Novel Index to Quantify the Risk of Surgery in the Setting of Adult Spinal Deformity: A Study on 10,912 Patients From the Nationwide Inpatient Sample

Preoperative Optimization: Risk Factors for Perioperative Complications and Preoperative Modification

Adult spinal deformity (ASD) is common and the complication rate in ASD surgery is high due to its invasiveness. There are several factors that increase the risk of complications with ASD surgery. These include age, past medical history, frailty, osteoporosis, or operative invasiveness. Risk factors for perioperative complications can be categorized as modifiable and non-modifiable. The purpose of this article is to present the current available evidence on risk factors for perioperative complications, with a focus on frailty, osteoporosis, surgical site infection prevention, and hip-spine syndrome. In addition, we present the latest evidence for patient-specific surgical risk assessment and surgical planning.

Factors Associated With Short Length of Stay After Long Fusions for Adult Spinal Deformity: Initial Steps Toward Developing an Enhanced Recovery Pathway

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

The identification of case types and institutional factors associated with reduced length of stay (LOS) is a key initial step to inform the creation of clinical care pathways that can assist hospitals to maximize the benefit of value-based payment models. The objective of this study was to identify preoperative, intraoperative, and postoperative factors associated with shorter than expected LOS after adult spinal deformity (ASD) surgery.

METHODS

A retrospective cohort study was performed of 82 patients with ASD who underwent ≥5 levels of fusion to the pelvis between 2013 and 2018. A LOS <6 days was determined as a basis for comparison, as 5.7 days was the "expected LOS" generated through Poisson regression modeling of the sample. Clinical, radiographic, surgical, and postoperative factors were compared between those staying ≥6 days (L group) and <6 days (S group). Logistic regression was used to identify factors associated with LOS <6 days.

RESULTS

A total of 35 patients were in group S (42.7%). Gender, age, body mass index, ASA (American Society of Anesthesiologists) class, and use of preoperative narcotics, revision surgery, day of admission, and surgical complications did not vary between the cohorts (P > .05). Mild-moderate preoperative sagittal deformity (sagittal Schwab modifiers 0 or +), lower estimated blood loss (<1200 mL), fewer levels fused (7 vs 10 levels), shorter operating room time, procedure end time before 15:00, and no intensive care unit stay, were associated with short LOS (P < .05). Only 1 major medical complication occurred in the short LOS group (P < .05).

CONCLUSIONS

This study identifies the ASD "case phenotype," intra-, and postoperative benchmarks associated with shorter LOS, providing targets for pathways designed to reduce LOS.

Biomechanical comparison of semirigid junctional fixation techniques to prevent proximal junctional failure after thoracolumbar adult spinal deformity correction

BACKGROUND CONTEXT

Adult spinal deformity patients treated operatively by long-segment instrumented spinal fusion are prone to develop proximal junctional kyphosis (PJK) and failure (PJF). A gradual transition in range of motion (ROM) at the proximal end of spinal instrumentation may reduce the incidence of PJK and PJF, however, previously evaluated techniques have not directly been compared.

PURPOSE

To determine the biomechanical characteristics of five different posterior spinal instrumentation techniques to achieve semirigid junctional fixation, or "topping-off," between the rigid pedicle screw fixation (PSF) and the proximal uninstrumented spine.

STUDY DESIGN

Biomechanical cadaveric study.

METHODS

Seven fresh-frozen human cadaveric spine segments (T8-L3) were subjected to ex vivo pure moment loading in flexion-extension, lateral bending and axial rotation up to 5 Nm. The native condition, three-level PSF (T11-L2), PSF with supplemental transverse process hooks at T10 (TPH), and two sublaminar taping techniques (knotted and clamped) as one- (T10) or two-level (T9, T10) semirigid junctional fixation techniques were compared. The ROM and neutral zone (NZ) of the segments were normalized to the native condition. The linearity of the transition zones over three or four segments was determined through linear regression analysis.

RESULTS

All techniques achieved a significantly reduced ROM at T10-T11 in flexion-extension and axial rotation relative to the PSF condition. Additionally, both two-level sublaminar taping techniques (CT2, KT2) had a significantly reduced ROM at T9-T10. One-level clamped sublaminar tape (CT1) had a significantly lower ROM and NZ compared with one-level knotted sublaminar tape (KT1) at T10-T11. Linear regression analysis showed the highest linear correlation between ROM and vertebral level for TPH and the lowest linear correlation for CT2.

CONCLUSIONS

All studied semirigid junctional fixation techniques significantly reduced the ROM at the junctional levels and thus provide a more gradual transition than pedicle screws. TPH achieves the most linear transition over three vertebrae, whereas KT2 achieves that over four vertebrae. In contrast, CT2 effectively is a one-level semirigid junctional fixation technique with a shift in the upper rigid fixation level. Clamped sublaminar tape reduces the NZ greatly, whereas knotted sublaminar tape and TPH maintain a more physiologic NZ. Clinical validation is ultimately required to translate the biomechanics of various semirigid junctional fixation techniques into the clinical goal of reducing the incidence of proximal junctional kyphosis and failure.

