CASO CLÍNICO

 

Mandibular osteosynthesis failure. Biomechanical and therapeutic considerations. Two clinical cases

Fracaso de la osteosíntesis mandibular. Consideraciones biomecánicas y tratamiento. A propósito de dos casos clínicos

 

 

 

I. Navarro¹, J.L. Cebrián², G. Demaría¹, M. Chamorro³, J.M. López-Arcas¹, J.M. Múñoz², J.L. Del Castillo², M. Burgueño⁴

1 Médico Interno Residente
2 Médico Adjunto
3 Jefe Clínico
4 Jefe de Servicio
Servicio de Cirugía Oral y Maxilofacial. Hospital Universitario La Paz. Madrid. España

Correspondence

 

 

 

---

ABSTRACT

Introduction: Mandibular osteosynthesis failure is not common. The purpose of this article is to examine the etiology and treatment of mandibular osteosynthesis failure.
Material and methods: Two clinical cases of mandibular osteosynthesis failure and its treatment are reported.
Discussion: The etiology of osteosynthesis failure and bone regeneration with suitable treatment is analyzed Exact knowledge of the biomechanical characteristics of the masticatory system is useful in approaching this condition.
Conclusion: Rigid fixation with locking plates and autologous grafts of iliac crest cancellous bone are the key to therapeutic success.

Key words: Osteosynthesis failure; Locking plates; Iliac crest graft.

---

RESUMEN

Introducción: El fracaso de la osteosíntesis mandibular no es una situación frecuente. El objetivo de este artículo es determinar su etiología y esbozar su tratamiento.
Material y métodos: Se presentan dos casos clínicos en los que se produjo un fracaso de la osteosíntesis y se indica su tratamiento.
Discusión: Se analiza la etiología del fracaso y cómo, con la terapéutica adecuada, se consigue una regeneración ósea. Un conocimiento exacto de las características biomecánicas del sistema masticatorio, ayuda a abordar esta patología.
Conclusión: Una fijación rígida con placas tipo "lock" junto a injerto esponjoso autólogo de cresta iliaca es la clave del éxito terapéutico.

Palabras clave: Fracaso de la osteosíntesis; Placas bloqueadas; Injerto de cresta ilíaca.

---

 

Introduction

The failure of mandibular osteosynthesis due to inadequate fixation is one of several causes (infection, systemic diseases like diabetes, and chronic corticoid use) of poor mandibular fracture consolidation.¹

In the last 50 years, the development of internal fixation methods for mandibular fractures and, especially, the idea that traumatology surgery should restore function have revolutionized the treatment of patients with facial and mandibular injuries.

The objective of the treatment of mandibular fractures is:²

1. Anatomically correct fracture reduction.

2. Stable osteosynthesis that satisfies local biomechanical demand.

3. Minimally traumatic surgical technique.

4. Active, painless, early mobilization of the muscles and joints adjacent to the fracture.

Exact knowledge of the mandibular anatomy and biomechanical characteristics of the masticatory musculoskeletal system, whether intact or deteriorated, is required for reducing mandibular fractures and performing the necessary osteosynthesis.

Throughout the history of osteosynthesis, authors have held differing views on these parameters, which led to the development of two competing schools of thought, one in favor of absolutely rigid fixation (AO/ASIF) and the other in favor of less rigid fixation³ (French school).

These two positions have now been conciliated by the adaptation of osteosynthesis requirements to the status of the injured system. Consequently, if system status is acceptable, the system can contribute to fracture healing with osteosynthesis, but if the system status is deficient, fracture healing should be entrusted fully to plates and screws to achieve consolidation. The concepts of load sharing and load bearing arose from this view. A load-bearing situation is one in which the osteosynthesis material sustains the entire functional load and the fracture locus is allowed to heal in complete repose.⁴ In contrast, in a load sharing situation the osteosynthesis material helps the competent jaw to cope with the functional load. In these situations a functionally stable fixation is sought and slight movement of the locus is allowed. Examples of load bearing situations are: comminuted fractures, infected fractures, situations of major soft-tissue loss, fractures of an atrophic (edentulous) mandible, and fractures with loss of continuity.

Functionally stable fixation is used in simple fractures and osteotomies.⁵

In the present study two clinical cases are reported in which the osteosynthesis failure resulted from overlooking these basic principles.

The causes of osteosynthesis failure were analyzed and treatment to ensure therapeutic success was proposed.

 

Clinical cases

Case 1

A 24-year-old woman with Down’s syndrome presented bilateral fracture of the mandibular body due to a facial injury of unknown etiology. She was intervened in another center to place two small plates on each mandible (Fig. 1).

The right fracture focus was approached extraorally (reduction and osteosynthesis with 2.5 reconstruction plates and 2.0 locking plates) and the left fracture focus was approached intraorally with 2.0 locking plates (Figs. 2 and 3). The patient left the operating room without maxillomandibular fixation.

Five months later she had a new right osteosynthesis failure (Fig. 4). A new cervicotomy was made and a new osteosynthesis with a 2.4 "unilock" type reconstruction plate and autologous iliac crest graft was performed. The patient left the operating room with elastic maxillomandibular fixation (Figs. 5 and 6).

One year after the second operation, the fracture was perfectly consolidated. New bone formation was evident in the follow- up orthopantomography (Fig. 7).

Case 2

The patient was a 43-year-old woman, former smoker, with no other background of interest. She had bicondylar intracapsular fractures and a right angle mandibular fracture (Fig. 8).

