N. Douglas Boardman

Mechanisms of rotator cuff tendinopathy: intrinsic, extrinsic, or both?

The etiology of rotator cuff tendinopathy is multi-factorial, and has been attributed to both extrinsic and intrinsic mechanisms. Extrinsic factors that encroach upon the subacromial space and contribute to bursal side compression of the rotator cuff tendons include anatomical variants of the acromion, alterations in scapular or humeral kinematics, postural abnormalities, rotator cuff and scapular muscle performance deficits, and decreased extensibility of pectoralis minor or posterior shoulder. A unique extrinsic mechanism, internal impingement, is attributed to compression of the posterior articular surface of the tendons between the humeral head and glenoid and is not related to subacromial space narrowing. Intrinsic factors that contribute to rotator cuff tendon degradation with tensile/shear overload include alterations in biology, mechanical properties, morphology, and vascularity. The varied nature of these mechanisms indicates that rotator cuff tendinopathy is not a homogenous entity, and thus may require different treatment interventions. Treatment aimed at addressing mechanistic factors appears to be beneficial for patients with rotator cuff tendinopathy, however, not for all patients. Classification of rotator cuff tendinopathy into subgroups based on underlying mechanism may improve treatment outcomes.

Neurologic complications of shoulder surgery.

Nerve injuries do occur during shoulder surgery. Studies of regional anatomy have defined the nerves at risk. The suprascapular nerve may lie no more than 1 cm from the glenoid rim. The axillary nerve may run no more than 3 mm from the inferior shoulder capsule and passes near the lower extent of the deltoid split used as an approach to the shoulder. The musculocutaneous nerve passes as near as 3.1 cm below the coracoid. Interscalene nerve block is not commonly implicated in nerve injuries. Three-dimensional knowledge of nerve anatomy is essential during arthroscopy for safe portal placement and trochar direction. Nerve injuries are reported to occur in 1% to 2% of patients undergoing rotator cuff surgery, 1% to 8% of patients undergoing surgery for anterior instability, and 1% to 4% of patients undergoing prosthetic arthroplasty. Surgical techniques for the shoulder are improving and nerves seldom are injured by direct laceration or incorporation in suture repair. Commonly, the nerve injuries occur secondary to traction or contusion. These are avoided best by careful attention to patient positioning, retractor placement, and arm manipulation during surgery. Because of the contemporary nature of these nerve injuries, observation is almost always the treatment of choice, with delayed electrodiagnostic testing should nerve recovery not occur within a 3 to 6-week period.

Effect of Posture on Acromiohumeral Distance With Arm Elevation in Subjects With and Without Rotator Cuff Disease Using Ultrasonography

STUDY DESIGN Controlled laboratory study. OBJECTIVES To examine the effects of altering posture on the subacromial space (SAS) in subjects with rotator cuff disease and subjects without shoulder pain. BACKGROUND Poor upper quadrant posture has been linked to altered scapular mechanics, which has been theorized to excessively reduce SAS. However, no study has examined the direct effects of altering upper quadrant posture on SAS. We hypothesized that upright posture would increase and slouched posture would decrease the SAS, as compared to a normal posture, when measured both with the shoulder at rest along the side of the trunk and when maintained in 45° of active shoulder abduction. METHODS Participants included 2 groups: the subjects with shoulder pain and rotator cuff disease, as diagnosed via magnetic resonance imaging (n = 31), and control subjects without shoulder pain (n = 29). The SAS was imaged with ultrasound using a 7.5-MHz linear transducer placed in the coronal plane over the posterior to midportion of the acromion. The SAS was measured on ultrasound images using the acromiohumeral distance (AHD), defined as the shortest distance between the acromion and the humerus. The AHD was measured in 2 trials at 2 arm angles (at rest along the trunk and at 45° of active abduction) and across 3 postures (normal, slouched, and upright), and averaged for data analysis. RESULTS Two mixed-model analyses of variance, 1 for each arm angle, were used to compare AHD across postures and between groups. There was no interaction between group and posture, and no significant main effect of group for either arm position. There was no significant main effect of posture for the arm at rest (P = .26); however, there was a significant main effect of posture on AHD at the 45° abduction arm angle (P = .0002), with a significantly greater AHD in upright posture (mean AHD, 9.8 mm), as compared to normal posture (mean AHD, 8.6 mm). CONCLUSION The effect of posture on SAS, as measured by the 2-dimensional AHD using ultrasound of the posterior to middle aspect of the SAS, is small. The AHD increased with upright posture by 1.2 mm compared to normal posture, when the arm was in 45° active abduction.

