Review of human supraspinatus tendon mechanics. Part II: tendon healing response and characterization of tendon health.

Overuse injuries of the rotator cuff, particularly of the supraspinatus tendon (SST), are highly prevalent and debilitating in work, sport, and daily activities. Despite the clinical significance of these injuries, there remains a large degree of uncertainty regarding the pathophysiology of injury, optimal methods of nonoperative and operative repair, and how to adequately assess tendon injury and healing. The tendon response to fatigue damage resulting from overuse is different from that of acute rupture and results in either an adaptive (healing) or a maladaptive (degenerative) response. Factors associated with the degenerative response include increasing age, smoking, hypercholesterolemia, biological sex (variable by tendon), diabetes mellitus, and excessive load post fatigue damage. After injury, the average healing rate of tendon is approximately 1% per day and may be significantly influenced by biologic sex (females have lower collagen synthesis rates) and excessive load after damage. Although magnetic resonance imaging (MRI) is considered the gold standard in assessing acute tears as well as tendinopathic change in the SST, ultrasonography has proven to be a valuable tool to measure tendinopathic change in real time. Ultrasonography can determine multiple mechanical and structural parameters of the SST that are altered in fatigue loading. Thus, ultrasonography may be utilized to understand how these parameters change in response to SST overuse, and may aid in determining the activity level that places the SST at greater risk of rupture.

Review of human supraspinatus tendon mechanics. Part I: fatigue damage accumulation and failure.

Repetitive stress injuries to the rotator cuff, and particularly the supraspinatus tendon (SST), are highly prevalent and debilitating. These injuries typically occur through the application of cyclic load below the threshold necessary to cause acute tears, leading to accumulation of incremental damage that exceeds the body's ability to heal, resulting in decreased mechanical strength and increased risk of frank rupture at lower loads. Consistent progression of fatigue damage across multiple model systems suggests a generalized tendon response to overuse. This finding may allow for interventions before gross injury of the SST occurs. Further research into the human SST response to fatigue loading is necessary to characterize the fatigue life of the tendon, which will help determine the frequency, duration, and magnitude of load spectra the SST may experience before injury. Future studies may allow in vivo SST strain analysis during specific activities, generation of a human SST stress-cycle curve, and characterization of damage and repair related to repetitive tasks.

Anomalous Forearm Muscles and Their Clinical Relevance.

Despite their relatively low prevalence in the population, anomalous muscles of the forearm may be encountered by nearly all hand and wrist surgeons over the course of their careers. We discuss 6 of the more common anomalous muscles encountered by hand surgeons: the aberrant palmaris longus, anconeus epitrochlearis, palmaris profundus, flexor carpi radialis brevis, accessory head of the flexor pollicis longus, and the anomalous radial wrist extensors. We describe the epidemiology, anatomy, presentation, diagnosis, and treatment of patients presenting with an anomalous muscle. Each muscle often has multiple variations or subtypes. The presence of most anomalous muscles is difficult to diagnose based on patient history and examination alone, given that symptoms may overlap with more common pathologies. Definitive diagnosis typically requires soft tissue imaging or surgical exploration. When an anomalous muscle is present and symptomatic, it often requires surgical excision for symptom resolution.

Fixation of Regan-Morrey Type II Coronoid Fractures: A Comparison of Screws and Suture Lasso Technique for Resistance to Displacement.

PURPOSE: The aim of this study was to compare the load to failure and stiffness achieved in coronoid fractures treated with a posterior-to-anterior screw versus a suture lasso technique. METHODS: We performed a biomechanical study using 10 pairs of fresh-frozen cadaveric elbows. A transverse osteotomy at the midpoint of the coronoid height was created to simulate a Regan-Morrey type II coronoid fracture. The specimens were randomized to screw fixation or suture lasso fixation. The load to failure and stiffness were then measured using a materials testing machine. RESULTS: Screw fixation provided greater strength and stiffness than suture lasso fixation. Mean load to failure was 405 N in the screw fixation group compared with a load to failure of 207 N for suture fixation. Screw fixation resulted in a mean stiffness of 284 kPa/mm compared with 119 kPa/mm after suture fixation. CONCLUSIONS: Screw fixation was biomechanically superior to fixation using a suture lasso technique. For coronoid fractures in which screw or suture fixation is feasible, screw fixation may provide greater resistance to displacement of the coronoid compared with a suture lasso technique. CLINICAL RELEVANCE: Clinical studies have reported a higher rate of failure after screw fixation compared with suture lasso fixation; however, this study demonstrated a greater stiffness and load to failure after screw fixation of type II coronoid fractures. Screw fixation may provide a stronger fixation construct for fractures of adequate size to support a screw. Further studies may be warranted to assess the importance of securing the anterior capsule to the coronoid tip when using a suture lasso construct because this may affect the stability of the elbow after fixation.

Acute Arterial Thrombosis of the Hand.

Arterial thrombosis of the hand occurs infrequently but may result in considerable morbidity and compromise of hand function. The hand surgeon may be called upon to direct management in cases of acute arterial thrombosis of the hand and should have an understanding of the available diagnostic tools and treatment modalities. This article discusses the vascular anatomy of the hand and clinical manifestations of arterial thrombosis. Differences between isolated thrombosis and diffuse intravascular injury are detailed, and treatment options for these conditions are described. Appropriate care often requires coordination with interventional radiologists or vascular surgeons. Outcomes after treatment of arterial thrombosis of the hand are variable, and prognosis may be related to whether isolated thrombosis or diffuse intravascular injury is present.

Ganglions in the Hand and Wrist: Advances in 2 Decades.

Ganglion cysts represent the most common soft-tissue mass in the hand and wrist. Ganglion cysts are most commonly encountered at the dorsal or volar aspects of the wrist, although cysts may arise from the flexor tendon sheath, interphalangeal joint, and extensor tendons. Intraosseous and intraneural ganglion cysts have also been described. Diagnosis of ganglion cysts relies primarily on history and physical examination. Transillumination and aspiration of masses may be useful adjuncts to diagnosis. Imaging such as radiography and ultrasonography may be indicated to evaluate for associated conditions, such as degenerative joint disease, or to rule out a solid or heterogeneous mass. Advanced imaging such as MRI is generally reserved for patients in whom occult ganglions, intraosseous ganglions, or solid tumors, including sarcoma, remain a concern. Treatment of ganglion cysts includes observation, aspiration or puncture with possible corticosteroid injection, and surgical excision. Nonsurgical management may result in cyst resolution in over 50% of patients. Surgical excision is associated with recurrence rates of 7% to 39%. Advances in surgical techniques have allowed surgeons to conduct arthroscopic ganglion excision, with recurrence rates similar to those of open management. This study highlights the advances in diagnosis, treatment, and outcomes that have taken place over the past 2 decades for this common condition affecting the hand and wrist in the adult population.

Pyogenic Extensor Tenosynovitis of the Wrist-A Cause of Spontaneous Extensor Tendon Rupture: A Report of 2 Cases.

CASES: We present 2 cases of spontaneous extensor tendon rupture in the setting of pyogenic extensor tenosynovitis of the wrist caused by penetrating wounds-a cat bite and injection drug use in patients 1 and 2, respectively. Patient 1 underwent reconstruction of the extensor digitorum communis tendons with palmaris longus autograft. Patient 2 declined surgical reconstruction. CONCLUSIONS: These cases highlight a rare but severe complication of dorsal hand/wrist infection. Early surgical intervention should be considered to prevent this complication, which may have permanent functional consequences and requires complex reconstructive and rehabilitative efforts.