Three-dimensional (3D) printing is a precise method of reproducing complex structures. Orthopaedic surgeons may utilize 3D imaging to better plan procedures, design implants, and communicate with other providers and patients. However, one of the limitations of 3D printed models has been the high cost associated with third-party creation of such tools. With the recent increases in the use of 3D printing many publically available software programs have been developed, which allow for inexpensive office-based production of models. We present a simple, inexpensive technique which can be used by surgeons for the rapid fabrication of 3D models in-office. CT scan and MRI's are stored in DICOM type format which must be transformed into a 3D image. This can be achieved using publically available programs (for example, 3D slicer (Introduction
Technique
In patients with significant bone loss and a nonfunctioning extensor mechanism, the approach to revision is complicated. We describe a unique approach to solve this complex problem to help restore clinically satisfactory results. Our technique involves the use of a donor allograft that consists of proximal tibia along with the attached extensor mechanism (patellar tendon-patella-quadriceps tendon). Five reconstructions utilizing bone allografts and extensor mechanisms were performed by two surgeons. Each has extensive surgical history on the affected knee and presented with gross instability, considerable bone loss, and significant extensor lag or total loss of extension. The implants used were press-fit stems with the tibial baseplate cemented into the allograft prior to implantation. In this series, either hinged or total stabilized prostheses were used. The follow up ranged from 1 to 5 years. The only complication to date was reported in one patient who required irrigation and debridement with surgical wound closure after partial dehiscence. However the patency of the allograft was not disrupted. All prostheses have been noted to be stable with no signs of loosening. This procedure presented should be considered a salvage procedure for bone stock and extensor mechanism deficiency in revision total knee arthroplasty. The advantage to our allograft is the inherent stability of the proximal tibia with the tibial tubercle and associated extensor mechanism. For patients with this complex deficiency, there has been no effective method of treatment and we advocate the use of this procedure to restore function and relieve pain to an otherwise grossly unstable and functionally limited joint.
