Causation in medical liability: Determining who is at fault

Despite good faith and prudent care, some outcomes go bad through unexpected events.

Editors’ Note: Periodically, we report on actual cases, with some identifiers and details changed for discretionary reasons, in which the outcome has educational and informative value for our readers. In this column, we report on a case in which a series of complications occurred after a total knee replacement (TKR), ultimately resulting in litigation. The case is a useful platform to illustrate the concept of causation that links professional conduct to the alleged injury.

Among the elements an injured patient must prove in order to prevail in a medical malpractice trial is that of causation. Surgeons are familiar that successful medical malpractice litigation requires proof that the professional’s conduct fell below the standard of care. But substandard care alone, even though it may be worthy of condemnation and peer-criticism, is insufficient to make a legal case of professional negligence. More is required, namely that the substandard conduct must relate to the injury alleged.

Where such relationship between substandard conduct and injury is such that no intervening causes exist between conduct and the resulting harm, direct causation is said to exist. In other words, conduct directly caused the injury alleged.

Causation tests

A related concept in causation is that of “but-for” causation. This type of causation refers to a legal test used to determine if harm would have resulted but-for the alleged conduct. As an example, an accident would not have occurred, but for the fact that one driver ran a red light. This type of causation, also known as “cause-in-fact,” does not assign culpability, but seeks to tie together an act and the resulting harm from that act.

Lawrence H. Brenner

B. Sonny Bal

Further inquiry into causation leads to the concept of proximate causation. This legal test is based on reason which seeks to find out if an event is sufficiently related to an injury, so that it can be held as a cause of that injury. Proximate causation fails when the link between the event and injury is sufficiently attenuated.

These two types of causation in the law, cause-in-fact and proximate (or legal) cause, must be satisfied if substandard professional conduct is held to cause the alleged injury.

There are other types of causation that can complicate the inquiry — such as concurrent causes, or sufficient combined causes — and other related principles that are used in cases where multiple independent causes combine to result in injury, and where any one of them, or all of them together would be necessary to cause the injury.

Case example

These concepts of causation between events on the one hand, and resulting harm on the other are illustrated in a recently published medical malpractice verdict. In that case, a healthy man in his early 50s injured his right knee while teaching a vocational auto-body shop class; The bumper of a car struck his knee. In the remote past, he had undergone two arthroscopic procedures in that knee with partial meniscectomies, but reported no problems with the knee at the time of the accident.

Following the incident, knee pain flared up again and the treating orthopedic surgeon diagnosed a sprain and contusion, in the setting of existing arthritis. The surgeon prescribed reasonable conservative means to manage the knee symptoms, including injections, bracing and exercise. When these failed, another arthroscopy was performed but it failed to produce lasting relief.

Since diffuse degenerative changes were seen during arthroscopy and on radiographs, a TKR was advised, and performed, some 10 months after the knee had flared up from being struck by the car.

A PCL-sacrificing knee design was used with a deep-dish style of polyethylene insert to provide posterior stability. The patella was not resurfaced. Records showed an uneventful operation and recovery afterwards.

Further events

Unfortunately, the patient fell down some stairs a few months later, while still recovering from surgery, and ruptured the MCL in the operated knee. A partial tear of the quadriceps was also suspected and when reasonable conservative treatment failed to help, surgery was done to repair both the MCL and the quadriceps injuries.

The postoperative course was complicated by continued pain, difficulty with fitting a brace to control the leg and another fall. Examination showed knee instability and anterior knee pain; neither responded to physical therapy. Another operation followed, to imbricate and tighten the MCL, re-repair the quadriceps tendon, and resurface the patella.

After more therapy, and bracing, the knee pain improved but the patient felt that the knee had excess laxity when he walked. Examination by the surgeon confirmed mediolateral instability, and a thicker polyethylene insert was felt to be indicated. Following this latest procedure, the patient regained knee stability, but gradually lost it, and 2 years after the initial TKR he sought help from another surgeon for complaints related to the knee feeling loose.

