Several years ago, I was with a client who was going in for a lumbar revision surgery at a major American hospital with a leading spine surgeon. His lowest lumbar level was already fused and he was having surgery at the level above, based on discography results.
Looking at the xrays, it seemed that L5-S1 was fused. Per the discography results, L4-5 was going to get ADR. While he was going through the consenting process, I was reading his reports. This patient had a ‘transitional segment’. He had a 6th lumbar vertebra. I had noticed that references his spine were not consistent. In some cases, they referred to the fused level as L5-S1. In some cases, it was referred to as L6-S1. Some referred to the next level as L4-L5, while others referred to it as L5-L6. Amazingly, not only were different reports inconsistent, but the discography report was inconsistent! In some places, it referred correctly to the transitional segment, while in other places, it incorrectly ignored that fact and mislabeled the levels.
I flagged this to the nurse that was consenting the patient and asked if the surgery that was supposed to be on L4-5 was going to be on the real L4-L5, or if it was supposed to be on L5-L6 (which looks like L4-5 to everyone looking at the imaging. Are they starting at the sacrum and numbering upwards? Are they starting at T12 and numbering downwards? The nurse was uncertain, but assured me that the surgeon knew what he was doing. I insisted that I speak to the doctor before the surgery started. This was inconvenient and the staff was clearly miffed that I was slowing things down.
When the surgeon came out, he hadn’t noticed the inconsistent references to the levels and was unsure which disc was flagged as the painful one. Everything was held in limbo while they tried to reach the doctor who performed the discography. I took a while because they had to get him out of a surgery. (He was an anesthesiologist.) Fortunately, he remembered the procedure and verified that while the report indicated that L4-5 was the painful level, it was really L5-L6.
We’ll never know if they would have performed the surgery on the correct level. Had they assumed that L4-5 was the 2nd level up, they would have been correct. Had they correctly started numbering down from T12 and assumed that the discography report was correct, the surgery would have been performed at the wrong level. (Since the discography report mentioned the transitional segment, I think the error is more likely, but we’ll never know.)
It’s especially easy to operate on the wrong level if there is a transitional segment. That may be a lumbarized sacral vertebra (creating an L6-S1 disc) or a sacralized lumbar vertebra (L4-S1 disc). In papers I’ve seen presented at the conferences, this may be as common as in 17% of spine patients. However, it’s only a potential problem if there are multiple degenerated discs and it’s not obvious from the imaging which ones are to be operated on.
Mark
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