R. Kotz

ELEVATED SERUM COBALT WITH METAL-ON-METAL ARTICULATING SURFACES

We determined serum cobalt levels in 55 patients by atomic absorption spectrophotometry before and after implantation of uncemented total hip arthroplasties. In a randomised, prospective trial 27 wrought Co-28Cr-6Mo-0.2C metal-on-metal articulations were compared with 28 ceramic-on-polyethylene hips which did not contain cobalt. Other sources of iatrogenic cobalt loading were excluded. The metal-on-metal group produced detectable serum cobalt levels (median 1.1 microg/l after one year) which were significantly different (p < 0.0001) from those of the ceramic-on-polyethylene control group (median below detection limit of 0.3 microg/l after one year). Our findings indicate that metal-on-metal bearings generate some systemic release of cobalt.

Failure Mode Classification for Tumor Endoprostheses: Retrospective Review of Five Institutions and a Literature Review

BACKGROUND Massive endoprostheses provide orthopaedic oncologists with many reconstructive options after tumor resection, although failure rates are high. Because the number of these procedures is limited, failure of these devices has not been studied or classified adequately. This investigation is a multicenter review of the use of segmental endoprostheses with a focus on the modes, frequency, and timing of failure. METHODS Retrospective reviews of the operative databases of five institutions identified 2174 skeletally mature patients who received a large endoprosthesis for tumor resection. Patients who had failure of the endoprosthesis were identified, and the etiology and timing of failure were noted. Similar failures were tabulated and classified on the basis of the risk of amputation and urgency of treatment. Statistical analysis was performed to identify dependent relationships among mode of failure, anatomic location, and failure timing. A literature review was performed, and similar analyses were done for these data. RESULTS Five hundred and thirty-four failures were identified. Five modes of failure were identified and classified: soft-tissue failures (Type 1), aseptic loosening (Type 2), structural failures (Type 3), infection (Type 4), and tumor progression (Type 5). The most common mode of failure in this series was infection; in the literature, it was aseptic loosening. Statistical dependence was found between anatomic location and mode of failure and between mode of failure and time to failure. Significant differences were found in the incidence of failure mode Types 1, 2, 3, and 4 when polyaxial and uniaxial joints were compared. Significant dependence was also found between failure mode and anatomic location in the literature data. CONCLUSIONS There are five primary modes of endoprosthetic failure, and their relative incidences are significantly different and dependent on anatomic location. Mode of failure and time to failure also show a significant dependence. Because of these relationships, cumulative reporting of segmental failures should be avoided because anatomy-specific trends will be missed. Endoprosthetic design improvements should address failure modes specific to the anatomic location.

Treatment of Full-Thickness Chondral Defects With Hyalograft C in the Knee A Prospective Clinical Case Series With 2 to 7 Years’ Follow-up

Background Tissue engineering has become available for cartilage repair in clinical practice. Hypothesis The treatment of full-thickness chondral defects in the knee with a hyaluronan-based scaffold seeded with autolo-gous chondrocytes provides stable improvement of clinical outcome up to 7 years. Study Design Case series; Level of evidence, 4. Methods Fifty-three patients with deep osteochondral defects in the knee were treated with Hyalograft C. The mean age at implantation was 32 6 12 years, the mean defect size was 4.4 6 1.9 cm2, and the mean body mass index was 24.5 6 3.8 kg/m2. Implantations were performed with miniarthrotomy or arthroscopy. The primary indications for implantation with Hyalograft C included young patients with a stable joint, normal knee alignment, and isolated chondral defects with otherwise healthy adjacent cartilage. The secondary indications were patients who did not meet the primary indication criteria or were salvage procedures. Forty-two patients with primary indications and 11 patients with secondary indications were evaluated. Outcome was evaluated with the International Cartilage Repair Society and International Knee Documentation Committee scales, the Lysholm score, the modified Cincinnati score, and with Kaplan-Meier survival analysis. Statistical analysis consisted of bivariate correlation analysis and unpaired, 2-tailed t tests. Results A highly significant increase (P<001) in all knee scores was found in patients treated for the primary indications. Nine of 11 secondary indication cases underwent total knee arthroplasty due to persisting pain between 2 and 5 years after implantation. Graft failure occurred in 3 of 42 patients with primary indication between 6 months and 5 years after implantation. Kaplan-Meier survival demonstrated significantly different chances for survival between primary and secondary outcome and between simple, complex, and salvage cases, respectively (P <.001). Conclusion Hyalograft C autograft provides clinical improvement in healthy young patients with single cartilage defects. Less complicated surgery and lower morbidity are considered advantages of the technique. The results of treatment with Hyalograft C as a salvage procedure or in patients with osteoarthritis are poor.

