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Rotator cuff and biceps tendons that appeared grossly normal were procured from adult cadavers without a history of shoulder problems. These tendons were analyzed for the amount and type of glycosaminoglycan, type of proteoglycan, and histology. When compared with the distal/tensional region of biceps tendon, the glycosaminoglycan content of supraspinatus, infraspinatus, and subscapularis tendons was 2.5-fold higher and the glycosaminoglycan content of the proximal/compressed region of biceps tendon was 3-fold higher. The ratio of hyaluronic acid to chondroitin sulfate/dermatan sulfate in all three cuff tendons was approximately 1. Rotator cuff tendons contained large proteoglycan similar to aggrecan, as demonstrated by sodium dodecyl sulfate-polyacrylamide gel migration elution from Sepharose CL-4B, and content of both chondroitin sulfate and keratan sulfate chains. Both decorin and biglycan were also present, as demonstrated by migration in sodium dodecyl sulfate-polyacrylamide gels and core protein immunoreactivity. In contrast decorin was the only proteoglycan prominent in distal/tensional regions of biceps tendon. Histological analysis showed layers of loosely organized alcian blue-stained material running between the longitudinal collagen fiber bundles. The proteoglycan content of rotator cuff tendons was similar to fibrocartilage in tendons that have been subjected to compressive loads in situ. This suggests that cells of normal adult rotator cuff tendons have adapted to loads distinct from pure tension. However, the histological organization did not resemble mature fibrocartilage. The increased amount of proteoglycan in rotator cuff tendons may serve to separate and lubricate collagen bundles as they move relative to each other during normal shoulder motion.

Over 50% of all knee injuries involve partial or com plete tear of the anterior cruciate ligament. Surgical reconstruction of this ligament using an isometrically placed bone-patellar tendon-bone autograft is the cur rent technique of choice; however, harvest of patellar tendon as a free graft can lead to increased morbidity. To address this issue, allogenic patellar tendon grafts have been introduced as alternatives to autogenic graft material. The purpose of this study was to exam ine effects of age and strain rate on tensile strength, modulus, and failure mode of bone-patellar tendon- bone allografts from a typical population of tissue do nors. Eighty-two, fresh-frozen, bone-patellar tendon- bone allografts were harvested from 25 different donors, aged 17 to 54. Paired grafts from individual patellar tendons were assigned randomly to tensile testing at either 10% or 100% elongation per second. Tensile strength, modulus, and failure mode were not significantly different for tests conducted at these 2 strain rates. Correlations between tensile strength and age were not significant for tests conducted at either strain rate. Specimens tested at a strain rate of 100% per second exhibited weak but significant negative correlation between modulus and age, with modulus decreasing 25% over the age range examined.

Fifty-eight patients with 62 pathologic fractures secondary to metastatic disease were admitted to a rehabilitation hospital during a 5-year period. Thirty-four patients were discharged home, 7 were transferred to other facilities, and 17 died. The average hospital stay for the patients who went home (37 days) was only 3 days longer than for patients with nonpathologic fractures. No patient could transfer independently or ambulate at the time of admission, but 26 and 23, respectively, could do so by the time of discharge; 27 patients showed significant improvement in their ability to perform activities of daily living as measured by Kenny scores. All 11 patients who had hypercalcemia died. Eleven of 13 patients requiring parenteral narcotics died. Patients with pathologic fractures secondary to metastatic disease are excellent candidates for intensive rehabilitation programs, but hypercalcemia and administration of parenteral narcotics suggest a poor rehabilitation outcome.

Grossly normal supraspinatus tendons were analyzed by stereomicroscope dissection and three-dimensional serial-section reconstruction. Four structurally independent subunits were identified: the tendon proper extended from the musculotendinous junction to approximately 2.0 cm medial to the greater tuberosity. It was composed of parallel collagen fascicles oriented along the tensional axis and separated by a prominent endotenon region. There was no interdigitation of fascicles, and an 18% incidence of fascicle convergence as the fascicles coursed from muscle toward greater tuberosity. The attachment fibrocartilage extended from the tendon proper to the greater tuberosity, consisted of a complex basket-weave of collagen fibers, and stained diffusely with alcian blue. The densely packed unidirectional collagen fibers of the rotator cable extended from the coracohumeral (CH) ligament posteriorly to the infraspinatus, coursing both superficial and deep to the tendon proper. The capsule was composed of thin collagen sheets each with uniform fiber alignment that differed slightly between sheets. These data describe a specialized tendon capable of internally compensating for changing joint angles through fascicles which are structurally independent and can slide past one another. The tendon attachment exhibits a structure adapted to tensional load dispersion and resistance to compression.

