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Pathological changes after the surgical creation of a vertical intracapsular condylar fracture
Int. J. Oral Maxillofac. Surg. 2007; 36: 834–837 doi:10.1016/j.ijom.2007.06.002, available online at http://www.sciencedirect.com
Research Paper Trauma
Pathological changes after the surgical creation of a vertical intracapsular condylar fracture
X. Long1, A. N. Goss2 1 Department of Oral and Maxillofacial Surgery, Key Lab for Oral Biomedical Engineering of Ministry of Education, School and Hospital of Stomatology, Wuhan University, PR China; 2Oral and Maxillofacial Surgery Unit, The University of Adelaide, Australia
X. Long, A. N. Goss: Pathological changes after the surgical creation of a vertical intracapsular condylar fracture. Int. J. Oral Maxillofac. Surg. 2007; 36: 834–837. # 2007 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Abstract. The aim of this study was to create in a sheep model an intracapsular oblique vertical split fracture, and observe the histopathological changes in the temporomandibular joint (TMJ) condylar head. In 10 sheep, the right TMJ was operated through the preauricular region. The anterior and posterior attachments of the disc were cut; an oblique vertical osteotomy was made from the lateral pole of the condyle to the medial side of condylar neck. The condylar fragment was pushed anteriorly, inferiorly and medially together with the disc. The non-operated left TMJ served as control. Two sheep were killed at 1 week and four at both 4 and 12 weeks. Computed tomography scans were taken and histopathological changes of the joint observed. There was severe bone erosion and a new bony outgrowth on the lateral side of the condylar stump and temporal bone. The joint spaces were filled with fibrous tissue, cartilage tissue and bone in the 4 and 12 weeks operated groups. These results show that an oblique vertical intracapsular fracture through the lateral condylar pole, combined with an anteriorly and medially displaced condylar fragment and disc and damaged lateral capsule, are likely to result in the pathological changes of osteoarthritis, and the progressive development of ankylosis in a sheep TMJ.
The classification, diagnosis and management of condylar fractures is controversial5,28,30. They may be divided into condylar head, condylar neck and subcondylar region types according to the anatomic location of the fracture11. Other authors have classified condylar fractures as intracapsular, high condylar neck or low condylar neck8. There are three types of intracapsular fracture: type A, fractures pass through the medial condylar pole; type B, fractures pass through the 0901-5027/090834 + 04 $30.00/0
lateral condylar pole with loss of vertical height of the mandibular ramus; and type M, multiple fragments or comminuted fractures20. The complications of a condylar fracture are pain, restricted mandibular movement, muscle spasm, deviation of the mandible, malocclusion, pathological changes in the temporomandibular joint (TMJ), osteonecrosis, facial asymmetry and ankylosis, irrespective of whether surgical treatment is performed or not5,6–8,11,12,21,22,24–28,30.
Key words: vertical intracapsular condylar fracture; pathological change; ankylosis; animal model. Accepted for publication 26 June 2007 Available online 4 September 2007
Condylar fracture experimental studies have included unilateral and bilateral condylectomy, condylar neck fracture, subcondylar fracture, and removal of the disc to observe the TMJ changes, ankylosis and facial asymmetry13,15,19,23,26. These animal studies do not help to define the relationship between the different types of intracapsular condylar fracture and TMJ changes. The aim of this study was to create an intracapsular oblique vertical split fracture and observe the
# 2007 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Vertical intracapsular condylar fracture pathological changes in the sheep TMJ condylar head. Material and methods
The animals used in this study were 10 2year-old adult Merino male sheep. The study was conducted in accordance with the ethical requirement of South Australia9. The animals were monitored for their general condition and eating behavior. The sheep were divided into three groups, with two in the 1-week group, and four each in the 4-week and 12-week groups. The right side of the TMJ was the experimental side and the left side unoperated to serve as control. General anaesthesia was induced with an intravenous injection of 20 mg/kg thiopentone. The sheep was then intubated and connected to the anaesthetic machine on 2% halothane with an oxygen flow