Etiological Factors of Proximal Junctional Kyphosis and Failure in Adult Spinal Deformity

Thursday, June 1, 2023

8:30 AM – 6:15 PM

Location: Salons 7-8

Co-Author(s)

JM

Jamshaid M. Mir, MD

Research Fellow
NYU Langone Health | NY Spine Institute, United States
TW

Tyler K. Williamson, MS

Medical Student/Clinical Researcher
University of the Incarnate Word SOM
San Antonio, Texas, United States
PT

Peter S. Tretiakov, BS

United States
PD

Pooja R. Dave

Miami, Florida, United States
OK

Oscar Krol

United States
RL

Renaud Lafage, MS

Senior Biomedical engineer
Lenox Hill Hospital
new york, New York, United States
Virginie Lafage, PhD

AVP, Clinical Research
Lenox Hill | Northwell
Hospital for Special Surgery
New York, New York, United States
SV

Shaleen Vira, MD

Assistant Professor, Orthopaedic Surgery & Neurosurgery
UT Southwestern Medical Center
Dallas, Texas, United States
AM

Angel Macagno

United States
TR

Timothy Roberts

Orthopaedic Spine Surgeon
Westbury, New York, United States
MJ

M. Burhan Janjua

United States

Presenting Author (Person doing the Podium Present(s)

PP

Peter G. Passias, M.D.

Spine Surgeon
NYU Langone Orthopedic Hospital
New York, New York, United States

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Submitter(s)

PP

Peter G. Passias, M.D.

Spine Surgeon
NYU Langone Orthopedic Hospital
New York, New York, United States

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Disclosure(s):

Peter G. Passias, MD: No relevant disclosure to display

Background: Proximal junctional kyphosis although mostly asymptomatic, entails a spectrum, with the severe end classified as proximal junctional failure. Despite proximal junctional kyphosis being a well-studied entity, there is a paucity of studies evaluating factors associated by different PJK etiologies.

Objective: To assess realignment differences between acute and chronic development of proximal junctional kyphosis/failure.

Methods: ASD patients with 4 year(4Y) data, fused from at least T1-sacrum were included. Groups based on development of early(before 6M) and late(after 6M) PJK/PJF using published values for PJK and PJF based on Lafage PJF criteria. Sub-analysis of upper instrumented vertebra(UIV) at lower thoracic or upper thoracic regions was conducted. Passias modified frailty index(mFI) and Lafage sagittal age-adjusted score(SAAS) was used. Thoracolumbar inflection point(IP), lumbar lordosis apex(LLA) was assessed. Thoracic decompensation(TD) was defined as >15° change in unfused thoracic vertebrae. ANCOVA and multivariable logistic regression was used, controlling for baseline deformity(PT, PI-LL, SVA), patient and surgical factors.

Results: 683 were included(64±9.5yrs, 77%F, BMI 28.4±5.7kg/m2, CCI 2.0±1.7, mFI 8.2±4.9). 28.8% was matched in SAAS at 6W, 49.5% were overcorrected and 21.5% were overcorrected. 67.5% of the cohort had no PJK or PJF(nPJK), 14.3% had TD, 20.5% had early PJK with no PJF later(PJKe), 11.1% had late PJK (PJKL), 6.3% had early PJF(PJFe), and 10.2% developed PJF late (PJFL). PJFL had higher CCI and lower baseline deformity compared to PJFe(both p< 0.05). No difference in LLA, however IP at BL was 1 level lower at L2 body in PJFe compared to nPJK(p <.05). SAAS overcorrected had the highest rates of PJF (16.3%) and PJK (38.8%), while SAAS matched had lowest rates of PJK (25.9%), PJF (5.1%), and PJFL (6.0%). SAAS undercorrected cohort had lowest rates of PJKe(11.6%) and PJFe(5.8%). 19% of PJFe had implant failure, of which 16% were due to rod fracture. PJFL had 33% implant failure, 20% rod fracture, and 9% implant dislocation. Major rod breakage rates were higher in PJFL(22%) and TD(15%) compared to PJKL(7%, both p<.05). In those with lower thoracic UIV, PJFe had significantly higher SVA compared to PJFL(12.0cm vs 5.9cm, p=0.003). In those that had UIV in the upper thoracic region, SVA was similar in those that developed PJFe and PJFL(9.3cm vs 9.4cm), with PJFe being overcorrected in SVA relative to PJFL. Higher postoperative PT and decreased postoperative PI-LL to be predictive of PJFe and PJFL in those fused to lower thoracic (PT 6W OR: 1.319 [1.193-1.459], p< 0.001, PI-LL 6W OR: 0.761 [0.698-0.831], p< 0.001). Whereas, for those fused to upper thoracic depicted decreased postoperative PT was predictive of PJFe(OR: 0.877 [0.777-0.989], p=0.032).

Conclusions: PJK and PJF have different risk factors for occurrence that also depends on timing of occurrence. Earlier PJF was associated with hardware failure or fracture tend to occur in highly frail overcorrected patients, whereas junctional failure that were mild and early tended to be associated with earlier suboptimal inclination of UIV. Delayed mild PJK were more related to pelvic tilt and suboptimal LDI. Patients who developed proximal junctional failure were more likely to have higher upper instrumented vertebra inclination angles.