A novel 3D MRI-based approach for assessing supraspinatus muscle length.

Rotator cuff (RC) tears are a common source of pain and decreased shoulder strength. Muscle length is known to affect muscle strength, and therefore evaluating changes in supraspinatus muscle length associated with RC pathology, surgical repair, and post-operative recovery may provide insights into functional deficits. Our objective was to develop a reliable MRI-based approach for assessing supraspinatus muscle length. Using a new semi-automated approach for identifying 3D location of the muscle-tendon junction (MTJ), supraspinatus muscle length was calculated as the sum of MTJ distance (distance between 3D MTJ position and glenoid plane) and supraspinatus fossa length (distance between root of the scapular spine and glenoid plane). Inter- and intra-operator reliability of this technique were assessed with intraclass correlation coefficient (ICC) and found to be excellent (ICCs > 0.96). Muscle lengths of 6 patients were determined before RC repair surgery and at 3- and 12-months post-surgery. Changes in normalized muscle length (muscle length as a percentage of pre-surgical muscle length) at 3 months post-surgery varied considerably across patients (16.1 % increase to 7.0 % decrease) but decreased in all patients from 3- to 12-months post-surgery (0.3 % to 17.2 %). This study developed a novel and reliable approach for quantifying supraspinatus muscle length and provided preliminary demonstration of its utility by assessing muscle length changes associated with RC pathology and surgical repair. Future studies can use this technique to evaluate changes over time in supraspinatus muscle length in response to clinical intervention, and associations between muscle length and shoulder function.

Intervertebral kinematics during neck motion 6.5 years after fusion and artificial disc replacement.

BACKGROUND: Arthroplasty with artificial disc replacement for surgical treatment of cervical spine degeneration was introduced with the notion that motion-preserving approaches would prevent development of adjacent segment disease. Though clinical outcomes favor arthroplasty over the commonly used anterior cervical discectomy with fusion approach, clinical studies confirming the biomechanical basis of these results are lacking. The aim of this study was to compare intervertebral kinematics between arthroplasty and fusion patients 6.5 years post-surgery during physiological motion of the neck. METHODS: Using a biplane dynamic X-ray system, computed tomography imaging and model based tracking algorithms, three dimensional intervertebral kinematics were measured during neck axial rotation and extension in 14 patients treated for cervical radiculopathy with fusion (n = 8) or arthroplasty (n = 6). The measurements were performed at 2-year (baseline) and 6.5 year post-surgical time points, with the main interest being in the interaction between surgery types and time points. 3 translations and 3 rotations were investigated for the index (C5C6), and upper- (C4C5) and lower adjacent levels (C6C7). FINDINGS: Surgery-time interaction was significant for axial rotation (P < 0.04) and flexion-extension rotation (P < 0.005) in C4C5 during neck axial rotation, left-right translation (P < 0.04) in C5C6 and anterior-posterior translation in C6C7 (P < 0.04) during neck extension. In contrast with the expectations, axial rotation and flexion-extension decreased in C4C5 during neck rotation and anterior-posterior translation decreased in C6C7 during neck extension for fusion. INTERPRETATION: The findings do not support the notion that adjacent segment motion increases after fusion.

In Vivo Static Retraction and Dynamic Elongation of Rotator Cuff Repair Tissue After Surgical Repair: A Preliminary Analysis at 3 Months.

Background: Rotator cuff repair is a common orthopaedic procedure that provides pain relief for many patients, but unfortunately, an estimated 20% to 70% of repair procedures will fail. Previous research has shown that elongation (ie, retraction) of a repaired tendon is common even in patients with a repair construct that appears intact on magnetic resonance imaging. However, it is unknown how this repair tissue functions under dynamic conditions. Purpose: To quantify static retraction and maximum dynamic elongation of repair tissue after rotator cuff repair. Study Design: Case series; Level of evidence, 4. Methods: Data from 9 patients were analyzed for this study. During surgery, a 3.1-mm tantalum bead was sutured to the supraspinatus tendon, medial to the repair site. Glenohumeral kinematics were assessed at 1 week (static) and 3 months (static and during scapular-plane abduction) after surgery using a biplanar videoradiographic system. The 3-dimensional position of the bead was calculated relative to the tendon's insertion on the humerus (ie, bead-to-insertion distance). Static retraction was calculated as the change in the bead-to-insertion distance under static conditions between 1 week and 3 months after surgery, and maximum dynamic elongation was calculated as the maximal positive change in the bead-to-insertion distance during dynamic motion relative to the start of motion. The magnitudes of static retraction and maximum dynamic elongation were assessed with 1-sample t tests. Results: At 3 months after surgery, static retraction occurred in all patients by a mean of 10.0 ± 9.1 mm (P = .01 compared with no elongation). During scapular-plane abduction, maximum dynamic elongation averaged 1.4 ± 1.0 mm (P < .01 compared with no elongation). Descriptively, dynamic elongation consistently took 1 of 2 forms: an initial increase in the bead-to-insertion distance (mean, 2.0 ± 0.6 mm) before decreasing until the end of motion or an immediate and substantial decrease in the bead-to-insertion distance at the onset of motion. Conclusion: Repair tissue elongation (static retraction and maximum dynamic elongation) appeared to be a common and significant finding at 3 months after arthroscopic rotator cuff repair. Dynamic elongation of repair tissue during scapular-plane abduction exhibited 1 of 2 distinct patterns, which may suggest different patterns of supraspinatus mechanical and neuromuscular function.

