The water jet as a new tool for endoprosthesis revision surgery--an in vitro study on human bone and bone cement

In revision surgeries of endoprostheses, the interface between implant and bone cement or bone must be loosened. Conventional tools have many disadvantages because of their size and limited range. Taking advantage of the selective and athermic cutting process, a plain water jet is already used in order to cut soft tissues. This study investigates the possibilities of both a plain and an abrasive water jet as cutting tools for revision surgery. Samples of the mid-diaphysis of human femora and bone cement (CMW3) were cut with a plain water jet (PWJ) and an abrasive water jet (AWJ) at two different jet-to-surface angles (30 degrees,90 degrees ) and at five different pressure levels (30, 40, 50, 60, 70 MPa). For a PWJ a selective pressure range was identified, where only bone cement was cut. Injecting a bio-compatible abrasive (lactose) to the jet stream resulted in significantly higher cut depths in both materials. Material removal in bone was significantly less at the smaller jet-to-surface angle for both techniques. No clear selectivity between bone and bone cement was observed for application of the AWJ. However, the material removal rate was significantly higher for bone cement than for bone at all pressure levels. The results indicate that an AWJ might be an alternative tool for cement removal. The possibility for localised cutting at interfaces could be an advantage for revision of a non-cemented prosthesis.     

The presence of positive surgical margins in patients with organ-confined prostate cancer results in biochemical recurrence at a similar rate to that in patients with extracapsular extension and PSA≤10 ng/ml

PurposesWe investigated whether patients with organ-confined prostate cancer (PCa) and positive surgical margins (SMs) had a similar biochemical recurrence (BCR) risk compared with patients with pT3a and preoperative prostate-specific antigen (PSA) levels≤10 ng/ml. Furthermore, we examined the effects of incorporating SM status, Gleason score (Gls), and preoperative PSA level into the discrimination accuracy of the current tumor node metastasis-staging system.Materials and methodsWe analyzed 863 PCa patients treated with radical prostatectomy from 1999 to 2008. Only individuals with pT2N0 or pT3N0, without neoadjuvant or adjuvant therapy, were included. We performed chi-square automatic interaction detection analysis to generate a classification model for predicting BCR by analyzing interactions between age at surgery, SM status, Gls, PSA, and tumor stage, tumor volume and relative tumor volume. Cox regression analyses tested the relationship between SM status and BCR rate after stratification according to T-stage and the novel classification. The predictive and discrimination accuracy of the current T-stage and of the classification model was quantified with time-dependent receiver operating characteristics and integrated discrimination improvement. The topographical association between extracapsular extension of PCa and positive SM was analyzed in patients with pT3aR1 using a computational reconstruction diagram of the prostate.ResultsThe chi-square automatic interaction detection analysis found interactions among pT Stage, SM status, PSA and Gls and generated a classification model for BCR prediction: pT2R0, pT2R1, pT3a PSA≤10 ng/ml, pT3a PSA>10 ng/ml and pT3b. Men with pT2R1 had a shorter time to BCR compared with men with pT3a-PSA≤10 ng/ml (P<0.0001). Gls≥7a was correlated with a poorer BCR rate than Gls≤7a in men with pT2R1 or pT3a PSA≤10 ng/ml (P = 0.012). The rank order (highest to lowest) for the risk of developing BCR was pT3b>pT2R1/pT3a-PSA>10 ng/ml>pT2R1/pT3a PSA≤10 ng/ml>pT2R0 (P<0.0001). Discrimination accuracy gains were observed when PCa was stratified according to the novel classification (P<0.0001). A topographical association between extracapsular extension and positive SM was found in patients with pT3aR1 (P = 0.01).ConclusionPatients with pT2R1 develop a similar BCR risk to that of patients with pT3a PSA≤10 ng/ml. Gls≥7b is associated with a high BCR risk in these patient groups. Including SM status, PSA, and Gls in pT stage appears to improve prognostic stratification in patients with PCa.     

