Influence of tibial rotation in total knee arthroplasty on knee kinematics and retropatellar pressure: an in vitro study

Coronal Knee Alignment and Tibial Rotation in Total Knee Arthroplasty: A Prospective Cohort Study of Patients with End-Stage Osteoarthritis

Several studies have found a relationship between the rotational anatomy of the distal femur and the overall coronal lower limb alignment in knees with osteoarthritis (OA). Less is known about the rotation of the proximal tibia, especially in the context of total knee arthroplasty (TKA), where one of the goals of the surgery is to achieve the appropriate component-to-component rotation. The aim of this study was to investigate the relationship between the coronal alignment of the lower extremity and the relative proximal tibial rotation. A prospective cohort study of patients with an end-stage OA scheduled for TKA was conducted. All patients underwent a computed tomography (CT) scan and a standing X-ray of both lower limbs. A relative femorotibial rotation was measured separately for mechanical and kinematic alignment. A statistically significant correlation was found between the tibial varus and the external tibial rotation (p < 0.001). Out of 14 knees with high tibial varus (>5°), 13 (93%) and 7 (50%) knees had >10° of femorotibial rotation for the mechanical and kinematic alignment landmarks, respectively. In order to keep the component-to-component rotation within the 10° margin, more internal rotation of the tibial component is required in knees with higher tibial varus.

Patella Fracture After Total Knee Arthroplasty: A Review

The management and underlying causes of patellar periprosthetic fractures (PPF) after total knee arthroplasty (TKA) constitute an issue of growing importance given the rising frequency of these procedures. Patella periprosthetic fractures, though relatively rare, pose significant challenges and are a frequent indication for revision surgeries. Despite a decrease in overall incidence, PPFs remain the second most common type of periprosthetic fractures after TKA. Several factors have been identified and associated with patient-specific factors, surgical technique errors, and implant-related causes. Currently extensor apparatus integrity, bone stock, and component loosening are the major concerns and indications for the selective treatment approach. In this study, a thorough review of the existing literature was performed summarizing the epidemiology, clinical manifestation, treatment approach, and functional outcome of PPF. This review aims to underline the significance of such predisposing factors, point out the severity of PPF, and offer insights into the optimal intra- and post-operative management of the patella.

The anteroposterior distance between the posterior edge of the medial tibial condyle and the posterior edge of the fibular head in the lateral view can be a reference in determining the axis perpendicular to the tibial anteroposterior axis

BACKGROUND

Obtaining an accurate tibial lateral view is important during high tibial osteotomy. This study investigated whether the posterior edge of the medial/lateral tibial condyle (PEMTC/PELTC) and the posterior edge of the fibular head (PEFH) in a lateral view could be a reference for determining the accurate tibial lateral view.

METHODS

A total of 75 lower limbs in 38 subjects were evaluated in this study. In order to target healthy knees, subjects undergoing primary total hip arthroplasty were selected. The MF/LF, comprising the anteroposterior distance between PEMTC/PELTC and PEFH, was measured on the lateral view of the tibial bone model based on the tibial anteroposterior (AP) axis (true lateral view: TLV). In addition, measurements were calculated in the model with a 10° external/internal rotation. Using these measurements, linear regression analysis was performed to predict the tibial rotation with MF/LF.

RESULTS

The mean MF/LF was 0.9/4.6 mm (P < 0.001). MF and LF increased with incremental tibial rotation. Regression formulas were derived from these results as follows: Tibial rotation = (1) -1.01 + 1.06 × MF (R2 = 0.87, P < 0.001), (2) -8.70 + 1.86 × LF (R2 = 0.51, P < 0.001). The mean tibial rotation angle when MF was 0 mm was -0.9°.

CONCLUSIONS

Based on formula (1) and actual measurements, the mean tibial rotation angle when MF is 0 mm is an internal rotation of about 1°. Therefore, a lateral view, in which PEMTC and PEFH are seen colinearly, can be the approximate TLV. The MF can be a suitable intraoperative reference in determining TLV.

Influence of kinematic alignment on femorotibial kinematics in medial stabilized TKA design compared to mechanical alignment

INTRODUCTION

Worldwide more and more primary knee replacements are being performed. Kinematic alignment (KA) as one of many methods of surgical alignment has been shown to have a significant impact on kinematics and function. The aim of the present study was to compare KA and mechanical alignment (MA) with regard to femorotibial kinematics.

MATERIALS AND METHODS

Eight fresh frozen human specimens were tested on a knee rig during active knee flexion from 30 to 130°. Within the same specimen a medial stabilized (MS) implant design was used first with KA and then with MA.

RESULTS

The femorotibial kinematics showed more internal rotation of the tibia in KA compared to MA. At the same time, there was a larger medial rotation point in KA. Both alignment methods showed femoral rollback over the knee bend.

CONCLUSION

Relating to an increased internal rotation and a more precise medial pivot point, it can be concluded that KA combined with a MS implant design may partially support the reproduction of physiological knee joint mechanics.

Reference Axes for Tibial Component Rotation in Total Knee Arthroplasty: Computed Tomography-Based Study of 1,351 Tibiae

BACKGROUND

Many anatomic landmarks have been described for setting tibial component rotation intraoperatively. There is no consensus as to which axis is best for reducing outliers and preventing malrotation.

METHODS

The SOMA (Stryker Orthopaedic Modeling and Analytics) database (Stryker) was used to identify 1,351 computed tomography (CT) scans of the entire tibia. Several reference axes for the tibia (including the Mayo axis, Akagi line, Insall line, anterior condylar axis [ACA], posterior condylar axis [PCA], lateral tibial cortex [LTC], Cobb axis, tibial crest line [TCL], and transmalleolar axis [TMA]) were constructed according to published guidelines. The Berger method served as the reference standard.

RESULTS

The Mayo method (involving a line connecting the medial and middle one-thirds of the tibial tubercle and the geometric center of the tibia) and the Insall line (involving a line connecting the posterior cruciate ligament [PCL] insertion and the intersection of the middle and medial one-thirds of the tibial tubercle) both had low variability relative to the Berger method (7.8° ± 1.0° and 5.1° ± 2.2°, respectively) and a low likelihood of internal rotation errors (0.7% and 1.8%, respectively). No clinically significant gender-based differences were found (<0.7° for all). The same was true for ethnicity, with the exception of consistently greater tibial intorsion in Asian versus Caucasian individuals (mean difference in TCL position, +4.5° intorsion for Asian individuals; p < 0.001).

CONCLUSIONS

This CT-based study of 1,351 tibiae (which we believe to be the largest study of its kind) showed that the Mayo and Insall methods (both of which reference the medial and middle one-thirds of the tibial tubercle) offer an ideal balance of accuracy, low variability, and a reduced likelihood of internal rotation errors. Setting rotation on the basis of distal landmarks (tibial shaft and beyond) may predispose surgeons to substantial malrotation errors, especially given the differences in tibial torsion found between ethnic groups in this study.

LEVEL OF EVIDENCE

Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Computer-based analysis of different component positions and insert thicknesses on tibio-femoral and patello-femoral joint dynamics after cruciate-retaining total knee replacement

BACKGROUND

Positioning of the implant components and tibial insert thickness constitute critical aspects of total knee replacement (TKR) that influence the postoperative knee joint dynamics. This study aimed to investigate the impact of implant component positioning (anterior-posterior and medio-lateral shift) and varying tibial insert thickness on the tibio-femoral (TF) and patello-femoral (PF) joint kinematics and contact forces after cruciate-retaining (CR)-TKR.

METHOD

A validated musculoskeletal multibody simulation (MMBS) model with a fixed-bearing CR-TKR during a squat motion up to 90° knee flexion was deployed to calculate PF and TF joint dynamics for varied implant component positions and tibial insert thicknesses. Evaluation was performed consecutively by comparing the respective knee joint parameters (e.g. contact force, quadriceps muscle force, joint kinematics) to a reference implant position.

RESULTS

The PF contact forces were mostly affected by the anterior-posterior as well as medio-lateral positioning of the femoral component (by 3 mm anterior up to 31 % and by 6 mm lateral up to 14 %). TF contact forces were considerably altered by tibial insert thickness (24 % in case of + 4 mm increase) and by the anterior-posterior position of the femoral component (by 3 mm posterior up to 16 %). Concerning PF kinematics, a medialised femoral component by 6 mm increased the lateral patellar tilt by more than 5°.

CONCLUSIONS

Our results indicate that regarding PF kinematics and contact forces the positioning of the femoral component was more critical than the tibial component. The positioning of the femoral component in anterior-posterior direction on and PF contact force was evident. Orthopaedic surgeons should strictly monitor the anterior-posterior as well as the medio-lateral position of the femoral component and the insert thickness.

