An active strategy to implement the Canadian C-Spine Rule led to a significant reduction in emergency department use of diagnostic imaging for alert, stable patients with blunt trauma of the head or neck. This effect was larger in community hospitals. No patients were found to have a missed fracture or adverse outcome after discharge. Despite low baseline imaging rates, a lower rate of imaging was achieved safely, with reductions at all the intervention sites. The resultant imaging rate of 53.3% was lower than the predicted minimal rate of 55.9%. Similar low rates of imaging should be achievable at many hospitals in the developed world. We believe that cervical spine imaging rates are over 90% in US emergency departments.
This study was designed and carried out according to strict methodological standards27 28
and represents the final stage of developing and testing a clinical decision rule,6 8 11
mirroring our previous studies to derive, validate, and implement the Ottawa Ankle Rules and the Ottawa Knee Rule.29 30 31 32 33 34 35
A small Australian study showed a reduction in imaging when the Canadian C-Spine Rule was applied to 113 patients.37
Few clinical decision rules have this level of evaluation and we are unaware of other rules for imaging the cervical spine that have undergone explicit testing of implementation. Our 12 study nurses included a strictly defined population based cohort at each site, as defined by the operations manual. The matched pair design, in which the unit of allocation was the hospital rather than the patient, offered several advantages. By matching on baseline imaging rates we prevented an imbalance between the control and intervention groups. This design also helped to preserve the power of analysis where relatively few clusters were studied.
Previous Canadian studies showed large reductions in ankle and knee imaging after implementation of our ankle and knee rules.32 33 36
Although the reductions noted in this trial were not as large, our previous implementation trials used expensive strategies, many of which were not practical for routine use. The implementation strategies used in this study were simple, inexpensive, and could easily be adopted on a permanent basis. It is well documented that implementation of guidelines can be difficult. A systematic review of 235 studies with rigorous evaluations of guideline dissemination and implementation strategies found that most interventions observed modest improvements in care with median absolute improvements in performance ranging from 6.0% to 13.1%.38
Some study limitations warrant comment. The baseline cervical spine imaging rates at the intervention and control sites (61.7% and 52.8%) were much lower than the 76% seen in the validation study and not as balanced as planned. The relative decrease in imaging rates, although shown at all intervention sites in our trial, was modest and less than the 15% difference that we had targeted. We speculate that because seven of the sites had participated in the previous validation study (three intervention and four control hospitals), the behaviour of the doctors may have already changed to follow the rule. Nevertheless, the final imaging rate at the intervention sites (53.3%) was low, less than the 55.9% potential rate predicted, and was actually a 30% relative reduction compared with the expected baseline rate of 76%. At the same time imaging rates went up at all six control sites, possibly reflecting a secular trend in usage of diagnostic imaging in increasingly crowded emergency departments. Doctors at these sites were not aware that they were in this study and were given no instructions on cervical spine imaging. The impact was greater at community hospitals, possibly because five of these sites had not participated in the validation study or perhaps because the severity of injury is generally less at such sites. Our 12 month follow-up data confirm the ongoing divergent trends in imaging use, with rates continuing to decrease at the intervention sites and continuing to increase at the control sites. This supports our belief that there is a general trend towards increased use of imaging.
While the impact may seem modest, we showed a greater than 25% difference in imaging effect between the intervention and control sites. The overall imaging rate achieved in the after period at the intervention sites was very low and would be a worthy accomplishment for any hospital. The subgroup of three community hospitals in the intervention group had not previously participated in the developmental studies and had the most impressive results, with an extremely low final imaging rate of 42.7% and a relative reduction of 18%. Another issue is that the absolute number of patients increased in the after period in both intervention and control sites. However, the absolute number of imaging procedures declined at the intervention sites and increased at the control sites and we are confident that there was no change in the characteristics of patient populations from the before to the after periods and no selection bias. Finally, while we are confident that we missed no adverse outcomes, it is conceivable but unlikely that a few patients subsequently underwent diagnostic imaging at a non-study hospital.
Although our strategy was simple and inexpensive to implement, doctor compliance with the requisition was more difficult than expected. This strategy required the radiology technicians to act as gatekeepers, a role with which they were not always comfortable. In the implementation studies for the Ottawa Ankle Rules and Ottawa Knee Rule, doctor compliance was 95% and 93%, respectively.33 36
Additionally, there was some misinterpretation of the rule by doctors, which may reflect the greater complexity of this rule or perhaps a desire to order imaging despite the rule.
This trial supports the previous findings that the Canadian C-Spine Rule is highly sensitive for identifying clinically important injuries of the cervical spine9 10
and also shows that it can be widely implemented in emergency departments by doctors. Most importantly, this implementation can be achieved safely with minimal risk to patients because the rule was designed to be sensitive for injuries and only modestly specific. For 380 patients with injury the cumulative sensitivity of the rule in the combined derivation, validation, and implementation studies was 99.7% (95% confidence interval 98% to 100%), with no harm to any patient. The issues of doctors’ compliance and misinterpretation should be addressed by training that emphasises correct interpretation of high and low risk criteria. Although the study was carried out in Canada, we see no reason why the results would not be applicable to emergency departments throughout most of the developed world. We recognise that some US jurisdictions, due to a private hospital system and doctors’ fear of litigation, may be more challenged to implement the Canadian C-Spine Rule. Widespread adoption of the rule could lead to optimisation of diagnostic imaging rates, less exposure to radiation, and improved patient flow in busy emergency departments. This would prevent prolonged and uncomfortable immobilisation on high acuity area beds for patients with relatively minor injuries.
In conclusion, an active strategy to implement the Canadian C-Spine Rule led to a significant decrease in the use of cervical spine imaging without missed injuries or patient morbidity. Final imaging rates were low compared with most hospitals in the United States. Widespread implementation of the Canadian C-Spine Rule could safely lead to reduced healthcare costs and more efficient patient flow in busy emergency departments.
What is already known on this topic
- Use of diagnostic imaging to exclude cervical spine injury is inefficient in emergency departments
- Prolonged unnecessary immobilisation of the cervical spine adds to overcrowding in emergency departments and patient discomfort
- Previous studies have shown the potential of the Canadian C-Spine Rule to reduce safely the use of cervical spine imaging and immobilisation
What this study adds
- Imaging rates for cervical spine injuries were significantly reduced in hospitals that implemented the Canadian C-Spine Rule compared with control hospitals
- Intervention hospitals had very low imaging rates after implementation
- No fractures were missed and no adverse events occurred