TKA design-integrated trochlea groove rotation reduces patellofemoral pressure

Variations in Trochlear Morphology of Contemporary and Legacy Total Knee Arthroplasty Prostheses: A Review of 22 Designs

BACKGROUND

The morphology of the trochlear compartment of total knee arthroplasty (TKA) prostheses is a major determinant of postoperative patello-femoral kinematics, particularly with unresurfaced patellae. The objective of this study was to quantify and compare the trochlear morphology of a large series of contemporary and legacy TKA designs.

METHODS

The 3-dimensional surface models of 22 femoral components (13 contemporary and 9 legacy) were created using high-resolution laser scanning. The trochlear profile of each component was analyzed from proximal to distal in 15° increments around the trochlear axis. In each profile, the following variables were measured: sulcus angle, medio-lateral deviation of the sulcus, the height and width of the facets, and the trochlear groove orientation.

RESULTS

In the contemporary group, the sulcus angle decreased progressively along the trochlear arc to varying degrees, except for 2 symmetrical designs, whereas the sulcus angle of the legacy designs showed considerable variability. The height of the medial facet was very strongly correlated with that of the lateral facet in the contemporary group (R2 = 0.89), whereas the correlation was weak for the legacy designs (R2 = 0.36). Moreover, the trochlear sulcus deviated laterally from distal to proximal in 10 contemporary designs and 7 legacy designs, resulting in a trochlear groove orientation of 4.2 to 11.1° and 4.3 to 10.5°, respectively. In the remaining 5 designs (3 contemporary and 2 legacy), the sulcus was vertical.

CONCLUSIONS

There is more consistency in trochlear morphology of contemporary TKA designs compared to that of legacy designs, yet there are still large variations between different designs.

Patellar resurfacing might not be mandatory in contralateral second total knee replacement even if performed during replacement of the first knee

INTRODUCTION

The appropriateness or necessity of patellar resurfacing in total knee arthroplasty (TKA) is not clearly established. The objective of the present study was to compare the clinical and functional results of patients with bilateral involvement, operated on in one knee by TKA with patellar resurfacing and in the other knee by TKA without resurfacing. The hypothesis was that there was no difference in results between the two sides.

METHOD

This was a retrospective cohort of patients operated on by TKA without patellar resurfacing in a second osteoarthritic knee after contralateral TKA with patellar resurfacing. Twenty consecutive patients who underwent second primary TKA constituted their own control group (40 knees). Iwano scores were comparable. Mean age was 75.9±6.2years. Mean time between the two procedures was 20.6±11.9months.

RESULTS

There were no differences in SF-36, KOOS or Lille patellofemoral scores between the right and left knees. Sixty-five percent of patients were unable to differentiate the performance of their knees in activities of daily living.

CONCLUSION

The present study did not differentiate results according to patellar resurfacing, showing the limitations of resurfacing for early functional gain after primary TKA. Resurfacing might thus not be essential, even if it was performed in replacement of the first knee.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

The Trochlear Paradox in Native Knees and Its Potential Impact on Total Knee Arthroplasty: An MRI-Based Correlation Study Investigating the Effect of Varying Posterior Femoral Condyle Angles on the Patellofemoral Joint

BACKGROUND

Since the beginning of total knee arthroplasty, implant alignment has been a central point of discussion. As diverse as the discussed alignment theories are, as uniform is the implant design, which is supposed to be based on the "average knee." Steady upgrades in prosthesis design and modern alignment theories have achieved improvements. However, knee arthroplasty continues to be burdened by a significant percentage of dissatisfied patients. In current knee arthroplasty, femoral implant alignment is referenced by the dorsal and distal condylar axes. The patellofemoral joint variance is not sufficiently considered. Predominantly dorsal and distal referencing at the femoral condyle determines the postoperative shape of the anterior knee joint. The present study investigated a possible relationship between dorsal and distal joint parameters and the patellofemoral joint.

