< Back Total Knee Arthroplasty (TKA) Previous Next

< Back Dr. Osman Emre Aycan Aneurysmal Bone Cyst (ABC) Aneurysmal bone cyst (ABC) is a benign but locally aggressive, expansile osteolytic lesion composed of blood-filled cavities separated by fibrous septa. It primarily affects children and young adults, typically in the first two decades of life, with no clear sex predilection. Although non-malignant, it can cause significant pain, swelling, and pathological fractures due to rapid growth and cortical thinning. Epidemiology Accounts for approximately 1–2% of all primary bone tumors . Most common sites: long bones (femur, tibia, humerus) and posterior elements of the spine . Less frequently seen in the pelvis, clavicle, or small bones of the hands and feet. Pathophysiology The exact etiology remains unclear, but two forms are recognized: Primary ABC – arises de novo, often associated with a translocation involving the USP6 gene (17p13) , leading to osteolytic activity and vascular proliferation. Secondary ABC – develops in association with another lesion such as giant cell tumor, chondroblastoma, osteoblastoma, or fibrous dysplasia . The lesion consists of multiple blood-filled spaces without endothelial lining , separated by septa containing fibroblasts, osteoclast-type giant cells, and reactive bone. Clinical Presentation Progressive pain, swelling, and restricted motion near the affected site. Palpable mass may be present. Pathologic fracture is a common first presentation in long bones. Neurological deficits can occur when lesions arise in the spine due to canal compression. Imaging Features Radiographs: Expansile, lytic lesion with “blow-out” or balloon-like appearance . Thin cortical shell and possible septations. May show fluid–fluid levels if internal hemorrhage is present. MRI: Multiple fluid–fluid levels due to different blood degradation stages. Surrounding bone marrow edema and soft tissue extension are possible. Contrast enhancement in septa but not in cystic cavities. CT: Useful for cortical evaluation and surgical planning. Histopathology Multiple cystic spaces filled with blood, lacking endothelial lining . Septa contain fibroblasts, osteoid tissue, and multinucleated giant cells. No malignant cells are present. Differential Diagnosis Lesion Distinguishing Features Telangiectatic Osteosarcoma Malignant cells, atypia, and osteoid production Giant Cell Tumor (GCT) Occurs after skeletal maturity, lacks fluid–fluid levels Chondroblastoma Epiphyseal location, presence of calcifications Fibrous Dysplasia Ground-glass matrix, lacks hemorrhagic cavities Simple Bone Cyst Single cavity, no septations, usually in metaphysis Treatment Management depends on lesion size, location, and aggressiveness: Extended curettage and high-speed burring – mainstay for most cases. Adjuvant therapies to reduce recurrence:Argon beam coagulation, phenol, or liquid nitrogen. Filling of cavity with bone graft or bone cement . Selective arterial embolization (SAE) – used for spinal or pelvic lesions or as preoperative adjunct. Percutaneous sclerotherapy (e.g., doxycycline or polidocanol) is increasingly used as a minimally invasive alternative. En bloc resection reserved for recurrent or inaccessible lesions. Prognosis Recurrence rate: 10–30%, usually within the first two years post-treatment. Risk factors for recurrence include younger age , open physes , and incomplete excision . Long-term prognosis is excellent with appropriate treatment; malignant transformation is exceedingly rare. Key Points ABC is a benign, vascular, expansile bone lesion with locally destructive potential. USP6 translocation confirms diagnosis in ambiguous cases. Fluid–fluid levels on MRI are suggestive but not pathognomonic. Minimally invasive approaches (e.g., sclerotherapy, embolization ) show recurrence rates comparable to surgery in recent studies. Extended curettage with adjuvant remains the gold standard for accessible lesions in long bones. Recurrent cases may benefit from a combined strategy (embolization → curettage → bone graft). References Oliveira AM et al. USP6 Gene Rearrangement in Aneurysmal Bone Cyst. Am J Pathol. 2021;191(7):1210–1220. Mascard E, Gomez-Brouchet A, Lambot K. Aneurysmal Bone Cyst: Clinical and Therapeutic Update. Orthop Traumatol Surg Res. 2015;101(1 Suppl)–S19. Park HY et al. Treatment of Aneurysmal Bone Cysts: A Review of Current Concepts. J Bone Joint Surg Am. 2020;102(4):280–289. Rastogi S et al. Percutaneous Doxycycline Sclerotherapy in Aneurysmal Bone Cyst. J Orthop Surg. 2019;27(3):2309499019878422. Rapp TB et al. Aneurysmal Bone Cyst: A Review of Pathophysiology and Current Management. J Am Acad Orthop Surg. 2012;20(4):233–241. Treatment Modality Description / Technique Recurrence Rate Advantages Limitations / Complications Extended Curettage + Adjuvant (Phenol / Argon / Cryotherapy) Thorough curettage of lesion cavity with mechanical and chemical adjuvant use 10–25% Effective local control, joint preservation Risk of growth plate injury or fracture Curettage + Bone Graft / Bone Cement Filling Cavity filled after curettage to provide stability 15–20% Restores bone strength, simple procedure Possible graft resorption, infection En Bloc Resection Complete excision with margin of healthy bone <10% Lowest recurrence rate Loss of function, reconstructive need Selective Arterial Embolization (SAE) Preoperative or definitive occlusion of feeding vessels 10–20% Minimally invasive, useful in spine/pelvis Risk of incomplete occlusion, recurrence Percutaneous Sclerotherapy (Doxycycline / Polidocanol) Chemical ablation via multiple percutaneous injections 5–15% Outpatient, minimal morbidity, excellent cosmetic results Requires multiple sessions, rare skin necrosis Radiotherapy (rarely used) Reserved for inoperable or recurrent cases Variable (~20%) Non-surgical alternative Radiation-induced sarcoma risk, growth disturbance Treatment Options and Recurrence Rates in Aneurysmal Bone Cyst (ABC) Axial and coronal MRI images of the sacrum demonstrate an expansile, multiloculated cystic lesion centered at the S1 level. The lesion shows multiple fluid–fluid levels with low-to-intermediate signal on T1-weighted, high signal on T2-weighted images, and thin peripheral and septal enhancement after gadolinium administration. Imaging features are characteristic of a benign aneurysmal bone cyst without evidence of solid enhancement or soft-tissue invasion. Previous Next

