Introduction: Patellofemoral complications are one of the major causes for revision surgery. In the prosthetic knee, the main determinant within the patellofemoral mechanism is said to be the design of the groove (Kulkarni et al., 2000). Other studies characterising the native trochlear groove used indirect methods such as photography, plain radiographs and measurements using probes and micrometer. The aim of this study was to define the 3-dimensional geometry of the femoral trochlear groove. We used CT scans to describe the geometry of the trochlear groove and its relationship to the tibiofemoral joint in terms of angles and distances. Materials and Methods: CT scans of 45 normal femurs were analysed using custom designed imaging software. This enabled us to convert the scans to 3D and measure distances and angles. The flexion axis of the tibiofemoral joint was found to be a line connecting the centres of the spheres fitted to posterior femoral condyles. These two centres and the femoral head centre form a frame of reference for reproducible femoral alignment. The trochlear geometry was defined by fitting circles to cross sectional images and spheres to 3D surfaces. Axes were constructed through these centres. The deepest points on the trochlear groove were identified using quad images and Hounsfield units. After aligning the femur using different axes, the location of the groove was examined in relation to the mid plane between the centres of flexion of the condyles. Results: The deepest points on the trochlear groove can be fitted to a circle with a radius of 23mm (S.D. 4mm) and an R.M.S error of 0.3mm. The groove is positioned laterally (especially in its mid portion) in relation to the femoral mechanical and anatomical axes. It was also lateral to the perpendicular bisect of the transcondylar axes. After aligning the anatomical axis in screen the trochlear groove can be described on average to be linear with less than 2 mm medial/lateral translation. In the sagital view, the centre of the circle is offset by 21mm (S.D.3mm) at an angle of 67° (S.D. 7°) from a line connecting the midpoint between the centres of the femoral condyles and the femoral head centre. On either end of this line, the articular surface of the trochlea can be fitted to spheres of radius 30mm (S.D. 6mm) laterally and 27mm (S.D. 5mm) medially, with an rms of 0.4mm. Discussion: The location and configuration of the inter-condylar groove of the distal femur is clinically significant in the mechanics and pathomechanics of the patellofemoral articulation. This investigation has allowed us to characterise the trochlear groove. This can be of use in planning and performing joint reconstruction and have implications for the design of patello-femoral replacements and the rules governing their position.

The geometry of trochlear groove

Personalized Hip and Knee Joint Replacement

Kinematic alignment (KA) is an alternative philosophy for aligning a total knee replacement (TKR) which aims to restore all three kinematic axes of the native kneeMany of the studies on KA have actually described non-KA techniques, which has led to much confusion about what actually fits the definition of KAAlignment should only be measured using three-dimensional cross-sectional imaging Many of the studies looking at the influence of implants/limb alignment on total knee arthroplasty outcomes are of limited value because of the use of two-dimensional imaging to measure alignment, potentially leading to inaccuracyNo studies have shown KA to be associated with higher complication rates or with worse implant survival; and the clinical outcomes following KA tend to be at least as good as mechanical alignmentFurther high-quality multi-centre randomized controlled trials are needed to establish whether KA provides better function and without adversely impacting implant survival Cite this article: EFORT Open Rev 2020;5:380-390 DOI: 101302/2058-52415200010

Kinematic alignment in total knee arthroplasty.

