Kinematics of the stiff total knee arthroplasty

The kinematics of 10 total knee replacements with poor flexion (<90°) were compared with 11 replacements with good flexion (>110°) at a mean of 3 years from surgery using optical calibration with implant shape-matching techniques from radiographs taken in standing, early-lunge, and late-lunge positions. There were no significant differences between groups in anteroposterior translation of the medial and lateral femoral condyles or tibial rotation during standing and early lunge. Groups differed in amount of posterior translation of the femoral condyles during late lunge because of the poor-flexion group's inability to achieve the same amount of flexion as the good-flexion group. Poor flexion after total knee arthroplasty, we conclude, is not associated with abnormal kinematics in the setting of well-aligned, well-fixed implants.     

In vivo comparison of knee kinematics for subjects having either a posterior stabilized or cruciate retaining high-flexion total knee arthroplasty

The objective of this study was to determine the in vivo kinematics for subjects having either a fixed posterior stabilized (PS) or cruciate retaining (CR) high-flexion total knee arthroplasty (TKA). Three-dimensional kinematics from full extension to maximum flexion were determined for 30 subjects (15 PS, 15 CR) using fluoroscopy. On average, the PS subjects demonstrated 112 degrees of weight-bearing (WB) flexion, -6.4 mm of posterior femoral rollback, and 2.9 degrees of axial rotation. The CR subjects averaged 117 degrees of WB flexion, -4.9 mm of posterior femoral rollback, and 4.8 degrees of axial rotation. Posterior femoral rollback of the lateral condyle occurred for all PS TKAs and in 93% of the CR TKAs. Only 2 subjects in each group experienced greater than 1.0 mm of condylar lift-off. Subjects in both TKA groups demonstrated excellent WB ranges of motion and kinematic patterns similar to the normal knee, but less in magnitude.     

The posterior cruciate ligament in total knee arthroplasty

The purpose of this study was to answer 2 questions: Does the posterior cruciate ligament (PCL) produce femoral rollback in a single-design, cruciate-sparing total knee arthroplasty (TKA)? Does the PCL prevent posterior tibial displacement when it is retained after a single-design, cruciate-sparing TKA? Knee kinematics and limits of motion were measured with the knees in the following states: (1) intact knee, (2) anterior cruciate-deficient knee, (3) PCL-retaining total knee of a single design (TKA), (4) PCL-retaining TKA with PCL cut, and (5) PCL-substituting TKA. Femoral rollback was then calculated from the above data. The results showed that the PCL was able to prevent posterior translation and maintain femoral rollback when it was preserved during TKA. Therefore, the PCL can be functional after TKA, in a single-design, cruciate-sparing TKA. When the PCL was cut, significant changes in knee kinematics were observed.     

Intraoperative passive kinematics of osteoarthritic knees before and after total knee arthroplasty.

Total knee arthroplasty is a successful procedure to treat pain and functional disability due to osteoarthritis. However, precisely how a total knee arthroplasty changes the kinematics of an osteoarthritic knee is unknown. We used a surgical navigation system to measure normal passive kinematics from 7 embalmed cadaver lower extremities and in vivo intraoperative passive kinematics on 17 patients undergoing primary total knee arthroplasty to address two questions: How do the kinematics of knees with advanced osteoarthritis differ from normal knees?; and, Does posterior substituting total knee arthroplasty restore kinematics towards normal? Osteoarthritic knees displayed a decreased screw‐home motion and abnormal varus/valgus rotations between 10° and 90° of knee flexion when compared to normal knees. The anterior–posterior motion of the femur in osteoarthritic knees was not different than in normal knees. Following total knee arthroplasty, we found abnormal varus/valgus rotations in early flexion, a reduced screw‐home motion when compared to the osteoarthritic knees, and an abnormal anterior translation of the femur during the first 60° of flexion. Posterior substituting total knee arthroplasty does not appear to restore normal passive varus/valgus rotations or the screw motion and introduces an abnormal anterior translation of the femur during intraoperative evaluation. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1607–1614, 2006     

Kinematic analysis of a posterior cruciate retaining mobile-bearing total knee arthroplasty

Using video fluoroscopy, 10 subjects having a mobile-bearing posterior cruciate-retaining total knee arthroplasty were analyzed to determine their in vivo kinematic patterns. Under weight-bearing conditions, while in extension, the average contact position was posterior to the mid-tibia sagittal plane with posterior translation of both condyles to 60 degrees of flexion, followed by anterior translation to 120 degrees of flexion. Under non-weight-bearing conditions, the average condylar contact positions were significantly more anterior from full extension to 90 degrees of knee flexion (P=.01). The average range of motion was 129 degrees under non-weight-bearing conditions and 119 degrees during weight-bearing. Although subjects in this study exhibited variable motion patterns, they are accommodated by the unconstrained optimized articulation of this highly conforming mobile-bearing implant.     

