Computer-assisted fluoroscopic navigation of percutaneous spinal interventions.

PURPOSE: Percutaneous 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. METHODS: A 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. RESULTS: The 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. CONCLUSIONS: Percutaneous spine interventions can be safely and accurately navigated using epiDRB with minimal trauma or radiation exposure and without additional skin incisions.

Revision knee arthroplasty including reconstruction of the lateral collateral ligament by allograft: a case report.

A 53-year-old woman presented with an unstable and painful total knee arthroplasty 6 months after the index procedure. Disruption of both collateral ligaments as a young adult and the subsequent development of traumatic arthritis required repeated surgical and extensive conservative treatment before a prosthesis was implanted. Examination disclosed marked instability of the lateral collateral ligament (LCL) and loosening of the tibial and the femoral components. Review of the MRI obtained prior to the total knee replacement revealed discontinuity of the LCL with intense scarring of the posterolateral ligament complex. Definitive management of this twofold problem was not helped by literature review, which failed to reveal a gold standard or a broad consensus as a rationale for treatment. Consequently, an individual approach to the problem was defined: A one-stage revision arthroplasty was performed using a modular non-articulated constrained prosthesis and a bone-tendon-bone allograft to reconstruct the LCL in a one-stage operation. Postoperative rehabilitation included continuous passive motion, which was begun immediately after surgery and was gradually increased to 90° of flexion. The LCL reconstruction was initially protected in a hinged knee brace and weight-bearing was initially limited to toe-touch and gradually increased over 6 weeks. Pain-free motion to 0-115° flexion was achieved at 3 months after surgery and the patient had returned to her normal activities. The 4-year-follow-up displayed a stable and functional knee with no evidence of loosening or wear.

Perthes' or Perthes' resembling disease in 13-month-old boy.

Onset of Perthes' disease is reported frequently from the age of 2 years. Latest publications showed cases with onset of this disease in infancy at ages of 17 and 18 months. We report the case of a 13-month-old boy, who presented with left-sided limping. Radiological examination showed reduced height and fragmentation of the femoral head. Magnetic resonance imaging showed the typical signs of an avascular necrosis. Follow-up was done after 3, 7 and 15 months. Plain radiography showed the femoral head in a state of reparation. This is the youngest documented case of Legg-Calvé-Perthes' disease and is discussed under consideration of the current literature.

Lack of effect on bone healing of injectable BMP-2 augmented hyaluronic acid.

INTRODUCTION: Autologous bone graft is the gold standard for the filling of large osseous defects. Because of its limited supply and complications such as pain, bleeding or infection, the development of alternative bone substitutes has been the subject of several studies. In clinical practice, the most commonly used bone substitutes are calcium phosphates like hydroxyapatite or tricalcium phosphate. With the aim to improve the osseointegration of these materials, growth factors such as bone morphogenetic protein-2 (BMP-2) have been added. Preferably, an injectable bone substitute should be made available. Hyaluronic acid is a component of the extracellular matrix of many tissues, including bone. We examined the bone regenerative effect of commercially available, injectable hyaluronic acid (Hyalart) with and without addition of bone morphogenetic protein-2 (BMP-2). MATERIALS AND METHODS: Trepanation defects of 9.4 mm diameter in the intercondylar groove of sheep femora were filled with pure and augmented (200 microg BMP-2) hyaluronic acid. As controls, empty defects and defects treated with autologous bone graft harvested from the contralateral side were used. After 3 months, the defects were analysed by fluorescence microscopy after intravital fluorescence staining, contact microradiography, histology and histomorphometry. RESULTS: Treatment of the defects with loaded and unloaded hyaluronic acid resulted in a significant lack of bone formation inside the defects. Untreated defects showed an amount of 5.1% newly formed bone, and defects treated with autologous bone graft revealed a bone content of 20%. The difference between both groups was statistically significant (P < 0.05). Furthermore, there was neither a remarkable effect in the periphery of the defects nor ectopic bone formation. CONCLUSION: The application of the used injectable hyaluronic acid (Hyalart) with and without BMP-2 is not advantageous as sole bone substitute for the filling of osseous defects.

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 beta-tricalcium phosphate cement (TCP) is tested. Trepanation defects in the bovine distal femoral epiphysis are filled with a composite consisting of TCP and 200 microg 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.

A bFGF/TCP-composite inhibits bone formation in a sheep model.

Basic fibroblast growth factor is a well known osteostimulative protein. The effects of basic fibroblast growth factor are dose-dependent and, when used with a carrier, influenced by the release kinetics. Aim of our study was to determine the effects of a composite of basic fibroblast growth factor and a newly developed, in situ setting tricalcium phosphate (TCP) cement. A trepanation defect in the distal femoral epiphysis of Merino-Mix sheep with a diameter of 9.4 mm and 10 mm depth was filled with the in situ setting TCP cement combined with 0 or 200 microg of bFGF/cm(3) TCP, autologous bone graft or left empty. The sheep were euthanized after 3 months. The defect and the periimplant area were examined by microradiography, histology, and histomorphometry. The data was analyzed with the help of the Wilcoxon and Kruskal-Wallis tests. Defects filled with TCP with or without bFGF showed a close bone-cement contact. The histomorphometric analysis revealed that the addition of bFGF inhibited the ingrowth of bone significantly, while the resorption of the cement was not influenced. In conclusion, the clinical application of this bFGF/TCP-composite does not seem promising. The reason for the inhibition of new bone formation will be discussed, but requires further investigation.

Epithelioid sarcoma in the thoracic spine.

Epithelioid sarcoma is a rare and highly malignant soft tissue tumor that is commonly found in the extremities and rarely in the trunk area. This malignant tumor often mimics granuloma or nodular fasciitis, which causes a delay in establishing the diagnosis. This type of cancer has a high recurrence rate. Surgical treatment requires wide radical resection. The objective of this case report is to highlight the unique location of a rare neoplasm and to illustrate the relentless course of epithelioid sarcoma despite initial radical resection. A 14-year-old boy was admitted to our facility with a soft tissue mass on the right lower thoracic spine. The large tumor mass had deeply penetrated into the muscles, infiltrated the neuroforamen of T9-T10 level, and compressed the dural sac. Immunohistological study of the biopsy was highly consistent with an epithelioid sarcoma. Wide excision of the mass, laminectomy and spine fusion with instrumentation was performed. The patient received chemotherapy and irradiation. The first recurrence of the neoplasm was seen as a contralateral metastasis 21 months after the resection. On the last follow-up, 3 years postoperatively, the patient was in a good general condition. However, further progression of the sarcoma had to be recognized. Our case encompasses multiple features that represent negative prognostic factors. Initial wide excision of the neoplasm and adjuvant therapy including chemotherapy and irradiation seem to slow down the relentless course of epithelioid sarcoma in the trunk.

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 tompgraphy data set, confirmed these results with a mean error about 1 mm.