To know the current indications for meniscal allograft transplantation (MAT)
To become familiar with the different techniques used in MAT.
Expected post-operative MRI appearances and common complications after MAT
To know the MRI techniques best used for followup of meniscal allografts.
Understanding the normal and
appearances after meniscal
allograft transplant TIMOTHY WOO
UNIVERSITY HOSPITAL COVENTRY AND WARWICKSHIRE
CLIFFORD BRIDGE ROAD, COVENTRY, UK
• The menisci are a crucial load bearing structure of the knee helping
to decrease peak contact pressure and removal and debridement of
irreparable (“white-zone”) meniscal tears greatly accelerate
development of knee cartilage damage and osteoarthritis1,2
• The first human meniscal allograft transplant was performed in
19843 and since then thousands of procedures have been
• Timing of transplant and the patient groups likely to benefit are still
debated as well as whether it is truly chondroprotective
• It is well-tolerated and has proven short to medium term
Image credit Wikimedia commons: https://commons.wikimedia.org/wiki/File:Meniscus_tear_2010_-_closeup.JPG
• To know the current indications for meniscal allograft transplantation (MAT)
• To become familiar with the different techniques used in MAT and the
different graft types.
• Expected post-operative MRI appearances and common complications after
• To know the MRI techniques best used for follow-up of meniscal allografts.
1. Unicompartmental pain in the
presence of a total or subtotal
2. As a concomitant procedure to ACL
reconstruction if meniscus deficiency is
believed to be a contributing factor to
3. As a concomitant procedure to
cartilage repair in a meniscus deficient
1. Articular cartilage loss Outerbridge grade 3
2. Any ligamentous deficiency or
malalignment not surgically treatable.
3. Inflammatory arthritis or previous septic
4. Severe obesity (although no specific BMI
threshold has been agreed on)
5. Paediatric patient/immature skeleton
No age limit above which MAT not thought to be beneficial
Consensus statement from the International Meniscus Reconstruction Experts Forum in 20154
Several large case studies explore the outcomes following MAT, but the majority of these are
only Level IV evidence (One long term level III study5)
Heterogenous in outcome measures, exclusion criteria and patient cohort selection.
procedure with low
failure rate (~10%)
and low rate of
2. All studies
in Patient Reported
(e.g. 55.7(poor) →
Lysholm scale)7 and
at 14 years
3. No difference in
4. Uncertainty as to whether there is a chondroprotective
2 studies using contralateral
knee control showed no
Other studies show progression
of OA but often without
Probably there is a small chondroprotective effect but
masked by a heterogenous cohort
BONE BRIDGE TECHNIQUE
• Meniscus is harvested together with
the meniscal roots attached to a
“bone bridge” from the donor tibia.
• An identical receptor site is cut into
the patient’s native tibia and the
bone bridge attached with the
meniscal roots using suture anchors
or interference screws.
• Can be used for both medial and
BONE PLUG TECHNIQUE
• Meniscus is harvested together with small bone plugs
from the donor tibia, one attached to each root by long
• Suture tunnels are drilled from the root attachments to
the anterior tibial cortex and the root sutures with the
bone plugs are pulled through, tensioned and fixed –
usually with a device such an endobutton
SOFT TISSUE TECHNIQUE
• No bone graft is used – Suture
tunnels are drilled and used as
for the bone plug technique
• Some authors believe that the
suture tunnel technique is not
suitable for affixing the lateral
meniscus due to the root
proximity and risk of tunnel
coalescence although there is
no proven increased risk
After root fixation, the remainder of
the donor meniscus is attached to the
recipient’s residual meniscal rim
(if any) and/or joint capsule.
Allografts currently available are either fresh frozen
or cryopreserved with fresh frozen generally being
preferred but there is no difference in outcome
measures between groups. Rarely, fresh grafts are
also used although these have logistical challenges.
Fresh frozen soft
Spalding T. et al.
Previously, lyophilised grafts
were also used, but these
shrinkage at second look
arthroscopy and outcomes
similar to meniscectomy
groups in early case series13
Grafts are stored in antibiotic
solution while frozen to
prevent pathogen transfer.
Previously, some grafts were
irradiated, but this also was
found to compromise graft
quality and this is no longer
Artificially engineered graft material is much less commonly
used with available products such as Collagen Meniscal
Implant (Ivy Sports Medicine, Germany) which is composed
of Achilles tendon Type I collagen and acellular polyurethane
polymer scaffold (Actifit, Orteq Bioengineering, UK), but
these are only usable for partial meniscal defects and require
a viable meniscal rim and at least one root attachment.