Midterm results of cruciate retaining total knee arthroplasty in patellectomized patients

Background:

Total knee arthroplasty (TKA) in patellectomized patients gives inferior results when compared with those in which the patella is present. The literature is ambiguous about the role of cruciate retaining or sacrificing implants for these knees. In this study, we assessed the midterm results of TKA in patellectomized knees using a cruciate retaining implant.

Materials and Methods:

Thirty three patients with a prior patellectomy underwent a cruciate retaining TKA and were followed up for an average of 9.3 years (range 2-14 years). At each followup visit, they were evaluated clinically, radiologically and by the Hospital for Special Surgery Scoring System.

Results:

Twenty one knees did not have any pain or difficulty in climbing stairs, 10 knees were slightly painful on stairs but pain free on walking on flat ground and two knees experienced mild to moderate pain on walking up and down stairs as well as on flat ground. The average range of motion preoperatively was 87°, which postoperatively increased to 118°. The average Hospital for Special Surgery Knee scores increased from 52 to 89 points. None of the knees showed any progressive radiolucencies or evidence of any loosening/osteolysis or fractures in followup.

Conclusion:

Cruciate retaining TKA offers good results at midterm followup in patients with a prior patellectomy.     

In vivo determination of total knee arthroplasty kinematics: a multicenter analysis of an asymmetrical posterior cruciate retaining total knee arthroplasty

The objective of this study was to determine if consistent posterior femoral rollback of an asymmetrical posterior cruciate retaining (PCR) total knee arthroplasty was mostly influenced by the implant design, surgical technique, or presence of a well-functioning posterior cruciate ligament (PCL). Three-dimensional femorotibial kinematics was determined for 80 subjects implanted by 3 surgeons, and each subject was evaluated under fluoroscopic surveillance during a deep knee bend. All subjects in this present study having an intact PCL had a well-functioning PCR knee and experienced normal kinematic patterns, although less in magnitude than the normal knee. In addition, a surprising finding was that, on average, subjects without a PCL still achieved posterior femoral rollback from full extension to maximum knee flexion. The findings in this study revealed that implant design did contribute to the normal kinematics demonstrated by subjects having this asymmetrical PCR total knee arthroplasty.     

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     

Range of motion of standard and high-flexion cruciate retaining total knee prostheses

Recently, use of high-flexion design was introduced in cruciate-retaining (CR) total knee prostheses. The purpose of this study was to prospectively compare the ranges of motion (ROMs) of 89 knees with standard and 87 knees with high-flexion CR total knee prostheses. Differences in age, gender, diagnosis, preoperative ROM of the knee, and Knee Society Score between the 2 groups were not statistically significant. At 12-month follow-up, average ROM was 112.0 degrees +/- 12.6 degrees for standard, and 115.3 degrees +/- 13.4 degrees for high-flexion CR prosthesis (P = .101). To our knowledge, this is the first report on the ROM with the high-flexion CR total knee prosthesis. Using the technique of anterior referencing for femoral component sizing and using a fixed 7 degrees slope for the tibial component, we found no significant differences between groups with regard to ROM, clinical, or radiographic parameters.     

Sagittal laxity after posterior cruciate ligament-retaining mobile-bearing total knee arthroplasty

Posterior cruciate ligament stretching after posterior cruciate ligament-retaining (CR) total knee arthroplasty (TKA) can lead to an increase in sagittal laxity, knee dysfunction, or accelerated damage to the tibial bearing surface. We conducted a prospective study on 74 consecutive mobile-bearing CR TKA to determine if knee laxity changed with time or if knees with large initial laxity experienced greater increases in laxity. Patients were studied with radiographic posterior and anterior drawer examinations at 3 and 23 months. Model-based shape-matching techniques were used to measure TKA kinematics. We found a 1-mm increase in posterior drawer. Knees with large postoperative drawers did not exhibit increased laxity at last follow-up. The use of a mobile-bearing CR TKA did not significantly modify the midterm knee sagittal laxity.     

Computational analysis of customized cruciate retaining total knee arthroplasty restoration of native knee joint biomechanics

The purpose of this study was to verify if customized prosthesis better preserves the native knee joint kinematics and provides lower contact stress on the polyethylene (PE) insert owing to the wider bone preservation than that of standard off‐the‐shelf prosthesis in posterior cruciate‐retaining type total knee arthroplasty (TKA). Validated finite element (FE) models for were developed to evaluate the knee joint kinematics and contact stress on the PE insert after TKA with customized and standard off‐the‐shelf (OTS) prostheses as well as in normal healthy knee through FE analysis under dynamic loading conditions. The contact stresses on the customized prosthesis decreased by 18% and 8% under gait cycle loading conditions, and 24% and 9% under deep‐knee‐bend loading conditions, in the medial and lateral sides of the PE insert, respectively, compared with the standard OTS prosthesis. The anterior‐posterior translation and internal‐external (IE) rotation in customized TKA were more similar to native knee joint behaviors compared with standard OTS TKA under gait loading conditions. The difference from normal knee kinematics was lower for femoral rollback and IE rotation in customized TKA than in standard OTS TKA in the deep‐knee‐bend condition. In general, customized prostheses achieve kinematics that are close to those of the native healthy knee joint and have better contact stresses than standard OTS prostheses in gait and deep‐knee‐bend loading conditions.     

