Felix Ragnar Merlin Koenig

Objectives: To introduce the magnetic resonance observation of bone and cartilage repair tissue (MOBCART) bone score as a dedicated add-on to the established MOCART 2.0 knee score, and to evaluate its reproducibility for MRI-based assessment of the osseous component after osteochondral reconstruction of the knee. Materials and methods: Thirty-two postoperative knee MRI examinations from 23 patients were scored using the three-domain MOBCART add-on (Integration, Normalization, Cysts; 0–50 points) by four independent readers (expert musculoskeletal radiologist, expert orthopedic cartilage specialist, radiology resident, orthopedic resident). Inter- and intrarater reliability were assessed using linear weighted kappa for individual ordinal domains and intraclass correlation coefficients (ICC; two-way mixed, absolute agreement, single measures) for the total score. Two readers repeated scoring for intrarater reliability. Results: Interrater reliability across all four readers was moderate-to-good for the total score (ICC(A,1) = 0.72) and substantial-to-almost perfect for domain scores (κ = 0.71–0.82). Expert-reader agreement was good for the total score (ICC(A,1) = 0.90) and almost perfect for all domains (κ = 0.93–0.95). Intrarater reliability was excellent for Reader 1 (ICC(A,1) = 0.98) and good for Reader 4 (ICC(A,1) = 0.85). Conclusions: The MOBCART add-on score is a reproducible, bone-focused supplement to the MOCART 2.0 knee score that enables standardized MRI reporting of osseous features after osteochondral reconstruction. Key Points: Question Can a dedicated MRI add-on score to MOCART 2.0 reliably assess the osseous component after osteochondral knee repair across readers of varying experience? Findings The MOBCART add-on showed moderate-to-good interrater reliability across mixed-experience readers, good agreement between experts, and high test–retest reliability for both experienced and resident readers. Critical relevance statement As a complement to the MOCART 2.0 knee score, the MOBCART add-on score may facilitate standardized reporting of the osseous compartment after osteochondral reconstruction and enable objective comparison of bone-related imaging outcomes across procedures and studies.

Background/Objectives: To test whether routine T1-weighted spin-echo (T1-SE) and proton-density fast spin-echo (PD-FSE) MRI signal intensity (SI) can index bone regeneration after osteochondral scaffold implantation by correlating MRI metrics with micro-CT and histology. Methods: Twenty-eight sheep with bilateral trochlear defects were evaluated in separate cohorts at 30, 180, and 365 days (n = 7, 11, and 10, respectively). One knee received a tri-layered resorbable scaffold; the contralateral defect was left empty. MRI (T1-SE, PD-FSE) was read by two blinded musculoskeletal radiologists using 10-point Likert scales (T1: apparent mineralization; PD: SI normalization). Contrast-to-noise ratio (CNR) between repair-bone and reference bone was computed. MRI measures were correlated with micro-CT (new bone volume; trabecular bone volume) and histology (ICRS subchondral bone reconstruction; new bone; filling). Results: Likert ratings on both T1-SE and PD-FSE correlated with micro-CT new bone volume and trabecular bone volume and with histological measures of repair. PD-FSE CNR was inversely associated with micro-CT new bone volume and trabecular bone volume (both p < 0.001), indicating lower CNR with greater bone regeneration, whereas T1-SE CNR showed no significant associations. Inter-reader agreement was excellent (ICC 0.947 individual; 0.973 average), with good-to-excellent intra-reader reliability (0.920–0.963). Conclusions: Reader-based Likert assessment on both sequences and PD-FSE CNR provide complementary, non-invasive markers of subchondral bone regeneration, supporting MRI for radiation-free follow-up and endpoint selection in future translational studies. T1-SE CNR did not track incremental mineralization and should not be used as a stand-alone quantitative marker in early healing.

