Intraoperative passive knee kinematics during total knee arthroplasty surgery

Surgical navigation systems for total knee arthroplasty (TKA) surgery are capable of capturing passive three‐dimensional (3D) angular joint movement patterns intraoperatively. Improved understanding of patient‐specific knee kinematic changes between pre and post‐implant states and their relationship with post‐operative function may be important in optimizing TKA outcomes. However, a comprehensive characterization of the variability among patients has yet to be investigated. The objective of this study was to characterize the variability within frontal plane joint movement patterns intraoperatively during a passive knee flexion exercise. Three hundred and forty patients with severe knee osteoarthritis (OA) received a primary TKA using a navigation system. Passive kinematics were captured prior to (pre‐implant), and after prosthesis insertion (post‐implant). Principal component analysis (PCA) was used to capture characteristic patterns of knee angle kinematics among patients, to identify potential patient subgroups based on these patterns, and to examine the subgroup‐specific changes in these patterns between pre‐ and post‐implant states. The first four extracted patterns explained 99.9% of the diversity within the frontal plane angle patterns among the patients. Post‐implant, the magnitude of the frontal plane angle shifted toward a neutral mechanical axis in all phenotypes, yet subtle pattern (shape of curvature) features of the pre‐implant state persisted. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1611–1619, 2015.     

Kinematics of medial osteoarthritic knees before and after posterior cruciate ligament retaining total knee arthroplasty

Total knee arthroplasty (TKA) is a widely accepted surgical procedure for the treatment of patients with end‐stage osteoarthritis (OA). However, the function of the knee is not always fully recovered after TKA. We used a dual fluoroscopic imaging system to evaluate the in vivo kinematics of the knee with medial compartment OA before and after a posterior cruciate ligament‐retaining TKA (PCR‐TKA) during weight‐bearing knee flexion, and compared the results to those of normal knees. The OA knees displayed similar internal/external tibial rotation to normal knees. However, the OA knees had less overall posterior femoral translation relative to the tibia between 0° and 105° flexion and more varus knee rotation between 0° and 45° flexion, than in the normal knees. Additionally, in the OA knees the femur was located more medially than in the normal knees, particularly between 30° and 60° flexion. After PCR‐TKA, the knee kinematics were not restored to normal. The overall internal tibial rotation and posterior femoral translation between 0° and 105° knee flexion were dramatically reduced. Additionally, PCR‐TKA introduced an abnormal anterior femoral translation during early knee flexion, and the femur was located lateral to the tibia throughout weight‐bearing flexion. The data help understand the biomechanical functions of the knee with medial compartment OA before and after contemporary PCR‐TKA. They may also be useful for improvement of future prostheses designs and surgical techniques in treatment of knees with end‐stage OA. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:40–46, 2011     

Posterior cruciate ligament removal contributes to abnormal knee motion during posterior stabilized total knee arthroplasty

Abnormal anterior translation of the femur on the tibia has been observed in mid flexion (20–60°) following posterior stabilized total knee arthroplasty. The underlying biomechanical causes of this abnormal motion remain unknown. The purpose of this study was to isolate the effects of posterior cruciate ligament removal on knee motion after total knee arthroplasty. We posed two questions: Does removing the posterior cruciate ligament introduce abnormal anterior femoral translation? Does implanting a posterior stabilized prosthesis change the kinematics from the cruciate deficient case? Using a navigation system, we measured passive knee kinematics of ten male osteoarthritic patients during surgery after initial exposure, after removing the anterior cruciate ligament, after removing the posterior cruciate ligament, and after implanting the prosthesis. Passively flexing and extending the knee, we calculated anterior femoral translation and the flexion angle at which femoral rollback began. Removing the posterior cruciate ligament doubled anterior translation (from 5.1 ± 4.3 mm to 10.4 ± 5.1 mm) and increased the flexion angle at which femoral rollback began (from 31.2 ± 9.6° to 49.3 ± 7.3°). Implanting the prosthesis increased the amount of anterior translation (to 16.1 ± 4.4 mm), and did not change the flexion angle at which femoral rollback began. Abnormal anterior translation was observed in low and mid flexion (0–60°) after removing the posterior cruciate ligament, and normal motion was not restored by the posterior stabilized prosthesis. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1494–1499, 2008     

