A tissue expander is a temporary, inflatable medical device used in reconstructive surgery to generate extra skin and soft tissue. This process relies on the skin’s natural ability to grow and stretch when subjected to gradual, constant pressure. The volume of fluid added to the device is measured in cubic centimeters (cc). The total volume is highly individualized and accumulated over a period of time, representing the fluid needed to create a tissue envelope large enough for the final reconstruction.
Anatomical and Surgical Determinants of Capacity
The overall capacity of a tissue expander is limited by the manufacturer’s design, with predetermined sizes ranging from 300 cc up to 800 cc. The surgeon selects the initial expander size based on the patient’s existing anatomy, including the size of the area being reconstructed and the laxity of the surrounding tissue. For example, a patient’s chest wall dimensions influence the required base width and projection of a breast expander.
The true final volume achieved is dictated by the specific surgical goal, such as matching the size of a contralateral breast or covering a specific defect. Surgeons commonly fill the expander slightly beyond the final desired volume, a process known as overfilling. This technique ensures a generous amount of stretched tissue is available for the permanent implant or reconstruction, allowing for a small amount of tissue recoil after the expander is removed.
Overfilling may involve adding an extra 10 to 20 percent of volume above the target size to adequately stretch the skin envelope. The ultimate limit to the volume is the capacity of the patient’s remaining skin to tolerate the pressure without compromising blood flow or causing complications. The final cc count is a dynamic measurement, determined by the patient’s physiological response to the expansion.
The Incremental Filling Process
The desired final capacity is reached through a staged process where saline solution is introduced into the expander over time. Patients typically attend appointments every one to two weeks, allowing the skin adequate time to adapt to the new volume between sessions. The saline is injected through a specialized, self-sealing port that may be integrated into the expander or placed remotely beneath the skin.
During a typical filling session, the volume of saline added is carefully monitored, often ranging from 50 to 100 cc per visit. This amount is adjusted based on the patient’s tolerance and the tension observed in the overlying skin. The patient generally feels pressure and tightness, which usually subsides within a day or two as the skin stretches to accommodate the new volume.
The entire expansion phase can last from several weeks to many months, depending on the total volume required and how quickly the patient’s tissue responds. Surgeons continue adding volume until the target cc count is reached, or until the overlying skin begins to show signs of excessive tension, such as blanching or paleness.
Typical Volume Ranges by Surgical Application
The number of cc’s required in a tissue expander varies dramatically depending on the location and purpose of the reconstruction. In breast reconstruction, the volume can range widely, often starting around 300 cc and frequently exceeding 800 cc, sometimes reaching 1000 cc or more in larger reconstructions. Achieving a medium to large cup size often requires a final volume of 450 cc to 600 cc or higher in the expander, particularly in a post-mastectomy setting where the expander must create both skin and volume.
Scalp and Forehead Reconstruction
For smaller, more localized procedures such as scalp or forehead reconstruction, the required volume is significantly less. Expanders used in these areas may have maximum capacities of 125 cc to 350 cc. The goal is to generate just enough healthy skin to cover the defect after the expander is removed.
Extremity or Trunk Reconstruction
In extremity or trunk reconstruction, the volumes are determined by the size of the wound or defect that needs covering. For small wounds, relatively modest volumes are used. For large areas on the back or limbs, the expander may be a rectangular or crescent shape with a capacity in the 500 cc to 800 cc range.