A New Morphologic Classification of Proximal Junctional Kyphosis Following Lower Thoracic to Pelvis Fusion in Adult Spinal Deformity Predicts Revision Surgery and Neurologic Complications
Spine Surgery Fellow The Johns Hopkins Hospital Johns Hopkins
Disclosure(s):
Micheal Raad, MD: No financial relationships to disclose
Introduction: PJK is one of the most common complications after surgery for adult spinal deformity (ASD). There has been interest in better understanding the development of PJK in ASD. However, most studies are limited by heterogenous surgeries and short term follow up. Therefore, the goals of our study are to investigate a new morphologic classification system for PJK following lower thoracic to pelvis fusion.
Methods: Adult patients who underwent T9-L1 fusion to the pelvis for ASD with minimum 1-year follow-up were included. PJK was defined as 10° change in the angle of the upper instrumented vertebra (UIV) to UIV+2 from preoperative radiographs. A new system was used to classify patients into 1A (equivalent distribution of kyphosis through segments), 1B (>2/3 of kyphosis comes from one segment), 2A (fracture and loss of >20% of anterior body height at the UIV) and 2B (fracture and loss of >20% of anterior body height at the UIV+1).
Results: A total of 69 patients were analyzed, 69.6% (48/69) were women with overall mean age of 63.8 years and follow-up of 3.7 years. PJK occurred in 52.2% (36/69) of patients, with 15.9% (11/69) requiring revision for PJK within the study period. Average time to develop PJK was 17 months. The most common PJK type was 1A (38.9%), then 1B (25.0%), 2B (19.4%) and 2A (16.7%). Neurologic deficits were highest in the 2B group (71.4%), followed by 2A (16.7%) and 1B (11.1%) (p=0.001). Revision for PJK was highest in the 2B group (71.4%), followed by 2A (50.0%), 1B (33.3%), and 1A (0.0%) (p < 0.01). Type 2A PJK occurred 100% of the time within 90 days of surgery, 1B (44%), 1A (29%) and 2B (29%) (p=0.02). The highest PJK progression occurred in Type 2B (17.4°), followed by 1A (7.7°), 1B (7.2°) and 2A (5.6°) (p=0.003).
Conclusion : The proposed PJK classification utilizes 4 discrete groups based on morphology. The classification system is associated with risk of revision, neurologic deficits, timing of PJK development and exhibited varying patterns of progression.