Ph Robinson

A new PLLA/PCL copolymer for nerve regeneration

The aim of this study is to evaluate the functional and cell biological applicability of a two-ply nerve guide constructed of a PLLA/PCL (i.e. poly-l-lactide and poly-ε-caprolactone) copolymer. To do so, we performed a cytotoxicity test, a subcutaneous biodegradation test and an in situ implantation study in the sciatic nerve of the rat. The nerve guide copolymer was found to be non-toxic, according to ISO/EN standards, and it showed a mild foreign body reaction and complete fibrous encapsulation after implantation. Onset of biodegradation of the inner layer was seen after one month of implantation. After 18 months of implantation complete fragmentation was observed, as well as a secondary inflammatory response characterized by foreign body giant cell activity and phagocytosis of polymer debris. Recovery of both motor and sensory nerve function was observed in all nerve guides.

Two-ply biodegradable nerve guide: basic aspects of design, construction and biological performance

A synthetic biodegradable nerve guide was constructed of two polymeric layers: an inner microporous layer prepared from a copolymer of L-lactide and epsilon-caprolactone (pore size range 0.5-1 micron) and an outer microporous layer prepared from a polyurethane/poly(L-lactide) mixture (pore size range 30-70 microns). This nerve guide was used to bridge a 7 mm gap in the right sciatic nerve of rats. It enabled the sciatic nerve to regenerate across the gap, forming a new, well-defined nerve that effectively re-established the contact between the proximial and distal nerve end, as effective as an autograft.

EVALUATION OF FUNCTIONAL NERVE RECOVERY AFTER RECONSTRUCTION WITH A NEW BIODEGRADABLE POLY (DL-LACTIDE-EPSILON -CAPROLACTONE) NERVE GUIDE

The aim of this study was to evaluate functional nerve recovery following reconstruction of a 1 cm gap in the sciatic nerve of a rat, using a new biodegradable p (DLLA-∊-CL) nerve guide. To evaluate both motor and sensory nerve recovery, walking track analysis and electrostimulation tests were carried out after implantation periods, ranging from 3 to 15 weeks post-operatively. The first signs of functional nerve recovery were observed after 3 weeks. After 15 weeks, 70% of the motor - and 90% of the sensory nerve function was re-established. Return of nerve function was better, in comparison with results from other studies. This study demonstrated successful functional nerve recovery after the reconstruction of a 1 cm nerve gap with a biodegradable p(DLLA-∊-CL) nerve guide.

Carpometacarpal arthritis of the thumb

Forty-five flexor carpi radialis (FCR) tendon interposition arthroplasties of the trapezium for the treatment of carpometacarpal osteoarthritis were reviewed. The average follow-up period was 103 months (range, 22-213 months). Pain was reduced in 42 (93%) of the cases. Mobility was equal to that of the unoperated side. Key pinch and grip strengths compared to the unoperated thumb measured 86% and 90%, respectively. The mean distance between the scaphoid and the base of the first metacarpal bone was 7 mm (range, 2-12 mm). Function was improved in 39 (87%) of the cases, and in 42 (93%) of the cases the overall results were satisfactory. The results of this study show that FCR tendon interposition arthroplasty gives satisfactory long-term results.

CORRECTION OSTEOTOMIES OF PHALANGES AND METACARPALS FOR ROTATIONAL AND ANGULAR MALUNION - A LONG-TERM FOLLOW-UP AND A REVIEW OF THE LITERATURE

Correction osteotomies of nine phalanges and six metacarpals for rotational and angular malunion were performed in 15 patients ranging from 20 to 75 years of age and followed a mean period of 4.5 years, ranging from 1 to 11 years. Full correction of the preoperative deformity was achieved in 13 of the 15 patients (87%), bony union in 100%, and no loss of preoperative range of motion was observed, except in one patient who underwent additional arthrodesis. A high satisfaction rate was seen among 13 of the 15 patients. These results underline that osteotomies of phalanges and metacarpals for angular and rotational malunion can have significant functional benefits for the well-being of patients.

