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Study reveals complexity of revising primary unicompartmentals to total knees
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Revising a primary medial unicompartmental knee arthroplasty to a total knee arthroplasty is more complex than a primary total knee procedure because of greater bone loss and the greater need for constrained implants, according to a study presented by Khaled M. Sarraf, MRCS, at the SICOT XXV Triennial World Congress 2011.
“We have shown that the mean polyethylene thickness for revision of [unicompartment knee arthroplasty] UKA to [total knee arthroplasty] TKA is greater than that in primary and complex primary TKA, but less than that employed in revision TKA to TKA procedures,” Sarraf told Orthopedics Today. “The level of constraint required is also greater in the revision UKA to TKA group than the primary TKAs. Both these factors can be interpreted as increased complexity of the revision UKA to TKA procedures.”
He added, “Although the UKA to TKA revisions are technically feasible, greater bone loss and a higher rate of constrained design use leads to challenges at the time of failure and time of revision of the UKA. Furthermore, the decrease in longevity of UKA to TKA revisions shown in various joint registries poses further obstacles in the subsequent revisions for both the patient and the surgeon.” However, Sarraf noted that adhering to the indications for UKA may improve implant longevity and clinical results.
Using data from the National Joint Registry of England and Wales, Sarraf and colleagues studied 251,803 primary TKAs, 12,356 single-stage revisions of a primary TKA to a secondary TKA and 439 primary UKAs that were revised TKRs. The team used the thickness of the polyethylene bearing as a surrogate for bone loss.
“The large sample size allows for interpretation of the mean thickness data for each procedure,” Sarraf said in his presentation at SICOT.
The investigators found a mean polyethylene thickness of 10.43 mm for the primary TKAs, 11.31 mm for the complex primary TKAs, 12.79 mm for primary UKAs revised to TKA and 14.86 mm for single-stage revisions of primary TKAs to a secondary TKA. They found that constrained knee replacements were used in 2.15% of all primary TKA procedures and 4.19% UKAs revised to TKA. – by Renee Blisard
Reference:
- Sarraf KM, Oussedik S, Somashekar N, Haddad FS. 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.
- Khaled M. Sarraf, MRCS, can be reached at the Department of Orthopaedic Surgery, Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH; email: ksarraf@gmail.com.
- Disclosure: Sarraf has no relevant financial disclosures.