The Compress® transcutaneous implant for rehabilitation following limb amputation.

Amputation is an unfortunate outcome of a variety of orthopedic conditions. Many amputees can be functionally fitted with conventional suspension sockets. A substantial subset, however, fails this conventional treatment and is unable to function. In Europe, an alternative to socket-based prostheses has been available for 25 years. Patients there who are unable to functionally use socket-based prostheses have been offered the possibility for transcutaneous osseointegration. With this technology, the prosthetic limb can be rigidly attached to the residual bone, and the socket is eliminated, in many cases enabling improved function and patient satisfaction. In the United States, regulatory barriers have greatly limited the adoption and acceptance of transdermal osseointegration. The Compress® device was developed as an alternate means of fixation for massive endoprostheses, such as distal femoral replacements. A uniquely designed prosthesis is rigidly anchored to the end of the cortical bone and is then subjected to a large axial stress. The bone then grows avidly into the device, providing permanent osseointegration. We have recently adopted this device for transcutaneous use. These procedures have been performed in the United States on a custom regulatory basis. Results of this have been encouraging, and we are planning to begin a regulatory trial in the near future.

Mechanical properties of the long head of the biceps tendon.

In this study, the geometric and mechanical properties of the long head of the biceps tendon were determined in order to elucidate its role in shoulder stability. We used a laser-micrometer system to measure the cross-sectional area and shape of seven fresh-frozen tendons at three levels: proximal, middle, and distal levels. The cross-sectional areas were found to be 22.7 +/- 9.3 mm2, 22.7 +/- 3.5 mm2, and 10.8 +/- 2.7 mm2, respectively. While statistically significant differences could not be demonstrated between the magnitudes of the areas, a consistent difference in shape was noted between the proximal and middle levels, the tendon being flatter as it progressed over the humeral head and more triangular as it passed through the bicipital groove. We then performed cyclic relaxation tests and uniaxial tensile testing of the tendons which revealed a cyclic stress relaxation of 18 +/- 4% over ten cycles. All tensile failures occurred within the mid-portion of the tendon substance. Additionally, the modulus was calculated between 3% and 6% strain and found to be 421 +/- 212 MPa, while the ultimate tensile strength, ultimate strain, and strain energy density were 32.5 +/- 5.3 MPa, 10.1 +/- 2.7 %, and 1.9 +/- 0.4 MPa, respectively. These mechanical properties of the long head of the biceps tendon are of the same order of magnitude as tendons from other joints. The high stiffness of this tendon indicates that it has an ability to support the large load transferred to it by the muscle and to act as a humeral head depressor.