Can patient-specific precontoured rod instrumentation reduce the rate of proximal junctional kyphosis for adult spinal deformity? A propensity score-matched analysis.

Abstract

Objective: The objective of this study was to determine whether patient-specific precontoured rod (PCR) instrumentation is associated with lower rates of proximal junctional kyphosis (PJK) compared with manually contoured conventional rods (CRs) in adult spinal deformity (ASD) surgery.

Methods: The data of ASD patients (age ≥ 18 years) undergoing posterior spinal instrumentation and fusion of a minimum of 5 levels were consecutively reviewed from 2016 to 2021. A propensity score-matching algorithm was used to match patients undergoing instrumentation with PCRs (n = 80) to those treated with CRs (n = 210). The primary outcome was the rate of radiographic PJK at a minimum follow-up of 1 year. PJK was defined by two criteria: a postoperative proximal junctional sagittal angle (PJA) 1) ≥ 10° and 2) at least 10° greater than the preoperative measurement.

Results: Following propensity score matching, 160 patients were included in the study (80 per group). Patients demonstrated similar preoperative baseline characteristics and preoperative radiographic alignment. Preoperatively, the mean PJAs measured 9.24° ± 6.8° and 8.8° ± 7.3° for the PCR and CR groups, respectively (p = 0.751). At the most recent follow-up, the PCR and CR groups demonstrated mean PJAs of 11.6° ± 9.1° and 10.8° ± 8.3°, respectively (p = 0.545). Ten (12.5%) patients experienced PJK in the PCR group compared to 16 (20%) patients in the CR group (p = 0.199). In patients with upper instrumented vertebrae in the lower thoracic region, 5 (11.1%) patients in the PCR group experienced PJK versus 12 (26.7%) patients in the CR group (p = 0.059). Furthermore, 7 (10.9%) patients in the PCR group experienced PJK compared to 14 (21.5%) patients in the CR group after including patients with fusion to the sacrum/pelvis (p = 0.103).

Conclusions: Lower rates of PJK were observed in the PCR group when compared to the CR cohort. However, this relationship was not statistically significant. Future studies with longer-term follow-up and larger sample sizes are warranted to investigate the relationship between PCR instrumentation and PJK prophylaxis. While PCR technology alone is likely not a definitive solution for preventing PJK, its strength lies in enabling rigorous preoperative planning and thoughtful deformity correction strategies. When integrated into a comprehensive approach to patient optimization, alignment, and junctional control, PCRs may serve as a useful adjunct in mitigating PJK risk.