CHAPTER 34
Eminectomy

Joseph P. McCain1 and Reem Hamdy Hossameldin2

1Private Practice; Baptist Health Systems; and Oral and Maxillofacial Surgery, Herbert Wertheim College of Medicine, Florida International University Miami, Florida, USA; and Nova Southeastern School of Dental Medicine, Fort Lauderdale, Florida USA

2Department of Oral and Maxillofacial Surgery, Faculty of Dental Medicine, Cairo University, Cairo, Egypt; and General Surgery Department, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida, USA

A procedure performed to correct chronic dislocation or closed lock of the mandible with surgical reduction of the articular eminence.

Indications

  1. Habitual chronic dislocation of the mandible, where all conservative and minimally invasive methods are either unsuccessful or contraindicated
  2. Treatment of closed lock of the temporomandibular joint (TMJ) (modified eminectomy)

Contraindications

  1. Chronic mandibular dislocation cases involving a shallow articular eminence
  2. Radiological evidence of a pneumatized eminence (increased risk of infection as a result of communication between the joint space and the mastoid air cells)
  3. Radiographic evidence of a vascularized eminence (intracranial hemorrhage)

Anatomy

  • Superficial temporal vessels: Emerge from the superior aspect of the parotid gland and accompany the auriculotemporal nerve (Figure 34.1). The superficial temporal artery (STA) arises from the parotid gland as a bifurcation of the external carotid artery (ECA). The STA is a common source of bleeding during approaches to the TMJ. The superficial temporal vein lies superficial and usually posterior to the artery.

  • Transverse facial vessels: Branch off of the superficial temporal vessels and course inferior and relatively parallel to the zygomatic arch (Figure 34.1).
  • Auriculotemporal nerve: Courses from the medial aspect of the posterior neck of the condyle and turns superiorly, coursing superficial to the zygomatic root of the temporal bone (Figure 34.1). Just anterior to the auricle, the nerve divides into its terminal branches within the skin of the temporal area. The auriculotemporal nerve accompanies, and is posterior to, the STA. Pre-auricular exposure of the TMJ area almost always invariably injures this nerve. Damage is minimized by incision and dissection in close apposition to the cartilaginous portion of the external auditory meatus. Temporal extension of the skin incision should be located posteriorly so that the main distribution of the nerve is dissected and retracted forward within the flap. Patients rarely complain about sensory disturbances that result from damage to the auriculotemporal nerve.
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Figure 34.1. Image depicting the orientation of the superficial temporal artery and vein, auriculotemporal nerve, and transverse facial artery and vein at the root of the zygoma.

Pre-auricular Dissection Layers

  • Temporoparietal fascia (superficial temporal ­fascia): The temporoparietal fascia, which is the most superficial fascia layer beneath the subcutaneous fat, is the lateral extension of the galea and is continuous with the superficial musculoaponeurotic layer (SMAS). The blood vessels of the scalp, such as the superficial temporal vessels, run along its superficial aspect closely related to the subcutaneous fat. Motor nerves, such as the temporal branch of the facial nerve, run on the deep surface of the temporoparietal fascia.
  • Subgaleal fascia: The subgaleal fascia within the temporoparietal region is well developed and can be dissected as a discrete fascial layer if desired, but it is usually used only as a cleavage plane in the standard pre-auricular approach.
  • Temporalis fascia (deep temporal fascia): The dense, white fascia overlying the temporalis muscle. This thick fascia arises from the superior temporal line and fuses with the pericranium. The temporalis muscle arises from the deep surface of the temporal fascia and the whole of the temporal fossa. Inferiorly, the temporal fascia splints into a superficial and a deep layer above the zygomatic arch. A small quantity of fat between the two layers is referred to as the superficial temporal fat pad. A large vein frequently runs just deep to the superficial layer of temporalis fascia.

