Tibial Component Migration After Total Knee Arthroplasty With High-Viscosity Bone Cement

BackgroundHigh-viscosity (HV) bone cements have been formulated to offer potentially advantageous handling characteristics. However, alteration in the handling characteristics could influence implant fixation and survival. The primary objective of this study was to use radiostereometric analysis after total knee arthroplasty to assess the migration of the Triathlon tibial component fixed with HV cement (Simplex HV).MethodsTwenty-three patients were followed for two years with radiostereometric analysis examinations at 6 visits. Migration was compared with published thresholds and with a control group from a previously published study from the same center using the same implants fixed with a medium viscosity cement. Inducible displacement was assessed, and Oxford 12 Knee Scores and satisfaction were recorded.ResultsMean maximum total point motion migration reaching 0.40 mm (SD 0.16) at one year, and 0.41mm (SD 0.17) at two years, demonstrating a pattern of stable fixation, below published thresholds of acceptable migration, and not significantly different from the control group. One implant had continuous migration between 1 and 2 years but was clinically asymptomatic. Mean maximum total point motion inducible displacement measured at least one year postoperatively was 0.3 mm (SD 0.12). Mean Oxford 12 Knee Scores improved from 19 (SD 7) preoperatively to 42 (SD 8) 2 years postoperatively.ConclusionsThe use of HV cement demonstrated an acceptable pattern of migration at 2 years, indicating low risk for aseptic loosening.     

Contact Kinematic Differences Between Gap Balanced vs Measured Resection Techniques for Single Radius Posterior-Stabilized Total Knee Arthroplasty

Background

Measured resection (MR) and gap balancing (GB) are common surgical techniques for total knee arthroplasty (TKA). Controversy has arisen as each conceptually differs in how the knee is balanced through bone and soft tissue management. The objective of the present study was to compare both the frequency of condylar liftoff and the location of femorotibial contact from extension through midflexion between patients undergoing GB or MR TKA.

Comparison of Contact Kinematics in Posterior-Stabilized and Cruciate-Retaining Total Knee Arthroplasty at Long-Term Follow-Up

BackgroundThere is controversy regarding the superiority of posterior-stabilizing (PS) total knee arthroplasty (TKA) and cruciate-retaining (CR) TKA. Substantial work has made comparisons between PS and CR TKA at follow-ups of less than 5 years. It was the goal of the present study to compare the kinematics at greater than 5 years postoperatively between CR and PS TKA, with a secondary goal of comparing patient function.MethodsA total of 42 knees were investigated, with equal representation in the PS and CR TKA groups. Patients underwent radiostereometric analysis imaging at 0°, 20°, 40°, 60° 80°, and 100° of flexion. Contact position, magnitude of excursion, and condylar separation on each condyle were measured. A Timed-Up-and-Go functional test was also performed by patients, with the total test time being measured. Preoperative and postoperative clinical outcome scores were also collected.ResultsThere were differences in contact position on both the medial and lateral condyles at multiple angles of flexion (P < .05). There was no difference (P = .89) in medial excursion; however, PS TKA had greater lateral excursion than CR TKA (P < .01). No difference (P > .99) was found in frequency of condylar separation. PS TKA was associated with faster (P = .03) total Timed-Up-and-Go test times. There were no differences in clinical outcome scores between the groups preoperatively or postoperatively.ConclusionWe found kinematic and functional differences that favor PS TKA. Our results suggest posterior cruciate ligament insufficiency in CR TKA, indicating that perhaps the cam/post systems in PS TKA better maintain knee kinematics and function long term.     

Posterior Femoral Condylar Offset After Total Knee Replacement in The Risk of Knee Flexion Contracture

The aim of this study was to clarify the risk of knee flexion contracture associated with a posterior femoral condylar offset after total knee replacement (TKR). Radiographs from 100 healthy Japanese volunteers were included in the study. We evaluated femoral component posterior offset in various implants and compared them with the normal Japanese knee. Posterior offset of the femoral condyle is up to a maximum of 4.7 times greater than that of the healthy Japanese knee in all knee implants. Excess posterior offset of the femoral condyle in TKR prostheses may cause knee joint flexion contracture due to the relative shortening of the posterior soft tissue.     

