# Condylar Hyperplasia and Asymmetry

## Overview

Condylar hyperplasia (CH) is a progressive, non-neoplastic overgrowth of the mandibular condyle that results in facial asymmetry, malocclusion, and TMJ dysfunction. It most commonly presents in adolescence and young adulthood between the ages of 10 and 25. The condition must be differentiated from other causes of mandibular asymmetry. Whether the condylar growth is active or inactive (burned-out) determines surgical timing and approach.

## Classification

### Obwegeser and Makek Classification

Hemimandibular hyperplasia (HMH) produces vertical excess of the condyle, ramus, and body, with unilateral elongation of the face inferiorly. An ipsilateral open bite with contralateral premature contact develops, the chin remains near the midline (as the vertical vector predominates), and an occlusal cant is present. Hemimandibular elongation (HME) produces horizontal elongation of the mandible with the chin deviated to the contralateral side. A crossbite develops on the contralateral side, the affected side shows prognathism, and the occlusal cant is usually less pronounced. Combined or hybrid forms exhibit features of both HMH and HME.

### Wolford Classification

| Type | Pathology | Growth Vector | Key Features | Histology |
|---|---|---|---|---|
| CH1 | Accelerated condylar growth | Primarily horizontal | Condyle enlarges in all dimensions; chin deviation contralateral | Hyperplastic cartilage cap, active endochondral ossification |
| CH2 | Osteochondroma | Any direction | Exophytic mass (pedunculated or sessile) | Cartilage cap with lobular architecture |
| CH3 | Other tumors (osteoma, chondroma) | Variable | Rare | Tumor-specific |

Type 1 (CH1) represents accelerated and prolonged growth of the condylar head with a primarily horizontal vector. It produces mandibular asymmetry with chin deviation to the contralateral side, and the condyle enlarges in all dimensions. Histologically, a hyperplastic cartilage cap with active endochondral ossification is seen. Type 2 (CH2) is an osteochondroma -- an exophytic bony or cartilaginous mass arising from the condyle that may be pedunculated or sessile and can grow in any direction. Histology shows a cartilage cap with the characteristic endochondral ossification pattern. Type 3 includes other rare condylar tumors such as osteoma and chondroma.

<image>3D CT reconstructions showing the key clinical and skeletal differences between hemimandibular hyperplasia (vertical elongation with occlusal cant, chin near midline) and hemimandibular elongation (horizontal overgrowth with chin deviation to the contralateral side and crossbite), along with a condylar osteochondroma producing an exophytic mass at the condylar head</image>

## Etiology and Pathogenesis

The exact cause is unknown and likely multifactorial. Theories include a growth factor abnormality with increased local growth factor activity in the condylar cartilage, vascular anomaly altering blood supply to the condylar growth center, hormonal influence involving growth hormone or estrogen receptors, childhood condylar trauma stimulating compensatory overgrowth, and genetic factors with rare familial cases reported. Histologically, a hyperplastic cartilage cap with active endochondral ossification at the condylar surface is found. The condition is self-limiting -- growth eventually ceases, but the resulting asymmetry is permanent.

## Diagnosis

### Clinical Examination

Patients present with progressive facial asymmetry including chin deviation and fullness of the affected side. An occlusal cant develops from maxillary compensation over time. A crossbite on the contralateral side is seen in HME, while an ipsilateral open bite occurs in HMH. TMJ symptoms including clicking, pain, and limited opening are variable. Serial photographs document progression, and clinical measurements assess facial proportions including chin point deviation from the midline, ramus heights, and facial thirds.

### Imaging

#### Panoramic Radiograph

The panoramic radiograph serves as a screening tool to evaluate condylar morphology, condylar neck length, and ramus height asymmetry. Osteochondroma may appear as an exophytic mass.

#### CT (3D Reconstruction)

CT provides condylar size comparison (volume, height, width), morphologic assessment of the condylar head, ramus height measurement, maxillary cant assessment, and information for surgical planning.

#### SPECT/Bone Scintigraphy (Gold Standard for Activity)

SPECT (Single Photon Emission Computed Tomography) using Tc-99m bone scan evaluates metabolic activity of the condyles through quantitative comparison of uptake between right and left condyles. An asymmetry index greater than 10% suggests active condylar growth. Sensitivity is 70-85% for active condylar hyperplasia. Limitations include false positives from inflammatory conditions and degenerative joint disease, and false negatives from low-grade activity. Hybrid SPECT/CT combines functional (SPECT) and anatomic (CT) data for improved localization.

#### MRI

MRI evaluates disc position and soft tissue changes and can identify osteochondroma through its cartilage cap, but it is less useful for growth activity assessment.

### Histopathology

The condylectomy specimen confirms the diagnosis. Active CH shows a thickened cartilage cap (greater than 1 mm), endochondral ossification with islands of cartilage in subchondral bone. Osteochondroma demonstrates a characteristic cartilage cap with lobular architecture and endochondral ossification.

## Management

### Determining Activity Status

In active CH, the asymmetry is progressive and SPECT shows increased uptake on the affected side. Surgery should include condylectomy to halt growth before correcting the asymmetry. In inactive (burned-out) CH, the asymmetry is stable with no change on serial photos or cephalograms over 12 months and SPECT shows symmetric uptake. Orthognathic surgery alone can address the established asymmetry.