Presurgical tear characteristics and estimated shear modulus as predictors of repair integrity and shoulder function one year after rotator cuff repair.

BACKGROUND: Rotator cuff repair provides pain relief for many patients; however, retears are relatively common and affect approximately 20%-70% of patients after repair. Although magnetic resonance imaging (MRI) offers the ability to assess tissue characteristics such as tear size, retraction, and fatty infiltration, it provides little insight into the quality of the musculotendinous tissues the surgeon will encounter during surgery. However, shear wave elastography (SWE) could provide an indirect assessment of quality (ie, stiffness) by measuring the speed of shear waves propagating through tissue. The objective of this study was to determine the extent to which estimated shear modulus predicts repair integrity and functional outcomes 1 year after rotator cuff repair. METHODS: Thirty-three individuals scheduled to undergo arthroscopic rotator cuff repair were enrolled in this study. Before surgery, shear modulus of the supraspinatus tendon and muscle was estimated using ultrasound SWE. MRIs were obtained before and 1 year after surgery to assess tear characteristics and repair integrity, respectively. Shoulder strength, range of motion, and patient-reported pain and function were assessed before and after surgery. Functional outcomes were compared between groups and across time using a two-factor mixed model analysis of variance. Stepwise regression with model comparison was used to investigate the extent to which MRI and shear modulus predicted repair integrity and function at 1 year after surgery. RESULTS: At 1 year after surgery, 56.5% of patients had an intact repair. No significant differences were found in any demographic variable, presurgical tear characteristic, or shear modulus between patients with an intact repair and those with a recurrent tear. Compared with presurgical measures, patients in both groups demonstrated significant improvements at 1 year after surgery in pain (P < .01), self-reported function (P < .01), range of motion (P < .01), and shoulder strength (P < .01). In addition, neither presurgical MRI variables (P > .16) nor shear modulus (P > .52) was significantly different between groups at 1 year after surgery. Finally, presurgical shear modulus generally did not improve the prediction of functional outcomes above and beyond that provided by MRI variables alone (P > .22). CONCLUSION: Although SWE remains a promising modality for many clinical applications, this study found that SWE-estimated shear modulus did not predict repair integrity or functional outcomes at 1 year after surgery, nor did it add to the prediction of outcomes above and beyond that provided by traditional presurgical MRI measures of tear characteristics. Therefore, it appears that further research is needed to fully understand the clinical utility of SWE for musculoskeletal tissue and its potential use for predicting outcomes after surgical rotator cuff repair.

Quantifying shoulder activity after rotator cuff repair: Technique and preliminary results.

Repair tissue healing after rotator cuff repair remains a significant clinical problem, and excessive shoulder activity after surgical repair is believed to contribute to re-tears. In contrast, small animal studies have demonstrated that complete removal of activity impairs tendon healing and have advocated for an "appropriate" level of activity, but in humans the appropriate amount of shoulder activity to enhance healing is not known. As an initial step toward understanding the relationship between postoperative shoulder activity and repair tissue healing, the objectives of this study were to assess the precision, accuracy, and feasibility of a wrist-worn triaxial accelerometer for measuring shoulder activity. Following assessments of precision (±0.002 g) and accuracy (±0.006 g), feasibility was assessed by measuring 1 week of shoulder activity in 14 rotator cuff repair patients and 8 control subjects. Shoulder activity was reported in terms of volume (mean acceleration, activity count, mean activity index, active time) and intensity (intensity gradient). Patients had significantly less volume (p ≤ .03) and intensity (p = .01) than controls. Time post-surgery was significantly associated with the volume (p ≤ .05 for mean acceleration, activity count, and mean activity index) and intensity (p = .03) of shoulder activity, but not active time (p = .08). These findings indicate this approach has the accuracy and precision necessary to continuously monitor shoulder activity with a wrist-worn sensor. The preliminary data demonstrate the ability to discriminate between healthy control subjects and patients recovering from rotator cuff repair and provide support for using a wearable sensor to monitor changes over time in shoulder activity.

