Digital mapping of shoulder pain in patients with shoulder disorders: a reliability study.

INTRODUCTION: Digital body mapping can be used to document and quantify the area and location (distribution) of pain and discomfort and support assessment, monitoring, and treatment in clinical populations. This study determines the test-retest reliability of drawings detailing pain and pins and needles using digital body charts and their relationship to pain intensity and patient-reported shoulder function. METHODS: Sixty-two participants with shoulder disorder completed pain and pins and needles drawings with test-retest interval of 30 minutes. Pain intensity in the last week and the patient-reported shoulder function questionnaires were completed. Area and radiating extent were determined using customized software. To assess relative and absolute test-retest reliability, the intraclass correlation coefficient (ICC3,1), standard error of measurement (SEM) and minimal detectable change (MDC95) were calculated. Regression analysis evaluated relation between area and radiating extent of pain and pins and needles with patient-reported function questionnaires. RESULTS: Relative reliability for pain area and radiating extent was excellent (>0.90). Absolute reliability (SEM and MDC95) values for the pain area and radiating extent were 0.20%/34 pixels and 0.57%/94 pixels. Absolute reliability improves for smaller pain areas. Regression analysis revealed the area and radiation extent for both pain and pins and needles are independent constructs to the patient-reported function outcome when adjusted for pain intensity. CONCLUSIONS: Digital body mapping assessing pain area and radiation extent in patients with shoulder disorders are reliable. The magnitude of absolute reliability suggests other sources of variability on repeat testing in this population. Pain area and radiation extent appear to be independent constructs.

Lower strength of the human posterior patellar tendon seems unrelated to mature collagen cross-linking and fibril morphology.

The human patellar tendon is frequently affected by tendinopathy, but the etiology of the condition is not established, although differential loading of the anterior and posterior tendon may be associated with the condition. We hypothesized that changes in fibril morphology and collagen cross-linking would parallel differences in material strength between the anterior and posterior tendon. Tendon fascicles were obtained from elective ACL surgery patients and tested micromechanically. Transmission electron microscopy was used to assess fibril morphology, and collagen cross-linking was determined by HPLC and calorimetry. Anterior fascicles were markedly stronger (peak stress: 54.3 +/- 21.2 vs. 39.7 +/- 21.3 MPa; P < 0.05) and stiffer (624 +/- 232 vs. 362 +/- 170 MPa; P < 0.01) than posterior fascicles. Notably, mature pyridinium type cross-links were less abundant in anterior fascicles (hydroxylysylpyridinoline: 0.859 +/- 0.197 vs. 1.416 +/- 0.250 mol/mol, P = 0.001; lysylpyridinoline: 0.023 +/- 0.006 vs. 0.035 +/- 0.006 mol/mol, P < 0.01), whereas pentosidine and pyrrole concentrations showed no regional differences. Fibril diameters tended to be larger in anterior fascicles (7.819 +/- 2.168 vs. 4.897 +/- 1.434 nm(2); P = 0.10). Material properties did not appear closely related to cross-linking or fibril morphology. These findings suggest region-specific differences in mechanical, structural, and biochemical properties of the human patellar tendon.

Glutaraldehyde cross-linking of tendon--mechanical effects at the level of the tendon fascicle and fibril.

Conclusive insight into the microscopic principles that govern the strength of tendon and related connective tissues is lacking and the importance of collagen cross-linking has not been firmly established. The combined application of whole-tissue mechanical testing and atomic force spectroscopy allowed for a detailed characterization of the effect of cross-linking in rat-tail tendon. The cross-link inducing agent glutaraldehyde augmented the tensile strength of tendon fascicles. Stress at failure increased from approximately 8 MPa to approximately 39 MPa. The mechanical effects of glutaraldehyde at the tendon fibril level were examined by atomic force microscopy. Peak forces increased from approximately 1379 to approximately 2622 pN while an extended Hertz fit of force-indentation data showed a approximately 24 fold increase in Young's modulus on indentation. The effect of glutaraldehyde cross-linking on the tensile properties of a single collagen fibril was investigated by a novel methodology based on atomic force spectroscopy. The Young's modulus of a secluded fibril increased from approximately 407 MPa to approximately 1.1 GPa with glutaraldehyde treatment. Collectively, the findings indicate that cross-linking at the level of the collagen fibril is of key importance for the mechanical strength of tendon tissue. However, when comparing the effects at the level of the tendon fascicle and fibril, respectively, further questions are prompted regarding the pathways of force through the tendon microstructure as fibril strength seems to surpass that of the tendon fascicle.

Corticosteroids reduce the tensile strength of isolated collagen fascicles.

BACKGROUND: Overuse tendon injuries are frequent. Corticosteroid injections are commonly used as treatment, although their direct effects on the material properties of the tendon are poorly understood. PURPOSE: To examine the influence of corticosteroids on the tensile strength of isolated collagen fascicles. STUDY DESIGN: Controlled laboratory study. METHODS: Single strands (300-500 mum) of rat-tail collagen fascicles were incubated in either high (1 mL of 40 mgmL(-1) mixed with 0.5 mL saline 9%) or low (1 mL of 40 mgmL(-1) mixed with 2 mL saline 9%) concentration of methylprednisolone acetate (Depomedrol) for 3 or 7 days, while the control segment from the same fascicle was kept in saline (N = 64). After the incubation period, the fascicles underwent displacement to failure in a mechanical test rig at 0.13 mm/s, and thereafter hydroxylysyl pyridinoline and lysyl pyridinoline cross-link content was evaluated in a high-performance liquid chromatography system. Data for each group were analyzed with a 2-way analysis of variance (time x incubation) for ultimate stress (mean +/- standard deviation). RESULTS: In the high-concentration groups, strength was reduced after 3 (16.6 +/- 4.6 MPa) and 7 (8.6 +/- 1.7 MPa) days compared to the controls (30.2 +/- 5.0 MPa and 25.6 +/- 4.6 MPa, respectively; P < .05). In the low-concentration groups, strength was reduced after 3 (12.0 +/- 3.1 MPa) and 7 days (10.9 +/- 2.5 MPa) compared to the controls (31.5 +/- 5.0 MPa and 32.4 +/- 5.6 MPa, respectively; P < .05). The amount of cross-linking was unaffected by the intervention. CONCLUSION: Data show that the tensile strength of isolated fascicles is markedly reduced after 3- and 7-day incubation in both high and low concentration of corticosteroids, although the observed effect on whole tendon remains unknown. CLINICAL RELEVANCE: Corticosteroids may weaken specific regions of the injected tendon and leave it more prone to rupture. This weakening effect is manifested in the individual collagen fascicles that constitute the tendon.