近位癒合部後弯症および近位癒合部不全の異なるメカニズムとその臨床的意義

Retrospective cohort study.

In patients undergoing adult spinal deformity (ASD) surgery, we sought to: (1) describe mechanisms of Proximal junctional kyphosis/failure (PJK/F), and (2) compare time-to-diagnosis, proximal junctional angle (PJA), reoperation, and neurologic deficit between PJK/F mechanisms.

PJK/F includes several different failure mechanisms.

ASD patients (2009-21) with ≥5-level fusion, sagittal/coronal deformity, and 2-year follow-up were included. Primary outcome was mechanism of PJK/F, defined as a PJA≥10° and ≥10° change from preoperative. PJK/F mechanisms were: screw pullout, UIV fracture, UIV+1 fracture, screw lucency, fracture dislocation, supradjacent disc-degeneration with/without listhesis, and radiographic kyphosis only. Descriptive and bivariate statistics were performed.

Among 238 patients, 113(47.5%) developed PJK/F: screw pullout (7.1%), UIV fracture (15.0%), UIV+1 fracture (8.0%), screw lucency (12.4%), fracture dislocation (11.5%), supradjacent disc-degeneration with/without listhesis (31.0%), and radiographic kyphosis only (15.0%). One mechanism was seen in 91(80.5%) patients, and 2+ mechanisms in 22(19.5%). Median time-to-PJK/F diagnosis was 5.3 (IQR: 1.4-17.7) months: screw pullout (8.3m, PJA=19.9°), UIV fracture (3.8m, 25.6°), UIV+1 fracture (11.8m, 28.0°), screw lucency (12.8m, 19.0°), fracture dislocation (1.6m, 27.9°), disc-degeneration (4.5m, 25.6°), and radiographic kyphosis only (6.1m, 19.5°) (P=0.986, P<0.001). Reoperation occurred in 45(39.8%) patients: 6/8(75.0%) screw pullout, 6/17(35.2%) UIV fracture, 4/9(44.4%) UIV+1 fracture, 9/14(64.3%) screw lucency, 6/13(46.1%) fracture dislocation, 9/35(25.2%) disc-degeneration, and 5/17(29.4%) radiographic kyphosis only (P=0.068). Neurologic Deficits occurred in 15(13.3%) patients: UIV fracture 3(17.6%), UIV+1 fracture 2(22.2%), screw lucency 5(35.7%), fracture dislocation 2(15.4%), disc-degeneration 2(5.7%), kyphosis only 1(5.9%) (P=0.093).

Supradjacent disc-degeneration was the most common PJK mechanism. Fracture dislocation presented earliest and with greatest kyphosis. Reoperation was most frequent with screw pullout, lucency, and UIV+1 fracture, while neurologic deficits were most common with lucency and UIV+1 fracture. These results demonstrate that PJK/F occurs in many different forms and ideally should be analyzed independently to further improve our treatment of this vexing complication.