Variability of glenohumeral positioning and bone-to-tendon marker length measurements in repaired rotator cuffs from longitudinal computed tomographic imaging.

BACKGROUND: To address the need for more objective and quantitative measures of tendon healing in research studies, we intend to use computed tomography (CT) with implanted radiopaque markers on the repaired tendon to measure tendon retraction following rotator cuff repair. In our small prior study, retraction at 1-year follow-up averaged 16.1± 5.3 mm and exceeded 10.0 mm in 12 of 13 patients, and thus tendon retraction appears to be a common clinical phenomenon. This study's objectives were to assess, using 5 longitudinal CT scans obtained over 1 year following rotator cuff repair, the variability in glenohumeral positioning because of pragmatic variations in achieving perfect arm repositioning and to estimate the associated measurement variability in bone-to-tendon marker length measurements. METHODS: Forty-eight patients underwent rotator cuff repair with intraoperative placement of radiopaque tendon markers at the repair site. All patients had a CT scan with their arms at the side on the day of surgery and at 3, 12, 26, and 52 weeks postoperatively. Glenohumeral position (defined by the orientation and distance of the humerus with respect to the scapula) and bone-to-tendon marker lengths were measured from each scan. Within-patient variation in glenohumeral position measurements was described by their pooled within-patient standard deviations (SDs), and variation in bone-to-tendon marker lengths by their standard errors of measurement (SEMs) and 95% confidence level minimally detectable distances (MDD95) and changes (MDC95). RESULTS: The mean glenohumeral orientation from the 5 longitudinal CT scans averaged across the 48 patients was 12.6° abduction, 0.4° flexion, and -0.1° internal rotation. Within-patient SDs (95% confidence intervals) of glenohumeral orientation were 3.0° (2.7°-3.4°) in extension/flexion, 5.2° (4.6°-5.8°) in abduction/adduction, and 8.2° (7.3°-9.2°) in internal/external rotation. The SDs of glenohumeral distances were less than 1 mm in any direction. The estimated SEMs of bone-to-tendon lengths were consistent with a common value of 2.4 mm for any of the tendon markers placed across the repair, with MDD95 of 4.7 mm and MDC95 of 6.7 mm. CONCLUSION: Apparent tendon retraction of 5 mm or more, when measured as the distance from a tendon marker's day of surgery location to its new location on a volumetrically registered longitudinal CT scan, may be considered above the usual range of measurement variation. Tendon retraction measured using implanted radiopaque tendon markers offers an objective and sufficiently reliable means for quantifying the commonly expected changes in structural healing following rotator cuff repair.

Dynamic foraminal dimensions during neck motion 6.5 years after fusion and artificial disc replacement.

OBJECTIVE: To compare changes in foraminal motion at two time points post-surgery between artificial disc replacement (ADR) and anterior cervical discectomy and fusion (ACDF). METHODS: Eight ACDF and 6 ADR patients (all single-level C5-6) were tested at 2 years (T1) and 6.5 years (T2) post-surgery. The minimum foraminal height (FH.Min) and width (FW.Min) achieved during neck axial rotation and extension, and the range of these dimensions during motion (FH.Rn and FW.Rn, respectively) were measured using a biplane dynamic x-ray system, CT imaging and model-based tracking while patients performed neck axial rotation and extension tasks. Two-way mixed ANOVA was employed for analysis. RESULTS: In neck extension, significant interactions were found between year post-surgery and type of surgery for FW.Rn at C5-6 (p<0.006) and C6-7 (p<0.005), and for FH.Rn at C6-7 (p<0.01). Post-hoc analysis indicated decreases over time in FW.Rn for ACDF (p<0.01) and increases in FH.Rn for ADR (p<0.03) at the C6-7 adjacent level. At index level, FW.Rn was comparable between ACDF and ADR at T1, but was smaller for ACDF than for ADR at T2 (p<0.002). In axial rotation, differences were found between T1 and T2 but did not depend on type of surgery (p>0.7). CONCLUSIONS: Changes were observed in the range of foraminal geometry at adjacent levels from 2 years to 6.5 years post-surgery that were different between ACDF and ADR for neck extension. These changes are contrary to the notion that motion at adjacent levels continue to increase following ACDF as compared to ADR over the long term.

Correlation of neural foraminal motion after surgical treatment of cervical radiculopathy with long-term patient reported outcomes.

