Combining different rotational alignment axes with navigation may reduce the need for lateral retinacular release in total knee arthroplasty

Development of a Machine-Learning Model for Anterior Knee Pain After Total Knee Arthroplasty With Patellar Preservation Using Radiological Variables

BACKGROUND

Anterior knee pain (AKP) following total knee arthroplasty (TKA) with patellar preservation is a common complication that significantly affects patients' quality of life. This study aimed to develop a machine-learning model to predict the likelihood of developing AKP after TKA using radiological variables.

METHODS

A cohort of 131 anterior stabilized TKA cases (105 patients) without patellar resurfacing was included. Patients underwent a follow-up evaluation with a minimum 1-year follow-up. The primary outcome was AKP, and radiological measurements were used as predictor variables. There were 2 observers who made the radiological measurement, which included lower limb dysmetria, joint space, and coronal, sagittal, and axial alignment. Machine-learning models were applied to predict AKP. The best-performing model was selected based on accuracy, precision, sensitivity, specificity, and Kappa statistics. Python 3.11 with Pandas and PyCaret libraries were used for analysis.

RESULTS

A total of 35 TKA had AKP (26.7%). Patient-reported outcomes were significantly better in the patients who did not have AKP. The Gradient Boosting Classifier performed best for both observers, achieving an area under the curve of 0.9261 and 0.9164, respectively. The mechanical tibial slope was the most important variable for predicting AKP. The Shapley test indicated that high/low mechanical tibial slope, a shorter operated leg, a valgus coronal alignment, and excessive patellar tilt increased AKP risk.

CONCLUSIONS

The results suggest that global alignment, including sagittal, coronal, and axial alignment, is relevant in predicting AKP after TKA. These findings provide valuable insights for optimizing TKA outcomes and reducing the incidence of AKP.

Averaging rotational landmarks during total knee arthroplasty reduces component malrotation caused by femoral asymmetry

Background

Femoral component malrotation is a common cause of patient dissatisfaction after total knee arthroplasty. The sulcus line (SL) is more accurate than Whiteside’s line as it corrects for variation in the coronal orientation of the groove. The hypothesis is that averaging the SL and posterior condylar axis (PCA) will reduce femoral malrotation.

Methods

The component was inserted at a position between the SL and PCA in 91 patients. An intraoperative photograph was taken showing the landmarks. These were compared to the component position achieved relative to the surgical epicondylar axis (SEA) on a postoperative CT scan. The component position was compared to the position achieved using the individual landmarks.

Results

Relative to the SEA, the final component position was 0.6° (SD 1.4°, range −3.8° to +4.0°), the coronally corrected SL position was −0.7° (SD 2.3°, −5.5° to +4.6°), the PCA position was 0.9° (SD 1.9°, −6.1° to +5.0°). Averaging the landmarks significantly decreased the variance of the component position compared to using the SL and PCA individually. The number of outliers (>3° from SEA) was also significantly less (p < 0.05) for the average position (2/84) when each was compared to the SL (16/84) and PCA (14/84) individually. In 21/84 (25%) of cases, there was more than 4° of divergence between the SL and PCA.

Conclusions

Averaging the SL and the PCA decreases femoral component malrotation. Femora are frequently asymmetrical in the axial plane. Referencing posterior condyles alone to set rotation is likely to cause high rates of patellofemoral malalignment.

Referencing the sulcus line of the trochlear groove and removing intraoperative parallax errors improve femoral component rotation in total knee arthroplasty

PURPOSE

Firstly, to assess and compare the accuracy and reproducibility of the sulcus line compared to Whiteside's line. Secondly, to assess the accuracy of intraoperative techniques for using the rotational alignment of the trochlear groove to set femoral rotation. Thirdly, to assess the reproducibility of a trochlear alignment guide which removes parallax errors that occur when projecting the sulcus line onto the surface of the femur. Finally, to measure the result of combining the geometrically accurate sulcus line and the posterior condylar axis.

METHODS

Three surgeons measured eight rotational angles on ten cadaveric femora. This included Whiteside's line, the sulcus line and the techniques in which they can be referenced during surgery.

RESULTS

Relative to the anatomical epicondylar axis, the sulcus line (mean -2.8°, SD 2.0°, range -5.4° to 0.8°) had significantly lower variance (F = 5.16, p = 0.036) than Whiteside's line (mean -2.0°, SD 3.7°, range -6.0° to 3.4°). The trochlear alignment guide produced the best results of the intraoperative techniques by maintaining the accuracy of the sulcus line and projecting it onto the distal cut surface of the femur without change in rotational angle.

CONCLUSION

The sulcus line is more accurate and reproducible than Whiteside's line. Removing parallax errors during surgery improves femoral component rotation. The trochlear alignment guide produced accurate results suggesting that it may be beneficial in a clinical setting. Averaging the sulcus line and posterior condylar axis on the cut surface of the femur improved accuracy over the individual landmarks. Femoral component malrotation is a common cause of patient dissatisfaction and revision surgery. By isolating the rotational alignment of the trochlear groove using the sulcus line, and maintaining its accuracy with an intraoperative guide, we can decrease the risk of femoral component malrotation and improve patient outcomes.

