OATS review, 20 years later

1. Autologous Osteochondral Grafting (OATS)
Historical Perspective
Prof Vladimir Bobić, Consultant Orthopaedic Knee Surgeon,
Chester Knee Clinic, Nuffield Health, The Grosvenor Hospital Chester, UK
vbobic@kneeclinic.info www.kneeclinic.info @ChesterKnee
ICRS Heritage Summit
Celebration of 20 Years of the ICRS
Göteborg, Swerige, 29 June to 1 July 2017

2. No financial or any other benefits from Arthrex, as inventor of OATS technology
Disclosure:

3. Celebration of 20 Years of ICRS
An Opportunity for Reflective Thoughts:
• My contributions to articular cartilage imaging, repair and rehab
and the ICRS which I introduced, presented and worked on for
the past 20 years:
• Balanced, non-commercial (often critical) view on autologous
osteochondral grafting (OATS Inventor), since 1996.
• Founding member of the ICRS, Fribourg, Switzerland 1997.
• Chondral and Subchondral MR imaging (as a founder and a
chair of the ICRS Imaging Committee, Boston 1998).
• Perioperative Cartilage Repair Rehabilitation (as a founder
and a chair of the ICRS Rehabilitation Committee), since 2003.
• Keen interest on the concept of Osteochondral Unit and the
importance of Subchondral bone, since 2003.
• Morphology and Biology Lamina Splendens, since 2015.

5. The Good and The Bad News About
Osteochondral Grafting
Vladimir Bobic, RLBUH Liverpool, UK
Svensk Idrottsmedicinsk Förenings Vårmöte
Göteborg, Sverige, 10 -12 maj, 2002

6. How did all this start?

7. OATS donor sites
• Above the sulcus terminals: good
concavity match to the MFC
• Lateral ICN: same as notchplasty
and roofplasty area

8. OATS Concept:
• The aim of articular cartilage repair is
restoration of a functional weight-bearing
articular surface.
• OAT provides an immediately available firm
articulating surface with autologous hyaline
cartilage and a firm bone carrier …
• … it delivers the finished product, with all the
right autologous ingredients, in the right
proportion and sequence,
• The contour of the reconstructed articulating
surface can be restored reasonably well,
• Press-fit fixation enables fast rehabilitation.

9. OATS Indications: the “ideal” chondral lesion is
relatively small, full-thickness defect (10 to 15 mm in
diameter), without subchondral bone loss. This lesion
should be treated early, in an attempt to contain the
defect and to repair the lost hyaline cartilage with
hyaline cartilage.
Osteochondral Autograft Transplantation (OATS)

10. What I did not know (1994 – 1998) is that what
matters is not only the (articulating) surface but
also the subchondral bone
However, the concept was inuitively good as it was based on
transplantation of the entire autologous osteochondral unit
(unlike any other autologous cartilage repair technology),
well before we started talking about subchondral bone

11. JBJSA March 1974

12. The Subchondral Unit: A New Frontier
re-drawn from Imhof et al. 1999
Henning Madry, Saarland University, Homburg/Saar, Germany
Imhof H, Breitenseher M, Kainberger F, Rand T, Trattnig S. (1999): Importance of subchondral
bone to articular cartilage in health and disease. Top Magn Reson Imaging 10:180–192

13. OATS Contraindications
• Large and deep
osteochondral defects
• Arthritic lesions and DJD
• Lesions with areas of
unstable, semidetached
surrounding cartilage
• Angular deformities
• Untreated instability
• Major meniscal deficiency

14. 2002: What have we learnt since 1994?
• Let’s talk about:
• Mid- and long-term outcomes
• Histology
• Cartilage integration
• Donor site issues
• Biomechanics
• Durability and quality of restored
articulatingsurfaces

16. Trochlear OATS
Uniform, excellent functional outcomes, no pain
(9 patients, 4 to 6 years f/u) - the best OATS by far. Why?
RLBUH UK

