Ludger Kirsch

Biomechanical Properties of Commonly Used Autogenous Transplants in the Surgical Treatment of Chronic Lateral Ankle Instability

The purpose of this study was to evaluate the biomechanical properties of commonly used autogenous transplants for the surgical stabilization of chronic lateral ankle instability. We dissected the transplants (peroneus longus, peroneus brevis, Achilles and plantaris tendon, periosteal flap, fascia, corium) and the anterior talofibular ligament from 13 fresh anatomic specimens. After laser-assisted measurement of the transplant diameter, we assessed their biomechanical properties with a universal testing device. Biomechanical stability of the peroneus longus, peroneus brevis, and Achilles tendons was significantly higher than the other transplants. The stability parameters of the periosteal flap were in the range of the anterior talofibular ligament but inferior to the tendons. The application of a transplant with low biomechanical stability, such as the periostal flap, requires more postoperative immobilization as in a strong orthosis or cast.

A system for engineering an osteochondral construct in the shape of an articular surface: Preliminary results

A tissue-engineered articular condyle could provide a new alternative approach to joint replacement. This study describes progress made towards engineering an articular condyle in vitro using human bone marrow stromal cells (hBMSCs) in a biphasic matrix. hBMSCs were transferred to a rat collagen-I hydrogel which was then pressed onto a bovine cancellous bone matrix. The gel/cell suspensions, each at a density of approximately 5 x 10(5)cells/ml containing fourth passage cells pressed into an adult human tibial condyle form using CT scan based moulds. The osteochondral constructs fabricated in vitro were stimulated in a bioreactor using cyclic compression and continuous perfusion. Penetration and cell distribution were demonstrated as homogeneous and cells were found to be viable after gel compression. The filamentous structure of the collagen fibres was more dense and homogeneous using compression. Mechanical tests showed a significant enhancement of primary matrix stability after initial compression. Stiffness was not observed to increase significantly over 7 days under loading in a bioreactor. The successful integration of mechanical stimulation in the tissue engineering process leads to an improvement in the structural and biomechanical properties of these tissues and offers new possibilities in the management of joint injuries and degenerative diseases. Remarkably, the stiffness was enhanced in our setting after initial compression of the construct in the glass cylinder without observing a negative influence on cell viability. Further studies need to clarify the influence of compression and various mechanical and hydrostatic stress patterns over different periods of time.

Biomechanical analysis for primary stability of shoulder arthrodesis in different resection situations

BACKGROUND Only very few publications dealing with shoulder arthrodesis after bone resection procedures and no biomechanical studies are available. The presented biomechanical analysis should ascertain the type of arthrodesis with the highest primary stability in different bone loss situations. METHODS On 24 fresh cadaveric shoulder specimens three different bone loss situations were investigated under the stress of abduction, adduction, anteversion and retroversion without destruction by the use of a material testing machine. In each of the testings a 16-hole reconstruction plate was used and compared to arthrodesis with an additional dorsal 6-hole plate. FINDINGS The primary stability of shoulder arthrodesis with a 16-hole reconstruction plate after humeral head resection could be increased significantly if an additional dorsal plate was used. However, no significant improvement with the additional plate was detected after resection of the acromion. Of all investigated forms, arthrodesis after humeral head resection with additional plate showed the highest and arthrodesis after humeral head resection without additional plate showed the lowest force values. The mean values for forces achieved in abduction and adduction were considerably higher than those in anteversion and retroversion. INTERPRETATION There are no consistent specifications of arthrodesis techniques after resection situation available, thus the presented biomechanical testings give important information about the most stable form of arthrodesis in different types of bone loss. These findings provide an opportunity to minimize complications such as pseudarthrosis for a satisfying clinical outcome.

Ultrasound Volume Guided Navigated Implantation of the Humeral Part of a Shoulder Prosthesis

Diagnostic ultrasound in the shoulder area is nowadays usually limited to conventional, two-dimensional (2-D) ultrasound images taken in predefined, standardized sonogram acquisition orientations. This only provides limited insights into the joint’s three-dimensional (3-D) geometry. In contrast, 3-D freehand acquired ultrasound volumes can cover the anatomic structures necessary e.g. for planning the implantation of the humeral part of a shoulder prosthesis. In a pilot study, such landmarks were determined from the semiautomatically segmented volumes. A first verification of the approach was performed using an experimental prototype for surgical planning and navigation in a cadaver study.

Ultrasound Volume Based Surgical Planning for Prosthesis Implantation in the Shoulder Joint

Surgical planning for the implantation of a prosthesis in the shoulder joint is at present usually done using CT, MRI and X-ray imaging. Apart from being expensive and hard to use in some settings, modalities like CT and X-ray additionally expose the patient to ionizing radiation. In comparison, ultrasound is an easy to use, cheap modality. By combining a conventional two dimensional probe with a localizer system, even larger anatomical structures like the humerus can be examined and delineated using ultrasound. In a pilot study, we investigated the use of such three-dimensional volumes for surgical planning in the shoulder joint.