Computed Tomography Analysis of Postsurgery Femoral Component Rotation Based on a Force Sensing Device Method versus Hypothetical Rotational Alignment Based on Anatomical Landmark Methods: A Pilot Study

Rotation of the femoral component is an important aspect of knee arthroplasty, due to its effects on postsurgery knee kinematics and associated functional outcomes. It is still debated which method for establishing rotational alignment is preferable in orthopedic surgery. We compared force sensing based femoral component rotation with traditional anatomic landmark methods to investigate which method is more accurate in terms of alignment to the true transepicondylar axis. Thirty-one patients underwent computer-navigated total knee arthroplasty for osteoarthritis with femoral rotation established via a force sensor. During surgery, three alternative hypothetical femoral rotational alignments were assessed, based on transepicondylar axis, anterior-posterior axis, or the utilization of a posterior condyles referencing jig. Postoperative computed tomography scans were obtained to investigate rotation characteristics. Significant differences in rotation characteristics were found between rotation according to DKB and other methods (P < 0.05). Soft tissue balancing resulted in smaller deviation from anatomical epicondylar axis than any other method. 77% of operated knees were within a range of ±3° of rotation. Only between 48% and 52% of knees would have been rotated appropriately using the other methods. The current results indicate that force sensors may be valuable for establishing correct femoral rotation.

Varus-valgus stress radiograph as a predictor for extensive medial release in total knee arthroplasty

PURPOSE

The purpose of this study was to identify the risk factors for predicting the reduction osteotomy as extensive medial release during total knee arthroplasty (TKA) using multivariate logistic regression.

METHODS

A total of 404 TKAs were enrolled and sorted into two groups according to the extent of medial release and then analysed for the statistical significance of various risk factors including age, gender, body mass index (BMI), pre-operative knee mechanical axis angle (KMAA), mechanical varus stress angle (MVrSA), mechanical valgus stress angle (MVgSA), and sum of the mechanical varus and valgus stress angles (SMVVA) with use of multivariate logistic regression analysis.

RESULTS

SMVVA to a more varus direction was found to be a significant risk factor for the reduction osteotomy (p < 0.0001, adjusted odds ratio (OR) = 2.705 with 95 % CI 2.126-3.443). KMAA and MVgSA to a more varus direction were also significant risk factors (p = 0.010, adjusted OR = 1.189 with 95 % CI 1.041-1.357, and p = 0.005, adjusted OR = 1.401 with 95 % CI 1.109-1.767). The other variables were not significant risk factors.

CONCLUSIONS

The overall results suggest that careful attention should be given to the need for extensive medial release and failure of the conventional soft tissue release technique during TKA in patients with a greater varus angle in the pre-operative SMVVA, MVgSA, and KMAA, especially with a greater varus SMVVA, which was the strongest predictor of reduction osteotomy.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

The combined Whiteside's and posterior condylar line as a reliable reference to describe axial distal femoral anatomy in patient-specific instrument planning

PURPOSE

Aligning the femoral component in the axial plane parallel to the surgical epicondylar axis (SEA) has been generally recommended. In this retrospective study on the axial anatomy of the distal femur, as determined by the patient-specific instruments (PSI) planning tool based on MRI and 3D reconstructions, the different rotational axes were compared. The purpose of this study was to compare the impact of posterior axial anatomy on anterior anatomy and to compare the different angles of rotation obtained by a PSI-planning engineer.

METHODS

The preoperative planning of 77 PSI patients with a mean (SD) age of 65.6 (9.6) years undergoing primary total knee replacement for osteoarthritis was analysed for rotational anatomy of the distal femur. The angles between the posterior condylar line (PCL) and the SEA called posterior condylar angle (PCA), between Whiteside's line and the SEA and finally between Whiteside's line and the PCL, were retrieved from the PSI axial rotation planning screen.

RESULTS

The mean (SD) PCA was 3.2° (1.4°). The mean (SD) angle between Whiteside's line and the SEA was 91.4° (2.2°), and the mean (SD) angle between Whiteside's line and the PCL was 94.5° (2.3°). No significant difference for this last rotational parameter was found in between varus and valgus knees.

CONCLUSION

Patient-specific instrument's preoperative planning found consistent angles to describe the distal femoral anatomy as previously published in the literature. The angle between Whiteside's line and the PCL as measured on PSI planning is a mean angle of 94.5° (2.3°) for both varus and valgus knees. Setting a fixed PCA of 5° of external rotation referenced of the PCL makes this planning repeatable during conventional surgery.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

Partial lateral patellar facetectomy as an alternative to lateral release in Total Knee Arthroplasty (TKA)

This study presents the selective use of partial patellar lateral facetectomy for maltracking during primary TKA, as an alternative to lateral release. Twenty three partial facetectomies were performed out of 191 TKAs (12%). Balanced tracking was achieved in 22 knees. At follow-up 2 patients had persistent anterior knee pain. Mean Knee Society score (KSS) was 94 and mean functional KSS was 86. Mean patellar score was 28. Patellar tilt angles were within 2 degrees in all but one knee. Patellar translation was within 2 mm in all cases. No complications were recorded. A control group of 46 matched patients had similar functional and radiographic results. If tracking is not satisfactory at the conclusion of TKA, our method of choice would be partial lateral facetectomy.