• Most of the fixation used in meniscal
allograft transplant is non-metal except
for the endobutton which is distant from
the graft fixation
• 3 Tesla imaging with fluid sensitive fat
saturated structural sequences such as
fat-saturated proton-density images using
a dedicated knee coil in three orthogonal
Proton-density weighted coronal MRI of the knee
with a lateral meniscal transplant showing peripheral
• Some authors advocate the use of
arthrography to investigate graft/capsule
healing as this is obscured by suture
artefact. However, the clinical benefit of
this is debated.
• Arthrography can be used to tell
between non-displaced graft tears and
healing tissue and to investigate
Normal post-operative appearances
• Similar to ACL graft
• Initial T1/T2 high signal
peaking at 6m then declining
to T1/T2 low signal over the
next 18 months
• Commonly seen and not
associated with worse PROMs15
• However, thought undesirable
as represents incompetence of
• Assessed by fluid/contrast tracking
between graft and capsule
• Thought desirable – especially in soft
tissue only fixations.
• However, even arthrography
• Not of clinical consequence
• Increasing on serial imaging
• True fluid signal
Normal MRI of soft tissue only fixation lateral meniscus allograft
Top: Normal appearances of the two suture tunnels on sagittal PDFS
and T1-weighted images (arrowheads)
Bottom: linear high signal in posterior horn found at arthroscopy to be
unresorbed suture material
• As with other joint procedures,
superficial and deep joint
infections are non-specific on
imaging presenting early with
synovitis and effusion
• Root suture fixation sites are a potential site of failure in
soft tissue fixation
• Sutures should run continuously between the suture tunnel
and the donor root
• Anterior horn suture can often be poorly defined and
detecting tears/suture failure here has low specificity
Sagittal and coronal PD-weighted MRI of lateral meniscal allograft
showing apparent absent anterior horn with no meniscal material visible
continuous with the suture tunnel suggestive of a suture failure/tear
The allograft was normal on arthroscopy.
Early post-operative MRI of a patient with
lateral meniscal allograft after re-presenting
with tibial wound infection. PD-weighted
sagittal images showing infrapatellar fat pad
oedema, synovial thickening and effusion
suspicious for joint infection
NON-INCORPORATION OF BONEPLUGS/BONE-BRIDGE
• The bonegraft should be visible on immediate and
sometimes at 3 month post-operative imaging but
should be completely incorporated by 6 months.
• Signs of failure are as elsewhere with progressive
sclerosis and cortication and persistent fluid cleft at
• Graft tear is the most common indication for non-
routine followup MRI.
• Linear high signal is normal in the graft meniscus
usually representing suture material or
granulation/epithelisation but tear is favoured if:
• Displaced fragment
• Increasing fluid signal over serial MRI scans esp if new
• Imbibition of contrast on MRI arthrogram
Sagittal PD-weighted MRI of a
lateral meniscal allograft showing
flipped tear of the posterior horn
of the graft with empty posterior
Immediate and 3 month postoperative radiographs showing normal
incorporation of tibial bone-bridge of a lateral meniscal allograft
• As with ACL graft reconstruction,
meniscus transplant can rarely result in
intra-articular scar mass formation or
arthrofibrosis which usually presents as
progressive restriction of range of
• Low signal soft tissue foci – often more
evident on non-fat-saturated images are
sometimes seen and MRI arthrography
can sometimes also be helpful but most
patients in which this is suspected
progress to arthroscopy.
PROGRESSION OF OSTEOARTHRITIS
• In the medium to long term, progression
of cartilage loss is important to note as
this can indicate a functionally
incompetent graft and can relate to
recurrent patient pain (imaging after two
years is often only undertaken in the
context of new symptoms).