BACKGROUND: Post-surgical changes in adjacent segment motion are considered a factor in further development of degeneration and cervical radiculopathy. The objective was to examine the extent of correlations between physiological motion of cervical foramina and long-term patient reported outcomes (PRO). METHODS: Biplane X-ray imaging and CT-based markerless tracking were used to measure 3D static and dynamic dimensions during neck axial rotation and extension from 18 patients treated for C5-6 radiculopathy with fusion or arthroplasty. Minimum foraminal height (FH.Min) and width (FW.Min), and their range (FH.Range and FW.Range) achieved during a motion task were calculated for adjacent levels (C4-5 and C6-7) at 2.0±0.6 years post-surgery. The modified Japanese Orthopedic Association score (mJOAS), the Neck Disability Index (NDI) including the visual analogue scale (VAS) for neck and arm pain, and the EuroQol EQ-5D score were recorded at 6.5±1.1 years post-surgery. The relationships between 6.5-year outcomes and 2-year foraminal motion were examined using regression. RESULTS: Worsening patient-reported outcomes were generally associated with lower values of FW.Min (P<0.05 to P<0.008), the associations being stronger for neck extension (r2 up to 0.43). Dynamic foraminal measurements from the C6-7 level more significantly and consistently correlated with mJOAS, EQ-5D and NDI Arm Pain VAS (r2=0.27 to 0.43; P<0.03 to P<0.008), whereas those from the C4-5 level correlated with NDI Neck Pain VAS (r2=0.33; P<0.02). CONCLUSIONS: Dynamic 3D foraminal dimensions at 2-year post-surgery, notably FW.Min measured in neck extension at adjacent levels, were associated with PRO at 6.5 years post-surgery. These relationships provide insight into the motion related factors in development of pain and loss of function, and may help develop markers or objective outcome measures.

Shear wave elastography of the healing human patellar tendon following ACL reconstruction.

PURPOSE: Anterior cruciate ligament (ACL) ruptures are common and are frequently reconstructed using a patellar tendon (PT) autograft. Unfortunately, the time course of PT healing after ACL reconstruction is not particularly well understood. Thus, the primary objective of this study was to use shear wave elastography (SWE) to evaluate the extent to which shear wave speed (SWS) is associated with time after ACL reconstruction. METHODS: Longitudinal SWE images were acquired from lateral, central, and medial regions of the PT from two groups: 30 patients who had undergone ACL reconstruction with a PT autograft within the preceding 40 months, and 30 age-matched asymptomatic control subjects. SWE images were acquired at 20° and 90° of passive flexion from both knees. In each subject group, statistical analyses assessed changes in mean SWS with time post-surgery, as well as differences in mean SWS between PT regions and limbs. RESULTS: In the ACL reconstruction patients, mean SWS increased with time post-surgery in the lateral region of the involved knee (p = 0.025) and decreased with time post-surgery in the central region of the contralateral knee (p = 0.022). CONCLUSION: The findings suggest that there is an association between the mechanical properties of the PT and time post-surgery in both the involved and contralateral limbs after ACL reconstruction. These changes are likely due to maturation of the donor site tissue and changes in gait/loading patterns following ACL rupture and reconstruction. LEVEL OF EVIDENCE: Level II - Prospective Cohort.

Dynamic foraminal dimensions during neck extension and rotation in fusion and artificial disc replacement: an observational study.

BACKGROUND: Changes in the dimensions of the cervical neural foramina (CNF) are considered to be a key factor in nerve root compression and development of cervical radiculopathy. However, to what extent foraminal geometry differs between patients who underwent anterior cervical discectomy and fusion (ACDF) and those who underwent total disc arthroplasty with an artificial disc (AD) during physiological motion is largely unknown. PURPOSE: The objective of this study is to compare CNF dimensions during physiological neck motion between ACDF and AD. STUDY DESIGN/SETTING: This is a retrospective comparative analysis of prospectively collected, consecutive, non-randomized series of patients at a single institution. PATIENT SAMPLE: A total of 16 single-level C5-C6 ACDF (4 males, 12 females; 28-71 years) and 7 single-level C5-C6 cervical arthroplasty patients (3 males, 4 females; 38-57 years), at least 12 months after surgery (23.6±6.8 months) were included. OUTCOME MEASURES: Patient demographics, preoperative magnetic resonance imaging (MRI)-based measurements of cervical spine degeneration, and 2-year postoperative measurements of dynamic foraminal geometry were the outcome measures. METHODS: Biplane X-ray images were acquired during axial neck rotation and neck extension. A computed tomography scan was also acquired from C3 to the first thoracic vertebrae. The subaxial cervical vertebrae (C3-C7) were reconstructed into three-dimensional (3D) bone models for use with model-based tracking. Foraminal height (FH) was calculated as the 3D distance between the superior point of the inferior pedicle and the inferior point of the superior pedicle using custom software. Foraminal width (FW) was similarly calculated as the 3D distance between the anterolateral aspect of the superior vertebral body inferior notch and the posterolateral aspect of the inferior vertebral body superior notch. Dynamic foraminal dimensions were quantified as the minimum (FH.Min, FW.Min), the range (FH.Range, FW.Range), and the median (FH.Med, FW.Med) of each trial and then averaged over trials. Mixed model analysis of variance framework was used to examine the differences between ACDF and AD groups. The initial severity of disc degeneration as determined from preoperative MRI images was introduced as covariates in the models. RESULTS: At the operated level (C5-C6), FH.Med and FH.Range were smaller in ACDF than in AD during axial rotation and neck extension (p<.003 to p<.05). At the superior adjacent level (C4-C5), no significant difference was found. At the inferior adjacent level (C6-C7), FW.Range was greater in ACDF than in AD during axial rotation and extension (p<.05). At the non-adjacent level (C3-C4), FW.Range was greater in ACDF than in AD during extension (p<.008). CONCLUSIONS: This study demonstrated decreases in foraminal dimensions and their range for ACDF compared with AD at the operated level. In contrast, it demonstrated increases in the range of foraminal dimensions during motion for ACDF compared with AD at the non-operated segments. Together, these data support the notion that increased mobility at the non-operated segments after ACDF may contribute to a greater risk for adjacent segment degeneration. Because of the significant presence of range variables in the findings, the current data also indicate that a dynamic evaluation is likely more appropriate for evaluation of the differences in foramina between ACDF and AD than a static evaluation.