Technique

  1. The patient is placed supine on the operating room table and nasally intubated.
  2. The patient is prepped and draped, allowing for visualization of the entire ear and lateral canthus of the eye. The pre-auricular hair is shaved, and the remainder of the patient's hair is positioned under a surgical head cap. An ear wick soaked in antibiotic solution is placed within the external auditory canal.
  3. No local anesthetic or vasoconstrictors are injected.

  4. The pre-auricular incision is marked along an actual skin crease, contouring the incision around the tragal cartilage (Figure 34.5 [all figures cited in this list appear in Case Report 34.1]). The incision originates at the top of the ear and extends just inferior to the tragal cartilage. The incision does not extend to the pinna. The incision initially transverses skin and subcutaneous tissue only (Figure 34.6). Small bleeding points are cauterized with needlepoint cautery at the coagulation mode of 20.

  5. The dissection can be divided into thirds. The upper third is performed first. A curved hemostat is used to dissect bluntly through the horizontal auricular muscles down to the glistening white temporalis fascia (Figure 34.7). The neurovascular bundle is kept forward. Occasionally, a horizontal vessel is encountered arising from the superficial temporal artery or vein that crosses the dissection site (transverse facial vessels) and requires cauterized or suture ligation. Once the glistening white temporalis fascia is identified, a Messer retractor is placed to confirm that position and to reflect the flap anteriorly.
  6. The second part of the dissection is within the lower third of the incision. The tragal cartilage is skeletonized (Figure 34.8) to its apex with a curved hemostat. A small tag of tissue may be retained (4 to 6 mm) along the tragal cartilage to provide a point to place subcutaneous sutures during closure. With the upper and the lower aspects of the dissection completed, two points of depth are established: one within the superior third of the dissection at the level of the temporalis fascia, and a second at the inferior third of the dissection at the level of the tragal cartilage apex that goes to the capsule.
  7. The third part of the dissection connects the middle third of the incision to the superior and inferior thirds of the dissection (Figure 34.9). Sharp dissection proceeds through the horizontal auricular muscles to expose and connect the temporalis fascia with the superior dissection and the tragal tip with the inferior dissection.

  8. A periosteal elevator is utilized in a sweeping motion to flap forward the tissue within the layer superficial to the temporalis fascia (Figure 34.10). A sharp incision from the apex of the tragal cartilage to the superior aspect of the incision is made. Methylene blue mark can be used to mark the incision site (Figure 34.12). The Messer retractor is used to pull the flap superior to allow for a release of the temporalis fascia so that the skin incision does not need to be extended for additional exposure. The incision extends from the tip of the tragal cartilage, superiorly through the temporalis fascia and temporalis muscle, and down to bone (Figure 34.13). The temporalis muscle is transected with the cautery mode at 20 to 30. The parotid gland can be swept inferiorly with a Messer retractor if encountered.

  9. A periosteal elevator is used to dissect within the subperiosteal plane from the root of the zygoma anteriorly to expose the articular eminence (Figures 34.14 and 34.15). The periosteal elevator is used in an inferior sweeping motion to expose the capsule of the TMJ.

  10. The capsule of the TMJ is incised with a #15 blade from the posterior glenoid process onto the maximum concavity of the fossa located at the back slope of the articular eminence. A periosteal elevator is used to dissect free the superior joint space from the articular eminence, trying to preserve articular cartilage (Figure 34.16). In articular eminectomy, it is not necessary to enter the inferior joint space.

  11. After disarticulation of the superior joint space and isolation of the articular eminence (Figure 34.17), a 101 bur is utilized to score the anticipated osteotomy at the level of the zygomatic process of the temporal bone (Figure 34.18). The osteotomy of the articular eminence is completed with a sharp straight osteotome angled inferiorly 10° (Figure 34.19). Failure to angle the chisel slightly inferiorly will increase the risk of inadvertent damage or penetration of the skull base.

