The Effect of Autogenous Costochondral Grafts on Temporomandibular Joint Fibrous and Bony Ankylosis: A Preliminary Experimental Study

J Oral Maxillofac Surg 64:1517-1525, 2006

The Effect of Autogenous Costochondral Grafts on Temporomandibular Joint Fibrous and Bony Ankylosis: A Preliminary Experimental Study Hiroaki Matsuura, DDS, PhD,* Hizuru Miyamoto, DDS, PhD,† Kenichi Kurita, DDS, PhD,‡ and Alastair N. Goss, DDSc, FRACDS, OMS, FICD§ Purpose: The purpose of this study was to test the functional and histologic fate of costochondral

grafts (CG) in temporomandibular joint (TMJ) reconstruction for unilateral ankylosis in the sheep. Materials and Methods: Five pure-bred adult Merino sheep were used. Ankylosis was induced by

articular damage, disc removal, and placement of a bone graft. At 3 months, a gap arthroplasty was performed with a CG from the thirteenth rib. The sheep were sacrificed 3 months after CG reconstruction. The range of jaw movements were recorded at first operation, at lysis of ankylosis, and at sacrifice. The joints were examined radiologically, macroscopically, and histologically. Results: All sheep showed a decrease in masticatory function, as shown by weight loss and decreased jaw opening, during the ankylosis period. On release, they regained weight and increased the range of jaw movement. Histologically, the joint space was filled with fibrous tissue. However, the partial spaces around the CG head were covered by fibrous tissue and/or fibrous cartilage. Conclusions: This study shows that, when CGs are used with a gap arthroplasty in a fibrous and bony ankylosed TMJ, masticatory function is restored. © 2006 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 64:1517-1525, 2006

*Lecturer, The First-Department of Oral and Maxillofacial Surgery, Aichi-Gakuin University School of Dentistry, Nagoya, Japan; Former Visiting Research Fellow, Oral and Maxillofacial Surgery Unit, Dental School, The University of Adelaide, Adelaide, South Australia, Australia. †Visiting Research Fellow, Oral and Maxillofacial Surgery Unit, Dental School, The University of Adelaide, Adelaide, South Australia, Australia. ‡Professor, The First-Department of Oral and Maxillofacial Surgery, Aichi-Gakuin University School of Dentistry, Nagoya, Japan. §Professor and Director, Oral and Maxillofacial Surgery Unit, Dental School, The University of Adelaide, Adelaide, South Australia, Australia. Address correspondence and request reprints to Dr Matsuura: The First-Department of Oral and Maxillofacial Surgery, AichiGakuin University School of Dentistry, 2-11 Suemori-dori Chikusa-ku Nagoya 464-8651, Japan; e-mail: [email protected] © 2006 American Association of Oral and Maxillofacial Surgeons

0278-2391/06/6410-0010$32.00/0 doi:10.1016/j.joms.2006.06.256

Costochondral grafts (CG) have been used in ankylosed temporomandibular joints (TMJ) in combination with gap arthroplasties.1-3 This combination both releases the ankylosis and restores joint function.4,5 If gap arthroplasty alone is used, there are commonly problems with occlusal disharmony and loss of function. Reankylosis occurs with both techniques. Specific complications of CGs are mandibular overgrowth and cartilage fracture.2,3,6-8 In an experimental study of CG after unilateral condylectomy in nongrowing rhesus Macaca mulatta monkeys, it was reported that the original graft remained unchanged morphologically, but that new bone and cartilage progressively encompassed it, creating a form similar to the native condyle.9 In animal experimental studies, it has been reported that the costochondral regeneration comes from the perichondrium and not from the cartilage. The perichondrium of the rib shows the same structural character independent of the animal species or joint.9-14 In our previous experimental study,15 which used the CG in sheep TMJ reconstruction after condylectomy, the rib was well-attached to the mandibular ramus by 3 months after operation. Jaw movements

