In vivo kinematic analysis of a high-flexion posterior stabilized fixed-bearing knee prosthesis in deep knee-bending motion

The objective of this study was to evaluate in vivo kinematics of a high-flexion, posterior-stabilized fixed-bearing, total knee arthroplasty in weight-bearing deep knee-bending motion. A total of 20 knees implanted with the Scorpio Non-Restrictive Geometry knee system in 17 patients were assessed in this study. The Scorpio Non-Restrictive Geometry is a recent implant design with modifications made to accommodate a higher flexion range of motion and greater axial rotation, particularly during more functionally demanding activities. Patients were examined during a deep knee-bending motion using fluoroscopy, and femorotibial motion was determined using a 2-dimensional to 3-dimensional registration technique. The average flexion angle was 126.5° (110°-149°). The femoral component demonstrated a mean of 13.5° (5.2°-21°) external rotation. The external rotation increased up to maximum flexion. The pivot pattern was a medial pivot pattern similar to that reported in normal knee kinematics.     

The effect of preoperative knee deformity on the initial results of cruciate-retaining total knee arthroplasty

Between November 1985 and June 1987, 751 posterior cruciate-sparing total knee arthroplasties were performed on 523 patients who exhibited fixed varus or valgus deformities. Patients excluded from this study included the following: those with a postoperative follow-up period of less than 2 years (including patients who had died), patients who became infected, and patients with previous failed total knee arthroplasty in the same knee. A total of 473 knees left for evaluation. All arthroplasties were measured using anatomic axis for alignment measurement. The Hospital for Special Surgery scoring system was used to determine the clinical scores prior to the end of each follow-up examination. All ligament releases were performed sequentially, including balancing of the posterior cruciate ligament. All arthroplasties were divided into six separate groups depending upon the degree of varus or valgus deformity. Kaplan-Meier curves were constructed using three methods of failure definition. Curves were then compared between groups. The mean Hospital for Special Surgery score was no different between any of the groups, except for the group of 6 degrees-10 degrees varus, which was significantly higher than the mean score of the 11 degrees and higher valgus group. All other groups were the same statistically. It is concluded that severe varus and valgus deformities may be satisfactorily corrected with the use of a cruciate-retaining type of total knee arthroplasty.     

In vivo kinematic analysis of total knee arthroplasty with four different polyethylene designs

The femorotibial contact point on the sagittal plane was measured under weight-bearing conditions in 45 subjects with implanted and nonimplanted knees. They consisted of 11 knees with flat bearing inserts, 16 knees with shallow dished inserts, 10 knees with posterior lipped inserts, 10 knees with posterior stabilized bearing inserts, and 8 normal knees selected as controls. The average amount of anterior translation of the knee with a flat bearing insert was significantly larger than that of the other implanted knees. The average femorotibial contact point did not differ significantly among knees with shallow dished, posterior lipped, and posterior stabilized bearing inserts, but posterior stabilized knees exhibited most frequently a normal posterior movement. Based on our results, it may be safer to use more anteroposterior constrained bearing inserts in total knee arthroplasty, particularly when the posterior cruciate ligament is loose.     

Knee Kinematics in Anterior Cruciate Ligament-Substituting Arthroplasty With or Without the Posterior Cruciate Ligament

Few studies have compared functional kinematics in knees using identical prostheses with or without the posterior cruciate ligament (PCL). This study contrasted in vivo knee kinematics with an anterior cruciate ligament-substituting arthroplasty with and without PCL retention. We hypothesized that knees without PCLs would exhibit less femoral posterior translation, and consequently less maximum knee flexion. Fifty-six knees were studied using dynamic radiography at least one year post-surgery, with twenty-seven knees retaining the PCL and twenty-nine knees having the PCL sacrificed. Consistent with our hypothesis, PCL-sacrificing knees showed more anterior femoral condylar positions. Contrary to our hypothesis, PCL-sacrificing knees demonstrated greater knee flexion during kneeling (122° versus 115°). Contracted PCLs in severely deformed knees likely were the cause of limited flexion in some retaining knees.     

Gait analysis after total knee arthroplasty. Comparison of posterior cruciate retention and substitution

The objective of this study was to measure three-dimensional knee motion during gait in patients with total knee replacements which either retained the posterior cruciate ligament (n = 11), or required sacrifice of the posterior cruciate ligament and replacement of its function with a posterior stabilizing articular surface (n = 9). Clinically meaningful translations (anterior and posterior, medial and lateral, proximal and distal) and rotations (flexion and extension, internal and external rotation, abduction and adduction) were measured using an instrumented spatial linkage. Although patients from both groups were able to achieve passive full extension and a minimum of 95° flexion, some of their translations and rotations during free speed walking were consistently less than those in a group of healthy controls. Motion during the swing phase of gait was similar for both knee replacement groups. However, abduction and adduction and proximal and distal translation were larger (but neither difference was significant) for the patients with implants with a posterior stabilizing surface, which suggests that the stabilizing surface may not reliably provide as much stability in these directions as does retention of the posterior cruciate ligament. Received for publication on Aug. 28, 1997; accepted on June 10, 1998     

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.     

