Does robot-assisted navigation influence pedicle screw selection and accuracy in minimally invasive spine surgery?

OBJECTIVE: The accuracy of percutaneous pedicle screw placement has increased with the advent of robotic and surgical navigation technologies. However, the effect of robotic intraoperative screw size and trajectory templating remains unclear. The purpose of this study was to compare pedicle screw sizes and accuracy of placement using robotic navigation (RN) versus skin-based intraoperative navigation (ION) alone in minimally invasive lumbar fusion procedures. METHODS: A retrospective cohort study was conducted using a single-institution registry of spine procedures performed over a 4-year period. Patients who underwent 1- or 2-level primary or revision minimally invasive surgery (MIS)-transforaminal lumbar interbody fusion (TLIF) with pedicle screw placement, via either robotic assistance or surgical navigation alone, were included. Demographic, surgical, and radiographic data were collected. Pedicle screw type, quantity, length, diameter, and the presence of endplate breach or facet joint violation were assessed. Statistical analysis using the Student t-test and chi-square test was performed to evaluate the differences in pedicle screw sizes and the accuracy of placement between both groups. RESULTS: Overall, 222 patients were included, of whom 92 underwent RN and 130 underwent ION MIS-TLIF. A total of 403 and 534 pedicle screws were placed with RN and ION, respectively. The mean screw diameters were 7.25 ± 0.81 mm and 6.72 ± 0.49 mm (p < 0.001) for the RN and ION groups, respectively. The mean screw length was 48.4 ± 4.48 mm in the RN group and 45.6 ± 3.46 mm in the ION group (p < 0.001). The rates of "ideal" pedicle screws in the RN and ION groups were comparable at 88.5% and 88.4% (p = 0.969), respectively. The overall screw placement was also similar. The RN cohort had 63.7% screws rated as good and 31.4% as acceptable, while 66.1% of ION-placed screws had good placement and 28.7% had acceptable placement (p = 0.661 and p = 0.595, respectively). There was a significant reduction in high-grade breaches in the RN group (0%, n = 0) compared with the ION group (1.2%, n = 17, p = 0.05). CONCLUSIONS: The results of this study suggest that robotic assistance allows for placement of screws with greater screw diameter and length compared with surgical navigation alone, although with similarly high accuracy. These findings have implied that robotic platforms may allow for safe placement of the "optimal screw," maximizing construct stability and, thus, the ability to obtain a successful fusion.

The structural basis of HLA-associated drug hypersensitivity syndromes.

Recent data suggest alternative mechanisms that promote human leukocyte antigen (HLA)-associated drug syndromes. Hypersensitive responses have been attributed to drug interactions with HLA molecules, peptides presented by HLA molecules and T-cell antigen receptors. Definition of an increasing number of HLA-associated drug syndromes suggests that polymorphism in the antigen-binding cleft residues influence recognition of specific drugs. Recent data demonstrate that small molecule drugs bind within the antigen-binding cleft of HLA in a manner that alters the repertoire of HLA-bound peptide ligands. This drug recognition mechanism permits presentation of self-peptides to which the host has not been tolerized. This altered repertoire mechanism is analogous to massive polyclonal T-cell responses occurring in mismatched HLA organ transplantation in which the drug in effect creates a novel HLA allele. Alteration of the self-peptide repertoire by HLA-binding small molecules may be the mechanistic basis for a diverse set of deleterious T-cell responses since the antigen-binding cleft has structural features that are compatible with binding drug-like small molecules. Small molecule drugs that bind elements of the trimolecular complex (T-cell receptor, peptide, and HLA) may cause short- and long-term adverse effects by a diverse set of mechanisms.

Drug hypersensitivity caused by alteration of the MHC-presented self-peptide repertoire.

Idiosyncratic adverse drug reactions are unpredictable, dose-independent and potentially life threatening; this makes them a major factor contributing to the cost and uncertainty of drug development. Clinical data suggest that many such reactions involve immune mechanisms, and genetic association studies have identified strong linkages between drug hypersensitivity reactions to several drugs and specific HLA alleles. One of the strongest such genetic associations found has been for the antiviral drug abacavir, which causes severe adverse reactions exclusively in patients expressing the HLA molecular variant B*57:01. Abacavir adverse reactions were recently shown to be driven by drug-specific activation of cytokine-producing, cytotoxic CD8(+) T cells that required HLA-B*57:01 molecules for their function; however, the mechanism by which abacavir induces this pathologic T-cell response remains unclear. Here we show that abacavir can bind within the F pocket of the peptide-binding groove of HLA-B*57:01, thereby altering its specificity. This provides an explanation for HLA-linked idiosyncratic adverse drug reactions, namely that drugs can alter the repertoire of self-peptides presented to T cells, thus causing the equivalent of an alloreactive T-cell response. Indeed, we identified specific self-peptides that are presented only in the presence of abacavir and that were recognized by T cells of hypersensitive patients. The assays that we have established can be applied to test additional compounds with suspected HLA-linked hypersensitivities in vitro. Where successful, these assays could speed up the discovery and mechanistic understanding of HLA-linked hypersensitivities, and guide the development of safer drugs.