1517

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COSTOCHONDRAL GRAFTS IN TMJ RECONSTRUCTION

FIGURE 1. A, The right thirteenth rib of a sheep (scale in mm). B, Histologic section of the thirteenth rib of a sheep (Hematoxylin-eosin stain, original magnification ⫻ 2.7). C, Histologic section of the thirteenth rib (Hematoxylin-eosin stain, original magnification ⫻ 20.5). The cartilage tissue consists of hyaline cartilage, and the bone tissue consists of a thin cortical layer with cancellous marrow. The cells have arranged parallel columns. H, hyaline cartilage. Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

were not affected despite adhesions in the inferior joint space. No complications occurred. Importantly, the graft took on the appearance of a condylar head, and the cartilage layer showed an increase in thickness. All the experimental studies on the CG involved normal TMJs9,11-14 rather than pathologic joints. This does not mimic the human situation, as normal joints do not require surgical reconstruction. A reproducible sheep TMJ ankylosis model has been reported,16-19 which describes that severe articular damage and removal of the disc resulted in fibrous ankylosis in the sheep TMJ by 3 months.16 The maximal mouth opening decreased 34.4% in this model. More extensive fibrous and bony ankylosis occurred. If the joint was also immobilized or bone grafted, it would not be possible for ethical reasons to achieve full bony ankylosis of the joint, as then the animals are unable to eat. The aim of this study is to test the functional and histologic fate of a costochondral rib graft used in reconstruction of an ankylosed TMJ.

Materials and Methods Five pure-bred adult Merino sheep weighing an average of 57 kg were used. All right joints were operated on, and all left joints served as controls. Ankylosis was induced in the right TMJ by articular damage, disc removal, and placement of a bone graft.17 At 3 months, a gap arthroplasty with CG reconstruction was performed. Anesthesia was induced with intravenous injection of 500 to 1,000 mg thiopentone sodium into the external jugular vein. Intubation was performed, and anesthesia was maintained with 3% halothane/oxygen and nitrous oxide through an orotracheal tube. Jaw movements were measured vertically and laterally. The right preauricular area was shaved and prepared with antiseptic solution; the field was isolated with sterile drapes. A 4-cm vertical preauricular skin incision was made over the lateral capsule of the TMJ. The inferior joint space was then opened by a horizontal incision

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MATSUURA ET AL

FIGURE 2. Intraoperative appearance. The rib bone was placed and fixed in 2 places with 0.5-mm metal wires. T, temporal bone; R, rib bone; M, mandibular ramus). Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

through the joint capsule. The condylar articular head was excised with a fissure bur at a measured 5 mm from the articular surface. The articular layer on the temporal compartment was removed with a round and a fissure bur until bleeding was encountered. The disc was also removed. A bone graft collected from the anterior body of the mandible, approximately 8 ⫻ 6 ⫻ 3 mm in size, was placed between the temporal and condylar bone, and was fixed with 0.5-mm metal wire. The jaw also was immobilized at the same time. Debris was removed by irrigation and suction, and

then the capsule and overlying tissues were repaired in layers.17 Four hundred mg benzyl penicillin and 500 mg streptomycin sulphate were administered intramuscularly twice for 2 days. The sheep were managed in a covered animal house for 1 week after surgery, and after that in the field. Three months after the first operation, the sheep were reanesthetized. Their jaw movements were measured vertically and laterally. The right preauricular area and costal area were shaved, and the surgical fields were draped in a sterile manner. A 6-cm skin incision was made over the thirteenth rib of the right side. The costochondral bone with perichondrium was harvested from the thirteenth rib to a length of 90 mm (Fig 1). This wound was primarily closed. The preauricular incision was made along the same incision as in the first operation. The underlying layers were dissected with dissecting scissors to the TMJ. The ankylotic area was removed en bloc with fissure and round burs, and the gap arthroplasty completed. The gap was a mean 22 mm (range, 20 to 23 mm) wide. The immobilization wire suture was removed. In order to fit the graft, the posterior margin of mandibular ramus was reduced to half thickness. The rib was trimmed to a mean 69 mm length with a 2 mm cartilaginous component. The periosteum of the costochondral bone was removed only at the contact surface with the mandibular ramus. The CG

Table 1. CRITERIA AND SCORE FOR RADIOLOGICAL ASSESSMENT15,17-20

Score Items

Criteria

0 (No Change)

Shape

Change of a joint form

Erosion

Concavity in the cortical plate of a joint surface with an indistinct outline

May include reformed joint This stage in all items includes normal joint and recent surgical intervention

