T12-L3 Fixation across L2: Burst Fracture
The patient is a 27-year-old male with a L2 burst fracture from a ski-jumping accident. Pain is 4/10 to 5/10 (supine). Axial low back pain radiates to S1 with paresthesias into the anterior thighs. No leg pain.
- Lumbar spinal palpation reveals no interspinous tenderness
- Lower extremity musculoskeletal examination is normal
- Bowel/bladder examination reveals no defects
- Bilateral sensory deficit in the L2-L3 dermatomes
- Reflexes are intact
The patient's radiological examination notes a burst fracture with 15 degrees of kyphosis in the supine position with the burst component filling 90% of the canal. There is a laminar split through the spinous process. This type of vertebral fracture reduces the normal lordosis and has significant canal stenosis. Pre-operative imaging (CT) is of limited use for navigation and 2D imaging is limiting in that it does not provide valuable views and information about canal stenosis.
Figure 1. Snapshot image of the O-arm® System (Medtronic Navigation Inc., Boulder, CO) display shows the axial, coronal and sagittal views of the L2 burst fracture. The axial view reveals spinal cord occlusion is 90-95%.
L2 burst fracture with 90% canal compromise
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- T12-L3 were instrumented and fused.
- Fusion was interspinous, facet and transverse process at all levels except L2.
- At L2 a facet and transverse fusion secondary to laminotomy was performed without pedicle screws.
- Sublaminar hooks were placed at L3 with pedicle screws.
- Local bone and osteogenic agents were utilized for graft purposes.
The O-arm® Imaging System with StealthStation® Navigation System (Medtronic Navigation Inc., Boulder, CO) allowed visualization of the pedicle preparation and screw placement at all affected levels while utilizing instrumentation and bone graft material. Additionally, the O-arm® System in combination with the StealthStation® System reduces surgeon and staff radiation exposure.
Figure 2. Operating room setup shows the display. O-arm was utilized to navigate use of the Awl/Probe/Tap instrument.
Figure 3. Snapshot from the StealthStation® System's display shows navigation of a screw with the Awl/Probe/Tap instrument.
Figure 4. Snapshot from the StealthStation® System's display shows navigation of the Tactile Probe prior to screw placement.
Figure 5. Snapshot image taken by the O-arm® System displays intra-operative confirmation of screw placements.
After the pedicle screws and rods were placed, the O-arm® System was utilized to determine the amount of correction to make to the fragmented vertebral body and resultant lordotic alignment. In this instance, bone fragments did not reduce back to a normal position and subsequently, a more aggressive correction was performed by using a guided tamp to reduce bony fragments. Another spin during the case was obtained to make sure the fragments were successfully reduced.
Utilizing the O-arm® System in this way avoided a second surgery and additional hospital and patient costs, while improving patient outcome. Additionally, it allowed me to provide a superior level of care to this patient by assessing his fracture reduction and determining whether or not fragments remained in the canal.
There were no complications during or after surgery. The patient was braced for three months (TLSO) with prescribed at-home exercise. He progressed through an organized physical therapy program. His range of motion is "good" but not "perfect". The patient can flex and touch his toes, extend backward 20-degrees, and perform side-bending bilaterally 25-degrees.
The algorithm for surgical correction includes significant narrowing of the central canal. This patient had 90% canal stenosis at L2. This fact, and the location at L2, allows different surgical possibilities than the same fracture at L1. At L1, with the conus, manipulation around the dural sac could theoretically put the conus at risk.
Conus injury is a central nervous system injury versus a peripheral nervous system injury at L2. At L2 you can manipulate the dura around to allow impacting or tamping of the fragments back into the body versus at L1. So the choice of level does dictate what is available for fixation. If this injury was at L1, consideration would be given to an anterior procedure, especially if a conus injury was present.
In regard to reduction of fragments, you can use indirect reduction or ligamentotaxis. This is what Dr. Charles C. Edwards did so many years ago with the modular spinal fixation system and the use of the Edwards Spacers. By implanting hooks or pedicle screws and causing distraction and lordosis you can indirectly reduce the fragments without actually having to physically tamp them back in, as long as the fragments are connected to disc or ligament. However, in this case, the vertebral body is so comminuted and disrupted there is no significant connections between the fragments.
Another consideration is how many levels to incorporate into the fusion? There are some surgeons who utilize a one up - one down technique. A L2 burst fracture would therefore involve a L1-L3 fusion. In general, that has been proven to have a higher failure rate for the upper instrumentation because of cantilever bending on the upper screws. It comes down to a race between the fracture consolidation, fusion and metal fatigue. To be safe, typically two levels above and one below need to be included with the fusion. On the inferior side, only one level needs to be included. To supplement the inferior fixation, inferior laminar hooks can help to reduce the cantilever bending forces on the bottom screws.
