Direct Lateral Interbody Fusion using the Aspen™ Device
The patient is a 63-year-old active male who enjoys hiking, fishing and golf. He presents with lower back pain that radiates down the anterolateral thigh just to the knee; pain is mostly right-sided. Although he reports having back pain the past 1.5 years, pain has progressively worsened the last 4 months. He is unable to ambulate without pain, cannot tie his shoe laces, get up out of a chair, or drive a car.
He is 6'-2" tall and weighs 205 pounds. His hypertension is treated with medication.
- Pain is severe on lateral bending at the waist, with reproduction of radiation down the right leg
- Antalgic gait
- Minimal loss of right-sided quadriceps and dorsiflexion function
- Ice, heat
- Non-steroidal anti-inflammatory drugs (NSAIDs)
- Prescription pain medication
- Physical therapy
- Core reconditioning program
- Transforaminal epidural injections provided major but, temporary pain relief
He was not able to fully participate in physical therapy (outpatient and home program) because of incapacitating pain.
Figure 1. Sagittal T2 lumbar spine; specifically focusing on L3-L4
Figure 2. Axial T2 lumbar spine specifically; focusing on L3-L4
- Advanced degenerative disc disease, L3-L4
- Degenerative scoliosis
- Lumbar stenosis
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The patient exhausted all conservative treatment measures and was experiencing significant ambulatory difficulty. A minimally invasive operative strategy was chosen via direct lateral interbody fusion and posterior microdecompression with posterior fusion using the Aspen device for posterior fixation (Aspen™ Spinous Process Fixation System, LANX®, Broomfield, CO)
The Aspen™ device provides a less invasive option for immediate posterior stabilization to augment an interbody fusion.
Following the interbody placement via the lateral approach, the patient underwent a minimally invasive microscopic decompression at L3-L4 followed by immediate placement of the Aspen device. Pre-clinical biomechanical studies found an increase in foraminal height in conditions that included the device, suggesting the unique design may help maintain foraminal height. In addition it provides a scaffold for posterior interspinous and interlaminar bone grafting.
The patient has done very well throughout and is involved in an aggressive rehabilitation exercise program.
Figure 3. Posteroanterior (PA) x-ray at 1 month post-op
At 6 months plus, the patient returned to hiking, fishing, walking, and a regimen of general exercise. He reports only minimal symptoms of mild intermittent aching in the lower back during exertion.
Figure 4. Lateral x-ray 6 months post-op
Post-operative sagittal CT scans at 6 months demonstrate the Aspen™ Spinal Fixation device and fusion. The PEEK (polyether ether ketone) cages are visualized between L3-L4 (Figs. 5A-5D).
Post-operatively, the patient lost some weight, underwent gallbladder surgery (after spine surgery), but most importantly, he is able to physically function well, which includes walking and hiking. These activities are important to recruit blood flow to build truncal musculature.
The descriptions of the results obtained from use of the Aspen Spinal Fixation System in this promotional piece are based on the physician's actual experience. The results achieved in any particular case using the Aspen device can vary and the results achieved in the case may not be typical. The use of the Aspen device entails certain risks, such as the possibility of implant bending or breakage, loosening, movement or migration of the device, or bone or spinous process fracture. In addition, the Aspen device should be used for only those indications described in the Package Insert for the Aspen device, entitled "Important Information on the Lanx Spinal Fixation System," a copy of which may be obtained by contacting Lanx Customer Service at 1.866.378.4195. Refer to the Package Insert for a more complete description of indications, contraindications, warnings and other information about the product.
*The physician author of this case has been compensation for his illustration by Lanx, Inc.
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The case provided by Dr. Vokshoor illustrates a clinical scenario frequently encountered by spine care providers. The patient's history and clinical data presented suggests a L3 radiculopathy secondary to foraminal stenosis. The patient has undergone a thorough pre-operative evaluation and non-operative care without acceptable long-term clinical improvement.
As surgeons, we are typically convinced that our plan for the patient is in their best interest and seek to convince them of this as well. Unfortunately, the level of evidence supporting or refuting any of the choices provided by Dr. Vokshoor is limited. In the absence of definitive evidence, surgeon bias, regional variation, and practice pattern begin to flavor our surgical choices.
This surgeon likes the decision regarding a minimally invasive approach, but would have chosen "other" from the choices provided. Indirect decompression of the L3-L4 foramen has worked well in my hands. Therefore, a direct lateral transpsoas approach would serve as the primary treatment option. Stand-alone transpsoas procedures have been carried out but often lead to subsidence and, in my practice, have fallen out of favor.
Providing additional stabilization through the anterior column is a viable option worthy of consideration. Dr. Vokshoor has chosen a novel posterior column approach. In conjunction with spinous process stabilization a second, direct decompression was also provided for the patient. As surgeons, we have multiple choices for posterior fixation and, in the face of stable anterior column constructs, the posterior tension band techniques do not have to be as robust.
Interspinous process devices have been used in other settings. Multiple patients and long-term follow up will be necessary before any definitive decisions can be made. Multiple percutaneous pedicle screw systems provide superior stability with similar MIS principles and better maintenance of important midline ligamentous structures. In this particular case, decompression of the L3 nerve root was accomplished but at 6 months it is too soon to tell whether stable fixation provided ample environment for healthy fusion to occur.
The discussion provided by Dr. Reginald Q. Knight is relevant and accurate. I appreciate that many of our current surgical methods do not have "robust" (level ONE) evidence to support or refute these methods. However, our surgical principles involve decompressing neural elements and, if necessary, restoring the height and alignment of a diseased motion segment. These principles are sound when they correspond to the patient's clinical symptoms and are ubiquitous concepts supported by most spine surgeons.
Both Dr. Knight and I agree to a direct lateral transpsoas approach at L3-L4 supported by posterior instrumentation. Stability and clinical outcomes of posterior fixation with bilateral pedicle screw-rod constructs are sound, with percutaneous systems offering additional clinical (MIS) benefit.
Although long-term follow up is currently lacking for spinous process fixation, biomechanical studies have shown equivalent stability compared to bilateral pedicle screw-rod constructs when combined with an ALIF interbody graft. There is additional agreement that, in the face of a stable anterior column construct, the posterior tension band techniques do not have to be as robust.
This particular patient suffered from severe L3 and L4 radiculopathy. In my opinion, direct decompression of the severely stenotic lateral recess was essential in addition to the indirect decompression attainable through a transpsoas approach. Thus, a minimal opening for a laminoforaminotomy and direct microscopic decompression of the subarticular zone (severely stenotic on the axial pre-operative MRI) is essential in this case.
The clinical superiority of bilateral pedicle screws over spinous process fixation, when used to support a directed lateral transpsoas approach can be challenged, especially in the setting of a large anterior column interposition graft. The design of the Aspen device allows for placement through a small midline incision and eliminates the surgical risk associated with screw placement. In this patient, the unique shape of the Aspen device may offer an increase in foraminal height, as seen in the cadaveric biomechanical testing model. This alternative approach to posterior fixation offers a surgical solution worthy of additional consideration.
Dr. Knight's feedback is much appreciated and I look forward to further discussions on this surgical method.