Sclerosis

Cortical thickening of a joint surface

Marrow

Change of underlying trabecular bone

Calcification

Development of calcification across the joint space

No calcification

1 (Mild Change)

2 (Moderate Change)

3 (Severe Change)

Destruction

Multiple osteophytes

In a third of the joint surface

In two thirds of the joint surface

Outgrowth (marginal proliferation) All over joint surface

Sclerosis in a third of the joint surface Atrophy or absorption

Sclerosis in two thirds of joint surface

Sclerosis over all joint surface

Sclerosing change in half of marrow

In a third of the joint space

In two thirds of the joint space

Sclerosing change whole marrow Bony fusion across the joint space

Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

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COSTOCHONDRAL GRAFTS IN TMJ RECONSTRUCTION

Table 2. HISTOLOGIC STAGE AND SCORE FOR THE TEMPORAL AND RAMUS STUMPS, AND THE GAP20

Stage 1 2 3 4 5 6

Temporal and Ramus Stump Bone remodeling Marrow fibrosis Downgrowth of articular soft tissue Osteophyte Complete loss of trabecular pattern Bony destruction

Score

Stage

The Gap

Score

0 1 2

1 2 3

No fibrous invasion into gap The partial fibrous invasion into the gap The partial fibrous invasion plus neovascularization into the gap

0 1 1.5 2

3 4

4

The fibrous tissue replacement into the gap

5

5

The fibrous tissue replacement plus neovascularization into the gap The fibrous cartilage formation into the gap The partial fibrous cartilage formation (1-25%) The partial fibrous cartilage formation (26-50%) The partial fibrous cartilage formation (51-75%) The partial fibrous cartilage formation (76-99%) The partial fibrous cartilage formation (100%) The calcified cartilage formation into the gap The bone formation into the gap The bone bridge formation across to the gap

6

7 8 9

2.5 3.0 3.2 3.4 3.6 3.8 4 5 6

Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

was placed in the joint space with a mean 16 mm (range, 15 to 18 mm) projection above the resection of the articular process. It was fixed in 2 places with a 0.5-mm metal wire (Fig 2). Debris was removed by irrigation and suction, and then the overlying tissues were repaired in layers. Just after lysis of ankylosis, the jaw movements were measured again, vertically and laterally. No intermaxillary fixation was used. Benzyl penicillin and streptomycin sulphate were administered intramuscularly twice for 2 days. The sheep were managed in a covered animal house for 1 week, and then returned to the field. Body weight was recorded weekly until sacrifice. We gave the same diet sheep usually eat throughout the research

Table 3. BODY WEIGHT (KG)

Sheep

Commencement of the Experiment

3 Months Ankylosis

3 Months after Reconstruction

1 2 3 4 5 Mean

57.0 59.0 66.0 59.0 44.0 57.0

49.0 51.0 57.0 50.0 41.5 49.7*

61.0 57.0 68.0 61.5 58.5 61.2*

There was no statistically significant difference (NSSD) between commencement of the experiment and 3 months ankylosis. There was a statistically significant difference between 3 months ankylosis and 3 months after reconstruction (*P ⬍ .05; Scheffe F method). There was a NSSD between commencement of the experiment and 3 months after reconstruction. Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

period, on a standard veterinary supervised diet throughout. Three months after the CG reconstruction, all sheep were sacrificed by an anesthetic overdose with pentothal. Just after sacrifice, the occlusal relation and the range of jaw movements were recorded. Immediately, the joints were removed en bloc with a band saw, and fixed in 10% neutral buffered formalin. Plain films of TMJs were radiographed laterally and anterior-posteriorly under standardized conditions. The radiographs were assessed according to the criteria for ankylotic assessment16 (Table 1). The morphologic features of shape, erosion, and sclerosis, which are each scored 0 for normal to 3 for gross deviation, respectively, were investigated for both the condyle and temporal surfaces on both laterally and anterior-posteriorly radiographs. Therefore, the maximum score was 36. Calcification of the joint space was scored in both radiographs, ranging from 0 to 6. Marrow changes of condyles were recorded in the both radiographs, ranging from 0 to 6. Marrow change of temporal surface was scored in only anterior-posterior radiograph, ranging from 0 to 3. Thus, a maximum score of 51 could be assigned to a joint. The specimens were decalcified with 9.5% hydrochloric acid 1% sodium acetate over saturated ethylenediaminetetra-acetic (EDTA). Then the TMJs were divided into 3 blocks, lateral, central, and medial segments, and were processed for histologic evaluation and stained with hematoxylin and eosin. The histologic findings were assessed microscopically. Microscopically, each histologic specimen was assessed

