Hyperextension following two different designs of fixed-bearing posterior-stabilized total knee arthroplasty.

PURPOSE: Hyperextension after total knee arthroplasty (TKA) is related to worse functional outcomes. Among the reported predictive factors, it is unclear whether prosthesis design affects postoperative hyperextension. Hence, our objectives were to (1) compare time-dependent changes of the extension angle following multi-radius (MR) and single-radius (SR) TKA and (2) assess predictive factors for the hyperextension. METHODS: In this study, consecutive 136 MR TKAs and consecutive 71 SR TKAs performed by a single surgeon were reviewed. The extension angle was evaluated by digitized full-extension lateral radiographs at preoperative, 3 months and at 1 and 2 years after TKA. A positive value was defined as hyperextension. A multiple regression analysis was used to determine predictive factors for the extension angle and the risk of hyperextension > 5°. RESULTS: The postoperative extension angle of both groups gradually increased during the first 2 years and the SR group finally progressed with 4.04° greater extension than the MR group (p < 0.01). The incidence of hyperextension > 5° in the SR group was 18.3% and for the MR group, 7.4% (p = 0.02). However, the Oxford knee scores was nonsignificant different between the groups (p = 0.15). Preoperative extension angle, sagittal femoral component angle (SFA) and SR prosthesis were predictive factors for the extension angle at 2 years after TKA and were also associated with hyperextension > 5°. CONCLUSIONS: The extension angle of the SR group became significantly more extended than that of the MR group during the first two years after TKA. Hence, ideal extension position immediately after SR TKA may be different from that of the MR TKA prosthesis. The preoperative extension angle, SFA and SR prosthesis were factors that were associated with postoperative hyperextension.

Usefulness of an accelerometer-based navigation system in bilateral one-stage total knee arthroplasty.

BACKGROUND: Bilateral one-stage total knee arthroplasty (BTKA) have increased because it provides a number of advantages. Recently, Accelerometer-based navigation (ABN) system which guide the cutting plane without intramedullary disturbance might result in less endothelial and microvascular damage. Therefore, we hypothesized that the ABN may reduce blood loss, reduce postoperative pain, and better restore BTKA alignment compared to conventional instruments. METHODS: We retrospectively compared 44 consecutive patients receiving ABN assisted BTKA (iBTKA) to 57 patients with conventional instruments (cBTKA). Identical pre- and post-operative care was utilized to all patients. The outcome measures assessed were hemoglobin (Hb), calculated blood loss (CBL), blood transfusion, VAS score for pain, morphine consumption, knee flexion angle, and length of stay (LOS). Radiographic assessment included mechanical axis (MA) and component positioning at 3-6 months of follow up. RESULTS: Both iBTKA and cTKA groups had equivalent demographic data. Postoperative Hb of the cBTKA group was significantly lower than those in the iBTKA group at 24 h (p = 0.02), but there was no significant difference in drain volume, CBL, and blood transfusion rate. For radiographic measures, the iBTKA group had more accurate MA and component orientation, and had a lower number of outliers than those in the cBTKA group (p ≤ 0.01), except for the sagittal femoral component angle. CONCLUSION: The ABN assisted BTKA could not reduce blood loss or postoperative pain more than cBTKA, nor improve functional recovery. However, the ABN significantly improved the accuracy of MA and prostheses positioning. TRIAL REGISTRATION: The protocol of this study was registered in the Thai Clinical Trials Registry database No. TCTR20180731001 # on 25 July 2018.