In‐Vivo knee kinematics in rotationally unconstrained total knee arthroplasty

Total knee replacement designs claim characteristic kinematic performance that is rarely assessed in patients. In the present study, in vivo kinematics of a new prosthesis design was measured during activities of daily living. This design is posterior stabilized for which spine–cam interaction coordinates free axial rotation throughout the flexion–extension arc by means of a single radius of curvature for the femoral condyles in the sagittal and frontal planes. Fifteen knees were implanted with this prosthesis, and 3D video‐fluoroscopic analysis was performed at 6‐month follow‐up for three motor tasks. The average range of flexion was 70.1° (range: 60.1–80.2°) during stair‐climbing, 74.7° (64.6–84.8°) during chair‐rising, and 64.1° (52.9–74.3°) during step‐up. The corresponding average rotation on the tibial base‐plate of the lines between the medial and lateral contact points was 9.4° (4.0–22.4°), 11.4° (4.6–22.7°), and 11.3° (5.1–18.0°), respectively. The pivot point for these lines was found mostly in the central area of the base‐plate. Nearly physiological range of axial rotation can be achieved at the replaced knee during activities of daily living. © 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29: 1484–1490, 2011     

计算机导航在人工全膝关节置换术中的应用

近十年来,随着电子计算机技术的飞速发展,骨科手术学进入了一个崭新的研究领域--计算机辅助骨科手术, 亦称为计算机手术导航.该技术是将空间导航技术、计算机图像处理技术与医学影像技术及机器人技术的结合.     

Knee stability before and after total and unicondylar knee replacement: in vivo kinematic evaluation utilizing navigation

Surgical navigation systems are currently used to guide the surgeon in the correct alignment of the implant. The aim of this study was to expand the use of navigation systems by proposing a surgical protocol for intraoperative kinematics evaluations during knee arthroplasty. The protocol was evaluated on 20 patients, half undergoing unicondylar knee arthroplasty (UKA) and half undergoing posterior-substituting, rotating-platform total knee arthroplasty (TKA). The protocol includes a simple acquisition procedure and an original elaboration methodology. Kinematic tests were performed before and after surgery and included varus/valgus stress at 0 and 30 degrees and passive range of motion. Both UKA and TKA improved varus/valgus stability in extension and preserved the total magnitude of screw-home motion during flexion. Moreover, compared to preoperative conditions, values assumed by tibial axial rotation during flexion in TKA knees were more similar to the rotating patterns of UKA knees. The analysis of the anteroposterior displacement of the knee compartments confirmed that the two prostheses did not produce medial pivoting, but achieved a postoperative normal behavior. These results demonstrated that proposed intraoperative kinematics evaluations by a navigation system provided new information on the functional outcome of the reconstruction useful to restore knee kinematics during surgery.     

Component alignment and functional outcome following computer assisted and jig based total knee arthroplasty

Background:

Incorrect positioning of the implant and improper alignment of the limb following total knee arthroplasty (TKA) can lead to rapid implant wear, loosening, and suboptimal function. Studies suggest that alignment errors of > 3° are associated with rapid failure and less satisfactory function. Computer navigated systems have been developed to enhance precision in instrumentation during surgery. The aim of the study was to compare component alignment following computer assisted surgery (CAS) and jig based TKA as well as functional outcome.

Materials and Methods:

This is a prospective study of 100 knees to compare computer-assisted TKA and jig-based surgery in relation to femoral and tibial component alignment and functional outcome. The postoperative x-rays (anteroposterior and lateral) of the knee and CT scanogram from hip to foot were obtained. The coronal alignment of the femoral and tibial components and rotational alignment of femoral component was calculated. Knee society score at 24 months was used to assess the function.

Results:

Results of our study show that mean placement of the tibial component in coronal plane (91.3037°) and sagittal planes (3.6058°) was significantly better with CAS. The difference was statistically insignificant in case of mean coronal alignment of the femoral components (90.34210° in navigation group and 90.5444° in jig group) and in case of the mean femoral condylar twist angle (external rotation 2.3406° in navigation group versus 2.3593° in jig group).

Conclusions:

A significantly improved placement of the component was found in the coronal and sagittal planes of the tibial component by CAS. The placement of the components in the other planes was comparable with the values recorded in the jig-based surgery group. Functional outcome was not significantly different.     

Rotational kinematics of a modern fixed-bearing posterior stabilized total knee arthroplasty

The purpose of this study was to evaluate the rotational kinematics of a fixed-bearing posteriorly stabilized total knee design in moderate and deep flexion. Three-dimensional kinematics analyses were conducted on 20 knees in 4 weight-bearing positions using 3-dimensional shape-matching techniques. Average maximum skeletal flexion was 138 degrees . Internal tibial rotation was demonstrated in 19 of 20 knees. The average internal tibial rotation in midflexed lunge was 5.5 degrees (-3.8 degrees to 14.1 degrees ) and in maximum flexion kneeling was 4.0 degrees (-3.1 degrees to 10.6 degrees ). Separation of articular surfaces was not identified. In this study, patients with this device demonstrated patterns of rotation similar to those previously reported for both the normal knee and rotating platform designs.     