The Effect of Bone Quality on Tibial Component Migration in Medial Cemented Unicompartmental Knee Arthroplasty. A Prospective Cohort Study Using Dual X-Ray Absorptiometry and Radiostereometric Analysis

BackgroundPeriprosthetic bone mineral density (BMD) may influence implant fixation and subsequent loosening. Unicompartmental knee arthroplasty (UKA) restores normal knee kinematics and load distribution to the surrounding bone. We studied the influence of systemic and periprosthetic BMD of the proximal tibia on migration of the tibial component of cemented medial UKA.MethodsThe cohort was dichotomized into a normal BMD group (T-score ≥ −1; n = 37) and a low BMD group (T-score < −1; n = 28) according to World Health Organization criteria. BMD of the proximal tibia and migration of the tibial component were measured with dual X-ray absorptiometry scans and stereoradiographs with 2-year follow-up.ResultsPatients with normal systemic BMD had an 11% to15% higher BMD in all regions of interest (ROIs) compared to patients with low systemic BMD throughout follow-up. Over time, a decrease in periprosthetic BMD in ROI 1-3 was seen for both groups. The operated knees and contralateral knees showed a similar reduction in BMD in all ROIs between preoperative and 24 months.Between 12 and 24 months, the normal BMD group migrated (maximal total point motion) 0.03 mm (95% confidence interval, −0.01, 0.08) and the low BMD group migrated 0.02 mm (95% confidence interval, −0.03, 0.07). Migration over time was not influenced by change in periprosthetic BMD.ConclusionMigration of cemented medial tibial UKA was low until 24 months and was neither affected by preoperative systemic BMD nor affected by postoperative change in periprosthetic BMD. This suggests good long-term fixation despite an index difference in proximal tibial BMD.     

Influence of Posterior Tibial Slope on Kinematics After Cruciate-Retaining Total Knee Arthroplasty

Background

The purpose of this study was to investigate the influence of posterior tibial slope (PTS) on knee kinematics after cruciate-retaining total knee arthroplasty (CR-TKA). These influences were evaluated using a prosthesis designed with high geometric conformity to the medial articular surface under the weight-bearing condition of deep knee bending.

Correlation Between Knee Kinematics and Patellofemoral Contact Pressure in Total Knee Arthroplasty

The aim of this study is to evaluate the relationship between patellofemoral contact stress and intraoperative knee kinematic patterns after mobile bearing total knee arthroplasty (TKA). Medial osteoarthritic knees of forty-six posterior-stabilized total knee prostheses were evaluated using a computed tomography-guided navigation system. Subjects were divided into two groups based on intraoperative knee kinematic patterns: the medial pivot group (n = 19) and the non-medial pivot group (n = 27). Mean intraoperative patello-femoral contact stress was significantly lower in the medial pivot group than in the non-medial pivot group (1.7 MPa vs. 3.2 MPa, P < 0.05). An intraoperative medial pivot pattern results in reduced patello-femoral contact stress.     

Effects of Posterior Tibial Slope on a Posterior Cruciate Retaining Total Knee Arthroplasty Kinematics and Kinetics

