FRACTURES A DIFFERENT APPROACH: THE ROLE OF EARLY BONE SCANNING

Christopher O’Brien MDCM; FRCPC
Medical Director,
Nuclear Medicine
Brantford General Hospital
Ontario, Canada

FRACTURES A DIFFERENT APPROACH: THE ROLE OF EARLY BONE SCANNING

The three-phase bone scan is a very sensitive technique used in the detection of fractures of any cause. The sensitivity can be further increased through the use of SPECT and the specificity can be improved by adding the technique of SPECT/CT. The sensitivity ranges from 80% to 98% depending on when imaging is performed and whether SPECT is used, or 24 hour delayed imaging is obtained. Thus the sensitivity at 24 hours post event is 80%, 95% by 72 hours and 98% by one week.

The reason that the sensitivity is lower with early imaging is that the osteoblasts must become activated and it is osteoblastic activity that is assessed with the bone scan. The higher sensitivity is usually achieved by 48 hours after the event. Up to 72 hours post event may be required for the severely osteopenic patient.. A bone scan can be tailored to assess a specific site only (e.g. the hand or foot) or a more regional assessment (e.g. the pelvis and lower extremities). At times a whole bone assessment may be required, especially in cases of more severe trauma. By tailoring the study, one can assess both the area of discomfort and also have the ability to assess for referred pain from occult fractures elsewhere.

It is important to realize that there is no increase in radiation exposure as one takes more images, as the radiation exposure comes from the injection. The addition of SPECT does not add any more radiation either as this is a simple 3-dimensional reconstruction technique. SPECT/CT, however, does add a very small amount of extra exposure linked to the CT, but a low dose technique is used to keep this exposure to a minimum.

PATIENT MANAGEMENT ISSUES

When a patient presents complaining of bone pain, it is important to obtain a history to assess for possible post-traumatic causes, perhaps insufficiency causes, or perhaps neoplastic causes. After the history and if clinical indication exists, then the first imaging is usually plain film X-ray of the area of discomfort. If X-rays are obtained very shortly after the event, the sensitivity is low: 10 to 15% (especially with stress fractures and in those individuals with low bone density), and it may take up to two weeks or more before changes become more apparent with plain film X-ray. Thus there is the need for a follow-up X-ray if clinical symptoms persist.

However, even with this we see many patients presenting to Nuclear Medicine to obtain a bone scan to assess the possibility of fracture, even one month after the event because X-rays are still normal or inconclusive, and because of this the patient may not have received optimal clinical care.

To maximize patient care, one could consider a bone scan as the next imaging technique if initial X-rays are normal and clinical symptoms remain. Thus, one could consider performing a bone scan much earlier in the work-up of the patient due to its very high sensitivity which rivals MRI (sensitivity of 85 to 95%).

If referring physicians begin to request bone scanning earlier after initially negative X-rays in order to optimize patient management, then it will be necessary for the Nuclear Medicine department to establish a rapid response process to fast track patients with suspected fractures. If the waiting time is 2 to 3 weeks, this does not do the patient any good. In addition, the Canadian Medical Association Wait Time Alliance has suggested that urgent cases (which include fractures) should obtain a bone scan within one week of the request and preferably within around 48 hours of the request, in ideal situations.

I believe that by following this approach, the diagnosis of fractures will be made quicker, patients can then be referred for appropriate management sooner, and the patient will be able to return to routine activities of daily life and will also have better pain control.

In conclusion, the routine bone scan is a safe and highly sensitive technique (98% at one week) and with the addition of SPECT/CT, it now has high specificity as well. It should be considered as the next imaging technique if X-rays are normal and clinical symptoms persist one week after the initial X-rays. In addition, the Nuclear Medicine departments will have to set up a process to fast track these requests in order to optimize patient care.