Background/Objectives: Pleura-based pulmonary nodules in soft-tissue sarcoma (STS) patients remain diagnostically challenging, and entity-specific contrast-enhanced ultrasound (CEUS) data are scarce. We aimed to characterize CEUS perfusion patterns of pleura-based STS pulmonary metastases in a pilot cohort. Methods: We investigated a single-center retrospective cohort at a tertiary STS referral center (Dec 2024–Dec 2025). Of 51 consecutive STS patients with suspected pulmonary metastases screened, 32 lacked pleural contact and 6 were excluded for logistical reasons; the remaining 13 underwent standardized CEUS of a pleura-contacting lesion (≥5 mm) visible on B-mode lung ultrasound (B-LUS), with 1 excluded on biopsy (anaplastic lymphoma). The reference standard combined histology, therapy-related size reduction of the index lesion, and/or documented distant metastatic STS. Two readers rated all examinations independently, with adjudication by a third senior reader. Wilson 95% confidence intervals (CIs) and Cohen’s κ were computed. Results: In the 12 analyzed patients (mean age 58.8 ± 17.8 years; 7 male), the index lesion was histologically confirmed in 4 (33.3%). On CEUS, bronchial-arterial (BA) enhancement predominated (10/12; 83.3%, 95% CI 55.2–95.3%) and pulmonary-arterial timing occurred in 2/12 (16.7%). Marked enhancement was present in 9/12 (75.0%), homogeneous in 8/12 (66.7%), and rapid washout (<120 s) in all lesions (12/12; 100%, 95% CI 75.8–100%). Inter-reader agreement was substantial to almost perfect for the diagnostically relevant CEUS perfusion variables (enhancement κ = 0.75; EE κ = 0.80; HE κ = 0.82) and moderate for the descriptive shape variable (Form κ = 0.47). Conclusions: In this selected pilot cohort, pleura-based STS lung metastases most commonly showed BA-dominant enhancement with universal rapid washout. The findings are hypothesis-generating and require validation in larger, prospective multicenter cohorts.

Background/Objectives: Acromioclavicular (AC) joint injuries account for 9–12% of shoulder injuries, predominantly affecting young male athletes. While conservative treatment is established for Rockwood type I–II injuries and surgery is widely regarded as indicated for type V–VI, management of type III–IV injuries remains controversial. Biomechanical studies have shown superior results in combined reconstruction of the coracoclavicular and AC ligament complex, however clinical data is scarce. Therefore, the present study aimed to assess whether the addition of an acromioclavicular ligament reconstruction to an isolated coracoclavicular repair offers superior clinical and radiographic outcomes in the treatment of acute AC joint dislocations. Methods: A retrospective multicenter study was conducted on patients with Rockwood type III–VI AC joint injuries who underwent surgical treatment between 2019 and 2024. Patients were divided into two groups: isolated CC reconstruction (group I) and combined CC and AC ligament reconstruction (group II). Clinical outcome was assessed using patient-reported outcome measures (American Shoulder and Elbow Surgeons Score, Simple Shoulder Test, Single Assessment Numeric Evaluation, Visual Analogue Scale) and radiographic evaluations were performed regularly up to 6 months postoperatively. Results: Fifty-five patients (94.5% male, mean age 33.5 ± 10.9 years) were included in the present study. High patient satisfaction (group I: ASES 96.3 ± 7.9, SST 99.2 ± 3.3, SANE 95.3 ± 7.0; group II: ASES 95.8 ± 8.8, SST 96.8 ± 8.2, SANE 93.6 ± 12.8) was documented in both groups, but no significant differences were observed. The median coracoclavicular loosening ratio was 24.7% in the CC group and 32.6% in the CC and AC ligament reconstruction group (p = 0.830). Five complications occurred: two infections and three revision surgeries due to excessive secondary dislocations. Conclusions: Both surgical techniques demonstrated excellent clinical outcomes. In this study combined CC and AC ligament reconstruction did not yield superior clinical or radiological results compared to isolated coracoclavicular reconstruction. Our findings suggest that a routine AC ligament augmentation may not be necessary in all patients. Further randomized controlled trials are needed to validate these results.

