J. A. K. Ohnsorge

BMP-2 Incorporated in a Tricalcium Phosphate Bone Substitute Enhances Bone Remodeling in Sheep

Bone morphogenetic protein-2 (BMP-2) is a well-known osteoinductive protein, which requires a carrier for local application. As an alternative to the previously described carriers, an in situ hardening, resorbable, and osteoconductive β-tricalcium phosphate cement (TCP) is tested. Trepanation defects in the bovine distal femoral epiphysis are filled with a composite consisting of TCP and 200 μg rhBMP-2 per cm3 TCP, autologous bone graft, pure TCP, or left empty. A radiological follow-up is performed after 7 weeks and 3 months. The sheep are euthanized and bone samples are analyzed by microradiography, histology, and histomorphometry. Microradiography and histology show similar results for pure TCP and the composite. The defects are filled with trabecular bone and newly formed bone is in close contact with the remaining TCP-particles. The majority of the cement is resorbed, in the composite group the amount of remaining cement particles is reduced. Defects treated with autologous bone graft are filled completely, while untreated defects shows only a small amount of bone originating from the rim of the defect. Histomorphometry of the defects treated with pure TCP shows a significantly increased bone content in comparison to defects treated with the composite or autologous bone graft. Analysis of the remaining cement particles shows significantly less cement in the TCP/rhBMP-2 group in comparison to pure TCP. The sum of bone and cement content in the rhBMP-2 group shows amounts comparable to the calcified structures found following autologous bone grafting. The addition of rhBMP-2 to the TCP leads to faster remodeling of the defect comparable to autologous bone graft, while defects treated with pure TCP are not completely remodeled.

CT-Based Planning and Individual Template Navigation in TKA

Among the various modalities of alloarthroplasty of the knee joint the total endoprosthesis is the most often exe-cuted intervention in the world. Severe arthrosis and axial deformities up to 30o varus or valgus can thereby be equalized. Today’high quality standard of surgical treatment requires anatomically correct orientation and fitting of the implant aiming at optimal biomechanical functionality. Thus, the single components must be taken into account as well as functional changings of tension in the surrounding soft tissue.

Fluoroscopy-based 3-D reconstruction of femoral bone cement: a new approach for revision total hip replacement

In revision total hip replacement the removal of the distal femoral bone cement can be a time consuming and risky operation due to the difficulty in determining the three-dimensional (3-D) boundary of the cement. We present a new approach to reconstruct the bone cement volume by using just a small number of calibrated multiplanar X-ray images. The modular system design allows the surgeon to react intraoperatively to problems arising during the individual situation. When encountering problems during conventional cement removal, the system can be used on demand to acquire a few calibrated X-ray images. After a semi-automatic segmentation and 3-D reconstruction of the cement with a deformable model, the system guides the surgeon through a free-hand navigated or robot-assisted cement removal. The experimental evaluation using plastic test implants cemented into anatomic specimen of human femoral bone has shown the potential of this method with a maximal error of 1.2 mm (0.5 mm RMS) for the distal cement based on just 4-5 multiplanar X-ray images. A first test of the complete system, comparing the 3-D-reconstruction with a computed tompography data set, confirmed these results with a mean error about 1 mm.

Treatment of an old infection in a total hip replacement with an interim spacer prosthesis

SummaryWhen treating a septic hip-joint prosthesis with bone loss of the proximal femur secondary to osteomyelitis, we implanted a specially designed prosthesis to act as a local antibiotic and spacer between the acetabulum and femur until the infection abated. Arthroplasty could then be carried out with no trouble and there was no recurrence of infection.

