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Kevin S. Chen and Paul Park

This video details the minimally invasive approach for treatment of a symptomatic Grade II lytic spondylolisthesis with high-grade foraminal stenosis. In this procedure, the use of a navigated, guidewireless technique for percutaneous pedicle screw placement at the lumbosacral junction is highlighted following initial decompression and transforaminal interbody fusion. Key steps of the procedure are delineated that include positioning, exposure, technique for interbody fusion, intraoperative image acquisition, and use of a concise 2-step process for navigated screw placement without using guidewires.

The video can be found here: https://youtu.be/2u6H4Pc_8To.

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Anne Louise Oaklander

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William R. Stetler Jr., Paul Park, and Stephen Sullivan

Object

Tethering of the spinal cord has been a recognized cause of neurological symptoms in pediatric patients and is increasingly being recognized as a cause of symptoms in adults as well. The pathophysiology surrounding spinal cord tethering has begun to be understood in the pediatric population but is still unclear in adult patients.

Methods

Using a PubMed database literature search, the authors reviewed the pathology and pathophysiology surrounding the tethered spinal cord, focusing particularly on the pathophysiology of adult tethered cord syndrome (TCS).

Results

Experimental data obtained in pediatric patients at surgery and in animal models indicate that spinal cord tethering causes a reduction in spinal cord blood flow and dysfunction of neuronal mitochondrial terminal oxidase. Retrospective analyses of patients undergoing surgery for adult TCS show that many adults developed symptoms following an event that could stretch the spinal cord, while others did not. Many patients also were found to have structural lesions in addition to a tethered spinal cord at diagnosis.

Conclusions

Both adult and pediatric TCSs are likely the result of a relative lack of blood flow to the spinal cord, causing dysfunction in mitochondrial oxidative phosphorylation. The likely reason the syndrome present later and differently in adults is that a secondary threshold of tension or a cumulative effect of repetitive, transient tension is placed on the cord before symptoms are recognized.

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William R. Stetler Jr., Frank La Marca, and Paul Park

Object

Ossification of the posterior longitudinal ligament (OPLL) is a pathological process of ectopic calcification with a preponderance for the cervical spine. Epidemiological and familial studies have both indicated predisposition; however, the genetic inheritance pattern and responsible genes for OPLL are still uncertain. The aim of this study was to evaluate and summarize the current understanding of the genetics underlying OPLL.

Methods

The authors reviewed epidemiological and genetic studies surrounding OPLL, with a particular focus on inheritance patterns and potential genes responsible for OPLL, using a PubMed database literature search.

Results

Despite an unclear inheritance pattern, there appears to be a strong familial link in patients with OPLL. Examination of these patterns using linkage analysis has shown multiple candidate genes that could be responsible for the inheritance of OPLL. Genes for collagen, nucleotide pyrophosphatase, transforming growth factors, and the vitamin D receptor have all been implicated. Additionally, multiple cytokines and growth factors, including bone morphogenetic proteins as well as other proteins and interleukins involved in bone development, have been shown to be abnormally expressed in patients with OPLL. In addition, multiple mechanical and metabolic factors such as hyperinsulinemia and obesity have been shown to be linked to OPLL.

Conclusions

Ossification of the posterior longitudinal ligament has a complex inheritance pattern. It does not appear that OPLL follows a simple, single-gene Mendelian inheritance pattern. Development of OPLL is more likely multifactorial in nature and develops in patients with a genetic predisposition from a variety of different mutations in various genes on various chromosomes. Additionally, environmental factors and interaction by other pathological disease processes, such as obesity and diabetes mellitus, may play a role in the development of OPLL in susceptible individuals.

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Paul Park and Kevin T. Foley

Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is a relatively new surgical procedure that appears to minimize iatrogenic soft tissue and muscle injury. The authors describe a technique for MI-TLIF that permits the surgeon to reduce spondylolisthesis percutaneously. The results in 40 consecutive patients who underwent MI-TLIF for symptomatic spondylolisthesis utilizing this approach are reviewed. Thirty cases involved a degenerative spondylolisthesis while the remaining 10 were isthmic. The minimum follow-up was 24 months with a mean of 35 months. The mean preoperative Oswestry Disability Index score was 55, decreasing to a mean of 16 postoperatively. The mean leg and back pain visual analog scale scores were 65 and 52, respectively, improving to means of 8 and 15. Reduction of the spondylolisthesis was achieved in all cases, with a mean decrease in forward translation of 76%. The authors conclude that MI-TLIF for symptomatic spondylolisthesis appears to be an effective surgical option with results that compare favorably to open procedures.

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Jacob R. Joseph, Brandon W. Smith, Xilin Liu, and Paul Park

OBJECTIVE

Surgical robotics has demonstrated utility across the spectrum of surgery. Robotics in spine surgery, however, remains in its infancy. Here, the authors systematically review the evidence behind robotic applications in spinal instrumentation.

METHODS

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Relevant studies (through October 2016) that reported the use of robotics in spinal instrumentation were identified from a search of the PubMed database. Data regarding the accuracy of screw placement, surgeon learning curve, radiation exposure, and reasons for robotic failure were extracted.