Objectives: Cartilage repair (CR) surgery and anterior cruciate ligament reconstruction (ACL-R) are common joint procedures, particularly in younger patients. However, the impact of prior or concurrent ACL-R on the outcomes of CR remains uncertain. This study aimed to evaluate whether ACL-R affects the structural quality and clinical outcomes of CR tissue. Methods: In this retrospective multicenter study, 71 patients undergoing CR were followed up with magnetic resonance imaging (MRI) and clinical evaluations at 3, 12, and 60 months. Of these, 22 patients underwent ACL-R before or during CR. Morphological assessment was performed using Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) 2.0 scores; compositional analysis included T2 mapping ( n = 45). Patient-reported outcome measures (PROM) were assessed at all time points. Statistical tests included the Mann–Whitney U -test, Wilcoxon signed-rank test, and simulation-based power analysis. Results: MOCART 2.0 scores and T2 mapping values showed no significant group differences at any time point. Both groups demonstrated significant improvements in PROMs from baseline to 60 months. However, at 60 months, the ACL-R group had significantly lower PROMs than the non-ACL-R group. Conclusion: Although long-term clinical outcomes were worse in patients with ACL-R, all PROMs improved significantly from baseline to 60 months in both groups. MRI showed no significant differences in focal CR tissue quality, suggesting structural success regardless of ACL-R. While ACL-R patients remain at higher risk of joint degeneration, they can still experience mid-term clinical benefit from CR. These findings support its use in ACL-R patients when joint function is properly restored and expectations are managed.

Objectives: This study aimed to assess the impact of intralesional bony overgrowth (ILBO) after cartilage repair on the integrity of opposing articulating cartilage (OpAC) using T2 mapping and to correlate these findings with clinical outcomes. Methods: In this multicenter study, magnetic resonance imaging (MRI) examinations were performed in the follow-up after cartilage repair (Microfracturing (MFX) and Matrix-Induced Autologous Chondrocyte Implantation (MACI)) in 45 patients up to 5 years after surgery. T2 values of the OpAC after 3, 12, and 60 months in patients with and without ILBO after 60 months were conducted along with clinical assessments (International Knee Documentation Committee (IKDC) and Knee injury and Osteoarthritis Outcome Score (KOOS)). Results: At 60 months post-surgery, 44.4% of patients presented with ILBO, which was associated with significantly higher T2 values in OpAC ( P = 0.004). A tendency toward increased T2 values was observed after 12 months, although this did not reach statistical significance ( P = 0.06). However, no significant differences were found in clinical outcomes between patients with or without ILBO, nor between those with or without T2 values comparable to reference cartilage. Conclusion: ILBO significantly affects the biophysical MRI properties of OpAC as indicated by higher T2 values after 60 months. These alterations, though not reflected in any clinical score, can suggest potential long-term implications for cartilage degeneration and may inform future monitoring strategies for cartilage repair. Further research is required to evaluate the long-term effects of these altered mechanical impacts on articulating cartilage and their clinical implications.

Purpose: Description of the perfusion of pulmonary metastasis by contrast-enhanced ultrasound (CEUS) and their correlation with vascularization patterns represented by immunohistochemical CD34 endothelial staining. Patients and methods: The data of 54 patients with histologic proven peripheral pulmonary metastasis, investigated between 2004 and 2023 by CEUS. These CEUS parameters were evaluated: time to enhancement (TE), categorized as early pulmonary-arterial (PA) or delayed bronchial-arterial (BA) patterns; extent of enhancement (EE), either marked or reduced; homogeneity of enhancement (HE), homogeneous or inhomogeneous; and decrease of enhancement (DE), rapid washout (<120 s) or late washout (≥120 s). Additionally, tissue samples in 45 cases (83.3%) were stained with CD34 antibody for immunohistochemical analysis. Results: In total, 4 lesions (7.4 %) exhibited PA enhancement, and 50 lesions (92.6%) demonstrated BA enhancement. Furthermore, 37 lesions (68.5%) showed marked enhancement, while 17 lesions (31.5%) exhibited reduced enhancement. The enhancement was homogeneous in 28 lesions (51.86%) and inhomogeneous in 26 lesions (48.14%). Additionally, 53 lesions (98.1%) displayed a rapid washout. A chaotic vascular pattern indicative of a bronchial arterial blood supply was identified in all cases (45/45, 100%), including all 4 lesions with PA enhancement. Conclusion: Pulmonary metastases in CEUS predominantly reveal bronchial arterial enhancement and a rapid washout. Regarding EE and HE, pulmonary metastases show heterogeneous perfusion patterns. A PA enhancement in CEUS does not exclude BA neoangiogenesis.

