Purpose: The purpose of this study is to determine the histological fate of the full thickness skin graftwhen placed into the temporomandibular joint using a rabbit model.
Materials and Methods: Fourteen New Zealand white rabbits were used and divided into 3 groups.Two rabbits were used as controls (Group A) whereby a sham operation was undertaken with an incisionmade and immediately repaired without breaching the joint space of the left craniomandibular joint(CMJ). In 6 rabbits (Group B), the joint capsule of the left CMJ was surgically breached but the articulardisc was preserved and the wound was repaired. The remaining 6 rabbits (Group C) also had the left CMJsurgically exposed with preservation of the articular disc and the interpositional placement of a fullthickness skin graft that was taken from the skin of their necks. All grafts were placed above the articulardisc and head of condyle in the superior joint space and firmly secured to the surrounding tissues withnonresorbable sutures. The rabbits were sacrificed at 1, 3, and 5 months after surgery and the left CMJswere histologically prepared and examined under light microscopy.
Results: The condylar head in the regions where the disc was present appeared to closely resemble that of thecontrol rabbits. However, where the disc was breached by inadvertent surgical trauma (Group B), the underlyingcondyle showed an irregular outline with increased fibrosis and a marked reduction in mature cartilage. In thesubarticular bone there was increased osteoblast and osteoclast activity reflecting high bone activity indicative ofa remodeling rather than a degenerative process. The interpositional skin grafts in all experimental animals (GroupC) were found adjacent to the condyle on the lateral aspect rather than above the condylar head where it wasoriginally sutured in place. Significant atrophy and reduction in the number and size of the skin appendages suchas sweat glands and hair follicles was found within the grafted skin of all experimental animals (Group C) comparedwith normal skin. All the grafts showed evidence of epidermoid inclusion cysts.
he ideal disc replacement material after discec-omy for advanced temporomandibular joint (TMJ)nternal derangement has yet to be found.1 Alloplas-ic implants such as proplast-teflon and sialastic
eceived from St. Vincent’s Hospital Melbourne, University of Mel-
ourne, Melbourne, Victoria, Australia.
*Consultant Oral and Maxillofacial Surgeon, Department of Spe-
ial Surgery.
†Associate Professor, Department of Anatomical Pathology.
Address correspondence and reprint requests to Dr Dimitroulis:
2006 American Association of Oral and Maxillofacial Surgeons
278-2391/06/6407-0012$32.00/0
poi:10.1016/j.joms.2006.03.011
1075
ave yielded disastrous results through foreignody giant cell reactions.2 Autogenous ear cartilagerafts have also failed because of graft fragmenta-ion and joint fusion resulting in ankylosis.3 Thelinical use of the dermis graft as a disc replace-ent after discectomy in the human TMJ has been
eported,4 however, one side effect of using dermiss an interpositional graft within the TMJ has beenhe development of epidermoid cysts.5-7 It has beenuggested that remnants of epidermis left on theermal grafts may well be the trigger that results inhe formation of epidermoid cysts.6 This is an im-ortant issue because the use of full thickness skinrafts as interpositional material has already beenescribed for the treatment of TMJ ankylosis.8,9 The
urpose of this study is to determine the histolog-
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1076 FULL THICKNESS SKIN GRAFT IN THE RABBIT CRANIOMANDIBULAR JOINT
cal fate of the full thickness skin graft when placednto the TMJ using a rabbit model.
aterials and Methods
Fourteen New Zealand white rabbits were used inhis study (Table 1). The study was approved by thenimal Ethics Committee at St. Vincent’s Hospitalelbourne in accordance with guidelines put forth by
he National Health and Medical Research Council ofustralia governing animal experiments. Two rabbitsere used as controls (Group A) whereby a shamperation was undertaken with an incision made and
mmediately repaired without breaching the jointpace. The craniomandibular joints (CMJ) of theroup A rabbits were used as the normal controlsith which to compare the surgically treated joints of
he remaining rabbits. Six rabbits (Group B) had theeft CMJ surgically exposed before the wound wasepaired and the rabbits placed back in their cages.he remaining 6 rabbits (Group C) also had the artic-lar disc of the CMJ exposed with the interpositionallacement and suturing of a full thickness skin graft,hich was taken from the skin of their necks (Fig 1).
