Femoral Rollback Research Articles

L’alignement cinématique d’une prothèse totale de genou reproduit mieux le roulement-glissement et la laxité que l’alignement mécanique : une étude cadavérique comparative

BackgroundA growing body of evidence supports that kinematically aligned (KA) total knee arthroplasty (TKA) provides superior clinical outcomes and satisfaction than mechanically aligned (MA) TKA. In theory, KA TKA would restore knee kinematics closer to the native condition than MA TKA, but the current biomechanical evidence is lacking. HypothesisKA TKA would restore knee biomechanics to the native condition better than MA TKA. MethodsSeven pairs of cadavers were tested. For each pair, one knee was randomly assigned to KA TKA and the other to MA TKA. During KA TKA, the sizes of femur and tibia resections were equivalent to implant thickness to align with the patient-specific joint line. MA TKA was performed using conventional measured resection techniques. All specimens were mounted on a customized knee-testing system and digitized. Knee motions measured during flexion included rollback, axial tibiofemoral rotation, and laxities, specifically varus-valgus laxity, anterior-posterior translation, and internal-external rotation. ResultsThe pattern of knee motion following KA TKA was similar to the native knee. However, following MA TKA, both medial and lateral rollback and tibiofemoral axial rotation were decreased relative to those of the native knee. Valgus laxity was restored only after KA TKA, whereas varus laxity was restored only after MA TKA. Anterior translation was increased regardless of the alignment strategy. In addition, rotational laxities were restored after KA TKA, but external rotation laxity increased after MA TKA. ConclusionKA TKA restores femoral rollback and laxity to the native condition better than MA TKA. KA TKA may enhance functional performance and provide a more normal knee sensation. Level of evidenceII, Controlled laboratory study.

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.

Kinematically aligned total knee arthroplasty reproduces more native rollback and laxity than mechanically aligned total knee arthroplasty: A matched pair cadaveric study

BackgroundA growing body of evidence supports that kinematically aligned (KA) total knee arthroplasty (TKA) provides superior clinical outcomes and satisfaction than mechanically aligned (MA) TKA. In theory, KA TKA would restore knee kinematics closer to the native condition than MA TKA, but the current biomechanical evidence is lacking. HypothesisKA TKA would restore knee biomechanics to the native condition better than MA TKA. MethodsSeven pairs of cadavers were tested. For each pair, one knee was randomly assigned to KA TKA and the other to MA TKA. During KA TKA, the sizes of femur and tibia resections were equivalent to implant thickness to align with the patient-specific joint line. MA TKA was performed using conventional measured resection techniques. All specimens were mounted on a customized knee-testing system and digitized. Knee motions measured during flexion included rollback, axial tibiofemoral rotation, and laxities, specifically varus-valgus laxity, anterior-posterior translation, and internal-external rotation. ResultsThe pattern of knee motion following KA TKA was similar to the native knee. However, following MA TKA, both medial and lateral rollback and tibiofemoral axial rotation were decreased relative to those of the native knee. Valgus laxity was restored only after KA TKA, whereas varus laxity was restored only after MA TKA. Anterior translation was increased regardless of the alignment strategy. In addition, rotational laxities were restored after KA TKA, but external rotation laxity increased after MA TKA. ConclusionKA TKA restores femoral rollback and laxity to the native condition better than MA TKA. KA TKA may enhance functional performance and provide a more normal knee sensation. Level of evidenceII, Controlled laboratory study.

Clinical and functional outcome of posterior cruciate ligament retaining total knee arthroplasty

