WHAT IS FLUOROSCOPY

Surprisingly, the science of fluoroscopy (x-ray imaging during surgery) is not new but has been in use since the early 1900’s.  Today, fluoroscopy is widely accepted as an important anatomical guide during minimally invasive and microscopic procedures as well as many types of diagnostic tests.  Fluoroscopy is the standard guidance modality for most percutaneous musculoskeletal interventions in humans; including long bone fractures, spinal fusions, and bone biopsies.  It is an asset because of its good temporal resolution, excellent bone-tissue contrast and real-time imaging.  Advanced fluoroscopy has greatly improved the accuracy of incisions and hardware placement, while minimizing tissue trauma.  New procedures incorporating the use of fluoroscopy are continually being developed.

ADVANTAGES AND DISADVANTAGES

The use of fluoroscopic techniques in veterinary patients offers a number of advantages compared to more traditional therapies.  Because these procedures are minimally invasive, they lead to reduced peri-operative morbidity and mortality.  Fluoroscopy entails less disruption of the periarticular soft tissue since most implants are placed through 0.5 cm stab incisions or mini approaches.  Decreased soft tissue disruption leads to less pain, reduced blood loss, and less chance of infection.  In most cases, return to use of the limb is quicker because of the reduction in surgically induced pain.  Minimally invasive surgery techniques reduce the length of hospital stay, cut hospitalization and anesthesia charges, and diminish anesthesia time.  Lessening equipment-intensive procedures can result in shrinking overhead costs as well.

The primary disadvantages of fluoroscopic procedures include the required technical expertise, potential radiation exposure, and the specialized equipment necessary.  Radiation safety is a concern with the use of fluoroscopic imaging.  The amount of radiation to which the patient and surgeon are exposed is a consideration, although it is largely a function of surgical experience with minimally invasive techniques.  All studies recommend monitoring radiation exposure by wearing lead aprons, thyroid shields, glasses, and radiation-attenuating gloves.  It is also strongly suggested that all personnel stay 0.6 m from, and not come into direct contact with, the fluoroscopic beam. Following these guidelines permits routine use of fluoroscopy with negligible radiation exposure. Another disadvantage of fluoroscopy is the high equipment cost. Even though the price of fluoroscopic equipment is dropping, one can easily spend $40,000 – $80,000 including instrumentation.  Last, but not of least importance, fluoroscopic guided orthopedic procedures have a steep learning curve. They require considerable practice, advanced hand-eye coordination and repetitive usage in order for the surgeon to perform proficiently.

EQUIPMENT AND TECHNIQUE

As most fluoroscopic procedures are performed through small holes in the skin (minimally invasive), the traditional sterile operating room is not required, but still recommended.  Most of these procedures may be performed in orthopedic or fluoroscopic suites.  The entry sites receive the traditional sterile scrub, and operators wear full lead gowns, lead thyroid shields, caps, gowns, and masks. 

Fluoroscopic images are easily digitalized.  The images are recorded on a hard drive and may be saved to a floppy disc or CD.  Hard copies of these images can be printed out for inclusion in the patient record, sending to the referring veterinarian and handing to the owner to take home.

CURRENT VETERINARY APLICATIONS

Despite potential applications in veterinary orthopedic surgery, and  common usage in human orthopedic surgery, fluoroscopic techniques have not been widely adopted.  Examples of its use in the veterinary literature include reports of successful closed long bone and articular fracture reduction and fixation and closed spinal reduction and external fixation.  At VOSM Dr. Canapp is currently utilizing intra-operative fluoroscopy for the following procedures:

• Closed reduction and fixation of long bone and articular fractures
• Closed reduction and external fixation of spinal fractures
• Spinal fusion for Wobblers disease
• Guided bone biopsies
• Implant removals
• Corrective osteotomies/ostectomies:

*  Angular limb and growth deformities / distraction osteogenesis
*  Bone tumor limb spares / distraction osteogenesis                                   

• Confirmation of implant placement or fracture reduction prior to closure (articular fractures or periarticular implants.)
• Obtaining post-operative images (eliminates transport of patient to radiology and therefore decreases anesthesia time.)
• Myelograms for intervetebral disc disease
  
  

Long Bone and Articular Fractures

Closed fracture reduction and external fixation has been well described in both veterinary and human literature. One study, by Johnson A, et al., evaluates the effects of closed reduction and application of a type-II external fixator to comminuted fractures of the radius and tibia in dogs. In this study, all dogs healed with the original fixation device in place.  Mean time between surgery and the development of bridging callus was 11.4 weeks (range, four to 22 weeks) and mean time between surgery and fixation removal was 14.7 weeks (range, four to 27 weeks).  This study concludes that closed reduction and application of a type-II external fixator was an effective method of treating severely comminuted radial and tibial fractures.