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Table 4. RANGE OF JAW MOVEMENTS (MM)

Vertical movement Right movement Left movement

Commencement of the Experiment

3 Months Ankylosis

At Release of Ankylosis

3 Months after Reconstruction

56.6 ⫾ 7.9* 39.6 ⫾ 3.2* 40.4 ⫾ 3.6*‡

26.8 ⫾ 3.0*† 22.0 ⫾ 3.8*‡ 14.6 ⫾ 3.8*†

55.0 ⫾ 7.7* 39.4 ⫾ 4.4* 39.6 ⫾ 4.6*‡

48.0 ⫾ 5.7† 32.8 ⫾ 2.6‡ 29.6 ⫾ 3.8†‡

Each statistically significant difference in the table shows a comparison in each time stage. In the vertical and right movements, there were statistically significant differences (SSD) between commencement of the experiment and 3 months ankylosis, between 3 months ankylosis and at release of ankylosis, and between 3 months ankylosis and 3 months after reconstruction (*P ⬍ .0001; †P ⬍ .001; ‡P ⬍ .01; Scheffe F method). There was a NSSD between commencement of the experiment and 3 months after reconstruction. In the left movement, there was a SSD between commencement of the experiment and 3 months ankylosis and between 3 months ankylosis and at release of ankylosis (*P ⬍ .0001; Scheffe F method), and between commencement of the experiment and 3 months after reconstruction, between 3 months ankylosis and 3 months after reconstruction, and between at release of ankylosis and 3 months after reconstruction (*P ⬍ .001; †P ⬍ .01; Scheffe F method). Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

at its anterior, central, and posterior aspects, therefore dividing the joint into 9 zones assessed according to the stage and score of our previous TMJ ankylosis experiment20 (Table 2). In the gap, each slide was evaluated in terms of fibrous tissue, fibrous cartilage tissue, and bone formation, within a range of 0 for normal to 6 for gross deviation. In the temporal and ramus stumps, each slide was evaluated in terms of osteophytes, downgrowth of articular soft tissue, marrow fibrosis, changes in trabecular pattern, and bony destruction in the scores of the temporal and ramus stump, within a range of 0 for normal to 5 for gross deviation. These were assessed independently of each other and were scored. Thus, the average of the maximum score was 6 in the score of the gap and 5 in the score of the temporal and ramus stumps. Further, the thickness of the temporal and condylar bone surfaces, including the cartilage layers, and the discs of the control joints were measured in each zone.

The Scheffe’s F method of one-factor analysis of variance was used to compare the body weight and the range of jaw movements over time. The MannWhitney U analysis was used to compare the histologic scores. A statistically significant difference (SSD) of .05 was used.

Results The body weight changes are shown in Table 3. All sheep decreased in weight, with a mean of 7.3 kg (range, 2.5 to 9 kg) by 3 months after the first operation. Their body weights increased, with a mean of 11.5 kg (range, 4 to 17 kg) by 3 months after the second operation. There was an SSD between 3 months ankylosis and 3 months after reconstruction (P ⬍ .05) No malocclusions developed in either group in the experimental period.

Table 5. HISTOLOGIC SCORES OF THE GAP, SHOWING MEAN AND RANGE* Anterior

Medial

Anterior

2.4 ( 1–5)

3.1 (1.5–5)

2.9 (1.5–3.4)

2.3 (1.5–3.4)

3.3 (1.5–5)

3.2 (3–3.6)

1.8 (1–2.5)

3.5 (1.5–5)

3.6 (1.5–5)

Lateral Medial

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0.4 (0–1)

0.4 (0–1)

1.1 (0–1.5)

Posterior

Posterior

Operated joint†

Control joint†

Lateral

There was a statistically significant difference between operated and control joints (†P ⬍ .001, Mann-Whitney U analysis). *Ranges are shown in parentheses. Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