< Back Dr. Savas CAMUR Revision Knee Arthroplasty Revision TKA is a complex reconstructive procedure performed to address implant failure due to infection, aseptic loosening, instability, periprosthetic fracture, or stiffness. Proper diagnosis requires a combination of clinical, radiographic, and laboratory evaluation to identify the cause of failure. Management aims to restore joint stability, mechanical alignment, and bone stock while minimizing complications. Modern evidence supports the use of modular stemmed and constrained implants to improve fixation, with either cemented or press-fit stems achieving comparable alignment outcomes. Prevention of periprosthetic joint infection (PJI) remains crucial, and intraosseous antibiotic prophylaxis provides superior local drug concentrations and lower infection rates compared to traditional intravenous administration. Etiology The most common causes of TKA failure include: Infection (PJI): The leading indication for early revision (<2 years). Aseptic loosening: The most frequent cause of late revision (>2 years). Instability: Secondary to ligament imbalance or component malposition. Periprosthetic fracture: Increasing with aging and multiple prior surgeries. Arthrofibrosis and extensor mechanism failure: Contribute to stiffness and poor function. Epidemiological data indicate that infection and aseptic loosening together account for over two-thirds of revision cases. Evaluation Clinical Assessment Pain pattern (activity-related vs. rest pain) helps distinguish mechanical failure from infection. Examine gait, alignment, range of motion, stability, and prior incisions. Assess swelling, warmth, and effusion for infection. Laboratory Work-Up ESR and CRP are first-line screening tools. Joint aspiration for cell count, differential, and culture confirms infection per MSIS criteria. Imaging Radiographs: Serial AP/lateral and long-leg standing films evaluate loosening, wear, and alignment. CT scan: Assesses component rotation, bone loss, and defect mapping. Bone scan: May support diagnosis when loosening or infection is unclear, though nonspecific. Surgical Management Preoperative Planning Meticulous evaluation of bone loss, ligament integrity, and soft-tissue envelope guides implant selection. Digital templating and long-leg alignment analysis are essential. Fixation Strategy Cemented vs. Press-Fit Stems: A 2025 multicenter study found that short-cemented stems (<75 mm) achieved mechanical alignment equivalent to long-cemented or press-fit stems, with greater intraoperative flexibility and comparable hip-knee-ankle (HKA) anglesmain Stem choice: Short-cemented : ideal for controlled alignment correction and limited bone loss. Long-cemented : preferred for poor bone quality and extensive defects. Press-fit (hybrid) : used when strong diaphyseal engagement is achievable. Metaphyseal reconstruction: Metal augments, sleeves, or cones are indicated for AORI Type 2B–3 bone defects. Alignment Principles Mechanical alignment remains the gold standard, targeting neutral HKA (≈180°) and symmetric coronal balance. Femoral alignment is more variable than tibial, but both achieve acceptable mechanical restoration when stems are properly seated. Infection Prevention .Evidence supports intraosseous antibiotic prophylaxis , which delivers higher local antibiotic concentrations in bone and fat tissue and significantly reduces PJI risk compared with intravenous dosing (OR ≈ 0.26) without increased systemic complications. Complications Infection: 4–7% risk, higher than primary TKA. Neurovascular injury: Especially peroneal nerve during deformity correction. Wound complications: Optimize skin flaps, use negative-pressure dressings when indicated. Extensor mechanism disruption: Managed with allograft or mesh reconstruction. Residual pain or stiffness: Expect longer recovery compared to primary TKA. References Giabbani N, Innocenti M, Sangaletti R, et al. Coronal alignment in revision total knee arthroplasty: a comparison of cemented vs. press-fit stems for restoring mechanical axis. Arthroplasty Today. 2025;35:101863.main Lee S, Kang J, Moon Y, et al. Efficacy and safety of intraosseous versus intravenous antibiotic in primary and revision total joint arthroplasty: a systematic review and meta-analysis. Medicina. 2025;61(10):1750.medicina-61-01750-v2 [Additional supporting references from J Clin Med 2024 and J Arthroplasty 2025 can be appended for infection prevention and alignment optimization.] Type Indications Posterior-stabilized PCL deficiency Constrained condylar Collateral laxity, moderate instability Rotating hinge Global ligament deficiency, severe bone loss Megaprosthesis Salvage for massive defects or tumor resection Previous Next

