Have you ever heard the phrase, “When you’re a hammer you see everything as nails”? This common statement is an admonition to physicians to keep an open mind and not become myopic in their thought processes. Unfortunately, I often see this type of closed-mindedness.

Years ago, when I was first in practice, I saw a nurse from one of my local surgery centers. She had sought advice from a local vascular surgeon regarding her painful first metatarsophalangeal joint. The vascular surgeon ordered a bone scan and saw increased tracer uptake at the first metatarsal head. Thinking the patient had osteomyelitis, the doctor recommended amputating the great toe and part of the metatarsal (a partial 1^st ray amputation). The patient came to me for a second opinion.

Her history and physical examination did not look anything like a bone infection. She had no ulcer history (wasn’t even diabetic for that matter) and her examination demonstrated normal skin, no erythema or edema, and limited joint range of motion of the 1^st MTP joint. On radiographs, she had a simple dorsal 1^st metatarsal spur and some mild joint space narrowing.

Yes, friends; you guessed it: she had mild hallux limitus. And, yes, another doctor almost amputated it. I easily treated her with a simple cheilectomy. Biopsy and cultures of the bone during the procedure showed no evidence of bone infection. The patient recovered after surgery without issues.

The vascular surgeon made an almost disastrous error in thinking. This doctor was so used to treating patients with infections that he misread the bone scan, which is highly nonspecific in the first place. When he looked for infection, he found it – although “it” wasn’t what it actually was. The doctor was a hammer (someone seeing infections a lot) and saw the inflammation on the bone scan as infection (the nail). He failed to realize that increased bone scan uptake could represent something other than infection.

This physician suffered from a highly common error all of us make called confirmation bias. This logical fallacy is one of the most prevalent flaws from which modern people suffer. Confirmation bias is a tendency to interpret new evidence in a way that “confirms” previously held beliefs. This error is incredibly common in human society. Just look at politics as one example. Two people on opposite political spectrums can observe the same event in completely divergent ways, reaffirming their own beliefs.

---

“Confirmation bias is a tendency to interpret new evidence in a way that “confirms” previously held beliefs”

---

In podiatry, a common confirmation error of which we are guilty is the diagnosis of nonmechanical heel pain as mechanical in origin. How nice would it be if all of our heel pain patients suffered from plantar fasciitis? In my years of practice, this is a common error made by other podiatrists (and I’m sure I’ve done the same thing). I often see a patient with heel pain as a second opinion, hear a story that sounds atypical, and determine it’s a neurological issue such as spinal radiculopathy or Baxter’s neuritis. Just like anyone else, podiatrists are prey to confirmation bias.

So, when the stakes are high how do we prevent ourselves from suffering confirmation bias errors?

Consider how my story would have gone if the physician had instead taken a moment to stop and think in a way that fought his confirmation bias. He would have realized that without an ulcer or opening of some type, it was incredibly unlikely that the patient had an infection (hematogenous spread bone infections are vanishingly rare). He would have also recalled that three-phase bone scans are nonspecific tests that show anything that is inflammatory – such as common arthritis in the great toe joint, one of the most common joints in the body to acquire osteoarthritis. Things could have been much different for the patient.

---

“Three-phase bone scans are nonspecific tests that show anything that is inflammatory – such as common arthritis in the great toe joint”

---

Being conscious of confirmation bias provides each of us with a special “perspectoscope” through which we may see the world more clearly. If we use our perspectoscope appropriately, we won’t fall into the hammer/nail error. Keep your mind open and watchful for confirmation bias.