Residency · Residency · Oral Maxillofacial Surgery

Zygomatic Implants for the Severely Atrophic Maxilla

Overview

Zygomatic implants are long implants (30-55 mm) anchored in the zygomatic bone to support prosthetic rehabilitation of the severely atrophic maxilla. Originally described by Branemark in 1998 as an alternative to extensive bone grafting procedures, they bypass the need for sinus augmentation, onlay grafting, or Le Fort I osteotomy with interpositional grafting. They allow fixed prosthetic rehabilitation in patients who would otherwise require complex staged reconstruction.

Indications

Zygomatic implants are indicated for severely atrophic posterior maxillae (Cawood and Howell Class IV-VI) inadequate for conventional implants even with sinus augmentation, failed previous bone grafting procedures, maxillectomy defects from oncologic resection or trauma, patients declining extensive grafting procedures, patients unable to tolerate multiple staged surgeries due to medical comorbidities or advanced age, and those desiring immediate fixed rehabilitation without prolonged grafting and healing periods.

Contraindications

Contraindications include active sinus infection or chronic uncontrolled sinusitis, zygomatic bone pathology (tumor or fracture with inadequate bone stock), insufficient anterior maxillary bone for conventional implants (a relative contraindication that may be addressed with pterygoid or additional zygomatic implants), uncontrolled systemic disease precluding implant therapy, and inadequate interarch space for a prosthesis.

Anatomy

Zygomatic Bone

The zygomatic bone provides dense cortical bone for excellent anchorage. It forms the lateral and inferior orbital rim, the zygomatic arch, and the anterior wall of the infratemporal fossa. The zygomaticofacial foramen, which transmits a neurovascular bundle, is a key landmark. Bone thickness at the implant engagement site is typically 5-10 mm.

Maxillary Sinus Relationship

The original intrasinus trajectory passes through the maxillary sinus. The implant enters the alveolar crest, traverses the sinus, exits through the posterolateral maxillary wall, and engages the zygomatic bone. The Schneiderian membrane is penetrated and heals around the implant body.

Critical Structures

The orbital floor represents the superior limit, and implant encroachment must be avoided. The infraorbital nerve, the maxillary sinus, and the soft tissue of the buccal sulcus (where an extrasinus trajectory may cause cheek bulging) are additional structures of concern.

Surgical Approaches

Branemark (Original/Intrasinus) Technique

The implant follows an intrasinus path, entering at the palatal aspect of the alveolar crest in the premolar/molar region, passing through the maxillary sinus, and exiting through the posterolateral wall of the maxilla into the zygomatic bone. A window in the lateral sinus wall is created for visualization. The implant platform emerges palatally on the alveolar crest.

Exteriorized/Extrasinus (Stella/Warner) Technique

The implant follows a path along the lateral wall of the maxilla, external to the sinus cavity. This approach reduces sinus-related complications, but the implant platform emerges more buccally on the crest and may cause soft tissue bulging buccally.

ZAGA (Zygomatic Anatomy-Guided Approach) Classification

Developed by Aparicio in 2011, the ZAGA classification categorizes maxillary-zygomatic anatomy into zones (ZAGA 0-4) based on the concavity of the lateral maxillary wall. The implant trajectory is individualized based on anatomic classification. ZAGA 0 has a flat lateral wall suited for an intrasinus path. ZAGA 1-2 have mild to moderate concavity suited for a partially extrasinus path. ZAGA 3-4 have deep concavity suited for a predominantly extrasinus path. This allows patient-specific planning rather than a one-size-fits-all approach.

Quad Zygoma

In cases of complete maxillary atrophy including the anterior region, four zygomatic implants (two per side) eliminate the need for conventional anterior implants. Anterior zygomatic implants are angled more anteriorly and posterior ones more posteriorly, providing sufficient AP spread for a full-arch fixed prosthesis.

<image>Schematic diagram showing the three zygomatic implant trajectories (intrasinus, extrasinus, and ZAGA-guided) in a cross-sectional view of the maxilla and zygomatic bone, with annotations of the maxillary sinus, implant path, and prosthetic platform position</image>

Surgical Technique (General Steps)

Preoperative Planning

Planning involves CBCT with an extended field of view to include the zygomatic bones bilaterally, virtual surgical planning with implant trajectory simulation, optional surgical guides for guided zygomatic implant placement, assessment of anterior maxillary bone for conventional implants, and full-arch fixed prosthesis design.

Procedure

The procedure is performed under general anesthesia with nasotracheal intubation. A Le Fort I-type incision with full mucoperiosteal flap elevation exposes the lateral maxillary wall, infraorbital rim, and anterior zygomatic buttress. For the intrasinus approach, a lateral wall window is created; for the extrasinus approach, the external wall is traced. Sequential drilling with dedicated long zygomatic implant drills under copious irrigation follows, with verification that the drill engages zygomatic bone at the apex. The self-tapping zygomatic implant (30-55 mm length depending on anatomy) is placed with primary stability typically exceeding 35-45 Ncm. Conventional implants are placed in the anterior maxilla if bone is available. Prosthetic loading may be immediate or delayed based on primary stability. The flap is closed ensuring implant abutments are accessible, with tissue punches used for platform access if needed.