SURGICAL TECHNIQUE
Anesthetic induction was via an intravenous bolusf 1:1 mixture of ketamine (70 mg/mL) and xylozine10 mg/mL) at a rate of 1 mL/kg into the ear vein. Thenesthetic mixture provided 60 to 90 minutes of an-sthesia time. After anesthesia induction the fur in theeft preauricular region was shaved and depilatoryream was placed to remove all the fur around theurgical site. After injection with 1 mL of 2% ligno-aine with 1/80,000 adrenaline, a horizontal skin in-ision was made from just posterior to the lateralanthus of the eye to just anterior to the externalcoustic meatus. In the 2 control rabbits (Group A)he incision was immediately repaired withoutreaching the joint space. For the experimental rab-its (Groups B and C), the zygomatico-squamosal su-
Table 1. NUMBER OF RABBITS USED IN EACHGROUP
4Weeks
12Weeks
20Weeks
roup A controls - 1 1roup B no grafts 2 2 2roup C skin grafts 2 2 2
OTE. All Group C rabbits demonstrated lateral displacement ofhe graft and epidermoid cyst formation within the graft material.
imitroulis and Slavin. Full Thickness Skin Graft in the Rabbitraniomandibular Joint. J Oral Maxillofac Surg 2006.
ure line was exposed and a section of the zygomaticDC
rocess overlying the cranio-mandibular joint (CMJ)as carefully removed. The capsule of the CMJ was
ncised and the superior joint space was completelyxposed to show the articular disc, which was leftntact. The surgical wound in Group B rabbits waslosed immediately after exposure of the superioroint space. In Group C rabbits, a full thickness skinraft was harvested from the neck, which was de-uded of fur, and was carefully inserted into theuperior joint space above the articular disc and se-ured firmly to the surrounding tissues with 2 or 3 7-0rolene sutures (Fig 1). The wound was closed with-0 vicryl sutures. The analgesic carprofen was admin-
stered at the time of surgery and a follow-up dose (5g/kg SC) was given in the 6 hours after surgery.fter the operation the animals were fed a diet ofrushed pellets and fresh vegetables for the first weeknd water ad libitum. Their weight was measured at-week intervals postoperatively. After a week, allnimals were placed back on their normal diet of hardellets and vegetables.Each animal was housed individually in a double
en to prevent the risk of other animals disturbing theurgical wounds. Each group of rabbits was killed byuthanasia at 4 weeks, 12 weeks, and 20 weeks afterurgery (Table 1). Euthanasia was administered byntravenous sodium pentobarbitone (2 mg/kg).
After euthanasia, the jaw joints were dissected outnd placed in formalin. The specimens were decalci-ed prior to histological sectioning. Coronal sectionsere prepared of each craniomandibular joint foristological evaluation under light microscopy in theepartment of Anatomical Pathology. At least 8 sec-
ions from each joint were examined and pertinentndings were recorded using digital photography.
IGURE 1. Interpositional full thickness skin graft (white tissue) shownovering the condylar head of the rabbit craniomandibular joint at theime of surgery.
imitroulis and Slavin. Full Thickness Skin Graft in the Rabbitraniomandibular Joint. J Oral Maxillofac Surg 2006.
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DIMITROULIS AND SLAVIN 1077
esults
As this was a qualitative study, a statistical justifica-ion of animal numbers was not applicable. It wasecided by the authors that 14 animals was the min-
mum number for which useful comparisons could beade as described above (Table 1). The mean weight
f all 14 rabbits at the time of surgery was 2.44 kg �.17 kg and the mean age at surgery was 4.91 mo �.26 mo.
CONTROL RABBITS (GROUP A–2 RABBITS)
Both rabbits suffered no adverse side effects fromhe anesthetic and operative procedure. Their returno normal diet was within 48 hours and their woundsealed uneventfully. Histological examination of the
eft craniomandibular joints showed a well-roundedondylar head covered by healthy fibrocartilage. Aense fibrotic band of tissue representing the articularisc surrounded the condylar head with evidence ofynovial lining present along the lateral margins. Be-eath the fibrocartilage cap covering the condylaread was a graded layer of cartilagenous cells, which
n turn covered a well-defined layer of cortical bone.he marrow space beneath the cortical bone was
nterspersed with vascular channels and islands ofone trabeculae enclosing osteocytes with occasionalsteoblasts along the margins. It was apparent thathe operative procedure, which did not breach theoint space, had no effect on the joint itself at both 12nd 20 weeks.
