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,
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
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
“The large sample size allows for interpretation of the mean
thickness data for each procedure,” Sarraf said in his presentation at
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
- 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: firstname.lastname@example.org.
- Disclosure: Sarraf has no relevant financial disclosures.