·The leg was held by an assistant in about 90 degrees of hip flexion to simulate the usual positioning of the limb duringsurgery.
·Pijun Zhang found the entry point wasplaced along the medial axis (OI) passing through the central point of the ischialtuberosity (O) and the midpoint (I) between the most prominent point of anteriorsuperior iliac spine (A, ASIS) and that of posterior superior iliac spine (B,PSIS). The study showed showed that the entry point was preferablyset at the medial side of ASIS and PSIS, or at a point deflected slightly to ASIS. The AB distance (156.26±7.28mm and151.38±8.11mm), OI distance (139.53±7.56mm and 125.15±11.17mm), and diameter(12.19±1.97mm and 10.19±2.14mm) .
·Placementof a virtual cylindrical implant. (A, B), The most prominent point of anterior superior iliac spine and that ofposterior superior iliac spine. (C) The central point of the ischial tuberosity.
·Safety verification of the screwfixation in the ilium. (A) Medial view. (B) Longitudinalprofile. (C) Horizontal profile (the dark red area is the testing area).
·Zhangproposed that the most prominent points of ASIS and PSIS were equidistant from a point at the ischial tuberosity, based on which they further proposed that the lag screws might be placed percutaneously through the perpendicular bisectorof a line passing through the most prominent points of ASIS and PSIS.
The orifice o fthis cylinder from thei liacfossa (O) was determined as the entry point for the antegrade lag screw. Point D was found in the arcuate edge, making the distance of OD the shortest between the entry point and the arcuate edge. Point G was the frontmost edge of the sacroiliac joint, pointP was the iliopubic eminence, and points D and G wereconnected.
·Wei-dongMu found that The average length of lag screwwas 104.8 ± 4.2 mm. The average lateral distance was 16.8 ± 2.1 mm. The averageposterior distance was 23.5 ± 3.4 mm. The corresponding average retroversion angulation and extraversion angulation were 57° ± 4° and 119°± 2° respectively.
·Dienstknecht found that the distance of antegrade entry point for the posterior column screw to the anterior superior iliac spine was 7.4±0.86 cm, to the anterior inferior iliac spine was 5.3±0.22 cm, to the iliopectineal eminence was 5.1±0.97 cm, to the ischial spine was 8.0±1.38 cm, to the sacroiliac joint onheight lineaterminalis was 3.5±0.49 cm, and to the lineaterminalis was 1.5±0.99 cm in the malespecimens.
References
·[Starr,Adam J, Reinert Charles M, Jones Alan L.Percutaneousfixation of the columns of the acetabulum: anew technique.Journal of orthopaedic trauma 1998Jan;12(1):51-8]
·[KhalidAzzam, Justin Siebler, Karl Bergmann, et al. Percutaneous retrograde posterior column acetabular fixation: is thesciatic nerve safe? A cadaveric study. Journal of orthopaedic trauma 2014Jan;28(1):37-40]
·[Mu WD, Wang XQ, Jia TH, Zhou DS, Cheng AX (2009) Quantitative anatomicbasis of antegrade lag screw placement in posteriorcolumn of acetabulum. Arch OrthopTrauma Surg 129(11):1531–1537 ]
·[Dienstknecht T, Muller M, SelleiR, Nerlich M, Muller FJ, Fuechtmeier B et al (2012) Screw placement in percutaneousacetabular surgery: gender differences of anatomical landmarks ina cadaveric study. IntOrthop37(4):673–679 ]
·[ChenH,Wang G, Li R, et al. A novel navigationtemplate for fixation of acetabular posterior column fractures with antegrade lag screws: design and application.International Orthopaedics 2015;40:827–34]