Does Posterior Tibial Slope Influence Knee Kinematics in Medial Stabilized TKA?

BACKGROUND

During total knee arthroplasty (TKA), one of the key alignment factors to pay attention to is the posterior tibial slope (PTS). The PTS clearly influences the kinematics of the knee joint but must be adapted to the coupling degree of the specific TKA design. So far, there is hardly any literature including clear recommendations for how surgeons should choose the PTS in a medial stabilized (MS) TKA. The aim of the present study is to investigate the effects of different degrees of PTS on femorotibial kinematics in MS TKA.

MATERIALS AND METHODS

An MS TKA was performed in seven fresh-frozen human specimens successively with 0°, 3°, and 6° of PTS. After each modification, weight-bearing deep knee flexion (30-130°) was performed, and femorotibial kinematics were analyzed.

RESULTS

A lateral femoral rollback was observed for all three PTS modifications. With an increasing PTS, the tibia was shifted more anteriorly on the lateral side (0° PTS anterior tibial translation -9.09 (±9.19) mm, 3° PTS anterior tibial translation -11.03 (±6.72) mm, 6° PTS anterior tibial translation 11.86 (±9.35) mm). No difference in the tibial rotation was found for the different PTS variants. All PTS variants resulted in internal rotation of the tibia during flexion. With a 3° PTS, the design-specific medial rotation point was achieved more accurately.

CONCLUSIONS

According to our findings, we recommend a PTS of 3° when implanting the MS prosthesis used in this study.

Computer-assisted surgery and patient-specific instrumentation improve the accuracy of tibial baseplate rotation in total knee arthroplasty compared to conventional instrumentation: a systematic review and meta-analysis

PURPOSE

To determine whether patient-specific instrumentation (PSI), computer-assisted surgery (CAS) or robot-assisted surgery (RAS) enable more accurate rotational alignment of the tibial baseplate in primary total knee arthroplasty (TKA) compared to conventional instrumentation, in terms of deviation from the planned target and the proportion of outliers from the target zone.

METHODS

The authors independently conducted three structured electronic literature searches using the PubMed, Embase®, and Cochrane Central Register of Controlled Trials databases from 2007 to 2020. Studies were included if they compared rotational alignment of the tibial baseplate during TKA using conventional instrumentation versus PSI, CAS, and/or RAS, and reported deviation from preoperatively planned rotational alignment of the tibial baseplate in terms of absolute angles and/or number of outliers. Methodological quality of eligible studies was assessed by two researchers according to the Downs and Black Quality Checklist for Health Care Intervention Studies.

RESULTS

Fifteen studies, that reported on 2925 knees, were eligible for this systematic review, of which 6 studies used PSI, and 9 used CAS. No studies were found for RAS. Of the studies that reported on angular deviation from preoperatively planned rotational alignment, most found smaller deviations using PSI (0.5° to 1.4°) compared to conventional instrumentation (1.0° to 1.6°). All studies that reported on proportions of outliers from a target zone (± 3°), found lower rates of outliers using PSI (0 to 22%) compared to conventional instrumentation (5 to 96%). Most studies reported smaller angular deviation from preoperatively planned rotational alignment using CAS (0.1° to 6.9°) compared to conventional instrumentation (1.1° to 7.8°). Of the studies that reported on proportions of outliers from a target zone (± 3°), most found fewer outliers using CAS (10 to 61%) compared to conventional instrumentation (17 to 78%).

CONCLUSION

This systematic review and meta-analysis revealed that both CAS and PSI can improve the accuracy of rotational alignment of the tibial baseplate by decreasing angular deviation from the preoperatively planned target and reducing the proportion of outliers from the target zone. The clinical relevance is that PSI and CAS can improve alignment, though the thresholds necessary to grant better outcomes and survival remain unclear.

LEVEL OF EVIDENCE

IV.

Isolated effects of patellar resurfacing in total knee arthroplasty and their relation to native patellar geometry

The isolated effects of patellar resurfacing on patellar kinematics are rarely investigated. Nonetheless, knowing more about these effects could help to enhance present understanding of the emergence of kinematic improvements or deteriorations associated with patellar resurfacing. The aim of this study was to isolate the effects of patellar resurfacing from a multi-stage in vitro study, where kinematics after total knee arthroplasty before and after patellar resurfacing were recorded. Additionally, the influence of the native patellar geometry on these effects was analysed. Eight fresh frozen specimens were tested successively with different implant configurations on an already established weight bearing knee rig. The patello-femoral kinematics were thereby measured using an ultrasonic measurement system and its relation to the native patellar geometries was analysed. After patellar resurfacing, the specimen showed a significantly medialized patellar shift. This medialization of the patellar tracking was significantly correlated to the lateral facet angle of the native patella. The patellar shift after patellar resurfacing is highly influenced by the position of the patellar button and the native lateral patellar facet angle. As a result, the ideal medio-lateral position of the patellar component is affected by the geometry of the native patella.

Moderate External Rotation of Tibial Component Generates More Natural Kinematics Than Internal Rotation After Total Knee Arthroplasty

This study aimed to investigate the influence of tibial malrotation on knee kinematics after total knee arthroplasty (TKA). A symmetric fixed-bearing posterior-stabilized prosthesis was implanted in the validated knee model with different rotational alignments of the tibial component (neutral, 3° external rotation, 5° external rotation, 3° internal rotation, and 5° internal rotation). Computational kinematic simulations were used to evaluate the postoperative kinematics of the knee joint including anteroposterior translation femoral condyles and axial rotation of tibial component during 0°–135° knee flexion. The results revealed that the neutral position of the tibial component was not the closest kinematics to the intact knee, the model with 5° external rotation of the tibial component showed the closest lateral condyle translation and tibial axial rotation, and moderate external rotation could improve the kinematics after TKA.

Study on the morphological characteristics and rotational alignment axis of placement plane of the tibial component in total knee arthroplasty for hemophilia-related knee arthritis

Background

Abnormal epiphyseal growth plate development of the proximal tibia in hemophilia patients leads to notable morphological changes in the mature knee joint. This study aimed to compare the morphological characteristics of tibial component placement cut surface in patients with hemophilic arthritis (HA) and osteoarthritis (OA) and to determine the tibial component rotational alignment axis’ best position for HA patients.

Methods

Preoperative computed tomography scans of 40 OA and 40 HA patients who underwent total knee arthroplasty were evaluated using a three-dimensional (3D) software. The tibial component’s placement morphological parameters were measured. The tibial component’s rotational mismatch angles were evaluated, and the most appropriate 0°AP axis position for HA patients was investigated.

Results

In the two groups, the morphology was significantly different in some of the parameters (p < 0.05). The tibial component rotational mismatch angles were significantly different between both groups (p < 0.05). The medial 9.26° of the medial 1/3 of the patellar tendon was the point through which 0°AP axis passed for the HA patients. Similarly, the medial 13.02° of the medial 1/3 of the tibial tubercle was also the point through which the 0°AP axis passed.

Conclusions

The ratio of the anteroposterior length to the geometric transverse length of the placement section of the tibial component in HA patients was smaller than that in OA patients. The medial 9.26° of the medial 1/3 of the patellar tendon or the medial 13.02° of the medial 1/3 of the tibial tubercle seem to be an ideal reference position of the rotational alignment axis of the tibial component for HA patients.

Soft-tissue landmarks for tibial baseplate rotational alignment in total knee arthroplasty: A cadaveric study

The tip of the tibial tubercle (TTT) is used to assess tibial baseplate rotation in total knee arthroplasty (TKA); however, it can be difficult to palpate and visualize intraoperatively. Several more easily accessible soft-tissue structures have been proposed as intraoperative assessments, including the patellar tendon's medial border (MBPT) and the junction of the medial third of the patellar tendon (mt-PT). No studies have described the relationship between the TTT and these proposed landmarks. The aims of the study were to (1) determine the relationship of the soft-tissue landmarks to the TTT and (2) identify any sex differences in these measures. Measurements of the position of these soft-tissue landmarks relative to the TTT were made on 56 cadaveric knees (28 female) by two observers at the level of the standard tibial cut (10 mm distal to the lateral tibial plateau). The results obtained were compared by sex and side. On average, 50.7% (SD 6.79, range 33.1%-63.1%) of the patellar tendon footprint was medial to the TTT. There were no significant differences between the sexes or left and right lower limbs. However, there was large variability in the position of all the soft-tissue landmarks relative to the TTT. The results indicate that, on average, the patellar tendon footprint is evenly spread around the TTT. However, there is a large variability in the anatomical relationship between the soft-tissue landmarks and the TTT. Caution is advised if relying on these structures intraoperatively.