rate of 4 ml. Penicillin 25 mg/kg and ketoprofen 2.75 mg/kg were given intramuscularly after the sheep had been anaesthetized and immediately before surgery. Each sheep was positioned on the left side, the preauricular and temporal regions were shaved and then the right preauricular region prepared with povodine iodine. The surgical field was isolated with sterile drapes. A 4-cm curved preauricular skin incision was made exposing the zygomatic arch and panniculosus carnosus muscle to the surface of the TMJ capsule after elevating the skin flap. The capsule of the TMJ was exposed by blunt dissection and the inferior joint space was then opened by a horizontal incision through the capsule at the condylar neck. The condylar head was isolated with a periosteal elevator. The superior joint space was exposed by separation of the lateral attachment of the disc through the inferior joint space. The anterior and posterior attachments of the disc were cut. An oblique vertical osteotomy was made from the lateral pole of the condyle to the medial side of the condylar neck. The fragment of condyle was pushed anteriorly, inferiorly and medially together with the disc. The lateral side of the condylar stump was sutured at the outside of the capsule. The capsule was not sutured and the wound was closed in layers. Six hours after operation, the sheep was given a dose of 1.3 mg/kg ketopronfen and 20 mg/kg penicillin. Analgesia and antibiotics were maintained for 3 days. The experimental sheep were killed at times according to their group. The joints were removed en bloc using a band saw. The TMJ blocks were fixed in 10% neutral buffered formaldehyde for histological
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study. A computed tomography (CT) scan was taken before decalcification with a GE light speed 16-slice CT scanner, 120 kV, 80 mA, 0.8 s rotation time and 0.625 mm slice thickness. All the TMJ blocks were fixed in 10% formalin and decalcified in 10% formic acid, and were then embedded in paraffin blocks. Serial sections 5 mm thick were stained with haematoxylin and eosin for histologic examination. Results
There was a clear fracture line from the lateral pole of the condyle to the medial side of the condylar neck in the posterior part of the condyle and the antero-medially displaced fragment in the 1-week operated group compared to the control group in the coronal CT images (Fig. 1a and b). Erosive articular surfaces of the fractured condyle were visible and a bony outgrowth appeared in the lateral aspect of the condyle and bone fragments in the 4week operated group (Fig. 2). In the 12week operated group, there was new bone formation at the lateral aspect of the condyle and temporal bone. Bony consolidation had taken place and condylar fragments were connected to the ramus with bony tissue (Fig. 3). Histologically, there was a joint space between the temporal bone and condylar
Fig. 1. (A) CT showing normal TMJ structure; (B) 1 week after operation, CT showing a clear fracture line in the posterior part of the condyle. T: temporal bone, C: condyle.
Fig. 2. Four weeks after operation. CT shows erosive articular surfaces and a bony outgrowth arising from the lateral aspect of the condyle. T: temporal bone, C: condylar stump.
stump and fragment in the 1-week operated group compared to the unoperated sides. The pathological changes included erosion of the articular surface, osteophytes and outgrowth formation of the condylar stumps. The joint spaces were filled with fibrous tissue and there were bone resorption and some new bone formations on both the temporal bone and condylar stump at 4 weeks, but there was very narrow residual space in all joints (Fig. 4). All four joints had irregular new bone formation on the temporal and condylar bone. There were no joint space between the temporal bone and condylar stump in the 12-week operated group. The joint spaces were completely filled with fibrous tissue, cartilage tissue and bone (Fig. 5). There were no histological changes in the left control joints.
Fig. 3. Twelve weeks after operation. CT shows erosive articular surfaces and a bony outgrowth arising from the lateral aspect of the condyle and fossa. There is partial fibrous ankylosis between the condylar stump and fossa. T: temporal bone, C: condylar stump.
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Fig. 4. Four weeks. The joint space is filled with fibrous tissue with only a narrow residual joint space (arrow). The temporal and condylar bone surfaces show resorption and new bone formation. T: temporal bone, C: condylar stump. Haematoxylin & eosin stain, original magnification 0.8.
