For orthopedic coders, questions around arthroplasties and joint fusions can prove challenging. Dig into the following questions and answers that were presented during the 2025 virtual Advanced Specialty Coding Summit: Orthopedics to gain clear guidance.
Coding a hemi -to-total knee conversion
Question: How would you code conversion of a partial knee arthroplasty to a total knee replacement?
Answer: There isn’t technically a code for that, explains expert speaker and healthcare consultant Margie Scalley Vaught, CPC, COC, CCS-P, MCS-P, ACS-EM, ACS-OR.
“I reached out to the AMA and they said they and the American Academy of Orthopaedic Surgeons (AAOS) are working on a code,” she explained during the Day 1 Live Q&A at the November 2025 virtual Advanced Specialty Coding Summit: Orthopedics.
“For now, we should be using the unlisted code 27599 for a hemi-to-total knee conversion, according to the AMA,” she explained.
Practices can like the value of the procedure to a total knee arthroplasty (CPT 27447), Vaught advises. The only other option is to liken it to the knee revision code, 27487, she added.
Reporting open SI joint fusion with posterior lumbar arthrodesis
Question: When the surgeon does a posterior lumbar fusion at L5/S1, they want to additionally bill CPT code 27280. Is this appropriate? What documentation do we need?
Answer: Code 27280 describes an open sacroiliac (SI) joint fusion. “More and more, we’re starting to see where the physicians are adding this to a lumbar posterior fusion,” observed health care coding expert Alison Kuley, CPC, speaking during the Day 3 Live Q&A at the Advanced Specialty Coding Summit: Orthopedics in November 2025.
“My feeling is that the L5/S1 is a different area than the SI joint,” she said. “When you’re doing a posterior fusion of the L5/S1, you’re going over the posterior elements. You’re going over the back of the sacrum with the bone grafts. But when you’re doing the 27280, you’re in the pelvic girdle. You’re actually going into the SI joint to either place screws or place bone graft. So the first question is: What is the medical necessity of doing the SI joint fusion along with lumbar spinal fusion?”
If the indication is “radiculopathy, stenosis or back pain, that’s not going to support the SI joint fusion,” Kuley advised. The patient should have “some additional sacroiliac issues, such as M53.3 (Sacrococcygeal disorders, not elsewhere classified) or M46.1 (Sacroiliitis, not elsewhere classified). You want to see a reason why they’re adding the SI joint fusions during this procedure.”
Also check to “make sure they’re actually doing an open SI joint fusion and that they’re not placing the screw percutaneously laterally, because then that’s a percutaneous fusion, not an open SI joint fusion,” she added.
From a compliance standpoint, “you should not see that they are routinely trying to report an SI joint fusion with a posterior lumbar fusion,” Kuley warned. “They’ve got to have a medical necessity for fusing the SI joints. If they’re doing it with all the same diagnosis codes as the posterior fusion, I would question why they’re adding it in there.”