Impact of femoro-tibial size combinations and TKA design on kinematics

INTRODUCTION

The variability in patients' femoral and tibial anatomy requires to use different tibia component sizes with the same femoral component size. These size combinations are allowed by manufacturers, but the clinical impact remains unclear. Therefore, the goals of our study were to investigate whether combining different sizes has an impact on the kinematics for two well-established knee systems and to compare these systems' kinematics to the native kinematics.

MATERIALS AND METHODS

Six fresh frozen knee specimens were tested in a force controlled knee rig before and after implantation of a cruciate retaining (CR) and a posterior-stabilized (PS) implant. Femoro-tibial kinematics were recorded using a ultrasonic-based motion analysis system while performing a loaded squat from 30° to 130°. In each knee, the original best fit inlay was then replaced by different inlays simulating a smaller or bigger tibia component. The kinematics obtained with the simulated sizes were compared to the original inlay kinematics using descriptive statistics.

RESULTS

For all size combinations, the difference to the original kinematics reached an average of 1.3 ± 3.3 mm in translation and - 0.1 ± 1.2° in rotation with the CR implant. With the PS implant, the average differences reached 0.4 ± 2.7 mm and  - 0.2 ± 0.8°. Among all knees, no size combination consistently resulted in significantly different kinematics. Each knee showed a singular kinematic pattern. For both knee systems, the rotation was smaller than in the native knee, but the direction of the rotation was preserved. The PS showed more rollback and the CR less rollback than the native knee.

CONCLUSION

TKA systems designed with a constant tibio-femoral congruency among size combinations should enable to combine different sizes without having substantial impact on the kinematics. The rotational pattern was preserved by both TKA systems, while the rollback could only be maintained by the PS design.

The Influence of Mathematical Definitions on Patellar Kinematics Representations

A correlation between patellar kinematics and anterior knee pain is widely accepted. However, there is no consensus on how they are connected or what profile of patellar kinematics would minimize anterior knee pain. Nevertheless, answering this question by merging existing studies is further complicated by the variety of ways to describe patellar kinematics. Therefore, this study describes the most frequently used conventions for defining patellar kinematics, focusing on the rotations. The similarities and differences between the Cardan sequences and angles calculated by projecting axes are analyzed. Additionally, a tool is provided to enable the conversion of kinematic data between definitions in different studies. The choice of convention has a considerable impact on the absolute values and the clinical characteristics of the patello-femoral angles. In fact, the angles that result from using different mathematical conventions to describe a given patello-femoral rotation from our analyses differ up to a Root Mean Squared Error of 111.49° for patellar flexion, 55.72° for patellar spin and 35.39° for patellar tilt. To compare clinical kinematic patello-femoral results, every dataset must follow the same convention. Furthermore, researchers should be aware of the used convention’s implications to ensure reproducibility when interpreting and comparing such data.

Patellar management during total knee arthroplasty: a review

The optimal management of the patella during total knee arthroplasty (TKA) remains controversial and surgeons tend to approach the patella with one of three general mindsets: always resurface the patella, never resurface the patella, or selectively resurface the patella based on specific patient or patellar criteria.

Studies comparing resurfacing and non-resurfacing of the patella during TKA have reported inconsistent and contradictory findings.

When resurfacing the patella is chosen, there are a number of available patellar component designs, materials, and techniques for cutting and fixation.

When patellar non-resurfacing is chosen, several alternatives are available, including patellar denervation, lateral retinacular release, and patelloplasty. Surgeons may choose to perform any of these alone, or together in some combination.

Prospective randomized studies are needed to better understand which patellar management techniques contribute to superior postoperative outcomes. Until then, this remains a controversial topic, and options for patellar management will need to be weighed on an individual basis per patient.

Cite this article: EFORT Open Rev 2021;6:861-871. DOI: 10.1302/2058-5241.6.200156

Tibial baseplate position and posterior cruciate ligament status impact patient-reported outcomes in conforming dual-pivot bearing total knee arthroplasty

Background

In an effort to optimize clinical outcomes and enhance stability, ultracongruent bearings have been increasingly used in primary total knee arthroplasty (TKA). The importance of the posterior cruciate ligament (PCL) and optimal sagittal tibial baseplate position in ultracongruent bearing TKA remains unknown. This study sought to determine whether these modifiable, surgical-technique-dependent variables meaningfully impact patient-reported outcome measures.

Methods

A total of 759 primary TKAs of the same dual-pivot design performed using a consistent surgical technique between January 2016 and April 2019 were retrospectively reviewed. PCL status was recorded, and anteroposterior (AP) tibial baseplate position and posterior tibial slope were measured by two independent blinded raters. Patient-reported outcomes related to pain, function, satisfaction, and activity level were analyzed in relationship to PCL status, posterior tibial slope, and AP tibial baseplate position, in addition to other pertinent covariates.

Results

Median age and body mass index of the cohort were 68.3 years and 33.4 kg/m², respectively, with 73% being female. In multivariate analysis, partial or full release of the PCL was predictive of a knee “always” feeling normal (odds ratio 1.42, P = .041). Furthermore, tibial baseplate position closer to the middle of the tibia was associated with greater improvements in pain with level walking, pain while climbing stairs, and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement total scores (P ≤ .079).

Conclusion

In congruent dual-pivot bearing TKA, partially or fully releasing the PCL and AP tibial baseplate position closer to the middle of the tibia may provide greater improvement in pain and function scores at minimum 1-year follow-up.

Early migration of a medially stabilized total knee arthroplasty : a radiostereometric analysis study up to two years

Aims

Medial pivot (MP) total knee arthroplasties (TKAs) were designed to mimic native knee kinematics with their deep medial congruent fitting of the tibia to the femur almost like a ball-on-socket, and a flat lateral part. GMK Sphere is a novel MP implant. Our primary aim was to study the migration pattern of the tibial tray of this TKA.

Methods

A total of 31 patients were recruited to this single-group radiostereometric analysis (RSA) study and received a medial pivot GMK Sphere TKA. The distributions of male patients versus female patients and right versus left knees were 21:10 and 17:14, respectively. Mean BMI was 29 kg/m² (95% confidence interval (CI) 27 to 30) and mean age at surgery was 63 years (95% CI 61 to 66). Maximum total point motions (MTPMs), medial, proximal, and anterior translations and transversal, internal, and varus rotations were calculated at three, 12, and 24 months. Patient-reported outcome measure data were also retrieved.

Results

MTPMs at three, 12, and 24 months were 1.0 mm (95% CI 0.8 to 1.2), 1.3 mm (95% CI 0.9 to 1.7), and 1.4 mm (0.8 to 2.0), respectively. The Forgotten Joint Score was 79 (95% CI 39 to 95) and Knee Injury and Osteoarthritis Outcome Score obtained at two years was 94 (95% CI 81 to 100), 86 (95% CI 75 to 93), 94 (95% CI 88 to 100), 69 (95% CI 48 to 88), and 81 (95% CI59 to 100) for Pain, Symptoms, Activities of Daily Living, Sport & Recreation, and Quality of Life, respectively.

Conclusion

In conclusion, we found that the mean increase in MTPM was lower than 0.2 mm between 12 and 24 months and thus apparently stable. Yet the GMK Sphere had higher migration at one and two years than anticipated. Based on current RSA data, we therefore cannot conclude on the long-term performance of the implant, pending further assessment.

Cite this article: Bone Jt Open 2021;2(9):737–744.

Higher patellofemoral compressive force does not affect anterior knee pain in anatomical bi-cruciate retaining total knee arthroplasty: In vivo prospective analysis of guided motion prosthesis

BACKGROUND

The purposes of the present study are 1) to measure intraoperative patellofemoral compressive force in patients undergoing anatomical bi-cruciate retaining total knee arthroplasty and to assess the relationship between intraoperative patellofemoral compressive force and patient reported outcome measurements and 2) to compare patellofemoral compressive force and patient reported outcome measurements among patients who underwent anatomical bi-cruciate retaining, cruciate retaining, and bi-cruciate stabilized total knee arthroplasty.

METHODS

Twenty-two patients with varus osteoarthritis of the knee who underwent anatomical bi-cruciate retaining total knee arthroplasty, 20 patients who underwent cruciate retaining total knee arthroplasty, and 24 patients who underwent bi-cruciate stabilized total knee arthroplasty were assessed. Patient reported outcome measurements were evaluated at 1.5 years after surgery.

