Hazibullah Waizy

Biodegradable magnesium-based screw clinically equivalent to titanium screw in hallux valgus surgery: short term results of the first prospective, randomized, controlled clinical pilot study

PurposeNondegradable steel-and titanium-based implants are commonly used in orthopedic surgery. Although they provide maximal stability, they are also associated with interference on imaging modalities, may induce stress shielding, and additional explantation procedures may be necessary. Alternatively, degradable polymer implants are mechanically weaker and induce foreign body reactions. Degradable magnesium-based stents are currently being investigated in clinical trials for use in cardiovascular medicine. The magnesium alloy MgYREZr demonstrates good biocompatibility and osteoconductive properties. The aim of this prospective, randomized, clinical pilot trial was to determine if magnesium-based MgYREZr screws are equivalent to standard titanium screws for fixation during chevron osteotomy in patients with a mild hallux valgus.MethodsPatients (n=26) were randomly assigned to undergo osteosynthesis using either titanium or degradable magnesium-based implants of the same design. The 6 month follow-up period included clinical, laboratory, and radiographic assessments.ResultsNo significant differences were found in terms of the American Orthopaedic Foot and Ankle Society (AOFAS) score for hallux, visual analog scale for pain assessment, or range of motion (ROM) of the first metatarsophalangeal joint (MTPJ). No foreign body reactions, osteolysis, or systemic inflammatory reactions were detected. The groups were not significantly different in terms of radiographic or laboratory results.ConclusionThe radiographic and clinical results of this prospective controlled study demonstrate that degradable magnesium-based screws are equivalent to titanium screws for the treatment of mild hallux valgus deformities.

Biodegradable magnesium implants for orthopedic applications

The clinical application of degradable orthopedic magnesium implants is a tangible vision in medical science. This interdisciplinary review discusses many different aspects of magnesium alloys comprising the manufacturing process and the latest research. We present the challenges of the manufacturing process of magnesium implants with the risk of contamination with impurities and its effect on corrosion. Furthermore, this paper provides a summary of the current examination methods used in in vitro and in vivo research of magnesium alloys. The influence of various parameters (most importantly the effect of the corrosive media) in in vitro studies and an overview about the current in vivo research is given.

Long-term in vivo degradation behaviour and biocompatibility of the magnesium alloy ZEK100 for use as a biodegradable bone implant.

Magnesium alloys are the focus of research as resorbable materials for osteosynthesis, as they provide sufficient stability and would make surgery to remove implants unnecessary. The new degradable magnesium alloy ZEK100 was developed to improve the stability and corrosion resistance by alloying with zinc, rare earth metals and zirconium. As the implants were degraded to only a limited extent after 6 months implantation in a previous in vivo study the present study was conducted to evaluate the long-term degradation behaviour and biocompatibility in the same animal model over 9 and 12 months. Five rabbits each with intramedullary tibia implants were examined over 9 and 12 months. Three legs were left without an implant to serve as negative controls. Numerous examinations were performed in the follow-up (clinical examinations, serum analysis, and radiographic and in vivo micro-CT investigations) and after death (ex vivo micro-CT, histology, and implant analysis) to assess the in vivo degradation and biocompatibility. It could be shown that favourable in vivo degradation behaviour is not necessarily associated with good biocompatibility. Although ZEK100 provided a very high initial stability and positive biodegradation, it must be excluded from further biomedical testing as it showed pathological effects on the host tissue following complete degradation.

In vivo study of a biodegradable orthopedic screw (MgYREZr-alloy) in a rabbit model for up to 12 months

Biodegradable magnesium-based implants are currently being developed for use in orthopedic applications. The aim of this study was to investigate the acute, subacute, and chronic local effects on bone tissue as well as the systemic reactions to a magnesium-based (MgYREZr-alloy) screw containing rare earth elements. The upper part of the screw was implanted into the marrow cavity of the left femora of 15 adult rabbits (New Zealand White), and animals were euthanized 1 week, 12 weeks, and 52 weeks postoperatively. Blood samples were analyzed at set times, and radiographic examinations were performed to evaluate gas formation. There were no significant increased changes in blood values compared to normal levels. Histological examination revealed moderate bone formation with direct implant contact without a fibrous capsule. Histopathological evaluation of lung, liver, intestine, kidneys, pancreas, and spleen tissue samples showed no abnormalities. In summary, our data indicate that these magnesium-based screws containing rare earth elements have good biocompatibility and osteoconductivity without acute, subacute, or chronic toxicity.