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COSTOCHONDRAL GRAFTS IN TMJ RECONSTRUCTION

FIGURE 3. Radiographs of normal TMJ and operated TMJ, and the histologic sections of normal TMJ and operated TMJ. A, Normal TMJ radiograph. The articular surfaces are smooth. T; temporal bone, C; condyle. B, Operated TMJ radiograph (right/lateral). The temporal articular surface was smooth and the costochondral graft head appeared like a condylar head. T; temporal bone, CG; costochondral graft. C, Operated TMJ radiolgraph (right/lateral). The osteophyte extends upward from the temporal and graft surfaces. T, temporal bone; CG, costochondral graft; white and black arrows, osteophytes. Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

The ranges of jaw movements are shown in Table 4. The jaw movements of all sheep decreased in all directions at 3 months ankylosis (P ⬍ .0001). Immediately on release of ankylosis, the jaw movements returned to almost what they were at the commencement of the experiment (P ⬍ .0001). Three months after reconstruction, the jaw movements were more than when the joints were ankylosed (the vertical and left movements, P ⬍ .001; the right movements, P ⬍ .01), but less than at the commencement of the experiment (the vertical and right movements, no statistically significant difference [NSSD]; the left movement, P ⬍ .01) and after release of ankylosis (the vertical and right movements, NSSD; the left movement, P ⬍ .01). Radiologically, gaps were present between the temporal bone and the CG in 4 of 5 operated joints (Figs 3A,B). In 4 of 5 operated joints, the CG looked like a condylar head. In 1 of these 4, there was osteophyte on the temporal and graft surfaces (Fig 3C) and in another, there was a calcified body in the joint space.

In the remaining joint, the CG was not clear and there was moderate bone proliferation. The average of radiological scores on the operated joints was 11.8, and 1.4 in control joints. Histologically, all the CGs were well attached to the mandibular ramus. In all operated joints, the CG shape was maintained and the joint space was filled with fibrous connective tissue. There was a partial space around the CG head in 4 of 5 joints (Figs 4A-C). The graft head was covered by fibrous connective tissue and/or fibrous cartilage, with the fibrous connective tissue oriented parallel to the surface. The fibrous cartilage was observed in 4 of 5 joints. Under the fibrous cartilage, there was a layer of hyaline-like cartilage in all joints. In 1 of 5 joints, the rib cartilage cap had fractured and moved anteriorly (Fig 4D), but the cartilage cells had remained in the graft head, with an osteophyte in the anterior region of temporal bone surface. This corresponded with the joint, which radiologically showed a temporal osteophyte. In 2 of 5 joints, bony islands were present in the joint

MATSUURA ET AL

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FIGURE 4. Radiographs of operated TMJ and the histologic section of operated TMJ. A, Normal TMJ histological appearance (Hematoxylin-eosin stain, original magnification ⫻ 1.6) (right/lateral parasagittal section). The articular surface is covered by cartilage. The joint space, which consists of superior and inferior joint spaces, is separated by the disc. T, temporal bone; D, disc; C, condyle. B, Operated TMJ histological appearance (Hematoxylin-eosin stain, original magnification ⫻ 1.0) (right/lateral parasagittal section). The graft took on the appearance of the condylar head. The partial spaces are present between the condyle-like graft and the temporal bone. T, temporal bone; CG, costochondral graft; FC, fibrous cartilage; arrows, cartilage caps; big arrows, partial spaces. C, Operated TMJ histology (Hematoxylin-eosin stain, original magnification ⫻ 12.5) (right/lateral parasagittal section). At the cartilage-bone junction, the parallel columns of the chondrocytes are shown. CG, costochondral graft; HC, hyaline-like cartilage; arrows, fibrous cartilage. D, Operated TMJ histological appearance (Hematoxylin-eosin stain, original magnification ⫻ 1.0) (right/lateral parasagittal section). The rib cartilage cap was fractured and moved anteriorly. T, temporal bone; CG, costochondral graft; C, cartilage cap; F, fibrous connective tissue; arrows, osteophytes. Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