FINDINGS

Intraoperative patellofemoral compressive force was significantly lower with anatomical bi-cruciate retaining total knee arthroplasty than with cruciate retaining total knee arthroplasty at 60° to 140° of flexion and nearly equivalent to intraoperative patellofemoral compressive force with bi-cruciate stabilized total knee arthroplasty at all knee flexion angles examined. With anatomical bi-cruciate retaining total knee arthroplasty, there were no significant correlations between intraoperative patellofemoral compressive force and almost all patient reported outcome measurements except for 2011 Knee Society Score expectations, which was positively correlated with patellofemoral compressive force at 10° of flexion, and Patella score quadriceps strength, which was negatively correlated with patellofemoral compressive force at 60° of flexion.

INTERPRETATION

There were no significant correlations between intraoperative patellofemoral compressive force and anterior knee pain after anatomical bi-cruciate retaining total knee arthroplasty. Evidence level: 3.

The medial tangent of the proximal tibia is a suitable extra-articular landmark in determining the tibial anteroposterior axis

BACKGROUND

Tibial rotational alignment in total knee arthroplasty (TKA) is generally determined based on intra-articular structure, and can be difficult to ascertain in some cases. The aim of this study was to investigate whether the medial tangent angle of the tibia (MTAT) could be useful in determining the anteroposterior axis of the tibia.

METHODS

This study was performed on 103 lower limbs in 53 patients who underwent primary total hip arthroplasty. The selection criteria for our study were based on the assumption that knees in patients undergoing THA exhibit fewer degenerative changes than knees in patients undergoing TKA. Using computed tomography images, the MTAT, comprising the medial tangent of the proximal tibia and the anteroposterior (AP) axis of the tibia, was measured on three horizontal planes: at the distal edge of the tibial tubercle (A), at 5 cm distally (B), and at 10 cm further distally (C). The tibial medial surface was grouped into three classes according to shape: valley type, flat type, and hill type. The percentage at which these shapes were observed in each group was also calculated. Measurement reliability was calculated using the intraclass correlation coefficient.

RESULTS

The angles were 45.2° (interquartile range: IR 43.0-47.7) at A, 42.7° (IR 38.7-45.9) at B, and 42.4° (IR 38.2-45.9) at C. Intra-rater reliability and inter-rater reliability was 0.982 and 0.974 at A, 0.810 and 0.411 at B, and 0.940 and 0.811 at C, respectively. Regarding the tibial medial surface, the valley type was observed in all cases at A, and the hill type was observed in the highest percentage of cases at B and C.

CONCLUSIONS

The MTAT was approximately 45° at level A, and reproducibility was the highest among the three groups. The two points forming the valley on the tibial medial surface were bony ridges. Therefore, the medial tangent of the tibia at level A could be easily determined. Because the distal edge of the tibial tubercle exists at the surgical area and the extra-articular area, it can be a suitable intraoperative, extra-articular landmark in determining the tibial AP axis, even for revision TKA.

Secondary Patellar Resurfacing in TKA: A Combined Analysis of Registry Data and Biomechanical Testing

The German Arthroplasty registry (EPRD) has shown that different prosthesis systems have different rates of secondary patellar resurfacing: four years after implantation, the posterior-stabilized (PS) Vega prosthesis has a 3.2% risk of secondary patellar resurfacing compared to the cruciate-retaining (CR) Columbus prosthesis at 1.0% (both Aesculap AG, Tuttlingen, Germany). We hypothesized that PS implants have increased retropatellar pressure and a decreased retropatellar contact area compared to a CR design, which may lead to an increased likelihood of secondary patellar resurfacing. Eight fresh frozen specimens (cohort 1) were tested with an established knee rig. In addition, a possible influence of the registry-based patient collective (cohort 2) was investigated. No significant differences were found in patient data–cohort 2-(sex, age). A generally lower number of PS system cases is noteworthy. No significant increased patella pressure could be detected with the PS design, but a lower contact area was observed (cohort 1). Lower quadriceps force (100°–130° flexion), increased anterior movement of the tibia (rollback), greater external tilt of the patella, and increasing facet pressure in the Vega PS design indicate a multifactorial cause for a higher rate of secondary resurfacing which was found in the EPRD patient cohort and might be related to the PS’ principle function.

A new technique for determining the rotational alignment of the tibial component during total knee arthroplasty

BACKGROUND

We evaluated the effectiveness of our new technique "Range of motion-anatomical (ROM-A) technique" which is the combination of the self-positioning technique "Range of motion (ROM) technique" and the anatomical landmarks technique in determining the tibial component (TC) rotation alignment in total knee arthroplasty (TKA) using a navigation system.

METHODS

This retrospective study included 103 knees who underwent TKA. The ROM-A technique was consisted of two steps. First, the TC was set and marked by the ROM technique in knee extension. Second, the TC was set according to the marking in the knee flexion and the component rotational angle relative to the anatomical tibial anteroposterior (AP) axis was adjusted between 0° and 10° external rotation using the navigation system. The rotational angle of TC relative to the anatomical AP axis was measured using postoperative computed tomography. Moreover, the hypothetical rotational angle of the TC in the ROM technique was calculated only from the intraoperative difference between the two techniques.

RESULTS

The actual rotational angle by the ROM-A technique was externally rotated 3.0°, and the rotational outlier occurred in 3.0%. A significant difference in outlier rate was observed between the two techniques (p = 0.03). The hypothetical rotational angle of TC determined by the ROM technique (the first step only in the ROM-A technique) was externally rotated 4.6° and the TC rotational outlier (difference to AP axis: >10°) occurred in 11.7%.

CONCLUSION

Using the ROM-A technique, the TC was finally fixed in almost all targeted rotational positions, and this technique could reduce the anatomical rotational outlier compared with the ROM technique.

The prevalence of posterolateral tibial baseplate overhang: An anatomical CT study

Introduction

Total Knee Arthroplasty (TKA) is used in patients with osteoarthritis who have failed conservative management to reduce pain, improve functional outcomes and ultimately quality of life. However, less than optimal patient satisfaction has led to continued improvements in design and technology of TKA. One factor that can limit patient satisfaction is postero-lateral overhang of the tibial baseplate. The purpose of our study is to utilize pre-operative CT scans to assess the prevalence of posterolateral tibial overhang with the use of a symmetric tibial baseplate component in a popular knee system with robotic assistance.

Methods

Ninety-eight (98) consecutive patients who underwent robotic-assisted total knee arthroplasty (TKA) were included in this study. Using both the most medial aspect of the tibial tubercle and the medial ⅓ of the tibial tubercle as reference points, we quantified the extent of posterolateral overhang when determining the rotation of the tibial component.

Results

Using the most medial aspect of the tibial tubercle as a reference point for rotation of the tibial baseplate, 63% of the instances of reviewed CT scans (369/588) had posterolateral overhang. Furthermore, 81% (406/588) had posterolateral overhang when using the medial ⅓ aspect of the tibial tubercle as the reference for rotation of the tibial baseplate. The average posterolateral tibial baseplate overhang was 1.5 mm (range 0-8 mm) when using the most medial aspect of the tibial tubercle and 2.4 mm (range 0-8 mm) when using the medial ⅓ tibial tubercle as the centering point for the tibial baseplate.

Discussion

Tibial baseplate overhang could lead to potential pain from irritation of soft tissues. To our knowledge, this is the first study that was able to valencquantify the amount of tibial baseplate overhang using pre-operative CT scans. Rotational alignment of the tibial baseplate needs to be balanced to ensure minimal lateral overhang while achieving sufficient external rotation of the tibial component. An asymmetric tibial component may provide a compromise in certain situations.

Level of evidence

Diagnostic level IV case series.

Internal rotation of the tibial component in total knee arthroplasty can lead to extension deficit

PURPOSE

Stiffness is a common problem following total knee arthroplasty (TKA). Mal-rotated components have been claimed to be the major cause of pain and limited motion after TKA. The present study investigates whether intra-operative intentional malrotation of the tibial component would change in vivo kinematics. The hypothesis is excessive internal rotation of the tibial component would result in postoperative extension deficit.

METHODS

Thirty-one patients were enrolled in this study. After completing bony cuts and proper soft tissue balancing, the femoral and tibial trials were impacted and fixed using small pins. Lateral radiographs were used to measure and compare intraoperative full knee extension during normal and after intentional internal rotation of the tibial component. The extension deficit angles were also compared between the posterior stabilised (PS) and cruciate retaining (CR) implants.

RESULTS

For normal tibial component rotation, the median (interquartile range) extension deficit was 0° (4). The mean tibial trial intentional internal rotation was 21.2° (± 4.5). The median (interquartile range) extension deficit significantly increased to 6° (4) after tibial component internal rotation (p = 0.001). The use of PS spacers resulted in a significantly greater extension deficit after intentional internal rotation 9° (5) compared to that of the CR implant 1° (4) (p = 0.001).

