Mechanical and strain behaviour of human Achilles tendon during in vitro testing to failure

The Achilles tendon is the strongest tendon in the human body but its mechanical behaviour during failure has been little studied and the basis of its high tensile strength has not been elucidated in detail. In the present study, healthy, human, Achilles tendons were loaded to failure in an anatomically authentic fashion while the local deformation and strains were studied in real time, with very high precision, using digital image correlation (DIC). The values determined for the strength of the Achilles tendon were at the high end of those reported in the literature, consistent with the absence of a pre-existing tendinopathy in the samples, as determined by careful gross inspection and histology. Early in the loading cycle, the proximal region of the tendon accumulated high lateral strains while longitudinal strains remained low. However, immediately before rupture, the mid-substance of the Achilles tendon, its weakest part, started to show high longitudinal strains. These new insights advance the understanding of the mechanical behaviour of tendons as they are stretched to failure.

Biomechanical effectiveness of tendon transfers to restore active internal rotation in shoulder with deficient subscapularis with and without reverse shoulder arthroplasty

BACKGROUND

Loss of active shoulder internal rotation can be very disabling. Several tendon transfers have been described for the management of an irreparable subscapularis (SSC) tear. The purpose of this study was to determine and compare the internal rotation moment arm (IRMA) of the sternal head of the pectoralis major (PM), latissimus dorsi (LD), and teres major (TM) when transferred to different insertion sites to restore shoulder internal rotation with and without reverse shoulder arthroplasty (RSA).

METHODS

Six fresh-frozen right hemithoraces were prepared and evaluated using a custom tendon transfer model to determine the IRMA of different tendon transfers using the tendon and joint displacement method. Five tendon-transfer pairs were modeled using a single suture and tested before and after implantation of an RSA (Comprehensive; Zimmer-Biomet, Warsaw, IN, USA): PM to the insertion site of the SSC, LD to the anterior insertion site of the supraspinatus (SSP) tendon on the greater tuberosity, LD to SSC, TM to SSP, and TM to SSC. The SSC was not repaired at the end of the RSA procedure to simulate an SSC deficiency. The PM transfer was passed under the conjoined tendon when tested on the intact shoulder and above the conjoined tendon when tested with an RSA.

RESULTS

Tendon transfers were shown to have a significant effect on IRMA. The effect of transferred tendons was significantly affected by the position of the humerus. With the humerus adducted, the IRMA of the TM-SSP (14.1 mm ± 3.1 mm) was significantly greater than the other transfers. With the humerus abducted to 90°, the IRMAs of the LD-SSP (30.0 mm ± 5.4 mm) and TM-SSP (28.4 mm ± 6.6 mm) were significantly greater than the IRMAs of other transfer options. The IRMA of the native shoulder differed significantly from that of the RSA state for all tendon transfers. With the humerus adducted to the side of the body, the IRMA of the RSA PM-SSC transfer was significantly greater than that without an RSA (19.0 mm ± 6.4 mm vs. 7.1 mm ± 0.9 mm), demonstrating increased efficiency for internal rotation in the RSA state.

CONCLUSION

Tendon transfers to restore shoulder internal rotation differ in effectiveness and may be affected by arm position and by implantation of a lateralized humerus/lateralized glenoid RSA. The LD potentially results in superior restoration of shoulder internal rotation in a native shoulder (given the risk of nerve compression with the TM transfer) compared with PM and should be considered as a potential tendon transfer to restore internal rotation in selected patients. In combination with a lateralized humerus/lateralized glenoid RSA, the fulcrum provided by the biomechanics of the semiconstrained implant allows the PM transfer to become a more efficient tendon transfer to restore active internal rotation.

Gender differences in Ayrshire teenagers' attitudes to sexual relationships, responsibility and unintended pregnancies

Disadvantages and risks related to teenage pregnancy, together with a recent increase in Scottish conception rates among teenagers aged 13-15 years old, give cause for concern. Using an illustrated short story and questionnaire, attitudes of 129 Ayrshire teenagers aged 14-15 years old were examined to teenage pregnancy, and more generally to early sex. Seventy-three percent of girls advocated joint responsibility for contraceptive protection compared with only 46% of boys (p<0.01). Also, significantly more boys than girls saw nothing wrong with casual sex (21%vs. 5%, p<0.01), and significantly less boys than girls upheld the virtue of commitment in sexual relationships (27%vs. 54%, p<0.01). Sex education programmes should explore these gender-related disparities.

Eligibility criteria for NHS long stay care: the relationship between clinical need, dependency, and staff perception

A study was undertaken by a Scottish Health Authority to determine future provision of NHS long stay in-patient beds for young physically disabled people (aged < 65), and eligibility criteria for admission to such care. As part of the development of care in the community, only patients requiring specialist medical and nursing care should continue to be placed in NHS care. Resources freed from the resulting closure of NHS beds will be transferred to Social Services to develop alternative packages of care in the community, based on need rather than precedent. Achieving the balance, in terms of the correct level of continuance of NHS long stay care and redeployment of resources, requires careful planning. This study, involving all young physically disabled patients in NHS care in Argyll and Clyde Health Board, combined the assessment of dependency using validated scales (CAPE, FIM, and ERSS), with staff perception of dependency and with clinical criteria developed for a series of balance of care studies in this authority. These clinical criteria indicate the need for specialist medical and nursing care. By examining the relationship between dependency and staff perception, it has been possible to plan long stay provision on a population basis. The criteria for admission have been adopted for local clinical use and form the basis for appeals procedures for patients deemed appropriate for discharge.

Prevention of bone mineral loss in postmenopausal women by norethisterone

The effect of norethisterone on bone mineral metabolism was examined in 43 postmenopausal women. A significant decline in serum calcium, phosphate, and alkaline phosphatase in urinary calcium/creatinine ratio and in tubular maximum reabsorption of phosphate was demonstrated. There was no alteration in urinary hydroxyproline/creatinine ratio. The bone mineral content measured over two years by single photon absorptiometry was compared in 20 patients receiving norethisterone and a matched control group receiving placebo. There was significant protection against bone loss in the norethisterone group.