Four Rods Prevent Rod Breakage and Pseudarthrosis in Pedicle Subtraction Osteotomies (PSO)

Sachin Gupta, B.S.; Murat Sakir Eksi, M.D.; Christopher Ames, M.D.; Vedat Deviren, M.D. ; Blythe Durbin-Johnson, Ph.D.; Munish Gupta, M.D.

In the recent past, posterior only procedures have been performed more frequently than combined procedures. One of the posterior only based procedures, Pedicle Subtraction Osteotomy (PSO), has been widely used to treat severe spinal deformities. In rigid spinal deformities, the PSO is useful in maximizing the sagittal correction up to 30 or 40 degrees without the increased morbidity of a combined anterior and posterior approach, used widely in the past. Additional advantages include avoiding lengthening of the anterior vessels and viscera, and providing a greater, more stable correction. As a result, the PSO has become increasingly popular and can be used in a wide variety of patients with flatback or other sagittal plane deformities in order to increase the lordosis.

While a dual-rod technique or two longitudinal members has been widely used in PSO surgeries to treat rigid spinal deformities, it can often result in rod failure, nonunions, and other complications. On the other hand, a four-rod technique is useful because the two lateral rods help control the closing of the osteotomy and prevent any translation; the lateral rods hold the osteotomy closed while the long rods are being placed to connect the proximal and distal extent of the fusion levels independently. The four rods across the osteotomy site provide greater stability at the place where the instrumentation has the greatest mechanical stress. The two lateral rods are placed one level above and below the osteotomy site. The long rods are not placed into screws at the osteotomy site, avoiding severe in situ bending, which may notch the rod making it more vulnerable for early rod fracture, placing the patient at risk for a pseudarthrosis.

The purpose of this study was to assess two methods of posterior instrumentation involved in a surgical technique when performing pedicle subtraction osteotomies i.e. dual rod vs. four rod in terms of correction, rod failure and other complications.

Dedicated Spine Measurement Software (SMS) Quantifies Key Spino-Pelvic Parameters More Reliably Than Standard PACS Tools

Munish Gupta, Jensen K. Henry, Frank Schwab, Eric Klineberg, Justin S. Smith, Jeffrey Gum, David W. Polly, Jr, Barthelemy Liabaud, Bassel G. Diebo, D. Kojo Hamilton, Robert Eastlack, Peter G. Passias, Douglas Burton, Themistocles Protopsaltis, Virginie Lafage, ISSG

Accurate radiographic measurement of sagittal alignment is essential for evaluating adult spinal deformity (ASD). Sagittal spino-pelvic parameters, including sagittal vertical axis (SVA), pelvic incidence minus lumbar lordosis (PI-LL) mismatch, and pelvic tilt (PT) all correlate with patient-reported outcomes of pain and disability, and disregard for these parameters in pre-operative planning can lead to failures in surgical correction. Therefore, accurate assessment of sagittal spino-pelvic parameters is critical for diagnosis and pre-operative planning as well as evaluation of the patient post-operatively.

Once digitized radiographs began to take precedence over standard films, early studies demonstrated that computer-assisted methods were able to measure coronal and sagittal spinal parameters with greater precision, accuracy, and speed than manual methods. While all measurements depend on the landmarks used, digital methods help to eliminate potential sources of error by automating the projections and angular measurements.

Picture archiving and communication systems (PACS) were developed to provide electronic storage and access to multiple types of radiologic imaging modalities. While the convenience of digital imaging and radiologic assessment is undeniable, the measurement tools offered by PACS, such as rulers and angles, have limited capabilities. Deficiencies in PACS include the lack of spine-specific tools like the 4-point Cobb angle; redundant measurements in angles that share endplates; a radiograph cluttered by excessive measurements; and the lack of sophisticated techniques to identify more difficult spino-pelvic landmarks, such as the bi-coxo-femoral axis used to measure PI and PT.

As a reaction to the limitations of PACS, multiple types of spine measurement software (SMS) have been developed for research and clinical use and validated in previous studies. However, because these programs require identification of the superior and inferior endplates of each vertebra to generate measurements, their utility is primarily as a research tool.

Many surgeons still use PACS in their clinical assessment of ASD patient radiographs. Yet despite the substantial number of validation studies for both digitized measurements and SMS, no study has actually compared PACS to SMS. Thus, this study investigated the reliability of PACS versus SMS measurements of the sagittal spino-pelvic parameters, with the hypothesis that SMS would be more reliable.

