Relationship between bilateral humeral retroversion angle and starting baseball age in skeletally mature baseball players-existence of watershed age

Adaptive pathology: new insights into the physical examination and imaging of the thrower's shoulder and elbow

Throwing with high velocity requires extremes of glenohumeral external rotation of the abducted arm where particularly high forces in the shoulder and elbow are endured. Repeated throwing leads to dominant-arm bony remodeling of the humerus, glenoid, and elbow, and multiple soft tissue changes that would be considered abnormal. Many of these features are thought to be adaptive and protective. The purpose of this work is to (1) define the concept of adaptive pathology; (2) review the mechanics of the throwing motion; (3) review pertinent physical examination and imaging findings seen in asymptomatic throwers' shoulders and elbows and describe how these changes develop and may be adaptive-allowing the thrower to perform at high levels; and then (4) review the principles of surgical treatment in the throwing athletes, which should focus on reducing symptoms, but not necessarily restoring the thrower's anatomy to normal.

Bilateral Humeral Retrotorsion Angle Measured Using an Ultrasound-Assisted Technique in Asian Baseball Players

Background

Repetitive pitching is thought to restrict the physiological derotation process of the humeral head. Some studies have reported that side-to-side differences in the humeral retrotorsion angle (ΔHRA) occur between the ages of 9 and 11 years in baseball players. However, it remains unclear whether the ΔHRA in Asian baseball players depends on pitching skill or competitive level.

Purpose

To evaluate the ΔHRA in Asian collegiate and professional baseball players and to determine the effects of pitching activity on the physiological derotation process of the humeral head.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

We evaluated 128 shoulders in 64 Asian baseball players who were stratified into 4 groups as follows: 13 professional pitchers; 9 professional fielders; 8 collegiate pitchers; and 34 collegiate fielders. The throwing and nonthrowing side HRA was assessed using an ultrasound-assisted technique, and the ΔHRA was compared among the 4 groups. In addition, Pearson correlation analysis was used to assess the relationship between ΔHRA and glenohumeral range of motion, baseball starting age, and fastball velocity in pitchers.

Results

The HRA was significantly greater in the throwing arm than in the nonthrowing arm in each group, with no significant differences among the groups. There was no correlation between ΔHRA and range of motion or fastball velocity. There was a significant negative correlation between baseball starting age and ΔHRA in professional fielders (r = -0.633; P = .036).

Conclusion

The findings of the present study provide evidence that in Asian baseball players, the HRA was significantly greater in the throwing arm than in the nonthrowing arm. There were no clear associations between HRA and pitching ability or competitive level.

Identifying the underlying mechanisms responsible for glenohumeral internal rotation in professional baseball pitchers

Background and Hypothesis

Glenohumeral internal rotation deficit has been identified as a significant risk factor for upper-extremity injuries in pitchers across all ages. Humeral retroversion (HR), posterior capsule thickness (PCT), and posterior rotator cuff muscle pennation angle (PA) have been independently associated with internal rotation range of motion (IR ROM); however, these anatomic structures have not been collectively measured in baseball pitchers to determine the underlying mechanisms responsible for IR ROM. Therefore, the purpose of this study was to determine the contributions of HR, PCT, and posterior rotator cuff PA on IR ROM during a preseason evaluation in healthy professional baseball pitchers. The authors hypothesized that HR, PCT, and posterior rotator cuff PA would have a significant contribution to IR ROM.

Methods

This is a cross-sectional study. Healthy professional pitchers from a single organization were recruited at the beginning of the 2021 Major League Baseball Spring Training. Participants received bilateral IR ROM assessment while laying supine with the shoulder at 90 degrees of abduction and the scapula stabilized. Ultrasound imaging was also performed bilaterally to assess HR, PCT, infraspinatus (superficial + deep) PA, and teres minor (superficial + deep) PA. All ultrasound imaging processes were performed utilizing previously published, highly reliable techniques. A stepwise regression was performed, which included both arms to determine the mechanisms of IR ROM.

Results

Overall, 49 pitchers (88 shoulders) with an average age of 22.5 ± 2.2 years were included in the final data analysis. Stepwise linear regression found that only HR and PCT were associated with the preseason IR ROM. There was a moderate relationship between HR and PCT relative to IR ROM (R = 0.535, P < .001).

