How to Remove a Broken Single Transphyseal Screw

1. Introduction

The surgical correction of angular limb deformities is performed primarily for cosmetic appeal and as a means of altering a conformation thought to be associated with musculoskeletal injuries incurred during an athletic career. A relatively small number of surgeries are performed to correct severe congenital or acquired angular limb deformities. Retardation or temporary arrest of growth on one side of a physis by mechanical restriction is a commonly employed technique in the surgical correction of angular limb deformities.

A variety of techniques using implants, placed so they bridge the convex or long side of an open physis at the site of deviation of the affected limb, have been described.¹  These techniques employ the mechanical principle, whereby the cells producing growth by increase in length of the limb on the bridged side of the physis are temporarily compressed and inhibited. Growth continues on the contralateral side of the limb until the perceived deformity of the limb has corrected, at which time the implants are removed and normal growth is permitted to resume.² 

The use of a single cortical screw to traverse and temporarily close the physis on the convex side of the limb has been well-documented in recent years.^3–6 Implants that traverse or bridge an open physis must be removed promptly when the required degree of correction has been achieved, because failure to do so may result in overcorrection and deformity in the opposite direction. Implants still present at the time of radiographic closure of a physis are generally removed if the animal is likely to undergo a pre-purchase examination. Single cortical screws, placed so as to traverse a physis for correction of an angular limb deformity, are removed under standing sedation or general anesthesia, depending on the type of implant and location, surgeon preference, and temperament of the patient.

Complications associated with the placement and removal of a single transphyseal screw include breakage of the screw head or shaft and stripping of the screw head. Although these complications have been documented and a technique outlining removal of screws after stripping of the head exists within the literature, a comprehensive description of how to remove a broken screw does not exist.^{4,6 – 8}

The purpose of this report is to provide a concise description on how to remove a broken single transphyseal screw (Fig. 1). Other complications associated with screw removal will be briefly addressed.
 

2. Materials and Methods

If placing transphyseal screws for the correction of angular limb deformities, we recommend that one should be equipped with an extraction seta and also be familiar with its use. The set is comprised of a T-handle with quick coupling, a hollow bone reamer, an extraction bolt, and a conical extraction device for threaded washers (Fig. 2). Additional equipment required includes a selection of bone chisels and curettes, countersink or bone gouge, and some finger retractors such as a pair of Senn or Mathieu retractors. Appropriate surgical draping, a 15T scalpel blade, a balanced electrolyte solution with or without antibiotics, appropriate suture, and bandaging materials should also be at hand.
 

Intraoperative radiography is an essential component of successful screw extraction, and the process is greatly expedited through use of a digital system.

Surgical Procedure for Broken Screw Head (or Shaft)

Successful removal of a broken transphyseal screw requires that you have the necessary equipment at hand, that the patient is properly positioned under general anesthesia, and that there are appropriately trained assistants. Adequate personnel should include an anesthetist, surgical technician, assistant surgeon, and radiographer. All personnel involved in the procedure should be appropriately attired in lead aprons for the entire procedure.

The animal should be restrained in lateral recumbency under inhalant general anesthesia with the limb containing the implant in the uppermost position. If screw removal was initially approached with the horse standing, a light sterile bandage should be placed for induction of general anesthesia. The affected limb should be positioned so that both lateral to medial and dorsopalmar radiographs can be easily obtained without interfering with the surgical field.

After appropriate sterile preparation and surgical draping of the site and radiographic plate or panel, proper exposure of where the screw was placed is necessary. A 3- to 4-cm incision, centered over the head of the screw parallel to the long axis of the limb, is made down to cortical bone. The principle surgeon should be positioned so that the leading hand is closest to the limb (i.e., a right-handed surgeon should stand with his right side to the ventrum of the patient). This allows for easier alignment with the implant and the appropriate acute angle necessary for successful removal to be achieved.  [...]