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Abstract and Introduction
Abstract
Object Lateral minimally invasive thoracolumbar instrumentation techniques are playing an increasing role in the treatment of adult degenerative scoliosis. However, there is a paucity of data in determining the ideal candidate for a lateral versus a traditional approach, and versus a hybrid construct. The objective of this study is to present a method for utilizing the lateral minimally invasive surgery (MIS) approach for adult spinal deformity, provide clinical outcomes to validate our experience, and determine the limitations of lateral MIS for adult degenerative scoliosis correction.
Methods Radiographic and clinical data were collected for patients who underwent surgical correction of adult degenerative scoliosis between 2007 and 2012. Patients were retrospectively classified by degree of deformity based on coronal Cobb angle, central sacral vertical line (CSVL), pelvic incidence, lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic tilt (PT), presence of comorbidities, bone quality, and curve flexibility. Patients were placed into 1 of 3 groups according to the severity of deformity: "green" (mild), "yellow" (moderate), and "red" (severe). Clinical outcomes were determined by a visual analog scale (VAS) and the Oswestry Disability Index (ODI).
Results Of 256 patients with adult degenerative scoliosis, 174 underwent a variant of the lateral approach. Of these 174 patients, 27 fit the strict inclusion/exclusion criteria (n = 9 in each of the 3 groups). Surgery in 17 patients was dictated by their category, and 10 were treated with surgery outside of their classification. The average age was 61 years old and the mean follow-up duration was 17 months. The green and yellow groups experienced a reduction in coronal Cobb angle (12° and 11°, respectively), and slight changes in CSVL, SVA, and PT, and LL. In the green group, the VAS and ODI improved by 35 and 17 points, respectively, while in the yellow group they improved by 36 and 33 points, respectively. The red subgroup showed a 22° decrease in coronal Cobb angle, 15° increase in LL, and slight changes in PT and SVA. Three patients placed in the yellow subgroup had "green" surgery, and experienced a coronal Cobb angle and LL decrease by 17° and 10°, respectively, and an SVA and PT increase by 1.3 cm and 5°, respectively. Seven patients placed in the red group who underwent "yellow" or "green" surgery had a reduction in coronal Cobb angle of 16°, CSVL of 0.1 cm, SVA of 2.8 cm, PT of 4°, VAS of 28 points, and ODI of 12 points; lumbar lordosis increased by 15°. Perioperative complications included 1 wound infection, transient postoperative thigh numbness in 2 cases, and transient groin pain in 1 patient.
Conclusions Careful patient selection is important for the application of lateral minimally invasive techniques for adult degenerative scoliosis. Isolated lateral interbody fusion with or without instrumentation is suitable for patients with preserved spinopelvic harmony. Moderate sagittal deformity (compensated with pelvic retroversion) may be addressed with advanced derivatives of the lateral approach, such as releasing the anterior longitudinal ligament. For patients with severe deformity, the lateral approach may be used for anterior column support and to augment arthrodesis.
Introduction
Minimally invasive spine surgery was developed to address approach-related morbidity associated with traditional open spine surgery. Over the last decade the application of MIS techniques for the spine has continued to evolve and expand. As the field continues to advance, MIS techniques have been implemented in the treatment of more complex patient pathologies, including adult degenerative scoliosis, the prevalence of which has increased due to increasing life expectancy. In recent publications, Wang et al. described techniques for mini-open pedicle subtraction osteotomy as well as percutaneous iliac screw placement, which may become invaluable tools in the future treatment of adult degenerative scoliosis. The traditional surgical correction of adult degenerative scoliosis incorporates extensive open spinal mobilization and then reconstruction with long multilevel implants, and may confer significant morbidity. Less invasive techniques have the potential for muscle mass preservation and decreased physiological stress, blood loss, narcotic use, and length of hospital stay. However, MIS techniques have their own set of challenges and complications. Difficulties related to MIS correction of adult degenerative scoliosis are particularly associated with its steep learning curve and technical limitations, and require a full understanding of the fundamentals of spinal deformity correction as well as the technical limitations of MIS instrumentation.
Lateral MIS instrumentation techniques have played an increasing role in the treatment of adult degenerative scoliosis, which is characterized by spinal curvature greater than 10° with associated derangement of spinopelvic alignment. It can be used as a unique standalone treatment, or as a source of anterior column support to provide fusion and possible deformity correction. Progressive deformity that develops after skeletal maturity is related to asymmetrical degeneration of intervertebral discs, compression fractures, and/or osteoporosis. Classification of adult degenerative scoliosis severity, both radiographically and clinically, is critical to selecting the appropriate treatment paradigm. The timing of surgical intervention, the surgical approach, and the length of constructs for operative correction have been controversial.
Patient selection is an important factor when electing to use an MIS approach, because not all patients are candidates for this approach due to the extent of deformity. The MIS decision-making process includes a thorough analysis of clinical and radiographic parameters to establish benchmark surgical objectives for neural decompression, restoration, and maintenance of spinal balance in a similar fashion to traditional open techniques. Each lateral MIS surgical technique or variation has its unique impact on deformity correction and can be used alone or combined with others. There is a paucity of data in determining the ideal candidate for a lateral MIS versus a traditional open approach, and versus hybrid constructs. In this paper we present a follow-up study of our singlecenter experience with the lateral MIS technique for adult degenerative scoliosis, with a refined understanding of the importance of sagittal balance correction.
The purpose of this project is to provide a roadmap to guide the surgical treatment of adult degenerative scoliosis using minimally invasive lateral anterior/posterior interbody arthrodesis, anterior column release, posterior decompression, and posterior percutaneous instrumentation. We also discuss the use of hybrid constructs incorporating traditional posterior osteotomies. Our objectives of this project are to: 1) present and validate a surgical method for utilization of the lateral MIS approach for adult degenerative scoliosis; 2) analyze construct-specific clinical outcomes and complications; and 3) determine the limitation of lateral MIS for adult degenerative scoliosis. We discuss specific strategies we have developed and refined for realizing these objectives using our institutional standardized MIS adult degenerative scoliosis classification.
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