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Background: Previous biomechanical studies regarding deltoid function during glenohumeral abduction have primarily used static testing protocols. Hypotheses: (1) Deltoid forces required for scapular plane abduction increase as simulated rotator cuff tears become larger, and (2) maximal abduction decreases despite increased deltoid forces. Study Design: Controlled laboratory study. Methods: Twelve fresh-frozen cadaveric shoulders with a mean age of 67 years (range, 64-74 years) were used. The supraspinatus and anterior, middle, and posterior deltoid tendons were attached to individual shoulder simulator actuators. Deltoid forces and maximum abduction were recorded for the following tear patterns: intact, isolated subscapularis (SSC), isolated supraspinatus (SSP), anterosuperior (SSP + SSC), posterosuperior (infraspinatus [ISP] + SSP), and massive (SSC + SSP + ISP). Optical triads tracked 3-dimensional motion during dynamic testing. Fluoroscopy and computed tomography were used to measure critical shoulder angle, acromial index, and superior humeral head migration with massive tears. Mean values for maximum glenohumeral abduction and deltoid forces were determined. Linear mixed-effects regression examined changes in motion and forces over time. Pearson product-moment correlation coefficients (r) among deltoid forces, critical shoulder angles, and acromial indices were calculated. Results: Shoulders with an intact cuff required 193.8 N (95% CI, 125.5 to 262.1) total deltoid force to achieve 79.8° (95% CI, 66.4° to 93.2°) of maximum glenohumeral abduction. Compared with native shoulders, abduction decreased after simulated SSP (–27.2%; 95% CI, –43.3% to –11.1%, P = .04), anterosuperior (–51.5%; 95% CI, –70.2% to –32.8%, P < .01), and massive (–48.4%; 95% CI, –65.2% to –31.5%, P < .01) cuff tears. Increased total deltoid forces were required for simulated anterosuperior (+108.1%; 95% CI, 68.7% to 147.5%, P < .01) and massive (+57.2%; 95% CI, 19.6% to 94.7%, P = .05) cuff tears. Anterior deltoid forces were significantly greater in anterosuperior (P < .01) and massive (P = .03) tears. Middle deltoid forces were greater with anterosuperior tears (P = .03). Posterior deltoid forces were greater with anterosuperior (P = .02) and posterosuperior (P = .04) tears. Anterior deltoid force was negatively correlated (r = −0.89, P = .01) with critical shoulder angle (34.3°; 95% CI, 32.0° to 36.6°). Deltoid forces had no statistical correlation with acromial index (0.55; 95% CI, 0.48 to 0.61). Superior migration was 8.3 mm (95% CI, 5.5 to 11.1 mm) during testing of massive rotator cuff tears. Conclusion: Shoulders with rotator cuff tears require considerable compensatory deltoid function to prevent abduction motion loss. Anterosuperior tears resulted in the largest motion loss despite the greatest increase in deltoid force. Clinical Relevance: Rotator cuff tears place more strain on the deltoid to prevent abduction motion loss. Fatigue or injury to the deltoid may result in a precipitous decline in abduction, regardless of tear size. [ABSTRACT FROM AUTHOR]

The article focuses on a controlled laboratory study conducted to determine the impact of intratendinous ossifications, retrocalcaneal bursitis or intratendinous necrosis in healing tendon injuries. These factors are normally associated with insertional tendinosis which results in complete detachment of Achilles tendon from bone-to-tendon junction. The results showed that for Achilles tendonitis biomechanical stability is restored after good postoperative healing.

Background: Clinical application of platelet-rich plasma (PRP) in the realm of orthopaedic sports medicine has yielded variable results. Differences in separation methods and variability of the individual may contribute to these variable results. Purpose: To compare the effects of different PRP separation methods on human bone, muscle, and tendon cells in an in vitro model. Study Design: Controlled laboratory study. Methods: Blood collected from 8 participants (mean 6 SD age 31.6 6 10.9 years) was used to obtain PRP preparations. Three different PRP separation methods were used: a single-spin process yielding a lower platelet concentration (PRPLP), a single-spin process yielding high platelet and white blood cell concentrations (PRPHP), and a double-spin that produces a higher platelet concentration and lower white blood cell concentration (PRPDS). Human bone, muscle, and tendon cells obtained from discarded tissue samples during shoulder surgery were placed into culture and treated with the 3 PRP preparations, control media (2% fetal bovine serum [FBS] and 10% FBS), and native blood. Radioactive thymidine assays were obtained to examine cell proliferation, and testing with enzyme-linked immunosorbent assay was used to determine growth factor concentrations. Results: Addition of PRPLP to osteocytes, myocytes, and tenocytes significantly increased cell proliferation (P .05) compared with the controls. Adding PRPDS to osteoblasts and tenocytes increased cell proliferation significantly (P .05), but no significance was shown for its addition to myocytes. The addition of PRPHP significantly increased cell proliferation compared with the controls only when added to tenocytes (P .05). Osteoblasts: Proliferation was significantly increased by addition of PRPLP compared with all controls (2% FBS, 10% FBS, native blood) (P .05). Addition of PRPDS led to significantly increased proliferation compared with all controls, native blood, and PRPHP (P .05). Proliferation was significantly less when PRPHP was added compared with PRPDS (P .05). Myocytes: Proliferation was significantly increased by addition of PRPLP compared with native blood (P .05). Adding PRPHP or PRPDS to myocytes showed no significant increase in proliferation compared with the controls or the other separations. Tenocytes: Proliferation was significantly increased by addition of PRPLP compared with all controls (2% FBS, 10% FBS, native blood) (P .05). Addition of PRPDS showed a significant increase compared with the controls and native blood. For tenocytes, there was a significant increase (P .05) seen when PRPHP was added compared with the controls and native blood but not compared with the other separations. Conclusion: The primary findings of this study suggest the application of different PRP separations may result in a potential beneficial effect on the clinically relevant target cells in vitro. However, it is unclear which platelet concentration or PRP preparation may be optimal for the treatment of various cell types. In addition, a ‘‘more is better’’ theory for the use of higher platelet concentrations cannot be supported. This study was not intended to prove efficacy but to provide a platform for future research to be built upon. Clinical Relevance: The utilization of different PRP separations may result in a potentially beneficial effect on the clinically relevant target cells in vitro, but it is unclear which platelet concentration or PRP preparation may be optimal for the treatment of various cell types. [ABSTRACT FROM AUTHOR]

