Risk factors for adjacent segment pathology requiring additional surgery after single-level spinal fusion: impact of pre-existing spinal stenosis demonstrated by preoperative myelography.
We determined the incidence of and risk factors for clinical adjacent segment pathology (C-ASP) requiring additional surgeries among patients previously treated with one-segment lumbar decompression and fusion surgery.



We retrospectively analysed 161 consecutive patients who underwent one-segment lumbar decompression and fusion surgery for L4 degenerative spondylolisthesis. Patient age, sex, body mass index (BMI), facet orientation and tropism, laminar inclination angle, spinal canal stenosis ratio [on myelography and magnetic resonance imaging (MRI)], preoperative adjacent segment instability, arthrodesis type, pseudarthrosis, segmental lordosis at L4-5, and the present L4 slip were evaluated by a log-rank test using the Kaplan-Meier method. A multivariate Cox proportional-hazards model was used to analyse all factors found significant by the log-rank test.



Of 161 patients, 22 patients (13.7 %) had additional surgeries at cranial segments located adjacent to the index surgery's location. Pre-existing canal stenosis ≥47 % at the adjacent segment on myelography, greater facet tropism, and high BMI were significant risk factors for C-ASP. The estimated incidences at 10 years postoperatively for each of these factors were 51.3, 39.6, and 32.5 %, and the risks for C-ASP were 4.9, 3.7, and, 3.1 times higher than their counterparts, respectively. Notably, spinal canal stenosis on myelography, but not on MRI, was found to be a significant risk factor for C-ASP (log-rank test P < 0.0001 and 0.299, respectively).



Pre-existing spinal stenosis, greater facet tropism, and higher BMI significantly increased C-ASP risk. Myelography is a more accurate method for detecting latent spinal canal stenosis as a risk factor for C-ASP.
Department of Orthopaedic Surgery, Japan Labour Health and Welfare Organization Spinal Injuries Center, 550-4 Igisu, Iizuka, Fukuoka, Japan. iyugue@orange.ocn.ne.jp.
Itaru
I
Yugué
Department of Orthopaedic Surgery, Kyushu University, Fukuoka, Japan.
Seiji
S
Okada
Department of Orthopaedic Surgery, Japan Labour Health and Welfare Organization Spinal Injuries Center, 550-4 Igisu, Iizuka, Fukuoka, Japan.
Muneaki
M
Masuda
Department of Orthopaedic Surgery, Japan Labour Health and Welfare Organization Spinal Injuries Center, 550-4 Igisu, Iizuka, Fukuoka, Japan.
Takayoshi
T
Ueta
Department of Orthopaedic Surgery, Japan Labour Health and Welfare Organization Spinal Injuries Center, 550-4 Igisu, Iizuka, Fukuoka, Japan.
Takeshi
T
Maeda
Department of Orthopaedic Surgery, Japan Labour Health and Welfare Organization Spinal Injuries Center, 550-4 Igisu, Iizuka, Fukuoka, Japan.
Keiichiro
K
Shiba
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D019299:Decompression, Surgical; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009192:Myelography; D057234:Preoperative Period; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D013123:Spinal Fusion; D013130:Spinal Stenosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D013168:Spondylolisthesis / Q000601:surgery*
Adjacent segment pathology; Body mass index; Degenerative spondylolisthesis; Facet tropism; Pre-existing spinal stenosis