Improved joint function when reaching behind the back is associated with patient reported outcomes in individuals with rotator cuff tears following exercise therapy.

BACKGROUND: Reaching behind the back is painful for individuals with rotator cuff tears. The objectives of the study were to determine changes in glenohumeral kinematics when reaching behind the back, passive range of motion (RoM), patient reported outcomes and the relationships between kinematics and patient reported outcomes following exercise therapy. METHODS: Eighty-four individuals with symptomatic isolated supraspinatus tears were recruited for this prospective observational study. Glenohumeral kinematics were measured using biplane radiography during a reaching behind the back movement. Passive glenohumeral internal rotation and patient reported outcome measures were collected. Depending on data normality, appropriate tests were utilized to determine changes in variables. Spearman's correlations were utilized for associations, and Stuart-Maxwell tests for changes in distributions. FINDINGS: Maximum active glenohumeral internal rotation increased by 3.2° (P = 0.001), contact path length decreased by 5.5% glenoid size (P = 0.022), passive glenohumeral internal rotation RoM increased by 4.9° (P = 0.001), and Western Ontario Rotator Cuff Index and American Shoulder and Elbow Surgeons scores increased by 29.8 and 21.1 (P = 0.001), respectively. Changes in Western Ontario Rotator Cuff Index scores positively associated with changes in maximum active glenohumeral internal rotation and negatively associated with changes in contact path lengths (P = 0.008 and P = 0.006, respectively). INTERPRETATION: The reaching behind the back movement was useful in elucidating in-vivo mechanistic changes associated with patient reported outcomes. Glenohumeral joint function and patient reported outcomes improved, where changes in Western Ontario Rotator Cuff Index scores were associated with kinematics. These findings inform clinicians of functional changes following exercise therapy and new targetable treatment factors.

Individuals with rotator cuff tears unsuccessfully treated with exercise therapy have less inferiorly oriented net muscle forces during scapular plane abduction.

Exercise therapy for individuals with rotator cuff tears fails in approximately 25.0 % of cases. One reason for failure of exercise therapy may be the inability to strengthen and balance the muscle forces crossing the glenohumeral joint that act to center the humeral head on the glenoid. The objective of the current study was to compare the magnitude and orientation of the net muscle force pre- and post-exercise therapy between subjects successfully and unsuccessfully (e.g. eventually underwent surgery) treated with a 12-week individualized exercise therapy program. Twelve computational musculoskeletal models (n = 6 successful, n = 6 unsuccessful) were developed in OpenSim (v4.0) that incorporated subject specific tear characteristics, muscle peak isometric force, in-vivo kinematics and bony morphology. The models were driven with experimental kinematics and the magnitude and orientation of the net muscle force was determined during scapular plane abduction at pre- and post-exercise therapy timepoints. Subjects unsuccessfully treated had less inferiorly oriented net muscle forces pre- and post-exercise therapy compared to subjects successfully treated (p = 0.039 & 0.045, respectively). No differences were observed in the magnitude of the net muscle force (p > 0.05). The current study developed novel computational musculoskeletal models with subject specific inputs capable of distinguishing between subjects successfully and unsuccessfully treated with exercise therapy. A less inferiorly oriented net muscle force in subjects unsuccessfully treated may increase the risk of superior migration leading to impingement. Adjustments to exercise therapy programs may be warranted to avoid surgery in subjects at risk of unsuccessful treatment.

Do Intramedullary Screws Provide Adequate Fixation for Humeral and Ulnar Components in Total Elbow Arthroplasty? A Cadaveric Analysis.

PURPOSE: The objective of this study was to determine the structural properties of the cadaver bone-screw interface for cementless intramedullary screw fixation in the context of total elbow arthroplasty. METHODS: The intramedullary canals of seven humerus and seven ulna specimens from fresh-frozen cadavers were drilled using custom drill bits until the inner cortex was reached and then hand tapped for the corresponding thread size. Titanium screws were advanced into the tapped holes until securely seated. The bones were potted and then mounted on a uniaxial material testing machine. A tensile load was applied, and end-of-test elongation, failure load, energy absorbed, and stiffness were determined. End-of-test load and elongation were defined as the elongation and load experienced by the structure at 3,000 N or failure. Each specimen was inspected for evidence of pullout, loosening, or visible fractures. RESULTS: The end-of-test load and elongation for the humerus specimens were 2721 ± 738 N and 3.0 ± 0.9 mm, respectively. The ulna specimens reached 92% of the humerus specimens' end-of-test load at 2,514 ± 678 N and 120% of their end-of-test elongation (3.6 ± 0.6 mm). The stiffness of the humerus specimens was 1,077 ± 336 N/mm, which was 1.3 times greater than the stiffness of the ulna specimens (790 ± 211 N/mm). Lastly, the energy absorbed by the humerus samples was 3.6 ± 1.6 J, which was 92% of the energy absorbed by the ulna samples at 3.9 ± 1.1 J. One humerus and three ulnas failed before the end-of-test load of 3,000 N. Two failures were caused by screw pullout and two by bone fracture. CONCLUSIONS: Our findings demonstrate that intramedullary screw fixation is successful in withstanding forces that are greater than required for osseointegration. CLINICAL RELEVANCE: Uncemented fixation may be beneficial in elbow arthroplasty.

