Flatback following Non-instrumented Adolescent Idiopathic Scoliosis Surgery

Patient History

The patient is a 56-year-old woman treated with non-instrumented fusion and casting as a teenager. Her chief complaint is low back pain, fatigue with ambulation, and pitched forward posture. Ambulatory endurance is less than a block and pain has become constant.

Examination

Marked truncal inclination is noted, no motor or sensory deficits to the extremities.

Prior Treatment

Prior treatment included pain management, bracing, and physical therapy.

Images

Long cassette standing films show significant sagittal plane imbalance and pelvic retroversion. Analysis with Surgimap Spine software shows an SVA in excess of 10-cm and pelvic tilt of 54-degrees. The lumbar lordosis is 26-degrees. (Fig. 1)

Figure 1

Diagnosis

• Flatback syndrome, fixed sagittal imbalance
• Spino-pelvic malalignment, high PT/SVA

Selected Treatment

Surgimap Spine was applied to test several osteotomy combinations necessary for spino-pelvic realignment. Goals: SVA<55mm, PT<25. (Fig. 2)

Figure 2. Osteotomy drawing

All posterior realignment was performed using a large L4 PSO; extension to the fusion with iliac fixation was pursued. (Fig. 3)

Figure 3. PSO planning

Figure 4. Postoperative radiographs

Outcome

• The patient has had substantial pain relief and takes no pain medication.
• Her ambulation was increased to more than a mile; she is very happy with her posture.
• Spino-pelvic realignment has been achieved.
• However, at 1-year follow-up a broken rod is noted. Should this be revised for suspected pseudarthrosis despite the pain free status?

Case Discussion

Baron S. Lonner, MD

Professor of Orthopaedic Surgery

Mount Sinai Hospital

This case, of a 56-year-old woman with history of non-instrumented spinal fusion for scoliosis approximately four decades earlier, illustrates classic flatback syndrome. The low back pain, fatigue, and difficulty standing upright, with limited ability to walk, are typical features of this problem. These patients often have diffuse thoracolumbar back pain, fatigue, and pain in the thigh musculature, as well as knee pain as a result of a flexed hip and knee posture assumed in order to stand upright.

This patient failed nonoperative modalities and was a good candidate for a realignment procedure. There are various options for realignment, which in this case is predominantly a sagittal plane problem. This could be done with posterior-anterior-posterior procedures, in which Chevron posterior osteotomies combined with anterior structural grafting at multiple levels in the lumbar spine are performed, followed by posterior instrumentation. I would favor a posterior procedure in which realignment is done all from the posterior approach by pedicle subtraction osteotomy. This followed by anterior structural grafting of previously unfused caudal motion segments. The latter could also be achieved through a posterior TLIF approach. Anterior grafting is done in order to minimize pseudarthrosis associated with long fusion to the sacrum.

This particular case is well-executed using Surgimap software, which assists the surgeon to choose the level and magnitude of the osteotomy to achieve realignment of the sagittal vertical axis. This software takes into account parameters of global alignment, thoracic kyphosis, lumbar lordosis and pelvic tilt, which also impacts the end result. The chosen procedure, pedicle subtraction osteotomy, adhered to the surgical plan as outlined with the assistance of Surgimap, resulted in excellent clinical results. A possible asymptomatic pseudarthrosis occurred in this patient. In light of her high level of functioning without symptoms, I personally would not choose to surgically address the rod breakage and would simply observe her over time. If the patient develops pain or loss of sagittal alignment, that would be an opportunity to address a presumed pseudarthrosis.

This case very nicely illustrates the importance of sagittal balance for the functioning of an individual, particularly with a fused spine, and the utility of the spinal software to assist in planning and execution of a realignment procedure.