Helmut Ahrens

Endoprosthetic reconstruction in 250 patients with sarcoma

We assessed the clinical results and complications associated with a new endoprosthetic replacement system (Mutars®) used in 250 patients with a malignant bone or soft tissue tumor. The key features of the system are its cementless, hexagonal-shaped stem (titanium alloy), the possibility of torsion adjustments in 5°-increments, and the Trevira® tube for soft tissue attachment. The mean age of the patients was 30.7 years, and the mean followup was 45 months. Prosthetic survival at 5 years was 89.7% for the upper extremity and 68.5% for the lower extremity. Prosthetic survival without any reoperation was 73.4% at 3 years postoperatively and 60.4% at 5 years postoperatively. Prosthetic failure was caused by deep infection in 12% (30 patients) of patients and aseptic loosening in 8% (20 patients) of patients. Stem fracture occurred in only 1.6% (four patients) of patients. Dislocation rates were reduced by using the Trevira® tube. Limb survival was achieved in 82.6% to 93.1% of patients depending on the endoprosthetic replacement site, and functional results ranged between 63% to 83% according to the Tumor Society score. Our results suggest limb salvage with the Mutars® endoprosthesis is successful with good functional results.Level of Evidence: Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Reduction of periprosthetic infection with silver-coated megaprostheses in patients with bone sarcoma.

The placement of megaprostheses in patients with bone sarcoma is associated with high rates of infection, despite prophylactic antibiotic administration. In individual cases, secondary amputation is unavoidable in the effort to cure infection.

The influence of elementary silver versus titanium on osteoblasts behaviour in vitro using human osteosarcoma cell lines.

Purpose. The antimicrobial effect of a silver-coated tumor endoprosthesis has been proven in clinical and experimental trials. However, in the literature there are no reports concerning the effect of elementary silver on osteoblast behaviour. Therefore, the prosthetic stem was not silver-coated because of concerns regarding a possible inhibition of the osseointegration. The aim of the present study was to investigate the effect of 5–25 mg of elementary silver in comparison to Ti-6Al-4V on human osteosarcoma cell lines (HOS-58, SAOS). Methods. Cell viability was determined by measuring the MTT proliferation rate. Cell function was studied by measuring alkaline phosphatase (AP) activity and osteocalcine production. Results. In the HOS-58 cells, the AP activity was statistically significant (P < 0.05) higher at a supplement of 5–10 mg of silver than of Ti-6 Al-4V at the same doses. For both cell lines, a supplement above 10 mg of silver resulted in a reduced AP activity in comparision to the Ti-6 Al-4V group, but a statistically significant difference (P < 0.05) was observed at a dose of 25 mg for the SAOS cells only. At doses of 20–25 mg in the HOS-58 cells and 10–25 mg in the SAOS cells, the reduction of the proliferation rate by silver was statistically significant (P < 0.05) compared to the Ti-6 Al-4V supplement. Discussion. In conclusion, elementary silver exhibits no cytotoxicity at low concentrations. In contrast, it seems to be superior to Ti-6 Al-4V concerning the stimulation of osteogenic maturation at these concentrations, whereas at higher doses it causes the known cytotoxic properties.

Giant Cell Tumors of the Axial Skeleton

Background. We report on 19 cases of giant cell tumor of bone (GCT) affecting the spine or sacrum and evaluate the outcome of different treatment modalities. Methods. Nineteen patients with GCT of the spine (n = 6) or sacrum (n = 13) have been included in this study. The mean followup was 51.6 months. Ten sacral GCT were treated by intralesional procedures of which 4 also received embolization, and 3 with irradiation only. All spinal GCT were surgically treated. Results. Two (15.4%) patients with sacral and 4 (66.7%) with spinal tumors had a local recurrence, two of the letter developed pulmonary metastases. One local recurrence of the spine was successfully treated by serial arterial embolization, a procedure previously described only for sacral tumors. At last followup, 9 patients had no evidence of disease, 8 had stable disease, 1 had progressive disease, 1 died due to disease. Six patients had neurological deficits. Conclusions. GCT of the axial skeleton have a high local recurrence rate. Neurological deficits are common. En-bloc spondylectomy combined with embolization is the treatment of choice. In case of inoperability, serial arterial embolization seems to be an alternative not only for sacral but also for spinal tumors.

Modular Endoprosthetic Reconstruction in Malignant Bone Tumors: Indications and Limits

Modular tumor prostheses are well established today for the reconstruction of osseous defects after resection of malignant bone tumors. Almost every joint and even total bones (e.g., total femur or humerus) can be replaced with promising functional results, dramatically reducing the need for ablative procedures. Although the complication rate with the use of modern modular endoprostheses is constantly decreasing, the need for revision surgery is still significantly higher than in primary joint arthroplasty. In this review we present the modular endoprosthesis system developed in our institution, summarize the postoperative management, and discuss the indications, limits, and complications as well as the functional results.

