Computed tomographic study of the optimal safe implantation corridors in feline thoraco-lumbar vertebrae

Summary

Objective: To define the implantation corridors in feline thoraco-lumbar vertebrae (T10-L7) using computed tomography (CT) for optimal safe placement of the implants (screws/pins) in spinal column stabilization.

Study design: Computed tomographic study.

Materials and methods: Computed tomography images of feline spinal column (n = 10) were used to define the optimal safe implantation corridors (OSIC) in the transverse plane. The OSIC were defined as corridors allowing the greatest amount of bone purchase with safe margins for implantation of the bicortical implants. They were characterized by their insertion point, optimal angle (from the midsagital plane), maximum and minimum safe angles (from the same insertion points), length, and width.

Results: The OSIC are located within the vertebral bodies. Insertion points were situated at the level of the vertebro-costal joint or the base of the transverse process of the vertebral body for thoracic and lumbar vertebrae, respectively. The mean optimal angle of the OSIC was 90.2° with a maximum deviation angle from optimal angle of 10° dorsally and 8.8° ventrally in thoracic vertebrae, and 90.5° with a maximum deviation angle from the optimal angle of 8.4° dorsally and 7.6° ventrally in lumbar vertebrae.

Conclusion and clinical relevance: Corridors drilled in the vertebral body perpendicular to the midsagital plane (90°) or with a small angle (≤10°) of deviation from the optimal angle provide an optimal safe placement of bicortical implants. However, perpendicular implant placement may not always be feasible due to surrounding soft tissue structures.