Intraoperative Verification

Direct visualization confirms zygomatic bone engagement. A finger placed on the lateral orbital rim confirms the drill does not breach the orbit. Depth gauge verification is performed, and some surgeons use intraoperative navigation for precise placement.

Prosthetic Considerations

The prosthesis is a full-arch fixed screw-retained design. The most common configuration adapts the All-on-4 concept with 2 zygomatic and 2 anterior conventional implants. Quad zygoma uses 4 zygomatic implants when no anterior bone is available. Immediate loading with a rigid PMMA provisional within 24-48 hours requires high primary stability. Final prosthetic options include metal-ceramic, metal-acrylic (hybrid), or zirconia, placed after 3-6 months. Multi-unit abutments correct the divergent angulation between zygomatic and conventional implants.

Complications

Sinusitis

Sinusitis is the most common complication, occurring in 2-25% of cases depending on the study and technique. The intrasinus technique has a higher sinusitis rate than the extrasinus approach. Management includes antibiotics, decongestants, and ENT referral for FESS if refractory. Some surgeons advocate prophylactic middle meatal antrostomy to maintain sinus drainage.

Soft Tissue Complications

Soft tissue issues include buccal cheek swelling or bulging (with the extrasinus trajectory), peri-implant soft tissue inflammation, oroantral fistula around the implant platform, and soft tissue recession exposing the implant body.

Other Complications

Other complications include infraorbital nerve paresthesia (usually transient), orbital penetration (rare with proper technique and verification), implant fracture (rare), prosthetic complications (fracture, screw loosening), and implant failure (rare, as the dense cortical zygomatic bone provides excellent anchorage with survival rates of 95-98%).

<image>Panoramic radiograph of a patient rehabilitated with zygomatic implants bilaterally and two conventional anterior maxillary implants, supporting a full-arch fixed prosthesis, demonstrating the implant trajectory through the maxillary sinus into the zygomatic bone</image>

Zygomatic Implants vs. Conventional Grafting

Advantages of Zygomatic Implants

Zygomatic implants eliminate or reduce the need for bone grafting, require fewer surgical stages (often single-stage), allow immediate loading so patients receive fixed teeth the same day, reduce overall treatment time (months versus 1-2 years for grafting with staged implants), avoid donor site morbidity, and achieve high survival rates in severely atrophic maxillae.

Advantages of Conventional Grafting + Implants

Conventional grafting provides more anatomic reconstruction of the alveolar ridge, allows for standard implant prosthetics with simpler maintenance, carries lower sinusitis risk, has more long-term data (decades of follow-up), and offers easier prosthetic retrieval and maintenance.

Current Controversy

No randomized controlled trials directly compare zygomatic implants to grafting with conventional implants. The decision should be individualized based on the degree of atrophy, patient preference, systemic health, surgeon experience, and willingness to undergo multiple surgeries. The trend favors zygomatic implants as the primary option for severe atrophy due to reduced morbidity and treatment time.

Clinical Pearls

Zygomatic implant surgery has a steep learning curve, and training with cadaver courses and mentorship is essential before independent practice. The orbital rim must always be palpated during drilling to verify that the trajectory does not enter the orbit, as orbital penetration is the most feared complication. Sinus health should be optimized preoperatively, with any sinusitis treated before surgery. The ZAGA classification should be used to individualize the implant trajectory rather than applying a rigid intrasinus or extrasinus approach to all patients. Immediate loading is a major advantage, and it should be capitalized upon by achieving high primary stability and using rigid cross-arch splinting. Long-term follow-up for sinusitis symptoms is important, as some patients develop late-onset sinusitis. Patient education is critical, since zygomatic implants require specific hygiene techniques and regular professional maintenance.

References

• Branemark PI, et al. Surgery and fixture installation. Zygomaticus fixture clinical procedures. Nobel Biocare. 1998.
• Aparicio C, et al. The Zygomatic Anatomy-Guided Approach (ZAGA) concept. Clin Implant Dent Relat Res. 2011.
• Malo P, et al. Zygomatic implants placed with a 2-stage procedure: a 5-year retrospective study. Eur J Oral Implantol. 2015.
• Chrcanovic BR, Albrektsson T, Wennerberg A. Survival and complications of zygomatic implants: an updated systematic review. J Oral Maxillofac Surg. 2016.
• Bedrossian E. Rehabilitation of the edentulous maxilla with the zygoma concept: a 7-year prospective study. Int J Oral Maxillofac Implants. 2010.

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