Preoperative planning with three-dimensional CT vs. three-dimensional magnetic resonance imaging does not change surgical management for shoulder instability.

Background: This study aims to determine the effect of time and imaging modality (three-dimensional (3D) CT vs. 3D magnetic resonance imaging (MRI)) on the surgical procedure indicated for shoulder instability. The hypothesis is there will be no clinical difference in procedure selection between time and imaging modality. Methods: Eleven shoulder surgeons were surveyed with the same ten shoulder instability clinical scenarios at three time points. All time points included history of present illness, musculoskeletal exam, radiographs, and standard two-dimensional MRI. To assess the effect of imaging modality, survey 1 included 3D MRI while survey 2 included a two-dimensional and 3D CT scan. To assess the effect of time, a retest was performed with survey 3 which was identical to survey 2. The outcome measured was whether surgeons made a "major" or "minor" surgical change between surveys. Results: The average major change rate was 14.1% (standard deviation: 7.6%). The average minor change rate was 12.6% (standard deviation: 7.5%). Between survey 1 to the survey 2, the major change rate was 15.2%, compared to 13.1% when going from the second to the third survey (P = .68). The minior change rate between the first and second surveys was 12.1% and between the second to third interview was 13.1% (P = .8). Discussion: The findings suggest that the major factor related to procedural changes was time between reviewing patient information. Furthermore, this study demonstrates that there remains significant intrasurgeon variability in selecting surgical procedures for shoulder instability. Lastly, the findings in this study suggest that 3D MRI is clinically equivalent to 3D CT in guiding shoulder instability surgical management. Conclusion: This study demonstrates that there is significant variability in surgical procedure selection driven by time alone in shoulder instability. Surgical decision making with 3D MRI was similar to 3D CT scans and may be used by surgeons for preoperative planning.

Total Hip Replacement Interrupted by Intraoperative Arrest with a Final Component in Place: A Case Report.

No consensus recommendations exist as to the management of implants exposed during an interrupted total hip arthroplasty (THA). Given the infrequency of such events, documentation of successful outcomes in single case reports aids in decision-making. A 71-year-old male with a history of coronary artery disease and a BMI of 39.5 went into ventricular fibrillation half-way through a THA, after placement of a cementless acetabular component but before femoral preparation could begin. Continuation of the planned arthroplasty was aborted, the patient's wound was packed with sterile sponges and covered with an iodoform dressing, and he was flipped supine for CPR. He returned to the OR 6-hours following his arrest and his arthroplasty was completed with the original acetabular implant left in place. The patient was placed empirically on 2 weeks of IV vancomycin and 3 months of oral doxycycline based on infectious disease recommendations, and healed uneventfully. While validation of our strategy is challenging due to the infrequent nature of this event, it is hoped that this description and discussion may provide a template to those who encounter a similar challenging situation.

Glenoid Version Assessment When the CT Field of View Does Not Permit the Friedman Method: The Robertson Method.

Background: To improve spatial resolution, current clinical shoulder cross-sectional imaging studies reduce the field of view of the shoulder, excluding the medial scapula border and preventing glenoid version measurement according to the Friedman method. Purpose: To evaluate a method to accurately and reliably measure glenoid version on cross-sectional shoulder images when the medial scapula border is not included in the field of view, and to establish measurements equivalent to the Friedman method. Study Design: Controlled laboratory study. Methods: Sixty-five scapulae underwent computed tomography (CT) scanning with an optimal shoulder CT-positioning protocol. Glenoid version was measured on CT images of the full scapula using the Friedman method. We developed a measurement method (named the Robertson method) based on the glenoid vault version from partial scapula images, with a correction angle subtracted from the articular-surface-glenoid vault measurement. Comparison with the Friedman method defined the accuracy of the Robertson method. Three observers tested inter- and intraobserver reliability of the Robertson method. Accuracy was statistically evaluated with t tests and reliability with the intraclass correlation coefficient (ICC). Results: The statistical distribution of glenoid version was similar to published data,-0.5° ± 3° [mean ± SD]. The initial measurement using the Robertson method resulted in a more retroverted angle compared with the Friedman method, and a correction angle of 7° was then applied. After this adjustment, the difference between the 2 methods was nonsignificant (0.1° ± 4°; P > .65). Reliability of the Robertson method was excellent, as the interrater ICC was 0.77, the standard error of measurement (SEM) was 1.1° with P < .001. The intrarater ICC ranged between 0.84 and 0.92, the SEM ranged between 0.9° and 1.2° with P < .01. Conclusion: A validated glenoid version measurement method is now available for current clinical shoulder CT protocols that reliably create Friedman-equivalent values. Clinical Relevance: Friedman-equivalent values may be made from common clinical CTs of the shoulder and compared with prior and future Friedman measurements of the scapula.