BackgroundIt has been hypothesized that increasing posterior tibial slope can influence condylar rollback and play a role in increasing knee flexion. However, the effects of tibial slope on knee kinematics are not well studied. The objective of this study is to assess the effects of tibial slope on femorotibial kinematics and kinetics for a posterior cruciate retaining total knee arthroplasty design.MethodsA validated forward solution model of the knee was implemented to predict the femorotibial biomechanics of a posterior cruciate retaining total knee arthroplasty with varied posterior slopes of 0°-8° at 2° intervals. All analyses were conducted on a weight-bearing deep knee bend activity.ResultsIncreasing the tibial slope shifted the femoral component posteriorly at full extension but decreased the overall femoral rollback throughout flexion. With no tibial slope, the lateral condyle contacted the polyethylene 6 mm posterior of the midline, but as the slope increased to 8°, the femur shifted an extra 5 mm, to 11 mm posterior of the tibial midline. Similar shifts were observed for the medial condyle, ranging from 7 mm posterior to 13 mm posterior, respectively. Increasing posterior slope decreased the posterior cruciate ligament tension and femorotibial contact force.ConclusionThe results of this study revealed that, although increasing the tibial slope shifted the femur posteriorly at full extension and maximum flexion, it reduced the amount of femoral rollback. Despite the lack of rollback, a more posterior location of condyles suggests lower chances of bearing impingement of the posterior femur and may explain why increasing slope may lead to higher knee flexion.     

In Vivo Knee Kinematics for a Cruciate Sacrificing Total Knee Arthroplasty Having Both a Symmetrical Femoral and Tibial Component

BackgroundEarly total knee arthroplasty (TKA) designs were symmetrical, but lead to complications due to over-constraint leading to loosening and poor flexion. Next-generation TKAs have been designed to include asymmetry, pertaining to the trochlear groove, femoral condylar shapes, and/or the tibial component. More recently, an advanced posterior cruciate sacrificing (PCS) TKA was designed to include both a symmetrical femoral component with a patented V-shaped trochlear groove and a symmetrical tibial component with an ultracongruent insert, in an attempt to reduce inventory costs. Because previous PCS TKA designs produced variable results, the objective of this study is to determine and evaluate the in vivo kinematics for subjects implanted with this symmetrical TKA.MethodsTwenty-one subjects, implanted with symmetrical PCS fixed-bearing TKA, were asked to perform a weight-bearing deep knee bend (DKB) while under fluoroscopic surveillance. A 3-dimensional to 2-dimensional registration technique was used to determine each subject’s anteroposterior translation of lateral and medial femoral condyles as well as tibiofemoral axial rotation and their weight-bearing knee flexion.ResultsDuring the DKB, the average active maximum weight-bearing flexion was 111.7° ± 13.3°. On average, from full extension to maximum knee flexion, subjects experienced −2.5 ± 2.0 mm of posterior femoral rollback of the lateral condyle and 2.5 ± 2.2 mm of medial condyle motion in the anterior direction. This medial condyle motion was consistent for the majority of the subjects, with the lateral condyle exhibiting rollback from 0° to 60° of flexion and then experienced an average anterior motion of 0.3 mm from 60° to 90° of knee flexion. On average, the subjects in this study experienced 6.6°± 3.3° of axial rotation, with most of the rotation occurring in early flexion, averaging 4.9°.ConclusionAlthough subjects in this study were implanted with a symmetrical PCS TKA, they did experience femoral rollback of the lateral condyle and a normal-like pattern of axial rotation, although less in magnitude than the normal knee. The normal axial rotation pattern occurred because the lateral condyle rolled in the posterior direction, while the medial condyle moved in the anterior direction. Interestingly, the magnitude of posterior femoral rollback and axial rotation for subjects in this study was similar in magnitude reported in previous studies pertaining to asymmetrical TKA designs. It is proposed that more patients be analyzed having this TKA implanted by other surgeons.     

Does Maximal External Tibial Component Rotation Influence Tibiofemoral Load Distribution in the Primary Knee Arthroplasty Setting: A Comparison of Neutral vs Maximal Anatomical External Rotatory States

Background

Tibial component rotation at time of knee arthroplasty can influence conformity, load transmission across the polyethylene surface, and perhaps ultimately determined survivorship. Optimal tibial component rotation on the cut surface is reliant on standard per operative manual stressing. This subjective assessment aims to balance constraint and stability of the articulation through a full arc of movement.