19. Makino T et al, Arthroscopy, September 2001, 747-751

20. Makino T et al, Arthroscopy, September 2001, 747-751
“… However, the histologic examination revealed that the grafted
cartilage was not maintained … as normal cartilage. The thickness of
the cartilage and the number of cells in the implanted osteochondral grafts
were obviously different from those of normal articular cartilage throughout
the entire observation periods …”

21. 2 years

22. donor
recipient
2 years

23. The same area, after 4 years …
… does not look too good

24. Deterioration of the recipient cartilage
MFC OAT graft after 3 years

25. Lane JG et al, Arthroscopy, October 2001, 856 - 863

26. • The edges of the articular cartilage did not show any incorporation with
the host articular cartilage. Full-thickness clefts were present at the
junction of the host and recipient articular cartilage and there was no
evidence of healing of this cartilaginous junction.
• Confocal microscopy: 95% of the cells counted manually in the bone plug
transplanted from the trochlea to the medial femoral condyle were viable
when the animals were killed 3 months after transplantation.
• Biomechanical testing has risen the concern of increased subchondral
bone density, as a potential factor in the progression of osteoarthritis.
Lane JG et al, Arthroscopy, October 2001, 856 - 863

27. OAT LFC donor site, a year after harvesting
RLBUH UK
Donor site issues

28. Ahmad CS et al, Arthroscopy, January 2002, 95 - 98
“ … the tissue obtained from the donor site grossly appeared fibrous and
extended well above the margins of adjacent normal cartilage.
Histologically, the tissue resembled a transitional tissue predominantly composed
of dense fibrous tissue with regions of immature bone and cartilage. In addition,
the tissue had material properties different from normal cartilage … “

29. OATS Problems

31. It is very important that transplanted
cartilage is flush with surrounding
cartilage, and that the graft is
positioned correctly in all planes.
Correct surgical technique is essential!

32. Correct Surgical Technique?
MRI: Dr Michael Recht, CCF

33. (In)correct Surgical Technique!
MRI: Dr Michael Recht, CCF

34. OAT MFC recipient site, a year after implantation

35. • A study done by K Burns (SLC, University of
Utah) demonstrates that positioning the graft
flush or slightly proud approximates normal
articular pressures most closely …
• … and that placing the graft even 1 mm
recessed was no different than having a
defect in terms of articular contact
pressure.
• This study emphasizes the importance of
obtaining congruity between the transplanted
cartilage surface and the surrounding,
recipient articular cartilage.
Correct OATS Surgical Technique

36. MFC 10 mm
autograft after
5 years
RLBUH UK

37. OAT Complications
• Mainly consequences
of technical (surgical)
errors:
• failure to extract the
graft,
• graft damage and
fracture,
• donor site deformation,
• graft harvested and
inserted at an
inappropriate angle
• loose bodies
• haemarthrosis
• donor site pain

39. OAT MRI Evaluation
RLBUH UK

40. OAT MRI Evaluation
1 year 1 year
RLBUH UK

41. Original OCD lesion
Failed graft after one year

42. Arthroscopy, October 2000, E16

43. OAT Problems
• Problems with large defects: limited availability
of autologous grafts, donor site morbidity, the
lack of chondral integration.
• Technical (spatial) problems with harvesting and
positioning of multiple, relatively long grafts,
needed to cover a large and deep defect.
• Multiple graft transfer is technically difficult for
most surgeons, which has resulted in a high
incidence of intra-operative complications and
poor outcomes.
• A potential for significant donor-site problem
with multiple graft harvesting, including
chondral degeneration, local AVN and condylar
fractures.

44. ICRS Gothenburg, Sweden, April 2000
The lack of graft integration and
degeneration of surrounding cartilage

45. MARIARC MRI, UK (1997)
The orange pixels correspond to normal T2 values for bone. The blue and purple pixels
are anomalous: the T2 relaxation times are elevated because the tissue is "wetter" than
normal (the fluid interface between recipient and donor bone).
OATS MRI analysis (1997!)

