Tyler R. Koski

Changes in coronal and sagittal plane alignment following minimally invasive direct lateral interbody fusion for the treatment of degenerative lumbar disease in adults: A radiographic study - Clinical article

OBJECTIVE The lateral transpsoas approach for lumbar interbody fusion is a minimal access technique that has been used by some to treat lumbar degenerative conditions, including degenerative scoliosis. Few studies, however, have analyzed its effect on coronal and sagittal plane correction, and no study has compared changes in segmental, regional, and global coronal and sagittal alignment after this technique. The object of this study was to determine changes in sagittal and coronal plane alignment occurring after direct lateral interbody fusion (DLIF). METHODS The authors performed a review of the radiographic records of 36 patients with lumbar degenerative disease treated with the DLIF technique. Thirty-five patients underwent supplemental posterior fixation to maintain correction. Preoperative and postoperative standing anteroposterior and lateral lumbar radiographs were obtained in all patients for measurement of segmental and regional coronal and sagittal Cobb angles. Standing anteroposterior and lateral 36-in radiographs were also obtained in 23 patients for measurement of global coronal (center sacral vertebral line) and sagittal (C-7 plumb line) balance. RESULTS The mean coronal segmental Cobb angle was 4.5° preoperatively, and it was 1.5° postoperatively (p < 0.0001). The mean pre- and postoperative regional lumbar coronal Cobb angles were 7.6° and 3.6°, respectively (p = 0.0001). In 8 patients with degenerative scoliosis, the mean pre- and postoperative regional lumbar coronal Cobb angles were 21.4° and 9.7°, respectively (p = 0.0004). The mean global coronal alignment was 19.1 mm preoperatively, and it was 12.5 mm postoperatively (p < 0.05). In the sagittal plane, the mean segmental Cobb angle measured -5.3° preoperatively and -8.2° postoperatively (p < 0.0001). The mean pre- and postoperative regional lumbar lordoses were 42.1° and 46.2°, respectively (p > 0.05). The mean global sagittal alignment was 41.5 mm preoperatively and 42.4 mm postoperatively (p = 0.7). The average clinical follow-up was 21 months in 21 patients. The mean pre- and postoperative visual analog scale scores were 7.7 and 2.9, respectively (p < 0.0001). The mean pre- and postoperative Oswestry Disability Indices were 43 and 21, respectively (p < 0.0001). CONCLUSIONS Direct lateral interbody fusion significantly improves segmental, regional, and global coronal plane alignment in patients with degenerative lumbar disease. Although DLIF increases the segmental sagittal Cobb angle at the level of instrumentation, it does not improve regional lumbar lordosis or global sagittal alignment.

Abdominal complications following kyphosis correction in ankylosing spondylitis

Spinal deformity surgery is associated with high rates of morbidity and a wide range of complications. The most significant abdominal complications following kyphosis correction, while uncommon, can certainly pose significant infectious and hemodynamic risks to the patient. Abdominal compartment syndrome is the most severe of the sequelae. It is the end result of elevated abdominal compartment pressure with physiological compromise and end organ system dysfunction. Although most commonly associated with trauma, abdominal compartment syndrome has also been witnessed following massive fluid shifts, which can occur during adult spinal deformity surgery. In this manuscript, we report on 2 patients with ankylosing spondylitis who developed significant abdominal pathology requiring exploratory laparotomy following kyphosis correction. In addition to describing the details of each case, we propose explanations of the relevant pathophysiology and review diagnostic and treatment strategies for such events. The key to effectively treating such a debilitating complication is to recognize it quickly and intervene rapidly and aggressively.

Mathematical calculation of pedicle subtraction osteotomy size to allow precision correction of fixed sagittal deformity.

