Veterinary Surgery, 19,2, 117-1 21, 1990

Surgical Repair of Tibia1 Tuberosity Avulsion Fractures in Four Horses BARBARA L. SMITH, DVM, MS, JOERG A. AUER, DrMedVet, MS, DiplomateACVS, and JEFFREY P. WATKINS, DVM, MS, DiplomateACVS

Four horses, 2 to 17 years old, were treated for unilateral avulsion fractures of the tibial tuberosity. Two horses were treated successfully with tension band wiring or plating in combination with lag screw fixation. One horse was euthanatized because of implant failure during recovery and one was euthanatized on day 11 because a longitudinal fracture of the tibial tuberosity occurred through the plane of the screws used for stabilization.

For surgery, the horse was positioned in lateral recumbency with the affected limb down and in extension. A curvilinear incision was made on the craniomedial aspect of the tibial crest. The surgeon placed a finger into the lateral femorotibial pouch to aid reduction at the joint surface. Internal fixation was achieved with a 7 hole narrow self-compressing bone plate placed on the craniomedial aspect of the cranial border (tibial crest), just distal to the insertions of the middle and medial patellar ligaments. The proximal four screws (4.5 mm diameter) were placed through the plate in lag fashion. For additional stabilization, a 5.5 mm diameter cancellous screw was placed in lag fashion just proximal to the plate. Despite the age of the fracture, reduction of the fragment was not difficult. Adequate reduction of the fragment and reconstruction of the joint surface were confirmed radiographically. The horse was tied in the stall to prevent lying down and subsequent stress on the fixation during rise from recumbency. The horse bore weight on the limb by day 2. On day 1 1 , the horse was not bearing weight on the affected limb. Radiographically, a sagittal fracture extending the length ofthe tibial tuberosity was visible. The fragment split along a vertical line connecting the four proximal screws. The horse was euthanatized because of a grave prognosis for a second repair.

of the tibial tuberosity are unA common injuries in humans and dogs. The quadriceps muscle group exerts a great distracting force through VULSION FRACTURES

the patellar ligament, producing separation of the physis of the tibial tuberosity and proximal displacement of the fragments.'-' In dogs, these fractures are most common between the ages of 4 and 8 months and are usually associated with a faL5 In humans, the injury occurs most frequently in adolescent males (82%) involved in sports activities at the time of injury and is probably due to a sudden forceful contraction of the quadriceps muscle group with the knee in flexion.'.' In dogs and humans, the prognosis after surgical treatment is usually good for return to athletic a~tivity.~.',' Trauma to the limb was a cause of avulsion fracture of the tibial tuberosity in one reported case in a horse.* The fracture was closed and produced little swelling, but resulted in total incapacity of the limb. Because of marked displacement of the fracture fragment, conservative treatment consisting of box stall rest was not used. This is a report of the surgical treatment of four horses with avulsion fractures of the tibial tuberosity. Case Reports

Horw 1 A I7 year old, 400 kg Arabian gelding was treated for an injury caused by a kick 3 weeks earlier. An avulsion fracture ofthe tibial tuberosity that extended through the proximal tibial epiphysis into the stifle joint was visible radiographically.

Horse 2 A 2 year old, 450 kg Thoroughbred colt was treated for an injury caused by a kick from another horse 1 week

From the Department of Large Animal Medicine and Surgery, Texas Veterinary Medical Center, Texas A&M University, College Station. Texas Reprint requests Barbara L Smbth, DVM, Department of PhysiologicalSciences. School of Veterinary Medicine, University of California, Davis, CA 95616

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port. The horse had a violent recovery from anesthesia. The main fracture fragment comminuted around the two proximal screws during an attempt to stand. The horse was subsequently euthanatized.