Introduction: Posterior Cruciate Ligament (PCL) retention achieves an increased potential range of motion by effective femoral roll back and a relatively flat tibial articular surface in Total Knee Arthroplasty.Objective: To study the clinical and functional outcome of patients who undergo posterior cruciate ligament (PCL) retaining total knee arthroplasty.Methods: The purpose was to determine the clinical and functional outcome during the acute and midterm (One year) follow up after posterior cruciate ligament retaining total knee arthroplasty (CR TKA). Thirty patients scheduled for CR TKR were evaluated preoperatively, 1 month, 3 months, 6 months and 12 months postoperatively using the knee society clinical and functional scores.Results: The mean pre- operative knee society clinical and functional scores of the 30 cases were 36.5 (Ranging from 20 to 64) and 31.8 respectively. The mean knee society clinical score at the 1st follow up was 76.5, at the 2nd follow up was 83.5, 3rd follow up was 88.6 and 4th follow up was 92.4. The mean knee society functional score at the 1st follow up was 72.5.5, at the 2nd follow up was 80.5, 3rd follow up was 87.5 and 4th follow up was 90.6.Conclusion: We found out that twenty nine out of thirty patients undergoing TKR had excellent clinical and functional scores; one patient had good functional scores at the end of one year. More than 90% of patients in our study had excellent functional scores at the end of one year. Posterior cruciate ligament retaining total knee arthroplasty is a good surgical option for osteoarthritis of knee.

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.

Effect of geometric variations on tibiofemoral surface and post-cam design of normal knee kinematics restoration

BackgroundRestoration of natural knee kinematics for a designed mechanism in knee implants is required to achieve full knee function in total knee arthroplasty (TKA). In different posterior-stabilized TKAs, there are wide variations in tibiofemoral surfaces and post-cam design. However, it is not known whether these design variations preserve natural knee kinematics. The purpose of this study was to determine the most appropriate tibiofemoral surface and post-cam designs to restore natural knee kinematics of the TKA.MethodsA subject-specific finite element knee modal was used to evaluate tibiofemoral surface and post-cam design. Three different posts in convex, straight, and concave geometries were considered with a fixed circular cam design in this study. In addition, this post-cam design was applied to three different surface conformities for conforming, medial pivot, and subject anatomy mimetic tibiofemoral surfaces. We evaluated the femoral rollback, internal-external rotation, and quadriceps muscle force under a deep-knee-bend condition.ResultsThe three different tibiofemoral conformities showed that the convex post provided the most natural-knee-like femoral rollback. This was also observed in internal rotation. In surface conformity, subject anatomy mimetic tibiofemoral surfaces showed the most natural -knee-like kinematics and quadriceps force.ConclusionsThis study confirmed that convex post design and subject anatomy mimetic tibiofemoral surfaces provided the most natural-knee-like kinematics. This study suggested that post-cam design and tibiofemoral surface conformity should be considered in conventional and customized TKA.

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

BackgroundBi-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. MethodsTwenty-nine unilateral BCR TKA patients were evaluated for both knees during single deep lunges, step-ups, and sit-to-stand (STS) using a validated combined computer tomography and dual fluoroscopic imaging system. Medial and lateral condylar contact positions were quantified during weight-bearing flexion. ResultsContact excursions of the lateral condyle in BCR TKAs were significantly more anteriorly located than the contralateral non-operated knees during STS (−4.9 ± 3.1 vs −9.7 ± 4.6 mm, P < .05), single deep lunge (−5.7 ± 3.2 vs −10.0 ± 4.5 mm, P < .05), and step-ups (−4.8 ± 3.6 vs −9.1 ± 3.9 mm, P < .05). Contact points of BCR TKAs indicated reduced femoral external rotation during STS (2.1 ± 4.8° vs 7.7 ± 5.4°, P < .05), single deep lunges (1.8 ± 4.8° vs 7.0 ± 7.1°, P < .05), and step-ups (0.1 ± 4.1° vs 6.2 ± 4.9°, P < .05). Medial pivoting patterns were observed in only 59%, 56%, and 48% of the BCR TKA knees for step-ups, STS, and single deep lunge, respectively. ConclusionThe contemporary BCR TKA design demonstrated asymmetric femoral rollback, medial translation, as well as lateral pivoting in about half of the patient cohort, suggesting that in vivo tibiofemoral kinematic parameters were not fully restored in BCR patients during strenuous flexion activities.

Effect of Post-Cam Design for Normal Knee Joint Kinematic, Ligament, and Quadriceps Force in Patient-Specific Posterior-Stabilized Total Knee Arthroplasty by Using Finite Element Analysis.

