Intraoperative assessment of midflexion laxity in total knee prosthesis.
BACKGROUND
Soft-tissue balancing of the knee is fundamental to the success of a total knee arthroplasty (TKA). In posterior-stabilized TKA, there is no stabilizer of the anterior-posterior translation in the midflexion range in which the cam-post mechanism does not engage yet. Therefore, instability in the midflexion range is suspected to occur in posterior-stabilized TKA. The purpose of this study was to measure the joint gap throughout a full range of motion and to analyze the joint gap laxity in the midflexion range after implantation of a mobile-bearing posterior-stabilized total knee prosthesis.


METHODS
Joint gap kinematics in 259 knees with varus osteoarthritis were measured during TKAs using a tensor device with the same shape of a total knee prosthesis of the same design was used. After the implantation of a mobile-bearing posterior-stabilized prosthesis and the reduction of the patellofemoral joint, the joint gap was measured at 0°, 30°, 60°, 90°, 120°, and 145° of flexion.


RESULTS
The center size of the joint gap was tight in extension and deep flexion and loose at midflexion ranges, especially at 30° of flexion (p<0.001). The symmetry of the joint gap was varus at 0° and 145° of flexion (p<0.001).


CONCLUSIONS
Our results showed the joint gap laxity in the midflexion range after the implantation of a mobile-bearing posterior-stabilized prosthesis. Our new tensor device, which can attach the polyethylene insert trial, will provide the important information about the joint gap kinematics after implantation of total knee prostheses.


METHODS
IV.
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan. Electronic address: yminoda@msic.med.osaka-cu.ac.jp.
Yukihide
Y
Minoda
Department of Orthopaedic Surgery, Osaka Rosai Hospital, 1179-3, Nagasone-cho, Kita-ku, Sakai, Osaka 591-8025, Japan.
Shigeru
S
Nakagawa
Department of Orthopaedic Surgery, Osaka General Hospital, 3-1-56 Mandaihigashi, Sumiyoshi-ku, Osaka 558-8558, Japan.
Ryo
R
Sugama
Hanwa Joint Reconstruction Center, 3176 Fukaikitamachi, Naka-ku, Sakai, Osaka 599-8271, Japan.
Tessyu
T
Ikawa
Department of Orthopaedic Surgery, Shinbeppu Hospital, 3898 Tsurumi, Beppu, Oita 874-0833, Japan.
Takahiro
T
Noguchi
Department of Orthopaedic Surgery, Oita University Faculty of Medicine, Graduate School of Medicine, 1-1 Idaigaoka, Hazama-cho, Yufu, Oita 879-5593, Japan.
Masashi
M
Hirakawa
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan.
Hiroaki
H
Nakamura
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D007593:Joint Instability / Q000473:pathology*; D007719:Knee Joint / Q000473:pathology* / Q000503:physiopathology; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology*; D020127:Recovery of Function
Intra-operative joint kinematics; Midflexion instability; Tensor device; Total knee arthroplasty