Uncorrected sagittal plane imbalance predisposes to symptomatic instrumentation failure.
BACKGROUND
Elucidation of the factors responsible for symptomatic failure of spinal instrumentation has been a keen interest for many investigators.


OBJECTIVE
To quantitate the number of symptomatic instrumentation failures (SIFs) encountered during a 2-year period. The effect of sagittal plane imbalance (corrected or uncorrected) on the rate of SIF was evaluated.


METHODS
Retrospective evaluation of all patients requiring spinal instrumentation to determine which factors predispose toward instrumentation failure.


METHODS
All patients requiring spinal instrumentation over a 2-year period were retrospectively studied.


METHODS
Sagittal plane imbalance pre- and postoperatively was determined using Cobb angle analysis on plain X-rays. SIF was defined as screw back-out and/or breakage, pseudarthrosis, cage migration, or rod disconnection in patients with concordant symptoms. Asymptomatic patients did not demonstrate instrumentation failure on the routine postoperative X-rays.


METHODS
Of the 355 patients who fit the criteria, 47 patients presented with either idiopathic or secondary sagittal plane deformity preoperatively. Additionally, long-segment fixation, smoking, age, and fixation across junctional segments were evaluated as risk factors for SIF.


RESULTS
Of the 47 patients with sagittal plane deformity, 40 patients (85%) achieved correction demonstrated on postoperative radiographs whereas in 7 (15%), the sagittal plane imbalance was not corrected. Of these seven cases, five suffered instrumentation failure (failure rate 71.5%) versus no instrumentation failures (failure rate 0%) for the remaining 40 patients. SIF was demonstrated in 10 patients overall (failure rate of 2.8%). There was no correlation found between factors such as age, indications for surgery, or long-segment fixation, and instrumentation failure.


CONCLUSIONS
Failure to correct sagittal plane deformity intraoperatively predisposes patients to SIF regardless of age, level of surgery, or indication of surgery.
Gilad
Ronit
R
Department of Neurosurgery, Mount Sinai School of Medicine, New York, NY 10029, USA. Ronit.Gilad@mssm.edu
Gandhi
Chirag D
CD
Arginteanu
Marc S
MS
Moore
Frank M
FM
Steinberger
Alfred
A
Camins
Martin
M
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging / Q000453:epidemiology; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000601:surgery*; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000453:epidemiology*; D011475:Prosthesis Failure; D011542:Pseudarthrosis / Q000000981:diagnostic imaging / Q000453:epidemiology; D011859:Radiography; D012189:Retrospective Studies; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology; D013122:Spinal Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000601:surgery*; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation / Q000706:statistics & numerical data; D055815:Young Adult