CLINICAL SIGNIFICANCE

The direct biomechanical comparison of multiple instrumentation techniques that aim to reduce the incidence of PJK after thoracolumbar spinal fusion surgery provides a basis upon which clinical studies could be designed. Furthermore, the data provided in this study can be used to further analyze the biomechanical effects of the studied techniques using finite element models to better predict their post-operative effectiveness.

Instrumentation techniques to prevent proximal junctional kyphosis and proximal junctional failure in adult spinal deformity correction-a systematic review of biomechanical studies

BACKGROUND CONTEXT

Correction of adult spinal deformity (ASD) by long segment instrumented spinal fusion is an increasingly common surgical intervention. However, it is associated with high rates of complications and revision surgery, especially in the elderly patient population. The high construct stiffness of instrumented thoracolumbar spinal fusion has been postulated to lead to a higher incidence of proximal junctional kyphosis (PJK) and failure (PJF). Several cadaveric biomechanical studies have reported on surgical techniques to reduce the incidence of PJF/PJK. As yet, no overview has been made of these biomechanical studies.

PURPOSE

To summarize the evidence of all biomechanical studies that have assessed techniques to reduce PJK/PJF following long segment instrumented spinal fusion in the ASD patient population.

STUDY DESIGN

A systematic review.

METHODS

EMBASE and MEDLINE databases were searched for human and animal cadaveric biomechanical studies investigating the effect of various surgical techniques to reduce PJK/PJF following long segment instrumented thoracolumbar spinal fusion in the adult patient population. Studied techniques, biomechanical test methods, range of motion (ROM), intervertebral disc pressure (IDP) and other relevant outcome parameters were documented.

RESULTS

Twelve studies met the inclusion criteria. Four of these studies included non-human cadaveric material. One study investigated the prophylactic application of cement augmentation (vertebroplasty), whereas the remaining studies investigated semi-rigid junctional fixation techniques to achieve a gradual transition zone of forces at the proximal end of a fusion construct, so-called topping-off. An increased gradual transition zone in terms of ROM compared to pedicle screw constructs was demonstrated for sublaminar tethers, sublaminar tape, pretensioned suture loops, transverse hooks and laminar hooks. Furthermore, reduced IDP was found after the application of sublaminar tethers, suture loops, sublaminar tapes and laminar hooks. Finally, two-level prophylactic vertebroplasty resulted in a lower incidence of vertebral compression fractures in a flexion-compression experiment.

CONCLUSIONS

A variety of techniques, involving either posterior semi-rigid junctional fixation or the reinforcement of vertebral bodies, has been biomechanically assessed. However, the low number of studies and variation in study protocols hampers direct comparison of different techniques. Furthermore, determination of what constitutes an optimal gradual transition zone and its translation to clinical practice, would aid comparison and further development of different semi-rigid junctional fixation techniques. Even though biomechanics are extremely important in the development of PJK/PJF, patient-specific factors should always be taken into account on a case-by-case basis when considering to apply a semi-rigid junctional fixation technique.

The radiographic, pulmonary, and clinical outcomes of patients with severe rigid spinal deformities treated via halo-pelvic traction

Background

The severe rigid deformity patients with pulmonary dysfunction could not tolerate complicated corrective surgery. Preoperative traction are used to reduce the curve magnitude and improve the pulmonary function before surgery, including halo-gravity traction (HGT) and halo-pelvic traction (HPT). The present study aimed to retrospectively compare the radiographic, pulmonary and clinical outcomes of preoperative HGT and HPT in severe rigid spinal deformity with respiratory dysfunction.

Methods

81 cases of severe rigid kyphoscoliosis treated with preoperative traction prior to corrective surgery for spinal deformity between 2016 and 2019 were retrospectively reviewed. Two patient groups were compared, HPT group (N = 30) and HGT group (N = 51). Patient demographics, coronal and sagittal Cobb angles and correction rates, pulmonary function, traction time, osteotomy grade, and postoperative neurological complications were recorded for all cases.

Results

The coronal Cobb angle was corrected from 140.67 ± 2.63 to a mean of 120.17 ± 2.93° in the HGT group, and from 132.32 ± 4.96 to 87.59 ± 3.01° in the HPT group (mean corrections 15.33 ± 1.53 vs. 34.86 ± 3.11 %) (P = 0.001). The mean major sagittal curve decreased from 134.28 ± 3.77 to 113.03 ± 4.57° in the HGT group and from 129.60 ± 8.45 to 65.61 ± 7.86° in the HPT group (P < 0.001); the mean percentage corrections were 16.50 ± 2.13 and 44.09 ± 9.78 % (P < 0.001). A significant difference in the pulmonary function test results was apparent between the two groups; the mean improvements in the FVC% of the HGT and HPT groups were 6.76 ± 1.85 and 15.6 ± 3.47 % (P = 0.024). The HPT group tended to exhibit more FEV% improvement than the HGT group, but the difference was not significant (5.15 ± 2.27 vs. 11.76 ± 2.22 %, P = 0.91).

Conclusions

Patients with severe rigid kyphoscoliosis who underwent preoperative HPT exhibited better radiographic correction of the deformity, and pulmonary function, and required fewer osteotomies compared to the HGT group. Thus, HPT may be useful for severe rigid spinal deformity patients with pulmonary dysfunction.