Tendon tissue engineering: progress, challenges, and translation to the clinic.

The tissue engineering field has made great strides in understanding how different aspects of tissue engineered constructs (TECs) and the culture process affect final tendon repair. However, there remain significant challenges in developing strategies that will lead to a clinically effective and commercially successful product. In an effort to increase repair quality, a better understanding of normal development, and how it differs from adult tendon healing, may provide strategies to improve tissue engineering. As tendon tissue engineering continues to improve, the field needs to employ more clinically relevant models of tendon injury such as degenerative tendons. We need to translate successes to larger animal models to begin exploring the clinical implications of our treatments. By advancing the models used to validate our TECs, we can help convince our toughest customer, the surgeon, that our products will be clinically efficacious. As we address these challenges in musculoskeletal tissue engineering, the field still needs to address the commercialization of products developed in the laboratory. TEC commercialization faces numerous challenges because each injury and patient is unique. This review aims to provide tissue engineers with a summary of important issues related to engineering tendon repairs and potential strategies for producing clinically successful products.

Relationship between MRI and clinical findings in the acromioclavicular joint.

OBJECTIVE: To determine the relationship between the magnetic resonance (MR) appearance of the acromioclavicular (AC) joint and the physical findings. DESIGN: A total of 116 consecutive patients underwent routine MR imaging (MRI) of the shoulder over an 18-month period. All MR studies were interpreted by a blinded, experienced musculoskeletal radiologist. Eleven variables were studied: the presence of osteophytes; fluid in the joint; fluid outside the joint; high signal in the clavicle or in the acromion; fluid in the subacromial bursa; irregularity of the joint margins; bulging of the capsule; widening of the joint; the age of the patient; and the presence of a rotator cuff tear. The clinical information was supplied by an experienced shoulder surgeon blinded to the MRI findings. A control group of 23 normal volunteers was also studied. RESULTS: The only statistically significant correlation ( P=0.0249) was between high signal in the distal clavicle and degenerative changes found clinically. A weaker relationship existed between fluid in the joint and the clinical examination and between increasing degenerative changes and advancing age. Otherwise, no material relationship was found between any of the other MR abnormalities and the clinical picture. CONCLUSION: There appears to be no real correlation between the MR appearances and the clinical findings in the AC joint.

Mucoid degeneration of the anterior cruciate ligament.

A case of intraligamentous mucoid degeneration of the anteromedial band of the anterior cruciate ligament (ACL) is presented. The patient had knee pain without clinical or diagnostic evidence of instability. Isolated debridement of the anteromedial band resulted in immediate pain relief with rapid return to athletic activities without instability. We present this case to demonstrate the presence of intraligamentous mucoid degeneration in the ACL as a source of knee pain without instability. Partial ACL debridement did not preclude adequate knee stability.

Radiologic case study. Pigmented villonodular synovitis.

Pigmented villonodular synovitis is a benign, locally aggressive disorder characterized by a unique clinical radiographic, and histopathologic presentation. While it is considered to be a rare disorder, a delay in diagnosis and treatment can potentially result in severe disruption of joint function due to subchondral invasion. Once the diagnosis is confirmed, treatment should consist of complete synovectomy. Recurrence is common, but malignant transformation is rare. The etiology of PVNS is still unknown, and perhaps its future discovery will assist in the definitive treatment of this disorder.

Pediatric traumatic atlanto-occipital dislocation: five cases and a review.

Traumatic atlanto-occipital dislocation (AOD) has been thought to be a rare and fatal injury. Recently, more survivors, especially children, have been reported. During a 10-year period, the authors have encountered five children with traumatic AOD. A retrospective review of traumatic AOD in children from 1985 to 1995 was performed. Clinical presentation, initial radiologic findings, and final outcome were emphasized. Distance from the dens to the basion and the ratio of Powers were measured from initial lateral cervical spine radiographs. The average distance from the dens to the basion was 9.8 mm. The average ratio of Powers was 1.38. There were three survivors, two having a concomitant spinal cord injury. All survivors underwent a posterior occipitovertebral fusion. Three cases initially went undiagnosed. The diagnosis of AOD by lateral cervical spine radiographs can be difficult. The authors recommend detailed measurements of the initial cervical spine radiographs in pediatric patients at risk for traumatic AOD.

Acute elbow injuries in the National Football League.