METHODS

In this explorative retrospective monocentric study, MRI cross-sectional images of 100 native knee joints were evaluated. By determining parametric correlations according to Pearson, the study investigates whether the independent variables "posterior femoral condyle angle" and "lateral distal femoral angle" are related to "lateral trochlear inclination", "patella tilt", and "bisect offset".

RESULTS

The posterior condylar angle significantly correlates with lateral trochlear inclination, patella tilt, and bisect offset. There is a positive correlation with patella tilt and bisect offset but a negative correlation with lateral trochlear inclination. The lateral distal femoral angle did not correlate with the studied parameters.

CONCLUSION

The lateral trochlear inclination decreases with an increased posterior femoral condylar angle. The posterior referencing of the femoral component in total knee arthroplasty simultaneously establishes the shape of the anterior knee joint. Our results indicate that increasing posterior condyle angles significantly correlate with flattened lateral trochlear inclinations in native knees and suggest a systematic biomechanical conflict in total knee arthroplasty.

Factors that impact the patellofemoral contact stress in the TKA: a review

Abnormal retro patellar stress is believed to contribute to patellofemoral complications after total knee arthroplasty (TKA), but the causal link between TKA and patellofemoral contact stress remains unclear. By reviewing the relevant studies, we found that both TKA implantation and additional patellar resurfacing increase retro patellar pressure. The rotation and size of the femoral component, thickness and position of the patellar component, installation of the tibial component, prosthesis design and soft tissue balance further influence patellofemoral stress. Specific measures can be applied to reduce stress, including the installation of the femoral prosthesis with an appropriate external rotation angle, placing the tibial component at a more posterior position and the patellar button at a more medial position, avoiding over-sized femoral and patellar components, selecting posterior-stabilized design rather than cruciate-retaining design, using gender-specific prosthesis or mobile-bearing TKA system, and releasing the lateral retinaculum or performing partial lateral facetectomy. Despite these measures, the principle of individualization should be followed to optimize the patellofemoral biomechanics.

Mismatch between trochlear coronal alignment of arthritic knees and currently available prosthesis: a morphological analysis of 4116 knees and 45 implant designs

PURPOSE

In up to a fifth of total knee replacements (TKR), surgeons are not capable of achieving good clinical and functional results. Despite comprehensive diagnostic workup, an underlying cause is not always identified in these patients. The purpose of this study is to compare native and prosthetic trochlear anatomies, to evaluate a potential source of morphologic mismatch and theoretically, of poor clinical outcomes.

METHODS

Native trochlear angles of 4116 knee CTs from 360 Knee Systems database of arthritic pre-operative TKR patients were evaluated. A semi-automated tridimensional analysis was performed to define the native trochlear angle in the coronal plane (NTA) among other 142 parameters. An active search was conducted to identify currently available TKR models; prosthetic trochlear orientation in the coronal plane (PTA) was extracted from the technical data provided by manufacturers.

RESULTS

The mean native trochlear angle (NTA) was 1.6° ± 6.6° (valgus) with a range from - 23.8° (varus) to 30.3°(valgus). A valgus NTA was present in 60.6% of the knees and 39.4% of them had a varus NTA. 89 TKR models were identified; trochlear details were available for 45 of them, of which 93% were designed with a valgus orientation of the prosthetic trochlear angle (PTA) and 6.9% showed a neutral (0°) PTA. Varus alignment of PTA was not present in any system. Angular numeric values for PTA were available for 34 models; these ranged from 0° to 15° of valgus, with a median value of 6.18° (SD ± 2.88°).