Effects of asymptomatic rotator cuff pathology on in vivo shoulder motion and clinical outcomes.

BACKGROUND: The incidence of asymptomatic rotator cuff tears has been reported to range from 15% to 39%, but the influence of asymptomatic rotator cuff pathology on shoulder function is not well understood. This study assessed the effects of asymptomatic rotator cuff pathology on shoulder kinematics, strength, and patient-reported outcomes. METHODS: A clinical ultrasound examination was performed in 46 asymptomatic volunteers (age: 60.3 ± 7.5 years) with normal shoulder function to document the condition of their rotator cuff. The ultrasound imaging identified the participants as healthy (n = 14) or pathologic (n = 32). Shoulder motion was measured with a biplane x-ray imaging system, strength was assessed with a Biodex (Biodex Medical Systems, Inc., Shirley, NY, USA), and patient-reported outcomes were assessed using the Western Ontario Rotator Cuff Index and visual analog scale pain scores. RESULTS: Compared with healthy volunteers, those with rotator cuff pathology had significantly less abduction (P = .050) and elevation (P = .041) strength, their humerus was positioned more inferiorly on the glenoid (P = .018), and the glenohumeral contact path length was longer (P = .007). No significant differences were detected in the Western Ontario Rotator Cuff Index, visual analog scale, range of motion, or acromiohumeral distance. CONCLUSIONS: The differences observed between the healthy volunteers and those with asymptomatic rotator cuff pathology lend insight into the changes in joint mechanics, shoulder strength, and conventional clinical outcomes associated with the early stages of rotator cuff pathology. Furthermore, these findings suggest a plausible mechanical progression of kinematic and strength changes associated with the development of rotator cuff pathology.

Pre- and Postseason Dynamic Ultrasound Evaluation of the Pitching Elbow.

PURPOSE: To use ultrasound imaging to document changes over time (i.e., preseason v postseason) in the pitching elbow of high school baseball pitchers. METHODS: Twenty-two high school pitchers were prospectively followed. Pitchers were evaluated after a 2-month period of relative arm rest via preseason physical exams, dynamic ultrasound imaging of their throwing elbow, and the Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) assessment. Players were reevaluated within 1 week of their last game. Dynamic ultrasound images were then randomized, blinded to testing time point, and evaluated by 2 fellowship-trained musculoskeletal radiologists. RESULTS: Average pitcher age was 16.9 years. Average pitches thrown was 456.5, maximum velocity 77.7 mph, games pitched 7.3, and days off between starts 6.6. From preseason to postseason, there were significant increases in ulnar collateral ligament (UCL) thickness (P = .02), ulnar nerve cross-sectional area (P = .001), UCL substance heterogeneity (P = .001), and QuickDASH scores (P = .03). In addition, there was a nonsignificant increase in loaded ulnohumeral joint space (P = .10). No pitchers had loose bodies on preseason exam, while 3 demonstrated loose bodies postseason. The increase in UCL thickness was significantly associated with the number of bullpen sessions per week (P = .01). The increase in ulnar nerve cross-sectional area was significantly associated with the number of pitches (P = .04), innings pitched (P = .01), and games pitched (P = .04). CONCLUSIONS: The stresses placed on the elbow during only one season of pitching create adaptive changes to multiple structures about the elbow including UCL heterogeneity and thickening, increased ulnohumeral joint space laxity, and enlarged ulnar nerve cross-sectional area. LEVEL OF EVIDENCE: Level II prospective observational study.