< Back Timing of Soft Tissue Coverage soft-tissue-coverage-timing Previous Next

< Back Masquelet Technique masquelet-technique Previous Next

< Back Ankle Arthroplasty Previous Next

< Back Knee Joint Anatomy & Biomechanics Previous Next

< Back Throwing Athlete Injuries throwing-athlete-injuries Previous Next

< Back Mirels' Score for Upper Limb Metastatic Lesions: Do We Need a Different Cutoff for Recommending Prophylactic Fixation? Conclusions: This study demonstrates moderate to substantial agreement between and within raters using Mirels’ score on upper limb radiographs. However, Mirels’ score had a poor ensitivity and specifity in predicting upper extremity fractures. Until a more valid scoring system has been developed, based on our study, we recommend a Mirels’ threshold of 7/12 for considering prophylactic fixation of impending upper limb pathologic fractures. This contrasts with the current 9/12 cutoff, which is recommended for lower limb pathologic fractures. 🧠 Key Points: Mirels score was originally proposed for metastatic lesions in the lower extremities; its applicability to the upper extremity has been questioned. A score of ≥7 may be sufficient to consider prophylactic fixation in upper extremity metastases. This was a retrospective study analyzing 138 cases. JSES International (2022), Vol 6(4): 675–681 DOI:10.1016/j.jseint.2022.03.006 Previous Next

< Back Child Abuse child-abuse Previous Next

Basic Science Musculoskeletal Science & Biomechanics Pharmacology, Systemic Disease & Toxicity Molecular, Cellular & Clinical Foundations • Bone and Joint Biology • Biologic Tissues • Skeletal Muscle • Tendons • Articular Cartilage • Skeletal Development • Peripheral Nerve Structure and Function • Articular Cartilage: Structure, Components, and Clinical Relevance Overview • Biomechanics • Cellular and Molecular Biology, Immunology and Genetics Terminology • Skeletal Medicine • Musculoskeletal Infections • Coaghulopathies • Anticoagulants • Clinical Research, Statistical Concepts, and Tests • Evidence-Based Medicine • Professionalism and Ethical Principles • Bone Grafts, BMP, and Bone Substitutes • Biomaterials • Bioabsorbable Materials • Imaging in Orthopaedics • Orthoses

< Back Surgical Timing A A surgical-timing Previous Next