### Surgical Options

#### Condylectomy

High condylectomy (proportional condylectomy) removes the hyperplastic condylar cap (3-5 mm), eliminating the growth center while preserving most of the condyle and ramus height. It carries lower risk of malocclusion and may be combined with disc repositioning. Low condylectomy involves more aggressive resection of the condylar head, with greater risk of shortening the ramus and creating an ipsilateral open bite. It is reserved for large osteochondromas requiring complete condylar head removal and may require costochondral graft or alloplastic reconstruction.

#### Orthognathic Surgery

Orthognathic surgery addresses the dentofacial deformity caused by condylar hyperplasia. Le Fort I osteotomy corrects the maxillary cant, BSSO corrects mandibular asymmetry, and genioplasty corrects chin point deviation. These procedures may be performed simultaneously with condylectomy (single-stage) or staged.

#### Single-Stage vs. Staged Approach

The single-stage approach (condylectomy plus orthognathic surgery) offers the advantages of one anesthesia, one recovery, and immediate correction. However, it requires careful planning because condylectomy changes condylar height and position, affecting the orthognathic plan, and VSP is highly recommended. Many experienced surgeons prefer this approach for efficiency. The staged approach (condylectomy first, orthognathic 6-12 months later) allows adaptation after condylectomy before planning orthognathic surgery and may result in more precise orthognathic outcomes. Its disadvantages include two surgeries, prolonged treatment time, and the potential for compensatory changes to develop between stages.

#### Disc Management During Condylectomy

The articular disc is displaced superiorly during condylectomy. Options include disc repositioning and suturing to the lateral capsule, disc removal with fat graft interpositional material, and disc preservation in situ without formal repositioning. Wolford advocates disc repositioning to optimize joint function post-condylectomy.

<image>SPECT/CT images demonstrating increased radionuclide uptake in the right mandibular condyle compared with the left, indicating active condylar hyperplasia, alongside the corresponding 3D CT showing the enlarged right condyle with right hemimandibular elongation and chin deviation to the left</image>

## Outcomes

Condylectomy effectively halts progressive growth in active CH. Single-stage condylectomy with orthognathic surgery achieves high satisfaction rates and acceptable stability. Recurrence after condylectomy is rare if the cartilage cap is adequately removed. Post-condylectomy complications include temporary occlusal changes and TMJ symptoms that are usually self-limiting. Orthognathic stability is comparable to standard orthognathic cases once growth is arrested.

## Differential Diagnosis of Mandibular Asymmetry

The differential includes condylar hyperplasia and osteochondroma, condylar hypoplasia (contralateral, which mimics ipsilateral hyperplasia), unilateral condylar fracture with growth disturbance from childhood, unilateral TMJ ankylosis, fibrous dysplasia of the mandible, hemifacial microsomia (first and second branchial arch syndrome), vascular malformations, and neoplasms (osteosarcoma, chondrosarcoma).

## Controversies

### High vs. Low Condylectomy

High condylectomy preserves more condylar anatomy with lower morbidity, but the surgeon must ensure complete removal of the growth center. Low condylectomy provides more definitive removal of pathology but has greater functional implications. The trend favors proportional (high) condylectomy with simultaneous orthognathic surgery.

### Timing of Orthognathic Surgery

The single-stage approach is increasingly preferred but requires expertise and VSP. The staged approach offers the theoretical advantage of more predictable orthognathic outcomes. No high-quality comparative studies exist.

### Reliability of SPECT

SPECT has limitations with sensitivity that is not 100%. Some advocate clinical and radiographic monitoring (serial cephalograms) as an alternative or adjunct. Hybrid SPECT/CT improves accuracy but is not universally available. Clinical progression documented through serial photographs and models remains important regardless of SPECT findings.

## Clinical Pearls

Condylar growth activity should always be assessed before planning orthognathic surgery, because operating on an actively growing condyle without condylectomy risks recurrence of asymmetry. SPECT is the best available test for growth activity, but clinical and radiographic monitoring supplements its findings. High condylectomy is sufficient in most cases, and aggressive resection is rarely needed. VSP is invaluable for single-stage condylectomy and orthognathic surgery because it accounts for the change in condylar height and allows accurate splint fabrication. The maxillary cant is a secondary (compensatory) deformity, and Le Fort I osteotomy is almost always needed in conjunction with BSSO. Osteochondromas should be completely excised because the cartilage cap contains the proliferative zone. Histopathologic analysis of the condylectomy specimen should always be performed to confirm the diagnosis and rule out malignancy. Patients should be counseled that mild residual asymmetry may persist, as perfect symmetry is rarely achievable.

## References
- Obwegeser HL, Makek MS. Hemimandibular hyperplasia-hemimandibular elongation. J Maxillofac Surg. 1986.
- Wolford LM, Movahed R, Perez DE. A classification system for conditions causing condylar hyperplasia. J Oral Maxillofac Surg. 2014.
- Saridin CP, et al. Bone scintigraphy of the condyle in unilateral condylar hyperplasia. Int J Oral Maxillofac Surg. 2011.
- Villanueva-Alcojol L, et al. Condylar hyperplasia: clinical, histopathological, and treatment considerations. J Craniomaxillofac Surg. 2011.
- Wolford LM, et al. Outcomes of condylectomy with orthognathic surgery for condylar hyperplasia. J Oral Maxillofac Surg. 2014.
- Nitzan DW, et al. Condylar hyperplasia and facial asymmetry: a comprehensive review. Oral Surg Oral Med Oral Pathol Oral Radiol. 2022.