Conclusion

HR and PCT were found to be the primary mechanisms responsible for the preseason glenohumeral IR ROM. The posterior rotator cuff was not found to be significantly related to IR ROM. Future research evaluating these anatomic structures longitudinally-both acutely and chronically-will help clinicians optimize ROM management throughout the season. As glenohumeral internal rotation deficit can have harmful effects in baseball pitchers, understanding which anatomic structures are most responsible for IR ROM is important for injury prevention and treatment.

Increased external rotation related to the soft tissues is associated with pathologic internal impingement in high-school baseball players

BACKGROUND

Changes in soft-tissue structures such as anterior laxity and posterior tightness are thought to contribute to the development of pathologic internal impingement in baseball players. Although side-to-side differences in shoulder rotational range of motion (ROM) is commonly used in clinical practice to quantify the soft-tissue changes, the ROM does not accurately reflect the soft-tissue changes because the ROM is affected not only by the soft tissues, but also by the bone. Increased retroversion of the humeral head is often observed in the dominant shoulder of throwing athletes. The purpose of this study was to determine the relationship between the soft-tissue-related (STR) ROM and pathologic internal impingement in baseball players.

METHODS

Bilateral humeral retroversion and ranges of glenohumeral external rotation (ER) and internal rotation (IR) were investigated in 81 high-school baseball players. The players were divided into two groups: the internal impingement group (19 players) and the control group (62 players). Humeral retroversion was measured using the ultrasound-assisted technique to assess the bone-related ER and IR. The STR ER and IR were defined as subtracting the amount of humeral retroversion from the measured ER and IR.

RESULTS

The side-to-side difference (throwing shoulder - nonthrowing shoulder) in humeral retroversion showed no significant difference between the internal impingement group (6° ± 10°) and control group (11° ± 11°) (P = .064). The side-to-side difference in STR ER was significantly greater in the internal impingement group (12° ± 12°) than that in the control group (1° ± 14°) (P = .002). No significant difference was observed in the side-to-side difference in STR IR between the internal impingement group (-7° ± 16°) and control group (-5° ± 15°) (P = .696). Pathologic internal impingement was significantly associated with the side-to-side difference of STR ER (odds ratio, 1.06 for increase of 1°; 95% confidence interval, 1.02-1.11; P = .008).

CONCLUSION

In high-school baseball players, the increased STR ER in the throwing shoulder may be associated with pathologic internal impingement. An increase of 10° in side-to-side difference in STR ER would increase the risk of pathologic internal impingement by 1.8 times.

Common Upper Extremity Injuries in Pediatric Athletes

PURPOSE OF REVIEW

The aim of this study is to review the most recent literature on common upper extremity injuries in pediatric athletes and discuss their diagnosis, management, and outcomes. We also highlight ultrasound as a tool in their evaluation.

RECENT FINDINGS

Shoulder conditions presented include little league shoulder, glenohumeral rotation deficit, acute traumatic shoulder dislocation, and multidirectional shoulder instability. Elbow conditions include capitellar OCD, medial epicondyle avulsion fracture, and medial epicondylitis. We also review scaphoid fractures and gymnast wrist. Not all physeal injuries lead to long-term growth disruption. Ultrasound has been shown to be useful in the diagnosis of scaphoid fracture, medial epicondyle avulsion fractures, and capitellar OCD. It can also be helpful in assessing risk for shoulder and elbow injuries in overhead athletes. There is a rising burden of upper extremity injuries among pediatric athletes. Knowledge of their sport specific mechanics can be helpful in diagnosis. As long-term outcome data become available for these conditions, it is clear, proper diagnosis and management are critical to preventing adverse outcomes. We highlight many of these injuries, best practice in care, and controversies in care in hopes of improving outcomes and preventing injury for pediatric athletes.

Chronic adaptations of the long head of the biceps tendon and groove in professional baseball pitchers

BACKGROUND AND HYPOTHESIS

The long head of the biceps tendon (LHBT) plays a significant shoulder stabilizing role during pitching, with the large forces and repetitions involved in overhead throwing likely contributing to LHBT pathology. Determining whether the LHBT undergoes adaptive changes in baseball pitchers and how these changes relate to bicipital groove morphology can improve our understanding of the biceps function at the glenohumeral joint. Therefore, the purpose of this study was to determine the chronic adaptations of the bicipital groove morphology and the LHBT in professional baseball pitchers, with a secondary purpose of evaluating biceps integrity as it relates to torsional changes of the bicipital groove. We hypothesized that the throwing arm of professional baseball pitchers would exhibit chronic adaptations of the LHBT compared with their nonthrowing arm, and that these adaptations would be related to the bicipital groove morphology.

