Patello-femoral joint - the forgotten third space. How can robotics help?

There is increasing interest in the function of the patello femoral joint in total knee replacement. The anterior part of the knee (3rd space) appears to be important in the soft tissue outcome of knee surgery. Whilst greater understanding of the tibio-femoral joint has led to significant advances in instrumentation in knee replacement, the complex and mobile nature of the tissues around the patella-femoral joint and the dynamic nature of the 3rd space have rendered it difficult to design appropriate standard instruments to address the challenges of balancing the third space in ways similar to that of the flexion and extension spaces. Robotics and other digital technology offer the promise of greater understanding of the pressures and functions of the 3rd space. Additionally, the use of robotics to execute surgery around the third space allows the complex anatomy of this area in three dimensions to be replicated and addressed in a way that is not possible with standard instrumentation. Different cutting technologies coupled with 3 dimensional planning and execution of the surgery on the basis of CT scan or bone morphing rather than two-dimensional X-rays as is the present situation, offer the hope of a more effective intervention in this difficult and complex area. An early advance in this area is the development of a pressure measurement system that allows recording of patello-femoral compression forces dynamically during knee replacement, allowing an objective approach to balancing the third space. Further work shows patella-femoral pressure may be altered by selective resection of patellar bone and the possibility of linking artificial intelligence to the interpretation of the complex movements of the patella on the pressures in the third space, offers the possibility of significant improvement or enablement for the surgeons in dealing with the challenges in this complex area.