Design Modifications May Improve Range of Motion Following Posteriorly Stabilized Total Knee Replacement: a Matched Pair Study

Background

Our institution’s latest knee implant design modifications aimed to decrease anterior knee pain, reduce the amount of bone that is resected in the femoral box, and improve range of motion.

Questions/Purposes

Does this new knee design achieve desired clinical improvement in our patient population? This study was designed to compare our new design to that of its predecessor in a matched pair analysis.

Methods

A consecutive group of 100 knees underwent total knee arthroplasty using the newer box reamer (BR) posterior-stabilized design was matched by age, gender, and body mass index (BMI) to patients with the classic posterior-stabilized (PS) component. Average follow-up was 29.6 months (range 21–47) in the new group. Preoperative range of motion (ROM) and clinical scores, such as Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society Scores, were obtained and compared to the patients’ most recent follow-up. Manipulation under anesthesia (MUA) and revision of the implant for any reason were also analyzed. Ability to attain ROM of >120°, >130°, and >140° was also determined in each cohort.

Results

At 2-year follow-up, 41% of BR knees achieved >130° flexion compared with 19% in the PS design group. WOMAC improved from pre-op 47 to 80 at 1 year in the newer BR design group and 48 to 80 in the classic PS design group. There were 9 MUAs in the newer BR design group compared with 14 in the classic PS design group. There were three revisions in the PS group and none in the BR group.

Conclusions

Design improvements to this newer knee allowed more patients to achieve greater flexion and appear to have achieved clinical and design goals of the engineering modifications.

Electronic supplementary material

The online version of this article (doi:10.1007/s11420-014-9402-z) contains supplementary material, which is available to authorized users.     

A Randomized Controlled Trial Comparing a Medial Stabilized Total Knee Prosthesis to a Cruciate Retaining and Posterior Stabilized Design: A Report of the Clinical and Functional Outcomes Following Total Knee Replacement

BackgroundThe purpose of this randomized controlled trial was to compare the performance of 3 total knee joint replacement (TKJR) designs 6 months after the surgery.MethodsPatients were recruited between March 2015 and March 2018. Patients with osteoarthritis consented for TKJR were randomly allocated to a medial stabilized (MS), cruciate retaining (CR), or posterior stabilized (PS) design. Primary outcome measures were self-reported improvement in pain and function 6 months after TKJR, using the Oxford Knee Score. Secondary outcome measures were the Western Ontario and McMaster Universities Osteoarthritis Index, Veterans RAND 12-item Health Survey, Knee Society Score 2011, Timed Up and Go test, and Six-Minute Walk Test. Twelve-month outcomes were also measured.ResultsNinety participants enrolled, 83 were randomized: PS (n = 26), CR (n = 28), and MS (n = 29) designs. One case withdrew before surgery: planned use of non-study implant; 7 did not complete all outcome measures. No 6-month between-group difference was observed for the primary outcome. A 6-month difference was observed in Knee Society Score 2011 Satisfaction: MS favored over CR and PS. Clinically meaningful 12-month differences in Western Ontario and McMaster Universities Osteoarthritis Index Pain, Function, and Global Subscales were observed: MS favored over CR. Twelve-month differences occurred in Veterans RAND 12-item Health Survey mental well-being, favoring MS and PS over CR.ConclusionMS prosthesis can be expected to yield similar clinical and functional outcomes to PS and CR designs 6 months after TKJR, and patients were more satisfied with their outcome. Compared with CR, patients with MS prosthesis also reported superior pain, function, and quality-of-life outcomes at 12 months.     

Stair Climbing and High Knee Flexion Activities in Bi-Cruciate Retaining Total Knee Arthroplasty: In Vivo Kinematics and Articular Contact Analysis

Background

Bi-cruciate retaining (BCR) total knee arthroplasty (TKA) preserves both anterior and posterior cruciate ligaments with the potential to restore normal posterior femoral rollback and joint kinematics. However, there is limited information regarding articular contact behavior in the contemporary BCR TKA design during high knee flexion activities. This study aimed to investigate the articular knee contact performance in unilateral BCR TKA patients during strenuous flexion activities.

