Multilevel Stabilization Screws Prevent Proximal Junctional Failure and Kyphosis in Adult Spinal Deformity Surgery: A Comparative Cohort Study

S1 Vertebral Bone Quality Score Independently Predicts Proximal Junctional Kyphosis After Posterior Hemivertebra Resection With Transpedicular Instrumentation

OBJECTIVE

Proximal junctional kyphosis (PJK) is a prevalent postoperative complication after posterior hemivertebra (HV) resection. Previous research has demonstrated a strong correlation between the development of PJK and reduced bone mineral density. The vertebral bone quality (VBQ) score, derived from magnetic resonance imaging, is considered a predictive and evaluative tool for bone mineral density. However, obtaining accurate magnetic resonance imaging signal intensity at the L1-L4 vertebrae is challenging in patients with HV. Consequently, a novel S1 VBQ score has been proposed, which exhibits high accuracy. This study aimed to evaluate the efficacy of S1 VBQ scores in predicting the incidence of PJK in these patients.

METHODS

We conducted a retrospective analysis of patients diagnosed with HV who underwent posterior HV resection with transpedicular instrumentation at our department from 2010 to 2020. Comprehensive demographic and radiographic data were collected. To identify potential preoperative risk factors for the incidence of PJK, we utilized the least absolute shrinkage and selection operator method. Subsequently, a multivariate logistic regression model was constructed to evaluate the risk factors identified through the least absolute shrinkage and selection operator analysis. Cutoff values were determined through receiver operating characteristic analysis to assess the predictive value of the S1 VBQ score for PJK.

RESULTS

A total of 88 patients met the inclusion criteria, with 14 patients (15.9%) developing PJK. Five potential risk factors were selected, including S1 VBQ scores, Risser sign, thoracic kyphosis, pelvic tilt, and proximal junctional angle. The multivariate logistic regression model demonstrated that the S1 VBQ score is an independent risk factor for predicting PJK. The area under the receiver operating characteristic curve (area under the curve) for S1 VBQ scores was 0.770 with an optimal threshold of 2.793 (sensitivity: 78.6%, specificity: 67.6%).

CONCLUSION

A higher S1 VBQ score is an independent risk factor for PJK, with a diagnostic accuracy of 77%. The S1 VBQ threshold of 2.793 was found to be effective in identifying PJK.

LEVEL OF EVIDENCE

Level III.

Tri-cortical Pedicle Screw Fixation in the Most Cranial Instrumented Segment to Prevent Proximal Junctional Kyphosis

BACKGROUND CONTEXT

Proximal junctional kyphosis (PJK) is a common complication of deformity correction for degenerative kyphoscoliosis (DKS) with an incidence between 20% and 40%. Multiple techniques have been proposed to prevent PJK, however, the clinical efficacy of these techniques remains unclear. Here, we investigate the influence of thoracic tri-cortical pedicle screw (TPS) in the most cranial instrumented segment on PJK.

PURPOSE

To evaluate the clinical outcomes and mechanical complications in corrective surgery for DKS at a minimum 2-year follow-up using TPS compared to a control group.

STUDY DESIGN

Retrospective study PATIENT SAMPLE: 115 patients with DKS from January 2020 to April 2022 OUTCOME MEASURE: Patient reported outcome measures included: SRS-22, ODI, VAS scores. Radiographic measures included: Cobb angle, coronal balance distance (CBD), regional kyphosis (RK), and sagittal vertical axis (SVA).

METHODS

Patients were divided into two groups: 67 patients in TPS group and 48 patients who with traditional pedicle screws in the most cranial instrumented segment in control group. The radiographic parameters were measured pre-, post-operative period, and at the last follow-up. Complications, including PJK, proximal junctional failure (PJF), and intercostal neuralgia were recorded. PJK was defined as: 10° or higher increase in kyphosis angle which between the inferior endplate of upper instrumented vertebra (UIV) and the superior endplate of the UIV + 2 (PJA). PJF was defined as: fracture of UIV or UIV + 1, need for proximal extension of fusion, or implant failure of UIV.

RESULTS

There was no significant difference in pre-operative radiographic parameters between two groups. After surgery, the Cobb angle of the major curve improved significantly in both groups (36.7°±20.4° to 15.3°±11.5° in TPS group, 37.1°±16.0° to 16.8°±9.0° in control group, P<0.001). Significant improvements in RK, CBD, and SVA were observed after surgery, and no loss of correction was found during follow-up (P > 0.05). Patients in both groups had significant improvement in health-relative quality of life (HRQoL) scores, including SRS-22, ODI score (46.5±16.2 to 21.3±13.2 in TPS group; 44.7±18.6 to 23.8±16.4 in control group; P < 0.05), and VAS (6.5±2.2 to 2.1±1.6 in TPS group; 6.0±2.9 to 2.3±2.2 in control group; P < 0.05). During the follow-up period, two patients in TPS group developed PJK (3.0%), compared to 13 patients in the control group (27.1%) (P<0.001). Notably, 5 patients in TPS group developed intercostal neuralgia which was not observed in control group, though all had full recovery following conservative treatment during three weeks.

CONCLUSION

TPS fixation technique at the most cranial segment can produce satisfactory clinical outcomes in the surgical correction of DKS with a lower risk of PJK. However, it does incur a higher risk for intercostal neuralgia, likely from nerve root irritation from the screw.

Risk Factors of Proximal Junctional Failure After Adult Spinal Deformity Surgery: A Systematic Review and Meta-Analysis

OBJECTIVE

This study aimed to identify surgical, patient-specific, and radiographic risk factors for proximal junctional failure (PJF), a complex complication following adult spinal deformity (ASD) surgery.