CONCLUSION

Internal rotation of the tibial component in total knee arthroplasty can lead to postoperative extension deficit. This could be attributed to interference with "screw home" mechanism that requires full external rotation of the tibia on the femur. Consequently, this deficit may cause pain and knee stiffness following TKA.

LEVEL OF EVIDENCE

III.

Tibiofemoral rotation alignment in the normal knee joints among Chinese adults: a CT analysis

Background

Consensus on tibial rotation in total knee arthroplasty (TKA) remains controversial. The present study aimed to investigate the closest anatomical reference to surgical epicondylar axis (SEA) among 10 tibial markers in Chinese adults.

Methods

This study included examination of 122 normal lower extremities. Briefly, 10 axes were drawn on the axial sections: transverse axis of tibia (TAT), axis of medial edge of patellar tendon (MEPT), axis of medial 1/3 of patellar tendon attachment (M1/3), Akagi line, Insall line, axis of medial border of tibial tubercle (MBTT), and axis of anterior border of the tibia 1–4 (ATC1–4). The mean angles between TAT and SEA and that between other axes and the line perpendicular to SEA were measured. Pairwise differences among the 10 tibial axes were examined by applying one-way analysis of variance (ANOVA) and paired t-test.

Results

In all the knees, the mean angles of M1/3, Akagi line, Insall line, MBTT, ATC1, ATC2, ATC3, and ATC4 axes were compared to the line perpendicular to the projected SEA and found to be 10.2 ± 5.1°, 1.4 ± 5.0°, 11.9 ± 5.4°, 3.6 ± 4.8°, 12.0 ± 6.9°, 7.2 ± 8.6°, 7.1 ± 10.4°, and 6.6 ± 13.5° external rotation, respectively, and the MEPT axis was 1.6 ± 4.5° internal rotation. The mean angle for TAT was 4.1 ± 5.3° external rotation. The M1/3 and Insall line were significantly more externally rotated than Akagi line, MEPT, MBTT, TAT, ATC2, ATC3, and ATC4 axes. No significant differences were noted between the TAT axis and the MBTT axis and among the ATC2, ATC3, and ATC4 axes.

Conclusion

The Akagi line, MBTT, and TAT showed good consistency with SEA in the axial femorotibial alignment with knee in extension. The middle segment of the anterior tibial crest also demonstrated good alignment consistency with SEA for the axial femorotibial alignment. Hence, these markers can be used as reliable references for rotational alignment of the tibial component in TKA.

Musculoskeletal Multibody Simulation Analysis on the Impact of Patellar Component Design and Positioning on Joint Dynamics after Unconstrained Total Knee Arthroplasty

Patellofemoral (PF) disorders are considered a major clinical complication after total knee replacement (TKR). Malpositioning and design of the patellar component impacts knee joint dynamics, implant fixation and wear propagation. However, only a limited number of studies have addressed the biomechanical impact of the patellar component on PF dynamics and their results have been discussed controversially. To address these issues, we implemented a musculoskeletal multibody simulation (MMBS) study for the systematical analysis of the patellar component’s thickness and positioning on PF contact forces and kinematics during dynamic squat motion with virtually implanted unconstrained cruciate-retaining (CR)-TKR. The patellar button thickness clearly increased the contact forces in the PF joint (up to 27%). Similarly, the PF contact forces were affected by superior–inferior positioning (up to 16%) and mediolateral positioning (up to 8%) of the patellar button. PF kinematics was mostly affected by the mediolateral positioning and the thickness of the patellar component. A medialization of 3 mm caused a lateral patellar shift by up to 2.7 mm and lateral patellar tilt by up to 1.6°. However, deviations in the rotational positioning of the patellar button had minor effects on PF dynamics. Aiming at an optimal intraoperative patellar component alignment, the orthopedic surgeon should pay close attention to the patellar component thickness in combination with its mediolateral and superior–inferior positioning on the retropatellar surface. Our generated MMBS model provides systematic and reproducible insight into the effects of patellar component positioning and design on PF dynamics and has the potential to serve as a preoperative analysis tool.

Impact of tibial baseplate malposition on kinematics, contact forces and ligament tensions in TKA: A numerical analysis

PURPOSE

Malposition of implant components in total knee arthroplasty (TKA) has consequences on tibiofemoral kinematics, contact forces and ligament tensions. To evaluate the impact of tibial baseplate malpositioning in the same knee, we conducted a computer simulation.

METHODS

An established weight-bearing finite element model of a fixed bearing TKA was used for the computer simulation. To evaluate the influence of tibial baseplate malposition, calculations were consecutively performed in neutral position, at 3° and 6° of internal and external rotation and at 3 mm and 6 mm of medial and lateral translation.

RESULTS

The highest effect of malposition was observed for ligament tensions, with a tendency of a greater influence for the 6 mm translation compared to 6° of rotation. Changes in contact forces and tibiofemoral kinematics were according to the alterations of ligament tensions. The highest ligament tension, contact force and femoral roll-back were registered for 6 mm medialization of the tibial baseplate.

DISCUSSION

Tibial baseplate malposition effects ligament tensions, tibiofemoral contact forces and kinematics and has a risk of unfavorable clinical results due to postoperative pain, reduced range of motion, instability and a higher rate of early loosening. Therefore, surgeons should aim for a neutral position of the tibial baseplate.

Tibial Tubercle-Trochlear Groove Distance Influences Patellar Tilt After Total Knee Arthroplasty

BACKGROUND

Tibial tubercle-trochlear groove (TT-TG) distance is associated with a greater risk of recurrent patellar dislocation in young, active patients. However, the effect of TT-TG distance after total knee arthroplasty (TKA) has not been investigated. The purpose is to analyze the effect of TT-TG distance and component rotation on patellar tilt and patellar shift after TKA.

METHODS

After TKA, axial computed tomography scans and axial radiograph were taken in 115 consecutive knees. TT-TG distance was measured between the most anterior point of the tibial tuberosity and the deepest point of the femoral component relative to a line connecting the anterior condyles. Femoral and tibial component rotation was measured relative to the femoral and tibial rotational axis, respectively. Pearson correlation coefficients were calculated.

RESULTS

TT-TG distance had a significant correlation with patellar tilt in extension (R = 0.220, P = .018), patellar tilt in flexion (R = 0.438, P < .001), and patellar shift (R = 0.330, P < .001). Tibial component rotation had a significant correlation with patellar tilt in flexion (R = -0.251, P = .007) and patellar shift (R = -0.360, P < .001). Femoral component rotation had no significant correlations. Tibial component rotation had a significant correlation with TT-TG distance (R = -0.573, P < .001), whereas femoral component rotation had no correlation (P = .192).

CONCLUSION

TT-TG distance had a significant correlation with patellar tilt and patellar shift. Surgeons need to understand the factors affecting TT-TG distance and to pay attention to avoiding excessive TT-TG distance after TKA.

Effect of surgical parameters on the biomechanical behaviour of bicondylar total knee endoprostheses - A robot-assisted test method based on a musculoskeletal model

The complicated interplay of total knee replacement (TKR) positioning and patient-specific soft tissue conditions still causes a considerable number of unsatisfactory outcomes. Therefore, we deployed a robot-assisted test method, in which a six-axis robot moved and loaded a bicondylar cruciate-retaining (CR)-TKR in a virtual lower extremity emulated by a musculoskeletal multibody model. This enabled us to systematically analyse the impact of the posterior cruciate ligament (PCL), tibial slope, and tibial component rotation on TKR function while considering the physical implant components and physiological-like conditions during dynamic motions. The PCL resection yielded a decrease of femoral rollback by 4.5 mm and a reduction of tibiofemoral contact force by 50 N. A reduced tibial slope led to an increase of tibiofemoral contact force by about 170 N and a decrease of femoral rollback up to 1.7 mm. Although a higher tibial slope reduced the contact force, excessive tibial slopes should be avoided to prevent joint instability. Contrary to an external rotation of the tibial component, an internal rotation clearly increased the contact force and lateral femoral rollback. Our data contribute to improved understanding the biomechanics of TKRs and show the capabilities of the robot-assisted test method based on a musculoskeletal multibody model as a preoperative planning tool.

Intraoperative Tibial Anteroposterior Axis Could Not Be Replicated After Tibial Osteotomy in Total Knee Arthroplasty

BACKGROUND

We evaluated the effect of the anteroposterior (AP) axis of the proximal tibia defined at the cutting surface using an image-free navigation system in total knee arthroplasty.