The purpose of this study is to investigate post-cam design via finite element analysis to evaluate the most normal-like knee mechanics. We developed five different three-dimensional computational models of customized posterior-stabilized (PS) total knee arthroplasty (TKA) involving identical surfaces with the exception of the post-cam geometry. They include flat-and-flat, curve-and-curve (concave), curve-and-curve (concave and convex), helical, and asymmetrical post-cam designs. We compared the kinematics, collateral ligament force, and quadriceps force in the customized PS-TKA with five different post-cam designs and conventional PS-TKA to those of a normal knee under deep-knee-bend conditions. The results indicated that femoral rollback in curve-and-curve (concave) post-cam design exhibited the most normal-like knee kinematics, although the internal rotation was the closest to that of a normal knee in the helical post-cam design. The curve-and-curve (concave) post-cam design showed a femoral rollback of 4.4 mm less than the normal knee, and the helical post-cam design showed an internal rotation of 5.6° less than the normal knee. Lateral collateral ligament and quadriceps forces in curve-and-curve (concave) post-cam design, and medial collateral ligament forces in helical post-cam design were the closest to that of a normal knee. The curve-and-curve (concave) post-cam design showed 20% greater lateral collateral ligament force than normal knee, and helical post-cam design showed medial collateral ligament force 14% greater than normal knee. The results revealed the variation in each design that provided the most normal-like biomechanical effect. The present biomechanical data are expected to provide useful information to improve post-cam design to restore normal-like knee mechanics in customized PS-TKA.

Patient-specific design for articular surface conformity to preserve normal knee mechanics in posterior stabilized total knee arthroplasty.

Contemporary total knee arthroplasty (TKA) provides remarkable clinical benefits. However, the normal function of the knee is not fully restored. Recent improvements in imaging and manufacturing have utilized the development of customized design to fit the unique shape of individual patients. The purpose of the present study is to investigate the preservation of normal knee biomechanics by using specific articular surface conformity in customized posterior stabilized (PS)-TKA. This includes customized PS-TKA, PS-TKA with conforming conformity (CPS-TKA), medial pivot conformity with PS-TKA (MPS-TKA), and PS-TKA with mimetic anatomy femoral and tibial articular surface (APS-TKA). In this study, kinematics, collateral ligament force and quadriceps force were evaluated using a computational simulation under a deep knee bend condition. A conventional TKA did not provide the normal internal tibial rotation with flexion leading to abnormal femoral rollback. The APS-TKA exhibited normal-like femoral rollback kinematics but did not exhibit normal internal tibial rotation. However, APS-TKA exhibited the most normal-like collateral ligament and quadriceps forces. Although the APS-TKA exhibited more normal-like biomechanics, it did not restore normal knee biomechanics owing to the absence of the cruciate ligament and post-cam mechanism.

Kinematic component alignment in total knee arthroplasty leads to better restoration of natural tibiofemoral kinematics compared to mechanic alignment.

Kinematically aligned total knee arthroplasty is associated with superior pain relief, increased flexion and a more normal feeling knee. It was hypothesized that due to restoring the knee's natural anatomy, kinematically aligned knees show more physiological tibiofemoral kinematics than mechanically aligned knees. Investigations were performed in nine healthy cadaveric knees of whole bodies fixed by the Thiel method. Tibiofemoral kinematics of healthy knees and after kinematically and mechanically aligned total knee arthroplasty were assessed between 0° and 90° of flexion by a navigational device. Regarding tibial internal rotation or femoral roll back, respectively, kinematically aligned total knee arthroplasties showed no significant differences between 0° and 70° of flexion in comparison to knees before total knee arthroplasty. In contrast, mechanically aligned total knee arthroplasties showed significant changes between 10° and 90° of flexion. Kinematically aligned knees showed a significant changed abduction/adduction between 20° and 70° of flexion, mechanically aligned knees within 20° and 90° of flexion. In the present study setting kinematically aligned total knee arthroplasties showed more natural and physiological tibiofemoral kinematic pattern with regard to tibial internal rotation or femoral rollback, respectively, and tibial adduction than mechanically aligned total knee arthroplasties. While these results may support promising early clinical results of kinematical alignment proposing a better function, long-term results especially implant survival need to be awaited.