Revision of the Kotz type of tumour endoprosthesis for the lower limb

In 251 patients over a period of 15 years an uncemented Kotz modular femoral and tibial reconstruction mega prosthesis was implanted after resection of a malignant tumour of the lower limb. Twenty-one patients (8.4%) underwent revision for aseptic loosening, again using an uncemented prosthesis, and five of these required a further revision procedure. The median follow-up time from the first revision was 60 months (11 to 168) and after a second revision, 33 months (2 to 50). The probability of a patient avoiding aseptic loosening for ten years was 96% for a proximal femoral, 76% for a distal femoral and 85% for a proximal tibial implant. At the time of follow-up all radiographs were assessed according to the International Symposium of Limb Salvage criteria. The first radiological signs of aseptic loosening were always seen at the most proximal or distal part of the anchorage stem at a mean of 12 months (4 to 23) after the first implantation. Using the Musculoskeletal Tumor Society score for evaluation, the clinical results showed a mean of 88% of normal function.

Metatarsal reconstruction with use of free vascularized osteomyocutaneous fibular grafts following resection of malignant tumors of the midfoot. A series of six cases.

BACKGROUND Bone and soft-tissue sarcomas are uncommon, and their location in the foot is extremely rare. While limb salvage has become the standard of care in the treatment of sarcoma in an extremity, the unique anatomy of the foot presents challenges in reconstructing a viable and functional limb. METHODS Between 1998 and 2005, we used free microvascularized osteomyocutaneous fibular grafts to reconstruct the defects created after extensive midfoot resection in six consecutive patients with a primary malignant tumor. In all but one patient, the extent of the resection involved at least two metatarsals. The mean age (and standard deviation) at the time of the operation was 30+/-13 years. At the final follow-up examination, clinical and radiographic evaluations were performed on all patients, and functional outcome and quality of life were assessed with use of the Musculoskeletal Tumor Society score, the American Orthopaedic Foot and Ankle Society Score, and the Toronto Extremity Salvage Score. RESULTS The median duration of follow-up was 52.2 months. Limb salvage was achieved in five patients. In the remaining patient, amputation was necessary because of flap failure. Revision surgery was necessary in all patients because of complications (skin ulcerations in three patients; hematoma in two patients; and infection, necrosis of the second toe, and flap necrosis in one patient each). At the time of final follow-up, five patients had satisfactory function and reported good quality of life. The average Musculoskeletal Tumor Society, American Orthopaedic Foot and Ankle Society, and Toronto Extremity Salvage scores were 82%, 75 points, and 92%, respectively. At the time of the final follow-up, five patients had no evidence of disease and one patient had disease. CONCLUSIONS Following the resection of a malignant tumor in the midfoot, the use of microvascularized osteomyocutaneous fibular grafts has proven to be a successful surgical technique, offering an alternative to ablative surgery with functional restoration of the salvaged limb.

Microarray analysis identifies distinct gene expression profiles associated with histological subtype in human osteosarcoma

Osteosarcoma is the most common primary malignant bone tumour. Currently osteosarcoma classification is based on histological appearance. It was the aim of this study to use a more systematic approach to osteosarcoma classification based on gene expression analysis and to identify subtype specific differentially expressed genes. We analysed the global gene expression profiles of ten osteosarcoma samples using Affymetrix U133A arrays (five osteoblastic and five non-osteoblastic osteosarcoma patients). Differential gene expression analysis yielded 75 genes up-regulated and 97 genes down-regulated in osteoblastic versus non-osteoblastic osteosarcoma samples, respectively. These included genes involved in cell growth, chemotherapy resistance, angiogenesis, steroid- and neuropeptide hormone receptor activity, acute-phase response and serotonin receptor activity and members of the Wnt/ß-catenin pathway and many others. Furthermore, we validated the highly differential expression of six genes including angiopoietin 1, IGFBP3, ferredoxin 1, BMP, decorin, and fibulin 1 in osteoblastic osteosarcoma relative to non-osteoblastic osteosarcoma. Our results show the utility of gene expression analysis to study osteosarcoma subtypes, and we identified several genes that may play a role as potential therapeutic targets in the future.

