We report on the long-term effects of degrading magnesium implants on bone tissue in a growing rat skeleton using continuous in vivo micro-Computed Tomography, histological staining and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Two different magnesium alloys-one rapidly degrading (ZX50) and one slowly degrading (WZ21)-were used to evaluate the bone response and distribution of released Mg and Y ions in the femur of male Sprague-Dawley rats. Regardless of whether the alloy degrades rapidly or slowly, we found that bone recovers restitutio ad integrum after complete degradation of the magnesium implant. The degradation of the Mg alloys generates a significant increase in Mg concentration in the cortical bone near the remaining implant parts, but the Mg accumulation disappears after the implant degrades completely. The degradation of the Y-containing alloy WZ21 leads to Y enrichment in adjacent bone tissues and in newly formed bone inside the medullary space. Locally high Y concentrations suggest migration not only of Y ions but also of Y-containing intermetallic particles. However, after the full degradation of the implant the Y-enrichment disappears almost completely. Hydrogen gas formation and ion release during implant degradation did not harm bone regeneration in our samples. Magnesium is generally considered to be one of the most attractive base materials for biodegradable implants, and many magnesium alloys have been optimized to adjust implant degradation. Delayed degradation, however, generates prolonged presence in the organism with the risk of foreign body reactions. While most studies so far have only ranged from several weeks up to 12months, the present study provides data for complete implant degradation and bone regeneration until 24months, for two magnesium alloys (ZX50, WZ21) with different degradation characteristics. μCT monitoring, histological staining and LA-ICP-MS illustrate the distribution of the elements in the neighboring bony tissues during implant degradation, and reveal in particular high concentrations of the rare-earth element Yttrium.

Background: Fear avoidance can play a prominent role in maladaptive responses to an injury. In injured athletes, such pain-related fear or fear avoidance behavior may have a substantial influence on the recovery process. Specifically, it may explain why some are able to reach their preinjury abilities, whereas others are unable to return to sport. Questions/purposes: (1) Is fear avoidance in athletes associated with decreased physical function after injury? (2) To what degree is fear avoidance associated with athletes’ pain intensity? Methods: In a cross-sectional study, we recruited injured athletes—defined as patients with sports-related injury, weekly engagement in sport activities, participation in competitive events as part of a team or club, self-identification as an athlete, and a desire to return to sport after recovery—from an orthopaedic sports medicine center at a major urban university hospital. Of 130 approached patients, 102 (84% men; mean ± SD age 25 ± 8.5 years) met the inclusion criteria. Participants completed a demographic questionnaire, the Athlete Fear Avoidance Questionnaire, which assesses injury-related fear and avoidance behavior specifically in an athletic population, the Pain Catastrophizing Scale, the Hospital Anxiety and Depression Scale, and two Patient-Reported Outcomes Measurement Information System measures: Physical Function Computerized Adaptive Testing (CAT) and Pain Intensity CAT. Results: After controlling for age, injury region (upper versus lower extremity), catastrophic thinking, and emotional distress, we found that an increase in athletes’ fear avoidance was associated with a decrease in physical function (b = -0.32; p = 0.002). The model explained 30% of the variation in physical function with 7.3% explained uniquely by fear avoidance. After controlling for initial appointment/followup, surgery for the current condition, multiple pain conditions, history of prior sport-related injury/surgery, pain medication prescription, catastrophic thinking, and emotional distress, athletes' fear avoidance was not associated with pain (b = -0.14; p = 0.249). The model explained 40% of the variation in pain intensity and pain catastrophizing (b = 0.30; p = 0.001) uniquely explained 7.1% of this variation. Conclusions: In injured athletes, fear avoidance is independently associated with decreased physical function, whereas pain catastrophizing is associated with high pain intensity. Both level of an athlete’s fear avoidance and catastrophic thinking about pain should be accounted for in clinical interventions aimed at helping athletes improve recovery and return to sport. Level of Evidence: Level II, prognostic study.