Kinematics of knees with osteoarthritis show reduced lateral femoral roll-back and maintain an adducted position. A systematic review of research using medical imaging

BackgroundWhile several studies describe kinematics of healthy and osteoarthritic knees using the accurate imaging and computer modelling now possible, no systematic review exists to synthesise these data. MethodA systematic review extracted quantitative observational, quasi-experimental and experimental studies from PubMed, Scopus, Medline and Web of Science that examined motion of the bony or articular surfaces of the tibiofemoral joint during any functional activity. Studies using surface markers, animals, and in vitro studies were excluded. Results352 studies were screened to include 23 studies. Dynamic kinematics were recorded for gait, step-up, kneeling, squat and lunge and quasi-static squat, knee flexion in side-lying or supine leg-press. Kinematics were described using a diverse range of measures including six degrees of freedom kinematics, contact patterns or the projection of the femoral condylar axis above the tibia. Meta-analysis of data was not possible since no three papers recorded the same activity with the same measures. Visual evaluation of data revealed that knees with osteoarthritis maintained a more adducted position and showed less posterior translation of the lateral femoral condylar axis than healthy knees. Variability in activities and in recording measures produced greater variation in kinematics, than did knee osteoarthritis. ConclusionDifferences in kinematics between osteoarthritic and healthy knees were observed, however, these differences were more subtle than expected. The synthesis and progress of this research could be facilitated by a consensus on reference systems for axes and kinematic reporting.

A lateral retinacular release during total knee arthroplasty changes femorotibial kinematics: an in vitro study

Lateral retinacular release (LRR) is a common procedure during total knee arthroplasty (TKA), especially if patellar maltracking is observed intraoperatively. The impact of LRR on patellofemoral kinematics is well-examined, but the influence on femorotibial kinematics requires more elucidation. Therefore, the aim of this study was to evaluate the effects of LRR on femorotibial kinematics in vitro. A fixed bearing TKA was implanted in six human knee specimens. Femorotibial kinematics were measured dynamically through the use of a custom-constructed knee rig which flexes the knee from 20° to 120° under weight bearing conditions. Measurements were performed before and after LRR. LRR was performed completely including transection of synovium, retinaculum and tractus fibers. For the registration of tibiofemoral kinematics a 3-dimensional-ultrasound-based motion analysis system was used. LRR revealed a significant reduction of femoral rollback at the lateral compartment (9.4 ± 5.0 vs 7.8 ± 9.4mm; p < 0.01), whereas the present decrease of femoral rollback at the medial compartment was not significant (3.4 ± 4.7 vs 2.3 ± 5.9mm; p = 0.34). Accordingly, LRR significantly reduced internal rotation of the tibia (0.8°; p < 0.01). The results suggest that LRR significantly decreases lateral femoral rollback as well as internal rotation of the tibia, probably by changing the tension of the iliotibial band. When performing a LRR in clinical routine, surgeons should be aware of altering not only patellofemoral kinematics but also the femorotibial kinematics.

Measurement of Posterior Tibial Slope Using Magnetic Resonance Imaging.

Posterior tibial slope (PTS) is an important factor in the knee joint biomechanics and one of the bone features, which affects knee joint stability. Posterior tibial slope has impact on flexion gap, knee joint stability and posterior femoral rollback that are related to wide range of knee motion. During high tibial osteotomy and total knee arthroplasty (TKA) surgery, proper retaining the mechanical and anatomical axis is important. The aim of this study was to evaluate the value of posterior tibial slope in medial and lateral compartments of tibial plateau and to assess the relationship among the slope with age, gender and other variables of tibial plateau surface. This descriptive study was conducted on 132 healthy knees (80 males and 52 females) with a mean age of 38.26±11.45 (20-60 years) at Imam Reza hospital in Mashhad, Iran. All patients, selected and enrolled for MRI in this study, were admitted for knee pain with uncertain clinical history. According to initial physical knee examinations the study subjects were reported healthy. The mean posterior tibial slope was 7.78± 2.48 degrees in the medial compartment and 6.85± 2.24 degrees in lateral compartment. No significant correlation was found between age and gender with posterior tibial slope (P≥0.05), but there was significant relationship among PTS with mediolateral width, plateau area and medial plateau. Comparison of different studies revealed that the PTS value in our study is different from other communities, which can be associated with genetic and racial factors. The results of our study are useful to PTS reconstruction in surgeries.

