Recently, three‐dimensional (3D) printing has become increasingly popular in the medical sector for the production of anatomical biomodels, surgical guides, and prosthetics. With the availability of low‐cost desktop 3D printers and affordable materials, the in‐house or point‐of‐care manufacturing of biomodels and Class II medical devices has gained considerable attention in personalized medicine. Another projected development in medical 3D printing for personalized treatment is the in‐house production of patient‐specific implants (PSIs) for partial and total bone replacements made of medical‐grade material such as polyetheretherketone (PEEK). We present the first in‐hospital 3D printed scaphoid prosthesis using medical‐grade PEEK with fused filament fabrication (FFF) 3D printing technology.

Reconstruction of a non-united scaphoid with a humpback deformity involves resection of the non-union followed by bone grafting and fixation of the fragments. Intraoperative control of the reconstruction is difficult owing to the complex three-dimensional shape of the scaphoid and the other carpal bones overlying the scaphoid on lateral radiographs. We developed a titanium template that fits exactly to the surfaces of the proximal and distal scaphoid poles to define their position relative to each other after resection of the non-union. The templates were designed on three-dimensional computed tomography reconstructions and manufactured using selective laser melting technology. Ten conserved human wrists were used to simulate the reconstruction. The achieved precision measured as the deviation of the surface of the reconstructed scaphoid from its virtual counterpart was good in five cases (maximal difference 1.5 mm), moderate in one case (maximal difference 3 mm) and inadequate in four cases (difference more than 3 mm). The main problems were attributed to the template design and can be avoided by improved pre-operative planning, as shown in a clinical case. Level of evidence: V

Background: Numerous anatomical features of the first carpometacarpal (CMC I) joint have been investigated as potential predispositions for CMC I osteoarthritis (OA). Even though load transmission through the CMC I joint—and, therefore, the development of osteoarthritis—is believed to be influenced by the geometry of the first metacarpal (MC I) bone, there is no common definition of the MC I axes. Methods: CT scans of twenty healthy volunteers and pre- and postoperative CT scans of six patients with CMC I OA undergoing Wilson osteotomy were analyzed. We proposed a calculation method based on anatomical landmarks for the proximal joint surface axis (PA) angle and the definition of an anatomical (AA) and a mechanical (MA) longitudinal axis. We hypothesized that for an MC I extension osteotomy to be effective, the AA and MA need to be aligned surgically. Results: To align AA and MA, an average correction angle of 22.60° (SD 2.53°) at 1 cm and 26.73° (SD 2.55°) at 1.5 cm distal to the CMC I joint line is required. Conclusions: The hereby proposed method for patient-specific calculation of the correction can be used to improve the surgical technique.

Background: Cadaveric specimens used in research are commonly frozen when stored and may undergo multiple freeze–thaw cycles during experimental procedures. To streamline workflows and minimize potential tissue degradation from repeated thawing, this study evaluated whether a frozen cadaver wrist can be reliably used to model a scaphoid for the development of a patient-specific prosthesis design method in a preclinical setting. Additionally, we assessed the impact of segmentation smoothing techniques on the accuracy of the prosthesis model. Methods: High-resolution computed tomography (CT) scans were performed on a cadaver wrist in both frozen and thawed states. Scaphoid bones were segmented using two approaches: a tight (native surface) segmentation and a smoothened version optimized for prosthetic articulation. The resulting 3D models were registered, and volume and shape differences between frozen and thawed states, as well as between segmentation methods, were quantified. Results: No statistically significant volume differences were observed between scaphoid models segmented from frozen and thawed conditions (p = 0.46). The average difference was 0.14% (SD 0.55). Furthermore, smoothing segmentation had minimal impact on the overall dimensions of the scaphoid model. Conclusions: Frozen cadaver wrists can be used to accurately model scaphoid bones for patient-specific prosthesis design without introducing significant volumetric deviations. Segmentation smoothing, which is necessary for prosthesis fabrication, does not compromise anatomical accuracy, supporting the feasibility of using frozen specimens for preclinical modeling.