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COSTOCHONDRAL GRAFTS IN TMJ RECONSTRUCTION

Table 6. HISTOLOGIC SCORES OF THE TEMPORAL STUMP, SHOWING MEAN AND RANGE* Anterior

Medial

Anterior

0.4 (0–1)

2.4 (0–3)

1 (0–3)

1.6 (0–3)

1.8 (1–3)

1.4 (1–3)

1.2 (0–3)

1 (0–3)

0.8 (0–3)

Lateral Medial

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

Posterior

Posterior

Operated joint†

Control joint†

Lateral

There was a statistically significant difference between operated and control joints (†P ⬍ .001, Mann-Whitney U analysis). *Ranges are shown in parentheses. Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

spaces; one was detectable radiologically, but the other was not. In 3 of the control joints, thinning of the cartilage layer of the condylar surface was observed, but the thicknesses of the temporal surface, disc, and acellular fibrous layer of condylar surface were unchanged. The histologic scores of the gaps and temporal and ramus stumps are shown in Tables 5–7. In the score of the gaps (Table 5), the average score in an operated joint was 2.9 with a range of 1 to 5, and 0.2 with a range of 0 to 1.5 in the control joints. This was statistically significant (P ⬍ .001, MannWhitney U analysis). In the score of the temporal stumps (Table 6), the average score in an operated joint was 1.3 with a range of 0 to 3, and 0 in control joints. This was statistically significant (P ⬍ .001, Mann-Whitney U analysis). In the score of the ra-

mus stumps (Table 7), the average score in an operated joint was 1.0 with a range of 0 to 3, and 0.2 with a range of 0 to 1 in control joints. This was not statistically significant (P ⫽ .97, Mann-Whitney U analysis).

Discussion This study shows that the CG and gap arthroplasty reconstruction of ankylosis returned the TMJ to a near-normal state. This was shown by the return to normal of both weight and jaw movements as indicators of masticatory function. Histologically, the joint spaces were filled with the fibrous connective tissue. A gap was present around the graft head, and the fibrous connective tissue, which includes the fibrous cartilage, covered the condylar head. The origin of

Table 7. HISTOLOGIC SCORES OF THE RAMUS STUMP, SHOWING MEAN AND RANGE* Anterior

Medial

Anterior

0.3 (0–1)

2.4 (0–3)

1.6 (0–3)

0.7 (0–1)

1.6 (0–3)

0.2 (0–1)

0 (0)

2.2 (1–3)

0.2 (0–1)

Lateral Medial

0.6 (0–1)

0 (0)

( 0.2 0–1)

0.4 (0–1)

0 (0)

0 (0)

0 (0)

0.4 (0–1)

0.4 (0–1)

Posterior

Posterior

Operated joint†

Control joint†

Lateral

There was no statistically significant difference between operated and control joints. †P ⫽ .97, Mann-Whitney U analysis. *Ranges are shown in parentheses. Matsuura et al. Costochondral Grafts in TMJ Reconstruction. J Oral Maxillofac Surg 2006.

MATSUURA ET AL

fibrous cartilage is unknown. However, we assume that the hyaline cartilage of the rib changed to the fibrous cartilage by mechanical stress because the thickness of the hyaline cartilage decreased after CG reconstruction. Hence, the CG had been stabilized functionally and histologically within the sheep TMJ. This is a superior result to gap arthroplasty alone.20 These results were similar to CG in normal joints in sheep,15 and in the study using young cynomologous monkeys.11 In our previous experimental study of CG reconstruction after condylectomy,15 the jaw movements were not affected in spite of the adhesions in the inferior joint space, and a partial inferior joint space was present. No complications occurred. Therefore, it may be considered that the existence of the joint space is a functionally and histologically important factor after CG. This 3-month follow-up after reconstruction might be short because reankylosis can occur clinically in humans even after a few years. Further research with a longer observation period after reconstruction is needed to know the fate of the CG. We have had a few animals that have been allowed to go longer, and it appears that there is no difference in the 3-month group. There are significant research cost issues to longer experiments. However, our preliminary results indicate that CG seems to be a promising method for TMJ ankylosis release. In this study, cartilage fracture occurred in 1 of 5 sheep. It has been suggested that a smaller cartilage cap prevents fracture at the costochondral junction and may also play a role in diminishing the potential for overgrowth of the graft.21 Most reports describe a cartilage length ranging from 0.5 to 2.5 cm.6,22 Hence, in this study, we used a CG with 2 mm of cartilage, and the rib bone projected 80% into the gap. This study concludes that in the short term, a CG with gap arthroplasty is an effective way of reconstructing ankylosed temporomandibular joints in the sheep model.

