A Prospective Randomised Controlled Trial Comparing Cementless Mako Robotic-arm Assisted Total Knee Arthroplasty Versus Cemented Mako Robotic-arm Assisted Total Knee Arthroplasty.

Osteoarthritis of the knee accounts approximately for 85% of the disease burden across the globe10. Almost one in six people is affected by knee arthritis and according to the latest National Joint Registry (NJR) report; over the last three years in England and Wales more than 100,000 patients underwent total knee replacement each year.

Registry-based studies have shown good clinical outcomes and survivorship following TKA, however despite these results aseptic loosening and lysis remain the leading indications for revision. Furthermore, there is a higher incidence of patient dissatisfaction compared to total hip arthroplasty, with up to 20% of patients reporting dissatisfaction in an otherwise uncomplicated TKA. There has been an exponential rise in the number of TKAs performed in the UK and around the world, with a sharp increase in the percentage of younger patients undergoing TKA11. Notwithstanding, younger patients have consistently shown poorer outcomes following TKAs and younger age has been recognised as a risk factor of aseptic loosening; thus raising a concern given the demographic trend of younger patients seeking TKA.

The optimal component fixation mode has been contentious, and it is yet to be established whether one is superior to the other. Early reports of cementless TKAs had risen concerns in relation to suboptimal fixation and early failure. However, since then, there has been a dramatic improvement in the design and technique of cementless TKA, reflected on several studies reporting promising and favourable outcomes with cementless fixation; a recent systematic review and meta-analysis has shown a 96% - 100% survival at ten- to 15-years. Proponents of the technique highlight the potential of biologic fixation and better osseointegration, given highly porous surfaces on TKA designs prevent a mismatch in stiffness and approximate the pore size and elasticity of trabecular bone. Moreover, cementless implants do not produce cement debris, averting the risk of cement degradation leading to prosthesis loosening. Commonly, cementless prostheses are more expensive than cemented, however a recent study reported a lower overall cost associated with cementless TKA; showing that the additional cost could be offset when additional variables are taken into account such as operating time, implant, cement and cementing accessories.

The evolution of surgical technology has led to the development of robotic-arm assisted TKA, which uses three dimensional images of each patient's unique anatomy to guide bone resection, implant positioning, and optimise limb alignment. The robotic arm interactive orthopaedic (RIO) system (Mako surgical) uses preoperative computerised tomography scans to build a computer-aided design (CAD) model of the patient's knee joint. The Mako robotic software processes this information to calculate the volume of bone requiring resection and creates a three-dimensional haptic window for the robotic arm to resect. The robotic arm has tactile and audio feedback to resect bone to a high degree of accuracy and preserve as much bone stock as possible. The surgeon can then plan and execute optimal sizing and positioning of the prosthesis to achieve the required bone coverage, minimise bone resection, and obtain the desired limb alignment. The Mako software also creates a patient-specific computer aided design model using the preoperative CT scan, which means that only bone anatomy is segmented. The surgeon is able to compensate for wear when creating the surgical alignment plan and uses intraoperative bone registration to map the patient's anatomy.

There are very few randomised prospective studies exploring clinical and radiological outcomes in cemented versus uncemented TKA. Prospective studies comparing functional outcomes between the treatment groups have been performed but the main limitation of these studies has been the inability to achieve the implant position to a high degree of accuracy. Furthermore, there is a paucity of long-term studies and limited data correlating radiological outcomes to clinical findings.