Controversias en Cirugía Oral y Maxilofacial: Parte I

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Reconstruction of the temporomandibular joint (TMJ): alloplastic prostheses

Reconstrucción de la articulación temporomandibular (ATM):
prótesis aloplástica

 

C. Goizueta Adame

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Abstract: Incapabability to develop effective inert systems to total temporomandibular joint substitution during decades has genered several biologic solutions for a biomecanic question. Autologous grafts don´t offer security in functioning, simmetry, or oclusal estability; its have more coplex technique and more potencial morbility. Alloplastic reconstruction guarantees oclusal stability, single and reproducible technique, predictable time in hospital, and low morbility with actual prosthetic systems. Patients whos prostheses is only one option are going to exist always, so that it is primordial measures of magnitude of implicated strenghts in TMJ mecanic to can design prosthesis based on reliable models like others articulations which have just resolved the question. Key words: TMJ prostheses; Alloplastic temporomandibular reconstruction; Autologous temporomandibular reconstruction.

Resumen: La incapacidad de desarrollar sistemas inertes eficaces para la sustitución completa de la articulación temporo-mandibular durante décadas ha generado una variedad de soluciones biológicas para un problema biomecánico. Los injertos autólogos no ofrecen garantías en funcionalidad, simetría, o estabilidad oclusal; resultan técnicamente más complejos y tienen mayor potencial morbilidad. El paciente candidato a reconstrucción completa de la ATM debe contar con la posibilidad de una prótesis si otras opciones fracasan. La reconstrucción aloplástica garantiza estabilidad oclusal, técnica sencilla y reproducible, estancia hospitalaria predecible y baja tasa de complicaciones con los sistemas protésicos actuales. Siempre van a existir pacientes en los que ésta sea la única opción, por lo tanto es primordial la medición de la magnitud de las fuerzas implicadas en la mecánica de la ATM para poder diseñar prótesis en base a modelos fiables como en otras articulaciones en las que ya han resuelto el problema. Palabras clave: Prótesis de ATM; Reconstrucción temporomandibular aloplástica; Reconstrucción temporomandibular autóloga.

Recibido: 05-11-2004

Aceptado: 18-11-2004

 

 

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Médico Adjunto
Servicio de Cirugía Oral y Maxilofacial.
Hospital Universitario de San Juan, Alicante, España

Correspondencia:
c/ Tridente 4, bgw 5
Cabo Huertas, 03540
Alicante, España
goizu15@hotmail.com

 

Introduction

The particularization of the materials used in prosthesis systems during the past decades, the excessive wear or foreign body reactions,^1-3 together with an aggressive philosophy with regard to the surgical treatment of the temporomandibular joint (TMJ), has led to the development of autograft techniques (costochondral, sternoclavicular, metatarsal-phalangeal, fibular)^4-7 for substituting this joint more than any other joint in the anatomy. There are in fact practically no autografts in the peripheral joints that can be used for total joint reconstruction.

The use of autologous tissue achieves a functional outcome that is acceptable without the need to resort to alloplastic material, given the limited size of the area to be reconstructed.

It can be firmly fixed intraoperatively as if it were a prosthesis, given that it is secured to the remaining ramus with screws, plates or wires, and it can be adapted to the bed and to the case anatomy. Intermaxillary fixation (IMF) may be required to ensure stability. The technique can be completed by using a covering of soft tissue (dermis, fascia, or muscular-fascia, etc.) for the glenoid pit. This is an established and widely accepted option in the literature^8,9 for reconstructing the TMJ in ankylosis, AO dysfunction, oncology, traumatology, and in general it has been used for severe joint deformity of any origin.¹⁰ The graft that has been most used and reported is the costochondral graft.

But these grafts can fail, because of resorption or excessive growth,¹¹ or because of ankylosis, leading to an open bite, malocclusion or severe limitation of movements.^12,4 If any of this occurs, we need to be able to rely on an alloplastic system that is capable of correcting a failure, or that can resolve if an autograft has been rejected as a first option. Therefore there is apparently no such controversy, each to his own. With regard to total TMJ replacement by means of a prosthetic device, the principal problem faced is that, as with any other joint, this will have to be replaced.

Indications

During the growing years there is no doubt as to the best option (Fig. 1). In general excellent results are obtained with autologous grafts as they adapt to changes within the patient, and they can be combined with orthopedic/orthodontic or distraction treatment. For adults there are certain factors that can influence the indications for one or another option such as age, origin of the problem, time evolved, and previous treatment, especially if surgical.