Discussion
In the present study, an animal model was created of an oblique vertical condylar head fracture. There were degenerative changes and TMJ ankylosis progressively developed between the condylar stump and temporal bone in the surgical groups. The coronal CT scans showed marked degenerative changes in the 4- and 12week operated groups. There was new bone formation on the lateral aspect of the condyle and temporal bone. Bony consolidation had taken place and condylar fragments were connected to the ramus with bony tissue at 12 weeks. Histological examination showed that the contour of
the condylar stump, condylar fragment and temporal bone had progressively changed in all surgical groups. There were severe bone erosion and new bony outgrowth in the lateral side of the condylar stump. The joint space became narrow and indistinct at 4 and 12 weeks. There have been many animal experiments on condylar fractures. The aim of most studies was to create condylar neck, subcondylar or intracapsular condylar fractures, and remove the disc to observe the complications of ankylosis and facial asymmetry. MARKEY et al.13 created an intracapsular condylar fracture surgically in young monkeys followed by prolonged intermaxillary fixation to observe the
Fig. 5. Twelve weeks. The joint space is filled with mature fibrous connective tissue. There is marked resorption and new bone formed on both temporal and condylar surfaces. T: temporal bone, C: condylar stump, arrows: new bone. Haematoxylin & eosin stain, original magnification 0.8.
facial asymmetry and TMJ ankylosis. This experiment showed no evidence of ankylosis or significant limitation of jaw movement. Most intracapsular condylar fracture animal models were made by a horizontal cut at the condylar head. MIYAMOTO et al.17 removed the articular layer on the temporal compartment, the condylar articular surface and the disc, with the jaw movements being limited by a wire. They found that limitation of jaw motion hastened the progress of TMJ ankylosis in sheep. WANG et al.29 created a sagittal fracture of the mandibular condyle in immature miniature pigs. They exposed the lower cavity of the TMJ, the mandibular condyle was vertically split into two along its inner one third, and the medial part of the fractured condyle was dislocated. Histological finding showed that disc and condyle adhesion occurred and a bifid condyle was formed. Sagittal or vertical fractures of the mandibular condyle and chip fractures of the medial part of the condylar head are rarely reported after examination of conventional radiographs but more commonly with CT examination1,2,14,28. HLA7 WITSCHKA & ECKELT evaluated 40 patients with 50 intracapsular fractures of the mandibular condyle, with follow up for an average of 22 weeks after closed treatment. Clinical examination showed that mouth opening was only slightly less favourable compared to average values in healthy subjects. In contrast, protrusion and mediotrusion of the mandible were significantly impeded. Radiological examination found that the type B and M fractures resulted in the most marked pathologic changes. The poor functional and radiological results encountered with these fracture types showed the limitations of closed functional treatment. In this study, an oblique vertical osteotomy was made from the lateral pole of the condyle to the medial side of the condylar neck in sheep. The anterior and posterior attachments of the disc were cut. The fragment of condyle was pushed anteriorly, inferiorly and medially together with the disc, and the lateral side of the condylar stump was sutured at the outside of the capsule to limit jaw movement. This kind of animal model is similar to a type B intracapsular fracture in humans. There were severe pathological changes in the operated TMJ at 4 and 12 weeks, including erosion of the articular surface, osteophytes and outgrowth formation of the condylar stumps. The joint spaces filled with fibrous tissue, cartilage tissue and bone. CASCONE et al.4 reported two cases of intracapsular condylar fracture: histological study of the condylar specimens revealed signs of