New-onset head and neck dermatitis in adolescent patients after dupilumab therapy for atopic dermatitis.

BACKGROUND/OBJECTIVES: Head and neck dermatitis after dupilumab therapy for atopic dermatitis has been frequently reported in adults and only rarely in adolescents. No cases detailing disease course and treatment response have previously been described in adolescents. METHODS/RESULTS: This case series presents five adolescent patients who developed new-onset or worsening head and neck dermatitis after dupilumab therapy for atopic dermatitis. All five patients improved after oral antifungal therapy. CONCLUSIONS: The clinical features, treatment response, and potential disease pathogenesis in pediatric patients are described. Adolescents with new-onset head and neck dermatitis after dupilumab therapy may clinically improve with antifungal therapy, suggesting that Malassezia species may be a contributing factor or antifungal therapy may be an effective antiinflammatory agent.

Surgical treatment for recurrent shoulder instability: factors influencing surgeon decision making.

BACKGROUND: The optimal surgical approach for recurrent anterior shoulder instability remains controversial, particularly in the face of glenoid and/or humeral bone loss. The purpose of this study was to use a contingent-behavior questionnaire (CBQ) to determine which factors drive surgeons to perform bony procedures over soft tissue procedures to address recurrent anterior shoulder instability. METHODS: A CBQ survey presented each respondent with 32 clinical vignettes of recurrent shoulder instability that contained 8 patient factors. The factors included (1) age, (2) sex, (3) hand dominance, (4) number of previous dislocations, (5) activity level, (6) generalized laxity, (7) glenoid bone loss, and (8) glenoid track. The survey was distributed to fellowship-trained surgeons in shoulder/elbow or sports medicine. Respondents were asked to recommend either a soft tissue or bone-based procedure, then specifically recommend a type of procedure. Responses were analyzed using a multinomial-logit regression model that quantified the relative importance of the patient characteristics in choosing bony procedures. RESULTS: Seventy orthopedic surgeons completed the survey, 33 were shoulder/elbow fellowship trained and 37 were sports medicine fellowship trained; 52% were in clinical practice ≥10 years and 48% <10 years; and 95% reported that the shoulder surgery made up at least 25% of their practice. There were 53% from private practice, 33% from academic medicine, and 14% in government settings. Amount of glenoid bone loss was the single most important factor driving surgeons to perform bony procedures over soft tissue procedures, followed by the patient age (19-25 years) and the patient activity level. The number of prior dislocations and glenoid track status did not have a strong influence on respondents' decision making. Twenty-one percent glenoid bone loss was the threshold of bone loss that influenced decision toward a bony procedure. If surgeons performed 10 or more open procedures per year, they were more likely to perform a bony procedure. CONCLUSION: The factors that drove surgeons to choose bony procedures were the amount of glenoid bone loss with the threshold at 21%, patient age, and their activity demands. Surprisingly, glenoid track status and the number of previous dislocations did not strongly influence surgical treatment decisions. Ten open shoulder procedures a year seems to provide a level of comfort to recommend bony treatment for shoulder instability.

Implementation of a pediatric provider-to-provider store-and-forward teledermatology system: Effectiveness, feasibility, and acceptability in a pilot study.

BACKGROUND/OBJECTIVES: Long wait times for in-person appointments in pediatric dermatology can lead to delays in specialty care, additional health system touchpoints, patient and family dissatisfaction, poorer outcomes, and increased overall health care costs. Store-and-forward teledermatology may address these challenges and improve access to care in pediatric dermatology. METHODS: We describe a prospective, non-blinded cohort study with follow-up surveys conducted from March 1, 2018, to September 20, 2018. The study was conducted at a single center, in primary care and specialist settings. Patients included were <18 years old and received care at one of our affiliated primary care sites. Primary care providers submitted teledermatology consultations through a shared electronic medical record. A board-certified pediatric dermatologist evaluated each consultation; primary care providers conveyed recommendations to families. RESULTS: Forty-three consultations for patients (23 male, 20 female; median age: 7 years [IQR: 2.4-12]) were entered by primary care providers. Median time from consult request to dermatologist initiating consult was 12.1 hours [IQR: 1.9-18.8]; median time to complete consult note was 7 minutes [IQR: 5-10.5]. Median time from primary care provider initially consulting to conveying teledermatology recommendations to families was 3 days [IQR: 1-5]. All but one consult (42/43, 98%) were completed in the intended workflow. Follow-up in-person visits with pediatric dermatologists occurred with 10/43 (23%) patients. In follow-up surveys, parents were 83% likely to recommend the service to family and friends. All primary care providers and dermatologists felt the service improved quality of care. CONCLUSIONS: Provider-to-provider teledermatology consultation appears to be a feasible and acceptable method of providing care quickly and effectively to pediatric patients.