  12. It is important to resect the articular tubercle so that laterally the eminence and medially the tubercle are preserved. If the articular tubercle is not resected, there is a high incidence of future dislocation.
  13. Once the bulk of the eminence is resected, a reciprocating bone rasp is used to further flatten and smooth the remaining portion of the articular eminence. Care is taken to maintain a 10° inferior angulation and to flatten the difficult-to-visualize medial aspect of the eminence.
  14. Copious irrigation is used to debride any bony remnants within the surgical field. The site is inspected for hemostasis, and any areas of concern are managed prior to closing or proceeding to the contralateral side. In cases involving bilateral eminectomy, the same procedure is performed on the contralateral side.
  15. The patient is functioned to verify no areas of entrapment or dislocation and to ensure smooth translations of the condyles.
  16. The pre-auricular incision is closed in a layered fashion (Figure 34.20) with closure of the deeper fascial layers, subcuticular tissues, and skin. Bacitracin ointment is applied to skin incisions, and the wound is dressed.
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Figure 34.2. Chronic dislocation of the mandible as evidenced by a maximum vertical opening of over 5 cm.


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Figure 34.3. Orthopantomogram demonstrating steep bilateral articular eminences and dislocations.


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Figure 34.4. Arthroscopic evaluation of the left temporomandibular joint demonstrating a normal-appearing joint with appropriate position and function of the disc. The joint space is free of chondromalcia, synovitis, and adhesions.


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Figure 34.5. A standard pre-auricular incision is marked within a well-developed pre-auricular skin crease.


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Figure 34.6. A #15 blade is used to transect skin and subcutaneous tissues.


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Figure 34.7. Blunt dissection through the horizontal auricular muscles to expose the glistening white temporalis fascia.


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Figure 34.8. Sharp dissection over the tragal cartilage in close proximity to the perichondrium to expose the tip of the tragal cartilage.


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Figure 34.9. The pre-auricular soft tissue is transected down to the temporalis fascia.


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Figure 34.10. A periosteal elevator is utilized in a sweeping motion to flap forward the tissue within the layer superficial to the temporalis fascia. The parotid is bluntly swept inferiorly with a periosteal elevator and retracted with a Messer retractor.


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Figure 34.11. A towel clamp was placed at the angle of the mandible, and the condyle was palpated.


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Figure 34.12. Methylene can be used to mark an incision line from the superior aspect of the incision inferiorly to the apex of the tragal cartilage.


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Figure 34.13. A releasing incision is made with the cautery from the posterior glenoid process to the tip of the incision; through the temporalis fascia, temporalis muscle, and periosteum; down to the bone.


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Figure 34.14. The flap is swept subperiosteally along the zygomatic process of the temporal bone anterior to the articular eminence.


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Figure 34.15. A periosteal elevator is used to dissect in a subperiosteal plane from the root of the zygoma anteriorly to expose the articular eminence.


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Figure 34.16. Once ample visualization of the eminence is achieved, a periosteal elevator is used to carefully dissect the superior joint space free from the eminence.


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Figure 34.17. A periosteal elevator is used to protect the disk and condyle from further instrumentation.


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Figure 34.18. A 101 bur was used to identify and score the osteotomy site, which is planed in a 10° plane perpendicular to the superior most concavity of the glenoid fossa.


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Figure 34.19. The medial osteotomy is completed with a sharp straight chisel, and the eminence is fractured laterally and inferiorly. Irregular edges are re-contoured using a reciprocal rasp or bone files.


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Figure 34.20. Layered closure of the pre-auricular incision.

Postoperative Management

  1. Following eminectomy, ice packs are applied to the surgical area for 24 hours postoperatively.
  2. Dressings on surgical wounds are to be removed after 24 hours. Incisions are cleaned with a mixture of half normal saline and half hydrogen peroxide. A thin layer of bacitracin ointment is applied to all skin incisions to minimize the risk of infection.
  3. Intravenous antibiotics are employed for inpatients. Oral antibiotics are prescribed for 7 days after discharge. Cephalosporin is typically selected unless the patient is allergic to penicillin. Clindamycin is used for penicillin-allergic patients.
  4. One or two doses of postoperative corticosteroids are administered for anti-inflammatory purposes.
  5. Prescription analgesics are prescribed for pain management.
  6. Patients are placed on a clear to full liquid diet, which advances to a soft mechanical diet once the patient is capable.
  7. Patients are instructed in Stage I exercises for the first 2 weeks, followed by Stage II full-range-of-motion exercises afterward.
  8. Skin sutures are removed routinely after 6 days.

