Histopathological Analysis of PEEK Wear Particle Effects on the Synovial Tissue of Patients.

Introduction. Increasing interest developed in the use of carbon-fiber-reinforced-poly-ether-ether-ketones (CFR-PEEK) as an alternative bearing material in knee arthroplasty. The effects of CFR-PEEK wear in in vitro and animal studies are controversially discussed, as there are no data available concerning human tissue. The aim of this study was to analyze human tissue containing CFR-PEEK as well as UHMWPE wear debris. The authors hypothesized no difference between the used biomaterials. Methods and Materials. In 10 patients during knee revision surgery of a rotating-hinge-knee-implant-design, synovial tissue samples were achieved (tibial inserts: UHMWPE; bushings and flanges: CFR-PEEK). One additional patient received revision surgery without any PEEK components as a control. The tissue was paraffin-embedded, sliced into 2 µm thick sections, and stained with hematoxylin and eosin in a standard process. A modified panoptical staining was also done. Results. A "wear-type" reaction was seen in the testing and the control group. In all samples, the UHMWPE particles were scattered in the tissue or incorporated in giant cells. CFR-PEEK particles were seen as conglomerates and only could be found next to vessels. CFR-PEEK particles showed no giant-cell reactions. In conclusion, the hypothesis has to be rejected. UHMWPE and PEEK showed a different scatter-behavior in human synovial tissue.

Development and validation of a new method for the radiologic measurement of the tibial slope.

PURPOSE: The posterior tibial slope has a huge influence on the kinematics of the knee. In several orthopedic interventions such as high tibial osteotomy and unicondylar or bicondylar knee replacement changing, the tibial slope can result in altered knee mechanics. Therefore, an exact preoperative measurement of the posterior tibial slope is mandatory. Several methods are used on conventional radiographs and CT scans, but until now there is no standard validated method. The aim of this study was to compare several methods and imaging techniques to measure the posterior tibial slope and to establish a standard and reliable measurement method by radiography. METHODS: Fourteen knees (seven cadavers) were scanned by a 64-slice CT, a 3T-MRI, and true lateral radiographs were performed. The anatomical references (TPAA = tibial proximal anatomical axis; ATC = anterior tibial cortex; PTC = posterior tibial cortex) and the new computed reference (MPA = mean of PTA and ATC) were compared by short as well as long radiographs, CT scan and MRI. The influence of a malrotation in radiographs of the knees was also analyzed. RESULTS: CT scan and MRI are suitable for the measurement of the medial and lateral posterior tibial slopes, the results of the radiographs varied depending on the method used. The new method (MPA) showed the best correlation to the CT scan (r = 0.997), even on short radiographs (10 cm distal the joint line). CONCLUSION: The measurement of the posterior tibial slope on a short lateral radiograph using the MPA is a reliable method and should be established as a standard. LEVEL OF EVIDENCE: Diagnostic study, Level II.

Crosslinked polyethylene in knee arthroplasty: a simulator study evaluating the positive influence on the tribocontact area in the fixed-bearing knee.

BACKGROUND: Crosslinked polyethylene (XPE) was developed to reduce the wear rate in hip as well as knee arthroplasty. The crosslinking process reduces the mechanical properties of ultra-high-molecular-weight polyethylene (UHMWPE), particularly its fatigue strength. UHMWPE fatigue occurs more frequently in the knee than in the hip joint due to its changing tribocontact areas (TCAs) combined with high weight bearing. This is why XPE is still controversially discussed for use in total knee arthroplasty. Therefore, the potential advantage of using XPE in the knee was analysed in a simulator study with a focus on potential fatigue wear mechanisms. METHODS: Three different kinds of XPE and one conventional UHMWPE were tested over 5 million cycles in fixed-bearing knee designs. The TCAs were examined by replicas, and their extent was measured. The wear mechanism was analysed by scanning electron microscopy. RESULTS: The extent of the TCAs was less than 5% for all XPEs, whereas 35% for the conventional UHMWPE. Fatigue wear mechanisms were not observed. CONCLUSION: The measured small extent of the TCAs as a predictor of a low wear rate without any fatigue wear mechanism shows a possible advantage for the use of XPE even in knee arthroplasty.

The influence of adjuvants on local recurrence rate in giant cell tumour of the bone.

