Are allogenic or xenogenic screws and plates a reasonable alternative to alloplastic material for osteosynthesis—A histomorphological analysis in a dynamic system

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.

A comparative study of autogenous, allograft and artificial bone substitutes on bone regeneration and immunotoxicity in rat femur defect model

Repair and reconstruction of large bone defect were often difficult, and bone substitute materials, including autogenous bone, allogenic bone and artificial bone, were common treatment strategies. The key to elucidate the clinical effect of these bone repair materials was to study their osteogenic capacity and immunotoxicological compatibility. In this paper, the mechanical properties, micro-CT imaging analysis, digital image analysis and histological slice analysis of the three bone grafts were investigated and compared after different time points of implantation in rat femur defect model. Autogenous bone and biphasic calcium phosphate particular artificial bone containing 61.4% HA and 38.6% β-tricalcium phosphate with 61.64% porosity and 0.8617 ± 0.0068 g/cm³ density (d ≤ 2 mm) had similar and strong bone repair ability, but autogenous bone implant materials caused greater secondary damage to experimental animals; allogenic bone exhibited poor bone defect repair ability. At the early stage of implantation, the immunological indexes such as Immunoglobulin G, Immunoglobulin M concentration and CD4 cells' population of allogenic bone significantly increased in compared with those of autologous bone and artificial bone. Although the repair process of artificial bone was relatively inefficient than autologous bone graft, the low immunotoxicological indexes and acceptable therapeutic effects endowed it as an excellent alternative material to solve the problems with insufficient source and secondary trauma of autogenous bone.

Effect of xenogenic cortical bone on fracture healing in a canine fracture model

The purpose of this study was to investigate the effect of xenogenic cortical bone (XCB) on fracture repair in the canine ulna. The entire group of animals (n = 12) had a transverse resection of 5 mm length at the middle part of the right ulnar diaphysis. In Group A (eight beagles), the fracture was treated with XCB and metal bone screw. In Group B (four beagles), the fracture was treated with metal bone plate and screw. Radiological, micro-computed tomography (micro-CT), histological examination and mechanical testing were employed to evaluate bone healing and reaction of XCB in the host bone. In Group A, bone union was noticed in 6 out of 8 dogs (75%), starting from the 4th week onwards. Micro-CT and histological examinations showed that the XCB was absorbed and incorporated into the host bone. Incorporation of XCB was observed in 7 cases (88%); it started from the 10th week onwards and continued to week 32 after surgery. Biomechanical strength of the bone fracture site was higher in Group A than in Group B, and was similar to that of normal bone. XCB enhances the bone healing process and can be used as absorbable internal fixation for the management of long bone fractures in dogs.

Hybrid distraction: a novel method for distraction osteogenesis of the alveolar process

Segmental distraction osteogenesis of the anterior alveolar process is a sufficient method to enlarge the alveolar arch. Indications for this method are dental crowding, retroalveolism, and leveling of the curve of Spee. However, after the distraction period, the anterior alveolar segment often shows an unfavorable inclination resulting in nonphysiologic load on the lower incisors.The aim of this paper was to introduce a new approach in segmental distraction osteogenesis of the anterior alveolar process. This new method combines 2 different surgical techniques: a segmental osteotomy for the alveolar ridge with instant fixation in the desired position and a distraction procedure for the alveolar segment. This hybrid distraction avoids an unfavorable inclination of the lower incisors after front-block distraction procedures.

Biocompatibility evaluation of a new bioresorbable pin for membrane fixation

The aim of this study was to morphometrically analyze the tissue response to a customized pin obtained from devitalized bovine cortical bone (DBCB-pin) implanted in the subcutaneous tissue of rats, as well as to assess its microstructural aspect by scanning electron microscopy (SEM). The pins were implanted in the subcutaneous tissue of 20 rats, which were killed at 7, 14, 28 and 60 days (5 rats/period) after implantation. In the subcutaneous tissue, DBCB-pin promoted the formation of a fibrous capsule. At 7 days, capsule showed thickness of 70 ± 3.2 µm with higher density of newly formed capillaries and smaller density of collagen fibers. Between 14 and 60 days, more organized fibrous capsule exhibited smaller thickness (53 ± 5.5 µm) with higher density of fibroblasts and collagen fibers. In this period, a small and slow bioresorption of the DBCB-pin by macrophages and rare multinucleated giant cells without tissue damage was observed. The thickness of DBCB-pin resorbed was in mean only of 9.3 µm. During all experimental periods not occurred presence of immune reaction cells as lymphocytes and plasma cells. It was concluded that the pin derived from cortical bovine bone was well tolerated by subcutaneous tissue of rats and slowly resorbed could be an alternative material for membrane fixation in the guided tissue regeneration procedures.