Effect of Arthroscopic Stabilization on In Vivo Glenohumeral Joint Motion and Clinical Outcomes in Patients With Anterior Instability.

BACKGROUND: Glenohumeral joint (GHJ) dislocations are common, and the resulting shoulder instability is often treated with arthroscopic stabilization. These procedures result in favorable clinical outcomes, but abnormal GHJ motion may persist, which may place patients at risk for developing osteoarthritis. However, the effects of shoulder instability and arthroscopic stabilization on GHJ motion are not well understood. HYPOTHESIS: GHJ motion is significantly influenced by anterior instability and arthroscopic stabilization, but postsurgical measures of GHJ motion are not different from those of control subjects. STUDY DESIGN: Controlled laboratory study. METHODS: In vivo GHJ motion was measured by applying a computed tomographic model-based tracking technique to biplane radiographic images acquired during an apprehension test in healthy control subjects (n = 11) and anterior instability patients (n = 11). Patients were tested before surgery and at 6 months after surgery. Control subjects were tested once. Shoulder strength, active range of motion (ROM), and the Western Ontario Shoulder Instability (WOSI) index were also measured. RESULTS: Before surgery, the humerus of the instability patients during the apprehension test was located significantly more anteriorly on the glenoid (7.9% of glenoid width; 2.1 mm) compared with that of the controls (P = .03), but arthroscopic stabilization moved this joint contact location posteriorly on the glenoid (4.7% of glenoid width; 1.1 mm; P = .03). After surgery, GHJ excursion during the apprehension test was significantly lower (14.7% of glenoid width; 3.6 mm) compared with presurgical values (19.4% of glenoid width; 4.7 mm; P = .01) and with that of the controls (22.4% of glenoid width; 5.7 mm; P = .01). The external and internal rotation strength of patients was significantly lower than that of the controls before surgery (P < .05), but differences in strength did not persist after surgery (P > .17). External rotation ROM in patients was significantly lower than that in control subjects both before and after arthroscopic stabilization (P < .01). The WOSI score improved significantly, from 48.3 ± 13.1 presurgery to 86.3 ± 16.5 after surgery (P = .0002). CONCLUSION: In patients with anterior instability, arthroscopic stabilization significantly improves measures of strength, ROM, and clinical outcome. However, GHJ excursion is not fully restored to levels seen in the control subjects. CLINICAL RELEVANCE: Although arthroscopic stabilization satisfactorily restores most clinical outcome measures, GHJ excursion and external rotation ROM remain compromised compared with healthy control subjects and may contribute to the development of osteoarthritis in patients with anterior instability.

Differences in glenohumeral joint morphology between patients with anterior shoulder instability and healthy, uninjured volunteers.

BACKGROUND: Traumatic glenohumeral joint (GHJ) dislocations are common, resulting in significant shoulder disability and pain. Previous research indicates that bony morphology is associated with an increased risk of injury in other joints (eg, the knee), but the extent to which bony morphology is associated with traumatic GHJ dislocation is unknown. This study assessed GHJ morphology in patients with anterior GHJ instability and in a control population of healthy volunteers. METHODS: Bilateral computed tomography scans were used to measure GHJ morphology in both shoulders of 11 patients with instability and 11 control subjects. Specific outcome measures included the glenoid radius of curvature (ROC) in the anterior/posterior (A/P) and superior/inferior (S/I) directions, humeral head ROC, A/P and S/I conformity index, and A/P and S/I stability angle. RESULTS: Compared with the control subjects, the glenoid of the instability the injured shoulder in patients with instability was flatter (ie, higher ROC) in the A/P (P = .001) and S/I (P = .01) directions and this finding was also true for uninjured, contralateral shoulder (A/P: P = .01, S/I: P = .03). No differences in GHJ morphology were detected between the instability patients' injured and contralateral shoulders (P > .07). Similarly, no differences in GHJ morphology were detected between the control subjects' dominant and nondominant shoulders (P > .51). CONCLUSIONS: There are significant differences in GHJ morphology between healthy control subjects and both shoulders (injured and uninjured, contralateral) of patients diagnosed with anterior instability after GHJ dislocation. These findings are important clinically because they suggest that glenoid morphology may influence the risk of GHJ dislocation.

Pitching performance and longevity after revision ulnar collateral ligament reconstruction in Major League Baseball pitchers.

