Amer Sebaaly1, Rami El Rachkidi2, Pierre Grobost3, Marion Burnier3, Hubert Labelle4, Pierre Roussouly3. 1. Department of Orthopedic Surgery, Clinique médico-chirurgicale des Massues, 92 Rue Edmond Locard, 69005 Lyon, France; Faculty of Medicine, Saint Joseph University, Damascus Rd, 1107 2180, Beirut, Lebanon. Electronic address: amersebaaly@hotmail.com. 2. Faculty of Medicine, Saint Joseph University, Damascus Rd, 1107 2180, Beirut, Lebanon; Department of Orthopedic Surgery, Hotel Dieu de France, Alfred Naccache St, 166830, Achrafieh, Beirut, Lebanon. 3. Department of Orthopedic Surgery, Clinique médico-chirurgicale des Massues, 92 Rue Edmond Locard, 69005 Lyon, France. 4. Sainte-Justine University Hospital Center, 3175 Chemin de la Côte-Sainte-Catherine, Montréal, QC H3T 1C5, Canada.
Abstract
BACKGROUND: In high-grade spondylolisthesis (HGSPL), the pelvic incidence (PI) is not a reliable measurement because of doming of the sacrum. Measurement of L5 incidence (L5I) was described as a tool to measure pelvic morphology in HGSPL and for surgical follow-up. OBJECTIVE: We aimed to evaluate L5I in HGSPL and its relationship to other spinopelvic parameters. STUDY DESIGN: A retrospective study of a cohort of 184 patients with HGSPL was carried out. METHODS: Whole spine radiographs were analyzed for PI, pelvic tilt (PT), sacral slope, lumbar lordosis (LL), L5I, L5 tilt (L5T), L5 slope, lumbosacral kyphosis, and slip percentage. Statistical analysis and correlation were made (Pearson correlation test; p<.05). In accordance to Cohen, statically significant correlation were considered strong if R>0.5, moderate if 0.3<R<0.5, and small if R<0.3. RESULTS: A total of 184 cases were analyzed, with a female-to-male ratio of 2.35 and a mean age of 20.1 years. Sacral doming was present in 73% of the cases. Mean L5I incidence was 65.2° and strongly correlated to other sagittal parameters, especially PT (R=0.7), LL (R=0.7), L5T (R=0.77), and L5 slope (R=0.83). There was less but still strong correlation to Dubousset lumbosacral kyphosis (Dub-LSK) angle (R=-0.63) and percentage of slippage (R=0.56). L5 tilt showed nearly perfect correlation to PT (R=0.95). Forty-four percent of the cases were balanced HGSPL, whereas 56% of the cases were unbalanced HGSPL. L5 incidence was found to be a good predictor of local imbalance with a cutoff of L5I=61. CONCLUSION: This paper describes L5I, which is a positional parameter in HGSPL. L5 incidence is a simple and reliable measure in the preoperative setting in HGSPL. Its correlation with spinal sagittal parameters (especially PT and LL) is strong and was found to be better than Dub-LSK. There is also a good correlation between L5I and HGSPL pelvic parameters (slip percentage and lumbosacral kyphosis). We recommend its use for evaluation of surgical correction and recommend the value of 60° as cutoff value to define spinopelvic balance in HGSPL.
BACKGROUND: In high-grade spondylolisthesis (HGSPL), the pelvic incidence (PI) is not a reliable measurement because of doming of the sacrum. Measurement of L5 incidence (L5I) was described as a tool to measure pelvic morphology in HGSPL and for surgical follow-up. OBJECTIVE: We aimed to evaluate L5I in HGSPL and its relationship to other spinopelvic parameters. STUDY DESIGN: A retrospective study of a cohort of 184 patients with HGSPL was carried out. METHODS: Whole spine radiographs were analyzed for PI, pelvic tilt (PT), sacral slope, lumbar lordosis (LL), L5I, L5 tilt (L5T), L5 slope, lumbosacral kyphosis, and slip percentage. Statistical analysis and correlation were made (Pearson correlation test; p<.05). In accordance to Cohen, statically significant correlation were considered strong if R>0.5, moderate if 0.3<R<0.5, and small if R<0.3. RESULTS: A total of 184 cases were analyzed, with a female-to-male ratio of 2.35 and a mean age of 20.1 years. Sacral doming was present in 73% of the cases. Mean L5I incidence was 65.2° and strongly correlated to other sagittal parameters, especially PT (R=0.7), LL (R=0.7), L5T (R=0.77), and L5 slope (R=0.83). There was less but still strong correlation to Dubousset lumbosacral kyphosis (Dub-LSK) angle (R=-0.63) and percentage of slippage (R=0.56). L5 tilt showed nearly perfect correlation to PT (R=0.95). Forty-four percent of the cases were balanced HGSPL, whereas 56% of the cases were unbalanced HGSPL. L5 incidence was found to be a good predictor of local imbalance with a cutoff of L5I=61. CONCLUSION: This paper describes L5I, which is a positional parameter in HGSPL. L5 incidence is a simple and reliable measure in the preoperative setting in HGSPL. Its correlation with spinal sagittal parameters (especially PT and LL) is strong and was found to be better than Dub-LSK. There is also a good correlation between L5I and HGSPL pelvic parameters (slip percentage and lumbosacral kyphosis). We recommend its use for evaluation of surgical correction and recommend the value of 60° as cutoff value to define spinopelvic balance in HGSPL.