Is additional epidural sympathetic block in microvascular surgery contraindicated? A preliminary report

The use of additional epidural sympathetic block during and after microvascular surgery in the lower extremities to prevent vasospasm is generally agreed on. However, a significant fall in the perfusion rate of the transplants was seen after application of bupivacaine (Marcain) via the epidural catheter. This effect has, to our knowledge, not been described before and is probably caused by the sympathectomy effect of this type of analgesia.

Microarterial grafting into the carotid artery of the rabbit: some considerations concerning species- dependent thrombogenicity

This study was undertaken to obtain more insight into the performance of microarterial prostheses in an experimental animal that resembles the human thrombogenically more closely than the rat. Therefore, microarterial polyurethane-based (PU) prostheses and polytetrafluoroethylene (PTFE) prostheses were implanted into the carotid artery of the rabbit and were compared with regard to patency and thrombus formation at 1 hour (n = 4), 1 day (n = 4), 2 days (n = 4), 1 week (n = 4), 2 weeks (n = 6), 3 weeks (n = 6) and 6 weeks (n = 6) after implantation. Arterial autografts (n = 22), followed up for 2 weeks after implantation, served as a control for the surgical procedure. All arterial autografts were patent at the time of harvesting. In contrast, although all microarterial prostheses were patent at 1 hour and some were patent at 1 day, 2 days and 1 week, none of them were patent at 2, 3 and 6 weeks. The patent PTFE prostheses showed remarkably less thrombus accumulation on the graft surface when compared to the patent PU prostheses. However, all prostheses had the same amount of thrombus formation at the distal anastomosis.

Bilateral osteoarthritis of the trapeziometacarpal joint treated by bilateral tendon interposition arthroplasty

Twenty-four flexor carpi radialis (FCR) tendon interposition arthroplasties of the trapezium for bilateral trapeziometacarpal osteoarthritis were reviewed. Pain was reduced in all cases. Function was improved in all right hands and in 92% of the left hands. FCR tendon interposition arthroplasty for bilateral trapeziometacarpal osteoarthritis yields satisfactory long-term results on both sides.

Reduced thrombogenicity of artificial materials by coating with ADPase

A novel coating solution for the improvement of biocompatibility of polyurethane-based vascular prostheses was tested in rabbits and rats in vivo. Segments of coated and uncoated vascular prostheses were implanted into the peritoneal cavity of rats, followed by induction of experimental haemorrhage; otherwise whole vascular prostheses were implanted in the carotid artery of rabbits using microsurgical procedures. While in both rats and rabbits, the uncoated material showed abundant formation of fibrinoid thrombi, clear reduction of thrombus formation was seen in all ADPase coated materials following implantation in vivo.

Patency and long-term biological fate of a two-ply biodegradable microarterial prosthesis in the rat

This study was undertaken to determine the long-term performance of a two-ply biodegradable, compliant microarterial prosthesis for its ability to function successfully as a temporary scaffold for the regeneration of a neoartery. Two-ply microarterial prostheses (internal diameter 1.5 mm, length 1 cm), prepared from a polyurethane-based (PU) material, were implanted into the abdominal aorta of rats (n = 22) and were evaluated at 3 months (n = 6), 6 months (n = 6) and one year (n = 10) after implantation, by means of macroscopic inspection, light microscopy and electron microscopy. All implants were patent and all, except two with a very small local dilatation at one year, were normally shaped. Arterial pulsations were reduced but still visible in all implants. In all implants a neoartery had regenerated: (1) a complete neointima composed of endothelial cells, (2) a neomedia composed of smooth muscle cells surrounded with elastin and collagen and of comparable thickness to rat media, and (3) a neoadventitia composed of fibrohistiocytic tissue that had organised the graft wall. In 2 out of the 10 one-year implants, smooth muscle cells were predominantly circularly arranged as in normal arterial tissue; in all other implants smooth muscle cells were predominantly longitudinally arranged. These results demonstrate that two-ply biodegradable PU-based prostheses have a good long-term performance when implanted into rat abdominal aortas.