In severe cases of total knee & hip arthroplasty, where off-the-shelf implants are not suitable (i.e., in cases with extended bone defects or periprosthetic fractures), 3D-printed custom-made knee & hip revision implants out of titanium or cobalt-chromium alloy represent one of the few remaining clinical treatment options. Design verification and validation of such custom-made implants is very challenging. Therefore, a methodology was developed to support surgeons and engineers in their decision on whether a developed design is suitable for the specific case. A novel method for the pre-clinical testing of 3D-printed custom-made knee implants has been established, which relies on the biomechanical test and finite element analysis (FEA) of a comparable clinically established reference implant. The method comprises different steps, such as identification of the main potential failure mechanism, reproduction of the biomechanical test of the reference implant via FEA, identification of the maximum value of the corresponding FEA quantity of interest at the required load level, definition of this value as the acceptance criterion for the FEA of the custom-made implant, reproduction of the biomechanical test with the custom-made implant via FEA, decision making for realization or re-design based on the acceptance criterion is fulfilled or not. Exemplary cases of custom-made knee & hip implants were evaluated with this new methodology. The FEA acceptance criterion derived from the reference implants was fulfilled in both custom-made implants and subsequent biomechanical tests verified the FEA results. The suggested method allows a quantitative evaluation of the biomechanical properties of custom-made knee & hip implant without performing physical bench testing. This represents an important contribution to achieve a sustainable patient treatment in
Introduction and Objective. In recent years, along with the extending longevity of patients and the increase in their functional demands, the number of annually performed RSA and the incidence of complications are also increasing. When a complication occurs, the patient often needs multiple surgeries to restore the function of the upper limb. Revision implants are directly responsible for the critical reduction of the bone stock, especially in the shoulder. The purpose of this paper is to report the use of allograft bone to restore the bone stock of the glenoid in the treatment of an aseptic glenoid component loosening after a reverse shoulder arthroplasty (RSA). Materials and Methods. An 86-years-old man came to our attention for aseptic glenoid component loosening after RSA. Plain radiographs showed a complete dislocation of the glenoid component with 2 broken screws in the neck of glenoid. CT scans confirmed the severe reduction of the glenoid bone stock and critical bone resorption and were used for the preoperative planning. To our opinion, given the critical bone defect, the only viable option was revision surgery with restoration of bone stock. We planned to use a bone graft harvested from distal bone bank femur as component augmentation. During the revision procedure the baseplate with a long central peg was implanted “on table” on the allograft and an appropriate osteotomy was made to customize the allograft on the glenoid defect according to the CT-based preoperative planning. The Bio-component was implanted with stable screws fixation on residual scapula. We decided not to replace the humeral component since it was stable and showed no signs of mobilization. Results. The new bio-implant was stable, and the patient gained a complete functional recovery of the shoulder. The scheduled radiological assessments up to 12 months showed no signs of bone resorption or mobilization of the glenoid component. Conclusions. The use of bone allograft in revision surgery after a RSA is a versatile and effective technique to treat severe glenoid bone loss and to improve the global stability of the implant. Furthermore, it represents a viable alternative to autologous graft since it requires shorter operative times and reduces graft site complications. There are very few data available regarding the use of allografts and, although the first studies are encouraging, further investigation is needed to determine the biological capabilities of the transplant and its validity in
With increasing numbers of total joint arthroplasties being performed, peri-prosthetic fracture incidence is rising, and operative management remains the gold standard. Short-term survivorship up to 12 months has been well-documented but medium to long-term is almost unknown. We present survivorship review from a district general hospital, undertaking 800 primary hip and knee arthroplasties per year. Patients with peri-prosthetic fractures and background total knee replacements were identified using our computer database between 2006–2011. All patients were operated on our site; methods used include open reduction, internal fixation (ORIF) using Axsos (Stryker Newbury) locking plates (28), intra-medullary nailing (1) or
