Joseph A. Abboud

Effect of altered matrix proteins on quasilinear viscoelastic properties in transgenic mouse tail tendons

AbstractTendons have complex mechanical behaviors that are viscoelastic, nonlinear, and anisotropic. It is widely held that these behaviors are provided for by the tissues composition and structure. However, little data are available to quantify such structure–function relationships. This study quantified tendon mechanical behaviors, including viscoelasticity and nonlinearity, for groups of mice that were genetically engineered for altered extracellular matrix proteins. Uniaxial tensile stress-relaxation experiments were performed on tail tendon fascicles from the following groups: eight week old decorin knockout, eight week old reduced type I collagen, three week old control, and eight week old control. Data were fit using Fungs quasilinear viscoelastic model, where the model parameters represent the linear viscoelastic and nonlinear elastic response. The viscoelastic properties demonstrated a larger and faster stress relaxation for the decorin knockout and a smaller and slower stress relaxation for the three week control. The elastic parameter, A, in the eight week control group was significantly greater than in the collagen reduction and three week control groups. This study provides quantitative evidence for structure–function relationships in tendon, including the role of proteoglycan in viscoelasticity. Future studies should directly correlate composition and structure with tendon mechanics for the design and evaluation of tissue-engineered constructs or tendon repairs.

Current review of adhesive capsulitis

Adhesive capsulitis, also known as frozen shoulder, is a common condition involving scapulohumeral pain and loss of motion. This condition was termed ‘‘peri-arthritis scapulohumerale’’ by Duplay in 1896. Codman, in 1934, characterized the diagnosis of ‘‘frozen shoulder’’ as a condition characterized by pain and reduced range of motion in the affected shoulder. Neviaser, in the prearthroscopic era, subsequently used the term ‘‘adhesive capsulitis’’ to describe the findings of chronic inflammation and fibrosis of the joint capsule, although arthroscopic examination would support the term ‘‘fibrotic capsulitis’’ with the absence of adhesions. The current consensus definition of the American Shoulder and Elbow Surgeons is ‘‘a condition of uncertain etiology characterized by significant restriction of both active and passive shoulder motion that occurs in the absence of a known intrinsic shoulder disorder.’’ Despite the large number of patients affected by this condition, our understanding of the condition is limited. In the past, the term ‘‘frozen shoulder’’ has often been used to describe other shoulder conditions such as subacromial bursitis and calcific tendonitis. Neviaser and Neviaser described the term ‘‘frozen shoulder’’ as a ‘‘waste-can diagnosis,’’ because it was often overused and misapplied to patients with a stiff and painful shoulder. Conditions such as calcific tendonitis, bicipital tenosynovitis, glenohumeral and acromioclavicular arthritis, and tears of the rotator cuff can lead to a stiff and painful shoulder, causing apparent limitation of active range of motion, but they lack true

The Effect of Hypercholesterolemia on Rotator Cuff Disease

BackgroundThe causes of rotator cuff tendon rupture are multifactorial and still unclear. Intrinsic and extrinsic factors have been implicated as predisposing risk factors for rotator cuff rupture. Previous studies have suggested a relationship between elevated serum lipid profiles and tendon ruptures, although not rotator cuff tears specifically.Questions/purposesWe therefore asked whether patients with rotator cuff tears were more likely to have higher levels of hypercholesterolemia than patients with shoulder pain but without tears.MethodsWe prospectively collected serum cholesterol and lipid profiles on two age-matched populations of patients; 74 (mean age, 66.3xa0years) had ruptures of their rotator cuff tendons, whereas a control group of 73 patients (mean age, 67.4xa0years) were seen for nontendon-related shoulder complaints.ResultsTotal cholesterol, triglycerides, and low-density lipoprotein cholesterol concentrations of the patients with rotator cuff tendon tears were higher, and their high-density lipoprotein cholesterol showed a trend to being lower than the control group. Forty-seven of 74 patients (63%) with rotator cuff tears had an elevated serum cholesterol (total cholesterol greater than 240xa0mg/dL) as compared with an overall rate of 28% in our control group.ConclusionsPatients with rotator cuff tears were more likely to have hypercholesterolemia when compared with the control group.Clinical relevanceMeasurement of serum cholesterol in patients presenting with torn rotator cuff tendons should be considered in patients whose cholesterol profiles are unknown. Future consideration of drug treatment may reduce risk for future tendon degeneration, as well as improve quality of life and reduce mortality.Level of EvidenceLevel II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Use of locking plates in the treatment of proximal humerus fractures

