The kinematically-aligned total knee arthroplasty (KA TKA) is predicted on the pioneering work of Hungerford (fig.1), Kenna and Krackow, who designed the porous-coated anatomic (PCA) [1], total knee system striving to position the femoral and tibial component in order to anatomically recreate the joint line with the overall component alignment at 2°–3° of varus in relation to the mechanical axis of the lower limb [2]. 

fig.1 - Prof. David HUNGERFORFD

This method can also be defined as “Anatomical Alignment” (AA), a systematic approach that requires to perform the femoral cut at approximately 8-9° of valgus combined with the 2°–3° of varus angulation of the tibial cut (fig.2).

fig.2 - Anatomical vs Mechanical Alignment (from Rivier C et al Alignment options for total knee arthroplasty: A systematic review. Orthop Traumatol Surg Res. 2017)

Described by Insall [3] (fig.3), the mechanical alignment (MA) is the widest method used in TKA, for Insall himself an "aceptable compromize". It requires to create a straight limb perpendicular to the mechanical axis doing the femoral cut at approximately 4-5° of valgus combined with the 0° of varus angulation of the tibial cut [4]. The Hip Knee Ankle angle (HKA) is at the end of surgery still neutral.

dr John insall.jpg

fig.3 - Prof. John INSALL

A recent study of Michael Hirshmann found more than 40 different functional knee phenotypes showing that a more individualized approach to TKA alignment could be needed [5].

fig.4 - Prof. Michael HIRSCHMANN

Michael Hirschmann.jpg

fig.5 - Knee phenotypes (from HIRSCHMANN M et al Functional knee phenotypes: a novel classification for phenotyping the coronal lower limb alignment based on the native alignment in young non-osteoarthritic patients. Knee Surg Sports Traumatol Arthrosc. 2019)

fig.3 - Prof. John INSALL

fig.3 - Prof. John INSALL

The concept of preserving the entire constitutional knee alignment REPRODUCING THE NATIVE TIBIAL AND FEMORAL ANGLES OF THE KNEE has been developed by Howell (fig.6) and Hull since 2006 with the KA TKA technique [5, 6].

fig.4 - Prof. Michael HIRSCHMANN

fig.4 - Prof. Stephen HOWELL 

KA is not a modification of the MA or AA, but rather a new surgical technique for TKA, with only the sagittal positioning of the femoral component shared with the MA technique [4]. KA reproduce the knee angles in a patient specific and individualized way (fig.7).

fig.7 - KA differ than MA or AA Alignment

(from Rivier C et al Alignment options for total knee arthroplasty: A systematic review. Orthop Traumatol Surg Res. 2017)

fig.2 - Anatomical vs Mechanical Alignment (from Rivier C et al Alignment options for total knee arthroplasty: A systematic review. Orthop Traumatol Surg Res. 2017)

KA was first performed by Howell in January 2006 using the world wide first patient-specific guides.

 

Today the KA technique can be performed with the use of navigation [7], patient-specific instrumentation [8], robotic [9], and mostly conventional instrumentation using the calipered “shape match” technique [10]. It is important to notice that the unique and original Howell's KA technique is CALIPERED, each other one isn't and has to be different named (i.e. the recently described "reverse KA technique" is not a KA technique).

KA co-aligns the axes and joint lines of the components with the three «kinematic» axes and joint lines of the pre-arthritic or native knee without placing restrictions on the pre-operative deformity and post-operative correction [5, 6].

fig.8- 3D axis considered performing KA TKA technique

verification checks.png

The “calipered shape match” KA technique uses verification checks (fig.9) to record caliper measurements of femoral and tibial resections that are adjusted within ±0.5mm of the thickness of femoral and tibial components after compensating for cartilage, bone wear and 1-mm kerf from the saw cut. No ligaments release are needed [5, 6, 10]. 

fig.9 - Verification checks for the original Howell's KA TKA technique

BIBLIOGRAPHY

1- Schiraldi M, Bonzanini G, Chirillo D, de Tullio V. Mechanical and kinematic alignment in total knee arthroplasty. Ann Transl Med. 2016;4(7):130.

2- Insall & Scott surgery of the knee / editor, W. Norman Scott.—5th ed.

3- Rivière C, Iranpour F, Auvinet E, Howell S, Vendittoli PA, Cobb J, Parratte S. Alignment options for total knee arthroplasty: A systematic review. Orthop Traumatol Surg Res. 2017 Nov;103(7):1047-1056.

4- Hirschmann MT, Moser LB, Amsler F, Behrend H, Leclerq V, Hess S. Functional knee phenotypes: a novel classification for phenotyping the coronal lower limb alignment based on the native alignment in young non-osteoarthritic patients. Knee Surg Sports Traumatol Arthrosc. 2019 May;27(5):1394-1402.

5- Kinematic Alignment in Total Knee Arthroplasty Definition, History, Principle, Surgical Technique, and Results,  April / 2014 Arthropaedia

6- Howell SM, Howell SJ, Kuznik KT, Cohen J, Hull ML. Does a kinematically aligned total knee arthroplasty restore function without failure regardless of alignment category? Clin Orthop Relat Res. 2013 Mar;471(3):1000-7.

7- Dossett Hg, swartz gJ, Estrada na, lefevre gW, Kwasman Bg. Kinematically versus mechanically aligned total knee arthroplasty. Orthopedics 2012;35:e160-9.

8- Calliess T, Ettinger M, Savov P, Karkosch R, Windhagen H. Individualized alignment in total knee arthroplasty using image-based robotic assistance: Video article. Orthopade. 2

9- Hutt Jr, leBlanc Ma, Massé V, lavigne M, Vendittoli Pa. Kinematic TKA using navigation: surgical technique and initial results. Orthop Traumatol Surg Res 2016;102:99-104

018 Oct;47(10):871-879.

10- Howell SM. Calipered Kinematically Aligned Total Knee Arthroplasty: An Accurate Technique That Improves Patient Outcomes and Implant Survival. Orthopedics. 2019 May 1;42(3):126-135.

 

 2020 - created by dr. michele malavolta (cod.fis. MLVMHL74A27L781A)