Regenerating Critical Size Rat Segmental Bone Defects with a Self-Healing Hybrid Nanocomposite Hydrogel: Effect of Bone Condition and BMP-2 Incorporation

The aim of the current study is to assess the biological performance of self-healing hydrogels based on calcium phosphate (CaP) nanoparticles and bisphosphonate (BP) conjugated hyaluronan (HA) in a critical size segmental femoral bone defect model in rats. Additionally, these hydrogels are loaded with bone morphogenetic protein 2 (BMP-2) and their performance is compared in healthy and osteoporotic bone conditions. Treatment groups comprise internal plate fixation and placement of a PTFE tube containing hydrogel (HA_BP -CaP) or hydrogel loaded with BMP-2 in two dosages (HA_BP -CaP-lowBMP2 or HA_BP -CaP-highBMP2). Twelve weeks after bone defect surgery, bone formation is analyzed by X-ray examination, micro-CT analysis, and histomorphometry. The data show that critical size, segmental femoral bone defects cannot be healed with HA_BP -CaP gel alone. Loading of the HA_BP -CaP gel with low dose BMP-2 significantly improve bone formation and resulted in defect bridging in 100% of the defects. Alternatively, high dose BMP-2 loading of the HA_BP -CaP gel does not improve bone formation within the defect area, but leads to excessive bone formation outside the defect area. Bone defect healing is not affected by osteoporotic bone conditions.

The performance of CPC/PLGA and Bio-Oss® for bone regeneration in healthy and osteoporotic rats

The current study aimed to evaluate the biological performance of calcium phosphate cement (CPC) with polylactic-co-glycolic acid (PLGA) micro-particles and Bio-Oss^® in ovariectomized and healthy rats. Thirty-two Wistar rats received alternating experimental CPC/PLGA and Bio-Oss^® in femoral condyle defects in both femurs 6 weeks after ovariectomy (OVX, n = 16) or sham operation (SHAM, n = 16). Six weeks after OVX or SHAM surgery, bone morphology was analyzed by in vivo computed tomography (CT) to confirm osteoporotic bone condition. Analysis of bone formation and material remnants at 4 and 12 weeks after material implantation was performed by micro-CT, descriptive histology, histomorphometry and bone dynamics by fluorochrome labeling. The in vivo CT scans showed effective induction of osteoporotic bone condition by ovariectomy. Our data showed CPC/PLGA degraded relatively faster and more steadily. However, Bio-Oss^® had significantly less material remnants and showed significantly more bone formation compared to CPC/PLGA. Overall, our data showed relatively high amounts of CPC/PLGA for each time point, hampering new bone formation within the defect area. Osteoporotic conditions proved to significantly affect degradation rates, but did not significantly influence bone formation. An osteoporotic bone condition affects degradation of CPC/PLGA, which is vital information for its potential use in osteoporotic conditions. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 131-142, 2018.

Comparison of three different incision techniques in A1 pulley release on scar tissue formation and postoperative rehabilitation

INTRODUCTION

The optimal surgical approach for trigger finger release remains controversial in hindsight of postoperative rehabilitation as well as scar tissue formation. In this study, we comparatively evaluated the outcome of three different types of skin incision by employing the "Disability of the Arm Shoulder and Hand Score" (DASH) and by quantitative ultrasound measurements of scar tissue volume.

MATERIALS AND METHODS

Thirty patients (32 triggerfingers) were enrolled in this study and randomly assigned to one of three groups: incision placed (1) transversal in distal palmar crease, (2) transversal and 2 mm distal from distal palmar crease, (3) longitudinally over MCP joint without crossing the distal palmar crease. Patients characteristics were noted and DASH scores were retrieved at four time points, (1) preoperatively (baseline), (2) 1 month, (3) 3 months, (4) 12 months postoperatively. Scar volume formation was assessed by ultrasound at 3 months postoperatively in 28 patients.

RESULTS

All groups showed a significant reduction in DASH values at 3 and 12 months postoperatively when compared to their own baseline levels. Group 3 showed the fastest and most pronounced reduction in DASH values at 1 month. Scar tissue formation was almost 57 % increased in group 1 vs group 2 and 3, however, not significant.

CONCLUSION

There is no clear benefit of one incision technique over another. However, based on scar volume parameters, the significant faster recovery in the first month and the surgical ease of exposure and wound closure inclines us to favor the longitudinal incision (group 3) in future patients.

Bone regeneration and gene expression in bone defects under healthy and osteoporotic bone conditions using two commercially available bone graft substitutes

Biosilicate(®) and Bio-Oss(®) are two commercially available bone substitutes, however, little is known regarding their efficacy in osteoporotic conditions. The purpose of this study was to evaluate the osteogenic properties of both materials, at tissue and molecular level. Thirty-six Wistar rats were submitted to ovariectomy (OVX) for inducing osteoporotic conditions and sham surgery (SHAM) as a control. Bone defects were created in both femurs, which were filled with Biosilicate(®) or Bio-Oss(®), and empty defects were used as control. For the healthy condition both Biosilicate(®) and Bio-Oss(®) did not improve bone formation after 4 weeks. Histomorphometric evaluation of osteoporotic bone defects with bone substitutes showed more bone formation, significant for Bio-Oss(®). Molecular biological evaluation was performed by gene-expression analysis (Runx-2, ALP, OC, OPG, RANKL). The relative gene expression was increased with Biosilicate(®) for all genes in OVX rats and for Runx-2, ALP, OC and RANKL in SHAM rats. In contrast, with Bio-Oss(®), the relative gene expression of OVX rats was similar for all three groups. For SHAM rats it was increased for Runx-2, ALP, OC and RANKL. Since both materials improved bone regeneration in osteoporotic conditions, our results suggest that bone defects in osteoporotic conditions can be efficiently treated with these two bone substitutes.