Armamentarium

History of the Procedure

Bone is an organ that is constantly undergoing remodeling by resorption with osteoclasts and bone formation by osteoblasts. A proper balance is necessary for continued bone development. Interruption of this cycle can lead to altered bone anatomy in addition to osteoporosis or osteosclerosis. The recently discovered progressive ankylosis gene (ANK) encodes a transmembrane protein that transports intracellular pyrophosphate to the extracellular milieu. This is necessary for mineralization of bone. Human mutations in ANK have been discovered that lead to craniometaphyseal dysplasia with resultant thickening of craniofacial bone. Recent studies in a murine model of ANK-deficient mice showed delayed osteoblastogenic and osteoclastogenic differentiation. The exact role and signaling pathways by which this occurs is unknown but is the subject of current research. Nevertheless, the ANK gene is one that might be involved in temporomandibular joint (TMJ) ankylosis.

Ankylosis can be classified by location, type of tissue (fibrous or bony), and extent of fusion (complete or partial). Multiple etiologies account for hypomobility and ankylosis of the TMJ, which ultimately lead to progressive decreased translation and rotation. Trauma is the most common cause, and other causes include otitis media, mastoiditis, ankylosing spondylitis, rheumatoid arthritis, osteoarthritis, scleroderma, irradiation, previous surgery, internal derangements, and perinatal events. Patients with a fibrous or bony ankylosis may have a facial asymmetry, restricted range of motion, malocclusion, anterior open bite from a shortened ramus, or possibly midface abnormalities, including those of the piriform rim and orbits. The current treatment for ankylosis must be individualized based on the cause and other patient factors and is almost always surgical. The form of surgery includes gap arthroplasty, with or without interpositional tissue or joint reconstruction using autogenous grafts or alloplastic material.

Multiple graft sources have been used over the years, including costochondral, sternoclavicular, fibular, iliac crest, and metatarsophalangeal tissue. The most widely used graft, particularly in children, is the costochondral graft, which was first described in the 1920s by Harold Gillies. Several authors have supported the use of costochondral grafts for reconstruction of the TMJ due to the graft’s growth potential in juveniles. Unfortunately, the costochondral graft has been shown to have an unpredictable growth pattern and to result in more complications. Regardless of these problems, the costochondral graft is still considered by some to be the operative management of choice in children and adults who have not had prior surgery.

TMJ reconstruction with alloplastic material developed from dissatisfaction with autogenous material and should be considered in patients with recurrent ankylosis, failed tissue grafts, unpredictable overgrowth, and inflammatory arthritis not responsive to other treatment modalities. The history of the total joint replacement is long, dating back to at least 1840, when John Murray Carnochan used wood to mobilize an ankylosed joint after a gap was created. Currently, three devices approved by the U.S. Food and Drug Administration (FDA) are available: the pre-1976 Amendment Christensen stock joint and the Christensen/Garrett custom device; the TMJ Concepts custom joint, which was approved by the FDA in 1999; and the Biomet Microfixation total joint stock device, which was approved in 2006. Stock joints must be bent or shimmed into bone, or the host bone must be altered. All of this can lead to material fatigue or overload. In addition, the micromotion that this creates can lead to fibrous connective tissue around the implant and eventual premature loss of the implant, which relies on the principle of osseointegration. For these reasons, a custom implant prosthesis is more appropriate for complex cases. In addition, Wolford et al. have demonstrated that the custom total joint prosthesis does well long term, especially for patients with prior surgery and abnormal anatomy.

Distraction osteogenesis is a technique that induces bone formation along the vector of movement without a bone graft. This technique has been used in orthopedics for long-bone procedures since Ilizarov first described the procedure. Stucki-McCormick et al. have reported on the use of distraction osteogenesis to reconstruct the condyle, with favorable outcomes. This includes the formation of a fibrous tissue layer, seen on postdistraction magnetic resonance imaging (MRI), that functions as a neocondyle. Cheng and Lo have suggested leaving a gap between distracted bone and the glenoid fossa during activation to allow space and time for fibrous tissue to form and prevent ankylosis.

History of the Procedure

Bone is an organ that is constantly undergoing remodeling by resorption with osteoclasts and bone formation by osteoblasts. A proper balance is necessary for continued bone development. Interruption of this cycle can lead to altered bone anatomy in addition to osteoporosis or osteosclerosis. The recently discovered progressive ankylosis gene (ANK) encodes a transmembrane protein that transports intracellular pyrophosphate to the extracellular milieu. This is necessary for mineralization of bone. Human mutations in ANK have been discovered that lead to craniometaphyseal dysplasia with resultant thickening of craniofacial bone. Recent studies in a murine model of ANK-deficient mice showed delayed osteoblastogenic and osteoclastogenic differentiation. The exact role and signaling pathways by which this occurs is unknown but is the subject of current research. Nevertheless, the ANK gene is one that might be involved in temporomandibular joint (TMJ) ankylosis.