Vertical intracapsular condylar fracture osteoarthrosis of the articular surface and chondroid metaplasia of the bilaminar zone with early onset of ankylosis. TOYAMA et al.27 suggested that coronal CT scans delineating erosive articular surfaces and a bony outgrowth arising from the tuber over the lateral aspect of the condyle indicated early fibrous ankylosis of the bilateral TMJs and the initial stage of bony ankylotic changes in the left TMJ. The TMJ disc plays an important role as a barrier preventing ankylosis10,16. MIYA18 MOTO et al. reported an animal model of unilateral mandibular condylectomy. The condyle was excised 5 mm from the top of the articular surface and the disc was left intact. All four condylar heads were completely reformed medially 3 months postoperatively. The reformed condylar cartilage was irregular, but usually displayed four layers. Damaged or displaced discs allow progression of ankylosis31. BJORNLAND & HAANAES3 demonstrated minor to major changes in 12 of 14 monkey TMJs after discectomy. The most serious changes were seen in three joints with fibrous ankylosis, and five joints showed marked destruction of the articular cartilage. It is concluded that a vertical intracapsular fracture through the lateral condylar pole, combined with an anteriorly and medially displaced condylar fragment and disc and damaged lateral capsule, is likely to result in osteoarthritic changes. Fibrous adhesions developed across the joint space. This was consistent with histologic changes seen in a series of ankylosis experiments15– 18 . With this type of injury, the probability that ankylosis will occur is high. References 1. Antoniades K, Karakasis D, Elephtheriades J. Bifid mandibular condyle resulting from a sagittal fracture of the condylar head. Br J Oral Maxillofac Surg 1993: 31: 124–126. 2. Avrahami E, Horowitz I. Chip fractures of the mandibular condyle. Head Neck Surg 1984: 6: 978–981. 3. Bjornland T, Haanaes HR. Discectomy of the temporomandibular joint: an experimental study in monkeys. J Craniomaxillofac Surg 1999: 27: 113–116. 4. Cascone P, Leonardi R, Marino S, Carnemolla ME. Intracapsular fractures of mandibular condyle: diagnosis, treatment, and anatomical and pathological evaluations. J Craniofac Surg 2003: 14: 184–191. 5. Choi BH. Magnetic resonance imaging of the temporomandibular joint after functional treatment of bilateral condylar fractures in adults. Int J Oral Maxillofac Surg 1997: 26: 344–347.
6. Ellis III E, Throckmorton GS. Treatment of mandibular condylar process fractures: biological considerations. J Oral Maxillofac Surg 2005: 63: 115–134. 7. Hlawitschka M, Eckelt U. Assessment of patients treated for intracapsular fractures of the mandibular condyle by closed techniques. J Oral Maxillofac Surg 2002: 60: 784–791. 8. Hovinga J, Boering G, Stegenga B. Long-term results of nonsurgical management of condylar fractures in children. Int J Oral Maxillofac Surg 1999: 28: 429– 450. 9. Ishimaru J, Goss AN. A model for osteoarthritis of the temporomandibular joint. J Oral Maxillofac Surg 1992: 50: 1191–1195. 10. Long X, Li X, Cheng Y, Yang X, Qin L, Qiao Y, Deng M. Preservation of disc for treatment of traumatic temporomandibular joint ankylosis. J Oral Maxillofac Surg 2005: 63: 897–902. 11. Marker P, Nielsen A, Bastian HL. Fractures of the mandibular condyle. Part 1: Patterns of distribution of types and causes of fractures in 348 patients. Br J Oral Maxillofac Surg 2000: 38: 417–421. 12. Marker P, Nielsen A, Bastian HL. Fractures of the mandibular condyle. Part 2: Results of treatment of 348 patients. Br J Oral Maxillofac Surg 2000: 38: 422–426. 13. Markey RJ, Potter BE, Moffett BC. Condylar trauma and facial asymmetry: an experimental study. J Maxillofac Surg 1980: 8: 38–51. 14. McDonnell DG, Masterson J, Barry HJ, Browne A. The use of two-dimensional CT reconstruction to demonstrate a vertical fracture of the condylar head. Dentomaxillofac Radiol 1990: 19: 34–36. 15. Miyamoto H, Kurita K, Ishimaru J-I, Goss AN. A sheep model for temporomandibular joint ankylosis. J Oral Maxillofac Surg 1999: 57: 812–817. 16. Miyamoto H, Kurita K, Ogi N, Ishimaru JI, Goss AN. The role of the disk in sheep temporomandibular joint ankylosis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999: 88: 151–158. 17. Miyamoto H, Kurita K, Ogi N, Ishimaru JI, Goss AN. Effect of limited jaw motion on ankylosis of temporomandibular joint in sheep. Br J Oral Maxillofac Surg 2000: 38: 148–153. 18. Miyamoto H, Shigematsu H, Suzuki S, Sakashita H. Regeneration of mandibular condyle following unilateral condylectomy in canines. J Craniomaxillofac Surg 2004: 32: 296–302. 19. Monje F, Delgado E, Navarro MJ, Miralles C, Alonso del Hoyo JR. Changes in temporomandibular joint after mandibular subcondylar osteotomy: an experimental study in rats. J Oral Maxillofac Surg 1993: 51: 1221–1234. 20. NEFF A, KOLK A, DEPPE H, HORCH HH. New aspects for indications of surgical management of intra-articular and high temporomandibular dislocation fractures.