BACKGROUND/HYPOTHESISnOpen reduction and internal fixation (ORIF) using locked plating has demonstrated promise in the treatment of displaced proximal humerus fractures. The purpose of this article is to describe the surgical technique and to report early clinical results with this technique.nnnMETHODSnImportant surgical principles to follow include adequate use of locking screws in the humeral head, bone graft or bone graft substitutes when needed, rotator cuff sutures to assist with reduction and augment fixation, and sufficient use of intraoperative fluoroscopic imaging. A review was performed to evaluate early outcomes of ORIF with proximal humerus locking plates. All cases were fixed with the described surgical technique. Postoperative assessment included radiographic imaging, PENN/ASES Shoulder Scores, range-of-motion (ROM), and complications.nnnRESULTSnFifty-two patients (54 shoulders) had minimum 6-month follow-up (13-month mean follow-up). Mean age was 65.5 years. Postoperatively, mean active forward elevation was 130.1 degrees, and mean active external rotation was 27.7 degrees. Mean post-op PENN shoulder score was 68.9 and mean post-op ASES score was 70.8. There were 11 (20.4%) complications in 10 (18.5%) shoulders after treatment with a proximal humerus locking plate. Three complications were classified as minor (5.6%), 8 as major (14.8%). Two shoulders (3.7%) required reoperation to address the complications.nnnCONCLUSIONnThe use of locking plates in the treatment of displaced proximal humerus fractures is becoming more widespread. With precise knowledge of and experience with the surgical technique, locked plating can be performed safely with good results. However, surgeons should be aware that complications can arise.

Outcomes of arthroscopic rotator cuff repairs in obese patients.

HYPOTHESISnRotator cuff tears are common orthopedic injuries and their arthroscopic treatment can be technically challenging. This study evaluated the outcomes of arthroscopic rotator cuff repairs in obese patients. We hypothesized that there would be a direct correlation between worse outcomes of arthroscopic rotator cuff repairs and increasing body mass index (BMI).nnnMATERIALS AND METHODSnA retrospective review of patients undergoing arthroscopic rotator cuff repair by one orthopedic surgeon between 2005 and 2008 was performed. The study included 149 rotator cuff repairs. Recorded data included age, sex, BMI, size of rotator cuff tear on magnetic resonance imaging and intraoperatively, number of anchors used for repair, functional outcomes (American Shoulder and Elbow Surgeons and University of Pennsylvania scores), surgery time, total time for anesthesia, positioning, and hospital stay. Tears were classified by size. Strict inclusion and exclusion criteria were used. Surgical procedures were performed with general anesthesia, interscalene block, beach chair positioning, and a standardized operative technique. Patients followed a standard postoperative rehabilitation protocol.nnnRESULTSnMean patient age was 66 years. Mean follow-up was 16.3 months. Tears were classified as high grade partial (12%), small (23%), medium (29%), large (22%), and massive (14%). Patients were classified as normal weight (38%), overweight (23%), obese (20%), and morbidly obese (19%). A statistically significant correlation was found between obesity and worse functional outcomes, longer operative times, and longer length of hospital stay.nnnDISCUSSIONnThis study reports new data concerning the association of BMI and early clinical outcome after arthroscopic rotator cuff repair surgery. Even though the obese group had greater limitations and lower rates of satisfaction at final follow-up than their non-obese counterparts, they still reported significant improvements from the surgery.nnnCONCLUSIONnObesity has a negative impact on the operative time of arthroscopic rotator cuff repairs, length of hospitalization, and functional outcomes.

Cumulative effects of hypercholesterolemia on tendon biomechanics in a mouse model

High cholesterol represents a significant healthcare problem. Clinical studies have linked hypercholesterolemia to Achilles tendon xanthomas and rotator cuff tears, and research in other systems indicates detrimental effects of high cholesterol; however, understanding of its impact on tendon properties and healing is limited. We hypothesized that tendons from aging hypercholesterolemic (APOE) mice would exhibit inferior baseline and healing mechanical properties compared to controls, while younger, but mature mice would be no different. Surprisingly, tensile testing of patellar tendons from 14‐week‐old APOE mice receiving a unilateral full‐thickness central defect resulted in normalized (injured:sham) cross‐sectional areas closer to baseline (pu2009=u20090.02) compared to controls. Uninjured data from 10‐month‐old APOE mice showed a decrease in elastic modulus (pu2009=u20090.02), indicating a detrimental effect of hypercholesterolemia on tendon properties in this model. These results could benefit patients through knowledge that high cholesterol could increase the likelihood of tendon tears. Furthermore, knowledge that tendon tears are indicative of high cholesterol could provide orthopedic clinicians with an additional preventive treatment opportunity for patients with undiagnosed hypercholesterolemia.

Total shoulder arthroplasty in older patients: increased perioperative morbidity?