Ankylosis can be classified by location, type of tissue (fibrous or bony), and extent of fusion (complete or partial). Multiple etiologies account for hypomobility and ankylosis of the TMJ, which ultimately lead to progressive decreased translation and rotation. Trauma is the most common cause, and other causes include otitis media, mastoiditis, ankylosing spondylitis, rheumatoid arthritis, osteoarthritis, scleroderma, irradiation, previous surgery, internal derangements, and perinatal events. Patients with a fibrous or bony ankylosis may have a facial asymmetry, restricted range of motion, malocclusion, anterior open bite from a shortened ramus, or possibly midface abnormalities, including those of the piriform rim and orbits. The current treatment for ankylosis must be individualized based on the cause and other patient factors and is almost always surgical. The form of surgery includes gap arthroplasty, with or without interpositional tissue or joint reconstruction using autogenous grafts or alloplastic material.

Multiple graft sources have been used over the years, including costochondral, sternoclavicular, fibular, iliac crest, and metatarsophalangeal tissue. The most widely used graft, particularly in children, is the costochondral graft, which was first described in the 1920s by Harold Gillies. Several authors have supported the use of costochondral grafts for reconstruction of the TMJ due to the graft’s growth potential in juveniles. Unfortunately, the costochondral graft has been shown to have an unpredictable growth pattern and to result in more complications. Regardless of these problems, the costochondral graft is still considered by some to be the operative management of choice in children and adults who have not had prior surgery.

TMJ reconstruction with alloplastic material developed from dissatisfaction with autogenous material and should be considered in patients with recurrent ankylosis, failed tissue grafts, unpredictable overgrowth, and inflammatory arthritis not responsive to other treatment modalities. The history of the total joint replacement is long, dating back to at least 1840, when John Murray Carnochan used wood to mobilize an ankylosed joint after a gap was created. Currently, three devices approved by the U.S. Food and Drug Administration (FDA) are available: the pre-1976 Amendment Christensen stock joint and the Christensen/Garrett custom device; the TMJ Concepts custom joint, which was approved by the FDA in 1999; and the Biomet Microfixation total joint stock device, which was approved in 2006. Stock joints must be bent or shimmed into bone, or the host bone must be altered. All of this can lead to material fatigue or overload. In addition, the micromotion that this creates can lead to fibrous connective tissue around the implant and eventual premature loss of the implant, which relies on the principle of osseointegration. For these reasons, a custom implant prosthesis is more appropriate for complex cases. In addition, Wolford et al. have demonstrated that the custom total joint prosthesis does well long term, especially for patients with prior surgery and abnormal anatomy.

Distraction osteogenesis is a technique that induces bone formation along the vector of movement without a bone graft. This technique has been used in orthopedics for long-bone procedures since Ilizarov first described the procedure. Stucki-McCormick et al. have reported on the use of distraction osteogenesis to reconstruct the condyle, with favorable outcomes. This includes the formation of a fibrous tissue layer, seen on postdistraction magnetic resonance imaging (MRI), that functions as a neocondyle. Cheng and Lo have suggested leaving a gap between distracted bone and the glenoid fossa during activation to allow space and time for fibrous tissue to form and prevent ankylosis.

Indications for the Use of the Procedure

The goals of treatment for ankylosis are release of the ankylotic mass and restoration of normal jaw function and form, prevention of reankylosis, and symmetric growth of the mandible in the growing patient. Other goals include reduction of suffering, containment of excessive treatment and cost, and prevention of further patient morbidity. If the patient has minimal fibrous tissue causing ankylosis, a more conservative arthroplasty may be performed. However, if the fibrous tissue is more involved or bony, gap arthroplasty may be needed, with or without interpositional tissue, autogenous graft, or total joint replacement. Currently, no single procedure provides absolute success. Regardless of the approach used, most complications involve limited range of motion and ankylosis. Costochondral grafts are most useful in children who need the cartilage for continued growth. Indications for alloplastic total joint reconstruction include inflammatory arthritis involving the TMJ that is not responsive to other treatment, recurrent fibrosis or ankylosis, failed tissue grafts or alloplastic reconstruction, and loss of vertical mandibular height. Distraction osteogenesis is useful in patients in whom the ankylosis is unilateral and involves facial asymmetry. In addition, when a functioning condyle and meniscus are needed, distraction osteogenesis is an autogenous alternative to prosthetic reconstruction.

Limitations and Contraindications