Background: Bone defects during revision procedures for failed UKA represent a challenge even for the most experienced surgeons; therefore, an accurate preoperative planning remains essential to prevent dramatic scenarios in the surgical theatre. Hypothesis: Our hypothesis is that bearing thickness used in original UKA represents a reliable predictor of severe tibial bone loss, requiring a metallic augment or constrained implant, during revision to TKA. Patients and methods: Forty-two patients who underwent a total knee arthroplasty from failed UKA were identified from our institutional database and evaluated clinically using the Knee Society Score (KSS). A multivariate logistic regression analysis was performed using the presence of tibial augments or the need of varus-valgus constrained (VVC) prosthesis as depend variables, and patients’ gender, age at revision procedure, side (medial or lateral), UKA tibial tray (all-polyethylene or metal back), bearing thickness (composite thicknesses of the metal-backed tray and insert or all-polyethylene tibial component ≤ 8 mm or more than 8 mm) and cause of failed UKA as independent variables. Results: A posterior-stabilized prosthesis was used in 27 cases (64.3%). An augment was necessary in 12 patients (28.6%). Initial bearing thickness greater than 8 mm was associated with greater likelihood of a VVC implant (OR = 11.78, 95% CI, 1.6583 to 83.6484, p = 0.0137) and a tibial augment (OR = 9.59, 95% CI, 1.327 to 69.395, p = 0.0251). Tibial tray design, patients’ gender or age during revision surgery, side or cause of failure were not associated to increased risk of augmentation or constrained implants. Discussion: Surgeons should be aware of the particular challenges that the conversion of a UKA to a TKA presents and be prepared to address them intraoperatively, with particular care to proper bone loss manage. Satisfying results can be achieved at mid-to-long term follow-up, if these procedures are planned accurately, and a precise analysis of failed UKA components, in particular bearing thickness, represents a helpful support in this context. Level of evidence: IV, retrospective case series.
Lo Presti M., Costa G.G., Grassi A., Agro G., Cialdella S., Vasco C., et al. (2020). Bearing thickness of unicompartmental knee arthroplasty is a reliable predictor of tibial bone loss during revision to total knee arthroplasty. ORTHOPAEDICS & TRAUMATOLOGY: SURGERY & RESEARCH, 106(3), 429-434 [10.1016/j.otsr.2019.12.018].
Bearing thickness of unicompartmental knee arthroplasty is a reliable predictor of tibial bone loss during revision to total knee arthroplasty
Lo Presti M.;Grassi A.;Cialdella S.;Vasco C.;Cucurnia I.;Zaffagnini S.
2020
Abstract
Background: Bone defects during revision procedures for failed UKA represent a challenge even for the most experienced surgeons; therefore, an accurate preoperative planning remains essential to prevent dramatic scenarios in the surgical theatre. Hypothesis: Our hypothesis is that bearing thickness used in original UKA represents a reliable predictor of severe tibial bone loss, requiring a metallic augment or constrained implant, during revision to TKA. Patients and methods: Forty-two patients who underwent a total knee arthroplasty from failed UKA were identified from our institutional database and evaluated clinically using the Knee Society Score (KSS). A multivariate logistic regression analysis was performed using the presence of tibial augments or the need of varus-valgus constrained (VVC) prosthesis as depend variables, and patients’ gender, age at revision procedure, side (medial or lateral), UKA tibial tray (all-polyethylene or metal back), bearing thickness (composite thicknesses of the metal-backed tray and insert or all-polyethylene tibial component ≤ 8 mm or more than 8 mm) and cause of failed UKA as independent variables. Results: A posterior-stabilized prosthesis was used in 27 cases (64.3%). An augment was necessary in 12 patients (28.6%). Initial bearing thickness greater than 8 mm was associated with greater likelihood of a VVC implant (OR = 11.78, 95% CI, 1.6583 to 83.6484, p = 0.0137) and a tibial augment (OR = 9.59, 95% CI, 1.327 to 69.395, p = 0.0251). Tibial tray design, patients’ gender or age during revision surgery, side or cause of failure were not associated to increased risk of augmentation or constrained implants. Discussion: Surgeons should be aware of the particular challenges that the conversion of a UKA to a TKA presents and be prepared to address them intraoperatively, with particular care to proper bone loss manage. Satisfying results can be achieved at mid-to-long term follow-up, if these procedures are planned accurately, and a precise analysis of failed UKA components, in particular bearing thickness, represents a helpful support in this context. Level of evidence: IV, retrospective case series.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