Background: Rotator cuff reconstructions may be improved by adding growth factors, cells, or other biologic factors into the repair zone. This usually requires a biological carrier (scaffold) to be integrated into the construct and placed in the area of tendon-to-bone healing. This needs to be done without affecting the constructs mechanics.Hypothesis/Purpose: The hypothesis was that scaffold placement, as an interposition, has no adverse effects on biomechanical properties of double-row rotator cuff repair. The purpose of this study was to examine the effect of scaffold interposition on the initial strength of rotator cuff repairs.Study Design: Controlled laboratory study.Methods: Twenty-five fresh-frozen shoulders (mean age: 65.5 ± 8.9 years) were randomly assigned to 5 groups. Groups were chosen to represent a broad spectrum of commonly used scaffold types: (1) double-row repair without augmentation, (2) double-row repair with interposition of a fibrin clot (Viscogel), (3) double-row repair with interposition of a collagen scaffold (Mucograft) between tendon and bone, (4) double-row repair with interposition of human dermis patch (ArthroFlex) between tendon and bone, and (5) double-row repair with human dermis patch (ArthroFlex) placed on top of the repair. Cyclic loading to measure displacement was performed to 3000 cycles at 1 Hz with an applied 10- to 100-N load. The ultimate load to failure was determined at a rate of 31 mm/min.Results: There were no significant differences in mean displacement under cyclic loading, slope, or energy absorbed to failure between all groups (P = .128, P = .981, P = .105). Ultimate load to failure of repairs that used the collagen patch as an interposition (573.3 ± 75.6 N) and a dermis patch on top of the reconstruction (575.8 ± 22.6 N) was higher compared with the repair without a scaffold (348.9 ± 98.8 N; P = .018 and P = .025). No significant differences were found for repairs with the fibrin clot as an interposition (426.9 ± 103.6 N) and the decellularized dermis patch as an interposition (469.9 ± 148.6 N; P = .73 and P = .35).Conclusion: Scaffold augmentation did not adversely affect the zero time strength of the tested standard double-row rotator cuff repairs. An increased ultimate load to failure was observed for 2 of the augmentation methods (collagen patch as an interposition and decellularized dermis patch on top of the reconstruction) compared with the nonaugmented repairs.Clinical Relevance: Scaffolds intended for application of growth factors or cellular components in a repair situation did not adversely jeopardize the stability of the operative construct. [ABSTRACT FROM PUBLISHER]

Background: Reconstructions of the coracoclavicular (CC) ligament in an open or arthroscopically assisted procedure are often combined with a resection of the distal clavicle to prevent or treat osteoarthritic degenerations of the acromioclavicular (AC) joint. However, increased horizontal translation leading to symptomatic instability may be associated with resection of the distal clavicle.Hypothesis: Horizontal translation increases in direct correlation to subsequent resection of the distal clavicle.Study Design: Controlled laboratory study.Methods: Twelve fresh-frozen specimens (mean age, 82.0 ± 5 years) were examined using a servohydraulic testing system. A 70-N force was applied in the anterior, posterior, and superior directions, and the translations were quantified for all directions. After native testing, sequential resection of the distal clavicle at 5 and 10 mm was performed after incision of the inferior capsule, and anterior-posterior loads were retested. Finally, the AC ligaments were incised, and repeated testing was performed.Results: Native mean (± standard deviation) anterior translation was 7.90 ± 2.62 mm. After section of the inferior AC capsule, anterior translation was 8.05 ± 2.62 mm (P = 1.0). After clavicle resection of 5 mm, anterior translation was 10.75 ± 2.38 mm (P = .122), and after resection of 10 mm, anterior translation was significantly increased to 11.6 ± 2.37 mm (P = .012). Complete AC capsule sectioning led to significantly greater amounts of anterior translation (12.12 ± 3.0 mm; P = .003). Posterior translation for the native specimen was 8.88 ± 2.63 mm. Sectioning of the inferior AC capsule resulted in 9.21 ± 2.71-mm translation (P = 1.0). After clavicle resection of 5 mm, posterior translation was 10.42 ± 2.42 mm (P = 1.0), and after 10-mm resection, it was 11.31 ± 2.86 mm (P = .39). Sectioning of the complete AC capsule led to significantly greater amounts of posterior translation (12.31 ± 3.12 mm; P = .043).Conclusion: Ten millimeters of resection increased anterior translation of the distal clavicle with both the superior and posterior AC capsules as well as the CC ligaments intact. Both anterior and posterior translations increased after 10-mm resection and complete AC capsule sectioning.Clinical Relevance: These results suggest that resection of the distal clavicle leads to increased horizontal translation despite an intact superior and posterior AC capsule. Only sparing resection of the distal clavicle should be performed and only if strictly indicated. Violation of the AC capsule further increases horizontal translation and should therefore be avoided, or if indicated in AC joint dislocations, a reconstruction of the AC capsule should be considered. [ABSTRACT FROM PUBLISHER]