The placement of a graft involves two fundamental risks:

• The acceptance and integration of the transplanted tissue implies the possibility of the original disease recurring, either because of its origin (neoplastic, systemic, autoimmune or metabolic), or because of a lack of control of the etiological factors (a leveling or erosion similar to osteoarthrosis) and even ankylosis.

• The non-acceptance and nonintegration of the transplanted material will lead to resorption, gradual malocclusion and musculoskeletal changes.

Reconstruction with alloplastic systems eliminates to some extent these possibilities. The result depends on the correct integration of the fixation material and contact surfaces in the phases of the system, and on a correct surgical technique.

In the opinion of the author, prosthetic reconstruction is the first option for:

1. Joints with a metabolic or autoimmune disease (Fig. 2).
2. Joints with primary or metastasic neoplasia.
3. Previous autograft failures.
4. Long-term ankylosed joints. It can also be for:

• Joints with damaged structures due to previous surgery (especially if on the condyle).
• Severe degenerative arthropathy (Figs. 3 and 4). In these cases (except for obvious reasons in neoplasia cases) there should be a severe mechanical problem or pain or both, with or without associated malocclusion, which should be corrected in a single act.

Surgical technique

For the total reconstruction of the TMJ the intraoperative objectives should be comparable, regardless of the use of autologous or alloplastic material, and the same technique is therefore used.

Once the mandibular fragment has been resected and the zygomatic-temporal vault freed from joint tissue, fibrous or scar tissue, or from any bone remains, and once the mandible has been checked for suitable mobility, the reconstruction is introduced through a cervical or retromandibular incision.

Autograft

• A soft tissue covering will be needed in the vault of the new joint (a fascia or muscular-fascia flap is advisable), or a cartilaginous finish for the new condyle (costochondral, sternoclavicular), or both.

• Adaptation can require the modification of both structures – mandibular ramus and graft– giving attention to possible weakening, loss of continuity or fracture of the graft.

• The fixation system (plates, screws and wires) is not preestablished, and to a large extent it will depend or the criteria of the surgeon and of the intraoperative conditions.

• Postsurgical intermaxillary fixation can be necessary and even indispensable.

• There are two surgical fields and two anatomical areas to supervise during the postoperative [period].

Prosthesis

Currently there are two prosthesis systems marketed in Spain for total reconstruction of the TMJ.

• The Christensen system (TMJ Implants, Inc., Golden CO) has been used since the 70s, and no significant modifications have been made to its design (Fig. 5). The design of the fossa-eminence prosthesis is based on 44 cadaver models for each side. It has a perforated flange and it is secured with screws to the zygomatic arch. On this cobalt chrome (Co-Cr) fossa a head of the same alloy is placed, with a (Co-Cr) shell that is secured to the outer surface of the ramus with screws of the same material. It can also be placed on the mandibular body using a flange in cases where there is little support. It can be made to measure with stereolithographic reconstruction. It can be used as hemi-arthroplasty (without the condylar part),¹³ although other authors have disputed this treatment.¹⁴ This prosthesis is the most used in the US and it has been endorsed by numerous publications. The results are predictable and, depending on the case, the technique is simple.

•The Lorenz system (W. Lorenz) is a stock prosthesis with a modified design of the cranial area. It has a lower center of rotation, which results in a prosthesis with a wide fossa-eminence with regard to the vertical position. It is made with ultra-high molecular weight polyethylene (UHMWPE) that is secured with screws to the zygomatic arch. It comes in three sizes and it can be cemented with PMMA in order to improve stability. The condylar component is made with chrome-cobalt and the area where there is contact with the host bone is coated with rough titanium-plasma. The design requires the resection of the most cranial part of the mandibular ramus. This design is based on the orthopedic literature that places polyethylene (the fossa eminence component) with metal (the mandibular component) and on Falkestrom and Van Loon's design innovations^15,16 for increasing the translatory effect (Figs. 6 and 7).

• The results published from 1995 onwards indicate that 30 to 34 mms should be the objective to reach. It is still in a study phase, but its use has been approved.