Preoperative opioids before adult spinal deformity surgery associated with increased reoperations and high rates of chronic postoperative opioid use at 3-year follow-up.

PURPOSE: To determine the association of preoperative opioid prescriptions with reoperations and postoperative opioid prescriptions after adult spina deformity (ASD) surgery. With the current opioid crisis, patients undergoing surgery for ASD are at particular risk for opioid-related complications due to significant preoperative disability and surgical morbidity. No previous studies consider preoperative opioids in this population. METHODS: A retrospective cohort study of patients undergoing posterior spinal fusion (7 or more levels) for ASD was performed. All patients had at least 3 years of postoperative follow-up 3 years postoperatively. Prescriptions for 4 different opioid medications (hydromorphone, oxycodone, hydrocodone, and tramadol) were identified within 3 months preoperatively and up to 3 years postoperatively. Multivariate regression was utilized to determine the association of preoperative use with reoperations and with postoperative opioid use, controlling for both patient and surgery-related confounding factors. RESULTS: A total of 743 patients were identified and 59.6% (443) had opioid prescriptions within 3 months preoperatively. Postoperative opioid prescriptions were identified in 66.9% of patients at 12 months postoperatively, and in 54.8% at 36 months postoperatively. The 3-year reoperation rate was 11.0% in patients without preoperative prescriptions, 16.0% in patients with preoperative any opioid prescriptions (P = 0.07), and 34.8% in patients with preoperative hydromorphone prescriptions (P < 0.01). In multivariate analysis, preoperative opioid prescriptions were associated with increased reoperations (odds ratio [OR]: 1.62, P = 0.04), and chronic postoperative opioid use (OR: 4.40, P < 0.01). Preoperative hydromorphone prescriptions had the strongest association with both reoperations (OR: 4.96; P < 0.01) and chronic use (OR: 5.19: P = 0.03). CONCLUSION: In the ASD population, preoperative opioids are associated with both reoperations and chronic opioid use, with hydromorphone having the strongest association. Further investigation of the benefits of preoperative weaning programs is warranted.

Extra-Axial Fluid Collections After Decompressive Craniectomy: Management, Outcomes, and Treatment Algorithm.

BACKGROUND: Extra-axial fluid collections (EACs) frequently develop after decompressive craniectomy. Management of EACs remains poorly understood, and information on how to predict their clinical course is inadequate. We aimed to better characterize EACs, understand predictors of their resolution, and delineate the best treatment paradigm for patients. METHODS: We reviewed patients who developed EACs after undergoing decompressive craniectomy for treatment of refractory intracranial pressure elevations. We excluded patients who had an ischemic stroke, as EACs in these patients have a different clinical course. We performed univariate analysis and multiple linear regression to find variables associated with earlier resolution of EACs and stratified our analyses by EAC phenotype (complicated vs. uncomplicated). We conducted a systematic review to compare our findings with the literature. RESULTS: Of 96 included patients, 73% were male, and median age was 42.5 years. EACs resolved after a median of 60 days. Complicated EACs were common (62.5%) and required multiple drainage methods before cranioplasty. These were not associated with a protracted course or increased risk of death (P > 0.05). Early bone flap restoration with simultaneous drainage was independently associated with earlier resolution of EACs (ß = 0.56, P < 0.001). Systematic review confirmed lack of standardized direction with respect to EAC management. CONCLUSIONS: Our analyses reveal 2 clinically relevant phenotypes of EAC: complicated and uncomplicated. Our proposed treatment algorithm involves replacing the bone flap as soon as it is safe to do so and draining refractory EACs aggressively. Further studies to assess long-term clinical outcomes of EACs are warranted.

Use of Intraoperative Ultrasound During Spinal Surgery.

STUDY DESIGN: Review and technical report. OBJECTIVE: Intraoperative ultrasound has been used by spine surgeons since the early 1980s. Since that time, more advanced modes of intraoperative imaging and navigation have become widely available. Although the use of ultrasound during spine surgery has fallen out of favor, it remains the only true real-time imaging modality that allows surgeons to visualize soft tissue anatomy instantly and continuously while operating. It is our objective to demonstrate that for this reason, ultrasound is a useful adjunctive technique for spine surgeons, especially when approaching intradural lesions or when addressing pathology in the ventral spinal canal via a posterior approach. METHODS: Using PubMed, the existing literature regarding the use of intraoperative ultrasound during spinal surgery was evaluated. Also, surgical case logs were reviewed to identify spinal operations during which intraoperative ultrasound was used. Illustrative cases were selected and reviewed in detail. RESULTS: This article provides a brief review of the history of intraoperative ultrasound in spine surgery and describes certain surgical scenarios during which this technique might be useful. Several illustrative cases are provided from our own experience. CONCLUSIONS: Surgeons should consider the use of intraoperative ultrasound when approaching intradural lesions or when addressing pathology ventral to the thecal sac via a posterior approach.