Biomorphometric analysis of ilio‐sacro‐iliacal corridors for an intra‐osseous implant to fix posterior pelvic ring fractures

Abstract

It is hypothesized that ilio-sacro-iliacal corridors for a new envisioned pelvic ring implant (trans-sacral nail with two iliacal bolts ¼ ISI-nail: ilio-sacro-iliacal nail) exists on the level of S1-or S2-vertebra in each patient. The corridors of 84 healthy human pelves (42x <; 42x ,, 18-85 years) were measured in high resolution CT scans using the Merlin Diagnostic Workcenter Software. Trans-sacral corridors (!9 mm diameter) on the level of S1 and S2 were found in 62% and 54% of pelves with a mean length [mm AE SD] of 164 AE 12.9 and 142 AE 10.2. Corresponding iliac corridors were present in all specimens in caudally tilted axial planes of 37.8 AE 0.67å nd 53.7 AE 0.94˚in relation to the operating table plane and divergent angulations of 69.0 AE 0.49˚and 70.1 AE 0.32˚in relation to the sagittal midline plane. Sacral dysmorphism, with compensatory larger S2 corridors were prevalent in 24% of pelves; ilio-sacro-iliacal osseous corridors for the envisioned implant were found in 88% of pelves on the level of S1 or S2. In the remaining 12% with too narrow corridors for any trans-sacral implant (screws, bars, ISI nail) alternative fixation methods have to be considered. Expected advantages of the envisioned ISI nail compared to available fixation devices are discussed. ß

Transsacral Osseous Corridor Anatomy Is More Amenable To Screw Insertion In Males: A Biomorphometric Analysis of 280 Pelves

“…These biomorphometric data support efforts to improve fixation techniques for posterior pelvic ring lesions by using the transsacral S1 osseous corridor for implant placement [9,11,12,21,26,36], primarily described in a case report for a bilateral S1 dislocation [38] and later as a salvage procedure in combination with a posterior tension plate for failed posterior pelvic ring fixations in seven cases [1]. Compared with the oblique sacroiliac screw fixation described by Matta and Saucedo [20], additional fracture pattern like central sacral fractures (Denis Zone III) and bilateral posterior pelvic lesions can be addressed through a unilateral approach, whereas alternative sacroiliac screw fixation from both sides was accompanied with an increased risk of screw misplacement [9,12].…”

“…The same is true for transsacral screw placement. Using a cylindrical-shaped volume for automatic measurement of the osseous corridor diameters does not respect the ovoidshaped osseous corridor at the level of the S1 vertebra and therefore represents only the maximum osseous corridor height, but not necessarily the larger corridor width [11,22,39], which could facilitate placement of an additional second screw in the same corridor [22].…”

“…A triangle ratio of 1.5 (calculated by the quotient of the anterior height and width of the first sacral body) represents the boundary ratio for the prevalence of sacral dysmorphism, defined as transsacral corridors with a diameter less than 7.3 mm, unsuitable for screw placement. In contrast to these studies, we defined sacral dysmorphism as the absence of a transsacral corridor at the level of the S1 vertebra, as a high sacral anatomic variability [4] and different corridor diameter cutoffs (5, 9, or 10 mm) exist for transsacral implant placement based on the implant types used (screws, bars, or nails), implant sizes (5-8 mm diameters), and insertion technique (fluoroscopic-controlled versus computer-guided navigation) [2,5,8,11,21,24,37]. Our study provides additional information regarding transsacral corridor-size distributions and proportions of pelves based on their individually set cutoffs in clinical settings (Fig.…”

“…(S1, 8 ± 0.9 mm; S2, 7 ± 3 mm). Minor differences in several studies may be attributed to heterogeneity of the groups based on sex or the measurement techniques as discussed in a recent study [11].…”

“…Furthermore there is limited ability to see all relevant bony structures on the intraoperative two-dimensional fluoroscopic images [7,22,29,31,40]. The corridor for the oblique sacroiliac screw placement in the first vertebra has been investigated in different biomorphometric studies [2,7,8,16], but data for transverse transsacral screw placement at the level of S1 and S2 are limited owing to the small size of study groups, different exclusion criteria, or measurement techniques [11,22,23,37,39].…”