METHODS

A systematic literature search was performed using PubMed, Embase, and the Cochrane Library. The literature on the risk factors for PJF after ASD surgery was included. The study patients were diagnosed with ASD and underwent surgery for ASD. PJF is defined as the occurrence of proximal junctional kyphosis, accompanied by one or more of the following characteristics: a fracture of the vertebral body at the upper instrumented vertebra (UIV) or UIV + 1 level, disruption of the posterior ligaments, or dislodgement of the instrumentation at the UIV. proximal junctional kyphosis, on the other hand, is determined by 2 criteria: a proximal junctional sagittal Cobb angle 1) of 10° and 2) at least 10° greater than the preoperative value.

RESULTS

Our pooled analysis of 11 unique studies (2037 patients) revealed significant differences in several preoperative and postoperative measures between PJF and non-PJF groups.

CONCLUSIONS

In ASD patients, the presence of concurrent osteoporosis or paravertebral muscle wasting significantly increases the risk of developing PJF. The use of bicortical screws, UIV screw angle exceeding 1°, and positioning the UIV in the lower thoracic or lumbar region also further elevate this risk. Lower preoperative SS, higher preoperative PI-LL, higher preoperative pelvic tilt, higher preoperative SVA, higher postoperative LL, and a greater change in LL characterize patients with PJF.

An evidence based conceptual framework for the multifactorial understanding of proximal junctional kyphosis

Introduction

Adult spinal deformity (ASD) is a debilitating pathology that arises from a variety of etiologies. Spinal fusion surgery is the mainstay of treatment for those who do not achieve symptom relief with conservative interventions. Fusion surgery can be complicated by a secondary deformity termed proximal junctional kyphosis (PJK).

Research question

This scoping review evaluates the modern body of literature analyzing risk factors for PJK development and organizes these factors according to a multifactorial framework based on mechanical, tissue or demographic components.

Materials and methods

An extensive search of the literature was performed in PubMed and Embase back to the year 2010. Articles were assessed for quality. All risk factors that were evaluated and those that significantly predicted the development of PJK were compiled. The frequency that a risk factor was predictive compared to the number of times it was evaluated was calculated.

Results

150 articles were reviewed. 57.3% of papers were of low quality. 76% of risk factors analyzed were focusing on the mechanical contribution to development of PJK versus only 5% were focusing on the tissue-based contribution. Risk factors that were most frequently predictive compared to how often they were analyzed were Hounsfield Units of vertebrae, UIV disc degeneration, paraspinal muscle cross sectional area and fatty infiltration, ligament augmentation, instrument characteristics, postoperative hip and lower extremity radiographic metrics, and postoperative teriparatide supplementation.

Discussion and conclusion

This review finds a multifactorial framework accounting for mechanical, patient and tissue-based risk factors will improve the understanding of PJK development.

Preoperative Robotics Planning Facilitates Complex Construct Design in Robot-Assisted Minimally Invasive Adult Spinal Deformity Surgery-A Preliminary Experience

(1) Background: The correction of adult spinal deformity (ASD) can require long, complex constructs with multiple rods which traverse important biomechanical levels to achieve multi-pelvic fixation. Minimally invasive (MIS) placement of these constructs has historically been difficult. Advanced technologies such as spinal robotics platforms can facilitate the design and placement of these constructs and further enable these surgical approaches in MIS deformity surgery. (2) Methods: A retrospective study was performed on a series of ASD patients undergoing MIS deformity correction with ≥eight fusion levels to the lower thoracic spine with preoperative robotic construct planning and robot-assisted pedicle screw placement. (3) Results: There were 12 patients (10 female, mean age 68.6 years) with a diagnosis of either degenerative scoliosis (8 patients) or sagittal imbalance (4 patients). All underwent preoperative robotic planning to assist in MIS robot-assisted percutaneous or transfascial placement of pedicle and iliac screws with multiple-rod constructs. Mean operative values per patient were 9.9 levels instrumented (range 8-11), 3.9 interbody cages (range 2-6), 3.3 iliac fixation points (range 2-4), 3.3 rods (range 2-4), 18.7 screws (range 13-24), estimated blood loss 254 cc (range 150-350 cc), and operative time 347 min (range 242-442 min). All patients showed improvement in radiographic sagittal, and, if applicable, coronal parameters. Mean length of stay was 5.8 days with no ICU admissions. Ten patients ambulated on POD 1 or 2. Of 224 screws placed minimally invasively, four breaches were identified on intraoperative CT and repositioned (three lateral, one medial) for a robot-assisted screw accuracy of 98.2%. (4) Conclusions: Minimally invasive long-segment fixation for adult spinal deformity surgery has historically been considered laborious and technically intensive. Preoperative robotics planning facilitates the design and placement of even complex multi-rod multi-pelvic fixation for MIS deformity surgery.

Proximal Junctional Kyphosis and Failure: Strategies for Prevention

Proximal junctional kyphosis (PJK) and proximal junctional failure/fractures (PJF) are common complications following long-segment posterior instrumented fusions for adult spinal deformity. As progression to PJF involves clinical consequences for patients and requires costly revisions that may undermine the utility of surgery and are ultimately unsustainable for health care systems, preventative strategies to minimize the occurrence of PJF are of tremendous importance. In this article, the authors present a detailed outline of PJK and PJF with a focus on surgical strategies aimed at preventing their occurrence..