Distal femoral cut perpendicular to the mechanical axis may induce varus instability in flexion in medial osteoarthritic knees with varus deformity in total knee arthroplasty: A pitfall of the navigation system

Ryuji Nagamine, Keiichi Kondo, Satoshi Ikemura, Atsushi Shiranita, Satoshi Nakashima, Toshihiko Hara, Hidetoshi Ihara, Yoichi Sugioka

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Two factors that influence the external rotation angle of the femoral rotational axis in total knee arthroplasty (TKA) were assessed in 40 medial osteoarthritic knees with varus deformity. First, the anatomic configuration of the femur was assessed using standardized radiographs of the patients' lower extremities before TKA. Second, the degree of medial soft tissue release was assessed during TKA. The radiographs showed that the characteristics of the femur were lateral bowing of the shaft and external rotation of the condyle in the coronal plane. Therefore, when the distal femur is cut perpendicular to the mechanical axis, the cut surface may be in too much of a valgus position. Furthermore, some degree of medial soft tissue release was necessary in all knees. Medial soft tissue release rotates the femur externally in extension in the coronal plane, and it rotates the femur externally around the femoral axis in flexion relative to the tibia. A distal femoral cut in too much of a valgus position and medial soft tissue release induces varus instability in flexion in knees with lateral bowing of the femoral shaft. Anatomic variation such as femoral bowing should be considered when a navigation system is used for TKA because the navigation system shows only the mechanical axis.

Original languageEnglish
Pages (from-to)555-559
Number of pages5
JournalJournal of Orthopaedic Science
Volume9
Issue number6
DOIs
Publication statusPublished - Nov 2004
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Surgery
  • Orthopedics and Sports Medicine

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