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Mund Kiefer Gesichtschir 1999: 3: 24– 29. Newmann L. A clinical evaluation of the long-term outcome of patients treated for bilateral fracture of the mandibular condyles. Br J Oral Maxillofac Surg 1998: 36: 176–179. Oikarinen KS, Raustia AM, Lahti J. Signs and symptoms of TMJ dysfunction in patients with mandibular condyle fractures. J Craniomandib Pract 1991: 9: 58– 62. Oztan HY, Ulusal BG, Aytemiz C. The role of trauma on temporomandibular joint ankylosis and mandibular growth retardation: an experimental study. J Craniofac Surg 2004: 15: 274–282. Sanders B, McKelvy B, Adams D. Aseptic osteomyelitis and necrosis of the mandibular condylar head after intracapsular fracture. Oral Surg Oral Med Oral Pathol 1977: 43: 665–670. Silvennoinen U, Raustia AM, Lindqvist C, Oikarinen K. Occlusal and temporomandibular joint disorders in patients with unilateral condylar fracture. A prospective one-year study. Int J Oral Maxillofac Surg 1998: 27: 280–285. Teixeira AC, Luz JG, Araujo VC, Araujo NS. Healing of the displaced condylar process fracture: an experimental study. J Craniomaxillofac Surg 1998: 26: 326–330. Toyama K, Kurita K, Koga N, Ogi M. Ankylosis of the temporomandibular joint developing shortly after multiple facial fractures. Int J Oral Maxillofac Surg 2003: 32: 360–362. Villarreal PM, Monje F, Junquera LM, Mateo J, Morillo AJ, Gonzalez C. Mandibular condyle fractures: determinants of treatment and outcome. J Oral Maxillofac Surg 2004: 62: 155–163. Wang Y, Wang Y, Yao J, Zhou J, Hu M, Liu H. Experimental study of sagittal fracture of the mandibular condyle. Chin J Dent Res 1999: 2: 38–43. Yamaoka M, Furusawa K, Iguchi K, Tanaka M, Okuda D. The assessment of fracture of the mandibular condyle by use of computerized tomography. Incidence of sagittal split fracture. Br J Oral Maxillofac Surg 1994: 32: 77–79. Yucel H, Ulusal BG, Aytemiz C. The role of trauma on temporomandibular joint ankylosis and mandibular growth retardation. J Craniofac Surg 2004: 15: 274–282.
Address: Xing Long Department of Oral Maxillofacial Surgery Key Lab for Oral Biomedical Engineering of Ministry of Education School and Hospital of Stomatology Wuhan University Wuhan Hubei 430079 PR China Tel: +86 27 87646312 E-mail: [email protected]
Research Paper Trauma
Pathological changes after the surgical creation of a vertical intracapsular condylar fracture
X. Long1, A. N. Goss2 1 Department of Oral and Maxillofacial Surgery, Key Lab for Oral Biomedical Engineering of Ministry of Education, School and Hospital of Stomatology, Wuhan University, PR China; 2Oral and Maxillofacial Surgery Unit, The University of Adelaide, Australia
X. Long, A. N. Goss: Pathological changes after the surgical creation of a vertical intracapsular condylar fracture. Int. J. Oral Maxillofac. Surg. 2007; 36: 834–837. # 2007 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Abstract. The aim of this study was to create in a sheep model an intracapsular oblique vertical split fracture, and observe the histopathological changes in the temporomandibular joint (TMJ) condylar head. In 10 sheep, the right TMJ was operated through the preauricular region. The anterior and posterior attachments of the disc were cut; an oblique vertical osteotomy was made from the lateral pole of the condyle to the medial side of condylar neck. The condylar fragment was pushed anteriorly, inferiorly and medially together with the disc. The non-operated left TMJ served as control. Two sheep were killed at 1 week and four at both 4 and 12 weeks. Computed tomography scans were taken and histopathological changes of the joint observed. There was severe bone erosion and a new bony outgrowth on the lateral side of the condylar stump and temporal bone. The joint spaces were filled with fibrous tissue, cartilage tissue and bone in the 4 and 12 weeks operated groups. These results show that an oblique vertical intracapsular fracture through the lateral condylar pole, combined with an anteriorly and medially displaced condylar fragment and disc and damaged lateral capsule, are likely to result in the pathological changes of osteoarthritis, and the progressive development of ankylosis in a sheep TMJ.