Procalcitonin (PCT) als Verlaufsparameter der Spondylodiszitis

AIM The diagnosis of spondylodiscitis is often prolonged, but it is an important differential diagnosis of backache. The discrimination between a bacterial infection and an aseptic inflammation with laboratory examinations like ESG, CRP or leukocytes is not possible. The aim of the present study was to determine the value of procalcitonin (PCT) as a diagnostic tool and monitoring parameter for spondylodiscitis and for the discrimination between bacterial infection and aseptic inflammation of the spine. METHOD A total of 17 patients with spondylodiscitis and 18 patients with disc herniation as control were included in this study and ESG, CRP, leukocytes, fibrinogen, PNM elastase und PCT were examined for 50 days. The median age was 65 (17-78) years and the ratio of males to females was 8 : 9 in patients with spondylodiscitis and 62 (32-87) years and 7 : 11 in patients with disc herniation. For microbiological examination, CT-guided punctures were performed in patients with spondylodiscitis. RESULTS In 64 % of the 17 patients with spondylodiscitis a microbiological agent was detected, in 73 % of these cases staphylococcus aureus was isolated. The laboratory parameters indicating an infection were increased except for two cases in patients with spondylodiscitis, the mean value of CRP was 115 mg/dL. Influenced by the therapy these parameters decreased during the observation period. Except for one patient with an infection of a cardiac pacemaker, the PCT concentration was not elevated in both groups (< 0.5 ng/mL). In the group with disc herniation there were no elevated laboratory parameters during the entire observation period. CONCLUSION PCT is not useful as diagnostic tool or monitoring parameter for spondylodiscitis. Furthermore, it is not useful for the discrimination between a bacterial infection and an aseptic inflammation of the spine.

In vitro elution characteristics of gentamicin and vancomycin from synthetic bone graft substitutes.

Objects: Beta tricalciumphosphate pellets loaded with individualized antibiotics may represent novel options in the treatment of osteomyelitis and infectious bone disease. Here, the in vitro antibiotic elution of vancomycin and gentamicin from the synthetic bone graft substitutes Cerasorb® and Cerasorb M® was tested. Methods: Antibiotic elution and concentration of gentamcin and vancomycin were measured using photometrically-based measurement and homogeneous particle-enhanced turbidimetric inhibition immunoassays (PETINIA). Results: Initially both materials showed a high release of the loaded antibiotics, with Cerasorb M® showing lower release levels for gentamicin and vancomycin than Cerasorb®. Gentamicin concentrations of Cerasorb M granules and Cerasorb were below the minimum detectiontreshold until day four and six of the experiment respectively. The vancomycin release-level followed a similar pattern, although the vancomycin concentration eluted by Cerasorb M® granules stayed above the detection threshold during the experimental time. Conclusions: Cerasorb® and Cersorb M® may represent a new treatment option in osteomyelitis and infectious bone disease.

Computer-assisted fluoroscopic navigation of percutaneous spinal interventions

PurposePercutaneous spine procedures may occasionally be difficult and subject to complications. Navigation using a dynamic reference base (DRB) may ease the procedure. Yet, besides other shortcomings, its fixation demands additional incisions and thereby defies the percutaneous character of the procedure.MethodsA new concept of atraumatic referencing was invented including a special epiDRB. The accuracy of navigated needle placement in soft tissue and bone was experimentally scrutinised. Axial and pin-point deviations from the planned trajectory were investigated with a CT-based 3D computer system. Clinical evaluation in a series of ten patients was also done.ResultsThe new epiDRB proved convenient and reliable. Its fixation to the skin with adhesive foil provided a stable reference for navigation that improves the workflow of percutaneous interventions, reduces radiation exposure and helps avoid complications.ConclusionsPercutaneous spine interventions can be safely and accurately navigated using epiDRB with minimal trauma or radiation exposure and without additional skin incisions.

