Spinal hardware has been adapted for fixation in the setting of anterior pelvic injury. This anterior subcutaneous pelvic fixator consists of pedicle screws placed in the supraacetabular region connected by a contoured connecting rod placed subcutaneously and above the abdominal muscle fascia.
We examined the placement of the components for anterior subcutaneous pelvic fixator relative to key vascular, urologic, bony, and surface structures.
We measured the CT scans of 13 patients after placement of the pelvic fixator to determine the shortest distances between the fixator components and important anatomic structures: the femoral vascular bundle, the urinary bladder, the cranial margin of the hip, the screw insertion point on the bony pelvis, the relationship between the pedicle screw and the corridor of bone in which it resided, and the position relative to the skin.
The average distance from the vascular bundle to the pedicle screw was 4.1 cm and 2.2 cm to the connecting rod. The average distance from the connecting rod to the anterior edge of the bladder was 2.6 cm. The average distance from the screw insertion point to the hip was 2.4 cm; none penetrated the hip. The average screw was in bone for 5.9 cm. The pedicle screws were on average 2.1 cm under the skin. The average distance from the anterior skin to the connecting rod was 2.7 cm.
Components of this anterior pelvic fixator are close to important anatomic structures. Careful adherence to the surgical technique should minimize potential risk.
Level IV, retrospective study. See Guidelines for Authors for a complete description of levels of evidence.
"In this context, it is important to mention that SIAF seems to be associated with irritation of the lateral femoral cutaneous nerve in up to 27% of cases and with heterotopic ossifications in up to 32% [11-13]. In addition, components of SIAF are close to important anatomic structures, like the femoral vascular bundle and the urinary bladder . "
[Show abstract][Hide abstract] ABSTRACT: Although useful in the emergency treatment of pelvic ring injuries, external fixation is associated with pin tract infections, the patient's limited mobility and a restricted surgical accessibility to the lower abdomen. In this study, the mechanical stability of a subcutaneous internal anterior fixation (SIAF) system is investigated.
A standard external fixation and a SIAF system were tested on pairs of Polyoxymethylene testing cylinders using a universal testing machine. Each specimen was subjected to a total of 2000 consecutive cyclic loadings at 1 Hz with sinusoidal lateral compression/distraction (+/-50 N) and torque (+/- 0.5 Nm) loading alternating every 200 cycles. Translational and rotational stiffness were determined at 100, 300, 500, 700 and 900 cycles.
There was no significant difference in translational stiffness between the SIAF and the standard external fixation when compared at 500 (p = .089), 700 (p = .081), and 900 (p = .266) cycles. Rotational stiffness observed for the SIAF was about 50 percent higher than the standard external fixation at 300 (p = .005), 500 (p = .020), and 900 (p = .005) cycles. No loosening or failure of the rod-pin / rod-screw interfaces was seen.
In comparison with the standard external fixation system, the tested device for subcutaneous internal anterior fixation (SIAF) in vitro has similar translational and superior rotational stiffness.
"Injury of the hip joint due to unintended intra-articular placement of the iliac screws . Perforation of the abdominal wall while subcutaneous advancement of the fixation rod is in progress with risk of organ lesion (iatrogenic urinary bladder-, sigma-, coecum lesion or injury to the small intestine). "
[Show abstract][Hide abstract] ABSTRACT: Fractures of the pelvic ring including disruption of the posterior elements in high-energy trauma have both high morbidity and mortality rates. For some injury pattern part of the initial resuscitation includes either external fixation or plate fixation to close the pelvic ring and decrease blood loss. In certain situations - especially when associated with abdominal trauma and the need to perform laparotomies - both techniques may put the patient at risk of either pintract or deep plate infections. We describe an operative approach to percutaneously close and stabilize the pelvic ring using spinal implants as an internal fixator and report the results in a small series of patients treated with this technique during the resuscitation phase.
Four patients were treated by subcutaneous placement of an internal fixator. Screw fixation was carried out by minimally invasive placement of two supra-acetabular iliac screws. Afterwards, a subcutaneous transfixation rod was inserted and attached to the screws after reduction of the pelvic ring.All patients were allowed to fully weight-bear. No losses of reduction or deep infections occurred. Fracture healing was uneventful in all cases.
Minimally invasive fixation is an alternative technique to stabilize the pelvic ring. The clinical results illustrate that this technique is able to achieve good results in terms of maintenance of reduction the pelvic ring. Also, abdominal surgeries no longer put the patient at risk of infected pins or plates.
BMC Research Notes 03/2014; 7(1):133. DOI:10.1186/1756-0500-7-133
"A technique of subcutaneous anterior pelvic fixation for anterior pelvic ring fractures has been recently reported and has been termed " infix " . It involves two supra-acetabular pins     and a subcutaneous rod, tunneled under the skin, at the top of the " bikini area "  . In a multicenter study, infix has been shown to be effective in the treatment of pelvic fractures when combined with the appropriate posterior fixation. "
[Show abstract][Hide abstract] ABSTRACT: Purpose. Comparison of monoaxial and polyaxial screws with the use of subcutaneous anterior pelvic fixation. Methods. Four different groups each having 5 constructs were tested in distraction within the elastic range. Once that was completed, 3 components were tested in torsion within the elastic range, 2 to torsional failure and 3 in distraction until failure. Results. The pedicle screw systems showed higher stiffness (4.008 ± 0.113 Nmm monoaxial, 3.638 ± 0.108 Nmm Click-x; 3.634 ± 0.147 Nmm Pangea) than the exfix system (2.882 ± 0.054 Nmm) in distraction. In failure testing, monoaxial pedicle screw system was stronger (360 N) than exfixes (160 N) and polyaxial devices which failed if distracted greater than 4 cm (157 N Click-x or 138 N Pangea). The exfix had higher peak torque and torsional stiffness than all pedicle systems. In torsion, the yield strengths were the same for all constructs. Conclusion. The infix device constructed with polyaxial or monoaxial pedicle screws is stiffer than the 2 pin external fixator in distraction testing. In extreme cases, the use of reinforcement or monoaxial systems which do not fail even at 360 N is a better option. In torsional testing, the 2 pin external fixator is stiffer than the pedicle screw systems.
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