Reconstruction after wide resection of the entire distal fibula in malignant bone tumours

In this study we present a series of patients (n = 11) with resection of the entire distal fibula in the case of sarcoma or metastasis. Moreover, we describe a new method to restore ankle stability with a tibiotalocalcaneal arthrodesis using a retrograde hindfoot nail (n = 4) in contrast to tibiotalar arthrodesis with screws (n = 5). The screw fixation failed in two patients due to osteopoenic bone. The crucial benefits of an arthrodesis with a retrograde nail are a stable arthrodesis, intramedullary stabilisation of the tibia and avoidance of extrinsic material in the wound area. An arthrodesis with a retrograde nail is a good alternative for reconstruction after a wide distal fibula resection. The additional arthrodesis of the subtalar joint was not associated with worse functional results in the MSTS and TESS scores.

Surgical difficulties encountered with use of modular endoprosthesis for limb preserving salvage of failed allograft reconstruction after malignant tumor resection.

We reviewed outcomes and discussed surgical difficulties encountered in 10 patients who had modular endoprosthesis for limb preserving salvage of failed allograft reconstruction after malignant tumor resection. Mean allograft survival time before failure was 127.4 months (range, 14-264 months). Mean length of follow-up since endoprosthesis revision surgery was 62.8 months (range, 16-132 months). There was one endoprosthesis failure, resulting in a mean endoprosthesis survival time of 56.9 months (range, 16-132). Complications included arterial laceration, nerve injury, periprosthetic crack fracture, aseptic loosening, and infection. Modular endoprosthesis remain a viable option that should be considered in any limb preserving salvage of failed allograft reconstructions. However, altered anatomy, poor/short remnant host bone, periprosthetic fractures, inadequate soft tissue coverage and infection remain important difficulties encountered.

Rotationplasty type BI versus type BIIIa in children under the age of ten years SHOULD THE KNEE BE PRESERVED

Type BI rotationplasty is currently indicated for children with tumours of the proximal femur whereas type BIIIa rotationplasty is reserved for those in which the entire femur has to be removed. Our aim was to compare these two types of rotationplasty and determine whether the knee should be preserved in children with tumours of the proximal femur. We compared the post-operative complications, oncological outcome, range of movement, Enneking score and radiographs of six children, who had undergone type BI rotationplasty with those of 12 who had undergone type BIIIa rotationplasty. Patients with type BI rotationplasty had a mean Enneking score of 21.6 compared with 24.4 in those with type BIIIa rotationplasty, and worse mean results in all of the parameters investigated. We conclude that type BI rotationplasty has a worse functional outcome and more complications than type BIIIa rotationplasty in children under the age of ten years.

Total tibia replacement using an allograft (in a patient with adamantinoma). Case report and review of literature

AbstractIntroductionAdamantinoma is a very rare, low-grade, malignant bone tumour that accounts for approximately 0.4% of all primary bone tumours. Radiographically, adamantinomas vary in length, have a clearly defined outline, with a bubbly appearance and increase the width of the bone. Histologically, epithelial cells, endothelial cells synovial cells have been implicated as cells of origin.Case presentationWe present a case of adamantinoma of the tibia, in which a resection of the whole tibia and reconstruction with a total tibia allograft was necessary.DiscussionThe histological diagnosis is sophisticated. It is often difficult to distinguish an adamantinoma from other tumours. The most frequent described method to treat adamantinoma is wide resection and the use of an allograft. The most common complication is fracture presented similarly in our patient. ConclusionA total tibia allograft as presented in our case is not described in the literature. It fractured due the first year after implantation. Using a prosthesis system instead of the allograft might have saved the limb of our patient.

Evaluation of Osseous Integration of PVD-Silver-Coated Hip Prostheses in a Canine Model

Infection associated with biomaterials used for orthopedic prostheses remains a serious complication in orthopedics, especially tumor surgery. Silver-coating of orthopedic (mega)prostheses proved its efficiency in reducing infections but has been limited to surface areas exposed to soft tissues due to concerns of silver inhibiting osseous integration of cementless stems. To close this gap in the bactericidal capacity of silver-coated orthopedic prostheses extension of the silver-coating on surface areas intended for osseous integration seems to be inevitable. Our study reports about a PVD- (physical-vapor-deposition-) silver-coated cementless stem in a canine model for the first time and showed osseous integration of a silver-coated titanium surface in vivo. Radiological, histological, and biomechanical analysis revealed a stable osseous integration of four of nine stems implanted. Silver trace elemental concentrations in serum did not exceed 1.82 parts per billion (ppb) and can be considered as nontoxic. Changes in liver and kidney functions associated with the silver-coating could be excluded by blood chemistry analysis. This was in accordance with very limited metal displacement from coated surfaces observed by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) 12 months after implantation. In conclusion our results represent a step towards complete bactericidal silver-coating of orthopedic prostheses.