Speaker: Neocortex formation after THA should not be of concern
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A distal neocortex that forms after total hip arthroplasty is a common finding in patients with a tapered wedge stem, but it is not one that indicates suboptimal outcomes or complications will develop, a presenter said.
In a retrospective review of THA performed with tapered wedge stems during a 10-year period by two surgeons at an academic medical, Christopher E. Pelt, MD, and colleagues found 558 of 825 patients evaluated had a formation of neocortex, which is sclerotic bone.
“The majority – 68% of our patients with this particular implant – actually had this finding of neocortex. No zones really demonstrated changes and radiolucencies over time, suggesting this is not a concern for progression or a loosening that’s progressive,” Pelt said.
Researchers hypothesized that, based on their previous clinical experience, neocortex around the distal nonporous coated portion of a tapered wedge stem was not indicative of loosening and was not associated with worse outcomes.
They reviewed the patients’ radiographs at 1 year postoperatively and the last available final follow-up radiographs for all patients, studying the stem in all of the 14 Gruen zones. They also read the final attending radiology reports in which the term “lucency” was recorded.
Researchers divided patients according to the presence or absence of a neocortex formation and performed further analysis.
“We did notice some minor differences in things that can be demonstrated in the table with age, gender, BMI and [American Society of Anesthesiologists] ASA and Charlson Comorbidity Index. None of it was clinically all that relevant. The one interesting finding that we actually demonstrated higher [Patient Reported Outcomes Measurement Information System] PROMIS scores in the group with neocortex despite the fact there wasn’t a significant difference between the two groups otherwise,” Pelt said.
Results showed the most common sites for evidence of neocortex were on lateral radiographs in Gruen zones 10 (56%), 11 (52%), and 12 (52%).
This was noted “distally around the smooth non-porous-coated portion of the stem,” as well as on the anteroposterior radiographs, distally in zones 3, 4 and 5, Pelt said.
“We had 99.8% [Kaplan-Meier] survivorship for this particular implant at 3 years that carried out beyond 10 years in the follow-up study, with loosening as an endpoint, and no significant difference was seen between the two groups,” he said.
“And there was no difference in complications between the two groups, including dislocation, infection, fracture, revision or reoperation; all the things that would be concerning for a loose stem,” Pelt said.
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Kellam PJ, et al. Paper 8. Presented at: American Association of Hip and Knee Surgeons Annual Meeting. Nov. 11 -14, 2021; Dallas (hybrid meeting).
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