The OSCAR 3 ultrasonic arthroplasty revision instrument for removing bone cement during prosthetic joint revision

Clinical and technical evidence

Five studies concerning the use of the OSCAR system for bone cement removal were identified. Two of these were laboratory studies and did not involve use of the device on living people. Three of the studies were related to clinical use of the technology: 1 retrospective case series (Fletcher et al. 2000), 1 case report (Smith and Eyres 1999) and 1 case report with an additional cadaveric study (Goldberg et al. 2005). One laboratory study used theatre air samples to investigate the environmental safety of the technology (Shewale and Briggs 2005). One laboratory study performed on ex vivo femur bone sections used the OSCAR system as a qualitative comparator to yttrium-aluminium-garnet laser irradiation (Birnbaum and Gutknecht 2010). Publication dates suggest that all of these studies used earlier versions of the OSCAR rather than the OSCAR 3, but as the core functionality of the device has not changed from previous versions, these studies were still considered to be relevant to this briefing.

The retrospective case series by Fletcher et al. (2000) investigated the potential for the first generation OSCAR system to preserve bone compared with mechanical cement removal (by allowing for an altered surgical approach), which would result in shorter replacement prostheses. The theatre records of 16 hip revision operations were analysed. The preoperative radiographs were used to undertake 'sham planning', whereby the proposed osteotomy length and consequent prosthesis replacement using conventional cement removal were estimated. These estimations were compared with the actual osteotomy shortenings and prostheses used following cement removal with the OSCAR or by mechanical means. Significantly shorter osteotomies and prostheses were needed for patients who had cement removed with the OSCAR compared with the sham predictions. A summary of the study and results is reported in table 1.

The case report by Smith and Eyres (1999) described the removal of a large quantity of cement from the pelvic cavity of a woman aged 83 years having hip revision. The intrapelvic cement mass was progressively removed using the OSCAR and the patient was reported to have responded well postoperatively, but no other clinical data were stated. A summary is reported in table 2.

The case report by Goldberg et al. (2005) described the use of the OSCAR on a woman aged 69 years having revision arthroplasty of the elbow. Although the bone cement was successfully removed, postoperatively it became apparent that the device had caused thermal necrosis of the bone. Following this case, the authors investigated the potential for the OSCAR to induce heat damage in bone using 6 human cadavers. The authors reported that the device had the potential to cause damage to the bone and the radial nerve. However, this effect could be mitigated through the use of intermittent ultrasound and frequent irrigation of the area with chilled saline solution, as well as avoiding the application of a tourniquet. A summary of the study is reported in table 3.

The laboratory study by Shewale and Briggs (2005) used gas chromatography-mass spectroscopy to analyse the fumes released by 4 types of bone cement when treated with the OSCAR. The potentially toxic gases styrene and methylmethacrylate were detected. However, the concentrations of these chemicals remained within safe limits set by occupational exposure standards.

The primary focus of the laboratory study by Birnbaum and Gutknecht (2010) was to investigate the effectiveness of yttrium-aluminium-garnet laser irradiation for removing cement from sagittal sections of an ex vivo human femur bone. The OSCAR system and manual cement extraction through curettage were included as comparators in this study. The researchers found the OSCAR caused less bone loss than curettage. The researchers also attributed the presence of microscopic cracks in the bone to the use of ultrasound. The results of the laboratory studies by Shewale and Briggs (2005) and Birnbaum and Gutneckht (2010) have not been included in tables 1–3.

Table 1 Summary of the retrospective case series by Fletcher et al. (2000)

Table 2 Summary of the Smith and Eyres (1999) case report

Table 3 Summary of the Goldberg et al. (2005) case report and follow-up study

Costs and resource consequences

No published evidence on resource consequences for the OSCAR 3 was identified.

The manufacturer stated that as of July 2014, approximately 130 centres and 200 surgeons are using the OSCAR system in the UK. The model versions in use are unknown. It is unclear how many OSCAR systems are in use under rental agreements. As of April 2014, there were 160 NHS acute trusts in England. This would suggest that the OSCAR system is already well established as a surgical option for orthopaedic surgeons within the NHS.

The OSCAR system is usually used alongside existing mechanical techniques for extracting cement from bone; therefore, implementation of the system would not replace existing mechanical methods. No other technologies would be needed to support the use of the OSCAR and service reorganisation would not be needed.

Strengths and limitations of the evidence

Published evidence to support the clinical effectiveness of the OSCAR cement removal system is lacking in both quantity and quality.

The retrospective case series by Fletcher et al. (2000) was the only available study that reported quantitative outcomes on the clinical effectiveness of using the OSCAR. The authors did not report their rationale or methodology for the selection of patients who were treated using the OSCAR (n=13) and those who were not (n=3), and patient characteristics were not fully described. This raised the potential for both selection and attrition bias. As there was no robust control group, the conclusion that treatment with the OSCAR led to improved bone preservation (and use of shorter prostheses) must be treated with caution. The rationale for the inclusion of outcomes reported was not described, and the study did not report on other potential clinical benefits of the OSCAR such as shorter surgery times, overall improved surgical outcomes, or patient-related outcome measures. Additionally, the study was relatively small, particularly with respect to the control group. However, it was explicitly stated that the OSCAR was not associated with specific adverse effects in these patients.

The case report by Smith and Eyres (1999) did not report any quantitative clinical outcomes, but did provide insight into the safe and effective application of the OSCAR in 1 problematic hip arthroplasty and reconstruction.

The case report by Goldberg et al. (2005) described a significant adverse effect associated with the use of the OSCAR but no quantitative data were reported. A follow-up technical study used human cadavers, and so did not provide evidence of clinical outcomes in living people.

The study by Shewale and Briggs (2005) did not report clinical or patient-relevant outcomes.

The OSCAR was not the primary focus of investigation in the study by Birnbaum and Gutknecht (2010), and quantitative clinical or patient-relevant outcomes were not reported.