import { ComparisonTable, ContentSection, EvidenceCard, ExamCheatSheet, ExamPearl, ExamWarning, InfoCard, InfoCardGrid, MedicalImage, MnemonicCard, OnePagerSummary, SafetyAlert, Tab, Tabs, Timeline, TimelineItem, VivaScenario, VivaScenarioSection } from '@/components/mdx' {/* SECTION 1: ONE-PAGER SUMMARY */} {/* SECTION 2: EXAM WARNING */} **Key exam point**: Microfracture produces Type I collagen fibrocartilage, not Type II collagen hyaline cartilage. Biomechanically inferior with lower compressive stiffness and wear resistance. **Under 2cm² optimal**. Larger lesions have progressively worse outcomes. Over 4cm² should be treated with OATS, ACI, or allograft. Examiners will test size threshold knowledge. **Non-weight-bearing 6-8 weeks** is essential. CPM or aggressive ROM promotes fibrocartilage maturation. Premature loading causes fibrocartilage failure. **Deterioration at 2-5 years** is well documented. Short-term results good (85%) but decline over time. May serve as bridge to definitive treatment. {/* SECTION 2.5: QUICK DECISION GUIDE */} {/* SECTION 3: MNEMONICS */} {/* SECTION 4: OVERVIEW AND EPIDEMIOLOGY */} Microfracture remains a first-line treatment for small cartilage lesions due to its simplicity, low cost, and single-stage nature. However, understanding its limitations is crucial for exam success - the fibrocartilage produced has inferior mechanical properties and outcomes deteriorate over time. - **Full-thickness cartilage defect** - **Lesion under 2cm²** - **Intact subchondral bone** - **Contained lesion with stable shoulders** - **Failed conservative management** - **Lesion over 4cm²** - **Degenerative OA (diffuse disease)** - **Bipolar (kissing) lesions untreated** - **Uncorrected malalignment** - **Inflammatory arthropathy** - **Subchondral bone disease** {/* SECTION 5: ANATOMY AND BIOMECHANICS */} **The critical distinction**: Microfracture produces fibrocartilage (Type I collagen) which is mechanically inferior to native hyaline cartilage (Type II collagen). Fibrocartilage has lower compressive stiffness, less water content, and poorer wear characteristics. This fundamental limitation explains the time-limited benefit. - **Subchondral penetration** releases marrow elements - **Mesenchymal stem cells** populate the defect - **Blood clot forms** as scaffold for healing - **CPM stimulates** cartilage-like differentiation - **Fibrocartilage fills** the defect over 6-12 months - **Fibrocartilage** is mechanically inferior - **Subchondral changes** develop over time - **Cyclic loading** degrades repair tissue - **Large lesions** cannot fill adequately - **Type I collagen** lacks resilience of Type II {/* SECTION 6: CLASSIFICATION SYSTEMS */} ### ICRS Cartilage Lesion Grading Microfracture is primarily indicated for ICRS Grade 4 lesions (full-thickness defects exposing subchondral bone). Grade 3 lesions may be suitable if symptomatic and unresponsive to conservative measures. ### Lesion Size Classification for Treatment Selection {/* SECTION 7: CLINICAL ASSESSMENT */} - **Mechanism**: Traumatic vs degenerative onset - **Symptoms**: Mechanical (catching, locking) vs pain - **Duration**: Acute vs chronic symptoms - **Activity level**: Sport demands and expectations - **Previous treatment**: Conservative measures tried - **Effusion**: Suggests synovitis/cartilage damage - **Joint line tenderness**: Over affected compartment - **Range of motion**: Usually preserved unless severe - **Alignment**: Varus/valgus assessment - **Stability**: Ligamentous integrity Malalignment is a major cause of microfracture failure. Always assess alignment clinically and radiographically. If significant varus (medial lesion) or valgus (lateral lesion), consider osteotomy before or with microfracture. {/* SECTION 8: INVESTIGATIONS */} **Weight-bearing AP, lateral, Rosenberg (45° PA), skyline**. Assess joint space narrowing, alignment, and OA grade. Normal X-rays do not exclude cartilage damage. **Cartilage-specific sequences essential**. Assess lesion location, size, depth, containment. Evaluate subchondral bone for edema or cysts. Identify associated meniscal or ligamentous pathology. Full-length standing alignment films if clinical concern for malalignment. Calculate mechanical axis deviation. Look for: cartilage defect location and size, subchondral edema (may indicate ongoing damage), cyst formation (relative contraindication), bone marrow lesions, and associated meniscal/ligamentous pathology that needs addressing. {/* SECTION 9: MANAGEMENT ALGORITHM */} **Under 2cm²** is the magic number for microfracture. Outcomes are significantly better in lesions under this threshold. Over 4cm², microfracture should generally be avoided in favor of OATS, ACI, or allograft. - Lesion under 2cm² - Age under 40 - Acute traumatic defect - Single lesion - Normal alignment - Compliant with rehab - Lesion over 4cm² - Age over 40 - Multiple lesions - Degenerative (vs traumatic) - Malalignment - Early weight-bearing - Subchondral bone disease {/* SECTION 12: EVIDENCE BASE */} {/* SECTION 13: VIVA SCENARIOS */} {/* SECTION 14: MCQ PRACTICE POINTS */} **Q: What type of collagen is produced after microfracture?** A: **Type I collagen** - Microfracture produces fibrocartilage containing Type I collagen, not the Type II collagen found in native hyaline cartilage. This is mechanically inferior and contributes to long-term deterioration. **Q: What is the optimal spacing between microfracture holes?** A: **3-4mm** - Holes should be 3-4mm apart to preserve subchondral bone bridges. Closer spacing can cause subchondral collapse; wider spacing leaves inadequate marrow access. **Q: What is the optimal lesion size for microfracture?** A: **Under 2cm²** - Best outcomes occur in lesions under 2cm². Lesions 2-4cm² have acceptable but reduced outcomes. Lesions over 4cm² should be treated with alternatives (OATS, ACI, allograft). **Q: How long should weight-bearing be restricted after microfracture?** A: **6-8 weeks non-weight-bearing** - Strict non-weight-bearing for 6-8 weeks is essential to protect the forming fibrocartilage. Premature loading is the most common cause of failure. **Q: When do microfracture results typically begin to deteriorate?** A: **2-5 years** - Short-term results are good (85% at 2 years) but deterioration occurs after 2-5 years in the majority of patients. This is due to the inferior mechanical properties of fibrocartilage. **Q: Why is CPM recommended after microfracture?** A: CPM is thought to promote **fibrocartilage differentiation** toward a more hyaline-like phenotype. It also prevents adhesions and maintains ROM. The mechanical stimulus during early healing influences tissue quality. {/* SECTION 15: AUSTRALIAN CONTEXT */} - Microfracture remains common first-line treatment - Increasing use of AMIC for medium lesions - Access to OCA limited in Australia (availability) - ACI/MACI available through specialized centers - PBS does not cover cartilage cell implantation - Document lesion size precisely at arthroscopy - Record alignment assessment - Document technical parameters (spacing, depth) - Record marrow bleeding confirmed - Consent for time-limited benefit **Key documentation requirements:** - Consent discussion must include: fibrocartilage vs hyaline limitation, time-limited benefit (2-5 years), possibility of deterioration and need for further surgery - Document lesion size at surgery - if over 4cm², document why microfracture chosen (if it was) - Record rehabilitation compliance in follow-up - If failure occurs, document was appropriate initial choice for lesion size {/* SECTION 16: EXAM CHEATSHEET */}

Microfracture Technique

Microfracture Technique