Rehabilitation

There are three causes leading to a limitation of joint movement: intra and periarticular tissue, muscular spasms and fibrous scarring, that many of these patients present. Orthopedic surgery for traumatology established decades ago¹⁷ the advantages of early mobilization of the muscles that support a treated joint. With autografts the reliance on the patient's metabolism (neovascularization, callus formation and good tissue integration), entails a period of conscious or forced immobilization (IMF) of at least three weeks. The musculoskeletal apparatus that has been afflicted for a long time and subjected to a surgical aggression, often having a previous cicatricial process, is immobilized. The definitive movement range of these patients will not be established until a year later.¹⁸

With prosthetic systems rehabilitation will commence during the first week postsurgery. The patient will be able to move the musculature from the first days and no donor area treatment; the patient is able to go back to his daily activities earlier.

Discussion

Reconstructive surgery of the TMJ has two fundamental objectives:

1. Restoring as far as possible mandibular function.
2. Reducing the symptoms of pain.
3. Avoiding the perpetuation of treatment.
4. Avoiding recurrence of the problem for as long as possible or definitively.
5. Containing the therapy costs for the patient as well as for the insurer.

Reconstruction with a prosthetic device meets these objectives as:

1. The technique is simple (for the surgeon that is familiar with the anatomical region and osteosynthesis systems), the surgical time is known, the hospital stay is predictable and there is lower associated morbidity (Fig. 8).
2. There is occlusal stability and vertical dimension stability. The behavior of the autologous graft is unpredictable. It can remain stable but it can also be resorbed. It can grow too much and it can lead to ankylosis.
3. Rehabilitation takes place earlier and is safer, with no IMF being necessary.

However there are inconveniences such as:

• Absence of the translatory factor in the movements of the mandible and, as a result, there is a poor maximum oral aperture.

There is no reconstruction restoring all the articular movements. With both options we will find that translatory movements are restricted. If the reconstruction head is situated in the anatomical center of the fossa, it will rotate during the aperture movement, even if we try to attach the pterygoid muscles to the reconstruction head (two millimeters of lateral movement in Wolford's hands,¹⁹ 3.5 mms in Collins' series)²⁰. If the graft works well, a satisfactory aperture range is to be expected, although a recent series with costochondral grafts of 76 joints in 57 patients⁴ reported an average increase in the interincisal opening of 21 to 24 mms, and no translatory movement. The inferior positioning of the center of rotation in the new design of artificial systems¹⁵ is having the effect of a pseudomovement that improves the interincisal opening by 8 to 10 mms. Obtaining 25 mms with a prosthetic system is a good result when it only permits the rotation of the mandible, as the remaining movements of the original TMJ are due to the translatory movement of the condyle on the disc and eminence as a result of the effect of the pterygoid muscles. If these are not inserted, as mentioned previously, the mechanical result would be limited. If the center of rotation is not situated on the condylar head, and if it is inferiorly positioned on the neck, the arc of rotation will be greater and aperture will improve.

• Lack of knowledge as to the magnitude of the forces implied in the cycles and, as a result, trial and error designs.

After more than 80 years of studies²¹ we have a proper understanding of articular biomechanics, but the magnitude of the forces related to the TMJ have not been established under normal conditions nor under pathologic conditions.^22,23 The difficulty in measuring these forces has led to an inability to develop inert systems capable of substituting the TMJ in an efficient manner such as in the hip or knee. This «delay» that we are still experiencing, together with the reduced dimension of the area to be treated, can justify in itself the use of autografts as a first option for many surgeons.

Conclusion

«A total alloplastic reconstruction is a biomechanical solution more than a biological solution for the treatment of serious articular disease».²⁴ The development of cell cultivation techniques and tissue engineering^25,26 will permit modification of some of the aspects in the balance, but we will always need to rely on a system that is efficient, safe, simple and fast in order to improve the quality of life of those patients that are not able to benefit from better options. Possibly the controversy is not related to the employment of a graft or a prosthesis, as prostheses are always going to be necessary. Currently what is in question is the type of prosthesis that has the best functional measurements, what materials are more cycle-resistant, what are the best load bearing surfaces and, more especially, the amount. There questions will not be resolved until there are reliable biomechanical models, with articular function parameters under normal or pathological conditions, as exists with the knee or hip.