The second surgeon recommended and performed a revision of all total knee components to a constrained condylar design. A lengthy period of rehabilitation followed, during which time the patient lost work, developed complex regional pain syndrome, became dependent on narcotic drugs, had a spinal stimulator implanted for pain control, and had bouts of depression.

Lawsuit filed

Ultimately the patient was weaned off the narcotic drugs and he improved. To recover for his lost wages and suffering, he filed a lawsuit against the first surgeon alleging that the wrong type of prosthetic implant had been used to address his ligamentous instability, and that all the complications and subsequent operations were caused by the failure of that surgeon to timely convert to a proper, constrained type of device.

The litigation advanced to a jury trial with competing expert orthopedic surgeon testimony vigorously supporting the respective parties. According to the Jury Verdict Reporter for the jurisdiction, the jury returned a verdict in excess of $1 million in favor of the aggrieved patient.

While the judicial reasoning and jury deliberations in the above case are unknown since a detailed opinion was not published, the outcome raises important questions related to the issue of causation. The case described is fairly typical of what many orthopedic surgeons will encounter in their practices. Despite good faith and the exercise of prudent, incremental care, the outcome in some memorable cases seems to ratchet steadily downwards, in a series of successive, frustrating complications that result in multiple operations, just as happened in the above case.

In hindsight, one might speculate that proceeding with a constrained style of knee replacement, or simply replacing the polyethylene to a design that conferred mediolateral stability while the repaired ligaments healed, might be the preferred option. The competing argument is that repairing damaged ligaments, avoiding component revision and protecting the repair with bracing reflects a prudent and cautious approach as the defendants’ experts must surely have opined.

Your opinion

What do you think? Did the car that struck an otherwise asymptomatic, arthritic knee set off a chain of events, causally related, that ultimately resulted in prolonged suffering and loss for the patient violate duty towards this patient? After all, but-for that traumatic event, the patient would never have sought surgical treatment for his knee, and the resulting complications would not have occurred. In that case, assuming the patient was struck negligently by the automobile, should all of the damages be ascribed to that culpable party, rather than to the surgeon who simply did the best he could?

The patient seemed to recover from his knee replacement; and then suffered a fall. Clearly, the ligament repairs necessary to stabilize the knee were causally related to that fall. Also, because of the quadriceps injury the unresurfaced patella seemed to develop symptoms, necessitating resurfacing during one of the subsequent operations. Assuming the fall was the patient’s fault, such as failure to use a walker or cane and knowing that subsequent events were causally linked to that fall, should the surgeon be relieved of any liability towards the patient? Or should be the surgeon be responsible for some damages, at least those that flowed from violating the standard of not using a constrained knee in this case, assuming expert testimony established that standard? If so, was the surgeon’s substandard conduct an independent cause that resulted in harm, thereby cutting off the causal link to the fall?

What if a young, aggressive surgeon had chosen the option of immediate revision of the total knee to a constrained condylar design, with repair of ligaments, and in so doing had accidentally damaged the popliteal artery and nerve, resulting in the same outcome, ie, chronic pain and suffering that resulted in the loss of work? Would major revision surgery, as opposed to incremental surgery designed to stabilize the knee while leaving the prosthetic components alone constitute a deviation from the standard of care? If so, and assuming that accidental injury to the popliteal structures was not negligent, should this aggressive surgeon be held responsible for the adverse outcome? After all, while his revision operation may have been outside the standard of care, it did stabilize the knee, and the adverse outcome was entirely from a popliteal mishap that did not constitute negligent conduct. Is a jury likely to understand these complex causal relationships and arrive at a just result?

For more information

• B. Sonny Bal, MD, JD, MBA, is associate professor of hip and knee replacement in the department of orthopedic surgery, University of Missouri School of Medicine.
• Lawrence H. Brenner, JD, is on the faculties of orthopedics at Yale University and the University of Southern California and practices in Chapel Hill, N.C. Address all correspondence to Brenner at lb@lawrencebrennerlaw.com.