Introduction

The management of thoracolumbar burst fractures is controversial. The goal of our study was to evaluate whether the psychological factors or the late spinal deformities influence outcome and in particular quality of life following surgical treatment of burst fractures of the thoracolumbar spine.

Introduction

Pedicle screw pullout or loosening is increased in the osteoporotic spine. Recent studies showed a significant increase of pullout forces especially for PMMA-augmentation. With application of conventional viscosity PMMA the risk of cement extravasation is associated. This risk can be reduced by using radiofrequency-responsive, ultrahigh viscosity bone cement.

Background

Radiofrequency Kyphoplasty (RFK) provides a new minimally invasive procedure to treat vertebral compression fractures (VCF).

Introduction: Femoral neck fractures are common and percutaneous insertion of three cannulated screws is an accepted method of surgical treatment. The accuracy of surgical performance is highly correlated with the cut-out percentages of the screws. The conventional technique relies heavily on fiuoroscopy and could lead to inappropriate implant placement. Further, multiple guidewire passes might prolong the operation time and weaken the cancellous bone. A computer-assisted planning and navigation system based on 2D-fiuoroscopy has been developed for guidewire insertion in order to perform insertion of a guidewire to perform screw insertion. The image acquisition process was supported by a radiation-saving procedure called “Zero-dose C-arm navigation”. The purpose of this experimental study was to compare this technique with conventional C-arm fiuoroscopy with respect to the number of fiuoroscopic images, the number of drilling attempts and operation time. We used two operative settings, with sawbones and with cadavers. For the sawbone study, we also compared the femoral neck and head perforation and the neck-width coverage (the relative area of the femoral neck held by screws).

Methods: Three cannulated hip screws were inserted into 12 femoral sawbones simulating femoral neck fractures and into 6 cadaveric femurs guided by the computer-based navigation. We compared them to the conventional fiuoroscopic technique also using 12 femoral sawbones and 6 cadaveric femurs.

Results: The computer-assisted technique significantly reduced the amount of intraoperative fiuoroscopy (sawbone study: P< 0.001; cadaver study: P< 0.001) and the number of guidewire passes (sawbone study: P< 0.05; cadaver study: P< 0.05) in the sawbone and the cadaver setting. Operation time was significantly longer (sawbone study: P< 0.001; cadaver study: P< 0.05) in the navigation assisted group also in both settings. In the sawbone study, there was no significant difference in the femoral neck and head perforation, whereas the relative neck area held by the screws was significantly (P< 0.05) larger than that in the conventional group.

Discussion: The addition of computer-assisted planning and surgical guidance supported by “Zero-dose C-arm navigation” may be useful for the fixation of femoral neck fractures by cannulated screws as it reduces the amount of intraoperative fiuoroscopy, requires fewer drill tracks and achieves a better neck coverage. Further studies with the goal of reducing the operation time by improving the learning curve are indispensable before integrating this navigation system into the clinical workfiow.

Introduction: Aseptic loosening of cemented total knee arthroplasties is still an unsolved problem. In this regard the adhesion strength of the metal-bone cement interface is of major interest.

Material und Methods: Cemented tibial components coated with a silica/silane interlayer system (n=8) were dynamically loaded within a knee-simulator (DIN ISO 14243). After loading, the components were cut by “high pressure water jet technique” (Fraunhofer Institute for Production Technology, Aachen, Germany) into 10 slices (thickness 5 mm each) parallel to the shaft axis according to a standardised protocol. To evaluate the metal-bone cement interface with regard to gaps and cement failure, the tibial slices were analysed by light and fluorescent microscopy. These data were matched with uncoated components (n=8).

Results: The coated tibial components yielded a significant reduction of gaps in the metal-bone cement interface (p < 0.05) as well as a highly significant reduction of cement mantle failure (p < 0.001).

Conclusion: With the help of the silica/silane coating, gaps in the metal-bone cement interface with consecutive early cement mantle failure due to mechanical overstressing can be significantly reduced.

Background: The aim of this prospective multi-center study was to evaluate the clinical and radiological results of a total of 314 uncemented femoral stem revisions using the modular MRP-titanium system.

Methods: 305 patients (111 males, 194 females, mean age 67.7) with 314 MRP-titanium systems were followed-up for a meantime of 3.2 years (1 to 9 years). Pre- and post-operatively all patients were clinically documented using the Harris hip score. Radiologically, the preoperative bony defects were assessed by the Paprosky classification. Post-operatively, periprosthetic bone remodeling was evaluated on the basis of radiographic evidence of bone apposition or resorption.

The modular MRP-titanium system has proven to be valuable in quite problematic cases of hip revision arthroplasty with extensive femoral defects. The system allows intraoperative adaptation of implant length and antetorsion angle to the actual situation, a feature not provided by non-modular femoral revision implants.

Aims: Prospective multi-center study to evaluate the mid-term results of 280 uncemented femoral stem revisions using the modular MRP-Titan system. Methods: 273 patients with 280 MRP-Titan systems, follow-up for a mean time of 3 years (1 to 8 years). Harris hip score for clinical evaluation, bony defect classification according to Paprosky [163 cases (58%) with type 2B, 2C and 3]. Results: Three aseptic loosenings (1%), three septic loosenings (1%), one additional re-revision because of periprosthetic fracture. Postoperative dislocations occurred in 23 cases (8%), 17 of these (6%) were managed by closed or open reposition without changing the implant. In 6 cases (2%) the antetorsion angle of the modular prosthesis neck was altered. Harris hip score: 38 points preoperatively, 85 points at the last follow-up postoperatively. In 18 cases (6.4%) radiolucient lines were seen, but with no progression and no migration of the stems. The overall survival-rate after 8 years of follow-up was 92%. Conclusions: The modular MRP-Titan system has proven to be valuable in quite problematic cases of hip revision arthroplasty with extensive femoral defects. The system allows intraoperative adaptation of implant length and antetorsion angle to the actual situation, a feature not provided by non-modular femoral revision implants.

Among the wide variety of bone substitutes presently available, pure β-tricalcium phosphate ceramics have become available (Biosorb®; Aesculap, Tuttlingen). During the first 12 months of a prospective clinical trial, Biosorb® products were implanted in 21 patients. The ceramics were used in a variety of clinical settings, ranging from pelvic osteotomies in children (n=9), to filling of bone cysts or osseous defects (n=4), to dorsal spondylodesis (n=6), as well as for the grafting of pseudarthroses (n=2). Average follow-up period was 13 (6–18) months.

The β-TCP granules, when used as part of a composite graft in combination with autologous bone, were completely resorbed after an average period of 14 weeks, while the cubes required 12 to 15 months. The more massive wedges have shown only a decrease in size and radio density. Due to the ability of the cubes and wedges to bear loads of up to 30 MPa, they were successfully implanted during pelvic osteotomies to augment or completely replace the bicortical grafts. Complications or foreign body reactions were not noted. The osseointegration was found to be favorable for all forms.

In light of the problems associated with autologous and allogeneic grafts, the use of synthetic bone substitutes will continue to increase. The combination of complete resorption, lack of risk of infection, and load sharing ability make the β-tricalcium phosphate implants a valuable addition to the spectrum of bone replacement products presently available. Their use in pediatric orthopedics could help avoid donor site morbidity including contour changes or growth disturbances, while providing a more stable graft. During the first phase of a prospective clinical trial, we have come to the conclusion, that the β-tricalcium phosphate ceramics represent a real alternative to other bone substitutes.