The Scapular Assistance Test Results in Changes in Scapular Position and Subacromial Space but Not Rotator Cuff Strength in Subacromial Impingement

STUDY DESIGN Controlled laboratory study. OBJECTIVES To determine the effect of the modified scapular assistance test (SAT) on 3-dimensional shoulder kinematics, strength, and linear measures of subacromial space in patients with subacromial impingement syndrome (SAIS). BACKGROUND Abnormal scapular kinematics have been identified in patients with SAIS. Increased scapular upward rotation and posterior tilt, as induced with manual assistance using the SAT, have been theorized to increase subacromial space and may alter shoulder strength. METHODS Forty-two subjects (21 with SAIS and 21 controls) participated in this study. The anterior outlet of the subacromial space, measured via the acromiohumeral distance on ultrasound images, and 3-dimensional scapular kinematics, measured using motion analysis, were determined with the arm at rest, and at 45° and 90° of active elevation with and without the SAT. A dynamometer was used to measure isometric shoulder strength. Full factorial mixed-model analyses of variance evaluated the effects of the SAT on variables between groups. RESULTS There was an increase in scapular posterior tilt at all angles, upward rotation at rest and 45° of elevation, and acromiohumeral distance at 45° and at 90° with the SAT. The SAT did not alter normalized isometric strength. There were no differences in response to the SAT between the SAIS and control groups. CONCLUSIONS Manual scapular assistance using the SAT influences factors associated with SAIS, such as subacromial space and potentially scapular orientation during static arm elevation, but not more so in individuals with SAIS than in healthy individuals. The SAT performed statically may be a way to identify potential subgroups of individuals with SAIS for whom subacromial space narrowing may be a contributing factor.

Complex varus elbow instability: a terrible triad model.

HYPOTHESIS The terrible triad is a debilitating injury that involves elbow dislocation with injury to the lateral collateral ligament (LCL) complex, the radial head, and the coronoid process. This study investigated the role of these components in varus stability of the elbow. MATERIALS AND METHODS We investigated the role of these components in varus stability of the elbow using 10 cadaveric fresh frozen upper extremities. The testing order allowed each of four states to be tested (intact, LCL complex deficient or repaired, radial head resected or replaced) at two flexion angles and multiple coronoid resection levels. Values for restraining load (newtons [N]) at 1.5 cm of varus displacement were obtained on a materials testing machine. RESULTS Beyond a 50% loss of the coronoid process, neither repair of the LCL nor replacing the radial head alone resulted in a statistically significant increase in varus stability. For a loss of the coronoid process between 67-75%, repair of the LCL and replacement of the radial head showed improved stability over repair alone, or radial head replacement alone. For loss of the coronoid beyond 75%, even repair of the LCL and replacement of the radial head did not improve varus stability of the elbow. CONCLUSION These findings provide a biomechanical basis for aggressive treatment of coronoid fractures as a component of the terrible triad injury. LEVELS OF EVIDENCE Basic science study.

Continuous versus single shot brachial plexus block and their relationship to discharge barriers and length of stay

BACKGROUND Brachial plexus block has been associated with improved pain control and decreased length of stay in patients undergoing upper extremity arthroplasty. Continuous delivery is associated with a shorter length of stay; however, comparisons to single-shot delivery in this setting are scarce. As the paradigm shifts to outpatient arthroplasty in the era of bundled payments, there exists a strong impetus to identify the most effective mode of analgesia associated with the least risk to patients. METHODS This is a retrospective review of 697 patients undergoing upper extremity arthroplasty comparing the rate of complications and incidence of potential barriers to discharge and length of stay of patients receiving continuous vs. single-shot perineural brachial plexus block. RESULTS No difference was observed in the complication rate between indwelling (n = 63 [12%]) and single-shot groups (n = 30 [17%]; P = .137). The majority of complications were pulmonary, 72% attributable to oxygen desaturation. The indwelling catheter group had 1.61 times higher odds (95% confidence interval, 1.07-2.42; P = .023) of exhibiting any potential barrier to discharge and exhibited a longer length of stay (P = .002). CONCLUSION There was no demonstrated disparity in the rate of complications associated with single-shot vs. continuous brachial plexus block. However, the continuous indwelling catheter was associated with an increased incidence of potential barriers to discharge and an increased length of stay compared with patients receiving single-shot regional anesthesia.

Conversion of Glenohumeral Fusion to Reverse Total Shoulder Arthroplasty

Case: A 41-year-old woman presented 5 years after glenohumeral arthrodesis. She experienced symptomatic relief following conversion to reverse total shoulder arthroplasty, regaining nearly full passive range of motion and >50% of normal active forward flexion, abduction, internal rotation, and external rotation. Conclusion: Conversion from glenohumeral arthrodesis to reverse total shoulder arthroplasty in a patient with a functioning deltoid and adequate bone stock may provide symptomatic relief and improved function in the setting of symptomatic glenohumeral arthrodesis refractory to conservative measures.