Today’s primary UKR may become tomorrow’s complicated revision (OrthoSuperSite)
PRAGUE — Researchers at London’s Chelsea and Westminster Hospital discovered in their recent analysis of register-based unicompartmental and total knee arthroplasty revision cases that the procedures were more complicated than primary cases due to increases in bone loss and use of constrained prostheses.
Using polyethylene bearing thickness as a surrogate for bone loss in their analysis of data in the National Joint Registry (NJR) for England and Wales, Khaled Sarraf and colleagues found mean bearing thicknesses of 10.43 mm for straightforward primary total knee replacement (TKR) that increased to as much as 14.86 mm for some revision TKRs in the registry.
According to results that Sarraf presented at the SICOT XXV Triennial World Congress 2011 here, revising a unicompartmental knee replacement (UKR) to a TKR proved most challenging, with a mean thickness of 12.79 mm for the revision polyethylene inserts used in those circumstances.
“Constrained knee replacements were used in 4.9% of UKR-to-TKR revision in comparison to 2.15% of primary TKR,” according to the abstract.
Sarraf said in his presentation, “The mean polyethylene thickness for revision of a unicompartmental knee replacement to a ‘total’ is greater than a primary knee … The level of constraint for a revision from a ‘uni’ to a ‘total’ is greater than the primary knee. So we believe that the increases in polyethylene thickness may represent greater bone loss and greater complexity.”
In all, the analysis included 273,146 primary TKRs, 13,943 revision TKRs and 512 revision UKRs performed in England and Wales between 2003 and 2009 and tracked in the NJR.
One upshot of these findings is a greater need for stabilized revision TKR, Sarraf noted, something orthopaedic surgeons should be more cognizant of when deciding on the most appropriate primary operation for patients.
“The revision of a unicompartmental knee replacement to a total knee replacement is still a good operation, however, we need to consider the increase in the bone loss as well as the increase in use of constrained designs, as this can lead to challenges when it comes to the ‘uni’ failure and the time of revision,” he said.
Reference:
- Sarraf K, Oussedik S, Somashekar N, Haddad F. Bone loss during revision unicompartmental and total knee replacement: An analysis of the National Joint Registry data. Paper #29375. Presented at the SICOT XXV Triennial World Congress 2011. Sept. 6-9. Prague.