New Appeal Court Judgment on Causation in Medical Malpractice

In the recently released decision in Rutherford v. Wiens, 2021 MBCA 84, the Manitoba Court of Appeal was faced with an interesting question in the context of alleged medical negligence: Should a judge deciding whether medical malpractice occurred consider the issue of causation before deciding whether the doctor breached the standard of care owed to the patient?

The case arose in the context of an alleged surgical error. The plaintiff was referred to an orthopedic surgeon for problems with her left foot. The defendant performed an arthroscopic surgery after symptoms progressed to the left knee. The defendant obtained informed consent and the surgery appeared to go smoothly. However, after surgery, the plaintiff’s leg did not have proper circulation; soon, she began complaining of pain.

It turns out there was a pseudoaneurysm in the plaintiff’s popliteal artery. This is an artery behind the knee that is essential to blood flow to the lower extremity. The plaintiff was then sent for emergency vascular surgery where it was confirmed that the artery had been affected by direct trauma – likely due to a surgical error. The plaintiff sued the doctor for damages arising form ongoing pain from the aneurysm.

At trial, the plaintiff called an expert witness in orthopedic surgery. This is important for any plaintiff in a medical malpractice case, as success usually depends on strong expert evidence. The plaintiff’s expert explained how an injury like this can occur during surgery when a surgical instrument penetrates the posterior capsule of the knee during surgery. The medical expert went on to explain that the surgeon should not have used the instrument in this area. In other words, the plaintiff claimed that her surgeon was negligent in his surgical performance. He used a surgical instrument improperly and this caused the aneurysm.

The defendant physician called his own expert, which is common in cases alleging medical negligence. This expert in arthroscopic surgery testified that this rare injury was an unavoidable complication of surgery and that the defendant met the standard of care when treating the plaintiff.

At trial, the judge found that the correct surgery had been performed and that, if a surgical instrument caused the injury, it was an unavoidable misstep that did not meet the standard of medical negligence. The plaintiff appealed on the basis that the trial judge did not determine how the incident occurred. From the plaintiff’s perspective, it was important for the judge to consider how the injury happened before determining whether the standard of a reasonably prudent surgeon had been met.

The question of how an injury occurred is often referred to as the legal issue of causation. To succeed in a malpractice case, whether against a doctor, nurses, a hospital, or other care providers, a plaintiff must show that a breach of the standard of care by a health professional is what caused their injury. Otherwise, even a negligent course of treatment will not produce a successful result at trial.

The issue of causation is usually among the most challenging aspect of a medical negligence case. In some cases, such as those alleging surgical errors, the plaintiff will need to prove that improper care is what caused the injury and that it was not simply an unfortunate outcome from the surgery. In other cases, such as those where a doctor is sued following a traumatic birth (often in the context of an infant diagnosed with cerebral palsy), the question will be whether the plaintiff can show that better care would have changed the outcome. In those cases, the infant plaintiff may have been subjected to a period of fetal distress. This may give rise to a lawsuit where a plaintiff alleges negligence against an obstetrician or the obstetrical team for failing to intervene in response to a concerning fetal heart rate. To prove causation in such a case, the plaintiff will need to show that, for instance, an emergency C-section would have changed the outcome by alleviating fetal distress and restoring oxygenation.

Returning to the case of Rutherford, the plaintiff was concerned that, because her theory of causation was so important to the determination of the standard of medical care, the trial judge should have considered how the injury occurred before deciding whether the surgeon met the standard of care. One judge on the panel agreed with this concern, stating: “this is a case where a determination of how the injury occurred would be relevant in determining whether the standard of care was met. … I am therefore of the view that the trial judge erred in not determining the cause in fact before proceeding to assess whether the standard of care had been met.”

The majority of the Court disagreed, holding that “the only basis for a finding of negligence on the present evidentiary record is to reweigh the evidence, to utilize a results-oriented approach and to reason backwards from causation.” The appeal was therefore dismissed.

This case serves as a useful reminder that plaintiffs in medical malpractice cases must seriously consider the relationship between the standard of care and the cause of their injury. While the Rutherford case was decided in the context of an alleged surgical error, it may have some application in other cases alleging malpractice, including those dealing with the complex issue of causation in birth trauma, shoulder dystocia, and other obstetrical cases.

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