Introduction: Heterotopic ossifications (HOs) are a well-known complication following total hip arthroplasty. Yet only little is known about the development of HOs following a femoral fracture and intramedullary stabilization in polytraumatized patients. Thus, the present study aimed to investigate whether the development of HOs is being observed more frequently in patients suffering polytrauma compared to those with single-extremity trauma. Materials and Methods: The retrospective outcome study was conducted at our level I trauma center. All patients admitted from 2010 to 2020 were included if they (1) presented with multiple injuries (≥2 body regions), (2) had an Injury Severity Score ≥16, (3) suffered a femoral fracture, and (4) were treated with intramedullary stabilization. Furthermore, a control group was established to match the polytrauma group (sex, age), who were suffering from single-extremity trauma (femoral fracture) which was treated with intramedullary stabilization. Subsequently, X-rays of the hip were performed and evaluated for up to one-year post-trauma. Results: Our study group consisted of 36 patients in total (91.7% male; mean age 39.4 ± 17.4 years, range: 18–82 years). The polytrauma (PT) group included 12 patients (mean age 39.5 years, median ISS 28), whereas the control group (single-extremity-trauma) included 24 patients (mean age 39.3 years). We documented HOs in nine (75%) patients in the PT group vs. five (20.8%) patients in the single-extremity group (p = 0.03). Conclusion: In this study, we were able to demonstrate that heterotopic ossifications are being observed significantly more frequently in patients suffering from polytrauma in comparison to patients with single-extremity trauma following intramedullary stabilization after a femoral fracture.

Objectives: Bone marrow edema-like signal (BMELS) after cartilage repair is common, but its clinical significance remains uncertain. This study aimed to investigate the clinical and structural significance of BMELS following microfracturing (MFX) and matrix-induced autologous chondrocyte implantation (MACI). Methods: In this multicenter study, MRI examinations were performed over a period of 5 years after cartilage repair surgery (MFX n = 17; MACI n = 28) in 45 patients. Morphological assessments, including the MOCART 2.0 (magnetic resonance observation of cartilage repair tissue), quantitative imaging biomarkers (QIB) with T2 mapping of the repair tissue, and, specifically, assessment of the presence and size of BMELS, were conducted along with patient-reported outcome measures, such as the Knee injury and Osteoarthritis Outcome Score (KOOS) and the International Knee Documentation Committee (IKDC). BMELS structural and clinical assessments were obtained after 3 months, 12 months, and 60 months. Statistical analysis included the Mann–Whitney U -test, Wilcoxon rank test, Shapiro–Wilk test, and simulation-based power analysis. Results: BMELS were a common finding 60 months after cartilage repair. The size of BMELS differed significantly only between MACI and MFX patients after 3 months, with larger BMELS occurring in the MFX group. There were no significant differences in patients with or without BMELS regarding the T2 ratio of the treated area, the MOCART 2.0, or clinical scores. Conclusion: BMELS frequently appeared after cartilage repair procedures. We could show that the postoperative size and change in the size of BMELS after MACI and MFX did not affect clinical scores, morphological MRI results, or biochemical properties of the treated area after 60 months. Key Points: Question What is the clinical significance of bone marrow edema-like signal (BMELS) appearance after matrix-induced autologous chondrocyte implantation (MACI) or microfracture (MFX) ? Finding There were no significant differences in patients with or without BMELS regarding the T2 ratio of the treated area, the MOCART 2.0, or clinical scores . Clinical relevance BMELS frequently appeared after cartilage repair, the appearance or the size dynamic after MACI and MFX did not affect clinical scores, morphological MRI results, or biochemical properties after 60 months .