References

1. Kent JN, Block MS, Halpern J, Fontenot M. Update on the Vitek partial and total temporomandibular joint system. J Oral Maxillofac Surg 1993;51:408-15.        [ Links ]

2. Bronstein SL, Retained alloplastic temporomandibular joint Disk implants: a retrospective study. Oral Surg Oral Med Oral Pathol 1987;64:135-45.        [ Links ]

3. Ta L, Phero JC. Clinical evaluation of patientes with temporomandibular joint implants. J Oral Maxillofac Surg 2002;60:1389-9.        [ Links ]

4. Saeed NR, Kent JN. A retrospective study of the costochondral graft in TMJ reconstruction. Plast Reconstr Surg 2003;112:31-6.        [ Links ]

5. Wolford LM, Cottreell DA, y cols. Sternoclvicular grafts for temporomandibular joint reconstruction. J Oral Maxillofac Surg 1994;52:119-28.        [ Links ]

6. Wax MK, Winslow CP, y cols. A retrospective analysis of temporomandibular joint reconstruction with free fibula microvascular flap. J Oral Maxillofac Surg 1999;57:789-98.        [ Links ]

7. Landa LE, Gordon C, et al. Evaluation of long-term second metatarsal reconstruction of the temporomandibular joint. J Oral Maxillofac Surg 2003;61:65-71.        [ Links ]

8. Lindquist C, Pihakari A. Autogenous costocondrhal grafts in temporomandibular joint arthroplasty. J Maxillofac Surg 1986;14:143-9.        [ Links ]

9. Nelson C, Butrtrum J. Costochondral grafts for posttraumatic temporomandibular joint reconstruction: A review of 6 cases. J Oral Maxillofac Surg 1989;47:1030.        [ Links ]

10. MacIntosh RB, Henry FA. A spectrum of application of autogenous costocohndral grafts. J Oral Maxillofac Surg 1977;5:257.        [ Links ]

11. Guyuron B, Lasa CI. Unpredictable growth pattern of costocondhral graft. Plast Reconstr Surg 1992;90:880-6.        [ Links ]

12. Politis C, Fossion E, Bossuyt M. The use of costochondral grafts in arthroplasty of the temporomandibular joint. J Cranio Max Fac Surg 1987;15:345-54.        [ Links ]

13. Park J, Keller EE. Surgical manegement of advanced degenerative arthritis of temporomandibular joint with metal fossa-hemijoint replacement prosthesis: An 8- year retrospective pilot study. J Oral Maxillofac Surg 2004;62:320-8.        [ Links ]

14. Wolford L. In Reply. (carta). J Oral Maxillofac Surg 2003;11:008.        [ Links ]

15. Falkestrom CH. Biomechanical design of total temporomandibular joint replacement (tesis). University of Groningen 1993.        [ Links ]

16. Van Loon J-P, Falkestrom CH. The optimal center of rotation for a temporomandibular joint prosthesis: A three-dimensional kinematical study. J Dent Res 1999;78:43-8.        [ Links ]

17. Salter RB. Continuous Passive Motion. Baltimore, MD, Williams & Wilkins, 1993.        [ Links ]

18. MacIntosh RB. The use of autogenous tissues for tempormandibular joint reconstruction. J Oral Maxillofac Surg 2000;58:63-9.        [ Links ]

19. Wolford LM, Cottrell DA. Temporomandibular joint reconstruction of the complex patient with the Techmedica custom-made total joint prosthesis. J Oral Maxillofac Surg 1994;52:2-10.        [ Links ]

20. Collins CP, Wilson KJ. Lateral pterygoid myotomy with reattachment to the condylar neck: an adjunt to restore function after total joint reconstruction. J Craniofac Surg 2002;13:809-15.        [ Links ]

21. Gysi A. Studies on the leverage problem of the mandible. Dental Digest 1921;27:74.        [ Links ]

22. Throckmorton GS. Temporomandibular joint biomechanics. Oral Maxillofac Surg Clin North Am 2000;12.        [ Links ]

23. Mercuri LG. The use of alloplastic prostheses for temporomandibular joint reconstruction. J Oral Maxillofac Surg 2000;58:70-5.        [ Links ]

24. Mercuri LG, Wolford LM. Custom CAD/CAM total tempormandibular joint reconstruction system: Preliminary multicenter report. J Oral Maxillofac Surg 1995;53:106- 15.        [ Links ]

25. Abukawa H, Terai H. Formation of a mandibular condyle in vitro by tissue enginee. J Oral Maxillofac Surg 2003;61:94-100.        [ Links ]

26. Cancedda R, Dozin B. Tissue engineering and cell therapy of cartilage and bone. Matrix Biol 2003;22:81-91.        [ Links ]