4 WEEKS
Exposure of Superior Joint Space, No Graft(Group B–2 Rabbits)Both rabbits suffered no adverse side effects from
he anesthetic and operative procedure. Their returno normal diet was within 7 days and their woundsealed uneventfully. The surgery had a significantarly effect on both rabbits but they quickly adaptednd by day 7, both were managing a routine normaliet with no apparent ill effects. At the histological
evel it was apparent that not all of the disc wasreserved, and remnants of surgically traumatizedisc were seen in some sections. In the sectionshere the disc was breached, the joint space waslled with blood and fibrin. The condylar head in theegions where the disc was present appeared tolosely resemble that of the control rabbits. However,here the disc was breached, the underlying condyle
howed an irregular outline with increased fibrosisnd a marked reduction in mature cartilage. In theubarticular bone, there was increased osteoblast andsteoclast activity, reflecting high bone activity indic-tive of a remodeling rather than a degenerative pro-
ess. l
Insertion of Skin Graft (Group C–2 Rabbits)Both rabbits suffered no adverse side effects from
he anesthetic and operative procedure. Their returno normal diet was within 7 days and their woundsealed uneventfully. The interpositional skin graftrocedure to the CMJ had a significant early effect onoth rabbits but they quickly adapted and by day 7,oth were managing a routine normal diet with nopparent ill effects.
At the histological level it was apparent that not allf the disc was preserved intact, and remnants ofraumatized disc were seen in some sections. The skinraft in both animals was seen to be adjacent to theondyle on the lateral aspect rather than over theead above the disc where it was originally sutured inlace. The skin graft was obviously vital, and bothpecimens showed evidence of epidermoid inclusionysts within the substance of each graft. There wasignificant atrophy and reduction in the number andize of the skin appendages such as sweat glands andair follicles within the grafted skin compared withormal skin. No evidence of skin was detected supe-iorly above the head of the condyle and it appearshe graft was displaced into the lateral position veryarly on after the surgery. The condyles in both ani-als showed the same remodeling process of in-
reased bone activity, fibrosis, and surface irregularityn areas where the disc was breached as that of theroup B specimens without the skin graft.
12 WEEKS
Exposure of Superior Joint Space, No Graft(Group B–2 Rabbits)Both rabbits suffered no adverse side effects from
he anesthetic and operative procedure. Their returno normal diet was within 7 days and their finaleight at sacrifice was 3,500 grams (9.2%) lighter
han the control rabbit sacrificed at the same timerame. In areas where the disc was surgicallyreached the condylar head showed marked flatten-
ng with subarticular trabecullae with increased os-eoblast and osteoclast activity. The condylar surfacedjacent to the area where the articular disc wasissing showed a marked reduction in fibrocartilage,ith increased bone formation (ie, osteoid deposits)
nd osteoblast activity whereby most of the cartilag-nous cap was replaced by bone (Fig 2).
Insertion of Skin Graft (Group C–2 Rabbits)Both rabbits suffered no adverse side effects from
he anesthetic and operative procedure. Their returno normal diet was within 7 days and their finaleight at sacrifice was 5,000 grams (11.8%) lighter
han the control rabbit sacrificed at the same timerame. Once again the full thickness skin graft was
aterally displaced relative to the condylar head. The
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1078 FULL THICKNESS SKIN GRAFT IN THE RABBIT CRANIOMANDIBULAR JOINT
raft tissue showed significant amounts of keratinith increased fibrosis compared with the 4-week
pecimens. The skin appendages within the grafthowed severe degeneration. Epidermal cysts werelso present in both specimens (Fig 2).
20 WEEKS
Exposure of Superior Joint Space, No Graft(Group B–2 Rabbits)Both rabbits suffered no adverse side effects from
he anesthetic and operative procedure. Their returno normal diet was within 7 days and their finaleight at sacrifice was 4,500 grams (7.1%) heavier
han the control rabbit sacrificed at the same timerame.
There was no evidence of surgical trauma to therticular disc, so the condylar morphology resembledhat of the control rabbits in both cases.
Insertion of Skin Graft (Group C–2 Rabbits)Both rabbits suffered no adverse side effects from
heir anesthetic and operative procedure. Their re-urn to normal diet was within 7 days and their finaleight at sacrifice was 4,600 grams (9.5%) heavier
han the control rabbit sacrificed at the same timerame. Both specimens showed lateral displacementf the graft as well as epidermoid cyst formationimilar to the other Group C rabbits sacrificed earliern the course of the experiment. Severe degenerationf all skin appendages was also noted in both grafts
IGURE 2. Photomicrograph depicting the condylar head on the rightnd the epidermoid cyst on the left with the lumen full of keratin. Theondylar head shows reactive changes where the articular disc isisrupted. Skin appendages lining the epidermoid cyst are severelytrophied in this specimen 12 weeks after graft implantation. Note the
ateral position of the graft (ie, cyst) relative to the condylar headhematoxylin-eosin stain; magnification �40).
imitroulis and Slavin. Full Thickness Skin Graft in the Rabbitraniomandibular Joint. J Oral Maxillofac Surg 2006.