High-flex posterior cruciate-retaining vs posterior cruciate-substituting designs in simultaneous bilateral total knee arthroplasty: a prospective, randomized study

The superiority between the posterior cruciate-retaining and the posterior cruciate-substituting designs still remains controversial. We performed a prospective, randomized control study for evaluation of the superiority of these designs. This study investigated 58 knees in 29 patients with simultaneous bilateral total knee arthroplasty, in which the high-flex CR design was randomly implanted in one knee and the high-flex PS design was implanted in the other knee. The follow-up duration averaged 5.0 years, with a minimum duration of 3 years. Postoperatively, Knee Score and pain points in Knee Score resulted in no significant differences between the 2 designs. However, postoperative arc of range of motion, patient satisfaction, and posterior knee pain at passive flexion in the PS design were significantly superior to that of the CR design.     

Factors affecting flexion gap tightness in cruciate-retaining total knee arthroplasty

With the exception of flexion gap tightness, which is common in cruciate-retaining (CR) total knee arthroplasty (TKA), the risk factors of flexion gap tightness have not been described. This retrospective study characterized factors that are associated with flexion gap tightness in CR TKA. Data on 203 consecutive knees that underwent CR TKA were reviewed. The prevalence rate of flexion gap tightness was 21.1%. By logistic regression analysis after adjusting for age, preoperative flexion contracture, and referencing method used for femoral sizing, insufficient tibial slope remained a significant independent risk factor of flexion gap tightness. Although excessive tibial slope should be avoided, the findings of the present study demonstrate that the risk of flexion gap tightness can be reduced by increasing the tibial slope in CR TKA.     

Long-term survival analysis of the posterior cruciate condylar total knee arthroplasty: A 10-year evaluation

Long-term survivorship analysis was applied to 394 cruciate condylar type total knee arthroplasties. Clinical and radiographic parameters were evaluated. Failure was defined in three separate survival curves as revision, radiographic loosening, and a pain rating of 20 or less on the HSS knee score scale. Survival at 10 years, using only revision or recommended revision as the criterion for failure, was 94.7%. With the addition of the other two criteria, survival fell to 81% at 10 years. The posterior cruciate condylar knee survival is comparable to that of the total condylar knee when using comparable definitions of failure.     

Sagittal laxity in vivo after total knee arthroplasty

Introduction A stress arthrometry study of 77 knees undergoing total knee arthroplasty was performed to determine the difference in anteroposterior (AP) laxity between posterior cruciate ligament (PCL)-retaining (PCLR) and PCL-substituting (PCLS) prostheses using the Genesis I TKA.Materials and methods Fifty-three knees had PCLR and 24 had PCLS prostheses. The selected patients had successful arthroplasties after a minimum follow-up of 5 years. AP laxity was measured with a KT-2000 arthrometer (Medmetric, San Diego, CA, USA) using standard protocols.Results At 30° of flexion, there was no statistical difference in anterior (PCLR: 4.7 mm, PCLS: 4.5 mm), posterior (PCLR: 1.1 mm, PCLS: 0.7 mm), or total (PCLR: 5.8 mm, PCLS: 5.3 mm) displacement. At 75°, significant differences were seen in both anterior (PCLR: 3.3 mm, PCLS: 2.3 mm) and total (PCLR: 4.8 mm, PCLS: 3.4 mm) displacement (p=0.001 and p=0.009, respectively), although there was no statistical difference in posterior displacement (PCLR: 1.5 mm, PCLS: 1.1 mm).Conclusion The above values are considered the suitable degree of AP laxity in total knee arthroplasty for a satisfactory clinical outcome 5–9 years after surgery. The PCL in a PCLR prosthesis and the central tibial spine and femoral cam in a PCLS prosthesis might play comparable roles in determining the laxity in the posterior direction in these prostheses.     

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.     

