A new bone adhesive candidate- does it work in human bone? An ex-vivo preclinical evaluation in fresh human osteoporotic femoral head bone

INTRODUCTION

The fixation of small intraarticular bone fragments is clinically challenging and an obvious first orthopaedic indication for an effective bone adhesive. In the present study the feasibility of bonding freshly harvested human trabecular bone with OsStic^R, a novel phosphoserine modified cement, was evaluated using a bone cylinder model pull-out test and compared with a commercial fibrin tissue adhesive.

METHODS

Femoral heads (n=13) were collected from hip fracture patients undergoing arthroplasty and stored refrigerated overnight in saline medium prior to testing. Cylindrical bone cores with a pre-inserted bone screw, were prepared using a coring tool. Each core was removed and glued back in place with either the bone adhesive (α-tricalcium phosphate, phosphoserine and 20% trisodium citrate solution) or the fibrin glue. All glued bones were stored in bone medium at 37°C. Tensile loading, using a universal testing machine (5 kN load cell), was applied to each core/head. For the bone adhesive, bone cores were tested at 2 (n=13) and 24 (n=11) hours. For the fibrin tissue adhesive control group (n=9), bone cores were tested exclusively at 2 hours. The femoral bone quality was evaluated with micro-CT.

RESULTS

The ultimate pull-out load for the bone adhesive at 2 hours ranged from 36 to 171 N (mean 94 N, SD 42 N). At 24 hours the pull-out strength was similar, 47 to 198 N (mean 123 N, SD 43 N). The adhesive failure usually occurred through the adhesive layer, however in two samples, at 167 N and 198 N the screw pulled out of the bone core. The fibrin tissue adhesive group reached a peak force of 8 N maximally at 2 hours (range 2.8-8 N, mean 5.4 N, SD 1.6 N). The mean BV/TV for femoral heads was 0.15 and indicates poor bone quality.

CONCLUSION

The bone adhesive successfully glued wet and fatty tissue of osteoporotic human bone cores. The mean ultimate pull-out force of 123 N at 24 hours corresponds to ∼ 300 kPa shear stress acting on the bone core. These first ex-vivo results in human bone are a promising step toward potential clinical application in osteochondral fragment fixation.

Destabilization of the medial meniscus leads to subchondral bone defects and site-specific cartilage degeneration in an experimental rat model

OBJECTIVE

This study aimed to investigate subchondral bone changes using micro-computed tomography (micro-CT) and regional differences in articular cartilage degeneration, focusing on changes of cartilage covered by menisci, in the early phase using a destabilization of the medial meniscus (DMM) model.

METHOD

The DMM model was created as an experimental rat osteoarthritis (OA) model (12 weeks old; n = 24). At 1, 2, and 4 weeks after surgery, the rats were sacrificed, and knee joints were scanned using a Micro-CT system. Histological sections of the medial tibial plateau, which was divided into inner, middle, and outer regions, were prepared and scored using the modified OARSI scoring system. The cartilage thickness was also calculated, and matrix metalloproteinase 13 (MMP13), Col2-3/4c, and vascular endothelial growth factor (VEGF) expression was assessed immunohistochemically.

RESULTS

Subchondral bone defects were observed in the middle region, in which the cartilage thickness decreased over time after surgery, and these defects were filled with MMP13- and VEGF-expressing fibrous tissue. The OARSI score increased over time in the middle region, and the score was significantly higher in the middle region than in the inner and outer regions at 1, 2, and 4 weeks after surgery. Col2-3/4c and MMP13 expression was observed primarily in the meniscus-covered outer region, in which the cartilage thickness increased over time.

CONCLUSION

Loss of meniscal function caused cartilage degeneration and subchondral bone defects in the early phase site-specifically in the middle region. Furthermore, our results might indicate cartilage covered by menisci is easily degraded resulting in osmotic swelling of the cartilage in early OA.