BACKGROUND: Medial ulnar collateral ligament (UCL) reconstruction is a common procedure performed on professional pitchers in Major League Baseball (MLB). Although a great deal is known about primary reconstruction, much less is known about revision reconstruction. PURPOSE/HYPOTHESIS: The purpose of this study was to evaluate statistical performance, return to play, and career longevity in MLB pitchers after revision UCL surgery, with the hypothesis that pitching performance and career longevity will decline after revision surgery. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 33 MLB pitchers who underwent revision UCL reconstruction surgery (UCL-R group) were identified and compared with 33 age- and position-matched controls (CTL group). Return to play, total years played, and statistical performance were evaluated and compared with controls. RESULTS: After revision surgery, 65.5% of UCL-R pitchers returned to the MLB level. On average, the UCL-R pitchers played 0.8 years less in the majors (P<.01) than did the control pitchers. The UCL-R pitchers who returned to the MLB level had a similar earned run average (UCL-R: 4.88, CTL: 4.76, P=.82) and walks/hits per innings pitched (UCL-R: 1.58, CTL: 1.44, P=.22) compared with the control pitchers. There were significant declines, however, in terms of innings pitched (UCL-R: 36.95, CTL: 75.00, P<.01), walks per 9 innings (UCL-R: 4.75, CTL: 3.49, P<.01), and wins (UCL-R: 1.88, CTL: 4.10, P<.01) as well as nonsignificant declines in wins above replacement (UCL-R: 0.25, CTL: 0.62, P=.06) and runs above replacement (UCL-R: 3.26, CTL: 6.91, P=.07). CONCLUSION: MLB pitchers who undergo UCL-R have a low rate of return to MLB play and have shortened careers after return. Pitchers who returned to the MLB level maintained performance in several statistics such as earned run average and walks/hits per innings pitched; however, pitchers returned with a significantly decreased workload.

The effects of medial ulnar collateral ligament reconstruction on Major League pitching performance.

BACKGROUND: Medial ulnar collateral ligament (MUCL) reconstruction is commonly performed on Major League Baseball (MLB) pitchers. Previous studies have reported that most pitchers return to presurgical statistical performance levels after MUCL reconstruction. METHODS: Pitching performance data--specifically, earned run average (ERA), walks and hits per inning pitched (WHIP), winning percentage, and innings pitched--were acquired for 168 MLB pitchers who had undergone MUCL reconstruction. These data were averaged over the 3 years before surgery and the 3 years after surgery and also acquired from 178 age-matched, uninjured MLB pitchers. RESULTS: Of the pitchers who had MUCL reconstruction surgery, 87% returned to MLB pitching. However, compared with presurgical data, pitching performance declined in terms of ERA (P = .001), WHIP (P = .011), and innings pitched (P = .026). Pitching performance also declined in the season before the surgery compared with previous years (ERA, P = .014; WHIP, P = .036; innings pitched, P < .001; winning percentage, P = .004). Compared with age-matched control pitchers, the MUCL reconstruction pitchers had significantly more major league experience at the same age (P < .001). CONCLUSION: MUCL reconstruction allows most players to return to pitching at the major league level. However, after MUCL reconstruction, there is a statistically significant decline in pitching performance. There appears to be a statistically significant decline in pitching performance the year before reconstructive surgery, and this decline is also a risk factor for requiring surgery. In addition, there is an increased risk of MUCL reconstruction for pitchers who enter the major leagues at a younger age.

Associations among shoulder strength, glenohumeral joint motion, and clinical outcome after rotator cuff repair.

Rotator cuff tears are a common condition causing pain and disability, but the relationships among clinical measures of shoulder function and measures of glenohumeral joint (GHJ) function are not well known. In the study reported here, dynamic in vivo GHJ motion was measured during abduction from biplane radiographs in 22 rotator cuff repair (RCR) patients and 36 control subjects. Isometric shoulder strength was measured and clinical outcomes were assessed using the Western Ontario Rotator Cuff (WORC) Index. Associations among WORC, GHJ motion, and several shoulder strength ratios were assessed with linear regression. An association was detected between higher ER/ABD (external rotation/coronal-plane abduction) strength ratio and a humerus positioned more inferiorly relative to the glenoid in control subjects and RCR patients. Higher ER/ABD strength ratio was also associated with better clinical outcome in RCR patients. These findings suggest a relationship between ER/ABD strength ratio and a more centrally located average superior/inferior contact center in RCR patients and control subjects. The ER/ABD strength ratio can be easily measured in a clinical setting and therefore can be used in larger studies to investigate its relation to clinical outcomes over time or perhaps to predict superior migration of the humeral head.

Bracing improves clinical outcomes but does not affect the medial knee joint space in osteoarthritic patients during gait.

