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BackgroundBioabsorbable implants are not widely used in spine surgery. This study investigated the clinical and radiological findings after anterior cervical discectomy and fusion (ACDF) in an ovine animal model with an experimental bioabsorbable cage consisting of magnesium and polymer (poly-ϵ-caprolactone, PCL) in comparison to a tricortical bone graft as the gold standard procedure.Materials and Methods24 full-grown sheep had ACDF of C3/4 and C5/6 with an experimental bioabsorbable implant (magnesium and PCL) in one level and an autologous tricortical bone graft in the second level. The sheep were divided into 4 groups (6 sheep each). After 3, 6, 12, or 24 weeks postoperatively, the cervical spines were harvested and conventional x-rays of each operated segment were conducted. The progress of interbody fusion was classified according to a three-point scoring system.ResultsThere were no operation related complications except for one intraoperative fracture of the anterior superior iliac spine and two cases of screw loosening and sinking, respectively. In particular, no vascular, neurologic, wound healing or infectious problems were observed. According to the time of follow-up, both interbody fusion devices showed similar behaviour with increasing intervertebral osseointegration and complete arthrodesis in 10 of 12 (83.3%) motion segments after 24 weeks.ConclusionsThe bioabsorbable magnesium-PCL cage used in this experimental animal study showed clinically no signs of incompatibility such as infectious or wound healing problems. The radiographic results regarding the osseointegration are comparable between the cage and the bone graft group.

F or the treatment of diseases of the bladder, a drug delivery system (DDS) has been developed which can be applied intravesically. The DDS is composed of multiple carriers that consist of non-absorbable, drug-carrying microspheres which are embedded in a foamed absorbable matrix. After degradation of the absorbable matrix, the nonabsorbable microspheres are eliminated through the urethra.The foamed absorbable matrix is fabricated out of a poly(D,L-lactide-co-glycolide)-co-polyethylene glycol di-block copolymer, due to its short degradation time. These polymers are temperature-sensitive and therefore manufactured by the controlled expansion of saturated polymers (CESP) process. The foam structure, which influences the degradation, is controlled by the process parameters.Within this paper the influence of the process parameters on the degradation of the implants is investigated.

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Conventional fusion devices ("cages") are often used to join two vertebrae of the human spine and generally remain in the body for a lifetime and can theoretically lead to any complications. Therefore, an absorbable hybrid fusion cage consisting of a magnesium skeleton infiltrated with an absorbable polymer [poly-ε-caprolactone (PCL)] has been developed. The primary objective of the cage is to ensure an adequate stiffness of the disc space directly after the operation and to encourage the ingrowth of the new bone tissue to secure long life stability. Once a sufficiently rigid bone connection is formed, the implant should be absorbed. The purpose of this first study on the new absorbable fusion cage was to investigate the mechanical properties in vitro. Tensile tests were performed with tensile specimens type 1BA according to DIN EN ISO 527 made of PCL foamed using controlled expansion of saturated polymers (CESP). Furthermore, cyclic compression tests and compression tests with steady movement were performed with different designs of the new cage. Compression tests were also performed with vertebral endplates of ovine cadaveric spines. Foaming of PCL resulted in a modulus of elasticity of 135 MPa, which is approximately one third of unfoamed PCL. The results indicate that the initial compression strength of the implants should be adequate for the implantation in the cervical spine.