This document discusses autologous chondrocyte transplantation (ACT), a treatment for cartilage defects. It covers the stages of ACT healing, indications, prerequisites, investigations, the implantation procedure, and rehabilitation goals. The proliferative, transition, and remodeling stages of healing are described. Advantages include producing hyaline-like cartilage to fill defects of any size. Disadvantages include being more invasive and expensive with a longer recovery than other options.

1. Autologous
Chondrocyte
Transplantation
Dr. Babloo

2. Chondral Injuries
Commonly these injuries heal by scar tissue formation :

3. - Arthroscopic Debridement :
- Arthroscopic lavage
- Subchondral drilling
- Microfracture Marrow stimulation techniques
- Abrasion arthroplasty
to induce the growth of fibrocartilage into the
chondral defect.
Treatment options

4. 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)

5. 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

6. 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

7. 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

8. • 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

9. 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)

10. • 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

11. Pre-requisites for surgery
• Appropriate biomechanical alignment
• Ligamentous stability
• Range of motion

12. Not recommended for patients who have :
• an unstable knee
• in children
• in any joint other than knee.

13. 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.

14. • 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

15. 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)

16. 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.

17. 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

18. 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.

19. • 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

20. • 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.

21. • 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

22. 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

23. MACI
• Matrix induced ACI
• Cultured chondrocytes seeded in bilayered
typeI/III collagen membrane
• Implanted using fibrin glue

24. 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

25. • 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.

26. • 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

27. • 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.

28. 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

29. Disadvantages
• More invasive
• Expense
• Longer recovery
• Overall failure rate is at present quoted as
being 10%.

30. 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