Wear, osteolysis the most critical factors for survival of total knee revision

Continued improvements in the design of total knee systems and the use of polyethylene components may result in the increased survivorship of revised total knees, according to a recently presented study.

C. Anderson Engh, Jr., MD, shared his group’s findings at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons, in San Diego.

“When faced with a patient that has wear or osteolysis, there are typically three options: a modular bearing exchange, a single component revision or a full total knee revision,” Engh said. “The purpose of this study was to look at a group of patients which we treated for wear or osteolysis, and to compare the re-revision rate for the three options selected, and also to report the influence of polyethylene sterilization.”

Wear and osteolysis

In the study, Engh and his team performed 177 total knee revisions with osteolysis as a primary or secondary diagnosis. According to the abstract, mean age at revision was 68 years and mean time in situ was 7.8 years. Overall, Engh reported, 72 knees underwent complete revision, 57 underwent only a tibial revision, 46 underwent isolated polyethylene exchange and two were femoral revisions.

In addition to standard clinical and radiographic evaluations, Engh and his group documented all re-revisions and complications, performing a survivorship analysis and a statistical analysis to assess the impact of revision type and osteolysis on overall outcome.

Engh reported 29 patients died with the knee intact — 21 before the 5-year follow-up. Overall, there were 104 cases that met the minimum follow-up period and had not undergone re-revision. Twenty-three cases, the abstract noted, underwent subsequent revision with the most common reported reason being osteolysis or wear in 11 cases and loosening in five cases. A further 12 complications, it was reported, did not actually involve the implants.

Engh reported an 88% 5-year survivorship, using component re-revision as an endpoint. Type of index revision, amount of bone loss, and reason for initial revision were unsuccessful at demonstrating any validity as predictors of failure.

“Our conclusion: We still favor an isolated polyethylene exchange, and we believe that polyethylene sterilization influences revision outcomes as it has for primary total knee,” Engh said.

Reference:

Engh CA, Parks NL, Engh GA. Outcome of 177 knees revised for osteolysis with minimum 5-year evaluation. Paper #244. Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19. San Diego.

Disclosure: Engh receives royalties from and owns stock or stock options in DePuy. He also has stock or stock options in Johnson & Johnson, Stryker, and Alexandria Research Technology.

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