Published on March 13, 2014
Autologous Chondrocyte Transplantation Dr. Babloo
Chondral Injuries Commonly these injuries heal by scar tissue formation :
- Arthroscopic Debridement : - Arthroscopic lavage - Subchondral drilling - Microfracture Marrow stimulation techniques - Abrasion arthroplasty to induce the growth of fibrocartilage into the chondral defect. Treatment options
Stages of ACI healing Healing process has several stages. They include the • proliferative stage (0 to 6 weeks), • the transition stage (7 to 12 weeks), and • a remodeling and maturation stage which occurs over a prolonged period (13 weeks to 3 years)
Proliferative stage • During this stage, a primitive cell response occurs with tissue fill of the defect and poor integration to underlying bone or adjacent cartilage. • Mostly type I and some type II collagen is produced. • The tissue is soft and jelly-like and easily damaged
Transition phase • This marks the production of type II collagen framework and the early production of proteoglycans. • The proteoglycans, which form the matrix, help imbibe water to give cartilage its viscoelastic properties. • The tissue is not yet firm or well integrated and has the consistency of a firm gelatin. • It is milkable when probed with an arthroscopic nerve hook, indicating incomplete integration to underlying bone
Stage of remodeling and maturation • The matrix proteins cross-link and stabilize in large aggregates. • The collagen framework reorganizes so as to integrate into the subchondral bone and form arcades of Benninghoff. • Usually by 4 to 6 months, the tissue has firmed up to a putty-like consistency and is integrated to the underlying bone
• At this stage, patients experience good symptom relief • During this stage excessive activity may cause repair tissue degeneration or continued improvement in remodeling • Hence, the concept of a time course of healing is critical during the rehabilitation phase of ACT
Indications for ACT • Symptomatic full-thickness chondral injury of the femoral articular surface (femoral weight- bearing condyles and sulcus or trochlea) in a physiologically young (<45 years) patient who is compliant with the rehabilitation protocol • osteochondritis dissecans (OCD)
• Results of chondral injuries of the patella and tibia (improved in 70% to 80% of patients) are not as consistently high as those of the femoral weight-bearing condyles and trochlea (85% to 90% improved) • ACT is not FDA approved as a treatment for OA, that is, bipolar chondral injuries with radiographic weight-bearing joint space loss
Pre-requisites for surgery • Appropriate biomechanical alignment • Ligamentous stability • Range of motion
Not recommended for patients who have : • an unstable knee • in children • in any joint other than knee.
Clinical examination • Assessing subtle PF maltracking is important because this may become more pronounced and symptomatic after arthrotomy, which may adversely affect the treatment outcome of a trochlea or patellar ACT • Assessment of predisposing factors for cartilage injury and degeneration may affect the prognostic outcome.
• These may include cruciate ligament insufficiency, genu varus or valgus, obesity, bone deficiency (AVN, OCD, and degenerative or ganglion bone cysts), inflammatory arthropathy, and familial osteoarthropathy • These must be assessed so that they may be either corrected in a staged or concomitant fashion with ACT
Investigations Wt bearing xray and skyline views • Evidence of joint space narrowing 50% with osteophyte formation, subchondral bony sclerosis or cyst formation eliminates patients from treatment (ie, if bone on bone changes are present)
MRI MRI scanning, while helpful for soft-tissue evaluation of meniscal or ligamentous injury as well as assessment of bone bruises and osteonecrosis, does not have a high sensitivity and specificity (75% to 93%) for determining the extent of a chondral injury or subtle chondromalacia changes.
The gold standard for determining whether a symptomatic patient is a candidate for ACT are normal radiographs, accompanied by an arthroscopic assessment showing focal pathology
A’scopy and Cartilage Biopsy • Extent of lesion, Menisci, AP length of lesion • Quality and thickness of the surrounding articular cartilage will determine whether healthy cartilage will be available for periosteal suturing or a non-contained chondral injury will require suturing through synovium or small drill holes through the bone.
• The most commonly chosen site for biopsy is the superior medial edge of the trochlea • Superior lateral femoral condyle • lateral intercondylar notch • superior transverse trochlea margin adjacent to the supracondylar synovium
• Approximately 200 to 300 mg of articular cartilage (approximately 5 mm wide and 1 cm long) is required for enzymatic digestion for cell culturing. • This contains approximately 2 to 3 lakh cells, which may be enzymatically digested and grown to approximately 120 lakh cells per 0.4 mL of culture media per implantation vial.
• After in-vitro expansion of cells 3 to 5 weeks later, a suitable number and volume of cells (usually one vial per each 4 to 6 sq cm defect) will be grown to accommodate the defect size required • Can be stored upto 2 years
Implantation of Autologous Chondrocytes Open implantation include arthrotomy, defect preparation, periosteum procurement from the tibia or femur, periosteum fixation, periosteum water-tight integrity testing, autologous or allogeneic fibrin glue sealant, chondrocyte implantation and wound closure
MACI • Matrix induced ACI • Cultured chondrocytes seeded in bilayered typeI/III collagen membrane • Implanted using fibrin glue
Rehabilitation goals ● Aggressive ROM exercises to enhance chondrocyte regeneration and decrease the likelihood of intraarticular adhesions ●Touch-weight bearing for 6 wks and full by 12 weeks to prevent periosteal overload and central degeneration or delamination of a weight bearing graft ● Isometric and gentle functional muscle exercises to regain muscle tone and prevent atrophy
• CPM is instituted as soon as cell attachment has occurred, usually 6 hours after surgery • This is utilized for approximately 6 to 8 hours daily for up to 6 weeks after surgery • Initially it is used for a range of 0° to 40° maximum. CPM from 40° to 70° is not recommended because maximal PF contact forces occur in this range.
• CPM for defects of trochlear defects is less vigorous • The remainder of the motion is obtained by the patient dangling a leg over the edge of the bed to regain further motion • On average, it takes 4 to 4 1/2 months for patients to discard their supports and walk comfortably
• Running is not permitted until graft hardness becomes similar to adjacent cartilage, which takes approximately 9 to 12 months • Kneeling and squatting are not permitted until 12 to 18 months after surgery • Osteochondritis dissecans may take 18 to 24 months.
Advantages • Can produce hyaline-like cartilage. • Can fill defects regardless of size with functional repair tissue. • Moderate to large defects that have failed previous intervention. • Repair tissue which matures, rather than deteriorates over time. • Expected outcome • Return to previous level of functioning
Disadvantages • More invasive • Expense • Longer recovery • Overall failure rate is at present quoted as being 10%.
Complications • Incomplete periosteal graft incorporation to host cartilage and hypertrophic graft edge response. • Clinically, this usually manifests as a proliferative hypertrophic periosteal healing response between 3 and 7 months after surgery • Intra-articular adhesions with resultant stiffness are uncommon • Post-op hematoma, hypertrophic synovitis
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