Adolescent idiopathic scoliosis (AIS) in adult life poses a unique problem when combined with kyphotic deformity. The relationship between pelvic incidence (PI) and lumbar lordosis (LL) with ideal pelvic tilt (PT) and sagittal vertical axis (SVA) correction to maximize the clinical improvement has been worked out.1 Nevertheless, many other factors determine surgical strategy. Problems commonly associated with AIS in adult deformity are medical comorbidities, rigid deformity, spinal stenosis and claudication and/or radicular pain, presence of osteopenia, and previous surgeries with/without old hardware, among others.
Pedicle subtraction osteotomy (PSO) produces around 35° of kyphosis correction at each segment, whereas a Ponte osteotomy or posterior column osteotomy (PCO) produces around 10 degrees of correction per segment. A distal location of PSO produces greater correction of sagittal imbalance.2 The core measures of an ideal deformity correction may involve LL restored within 10° of PI, PT of <25°, and SVA ±5 cm, among others. To achieve ideal correction, the surgical intervention may need mid-thoracic spine-to-pelvis fixation, one- or two-level PSO, and multiple-level PCOs, as well as paying special attention to prevent PJK and distal junctional failure.3 L5–S1 interbody fusion may prevent sacral fixation failure, as well as the restoration of lordosis. Additional rods may be needed to prevent rod breakage, which commonly occurs at the notches of the contoured rod. Foraminal stenosis may be indirectly corrected by distraction between the pedicle screws, but severe spinal stenosis may require laminectomy.
The factors that may strongly influence the surgical strategy may involve several other parameters. To fulfill all of these requirements, the surgical time may exceed 6 to 8 hours, and consideration may be given to staging the procedure. Longer-duration surgery may require an ICU stay and the need for overnight or longer ventilatory support, which may increase incidence of respiratory complications. Estimated blood loss >1500 mL may increase the complications rate. A distal PSO has the advantage of greater correction of sagittal balance, but PSO at L4 or L5 will reduce the number of pedicle anchor points distal to the osteotomy, and weaken the distal fixation. The apex of kyphosis may determine the ideal location of the PSO, but when the apex is at L1 or L2, the PSO may need to be done at the level of conus medullaris, increasing the risk of neurogenic complication. Previous surgery for either degenerative condition or for scoliosis may further restrict the surgical strategies.
Figure 1 presents a 56F with an apex of associated Scheuermann kyphosis in the lower thoracic spine (A,B), needing thoiracic PSO (D), but the apex of scoliosis is in the mid-lumbar spine, corrected by multiple PCOs. The two deformities corrected separately, and rod-to-rod connectors completed the fixation in a single-stage surgery (C,D,E). Figure 2 presents an example of a 71 F, with previous distal lumbar fusion (A,B), requiring hardware revision and L3 PSO (C,D) as the initial stage; she required a further revision surgery with additional rods, to address rod breakage (E).
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Figure 1: 56 F c/o lower thoracic kyphosis and lumbar scoliosis.
Figure 2: 71 F, a retired doctor c/o severe back plus L2 radicular pain and fatigue.
References
1. Lafage V, Schwab F, Patel A, et al. Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity.
Spine (Phila Pa 1976) 2009; 34:E599–E606.
2. Sengupta DK. Spinopelvic balance.
JBJS Rev 2014; 2:pii: 01874474–201408000–00005.
3. Sengupta DK. Clinical incidence of PJK/ASD in adult deformity surgery: a comparison of rigid fixation and semirigid fixation-semirigid.
Spine (Phila Pa 1976) 2016; 41 (suppl 7):S37–S38.
