Introduction: Periprosthetic fractures occurring during implantation of non-cemented Total Hip Arthroplasty (THA) are considered major surgical complications. As a shot-term disadvantage, patients are required to partially weight-bear. Additionally, high risks of stem migration and joint luxation can be assumed. On the other hand, in fear of fracture surgeons may undersize stems and subsequently trigger failure rates in THA.

As the long-term consequences of Vancouver A and B1 fractures are not fully known, the goal of this study now was to analyze the postoperative performance of non-cemented THA with respect to perioperative fractures.

Materials and Methods: Between 1997 and 2003 41 peri-operative hip fractures were monitored in 1216 primary Total Hip Arthroplasties using the non-cemented Bicon-tact THA stem. Pre-OP and after a follow-up period of 2,2 (+−3,1) years patients were examined clinically and radiographically. Investigation parameters were Harris-Hip-Scores, SF-36 scores, function score, hospitalization, implant survival /revisions and radiographic parameters (stem migration, trochanter migration, osteolysis, bone union, callus formation and bone quality). Fractures were graded using the Vancouver and Mont+Maar classifications. Patients were compared to a comparable collective of THA patients without perioperative fractures. Pooled data of both groups were compared using non-parametric Kruskal-Wallis tests.

Results: Results showed a significant increase in Harris-Hip scores for all THA of 36 (+−17,7) points. There were no differences in function scores (2,3; score 1–6), postoperative pain (4,8; score 1–10), and time of hospitali-sation (21,3d; +−3,7 range, 14 – 32). The non-union rate was 13%, with 85% of trochanteric fractures showing migration. 47% of the Patients in the fracture group were instructed to maintain restricted weight bearing for 6 weeks. No Trendelenburg signs were observed in the fracture group. Stem migration of mean 0,6 cm (+−0,4) was observed in 13% of Vancouver A and B1 patients (6,4% of A, 20,1% of B1). Long-term cerclage wire failure was observed in 20%. Joint luxation was observed in 1 patient. No hips were revised during the follow-up period.

Discussion: Follow-ups of perioperative fractures classes Vancouver A and B1 during non-cemented THA using the Bicontact stem show associations with stem migration, long-term stabilization implant failure and non-union. However, none of these observations seem to be influencing the overall THA performance and patient satisfaction. Specifically, complications commonly associated with perioperative primary prosthetic fractures as luxation and limping were not signifi-cant. At a short-term perspective, perioperative THA fractures prohibit early weight-bearing. However at a mid to long-term perspective, no disadvantages were apparent in comparison to primary THA without fracture complications.

Introduction: Despite advances in endoprosthesis fixation by implant surface alteration, the problem of aseptic implant loosening still exists. Especially in patients with revisions osseointegration and filling of gaps at the bone-implant interface is mandatory for implant survival. Simple BMP-2 immersion has been introduced previously to act as an osteoinductive coating for advanced osseointegration. However, because of the uncontrolled release kinetics and subsequent molecular action and activity of BMP-2, purely osteoinductive actions are hard to differentiate from osteoclastic BMP-actions leading to bone remodelling, which could counteract the implant fixation process and might be the reason for failed attempts to use BMP-2 for implant fixation. In this study we investigated the osteoinductive potency of BMP-2 bound to titanium surfaces by a highly controlled molecular coupling with specifically designed polymers, allowing a slow controlles release kinetics. We present the first results of two different polymers that were implanted in the tibia and femora of New Zealand White Rabbits.

Methods: In this study we designed cylindrical titanium-implants with an inner thread (Ti6-Alï·& #8220;4V, 3 mm hight x 3 mm diameter) and an electropolished outer surface that were coated with different polymers. The polymers were fixed to the surface using the photochemical method of grafting. The implants were implanted in the proximal tibia and distal femora of New Zealand White Rabbits. The anatomical locations of the implants were alternated to test their osseointegration in different quality of bone (cancellous vs. cortical bone). After 4 weeks the animals were sacrificed and DEXA-scans (Dual-energy X-ray absorptiometry), micro-CT and histological analysis were performed. ANOVA and t-test were used for statistic analysis.

Results: In high-resolution DEXA-scans we found a difference in bone mineral density (BMD) between PVBP and a control implant in the distal femora (PVBP 0,720 g/cm², control 0,661 g/cm²) and in the proximal tibia (PVBP 0,633 g/cm², control 0,431 g/cm²) with an increase of bone mineral density. In the histological investigation we found an increase of osteoblasts around the implants coated with PVBP and PVBP-Co-Acryloxysuccimid. Furthermore, the micro-CT scans showed an increase of BV/TV (bone volume/total volume) for both polymers.

Discussion: In this study we present the first results of the investigation of polymer-coated titanium-implants implanted in the proximal tibia and distal femora of New Zealand White Rabbits. The results of DEXA-scans, micro-CT and histological analysis showed an increase of osseointegration. We suggest that controlled release kinetics after coupling of these polymers with BMP-2 can additionally increase osseointegration. To get a closer look on the polymers, their characteristics in-vivo, and coupling with BMP-2 further investigations are conducted.

The ability to predict load-bearing capacity during the consolidation phase in distraction osteogenesis by non-invasive means would represent a significant advance in the management of patients undergoing such treatment. Measurements of stiffness have been suggested as a promising tool for this purpose. Although the multidimensional characteristics of bone loading in compression, bending and torsion are apparent, most previous experiments have analysed only the relationship between maximum load-bearing capacity and a single type of stiffness. We have studied how compressive, bending and torsional stiffness are related to the torsional load-bearing capacity of healing callus using a common set of samples of bone regenerate from 26 sheep treated by tibial distraction osteogenesis.

Our findings showed that measurements of torsional, bending and compressive stiffness were all suitable as predictors of the load-bearing capacity of healing callus. Measurements of torsional stiffness performed slightly better than those of compressive and bending stiffness.