Johannes Gijsbertus Gerardus Dobbe

Introduction: First metacarpal extension (Wilson) osteotomy combined with modified Brunelli ligamentoplasty is performed for early thumb carpometacarpal (CMC1) osteoarthritis to improve pain and function. The purpose of this study was to quantify in vivo changes in CMC1 joint contact distribution and kinematics after this combined procedure and to determine whether postoperative patterns resemble those of healthy volunteers. We hypothesized that the procedure would reduce cumulative palmar contact during opposition–retroposition. Materials and methods: In a prospective single-center observational cohort study, six adults with early CMC1 osteoarthritis (Eaton–Littler I–II) underwent standardized preoperative and 6-month postoperative four-dimensional computed tomography (4D CT) of the CMC1 joint during active opposition–retroposition. Five healthy volunteers served as reference with a single 4D CT scan. First metacarpal–trapezium motion was registered across frames. Joint contact was estimated using a 2.0 mm proximity surrogate on the trapezial surface. The primary outcome was change in cumulative palmar contact area. Secondary outcomes included change in dorsoradial contact, temporal variability of contact curves, and contact-centroid path length and mean position. Within-subject pre- versus postoperative comparisons were performed; healthy scans provided reference patterns. Results: Healthy volunteers showed reproducible patterns with increasing palmar contact toward terminal opposition and near-mirror symmetry on retroposition. Preoperatively, patients demonstrated elevated palmar contact persisting into retroposition and loss of symmetry. Postoperatively, the procedure did not consistently reduce cumulative palmar contact. Instead, most patients exhibited increased palmar contact, flattening of contact-versus-time curves, and a shorter contact-centroid path with a palmar–ulnar shift in mean position. These changes suggest a stabilizing effect more consistent with functional partial arthrodesis than selective palmar unloading. Conclusion: Wilson osteotomy with modified Brunelli ligamentoplasty did not produce the anticipated palmar unloading during functional thumb motion. The dominant postoperative effect was palmar loading with reduced dynamic variability. These findings refine the biomechanical rationale for this joint-preserving procedure and support future studies isolating the osteotomy from ligamentoplasty using load-standardized tasks. Level of evidence: Therapeutic, IV.

Background: This narrative literature review aims to evaluate the evolution, current concepts, indications and clinical evidence of total scaphoid replacement as a treatment option for non-reconstructable scaphoid pathology. Particular emphasis is placed on implant design, materials, fixation strategies, and the biomechanical rationale underlying modern patient-specific prosthetic approaches. Methods: A comprehensive literature search was performed in PubMed, Scopus, Embase, and Google Scholar and was supplemented by reference screening and relevant book chapters. Studies reporting full scaphoid replacement were included, while partial replacements, non-original articles, and publications outside predefined languages were excluded. Data were synthesized qualitatively with respect to anatomy, biomechanics, implant materials, surgical techniques, fixation strategies, and clinical outcomes. Results: A total of 397 records were identified through database and manual searches. After removal of duplicates, non-topic-related articles, and non-retrievable studies, 33 publications were included in the final analysis. Early acrylic and silicone prostheses showed high complication rates, with implant removal required in up to 70% of early acrylic series and secondary procedures reported in approximately 24% of silicone implant cases. Radiographic abnormalities, including cyst formation and carpal malalignment, were reported in up to 43% of silicone implants despite acceptable short-term clinical outcomes. Modern metallic and patient-specific prostheses demonstrated improved resultsand implant removal required in a minority of cases. Functional outcomes, assessed by DASH and PRWE scores where available, showed significant postoperative improvement, and pain relief was reported in more than 90% of patients in larger titanium implant series. However, follow-up durations varied widely, ranging from 6 months to 43 years, and most studies consisted of small retrospective case series. Conclusions: Total scaphoid replacement has progressed from a spacer-based salvage concept to a patient-specific reconstructive strategy informed by anatomy and biomechanics. Quantitative evidence suggests that modern prostheses can achieve high rates of pain relief and acceptable complication profiles in carefully selected patients. Nevertheless, the current literature is limited by small sample sizes, heterogeneous methodologies, and a lack of long-term prospective data. Further studies with standardized outcome measures and dynamic assessment of wrist kinematics are required to define the long-term role of total scaphoid replacement.