Fig 3).DC
iscussion
In clinical practice, full thickness skin grafts arearely used to reconstruct human temporomandibularoint. Instead, dermal grafts are preferred to avoid theisk of inclusion cyst formation, which has been re-orted in the literature. Unfortunately, the evidence
or cyst formation has largely been in the form oflinical case reports.5-7 What this study has clearlyhown is that the presence of epidermis does in factesult in epidermoid cyst formation in all grafts im-lanted into the CMJ of all the rabbits.In 1902, Gluck10 first reported the use of skin grafts
or arthroplasty. A scan of the literature showed 2rticles that reported the use of full thickness skin asn interpositional graft in the human TMJ.8,9 Bothere for the management of TMJ ankylosis. Popescu
nd Vasiliu8 published the first report in 1977 on these of full thickness skin grafts for TMJ ankylosis.nterestingly, they reported that one of the majorroblems associated with this technique was the dis-
IGURE 3. Photomicrograph showing another graft specimen at 20eeks. The graft is on the right side and shows obvious epidermoidyst formation. The condylar head is on the left side and appearselatively normal as the disc was fully preserved. Note once again theateral position of the graft tissue (ie, cyst) relative to the condylar head.
idway down the medial lining of the cyst there are severely atro-hied hair follicles visible (hematoxylin-eosin stain; magnification40).
imitroulis and Slavin. Full Thickness Skin Graft in the Rabbitraniomandibular Joint. J Oral Maxillofac Surg 2006.
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DIMITROULIS AND SLAVIN 1079
lacement of the graft due to poor suturing.8 In aecent study using full-thickness skin grafts as inter-ositional material in the management of TMJ anky-
osis, only 1 of 31 patients developed an epidermoidyst.9 Popescu and Vasiliu8 reported no cyst forma-ion after 4 to 6 years.
Although no deliberate attempt was made to re-ove the articular disc when the full thickness skin
raft was inserted, there were numerous instanceshere a breach in the disc was found as a result of
nadvertent surgical trauma. Interestingly, in areashere the disc was breached, the underlying condy-
ar head showed significant remodeling, supposedlys an adaptational response to exposed surface thatas normally protected by the overlying articularisc. In 1963, Sprinz11 also showed gross condylarhanges after menisectomy in the CMJ in rabbits.nfortunately, because the interpositional graft had
hifted to the lateral aspect of the condyle, there waso way to determine if in fact the graft may or mayot have provided the protective covering necessaryo prevent the extensive remodeling seen in all ex-osed surfaces of the condylar head where the discas breached (Fig 2).Cyst formation in grafted dermis is occasionally
eported in the literature.5-7 In the present study,pidermoid cysts were detected in all skin graft spec-mens that were placed as interpositional material
ithin the rabbit CMJ (Fig 4). The 2 clinical studies8,9
hat used full-thickness skin grafts to treat TMJ anky-osis in humans reported only a single case of cyst
IGURE 4. Photomicrograph showing severely atrophied epithelialining surrounding the epidermoid cyst with clear evidence of a thickermal layer and subdermal fibrofatty tissue in the deeper layers. Theermal layer in this 20-week specimen is composed of regularlyrranged collagen interspersed with fibroblasts with no evidence ofkin appendages such as hair follicles or sweat glands (hematoxylin-osin stain; magnification �100).
imitroulis and Slavin. Full Thickness Skin Graft in the Rabbitraniomandibular Joint. J Oral Maxillofac Surg 2006.
ormation in the grafts and yet the present study in t
he rabbit model showed epidermoid cyst formationithin all the grafted joints. The question, therefore,
rises as to whether the mutilated joint (ie, TMJ gaprthroplasty) is less likely to result in epidermoid cystormation within the graft as opposed to a graftlaced into a relatively normal joint as used in theresent study. To answer this question, a furthertudy involving skin grafts inserted into gap arthro-lasties instead of normal joints is required, as theynamics of a mutilated joint would be different tohat of a normal joint, and therefore the forces on theraft would be different. However, if the trigger foryst formation in a skin graft is the dynamic forces offunctioning joint, then one would expect the cyst to
orm in all skin grafts placed into a functional joint,egardless of whether the joint is normal or mutilated.his is in contrast to full thickness skin such as radial
orearm flaps, which are used to line the cranial basefter resection. The static environment in which theatter graft or flap is placed is not known to have everesulted in epidermoid cyst formation.
