This study aimed to present the change in humeral retroversion (HR) angle (HRA) that occurs in childhood and young adulthood and the potential developmental difference that is observed in wrestlers. METHODS: HRA of dominant and non-dominant shoulders (DSHRA and NDSHRA, respectively) were measured using ultrasonography in a group of 30 wrestlers who started wrestling before the age of 13 years (Group 1), a group of 30 young adults, aged between 16-20 years, who were not actively engaged in any branch of overhead sports (Group 2) and a group of children aged between 11-13 years and not actively engaged in any branch of overhead sports (Group 3). Range of motion (ROM) degrees of dominant and non-dominant shoulders in all groups were compared within each group and between the groups. RESULTS: DSHRA (mean: 88.73°, 88.93° and 89.40°) values were significantly higher than NDSHRA (mean: 81.13°, 81.83° and 84.37°) values (p < 0.001, p < 0.001 and p < 0,05) in Groups I, II and III, respectively. Internal rotation and total ROM degrees of the dominant shoulder in Group 1 and 3 were higher than those in Group 2. CONCLUSION: There is no significant change in terms of HRA in people aged between 11-13 and 16-20 years because of natural development or wrestling. DSHRA values are higher than NDSHRA ones. In contrast to the shoulders of throwers, the shoulders of wrestlers are characterized by an increase in internal rotation, described as "Wrestler's shoulder." LEVEL OF EVIDENCE: Level III.

Chronic Nicotine Exposure Minimally Affects Rat Supraspinatus Tendon Properties and Bone Microstructure.

Cigarette smoking is the largest cause of preventable deaths, and a known risk factor for musculoskeletal issues including rotator cuff tendon tears. Tendon degeneration is believed to be due in part to changes in tendon cell health and collagen structure. Several studies have demonstrated that exposure to nicotine negatively impacts tendon healing, but surprisingly, nicotine exposure was shown to increase rat supraspinatus tendon stiffness. In order to address this seeming contradiction, the objective of this study was to comprehensively investigate the effects of long-term (18 weeks) exposure of nicotine on tendon-to-bone microstructural properties in a rat model. We hypothesized that long term subcutaneous nicotine delivery would lead to diminished tendon mechanical properties, decreased bone microstructure in the humeral head, and altered tendon cell morphology compared to age-matched control rats receiving saline. Results demonstrated a small decrease in tendon size and stiffness, with decreased cell density in the tendon midsubstance. However, no differences were found in the enthesis fibrocartilage or in the underlying subchondral or trabecular bone. In conclusion, our study revealed limited effects of nicotine on the homeostatic condition of the supraspinatus tendon, enthesis, and underlying bone. Future studies are needed to ascertain effects of other components of tobacco products.

Replicating dynamic humerus motion using an industrial robot.

Transhumeral percutaneous osseointegrated prostheses provide upper-extremity amputees with increased range of motion, more natural movement patterns, and enhanced proprioception. However, direct skeletal attachment of the endoprosthesis elevates the risk of bone fracture, which could necessitate revision surgery or result in loss of the residual limb. Bone fracture loads are direction dependent, strain rate dependent, and load rate dependent. Furthermore, in vivo, bone experiences multiaxial loading. Yet, mechanical characterization of the bone-implant interface is still performed with simple uni- or bi-axial loading scenarios that do not replicate the dynamic multiaxial loading environment inherent in human motion. The objective of this investigation was to reproduce the dynamic multiaxial loading conditions that the humerus experiences in vivo by robotically replicating humeral kinematics of advanced activities of daily living typical of an active amputee population. Specifically, 115 jumping jack, 105 jogging, 15 jug lift, and 15 internal rotation trials-previously recorded via skin-marker motion capture-were replicated on an industrial robot and the resulting humeral trajectories were verified using an optical tracking system. To achieve this goal, a computational pipeline that accepts a motion capture trajectory as input and outputs a motion program for an industrial robot was implemented, validated, and made accessible via public code repositories. The industrial manipulator utilized in this study was able to robotically replicate over 95% of the aforementioned trials to within the characteristic error present in skin-marker derived motion capture datasets. This investigation demonstrates the ability to robotically replicate human motion that recapitulates the inertial forces and moments of high-speed, multiaxial activities for biomechanical and orthopaedic investigations. It also establishes a library of robotically replicated motions that can be utilized in future studies to characterize the interaction of prosthetic devices with the skeletal system, and introduces a computational pipeline for expanding this motion library.