References 1. Kaban LB, Perrott DH, Fisher K: A protocol for management of temporomandibular joint ankylosis. J Oral Maxillofac Surg 48: 1145, 1990

1525 2. Lindqvist C, Pihakari A, Tasanen A, et al: Autogenous costochondral grafts in temporo-mandibular joint arthroplasty. A survey of 66 arthroplasties in 60 patients. J Maxillofac Surg 14:143, 1986 3. Munro IR, Chen YR, Park BY: Simultaneous total correction of temporomandibular ankylosis and facial asymmetry. Plast Reconstr Surg 77:517, 1986 4. Topazian RG: Comparison of gap and interposition arthroplasty in the treatment of temporomandibular joint ankylosis. J Oral Surg 24:405, 1966 5. Miller GA, Page HL Jr, Griffith CR: Temporomandibular joint ankylosis: Review of the literature and report of two cases of bilateral involvement. J Oral Surg 33:792, 1975 6. Ware WH, Brown SL: Growth centre transplantation to replace mandibular condyles. J Maxillofac Surg 9:50, 1981 7. Caldwell JB: Surgical management of temporomandibular joint ankylosis in children. Int J Oral Surg 7:354, 1978 8. Merkx MA, Freihofer HP: Fracture of costochondral graft in temporomandibular joint reconstructive surgery: An unexpected complication. Int J Oral Maxillofac Surg 24:142, 1995 9. Perrott DH, Vargervik K, Kaban LB: Costochondral reconstruction of mandibular condyles in nongrowing primates. J Craniofac Surg 6:227, 1995 10. Bruns J, Meyer-Pannwitt U, Silbermann M: The rib perichondrium. An anatomical study in sheep of a tissue used as transplant in the treatment of hyaline-cartilage defects. Acta Anat (Basel) 144:258, 1992 11. Ware WH, Taylor RC: Cartilaginous growth centers transplanted to replace mandibular condyles in monkeys. J Oral Surg 24:33, 1966 12. Poswillo D: Experimental reconstruction of the mandibular joint. Int J Oral Surg 3:400, 1974 13. Peltomaki T: Growth of a costochondral graft in the rat temporomandibular joint. J Oral Maxillofac Surg 50:851, 1992 14. Daniels S, Ellis ED, Carlson DS: Histologic analysis of costochondral and sternoclavicular grafts in the TMJ of the juvenile monkey. J Oral Maxillofac Surg 45:675, 1987 15. Matsuura H, Miyamoto H, Ishimaru J-I, et al: Costochondral grafts in reconstruction of the temporomandibular joint after condylectomy: An experimental study in sheep. Br J Oral Maxillofac Surg 39:189, 2001 16. Miyamoto H, Kurita K, Ishimaru J, et al: A sheep model for temporomandibular joint ankylosis. J Oral Maxillofac Surg 57: 812, 1999 17. Miyamoto H, Kurita K, Ogi N, et al: The effect of an intraarticular bone fragment in the genesis of temporomandibular joint ankylosis. Int J Oral Maxillofac Surg 29:290, 2000 18. Miyamoto H, Kurita K, Ogi N, et al: The role of the disk in sheep temporomandibular joint ankylosis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 88:151, 1999 19. Miyamoto H, Kurita K, Ogi N, et al: Effect of limited jaw motion on ankylosis of the temporomandibular joint in sheep. Br J Oral Maxillofac Surg 38:148, 2000 20. Matsuura H, Miyamoto H, Ogi N, et al: The effect of gap arthroplasty on temporomandibular joint ankylosis: An experimental study. Int J Oral Maxillofac Surg 30:431, 2001 21. Tideman H, Doddridge M: Temporomandibular joint ankylosis. Aust Dent J 32:171, 1987 22. Kaban LB, Perrott DH: Discussion. Unpredictable growth pattern of costochondral graft. Plast Reconstr Surg 90:887, 1992