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J Knee Surg 2022; 35(10): 1119-1125
DOI: 10.1055/s-0040-1722325
Original Article

A Flexible Intramedullary Guide Can Reduce the Anteroposterior Oversizing of Femoral Components Used in Total Knee Arthroplasty in Patients with Osteoarthritis and Severe Distal Femoral Sagittal Bowing

Do Weon Lee
1   Department of Orthopedic Surgery, Seoul National University Hospital, Seoul, South Korea
,
Joonhee Lee
2   Division of Knee Surgery, CM Hospital, Seoul, South Korea
,
Junpyo Lee
1   Department of Orthopedic Surgery, Seoul National University Hospital, Seoul, South Korea
,
Du Hyun Ro
1   Department of Orthopedic Surgery, Seoul National University Hospital, Seoul, South Korea
,
Myung Chul Lee
1   Department of Orthopedic Surgery, Seoul National University Hospital, Seoul, South Korea
,
Hyuk-Soo Han 
1   Department of Orthopedic Surgery, Seoul National University Hospital, Seoul, South Korea
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Funding None.
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Abstract

Traditionally, a rigid intramedullary rod has been used as the reference guide for femoral cutting in total knee arthroplasty (TKA). However, correct positioning of this rigid rod is difficult, especially in the knees with severe distal femoral sagittal bowing. A flexible intramedullary rod has been developed to address this problem. This study was performed to compare the sagittal alignment and clinical outcomes of TKAs performed with flexible and rigid femoral intramedullary guides. Thirty-eight knees that underwent primary TKAs with flexible intramedullary rods as femoral cutting guides were matched according to patient height and sex with 38 knees that underwent TKAs using conventional rigid rods. Clinical outcomes, including the range of motion and functional scores, and radiological variables, including the distal femoral bowing angle (DFBA), femoral component flexion angle (FFA), and mediolateral overhang and anteroposterior (AP) oversizing of femoral components, were evaluated. Clinical and radiological outcomes did not differ significantly between the flexible rod and conventional rigid rod groups. A subgroup analysis of knees with severe distal femoral sagittal bowing (DFBA >4 degrees) showed that the FFA was significantly larger in the flexible rod group than in the rigid rod group, with an average difference of 3 degrees (5.2 ± 2.4 vs. 2.2 ± 1.6 degrees, respectively, p = 0.022). In addition, the incidence of AP oversizing of femoral components was lower in the flexible rod group than in the rigid rod group (11.1 vs. 60.0%, respectively, p = 0.027). Relative to TKA with a rigid rod, TKA performed with a flexible femoral intramedullary guide resulted in more flexed sagittal alignment of femoral components in patients with severe distal femoral sagittal bowing. This greater flexion of the femoral component resulted in less AP oversizing. However, the use of a flexible rod had no impact on short-term clinical outcomes.

Keywords

flexible intramedullary guide - total knee arthroplasty - sagittal alignment - femoral component flexion

Note

This is a retrospective comparative study; therefore, we exempted the consent to participate.


Ethical Approval

This retrospective comparative study was approved by the Institutional Review Board (no. H- 2004-015-1115).


Authors' Contributions

D.W.L. conducted data analysis, data interpretation, and drafting of the manuscript. J.L. and J.L. performed data acquisition and data analysis. D.H.R. and M.C.L. did data acquisition and data interpretation. H.-S.H. conducted design, data acquisition, data interpretation, and manuscript revision.




Publication History

Received: 30 April 2020

Accepted: 12 November 2020

Article published online:
05 February 2021

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