Total knee arthroplasty with posterior cruciate ligament retention

Total knee arthroplasty with posterior cruciate ligament retention requires strict attention to the restoration of femoraland tibial anatomy, restoration of the joint line, and soft-tissue balancing. Component sizing and orientation are dependent on an understanding of normal knee anatomy and play a critical role in the success of the reconstruction. The results of knee arthroplasty with this technique have been excellent, and with continued refinements in prosthesis design and polyethylene manufacturing and sterilization, total knee arthroplasty with posterior cruciate ligament retention should continue to play a significant role in the management of patients with debilitating arthritis of the knee.     

不均匀沉降术与全膝关节置换术治疗内侧间室膝关节骨性关节炎的对比分析

目的评价不均匀沉降术与全膝关节置换术(TKA)治疗内侧间室膝关节骨性关节炎(KOA)的临床效果。方法 34例KOA患者,左膝14例,右膝20例,均为内侧间室受累为主的KOA患者。根据手术方法的不同将34例患者分为不均匀沉降术组(16例,观察组)和TKA组(18例,对照组),对两组患者术后膝关节疼痛缓解程度、HSS膝关节评分以及住院时间和治疗费用进行比较。结果 34例患者术后均获随访,随访时间12~36个月,平均(15.00±6.17)个月。观察组患者术后VAS评分、术后优良率、HSS评分虽劣于对照组,但组间比较差异无统计学意义(P0.05);观察组治疗费用、住院时间少于对照组,差异有统计学意义(P0.05)。结论应用不均匀沉降术治疗内侧间室KOA,有创伤小、操作简单、住院时间短、费用低廉、疗效确切。     

Management options for total knee arthroplasty in osteoarthritic knees with extra-articular tibial stress fractures: a 5-year experience

Difficult primary knees are fairly common in Asian countries, and tibial stress fractures in deformed osteoarthritic knees add to the challenge. Management options are ill-defined because of limited experience; for 5 years, 8 osteoarthritic knees with extra-articular tibial stress fractures ranging from unicortical stress lesions to frankly mobile fractures were managed by total knee arthroplasty. At mean 42.25 months follow-up, average Knee Society Score improved from 23.62 to 80.87; and average functional score improved from 18.75 to 67.75. All 8 fractures united; 1 (plate plus stem extender) had wound breakdown and delayed union. We present our learning experience with single-stage modular total knee arthroplasty using stem extenders or plates; with proper planning and additional use of image intensifier, these unique cases can reliably be managed with satisfactory outcomes.     

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.     

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.     

Measurement of knee joint gaps without bone resection: “Physiologic” extension and flexion gaps in total knee arthroplasty are asymmetric and unequal and anterior and posterior cruciate ligament resections produce different gap changes

General agreement is that flexion and extension gaps should be equal and symmetrical in total knee arthroplasty (TKA) procedures. However, comparisons using a standard TKA approach to normal knee joints that have not undergone bone resection are currently unavailable. Since bony preparation can influence capsule and ligament tension, our purpose was to perform measurements without this influence. Ten normal cadaveric knees were assessed using a standard medial parapatellar TKA approach with patellar subluxation. Gap measurements were carried out twice each alternating 100 and 200 N per compartment using a prototypical force‐determining ligament balancer without the need for bony resection. Initial measurements were performed in extension, followed by 90° of flexion. The ACL was then resected, and finally the PCL was resected, and measurements were carried out in an analogous fashion. In general, the lateral compartment could be stretched further than the medial compartment, and the corresponding flexion gap values were significantly larger. ACL resection predominantly increased extension gaps, while PCL resection increased flexion gaps. Distraction force of 100 N per compartment appeared adequate; increasing to 200 N did not improve the results. © 2011 Orthopaedic Research Society. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:522–527, 2012     

Impact of medial opening or lateral closing tibial osteotomy on bone resection and posterior cruciate ligament integrity during knee arthroplasty

To compare lateral closing to medial opening wedge high tibial osteotomy regarding change in proximal tibial anatomy and PCL tibial attachment integrity after standard tibial arthroplasty resection. Controlled cadaveric study. Ten cadaveric lower limbs received either a 12° lateral closing or 12.5-mm medial opening wedge high tibial osteotomy. Radiographs were performed before and after each osteotomy, and each PCL tibial attachment was dissected. Postosteotomy, tibial arthroplasty resection was performed and the remaining PCL attachment area calculated. Lateral closing wedge specimens demonstrated a greater change in proximal tibial anatomy. After tibial arthroplasty resection, there was a significant difference in remaining PCL tibial attachment percentage area. Proximal tibial anatomy is altered differently for each type of osteotomy despite similar correction angles. Arthroplasty conversion may be more challenging after lateral closing wedge procedures.     

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.