Core decompression and osteonecrosis intervention rod in osteonecrosis of the femoral head: clinical outcome and finite element analysis

The osteonecrosis of the femoral head implies significant disability partly due to pain. After conventional core decompression using a 10-mm drill, patients normally are requested to be non-weight bearing for several weeks due to the risk of fracture. After core decompression using multiple small drillings, patients were allowed 50% weight bearing. The alternative of simultaneous implantation of a tantalum implant has the supposed advantage of unrestricted load bearing postoperatively. However, these recommendations are mainly based on clinical experience. The aim of this study was to perform a finite element analysis and confirm the results by clinical data after core decompression and after treatment using a tantalum implant. Postoperatively, the risk of fracture is lower after core decompression using multiple small drillings and after the implantation of a tantalum rod according to finite element analysis compared to core decompression of one 10-mm drill hole. According to the results of this study, a risk of fracture exists only during extreme loading. The long-term results reveal a superior performance for core decompression presumably due to the lack of complete bone ingrowth of the tantalum implant. In conclusion, core decompression using small drill holes seems to be superior compared to the tantalum implant and to conventional core decompression.

Magnesium-based bone implants: immunohistochemical analysis of peri-implant osteogenesis by evaluation of osteopontin and osteocalcin expression.

The functions of some bone proteins, as osteopontin (OPN) and osteocalcin (OC), have been discovered by the latest studies. This fact suggests the possibility of their immunodetection to characterize peri-implant osteogenesis and implant impact on it. Cylindrical pins of Mg alloys (MgCa0.8, LAE442, ZEK100, LANd442) and titanium alloy (TiAl6V4) were implanted into the tibial medullae of 46 rabbits. Each group was divided regarding to implant duration (3 and 6 months). Bone samples adjacent to the implants were decalcified and treated with routine histological and immunohistochemical protocols using OC and OPN-antibodies. OC was detected in matrix of compact bone, but very rarely in osteoid and bone cells. OPN was detected intracellularly and in osteoid. After 3 months, the highest level of both markers was found in titanium group, followed by LAE442-group. In contrast to LAE442 and TiAl6V4, the other Mg alloys showed increasing levels of OC after 6 months. Lower levels of OP and OC compared to the control group are related to the continuous implant degradation and instability of bone-implant interface in early post-surgical period. Reduced markers expression in LAE442 and TiAl6V4 groups after 6 months may indicate stabilization of bone-implant interface and completion of peri-implant neo-osteogenesis. Declining characters of OC and OPN expression over the implantation time, as well as their lowest levels in late post-surgical term, suggest a more appropriate biocompatibility of LAE442, which therefore seems to be the most preferable of the tested materials for the use in orthopaedic applications.

Degrading magnesium screws ZEK100: biomechanical testing, degradation analysis and soft-tissue biocompatibility in a rabbit model

Magnesium alloys are promising implant materials for use in orthopaedic applications. In the present study, screws made of the Mg-alloy ZEK100 (n = 12) were implanted in rabbit tibiae for four and six weeks, respectively. For degradation analysis, in vivo µ-computed tomography (µCT), a determination of the weight changes and SEM/EDX examinations of the screws were performed. Screw retention forces were verified by uniaxial pull-out tests. Additionally, soft-tissue biocompatibility was estimated using routine histological methods (H&E staining) and the immunohistological characterization of B- and T-cells. After six weeks, a 7.5% weight reduction occurred and, in dependence of the implant surrounding, the volume loss (µCT) reached 9.6% (screw head) and 5.0% for the part of the thread in the marrow cavity. Pull-out forces significantly decreased to 44.4% in comparison with the origin value directly after implantation. Soft tissue reactions were characterized by macrophage and lymphocyte infiltration, whereas T-cells as well as B-cells could be observed. In comparison to MgCa0.8-screws, the degradation rate and inflammatory tissue response were increased and the screw holding power was decreased after six weeks. In conclusion, ZEK100-screws seem to be inferior to MgCa0.8-screws, although their initial strength was more appropriate.

