How to Remove a Broken Single TransphysealScrew

Thomas O’Brien, MVB; Robert J. Hunt, DVM, MS, Diplomate ACVS;Jorge Gomez, MVZ, MS, Diplomate ACVS; Michael A. Livesey, BVMS;Dwayne H. Rodgerson, DVM; Michael A. Spirito, DVM

Author’s addresses: Department of Surgical Sciences, Veterinary Medical Teaching Hospital, Uni-versity of Wisconsin, 2015 Linden Drive, Madison, Wisconsin 53706 (O’Brien and Livesey); DavidsonSurgery Center, Hagyard Equine Medical Institute, 4250 Iron Works Pike, Lexington, Kentucky40511 (Hunt, Gomez, Rodgerson, Spirito); e-mail: tomob20@yahoo.com © 2010 AAEP.

1. Introduction

The surgical correction of angular limb deformitiesis performed primarily for cosmetic appeal and as ameans of altering a conformation thought to be as-sociated with musculoskeletal injuries incurred dur-ing an athletic career. A relatively small number ofsurgeries are performed to correct severe congenitalor acquired angular limb deformities. Retardationor temporary arrest of growth on one side of a physisby mechanical restriction is a commonly employedtechnique in the surgical correction of angular limbdeformities.

A variety of techniques using implants, placed sothey bridge the convex or long side of an open physisat the site of deviation of the affected limb, havebeen described.1 These techniques employ the me-chanical principle, whereby the cells producinggrowth by increase in length of the limb on thebridged side of the physis are temporarily com-pressed and inhibited. Growth continues on thecontralateral side of the limb until the perceiveddeformity of the limb has corrected, at which time

the implants are removed and normal growth ispermitted to resume.2

The use of a single cortical screw to traverse andtemporarily close the physis on the convex side ofthe limb has been well-documented in recentyears.3–6 Implants that traverse or bridge an openphysis must be removed promptly when the re-quired degree of correction has been achieved, be-cause failure to do so may result in overcorrectionand deformity in the opposite direction. Implantsstill present at the time of radiographic closure of aphysis are generally removed if the animal is likelyto undergo a pre-purchase examination. Singlecortical screws, placed so as to traverse a physis forcorrection of an angular limb deformity, are re-moved under standing sedation or general anesthe-sia, depending on the type of implant and location,surgeon preference, and temperament of thepatient.

Complications associated with the placement andremoval of a single transphyseal screw includebreakage of the screw head or shaft and stripping ofthe screw head. Although these complications

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have been documented and a technique outliningremoval of screws after stripping of the head existswithin the literature, a comprehensive description ofhow to remove a broken screw does not exist.4,6–8

The purpose of this report is to provide a concisedescription on how to remove a broken singletransphyseal screw (Fig. 1). Other complicationsassociated with screw removal will be brieflyaddressed.

2. Materials and Methods

If placing transphyseal screws for the correction ofangular limb deformities, we recommend that oneshould be equipped with an extraction seta and alsobe familiar with its use. The set is comprised of aT-handle with quick coupling, a hollow bone reamer,an extraction bolt, and a conical extraction device forthreaded washers (Fig. 2). Additional equipmentrequired includes a selection of bone chisels andcurettes, countersink or bone gouge, and some fingerretractors such as a pair of Senn or Mathieu retrac-tors. Appropriate surgical draping, a 15T scalpelblade, a balanced electrolyte solution with or with-out antibiotics, appropriate suture, and bandagingmaterials should also be at hand.

Intraoperative radiography is an essential compo-nent of successful screw extraction, and the processis greatly expedited through use of a digital system.

Surgical Procedure for Broken Screw Head (or Shaft)Successful removal of a broken transphyseal screwrequires that you have the necessary equipment at

hand, that the patient is properly positioned undergeneral anesthesia, and that there are appropriatelytrained assistants. Adequate personnel should in-clude an anesthetist, surgical technician, assistantsurgeon, and radiographer. All personnel involvedin the procedure should be appropriately attired inlead aprons for the entire procedure.

The animal should be restrained in lateral recum-bency under inhalant general anesthesia with thelimb containing the implant in the uppermost posi-tion. If screw removal was initially approachedwith the horse standing, a light sterile bandageshould be placed for induction of general anesthesia.The affected limb should be positioned so that bothlateral to medial and dorsopalmar radiographs canbe easily obtained without interfering with the sur-gical field.