Development and Initial Validation of a Multidimensional Acne Global Grading System Integrating Primary Lesions and Secondary Changes.

Importance: The qualitative grading of acne is important for routine clinical care and clinical trials, and although many useful systems exist, no single acne global grading system has had universal acceptance. In addition, many current instruments focus primarily on evaluating primary lesions (eg, comedones, papules, and nodules) or exclusively on signs of secondary change (eg, postinflammatory hyperpigmentation, scarring). Objectives: To develop and validate an acne global grading system that provides a comprehensive evaluation of primary lesions and secondary changes due to acne. Design, Setting, and Participants: This diagnostic study created a multidimensional acne severity feature space by analyzing decision patterns of pediatric dermatologists evaluating acne. Modeling acne severity patterns based on visual image features was then performed to reduce dimensionality of the feature space to a novel 2-dimensional grading system, in which severity levels are functions of multidimensional acne cues. The system was validated by 6 clinicians on a new set of images. All images used in this study were taken from a retrospective, longitudinal data set of 150 patients diagnosed with acne, ranging across the entire pediatric population (aged 0-21 years), excluding images with any disagreement on their diagnosis, and selected to adequately span the range of acne types encountered in the clinic. Data were collected from July 1, 2001, through June 30, 2013, and analyzed from March 1, 2015, through December 31, 2016. Main Outcomes and Measures: Prediction performance was evaluated as the mean square error (MSE) with the clinicians' scores. Results: The scale was constructed using acne visual features and treatment decisions of 6 pediatric dermatologists evaluating 145 images of patients with acne ranging in age from 0 to 21 years. Using the proposed scale to predict the severity scores on a new set of 40 images achieved an overall MSE of 0.821, which is smaller than the mean within-clinician differences (MSE of 0.998). Conclusions and Relevance: By integrating primary lesions and secondary changes, this novel acne global grading scale provides a more clinically relevant evaluation of acne that may be used for routine clinical care and clinical trials. Because the severity scores are based on actual clinical practice, this scoring system is also highly correlated with appropriate treatment choices.

Wait times, health care touchpoints, and nonattendance in an academic pediatric dermatology clinic.

BACKGROUND AND OBJECTIVES: Timely access to pediatric dermatology care remains a challenge. While awaiting appointments, many patients and families utilize so-called health care touchpoints outside of the dermatology clinic such as primary care or emergency department visits to address dermatologic concerns. Long waiting periods also factor into nonattendance rates at pediatric dermatology appointments. This observational retrospective study investigated wait times, relevant health care touchpoints, and factors related to nonattendance at a pediatric dermatology clinic. METHODS: We reviewed demographic, health care touchpoint, and nonattendance data for patients referred by a primary care affiliate to the Children's Hospital of Philadelphia (CHOP) pediatric dermatology clinic from February 2016 to May 2017. Descriptive statistics were used to identify trends among analyzed variables. RESULTS: We reviewed 250 patient records. The average number of touchpoints per patient was 0.56, and factors that significantly correlated with increased numbers of touchpoints included younger patient age and longer wait time while payer, primary diagnosis, and time of year were not associated. The nonattendance rate was 26%, and factors significantly associated with increased nonattendance rate included longer wait times and winter and spring appointments. CONCLUSION: Long wait times impact numbers of touchpoints and appointment attendance rate when referring to pediatric dermatology. A platform such as teledermatology may represent an opportunity to improve access to care by allowing for earlier input from the pediatric dermatologist.

Unilateral hypertrophy of the labia minora: A case series.