Horse 3

Fig. 1. Horse 2. Lateral-to-medial radiograph. There is an avulsion fracture of the tibial tuberosity with extension of the fracture through the proximal tibial epiphysis. An osseous fragment in the joint is displaced from the major fragment (arrow).

earlier. At admission, the horse was recumbent In the trailer and unable to rise. Anesthesia was induced in the trailer and the horse was transported to the surgical suite. Radiographically, there was an avulsion fracture of the right tibial tuberosity with cranial and proximal displacement. The fracture extended through the proximal tibial physis in the frontal plane and extended into the femorotibial joint to include the intercondylar eminence. A small bony fragment suspected to have originated from the cranial border ofthe tibia was visible in the stiflejoint (Fig. 1). With the horse positioned in lateral recumbency and the affected limb up, a 20 cm incision was made on the craniolateral aspect of the cranial border of the tibia. A finger was placed in the lateral femoropatellar joint to aid reduction and alignment of the joint surface. After reduction of the fracture, a 4.5 mm cancellous bone screw and washer were placed in lag fashion to maintain alignment of the fragments. The fracture was stabilized further by applying a 5 hole narrow self-compressing plate on the craniolateral aspect of the tibial tuberosity, between the middle and lateral patellar ligaments. The proximal two screws through the plate were placed in lag fashion (Fig. 2). The two distal screws were inserted through the plate into the bone distal to the fracture. Because the central hole of the plate was directly over the fracture line, no screw was placed there. Another lag screw and washer were placed across the fracture on the medial side of the tibial crest to provide additional sup-

A 6 year old, 525 kg Quarter horse gelding was presented immediately for a left hindlimb lameness resulting from a fall while entering a trailer. There were abrasions in the stifle region, with palpable crepitation over the cranial aspect of the stifle joint. The horse did not support weight on the limb when at rest and walked with a markedly shortened posterior phase of its stride. A nonarticular fracture of the tibial tuberosity, which was displaced cranially and proximally, was visible in a lateralto-medial radiograph of the left stifle (Fig. 3). The animal was positioned for surgery in right lateral recumbency. A curvilinear incision was made on the craniolateral aspect of the stifle joint, extending 16 cm distally from the proximal aspect of the tibia. After exposure and repositioning of the avulsed fragment, internal fixation was achieved with two 4.5 mm cancellous bone screws and washers placed in lag fashion in a caudomedial direction at the proximal and distal aspects of the fragment. A separate figure-of-eight tension band wire was placed around each screw and through a common hole drilled across the cranial border of the tibia 4

Fig 2 Horse 2 lntraoperative radiograph. Only partial reduction of the displaced tibial tuberosity has been achieved Two cancellous screws were inserted in lag fashion in addition to the plate

SMITH, AUER, AND WATKINS

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Fig. 3. Horse 3. Lateral-to-medialradiograph. The fracture fragment is displaced cranially and proximally, but does not enter the stiflejoint.

cm distal to the fracture line (Fig. 4). Postoperative care included tying the horse and forcing it to remain in a standing position. After surgery, the animal walked on the affected limb. Full weight-bearing was seen at week 3 and no lameness be detected at a The horse was discharged at month 1. The owner reported that the horse was sound for steer roping at a follow-up inquiry 5 years after the injury.

Fig. 5. Horse 4. Lateral-to-medial view. A fracture line separating the tibial tuberosity from the tibial body is visible, with moderate proximal displacement of the fragment,

Horse 4

Fig. 4. Horse 3. Postoperative radiograph.There is satisfactory fracture reduction with screws and tension-band wires.

A 15 year old, 425 kg Arabian gelding was evaluated for a nonweight-bearing right hindlimb lameness of 5 days’ duration resulting from stepping in a hole. Radiographically, there was an articular avulsion fracture of the tibial tuberosity with moderate proximal and cranial displacement (Fig. 5). The horse was positioned in dorsal recumbency with the right hindlimb in extension. A 20 cm curvilinear incision was made on the cranial aspect of the tibia from the apex of the patella to the distal aspect of the tibial tuberosity. A finger was placed into the femorotibial joint to aid reduction of the joint surface. Fixation was accomplished with a 5 hole narrow self-compressing plate placed across the fracture in tension-band fashion on the lateral aspect of the tibial tuberosity. The proximal two 4.5 mm diameter cortical screws were placed through the plate in lag fashion (Fig. 6). The middle hole was not used because of its close proximity to the fracture line. To provide lateral stability, a smaller round hole plate was placed across the fracture on the medial aspect