Reducing Rod Fracture and Pseudarthrosis in Pedicle Subtraction Osteotomy: The Importance of Rod Number and Configuration

Munish Gupta, MD; Jensen K. Henry, BA; Frank Schwab, MD; Christopher P. Ames, MD; Eric Klineberg, MD;  Justin S. Smith, MD, PhD; Vedat Deviren, MD; Christopher I Shaffrey, MD; Robert Hart, MD; Richard Hostin, MD; Gregory Mundis, MD; Han Jo Kim, MD; Douglas C. Burton, MD; Virginie Lafage, PhD; on behalf of the International Spine Study Group

In adult spinal deformity (ASD), sagittal malalignment is debilitating and often necessitates surgical realignment. Pedicle subtraction osteotomy (PSO) provides powerful correction for sagittal deformity by incorporating decompression, removal of posterior elements, and a wedge resection through all three vertebral columns. Though PSO’s can dramatically improve patient-reported outcomes and alignment, they are associated with increased complications.

Pseudarthrosis is a common complication after PSO causing substantial pain and disability. Moreover, pseudarthrosis greatly increases the likelihood of revision surgery. Pseudarthrosis also imparts a financial burden on patients and institutions: the cost of revision surgery is greater for pseudarthrosis than adjacent segment disease or stenosis, and is less-cost-effective in terms of patient quality of life measures. Implant failure and pseudarthrosis are intimately related, with rod fracture occurring in large number of pseudarthrosis cases.

This study first sought to develop a classification scheme for multiple rod configurations to facilitate communication among surgeons, patients, and researchers. Subsequently, this study investigated the impact of multiple rod configurations, as well as rod diameter, material, and interbody fusion, on pseudarthrosis and rod fracture. It was hypothesized that the addition of multiple rods would decrease the mechanical stress on the instrumentation at the level of the osteotomy, thus reducing pseudarthrosis and rod fracture.

Pedicle Subtraction Osteotomy (PSO) in the Revision versus Primary Adult Spinal Deformity (ASD) Patient: Is there a difference in correction and complications?

Gupta, Munish C.; Terran, Jamie S.; Mundis, Gregory M.; Smith, Justin S.; Shaffrey, Christopher I.; Kim, Han Jo; Boachie-Adjei, Oheneba; Lafage, Virginie; Bess, Shay ; Hostin, Richard; Burton, Douglas C.; Ames, Christopher P.; Kebaish, Khaled; Klineberg, Eric; Study Group, International Spine

Pedicle subtraction osteotomies (PSO) originally were described to attain correction of sagittal plane deformities in ankylosing spondylitis patients. However, currently, PSO are most often performed to correct sagittal plane deformity in patients with adult spinal deformity (ASD). PSO have become a widely used tool for correction of adult deformities and are done most commonly in the lumbar, rather than thoracic, spine. The osteotomy is used to correct a variety of sagittal deformities, ranging from degenerative disorders resulting in loss of lumbar lordosis and flat lumbar spine to multi-operated spinal deformities with severe thoracic and lumbar kyphosis. PSO are difficult procedures that have the potential for developing substantial intraoperative blood loss and risk for intraoperative and postoperative complications.

The surgery becomes even more difficult when the patient has had a previous surgical procedure. The removal of previous instrumentation and the mere dissection of the spine, scarred dura, and neural elements add additional operative time and risk for complications.   At the Scoliosis Research Society (SRS) meeting in 2011, similar complication rates were presented for revision and primary surgeries for patients undergoing adult spinal deformity correction. However, there is no such comparison that has been published for PSO in primary versus revision procedures. Most PSO are done in revision surgeries for patients that have had multiple previous spinal procedures. More recently, surgeons have begun to employ PSO in primary deformity corrections, as an alternative to a formal anterior release and fusion to decrease morbidity in the adult population. The purpose of this study was to evaluate the differences in the clinical and radiographic outcomes for patients undergoing PSO as a primary vs. revision spine procedure at one year follow up, and compare the complication rates between the two groups.

Coronal Imbalance May Be Neglected in Patients Undergoing Majority Sagittal Deformity Correction

Gupta, Munish C.; Boachie-Adjei, Oheneba; Cunningham, Matthew E.; Protopsaltis, Themistocles S.; Deviren, Vedat; Mundis, Gregory M.; Ames, Christopher P.; Hostin, Richard; Lafage, Virginie;Klineberg, Eric; Smith, Justin S.; Terran, Jamie S.; International Spine Study Group

Surgical correction of adult spinal deformity (ASD) is a difficult and complicated task, as surgeons must account for alignment in multiple planes as well as the rotation of the vertebrae during all stages of treatment planning. Correction of coronal and sagittal imbalance has been a primary aim of these procedures for as long as they have been performed, and the number of spino-pelvic parameters, which can influence global spinal balance, has been clearly documented. Surgical treatment for ASD is associated with higher complication rates and higher morbidity and mortality than comparable surgery on younger patients. Not only are the patients older with more medical problems, but their healing is slower and less robust (e.g. spinal fusion). Adults also have more degenerative joint changes in their knees and hips, which are sometimes associated with contractures. The standing posture of an adult therefore is influenced not only by the spinal deformity but also by leg length discrepancies, and possible joint contractures. Posture can also be influenced by central degenerative disorders and peripheral neuropathies. Additionally, the gradual kyphotic posture that occurs with age from collapsing disc spaces and compression of vertebral bodies results in a gradual inflexible tissue envelope around the trunk. All of the above are aspects of ASD which come into play in surgical treatment of these patients and make the planning and execution of surgery more difficult than in adolescents.