Asymmetric hypertrophy of the labia minora is a variant of normal anatomy that has not been described in the pediatric dermatology literature. Although often asymptomatic, in some cases, it can cause functional, emotional, and psychological problems. We report the clinical characteristics and outcomes of four children who presented with unilateral labium minus hypertrophy. This case series aims to establish awareness of this condition among pediatric dermatologists and provide recommendations regarding management.

Diagnostic Accuracy of Pediatric Teledermatology Using Parent-Submitted Photographs: A Randomized Clinical Trial.

Importance: Advances in smartphone photography (both quality and image transmission) may improve access to care via direct parent-to-clinician telemedicine. However, the accuracy of diagnoses that are reliant on parent-provided photographs has not been formally compared with diagnoses made in person. Objective: To assess whether smartphone photographs of pediatric skin conditions taken by parents are of sufficient quality to permit accurate diagnosis. Design, Setting, and Participants: A prospective study was conducted among 40 patient-parent dyads at a pediatric dermatology clinic at the Children's Hospital of Philadelphia from March 1 to September 30, 2016, to assess concordance between diagnoses made by an independent pediatric dermatologist based on in-person examination and those based on parental photographs. Half of the patient-parent dyads were randomized for a secondary analysis to receive instructions on how best to take photographs with smartphones. Clinicians were blinded to whether parents had received photography instructions. Exposures: Half of the patient-parent dyads received a simple, 3-step instruction sheet on how best to take photographs using a smartphone (intervention group); the other half did not (control group). Main Outcomes and Measures: Concordance between photograph-based vs in-person diagnosis in the intervention vs control groups, as quantified using Cohen κ, a measure of interrater agreement that takes into account the possibility of agreement occurring by chance. Results: Among the 40 patient-parent dyads (22 female children and 18 male children; mean [SD] age, 6.96 [5.23] years), overall concordance between photograph-based vs in-person diagnosis was 83% (95% CI, 71%-94%; κ = 0.81). Diagnostic concordance was 89% (95% CI, 75%-97%; κ = 0.88) in a subgroup of 37 participants with photographs considered of high enough quality to make a diagnosis. No statistically significant effect of photography instructions on concordance was detected (group that received instructions, 85%; group that did not receive instructions, 80%; P = .68). In cases of diagnostic disagreement, appropriate follow-up was suggested. Conclusions and Relevance: Parent-operated smartphone photography can accurately be used as a method to provide pediatric dermatologic care. Trial Registration: clinicaltrials.gov Identifier: NCT03246945.

Outcomes of tenodesis of the long head of the biceps tendon more than three months after rupture.

AIM: To demonstrate that long head of the biceps tendon (LHBT) tenodesis is possible more than 3 mo after rupture. METHODS: From September 2009 to January 2012 we performed tenodesis of the LHBT in 11 individuals (average age 56.9 years, range 42 to 73) more than 3 mo after rupture. All patients were evaluated by Disabilites of the Arm Shoulder and Hand (DASH) and Mayo outcome scores at an average follow-up of 19.1 mo. We similarly evaluated 5 patients (average age 58.2 years, range 45 to 64) over the same time treated within 3 mo of rupture with an average follow-up of 22.5 mo. RESULTS: Tenodesis with an interference screw was possible in all patients more than 3 mo after rupture and 90% had good to excellent outcomes but two had recurrent rupture. All of those who had tenodesis less than 3 mo after rupture had good to excellent outcomes and none had recurrent rupture. No statistical difference was found for DASH and Mayo outcome scores between the two groups (P <0.05). CONCLUSION: Tenodesis of LHBT more than 3 mo following rupture had outcomes similar to tenodesis done within 3 mo of rupture but recurrent rupture occurred in 20%.

Magnesium ring device to restore function of a transected anterior cruciate ligament in the goat stifle joint.

A bioresorbable, mono-crystalline magnesium (Mg) ring device and suture implantation technique were designed to connect the ends of a transected anterior cruciate ligament (ACL) to restabilize the knee and load the ACL to prevent disuse atrophy of its insertion sites and facilitate its healing. To test its application, cadaveric goat stifle joints were evaluated using a robotic/universal force-moment sensor testing system in three states: Intact, ACL-deficient, and after Mg ring repair, at 30°, 60°, and 90° of joint flexion. Under a 67-N anterior tibial load simulating that used in clinical examinations, the corresponding anterior tibial translation (ATT) and in-situ forces in the ACL and medial meniscus for 0 and 100 N of axial compression were obtained and compared with a control group treated with suture repair. In all cases, Mg ring repair reduced the ATT by over 50% compared to the ACL-deficient joint, and in-situ forces in the ACL and medial meniscus were restored to near normal levels, showing significant improvement over suture repair. These findings suggest that Mg ring repair could successfully stabilize the joint and load the ACL immediately after surgery, laying the framework for future in vivo studies to assess its utility for ACL healing. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2001-2008, 2016.