The classification, diagnosis and management of condylar fractures is controversial5,28,30. They may be divided into condylar head, condylar neck and subcondylar region types according to the anatomic location of the fracture11. Other authors have classified condylar fractures as intracapsular, high condylar neck or low condylar neck8. There are three types of intracapsular fracture: type A, fractures pass through the medial condylar pole; type B, fractures pass through the 0901-5027/090834 + 04 $30.00/0
lateral condylar pole with loss of vertical height of the mandibular ramus; and type M, multiple fragments or comminuted fractures20. The complications of a condylar fracture are pain, restricted mandibular movement, muscle spasm, deviation of the mandible, malocclusion, pathological changes in the temporomandibular joint (TMJ), osteonecrosis, facial asymmetry and ankylosis, irrespective of whether surgical treatment is performed or not5,6–8,11,12,21,22,24–28,30.
Key words: vertical intracapsular condylar fracture; pathological change; ankylosis; animal model. Accepted for publication 26 June 2007 Available online 4 September 2007
Condylar fracture experimental studies have included unilateral and bilateral condylectomy, condylar neck fracture, subcondylar fracture, and removal of the disc to observe the TMJ changes, ankylosis and facial asymmetry13,15,19,23,26. These animal studies do not help to define the relationship between the different types of intracapsular condylar fracture and TMJ changes. The aim of this study was to create an intracapsular oblique vertical split fracture and observe the
# 2007 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Vertical intracapsular condylar fracture pathological changes in the sheep TMJ condylar head. Material and methods
The animals used in this study were 10 2year-old adult Merino male sheep. The study was conducted in accordance with the ethical requirement of South Australia9. The animals were monitored for their general condition and eating behavior. The sheep were divided into three groups, with two in the 1-week group, and four each in the 4-week and 12-week groups. The right side of the TMJ was the experimental side and the left side unoperated to serve as control. General anaesthesia was induced with an intravenous injection of 20 mg/kg thiopentone. The sheep was then intubated and connected to the anaesthetic machine on 2% halothane with an oxygen flow rate of 4 ml. Penicillin 25 mg/kg and ketoprofen 2.75 mg/kg were given intramuscularly after the sheep had been anaesthetized and immediately before surgery. Each sheep was positioned on the left side, the preauricular and temporal regions were shaved and then the right preauricular region prepared with povodine iodine. The surgical field was isolated with sterile drapes. A 4-cm curved preauricular skin incision was made exposing the zygomatic arch and panniculosus carnosus muscle to the surface of the TMJ capsule after elevating the skin flap. The capsule of the TMJ was exposed by blunt dissection and the inferior joint space was then opened by a horizontal incision through the capsule at the condylar neck. The condylar head was isolated with a periosteal elevator. The superior joint space was exposed by separation of the lateral attachment of the disc through the inferior joint space. The anterior and posterior attachments of the disc were cut. An oblique vertical osteotomy was made from the lateral pole of the condyle to the medial side of the condylar neck. The fragment of condyle was pushed anteriorly, inferiorly and medially together with the disc. The lateral side of the condylar stump was sutured at the outside of the capsule. The capsule was not sutured and the wound was closed in layers. Six hours after operation, the sheep was given a dose of 1.3 mg/kg ketopronfen and 20 mg/kg penicillin. Analgesia and antibiotics were maintained for 3 days. The experimental sheep were killed at times according to their group. The joints were removed en bloc using a band saw. The TMJ blocks were fixed in 10% neutral buffered formaldehyde for histological
835
study. A computed tomography (CT) scan was taken before decalcification with a GE light speed 16-slice CT scanner, 120 kV, 80 mA, 0.8 s rotation time and 0.625 mm slice thickness. All the TMJ blocks were fixed in 10% formalin and decalcified in 10% formic acid, and were then embedded in paraffin blocks. Serial sections 5 mm thick were stained with haematoxylin and eosin for histologic examination. Results
There was a clear fracture line from the lateral pole of the condyle to the medial side of the condylar neck in the posterior part of the condyle and the antero-medially displaced fragment in the 1-week operated group compared to the control group in the coronal CT images (Fig. 1a and b). Erosive articular surfaces of the fractured condyle were visible and a bony outgrowth appeared in the lateral aspect of the condyle and bone fragments in the 4week operated group (Fig. 2). In the 12week operated group, there was new bone formation at the lateral aspect of the condyle and temporal bone. Bony consolidation had taken place and condylar fragments were connected to the ramus with bony tissue (Fig. 3). Histologically, there was a joint space between the temporal bone and condylar
Fig. 1. (A) CT showing normal TMJ structure; (B) 1 week after operation, CT showing a clear fracture line in the posterior part of the condyle. T: temporal bone, C: condyle.
