This medical illustration depicts the five-stage progression of osteomyelitis in the proximal humerus, categorized into acute and chronic phases. The series (A–E) visualizes the pathophysiology of bone infection: Stage A shows the initial metaphyseal focus of infection; Stage B demonstrates lateral spread toward the bone cortex; Stage C illustrates cortical penetration and subsequent periosteal elevation; Stage D identifies the formation of a thick involucrum (new bone growth surrounding infected tissue); and Stage E shows further expansion of the metaphyseal focus and extensive involucrum. The diagram highlights the anatomical relationship between the metaphysis, cortex, and periosteum during bacterial seeding and inflammatory response. Additionally, the content notes that chronic osteomyelitis is characterized by bone necrosis, formation of sequestra (detached dead bone), and large-surface ischemia. This anatomical diagram serves as an educational tool for medical students and clinicians to understand the radiological and pathological evolution of pediatric and adult bone infections.

This medical illustration is an anatomical diagram of the human hand skeleton, used for clinical epidemiological mapping. It depicts the dorsal or palmar view of the metacarpals, carpal bones, and phalanges. The diagram functions as a data visualization tool for a cohort study on hand osteomyelitis in patients with digital arterial calcification. Each individual bone—proximal, middle, and distal phalanges, as well as the metacarpals—is overlaid with two sets of numerical data. Numbers in red, bold font represent the incidence of osteomyelitis at that specific anatomical site, while numbers in blue, italic font indicate the frequency of amputation for that bone. Visually, the data shows a higher incidence of pathology in the distal and middle phalanges, particularly of the index and middle fingers. This anatomical map is intended for advanced medical education and orthopedic research to illustrate the distribution of infection and surgical outcomes in high-risk populations, such as those with diabetes mellitus or end-stage renal disease.

This composite educational image illustrates gross bone pathology in an experimental orthopedic model, focusing on implant-related infection. Panel A displays three longitudinal sections of animal femurs categorized by treatment group: TC (titanium coating), TC-AA(C/H)6 (multilayer coating), and TC-AA(C/H)6-G (gentamicin-loaded multilayer coating). The TC and TC-AA(C/H)6 specimens exhibit clear clinical signs of purulent osteomyelitis, characterized by visible intramedullary pus, severe structural degradation, and osteolytic lesions. In contrast, the TC-AA(C/H)6-G specimen shows preserved structural integrity with a healthy red marrow cavity and no visible signs of infection. Panel B provides a quantitative comparison through a bar graph of Gross Bone Pathology Scores. The TC group (gray bar) and TC-AA(C/H)6 group (red bar) show high pathology scores (approximately 3.0), whereas the TC-AA(C/H)6-G group (green bar) shows a significantly lower score (below 1.0). The asterisk (*) denotes statistical significance (p < 0.05). This visual demonstrates the efficacy of drug-loaded surface modifications in preventing implant-associated bone infections.

This diagnostic image set consists of Micro-CT (μ-CT) scans and 3D reconstructions of rat tibia used in a bone healing and infection study. Figure (a) illustrates an infection control group exhibiting characteristic signs of osteomyelitis. Red arrows highlight significant pathology, including a narrowing of the marrow space, deformed cortical bone, ectopic bone growth, and the presence of a sinus tract associated with a soft-tissue fibrous capsule. These features demonstrate severe osteolysis and disrupted bone architecture common in chronic infection. Figure (b) displays the treatment group using bioactive glass (BG). Green arrows indicate positive regenerative outcomes, specifically the formation of new immature cancellous and cortical bone within the previously drilled defect. The 3D and cross-sectional views show successful osseointegration and structural remodeling, contrasting the pathological destruction in the control group with the regenerative progression in the treatment group. This image is relevant for orthopedic research and the study of antibiotic-eluting bone graft substitutes.

This comparative micro-computed tomography (μ-CT) study illustrates the pathophysiology of osteomyelitis and subsequent bone regeneration in a rat tibia model. Section (a) displays an untreated control group at 8 weeks post-infection with Staphylococcus aureus, showing significant structural pathology including ectopic bone growth (indicated by red arrows), narrowing of the medullary marrow space, and the formation of a sinus tract and pus-filled fibrous capsule. Section (b) demonstrates the therapeutic outcome 8 weeks after implantation of a vancomycin-loaded polymer/bioglass (BG) bone void-filling putty. This treated group exhibits successful infection eradication and advanced bone healing, characterized by the formation of new cortical and cancellous bone within the previous drilling site (indicated by green arrows). The images provide high-resolution cross-sectional and 3D reconstructions to demonstrate the efficacy of antibiotic-loaded scaffolds in treating orthopedic infections and promoting osteogenesis. This visual serves as an educational resource for medical microbiology, orthopedics, and biomaterials engineering.