Structure modeling of the glenoid: Relevance to shoulder arthroplasty.

We applied shape modeling and principal component analysis (PCA) to discover glenoid bone structural relationships relevant to improving glenoid prosthesis features, fixation, and instrumentation. Knowledge of external bone morphology guides prosthesis shape and positioning, while internal bone morphology and bone density influence fixation. CT-based modeling defined nonarthritic glenoid subchondral bone surface and internal structure. First and second principal shape components were related to size and density. Reproducible structural parameters and glenoid feature relationships were discovered. Subchondral bone surface was approximated by a circle inferiorly and a triangle superiorly with the circle's center at a reproducible point along a superior-inferior line. Glenoid vault's maximum depth was at the circle's center, and the highest bone density was in posterior glenoid. Glenoid subchondral bone surface version varied from superior to inferior, but not by sex or side. Male subchondral bone surfaces were larger and more retroverted. Even if subchondral bone surfaces are deformed by arthritis, glenoid morphology can be identified by extra-articular landmarks, permitting location of the glenoid center and scapular orientation (glenoid version). Knowledge obtained from this study directs design of novel prosthesis features and instrumentation for use without pre-op CT or computer aided surgery.

What is the prevalence of senior-athlete rotator cuff injuries and are they associated with pain and dysfunction?

BACKGROUND: Older individuals with rotator cuff injuries may have difficulties not only with activities of daily living, but also with sports activities. QUESTIONS/PURPOSES: (1) How frequent and severe are rotator cuff abnormalities, as identified by ultrasound, in senior athletes? (2) To what degree does the severity of ultrasound-identified rotator cuff pathology correlate with pain and shoulder dysfunction? METHODS: We assessed pain and shoulder function in 141 elite athletes older than 60 years of age (median age, 70 years; range 60-84) at the Senior Olympics who volunteered to participate. An ultrasound evaluation of the rotator cuff of the dominant shoulder was performed by an experienced musculoskeletal radiologist in all of these elite athletes. We then determined the relationship between ultrasound findings and shoulder pain and shoulder function as assessed with the Disabilities of the Arm, Shoulder and Hand (DASH) and American Shoulder and Elbow Surgeons (ASES) scores. RESULTS: There were 20 shoulders with a normal cuff (14.2% [20 of 141], of which 5% [one of 20] were painful), 23 with tendinosis (16.3% [23 of 141], of which 30% [six of 20] were painful), 68 with a partial-thickness rotator cuff tear (48.2% [68 of 141], of which 32% [20 of 63] were painful), and 30 with a full-thickness rotator cuff tear (21.3% [30 of 141], of which 25% [seven of 28] were painful). Only 5% of athletes (one of 20) with a normal cuff on ultrasound evaluation reported shoulder pain, whereas 30% of athletes (33 of 111) with any degree of rotator cuff damage on ultrasound evaluation reported shoulder pain, This resulted in an odds ratio of 8.0 (95% confidence interval, 1.0-62.5). The proportion of patients who had pain was not different in those with different severities of rotator cuff pathology. Neither the ASES nor the DASH was different in those with different severities. CONCLUSIONS: The frequency of full-thickness rotator cuff tears in senior athletes was 21.3% (30 of 141). Pain was a predictor of rotator cuff injury but not of its severity. The odds of having shoulder pain was eight times greater in those athletes with any rotator cuff damage as compared with those without any rotator cuff damage. Those with pain had poorer shoulder function but the ASES and DASH were poor predictors of the severity of rotator cuff pathology. Rotator cuff tears in older individuals are often not painful and may not need to be repaired for successful participation in athletics. LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Collagen fiber alignment and maximum principal strain in the glenohumeral capsule predict location of failure during uniaxial extension.

