We propose that a major advantage of the Powered system is that it allows clinicians to more quickly complete the bone marrow sampling procedure. In our study, the mean time from needle to skin contact to removal of the needle using the Powered system was approximately half the time required using the Manual device 102.1 ± 86.4 seconds vs. 203.1 ± 149.5 seconds, respectively). Patients undergoing bone marrow biopsy procedures most likely expect some level of pain. Most patients are willing to undergo the procedure and a reasonable level of pain, providing the procedure time is relatively short. Assuming the validity of Kuball et al's finding that procedure time has the greatest impact on pain, use of the Powered system could have a positive effect on many patients' perception of the bone marrow procedure in general.
Another important finding from our study is that whereas patients generally expect pain during any invasive procedure, they may not expect or tolerate persistent residual pain afterwards. In our study, 67% of the patients who received the bone marrow biopsy procedure using the Powered device were pain-free within 24 hours compared to only 33% of patients who received the procedure with the Manual device, a statistically and clinically significant finding. In the Liden et al study using the Manual procedure, only 36% of patients were without pain after 24 hours, very similar to the results in the Manual group in our study .
As expected, there were few complications in our study with either the Powered or Manual bone marrow biopsy procedures. The two observed complications occurred with a single operator's use of the Powered device. In one case, a small portion of the patient's skin wrapped around the rotating needle. This could have been avoided by holding the skin tautly at the needle insertion site. In the other case, the operator's latex glove became wrapped around the rotating needle, which could have been avoided by not placing the gloved finger too close to the rotating needle. It is recognized that these types of complications are potentially serious and not likely to occur with manual devices. But it is felt that complications of this type can be avoided by emphasizing this potential problem and methods to avoid the problem during operator training. Moreover, considering that both these problems were experienced by only one of 13 operators participating in the study, their prevalence is not felt to be wide-spread.
Clinicians attempt to conduct bone marrow sampling procedures quickly and safely with as little pain and discomfort to the patient as possible; however, the ultimate goal of the procedure is to acquire a bone marrow specimen that is adequate for diagnosis by pathologists. Adequate specimens need to be of adequate size and free of crush trabecular distortion and other artifact. Inadequate specimens can diminish the clinician's ability to make an accurate diagnosis and/or assessment of the patient's clinical status. Bishop et al found only 42% of bone marrow biopsy specimens were adequate for accurate diagnosis in a study involving 767 patients . In the current study, there were no differences between the two procedure types in specimen quality or length; however, use of the Powered device resulted in bone marrow core specimens that had 80% more volume than specimens obtained with the Manual device. Although length is generally the criteria used for determining the ideal size of a bone marrow core specimen, specimen volume may be a more relevant indicator of the amount of tissue available for analysis. Larger tissue volume of the specimen may increase the ability of the pathologist to conduct a thorough analysis and identify focal lesions.
The cost of using the Powered device must be considered in decisions regarding its use in the clinic. While the powered driver can be used up to 500 times, the needle and other components are for single use and part of a tray that generally costs $60 to $70 more than the Manual device. Although needle-for-needle, the cost of the Powered system is higher, the total cost for the disposable needle tray is covered by insurance reimbursement under most plans. While the seemingly high cost of the Powered device might negatively influence a decision to adopt its use, the concerns of most clinicians and patients are not simply the costs of the material and equipment required to do the procedure but the costs of these items together with their quality and patient outcome. Our study and other recent studies [17, 18], suggest that the Powered system enables clinicians to consistently obtain biopsy specimens of superior size and quality than those obtained using the Manual needles. In many cases, the lower cost of the Manual device may be offset by the necessity to repeat the procedure--requiring more materials and clinician time. Regardless of costs, we feel using the Powered system adds value to the process in terms of speed, efficiency, and patient comfort.
There were several limitations in this study. As with any new device, there is a learning curve that must be negotiated before operators can gain proficiency. While our study protocol stipulated that the operator complete 3 to 5 Powered device uses in non-study subjects before performing the procedure on study patients, in hindsight perhaps those numbers should have been higher. Another limitation was initially capturing patient pain scores as an "overall" event that included the aspiration portion of the bone marrow sampling procedure. Generally, bone marrow aspiration is painful regardless of the needle-type used to withdraw the liquid bone marrow specimen. This extreme pain during the aspiration phase may obscure any differentiation in pain levels between the two device types during the less painful phases of the procedure. This phenomenon was realized after the interim analysis. By the time the study protocol could be revised to include recording needle insertion pain, patient accrual was 72% complete. Thus, we were unfortunately able to collect very little data specifically on needle insertion pain. A final limitation was that relatively few core specimens were available for pathology analysis. Our initial plan was to conduct quality analysis for each specimen at a central laboratory, but some investigators were reluctant to send specimens to the central laboratory following analysis at their local laboratory. The compromise was that two specimens from each center were analyzed, one for each device type.