Analysis of lumbar interbody cage′s length based on anatomic measurement

English Keywords:Lumbar vertebrae  Tomography  X-ray computed  Interbody cage

English Abstract:

  【Abstract】 Objectives: To measure the anatomic parameters of Chinese lumbosacral vertebral endplates(L1-S1), and to explore its significance in the selection of interbody cage′s length used in transforaminal lumbar interbody fusion(TLIF) and posterior lumbar interbody fusion(PLIF). Methods: CT scan and reconstructions of lumbar and sacrum were obtained in 24 healthy adult volunteers. Mid-oblique diameter, max-oblique diameter, max-oblique angle, lat-sagittal diameter and width of apophyseal ring of L1 inferior endplate to S1 superior endplate were measured. Within the same gender and segment, mid-oblique diameter, max-oblique diameter, max-oblique angle and lat-sagittal diameter of the inferior and superior endplates were compared, and the length of the fusion under the different operation methods was calculated. Results: The maximum and minimum mid-oblique diameters were 39.58±2.60mm and 33.38±3.26mm in male, which were 34.89±1.55mm and 30.93±2.99mm in female, the width of apophyseal ring for which was within the range of 6-8mm. The maximum and minimum max-oblique diameters were 48.05±4.62mm and 42.83±2.28mm in male, which were 43.26±3.31mm and 38.00±2.53mm in female, which increased from L1 to S1. The maximum and minimum lat-sagittal diameters were 36.48±3.26mm and 32.11±2.50mm in male, which were 31.75±1.64mm and 28.36±2.32mm in female, the width of apophyseal ring for which was within the range of 5.5－7.5mm. Most of the differences between anatomic parameters of inferior and superior endplates in the same segment(L2－L5) was insignificant except for L1/2 and L5/S1. In L5/S1, there was no significant difference only in lat-oblique diameter(male: P=0.0522, female: P=0.6410). When TLIF was used, the lenght of interbody cage for L1-L4 should be no less than 31mm in male and 27mm in female. As for L4/5, it should be within the range of 30-38mm in male and 26-34mm in female. The range of length was more extensive for L5/S1, with 25-38mm in male and 23-33mm in female. When the cage was inserted, the insertion angle should be closed to max-oblique angle. When PLIF was used, the length of interbody cage for L1-L5 ranged from 28 to 30mm in male and 24 to 26mm in female. As for L5/S1, 26mm in male and 22mm in female were good choices. Conclusions: CT measurement provides the choice of lumbar interbody cage′s length with objective evidences. A preliminary estimation of the length can be made based on the oblique diameter, the lat-sagittal diameter and the width of apophyseal ring.