Internal Midface Distractor System
The Internal Midface Distractor provides an internal distraction device to correct severe midface retrusion and to treat patients born with craniofacial anomalies that result in severe midface deficiencies, including Apert Syndrome, Crouzon Syndrome, and Pfeiffer Syndrome. These syndromes produce severe midface retrusion and severe intracranial pressure which can lead to upper airway obstruction, degenerative vision, ulcerations of the cornea, potential blindness, sleep apnea, and psychosocial disorders.
The Internal Midface Distractor System provides several advantages in treating midface deficiencies over conventional osteotomies and bone grafting. For example, a LeFort III osteotomy in combination with bone grafts and rigid internal fixation is limited to approximately 10 mm of advancement due to the magnitude of the resulting soft-tissue forces resisting the advancement. Patients with severe midface retrusion of up to 40 mm can be treated with the Internal Midface Dis-tractor System in a single procedure because substantial soft-tissue forces exerted on the midface can be overcome.
The Internal Midface Distractor System also provides the ability to minimize relapse associated with the advancement. Employing distraction to correct these deformities provides a slow, controlled means for overcoming the forces of soft-tissue resistance which leads to an expectation (supported by clinical studies ) of a lesser degree of relapse. The presence of a buried distractor during bone consolidation further provides a rigid construct to counteract the soft-tissue forces until the bone has fully consolidated.
The Internal Midface Distractor System consists of a telescoping barrel attached to an anterior and a posterior footplate. It is placed subcutaneously with the anterior footplate fastened to the lateral orbital rim, extending down to the maxilla and spanning the zygomaticomaxillary suture, and the posterior footplate fastened to the temporal region of the cranium. The barrel of the distractor body lies sagittally against the cranium underneath the temporalis muscle, and its posterior end extends percutaneously into the external environment for activation. In a typical case, two devices are attached (one on each side) for advancement of the midface.
The outer barrel of the distractor body is threaded to accept both a hex nut and the posterior footplate. The posterior footplate is a fifteen-hole plate that can be moved anywhere along the threaded portion of the distractor body in 0.5 mm increments. The hex nut fixes the position of the posterior footplate once it has been chosen. The anterior foot plate attaches to the distractor body by a tongue and groove connection. This allows the surgeon to select from amongst five different styles of anterior footplates to fit the patients anatomy. A small machine screw can be used to rigidly secure the anterior footplate to the distractor body, or, if the machine screw is not used, the distractor body can be easily separated from the anterior footplate during removal without performing a full coronal incision. This enables a quick removal procedure of the distractor while leaving the anterior footplate implanted.
The device is offered in one length for up to 40 mm of distraction. The activation end of the device extends into the external environment on smaller patients, or, in the case of larger patients, an optional extension can be attached by a machine screw to lengthen the device. The extensions are offered in three versions: a rigid extension (20 mm length), an extension incorporating a universal joint (20 mm length), and an extension incorporating a flexible cable (40 mm length). The activation end of the distractor and the extensions engage with the patient screwdriver for advancements in 0.5 mm increments.
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