Comparison of ESIN and other minimally invasive techniques for anterior pelvic ring injury: a finite element analysis and case-control study

Abstract

Object: A novel technique, percutaneous elastic stable intramedullary nail fixation (ESIN), proposed by our team for the treatment of anterior pelvic ring injury. Finite element analysis and retrospective case-control study were used to compare biomechanical properties and clinical outcomes between ESIN and other techniques.

Methods: Four groups of finite element models of pelvic anterior ring injury were simulated, including ESIN (model A), retrograde transpubic screw fixation (RTSF, model B), subcutaneous internal fixator (model C), and external fixator (model D), and a vertical downward load of 500 N was applied to the S1 vertebral endplate. Stress and displacement distributions of intact pelvis, displacement distributions of pubic fracture fragments, and stress distributions of fixation devices were analysed. Then 31 patients with anterior pelvic ring injury (15 in the ESIN group and 16 in the RTSF group) were reviewed. Clinical outcomes were evaluated at the final follow-up. Postoperative complications were also recorded.

Results: Under 500N loading, the intact stability of the pelvis was compared as follows: model B (20.58 mm, 121.82 MPa), model A (20.80 mm, 129.97 MPa), model C (22.02 mm, 141.70 MPa), and model D (22.57 mm, 147.06 MPa). The regional stability of superior pubic ramus was compared as follows: model B (9.48 mm), model A (10.16 mm), model C (10.52 mm), and model D (10.76 mm). All 31 patients received follow-up at least 12 months postsurgery (range 12-20 months). Age, sex, injury mechanism, fracture type, time between the injury and operation, American Society of Anesthesiologists score, intraoperative blood loss, hospital stay, follow-up period, time to union, and Majeed scores did not differ significantly between the two groups ( P >0.05). However, the differences in the duration of unilateral surgery, unilateral intraoperative fluoroscopy and one-time success rate were significant ( P <0.05).

Conclusions: With sufficient biomechanical stability and minimally invasive advantage, the percutaneous technique using ESIN can be used to successfully treat anterior pelvic ring injuries. In addition, advantages over RTSF include a shorter duration of surgery, reduced requirement for intraoperative fluoroscopy, and a higher one-time success rate. ESIN therefore constitutes a good alternative to RTSF.

Figure 1

Four different fixing methods after assembling the 3D model. A: ESIN+ sacroiliac screw; B: RTSF+ sacroiliac screw; C: INFIX+ sacroiliac screw; D: EXFIX+ sacroiliac screw.

Figure 2

Flow diagram of patient’s exclusion. Thirty-one patients with anterior pelvic ring injuries were enroled from January 2017 to January 2022 at a level 1 regional trauma centre.

Figure 3

Schematic diagram of ESIN operation. A: Outlet view and inlet view showed the entry point for the nail. B: Inlet view and outlet view showed ESIN entered the superior rami of the pubis and the tip reached the superior cortex. C: Inlet view and outlet view showed ESIN rotates 180° to reach fracture. D: Obturator oblique view and inlet view showed ESIN passed through the fracture and rotated 180° again. E: Obturator oblique view and inlet view showed ESIN was further advanced and passed anteriorly and superiorly into the acetabular cavity. F: Obturator oblique view and inlet view showed ESIN was further advanced until its tip reached the lateral cortex of the ilium above the acetabulum.

Figure 4

The pelvic displacement distribution diagram of four models. A: group ESIN with the maximum pelvic displacement of 20.80mm; B: group RTSF with the maximum pelvic displacement of 20.58mm; C: group INFIX with the maximum pelvic displacement of 22.02mm; D: group EXFIX with the maximum pelvic displacement of 22.57mm.

Figure 5

The pelvic stress distribution diagram of four models. A: group ESIN with the maximum pelvic stress of 129.97MPa; B: group RTSF with the maximum pelvic stress of 121.82MPa; C: group INFIX with the maximum pelvic stress of 141.70MPa; D: group EXFIX with the maximum pelvic stress of 147.06MPa.

Figure 6

Displacement distribution of pubic fracture fragment of four models. A: group ESIN with the maximum displacement of 10.16mm; B: group RTSF with the maximum displacement of 9.48mm; C: group INFIX with the maximum displacement of 10.52mm; D: group EXFIX with the maximum displacement of 10.76mm.

Figure 7

Stress analysis of the anterior ring fixation in four models. A: group ESIN with the maximum stress of 53.63MPa; B: group RTSF with the maximum stress of 18.06MPa; C: group INFIX with the maximum stress of 35.57MPa; D: group EXFIX with the maximum stress of 52.33MPa.

Figure 8

A 53-year-old male suffered a pelvic fracture due to a fall from a height. A and B: X-ray and CT showed fractures of the anterior and posterior pelvic rings. C: Prebending of the ESIN. D: Inlet view showed the entry point for the nail. E: Outlet view showed that the ESIN reached above the acetabulum. F and G: Inlet view and obturator oblique view showed that the ESIN was passed the fracture and the acetabular cavity. The tip reached the lateral cortex of the ilium above the acetabulum. H: Incision for ESIN. I and J: Postoperative X-ray of anteroposterior view and CT showed the good location of the ESIN. K and L: X-ray of anteroposterior view and obturator oblique view during 1-year follow-up showed that the fracture healed well and the internal fixation was not been displaced.

Figure 9

A 51-year-old male with a bilateral pelvic fracture sustained during a fall from height. A, B and C: CT showed the anterior and posterior pelvic rings fracture. D: Inlet view of pelvic showed the entry point for the nail. E: Outlet view of pelvic showed that the ESIN reached above the acetabulum. F: Inlet view of pelvic showed one ESIN had been placed in one side of pubis superior rami and another entry point for the nail was performed. G: Incision for ESIN. H, I, and J: Postoperative X-ray of anteroposterior view and obturator oblique showed the good location of the ESIN bilaterally. K: X-ray of anteroposterior view during 1-year follow-up before removing the ESIN showed that the fracture healed well. L: X-ray of anteroposterior view after removing the ESIN.