Complications

Early Complications

  1. Hemorrhage: Minimized with a meticulous dissection and reduction technique. Controlled via direct compression, the use of hemostatic packs and materials, cauterization, and/or ligation of any visible bleeding vessels.
  2. Infection: Minimized by maintaining a sterile environment. Infections are initially managed with antibiotic administration, local irrigation, and close follow-up. For cases refractory to conservative measures, surgical intervention and debridement are warranted.
  3. Facial nerve palsy: Typically transient and results from tissue traction during surgery or subsequent postoperative edema and swelling of the surgical site. No intervention is required as the condition typically resolves within 6–9 months.

Late Complications

  1. Wound dehiscence: May be attributed to infection, poorly placed sutures, and poor tissue handling and management resulting in diminished blood supply of the dissected tissues. Conservative management is required using antibiotics and local debridement for secondary-intention wound healing.
  2. Recurrence of mandibular dislocation: Commonly from insufficient articular eminence reduction and/or unremoved articular tubercle. Treatment involves reoperation.

Key Points

  1. The key to a successful eminectomy procedure is proper patient selection. Ideal candidates possess steep articular eminences and have a history of chronic mandibular dislocation.
  2. Preoperative computed tomography scans are necessary to determine the anatomy of the surgical site and to rule out pneumatization of the articular eminence. Knowledge of the dimensions of the articular eminence prior to the eminectomy procedure will minimize the risk of infratemporal fossa or middle cranial fossa penetration.
  3. Postoperative rehabilitation is crucial to obtaining and maintaining a full range of motion after eminectomy procedures.
  4. With the success of arthroscopic procedures, arthroscopic eminoplasty can be performed in select cases according to Segami's method. With the patient under general anesthesia, diagnostic arthroscopy by means of the infero-lateral approach can be undertaken to visualize the shape of the eminence. The articular eminence is then reduced and smoothed using an electric shaver with a triangulation technique.
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Figure 34.21. Postoperative orthopantomogram demonstrating bilateral eminectomies.

References

  1. Ellis, E. and Zide, M.F., 2005. Surgical approaches to the facial skeleton. 2nd ed. Philadelphia: Lippincott Williams & Wilkins.
  2. Hall, M.B., Randall, W.B. and Sclar, A.G., 1984. Anatomy of the TMJ articular eminence before and after surgical reduction. Journal of Craniomandibular Practice, 2, 135–40.
  3. Kulikowski, B.M., Schow, S.R. and Kraut, R.A., 1982. Surgical management of a pneumatized articular eminence of the temporal bone. Journal of Oral and Maxillofacial Surgery, 40, 311.
  4. Sato, J., Segami, N., Nishimura, M., Suzuki, T., Kaneyama, K. and Fujimura, K., 2003. Clinical evaluation of arthroscopic eminoplasty for habitual dislocation of the temporomandibular joint: comparative study with conventional open eminectomy. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, 95 (4), 390–95.
  5. Segami, N., Kaneyama, K., Tsurusako, S. and Suzuki, T., 1999. Arthroscopic eminoplasty for habitual dislocation of the temporomandibular joint: preliminary study. Journal o Craniomaxillofacial Surgery, 27, 390–97.
  6. Tremble, G.E., 1934. Pneumatization of the temporal bone. Archives of Otolaryngology, 19, 172.
  7. Undt, U., 2011. Temporomandibular joint eminectomy for recurrent dislocation. Atlas of the Oral and Maxillofacial Surgery Clinics, 19 (2), 189–206.
  8. Williamson, R.A., McNamara, D. and McAuliffe, W., 2000. True eminectomy for internal derangement of the temporomandibular joint. British Journal of Oral and Maxillofacial Surgery, 38 (5), 554–60.