Purpose: After total knee arthroplasty (TKA), radiolucent lines on routine conventional radiographs are commonly interpreted as impaired tibial component fixation, although their relation to implant motion remains unclear. This necessitates a comparison with measured component displacement. Recently, a computed tomography (CT)‐based method measuring load‐induced tibial component displacement has been introduced. This study aimed to determine whether the extent of radiolucent lines observed on radiographic imaging truly implicates displacement of tibial components. Methods: Conventional radiographs and CT‐scans of 50 hybrid posterior stabilised TKA's with a cemented tibial baseplate were included in a post‐market 10‐year follow‐up study. The extent of radiolucent lines on conventional radiographs was classified according to the Modern Knee Society, by two independent raters, creating three subgroups: ‘none', ‘partial', and ‘complete'. Subsequently, load‐induced implant displacement was quantified using CT‐scans under valgus‐varus loading. Relative implant displacement was quantified using rotation about the helical axis, Maximum Total Point Motion (MTPM), and mean target registration error (mTRE). Hypothesising similar displacement between subgroups despite differences in radiolucency, a Two One‐Sided Tests (TOST) procedure, using the Smallest Detectable Change (SDC) as equivalence margins, was conducted. Statistical equivalence would indicate the subgroups showed similar displacement. Results: Median displacement values were comparable across subgroups. Median rotation ranged from 0.60 to 0.79 degrees, median MTPM from 0.59 to 0.85 mm, and median mTRE from 0.44 to 0.53 mm across the subgroups. Statistical equivalence was confirmed in eight of nine comparisons, indicating that the subgroups were similar. The comparison of mTRE between the ‘partial' and ‘complete' subgroups did not meet statistical equivalence ( p = 0.053). The inter‐observer Cohen's Kappa for subgroup classification was 0.95 (95% confidence interval: 0.84–1.00). Conclusion: These findings suggest that a greater number of radiolucent lines does not represent more load‐induced displacement of tibial components of TKA. This limits the diagnostic value of radiolucent lines for assessing tibial component fixation. Level of Evidence: Level III.

The lunate bone plays a central role in force transmission, proximal carpal row integrity, and kinematics of the wrist. In cases of irreparable pathologies to the lunate bone, prosthetic replacement is appealing to avoid salvage procedures. Previous attempts at lunate replacement yielded inconsistent results due to non-anatomical implant design and lack of ligament reconstruction, which posed a risk of dislocation and carpal collapse. Nowadays, the CAD design process and 3D printing of bio-compatible materials such as titanium make it possible to manufacture patient-specific lunate implants. We present a technique and first clinical results of a patient-specific lunate replacement that includes reconstruction of the most important perilunate ligaments to suspend the implant and restore carpal integrity.

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.

Purpose: 3D-printed patient-specific guides enable accurate pedicle screw placement in the treatment of paediatric spinal deformities. MRI-based synthetic CT (sCT) eliminates the radiation exposure associated with the preoperative planning CT, while still providing detailed bony morphology. It may therefore offer a radiation-free method for pedicle screw navigation. Thus, the aim of this study was to compare the accuracy of thoracic and lumbar pedicle screw placement using 3D-printed guides based on conventional CT versus sCT. Methods: Full-spine MRI and CT images of four human cadaveric spines were obtained, followed by AI-generation of sCTs, the digital planning of pedicle screws and 3D-printed guide manufacturing. A total of 62 K-wires were inserted, 30 sCT-based and 32 CT-based. Accuracy was evaluated by superimpose analysis of planned and achieved trajectories, and by the postoperative grading of the cortical breach rate using the Gertzbein-Robbins classification, based on projected screws along the K-wires. Results: Median translational entry-point deviations were 1.0 mm vertically and 0.5 mm horizontally for both sCT-based guides and CT-based guides. Angular deviations in the axial plane were 1.0˚ for sCT and 0.9˚ for CT. In the sagittal plane these were 1.8˚ and 2.1˚, respectively. No significant differences were observed between sCT and CT. Grading of pedicle’s cortical breach showed no severe malposition for both sCT- and CT-based guides. Conclusion: sCT matched the accuracy of conventional CT in providing source data for personalized 3D-printed guides for thoracic and lumbar pedicle screw placement in terms of translational- and angular deviations, and cortical breach rates in this cadaveric study.

