Postoperative Severity Assessment in Sheep.

INTRODUCTION: Sheep are frequently used in translational surgical orthopedic studies. Naturally, a good pain management is mandatory for animal welfare, although it is also important with regard to data quality. However, methods for adequate severity assessment, especially considering pain, are rather rare regarding large animal models. Therefore, in the present study, accompanying a surgical pilot study, telemetry and the Sheep Grimace Scale (SGS) were used in addition to clinical scoring for severity assessment after surgical interventions in sheep. METHODS: Telemetric devices were implanted in a first surgery subcutaneously into four German black-headed mutton ewes (4-5 years, 77-115 kg). After 3-4 weeks of recovery, sheep underwent tendon ablation of the left M. infraspinatus. Clinical scoring and video recordings for SGS analysis were performed after both surgeries, and the heart rate (HR) and general activity were monitored by telemetry. RESULTS: Immediately after surgery, clinical score and HR were slightly increased, and activity was decreased in individual sheep after both surgeries. The SGS mildly elevated directly after transmitter implantation but increased to higher levels after tendon ablation immediately after surgery and on the following day. CONCLUSION: In summary, SGS- and telemetry-derived data were suitable to detect postoperative pain in sheep with the potential to improve individual pain recognition and postoperative management, which consequently contributes to refinement.

Assessment of cellular reactions to magnesium as implant material in comparison to titanium and to glyconate using the mouse tail model.

PURPOSE: Nowadays, research in magnesium alloys as a biodegradable implant material has increased. The aim of this study was to examine osteoinductive properties and tissue responses to pure magnesium in comparison to conventional permanent (titanium) and to degradable (glyconate) implant materials. METHODS: Magnesium wires (0.4 mm in diameter, 10 mm length) were implanted into tail veins of mice and examined after 2, 4, 8, 16 and 32 weeks. Titanium and glyconate as controls were assessed after 2, 4, 8 and 24 weeks. µ-computed tompgraphy, histology and SEM examinations were performed. RESULTS: Magnesium implants showed increasing structural losses over time with fragmentation after an observation period of 32 weeks. Glyconate was fully degraded and titanium remained almost unaffected after 24 weeks. In contrast to some titanium and glyconate implants, first calcium and phosphate precipitations could be observed around magnesium implants after two weeks. However, ossification could not be observed even after 32 weeks, whereas enchondral ossification was found partially in the sourrounding of glyconate and titanium implants after eight weeks. Nevertheless, magnesium implants showed less inflammatory responses and fibrosing properties than the conventional implant materials. CONCLUSIONS: Although the assumed osteoinductive properties could not be detected, magnesium appears to be a promising degradable implant material because of the low sensitizing and inflammatory potential.

In vivo assessment of the host reactions to the biodegradation of the two novel magnesium alloys ZEK100 and AX30 in an animal model.

BACKGROUND: Most studies on biodegradable magnesium implants published recently use magnesium-calcium-alloys or magnesium-aluminum-rare earth-alloys.However, since rare earths are a mixture of elements and their toxicity is unclear, a reduced content of rare earths is favorable. The present study assesses the in vivo biocompatibility of two new magnesium alloys which have a reduced content (ZEK100) or contain no rare earths at all (AX30). METHODS: 24 rabbits were randomized into 4 groups (AX30 or ZEK100, 3 or 6 months, respectively) and cylindrical pins were inserted in their tibiae. To assess the biodegradation µCT scans and histological examinations were performed. RESULTS: The µCT scans showed that until month three ZEK100 degrades faster than AX30, but this difference is leveled out after 6 months. Histology revealed that both materials induce adverse host reactions and high numbers of osteoclasts in the recipient bone. The mineral apposition rates of both materials groups were high. CONCLUSIONS: Both alloys display favorable degradation characteristics, but they induce adverse host reactions, namely an osteoclast-driven resorption of bone and a subsequent periosteal formation of new bone. Therefore, the biocompatibility of ZEK100 and AX30 is questionable and further studies, which should focus on the interactions on cellular level, are needed.