import { ComparisonTable, ContentSection, EvidenceCard, ExamCheatSheet, ExamPearl, ExamWarning, InfoCard, InfoCardGrid, MedicalImage, MnemonicCard, OnePagerSummary, SafetyAlert, Tab, Tabs, Timeline, TimelineItem, VivaScenario, VivaScenarioSection } from '@/components/mdx' ### Imaging Gallery {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/1-the-study-design-acc-autologous-cartilage-chips-mf.png {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/1-the-study-design-acc-autologous-cartilage-chips-mf.png */} */} {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/2-macroscopic-images-of-a-a-single-defect-knee-and-b.png {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/2-macroscopic-images-of-a-a-single-defect-knee-and-b.png */} */} {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/3-histological-images-of-the-seven-groups-in-each-gr.png {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/3-histological-images-of-the-seven-groups-in-each-gr.png */} */} {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/4-mri-of-the-four-chondral-treatment-groups-a-empty-.png {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/4-mri-of-the-four-chondral-treatment-groups-a-empty-.png */} */} ACI requires **two surgeries**: Stage 1 harvests cartilage biopsy (200-300mg). Cells cultured for 4-6 weeks to expand. Stage 2 implants expanded cells. This is a key disadvantage vs single-stage OATS. **Third-generation MACI** uses a collagen scaffold seeded with cells. This eliminates periosteal harvest and reduces hypertrophy complications. MACI is the current standard of care. ACI produces **hyaline-like cartilage** with predominantly Type II collagen. Biopsy studies show 80%+ hyaline tissue at 2 years. This is superior to microfracture fibrocartilage. Unlike microfracture which degrades at 2-5 years, ACI results are **durable to 10-20 years**. Peterson series showed 84% good/excellent at 20 years follow-up. {/* At a Glance Table */} ACI/MACI is the gold standard for large cartilage lesions (over 2cm²) where microfracture outcomes are poor and OATS donor capacity is limited. Understanding the generations of ACI, the two-stage nature, and long-term outcomes is essential for examination success. - **Large lesions over 2cm²** - **Failed microfracture or OATS** - **Young active patients (under 45)** - **Single or multiple focal defects** - **Full-thickness cartilage damage (ICRS 3-4)** - **Diffuse OA** - **Inflammatory arthropathy** - **Uncorrected malalignment** - **Meniscal deficiency (unless treated)** - **Kissing lesions (relative)** - **Age over 55 (relative)** ACI produces hyaline-like cartilage with predominantly Type II collagen and organized matrix structure. Biopsy studies show 80%+ hyaline tissue at 2 years. This is biomechanically superior to the fibrocartilage (Type I collagen) produced by microfracture, explaining the superior long-term durability. - **Harvest**: 200-300mg cartilage biopsy - **Enzymatic digestion**: Release chondrocytes - **Expansion**: 4-6 weeks in culture - **Result**: 12-48 million cells - **Matrix**: MACI = cells seeded on collagen - **3 months**: Soft cartilage repair tissue - **6 months**: Increasing firmness - **12 months**: Near-normal stiffness - **18-24 months**: Full maturation - **Rehabilitation** reflects this timeline ### Evolution of ACI Techniques {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/1-the-study-design-acc-autologous-cartilage-chips-mf.png {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/1-the-study-design-acc-autologous-cartilage-chips-mf.png */} */} MACI (third-generation) is now the standard of care. The collagen scaffold is seeded with cells in the lab, delivered as a ready-to-implant product. This eliminates periosteal harvest, reduces hypertrophy, and allows minimally invasive implantation with fibrin glue. ### Treatment Selection by Size ACI is particularly valuable for lesions over 4cm² where OATS donor site limitations become significant. - **Prior cartilage surgery** (failed microfracture/OATS) - **Symptom duration** and progression - **Mechanical symptoms** (catching, locking) - **Activity level** and sport demands - **Willingness for two surgeries** and extended rehab - **Effusion** - common with cartilage damage - **Tenderness** - localized to compartment - **Crepitus** - may indicate damage - **Alignment** - assess for