Study Design. This is a retrospective review of 15 consecutive fixed sagittal plane deformity patients who have undergone pedicle subtraction osteotomies. The focus of this article is the application of a trigonometric equation that calculates the degree of correction needed to achieve sagittal balance. The intraoperative predictive accuracy and clinical radiographic results of using this mathematical equation are discussed. Objective. The need for a precise and reproducible planning tool for the correction of sagittal imbalance prompted us to apply a simple trigonometric equation to achieve the desired sagittal alignment of the spine. Summary of Background Data. Establishing sagittal balance has been widely recognized as one of the most important parameters in optimizing outcomes for spinal reconstruction patients. Preoperative planning for sagittal plane correction in adult spinal deformity has traditionally been done by estimation or with cumbersome film cutouts. To our knowledge, there has not been a consistent method of calculating the exact number of degrees needed to reestablish spinal balance. Methods. Patients’ C7 plumb lines are measured on a 36-inch radiograph to assess the degree of sagittal imbalance and determine how many degrees of correction (and subsequent millimeters of wedge resection) are needed. Applying a basic trigonometric formula for the tangent to the sagittal alignment is used to do this. Results. We have used this technique reliably in a series of 15 consecutive patients to reestablish sagittal balance. The predicted degree of correction was compared to the achieved degree of correction at the site of the osteotomy. This comparison was accurate to within 3° (the standard error of measurement for the method of Cobb) in all cases except 2. Conclusions. By using a simple mathematical equation, one can reliably determine the degree of pedicle subtraction osteotomy needed for correction of sagittal deformity. This technique is reproducible and has led to successful clinical outcomes.

Minimally invasive lateral lumbar interbody fusion and transpsoas approach-related morbidity

OBJECT Recently, the minimally invasive, lateral retroperitoneal, transpsoas approach to the thoracolumbar spinal column has been described by various authors. This is known as the minimally invasive lateral lumbar interbody fusion. The purpose of this study is to elucidate the approach-related morbidity associated with the minimally invasive transpsoas approach to the lumbar spine. To date, there have been only a couple of reports regarding the morbidity of the transpsoas muscle approach. METHODS A nonrandomized, prospective study utilizing a self-reported patient questionnaire was conducted between January 2006 and June 2008 at Northwestern University. Data were collected in 53 patients with a follow-up period ranging from 6 months to 3.5 years. Only 2 patients were lost to follow-up. RESULTS Thirty-six percent (19 of 53) of patients reported subjective hip flexor weakness, 25% (13 of 53) anterior thigh numbness, and 23% (12 of 53) anterior thigh pain. However, 84% of the 19 patients reported complete resolution of their subjective hip flexor weakness by 6 months, and most experienced improved strength by 8 weeks. Of those reporting anterior thigh numbness and pain, 69% and 75% improved to their baseline function by the 6-month follow-up evaluations, respectively. All patients with self-reported subjective hip flexor weakness underwent examinations during subsequent clinic visits after surgery; however, these examinations did not confirm a motor deficit less than Grade 5. Subset analysis showed that the L3-4 and L4-5 levels were most often affected. CONCLUSIONS The minimally invasive, transpsoas muscle approach to the lumbar spine has a number of advantages. The data show that a percentage of the patients undergoing the transpsoas approach will have temporary sensory and motor symptoms related to this approach. The majority of the symptoms are thought to be related to psoas muscle inflammation and/or stretch injury to the genitofemoral nerve due to the surgical corridor traversed during the operation. No major injuries to the lumbar plexus were encountered. It is important to educate patients prior to surgery of the possibility of these largely transient symptoms.

Surgical treatment of fixed cervical kyphosis with myelopathy.