MATERIALS AND METHODS

Fifty-three professional baseball pitchers were enrolled at the beginning of the 2015 Major League Baseball spring training. Ultrasound was used to bilaterally measure humeral retroversion and to capture images of the bicipital groove and the LHBT. MATLAB software was used to calculate the area of the bicipital groove, and ImageJ software was used to quantify the area, echogenicity, and circularity of the LHBT.

RESULTS

The dominant arm LHBT cross-sectional area was significantly smaller than the nondominant arm (9 mm² vs. 10 mm²; P = .011), whereas the dominant arm LHBT echogenicity was significantly higher than the nondominant arm (65 optical density vs. 59 optical density; P = .002). Pitchers with more bicipital groove rotational adaptation (more retroversion) had significantly more LHBT echogenicity adaptation compared with pitchers with less bicipital groove rotational adaptation (12 vs. 2; P = .023).

CONCLUSION

There are significant bilateral differences in the LHBT of professional baseball pitchers. An adaptation in bony rotation was associated with a larger bilateral difference in LHBT echogenicity but was not related to bilateral differences in LHBT area or circularity. Therefore, the bilateral difference in echogenicity is impacted by bony morphology, whereas the bilateral difference in cross-sectional area may be independent of bony morphology in this healthy population.

The Contribution of Posterior Capsule Hypertrophy to Soft Tissue Glenohumeral Internal Rotation Deficit in Healthy Pitchers

BACKGROUND

The relationship between posterior capsule adaptations and soft tissue glenohumeral internal rotation deficit (GIRD) in healthy pitchers remains unclear.

PURPOSE/HYPOTHESIS

This study aimed to identify if posterior capsule thickness (PCT) was associated with soft tissue GIRD in healthy pitchers. We hypothesized that there would be a positive relationship between soft tissue GIRD and PCT in the dominant arm, no relationship between soft tissue GIRD and PCT in the nondominant arm, and a strong positive relationship between soft tissue GIRD and the bilateral difference in PCT (posterior capsule hypertrophy [PCH]).

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 45 healthy collegiate and professional pitchers were included. Glenohumeral internal rotation and external rotation range of motion, humeral retroversion, and PCT were measured bilaterally. PCT was determined for unilateral posterior capsule measurements, and PCH of the throwing shoulder was calculated as the bilateral difference in PCT. Soft tissue GIRD was calculated as the sum of clinical GIRD and the bilateral difference in humeral retroversion. Pearson correlation coefficients were determined to evaluate the relationships between dominant arm PCT, nondominant arm PCT, and PCH and soft tissue GIRD.

RESULTS

Pearson correlations showed that both dominant arm PCT (R = -0.13; P = .378) and nondominant arm PCT (R = 0.21; P = .165) were not related to soft tissue GIRD. However, Pearson correlations did show that the amount of PCH was moderately related to soft tissue GIRD (R = 0.40; P = .007). Therefore, as the posterior capsule hypertrophied, soft tissue GIRD moderately increased.

CONCLUSION

Increased PCH was associated with an increase in soft tissue GIRD in healthy pitchers. If PCT measurements are feasible, clinicians should consider performing bilateral ultrasound assessments to isolate posterior capsule adaptations (ie, PCH). This will allow clinicians to identify pitchers with potentially maladaptive structural adaptations and optimize management strategies throughout the season to counteract them.

Proximal humeral coordinate systems can predict humerothoracic and glenohumeral kinematics of a full bone system

BACKGROUND

Clinical imaging often excludes the distal humerus, confounding definition of common whole-bone coordinate systems. While proximal anatomy coordinate systems exist, no simple method transforms them to whole-bone systems. Their influence on humeral kinematics is unknown.

RESEARCH QUESTION

How do humeral kinematics vary based on proximal and whole-bone coordinate systems, and can average rotation matrices accurately convert kinematics between them?

METHODS

Three proximal coordinate systems were defined by the lesser and greater tuberosities (LT, GT), Crest of the greater tuberosity, and humeral shaft. Average rotation matrices derived from anatomic landmarks on cadaver humeri were generated between the proximal and whole-bone coordinate systems. Absolute angle of rotation was used to determine if anatomical variability within the cadaver population influenced the matrices. The matrices were applied to humerothoracic and glenohumeral motion (collected previously) and analyzed using the proximal coordinate systems, then expressed in the whole-bone system. RMSE was used to compare kinematics from the proximal and whole-bone systems.