Osteosynthesis with two miniature plates was performed on the mandibular angle. The two condylar fractures were treated by maxillomandibular fixation.

Three months later, the patient presented pseudoarthrosis of the right mandibular angle (Fig. 9). An extraoral approach was used to remove the plates and perform a new reduction and osteosynthesis with two 2.0 locking plates of different profiles and a particulate cancellous iliac crest graft (Figs. 10 and 11).

Six months after surgery there were no clinical manifestations suggestive of osteosynthesis failure (Fig. 12).

 

Discussion

The old concept of treating fractures by simple apposing the bone fragments is now considered outmoded in most fields of traumatology.

Four objectives of the treatment of mandibular fractures were cited in the introduction. The first two, anatomically correct reduction and adaptation of the osteosynthesis to the biomechanical characteristics of the system, have already been outlined.

The last two objectives, minimally traumatic technique and early rehabilitation, are two mainstays for achieving successful osteosynthesis and preventing the deleterious consequences of immobilization.

The use of a suitable approach and osteosynthesis that does not compress the bone are the most important measures for ensuring minimally traumatic technique. The development of locking type osteosynthesis plates ⁶ or blockade makes it possible to achieve resistant unions without compressing the healing bone. Such devices transmit the load forces from the bone to the screws and from the screw to the plate. By redistributing the forces between the bone and plate, the bone tissue suffers less compression and less vascular compromise, thus contributing to successful osteosynthesis. Osteosynthesis plates were used to treat failure of fracture union in the cases reported here.

The first patient experienced osteosynthesis failure on two occasions.

More rigid fixation was needed because the patient had two different fracture loci. In addition, maxillomandibular blockade was necessary because the patient was not very cooperative due to her underlying pathology.

The second patient had three fractures. When more than one locus is involved, the mandibular lever forces changes and more rigid fixation is required in at least one focus (Fig. 13).⁷ Osteosynthesis failed because the situation was a combination of load supporting and load sharing, making osteosynthesis insufficient for the characteristics of the particular fracture.

Proper surgical technique includes the judicious use of autologous cancellous bone grafts (iliac crest). This type of graft has primitive mesenchymal cells and endothelial stem cells that resist ischemia well, stimulating neovascularization and primitive osteoformation in the fracture locus.⁸ Rigid fixation of the graft ensures good vascularization and adequate compression to prevent bone resorption.

Finally, early rehabilitation facilitated by correct osteosynthesis prevents socalled «fracture disease,» which consists of a reduction in the range of mandibular mobility after an injury.⁹ Immobilization by maxillomandibular fixation is harmful for all the elements of the mouth and jaw: bone, muscle, and the temporo-mandibular joint.¹⁰

 

Conclusions

In order to avoid mandibular osteosynthesis failures, it is necessary to understand the biomechanical characteristics of the system.

Osteosynthesis failure occurs most often in situations in which both load supporting and load sharing are required, meaning that functionally stable fixation is needed instead of rigid fixation.

The use of locking plates (internal-external fixation) produces less tissue damage because the loading forces are shared by the plate and bone.

When needed, cancellous bone grafts harvested from the patient’s own iliac crest should be used.

 

 

Correspondence:
Ignacio Navarro Cuéllar
Servicio de Cirugía Oral y Maxilofacial
Hospital Universitario La Paz
Paseo de la Castellana 264
28046 Madrid. España
E-mail: nnavcu@hotmail.com

Recibido: 15.10.07
Aceptado: 28.01.09

 

References

1. Moore Gf, Olson TS, Yonkers AJ. Complications of mandibular fractures: A retrospective review of 100 fractures in 56 patients. Nebr Med J 1985;70:120.        [ Links ]

2. Fonseca RJ, Walter RV, Betts NJ. Mandibular fractures. Oral Maxillofacial Trauma. 2nd ed, 1997.        [ Links ]

3. Champy M. y cols. Mandibular osteosynthesis by miniature screwed bone plates via a buccal approach. J Maxillofacial Surgery 1978;6:14.        [ Links ]

4. Ellis E. Treatment of mandibular fractures using the AO reconstruction plate. J Oral Maxilofac Surg 1993;51:250.        [ Links ]

5. Del Castillo JL, Demaría G, Arias J. Principios Básicos de Osteosíntesis. Manual de Traumatología Facial. 2007.        [ Links ]

6. Alpert B, Gutwald R, Schmelzeisen R. New innovation in craniomaxillofacial fixation: the 2.0 lock system. The Keio Journal of Medecine 2003;52:120-7.        [ Links ]

7. Passeri LA, Ellis E, Sinn DP. Complications of nonrigid fixation of mandibular angle fractures. J Oral Maxillofac Surg 1993;51:382.        [ Links ]

8. Ochandiano S, Navarro Vila C. Bases biológicas del injerto óseo. Tratado de Cirugía Oral y Maxilofacial. 2004.        [ Links ]

9. Cebrián y cols. Desarrollo de un simulador estático para estudios biomecánicos fotoelásticos del sistema músculo-esquelético masticatorio. Resúmenes y actas de del XVI Congreso Nacional de Ingeniería Mecánica. León. Diciembre, 2004.        [ Links ]

10. Ellis III E, Carlson DS. The effects of mandibular immobilization on the masticatory system. A review. Clin Plast Surg 1989;16:133-46.        [ Links ]