Keywords

Feline - spinal - fracture - luxation - implantation corridors

• References

• 1 McKee WM. Spinal trauma in dogs and cats: A review of 51 cases. Vet Rec 1990; 126: 285-289.
• 2 Weh M, Krauss KH. Spinal fractures luxations. In: Tobias KM, Johnston SA. editors. Veterinary Surgery: Small Animal. St Louis, Missouri: Elsevier Saunders; 2012. p. 2012-487.
• 3 Rouse GP, Miller JL. The use of methylmethacrylate for spinal stabilization. J Am Anim Hosp Assoc 1975; 11: 418-425.
• 4 Blass CE, Seim HB. Spinal fixation in dogs using Steinmann pins and methylmethacrylate. Vet Surg 1984; 13: 203-210.
• 5 Lumb WV, Brasmer TH. Improved spinal plates and hypothermia as adjucts to spinal surgery. J Am Vet Med Assoc 1970; 157: 338-342.
• 6 Gage ED. Surgical repair of spinal fractures in small-breed dogs. Vet Med Small Anim Clin 1971; 66: 1095-1101.
• 7 Dulisch ML, Withrow SJ. The use of plastic plates for fixation of spinal fractures in the dog. Can Vet J 1979; 20: 326-332.
• 8 Voss K, Montavon P. Tension band stabilisation of fractures and luxations of the thoracolumbar vertebrae in dogs and cats: 38 cases (1993-2002). J Am Vet Med Assoc 2004; 1: 78-83.
• 9 McAnulty JF, Lenehan TM, Maletz LM. Modified segmental spinal instrumentation in repair of spinal fractures and luxations in dogs. Vet Surg 1986; 15: 143-149.
• 10 Walker TM, Pierce WA, Welch RD. External fixation of the lumbar spine in a canine model. Vet Surg 2002; 31: 181-188.
• 11 Jeffery ND. Vertebral fracture and luxation in small animals. Vet Clin North Am Small Anim Pract 2010; 40: 809-828.
• 12 Heini P, Scholl E, Wyler D. et al. Fatal cardiac tamponade associated with posterior spinal instrumentation. A case report. Spine 1998; 23: 2226-2230.
• 13 Ludders JW, Ekstrom PM, Linn KA. Anesthesia case of the month. Complications during surgery for a spinal fracture in a dog. J Am Vet Med Assoc 1998; 213: 612-614.
• 14 Watine S, Cabassu JP, Catheland S. et al. Computed tomography study of implantation corridors in canine vertebrae. J Small Anim Pract 2006; 47: 651-657.
• 15 Garcia JN, Milthorpe BK, Russell D. et al. Biomechanical study of canine spinal fracture fixation using pins or bone screws with polymethylmethacrylate. Vet Surg 1994; 23: 322-329.
• 16 Wheeler JL, Cross AR, Rapoff AJ. A comparison of the accuracy and safety of vertebral body pin placement using a fluoroscopically guided versus an open surgical approach: an in vitro study. Vet Surg 2002; 31: 468-474.
• 17 Corlazzoli D. Bicortical implant insertion in caudal cervical spondylomyelopathy: a computed tomography simulation in affected Doberman Pinschers. Vet Surg 2008; 37: 178-185.
• 18 Feeney DA, Oliver JE. Blunt spinal trauma in the dog and cat: insight into radiographic lesions. J Am Anim Hosp Assoc 1980; 16: 885-890.
• 19 Bali MS, Lang J, Jaggy A. et al. Comparative study of vertebral fractures and luxations in dogs and cats. Vet Comp Orthop Traumatol 2009; 22: 47-53.
• 20 Voss K, Montavon PM. The spine. In: Montavon PM, Voss K, Langley-Hobbs SJ. editors. Feline orthopedic surgery and musculoskeletal disease. Edinburgh: Elsevier Saunders; 2009. pg. 2009-427.
• 21 Zindrick MR, Wiltse LL, Widell EH. et al. A biomechanical study of intrapeduncular screw fixation in the lumbosacral spine. Clin Orthop Related Res 1986; 203: 99-112.
• 22 Beaver DP, MacPherson GC, Muir P. et al. Methylmethacrylate and bone screw repair of seventh lumbar vertebral fracture-luxations in dogs. J Small Anim Pract 1996; 37: 381-386.
• 23 Sharp NJH, Wheeler SJ. Small Animal Spinal Disorders Diagnosis and Surgery. Edinburgh: Elsevier Mosby; 2004. p. 2004-281.
• 24 Wong WT, Emms SG. Use of pins and methylmethacrylate in stabilisation of spinal fractures and luxations. J Small Anim Pract 1992; 33: 415-422.
• 25 Méheust P, Mallet C, Marouze C. A new surgical technique for lumbosacral stabilization: arthrodesis using the pedicle screw fixation. Anatomical aspects. Pratique Medicale et Chirurgicale de l’Animal de Compagnie 2000; 35: 193-199.
• 26 Weh JM, Kraus KH. Use of a four pin and methylmethacrylate fixation in L7 and the iliac body to stabilize lumbosacral fracture-luxations: a clinical and anatomic study. Vet Surg 2007; 36: 775-782.
• 27 Swaim SF. Vertebral body plating for spinal immobilization. J Am Vet Med Assoc 1971; 158: 1683-1695.
• 28 Walter MC, Smith GK, Newton D. Canine lumbar spinal internal fixation techniques: a comparative biomechanical study. Vet Surg 1986; 15: 191-198.
• 29 Waldron DR, Shires PK, McCain W. et al. The rotational stabilizing effect of spinal fixation techniques in an unstable vertebral model. Progress in Veterinary Neurology 1991; 2: 105-110.
• 30 Grand JG, Bureau SC. Video-assisted thoracoscopic surgery for pneumothorax induced by migration of a K-wire to the chest. J Am Anim Hosp Assoc 2011; 47: 268-275.
• 31 Piermattei DL, Johnson KA. An Atlas of Surgical Approaches of the Bones and Joints of the Dog and Cat. Philadelphia, Pennsylvania: Elsevier Saunders; 2004. p. 2004-78.
• 32 Cabassu J, Moissonnier P. Surgical treatment of a vertebral fracture associated with a haematogenous osteomyelitis in a dog. Vet Comp Orthop Traumatol 2007; 20: 227-230.