METHODS

This prospective study included 68 patients (79 knees) who underwent total knee arthroplasty. The tibial AP axis was registered in the navigation system with reference to Akagi's line, connecting the middle of the posterior cruciate ligament to the medial border of the patellar tendon attachment at the tibial joint surface. After proximal tibial osteotomy, the AP axis was replicated as the AP(O) axis. We measured the difference between the AP axis defined at the joint surface and the AP(O) axis defined at the osteotomy surface.

RESULTS

The AP(O) axis at the osteotomy surface internally rotated 2.0° to the AP axis at the joint surface, and the AP(O) axis outlier (difference to AP axis: >3°) occurred in 54% (43 knees). In the >3° malrotation group, internal malrotation occurred in 37% (30 knees) and external malrotation occurred in 17% (13 knees). In the outlier analysis, the left knees were significantly found in the internal outlier group.

CONCLUSION

The tibial AP axis, connecting the middle of the posterior cruciate ligament to the medial border of the patellar tendon attachment defined at the tibial joint surface, could not be replicated at the tibial osteotomy surface. If the tibial components were set depending only on the AP axis defined at the osteotomy surface, the tibial components could internally rotate and have more outliers, especially in the left knees.

Association Between Femoral Component Sagittal Positioning and Anterior Knee Pain in Total Knee Arthroplasty: A 10-Year Case-Control Follow-up Study of a Cruciate-Retaining Single-Radius Design

BACKGROUND

Anterior knee pain is the most common complication of total knee arthroplasty (TKA). The purpose of this study was to assess whether sagittal femoral component position is an independent predictor of anterior knee pain after cruciate-retaining single-radius TKA without routine patellar resurfacing.

METHODS

A prospective cohort study of 297 cruciate-retaining single-radius TKAs performed in 2006 and 2007 without routine patellar resurfacing identified 73 patients (25%) with anterior knee pain and 89 (30%) with no pain (controls) at 10 years. Patients were assessed preoperatively and at 1, 5, and 10 years postoperatively using patient-reported outcome measures (PROMs), including the Short Form-12 (SF-12), Oxford Knee Score (OKS), and satisfaction and expectation questionnaires. Variables that were assessed as predictors of anterior knee pain included demographic data, the indication for the TKA, early complications, stiffness requiring manipulation under anesthesia, and radiographic criteria (implant alignment, Insall-Salvati ratio, posterior condylar offset ratio, and anterior femoral offset ratio).

RESULTS

The 73 patients with anterior knee pain (mean age, 67.0 years [range, 38 to 82 years]; 48 [66%] female) had a mean visual analog scale (VAS) score of 34.3 (range, 5 to 100) compared with 0 for the 89 patients with no pain (mean age, 66.5 years [range, 41 to 82 years]; 60 [67%] female). The patients with anterior knee pain had mean femoral component flexion of -0.6° (95% confidence interval [CI] = -1.5° to 0.3°), which differed significantly from the value for the patients with no pain (1.42° [95% CI = 0.9° to 2.0°]; p < 0.001). The patients with and those without anterior knee pain also differed significantly with regard to the mean anterior femoral offset ratio (17.2% [95% CI = 15.6% to 18.8%] compared with 13.3% [95% CI = 11.1% to 15.5%]; p = 0.005) and the mean medial proximal tibial angle (89.7° [95% CI = 89.2° to 90.1°] compared with 88.9° [95% CI = 88.4° to 89.3°]; p = 0.009). All PROMs were worse in the anterior knee pain group at 10 years (p < 0.05), and the OKSs were worse at 1, 5, and 10 years (p < 0.05). Multivariate analysis confirmed femoral component flexion, the medial proximal tibial angle, and an Insall-Salvati ratio of <0.8 (patella baja) as independent predictors of anterior knee pain (R = 0.263). Femoral component extension of ≥0.5° predicted anterior knee pain with 87% sensitivity.

CONCLUSIONS

In our study, 25% of patients had anterior knee pain at 10 years following a single-radius cruciate-retaining TKA without routine patellar resurfacing. Sagittal plane positioning and alignment of the femoral component were associated with long-term anterior knee pain, with femoral component extension being a major risk factor.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Improved Range of Motion and Patient-Reported Outcome Scores With Fixed-Bearing Revision Total Knee Arthroplasty for Suboptimal Axial Implant Rotation

BACKGROUND

Suboptimal implant rotation has consequences with respect to knee kinematics and clinical outcomes. We evaluated the functional outcomes of revision total knee arthroplasty (TKA) for poor axial implant rotation.

METHODS

We retrospectively reviewed 42 TKAs undergoing aseptic revision for poor axial implant rotation. We assessed improvements in Knee Society Score (KSS) and final range of motion (ROM). Subgroup analyses were performed for preoperative instability and stiffness, as well as the number of components revised and level of implant constraint used.

RESULTS

Revision for poor axial rotation in isolation improved KSS from 52 ± 22 to 84 ± 25 (P < .001), and flexion increased from 105 ± 21° to 115 ± 13° (P = .001). Revision in the setting of instability significantly improved the KSS (P < .001) but did not affect ROM (P = .172). Revision in the setting of stiffness significantly improved both KSS (P < .001) and ROM (P = .002). There was no statistically significant difference between the postoperative KSS (P = .889) and final knee flexion (P = .629) with single- or both-component revision TKA for isolated poor axial rotation or between the postoperative KSS (P = .956) and final knee flexion (P = .541) with or without the use of higher constraint during revision TKA for isolated poor axial rotation.

CONCLUSION

Revision TKA for poor axial alignment improves clinical outcomes scores and functional ROM.

Kinematically aligned total knee arthroplasty reproduces native patellofemoral biomechanics during deep knee flexion

PURPOSE

The implant positioning for kinematically aligned total knee arthroplasty (TKA) differs fundamentally from conventional mechanically aligned TKA. This difference may affect patellofemoral (PF) biomechanics after TKA. This cadaveric study tested the hypothesis that kinematically aligned TKA would restore PF biomechanics to the native condition better than mechanically aligned TKA.

METHODS

Seven pairs (14 knees) of fresh-frozen cadavers were tested. All specimens were mounted on a customized knee-testing system and digitized using a Microscribe 3DLX instrument (Revware Inc., Raleigh, NC, USA) to measure patellar kinematics in terms of patellar varus/valgus rotation, medial/lateral position, flexion/extension rotation and proximal/distal position at knee flexion angles of 0°, 30°, 60°, 90°, and 120°. The medial and lateral PF joint contact pressure distributions at 120° of knee flexion were measured using a K-scan system (Tekscan Inc., Boston, MA, USA). All patellae remained unresurfaced. For each pair, one knee was randomly assigned to kinematically aligned TKA and the other to mechanically aligned TKA performed using the conventional measured resection technique. During kinematically aligned TKA, the amount of femur and tibia resected was equivalent to implant thickness to maintain the patient-specific joint line. All patellar kinematics were measured and compared between the native condition and after surgery.

RESULTS

The patellae of mechanically aligned TKA rotated more valgus and was positioned more laterally compared with those of kinematically aligned TKA at knee flexion angles ≥ 90°. Neither the patellar flexion/extension rotation nor the proximal/distal position differed between either prosthetic knee design and the native knee at all flexion angles. The contact pressure distribution between the medial and lateral PF joint after kinematically aligned TKA were similar to those of the native knee, while the lateral PF joint contact pressure after mechanically aligned TKA was higher than that of the native knee (p = 0.038).

CONCLUSIONS

Kinematically aligned TKA better restores patellar kinematics and PF contact pressure distribution to the native condition than mechanically aligned TKA during deep knee flexion. These findings provide clues to understand why kinematically aligned TKA is associated with less anterior knee pain and better PF functional performance compared to mechanically aligned TKA. Patients undergoing kinematically aligned TKA may experience a more normal feeling during deep knee flexion activities.

A proposed new rotating reference axis for the tibial component after proximal tibial resection in total knee arthroplasty

Purpose

During total knee arthroplasty, few rotating reference axes can be reliably used after tibial resection. We speculated that a line that passes through the lateral edge of the posterior cruciate ligament (PCL) at its tibial attachment after resection and the most prominent point of the tibial tubercle [after-tibial resection (ATR) line] will provide a good reference axis. In this study, we aimed to evaluate the association between ATR and Akagi’s lines.

Materials and methods

In this case–control simulation study, we retrospectively evaluated 38 patients with varus knee and 28 patients with valgus knee. We defined the reference cutting plane as 10 mm distal from the lateral articular surface of the tibia in varus group and as 7 mm distal from the medial articular surface in the valgus group. We measured angles between Akagi’s line and the ATR line (ATR line angle) as well as between Akagi’s line and 1/3 Akagi’s line (1/3 Akagi’s line angle), which passes through the midpoint of PCL and the medial third of the patellar tendon. We used paired t-tests to determine the significance of differences between these angles, with p < 0.05 indicating statistical significance. Intra- and interclass correlation coefficients for the reproducibility of 1/3 Akagi’s line angle and ATR line angle were analyzed by two surgeons.