Greater tuberosity morphology is altered in individuals with symptomatic isolated supraspinatus tendon tears.

BACKGROUND: In the presence of an isolated supraspinatus tear, the force applied to the greater tuberosity is reduced, which may lead to bony morphologic changes. Thus, diagnostic or surgical identification of landmarks to properly repair the torn tendon might be difficult if the anatomy of the greater tuberosity is altered. The objectives of the study were to assess the presence of the superior, middle, and inferior facets of the greater tuberosity in individuals with symptomatic isolated supraspinatus tendon tears and the associations between tear size, tear location and presence of each facet. METHODS: Thirty-seven individuals with symptomatic isolated supraspinatus tendon tears were recruited to participate in the study. Individuals underwent a high-resolution computed tomography scan of the involved shoulder and images were segmented to generate subject specific models of each humerus. The vertices comprising each facet were identified; however, if even a single vertex comprising the facet was missing, the facet was considered altered. Percentage agreement for correctly identifying the presence of each facet was determined using 2 additional observers and 5 randomly selected humeri. Ultrasonography was performed to assess anterior-posterior (AP) tear size and tear location. Outcome parameters included presence of the superior, middle, and inferior facets; AP tear size; and tear location. Point-biserial correlations were used to determine the associations between AP tear size, tear location, and presence of the superior, middle, and inferior facets. RESULTS: Supraspinatus tear size and tear location was 13.1 ± 6.1 mm (range, 1.9-28.3 mm) and 2.0 ± 4.4 mm from the posterior edge of the long head of the biceps tendon (range, 0.0-19.0 mm), respectively. Overall, the superior, middle, and inferior facets were not altered in 24.3%, 29.7%, and 45.9% of individuals, respectively. Percentage agreement between observers was 83.4% on average. No associations were found between tear size or tear location and presence of the superior, middle, or inferior facet (P values ranged from .19 to .74). CONCLUSION: Individuals with symptomatic isolated supraspinatus tears experience significant alterations in the bony morphology of the greater tuberosity that were irrespective of supraspinatus tear size and location. This information is useful for radiologists and orthopedic surgeons as the altered anatomy may influence the ability to identify important anatomic landmarks during diagnostic imaging or surgical procedures.

Associations between range of motion, strength, tear size, patient-reported outcomes, and glenohumeral kinematics in individuals with symptomatic isolated supraspinatus tears.

BACKGROUND: Clinical failure associated with nonoperative treatment of rotator cuff tears may be due to inadequate characterization of the individual's functional impairments. Clinically, restricted passive range of motion (ROM) (restrictions imply capsular tightness), limitations in muscle strength, and larger rotator cuff tears are hypothesized to be related to altered glenohumeral kinematics. Understanding these relationships, as well as the relationship between glenohumeral kinematics and patient-reported outcomes (PROs) prior to exercise therapy, may help characterize functional impairments in individuals with rotator cuff tears. The objectives of the study were to describe the baseline presentation of individuals with an isolated supraspinatus tear, including passive ROM, rotator cuff muscle strength, tear size, PROs, and glenohumeral kinematics, and to determine associations among these variables. METHODS: One hundred one individuals with symptomatic isolated supraspinatus tears were recruited for the study and underwent assessments of passive glenohumeral ROM, isometric muscle strength, and ultrasonography to assess anterior-posterior tear size. Glenohumeral kinematics during scapular-plane abduction were measured using biplane radiography. Furthermore, PROs including the American Shoulder and Elbow Surgeons (ASES) score and the Western Ontario Rotator Cuff Index (WORC) score were collected. RESULTS: Individuals presented with decreased ROM, external rotation weakness compared with the uninvolved side, and pain and disability as measured by the ASES and WORC scores. These findings were not associated with glenohumeral kinematics, with the exception of a weak positive association between glenohumeral contact path lengths and WORC scores (ρ = 0.25, P = .03). Tear size was 11.7 ± 5.7 mm, and maximum anterior translation, superior translation, and contact path length were 3.0% ± 3.8% of glenoid width, 3.5% ± 3.8% of glenoid height, and 38.2% ± 20.7% of glenoid size, respectively. CONCLUSION: Individuals with a symptomatic isolated supraspinatus tear presented with decreased ROM, external rotation weakness, and pain and disability as measured by the ASES and WORC scores. However, no abnormal kinematics associated with these limitations were observed. Thus, given that the tear is isolated to the supraspinatus tendon and no capsular restrictions are present, normal function of the glenohumeral joint may be possible during scapular-plane abduction.