BackgroundMore elderly patients are becoming candidates for total shoulder arthroplasty with an increase in frequency of the procedure paralleling the rise in other total joint arthroplasties. Controversy still exists, however, regarding the perioperative morbidity of total joint arthroplasty in elderly patients, particularly those 80xa0years of age and older.Questions/purposesWe asked whether perioperative complications and mortality, transfusion requirements, inpatient length of stay, and discharge disposition after total shoulder arthroplasty were similar in patients 80xa0years and older compared with those in younger patients.MethodsWe retrospectively compared the 90-day complications, mortality, and other perioperative variables after total shoulder arthroplasty in 40 patients (43 shoulders) aged 80xa0years and older (Group A; mean age, 82xa0years) with 46 patients (47 shoulders) younger than 70xa0years (Group B; mean age, 61xa0years).ResultsWe found no differences in complication rates between Group A and B, including systemic (26% versus 11%) and local (5% versus 9%) complications or major (7% versus 2%) and minor (23% versus 17%) complications. There were no deaths in either group. Group A had an increased transfusion requirement (16% versus 2%) and a decreased number of direct to home discharges (67% versus 98%). Presence of systemic complications predicted increased length of stay in patients overall and in Group A patients.ConclusionsTotal shoulder arthroplasty can be performed in patients 80xa0years and older with rates of perioperative complications and mortalities comparable to those of younger patients, although these older patients may require a longer period of institutional care before return to home and may be more likely to require a blood transfusion.Level of EvidenceLevel III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Bicipital groove morphology on MRI has no correlation to intra-articular biceps tendon pathology

BACKGROUNDnMultiple authors have debated the contribution of intertubercular groove morphology to biceps tendon pathology. It has been proposed that the shallow groove, combined with the supertubercular ridge of Meyer, predisposes patients to bicipital disease. In this study we hypothesized that there would be a correlation between bicipital groove morphology and the intraoperative finding of biceps pathology.nnnMETHODSnSeventy-five consecutive patients (average age of 63) undergoing arthroscopic rotator cuff repair surgery had their biceps tendons and intertubercular groove morphologies prospectively evaluated on closed MRI T1 axial cut images. The opening angle and medial wall angle of the bicipital groove was measured for each patient. At the time of surgery, the biceps tendon was classified as normal, inflamed, partially ruptured, or ruptured and the findings correlated to the bicipital groove measurements.nnnRESULTSnThe average opening angle was 81 degrees for normal biceps tendons and 77 degrees for torn biceps tendons. The average medial wall angle was 47 degrees for normal biceps tendons and 49 degrees for torn biceps tendons. Using Chi-square analysis, we found no statistically significant correlation between the bicipital groove average opening angle and medial wall angle on MRI and intraoperative biceps tendon pathology.nnnCONCLUSIONnThis study does not support any correlation between intraarticular biceps tendon pathology and bicipital groove morphology.

Nerve Monitoring During Proximal Humeral Fracture Fixation: What Have We Learned?

BackgroundThe incidence of neurologic injury after proximal humerus fractures is variable, ranging from 6.2% to as much as 67%. However, it is unclear what factors might contribute to these injuries or whether they can be prevented by intraoperative nerve monitoring.Questions/purposesTherefore, using intraoperative nerve monitoring, we assessed the incidence, pattern of nerve involvement, and predisposing factors for nerve injury before and during shoulder fracture fixation.Patients and MethodsWe used continuous intraoperative monitoring of the brachial plexus in 37 patients undergoing open operative treatment of proximal humerus fractures. Impending intraoperative compromise of nerve function was signaled by sustained neurotonic EMG activity or greater than 50% amplitude attenuation of transcranial electrical motor evoked potentials (MEPs) (or both). When a nerve alert occurred, current surgical activity and arm and retractor position were recorded and adjustments were made to relieve tension.ResultsThe intraoperative affected nerves included axillary (46%), combined (mixed plexopathy) (23%), radial (23%), musculocutaneous (4%), and ulnar (4%). Postoperatively, three patients had transient nerve palsies, which fully resolved within 3xa0weeks of surgery. Low body mass index (BMI) (22.7xa0±xa02.8), history of cervical spine disease, diabetes mellitus, and delay in surgical treatment (14xa0±xa02.9xa0days from time of injury) were associated with an increased incidence of nerve dysfunction.ConclusionsOur observations suggest transcranial electrical MEPs are sensitive indicators of impending iatrogenic injury to the brachial plexus or peripheral nerves (or both) during open operative treatment of proximal humerus fractures. The use of intraoperative nerve monitoring during these procedures may be considered for the prevention of nerve injury, particularly in patients with underlying cervical spine disease, low BMI, diabetes mellitus, and/or delay in surgical treatment greater than approximately 14xa0days.Level of EvidenceLevel III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Soft-tissue management in revision total shoulder arthroplasty.

&NA; Revision total shoulder arthroplasty can be technically challenging. Results are inferior to those of primary arthroplasty, particularly when the indications for revision are related to soft‐tissue problems. Patient selection is important. In the stiff arthroplasty, the surgeon must address rotator cuff and capsular contractures as well as exuberant soft‐tissue adhesions. Unstable arthroplasty can be the result of asymmetric soft‐tissue balancing or deficiencies (eg, subscapularis deficiency) that can lead to loss of the rotator cuff force couples and, subsequently, to instability on attempted glenohumeral motion. Infection must be considered in the workup of the failed total shoulder. In this era of ever‐increasing use of shoulder arthroplasty, surgeons will be presented with growing numbers of patients who require revision surgery. An organized approach is needed to diagnose and manage the stiff or unstable total shoulder arthroplasty.