Image intensifier in orthopaedic surgery

A. G. SUTHERLAND AND D. F. FINLAYSON
Department of Orthopaedics, Raigmore Hospital, Inverness, UK

Image intensifier technology has been of great benefit to orthopaedic, but not a benign aid. We have examined the image intensifier screening times for trainees and consultants over a seven month period. Consultants did not always have shorter screening times, and there were no differences between radiographers. Surgeons of all grades should depend more upon anatomical knowledge and spatial orientation, and less upon the image intensifier.

The introduction and improvement of image intensifier technology has had a profound effect on orthopaedic trauma surgery. It allows the accurate positioning of orthopaedic implants to bone, with the intraoperative images showing progress much more easily than plain radiographs. Image intensifier machines which are able to store and show the images taken have the effect of greatly reducing the radiation dose to which the patient, surgeon and theatre staff are exposed. Technological improvements in image quality have been such that, under certain circumstances, post-operative check radiographs are unnecessary.¹ Although the doses involved are generally low, image intensification is not a benign aid, and radiation exposure may become significant over a surgeon's career.

Little work has been carried out on the radiation exposure to surgeons during the use of image intensifiers.² We have examined the perception held in our unit that image intensifier screening times during consultant-led procedures are lower than those for trainee-led procedures. This may have implications for the radiation exposure of patients, surgeons and theatre staff generally.

Data on the screening times for orthopaedic procedures were collected prospectively over a 7-month period at Raigmore Hospital, Inverness. The screening times for trainees and consultants for orthopaedic procedures were analysed and the radiographer’s identity was also recorded. If a trainee carried our the procedure supervised by a consultant, it was ascribed to the trainee. The screening time was measured in decimal fractions of minutes. The equipment was unable to record very short times, and these were given the shortest measurable time of 0.1 minute.

Over the 7-month period, 407 operations utilizing the image intensifier were analysed. Table 1 summarises the screening times for the most commonly carried our operations for consultants and trainees. Although the consultants had shorter times for the insertion of cannulated hip screws, the trainees had shorter times for the other four procedures. Although the numbers of patients are often small, a more detailed analysis by operator showed differing mean screening times for different consultants and trainees, and have led to a re-evaluation of practice.

For other procedures there were insufficient numbers of patients operated on by both trainees and consultants for meaningful interpretation. There was no apparent difference between the radiographers involved.

	Mean screening time (minutes)
Procedure	Consultant (n)	Trainee (n)
Dynamic hip screw	0.47(42)	0.33 (41)
Cannulated hip screws	0.36(5)	0.51(10)
K-wire fracture fixation	0.23(13)	0.18(16)
Fracture manipulation	0.13(55)	0.11 (85)
Intramedullary nailing	1.15 (53)	0.89(7)

Orthopaedic surgeons spend a significant amount of time working in close proximity to X-rays. Protection in the form of lead aprons is useful for reducing trunk exposure, but such protection is impractical for protection of the hands.^2,3Image intensifier radiation is rapidly scattered and exposure can be limited by keeping as far from the beam as physically possible.⁴Reduction of the time that the machine is operating should also reduce the potential exposure to harmful radiation. Screening times give a useful idea of the amount of time that the image intensifier machine is operating, but not of the radiation doses to the surgeon. Dose area product was available for some of the operations, but this reflects the radiation dose to the patient, nor to the surgeon or other staff. Actually, assessing the radiation dose to surgeons is feasible, but labour intensive, and tends to be carried out within hospitals on a small scale as part of ongoing safety assessments.⁵Screening time is the easiest measure of use of the image intensifier.

We have shown some differences between consultants and trainees in the use of image intensification. Although we had expected to see shorter times for more experienced surgeons, this was nor generally the case. The differences between the consultant’s individual times gave a broad spread. The longer screening times incurred by consultants may, in part, be explained by the fact that they often take on more technically demanding patients. We have found that the trainees generally performed favourably. There was no apparent difference between the various radiographers involved during the study period, suggesting that the screening time is controlled predominantly by the surgeon.

The audit is currently being extended to individual surgeons, as an aid to training. Although we would nor advocate the minimization of screening times at all costs, with a decrease in the benefit the image intensification brings to the accuracy of a procedure, the importance of radiation dosage is often neglected in orthopaedic training. Without suitable care, exposure over a career may be significant. This is reflected in the recent European Union Directives on reduction of radiation to both patients and staff.⁶Orthopaedic surgeons of all grades should be urged to depend more on anatomical knowledge and their own spatial orientation, and less on the image intensifier, which is a far from benign aid.

We thank the orthopaedic consultants and trainees and radiographers of Raigmore Hospital for permission to examine their practice, and to the Department of Medical Physics for their help in data collection.

Correspondence to: MrA.G. Sutherland, University of Aberdeen, Department of Orthopaedics, Polwarth Building, Foresterhill, Aberdeen, UK.