Background: Kinematic alignment (KA) in total knee arthroplasty (TKA) replicates individual knee joint line orientation and physiological soft tissue balance. There are limited data on the effect of KA on survivorship compared with other methods of implanting a TKA. The aim of this study was to compare the survivorship of the same design of TKA implanted with either patient-specific instrument (PSI) KA or with computer-assisted surgery and conventionally instrumented. Methods: We performed an observational study of data from 2 national joint registries on all patients who underwent a TKA with a Triathlon cruciate-retaining TKA (Stryker, Mahwah, NJ) from January 2011 to December 31, 2013. The outcomes of knees performed with unrestricted KA using patient-specific instrument were compared with computer-assisted surgery and conventionally instrumented Triathlon cruciate-retaining TKA. The principal outcome measure was time to first revision using Kaplan-Meier estimates of survivorship. Cox proportional hazard ratios, adjusted for age and gender, were used to compare the 2 groups. Results: There were 20,512 TKA procedures recorded, of which 416 were performed using KA-PSI. The KA-PSI group was younger (66.8 ± 8.2 vs 68.3 ± 9.2, P = .001), with an identical gender distribution. The cumulative revision rate at 7 years was 3.1% for the KA-PSI Triathlon cohort and 3.0% for the other Triathlon TKA cohort (P = .89). The most common reasons for revision in the KA-PSI group were maltracking, patella erosion, and arthrofibrosis. Conclusion: Kinematically aligned Triathlon TKA using PSI has similar revision rate as all other Triathlon TKA.

Similar Risk of Revision After Kinematically Aligned, Patient-Specific Instrumented Total Knee Arthroplasty, and All Other Total Knee Arthroplasty: Combined Results From the Australian and New Zealand Joint Replacement Registries.

This lecture outlines the various alignment philosophies for total knee arthroplasty (TKA). It is logical that our desire to improve clinical outcomes for TKA involves a more personalized and physiological implantation process that preserves each patient's anatomical features. We will take a deep dive into the kinematic alignment concept by describing its rationale, surgical steps and results. Kinematic implantation of TKA can be done reliably at a low cost and appears to achieve acceptable implant biomechanics. While its short-term clinical results are encouraging, it must be evaluated further. The thresholds for acceptable alignment (indications for restricted kinematic alignment) still need to be specified. LEVEL OF EVIDENCE: V; Expert opinion.

What you need to know about kinematic alignment for total knee arthroplasty.

Introduction Preserving constitutional patellofemoral anatomy, and thus producing physiological patellofemoral kinematics, could prevent patellofemoral complications and improve clinical outcomes after kinematically aligned TKA (KA TKA). Our study aims 1) to compare the native and prosthetic trochleae (planned or implanted), and 2) to estimate the safety of implanting a larger Persona® femoral component size matching the proximal lateral trochlea facet height (flange area) in order to reduce the native articular surfaces understuffing generated by the prosthetic KA trochlea. Methods Persona® femoral component 3D model was virtually kinematically aligned on 3D bone-cartilage models of healthy knees by using a conventional KA technique (group 1, 36 models, planned KA TKA) or an alternative KA technique (AT KA TKA) aiming to match the proximal (flange area) lateral facet height (10 models, planned AT KA TKA). Also, 13 postoperative bone-implant (KA Persona®) models were co-registered to the same coordinate geometry as their preoperative bone-cartilage models (group 2 implanted KA TKA). In-house analysis software was used to compare native and prosthetic trochlea articular surfaces and medio-lateral implant overhangs for every group. Results The planned and performed prosthetic trochleae were similar and valgus oriented (6.1 and 8.5, respectively), substantially proximally understuffed compared to the native trochlea. The AT KA TKAs shows a high rate of native trochlea surface overstuffing (70%, 90%, and 100% for lateral facet, groove, medial facet) and mediolateral implant overhang (60%). There was no overstuffing with conventional KA TKAs having their anterior femoral cut flush. Conclusion We found that with both the planned and implanted femoral components, the KA Persona® trochlea was more valgus oriented and understuffed compared to the native trochlear anatomy. In addition, restoring the lateral trochlea facet height by increasing the femoral component size generated a high rate of trochlea overstuffing and mediolateral implant overhang. While restoring a native trochlea with KA TKA is not possible, the clinical impact of this is low, especially on PF complications. In current practice it is better to undersize the implants even if it does not restore the native anatomy. Longer follow-up is needed for KA TKAs performed with current implant, and the debate of developing new, more anatomic, implants specifically designed for KA technique is now opened. Level of evidence : II, Laboratory controlled study.

Kinematic alignment of current TKA implants does not restore the native trochlear anatomy

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Kinematic alignment of current TKA implants does not restore the native trochlear anatomy