In Vivo Kinematic Comparison of a Bicruciate Stabilized Total Knee Arthroplasty and the Normal Knee Using Fluoroscopy

BackgroundThe bicruciate stabilized (BCS) total knee arthroplasty (TKA) features asymmetrical bearing geometry and dual substitution for the anterior cruciate ligament and posterior cruciate ligament (PCL). Previous TKA designs have not fully replicated normal knee motion, and they are characterized by lower magnitudes of overall rollback and axial rotation than the normal knee. MethodsIn vivo kinematics were derived for 10 normal knees and 40-second generation BCS TKAs all implanted by a single surgeon. Mobile fluoroscopy and three-dimensional-to-two-dimensional registration was used to analyze anterior-posterior motion of the femoral condyles and femorotibial axial rotation during weight-bearing flexion. Statistical analysis was conducted at the 95% confidence level. ResultsFrom 0° to 30° of knee flexion, the BCS subjects exhibited similar patterns of femoral rollback and axial rotation compared to normal knee subjects. From 30° to 60° of knee flexion, BCS subjects experienced negligible anterior-posterior motions and axial rotation while normal knees continued to rollback and externally rotate. Between 60° and 90° the BCS resumed posterior motion and, after 90°, axial rotation increased in a normal-like fashion. ConclusionSimilarities in early flexion kinematics suggest that the anterior cam-post is supporting normal-like anterior-posterior motion in the BCS subjects. Likewise, lateral femoral rollback and external rotation of the femur in later flexion provides evidence for appropriate substitution of the PCL via the posterior cam-post. Being discrete in nature, the dual cam-post mechanism does not lend itself to adequate substitution of the cruciate ligaments in mid-flexion during which anterior cruciate ligament tension is decreasing and PCL tension is increasing in the normal knee.

Preservation of kinematics with posterior cruciate-, bicruciate- and patient-specific bicruciate-retaining prostheses in total knee arthroplasty by using computational simulation with normal knee model.

ObjectivesPreservation of both anterior and posterior cruciate ligaments in total knee arthroplasty (TKA) can lead to near-normal post-operative joint mechanics and improved knee function. We hypothesised that a patient-specific bicruciate-retaining prosthesis preserves near-normal kinematics better than standard off-the-shelf posterior cruciate-retaining and bicruciate-retaining prostheses in TKA.MethodsWe developed the validated models to evaluate the post-operative kinematics in patient-specific bicruciate-retaining, standard off-the-shelf bicruciate-retaining and posterior cruciate-retaining TKA under gait and deep knee bend loading conditions using numerical simulation.ResultsTibial posterior translation and internal rotation in patient-specific bicruciate-retaining prostheses preserved near-normal kinematics better than other standard off-the-shelf prostheses under gait loading conditions. Differences from normal kinematics were minimised for femoral rollback and internal-external rotation in patient-specific bicruciate-retaining, followed by standard off-the-shelf bicruciate-retaining and posterior cruciate-retaining TKA under deep knee bend loading conditions. Moreover, the standard off-the-shelf posterior cruciate-retaining TKA in this study showed the most abnormal performance in kinematics under gait and deep knee bend loading conditions, whereas patient-specific bicruciate-retaining TKA led to near-normal kinematics.ConclusionThis study showed that restoration of the normal geometry of the knee joint in patient-specific bicruciate-retaining TKA and preservation of the anterior cruciate ligament can lead to improvement in kinematics compared with the standard off-the-shelf posterior cruciate-retaining and bicruciate-retaining TKA.Cite this article: Y-G. Koh, J. Son, S-K. Kwon, H-J. Kim, O-R. Kwon, K-T. Kang. Preservation of kinematics with posterior cruciate-, bicruciate- and patient-specific bicruciate-retaining prostheses in total knee arthroplasty by using computational simulation with normal knee model. Bone Joint Res 2017;6:557–565. DOI: 10.1302/2046-3758.69.BJR-2016-0250.R1.