PURPOSE: Osteoarthritis (OA) of the knee is commonly treated through the use of medial compartment unloading braces which have been shown to improve clinical symptoms. The objective of this study was to assess the effects of a medial compartment unloading brace on biomechanical measurements and clinical outcomes. We hypothesized that brace usage would lead to increased medial joint space and improved clinical outcomes. METHODS: Ten patients with medial compartment OA were prescribed a medial compartment unloading brace and underwent dynamic biplane radiograph imaging while walking with and without the brace. The Western Ontario and McMaster University Osteoarthritis (WOMAC) Index was used to assess pain before brace wear and at the time of testing. The 3D position and orientation of the femur and tibia were determined using a model-based tracking technique. RESULTS: Patients saw an average improvement of 33 % in their WOMAC scores (p = 0.01). This study failed to detect any statistically significant changes in the functional joint space, knee kinematics, or contact centre location between the braced and unbraced condition (n.s.). CONCLUSION: The data from this study, using a highly accurate (±0.6 mm and ±0.6°) 3D radiograph analysis of dynamic tibiofemoral motion, suggest that the brace is ineffective at increasing joint space. However, it was shown to be effective in improving clinical outcome and therefore should continue to be prescribed to patients even though the mechanism of its effectiveness remains unknown. LEVEL OF EVIDENCE: IV.

Failure with continuity in rotator cuff repair "healing".

BACKGROUND: Ten to seventy percent of rotator cuff repairs form a recurrent defect after surgery. The relationship between retraction of the repaired tendon and formation of a recurrent defect is not well defined. PURPOSE/ HYPOTHESES: To measure the prevalence, timing, and magnitude of tendon retraction after rotator cuff repair and correlate these outcomes with formation of a full-thickness recurrent tendon defect on magnetic resonance imaging, as well as clinical outcomes. We hypothesized that (1) tendon retraction is a common phenomenon, although not always associated with a recurrent defect; (2) formation of a recurrent tendon defect correlates with the timing of tendon retraction; and (3) clinical outcome correlates with the magnitude of tendon retraction at 52 weeks and the formation of a recurrent tendon defect. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Fourteen patients underwent arthroscopic rotator cuff repair. Tantalum markers placed within the repaired tendons were used to assess tendon retraction by computed tomography scan at 6, 12, 26, and 52 weeks after operation. Magnetic resonance imaging was performed to assess for recurrent tendon defects. Shoulder function was evaluated using the Penn score, visual analog scale (VAS) score for pain, and isometric scapular-plane abduction strength. RESULTS: All rotator cuff repairs retracted away from their position of initial fixation during the first year after surgery (mean [standard deviation], 16.1 [5.3] mm; range, 5.7-23.2 mm), yet only 30% of patients formed a recurrent defect. Patients who formed a recurrent defect tended to have more tendon retraction during the first 6 weeks after surgery (9.7 [6.0] mm) than those who did not form a defect (4.1 [2.2] mm) (P = .08), but the total magnitude of tendon retraction was not significantly different between patient groups at 52 weeks. There was no significant correlation between the magnitude of tendon retraction and the Penn score (r = 0.01, P = .97) or normalized scapular abduction strength (r = -0.21, P = .58). However, patients who formed a recurrent defect tended to have lower Penn scores at 52 weeks (P = .1). CONCLUSION: Early tendon retraction, but not the total magnitude, correlates with formation of a recurrent tendon defect and worse clinical outcomes. "Failure with continuity" (tendon retraction without a recurrent defect) appears to be a common phenomenon after rotator cuff repair. These data suggest that repairs should be protected in the early postoperative period and repair strategies should endeavor to mechanically and biologically augment the repair during this critical early period.

Measurement of in vivo tendon function.

Chronic tendon pathologies (eg, rotator cuff tears, Achilles tendon ruptures) are common, painful, debilitating, and a significant source of medical expense. Treatment strategies for managing tendon pathologies vary widely in invasiveness and cost, with little scientific basis on which to base treatment selection. Conventional techniques for assessing the outcomes of physical therapy or surgical repair typically rely on patient-based assessments of pain and function, physical measures (eg, strength, range of motion, or stability), and qualitative assessments using magnetic resonance imaging or ultrasound. Unfortunately, these conventional techniques provide only an indirect assessment of tendon function. The inability to make a direct quantitative assessment of the tendon's mechanical capabilities may help to explain the relatively high rate of failed tendon repairs and has led to an interest in the development of tools for directly assessing in vivo tendon function. The purpose of this article is to review methods for assessing tendon function (ie, mechanical properties and capabilities) during in vivo activities. This review will describe the general principles behind the experimental techniques and provide examples of previous applications of these techniques. In addition, this review will characterize the advantages and limitations of each technique, along with its potential clinical utility. Future efforts should focus on developing broadly translatable technologies for quantitatively assessing in vivo tendon function. The ability to accurately characterize the in vivo mechanical properties of tendons would improve patient care by allowing for the systematic development and assessment of new techniques for treating tendon pathologies.