222 - The incidence of Proximal Junctional Kyphosis (PJK) in Patients Underg...

General Session: MIS-4

Presented by: N. Anand - View Audio/Video Presentation (Members Only)


N. Anand(1), J. Cohen(1), R. Cohen(1), B. Khandehroo(1), E. Baron(1), S. Kahwaty(1)

(1) Cedars-Sinai Medical Center, Spine Center, Los Angeles, CA, United States


Introduction: Proximal junctional kyphosis (PJK) is a common complication following traditional ASD surgery but has not been well studied in cMIS patients. The clinical significance of PJK has been debated extensively in the literature. Moreover, there is no consensus on the diagnostic criteria for this radiologic phenomenon. The purpose of this study was to assess the incidence of PJK and subsequent clinical outcomes following cMIS correction of ASD.

Methods: A prospectively collected registry at a single center of all patients who had undergone cMIS correction of ASD was queried. Patients with 4 or more levels fused were included for this study. 131 patients were identified including 40 male and 91 female. Deformities included Degenerative Scoliosis (35), Idiopathic Scoliosis (81), Iatrogenic Scoliosis (7), and Kyphosis (7). Baseline radiographic measurements were analyzed on preoperative or immediate postoperative lateral standing 36” X-ray films. These were compared with final follow-up Xrays. PJK was defined as an angle greater than 10o and at least 10o greater than the baseline measurement when measured between the lower endplate of the uppermost instrumented vertebra (UIV) and the upper endplate of two vertebra supra-adjacent (UIV + 2),

Results: Mean follow-up was 53 months (range: 12-101 months). Mean age was 62.9 years (21-85). Mean operated levels were 7 levels (4-16 levels). PJK was identified in 15 of the 131(11.4%) patients. However, only 9 were symptomatic (6.9%) with 6 patients asymptomatic at the last follow-up. Of the 9 symptomatic patients, 7 underwent revision surgery including kyphoplasty and extended posterior instrumentation and the other 2 patients were managed conservatively with possible revision surgery in the near future. The average time to detect PJK was 16.6 months (1-47, SD 17.6). The UIV of the 15 patients with PJK were as follows: 2 lumbar (L1-L2), 4 thoracolumbar junction (T12-L1), 7 lower thoracic (T9-11) and 2 upper thoracic (T2-T4). In patients with PJK, average post-operative SVA was 29.6mm (4.8-98.4, SD 24) and PI/LL mismatch was 10.7o(0.5-28, SD 8.9). In patients without PJK, average post-operative SVA was 35.8mm(0-91.7, SD 26.6) and PI/LL mismatch was 12.5o (0-41.2, SD 9). In comparing PJK patients to non PJK patients, average delta change in SVA was 31.5mm(0.8-96.9) compared to 31.2mm(0-110) (p =.23) respectively and average delta PI/LL mismatch was 11.2o (0.8-49.1) compared to 6.5o (0.5-42.4)(p=.071) respectively. Furthermore, patients with PJK had a higher proportion of females (p< .05).

Conclusion: Our 11.4% PJK rate is lower then values reported in the literature for PJK following open surgery for ASD. This may suggest that cMIS correction of ASD may reduce the incidence of PJK. In comparing patients with PJK to non-PJK patients, we could show no difference in the final SVA, delta change in SVA, final PI/LL mismatch or delta change in PI/LL mismatch. Further investigation is needed to determine whether overcorrection may be a predisposing factor to developing PJK.