Results

We found that 1/3 Akagi’s line angle was 10.2° ± 1.3° in the varus group and 10.9° ± 1.3° in the valgus group (p = 0.017). The ATR line was positioned externally compared with Akagi’s line in all patients. Mean ATR line angles at 0°, 3° and 7° posterior slopes were 6.1° ± 1.9°, 5.8° ± 2.0° and 6.0° ± 1.7° in the varus group and 6.3° ± 2.3°, 6.2° ± 2.3° and 5.4° ± 2.1° in the valgus group, respectively. There were no significant differences in the ATR line angle between the varus and valgus groups. (p = 0.34–0.67) Intra- and interclass correlation coefficients for the reproducibility of 1/3 Akagi’s line angle were 0.936 and 0.986 and those for the reproducibility of ATR line angle were 0.811 and 0.839.

Conclusions

The ATR line was positioned between Akagi’s line and 1/3 Akagi’s line in all patients and was a valid option for evaluating rotational tibial alignment after tibial resection.

Do modern total knee replacements improve tibial coverage?

PURPOSE

The purpose of the present study is to compare newer designs of various symmetric and asymmetric tibial components and measure tibial bone coverage using the rotational safe zone defined by two commonly utilized anatomic rotational landmarks.

METHODS

Computed tomography scans (CT scans) of one hundred consecutive patients scheduled for total knee arthroplasty were obtained pre-operatively. A virtual proximal tibial cut was performed and two commonly used rotational axes were added for each image: the medio-lateral axis (ML-axis) and the medial 1/3 tibial tubercle axis (med-1/3-axis). Different symmetric and asymmetric implant designs were then superimposed in various rotational positions for best cancellous and cortical coverage. The images were imported to a public domain imaging software, and cancellous and cortical bone coverage was computed for each image, with each implant design in various rotational positions.

RESULTS

One single implant type could not be identified that provided the best cortical and cancellous coverage of the tibia, irrespective of using the med-1/3-axis or the ML-axis for rotational alignment. However, it could be confirmed that the best bone coverage was dependent on the selected rotational landmark. Furthermore, improved bone coverage was observed when tibial implant positions were optimized between the two rotational axes.

CONCLUSIONS

Tibial coverage is similar for symmetric and asymmetric designs, but depends on the rotational landmark for which the implant is designed. The surgeon has the option to improve tibial coverage by optimizing placement between the two anatomic rotational alignment landmarks, the medial 1/3 and the ML-axis. Surgeons should be careful assessing intraoperative rotational tibial placement using the described anatomic rotational landmarks to optimize tibial bony coverage without compromising patella tracking.

LEVEL OF EVIDENCE

III.

Native rotational knee kinematics are lost in bicruciate-retaining total knee arthroplasty when the tibial component is replaced

PURPOSE

To compare the kinematics between native knees and knees that have undergone bicruciate-retaining (BCR) total knee arthroplasty (TKA) with cruciate-retaining (CR) TKA converted from BCR TKA in the same whole-body cadaveric specimen using a navigation system and, if differences exist, to investigate the point at which normal kinematics are lost during the procedure.

METHODS

The rotational kinematics throughout passive flexion of the native knee and of knees after meniscectomy, femoral replacement, BCR TKA, or CR TKA were assessed in nine fresh frozen cadavers using an image-free navigation system.

RESULTS

The rotational kinematic pattern of a knee after BCR TKA was different from that of a native knee, especially in the early flexion phase, and was similar to that after CR TKA. Screw-home movement was not observed after BCR TKA, but still occurred after meniscectomy or femoral replacement with intact cruciate ligaments and an intact tibial articular surface.

CONCLUSION

The rotational kinematics of the native knee are not always preserved after BCR TKA. Native rotational kinematics are preserved after meniscectomy and femoral replacement, but are lost after tibial replacement in BCR TKA. Surgeons should pay close attention to maintain the anteroposterior stabilizing function of the ACL in BCR TKA, rather than to restore the native rotational kinematics.

Tibial internal rotation negatively affects clinical outcomes in total knee arthroplasty: a systematic review

PURPOSE

The aim of this systematic review is to analyze the effect of tibial rotational alignment after total knee arthroplasty (TKA) on clinical outcomes and assess the eventual cut-off values for tibial TKA rotation leading to poor outcomes.

METHODS

A detailed and systematic search from 1997 to 2017 of the Pubmed, Medline, Cochrane Reviews, and the Google Scholar databases was performed using the keyword terms "total knee arthroplasty", "total knee replacement", "tibial alignment", "tibial malalignement", "tibial rotation", "rotational error", "axis", "angle", "tibial malrotation", "clinical outcome", in several combinations. The modified Coleman scoring methodology (mCMS) was used. All the primary TKAs studies analyzing correlation between clinical results and tibial rotation were included.

RESULTS

Five articles met the inclusion criteria. A total of 333 arthroplasties were included in this review; 139 had tibial component malalignment, while 194 were in control groups. The mean age of patients was 67.3 (SD 0.57) years. The mean average postoperative follow-up delay was 34.7 months (range 21-70). The mean mCMS score was 59.2 points indicating good methodological quality in the included studies. Functional outcomes were assessed through KSS, OKS, KOOS and VAS, negatively related to tibial internal rotation.

CONCLUSIONS

Our review confirmed that excessive internal rotation of the tibial TKA component represents a significant risk factor for pain and inferior functional outcomes after TKA (> 10° of internal rotation demonstrated the common value), since external rotation does not affect the results. However, a universal precise cut-off value has not been found in the available literature and there remains a debate about CT rotation assessment and surgical intra-operative landmarks.

LEVEL OF EVIDENCE

III.

Medial stabilized and posterior stabilized TKA affect patellofemoral kinematics and retropatellar pressure distribution differently

PURPOSE

Patellofemoral kinematics and retropatellar pressure distribution change after total knee arthroplasty (TKA). It was hypothesized that different TKA designs will show altered retropatellar pressure distribution patterns and different patellofemoral kinematics according to their design characteristics.

METHODS

Twelve fresh-frozen knee specimens were tested dynamically in a knee rig. Each specimen was measured native, after TKA with a posterior stabilized design (PS) and after TKA with a medial stabilized design (MS). Retropatellar pressure distribution was measured using a pressure sensitive foil which was subdivided into three areas (lateral and medial facet and patellar ridge). Patellofemoral kinematics were measured by an ultrasonic-based three-dimensional motion system (Zebris CMS20, Isny Germany).

RESULTS

Significant changes in patellofemoral kinematics and retropatellar pressure distribution were found in both TKA types when compared to the native situation. Mean retropatellar contact areas were significantly smaller after TKA (native: 241.1 ± 75.6 mm², MS: 197.7 ± 74.5 mm², PS: 181.2 ± 56.7 mm², native vs. MS p < 0.001; native vs. PS p < 0.001). The mean peak pressures were significantly higher after TKA. The increased peak pressures were however seen in different areas: medial and lateral facet in the PS-design (p < 0.001), ridge in the MS design (p < 0.001). Different patellofemoral kinematics were found in both TKA designs when compared to the native knee during flexion and extension with a more medial patella tracking.

CONCLUSION

Patellofemoral kinematics and retropatellar pressure change after TKA in different manner depending on the type of TKA used. Surgeons should be aware of influencing the risks of patellofermoral complications by the choice of the prosthesis design.

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

INTRODUCTION

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.

MATERIALS AND METHODS

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.

RESULTS

LRR revealed a significant reduction of femoral rollback at the lateral compartment (9.4 ± 5.0 vs 7.8 ± 9.4 mm; p < 0.01), whereas the present decrease of femoral rollback at the medial compartment was not significant (3.4 ± 4.7 vs 2.3 ± 5.9 mm; p = 0.34). Accordingly, LRR significantly reduced internal rotation of the tibia (0.8°; p < 0.01).

CONCLUSION

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.

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

PURPOSE

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.

METHODS

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.

RESULTS

ML translation of the femoral component by 3 mm did not lead to a significant alteration in retropatellar peak pressure (medial 6.5 ± 2.5 MPa vs. lateral 6.0 ± 2.4 MPa). 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.

CONCLUSION

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.

Influence of mediolateral tibial baseplate position in TKA on knee kinematics and retropatellar pressure

PURPOSE

Anterior knee pain is a major reason for unsatisfied patients after total knee arthroplasty (TKA). Since malposition and increased retropatellar peak pressure are supposed to contribute to pain, we conducted this in vitro study to analyse the influence of mediolateral tibial component position on tibiofemoral and patella kinematics as well as retropatellar pressure.