47. Recipient-donor cartilage integration

48. Makino T et al, Arthroscopy, September 2001, 747-751
Recipient-donor cartilage integration

49. The dead spaces between grafts: does the
cobblestone appearance really matter? It certainly
does not help the graft integration.

50. MFC OAT after 4 years
Deterioration of the recipient cartilage
CKC GNH UK
RLBUH UK

51. Lateral Femoral Trochlea:
a reliable source of good cancellous bone and bone marrow, even in advanced OA
CKC UK
MFC AVN

52. An alternative approach to the treatment of
femoral and tibial Osteonecrosis, Chronic SONK
and Secondary OA:
• The knee is often not too bad (all 3 compartments) or it is too early
for a partial or a full knee replacement.
• Classic Microfracture and Core Decompression are probably not deep
enough.
• Looking at most MRIs it seems that we need to reach at least 15 to 20
mm deep into subchondral bone, which is where any cylindrical
osteochondral harvesters are very handy.
• Effectively, this is a combination of OAT and deep core (subchondral)
decompression, with a hand driven K-wire, through the bottom of the
recipient socket, with
• a mixture of autologous blood + bone marrow injected into the
recipient socket,
• and capped with 10 mm OATS plug, which was soaked in the same
mixture of bone marrow and blood.
• This “integrated” subchondral repair concept makes sense, it gives
most people quick and durable pain relief and better knee function,
but it is based on huge assumptions.
• The main question is weather unprocessed (and not concentrated)
autologous bone marrow, is powerful enough biologically?
CKC UK

53. SONK: sudden onset,
severe knee pain
MRI: “In the outer weight-
bearing portion of the medial
femoral condyle, there is an
osteochondral lesion (22mm ant-
post x 10mm med-lat x 2mm
deep), with fluid at the interface
with parent bone, mild reactive
marrow oedema and a cortical
break peripherally in keeping
with instability. Degenerative
changes in the medial
compartment with spontaneous
osteonecrosis of the medial
femoral condyle (SONK) and
unstable fragment.”
David Ritchie, Glasgow
CKC MRI 060506

54. FU MRI: “In the medial
compartment, the graft over the
central weight-bearing portion of
the medial femoral condyle has
incorporated with adjacent
bone and the overlying
articular cartilage is flush
with adjacent native
cartilage. A small focus of
marrow oedema is noted directly
beneath the graft but overall
there has been a reduction in
marrow oedema around the
graft. A small trace of
subcortical fluid in the peripheral
portion of the medial femoral
condyle is similar to the pre-
operative scan - presumably not
included in the repair.”
Dr David Ritchie, Glasgow
CKC MRI 030307

55. OATS: Conclusion
• Surgical technique is critically important.
• Large OCD-type defects are just not doable (single
large OAT allograft is more appropriate).
• Unknown long-term fate of multiple donor sites.
• The quality and durability of the restored articular
surface is questionable.
• Visible secondary changes in the recipient bone and
articular cartilage, often after two or more years,
are a source of further concern.
• OAT is today’s yesterday’s technology, it is far from
perfect, but it is still as good as cartilage autologous
osteochondral repair gets.
• However, patient long term satisfaction and
functional outcomes remain very high, especially
with OATS + Deep Drilling + IBMA.
• Indications, indications and indications!

56. • Mainly because we still do not seem to understand
complex biological and mechanical interaction of
articulating surface and subchondral bone.
• This is probably the reason why all mainstream cartilage
repair technologies suffer from two major problems:
• insufficient peripheral chondral integration
(biomechanical problem?)
• insufficient longitudinal subchondral integration
(nutritional and biomechanical problem?).
• We may have to accept that this is as good as it gets, at
this point in time.
• However, finding a biological solution for cartilage
regeneration is one of the fastest growing areas of
research and development in orthopaedics and
regenerative medicine in general.
So, Why is Cartilage Repair Still a Problem?

57. Thank you
OATS was a stepping stone … but the future of cartilage
repair is in less carpentry and a lot more biology