We performed a retrospective review to evaluate acute medial collateral ligament injuries of the elbow in professional football players from 1991 to 1996 (5 seasons). There were 5 acute medial collateral ligament injuries in 4 players (1 player with bilateral involvement). All injuries occurred with the hand planted on the playing surface while a valgus or hyperextension force was applied to the elbow. There were 2 centers, both involved with long-snapping situations, 1 running back, and 1 quarterback. All elbows had valgus instability on physical examination. Despite this instability, all players were able to function without operative reconstruction of the medial collateral ligament. No evidence of valgus instability was seen at the time of follow-up (average, 3.4 years). Next, we reviewed all acute elbow injuries in the National Football League from the same 5-season period. Ninety-one acute elbow injuries were reviewed. Overall, there were 70 (76.9%) elbow sprains, 16 (17.6%) dislocation/subluxation patterns, 4 (4.4%) fractures, and 1 (1.1%) miscellaneous injury. Review of the acute elbow sprains revealed 39 (55.7%) hyperextension injuries, 14 (20%) medial collateral ligament injuries, 2 (2.9%) lateral collateral ligament sprains, and 15 (21.4%) nonspecific sprains. The epidemiology of the 14 medial collateral ligament injuries was studied in more detail. The 2 most common mechanisms of injury were blocking at the line of scrimmage (50%) and the application of a valgus force with the hand planted on the playing surface (29%). There were 8 linemen, 4 receivers, 1 running back, and 1 quarterback. All injuries were managed with nonoperative treatment. The average time lost was 0.64 games (range, 0 to 4). We report 19 acute medial collateral ligament injuries of the elbow in elite football players, 2 of whom are considered overhead throwing athletes, who were able to function at a competitive level without surgical repair or reconstruction, in contrast to baseball players, in whom the mechanics and demands may differ.

Intra- and interobserver reproducibility of the shoulder laxity examination.

The present study evaluates the inter- and intraobserver reproducibility of clinical examination of glenohumeral laxity in the unanesthetized shoulder. Forty-three asymptomatic Division I collegiate athletes underwent bilateral shoulder laxity examination initially and again after 3 months. Translation of the humeral head on the glenoid fossa in the anterior, posterior, and inferior directions was graded by four physicians who were blinded to their own previous grading and that of the other examiners. Overall intraobserver reproducibility of examination was 46%. When grades 0 and 1 were equalized, overall intraobserver reproducibility improved to 74%. For both the equalized and non-equalized reproducibility values reported by all examiners, the kappa values for intraobserver correlation were less than 0.5, which suggests that correlations were not better than those achieved by chance alone. Overall interobserver reproducibility was 47%. When grades 0 and 1 were equalized, interobserver reproducibility improved to 78%. Kappa values were greater than 0.5 only in equalized posterior and inferior laxity. The data demonstrate that the laxity examination of the unanesthetized shoulder is not easily reproducible in either intra- or interobserver comparison. Equalization of grade 0 and grade 1 laxity improves both intra- and interobserver reproducibility. We recommend caution when determining diagnosis and treatment based on this examination.

Glenohumeral translation in the asymptomatic athlete's shoulder and its relationship to other clinically measurable anthropometric variables.

To determine the degree of shoulder translation in uninjured athletes, we examined 76 Division I collegiate athletes (44 women and 32 men) for passive range of motion in both shoulders and for knee and elbow hyperextension. Translation was based on a scale of 0 to 3+. Shoulders with symptoms of pain or a history of instability or dislocation were excluded from this study. Forty-six shoulders had 0 anterior translation, 75 had 1+, and 31 had 2+. Thirteen shoulders had 0 posterior translation, 56 had 1+, and 83 had 2+. Thirty-eight shoulders had 0 inferior translation, 105 had 1+, and 9 had 2+. No shoulder had translation of 3+ in any direction. Twenty-four athletes, 12 men and 12 women, had translational asymmetry of a minimum of one grade in at least one direction. No shoulder was asymmetric in all three directions. There was a significant correlation between dominant hand and increased translation; 19 of 24 athletes with asymmetric shoulders had greater translation in the nondominant extremity. There was no relationship between translation and range of motion, knee or elbow hyperextension, thumb-to-forearm distance, or years spent in sports participation. Asymmetry of shoulder translation may exist in the normal shoulder. This review shows that up to 2+ translation in any direction cannot be considered abnormal.