CONCLUSION

This study shows a significant mismatch between native and prosthetic trochlear angles. A relevant proportion of the studied knees (41.45%) fall out of the trochlear angle range of currently available implants; representing a potential source for biomechanical imbalance. While further research is warranted to fully understand the clinical implications of the present study, manufacturers may need to take these findings into account for future implant designs.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Alignment analysis of Brainlab knee 3 navigation-guided total knee arthroplasty using the adjusted mechanical method

Purpose

With the application of navigation technology in Total Knee Arthroplasty (TKA), TKA procedures have become various. Studies have shown that navigation can improve the alignment of patients' lower limbs. To verify this conclusion, we collected the clinical data from patients who underwent Brainlab knee 3 navigation-guided TKA. Brainlab knee 3 is a completely new software that takes a different approach to address the current challenges of navigated TKA. During the procedure, we applied the Adjusted Mechanical Alignment (AMA) principle and took soft tissue balance as a priority. We aim to explore the patients’ lower limb alignment changes who underwent the Brainlab knee 3 navigation-guided TKA using the AMA method.

Methods

Fifty consecutive patients who underwent total knee arthroplasty using the Brainlab knee3 knee navigation system (Smith&Nephew) from January to August 2021 by the same doctor (Yunsu Chen) in the Department of Joint Surgery of the Shanghai Sixth People's Hospital were included. Hip-Knee-Ankle Angle (HKAA), anatomic Femur Tibia Angle (FTA), Lateral Distal Femoral Angle (LDFA), and medial proximal tibia angle (MPTA) were measured on preoperative and postoperative full-length lower-limbs x-ray films or weight-bearing anterior and lateral knee radiographs for observational and descriptive study. The preoperative and postoperative knee alignment changes were analyzed through paired t-test or nonparametric Wilcoxon test using SPSS 25.0 software

Results

Pre-operative and post-operative HKAA both obeyed normal distribution. The mean preoperative HKAA was 169.8° (154.9–178.7°) with a standard deviation of 5.41; the postoperative HKAA was 175.7° (168.4–180.0°) with a standard deviation of 2.81. Using the two-sample paired t-test to analyze, the result showed P = 0.000 < 0.05; a statistically significant difference exists. The preoperative and postoperative FTA obeyed normal distribution as well. The mean preoperative FTA was 174.7° (163.4–179.9°) with a standard deviation of 3.90; postoperative 175.6° (167.0–179.9°) with a standard deviation of 2.77. Using the two-sample paired t-test to analyze, the result showed P = 0.140 > 0.05, the difference was not statistically significant. The preoperative LDFA was normally distributed, while postoperative LDFA was not. The mean preoperative LDFA was 90.7° (83.5–99.6°) with a standard deviation of 3.83; the median of postoperative LDFA was 91.6° (86.0–103.2°) with an interquartile range of 2.93. Using the two-sample paired Wilcoxon test, the result showed P = 0.052 > 0.05; the difference was not statistically significant. Preoperative MPTA obeyed normal distribution, while postoperative MPTA did not. The mean preoperative MPTA was 83.5° (72.7–92.9°), with a standard deviation of 3.66; the median of postoperative MPTA was 89.3° (84.6–95.6°), with an interquartile range of 1.45. Using the two-sample paired Wilcoxon test, the result shows P = 0.000 < 0.05; a statistically significant difference exists.

Conclusion

In our study, AMA alignment was applied in Brainlab Knee3 computer navigation-assisted total knee arthroplasty. The femoral and tibial osteotomy angles were minimally adjusted according to soft tissue situations to reduce soft tissue release. We found AMA alignment provides good control of knee alignment in the coronal plane of the lower limbs, which is a reliable technique.

The use of an asymmetrical tibial tray in TKA optimises tibial rotation when fitted to the posterior tibial plateau border

PURPOSE

The aim of this study was to evaluate the suitability of positioning an asymmetrical tibial tray relative to the posterior tibial edge and to analyse the relationship between the posterior fit and tibial rotation after computer-assisted total knee arthroplasty (TKA). It was hypothesised that an asymmetrical tray would adjust to the posterior border of the tibial plateau with proper tibial rotation.