In vitro corrosion of ZEK100 plates in Hank's Balanced Salt Solution

BackgroundIn recent years magnesium alloys have been intensively investigated as potential resorbable materials with appropriate mechanical and corrosion properties. Particularly in orthopedic research magnesium is interesting because of its mechanical properties close to those of natural bone, the prevention of both stress shielding and removal of the implant after surgery.MethodsZEK100 plates were examined in this in vitro study with Hanks Balanced Salt Solution under physiological conditions with a constant laminar flow rate. After 14, 28 and 42 days of immersion the ZEK100 plates were mechanically tested via four point bending test. The surfaces of the immersed specimens were characterized by SEM, EDX and XRD.ResultsThe four point bending test displayed an increased bending strength after 6 weeks immersion compared to the 2 week group and 4 week group. The characterization of the surface revealed the presence of high amounts of O, P and Ca on the surface and small Mg content. This indicates the precipitation of calcium phosphates with low solubility on the surface of the ZEK100 plates.ConclusionsThe results of the present in vitro study indicate that ZEK100 is a potential candidate for degradable orthopedic implants. Further investigations are needed to examine the degradation behavior.

Translation and validation of the German version of the foot and ankle outcome score

PurposeOutcome assessment is critical in evaluating the efficacy of orthopaedic procedures. The Foot and Ankle Outcome Score (FAOS) is a 42-item questionnaire divided into five subscales, which has been validated in several languages. Germany has no validated outcome score for general foot and ankle pathology. The aim of this study was to develop a German version of the FAOS and to investigate its psychometric properties.Materials and methodsForward and backward translation was executed according to official guidelines. The final version of the FAOS was investigated in 150 patients with various foot and ankle disorders. All patients completed the FAOS, Short Form-36, numeric rating scales for pain and disability, and the Hannover questionnaire. The FAOS was re-administered after 1 week. Test–retest reliability, internal consistency, minimal detectable change, construct validity, and floor and ceiling effects were analyzed.ResultsTest–retest reliability and internal consistency of each subscale were excellent (intraclass correlation coefficient, 0.88–0.95; Cronbach’s α, 0.94–0.98). The minimal detectable changes of each subscale were 17.1–20.8 at the individual level and 2.0–2.4 at group level. There were moderate to strong correlations between FAOS subscales and physical outcomes and low to moderate correlations between FAOS subscales and mental outcomes. Floor and ceiling effects were not present.ConclusionThe German version of the FAOS is a reliable and valid instrument for use in foot and ankle patients.

Ultrastructural changes of the intracellular surfactant pool in a rat model of lung transplantation-related events

BackgroundIschemia/reperfusion (I/R) injury, involved in primary graft dysfunction following lung transplantation, leads to inactivation of intra-alveolar surfactant which facilitates injury of the blood-air barrier. The alveolar epithelial type II cells (AE2 cells) synthesize, store and secrete surfactant; thus, an intracellular surfactant pool stored in lamellar bodies (Lb) can be distinguished from the intra-alveolar surfactant pool. The aim of this study was to investigate ultrastructural alterations of the intracellular surfactant pool in a model, mimicking transplantation-related procedures including flush perfusion, cold ischemia and reperfusion combined with mechanical ventilation.MethodsUsing design-based stereology at the light and electron microscopic level, number, surface area and mean volume of AE2 cells as well as number, size and total volume of Lb were determined in a group subjected to transplantation-related procedures including both I/R injury and mechanical ventilation (I/R group) and a control group.ResultsAfter I/R injury, the mean number of Lb per AE2 cell was significantly reduced compared to the control group, accompanied by a significant increase in the luminal surface area per AE2 cell in the I/R group. This increase in the luminal surface area correlated with the decrease in surface area of Lb per AE2. The number-weighted mean volume of Lb in the I/R group showed a tendency to increase.ConclusionWe suggest that in this animal model the reduction of the number of Lb per AE2 cell is most likely due to stimulated exocytosis of Lb into the alveolar space. The loss of Lb is partly compensated by an increased size of Lb thus maintaining total volume of Lb per AE2 cell and lung. This mechanism counteracts at least in part the inactivation of the intra-alveolar surfactant.