Mediolateral femoral component position in TKA significantly alters patella shift and femoral roll-back.

Increased retropatellar pressure and altered kinematics are associated with anterior knee pain and unsatisfied patients after total knee arthroplasty (TKA). Since malposition of the implant is believed to contribute to postoperative pain, we performed this in vitro study to evaluate the influence of mediolateral femoral component position on retropatellar pressure as well as tibio-femoral and patella kinematics. For the test, a fixed-bearing TKA was implanted in eight fresh frozen cadaver specimens. To determine the impact of mediolateral (ML) position, three variants of femoral components (3-mm medialization, neutral position and 3-mm lateralization) were produced using rapid prototyping replicas. In a knee rig, a loaded squat from 20° to 120° of flexion was applied. Retropatellar pressure distribution was measured with a pressure-sensitive film. Additionally, an ultrasonic-based three-dimensional motion analysis system was used to register patello- and tibio-femoral kinematics. ML translation of the femoral component by 3mm did not lead to a significant alteration in retropatellar peak pressure (medial 6.5±2.5MPa vs. lateral 6.0±2.4MPa). Following the ML translation of the femoral component, the patella was significantly shifted and tilted in the same directions. Varying the ML femoral component position also led to a significant alteration in femoral roll-back. In day-by-day use, ML position should be chosen with care since there is a significant influence on patella shift and femoral roll-back. Retropatellar pressure is not significantly altered, so there is no clear evidence of an impact on anterior knee pain.

Modifications of femoral component design in multi-radius total knee arthroplasty lead to higher lateral posterior femoro-tibial translation.

As the aims of changes in total knee arthroplasty (TKA) designs are to reinstate more natural kinematics, the current study evaluated the in vivo kinematics in patients who underwent a cruciate retaining gradually changing femoral radius ("G-CURVE") against a cruciate retaining conventional changing femoral radius ("J-CURVE") geometry TKA design. The hypothesis of the study is that the G-CURVE design would allow a substantial increase in the femoral rollback compared to the J-CURVE design. Retrospective study design. Thirty patients were included (G-CURVE, n=20; J-CURVE, n=10). Single-plane fluoroscopic analysis and marker-based motion capture gait analysis was performed to analyse dynamic tibiofemoral motion during weight-bearing and unloaded activities at 24month after index surgery. The analysis of the medial and lateral points on the tibia plateau during the unloaded flexion-extension and the weight-bearing lunge activities revealed a significant difference in femoral rollback in G-CURVE TKA above 60° (p=0.001) and 30° (p=0.02) of knee flexion, respectively. Moreover, the lateral condyle of the G-CURVE showed a higher extent of femoral rollback while the lateral condyle of the J-CURVE rolled forward. At 2years post-operative, the G-CURVE TKA showed significant differences in femoro-tibial translation in comparison with the J-CURVE system, in vivo. The G-CURVE resulted in an increased lateral rollback and simultaneously in an elimination of the paradoxical medial roll-forward present in the J-CURVE design. Moreover, knee kinematics analysis showed significant differences between unloaded and weight-bearing conditions revealing the impact of load and muscle force. The analysis conducted in this study contributes to further understand the principal movement characteristics in widely used older designs in comparison with recently developed concepts to get a better overview on their potential benefits on in vivo kinematics. III.

Different intraoperative kinematics, stability, and range of motion between cruciate-substituting ultracongruent and posterior-stabilized total knee arthroplasty.