Study Design. A retrospective clinical study. Objective. To investigate clinical and radiographic outcomes following the surgical treatment of fixed cervical kyphosis with myelopathy. Summary of Background Data. To our knowledge, a study specifically addressing the surgical treatment of fixed cervical sagittal deformity has never before been published. Methods. Sixteen patients treated surgically for fixed cervical kyphosis and myelopathy were followed for a mean of 4.5 years (range, 25–112 months). The study group consisted of 9 males and 7 females, with an average age of 52 years (range, 31–78 years). The principal etiologies of cervical deformity were prior laminectomy (63%), advanced spondylosis (19%), infection (6%), neuromuscular disease (6%), and metabolic disease (renal osteodystrophy) (6%). All patients were clinically evaluated by the Nurick classification and Odom criteria both before surgery and at the time of most recent follow-up. Radiographic analysis was performed using thin-cut CT scans, dynamic radiographs, and 14 × 36-inch scoliosis films. Results. The mean preoperative cervical Cobb angle as measured from the C2–C7 was +38° and improved to −10° at final follow-up, yielding an average correction of 48°. The mean number of anterior and posterior segments fused was 4.8 (range, 2–6) and 7.2 (range, 3–14), respectively. The mean Nurick score improved from 2.4 before surgery to 1.5 at the time of follow-up. According to Odom criteria, outcomes were as follows: excellent (38%), good (50%), fair (6%), and poor (6%). At the time of most recent follow-up, solid bony arthrodesis and maintenance of correction occurred in all patients; however, revision was required in one patient. Conclusion. The treatment of fixed cervical kyphosis with myelopathy using circumferential spinal osteotomies and instrumented reconstruction is technically demanding; however, restoration and maintenance of a neutral or lordotic cervical profile and excellent clinical outcomes are achievable.

Intraoperative neurophysiological monitoring in spine surgery: indications, efficacy, and role of the preoperative checklist

Spine surgery carries an inherent risk of damage to critical neural structures. Intraoperative neurophysiological monitoring (IONM) is frequently used to improve the safety of spine surgery by providing real-time assessment of neural structures at risk. Evidence-based guidelines for safe and efficacious use of IONM are lacking and its use is largely driven by surgeon preference and medicolegal issues. Due to this lack of standardization, the preoperative sign-in serves as a critical opportunity for 3-way discussion between the neurosurgeon, anesthesiologist, and neuromonitoring team regarding the necessity for and goals of IONM in the ensuing case. This analysis contains a review of commonly used IONM modalities including somatosensory evoked potentials, motor evoked potentials, spontaneous or free-running electromyography, triggered electromyography, and combined multimodal IONM. For each modality the methodology, interpretation, and reported sensitivity and specificity for neurological injury are addressed. This is followed by a discussion of important IONM-related issues to include in the preoperative checklist, including anesthetic protocol, warning criteria for possible neurological injury, and consideration of what steps to take in response to a positive alarm. The authors conclude with a cost-effectiveness analysis of IONM, and offer recommendations for IONM use during various forms of spine surgery, including both complex spine and minimally invasive procedures, as well as lower-risk spinal operations.

Maximizing the potential of minimally invasive spine surgery in complex spinal disorders.

Minimally invasive surgery (MIS) in the spine was primarily developed to reduce approach-related morbidity and to improve clinical outcomes compared with those following conventional open spine surgery. Over the past several years, minimally invasive spinal procedures have gained recognition and their utilization has increased. In particular, MIS is now routinely used in the treatment of degenerative spine disorders and has been shown to be as effective as conventional open spine surgeries. Although the procedures are not yet widely recognized in the context of complex spine surgery, the true potential in minimizing approach-related morbidity is far greater in the treatment of complex spinal diseases such as spinal trauma, spinal deformities, and spinal oncology. Conventional open spine surgeries for complex spinal disorders are often associated with significant soft tissue disruption, blood loss, prolonged recovery time, and postsurgical pain. In this article the authors review numerous cases of complex spine disorders managed with MIS techniques and discuss the current and future implications of these approaches for complex spinal pathologies.

Spinal cord compression in beta-thalassemia: case report and review of the literature

Study design: A case report of thoracic spinal cord compression in a 34-year-old male with beta-thalassemia is reported.Objectives: In patients with thalassemia, neurologic complaints should lead to a high index of suspicion for spinal cord compression from marrow expansion, ectopic bone formation and resultant stenosis. Initial presentation, diagnosis, radiographic findings, surgical treatment and follow-up are reviewed.Setting: This case is reported from Chicago, Illinois.Method: A chart review is performed for the purposes of this case report.Results: Patient underwent decompressive laminectomy with good surgical outcome.Conclusion: Rapid diagnosis and treatment of such a condition is essential to optimize the chances of recovery.

Thoracic pedicle subtraction osteotomy for fixed sagittal spinal deformity.

