An anterior cervical retractor utilizing a novel principle

Abstract

The alarmingly high soft-tissue complication rates after anterior cervical surgery suggests that the design of current retractors is inadequate. A review of retractor design and consideration of new designs is worthwhile. The author reviewed the literature and the 7 described devices (Cloward, Caspar, Thompson-Farley, Tresserras, Ozer, Takayasu, and Oh devices). With the exception of Cloward/Caspar and Thomson-Farley systems, the author's search of the literature failed to disclose any independent review or investigations of the other retractors, suggesting that the use of these devices is limited. The Cloward/Caspar-style retractors depend for stability on small teeth at the ends of the blades that impale and stretch the longus colli muscle. For stability this self-retaining design requires equal tissue counterpressure. These devices are thus ill suited for a wound with substantially greater pressure from the medial structures and are prone to migration. The Thomson-Farley type of systems use arms with mechanical joints fixed to a table-mounted frame. The releasable joints allow adjustability and independent relaxation. Their limitations include bulk causing obstruction to the surgeons and radiographs, increased setup time, and ease with which excessive force can be applied. The author describes a new anterior cervical retractor that is based on a novel principle. The principle is that bone fixation can be used to provide the retractor blade an axis of rotation inside the wound. This gives improved retractor blade stability with the mechanical advantage of a lever. The stable rotation produced allows adjustable retraction and tissue relaxation without compromise in stability. To the author's knowledge, there are no previously described retractors with this ability. The system consists of a small 2-piece sliding frame fixed to the spine with the distraction screws. Bone fixation is preferable to sharp teeth and longus colli dissection because it works better and heals without scarring. Surgery is carried out through the frame, which slides during distraction. Independent retractor blades are attached to the sides of the frame, which provides a stable craniocaudal axis inside the wound. The blades rotate to provide retraction or relaxation as required. Intermittent relaxation of tissues under retractors has been shown to be beneficial. Another advantage, compared with systems that maintain wounds with vertical sides, is the ease with which an oblique approach can be used. The mechanical advantage has 3 benefits. First, bulky external mechanisms for retraction are avoided, which improves access. Second, numerous blade lengths are unnecessary, reducing inventory. Third, radiolucent polymers can be used with "snap-fit" properties. The improved stability over conventional systems reduces the need for skilled assistance and avoids surgeon frustration after retraction migration. Over a 3-year period, 100 anterior cervical operations have been performed. Anecdotally, operations are quicker mainly because the retractors do not slip. Prospective clinical studies with independent evaluation are underway.