The aim of this study was the comparison of intraoperative kinematics, stability, and range of motion (ROM) between the native osteoarthritic knee and cruciate-substituting fixed-bearing total knee arthroplasty (TKA) using both an ultracongruent (UC) and a posterior-stabilized (PS) insert design in the same patient. We hypothesized less knee flexion and less antero-posterior stability in the UC TKA. Intraoperative measurements of kinematics, stability, and ROM were performed in 40 patients before soft-tissue release and bone cuts, and after implantation of the final femoral and tibial implants with both a UC insert and a PS insert. All measurements were performed using a navigation system. Kinematics changed significantly from a constant posterior femoral rollback before surgery to a paradoxical anterior translation during initial knee flexion with both inserts, but less pronounced with the PS insert (p < 0.001). There was significantly more posterior femoral rollback with the PS insert compared to the UC insert (p < 0.01). Stability measurements demonstrated no differences at full extension and 30° of knee flexion but significantly increased antero-posterior translation in 60° and 90° of knee flexion with the UC insert compared to the PS insert (p < 0.001). ROM measurements demonstrated improvement of knee flexion from 118° at the beginning of the surgery to 123° with the UC insert and 128° with the PS insert (p < 0.001). The use of a UC insert intraoperatively resulted in less antero-posterior stability and slightly less knee flexion compared to a PS insert. Surgeons should be aware of these differences when deciding for one of these options to substitute the posterior cruciate ligament (PCL). The impact of these findings on clinical outcome needs further investigation. II.

In Vivo Kinematics of Healthy and Osteoarthritic Knees During Stepping Using Density-Based Image-Matching Techniques.

The purpose of this study was to investigate in vivo kinematics in healthy and osteoarthritic (OA) knees during stepping using image-matching techniques. Six healthy volunteers and 14 patients with a medial OA knee before undergoing total knee arthroplasty performed stepping under periodic anteroposterior radiograph images. We analyzed the three-dimensional kinematic parameters of knee joints using radiograph images and CT-derived digitally reconstructed radiographs. The average extension/flexion angle ranged 6°/53° and 16°/44° in healthy and OA knees, with significant difference in extension (P = .02). The average varus angle was -2° and 6° in healthy and OA knees, with a significant difference (P = .03). OA knees showed 1.7° of significantly larger varus thrust (P = .04) and 4.2 mm of significantly smaller posterior femoral rollback (P = .04) compared with healthy knees. Coronal limb alignment in OA knees significantly correlated with varus thrust (R2 = .36, P = .02) and medial shift of the femur (R2 = .34, P = .03). Both normal and OA knees showed no transverse plane instability, including anteroposterior, mediolateral directions, or axial rotation. In conclusion, OA knees demonstrated different kinematics during stepping from normal knees: less knee extension, larger varus thrust, less posterior translation, and larger medial shift.

Customized versus Patient-Sized Cruciate-Retaining Total Knee Arthroplasty: An In Vivo Kinematics Study Using Mobile Fluoroscopy

BackgroundHistorically, knee arthroplasties have been designed using average patient anatomy. Recent advances in imaging and manufacturing have facilitated the development of customized prostheses designed to fit the unique shape of individual patients. The purpose of this study is to determine if improving implant design through customized total knee arthroplasty (TKA) improves kinematic function. MethodsUsing state-of-the-art mobile fluoroscopy, tibiofemoral kinematics were analyzed for 24 subjects with a customized individually made (CIM), cruciate-retaining TKA, and 14 subjects having an asymmetric condylar cruciate-retaining TKA. Subjects performed a weight-bearing deep knee bend and a rise from a seated position. Each patient was evaluated for weight-bearing range of motion, femorotibial translation, femorotibial axial rotation, and condylar liftoff occurrence. ResultsSubjects having a CIM TKA experienced greater weight-bearing knee flexion compared with the traditional posterior cruciate-retaining (PCR) TKA design. During flexion, the CIM TKA subjects consistently exhibited more posterior femoral rollback than the traditional PCR TKA subjects. The CIM TKA was found to have statistically greater axial rotation compared with the traditional PCR TKA (P = .05). Of note, only the CIM TKA patients experienced femoral internal rotation at full extension, as exhibited in a normal knee. Compared with the traditional PCR TKA, the CIM TKAs demonstrated minimal occurrences of paradoxical sliding and reverse rotation during flexion and extension. The CIM TKA subjects showed minimal liftoff and hence better stability in earlyflexion to midflexion compared with the traditional PCR subjects. ConclusionThe CIM TKA demonstrated kinematics more similar to a normal knee. Therefore, using customized implant technology through CIM TKA designs affords benefits including more normal motion compared with a traditional PCR TKA.