Treatment of scaphoid fractures and pseudarthroses with the human allogeneic cortical bone screw. A multicentric retrospective study.

BACKGROUND: Allograft bone screws are rarely described for the fixation of the scaphoid. When fresh fractures are treated, metal screws are mainly used; when pseudarthrosis is the indication, plates in combination with vascularized or non-vascularized bone grafts are mainly used. The necessity of metallic screw removal is under debate, but it is mandatory for plates because of movement restrictions due to the plate. The use of biomaterials in scaphoid fracture fixation was described as leading to union rates of between 64 and 100%. Brcic showed the incorporation of an allogeneic cortical bone screw at 10 weeks postoperative, along with revascularization and stable osteosynthesis with primary bone healing, without any signs of immunological rejection. The purpose of this retrospective study was to explore the results obtained using an allogenic cortical bone screw (Shark Screw®) in patients with fresh scaphoid fracture fixation and pseudarthroses with respect to union rates and time to union. PATIENTS AND METHODS: We retrospectively analyzed 75 patients: 31 with fresh fractures and 44 pseudarthrosis patients. The Shark Screw® was used for the fixation of the scaphoid in the fresh-fracture and pseudarthrosis patients. We evaluated the union rate, complication rate and time to union. RESULTS: Using the human allogeneic cortical bone screw for scaphoid fracture fixation led to a high union rate (94-96%). There were two nonunions in the fresh fracture group and two nonunions in the pseudarthrosis group. The complication rate was 1.3% (1 patient). Median time to union was 16, 18 and 29 weeks for the fresh-fracture, pseudarthrosis and delayed-union patients, respectively. The treatment of fresh scaphoid fractures and pseudarthroses showed similar union rates to those described in the literature, uses a shorter and less invasive surgical method with no need for hardware removal, and has a low complication rate. CONCLUSION: Using the human allogenic cortical bone screw (Shark Screw®) led to similar union rates in fresh fractures-but better union rates in pseudarthrosis patients-compared to those presented in the literature for other scaphoid fracture fixation techniques, and it enabled a short and low-invasive procedure without any donor site morbidity and without the necessity to remove the hardware in a second surgery. The pseudarthrosis patient group showed a particularly strong benefit from this new procedure. The physiological bone metabolism remodels the cortical bone screw without scars. LEVEL OF EVIDENCE: III: retrospective cohort study, therapeutic investigation of a treatment.

Indirect bandgap, optoelectronic properties, and photoelectrochemical characteristics of high-purity Ta3N5 photoelectrodes.

The (opto)electronic properties of Ta3N5 photoelectrodes are often dominated by defects, such as oxygen impurities, nitrogen vacancies, and low-valent Ta cations, impeding fundamental studies of its electronic structure, chemical stability, and photocarrier transport. Here, we explore the role of ammonia annealing following direct reactive magnetron sputtering of tantalum nitride thin films, achieving near-ideal stoichiometry, with significantly reduced native defect and oxygen impurity concentrations. By analyzing structural, optical, and photoelectrochemical properties as a function of ammonia annealing temperature, we provide new insights into the basic semiconductor properties of Ta3N5, as well as the role of defects on its optoelectronic characteristics. Both the crystallinity and material quality improve up to 940 °C, due to elimination of oxygen impurities. Even higher annealing temperatures cause material decomposition and introduce additional disorder within the Ta3N5 lattice, leading to reduced photoelectrochemical performance. Overall, the high material quality enables us to unambiguously identify the nature of the Ta3N5 bandgap as indirect, thereby resolving a long-standing controversy regarding the most fundamental characteristic of this material as a semiconductor. The compact morphology, low defect content, and high optoelectronic quality of these films provide a basis for further optimization of photoanodes and may open up further application opportunities beyond photoelectrochemical energy conversion.