Fig. 2. Four weeks after operation. CT shows erosive articular surfaces and a bony outgrowth arising from the lateral aspect of the condyle. T: temporal bone, C: condylar stump.
stump and fragment in the 1-week operated group compared to the unoperated sides. The pathological changes included erosion of the articular surface, osteophytes and outgrowth formation of the condylar stumps. The joint spaces were filled with fibrous tissue and there were bone resorption and some new bone formations on both the temporal bone and condylar stump at 4 weeks, but there was very narrow residual space in all joints (Fig. 4). All four joints had irregular new bone formation on the temporal and condylar bone. There were no joint space between the temporal bone and condylar stump in the 12-week operated group. The joint spaces were completely filled with fibrous tissue, cartilage tissue and bone (Fig. 5). There were no histological changes in the left control joints.
Fig. 3. Twelve weeks after operation. CT shows erosive articular surfaces and a bony outgrowth arising from the lateral aspect of the condyle and fossa. There is partial fibrous ankylosis between the condylar stump and fossa. T: temporal bone, C: condylar stump.
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Fig. 4. Four weeks. The joint space is filled with fibrous tissue with only a narrow residual joint space (arrow). The temporal and condylar bone surfaces show resorption and new bone formation. T: temporal bone, C: condylar stump. Haematoxylin & eosin stain, original magnification 0.8.
Discussion
In the present study, an animal model was created of an oblique vertical condylar head fracture. There were degenerative changes and TMJ ankylosis progressively developed between the condylar stump and temporal bone in the surgical groups. The coronal CT scans showed marked degenerative changes in the 4- and 12week operated groups. There was new bone formation on the lateral aspect of the condyle and temporal bone. Bony consolidation had taken place and condylar fragments were connected to the ramus with bony tissue at 12 weeks. Histological examination showed that the contour of
the condylar stump, condylar fragment and temporal bone had progressively changed in all surgical groups. There were severe bone erosion and new bony outgrowth in the lateral side of the condylar stump. The joint space became narrow and indistinct at 4 and 12 weeks. There have been many animal experiments on condylar fractures. The aim of most studies was to create condylar neck, subcondylar or intracapsular condylar fractures, and remove the disc to observe the complications of ankylosis and facial asymmetry. MARKEY et al.13 created an intracapsular condylar fracture surgically in young monkeys followed by prolonged intermaxillary fixation to observe the
Fig. 5. Twelve weeks. The joint space is filled with mature fibrous connective tissue. There is marked resorption and new bone formed on both temporal and condylar surfaces. T: temporal bone, C: condylar stump, arrows: new bone. Haematoxylin & eosin stain, original magnification 0.8.
