The mechanical alignment (MA) technique has been described as a ‘systematic’ technique, that standardises the approach to every TKR surgery, without considering the native knee alignment or individual differences in anatomy¹. It is biomechanically sound because it reduces the potential for unbalanced loads on the prosthesis, and so reduces the risk of accelerated wear and loosening¹.

MA was introduced at the dawn of knee arthroplasty, when poor quality polyethylene, and rudimentary cementing techniques and instrumentation, made it necessary to achieve acceptable implant survivorship¹.

Since then much has changed: the introduction of more anatomic implant designs, improved polyethylene, enhanced instrumentation and surgery-assisting technologies, and modern cement/cementing techniques allow precise and reproducible implantation and improved fixation¹.

Despite these improvements, and the excellent survivorship provided by MA, clinical results have been relatively poor when compared with those of THR¹. Rates of dissatisfaction and residual symptoms like pain, instability or stiffness have been reported at approximately 15% and 50%, respectively¹. Patients rarely perceive their MA TKR feels ‘normal’, and forgotten joints scores are low compared to THR/PKR^2,3.

The observation that advancements in knee design and surgical precision have not completely resolved these issues, has shone a light on the inherent technical limitations with the MA philosophy, which creates a non-physiological implant position by altering the native anatomy, physiological ligament balance and kinematics¹.

The solution could be a patient-specific and personalised surgical technique that aims to create a more physiological prosthetic knee by restoring the individual native anatomy, physiological soft-tissue balance, and kinematics¹. This technique, composed of a series of well-defined steps, is a true resurfacing, where the bone cuts are anatomical rather than mechanical, and soft-tissue release is largely avoided¹.

So far, the results for this technique have been promising, with early reports of low complication rates, and high function and patient satisfaction¹. Patients also appear to be at less risk of developing anterior knee pain, and are three times more likely to rate their TKR as feeling ‘normal’^1,4.

According to the authors, the next challenge is to verify the suitability of this technique for all patient anatomies/determine which anatomies or biomechanics should not be ‘fully restored’ with this technique¹.

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