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TlBlAL TUBEROSITY FRACTURES

IN HORSES

Fig. 6. Horse 4. Postoperative radiographs. The fracture was reduced with two bone plates, one on each side of the tibial tuberosity. Two screws were inserted in lag fashion proximal to the plates. A. Craniocaudal projection. B. Lateral-to-medialprojection.

of the tibial tuberosity. The lateral and middle patellar ligaments were split longitudinally to allow the proximal end of the plate better contact with the bone. This plate was used as a tension band, and 3.5 mm cortical bone screws were placed through only the proximal and distal holes in order to avoid failure of the bone-implant complex due to overfixation, as occurred in horse 1. Two 5.5 mm diameter cortical bone screws and washers were placed in lag fashion on each side of the tibial tuberosity to aid in securing the fragment. A 15 X 5 mm bone fragment was removed from the medial intercondylar tubercle before closure of the femorotibial joint. Some dificulty was encountered in removing the fragment because it was attached to a portion of the cranial cruciate ligament. The horse was tied in a standing position after surgery. By day 2, the horse was bearing almost full weight. His ability to use the limb continued to improve over the next week, and the animal was discharged on day 7. Radiographically, there was excellent reduction and alignment of the fragments. At month 3 , the horse was sound at a trot and there was no radiographic evidence of degenerative joint disease. At month 5 , the horse was being used as a trail horse

in the mountains and was still sound at last report 8 months after surgery.

Discussion The tibia has five ossification centers: the proximal epiphysis, tibial tuberosity, diaphysis, distal epiphysis, and lateral malleolus. The tibial tuberosity is a traction epiphysis and serves as the site of insertion for the quadriceps muscle group. In humans, it is believed to be a structural modification of the cranial portion of the proximal tibial epiphysis. The physis underlying the tibial tuberosity is comprised almost completely of fibrocartilage and is postulated to be a specific cytoarchitectural modification to resist the tensile stresses imparted by the quadriceps muscle In the horse, it is partially ossified at birth and fuses with the proximal tibial epiphysis during the second year of life. Radiographic union with the tibial shaft is not complete until 36 to 42 months of age." The diagnosis of a fracture is based on radiographic examination, but the diagnosis is uncertain without obvious cranial displacement of the fragment. I ' Radiographs should be made of both hindlimbs for comparison if doubt exists." In young horses, the tibial tuberosity often

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has an irregular radiographic appearance that may be erroneously confused with osteochondrosis. Osteochondrosis of the tibial tuberosity has been reported in the horse. The tibial tuberosity does not contain an articular component and therefore contributes neither to formation of the joint nor to longitudinal growth of the tibia. Therefore, growth disturbance is not believed to be associated with the injury.j In the cases presented here (with the exception of horse 2), displaced or articular fractures occurred after closure of the physis of the tibial tuberosity. Treatment required open reduction and internal fixation. A curvilinear incision on the cranial aspect ofthe tibial crest with the horse in lateral or dorsal recumbency was the simplest approach in all cases; however, reduction was easiest with the affected stifle placed in extension. A finger placed in the femorotibial joint during reduction aided anatomic restoration of the joint surface because visualization was obscured by the menisci. Wiring or plating the fracture in accordance with the tension-band principle was successful in horses 3 and 4.8 The distracting force of the quadriceps muscle group was converted to a compression force by the insertion of a tension band at the distal portion of the fracture fragment.* '' lfscrews and bone plates are used for the repair. placing one plate on each side of the tibial tuberosity would protect against possible failure caused by shear stresses imparted by uneven pull ofthe three patellar ligaments. Splitting the ligaments with a scalpel allows the plate to be in direct contact with the bone, and has not proven to interfere with a successful outcome thus far in horse 4. If only one plate is used, placing the plate on the lateral aspect of the tibial tuberosity is favored because of the soft tissue coverage provided by the long digital extensor muscle. Also, inserting two screws at the proximal end of the fragment will help protect it from the shear forces imparted by the pull of the patellar ligaments. This differs from dogs and humans. because each has only a single patellar ligament. Fractures that extend into the femorotibial joint can affect the cranial cruciate ligament by splitting it, or can avulse a portion of the intercondylar eminence of the tibia as in horse 4. Both of these conditions might be ex-