This diagnostic X-ray of the right hand demonstrates significant pathology localized to the third digit, consistent with chronic osteomyelitis. The imaging reveals extensive destruction of the cortical bone involving both the middle and distal phalanges. A hallmark finding of chronic infection, bone sequestration (sequestrum), is visible, characterized by fragments of necrotic, radiodense bone that have separated from the living bone tissue. The third finger shows marked anatomical deformity and soft tissue swelling. In contrast, the remaining phalanges, metacarpals, and visualized carpal bones maintain relatively normal bone density, cortical integrity, and joint alignment. This image serves as a clinical example of skeletal complications resulting from long-standing infections, such as those complicating cutaneous leishmaniasis with secondary bacterial superinfection. The primary educational focus is the radiological identification of cortical erosion and sequestrum formation in the context of chronic osteomyelitis.

This diagnostic radiograph of a long bone demonstrates classic features of chronic haematogenous osteomyelitis, specifically classified as Beit CURE Type B2. The image reveals a central sequestrum, which is an isolated piece of necrotic, devascularized bone appearing as an area of increased radiopacity within the medullary canal. Surrounding the sequestrum is a well-defined involucrum, representing a layer of new periosteal bone formation. This involucrum appears structural and relatively normal in morphology, indicating that it is sufficiently stable to maintain the bone's integrity despite the underlying infection. The radiological presentation illustrates the characteristic pathological progression of chronic osteomyelitis where the body attempts to wall off infected necrotic tissue with a sheath of living bone. The image is an essential educational example for orthopedic surgery and radiology, highlighting the distinction between necrotic sequestrum and regenerative involucrum.

This diagnostic image is an anteroposterior x-ray radiograph of a long bone (tibia) demonstrating classic features of chronic haematogenous osteomyelitis. The radiograph reveals Type B3 classification findings characterized by the presence of a sequestrum—a dense, radiopaque segment of necrotic bone isolated from the surrounding living tissue. Encasing the sequestrum is a prominent involucrum, which appears as a thick layer of new periosteal bone formation. This involucrum is described as structural, sclerotic, and expanded, exhibiting significantly increased bone density and a widened diameter compared to normal bone morphology. The image illustrates the body's attempt to wall off infected necrotic tissue by creating a sheath of reactive bone. This visual is clinically significant for medical students and orthopedic specialists for identifying the radiographic hallmarks of pediatric chronic osteomyelitis and understanding the Beit CURE (BC) classification system for bone infections.

This diagnostic image set consists of axial MR images of the lower leg from a 4-year-old male, illustrating classic features of chronic osteomyelitis: involucrum and sequestrum. Image (A) is an axial T2-weighted fat-suppressed MRI demonstrating diffuse, high-signal intensity (edema) within the tibial medullary canal and the surrounding musculature. Image (B) shows side-by-side axial T1-weighted fat-suppressed images, pre-contrast (left) and post-contrast (right). The primary pathology shows a central, non-enhancing necrotic bone segment (sequestrum) indicated by a long white arrow. Surrounding this is a peripheral shell of new, enhancing bone formation (involucrum), highlighted by short black arrows. The surrounding soft tissues exhibit extensive enhancement and edema (arrowheads and short white arrows), consistent with myositis. These findings are pedagogically significant for distinguishing between viable inflammatory tissue (involucrum, myositis) and non-viable necrotic bone (sequestrum) in pediatric musculoskeletal infections. Target concepts include radiological identification of chronic infection markers and differentiate enhancement patterns in osteomyelitis.

