Computer assisted Surgery (CAS) has now been around for almost 20 yrs. in various forms. With the advent of mechanical execution tools i.e. Robots, the surgical accuracy is excellent. Multiple studies show that computer navigated knee replacements have better alignment and less outliers.1
However most of these studies go on to state that there is no defined statistical benefit to the patient. i.e. the patient do not report a better subjective outcome when compared to the conventional techniques.2
Over the last 8-10yrs attention has focused on the positioning of the components. Gromov et al published a review article discussing the optimal alignment of the tibial and femoral components. They concluded that general consensus about the optimal alignment of the femoral and tibial components is still lacking.3
We at the Orthopaedic research institute of Qld, based in North Queensland are researching the outcomes of alternately aligned knee replacements. At a recent Meeting in Munich Germany, Dr Kaushik Hazratwala presented his results on the Outlier patient cohort.4
Outlier patients are those patients whose anatomy is aligned outside the aim of the traditional mechanical surgical technique. This is arbitrarily defined as +/- 3° either side of straight.5 The mechanical alignment technique will align the knee straight disregarding the natural pre-arthritic disease alignment. Recent publications have demonstrated that almost 30% of patients lie outside the +/-3°.6
In his presentation Dr Hazratwala compared the patient reported outcome (PROM’s) of those patients that were constitutional varus and were aligned using the mechanical surgical technique to neutral (+/-3°) with those patients who were corrected to their natural constitutional alignment.
He found that al all time points the Naturally aligned patients were doing better. They regained and mantained there Range of motion. They scored better on the post-operative pain scale, and their functional outcomes were quicker and better at all time points.
Naturally aligned knee replacement technique is a computer navigated surgical technique that recreates the patient’s alignment in extension and flexion whilst paying particular attention to the ligament balance in both positions.
Attached is a video of the surgical technique of the Computer Assisted Naturally Aligned Knee Replacement.
- Matsumoto T, Nakano N, Lawrence JE, Khanduja V. Current concepts and future perspectives in computer-assisted navigated total knee replacement. Int Orthop. May 2018. doi:10.1007/s00264-018-3950-7.
- Ollivier M, Parratte S, Lino L, Flecher X, Pesenti S, Argenson J-N. No Benefit of Computer-assisted TKA. Clin Orthop Relat Res. 2018;476(1):126-134. doi:10.1007/s11999.0000000000000021.
- Gromov K, Korchi M, Thomsen MG, Husted H, Troelsen A. What is the optimal alignment of the tibial and femoral components in knee arthroplasty? Acta Orthop. 2014;85(5):480-487. doi:10.3109/17453674.2014.940573.
- 3rd Global User Group Meeting on Orthopedic Navigation - Brainlab. https://www.brainlab.com/events/3rd-global-user-group-meeting-on-orthopedic-navigation/. Accessed July 29, 2018.
- Schiraldi M, Bonzanini G, Chirillo D, de Tullio V. Mechanical and kinematic alignment in total knee arthroplasty. Ann Transl Med. 2016;4(7):130-130. doi:10.21037/atm.2016.03.31.
- Delport H, Labey L, Innocenti B, De Corte R, Vander Sloten J, Bellemans J. Restoration of constitutional alignment in TKA leads to more physiological strains in the collateral ligaments. Knee Surgery, Sport Traumatol Arthrosc. 2015;23(8):2159-2169. doi:10.1007/s00167-014-2971-z.