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pected to increase the chances of degenerative joint disease, thereby worsening the prognosis for soundness. The horses treated successfully were nearly sound at a walk within 1 week of surgery. Cross-tying these animals and forcing them to remain standing in a stall for several weeks may have minimized the tension exerted by the quadriceps muscle group on newly reduced fractures and, therefore, helped prevent fixation failure in the early postoperative period. Surgical fixation should be accomplished as soon after the injury as possible. The two unsuccessful cases were horses treated after 1 and 3 weeks. Demineralization of the fragment from chronicity of the injury and overfixation (too many screws in one plane) may have contributed to the failure ofthe implants in these cases. References I . Ogden J A T r o s s RB. Murphy MJ. Fracturesofthe tibial tuberosity in adolescents. J Bone Joint Surg 1980:62:205-215. 2. Polakoff DR. Bucholz RW. Ogden JA. Tension band wiring ofdisplaced tibial tuberosity fractures in adolescents. Clin Orthop 1986209: 16 1-165. 3. Gebuhr P. Lyndrup P. Avulsion fractures ofthe tibial tuberosity in adolcscents. Acta Orthop Belg 1 987;53:59-62. 4. Leonard EP. O~rliopc~tlicSirr,~c,~!.o~'tlrr Do,rcindCh/ 2nd ed. Philadelphia: WB Saunders Co, I97 I : 128- I3 I . 5 . Winthrow S. DeAngelis M. Arnoczky S. Rosen H. Treatment of fracturesofthe tibial tuberosity in thedog. J Am Vet Med Assoc 1976: 168: 122-1 24. 6. Nanninga AJ. Josaputra HA. Tibial tuberosity fracture in adolescents: report o f a case and review of the literature. Neth J Surg 1982:39: 144- 146. 7. Hand WL. Hand CR. Dunn AW. Avulsion fractures of the tibial tubercle. J Bone Joint Surg 1971;53:1579-1583. 8. Gernng EL, Davies JV. Fracture of the tibial tuberosity in a polo pony. Equine VetJ 1982; 14:158-159. 9. Bolesta MJ. Fitch RD. Tibial tubercle avulsions. J Pediatr Orthop 1986;6: 186- 192. 10. Getty R. Sisson and Grossman's The. -Incl/ornyo/'Dornc?r/ic, ilnitnuk 5th ed. Philadelphia: WB Saunders Co, 1975:309. 1 I . Roomy JR. Bionwchunics o/ Lurnc~ncwin Hor.ser. Baltimore: Williams & Wilkins Co. 3969:2 10-2 l l . 12. Mcllwraith CW. Diseases ofjoints, tendons, ligaments. and related structures. In: Stashak TS. ed. Adatn.s'Lcitnmrr..s H o r w 4th ed. Philadelphia: Lea & Feabiger, 1987:729-730. 13. Baker RH. Osteochondrosis ofthe tibial tuberosity of the horse. J Am Vet Med Assoc 1960; I37:354-355. 14. Pettit GD. Siatter DH. Tension-band wires for tixation of an avulsed canine tibial tuberosity. J Am Vet Med Assoc 1973: 163: 242-244.

Surgical repair of tibial tuberosity avulsion fractures in four horses.

Four horses, 2 to 17 years old, were treated for unilateral avulsion fractures of the tibial tuberosity. Two horses were treated successfully with ten...
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