Perineurale sakrale Zysten als Ursache von Ischialgie und pathologischer Massa-lateralis-Fraktur des Os sacrum

We report on the case of an 81-year-old woman who was hospitalised because of severe pain at the sacro-iliacal joint radiating into the left leg without any accompanying neurological defect. X-rays demonstrated a step in the left massa lateralis of the sacrum, thus CT scans and MRI were performed, and multiple perineural cysts (Tarlovs cysts) were found. The patient underwent microsurgical treatment by fenestration of the cyst wall and evacuation of the fluid content in order to avoid further expansion of the cysts. Under consequent treatment with pain killers, complete mobilisation of the patient could be achieved. Ambulant follow-up by clinical controls and X-rays demonstrated a substantial resolution of the patients preoperative symptoms. Symptomatic perineural cysts should be included into differential diagnosis of severe low back pain, thus CT or MRI scans should be performed in case of long-lasting or intrackable pain.

Elektromagnetische Navigation transpedikulärer Punktionen@@@Electromagnetic navigation of transpedicular punctures: Präziser als der Standard?@@@More precise than the standard?

AIM Before clinical implementation of an approved electromagnetic tracking system (CAPPA IRAD EMT) an experimental trial was performed to investigate the accuracy of the system and its safety in application for transpedicular vertebral punctures in comparison to the classical fluoroscopic method. MATERIAL AND METHODS A total of 110 transpedicular punctures were performed bilaterally using 11 vertebrae of 5 realistic artificial phantoms and 1 pedicle was punctured with the conventional technique using c-arm fluoroscopy and the other with the electromagnetic tracking system. As a target a radiopaque non-ferromagnetic marker was implanted bilaterally in the anterior wall of the vertebrae. For evaluation of the precision the distance from the end of the puncture to the target and the gradual deviation of the actual channel from the ideal trajectory were assessed in three-dimensional computer tomography. Calculations and statistical analysis were performed according to the Wilcoxon test by means of SPSS 16.0.1 for Windows. RESULTS The mean distance from the target was 6.6 mm (± 3.9 mm standard deviation SD) with electromagnetic navigation compared to 3.2 mm (± 2.8 mm SD) with fluoroscopic assistance and the mean aberration from the ideal trajectory was 18.4° (± 4.6° SD) compared to 6.5° (± 3.5° SD), respectively. The difference of accuracy was highly significant regarding both parameters (p < 0.001). CONCLUSIONS The minimum requirement for accuracy of transpedicular punctures could not be achieved with electromagnetic navigation. Unless proven otherwise, the lack of accuracy is attributed to unstable referencing. Despite evidence of successful employment for soft tissue punctures the system cannot currently be recommended for osseous applications of the spine.

[Electromagnetic navigation of transpedicular punctures: more precise than the standard?].

AIM Before clinical implementation of an approved electromagnetic tracking system (CAPPA IRAD EMT) an experimental trial was performed to investigate the accuracy of the system and its safety in application for transpedicular vertebral punctures in comparison to the classical fluoroscopic method. MATERIAL AND METHODS A total of 110 transpedicular punctures were performed bilaterally using 11 vertebrae of 5 realistic artificial phantoms and 1 pedicle was punctured with the conventional technique using c-arm fluoroscopy and the other with the electromagnetic tracking system. As a target a radiopaque non-ferromagnetic marker was implanted bilaterally in the anterior wall of the vertebrae. For evaluation of the precision the distance from the end of the puncture to the target and the gradual deviation of the actual channel from the ideal trajectory were assessed in three-dimensional computer tomography. Calculations and statistical analysis were performed according to the Wilcoxon test by means of SPSS 16.0.1 for Windows. RESULTS The mean distance from the target was 6.6 mm (± 3.9 mm standard deviation SD) with electromagnetic navigation compared to 3.2 mm (± 2.8 mm SD) with fluoroscopic assistance and the mean aberration from the ideal trajectory was 18.4° (± 4.6° SD) compared to 6.5° (± 3.5° SD), respectively. The difference of accuracy was highly significant regarding both parameters (p < 0.001). CONCLUSIONS The minimum requirement for accuracy of transpedicular punctures could not be achieved with electromagnetic navigation. Unless proven otherwise, the lack of accuracy is attributed to unstable referencing. Despite evidence of successful employment for soft tissue punctures the system cannot currently be recommended for osseous applications of the spine.