Digital Twins in Surgical Planning: The Personalised Future of Orthopaedics

The concept of a digital twin — a virtual replica of a physical object or system, updated in real time from data generated by its physical counterpart — has its origins in aerospace and industrial engineering. Its application to surgical planning represents one of the most promising convergences of imaging technology, computational biomechanics, and clinical decision support that modern medicine has produced. In orthopaedics, the digital twin of a patient's joint — derived from CT imaging, enriched with bone density data, and animated with biomechanical models of implant behaviour — allows surgical planning at a level of personalisation and precision that conventional templating cannot approach.

What digital twin planning enables

In shoulder arthroplasty, CT-derived three-dimensional models of the patient's glenoid and proximal humerus allow virtual implant placement, real-time assessment of component positioning in all planes, simulation of the range of motion achievable with different implant configurations, and identification of potential impingement or instability before the procedure begins. The surgeon who arrives in the operating theatre having worked through the case virtually — having tested the planned component sizes, confirmed the correction of glenoid retroversion, and identified the optimal humeral stem version — is not merely better prepared. They are operating with a level of patient-specific anatomical familiarity that was previously achievable only through extensive experience with the specific individual's anatomy.

In fracture surgery, digital twin modelling of complex articular fractures — distal humerus, tibial plateau, acetabulum — allows virtual reduction and fixation planning that identifies the optimal implant configuration, the sequence of reduction steps, and the positions of fixation hardware before the patient reaches theatre. This planning capability reduces intraoperative decision time, reduces the need for implant exchanges, and produces more accurate reductions in complex fracture patterns where the three-dimensional anatomy is difficult to fully appreciate on standard imaging.

The convergence with augmented reality

The most powerful application of digital twin technology in surgery is its combination with intraoperative augmented reality navigation — overlaying the virtual plan onto the real surgical field in real time, creating a continuous visual reference between the planned and the actual procedure. This convergence — which I have experienced directly in AR-navigated shoulder arthroplasty — closes the loop between pre-operative planning and intraoperative execution in a way that neither technology achieves alone.

The validation requirements for digital twin surgical planning tools are the same as for any clinical AI application: external validation on diverse patient populations, transparent performance reporting, and ongoing monitoring to ensure that the computational models accurately represent the biology they are designed to simulate. These are not obstacles to adoption — they are the standards that make adoption responsible and the outcomes trustworthy.