Study Design. A retrospective clinical study. Objective. To find the corrective capacity of a thoracic pedicle subtraction osteotomy (PSO), determine if segmental correction is dependent on level, and to compute the impact of thoracic PSO on regional and global spinal balance. Summary of Background Data. PSO is a technique popularized in the lumbar spine primarily for the correction of fixed sagittal imbalance. Despite several studies describing the clinical and radiographic outcome of lumbar PSO, there is no study in literature reporting its application in the thoracic spine. Methods. We retrospectively analyzed patients with fixed thoracic kyphosis who underwent thoracic PSOs for sagittal realignment. Segmental pedicle screw instrumentation and intraoperative neurophysiologic monitoring was used in all patients. Data acquisition was performed by reviewing medical charts and radiographs to determine sagittal correction (segmental/regional/global) and complications. Clinical outcome using the Scoliosis Research Society-22 (SRS-22) instrument was determined by interview. Results. A total of 25 thoracic PSOs were performed (mean: 1.7 PSOs/patient, range: 1–3) in 15 patients (9 M/6 F). The study population had an average age of 56 years (range, 36–81 years) and was followed up after surgery for a mean of 3.5 years (range, 24–75 months). The osteotomies were carried out in the proximal thoracic spine (T2–T4, n = 6), midthoracic spine (T5–T8, n = 12), and distal thoracic spine (T9–T12, n = 7). Mean correction at the PSO for all 25 levels was 16.3° ± 9.6°. Stratified by region of the spine, thoracic PSO correction was as follows: T2–T4 = 10.7° ± 15.8°, T5–T8 = 14.7° ± 4.6°, and T9–T12 = 23.9° ± 4.1°. Mean thoracic kyphosis (T2–T12 Cobb angle) was improved from 75.7° ± 30.9° to 54.3° ± 21.4° resulting in a significant regional sagittal correction of 21.4° ± 13.7° (P < 0.005). Global sagittal balance was improved from 106.1 ± 56.6 to 38.8 ± 37.0 mm yielding a mean correction of 67.3 ± 54.7 mm (P < 0.005). One patient, in whom there was segmental translation during osteotomy closure, had a decline in intraoperative somatosensory-evoked potentials. No patient sustained a temporary or permanent neurologic deficit after surgery. The mean SRS-22 Questionnaire score at final follow-up was 82.4 ± 10.2. Conclusion. Thoracic PSO can be performed safely. Segmental sagittal correction appears to vary based on the region of the thoracic spine the PSO is performed. The distal thoracic segments, which more closely resemble lumbar segments in morphology, rendered the greatest sagittal correction after PSO, approximately 24°. There was no case of neurologic injury associated with thoracic PSO, and clinical outcomes according to the SRS-22 instrument were generally favorable.

Safety and efficacy of C2 pedicle screws placed with anatomic and lateral C-arm guidance.

Study Design. This is a retrospective review of 150 C2 pedicle screw placements. Candidates had their C2 pedicle morphology assessed through three-dimensional imaging, including preoperative image guidance. After surgery, the patients were serially CT scanned. Follow-up, with fusion assessment, ranged from 1 to 12 years. Objective. We will show that an open technique combined with lateral C-arm guidance provides rapid placement of C2 pedicle screws. Summary of Background Data. C2 pedicle screws can be successful anchors for a variety of cervical problems. Standard intraoperative image guidance, biplane fluoroscopy, or free hand techniques all have their drawbacks. Methods. After adequate C2 exposure, the C2 pedicle is palpated. The dissector remains stationary to provide coronal orientation while a lateral C-arm radiograph is obtained for sagittal orientation. The drill trajectory is set, the C2 pedicle cannulated, and a cancellous screw placed. Results. A total of 71 patients had bilateral screws placed and 8 patients had unilateral screws placed. The overall complication rate was 2.7%. Conclusions. In our series, we have found a consistent way to cannulate the C2 pedicle. C2 fixation serves as an integral part of cervical reconstruction. Preoperative planning, anatomic knowledge, and lateral C-arm orientation create a low morbidity method for C2 screw placement.