Reliable skeletal maturity assessment for an AIS patient cohort: external validation of the proximal humerus ossification system (PHOS) and relevant learning methodology.

STUDY DESIGN: Validation of classification system. OBJECTIVES: To externally validate the Proximal Humerus Ossification System (PHOS) as a reliable skeletal maturity scoring system and to assess the learning curve associated with teaching the procedure to individuals of varying levels of experience. BACKGROUND: Assessment of skeletal maturity is essential for treatment decisions in Adolescent Idiopathic Scoliosis (AIS). PHOS is a five-stage system that uses the proximal humeral physis in assessing skeletal maturity and has been shown to reliably grade skeletal age leading up to and beyond peak growth age (PGA). This system is advantageous in the AIS patient, as it is often captured in standard scoliosis films. METHODS: A medical student, an orthopedic surgery resident (PGY-2), spine fellow, and experienced scoliosis surgeon in his 25th year in practice were given a three-slide PHOS learning module. Each participant rated 100 X-rays on two separate occasions, separated by 1 week. Intra- and inter-observer reliability, as well as cross-institutional reliability, were calculated using intraclass correlation coefficients (ICC) with 95% confidence intervals [CI95]. RESULTS: Average intra-observer reliability ICC between scoring sessions was 0.94 [0.92, 0.96] and inter-observer reliability by level of training were 0.94 [0.91, 0.96], 0.93 [0.9, 0.95], 0.94 [0.91, 0.96], 0.96 [0.94, 0.97] for the medical student, PGY-2, fellow, and attending, respectively. Reliability across institutions was 0.99 [0.98, 0.99]. Combined rating observations (n = 400) showed 82% exact matches, as well as 17% and 1% mismatches by 1 and 2 stages, respectively. Similar to the PHOS developers, we found PHOS stage 3 to occur immediately after PGA. CONCLUSION: PHOS is easily learned and employed by raters with varying levels of training. It comprises a five-stage system to reliably measure bone age leading up to PGA and thereafter. This new system relies on visualization of the proximal humerus, which is readily available on standard scoliosis X-rays. LEVEL OF EVIDENCE: Level III.

Three-dimensional in vivo scapular kinematics and scapulohumeral rhythm: a comparison between active and passive motion.

BACKGROUND: The aim of this study was to compare the scapular kinematics and scapulohumeral rhythm of healthy participants during arm elevation and lowering and to find the difference between active motion and passive motion of the shoulder. METHODS: The study examined the shoulders of 10 healthy men (mean age, 23.5 years; age range, 22-28 years). The shoulders of participants were elevated and lowered while fluoroscopic images were taken, and 3-dimensional bone models were created from 2-dimensional to 3-dimensional images using model registration techniques. The Euler angle sequences of the models' scapular kinematics and scapulohumeral rhythm were compared during active and passive shoulder motion. RESULTS: There was a significant statistical difference of upward rotation during arm elevation between active and passive shoulder movements (P = .027). In particular, the upward rotation between 45° and 90° of elevation showed a statistically significant difference (P < .001). When the scapula was tilted posteriorly by active motion, it resulted in a statistically significant difference as there was more tilting in the high-degree range of motions than when it was tilted by passive motion (P < .001). There was no statistically significant difference between the 2 groups in scapular external rotation. However, during arm lowering, scapular kinematics did not show statistically significant difference between active and passive motion. CONCLUSIONS: The scapular kinematics showed statistically significant differences between active and passive motion of upward rotation and posterior tilting of the scapula during arm elevation, but there were none during lowering. In terms of upward rotation, active shoulders rotated more upward during arm elevation.

Humeral Retroversion and Participation Age in Professional Baseball Pitchers by Geographic Region.