In my opinion, patients, with these unstable burst fractures, who undergo this surgical technique, need post-operative brace treatment because there still is a relatively higher force placed upon the screws. I typically brace the patient for three months. If you allow the patient to go brace-free there is a greater cantilever force and the possibility of failure inferiorly. The vertebral fracture will heal itself eventually and create anterior column support.
The O-arm allowed a guided tamp to be used to reduce the canal fracture fragments. A post-fragment impaction O-arm scan made it possible to obtain a good indication of how well the canal was decompressed without having to take the patient back at a later point to obtain another CT or MRI.
Another critical choice is screw placement within the pedicle inferiorly, as this is where the construct bears most of the weight. The O-arm allowed the best positioning of the screw and use of the largest screw available, which reduced the stress within this patient's vertebral segment.
Note to patients: As you read this, please keep in mind that all treatment and outcome results are specific to the individual patient. Results may vary. Complications, such as infection, blood loss, bowel or bladder problems, are some of the potential adverse risks. Please consult with your physician for a complete list of indications, warnings, precautions, adverse events, clinical results, and other important medical information.
This therapy is not for everyone. Please consult your physician. A prescription is required. For further information, please call MEDTRONIC at (800) 876-3133.
Fusion was successful and he is neurologically intact. He has resumed skiing and mountain biking.
Plain films at 2-years post-op.
Figure 6A. AP x-ray
Figure 6B. Lateral x-ray
This case nicely illustrates the benefit of intra-operative imaging in the axial plane. While a number of imaging/navigation systems provide AP and lateral images, very few provide axial images, and even fewer provide them without relying on pre-operative scans. In this case, on-demand axial images helped perform and verify the direct and indirect decompression.
It is important to note that in a case such as this, instrumentation should be placed prior to bony manipulation as distraction will change the registration parameters and render navigation inaccurate until rescan and repeated registration.
Tjardes1 presents a nice up-to-date overview of the technical and procedural aspects of image-guided surgery. As expected, image-guided and image-verified constructs have been shown to reduce re-operation rates. Furthermore, image guidance greatly reduces, if not eliminates, radiation exposure to the operating room team as a number of recent studies have demonstrated.2,3 CT guidance markedly increases4 exposure rates to the patient compared to fluoroscopy. These differences persisted even when exposure reduction techniques were used with fluoroscopy. One case series5 reported up to 15 times higher radiation exposure to patients using CT guided screw placement than spot fluoroscopy shots. This is especially important to consider in a dynamic case such as this where three distinct spins were performed. However, the benefits of saving the patient an antero-lateral exposure are significant.
The quality of fixation obtained here is commendable with long and well medialized instrumentation. An effective posterior decompression and accurate instrumentation placement such as this is facilitated by intra-operative navigation. Certainly the benefits of such a system are well demonstrated by this case.
If you use standard fluoroscopy you can take the following measures to reduce your exposure:
- use appropriate shielding with leaded gowns and thyroid shields
- regularly inspect lead to ensure improper handling has not created stress fractures, which leak radiation
- wear radiation attenuating sterile gloves (approximately $40 USD/pair)
- use leaded eye-ware
- cannulate several pedicles at once using multiple probes
- collimate the beam
- use low-dose settings in thin patients
- use remote foot pedal control away from the field
- have the surgeon control the C-arm
1. Tjardes T, Shafizadeh S, Rixen D, et al. Image-guided spine surgery: state of the art and future directions. Eur Spine J. 2010 Jan;19(1):25-45.
2. Wood MJ, Mannion RJ. Improving accuracy and reducing radiation exposure in minimally invasive lumbar interbody fusion. J Neurosurg Spine. 2010 May;12(5):533-9.
3. Zausinger S, Scheder B, Uhl E, Heigl T, Morhard D, Tonn JC. Intraoperative computed tomography with integrated navigation system in spinal stabilizations. Spine. 2009 Dec 15;34(26):2919-26.
4. Schaeren S, Roth J, Dick W. Effective in vivo radiation dose with image reconstruction controlled pedicle instrumentation vs. CT-based navigation. Orthopade. 2002 Apr;31(4):392-6.
5. Slomczykowski M, Roberto M, Schneeberger P, Ozdoba C, Vock P. Radiation dose for pedicle screw insertion. Fluoroscopic method versus computer-assisted surgery. Spine. 1999 May 15;24(10):975-82; discussion 983.