malalignment - **Ligament/meniscal** integrity ACI requires significant patient commitment: two surgeries, 4-6 week wait for cell culture, and 12-18 month rehabilitation. Ensure patient understands and is prepared for this timeline. Non-compliant patients are poor candidates. Weight-bearing AP, lateral, Rosenberg, skyline. Assess alignment, joint space, OA changes. Rule out diffuse disease. Cartilage sequences for lesion mapping. Size, location, depth. Subchondral bone status. Associated meniscal/ligament pathology. Full-length standing films if malalignment suspected. Plan osteotomy if significant deviation. {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/5-mri-and-corresponding-ct-for-the-empty-osteochondr.png {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/5-mri-and-corresponding-ct-for-the-empty-osteochondr.png */} */} MRI helps identify all cartilage lesions for treatment planning. Unlike OATS (limited by donor), ACI can address multiple lesions simultaneously. Identify any lesion that needs treatment and plan to address at implantation. ### When to Choose ACI/MACI **Ideal candidates:** - Lesion over 2cm² (especially over 4cm²) - Failed prior microfracture or OATS - Multiple lesions - Good subchondral bone (no significant loss) - Motivated, compliant patient - Age under 45-50 **Alternative treatments:** - Under 2cm²: Consider microfracture first - 1-4cm²: OATS reasonable single-stage option - Bone loss present: OCA may be better - OCA unavailable: ACI good for large lesions This framework guides appropriate treatment selection based on lesion and patient characteristics. ### Addressing Malalignment If malalignment is present, it MUST be addressed or ACI will fail. Planning the staging of procedures is critical. Confirm indication for ACI. Plan biopsy location (non-weight-bearing area). Coordinate with cell laboratory. Patient counseling about timeline. Cells expanded in specialized laboratory. Patient rehab from biopsy (usually minimal). Plan stage 2 surgery date. Confirm cell culture successful. Plan implantation approach. Prepare MACI scaffold or membrane. Fibrin glue available. The biopsy for cell harvest should be taken from a non-weight-bearing area with healthy cartilage. Common sites include the superior margin of the intercondylar notch, the superomedial trochlear margin, or the peripheral edge of the lesion itself. ### Stage 1: Cartilage Harvest Arthroscopic or mini-open approach. Locate biopsy site (non-weight-bearing, healthy cartilage). Use curette or gouge to harvest 200-300mg of full-thickness cartilage. Typical size: 2-3 pieces, 4-5mm each. Place in specialized transport medium. Send to cell culture laboratory. Cells must remain viable during transport. Assess the cartilage lesion(s). Measure size for implantation planning. Identify any additional pathology. Stage 1 is a relatively minor procedure. Patients typically recover quickly and await cell culture completion. ### Stage 2: MACI Implantation Mini-arthrotomy or arthroscopic approach depending on lesion access. Adequate visualization of entire defect essential. Debride lesion to stable, vertical cartilage shoulders. Create contained defect. Curette to remove calcified cartilage layer. Preserve subchondral plate. Create template of defect using foil or similar material. Use to cut MACI scaffold to exact shape. Apply fibrin glue to defect base. Place MACI scaffold (cell side down). Apply additional fibrin glue to edges. Confirm secure fixation. Cycle knee through ROM to confirm scaffold stays in place. No sutures typically needed with MACI. Close in layers. The MACI scaffold has cells on one side. Ensure the cell-seeded side faces the subchondral bone (down). The smooth membrane side faces the joint. Incorrect orientation compromises the procedure. {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/2-macroscopic-images-of-a-a-single-defect-knee-and-b.png {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/2-macroscopic-images-of-a-a-single-defect-knee-and-b.png */} */} ### Key Technical Points - Maintain watertight seal (if using membrane ACI) - Cut MACI to exact defect size - Apply fibrin glue to dry surface - Confirm scaffold stability with ROM - Protect subchondral plate - Don't violate subchondral bone excessively - Don't leave gaps at edges - Don't allow fluid under scaffold - Don't place scaffold