[Effect of transplant length on functional and morphologic outcome of nerve transplantation--an experimental study]. / Der Einfluss der Transplantatlänge auf das funktionelle und morphologische Ergebnis der Nerventransplantation--Eine experimentelle Studie.

BACKGROUND: The present study was done in order to clarify whether the sometimes poor results after the use of long grafts for nerve reconstruction are due to the length of the graft itself or due to the concomitant big defect in the soft tissues necessitating the use of long grafts. METHODS: In 22 rabbits, the saphenous nerve was used as a nerve graft. Animals were separated into three groups with different lengths of the grafts, namely 3 cm (group 1), 5 cm (group 2) and 7 cm (group 3). In one hindlimb, the proximal end of the graft was coapted to the motor nerve branch of vastus medialis. In a second step, the distal end of the graft was coapted to the nerve branch of rectus femoris. After a total period of 15 months the maximum tetanic tensions in the reinnervated rectus femoris and in the contralateral untreated muscle were determined. Biopsies of the graft and the motor branch distal to the graft were taken in order to count the number of regenerated myelinated nerve fibers. RESULTS: The average maximum tetanic tension in the rectus femoris muscle reinnervated by the 3 cm long graft was 27.2 N; in group 2 the force amounted to 20.4 N. In group 3, the maximum force was 17.6 N, which meant an average loss of 29% compared to the contralateral untreated muscle. In accordance with the functional results, the mean number of regenerated myelinated fibres in the rectus femoris motor branch decreased from 1683 in group 1 to 1136 in group 3. CONCLUSIONS: The results show that the length of the graft influences the results after nerve grafting to a certain extent, but a combination of other factors like concomitant soft tissue injury and destroyed target organs may also be responsible for some of the poor results after the clinical use of long nerve grafts.

[Circulatory support by an electrically stimulated muscle flap. Experimental experiences]. / Kreislaufunterstützung durch elektrisch stimulierte Muskellappen. Experimentelle Erfahrungen.

Functional electrical stimulation of the latissimus dorsi muscle flap for circulatory assistance extends the traditional concept of using this flap for reconstructive procedures into the field of cardiac surgery. It requires a transformed muscle which is able to contract for long periods of time without fatigue. Two main groups of experiments have been carried out in sheep. In six sheep the latissimus dorsi muscle (MLD) was transformed into a fatigue-resistant muscle by the means of multichannel stimulation of the supplying motor nerve. After that, stimulation of MLD at a frequency of 70 contractions per minute could be performed continuously without significant muscle fatigue. The loss of maximal force caused by the conditioning procedure was about one third of the initial force. In a second series of acute experiments the MLD was used for cardiomyoplasty. The muscle was divided into two parts which were wrapped around the heart in two different forms. The resting tension of the muscle was preserved. EKG-synchronous stimulation resulted in an increase in left ventricular pressure between 12 and 53%. The increase in arterial pressure was between 10,6 and 58%.

The influence of the donor nerve on the function and morphology of a mimic muscle after cross innervation: an experimental study in rabbits.

In the present study we used the scutuloauricularis muscle in the rabbit to investigate the functional and morphometric alterations in the mimic-muscle system after cross-reinnervation. The scutuloauricularis muscle is the first experimental model that allows functional assessment of a mimic muscle by force measurements. A total of 36 rabbits were separated into three groups. In group 1 the scutuloauricularis nerve was cut and re-sutured to itself to achieve self-reinnervation; in group 2 the buccal nerve was used to cross-reinnervate the fast scutuloauricularis muscle and in group 3 the slow buccinator muscle was cross-reinnervated by the scutuloauricularis nerve. After a period of 6 months the maximal tetanic tensions of the reinnervated scutuloauricularis muscles were determined and histomorphometric examinations of muscle and nerve biopsies were carried out. Force measurements showed no loss of muscle force after self- and cross-reinnervation. The normal scutuloauricularis muscle contained 33%, and the buccinator muscle 46%, slow type I fibres. After self-reinnervation of the scutuloauricularis muscle the fibre-type composition remained unchanged. After cross-reinnervation we saw a significant fast-to-slow transformation of the scutuloauricularis muscle and a significant slow-to-fast transformation of the buccinator muscle. The number of myelinated nerve fibres in the scutuloauricularis nerve increased after cross-reinnervation from 1531 to 4077 (group 2) and to 3813 (group 3). The number of nerve fibres in the buccal nerve (3209) was unchanged after cross-reinnervation. The results of the present study might be relevant in the treatment of irreversible facial palsy by functional muscle transplantation and cross-face nerve grafting. The facial nerve branch used for cross-reinnervation seems to determine the functional outcome.

