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High incidence of radiolucent lines at the implant-cement interface of a new total knee replacement.

BACKGROUND
Recently introduced total knee arthroplasty (TKA) implants have been linked with the early development of periprosthetic radiolucency (PPRL). The aim of this study was to carry out a retrospective clinical and radiographical analysis of a consecutive series of a new TKA, and to assess the incidence and distribution of PPRL.


METHODS
A retrospective review of all new TKA implants performed by a single surgeon at a single hospital between March 2013 and October 2017 was performed. The minimum follow-up period was 3 months, with ongoing patient review at 6, 12 and 36 months. Sequential post-operative radiographs were performed to determine the presence of PPRL.


RESULTS
A total of 122 TKAs were identified in 112 patients over the 4.5-year study period. The average follow-up time was 21 months (range 3-51 months). PPRL was noted in 29 TKAs (23.8%). When comparing the PPRL group to those without PPRL, there was a difference in body mass index, with body mass index associated with an increased likelihood of PPRL (P = 0.003). There was no difference in constraint of implant (P = 0.818), cement type (P = 0.340), patella resurfacing (P = 0.286), age (P = 0.984) gender (P = 0.376) or initial mechanical axis deviation (P = 0.054) between groups. PPRL were most commonly seen in tibial anterior-posterior (AP) zone 1 and zone 2 (96.6%), followed by femoral lateral zone 5 (58.6%), tibia lateral zone 1 (55.2%) and tibial lateral zone 2 (53.2%). No patients have required revision surgery.


CONCLUSION
A high incidence of early PPRL is seen in patients undergoing primary TKA using a new implant system, mainly involving the tibial component. Ongoing clinical and radiological assessment for patients seems warranted based on these findings.