To study intra- and inter-observer variability with the use of the ultra-sound transducer and percutaneous digitiser point probes To assess the learning curve with the use of the ultrasound transducer probe As part of a larger cadaver study evaluating navigated total hip replacement via the posterior approach, we assessed data relating to acquisition of bony landmarks of the Anterior Pelvic Plane (APP) by four surgeons with an ultrasound transducer and a percutaneous point probe. The surgeons had differing levels of experience with hip surgery in general, and also with surgical navigation per se, but none of them had previously used the ultrasound probe for the specific purpose of landmark acquisition. Without fixing an absolute positional value for any of the bony landmarks, the points registered for individual landmarks by each surgeon were then studied, looking at the three-dimensional spread of these points relative to each other about the mean value. The data from all four surgeons were analysed, looking at the global dispersion of points acquired by the ultrasound and percutaneous point digitiser probes. Our results show that with the exception of a few isolated outliers, the ultrasound probe generated values fell within a +/− 10 mm range. For all four surgeons, the global spread of ultrasound-registered points was noted to be less than that acquired by percutaneous point probe acquisition. Of interest was the finding that points registered by individual surgeons using the ultrasound probe tended to be grouped distinctly together but spatially separate from those of the other surgeons; it would appear that each operator was “homing” in on what he perceived to be the bony landmark in question on the projected ultrasound image. With the percutaneous pointer probe, and with the anterior superior iliac spines as the target, there was closer grouping of points around the mean positional value for the two surgeons who were experienced with its use. However, at the symphysis pubis, the spread of points for these surgeons were not much different from the other two less experienced one, with these points showing a global spread as great as 25 mm. Regardless of the experience of the surgeon, the use of the ultrasound transducer probe appears to be more accurate than percutaneous pointer probe for acquisition of the bony landmarks that constitute the anterior pelvic plane. The learning curve associated with its use is seemingly short and steep. Its accuracy is limited by the fact that the identification of the bony land marks on the on-screen display is open to interpretation by the individual. Methods to standardise the identification of these landmarks on ultrasound images may help improve its accuracy in the future.
Patients undergoing primary knee arthroplasty at our unit routinely have two units of red cell concentrate cross-matched preoperatively. We assessed whether postoperative blood salvage and auto-transfusion reduced the need for allogenic blood transfusion as compared with standard suction drainage. Haemoglobin and haematocrit preoperatively and postoperatively were recorded. The amount of drainage and re-transfusion was noted as well as the amount of blood saved, used and wasted. 182 patients were audited. Patients were placed in one of two groups: Group A receiving auto-transfusion of blood salvaged postoperatively (128 patients); and Group B where suction wound drainage without salvage was utilized (54 patients). Pre- and postoperative haemoglobin and haematocrit estimations were similar in both groups. Total drainage averaged 1061mI (range 175–2230 ml) for group A and 760mI (range 100–2280 ml) for group B. Auto-transfusion volumes averaged 814ml (range 0–1700m1) in group A. Allogenic blood transfusion was required in 23% of patients in group A in contrast to 50% in group B. This resulted in an average wastage of 1.6 units in group A as opposed to 1.1 units in group B. Postoperative auto-transfusion of salvaged blood in patients undergoing primary total knee arthroplasty reduces the need for allogenic blood transfusion requirements. It would also serve to reduce the wastage in units of whole blood allowing such patients to be routinely “grouped and retained” rather than “crossmatched”.
