Does joint line elevation after revision knee arthroplasty affect tibio-femoral kinematics, contact pressure or collateral ligament lengths? An in vitro analysis

An MRI-Derived Formula for Estimating the Native Joint Line Position in the Presence of Distal Femoral Bone Loss

Background  In the presence of distal femoral condyle bone loss, estimation and restoration of the joint line (JL) position can be guided by extraarticular bony landmarks with the aid of mathematical formulas that rely on the innate correlations between periarticular measurements. To prevent JL elevation, the formula should incorporate the thickness of distal femoral articular cartilage. The aim of this study was to derive a formula to estimate native JL position. Methods One hundred and fifty knee magnetic resonance imaging (MRI) studies belonging to 150 patients were chosen from a database of scans. Multiple periarticular measurements were taken. Based on the strongest correlation between measurements, linear regression analysis was used to derive a regression equation to estimate the JL position. This formula was then tested to determine its accuracy and reliability in estimating the JL. Results  Using the Pearson correlation test, the strongest correlation was identified to be between adductor tubercle to joint line distance (ATJL) and transepicondylar width (TEW) with r = 0.723, p <.001. Using linear regression analysis, the following regression equation was obtained: ATJL in millimetres = 0.53 (TEW in millimetres) + 2.4mm. This formula estimated the JL within 4 mm of the native JL in 86% of measured knees and within 8 mm in 100% of measured knees. The mean difference between calculated ATJL and measured ATJL was 2.43 mm with a standard deviation of 1.94 mm. Conclusion  The current formula (ATJL = 0.53(TEW) + 2.4mm) reliably estimates native JL distance from the adductor tubercle (AT) to within a clinically significant range, using femoral TEW.

[Effect of prosthetic joint line installation height errors on insert wear in unicompartmental knee arthroplasty]

The clinical performance and failure issues are significantly influenced by prosthetic malposition in unicompartmental knee arthroplasty (UKA). Uncertainty exists about the impact of the prosthetic joint line height in UKA on tibial insert wear. In this study, we combined the UKA musculoskeletal multibody dynamics model, finite element model and wear model to investigate the effects of seven joint line height cases of fixed UKA implant on postoperative insert contact mechanics, cumulative sliding distance, linear wear depth and volumetric wear. As the elevation of the joint line height in UKA, the medial contact force and the joint anterior-posterior translation during swing phase were increased, and further the maximum von Mises stress, contact stress, linear wear depth, cumulative sliding distance, and the volumetric wear also were increased. Furthermore, the wear area of the insert gradually shifted from the middle region to the rear. Compared to 0 mm joint line height, the maximum linear wear depth and volumetric wear were decreased by 7.9% and 6.8% at -2 mm joint line height, and by 23.7% and 20.6% at -6 mm joint line height, the maximum linear wear depth and volumetric wear increased by 10.7% and 5.9% at +2 mm joint line height, and by 24.1% and 35.7% at +6 mm joint line height, respectively. UKA prosthetic joint line installation errors can significantly affect the wear life of the polyethylene inserted articular surfaces. Therefore, it is conservatively recommended that clinicians limit intraoperative UKA joint line height errors to -2-+2 mm.

Identification of the joint line in revision total knee arthroplasty using a multiple linear regression model: a cadaveric study

INTRODUCTION

The results of revision total knee arthroplasty (rTKA) may be compromised by excessive joint line (JL) elevation. It is critical but challenging in reestablishing the JL in rTKA. Previous studies have confirmed that, biomechanically and clinically, JL elevation should not exceed 4 mm. Image-based studies described several approaches to locate the JL intraoperatively, however magnification errors could occur. In this cadaveric study, we aim to define an accurate and reliable method to determine the JL.

MATERIALS AND METHODS

Thirteen male and eleven female cadavers were used, with an average age of death being 48.3 years. The transepicondylar width (TEW), the distance from the medial (MEJL) and lateral (LEJL) epicondyle, adductor tubercle (ATJL), fibular head (FHJL) and tibial tubercle (TTJL) to the JL were measured in 48 knees. Intra- and interobserver reliability and validity were tested prior to any additional analysis. Pearson correlation and linear regression analysis were used to examine the correlations between landmark-JL distances (LEJL, MEJL, ATJL, FHJL and TTJL) and the TEW, and to further derive models for intraoperative JL determination. The accuracy of different models, quantified by errors between estimated and measured landmark-JL distances, was compared using the Friedman and post hoc Dunn tests.

