Subjects
99 patients with KOA and 80 patients about six months after surgery (i.e. TKA, Unicompartmental Knee Arthroplasty (UKA), HTO, Distal Femoral Osteotomy (DFO) and Patellofemoral Arthroplasty (PFA)) from January 2019 to December 2019 in the Department of Joint Surgery at our hospital were selected. The exclusion criteria for patients included, (1) Patients without history of major trauma, surgery or knee-related symptoms. (2) Patients with rheumatoid arthritis, ankylosing spondylitis, and other autoimmune diseases. (3) Patients with knee joint tumor, infection, severe osteoporosis, and other diseases affecting osteotomy healing. (4) Patients with concurrent severe flexion contracture deformities. According to the lower limb anatomy (Hip-Knee-Ankle angle ) by measuring on standing full-length radiographs, the pre-operative patients with KOA [(-6° − 6°), (< -6° and > 6°)] and post-operative patients [(-3° − 3°), (< -3° and > 3°)] were divided into 2 groups respectively. This study was conducted based on the protocol approved by the Medical Ethics Committee of Shanghai Sixth People's Hospital, all methods were carried out in accordance with relevant guidelines and regulations, and informed consents were obtained from all participants. Patients participated in the experiment joined voluntarily and fully understood the clinical trial protocol.
Admission check and surgical method
After admission, routine preoperative examinations (CRP, ESR, liver and kidney function, electrocardiogram, etc.) and relevant examinations including bone density, CT and MRI scan of knee joints, full-length radiographs, short knee radiographs have been checked. According to the patients’ symptoms, signs, bone density, X-ray, CT and MRI examinations, different patients received the corresponding surgical methods:
(1)TKA: knee osteoarthritis grade of Kellgren-Lawrence Grade III or above; Multiple compartment osteoarthritis; medial articular surface “bone to bone”; severe patellofemoral joint degeneration;
(2)UKA: Single-compartment osteoarthritis of the knee joint; without severe line of force; The anterior cruciate ligament (ACL) and collateral ligament are in good condition; Intact or mild degeneration of cartilage in the contralateral compartment and patellofemoral joint;
(3)HTO: The patients who are younger than 60 years and require large activities; Single-compartment osteoarthritis patients with poor knee joint force; No or mild osteoarthritis in the tibiofemoral and patellofemoral joints; No osteoporosis; Varus deformity originates from the tibial side;
(4)DFO: Varus deformity originates from the femoral side;
(5)PFA: Patients with simple and severe patellofemoral osteoarthritis; without coaxial bone distortion, poor alignment of the lower limbs or large varus and valgus angles;
All surgeries were carried out by highly experienced surgeons from the joint department.
Gait analysis device
3D knee joint movement analysis system, as the integrated system for dynamic and real-time examination of knee joint movement function, could provide doctors with three-dimensional 6DOF of the knee joint quickly and accurately. It could measure the stability of knee joints under different states of motion such as flat walking, squatting, uphill and rotation to evaluate the function of knee joints before and after the operation, and it will generate inspection reports immediately. These reports, combined with X-ray/ CT/ MRI and other imaging examination of joint structure, helped doctors evaluate the knee joint movement function of subjects objectively.
Experimental procedure and functional assessment
A vivo infrared-based navigation three-dimensional knee joint movement analysis system (Opti-Knee®, Innomotion Inc, Shanghai, China) was used to record and analyse the kinematic data of the knees in 6DOF of both knees one day before surgery and six months after surgery at random (Fig. 1A).
Before the test, the doors and windows were closed, curtains were drawn to block external light. All luminous objects in the room were removed to avoid the interference of external interference on the data. The subjects took off the pants and fully exposed both lower limbs. The subjects were told to raise their head and chest, look straight ahead, maintain a standard standing posture, with arms akimbo to prevent the markers from being blocked, and then performed the test system calibration. Two rigid plates, each with four infrared light-reflecting markers (OK_Marquer; Innomotion), were attached to the thighs and shanks with bandages. The 3D motion of the rigid plates was tracked by a stereo binocular infrared camera at a frequency of 60 Hz (Fig. 1B). A hand-held digitizing probe, with four infrared reflective light-reflecting markers, was used to identify femoral and tibial landmarks on the femur and tibia (Fig. 1C). Femoral and tibial landmarks included the trochanter major, condylus lateralis, condylus medialis, medial tibial plateau, lateral tibial plateau, medial malleolus, and lateral malleolus (Fig. 1D).
When the patients walked freely and normally, an integrated synchronous high-speed camera was collecting walking videos and gait data at a frequency of 60 frames per second for the 60s to identify gait cycles and then calculate 3D knee kinematic parameters in real time. HKA measured by weight-bearing full-length X-ray images and 3D knee joint movement analysis were taken during the follow-up visit six months after surgery.
Statistical analysis
All data processing and statistical analyses were undertaken with sigmaplot 14.0 (Systat Software Inc., San Jose, CA, USA) and SPSS 26.0 (IBM Corp., Armonk, NY, USA), respectively. 6DOF of different groups and HKA measured by 3D knee joint movement analysis system were computed and compared to the HKA values (X-ray) using the Student's t test and the linear correlation analysis. Pearson correlation coefficients between 6 DOF and HKA values were analysed for the whole cohort and the different groups separately. Significance was set at an alpha of 0.05.