Armamentarium

History of the Procedure

The history of alloplastic temporomandibular joint (TMJ) reconstruction has been marred by failures secondary to inappropriate design, poor preclinical trials, and an ignorance of previous studies, particularly in the orthopedic literature. Initially, alloplastic materials were used almost exclusively for recurrent ankylosis. In 1946, Eggers used tantalum foil as an interpositional implant. In 1960, Robinson used a stainless steel fossa prosthesis, and Christensen used an array of cast Vitallium fossae that were secured to the zygomatic arch. Current systems use metal-on-plastic and metal-on-metal designs. A complete understanding of the biomechanics and occlusal considerations for the patient requiring total alloplastic joint reconstruction is essential. As fewer patients are presenting for revision alloplastic or failed autogenous graft, a higher proportion of patients undergo primary reconstruction for advanced degenerative joint disease (Wilkes stage IV or V, Table 131-1 ). In this patient population, stock alloplastic joint reconstruction is an option. These prostheses allow for easy intraoperative adaption, are readily available, and are cost-effective.

History of the Procedure

The history of alloplastic temporomandibular joint (TMJ) reconstruction has been marred by failures secondary to inappropriate design, poor preclinical trials, and an ignorance of previous studies, particularly in the orthopedic literature. Initially, alloplastic materials were used almost exclusively for recurrent ankylosis. In 1946, Eggers used tantalum foil as an interpositional implant. In 1960, Robinson used a stainless steel fossa prosthesis, and Christensen used an array of cast Vitallium fossae that were secured to the zygomatic arch. Current systems use metal-on-plastic and metal-on-metal designs. A complete understanding of the biomechanics and occlusal considerations for the patient requiring total alloplastic joint reconstruction is essential. As fewer patients are presenting for revision alloplastic or failed autogenous graft, a higher proportion of patients undergo primary reconstruction for advanced degenerative joint disease (Wilkes stage IV or V, Table 131-1 ). In this patient population, stock alloplastic joint reconstruction is an option. These prostheses allow for easy intraoperative adaption, are readily available, and are cost-effective.

Indications for the Use of the Procedure

In 2005, the U.S. Food and Drug Administration (FDA) approved the stock TMJ prosthesis after a 10-year prospective investigational device exemption (IDE) study. Data from 224 cases are available. At 3 years, patients were found to have significant improvement in pain; the mean pain score decreased from 8.5 out of 10 preoperatively to 2.8 after joint replacement. Mouth opening had improved from 20.1 to 29.3 mm at 3 years. Most important, patient satisfaction scores were high; 99% of patients stated that in hindsight, they would undergo the surgery again. Westermark recently reported on his experience with the stock TMJ prosthesis. Twelve patients were followed for up to 8 years. At the 1-year follow-up, mean jaw opening had increased from 3.8 to 30.2 mm. Joint-related pain had been eliminated in all but two patients, who reported persistent muscle pain. No postoperative infections or device failures were seen. In a recent study, Giannakopoulos et al. reviewed 288 patients who were followed for 3 years and found continued significant improvement in pain and jaw function with the stock TMJ prosthesis system. A 3.2% revision rate was seen, with no mechanical failures. Revisions were secondary to infection or heterotopic bone. Leandro et al. reported on their 10-year experience with the stock TMJ prosthesis system and found significant and sustained improvement in function and pain scores. This recent evidence supports the safe and effective use of stock alloplastic joint replacement in the temporomandibular joint with newer generation systems.

Indications for TMJ reconstruction include bony ankylosis, failed previous alloplastic and autogenous joint replacement, post-traumatic condylar injury, avascular necrosis, post-tumor reconstruction, developmental abnormalities, functional deformity, and severe inflammatory conditions that have failed to respond to conservative treatments ( Box 131-1 ). Current reconstructive options for the surgeon include the use of either autogenous or alloplastic materials. In the skeletally mature population, alloplastic joint replacement offers the advantage of immediate functioning, lack of donor site morbidity, reduced operative time and, most important, more predictable outcomes. In the pediatric population, autogenous reconstruction has the additional advantage of growth potential, particularly with costochondral grafts. However, in pediatric patients with ankylosis, growth has ceased, and alloplastic total joint reconstruction may be considered. The surgeon should take into account the ability to achieve predictable, safe, long-lasting, and cost-effective reconstruction when deciding on the method of joint replacement.

Careful preoperative planning and reasonable patient expectations are required for successful joint reconstruction. A maximal opening of 30 to 35 mm is a reasonable expectation for range of motion with a total joint prosthesis. Failure to achieve this range of motion intraoperatively may require coronoidectomy or muscle stripping. Patients with prolonged decreased range of motion often have muscle and soft tissue contracture and scarring. Patients should be aware that unilateral replacement causes deviation to the side of the prosthesis on terminal opening. Pain reduction for patients who have undergone multiple operations is often difficult to achieve. A direct correlation exists between the number of previous surgical procedures and the likelihood that presurgical symptoms will be reduced.

Limitations and Contraindications

Absolute contraindications to total joint replacement include the presence of infection in the operative field, allergy to the prosthetic components, and systemic conditions rendering the patient unable to tolerate the operative procedure ( Box 131-2 ). Nickel is the most common allergy seen in total joint replacement, and devices can be manufactured without this material. Skeletal immaturity also is considered a contraindication to alloplastic joint reconstruction. Recently, Mercuri and Swift argued for consideration of alloplastic TMJ reconstruction in the pediatric population with previously failed autogenous grafts, high inflammatory arthritis unresponsive to other modalities, and loss of vertical height due to bony resorption. Avoiding the complications associated with autogenous grafting, such as ankylosis and graft resorption, may make subsequent revision surgeries less complicated. The life span of the device is a concern in the younger patient population. It is unknown how long a TMJ prosthesis can reasonably be expected to last. In the young patient population, it is important to educate these patients that revision arthroplasty is expected, and the surgeon should plan their osteotomies accordingly. A custom implant system is usually necessary with a severe craniofacial deformity involving an anatomic discrepancy that precludes the use of a stock device.

Unacceptable failure rates in previous iterations of alloplastic TMJ implant systems provided valuable input for the development of newer, FDA-approved implants. Appreciation of biomechanical and orthopedic principles, along with appropriate clinical trials, has helped in the development of safe and effective devices. Nevertheless, it is important to recognize that these devices have limitations, including a finite life expectancy, limited translation, the development of wear debris, and the potential for infection. Fewer patients are requiring revision arthroplasty from previous failed devices; therefore, it can be expected that more primary joint reconstructions will be performed for conditions such as severe inflammatory arthritides, trauma, and ankylosis. A stock prosthetic device has the advantages of immediate availability, single-stage surgery, and lower cost, and it does not require recapitulation from a stereolithic model.

Technique: Alloplastic Temporomandibular Joint Reconstruction