Indications for Superior versus Inferior Based Flaps in Canal Wall Down Mastoidectomy
The choice between superior and inferior based flaps in canal wall down (CWD) mastoidectomy should be determined by the specific anatomical defects, extent of disease, and desired outcomes for cavity management, with inferior based flaps generally preferred for most routine cases due to better blood supply and more reliable healing.
Anatomical Considerations for Flap Selection
Inferior Based Flaps
- Primary Indications:
- Standard choice for routine CWD mastoidectomy procedures 1
- When reliable blood supply is critical (better vascularity from postauricular and occipital vessels)
- When complete mastoid cavity coverage is needed 2
- For sclerotic mastoid cavities requiring complete epithelialization
- When reducing cavity volume is a primary goal 3
Superior Based Flaps
- Primary Indications:
- When the inferior periosteum is compromised or unavailable
- For selective coverage of epitympanic or attic regions
- When combined with other reconstruction techniques (e.g., cartilage reconstruction)
- When preserving inferior blood supply for potential future procedures
- For smaller, more targeted defects requiring precise placement
Technical Considerations
Inferior Based Periosteal Flap Technique
- Harvested from the postauricular region with pedicle maintained inferiorly
- Can be designed with multiple pedicles (anterior, inferior, and superior) for optimal blood supply 1
- Provides excellent coverage of the mastoid cavity
- Can be combined with bone paté and split-thickness skin grafts for complete obliteration
- Results in 88-98% dry cavity rates at various follow-up intervals 1
Deep Temporal Fascial-Periosteal Flap
- Postauricular, inferiorly based pedicled flap
- Large enough to obliterate sclerotic mastoid cavities without additional flaps
- Shrinks less than muscular flaps during healing
- Promotes epithelialization over bone and shortens healing time 2
Outcomes and Complications
Advantages of Inferior Based Flaps
- Better vascular supply leading to more reliable healing
- Reduced cavity volume and improved epithelialization
- Lower rates of postoperative otorrhea
- Shorter healing time
- Less shrinkage compared to muscle flaps 2
Potential Complications to Consider
- Flap necrosis (more common with superior based flaps due to less reliable blood supply)
- Inadequate cavity obliteration
- Persistent otorrhea
- Delayed healing
- Need for revision surgery
Combined Approaches
For complex cases, consider:
- Double musculoperiosteal flaps with free-floating cartilages for canal reconstruction 4
- Combination of bone dust obliteration with inferiorly-based periosteal flap coverage 3
- Single flap with multiple pedicles (anterior, inferior, and superior) with bone paté and split-thickness skin grafts 1
Decision Algorithm
Assess the mastoid cavity size and configuration
- Large cavity → Inferior based flap (better coverage)
- Small, targeted defect → Either flap type may be appropriate
Evaluate local tissue availability and quality
- Compromised inferior periosteum → Superior based flap
- Intact periosteum → Inferior based flap preferred
Consider the primary goal
- Complete cavity obliteration → Inferior based flap with multiple pedicles
- Selective coverage → Choose flap based on target area
Evaluate patient factors
- History of previous surgery → May influence available tissue
- Comorbidities affecting wound healing → Favor inferior based flap (better blood supply)
In most routine CWD mastoidectomy cases, an inferior based periosteal flap provides the most reliable results with dry cavity rates exceeding 95% at long-term follow-up 1, 3, making it the preferred option for most surgeons when anatomically feasible.