Measurements on a high-performance switched Ethernet system are presented that reveal new insights into the statistical nature of le server and web server tra��c. Both le sizes and data requested from the web server are shown to match well a truncated Cauchy distribution. This is a distribution with heavy tails similar in nature to the commonly used Pareto distribution but with a much better t over smaller le/request sizes. We observe self similar characteristics in the tra��c at both servers and also at a CPU server elsewhere on the network. Tra��c from this server is predominantly targeted at the le and web servers, suggesting that self-similar properties at one point on a network are being propagated to other points. A simple simulation model of an isolated server is presented with Poisson arrivals and service (packet transmission) demands with the same Cauchy distribution as we observed. The departure process is shown to follow a power law and the corresponding power spectrum is shown to match extremely well that of the observed tra��c. This supports the suggested link between le/request size distribution and self-similarity. The resulting implication that self similarity and heavy tails are primarily due to server-nodes, rather than being inherent in o ered tra��c, leads to the possibility of using conventional queueing network models of performance. This idea is further supported by an additional simulation experiment and suitable models are proposed.

This paper considers the M/G/1 queue with regularly varying service requirement distribution. It studies the effect of the service discipline on the tail behavior of the waiting- or sojourn time distribution, demonstrating that different disciplines may lead to quite different tail behavior. The orientation of the paper is methodological: We outline three different methods of determining tail behavior, illustrating them for service disciplines like FCFS, Processor Sharing and LCFS.

The causes and incidence of rotator cuff injuries in patients under the age of 40 has not been clearly established. The present study focuses on a group of 10 male contact athletes with rotator cuff injuries re lated to trauma sustained during football (ages from 24 to 36 years). Symptoms included pain and dysfunction in all 10 patients and a positive shrug sign in 8 of 10. The diagnoses for these patients were two isolated contusions, five partial-thickness tears, and three full- thickness tears. Surgery was performed on all patients after nonoperative treatment failed. Three partial-thick ness tears were arthroscopically debrided. One full- thickness and two partial-thickness tears were repaired using the arthroscopically assisted miniarthrotomy technique. An open repair was performed in two pa tients. Two isolated rotator cuff contusions were arthro scopically debrided. The average followup was 21 months. Nine of 10 athletes returned to active partici pation in football, 7 of these at their preinjury levels. The diagnosis of rotator cuff injury should be consid ered in a contact athlete who has persistent shoulder pain, impingement signs, weakness, and a positive shrug sign. Arthroscopic debridement of the subacro mial space followed by debridement or repair of rotator cuff tears, as clinically indicated, resulted in a marked improvement in function and rapid return to sport for these patients.

Out of 78 patients identified who underwent mini-open cuff repair, 64 were interviewed and returned a detailed questionnaire and 47 returned for a physical examination. Their average age was 64 years (31 to 85 years); and the average follow-up was 29.2 months (range, 12 to 65 months). The average tear size was 8 cm2. Preoperatively, all patients complained of pain and weakness. Ninety-six percent of patients displayed positive impingement signs preoperatively compared with 16% postoperatively. Active elevation increased significantly (P.05) from 129 degrees to 166 degrees. At the time of follow-up there was no significant difference between active elevation in the operative and contralateral shoulders (P.05). Weakness was detectable by physical examination in 83% of patients initially, and in 22% at the time of the final examination. The average pain and function scores improved significantly. Eighty-nine percent were satisfied with the results of their surgery. Three patients required further surgery on their shoulder. We found no correlation between cuff tear size and final Hospital for Special Surgery shoulder score.