Flexion-distraction Injury at L4-L5 in Obese Patient
A 45-year-old overweight man (300+ pounds) had fallen out of a tree and presented complaining of back pain.
The patient was neurologically normal on examination, although he did have tender areas in the low back. Given the patient's size, it was impossible to feel any gaps or steps in the low back.
He had an ASIA score of E.
Figure 1: Plain x-rays demonstrating the gap between the L4-L5 facet, as well as an L4 fracture.
Figure 2: CT scans confirm splaying of the facets.
Figure 3: MRIs confirm soft tissue disruption of the posterior ligamentous complex and transdiscal. Note also the edema at L3, as well as a compression fracture at L3.
The patient was diagnosed with a flexion-distraction injury with combined bony and soft tissue injury at L4-L5. There is also an L3 compression fracture.
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The patient underwent MIS posterior instrumentation with facet fusion at L3-L5.
Figure 4: AP and lateral x-rays at 3 months after surgery.
The patient was able to return to work as a mason 6 months after surgery. He has mild but tolerable back pain, and he needs no medication.
Dr. Rampersaud presents a challenging clinical dilemma. The first interesting point is how did this 300 pound individual end up in the tree? While a somewhat humorous question it provides the insight that this is a mobile, active individual.
At some point, there is a body mass index that precludes successful use of external immobilization. I do not have a set figure, but in my experience patients with a BMI >40 do not succeed with brace or cast treatment. It may, in fact, be a lower number since all casting and orthoses depend upon achieving control through force against bony prominences (pelvis and typically sternum/rib cage). Therefore, I do not believe that bracing is a viable option in this scenario, regardless ofthe combination of injuries.
Conventional open surgery, of whatever strategy, is an option. It carries increased morbidity in obese patients in my estimation. However in the absence of a good alternative, these strategies are reasonable considerations. There is then the consideration of the specific effects of the surgical interventions. Conventional fracture surgery for low lumbar injuries gives unsatisfactory results in terms of loss of mobility. In the absence of a viable alternative, it would still be the treatment of choice.
Fracture stabilization without fusion has had a bad track record in the past when used for burst fractures. This has colored our perspective in a perhaps inappropriate fashion. This is especially true now that there is at least some underpowered level 1 data indicating that brace treatment is equivalent or superior to surgical treatment for throacolumbar burst fractures with kyphotic angles <25º. However, this patient does not have a burst fracture, nor is he a good candidate for brace treatment.
There is anecdotal evidence that brace or cast treatment for bony Chance fractures can give good results. In the past, expert opinion has been that ligamentous Chance injuries would not respond in a positive fashion to this treatment, although there is not good data to support this statement.
Minimally invasive surgery lessens the collateral damage to the soft tissue envelope for surgical stabilization and is changing our understanding of what may or may not work. That leaves me with the consideration of internal "bracing," ie, stabilization without fusion, or a minimally invasive stabilization and focal fusion. Since there is not compelling data, it leaves me thinking about principles and sequelae. If I fix him and do not fuse him, the potential sequelae is instrumentation fracture, not a horrible problem and can be salvaged. If I fuse him, then there is increased stress on adjacent segments, which when they degenerate, I do not have a good salvage strategy. So my final thought would be after a considered discussion with the patient, I would offer and recommend to him fixation without fusion presuming that I could get him adequately reduced on the operating table under general anesthesia, which I would expect to occur.
I would comment on the challenge of percutaneous instrumentation in large or obese patients. Fluoroscopy can be very challenging. Currently we use intra-operative 3D imaging (O-arm) with image guidance technology. We place a tracking arc on a spinous process and use this for navigation. One must be careful: if there is gross segmental instability, the tracking will be inaccurate and two separate tracking frames with separate image acquisitions or confirmatory fluoro imaging is prudent. I have certainly found intra-operative 3D imaging after screw placement to be useful to me as a surgeon to confirm placement and allow revision at the primary surgery rather than potentially needing to return to the OR to address implant malposition.
What is unclear to me is whether or not the ligamentous structures ever fully heal. Similarly, it is unclear to me if routine implant removal is prudent as well.
In this case, the patient has had a spectacularly good result.