CONTEXT: Baseball is played around the world, including in North America and Latin America. The repetitive and stressful act of throwing can lead to adaptations such as increased humeral retroversion (HR) in the throwing arm. This adaptation is often considered beneficial as it allows more glenohumeral external rotation during the cocking phase of pitching without soft tissue stretching. Therefore, it is speculated that throwing should be started at a young age to capitalize on this adaptation. Interestingly, athletes in different geographic regions of the world often begin organized baseball at different ages. However, range of motion (ROM), HR, and the starting age of baseball have never been examined based on geographic region. OBJECTIVE: To determine if ROM, HR, and the starting age of baseball players differed between professional baseball pitchers from North America and Latin America. DESIGN: Cross-sectional study. SETTING: Clinical setting. PATIENTS OR OTHER PARTICIPANTS: Thirty professional pitchers (North American = 19, Latin American = 11) with no current injury or surgery in the previous 6 months. MAIN OUTCOME MEASURE(S): Both ROM and HR were measured in the dominant and nondominant shoulder of each participant. The starting age for baseball was self-reported. RESULTS: The Latin American group had more dominant-arm HR (8.7°; P = .034), more nondominant-arm external rotation (5.3°; P = .049), and a trend toward more nondominant-arm HR (6.5°; P = .058), yet they started playing baseball at a later age (by 3.7 years; P = .021) compared with the North American group. CONCLUSIONS: Latin American players had greater HR but started playing baseball at an older age. These findings contradict current thinking that HR would be more pronounced if baseball was started at a younger age. Additional research is required to better understand HR and the genetic, environmental, and nutritional factors that contribute to its development.

Two-Staged Reconstruction for Symptomatic Humeral Medial Epicondyle Nonunion in Children: A Case Report.

Few cases of humeral medial epicondyle nonunion develop to symptomatic condition. We report a pediatric case of distally displaced nonunion. At first, the palliative repair surgery was chosen due to irreduciblity of the epicondyle fragment at 10 years old. After 2 years and 3 months wait for maturation of ossification at the trochlea, the definitive surgery consisting of epicondylectomy and ligament reconstruction was performed. This is the first pediatric case of humeral medial epicondyle nonunion with an unossified trochlea which needed a two-staged surgery. We highlight the surgical plan aimed at anatomical ligament reconstruction focusing an isometric point of MCL.

The differences of humeral torsion angle and the glenohumeral rotation angles between young right-handed and left-handed pitchers.

BACKGROUND: The differences between young right-handed and left-handed baseball players are not well known. This study compared the range of the shoulder motion and humeral torsion angle (HTA) between right-handed and left-handed young baseball pitchers. METHODS: A total of 65 young baseball pitchers (age, 9-12 years; 46 right-handed throwers, R group; and 19 left-handed throwers, L group) were analyzed. The glenohumeral internal rotation (IR) angle and external rotation (ER) angle were measured at 90° shoulder abduction, and HTA was assessed using indirect ultrasonographic techniques. The side-to-side difference in HTA (d-HTA), glenohumeral ER difference (GERD), and glenohumeral IR deficit (GIRD) were calculated. The adjusted GIRD and adjusted GERD were defined as the angles obtained by subtracting d-HTA from GIRD and GERD, respectively, to exclude the influence of humeral retrotorsion difference. RESULTS: HTA and ER of the throwing limb were significantly greater than those of the nonthrowing limb in the R group (HTA: 84° vs. 77°; P < .001, ER: 116° vs. 111°; P < .001), but no significant differences were observed in the L group (HTA: 79° vs. 77°, P = .103; ER: 113° vs. 114°, P = .380). Compared with the R group, the L group showed a significantly smaller d-HTA (2° vs. 8°, P < .001) and GERD (5° vs. -2°, P = .004), but no significant difference was observed in adjusted GERD between the groups (-3° vs. -4°, P = .690). CONCLUSION: Compared with the right-handed pitchers, the side-to-side differences of glenohumeral external rotation angle and humeral torsion angle were significantly smaller in the left-handed pitchers at a young age.

The effect of adipose-derived stem cells on enthesis healing after repair of acute and chronic massive rotator cuff tears in rats.