Precise landmarking in computer assisted total knee arthroplasty is critical to final alignment

Image‐free computer navigation systems build a frame of reference of a patient's knee from anatomical landmarks entered by the surgeon during the initial stage of total knee arthroplasty. We performed tibial cuts on 70 sawbones using computer navigation. All landmarks were marked identically except for the tibial mechanical entry point, which was marked correctly in 10 bones and with offsets of 5, 10, and 15 mm medially and laterally in the others. The actual coronal angle of the tibial cuts was measured directly and compared to the final angle given by the navigation system. Significant deviations of the coronal angle were observed in the trial groups. Landmarking errors during navigated TKA can lead to inaccurate tibial bone cuts. This navigation system did not have an iterative software method to verify landmarking errors that can lead to inaccurate tibia bone cuts. Published by Wiley Periodicals, Inc. J Orthop Res 28:1355–1359, 2010     

Continuous passive motion after total knee arthroplasty

Sixty-two patients undergoing primary total knee arthroplasty were studied prospectively. There were 42 patients in whom continuous passive motion (CPM) was used after surgery and 20 controls. The two groups were comparable with respect to age, diagnosis, sex, weight, and preoperative deformity and motion. The mean length of time required for CPM patients to achieve 90 degrees of flexion (9.1 days) was shorter than that for the control group (13.8 days). At the time of discharge from the hospital, however, there was no significant difference between the groups in amount of either flexion or extension. All patients had venograms performed after arthroplasty; the incidence of positive studies indicating thrombophlebitis was 45% in CPM patients and 75% in controls. These data demonstrate that CPM after knee arthroplasty enables patients to recover motion more quickly and affords some protection against deep vein thrombosis.     

Analysis of weight-bearing kinematics of posterior-stabilized total knee arthroplasty with novel helical post-cam design

We developed a new posterior-stabilized total knee arthroplasty (TKA) with a unique post-cam design that induces and accommodates internal tibial rotation with deep knee flexion. To validate the design concept of this system, we conducted an image analysis study employing a computer-aided diagnosis system for 24 TKA-implanted knees. In the analysis, the tibiofemoral relationship in the following 3 postures was evaluated: standing at extension, forward lunge, and kneeling with maximum knee flexion. The results of the image analysis showed achievement of consistent internal rotation of the tibia in deep flexion with a broad contact area at the post-cam interface as intended by the original design concept of this TKA system.     

Custom-fit total knee arthroplasty (OtisKnee) results in malalignment

We report on 4 patients who underwent total knee arthroplasty with OtisKnee system (OtisMed, Hayward, Calif). An image-free computer navigation system was used to evaluate the deformities and the recommended cuts. The recommended custom cuts were as follows: valgus/varus cuts on the femur (5.5 degrees valgus to 0.5 degrees varus) in reference to the mechanical axis, flexion cuts on the femur (4 degrees -9 degrees of flexion); femoral rotation was within 1 degrees of the epicondylar axis; valgus/varus cut on the tibia (3 degrees of valgus to 7.5 degrees of varus); tibial slope (5.5 degrees of anterior slope to 0.5 degrees of posterior slope). The custom OtisKnee system guides recommended alignment of the components that was more than 3 degrees off of mechanical axis. The potential for malalignment with this system places implants at high risk of early failure.     

Bony landmarks and rotational alignment in total knee arthroplasty for Chinese osteoarthritic knees with varus or valgus deformities

The purpose of this study was to investigate the rotational mismatch of total knee arthroplasty when taking the medial one third of the tibial tuberosity as a rotational landmark in Chinese osteoarthritic knees. Computed tomographic images of 49 osteoarthritic knees (42 with varus and 7 with valgus deformities) and 10 healthy knees were analyzed. The angle (alpha) between the 2 baselines for the anteroposterior axis of the femoral and tibial components was measured. The mean value of alpha in healthy knees was +6.45 degrees, which increased significantly to +11.53 degrees in varus knees (P = .002) and +12.17 degrees in valgus knees (P = .04). It showed that there is a tendency for the tibial component to be externally rotated when the medial one third of the tibial tuberosity is defined as a rotational landmark. This finding is particularly prominent in Chinese osteoarthritic knees with varus or valgus deformities.     

