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

Abstract

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.