BACKGROUND: Chronic massive rotator cuff tears heal poorly and often retear. This study investigated the effect of adipose-derived stem cells (ADSCs) and transforming growth factor-ß3 (TGF-ß3) delivered in 1 of 2 hydrogels (fibrin or gelatin methacrylate [GelMA]) on enthesis healing after repair of acute or chronic massive rotator cuff tears in rats. METHODS: Adult male Lewis rats underwent bilateral transection of the supraspinatus and infraspinatus tendons with intramuscular injection of botulinum toxin A (n = 48 rats). After 8 weeks, animals received 1 of 8 interventions (n = 12 shoulders/group): (1) no repair, (2) repair only, or repair augmented with (3) fibrin, (4) GelMA, (5) fibrin + ADSCs, (6) GelMA + ADSCs, (7) fibrin + ADSCs + TGF-ß3, or (8) GelMA + ADSCs + TGF-ß3. An equal number of animals underwent acute tendon transection and immediate application of 1 of 8 interventions. Enthesis healing was evaluated 4 weeks after the repair by microcomputed tomography, histology, and mechanical testing. RESULTS: Increased bone loss and reduced structural properties were seen in chronic compared with acute tears. Bone mineral density of the proximal humerus was higher in repairs of chronic tears augmented with fibrin + ADSCs and GelMA + ADSCs than in unrepaired chronic tears. Similar improvement was not seen in acute tears. No intervention enhanced histologic appearance or structural properties in acute or chronic tears. CONCLUSIONS: Surgical repair augmented with ADSCs may provide more benefit in chronic tears compared with acute tears, although there was no added benefit to supplementing ADSCs with TGF-ß3.

Model predictive controller-based spatiotemporal path tracking method for transhumeral prostheses.

BACKGROUND: Transhumeral prostheses are worn by transhumeral amputees to replace the missing upper limb segment between shoulder and elbow. Prostheses should be able to function as a natural limb for the user to gain the full advantage of wearing a prosthesis. When performing reach-to-grasp and pointing motions by the upper limb, the hand is capable of adhering to a straight-line path with a bell-shaped velocity profile. AIM: Aim was to develop a dynamic path-tracking method for transhumeral prostheses to gain the capability of adhering to a straight-line path. METHOD: Proposed method uses model predictive controller (MPC) developed based on the kinematic model of the prosthesis. Moreover, a shoulder matcher is proposed to match actual shoulder pose with the predicted shoulder pose and to select the best joint angles for the prosthesis for a particular instance. Furthermore, the proposed method is capable of dynamically updating the path if the human performs shoulder motions, which are not as planned by the MPC. RESULTS: Several experiments are conducted to validate the proposed method. The proposed method is capable of taking a straight-line path similar to a natural human. CONCLUSION: This paper proposed a dynamic path-tracking method based on a model predictive controller. The proposed method is capable of taking the prosthetic hand on a straight-line path, which is similar to a path taken by a natural human hand.

Abnormal origin of posterior circumflex humeral artery and subscapular artery: case report and review of the literature / Origem anômala das artérias circunflexa posterior do úmero e subescapular: relato de caso e revisão de literatura

The subscapular, anterior circumflex, and posterior circumflex arteries arise from the third part of the axillary artery. During dissection of the right upper limb of the cadaver of a 70-year-old male, a common trunk was observed arising from the third part of the axillary artery which, after traveling for 0.5 cm, bifurcated into subscapular and posterior circumflex humeral arteries. The common trunk was crossed anteriorly by the radial nerve. The medial nerve was formed by medial and lateral roots on the medial side of the third part of the axillary artery, remaining medial to the brachial artery up to the cubital fossa and then following its usual course thereafter. Awareness of the vascular variations observed in the present case is important when conducting surgical procedures in the axilla, for radiologists interpreting angiographs, and for anatomy-pathologists studying rare findings

As artérias subescapular, circunflexa anterior e circunflexa posterior se originam da terceira parte da artéria axilar. Durante a dissecção de membro superior direito de um cadáver humano com 70 anos de idade, do sexo masculino, um tronco comum foi observado originando-se da terceira parte da artéria axilar, após um percurso de 0,5 cm, bifurcando-se em artéria subescapular e artéria circunflexa posterior do húmero. O tronco comum era cruzado anteriormente pelo nervo radial. O nervo medial era formado por raízes medial e lateral, no lado medial da terceira parte da artéria axilar, permanecendo em posição medial à artéria braquial até a fossa cubital e seguindo seu curso usual a partir de então. Conhecimento das variações vasculares observadas neste caso é importante ao executar procedimentos cirúrgicos na axila, para radiologistas que interpretam radiografias, e também para anatomo-patologistas que estudam achados raros

Preseason screening of shoulder range of motion and humeral retrotorsion does not predict injury in high school baseball players.