After appropriate sterile preparation and surgicaldraping of the site and radiographic plate or panel,proper exposure of where the screw was placed isnecessary. A 3- to 4-cm incision, centered over thehead of the screw parallel to the long axis of thelimb, is made down to cortical bone. The principlesurgeon should be positioned so that the leadinghand is closest to the limb (i.e., a right-handed sur-geon should stand with his right side to the ventrumof the patient). This allows for easier alignmentwith the implant and the appropriate acute anglenecessary for successful removal to be achieved.

With overlying soft-tissue layers retracted, theshaft of the screw is exposed. If necessary, a bonechisel or bone gouge may be used to expose the endof the remaining screw shaft. A reamer is thenattached to the T-handle and fitted over the shaft ofthe screw, and a tract cut is made around the im-plant. It is important that the reamer follow theorientation of the screw without its teeth cominginto contact with the shaft (Fig. 3). Contact be-

Fig. 1. A dorsopalmar radiograph of a carpus after breaking of asingle transphyseal screw.

Fig. 2. An extraction set.a Shown from left to right are a quick-couple hand chuck, a hollow bone reamer, an extraction bolt, anda conical extraction device for threaded washers.

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tween the two will result in damage to the cuttinginstrument and creation of metallic debris withinthe tract, which is extremely difficult to completelyremove. Strong pressure and rotation in a counter-clockwise direction is needed to ensure that theteeth of the reamer engage the bone and cut a tract.Regular orthogonal radiographic evaluation is nec-essary to ensure proper alignment of the reamerover the screw shaft (Fig. 4).

If a bend is present in the screw, as is often thecase, reaming should continue just distal to the levelof the bend, if possible, stopping just before thereamer comes in contact with the screw shaft. Fail-ure to ream to this depth may result in breakage ofthe screw shaft at the bend during attempted extrac-tion, resulting in the entire process having to berepeated.

After a tract has been reamed to the appropriatedepth, the operator is ready to use the extractionbolt. This is attached to the T-handle and placed inthe tract over the screw fragment. By pressingdown strongly, the instrument is rotated in a coun-terclockwise direction until it engages the threads ofthe screw fragment. Because of the decrease indiameter of the extraction bolt from its mouth prox-imally, it rapidly tightens over the screw shaft (Fig.5). Continued strong counterclockwise rotation anddownward pressure will cause the screw to disen-gage from the bone and be removed (Fig. 6). If thescrew breaks for a second time, the entire processshould be repeated until all screw fragments areremoved.

If metallic fragments remain within the tract,light curettage and copious flushing using a bal-anced polyionic electrolyte should follow until repeatradiographs confirm removal of all fragments (Fig.7). The subcutaneous tissues and skin are closed ina routine manner, and the area is covered with asterile bandage.

Postoperative care is as for standard screw re-moval, with bandaging continued for 2–4 wk.4

After stall rest with hand walking, regular turnoutis resumed after suture removal 14-days post-oper-atively if healing is proceeding normally.

Fig. 3. A photograph highlighting the acute angle necessary toallow the hollow reamer to be appropriately aligned over thescrew shaft.

Fig. 4. A dorsopalmar radiograph shows proper alignment of thehollow reamer over the broken-screw shaft.

Fig. 5. A close-up photograph of the mouth of the extraction boltshows that the core is reverse-threaded and its internal diameterdecreases more proximally.

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3. Results

Approximately 800 physeal bridging procedures,500 of which involve the distal radial physis, areperformed at Hagyard Equine Medical Instituteeach year for the correction of angular limb defor-

mities using a single transphyseal screw. Of thisnumber, it is estimated that screw breakage occursin 3–4 patients each year, and using the techniqueoutlined above, all broken screws have been success-fully removed.

Intraoperative complications encountered duringbroken-screw removal included contact between thereamer and the screw, resulting in metallic debrisscattered within the tract, and further breakage ofthe screw during attempted removal because of fail-ure to ream beyond the bend in the screw. Themetallic debris was removed by copious lavage andgentle curettage, whereas repeated breakage of thescrew necessitated the entire process to be repeated.