The glenohumeral joint is frequently dislocated resulting in injury to the glenohumeral capsule. Repair techniques that focus on restoring the capsule after dislocation to re-establish its stabilizing function could benefit from predictions of the location of failure in this continuous sheet of tissue with a random collagen fiber alignment in the unloaded state. Therefore, the objective of this study was to determine the collagen fiber alignment and maximum principal strain in all regions of the capsule during uniaxial extension to failure and to determine whether these parameters could predict the location of tissue failure. Collagen fiber alignment, quantified using a small-angle light-scattering device, and maximum principal strain in the capsule were determined at 5% increments of elongation until tissue failure. A contingency table analyzed with Fischer's exact test demonstrated that peak collagen fiber alignment, represented by the normalized orientation index (p < 0.001) and maximum principal strain (p < 0.001), is significant in predicting location of failure. The direct correlation between the maximum principal strain and collagen fiber alignment measured prior to failure to the location of tissue failure suggests these parameters can be used as a predictive tool to help locate the areas of the glenohumeral capsule that are susceptible to failure. In the future, changes in collagen fiber alignment following injury could be used to develop a constitutive model for injured capsular tissue.

Changes to the mechanical properties of the glenohumeral capsule during anterior dislocation.

The glenohumeral joint is the most frequently dislocated major joint in the body, and instability due to permanent deformation of the glenohumeral capsule is a common pathology. The corresponding change in mechanical properties may have implications for the ideal location and extent of plication, which is a common clinical procedure used to repair the capsule. Therefore, the objective of this study was to quantify the mechanical properties of four regions of the glenohumeral capsule after anterior dislocation and compare the properties to the normal glenohumeral capsule. Six fresh-frozen cadaveric shoulders were dislocated in the anterior direction with the joint in the apprehension position using a robotic testing system. After dislocation, mechanical testing was performed on the injured glenohumeral capsule by loading the tissue samples in tension and shear. An inverse finite element optimization routine was used to simulate the experiments and obtain material coefficients for each tissue sample. Cauchy stress-stretch curves were then generated to represent the mechanical response of each tissue sample to theoretical loading conditions. Based on several comparisons (average of the material coefficients, average stress-stretch curve for each region, and coefficients representing the average curves) between the normal and injured tissue samples, the mechanical properties of the injured tissue samples from multiple regions were found to be lower than those of the normal tissue in tension but not in shear. This finding indicates that anterior dislocation primarily affects the tensile behavior of the glenohumeral capsule rather than the shear behavior, and this phenomenon could be caused by plastic deformation of the matrix, permanent collagen fiber rotation, and/or collagen fiber failure. These results suggest that plication and suturing may not be sufficient to return stability to the shoulder after dislocation in all individuals. Thus, surgeons may need to perform a procedure that reinforces or stiffens the tissue itself, such as reconstruction or augmentation, to improve repair procedures.

Effects of external rotation on anteroposterior translations in the shoulder: a pilot study.

BACKGROUND: Using physical examination to make the diagnosis of shoulder instability can be difficult, because typical examination maneuvers are qualitative, difficult to standardize, and not reproducible. Measuring shoulder translation is especially difficult, which is a particular problem, because measuring it inaccurately may result in improper treatment of instability. QUESTIONS/PURPOSES: The objective of this study was to use a magnetic motion tracking system to quantify the effects of external rotation of the abducted shoulder on a simulated simple translation test in healthy subjects. Specifically, we hypothesized that (1) increasing external rotation of the abducted shoulder would result in decreasing translation; (2) intraobserver repeatability would be less than 2 mm at all external rotation positions; and (3) mean side-to-side differences would be less than 2 mm at all external rotation positions. METHODS: The intraobserver repeatability and side-to-side differences of AP translation were quantified with a noninvasive magnetic motion tracking system and automated data analysis routine in nine healthy subjects at four positions of external rotation with the arm abducted. A shoulder positioning apparatus was used to maintain the desired arm position. RESULTS: No differences in translations between the positions of external rotation were found (p = 0.48). Intraobserver repeatability was 1.1 mm (SD, 0.8 mm) and mean side-to-side differences were small: 2.7 mm (SD, 2.8 mm), 2.8 mm (SD, 1.8 mm), 2.5 mm (SD, 1.8 mm), and 4.0 mm (SD, 2.6 mm) at 0°, 20°, 40°, and 60° of external rotation, respectively. CONCLUSIONS: The intraobserver repeatability was strong and the side-to-side differences in translation were small with the magnetic motion tracking system, which is encouraging for development of an improved quantitative test to assess shoulder translation for fast and low-cost diagnosis of shoulder instability. CLINICAL RELEVANCE: Clinicians may not have to position the contralateral, normal, abducted shoulder in precisely the same position of external rotation as the injured shoulder while performing side-to-side comparisons.