In vivo knee kinematics during stair and deep flexion activities in patients with bicruciate substituting total knee arthroplasty

Orthopedic surgeons and their patients continue to seek better functional outcomes after total knee arthroplasty. The bicruciate substituting (BCS) total knee arthroplasty design has been introduced to achieve more natural knee mechanics. The purpose of this study was to characterize kinematics in knees with BCS arthroplasty during deep flexion and stair activities using fluoroscopy and model-image registration. In 20 patients with 25 BCS knees, we observed average implant flexion of 128° during kneeling and consistent posterior condylar translations with knee flexion. Tibial rotations were qualitatively similar to those observed in the arthritic natural knee. Knee kinematics with BCS arthroplasty were qualitatively more similar to arthritic natural knees than knees with either posterior cruciate-retaining or posterior-stabilized arthroplasty.     

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.     

Intraoperative soft tissue balance reflects minimum 5-year midterm outcomes in cruciate-retaining and posterior-stabilized total knee arthroplasty

With the use of an offset type tensor for total knee arthroplasties (TKAs), intraoperative soft tissue balance including the joint component gap and ligament balance was measured in 41 varus-type osteoarthritic patients (19 cruciate-retaining [CR] TKAs and 22 posterior-stabilized [PS] TKAs), and the correlations between the intraoperative values and the postoperative values assessed by stress radiographs at extension and flexion were examined at a minimum 5-year follow-up. In CR TKAs, the postoperative soft tissue balances at both angles were significantly correlated with the intraoperative values. In PS TKAs, the postoperative soft tissue balances at extension, not flexion, were significantly correlated with the intraoperative values. In conclusion, the intraoperative condition of the soft tissue balance reflected the postoperative values especially in CR TKAs even at 5-year midterm follow-ups.     

In vivo kinematics of the ACL during weight-bearing knee flexion.

No study has investigated the three-dimensional morphological changes of the anterior cruciate ligament (ACL) during functional activities in vivo. The purpose of this study was to analyze the elongation, rotation (twist), and orientation of the ACL during weight-bearing flexion in five human subjects using dual-orthogonal fluoroscopic images and MR image-based computer models. The ACL consistently decreased in length with flexion. At 90 degrees , the length decreased by 10% compared to its length at full extension. The ACL twisted internally by only 20 degrees at 30 degrees of flexion. The ACL was oriented more vertically (approximately 60 degrees ) and slightly laterally (approximately 10 degrees ) at low flexion angles. These data on in vivo ligament elongation demonstrate that the ACL plays a more important role in lower flexion angles than at higher flexion angles during weight-bearing flexion. These data also suggest that successful ACL reconstruction should not only restore the ligament's elongation behavior, but also its rotational and orientation characteristics, so that normal ACL biomechanics are restored.     

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.     

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.     

The effect of tibial polyethylene insert design on range of motion: evaluation of in vivo knee kinematics by a computerized navigation system during total knee arthroplasty

Computer-assisted navigation for total knee arthroplasty offers the unique opportunity to assess in vivo knee kinematics during surgery and implement changes whenever appropriate. Using a computerized navigation system, the effect of 2 tibial polyethylene insert designs on knee kinematics in general and knee range of motion (ROM) in particular was evaluated in 37 knee arthroplasties in 30 patients. The Scorpioflex tibial insert was found to provide a significant increase in mean extension, mean flexion, and overall ROM of the knee compared with the standard tibial insert (P<.005) without affecting knee ligamentous balance. Navigation is a very effective and useful tool for intraoperative assessment of knee kinematics and accurate recording of ROM. Based on the information obtained from the navigation software, the surgeon can implement changes in selection of the knee components with beneficial effects in knee kinematics in general and knee ROM in particular. This may, in turn, translate to better clinical outcome of the knee arthroplasty.     

Kinematic analysis of kneeling in cruciate‐retaining and posterior‐stabilized total knee arthroplasties

Kneeling is an important function of the knee for many activities of daily living. In this study, we evaluated the in vivo kinematics of kneeling after total knee arthroplasty (TKA) using radiographic based image‐matching techniques. Kneeling from 90 to 120° of knee flexion produced a posterior femoral rollback after both cruciate‐retaining and posterior‐stabilized TKA. It could be assumed that the posterior cruciate ligament and the post‐cam mechanism were functioning. The posterior‐stabilized TKA design had contact regions located far posterior on the tibial insert in comparison to the cruciate‐retaining TKA. Specifically, the lateral femoral condyle in posterior‐stabilized TKA translated to the posterior edge of the tibial surface, although there was no finding of subluxation. After posterior‐stabilized TKA, the contact position of the post‐cam translated to the posterior medial corner of the post with external rotation of the femoral component. Because edge loading can induce accelerated polyethylene wear, the configuration of the post‐cam mechanism should be designed to provide a larger contact area when the femoral component rotates. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:435–442, 2008