RESULTS

The intra- and inter-observer measurements for TEW, MEJL, LEJL, ATJL, TTJL and FHJL did not differ significantly (p > 0.05). Between genders, significant differences were found on TEW, MEJL, LEJL, ATJL, FHJL and TTJL (p < 0.05). There was no association between TEW and either FHJL or TTJL (p > 0.05), while ATJL, MEJL, and LEJL were found to be correlated with TEW (p < 0.05). Six models were derived: (1) MEJL = 0.37*TEW (r = 0.384), (2) LEJL = 0.28*TEW (r = 0.380), (3) ATJL = 0.47*TEW (r = 0.608), (4) MEJL = 0.413*TEW - 4.197 (R² = 0.473), (5) LEJL = 0.236*TEW + 3.373 (R² = 0.326), (6) ATJL = 0.455*TEW + 1.440 (R² = 0.556). Errors were defined as deviations between estimated and actual landmark-JL distances. The mean absolute value of the errors, created by Model 1-6 was 3.18 ± 2.25, 2.53 ± 2.15, 2.64 ± 2.2, 1.85 ± 1.61, 1.60 ± 1.59 and 1.71 ± 1.5, respectively. The error could be limited to 4 mm in 72.9%, 83.3%, 72.9%, 87.5%, 87.5%, and 93.8% of the cases by referencing Model 1-6, respectively.

CONCLUSION

Compared to previous image-based measurements, the current cadaveric study most closely resembles a realistic view of intraoperative settings and could circumvents magnification errors. We recommend using Model 6, the JL can be best estimated by referencing the AT and the ATJL can be calculated as ATJL (mm) = 0.455*TEW (mm) + 1.440 (mm).

Use of a Spacer Block Tool for Assessment of Joint Line Position during Revision Total Knee Arthroplasty

There is a tendency of orthopaedic surgeons to elevate joint line (JL) in revision total knee arthroplasty (RTKA). Here, we ascertain the use of the spacer block tool (SBT) to determine JL more accurately for less experienced RTKA surgeons. To perform more precise restoration of JL, an SBT with markers was developed and produced using computer software and three-dimensional printers. The study was planned prospectively to include patients who received either condylar constrained or rotating hinge RTKA between January 2016 and December 2019. To determine JL, distance from fibular head (FH), adductor tubercle (AT), and medial epicondyle (ME) were measured on contralateral knee preoperative radiographs and on operated knee postoperative radiographs. Patients were randomized and grouped according to the technique of JL reconstruction. In Group 1, conventional methods by evaluating aforementioned landmarks and preoperative contralateral knee measurements were used to determine JL, whereas in Group 2, the SBT was used. The main outcome measure was the JL change in revised knee postoperatively in contrast to contralateral knee to compare effective restoration of JL between the groups. Twenty-five patients in Group 1 (3 males, 22 females, 72 years, body mass index [BMI] 32.04 ± 4.45) and 20 patients (7 males, 13 females, 74 years, BMI 30.12 ± 5.02) in Group 2 were included in the study. JL measurements for the whole group were FH-JL = 18.3 ± 3.8 mm, AT-JL = 45.8 ± 4.6 mm, and ME-JL = 27.1 ± 2.8 mm preoperatively, and FH-JL = 20.7 ± 4.2 mm, AT-JL = 43.4 ± 5.2 mm, and ME-JL = 24.7 ± 3.1 mm postoperatively. JL level differences in reference to FH, AT, and ME in Group 1 were 3.6 ± 3.1, 3.6 ± 3.5, and 3.4 ± 3.1 mm, respectively, and in Group 2 were 1.0 ± .0.9, 1.3 ± 1.3, and 1.1 ± 1.3 mm, respectively. There were statistically significant differences between the two groups in JL changes referenced to all of the specific landmarks (p < 0.05). The use of the SBT helped restore JL effectively in our cohort of RTKA patients. Therefore, this tool may become a useful and inexpensive gadget for less experienced and low-volume RTKA surgeons.

Functional stability: an experimental knee joint cadaveric study on collateral ligaments tension

INTRODUCTION

Applying proper tension to collateral ligaments during total knee arthroplasty surgery is fundamental to achieve optimal implant performance: low tension could lead to joint instability, over-tensioning leads to pain and stiffness. A "functional stability" must be defined and achieved during surgery to guarantee optimal results. In this study, an experimental cadaveric activity was performed to measure the minimum tension required to achieve knee functional stability.

MATERIALS AND METHODS

Ten knee specimens were investigated; femur and tibia were fixed in specifically designed fixtures and clamped to a loading frame; constant displacement rate was applied and resulting tension force was measured. Joint stability was determined as the slope change in the force/displacement curve, representing the activation of both collateral ligaments elastic region; the tension required to reach joint functional stability is then the span between ligaments toe region and this point. Intact, ACL (anterior cruciate ligament)-resected and ACL & PCL (posterior cruciate ligament)-resected knees were tested. The test was performed at different flexion angles; each configuration was analyzed three times.