A study by Dudley, et al., compared open reduction and bone plate fixation with closed reduction and external skeletal fixation as treatment for severely comminuted fractures of the tibia.  Results of this study in canines found no difference in time, from earliest radiographic evidence of bone healing, between fractures treated with a bone plate and those treated with an external fixator.  Dogs treated with an external fixator did, however, have shorter surgery times.  Additionally, patients treated with bone plate fixation suffered additional complications.

A recent study in the Journal of Orthopedic Trauma evaluated the use of  intraoperative fluoroscopy during acetabular surgery to determine fracture reduction and accurate placement of screws.  Results of this study revealed that intraoperative fluoroscopy confirmed the extra-articular position of all screws in question.  Postoperative CT scans confirmed the extra-articular placement of all screws assessed by fluoroscopy.  Quality of reduction using intraoperative fluoroscopic images had a 100 percent correlation with reduction on final radiographs.  One patient, with two screws placed without fluoroscopic evaluation, had intra-articular placement requiring revision surgery.

Spinal Fractures & Fusions

Traditionally, vertebral body pin placement for spinal fractures has involved an open dorsal approach to the spine with reflection of the epaxial musculature.  This leads to increased tissue trauma and potential destabilization of the spine by disruption of the supraspinous and interspinous ligaments and results in greater postoperative morbidity.  Fluoroscopically guided percutaneous placement of pins for stabilization of spinal fractures has been reported in human patients, and more recently in animals.  This technique decreases the amount of tissue trauma dissection needed, and lessens the degree of uncertainty involved in placing pins near the spinal cord and other vital soft tissue structures.  When compared to a standard open approach, fluoroscopic vertebral pin placement provided better observation of the vertebral body, allowing more precise control over pin placement as well as serving to decrease tissue trauma .  The complication incidence for thoracic vertebrae was significantly greater in the open group.  The results of that study suggest that a closed technique for placement of Steinmann pins in lumbar vertebrae, for use in external skeletal fixation, is a reasonable and safer alternative to the traditional open technique.

Additionally, fluoroscopy has been demonstrated as beneficial in spinal fusion for Wobblers Disease.  Not only does fluoroscopy provide a minimally invasive approach to the cervical spine, it allows for more accurate screw placement and therefore avoids the potentially disastrous effect of penetration into the spinal canal. 

Angular Limb Deformity and Distraction Osteogenesis

Fluoroscopy is a valuable tool when correcting angular limb deformities and performing distraction osteogenesis.  Treatment of angular limb deformities typically requires a corrective osteotomy at the site of maximum deformity.  Since the deformities are not simply one dimensional, but exist in three planes, correction must take this into account.  The osteotomy can be accurately performed utilizing a minimally invasive approach with fluoroscopy and the limb can be realigned with fluoroscopic guidance in all three planes.

Distraction osteogenesis is a technique which may be used to spread the bone (or bones) that have stopped growing (premature physeal closure) or that have been excised due to neoplasia (limb spares).  With the use of fluoroscopy, the osteotomy/ostectomy can be performed accurately with a minimally invasive approach, the limb realigned, and the circular external fixator applied under fluoroscopic guidance in all three planes.

Bone Biopsy

When performing a bone biopsy for the diagnosis of bone neoplasia, obtaining a core sample from the center of the lesion is a common error.  Obtaining samples from this location can result in a histological diagnosis of reactive or necrotic bone and lead to the necessity of a second anesthetic episode and surgical procedure.  To obtain the most accurate sample, the biopsy should originate from the periphery of the lesion.  This can be difficult when obtaining samples blindly.  With the use of fluoroscopy, the Jam Shidi needle can be guided to the periphery of the lesion and therefore increase the likelihood of a diagnostic sample.

CONCLUSION

It has been shown that fluoroscopy offers numerous advantages over traditional open approaches for the diagnosis and treatment of orthopedic conditions.  It is certainly recognized that all practices or hospitals may be unable to afford fluoroscopy units.  However, as surgeons further evaluate the costs and benefits of operating room efficiency, ease of surgical procedures, decreased morbidity, reduction in length of hospital stays and earlier return to function, these units will become commonplace in most veterinary orthopedic surgical facilities.

REFERENCES:

Wheeler JL, et al., 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;31:468-74.

Dudley M, et al. Open reduction and bone plate stabilization, compared with closed reduction and external fixation, for treatment of comminuted tibial fractures:  47 cases (1980-1995) in dogs.  J Am Med Assoc. 1997;15:1008-12.

Norris BL, et al., Intraoperative fluoroscopy to evaluate fracture reduction and hardware placement during acetabular surgery.  J Orthop Trauma. 2000;14:225.

Simon DA, et al., Accuracy validation in image-guided orthopedic surgery. Proceedings of 2nd international symposium on medical robotics and computer assisted surgery.  1995;185-192.

Sanders R, et al., Exposure of the orthopedic surgeon to radiation.  J Bone Joint Surg. 1993;75:326-330.