One of the more difficult aspects of ASD surgery is achieving coronal balance, as there are many factors that can influence coronal alignment. A standing full-length film before surgery, including at a minimum the cervical spine and femoral heads, is a good start in trying to plan the corrective surgical strategy.  The surgeon must additionally account for innate flexibility of the spine, typically measured with a supine film. During the surgical procedure, many strategies are used to ensure adequate correction; asymmetric osteotomies and on table in situ correction can be particularly effective in correcting coronal imbalance. Intra-operative films and T square rulers are good measures of correction prior to closure.  Even with all these steps, one may end up with post-operative coronal imbalance when the patient is in the standing position. In this study, we tried to evaluate the coronal plane balance before and after surgery to look for factors that contributed to postoperative coronal balance.

Perioperative Safety and Efficacy in Correcting Congenital Spine Deformity

Pumibal Wetpiriyakul, M.D., Munish Gupta, M.D., Zhiyue Li, M.D.

Congenital spinal deformity presents in many forms ranging from congenital scoliosis, kyphoscoliosis to a pure kyphosis depending on the congenital vertebral anomaly.  Localized curves are caused by developmental vertebral anomalies such as failure of formation, failure of segmentation and mixed type. Coronal curve deformities occurred in congenital scoliosis, sagittal curve deformities in congenital kyphosis and both coronal and sagittal curve deformities in congenital kyphoscoliosis. Congenital scoliosis can progress and result in significant deformity. Congenital kyphoscoliosis and kyphosis carries risk for paralysis with curve progression. Non-operative management has a very limited role in congenital spinal deformities treatment besides observation. Brace treatment may be indicated for controlling only the compensatory curves when primary congenital curve has not been treated by surgery.

Surgical management is necessary in treatment of congenital curve progression or severe curves at presentation. The objectives of surgery are to prevent further progression such as fusion in situ or to correct deformities. It is better to stabilize a curve when it is small, and thus prevent it from worsening, than to allow it to progress and then decide to correct the deformity when the child is skeletally mature. Correction may be gradual, allowing growth to correct the spine through the use of hemiepiphysiodesis. In addition, acute correction can be achieved by many techniques such as hemivertebra resection, anterior release, posterior release and vertebral resection with instrumentation and arthrodesis.  Surgical correction with instrumentation has been reported to be associated with high risk of neurologic complications. Qui et al reported total incidence of neurologic deficits with surgical correction as 1.89%. However, Ayvaz et al reported a neurologic complication rate of 9%. The objective of our study is to evaluate the safety and efficacy of the surgical correction of congenital spine deformity.

Unusual Presentation of Vertebral Endplate Modic Changes in Congenital Scoliosis Associated with Pain: A Report of Two Cases

Koopong Siribumrungwong, M.D., Sachin Gupta, B.S., Munish C. Gupta, M.D.

Congenital scoliosis is not normally associated with pain in young children. We are presenting two cases of young patients with congenital scoliosis and moderate to severe pain. There were no spinal cord abnormalities found in these patients. The MRI and CT scan revealed disc degeneration with Modic changes at the apex of the congenital scoliosis. We hypothesized that the mechanical instability resulting from poor spinal element formations associated with congenital scoliosis was responsible for causing the disc degeneration. Modic changes have been reported to be associated with pain in degenerative conditions of the spine. Both patients underwent a posterior spinal fusion and instrumentation, which relieved their pain immediately.

Technique for Preventing Cord Compression after PVCR in Severe Kyphosis Correction: Case Series

Kavita Gupta, B.S.; Vivek Mohan, M.D, M.S.; Josh Ellwitz, M.D.; Oheneba Boachie-Adjei, M.D.; Munish C Gupta, M.D.

Severe angular kyphosis from congenital anomalies or post tuberculosis collapse can result in spinal cord compression. The goal of surgery in these cases is to decompress the spinal cord and correct the deformity. The posterior approach is more effective than an anterior approach since it exposes the anterior and posterior column. The ventral decompression is then performed by a vertebrectomy, followed by a posterior column resection and correction. The risks of a neurologic injury during the correction of severe kyphotic deformities have been reported to be significantly higher than the reported complications for primary coronal plane deformity. As such, neural injury after kyphosis correction is still a significant complication, in up to 18.5% of cases in one series with permanent spinal cord injury a rare occurrence. Our objective is to present a previously unreported case of cord compression, from the deep paraspinal musculature, as well as a novel technique to protect the cord.