Modular Prosthetic Reconstruction of Major Bone Defects of the Distal End of the Humerus

BACKGROUND Bone defects of the distal end of the humerus require complex reconstructions, for which standard prostheses may be insufficient. We investigated the outcomes of distal humeral reconstruction with use of a modular prosthesis. METHODS Fifty-three elbows in fifty-two patients underwent reconstruction with a modular prosthesis (twelve total humeral replacements and forty-one distal humeral replacements) after tumor resection (thirty-eight elbows) or because of massive joint degeneration (fifteen elbows). In the tumor group, twenty-three patients (twenty-four elbows) had metastatic disease and fourteen had a primary tumor. Degenerative defects of the distal end of the humerus were caused by pseudarthrosis (six elbows), prosthetic failure (five), trauma (two), osteomyelitis (one), and supracondylar fracture (one). The mean duration of follow-up for all patients was twenty-eight months (median, thirteen months; range, one to 219 months). RESULTS The mean Inglis-Pellicci score in the tumor group was 84 points, and the mean Musculoskeletal Tumor Society score was 78%. Patients with total humeral reconstruction had worse scores than those with distal humeral reconstruction. Twenty-four patients died of disease at a mean of thirteen months after surgery. Local tumor control was achieved in all patients. In the revision group, the mean Inglis-Pellicci score was 76 points. The Inglis-Pellicci score was significantly better for patients in the tumor group. Eight patients (15%) had a deep periprosthetic infection, requiring amputation in one patient (2%) and prosthetic removal in two patients (4%). Four patients (8%) had the implants revised for aseptic loosening. CONCLUSIONS Modular prostheses of the distal end of the humerus provide a stable reconstruction of the elbow with satisfactory function and disease control in patients with a tumor, but careful patient selection is required when the prostheses are used for revision surgery in patients without a tumor.

Serum aluminium and cobalt levels after ceramic-on-ceramic and metal-on-metal total hip replacement

In a randomised study, 28 patients with a mean age of 62.2 years (32 to 81) with osteoarthritis or avascular necrosis of the hip received either a ceramic-on-ceramic or a metal-on-metal total hip replacement. Apart from the liners the acetabular and femoral components were made of Ti-Al-Nb alloy. The serum aluminium and cobalt levels were measured before, and at one year after surgery. The 15 patients in the ceramic-on-ceramic group had a median pre-operative aluminium level of 1.3 microg/l (0.25 to 8.4) and a cobalt level below the detection limit. At one year the aluminium level was 1.1 microg/l (0.25 to 2.3) and the cobalt level was 0.4 microg/l (0.15 to 0.7). The 13 patients in the metal-on-metal group had a median pre-operative aluminium level of 1.9 microg/l (0.25 to 4.4) and a cobalt level below the detection limit. At one year the median aluminium level was 0.9 microg/l (0.25 to 3.9) whereas the cobalt level was 1.4 microg/l (0.5 to 10.5). This increase in the cobalt level at one year was significant (p < 0.001). Our findings indicate that ceramic-on-ceramic bearings do not cause elevated levels of serum aluminium in the first post-operative year.

The impact of re‐excision of inadequately resected soft tissue sarcomas on surgical therapy, results, and prognosis: A single institution experience with 682 patients

Due to their rare incidence soft tissue sarcomas (STS) are often resected without clear margins. The aim of this study was to investigate the impact of re‐excision of STS on survival.

Treatment and outcome of parosteal osteosarcoma: biological versus endoprosthetic reconstruction.

Due to its good prognosis despite local recurrence, more and less invasive methods for surgical treatment of parosteal osteosarcoma (POS) have been described. Aim of this retrospective single‐center study was to investigate differences in outcome after biological and prosthetic reconstruction.