Alignment philosophy influences trochlea recreation in total knee arthroplasty: a comparative study using image-based robotic technology

Abstract

Purpose The ability of kinematic alignment (KA) to consistently restore trochlea anatomy in total knee arthroplasty (TKA) is unknown despite recreation of constitutional anatomy being its rationale for use. The purpose of this study was to assess if alignment choice in TKA effects the ability to restore the native trochlea groove. Methods One hundred and twenty-two consecutive patients undergoing robotic-assisted TKA using the MAKO image-based robotic platform had simulated femoral components placed according to kinematic, mechanical and functional alignment principals. Implant position and trochlea restoration between groups were compared. Restoration was assessed by shift (medial–lateral) and depth relative to the native groove from three consistent points; full extension (0°), mid-flexion (30°–40°) and deep flexion (70°–80°). Results Three hundred and sixty-six alignment options were analysed. Femoral alignment was significantly different between groups. Of KA, 13.1% compared to 3.3% of FA plans were outside safe coronal boundaries. The trochlear groove was translated the most by MA compared to KA and FA (full extension, MA 7.84 ± 1.99 mm lateral to the native groove, KA 6.40 ± 2.43 mm and FA 6.88 ± 1.74 mm, p ≤ 0.001). In full extension, FA most closely restored the trochlear groove depth in all three positions of flexion. Conclusion Alignment philosophy led to significant differences in trochlea groove recreation. A kinematically placed femoral component led to positioning considered unsafe in over 13% of cases. A functionally placed femoral component most closely restored trochlea depth in all three positions of flexion.

Definition of normal, neutral, deviant and aberrant coronal knee alignment for total knee arthroplasty

“…The consequence is an ongoing shift away from systematic mechanical alignment to more personalised alignment targets. There are by now numerous different alignment techniques and targets with standard off the shelf or customised implants [5–10, 23, 24]. The evidence about their impact is evolving, but still longer‐term comparative data is pending [6].…”

“…Personalised medicine has arrived in total knee arthroplasty (TKA) [1,2]. Personalised alignment methods such as kinematic alignment, functional alignment and customised patient specific TKA are intensively debated at meetings and in the current literature [3][4][5][6][7][8][9][10][11]. Fostered by the knee phenotype concept and the findings of several large database studies, there has been considerable discussion about what we consider as normal, abnormal and pathological alignment [3,4,[12][13][14][15].…”

The language of knee alignment

“…74,76 A recent CT-based radiological study reported FA results in less translation of native trochlear groove than either MA or KA, with the least alteration in groove depth of the three. 85 Furthermore, use of robotic capabilities with haptic boundary control has been demonstrated to decrease blood loss and soft-tissue trauma and to preserve the PCL footprint. 86,87…”

Functional Alignment Philosophy in Total Knee Arthroplasty—Rationale and Technique for the Valgus Morphotype Using an Image Based Robotic Platform and Individualized Planning

“…This is particularly relevant in the valgus morphotype where lateral condyle bone deficiency is encountered in at least 25% of cases [ 26 ], making the PCA an unreliable landmark. Recently it was demonstrated that using the PCA as reference for femoral component position, as is the case in KA, led to more than 20% of TKA’s having a femoral component that was more than 3° internally rotated relative to the TEA [ 24 ]. Use of the TEA as a landmark for rotation has in the past also been fraught with poor inter- and intra-observer reliability [ 68 ]; however, with the addition of CT landmarking in image-based robotic platforms, this issue is dealt with and the TEA becomes a more reproducible landmark for axial component positioning.…”

“…Functional alignment aims to reconstruct 3D constitutional alignment within set boundaries, with a key difference being the adjustment of implant positioning based on consideration of the patient’s soft tissue envelope to achieve gaps that are considered balanced [ 22 ]. Its use for the varus morphotype has recently been detailed [ 23 ] and was shown to be both bone preserving and more consistent in achieving tibiofemoral balancing and preserving the native trochlea groove compared to KA [ 23 , 24 ]. The technique and rationale for the valgus morphotype is yet to be described.…”