METHODS

Eight fresh frozen cadaver specimens were tested after a fixed-bearing TKA. To evaluate the influence of mediolateral tibial component position, special inlays with 3 mm of medialization and lateralization were constructed. For the analysis, a weight-bearing knee rig under a loaded squat from 20° to 120° of flexion was used. Tibiofemoral and patella kinematics were measured with an ultrasonic-based three-dimensional motion analysis system. Additionally, retropatellar pressure distribution was registered with a pressure-sensitive film.

RESULTS

Alteration of mediolateral tibial component position by 3 mm did not reveal a significant influence on retropatellar peak pressure (7.5 ± 2.5 vs. 7.2 ± 2.6 MPa). Regarding tibiofemoral kinematics, 3-mm medialization of the tibial baseplate significantly increased lateral femoral rollback and femorotibial external rotation. Medialization of 3 mm also significantly increased the relative medial patella shift and decreased lateral patella tilt.

DISCUSSION

Medialization of the tibial baseplate came along with more lateral rollback and external femorotibial rotation. For the positioning of the tibial baseplate, rotational alignment seems to be more important than mediolateral orientation. Since retropatellar peak pressure remained rather unchanged, the tibial baseplate should be placed by the surgeon looking for a maximal tibial coverage without overhang.

Comparison of fixed and mobile-bearing total knee arthroplasty in terms of patellofemoral pain and function: a prospective, randomised, controlled trial

BACKGROUND

Despite growing evidence in the literature, there is still a lack of consensus regarding the use of the mobile-bearing (MB) design total knee arthroplasty (TKA).

METHODS

In a prospective, comparative, randomised, single centre trial, 106 patients with end-stage osteoarthritis of the knee were randomised to either an MB or fixed-bearing (FB) group to receive posterior stabilised (PS)-TKA using a standard medial parapatellar approach and patellar resurfacing with follow-up (FU) for 5 years. The primary outcome was anterior knee pain (AKP) during the chair rise test and the stair climb test 5 years after surgery. The secondary outcome was the ability to rise from a chair and to climb stairs, range of motion (ROM), Knee Society Score (KSS), RAND-36 scores and radiological analysis of the patellar tilt.

RESULTS

No statistically significant difference was found between the two groups at 5 years FU in terms of median AKP during the chair rise test and the stair climb test (p = 0.5 and p = 0.8, respectively). There was no significant difference in any of the other secondary outcome parameters between the groups at 5 years FU.

CONCLUSION

A mobile-bearing TKA does not decrease AKP compared to fixed bearings.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT02892838 .

LEVEL OF EVIDENCE

II.

Superior-inferior position of patellar component affects patellofemoral kinematics and contact forces in computer simulation

BACKGROUND

Anterior knee pain has been reported as a major postoperative complication after total knee arthroplasty, which may lead to patient dissatisfaction. Rotational alignment and the medial-lateral position correlate with patellar maltracking, which can cause knee pain postoperatively. However, the superior-inferior position of the patellar component has not been investigated. The purpose of the current study was to investigate the effects of the patellar superior-inferior position on patellofemoral kinematics and kinetics.

METHODS

Superior, central, and inferior models with a dome patellar component were constructed. In the superior and inferior models, the position of the patellar component translated superiorly and inferiorly, respectively, by 3mm, relative to the center model. Kinematics of the patellar component, quadriceps force, and patellofemoral contact force were calculated using a computer simulation during a squatting activity in a weight-bearing deep knee bend.

FINDINGS

In the inferior model, the flexion angle, relative to the tibial component, was the greatest among all models. The inferior model showed an 18.0%, 36.5%, and 22.7% increase in the maximum quadriceps force, the maximum medial patellofemoral force, and the maximum lateral patellofemoral force, respectively, compared with the superior model.

INTERPRETATION

Superior-inferior positions affected patellofemoral kinematic and kinetics. Surgeons should avoid the inferior position of the patellar component, because the inferior positioned model showed greater quadriceps and patellofemoral force, resulting in a potential risk for anterior knee pain and component loosening.

Tibial component rotation in total knee arthroplasty

Background

Both the range of motion (ROM) technique and the tibial tubercle landmark (TTL) technique are frequently used to align the tibial component into proper rotational position during total knee arthroplasty (TKA).

The aim of the study was to assess the intra-operative differences in tibial rotation position during computer-navigated primary TKA using either the TTL or ROM techniques. The ROM technique was hypothesized to be a repeatable method and to produce different tibial rotation positions compared to the TTL technique.

Methods

A prospective, observational study was performed to evaluate the antero-posterior axis of the cut proximal tibia using both the ROM and the TTL technique during primary TKA without postoperative clinical assessment. Computer navigation was used to measure this difference in 20 consecutive knees of 20 patients who underwent a posterior stabilized total knee arthroplasty with a fixed-bearing polyethylene insert and a patella resurfacing.

Results

The ROM technique is a repeatable method with an interclass correlation coefficient (ICC2) of 0.84 (p < 0.001). The trial tibial baseplate was on average 4.56 degrees externally rotated compared to the tubercle landmark. This difference was statistically significant (p = 0.028). The amount of maximum intra-operative flexion and the pre-operative mechanical axis were positively correlated with the magnitude of difference between the two methods.

Conclusions

It is important for the orthopaedic surgeon to realise that there is a significant difference between the TTL technique and ROM technique when positioning the tibial component in a rotational position. This difference is correlated with high maximum flexion and mechanical axis deviations.

Development and validation of a weight-bearing finite element model for total knee replacement

Total knee arthroplasty (TKA) is a successful procedure for osteoarthritis. However, some patients (19%) do have pain after surgery. A finite element model was developed based on boundary conditions of a knee rig. A 3D-model of an anatomical full leg was generated from magnetic resonance image data and a total knee prosthesis was implanted without patella resurfacing. In the finite element model, a restarting procedure was programmed in order to hold the ground reaction force constant with an adapted quadriceps muscle force during a squat from 20° to 105° of flexion. Knee rig experimental data were used to validate the numerical model in the patellofemoral and femorotibial joint. Furthermore, sensitivity analyses of Young's modulus of the patella cartilage, posterior cruciate ligament (PCL) stiffness, and patella tendon origin were performed. Pearson's correlations for retropatellar contact area, pressure, patella flexion, and femorotibial ap-movement were near to 1. Lowest root mean square error for retropatellar pressure, patella flexion, and femorotibial ap-movement were found for the baseline model setup with Young's modulus of 5 MPa for patella cartilage, a downscaled PCL stiffness of 25% compared to the literature given value and an anatomical origin of the patella tendon. The results of the conducted finite element model are comparable with the experimental results. Therefore, the finite element model developed in this study can be used for further clinical investigations and will help to better understand the clinical aspects after TKA with an unresurfaced patella.

Distal femoral condyle is more internally rotated to the patellar tendon at 90° of flexion in normal knees

Background

The configuration of the distal surface of the femur would be more important in terms of the patellofemoral (PF) joint contact because the patella generally contacts with the distal surface of the femur in knee flexion. Some total knee arthroplasty (TKA) designs configurate medially prominent asymmetric femoral condyles. This difference in the design of distal femoral condyle may affect the PF joint congruity in knee flexion. Furthermore, some surgeons advocate a concept aligning the symmetric components parallel to the native joint inclination, not perpendicular to the mechanical axis. This concept would also make a difference on the PF joint congruity at the distal femur in knee flexion. However, no fundamental study has been reported on the PF congruity at the distal femur to discuss the theoretical priority of these concepts.

The current study investigated the angular relationship between the tibial attachment of the patellar tendon and the distal surface of the femur at 90° of flexion in normal knees.

Methods

The open magnetic resonance images of 45 normal knees at 90° of flexion were used to measure the angles between the tibial attachment of the patellar tendon, the equatorial line of the patella, and the distal surface of femoral condyles.

Results

The distal surface of femoral condyles was internally rotated relative to the tibial attachment of the patellar tendon and the equatorial line of the patella in all the knees (8.2° ± 3.5° and 5.8° ± 2.5°, respectively), not parallel.

Conclusions

Distal femoral condyle is internally rotated to the patellar tendon at 90° of flexion in normal knees. When the symmetric femoral component is aligned perpendicular to the femoral mechanical axis, the patellar tendon would be possibly more twisted than the condition in normal knees, and the deviation of the PF contact force on the patellar component might be caused. The configuration and alignment of the distal condyle of the femoral component can affect the PF joint congruity in knee flexion. In this respect, our results provide important information in considering designs and alignment in the distal femur of TKA and the PF joint congruity in knee flexion.