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

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. 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. 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). 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. 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. 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.