Medpor is a brand name for a synthetic surgical material primarily used in reconstructive and cosmetic procedures to replace or augment the underlying bone and soft tissue structures of the face and head. Surgeons select this implant for its ability to provide structural support while remaining compatible with human tissue. Its primary function is to serve as a permanent framework for restoring facial contour following trauma or correcting congenital deformities.
Composition and Properties of Medpor
The Medpor implant is made from porous high-density polyethylene (PHDPE), a synthetic polymer derived from ethylene molecules. This material is manufactured through sintering, where fine particles are fused together under high heat and pressure, resulting in a solid yet porous structure. The key characteristic of this implant is its specific, interconnected, open-pore design.
These pores are typically sized between 100 and 250 micrometers, allowing for tissue integration. This unique structure encourages fibrovascular ingrowth, where the patient’s own fibrous connective tissue and tiny blood vessels penetrate the implant’s matrix. This integration biologically anchors the implant to the surrounding tissue, enhancing stability and reducing the likelihood of displacement. The material is non-antigenic and does not provoke an immune reaction, making it highly biocompatible for long-term use.
Primary Surgical Applications
The material’s strength and ability to be sculpted make it a common choice for various procedures, particularly in the craniofacial skeleton. In craniofacial reconstruction, Medpor is employed to repair defects resulting from severe facial trauma. This includes repairing orbital floor fractures, which restore the support structure of the eye socket, and correcting defects in the cranium following neurosurgery.
The implant is used in ear reconstruction, most notably for the correction of microtia. For this procedure, a pre-contoured porous polyethylene framework is implanted and covered with the patient’s own tissue, providing a stable and durable form for the new ear structure. Its stiffness and malleability allow the surgeon to create a detailed and anatomically correct scaffold.
Medpor is also used in cosmetic augmentation to enhance facial contours. Surgeons use it for procedures like chin augmentation (mentoplasty), cheek augmentation (malar), and jawline contouring to improve skeletal projection and symmetry. Its use in the orbit extends to oculoplastic surgery, where it serves as a non-wrapped implant in the anophthalmic socket to replace volume lost after eye removal. Its porous nature allows for muscle attachment and tissue integration, which can improve the movement of a prosthetic eye.
The Implantation Process
The surgical process begins with pre-operative planning, often involving three-dimensional computed tomography (CT) scans to assess the defect size. While custom-designed implants based on patient scans are available, surgeons frequently utilize pre-manufactured, “off-the-shelf” stock implants adapted during the procedure. The ability to precisely modify the implant in the operating room is a benefit of the material.
The surgeon can cut, carve, and shape the implant with standard surgical instruments to achieve an optimal fit against the patient’s bone structure. The edges are often “feathered,” or tapered, to ensure a smooth transition from the implant to the natural bone contour, minimizing any visible step-off. Once positioned, the implant must be secured to the underlying bone to prevent post-operative migration.
Fixation is typically accomplished using small titanium screws and plates, which anchor the implant firmly in place. The high-density polyethylene is designed to accept these rigid fixation devices without cracking or fracturing, providing the surgeon with flexibility in securing the construct.
Managing Post-Surgical Complications
Despite its biocompatibility, the use of any implanted foreign material carries risks, with infection being a primary concern for porous materials. The interconnected pore structure, while promoting tissue ingrowth, can provide a larger surface area for bacteria to colonize if contamination occurs. An infection within the implant is difficult to treat with antibiotics alone because the porous matrix shields the bacteria from the medication.
If an infection is severe or persistent, the implant may require surgical removal due to the extensive tissue incorporation. Another complication, particularly in areas with thin soft tissue coverage like the nose or ear, is extrusion, where the implant pushes through the overlying skin. Signs such as persistent swelling, localized redness, or acute pain should be promptly evaluated by the surgeon. The risk of extrusion is heightened in areas of high stress or limited tissue volume, requiring careful patient selection and precise surgical technique. In cases of severe extrusion or chronic infection, the implant may need to be explanted.