Early post-operative complications included physitison the affected side of the limb, a prolonged period oflameness, and seroma formation. All postoperativecomplications responded favorably to conservativemanagement, including stall rest and systemic anti-inflammatory drugs. Long-term cosmetic outcomewas acceptable in all cases. Varying blemishes at thesurgical sites were seen, but no overcorrection becauseof premature closure of the physis was noted. Allhorses fulfilled their intended purpose.

4. Discussion

The extraction set, comprised of a hand chuck, hol-low bone reamer, extraction bolt, and conical extrac-tion device for threaded washers, is available forboth 3.5- and 4.5-mm cortical screws. Sparereamer tubes and extraction bolts should be kept instock, because the teeth of the reamers are oftendamaged during the procedure and the screw maybecome permanently engaged in the extraction bolt.Synthes also supply a forceps for broken-screw re-moval, but the authors have not found this instru-ment to be useful for the removal of transphysealscrews.

The conical extraction device for threaded wash-ers, provided with the extraction set, is used forscrew removal after stripping of the screw head, thethreads of which are orientated in the direction op-posite to those of the screw. As a result of strippingof the screw head, the hexagonal head of the screwdriver no longer fits snugly into the hexagonal in-dentation or recess within the screw head, known asthe screw drive. The extraction device is insertedin the stripped screw-head indentation or screwdrive and when turned in a counterclockwise direc-tion, engages the screw head and tightens. Contin-ued counterclockwise pressure applies an extractionforce, and the screw is removed.7

Although the distal radial physis is the most com-mon physis temporarily bridged by single transphy-seal screw placement, the frequency of screwbreakage at this site is disproportionally high.4

In general, technique of screw placement greatlyimpacts the risk of screw breakage, but the durationof implantation, the age at implantation, and thelength of screw used may all contribute to the in-

Fig. 6. A photograph shows the screw disengaging from the boneand being slowly removed with continued counterclockwise rota-tion after tightening of the extraction bolt over the screw shaft.

Fig. 7. After screw removal, a dorsopalmar radiograph revealsmetallic debris within the screw tract. Copious lavage with abalanced polyionic solution and light curettage will allow forremoval of all foreign material.

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creased frequency with which screw breakage occursat the distal radial physis.

Plastic deformation weakens the screw and mayresult in implant failure during removal. Plasticdeformation of the head-shaft junction may occurbecause of uneven load sharing across the screwhead or overtightening of the implant.9,10 Unevenload sharing may occur because of inadequatecountersinking of the hole to accommodate thescrew head. This may result from the head en-gaging the cortex unevenly as the screw is tight-ened or with continued growth, because the bonelengthens and places excessive stress on the screwhead.1,9 Overtightening of the implant may arisebecause of the technique of placement or durationof implantation.

The original description of the technique de-scribed placement of the transphyseal screw in lag-fashion but has since evolved to positional screwplacement for all locations, because it was felt thelag technique allowed overtightening of the implantat the time of placement or with continued limbgrowth.3,6 Also, after screw placement in lag fash-ion, the unfilled threads cut into the cis-cortex willrapidly fill in with bone, producing difficulty inscrew extraction, because this necessitates thethreads cut their own way through the bone.7

Some of the authors of this report favor placingthe screw fully (self-tapping), backing it out at leasthalf its entire length, and replacing it again. Theyrepeat this 2–3 times before replacing the screw toits full depth. After this, the screw is finally backedout one to two entire revolutions. It is speculatedthat both these steps in initial placement help seatthe screw and facilitate removal.5 These methodsin screw placement may wear down the threads cutinto the bone and reduce the degree to which thethreads fill with bone before implant removal.

Backing the screw out one entire revolution willresult in the head of the screw being raised abovethe contour of the bone, resulting in a palpable pro-tuberance beneath the skin, unless the hole wasdeeply countersunk. If it protrudes, the screw headmay then act as a pressure point, resulting in skinnecrosis. This can be avoided if the screw is placedpalmar/caudal to the medial or lateral mid-point ofthe metaphysis.

It has been some of the authors’ experience thatscrews remaining across a physis for a period longerthan 6–8 wk are at greater risk of breaking. Theauthors routinely monitor implants radiographi-cally, particularly those implants bridging a physisfor a period greater than 6 wk. The authors recom-mend replacing screws that show radiographic signsof bending or choose an alternative bridging tech-nique entirely.