RESULTS

Results demonstrated an overall tension of 40-50 N to be enough to reach stability in intact knees. Similar values are sufficient in ACL-resected knees, while significantly higher tension is required (up to 60 N) after cruciate ligaments resection. The tension required was slightly higher at 60° of flexion.

CONCLUSION

Results agree with other experimental studies, showing that the tensions required to stabilize a knee joint are lower than the ones applied nowadays via surgical tensioners. To reach functional stability, surgeons should consider such results intraoperatively and avoid ligament laxity or over-tension.

Joint line reestablishment in revision total knee arthroplasty

Background

In this study, the traditional “Anatomical Landmark-Distance Method (AL-DM)” in the formation of joint line (JL) was compared with “Adductor Tubercle-Ratios method” (AT-RM), and the effect of reestablishment of JL on clinical and functional outcomes were evaluated.

Materials and methods

16 revision total knee arthroplasties (rTKAs) were performed by using “AT-RM” (group 1) and 16 rTKA by using “AL-DM” (group 2) in our clinic between 2015 and 2018. The data were prospectively collected and a total of 32 knees of 31 patients were analyzed. At the final follow-up, knee functions were evaluated by using Knee Society Score (KSS) knee and function, Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores, Short Form-36 (SF-36) questionnaires and physical examinations.

Results

Postoperative flexion arc was higher in Group 1. KSS knee and function scores were better in group 1. In group1, JL was reestablished successfully in all revision rTKAs in terms of ATJL and the tibial tubercle TT-JL ratios. The improvement in KSS knee and function scores and WOMAC scores were also better in group 1. Measurements showed that the improvement in KSS scores increased as AT-JL and TT-JL distances approached the calculated values.

Conclusion

“AT-RM” was shown to be superior to the traditional distance method in terms of JL reestablishment. Functional results and patient satisfaction increased when JL was reestablished.

Elongation Patterns of the Collateral Ligaments After Total Knee Arthroplasty Are Dominated by the Knee Flexion Angle

The primary aim of this study was to assess the effects of total knee arthroplasty (TKA) implant design on collateral ligament elongation patterns that occur during level walking, downhill walking, and stair descent. Using a moving fluoroscope, tibiofemoral kinematics were captured in three groups of patients with different TKA implant designs, including posterior stabilized, medial stabilized, and ultra-congruent. The 3D in vivo joint kinematics were then fed into multibody models of the replaced knees and elongation patterns of virtual bundles connecting origin and insertion points of the medial and lateral collateral ligaments (MCL and LCL) were determined throughout complete cycles of all activities. Regardless of the implant design and activity type, non-isometric behavior of the collateral ligaments was observed. The LCL shortened with increasing knee flexion, while the MCL elongation demonstrated regional variability, ranging from lengthening of the anterior bundle to slackening of the posterior bundle. The implant component design did not demonstrate statistically significant effects on the collateral elongation patterns and this was consistent between the studied activities. This study revealed that post-TKA collateral ligament elongation is primarily determined by the knee flexion angle. The different anterior translation and internal rotation that were induced by three distinctive implant designs had minimal impact on the length change patterns of the collateral ligaments.

Are contemporary femoral components sizing and design likely to affect functional results in TKA? A mathematical model of an implanted knee to predict knee forces

PURPOSE

This study is aimed to investigate the effects of the choice of femoral and tibial components on several mechanical outputs that might be associated with total knee replacement surgery outcomes using a validated computational model: the Kansas knee simulator.

METHODS

Two models from the same range of implants were taken into account: Model 1, the femoral component fitted the femoral epiphysis, with physiological positioning of the articulating surface using a 10-mm-thick tibial component, and in Model 2, the femoral component was 4 mm smaller than in Model 1, and a 14-mm-thick tibial component was used with a similar tibial resection and the tibio-femoral joint line was 4 mm more proximal to compensate the increased posterior bone resection and maintain proper soft-tissue tension in flexion. Changes in reaction forces and contact pressures between the components, changes in extensor muscle forces and changes in patello-femoral joint kinematics during walking gait have been studied.

RESULTS

While the computational model predicted that most kinematic and kinetic outputs, including tibio-femoral and patello-femoral joint motions, contact forces, pressures and areas, were similar for Model 1 and Model 2, and a dramatic difference has been found in the extensor muscle forces necessary to flex and extend the knee. To reproduce the same knee motion with a knee reconstructed as in Model 2, a patient would need to generate approximately 40% greater extensor muscle force throughout the gait cycle in order to do so.