• This can sometimes necessitate graft
revision or in some cases joint
Left: 1 year postoperative and
Right: 3 year postoperative
coronal PD-weighted MRI studies
of a patient with lateral meniscal
allograft and new symptoms
showing definite interval cartilage
degeneration despite meniscal
T1-weighted MRI through the intercondylar notch
of a patient with lateral meniscal allograft with
bone-bridge technique showing low signal scar in
the infrapatellar fatpad and notch in keeping
Meniscal allograft transplant is an increasingly
popular choice for young to middle aged patients
with significant meniscal injuries and is proven to
have at least short to medium term symptomatic
There is an increasing chance of coming across a
patient who has undergone one of these
procedures in the past and it is important that
radiologists know the details of current and past
surgical techniques and expected post-operative
MRI appearances of these grafts to accurately
assess re-injury. Lateral meniscal allograft in situ postfixation arthroscopic image
From Spalding et al.12
1. Roos H, Laurén M, Adalberth T, Roos EM, Jonsson K, Lohmander LS. Knee osteoarthritis after meniscectomy: prevalence of radiographic changes after twenty-one years, compared with matched
controls. Arthritis Rheum. 1998 Apr;41(4):687-93.
2. Papalia R, Del Buono A, Osti L, Denaro V, Maffulli N. Meniscectomy as a risk factor for knee osteoarthritis: a systematic review. Br Med Bull. 2011;99:89-106.
3. Milachowski KA, Weismeier K, Wirth CJ. Homologous meniscus transplantation. Experimental and clinical results. Int Orthop. 1989;13(1):1-11.
4. Getgood A, LaPrade RF, Verdonk P, Gersoff W, Cole B, Spalding T; IMREF Group. International Meniscus Reconstruction Experts Forum (IMREF) 2015 Consensus Statement on the Practice of
Meniscal Allograft Transplantation. Am J Sports Med. 2017 May;45(5):1195-1205.
5. van der Wal RJP, Nieuwenhuijse MJ, Spek RWA, Thomassen BJW, van Arkel ERA, Nelissen RGHH. Meniscal allograft transplantation in The Netherlands: long-term survival, patient-reported
outcomes, and their association with preoperative complaints and interventions. Knee Surg Sports Traumatol Arthrosc. 2020 Nov;28(11):3551-3560.
6. Smith NA, MacKay N, Costa M, Spalding T. Meniscal allograft transplantation in a symptomatic meniscal deficient knee: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2015
7. Samitier G, Alentorn-Geli E, Taylor DC, Rill B, Lock T, Moutzouros V, Kolowich P. Meniscal allograft transplantation. Part 2: systematic review of transplant timing, outcomes, return to competition,
associated procedures, and prevention of osteoarthritis. Knee Surg Sports Traumatol Arthrosc. 2015 Jan;23(1):323-33.
8. Ha JK, Shim JC, Kim DW, Lee YS, Ra HJ, Kim JG. Relationship between meniscal extrusion and various clinical findings after meniscus allograft transplantation. Am J Sports Med. 2010
9. Sekiya JK, Giffin JR, Irrgang JJ, Fu FH, Harner CD. Clinical outcomes after combined meniscal allograft transplantation and anterior cruciate ligament reconstruction. Am J Sports Med. 2003 Nov-
10. Hommen JP, Applegate GR, Del Pizzo W. Meniscus allograft transplantation: ten-year results of cryopreserved allografts. Arthroscopy. 2007 Apr;23(4):388-93
11. Vundelinckx B, Bellemans J, Vanlauwe J. Arthroscopically assisted meniscal allograft transplantation in the knee: a medium-term subjective, clinical, and radiographical outcome evaluation. Am J
Sports Med. 2010 Nov;38(11):2240-7.
12. Spalding T, Parkinson B, Smith NA, Verdonk P. Arthroscopic Meniscal Allograft Transplantation With Soft-Tissue Fixation Through Bone Tunnels. Arthroscopy Techniques. 2015 Oct;4(5):e559–63.
13. Wirth CJ, Peters G, Milachowski KA, Weismeier KG, Kohn D. Long-term results of meniscal allograft transplantation. Am J Sports Med. 2002 Mar-Apr;30(2):174-81.
14. van Arkel ER, Goei R, de Ploeg I, de Boer HH. Meniscal allografts: evaluation with magnetic resonance imaging and correlation with arthroscopy. Arthroscopy. 2000 Jul-Aug;16(5):517-21.
15. Boutin RD, Fritz RC, Marder RA. Magnetic resonance imaging of the postoperative meniscus: resection, repair, and replacement. Magn Reson Imaging Clin N Am. 2014 Nov;22(4):517-55.
16. Lee DH, Lee BS, Chung JW, Kim JM, Yang KS, Cha EJ, Bin SI. Changes in magnetic resonance imaging signal intensity of transplanted meniscus allografts are not associated with clinical outcomes.
Arthroscopy. 2011 Sep;27(9):1211-8.