**Imaging Modality:** Axial Computed Tomography (CT) scan. **Anatomical Region:** Mid-shaft of a long bone (likely the femur or humerus) and surrounding soft tissues of the extremity. **Observed Pathology:** Chronic osteomyelitis with characteristic features of bone remodeling and sequestration. **Characteristic Visual Features:** * **Sequestrum:** A central, hyperdense fragment of necrotic bone is visible within the medullary cavity, detached from the surrounding living bone. * **Involucrum:** Marked circumferential cortical thickening and reactive sclerosis are present, representing the formation of new bone sheath around the infected site. * **Cortical Irregularity:** There is evidence of cortical erosion and architectural distortion. * **Soft Tissue Involvement:** Diffuse swelling and blurring of myofascial planes are noted in the adjacent soft tissues, suggesting associated inflammation or phlegmon. **Key Diagnostic Features:** The combination of a dense, sequestered bone fragment (sequestrum) surrounded by thickened reactive bone (involucrum) is pathognomonic for chronic osteomyelitis. This CT image effectively demonstrates the classic radiographic "bone within a bone" appearance used to differentiate chronic infectious processes from acute osteomyelitis or primary bone tumors.

This diagnostic image is a panoramic X-ray (orthopantomogram) of the human maxillofacial region, showing the complete mandible, maxilla, and surrounding dental structures. Two white arrows indicate distinct pathological findings located bilaterally at the mandibular angles. These areas are characterized as osteolytic zones, presenting as radiolucent (darker) regions with ill-defined borders compared to the surrounding radiopaque cortical and cancellous bone. The osteolysis is observed on both the right and left sides of the lower jaw, with the right side showing more prominent involvement. Multiple dental restorations and evidence of previous dental procedures are visible across the dentition. The image serves as a clinical teaching tool for recognizing mandibular bone loss and differential diagnosis of systemic diseases manifesting in the jaw, such as sarcoidosis, osteomyelitis, or malignancy.

**Imaging Modality:** Orthopantomogram (Panoramic Dental X-ray). **Anatomical Region:** Maxilla and mandible with associated dentition. **Observed Pathology:** Medication-related osteonecrosis of the jaw (MRONJ). **Characteristic Visual Features:** The radiograph demonstrates ill-defined radiolucent and mixed radiopaque-radiolucent (moth-eaten) bone destruction. There is evidence of cortical bone erosion and sequestration, particularly noted in the alveolar regions. Findings include non-healing extraction sockets and widened periodontal ligament spaces. **Dental Status and Landmarks:** Extensive dental restorations are visible, including multiple radiopaque fixed prosthodontic bridges (maxillary and mandibular) and endosseous dental implants. There is significant generalized alveolar bone loss consistent with periodontitis. **Diagnostic Differentiating Features:** The combination of localized sequestrum formation, osteosclerosis, and persistent radiolucency in a patient with a history of bisphosphonate therapy is characteristic of drug-induced osteonecrosis. These features distinguish the condition from simple osteomyelitis or primary bone malignancy by the specific pattern of bone turnover suppression and necrotic bone involvement.

This composite educational image features a panoramic dental radiograph (A) and multiplanar CT scans (B) of a 50-year-old patient with chronic osteomyelitis of the left mandible. Panel A shows a panoramic X-ray demonstrating significant distension and deformity of the left hemimandible. Multiple yellow arrows indicate a mixed radiopaque and radiolucent appearance extending from the right parasymphyseal/premolar region to the posterior ramus, characterizing a combination of bone sclerosis and osteolytic destruction. Panel B contains axial and coronal CT slices that provide detailed visualization of the mandibular pathology. The left hemimandible exhibits marked cortical expansion and a heterogeneous internal structure. Notable features include increased bone marrow attenuation and irregular sclerotic masses interspersed with lucent areas, consistent with proliferative periostitis and reactive new bone formation. The right side of the mandible serves as a normal anatomical comparison, appearing non-expanded with clear cortical borders. This imaging illustrates the typical radiological features of secondary chronic osteomyelitis and proliferative periostitis in the maxillofacial region.

This panoramic dental X-ray (orthopantomogram) displays extensive surgical intervention and reconstruction of the mandible. A prominent, large-caliber metallic reconstruction plate with multiple circular screw holes spans the entire lower border of the mandible from the right to the left ramus. The image reveals significant continuity defects: there is a complete absence of native bone structure on the left side of the mandible and a marked discontinuity on the right, consistent with radical resection. The reconstruction plate is secured to the remaining mandibular segments with multiple screws; notably, some screws appear fractured or displaced. Visible radiopaque metallic clips are also scattered near the surgical site. The maxillary dentition remains relatively intact, showing normal alignment and restorations. The clinical significance of this imaging is to demonstrate post-surgical management of Medication-Related Osteonecrosis of the Jaw (MRONJ), highlighting the challenges of re-osteosynthesis following the failure of previous fibula grafts due to chronic inflammation and osteolysis.