The other issue is the stability of the graft when firmlyutured over the condylar head. While Popescu andasiliu8 reported the problem of graft displacement in
heir article, Chossegros et al9 did not make any mentionf the possibility of graft displacement in their caseeries. All skin grafts in the present study were placedver the condylar head and firmly sutured to the sur-ounding joint capsule with nonresorbable sutures. In-ariably, none of the grafts were found above the con-ylar head where they were originally placed. All graftsere found displaced laterally beside the condyle when
he rabbits were sacrificed (Figs 2, 3). It is unlikely thathe displacement of the grafts occurred at the time ofpecimen handling and preparation, as all cysts wereurrounded and set in fibrous tissue that was clearlyutside the joint. This suggests that the lateral displace-ent of the grafts was an early phenomenon that oc-
urred very soon after surgery despite the use of non-esorbable sutures to secure the graft over the condylaread.A recent study by the first author4 using dermis
rafts in the human TMJ showed encouraging clinicalutcomes. However, most of the dermal grafts wereot secured into position with sutures but were pas-ively placed within the joint space, and the jointapsule was carefully repaired to prevent the graftrom spilling out of the joint cavity.4 While repair tohe joint capsule was undertaken in all the experimen-al rabbits, it appears that this effort, together with theirect anchorage of the graft with nonresorbable su-ures, was insufficient to prevent lateral displacementf the grafts in the present study.This study has shown that the autogenous full
hickness skin graft does survive when implanted into
he rabbit craniomandibular joint for up to 5 months
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1080 FULL THICKNESS SKIN GRAFT IN THE RABBIT CRANIOMANDIBULAR JOINT
Fig 4). However, despite being secured by non-esorbable sutures over the head of the mandibularondyle, all grafts were found to be laterally displacedelative to the condylar process.
While extrapolation to humans is difficult, there are 3ssential messages borne out of this study. The first ishat all remnants of epidermis must be totally eliminatedhen using dermis grafts in human TMJs. Secondly,
uturing the dermis graft to the surrounding tissues ofhe TMJ may be a waste of time, as the graft mayislodge and find itself in a position other than above theead of the condyle where it was meant to be. Andnally, perhaps what is required is a material to fill uphe intra-articular space vacated by the excised discather than a disc substitute. This is where the dermis-fatraft looks very promising.12
cknowledgment
This study was funded by the Australian & New Zealand Associ-tion of Oral & Maxillofacial Surgeons (ANZAOMS) Research &ducation Foundation.
eferences1. Dimitroulis G: The role of surgery in the management of dis-
orders of the temporomandibular joint: A critical review of the
literature Part 1. Int J Oral Maxillofac Surg 34:107, 2005
2. Yih W-Y, Merrill RG: Pathology of alloplastic interpositionalimplants in the temporomandibular joint. Oral Maxillofac SurgClin North Am 1:415, 1989
3. Yih W-Y, Zysset M, Merrill RG: Histological study of the fateof autogenous auricular cartilage grafts in the human tem-poromandibular joint. J Oral Maxillofac Surg 50:964, 1992
4. Dimitroulis G: The use of dermis grafts after discectomy forinternal derangement of the temporomandibular joint. J OralMaxillofac Surg. 63:173, 2005
5. Muto T, Tomioka K, Michiya H, et al: Epidermoid cyst in thetemporomandibular joint after dermal graft. J CraniomaxillofacSurg 20:270, 1992
6. Weinberg S, Kryshlalsky B: Epidermoid cyst in a temporoman-dibular joint dermal graft: Report of a case and review of theliterature. J Oral Maxillofac Surg 53:330, 1995
7. Bonnington G, Langan M, Joye D Jr: Epithelial inclusion cysts inthe temporomandibular joint after a dermal graft. J Oral Max-illofac Surg 45:705, 1987
8. Popescu V, Vasiliu D: Treatment of temporomandibular an-kylosis with particular reference to the interposition of fullthickness skin autotransplant. J Maxillofac Surg 5:3, 1977
9. Chossegros C, Guyot L, Cheynet F, et al: Full-thickness skingraft interposition after temporomandibular joint ankylosis sur-gery: A study of 31 cases. Int J Oral Maxillofac Surg 28:330,1999
0. Gluck J: Uber arthroplastik zur operation der ankilosis osseades kiefergelenks. Beitr Zum Zbl Chir 26:61, 1902
1. Sprinz R: The role of the meniscus in the healing processfollowing excision of the articular surfaces of the mandibularjoint in rabbits. J Anat 97:345, 1963
2. Dimitroulis G: The interpositional dermis-fat graft in the man-agement of temporomandibular joint ankylosis. Int J Oral Max-