Noninvasive monitoring of rotary blood pumps: necessity, possibilities, and limitations.

Although rotary blood pumps do not contain an inherent mechanism for adaptation to physiological flow necessities, hitherto only a few efforts have been made to obtain robust monitoring and control methods. This paper discusses the necessity of noninvasive monitoring of such pumps and the crucial points of sensor selection and development. A strategy of monitoring atrial pressure out of the data obtained by the collapse of the atrial wall around the inflow cannula and initial results on animal tests and computer simulation of this method are discussed. This approach might lead to reliable and demand-responsive controllers, if some basic criteria are fulfilled.

The influence of the graft length on the functional and morphological result after nerve grafting: an experimental study in rabbits.

Clinical experience shows that the results after the use of long nerve grafts for reconstruction are sometimes poor. Nevertheless several authors have stressed that the concomitant big defect in the soft tissues necessitating the use of long grafts is the reason for some of the failures. In 22 rabbits the saphenous nerve was used as a nerve graft. Animals were separated into 3 groups with different lengths of the grafts, namely 3 cm (group 1), 5 cm (group 2) and 7 cm (group 3). In the left hindlimb the proximal end of the graft was coapted to the cut motor nerve branch of vastus medialis. In a second stage the distal end of the graft was coapted to the nerve branch of rectus femoris. After a total period of 15 months the maximum tetanic tension in the reinnervated rectus femoris and in the contralateral unoperated muscle was determined. Biopsies of the graft and the motor branch distal to the graft were taken in order to count the number of regenerated myelinated nerve fibers. The average maximum tetanic tension in the rectus femoris muscle reinnervated by the 3 cm long graft was 27.2 N, in group 2 the force was 20.5 N. In group 3 the maximum force was 17.6 N, which meant an average loss of 29% compared to the contralateral unoperated muscle. The mean number of regenerated myelinated fibres distal to the graft in the rectus femoris motor branch was 1683 in group 1 and decreased to 1137 in group 3. The results show that the length of the graft influences the results after nerve grafting to a certain extent, but a combination of other factors like concomitant soft tissue injury and destroyed target organs may also be responsible for some of the poor results after the clinical use of long nerve grafts.

Experimental in situ conditioning of the latissimus dorsi muscle for circulatory assist by multichannel stimulation.

This study was undertaken to survey the changes in force and fatigue of the latissimus dorsi muscle during transformation into a fatigue-resistant muscle by indirect or nervous multichannel stimulation. In sheep, a silicone chamber connected to a pressure-transducing system was implanted under the left latissimus dorsi muscle. Muscle conditioning was performed by multichannel (carousel) stimulation of the thoracodorsal nerve. The program was started with active periods of 10 min/h producing 10 tetanic contractions/min. It was increased until 70 contractions/min could be performed during 24 h. The changes of muscle force and fatigue were monitored by the silicone balloon system. After a mean period of 22 weeks, fatigue resistance was reached. The fatigue-resistant muscle was able to produce a pressure of about 100 mm Hg in the balloon. After finishing the conditioning procedure, muscle forces and the fatigue resistance of the conditioned muscle were evaluated. The conditioned muscle showed only a minimal decrease of force during 20 min. Under a preload of 20 N, it exhibited a maximum tetanic tension of 95 N.