Lipids, particularly cholesterol, are critical components of red blood cell (RBC) membranes, influencing protein function, cell stability, and deformability. Reticulocytes (young RBC) derived from in vitro erythroid cultures have been reported to possess less cholesterol than their native counterparts, compromising their functional integrity and lifespan. However, variability in starting materials and culture protocols between studies has hindered deQnitive conclusions regarding the nature and consequences of this lipid deQciency. Here, we evaluated the influence of lipid sources on reticulocyte quality using a well-established CD34⁺ erythroid culture system. We compared the use of human AB-serum and Octaplas (solvent/detergent-treated pooled plasma) as lipid sources. Our results reveal that detergent-treated plasma leads to cholesterol-deQcient reticulocytes with impaired characteristics, including reduced Qltration yield, heightened osmotic fragility, and altered PIEZO1 activity. In contrast, AB-serum supported the generation of functionally stable reticulocytes, with cholesterol supplementation required to rescue the defects observed with plasma. Importantly, this study provides the Qrst integrated lipidomic, metabolomic, and proteomic characterisation of in vitro -derived reticulocytes cultured under distinct lipid conditions. These multi-omic datasets offer new insights into the consequences of reduced lipid availability during erythroid culture and offer new insights into how culture media affects the development and functionality of lab grown blood.

Purpose: To evaluate the outcome of ear reconstruction, the contralateral auricle is often used as a reference. Literature has shown that auricles are symmetric on a group level, but it is unknown if this is also true on an individual level. In this paper, the authors quantify bilateral symmetry of the auricle and hypothesize that quantifying bilateral differences on an individual level requires a technique that is more precise than conventional manual measurement methods. Methods: CT sinus scans of 42 healthy volunteers were used to determine the bilateral symmetry of the auricle using conventional manual measurement techniques and a high-precision computer-assisted surface-based technique with a high precision of measurement. Bilateral symmetry was evaluated for the following geometric auricle parameters: length, width, protrusion distance, auriculocephalic angle, inclination angle, posteroanterior and superoinferior position difference. Bilateral differences exceeding the reliability threshold, based on the precision of measurement for the manual and automated approaches, were considered true differences. Results: In both the manual and automated measurements, the authors found no statistically significant differences in bilateral auricle parameters at the group level when evaluating a group of L versus R ears. At the individual level, however, the automated algorithm established bilateral differences in auricle parameters in 74% to 100% of the cases, whereas manual measurements could only detect bilateral differences in 7% to 64% of the cases. Conclusions: The high-precision surface-based technique shows that human auricles are generally not symmetric on the individual level. Future research is needed to investigate which discrepancies are acceptable from a technical point of view and which left-right differences are considered acceptable from a cosmetic and reconstructive point of view.

The glucose transporter 1 (GLUT1) is 1 of the most abundant proteins within the erythrocyte membrane and is required for glucose and dehydroascorbic acid (vitamin C precursor) transport. It is widely recognized as a key protein for red cell structure, function, and metabolism. Previous reports highlighted the importance of GLUT1 activity within these uniquely glycolysis-dependent cells, in particular for increasing antioxidant capacity needed to avoid irreversible damage from oxidative stress in humans. However, studies of glucose transporter roles in erythroid cells are complicated by species-specific differences between humans and mice. Here, using CRISPR–mediated gene editing of immortalized erythroblasts and adult CD34+ hematopoietic progenitor cells, we generate committed human erythroid cells completely deficient in expression of GLUT1. We show that absence of GLUT1 does not impede human erythroblast proliferation, differentiation, or enucleation. This work demonstrates, to our knowledge, for the first time, generation of enucleated human reticulocytes lacking GLUT1. The GLUT1–deficient reticulocytes possess no tangible alterations to membrane composition or deformability in reticulocytes. Metabolomic analyses of GLUT1–deficient reticulocytes reveal hallmarks of reduced glucose import, downregulated metabolic processes and upregulated AMP-activated protein kinase signaling, alongside alterations in antioxidant metabolism, resulting in increased osmotic fragility and metabolic shifts indicative of higher oxidant stress. Despite detectable metabolic changes in GLUT1–deficient reticulocytes, the absence of developmental phenotype, detectable proteomic compensation, or impaired deformability comprehensively alters our understanding of the role of GLUT1 in red blood cell structure, function, and metabolism. It also provides cell biological evidence supporting clinical consensus that reduced GLUT1 expression does not cause anemia in GLUT1–deficiency syndrome.