Interobserver and intra-observer errors in obtaining visually selected anatomical landmarks during registration process in non-image-based navigation-assisted total knee arthroplasty

This study investigated the errors of obtaining visually selected anatomic landmarks for use in the registration process in a passive optical non-image-based computer-assisted total knee arthroplasty system in 5 fresh frozen cadavers. The projected maximum errors in the femoral mechanical axis (due to registration errors of the center of the distal femur) were 0.7 degrees in the coronal and 1.4 degrees in the sagittal plane. The projected maximum errors in the tibial mechanical axis arising from registration errors of the center of the proximal tibia were 1.3 degrees in the coronal and 2 degrees in the sagittal plane. The projected maximum errors in the transepicondylar axis were 9.1 degrees (registration errors of the medial femoral epicondyle) and 7.2 degrees (registration errors of the lateral femoral epicondyle). It should be noted that the results may be partly related to the use of the particular system in this experiment.     

NexGen LPS Flex全膝关节置换的近期疗效观察

目的探讨高屈曲型NexGen LPS—Flex人工全膝关节置换的近期疗效。方法41例（47膝）行高屈曲型NexGen LPS-Flex人工膝假体置换。术前、术后测量膝关节活动度,并根据HSS膝关节评分系统进行评估。结果获随访32例（38膝）,时间12～42（28．03±8．86）个月。活动度从术前平均67．45°±10．50°改善到术后平均125．68°±10．14°。各种并发症的发生率低。术前HSS评分平均为44．7分±11分,术后HSS评分平均为90．3分±12分;根据HSS评分系统评定疗效：优14例,良16例,中2例,优良率达93．75％。结论高屈曲型NexGen LPS—Flex全膝关节置换的近期临床效果满意,长期效果还需进一步观察。     

全膝关节置换治疗僵硬膝关节的早期疗效分析

目的 评价人工全膝关节置换治疗僵硬膝关节的疗效,探讨术中操作和术后康复的要点.方法 2005年2月至2009年4月,采用人工全膝关节置换治疗僵硬膝关节患者23例34膝,男3例4膝,女20例30膝;年龄25～73岁,平均为56.9岁.临床评价指标包括美国特种外科医院评分(hospital for special surgery knee score,HSS)及关节活动范围,并统计术后并发症.结果 平均随访时间为32.2个月(24～40个月),无失访病例.HSS评分术前平均(42.9±5.2)分(24～66分),术后1个月时平均为(72.4±7.1)分(58～82分),末次随访时平均为(85.7±4.3)分(66～94分),较术前增加42.8分.膝关节屈伸活动范围术前平均为42.6°±5.7°(25°～50°),术后1个月时平均为80.2°±9.2°(60°～105°),末次随访时平均为89.2°±40.5°(60°～110°),较术前增加46.6°.12例16膝因术后活动范围不足90°,在术后3～8周进行静脉麻醉下的手法松解.末次随访时仍有6例8膝活动范围不足90°.结论 术中大范围的软组织松解、术后充分的肌力和活动范围训练是获得良好疗效的关键,对于术后关节活动范围不足的病例应及时采取静脉麻醉下的手法按摩松解.     

Mini-subvastus approach for total knee arthroplasty

The mini-subvastus surgical technique avoids both quadriceps arthrotomy and patella eversion. Since March 2003, this quad-sparing minimally invasive surgical (MIS) technique has been applied to more than 98% of our primary total knee arthroplasty (TKA) patients. This study compares our first 150 MIS TKA patients to our previous 150 traditional TKA patients. Quadriceps recovery was rapid in the MIS group with 83% able to do a straight leg raise the day after surgery. Hospital length of stay was decreased in the MIS group, 3.4 days, vs the traditional group, 4.1 days (P = .00013). Fewer MIS patients required skilled nursing or rehabilitation center admission. Increased knee flexion was seen for the MIS patients throughout the first 2 years of follow-up. Mean knee flexion at 1 year was 127 degrees for the MIS patients vs 114 degrees in the traditional TKA patients (P < .0001). Comparison between the MIS and traditional techniques demonstrated no increase in the number or severity of complications and no difference in operating room time.     

Kneeling kinematics after total knee arthroplasty: anterior-posterior contact position of a standard and a high-flex tibial insert design

Deep flexion activities including kneeling are desired by patients after total knee arthroplasty. This in vivo radiographic study sought to reveal the effect of tibial insert design on tibiofemoral kinematics during kneeling. One group of patients received standard posterior stabilized tibial inserts, whereas the other group received posterior stabilized tibial inserts (Flex inserts) that were designed to allow more flexion. The patients with the Flex inserts achieved greater range of motion without different tibiofemoral contact behavior.