Summary MACI (autologous cultured chondrocytes on porcine collagen membrane) is made up of your own (autologous) chondrocytes that are expanded in culture and seeded onto a resorbable porcine type I/III collagen film; the film is absorbed back into host tissue over time as cells elaborate repair matrix It is implanted into the area where the damaged cartilage was removed (full-thickness debridement to stable vertical walls), with the cell-seeded surface placed down against the prepared defect bed and secured (typically with fibrin sealant) The resulting repair tissue is hyaline-like, exhibiting properties similar to durable hyaline articular cartilage without implying identity to native cartilage. Indications Repair of symptomatic cartilage damage of the adult knee Indicated for Repair of symptomatic Single or multiple, full-thickness cartilage defects of the knee with or without bone involvement in adults Limitations of use Effectiveness in joints other than the knee not established Safety and effectiveness in patients over 55 years not established Joint optimization before or concurrent with MACI Treat active infection/inflammation Restore/repair meniscal function Stabilize cruciate ligaments Correct varus/valgus malalignment and patellar tracking abnormalities Contraindications Known hypersensitivity to gentamicin or other aminoglycosides; hypersensitivity to porcine or bovine-derived products Severe osteoarthritis of the knee (Kellgren–Lawrence grade 3–4) Inflammatory arthritis or inflammatory joint disease; uncorrected congenital coagulation disorders Prior knee surgery within 6 months (excluding biopsy or a concomitant procedure to prepare the knee for MACI) Inability to cooperate with a physician-prescribed post-surgical rehabilitation program Precautions: unknown malignancy risk at biopsy/implant sites; theoretical transmissible disease risk; final sterility culture initiated prior to shipping but not available at implantation—use only if packaging is intact Anatomy Osteology Distal femur (medial/lateral condyles), trochlea, patella, and tibial plateaus; focus on lesion containment and load zones relevant to approach and rehab Muscles Quadriceps mechanism (patellofemoral tracking), hamstrings and gastrocnemius (posterior condylar access and postoperative loading) Ligaments ACL/PCL stability to limit shear. Evaluate and address MCL/LCL for coronal plane stability to protect the graft Nerves Standard portal and mini-arthrotomy awareness (saphenous, common peroneal) to avoid iatrogenic injury Blood supply Meticulous hemostasis; avoid breaching subchondral bone during prep to prevent bleeding that compromises adhesion Preoperative Planning Imaging MRI Approach Collection of Autologous Cartilage Biopsy Arthroscopic harvest from lesser load-bearing zones (e.g., lateral intercondylar notch; superior lateral or medial trochlear ridge) Obtain at least two healthy full-thickness specimens (~5 × 8 mm each; total ~200–300 mg) including a small amount of subchondral bone (removed during processing) Expect punctate bleeding at donor site; place specimens into provided transport medium using sterile technique Pre-Operative Preparation Verify patient identifiers on all MACI labels match the intended recipient Inspect outer shipping box and inner sterile pouch/bottle for leaks, damage, or contamination; do not use if compromised Store in original packaging at room temperature until the defect is prepared; do not refrigerate, freeze, or sterilize Approach planning: arthroscopic delivery for appropriately accessible lesions typically ≤4 cm²; arthrotomy for larger/irregular or less accessible lesions and for multi-procedure cases Technique Implantation Procedure Arthroscopic Delivery Plan portals to visualize and access the defect perpendicularly; localize cannula with a spinal needle Measure lesion dimensions; score the perimeter with a dedicated cutter; debride unstable cartilage to stable vertical walls For osteochondral defects, debride to healthy stable bone; do not penetrate the subchondral plate Achieve a dry field (turn off inflow, suction, hemostasis); remove any cannula dam before delivery Apply a thin, uniform fibrin layer to the base; load the cut MACI onto the V‑Shuttle with cell side up on the device (so it lands cell side down in the defect); deploy gently without compressing against bone Tamp to final position; allow ≥3 minutes for fibrin to set; verify with blunt probing and controlled knee ROM; apply rim sealant if needed For Arthroscopic and Arthrotomy Delivery Shared essentials Prepare a contained defect with stable vertical margins Avoid subchondral penetration Ensure hemostasis and a dry field Use fibrin on the base and optionally at the rim Discard unused implant/media per biohazard protocol Preparing MACI Implant Outside sterile field, open the shipper and pass the sealed sterile pouch; immediately before use, a non-sterile assistant opens the bottle and decants contents into a sterile dish Identify surfaces: rough side = cell-seeded; smooth side = non-seeded; orientation notch (lower-left in landscape) indicates cell side up Keep the implant hydrated with transport media; handle by edges/corners only with non-toothed forceps; avoid contact with the cell surface ASCII implant prep checklist Shaping the MACI implant Arthroscopic Delivery Use the dedicated MACI cutter sized to lesion measurements Place cutter on implant (cell side up) on a cutting block Press/tap to punch Return cut piece to media and preserve orientation Arthrotomy Delivery Create an exact template of the defect; mark orientation (e.g., anterior/medial) Flip the marked template under the implant against the smooth side (so final placement is cell side down with correct orientation); cut precisely along the template; return to media Placing MACI Implant Arthroscopic Delivery Drain the joint to dry Apply thin fibrin layer to the base Load graft on V‑Shuttle (cell side up on device) and deploy over center of the defect Avoid compression Tamp & hold ≥3 minutes verify adhesion with probe and ROM Optional rim sealant Arthrotomy Delivery Ensure a dry, blood-free field; apply a thin fibrin layer to the base; place graft cell side down; apply light digital pressure ~3 minutes Consider interrupted resorbable sutures if the defect is uncontained or lesion >10 cm²; probe and cycle ROM to confirm fixation; optional rim sealant For Arthroscopic and Arthrotomy Delivery Edge-seal with fibrin if desired; discard unused implant and media per biohazard protocol; close per standard practice Technical specifications Format Single-use 3 × 5 cm cellular sheet with ~0.5 cm² orientation notch Composition Porcine type I/III collagen membrane seeded with autologous chondrocytes at ≥500,000 cells/cm² (typical range 0.5–1.0 million/cm²) Handling/storage Keep at room temperature in original packaging Do not refrigerate/freeze/resterilize Use before expiration Maintain hydration with shipping media once opened Residuals Trace bovine proteins from culture medium may remain; residual gentamicin from manufacturing may be present Sterility Released for shipping after passing in-process microbial tests; final sterility test initiated before shipping but not available at implantation; provider will be notified if post-shipment positivity occurs Postoperative Surgeon-directed rehabilitation program emphasizing early controlled motion Progressive weight bearing, and staged return to activity as clinically appropriate Disclosure This content summarizes FDA-approved labeling and manufacturer materials; surgeons must consult full labeling and institutional protocols Pearls & Pitfalls Pearls Critically evaluate the 'shoulder' (the rim of healthy, surrounding cartilage) as the graft relies on stable tissue for secure integration A torn ACL or PCL that causes translation must be reconstructed either prior to or at the time of MACI Prioritize meniscal repair or preservation whenever possible, as a healthy meniscus is a critical load-sharing structure Pitfalls Not identifying adjacent areas of delaminated or softened (chondromalacic) cartilage, which must be debrided back to healthy tissue during implantation Placing a cell-based graft into a knee that exhibits dynamic instability introduces massive shear forces and guaranteeing early failure MACI success rates are lower in knees with total or near-total meniscectomy due to the significant increase in contact pressures across the joint