CONCLUSION

As a consequence of such a large increase in the extensor muscle force, the knee motions would probably be compromised and, subsequently, a patient with a knee reconstructed as in Model 2 would be less likely to be able to reproduce normal knee function and therefore more likely to report poor outcome.

The epicondylar ratio can be reliably used on X-ray of the knee to determine the joint line

PURPOSE

The epicondylar ratio (ER) is used to restore the individual joint line (JL), especially in revision total knee arthroplasty. It was first described in magnetic resonance imaging (MRI) but is usually applied to a.p. radiographs of the knee for preoperative planning. The objective of the current study was to define reliable landmarks in MRI and X-ray images of the knee, which allow comparison of the image modalities. Furthermore, the correlation of the measured ER in MRI and X-rays of the knee was calculated.

METHODS

A consecutive series of 87 patients who underwent an arthroscopical intervention of the knee were included into the present study. The lateral epicondyle was defined as the most lateral and distal prominence. On the medial side, the measurement was aligned to the epicondylar sulcus. The medial and lateral ER were calculated by dividing the perpendicular distance from the JL to the epicondyle by the transepicondylar distance. One observer determined the ER twice to calculate the intramethod intraobserver agreement, and a second observer obtained the intramethod interobserer agreement. The ER obtained from X-ray and MRI was compared to calculate the intermethod correlation.

RESULTS

The average lateral ER was 0.29 on X-ray versus 0.28 on MRI. The average medial ER was 0.33 and 0.33, respectively. Intramethod agreement ranged from 0.66 to 0.88 and intermethod correlation from 0.49 to 0.57.

CONCLUSIONS

The ER can be determined reliably on MRI and X-ray images of the knee. The correlation of the ER in MRI and X-ray is fair.

The medial and lateral epicondyle as a reliable landmark for intra-operative joint line determination in revision knee arthroplasty

Objectives

The purpose of this study was to develop an accurate, reliable and easily applicable method for determining the anatomical location of the joint line during revision knee arthroplasty.

Methods

The transepicondylar width (TEW), the perpendicular distance between the medial and lateral epicondyles and the distal articular surfaces (DMAD, DLAD) and the distance between the medial and lateral epicondyles and the posterior articular surfaces (PMAD, DLAD) were measured in 40 knees from 20 formalin-fixed adult cadavers (11 male and nine female; mean age at death 56.9 years, sd 9.4; 34 to 69). The ratios of the DMAD, PMAD, DLAD and PLAD to TEW were calculated.

Results

The mean TEW, DMAD, PMAD, DLAD and PLAD were 82.76 mm (standard deviation (sd) 7.74), 28.95 mm (sd 3.3), 28.57 mm (sd 3), 23.97 mm (sd 3.27) and 24.42 mm (sd 3.14), respectively. The ratios between the TEW and the articular distances (DMAD/TEW, DLAD/TEW, PMAD/TEW and PLAD/TEW) were calculated and their means were 0.35 (sd 0.02), 0.34 (sd 0.02), 0.28 (sd 0.03) and 0.29 (sd 0.03), respectively.

Conclusion

This method provides a simple, reproducible and reliable technique enabling accurate anatomical joint line restoration during revision total knee arthroplasty.

Cite this article: B. Ozkurt, T. Sen, D. Cankaya, S. Kendir, K. Basarır, Y. Tabak. The medial and lateral epicondyle as a reliable landmark for intra-operative joint line determination in revision knee arthroplasty. Bone Joint Res 2016;5:280–286. DOI: 10.1302/2046-3758.57.BJR-2016-0002.R1.

Revision knee surgery techniques

Revision total knee arthroplasty (rTKA) is a challenging, complex procedure. A comprehensive understanding of the anatomy, challenges and pitfalls is essential to achieve a good outcome for the patient.This review discusses the determinants of good outcomes of rTKA. These include, among other factors, the choice of the surgical approach, removal of the components, adequate reconstruction of the joint line and posterior condylar offset and the use of offset stems, as well as choosing the appropriate level of constraint.The modularity of many modern knee revision systems can help to address such issues as anatomical mismatch, gap balancing and malalignment.A well-planned surgical approach must be used in rTKA. A thorough understanding of related knee anatomy is essential.The incidence of joint-line elevation after rTKA is high. Contralateral radiographs, as well as algorithms based on the relationship between bony landmarks and the joint line, can help to reconstruct a physiological joint line during rTKA.Modularity added to systems, such as offset stems, are useful enhancements that may further improve the reconstruction of the anatomy.There are several options for managing the patella, with the best choice depending on the status of the patellar component and residual bone stock. Cite this article: Thienpont E. Revision knee surgery techniques. EFORT Open Rev 2016;1: 233-238. DOI: 10.1302/2058-5241.1.000024.