cell-side up - Don't allow early unprotected loading Meticulous surgical technique is essential for optimal outcomes. First-generation ACI with periosteal flap had 20-30% hypertrophy rates requiring secondary debridement. MACI has significantly reduced this complication. If hypertrophy occurs, arthroscopic debridement is usually effective. ### Weight-Bearing Protocol Toe-touch only with crutches. Brace for protection. Allows early cartilage maturation without load. Progressive weight-bearing 25% to 75%. Wean brace. Crutches until comfortable. Full weight-bearing without aids. No impact activities. Low-load exercises. ACI cartilage takes 12-18 months to fully mature. Early in healing, the tissue is soft and vulnerable. Weight-bearing and activity progression reflects this maturation timeline - slower than OATS or microfracture. ### Return to Activity Timeline Swimming, aqua jogging, stationary cycling. No impact. Jogging progression. Light sport-specific drills. Return to sport if MRI and clinical criteria met. Longer timeline than OATS or microfracture. Full return to high-level sport takes 12-18 months. This extended timeline reflects the cartilage maturation process. {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/4-mri-of-the-four-chondral-treatment-groups-a-empty-.png {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/4-mri-of-the-four-chondral-treatment-groups-a-empty-.png */} */} {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/3-histological-images-of-the-seven-groups-in-each-gr.png {/* MISSING IMAGE: /images/topics/autologous-chondrocyte-implantation/web-sourced/3-histological-images-of-the-seven-groups-in-each-gr.png */} */} The STAR trial (RCT) showed ACI superior to microfracture at 5 years. While microfracture results deteriorate at 2-5 years, ACI maintains improvement. For larger lesions, this difference is even more pronounced. **Q: How many surgical stages are required for ACI?** A: **Two stages** - Stage 1 is cartilage biopsy for cell harvest. Cells are cultured for 4-6 weeks. Stage 2 is implantation of expanded cells. This is a key disadvantage compared to single-stage OATS. **Q: How many cells are implanted during ACI?** A: **12-48 million cells** - The initial biopsy (200-300mg) contains approximately 200,000-300,000 chondrocytes. Cell culture expands this to 12-48 million cells for implantation. **Q: What does MACI stand for?** A: **Matrix-induced Autologous Chondrocyte Implantation** - MACI is third-generation ACI where cells are seeded on a collagen scaffold, eliminating the need for periosteal harvest or watertight membrane suturing. **Q: Which generation of ACI had the highest rate of graft hypertrophy?** A: **First-generation (periosteal ACI)** - Hypertrophy rates of 20-30% were seen with periosteal flaps. This was significantly reduced with collagen membranes (second-gen) and MACI (third-gen). **Q: What is the longest reported follow-up for ACI outcomes?** A: **20 years (Peterson series)** - The original Brittberg/Peterson series reported 84% good/excellent results at 20 years, demonstrating exceptional durability of the technique. **Q: What lesion size is typically considered ideal for ACI?** A: **Over 2cm²** - ACI is typically reserved for lesions over 2cm² where microfracture outcomes are suboptimal and OATS donor capacity may be limiting. It is especially valuable for lesions over 4cm². - MACI available through specialized centers - Requires TGA-approved cell culture facilities - PBS does not cover cell therapy costs - Significant out-of-pocket expense for patients - Some private insurers may provide partial coverage - Document two-stage consent thoroughly - Record cell culture laboratory and tracking - Document scaffold orientation at implantation - Record all associated procedures (osteotomy) - Consent must cover extended rehabilitation timeline **Key documentation requirements:** - Two-stage consent with clear explanation of process - Document cell culture tracking and viability confirmation - Record surgical technique details (scaffold orientation, fixation) - Consent must include: extended rehabilitation (12-18 months), two surgeries, cost implications, realistic sport expectations - If failure occurs, documentation of proper indication and technique is protective

Autologous Chondrocyte Implantation (ACI)

Autologous Chondrocyte Implantation (ACI)