RESULTS

A single average rotation matrix between a given proximal and whole-bone coordinate system achieved consistent error, regardless of landmarks. Elevation and plane of elevation had <2° mean error when proximal coordinate systems were transformed to whole-bone kinematics. Axial rotation had a mean 7° error, primarily due to variable humeral head retroversion. Absolute angles of rotation did not statistically differ between subgroups. The average rotation matrices were independent of sex, side, and motion.

SIGNIFICANCE

Proximal humerus coordinate systems can accurately predict whole-bone kinematics, with most error concentrated in axial rotation due to anatomic twist along the bone. These results enhance interpretability and reproducibility in expressing humerothoracic and glenohumeral motion data between laboratories by providing a simple means to convert data between common coordinate systems. This is necessitated by the lack of distal humerus anatomy present in most clinical imaging.

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.

Relationship of clinical measures with humeral torsion in young adults: a pilot study

PURPOSE

Humeral retroversion alters range of motion and has been linked to injury risk. Clinically,palpation of the bicipital groove is used to quantify humeral torsion, but the accuracy of this procedure has not been fully examined. The purpose of this study was to investigate the relationship between clinical and diagnostic ultrasound (US) assessment of humeral torsion while considering shoulder position of the participant and clinical expertise of the examiner.

METHODS

Seventeen participants (34 shoulders, 16/17 right handed, 10/17 history of throwing) were recruited. US was assessed by an experienced assessor. Two clinical assessments of humeral torsion were performed by two assessors of different experience (expert and novice). Humeral torsion was assessed at 90 degrees shoulder abduction (Palp90) and 45 degrees shoulder abduction (Palp45). Within assessor intraclass correlation coefficients (ICC (3, 1) were calculated. Correlation coefficients (Pearson's) were generated to determine relationship between clinical and US examination findings.

RESULTS

Intra-rater reliability for clinical tests were good (ICCs .73 - .92) for both raters. Of the palpation tests, only the expert assessor was significantly correlated to the US measurement (p<.001) at Palp45 (r = .64) and Palp90 (r = .62). For the expert, there was a significantly lower angle calculated for Palp45 compared to Palp90 (p<.001).

CONCLUSION

The accuracy of both palpation methods for assessing humeral retrotorsion may depend on the training background of the assessor. Further, the glenohumeral position of the patient during palpation should be consistent for the purposes of repeated testing.

Ulnar Collateral Ligament Reconstruction With the Modified Jobe Technique in Baseball Pitchers

Background:

Tearing and insufficiency of the ulnar collateral ligament (UCL) of the elbow result in valgus instability, which can lead to pain while throwing and decline in performance in overhead athletes.

Purpose:

To assess the clinical results of a modified UCL reconstruction technique using 1 bone hole in the ulna and 1 bone tunnel in the humerus in baseball players.

Study Design:

Case series; Level of evidence, 4.

Methods:

The inclusion criteria were medial elbow pain preventing effective playing, clinically medial elbow laxity, and magnetic resonance imaging results consistent with UCL injury. Patients who were engaged in other sports and in other positions in baseball except pitchers were excluded from this study. Our modified Tommy John procedure was performed via a muscle-splitting approach and an original single-bone-tunnel technique, using a suture anchor. After a minimum of 24 months, patients were evaluated using the Conway scale and the Timmerman-Andrews score.

Results:

Of 31 patients, 20 baseball pitchers (20 male: 5 high school, 5 collegiate, 8 nonprofessional, and 2 professional pitchers) were reviewed. The mean patient age at the time of operation was 21.9 years, and the mean postoperative follow-up period was 35.1 months (range, 24-66 months). The mean Timmerman-Andrews subjective score improved significantly from pre- to postoperatively (from 68.3 to 98.3; P < .05); the objective score also improved significantly (from 81.1 to 96.4; P = .01). No complications were detected at the latest follow-up. Overall, 19 patients were able to return to their preinjury level of sports or higher.

Conclusion:

UCL reconstruction with 1 bone hole in the ulna and 1 bone tunnel in the humerus demonstrated satisfactory results in baseball pitchers. Our modified technique was safe and achieved satisfactory clinical results, with a 95% rate of return to sports.

