April 15, 2016 22:19 ws-jmrr Journal of Medical Robotics Research, Vol. 0, No. 0 (2016) 1–9 c  World Scientific Publishing Company Intraoperative Manufacturing of Patient Specific Instrumentation for Shoulder Arthroplasty: a Novel Mechatronic Approach A. Darwood a , R. Secoli b , S. A. Bowyer b , A. Leibinger b , R. Richards c , P. Reilly b , A. Darwood a , A. Tambe d , R. Emery b and F. Rodriguez y Baena b a Prometheus Surgical Ltd. 24 Upper Wimpole St, London, United Kingdom. email: alastairdarwood@hotmail.com b Imperial College, London, United Kingdom c 3Cavendish Implants, London, United Kingdom d Derby Hospital NHS Trust, London, United Kingdom Optimal orthopaedic implant placement is a major contributing factor to the long term success of all common joint arthroplasty procedures. Devices such as three-dimensional (3D) printed, bespoke guides and orthopaedic robots are extensively described in the literature and have been shown to enhance prosthesis placement accuracy. These technologies, however, have significant drawbacks, such as logistical and temporal inefficiency, high cost, cumbersome nature and difficult theatre integration. A new technology for the rapid intraoperative production of patient specific instru- mentation, which overcomes many of the disadvantages of existing technologies, is presented here. The technology comprises a reusable table side machine, bespoke software and a disposable element comprising a region of standard geometry and a body of mouldable material. Anatomical data from Computed Tomography (CT) scans of 10 human scapulae was collected and, in each case, the optimal glenoid guidewire position was digitally planned and recorded. The achieved accuracy compared to the preoperative bespoke plan was measured in all glenoids, from both a con- ventional group and a guided group. The technology was successfully able to intraoperatively produce sterile, patient specific guides according to a pre-operative plan in 5 minutes, with no additional manufacturing required prior to surgery. Additionally, the average guide wire placement accu- racy was 1.58 mm and 6.82 ◦ degrees in the manual group, and 0.55 mm and 1.76 ◦ degrees in the guided group, also demonstrating a statistically significant improvement. Keywords: Arthroplasty; Computer Assisted Surgery; Medical Robotics 1. Introduction It is well known that the accurate placement of orthopaedic hard- ware, such as arthroplasty prostheses, into a biomechanically de- rived optimum position is of paramount importance for the long term success of these interventions. 1–3 Arthroplasty prosthesis malpositioning has been shown to decrease postoperative func- tion and implant longevity in many of the major joints. For ex- ample, De Haan et al. 3 show acetabular component malposition- ing to be a significant risk factor for revision hip arthroplasty, whilst Skirving et al. 4 similarly show poor glenoid component positioning to be a major reason for arthroplasty failure and sub- sequent revision. Choong et al. 2 showed that improved accuracy with respect to the anatomical alignment of implanted knee pros- theses resulted in an improvement of 19% in the post-operative international knee score. Similarly, in many orthopaedic proce- dures, it is advantageous or even essential to know the exact placement of hardware such as screws or pins, for example in spinal surgery, complex fracture reduction, or the position of os- teotomy cuts. The need for orthopaedic guidance has resulted in signifi- cant growth in technologies able to assist a surgeon in the place- ment of hardware or tools, with many companies marketing a number of guidance products to consumers. Guidance technolo- gies may be broadly split into three main categories: bespoke patient specific instrumentation, such as rapid manufactured (3D printed) guides, Computer Aided Surgery (CAS) systems, and intraoperative orthopaedic surgical robots. Bespoke 3D printed guides are commercially available from many large orthopaedic implant manufacturers and stan- dalone companies. Guides are digitally designed from manip- ulated Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) data of a patient, and subsequently 3D printed, sterilised and sent to a surgeon for intraoperative use. Guides 1