Automating the design of resection guides specific to patient anatomy in knee replacement surgery by enhanced 3D curvature and surface modeling of distal femur shape models

Personalized resection guides (PRG) have been recently proposed in the domain of knee replacement, demonstrating clinical outcome similar or even superior to both manual and navigated interventions. Among the mandatory pre-surgical steps for PRG prototyping, the measurement of clinical landmarks (CL) on the bony surfaces is recognized as a key issue due to lack of standardized methodologies, operator-dependent variability and time expenditure. In this paper, we focus on the reliability and repeatability of an anterior-posterior axis, also known as Whiteside line (WL), of the distal femur proposing automatic surface processing and modeling methods aimed at overcoming some of the major concerns related to the manual identification of such CL on 2D images and 3D models. We show that the measurement of WL, exploiting the principle of mean-shifting surface curvature, is highly repeatable and coherent with clinical knowledge.

Is it possible to re-establish pre-operative patellar kinematics using a ligament-balanced technique in total knee arthroplasty? A cadaveric investigation

PURPOSE

Several authors emphasise that the appearance of patellar maltracking after total knee arthroplasty (TKA) is caused by rotational malalignment of the femoral and tibial components. Ligament-balanced femoral component rotation was not found to be associated with abnormal postoperative patellar position. We hypothesised that a ligament-balanced technique in TKA has the ability to best re-establish patellar kinematics.

METHODS

In ten cadaveric knees TKA was performed assessing femoral rotation in ligament-balanced and different femoral and tibial component rotation alignments. Patellar kinematics after different component rotations were analysed using a commercial computer navigation system.

RESULTS

Ligament-balanced femoral rotation showed the best re-establishment of patellar kinematics after TKA compared to the healthy pre-operative knee. In contrast to tibial component rotation, femoral component rotation had a major impact on patellofemoral kinematics.

CONCLUSIONS

This investigation suggests that a ligament-balanced technique in TKA is most likely to re-establish natural patellofemoral kinematics. Tibial component rotation did not influence patellar kinematics.

Does computer-assisted total knee arthroplasty improve the overall component position and patient function?

PURPOSE

There remains controversy as to whether computer-navigated total knee replacement (TKR) improves the overall prosthesis alignment and patient function. The aim of this study was to determine whether computer-assisted total knee arthroplasty provides superior prosthesis positioning when compared to a conventional jig-assisted total knee replacement and whether this affected the functional outcome.

METHODS

This prospective, randomised controlled study compared computer navigated and conventional jig-assisted total knee replacement in 37 patients who underwent bilateral TKR. A quantitative assessment of the spatial positioning of the implant in the 74 total knee replacements was determined using a low-dose dual-beam CT scanning technique. This resulted in six parameters of alignment that were compared. Functional outcomes using the high activity arthroplasty score and Knee Society score were assessed pre-operatively, postoperatively, at three years and at five years. Patients also indicated which knee they felt was subjectively the best.

RESULTS

There was no statistically significant difference in the prosthesis alignment between both groups and the number of outliers was not decreased with navigation. All function scores improved from pre-operative to postoperative but there was no statistically significant difference between the groups at five years. At five years, 40.6% of patients thought their jig-assisted knee was the better knee compared with 21.9% their computer assisted knee and 37.5% of patients who felt they were the same.

CONCLUSION

Computer-assisted implantation of total knee replacements does not offer a significant advantage in prosthesis alignment. There was no difference in functional outcome or subjective "best knee" between the computer-assisted or jig-assisted knee.

Cutting and implanting errors in minimally invasive total knee arthroplasty using a navigation system

PURPOSE

The purpose of this study was to evaluate the accuracy of bone cutting and implantation in minimally invasive total knee arthroplasty with image-free navigation.

METHODS

The alignment of the tibial and femoral bone resection was measured in 40 knees during surgery. The alignment measurement was repeated after cementing the tibial and femoral components. We evaluated the cutting error and the implanting error.

RESULTS

The mean tibial cutting errors were 0.5 and 0.7° in the frontal and sagittal planes, respectively. The mean femoral cutting errors were 0.5 and 0.9° in the frontal and sagittal planes, respectively. The mean tibial implanting errors were 1.0 and 0.9° in the frontal and sagittal planes, respectively. The mean femoral implanting error was 0.7° in the frontal plane.

CONCLUSIONS

Computer-assisted navigation was useful in checking the alignment of both bone cut and cementation.