It is worth noting that screws have been placedacross the distal radial physis in individuals up to563 days of age, whereas patient age in individualswhere screws are placed across the distal metacar-pal or metatarsal physis usually does not exceed 112

days.4 The difference in patient age for screw im-plantation at both sites may also influence the fre-quency with which screw breakage is seen at eachsite. One would expect that, in older growing ani-mals, the bone density would be greater and propor-tionately more torque would be required for screwremoval.

The length of the screw used in the distal radialphysis ranges from approximately 48 to 60 mm,whereas those implanted across the distal metacar-pal or metatarsal physis range from 34 to 42 mm.Therefore, a greater length of bone-screw interfaceoccurs with implants placed across the distal radialphysis than those placed across the distal metacar-pus/metatarsus, requiring greater torque for im-plant removal.

Appropriate post-operative bandaging will helplimit the local tissue reaction and production offibrous tissue that impedes implant removal.4,6

However, during the healing process, granulationtissue and periosteal callus may encompass thescrew head and fill out the screw drive. This mayresult in difficulty locating and properly seatingthe end of the screwdriver in the hexagonal driveof the screw head. Inadequate seating can thenlead to stripping or breakage of the screwhead.1,4,11 To avoid either of these complications,it is imperative that encroaching bone and softtissue in and around the head of the screw beremoved before any attempt at screw looseningand removal. This is achieved through the use ofintraoperative radiographic control using 18-gauge, 1.5-in needles as radiographic markers.Having located the screw head, a stab incision ismade, and any fibrous tissue or periosteal callusoccupying the screw drive or surrounding thescrew head is removed using mosquito forceps,bone curette, or the tip of a hypodermic needle.Light tapping of the screwdriver with a hammermay help to seat the tip of the screwdriver in thehead properly while also helping to disrupt anyfurther callus that is impeding removal.4

In summary, recognizing the factors that may re-sult in screw breakage, such as proper technique inposition screw placement, suitable post-operativecare, and a methodical systematic approach in locat-ing and engaging the screw head during removal, isof paramount importance in avoiding complicationsassociated with screw removal. If complications doarise, having the appropriate equipment and knowl-edge of the necessary techniques required for re-moval will greatly facilitate the operator insuccessfully removing the affected screw.

References and Footnote1. Witte S, Hunt RJ. A review of angular limb deformities.

Equine Vet Edu 2009;21:378–387.2. Bramlage LR. The science and art of angular limb deformity

correction. Equine Vet J 1999;31:182–183.3. Witte S, Thorpe PE, Hunt RJ, et al. A lag-screw technique

for bridging of the medial aspect of the distal tibial physis inhorses. J Am Vet Med Assoc 2004;225:1581–1583.

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4. Kay AT, Hunt RJ, Thorpe PE, et al. Single screw transphy-seal bridging for correction of forelimb angular limb devia-tion, in Proceedings. 51st Annual American Association ofEquine Practitioners Convention 2005;306–308.

5. Hunt RJ. Pros and cons of surgical repair techniques formanagement of angular limb deviation, in Proceedings.14th European Society of Veterinary Orthopedics and Trau-matology 2008;245–248.

6. Hunt RJ. New techniques in transphyseal bridging, in Pro-ceedings. 41st American College of Veterinary SurgeonsSymposium 2006;168–169.

7. Auer JA. Principles of fracture treatment. In: Auer JA,Stick JA, eds. Equine surgery, 3rd ed. Philadelphia, PA:Saunders, 2006;1000–1029.

8. Richardson DW. Complications of orthopaedic surgery inhorses. Vet Clin North Am [Equine Pract] 2008;24:591–610.

9. Richardson DW. Fractures of the proximal phalanx. In:Nixon AJ, ed. Equine fracture repair. Philadelphia, PA:Saunders, 1994;117–128.

10. Nunamaker DM. Orthopedic implant failure. In: NixonAJ, ed. Equine fracture repair. Philadelphia, PA: Saun-ders, 1994;350–353.

11. Roberts BL, Railton D, Adkins AR. A single screw techniquecompared to a two screw and wire technique as a temporarytransphyseal bridge for correction of fetlock varus deformi-ties. Equine Vet Edu 2009;21:666–670.

aSynthes extraction set, Synthes Vet, West Chester, PA 19380.

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