BACKGROUND: Shoulder and elbow injuries are commonplace in high school baseball. Although altered shoulder range of motion (ROM) and humeral retrotorsion angles have been associated with injuries, the efficacy of preseason screening of these characteristics remains controversial. METHODS: We conducted preseason screenings for shoulder internal and external rotation ROM and humeral retrotorsion on 832 high school baseball players and tracked their exposure and incidence on throwing-related shoulder and elbow injuries during a subsequent season. Poisson regression with robust error variance was used to determine whether preseason screening could identify injury risk in baseball players and whether the injury risk was higher for pitchers compared with players who do not pitch. RESULTS: Shoulder rotation ROM or humeral retrotorsion at preseason did not predict the risk of throwing-related upper extremity injury (P = .15-.89). Injury risk was 3.84 higher for baseball players who pitched compared with those who did not (95% confidence interval, 1.72-8.56; P = .001). DISCUSSION: Preseason measures of shoulder ROM and humeral retrotorsion may not be effective in identifying players who are at increased injury risk. Because shoulder ROM is a measure that fluctuates under a variety of influences, future study should investigate whether taking multiple measurements during a season can identify at-risk players. The usefulness of preseason screening may also depend on rigor of participation in sports. Future studies should investigate how preseason shoulder characteristics and participation factors (ie, pitch count and frequency, competitive level, pitching in multiple leagues) interact to predict injury risk in baseball players.

Asymptomatic elite young tennis players show lateral and ventral growth plate alterations of proximal humerus on MRI.

PURPOSE: The specific aim of the study was to investigate and compare epiphyseal length and extension in the proximal humerus, closure in the growth plate and bone marrow signal intensity related to the proximal humeral physis in the dominant arm and the non-dominant arm of the asymptomatic adolescent elite tennis player. METHODS: The study sample included 35 asymptomatic elite young tennis players (15 males and 20 females, mean age 17.4 years ± 2.7). Each player contributed with two shoulders to the MRI measurement. The non-dominant arm was used as a control. RESULTS: Relative reliability between the radiologists was excellent (ICC 0.78-0.96). Statistically significant differences between dominant arm and non-dominant arm in epiphyseal length (mm) laterally (DA 27.3 vs NDA 26.7) were shown. Statistically significant differences were also found in epiphyseal extension (mm) laterally (DA 36.1 vs NDA 35.1) and ventrally (DA 36.2 vs NDA 34.8). No statistically significant differences were found between dominant arm and non-dominant arm in epiphyseal extension (mm) medially (DA 31.7 vs NDA 31.7) and dorsally (DA 22.6 vs NDA 22.1). CONCLUSIONS: Significant findings assessing MRI measurements of the epiphyseal plate in the asymptomatic adolescent elite tennis player might reflect a development of consecutive alterations in the epiphyseal plate in the dominant arm. LEVEL OF EVIDENCE: Diagnostic study, Level IV.

Biomechanical Comparison of the Latarjet Procedure with and without Capsular Repair.

BACKGROUND: The purpose of this study was to determine if capsular repair used in conjunction with the Latarjet procedure results in significant alterations in glenohumeral rotational range of motion and translation. METHODS: Glenohumeral rotational range of motion and translation were measured in eight cadaveric shoulders in 90° of abduction in both the scapular and coronal planes under the following four conditions: intact glenoid, 20% bony Bankart lesion, modified Latarjet without capsular repair, and modified Latarjet with capsular repair. RESULTS: Creation of a 20% bony Bankart lesion led to significant increases in anterior and inferior glenohumeral translation and rotational range of motion (p < 0.005). The Latarjet procedure restored anterior and inferior stability compared to the bony Bankart condition. It also led to significant increases in glenohumeral internal and external rotational range of motion relative to both the intact and bony Bankart conditions (p < 0.05). The capsular repair from the coracoacromial ligament stump to the native capsule did not significantly affect translations relative to the Latarjet condition; however it did cause a significant decrease in external rotation in both the scapular and coronal planes (p < 0.005). CONCLUSIONS: The Latarjet procedure is effective in restoring anteroinferior glenohumeral stability. The addition of a capsular repair does not result in significant added stability; however, it does appear to have the effect of restricting glenohumeral external rotational range of motion relative to the Latarjet procedure performed without capsular repair.