Effect of Younger Starting Pitching Age on Humeral Retrotorsion in Baseball Pitchers With an Ulnar Collateral Ligament Injury

BACKGROUND

Increased humeral retrotorsion (HRT) has been found to be a risk factor for ulnar collateral ligament (UCL) tears in baseball players. Recent work has demonstrated the age of 11 years as a potential watershed age for HRT development.

HYPOTHESIS

In a group of baseball pitchers with UCL injuries, athletes who started pitching before the age of 10 years will demonstrate significantly more dominant limb humeral retrotorsion (DHRT) when compared with a group of baseball pitchers who reported starting pitching at 10 years or older.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 84 baseball pitchers with a diagnosed UCL injury were divided into 2 groups based upon the age at which participants began pitching: 33 players reporting a starting pitching age of 10 years or older (group 1) were compared with 51 baseball pitchers reporting a starting pitching age under 10 years (group 2). Participants' DHRT and nondominant limb humeral retrotorsion (NDHRT) were measured using diagnostic ultrasound. Independent t tests were run to compare mean group differences of all patient data, starting pitching age, age at time of injury, DHRT, NDHRT, and humeral retrotorsion difference (HRTdiff).

RESULTS

There were no significant differences between groups with regard to age at time of injury, height, weight, or playing years' experience. There was a statistically significant difference in the participant-reported starting pitching age. Significant differences between groups were noted for DHRT (group 1: 20.0°± 9.4°, group 2: 14.5°± 10.3°, P = .015) and for NDHRT (group 1: 38.6°± 8.8°, group 2: 32.9°± 9.5°, P = .007). No significant differences between groups were found for HRTdiff (P = .940).

CONCLUSION

Baseball pitchers with a UCL injury who reported a starting pitching age younger than 10 years demonstrated significantly greater DHRT and NDHRT when compared with UCL-injured baseball pitchers who reported a starting pitching age at 10 years or later. The results of this study demonstrate that a younger starting pitching age results in increased HRT in players with UCL injuries.

Relationship between humeral retroversion and baseball positions during elementary and junior-high school

BACKGROUND

Humeral retroversion is greater in the dominant shoulder than in the nondominant shoulder in baseball players. However, the effect of different baseball positions during childhood on humeral retroversion remains unknown. The purpose of this study was to investigate the following: (1) the relationship between humeral retroversion and baseball positions played during elementary and junior-high schools; (2) the association between humeral retroversion and the prevalence of pain during the medical checkup and self-reported history of injuries in the dominant shoulder or elbow.

METHODS

We enrolled 149 male high-school baseball players who started playing baseball in elementary school. The subjects were classified into 3 groups according to their baseball positions in elementary and junior-high schools. All participants completed questionnaires regarding their current and past positions, current incidence and history of injuries in their shoulder or elbow joints, and the age they started playing baseball. Shoulder range of motion, humeral retroversion on ultrasonographic-assisted measurement, and the association between humeral retroversion and shoulder and elbow pain were evaluated.

RESULTS

Humeral retroversion was significantly greater in the dominant shoulder than in the nondominant shoulder in all groups (P < .001). In addition, humeral retroversion in the dominant shoulder was significantly greater in players who were pitchers in both elementary and junior-high schools than in those who were fielders during both periods (96.2° and 89.4°, respectively; P = .02). Humeral retroversion in the dominant shoulder was positively correlated (P = .005, r = 0.23) with the length of career as a pitcher during elementary and junior-high schools. Humeral retroversion was not correlated with the prevalence of pain during the medical checkup or self-reported history of injuries in the dominant shoulder or elbow (P values ranging from 0.09-0.99).

CONCLUSION

These results suggest that playing baseball as a pitcher during elementary school and junior-high school affects the increase in humeral retroversion in the dominant shoulder. Increased humeral retroversion in the dominant shoulder by repetitive throwing motion is an adaptive change, rather than a pathologic change.

Characteristics of Femoral Torsion Angles and Relationships Between Femoral Torsion Angles and Hip Rotational Motion Variables in Adult Baseball Players

Background:

Abnormalities in hip rotational motion (HRM) are risk factors for throwing injuries. To evaluate hip rotational motion, it is necessary to assess the torsion angle. However, no studies have investigated the femoral torsion angle (FTA) in baseball players.