METHODS

Ninety-three consecutive knees underwent total knee arthroplasty using a Persona fixed-bearing system (63 varus deformities and 30 valgus deformities) and a 3-month follow-up CT scan. An independent examiner measured different variables: the femoral angle between the clinical epicondylar axis and the posterior condylar line of the femoral component, the tibial angle between the posterior borders of the tibial tray and the tibial plateau, and the tibial rotation with respect to the femoral component. These measurements were also compared between varus and valgus subgroups.

RESULTS

For the varus and valgus subgroups, the mean postoperative femoral angle was 2.1º ± 1.2º and 2.5º ± 1.0º, respectively (n.s.). The mean posterior fitting angle of the tibial tray was 0.1º ± 2.4º and 1.4º ± 3.2º for the varus and valgus subgroups, respectively, with a significant difference between groups (p = 0.03). The tibial rotations with respect to the femoral component for the varus and valgus groups were 0.9º ± 3.3º and 2.2º ± 3.1º of external rotation, respectively (n.s.).

CONCLUSIONS

This study demonstrated that fitting an asymmetrical tibial tray to the posterior border of the tibial plateau could optimise tibial rotation. The posterior border was considered to be a reliable and easily identifiable landmark for proper tibial rotation and coverage during a primary TKA.

LEVEL OF EVIDENCE

IV.

Literature review of the causes of pain following total knee replacement surgery: prosthesis, inflammation and arthrofibrosis

Adverse knee pain occurs in 10–34% of all total knee replacements (TKR), and 20% of TKR patients experience more pain post-operatively than pre-operatively. Knee pain is amongst the top five reasons for knee replacement revision in the United Kingdom. The number of TKRs is predicted to continue increasing due to the ageing population.

A narrative literature review was performed on the different causes of pain following TKR. A database search on Scopus, PubMed, and Google Scholar was conducted to look for articles related to TKR, pain, and cause. Articles were selected based on relevance, publication date, quality of research and validation. Relevant sections were added to the review.

One hundred and fourteen articles were identified and potential causes of TKR pain included: arthrofibrosis, aseptic loosening, avascular necrosis, central sensitization, component malpositioning, infection, instability, nerve damage, overstuffing, patellar maltracking, polyethylene wear, psychological factors and unresurfaced patella.

It is important to tailor our approach to address the individual causes of pain. Certain controllable risk factors can be managed pre-operatively to minimize post-operative pain. Risk factors help to predict adverse pain outcomes and identify specific causes.

There are multiple causes of pain following TKR. Some factors will require further extensive studies, and as pain is a commonly attributed reason for TKR revision, its underlying aetiologies should be explored. Understanding these factors helps to develop effective methods for diagnosis, prevention and management of TKR pain, which help to improve patient outcomes.

Cite this article: EFORT Open Rev 2020;5:534-543. DOI: 10.1302/2058-5241.5.200031

The tibial cut influences the patellofemoral knee kinematics and pressure distribution in total knee arthroplasty with constitutional varus alignment

PURPOSE

The current literature suggests that kinematic total knee arthroplasty (kTKA) may be associated with better outcome scores in patients with constitutional varus alignment. The underlying patellofemoral kinematic changes (patella tilting and patella tracking) and patellofemoral pressure distribution have not yet been described. The present study compared the effects of different tibial cuts, as used in kTKA, on patellofemoral knee kinematics and the pressure distribution, in addition to comparisons with the natural constitutional varus knee.

METHODS

Seven cadaveric knee joints with constitutional varus alignment were examined in the native state and after 0°, 3°, or 6° tibial cut cruciate-retaining (CR)-TKA using an established knee joint simulator. The effects on patella rotation/patella tilting, patellofemoral pressure, and patellofemoral length ratios (= patella tracking) were determined. In addition, the natural knee joint and different tibial cuts in CR-TKA were compared (Student's t test).