The role of the scapula in preventing and treating shoulder instability.

The shoulder is a closed-chain mechanism that balances the mobility required by the ranges of motion in normal activities with the stability required to act as a stable ball and socket base for those activities. The scapula plays key roles in the closed-chain mechanism by being mobile enough to place the glenoid in optimal relation to the humerus to facilitate concavity/compression and by being a stable base for coordinated muscle activation to compress the humerus into the glenoid. Scapular dyskinesis alters these roles and is frequently present in many types of glenohumeral instability. It may create or exacerbate the abnormal glenohumeral kinematics in instability. Clinical evaluation methods can demonstrate scapular dyskinesis, and if dyskinesis is present, rehabilitation for the dyskinesis should be included in the non-operative, preoperative, or post-operative treatment. Rehabilitation for scapular dyskinesis can be performed by specific protocols and is more successful in muscle-predominant instabilities such as multidirectional instability and repetitive microtrauma instability. Level of evidence V.

In vivo three-dimensional elbow biomechanics during forearm rotation.

BACKGROUND: It is unclear how elbow kinematics changes during forearm rotation. This study investigated in vivo 3-dimensional elbow kinematics during forearm rotation. METHODS: We studied 12 normal elbows using in vivo 3-dimensional computed tomography data in maximum forearm supination, neutral, and maximum pronation with the elbows in extension. We measured the motion of the radius and ulna relative to the humerus using a markerless bone registration technique and the contact area of the radiocapitellar joint, proximal radioulnar joint, and ulnohumeral joint using a proximity mapping method. RESULTS: When the forearm rotated from the supinated position to the pronated position, the radius showed significant varus rotation, internal rotation, and extension relative to the humerus. The center of the radial head significantly translated anteriorly, proximally, and laterally. The ulna significantly rotated in valgus, and the deepest point on the sagittal ridge of the trochlear notch translated medially with forearm pronation. The contact area of the radiocapitellar joint was largest in pronation. The contact area of the proximal radioulnar joint was largest in supination. The contact area of the ulnohumeral joint showed no significant change during forearm rotation. CONCLUSIONS: In pronation, because of the proximal migration of the radial head, the radiocapitellar joint was most congruent compared with other positions. The proximal radioulnar joint was most congruent in supination. The ulnohumeral joint congruency was not affected by forearm rotation. This study provides useful information for understanding 3-dimensional elbow motion and joint osseous stability related to forearm rotation.

Comparison of humeral rotation co-activation of breast cancer population and healthy shoulders.

Upper limb morbidities are common amongst the breast cancer population (BCP) and have a direct impact on independence. Comparing muscle co-activation strategies between BCP and healthy populations may assist in identifying muscle dysfunction and promote clinical interpretation of dysfunction, which could direct preventative and therapeutic interventions. The purposes of this study were to define humeral rotation muscle co-activation of a BCP and to compare it with a previously defined co-activation relationship of a healthy population. Fifty BCP survivors performed 18 isometric internal and external rotation exertions at various postures and intensities. Surface and intramuscular electrodes recorded shoulder muscle activity. BCP co-activation was predicted at r(2)=0.77 during both exertion types. Humeral abduction angle and task intensity were important factors in the prediction of co-activation in both populations. Comparisons made between populations identified differing muscle strategies used by BCP to maintain postural control. Compared to healthy co-activation, the BCP demonstrated greater activation of internal (IR) and external rotator (ER) type muscles during their respective rotation type. The BCP demonstrated increased (⩾8.7%) activation of pectoralis major. This study has provided insight into how BCP muscles compensate during dysfunction. Continued advancement of this knowledge can provide more understanding of dysfunction, promote generation of evidence-based therapies, and can be useful in biomechanical modeling.