Purpose:

To investigate differences in hip FTA of adult baseball players through use of ultrasonography to evaluate the relationship between the FTA and HRM.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 149 elite male baseball players (mean age, 20.0 ± 1.8 years; 64 pitchers, 85 position players) were enrolled in this study. Ultrasonographic assessment of FTA was performed based on the tilting angles of the anterior surface of the femoral neck and condylar axis. The hip internal rotation (HIR) and hip external rotation (HER) were assessed at 0° and 90° of flexion. Data related to FTA and HRM were compared between hips and between pitchers and position players.

Results:

No significant difference was observed in the FTAs between hips for any player (lead hip, 20.5° ± 9.2°; trail hip, 19.6° ± 9.8°; P = .276). No significant difference was observed in FTAs of both hips between pitchers and position players (lead hip, 20.1° ± 9.4° and 20.9° ± 9.0°, respectively, P = .957; trail hip, 19.5° ± 9.8° and 19.7° ± 9.8°, P = .999). In terms of HER in 90° of hip flexion in both hips, significant differences were observed in HRM variables between pitchers and position players (lead hip, 33.0° ± 8.9° and 37.5° ± 9.8°, respectively, P = .024; trail hip, 35.6° ± 9.6° and 40.4° ± 10.2°, P = .035). Linear regression analysis revealed a significant agreement between the FTA and HIR at both 0° (R = 0.298, P < .001) and 90° of hip flexion (R = 0.279, P < .001).

Conclusion:

Our findings indicated that FTAs were not different between the hips of elite baseball players. Abnormalities of the HRM are not caused by differences in the FTA but rather involve soft tissue tightness around the hip area or other bony morphologic factors in the hip joint.

The influence of posture and scapulothoracic orientation on the choice of humeral component retrotorsion in reverse total shoulder arthroplasty

BACKGROUND

The literature suggests implantation of the humeral component in reverse total shoulder arthroplasty (RTSA) in 0°-40° of retrotorsion without further specification. We hypothesized that optimal humeral component retrotorsion to avoid notching and gain balanced rotational capacity would depend on scapular position and posture.

METHODS

We investigated 200 shoulders in 100 patients with available whole-body computed tomography scans and created 3-dimensional models. Implantation of a humeral component in 20° of retrotorsion was simulated, and a correction angle (CA) to yield perfect opposition to the glenosphere was calculated. Patient-specific variables such as age, sex, posture, and scapular orientation parameters were correlated with this CA.

RESULTS

Scapular orientation showed large interindividual differences. A highly significant correlation was seen between the CA and scapular internal rotation (R = 0.71, P < .001) and protraction (R = 0.39, P < .001). When the CA was adjusted for glenoid retroversion, the correlation coefficient of scapular internal rotation increased even further (R = 0.91, P < .001). Scapular internal rotation itself showed a correlation with thoracic kyphosis (R = 0.27, P < .001), protraction (R = 0.57, P < .001), tilt (R = 0.29, P < .001), and scapular translation (R = -0.23, P < .001).

CONCLUSION

Scapular orientation and posture should be integrated into the determination process of humeral component retrotorsion in RTSA. In theory, implantation of the humeral component with increased retrotorsion leads to improved neutral opposition of the RTSA components in patients with extensive internal rotation of the scapula. On the basis of varying scapular internal rotation, we propose the distinction of 3 different posture types (A-C) for enhanced appraisal of scapulothoracic orientation.

Ultrasonographic Assessment of Femoral Torsion Angle Based on Tilting Angles of Femoral Neck and Condylar Axis

Femoral anteversion has been assessed with ultrasound using femoral neck tilting angle (FN-TA); however, femoral torsion angle (FTA), which is defined using FN-TA and condylar axis tilting angle, has not been assessed with ultrasound. This study aimed to establish the ultrasonographic assessment of FTA (US-FTA) by comparing data obtained through US-FTA and computed tomography (CT). Twenty-one patients (age range, 38-82 y) with 21 intact hips were included. In the US-FTA, the femoral head and anterior tubercle of the greater trochanter were used as bony landmarks. The intra-rater and inter-rater reliabilities and standard error of measurement (SEM) of US-FTA were 0.994 (SEM 0.93) and 0.994 (SEM 0.94), respectively. A strong agreement was found between FTA variables obtained with ultrasound and CT (R = 0.939, p < 0.001). Ultrasound is useful and can be a valid alternative to CT for the evaluation of the femoral torsion angle without radiation exposure.