INTRODUCTION: Intralesional surgery of giant cell tumour of the bone (GCT) may result in a high rate of local recurrence. The introduction of local adjuvants, such as cementation, cryosurgery or phenolization, has proved to be successful in the reduction of recurrence rates. This study presents the results of a single institution in surgery of GCT with an evolution in treatment strategies. MATERIAL & METHODS: Forty primary and 25 recurrent surgical procedures in 46 patients with GCT of the bone with a median follow-up of 72 months were reviewed retrospectively. The mean age was 32.6 years (range 13.6-57.9 years). Forty-seven curettages and 18 resections were performed. For the curettages, a large bone window was cut followed by high speed burring and bone grafting or cementation. In 34 of 47 curettages and 7 of 18 resections, phenol was additionally applied. RESULTS: Two patients showed pulmonary metastasis, one died due to metastatic disease. In total, a third of the patients developed local recurrence (32.3%). This was evenly spread among primary and recurrent diesease (32.5% vs. 32%). Seven of 13 curettages without adjuvant recurred (53.9%), compared to 11 of 34 curettages with adjuvant phenol (32.4%). Three of 18 resections developed a recurrence (16.7%). No complications in respect to the use of phenol were seen. DISCUSSION: Phenolization is a safe local adjuvant therapy for GCT. Although the recurrence rate was lower with the use of phenol, this drop was not significant. The comparable high recurrence rate in our study, even if phenol was used, might be due to the fact that curettage was our favoured treatment, even in cases with an extensive juxta-articular tumour. We recommend adjuvant phenolization in the treatment of GCT of the bone after thorough curettage in applicable cases, including where cementation is used for defect filling.

[Prognosis-adapted surgical management of bone metastases]. / Prognoseadaptierte operative Behandlung von Knochenmetastasen.

Surgery in metastatic disease to the bone is the most common procedure in orthopaedic oncology. To assess an adequate therapeutic approach we analysed 513 surgeries performed on 453 patients between 1980 and 2005 and reviewed the literature.The most significant factor is the histology of the primary tumour. A biopsy is mandatory to confirm the diagnosis in an unknown primary tumour, especially in cases of solitary lesions. Pulmonary carcinoma has an unfavourable prognosis compared to breast and renal cell carcinoma patients. Radical resection in isolated metastatic disease in renal cell carcinoma reduces the risk of local recurrence and even may result in a long progression-free survival. In breast cancer osseous and visceral dissemination is the most decisive factor for prognosis. An interdisciplinary approach is mandatory in every patient.

Whole-body MRI at 1.5 T and 3 T compared with FDG-PET-CT for the detection of tumour recurrence in patients with colorectal cancer.

The purpose of this study was to assess the diagnostic accuracy of whole-body MRI (WB-MRI) at 1.5 T or 3 T compared with FDG-PET-CT in the follow-up of patients suffering from colorectal cancer. In a retrospective study, 24 patients with a history of colorectal cancer and suspected tumour recurrence underwent FDG-PET-CT and WB-MRI with the use of parallel imaging (PAT) for follow-up. High resolution coronal T1w-TSE and STIR sequences at four body levels, HASTE imaging of the lungs, contrast-enhanced T1w- and T2w-TSE sequences of the liver, brain, abdomen and pelvis were performed, using WB-MRI at either 1.5 T (n = 14) or 3 T (n = 10). Presence of local recurrent tumour, lymph node involvement and distant metastatic disease was confirmed using radiological follow-up within at least 5 months as a standard of reference. Seventy seven malignant foci in 17 of 24 patients (71%) were detected with both WB-MRI and PET-CT. Both investigations concordantly revealed two local recurrent tumours. PET-CT detected significantly more lymph node metastases (sensitivity 93%, n = 27/29) than WB-MRI (sensitivity 63%, n = 18/29). PET-CT and WB-MRI achieved a similar sensitivity for the detection of organ metastases with 80% and 78%, respectively (37/46 and 36/46). WB-MRI detected brain metastases in one patient. One false-positive local tumour recurrence was indicated by PET-CT. Overall diagnostic accuracy for PET-CT was 91% (sensitivity 86%, specificity 96%) and 83% for WB-MRI (sensitivity 72%, specificity 93%), respectively. Examination time for WB-MRI at 1.5 T and 3 T was 52 min and 43 min, respectively; examination time for PET-CT was 103 min. Initial results suggest that differences in accuracy for local and distant metastases detection using FDG-PET-CT and WB-MRI for integrated screening of tumour recurrence in colorectal cancer depend on the location of the malignant focus. Our results show that nodal disease is better detected using PET-CT, whereas organ disease is depicted equally well by both investigations.