RESULTS

In the patellofemoral joint, 6° CR-TKA was associated with the greatest similarity with the natural constitutional varus knee. By contrast, knees subjected to 0° CR-TKA exhibited the largest deviations of patellar kinematics. The smallest difference compared with the natural knee joint concerning patella tilting was found for 6° CR-TKA (mean 0.4°, p < 0.001), and the largest difference was noted for 0° CR-TKA (mean 1.7°, p < 0.001). Concerning patellofemoral pressure, 6° CR-TKA resulted in outcomes most similar to the natural knee joint, featuring a mean difference of 3 MPa. The largest difference from the natural knee joint was identified for 0° CR-TKA, with an average difference of 8.1 MPa (p < 0.001; total mean 17.7 MPa). Meanwhile, 3° and 6° CR-TKA induced medialization of the patella, with the latter inducing the largest medialization value of 4.5 mm at 90° flexion.

CONCLUSIONS

The improved outcome parameters in kTKA described in the literature could be attributable to the similar kinematics of the patellofemoral joint relative to the normal state. The current study confirmed the similar kinematics between the native constitutional varus knee joint and knee joints subjected to 3° or 6° CR-TKA (patellofemoral rotation/patella tilting and patella pressure). Conversely, there was pronounced medialization of the patella following 6° CR-TKA. Patella pressure and patella tilting are described in the literature as possible causes of anterior knee pain after TKA, whereas medialization of the patella, which is also influenced by other causes, might play a subordinate role.

LEVEL OF EVIDENCE

V, Biomechanical study.

Comparison of Patient Satisfaction Between Medial Pivot Prostheses and Posterior-Stabilized Prostheses in Total Knee Arthroplasty

OBJECTIVE

To compare medial pivot (MP) prostheses to two types of posterior-stabilized (PS) prostheses (NexGen and NRG) in terms of patient satisfaction, causes of dissatisfaction, and risk factors for dissatisfaction after total knee arthroplasty (TKA).

METHODS

A total of 453 patients who underwent primary TKA by one senior surgeon from August 2016 to August 2018 were investigated in a retrospective study, including 121, 219, and 113 patients in the MP, NexGen, and NRG groups, respectively. The mean age and follow-up time of patients were 70.82 ± 7.06 years and 20.64 ± 3.88 months. A survey was designed and responses were collected by telephone, WeChat, and outpatient follow up. Patient satisfaction, causes of dissatisfaction, post-TKA pain on a numeric rating scale (NRS), and range of motion (ROM) were compared among groups, and risk factors were investigated. Patient satisfaction included a five-level satisfaction rating (very satisfied, satisfied, neutral, dissatisfied, or very dissatisfied), with five options for causes of dissatisfaction (persistent pain, limited ROM, knee instability, asthenia, and/or other factors).

RESULTS

Overall, 89.84% of patients were satisfied with the results of primary TKA. There were no significant differences among the three groups regarding the side of the operation, the length of hospitalization in days, or the average follow-up time. Patient satisfaction was similar among the MP (87.38%), NexGen (89.89%), and NRG groups (90.32%). Persistent pain after TKA was the major cause of dissatisfaction (32/40), but no difference in the frequency of this complaint was found among the groups (P = 0.663). The NRS score (P = 0.598) and the ROM (P = 0.959) of the MP group were not significantly different from those of the NexGen and NRG groups. Gender, length of hospitalization, and follow-up time were all uncorrelated with patient satisfaction, but age showed a very weak correlation with patient satisfaction (r = 0.110, P = 0.033). Moreover, the NRS score (r = 0.459, P < 0.000) and the ROM (r = -0.175, P = 0.001) were significantly correlated with patient dissatisfaction. The odds ratio of dissatisfaction was 6.37 (P < 0.000) in patients with moderate to severe pain (NRS ≥ 3) compared to patients with mild pain (NRS < 3).

CONCLUSION

Patient satisfaction and function were not found to be higher in the MP group than in the two PS groups, and persistent pain was the major cause of and an important risk factor for patient dissatisfaction.

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.