RESULTS

Twenty-five studies describing 2 unique robots met inclusion criteria. Of these, 22 studies evaluated accuracy of spinal instrumentation. Although grading of pedicle screw accuracy was variable, the most commonly used method was the Gertzbein and Robbins system of classification. In the studies using the Gertzbein and Robbins system, accuracy (Grades A and B) ranged from 85% to 100%. Ten studies evaluated radiation exposure during the procedure. In studies that detailed fluoroscopy usage, overall fluoroscopy times ranged from 1.3 to 34 seconds per screw. Nine studies examined the learning curve for the surgeon, and 12 studies described causes of robotic failure, which included registration failure, soft-tissue hindrance, and lateral skiving of the drill guide.

CONCLUSIONS

Robotics in spine surgery is an emerging technology that holds promise for future applications. Surgical accuracy in instrumentation implanted using robotics appears to be high. However, the impact of robotics on radiation exposure is not clear and seems to be dependent on technique and robot type.

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Cheerag D. Upadhyaya, Paul Park, and Frank La Marca

✓ Chyloretroperitoneum is an uncommon complication following spinal surgery. The authors present the case of a patient in whom conservative treatment and initial surgical measures failed to relieve varied symptoms of postsurgical chyloretroperitoneum. Following attempts at conservative management, a peritoneal window was surgically created to divert lymphatic flow from the retroperitoneal space into the peritoneal space, where it was resorbed. This unique surgical technique provides yet another option in the treatment of refractory chyloretroperitoneum following anterior lumbar spinal surgery. The authors describe their technique and review retroperitoneal lymphatic anatomy along with similar case reports in the literature.

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Brandon W. Smith, Jacob R. Joseph, and Paul Park

Heparin-induced thrombocytopenia (HIT) is a state of thrombocytopenia with a paradoxically elevated thrombotic potential after exposure to heparin. Severe cases can present with multiorgan involvement with direct and secondary effects. Although HIT has been reported following other surgeries, to the authors’ knowledge there has not been a report of HIT after spinal surgery. The present case details the course of a patient who underwent elective lumbar surgery followed by delayed presentation of shortness of breath due to multiple pulmonary embolisms and right lower-extremity paralysis due to extensive iliofemoral clot burden with acute compartment syndrome. The patient was treated with intravenous argatroban for extensive thrombosis and also required open thrombectomy and fasciotomies for treatment of compartment syndrome. Although the patient eventually experienced motor recovery, residual sensory deficits persisted at last follow-up. In this report, the pathophysiology, clinical presentation, and treatment of HIT are reviewed.

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Cole Morrissette, Paul J. Park, Meghan Cerpa, and Lawrence G. Lenke

OBJECTIVE

The objective of this study was to examine the relationship between the mental health domain of the refined 22-item Scoliosis Research Society Outcome Questionnaire (SRS) and various postoperative outcome measures in the adult spinal deformity (ASD) population. Given the scale and involved nature of deformity surgery, some surgeons have proposed that preoperative mental health scores (MHSs) may assist in screening out poor surgical candidates. In this study, the authors aimed to further assess the SRS MHS as a preoperative metric and its association with postoperative outcomes and to comment on its potential use in patient selection and optimization for ASD surgery.

METHODS

The authors conducted a retrospective study of 100 consecutive patients who had undergone primary or revision ASD surgery at a single academic institution between 2015 and 2019. Each patient had a minimum 2-year follow-up. Patients were categorized on the basis of their baseline mental health per the SRS mental health domain, with a score < 4 indicating low baseline mental health (LMH) and a score ≥ 4 indicating high baseline mental health (HMH). Baseline and follow-up SRS and Oswestry Disability Index scores, surgical procedures, lengths of stay, discharge locations, intraoperative or postoperative complications, and other outcome metrics were then compared between the HMH and LMH groups, as well as these groups stratified by an age ≤ 45 and > 45 years.

RESULTS

Among patients aged ≤ 45 and those aged > 45, the LMH group had significantly worse baseline health-related quality-of-life (HRQOL) metrics in nearly all domains. The LMH group also had an increased median estimated blood loss (EBL; 1200 vs 800 ml, p = 0.0026) and longer average surgical duration (8.3 ± 2.8 vs 6.9 ± 2.6 hours, p = 0.014). Both LMH and HMH groups had significant improvements in nearly all HRQOL measures postoperatively. Despite their worse preoperative HRQOL baseline, patients in the LMH group actually improved the most and reached the same HRQOL endpoints as those in the HMH group.

CONCLUSIONS

While patients with lower baseline MHSs may require slightly longer hospital courses or more frequent discharges to rehabilitation facilities, these patients actually attain greater absolute improvements from their preoperative baseline and surprisingly have the same postoperative HRQOL metrics as the patients with high MHSs, despite their poorer starting point. This finding suggests that patients with LMH may be uniquely positioned to substantially benefit from surgical intervention and improve their HRQOL scores and thus should be considered for ASD surgery to an extent similar to patients with HMH.

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Paul Park, Juan Uribe, Tokumi Kanemura, and Dean Chou