facial asymmetry and TMJ ankylosis. This experiment showed no evidence of ankylosis or significant limitation of jaw movement. Most intracapsular condylar fracture animal models were made by a horizontal cut at the condylar head. MIYAMOTO et al.17 removed the articular layer on the temporal compartment, the condylar articular surface and the disc, with the jaw movements being limited by a wire. They found that limitation of jaw motion hastened the progress of TMJ ankylosis in sheep. WANG et al.29 created a sagittal fracture of the mandibular condyle in immature miniature pigs. They exposed the lower cavity of the TMJ, the mandibular condyle was vertically split into two along its inner one third, and the medial part of the fractured condyle was dislocated. Histological finding showed that disc and condyle adhesion occurred and a bifid condyle was formed. Sagittal or vertical fractures of the mandibular condyle and chip fractures of the medial part of the condylar head are rarely reported after examination of conventional radiographs but more commonly with CT examination1,2,14,28. HLA7 WITSCHKA & ECKELT evaluated 40 patients with 50 intracapsular fractures of the mandibular condyle, with follow up for an average of 22 weeks after closed treatment. Clinical examination showed that mouth opening was only slightly less favourable compared to average values in healthy subjects. In contrast, protrusion and mediotrusion of the mandible were significantly impeded. Radiological examination found that the type B and M fractures resulted in the most marked pathologic changes. The poor functional and radiological results encountered with these fracture types showed the limitations of closed functional treatment. In this study, an oblique vertical osteotomy was made from the lateral pole of the condyle to the medial side of the condylar neck in sheep. The anterior and posterior attachments of the disc were cut. The fragment of condyle was pushed anteriorly, inferiorly and medially together with the disc, and the lateral side of the condylar stump was sutured at the outside of the capsule to limit jaw movement. This kind of animal model is similar to a type B intracapsular fracture in humans. There were severe pathological changes in the operated TMJ at 4 and 12 weeks, including erosion of the articular surface, osteophytes and outgrowth formation of the condylar stumps. The joint spaces filled with fibrous tissue, cartilage tissue and bone. CASCONE et al.4 reported two cases of intracapsular condylar fracture: histological study of the condylar specimens revealed signs of
Vertical intracapsular condylar fracture osteoarthrosis of the articular surface and chondroid metaplasia of the bilaminar zone with early onset of ankylosis. TOYAMA et al.27 suggested that coronal CT scans delineating erosive articular surfaces and a bony outgrowth arising from the tuber over the lateral aspect of the condyle indicated early fibrous ankylosis of the bilateral TMJs and the initial stage of bony ankylotic changes in the left TMJ. The TMJ disc plays an important role as a barrier preventing ankylosis10,16. MIYA18 MOTO et al. reported an animal model of unilateral mandibular condylectomy. The condyle was excised 5 mm from the top of the articular surface and the disc was left intact. All four condylar heads were completely reformed medially 3 months postoperatively. The reformed condylar cartilage was irregular, but usually displayed four layers. Damaged or displaced discs allow progression of ankylosis31. BJORNLAND & HAANAES3 demonstrated minor to major changes in 12 of 14 monkey TMJs after discectomy. The most serious changes were seen in three joints with fibrous ankylosis, and five joints showed marked destruction of the articular cartilage. It is concluded that a vertical intracapsular fracture through the lateral condylar pole, combined with an anteriorly and medially displaced condylar fragment and disc and damaged lateral capsule, is likely to result in osteoarthritic changes. Fibrous adhesions developed across the joint space. This was consistent with histologic changes seen in a series of ankylosis experiments15– 18 . With this type of injury, the probability that ankylosis will occur is high. References 1. Antoniades K, Karakasis D, Elephtheriades J. Bifid mandibular condyle resulting from a sagittal fracture of the condylar head. Br J Oral Maxillofac Surg 1993: 31: 124–126. 2. Avrahami E, Horowitz I. Chip fractures of the mandibular condyle. Head Neck Surg 1984: 6: 978–981. 3. Bjornland T, Haanaes HR. Discectomy of the temporomandibular joint: an experimental study in monkeys. J Craniomaxillofac Surg 1999: 27: 113–116. 4. Cascone P, Leonardi R, Marino S, Carnemolla ME. Intracapsular fractures of mandibular condyle: diagnosis, treatment, and anatomical and pathological evaluations. J Craniofac Surg 2003: 14: 184–191. 5. Choi BH. Magnetic resonance imaging of the temporomandibular joint after functional treatment of bilateral condylar fractures in adults. Int J Oral Maxillofac Surg 1997: 26: 344–347.
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Address: Xing Long Department of Oral Maxillofacial Surgery Key Lab for Oral Biomedical Engineering of Ministry of Education School and Hospital of Stomatology Wuhan University Wuhan Hubei 430079 PR China Tel: +86 27 87646312 E-mail: [email protected]