Clinical map document based on XML (cMDX): document architecture with mapping feature for reporting and analysing prostate cancer in radical prostatectomy specimens

Background  

The pathology report of radical prostatectomy specimens plays an important role in clinical decisions and the prognostic evaluation in Prostate Cancer (PCa). The anatomical schema is a helpful tool to document PCa extension for clinical and research purposes. To achieve electronic documentation and analysis, an appropriate documentation model for anatomical schemas is needed. For this purpose we developed cMDX.     

Abrasive water jet cutting as a new procedure for cutting cancellous bone--in vitro testing in comparison with the oscillating saw

The quality of bone cuts is assessed by the accuracy and biological potency of the cut surfaces. Conventional tools (such as saws and milling machines) can cause thermal damage to bone tissue. Water jet cutting is nonthermal; that is, it does not generate heat. This study investigates whether the abrasive jet cutting quality in cancellous bone with a biocompatible abrasive is sufficient for the implantation of endoprostheses or for osteotomies. Sixty porcine femoral condyles were cut with an abrasive water jet and with an oscillating saw. alpha-lactose-monohydrate was used as a biocompatible abrasive. Water pressure (pW = 35 and 70 MPa) and abrasive feed rate (m = 0.5, 1, and 2 g/s) were varied. As a measure of the quality of the cut surface the cutting gap angle (delta) and the surface roughness (Ra) were determined. The surface roughness was lowest for an abrasive feed rate of m = 2 g/s (jet direction: 39 +/- 16 microm, advance direction: 54 +/- 22 microm). However, this was still significantly higher than the surface roughness for the saw group (jet direction: 28 +/- 12 microm, advance direction: 36 +/- 19 microm) (p < 0.001 for both directions). At both pressure levels the greatest cutting gap angle was observed for a mass flow rate of m = 1 g/s (pW = 35 MPa: delta = 2.40 +/- 4.67 degrees ; pW = 70 MPa: delta = 4.13 +/- 4.65 degrees), which was greater than for m = 0.5 g/s (pW = 35 MPa: delta = 1.63 +/- 3.89 degrees ; pW = 70 MPa: delta = 0.36 +/- 1.70 degrees) and m = 2 g/s (pW =70 MPa: delta = 0.06 +/- 2.40 degrees). Abrasive water jets are suitable for cutting cancellous bone. The large variation of the cutting gap angle is, however, unfavorable, as the jet direction cannot be adjusted by a predefined value. If it is possible to improve the cutting quality by a further parameter optimization, the abrasive water jet may be the cutting technique of the future for robotic usage.     

Tumor percentage but not number of tumor foci predicts disease-free survival after radical prostatectomy especially in high-risk patients

ObjectiveTo evaluate the predictive value of tumor volume (TV), tumor percentage (TP), and number of tumor foci (NF) in patients with prostate cancer.The prognostic relevance of TV, TP, and NF as predictors of biochemical recurrence (BCR) following radical prostatectomy (RPE) is controversial.Patients and methodsThe cohort consisted of 758 referred subjects who underwent RPE between 2000 and 2005 at the University of Muenster. The mean time of follow-up was 62 months. TV, TP, and NF were estimated visually with the assistance of a pathologic mapping grid for embedded whole-mount RPE specimens. In addition, TV and TP were assessed in a categorized fashion by using quartiles as cutoff points. Subgroup analyses for high- and low-risk patients using univariate and multivariate Cox proportional hazard analyses for BCR were performed.ResultsTV, TP, and NF were strongly related to tumor stage, Gleason score, surgical margin status, and preoperative prostate-specific antigen (PSA). In univariate analysis, all pathologic parameters including TV, TP, and NF were predictive for BCR. In multivariate analysis, only TP, tumor stage, and PSA level were independent predictors. In subgroup analysis, TP was an independent predictor for BCR in the high-risk group but not in the low-risk group.ConclusionsTP, but not TV or NF, was found to be an independent predictor for BCR in patients after RPE. TP seems to be more relevant in high-risk patients (i.e., any of the following:>pT2, Gleason score>6, or PSA>20 ng/ml).