Bi‐Cruciate Retaining Total Knee Arthroplasty Does Not Restore Native Tibiofemoral Articular Contact Kinematics During Gait

Bi‐cruciate retaining (BCR) total knee arthroplasty (TKA) design preserves both anterior and posterior cruciate ligaments with the potential to restore normal posterior femoral rollback and joint kinematics. Abnormal knee kinematics and “paradoxical” anterior femoral translation in conventional TKA designs have been suggested as potential causes of patient dissatisfaction. However, there is a paucity of data on the in vivo kinematics and articular contact behavior of BCR‐TKA. This study aimed to investigate in vivo kinematics, articular contact position, and pivot point location of the BCR‐TKA during gait. In vivo kinematics of 30 patients with unilateral BCR‐TKA during treadmill walking was determined using validated dual fluoroscopic imaging tracking technique. The BCR‐TKA exhibited less extension than the normal healthy knee between heel strike and 48% of gait cycle. Although the average external rotation trend observed for BCR TKA was similar to the normal healthy knee, the range of motion was not fully comparable. The lowest point of the medial condyle showed longer anteroposterior translation excursion than the lateral condyle, leading to a lateral‐pivoting pattern in 60% of BCR TKA patients during stance phase. BCR‐TKA demonstrated no statistical significant differences in anterior–posterior translation as well as varus rotation, when compared to normal healthy knees during the stance phase. However, sagittal plane motion and tibiofemoral articular contact characteristics including pivoting patterns were not fully restored in BCR TKA patients during gait, suggesting that BCR TKA does not restore native tibiofemoral articular contact kinematics. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1929–1937, 2019     

Effect of Medial Soft Tissue Releases During Posterior-Stabilized Total Knee Arthroplasty on Contact Kinematics and Patient-Reported Outcomes

BackgroundMinimal to extensive medial soft tissue releases are part of the exposure and achieving adequate varus knee balance in total knee arthroplasty (TKA). However, the effect of these releases on knee kinematics and patient-reported outcomes is unclear. Our objective was to compare the postoperative in vivo tibiofemoral contact kinematics of a posterior-stabilized TKA between patients who received minimal medial soft tissue releases intraoperatively to those who received extensive releases. We also compared these groups using patient-reported outcomes.MethodsA prospective imaging study was performed in a single-center over a 14-month period. Patients with end-stage osteoarthritis and varus deformity undergoing primary TKA were included. Baseline data were collected 1 month before surgery. The radiostereometric analysis imaging took place at least 1 year postoperatively and composed of weight-bearing radiographic stereo examinations of knee flexion starting in full extension and in 20° increments of flexion to a maximum of 120°. Intraoperative medial soft tissue releases were recorded. Patient-reported outcomes used included Short-Form 12, Western Ontario and McMaster Osteoarthritis Index, and Knee Society Score.ResultsFifty-one patients were included in the statistical analysis. Demographic characteristics were similar between all. Patients were divided into 3 groups depending on the amount of releases they received. No statistically significant differences in tibiofemoral contact positions or excursions on the medial or lateral condyles were found throughout flexion from 0° to 120°. Postoperative patient-reported outcome scores were not different.ConclusionCorrecting severe varus deformities with extensive medial soft tissue release largely did not alter knee kinematics or clinical outcome scores compared to those with minimal soft tissue release.     

Post-Cam Design and Contact Stress on Tibial Posts in Posterior-Stabilized Total Knee Prostheses: Comparison Between a Rounded and a Squared Design

Background

The post-cam mechanism in posterior stabilized (PS) prostheses plays an important role in total knee arthroplasty (TKA). The purpose of this study is to clarify the difference of the contact stress on the tibial post between a rounded post-cam design and a squared design during deep knee flexion and at hyperextension using the three-dimensional (3D) finite element models.