Tibial internal rotation is affected by lateral laxity in cruciate-retaining total knee arthroplasty: an intraoperative kinematic study using a navigation system and offset-type tensor.
OBJECTIVE
The purpose of this study was to test the hypothesis that intraoperative soft-tissue balance assessed by an offset-type tensor influences post-operative knee kinematics after cruciate-retaining (CR) total knee arthroplasty (TKA).


METHODS
The influence of intraoperative soft-tissue balance on knee kinematics in CR-TKA was retrospectively analysed in 30 patients. Intraoperative soft-tissue balance parameters such as varus angle (varus ligament balance), joint component gap (centre gap), and medial and lateral compartment gaps were measured in the navigation system while applying 40-lb joint distraction force at 0°, 10°, 30°, 60°, 90°, and 120° of knee flexion using an offset-type tensor with the patella reduced. Tibial internal rotation and tibial anterior translation were measured as the differences between the values at 60° and 120° of flexion using the navigation system. Correlations between the soft-tissue parameters and post-operative knee kinematics were analysed.


RESULTS
The varus ligament balance was positively correlated with tibial internal rotation at 60° and 90° of flexion (R = 0.54, P < 0.05; R = 0.60, P < 0.01, respectively). Furthermore, the joint component gap was positively correlated with tibial internal rotation at 90° of flexion (R = 0.44, P < 0.05), and the lateral compartment gap was positively correlated with tibial internal rotation at 60°, 90°, and 120° of knee flexion.


CONCLUSIONS
The intraoperative varus ligament balance and joint component gap values were factors that predicted post-operative knee kinematics after CR-TKA. Lateral laxity at mid-to-deep knee flexion plays a significant role in tibial internal rotation.


METHODS
III.
Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
Tokio
T
Matsuzaki
Tomoyuki
T
Matsumoto
Seiji
S
Kubo
Hirotsugu
H
Muratsu
Takehiko
T
Matsushita
Yohei
Y
Kawakami
Kazunari
K
Ishida
Shinya
S
Oka
Ryosuke
R
Kuroda
Masahiro
M
Kurosaka
D000368:Aged; D000369:Aged, 80 and over; D016118:Anterior Cruciate Ligament / Q000503:physiopathology / Q000601:surgery; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D006801:Humans; D007432:Intraoperative Period; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery*; D011184:Postoperative Period; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D012399:Rotation; D013977:Tibia / Q000503:physiopathology* / Q000601:surgery; D016896:Treatment Outcome