The invention of an iliosacral screw fixation guide and its preliminary clinical application

Abstract

Objective:  To introduce an iliosacral screw fixation guide and evaluate its efficacy in fixation of sacroiliac joint fracture‐dislocations.

Methods:  Between January 2011 and May 2011, eight patients (five men, three women) with sacroiliac joint fracture‐dislocation underwent percutaneous iliosacral screw fixation with the assistance of this minimally invasive guide and under CT guidance. The patients, aged from 26 to 56 years (mean 32 years), had vertically unstable pelvic fractures. Before surgery, six patients who had displacement of >2 cm in their sacroiliac joints underwent skeletal traction on the femoral condyle. The inserted sites were marked out on the affected side of their buttocks after the best screw trajectory had been determined under CT control. The gear that controls the direction of the minimally invasive guide was adjusted according to the inserting angle determined by CT scans. A K‐wire was inserted into the sacroiliac joint along the pilot sleeve of the guide, and a hollow screw (diameter 7.3 mm) was implanted into the sacroiliac joint along the K‐wire.

Results:  All eight operations were successful on the first attempt. The operations lasted from 10 to 20 minutes (mean 14 minutes). Immediate CT scans confirmed that all the screws had been placed in the desired positions, none had penetrated the bones and the configuration of the sacroiliac joints had been satisfactorily restored and firmly fixed. No patient experienced numbness or radiating pain in the lower limbs during surgery. There were no postoperative vascular or neurological complications.

Conclusion:  The minimally invasive guide can eliminate discrepancies resulting from the surgeon's own sensory input when inserting screws under the guidance of CT, making percutaneous iliosacral screw fixation more accurate, safe and simple.

Introduction

Internal screw fixation is commonly used for iliosacral joint fracture‐dislocations and sacral fractures ¹ , ² , ³ . Recently, percutaneous screw fixation has been increasingly adopted for minor iliosacral joint dislocations or fracture‐dislocations that can be treated by closed reduction ³ . Percutaneous iliosacral screw fixation under conventional C‐arm fluoroscopy is a lengthy procedure that often exposes the patient to prolonged radiation. Even experienced surgeons can have a high rate of screw malposition and nerve and vessel injuries ³ , ⁴ , ⁵ , ⁶ . Though computer‐navigated iliosacral screw insertion reduces the malposition rate, operation time and radiation exposure ⁷ , its widespread application has been limited because the technology is imperfect, the procedure complicated, huge facilities and expensive equipment are required and discrepancies occur between computer‐navigated images and the surgeon's sensory perceptions during the procedure. The potential advantages of CT‐guided placement of percutaneous hollow screws are that it is a simple operation, the screws are accurately located, there is less hemorrhage, minimal injuries and strong fixation is achieved ⁸ , ⁹ , ¹⁰ ; thus patients recover more quickly. In practice, however, we find that, although preoperative CT scans can determine the optimal inserting angle and depth, the surgeon can only determine the K‐wire angle based on his own sensory input, resulting in the actual insertion deviating from the preoperative CT‐measured optimal angle. The surgeon has no choice but to adjust the insertion angle repeatedly during the operation, which not only increases the operation time and patient radiation exposure, but promotes the risk of nerve or vessel injuries as well. For these reasons, we have invented a type of guide (Patent No: ZL 2010 2 0132491.2). According to the parameters obtained from preoperative CT scans, we adjust its controls to direct the K‐wire into an exact position along the predetermined trajectory. In a preliminary clinical trial, we have achieved improved results, bringing the screw fixation technique to a new level in accuracy, safety and simplicity.

Materials and methods

Introduction to the guide

The guide consists of a tripod that can adjust height and level, an angle control gear and a pilot sleeve (Fig. 1). The head of the pilot sleeve can be threaded with a K‐wire (diameter 2.8 mm), dismantled and sterilized. The angle control gear contains three scales (cross section, sagittal plane and coronal section) and three‐angle adjustment knobs, allowing the guide to be adjusted in three planes and latched. Relying on the parameters obtained from CT pre‐scans, we can determine the optimal angle and site of insertion, adjust the guide's three angles and steer the K‐wire into the ideal position along the predetermined trajectory.

Figure 1.

The structure of the guide.

Patient data

From January 2011 to May 2011, eight patients (five men, three women) with sacroiliac joint fracture‐dislocations were treated with percutaneous iliosacral screw fixation aided by the minimally invasive guide and CT. The patients, aged from 26 to 56 years (mean age 32 years), had vertically unstable pelvic fractures. The mechanism of injury was a traffic accident in five and a fall in three. Before surgery, six patients with displacement of >2 cm in their sacroiliac joints had skeletal traction applied to their femoral condyle. The traction weight was one eighth or one seventh of their body weights. They were operated on 3–15 days after injury (mean time of 5 days).

Screw placement aided by the minimally invasive guide

Preparation

After traction reduction by the femoral condyle, the patients lay prone on the CT bed. Sixteen‐slice spiral CT scans were performed with slice thickness of 3.75 mm, voltage of 120 kV and electric current of 30 mA. The best trajectory for insertion was determined on the CT computer screen. This trajectory is vertical to the sacroiliac joint plane and goes through the sacral pedicle into the S1 and/or S2 vertebral body, thus avoiding penetration of the sacral foramen. The location of the bed, lateral distance, and inserting angle and distance were recorded. The CT laser light was turned on and the injured side of the buttocks located and marked out.

Assembling the guide

The sterilized pilot sleeve was installed under sterile conditions and adjusted to be parallel to the CT bed and perpendicular to the original longitudinal state of the body. The angle control gear was adjusted to the insertion angle that had been predetermined from the CT scans, so that the pilot sleeve conformed to the requirements of insertion in three‐dimensional space (being parallel to the optimal trajectory). Finally, the bolts were fastened and fixed.

Screw placement

Lying in the prone posture, the patient was administered 1% lidocaine for local anesthesia, and draped under routine sterile conditions. While maintaining the middle angle of the control apparatus stable, the tripod was adjusted to the appropriate height or horizontal direction, gradually enabling the head of the pilot sleeve to reach the marked site on the skin. A K‐wire (diameter 2.8 mm) was inserted along the sleeve through the skin and muscle to the lateral ilium (Fig. 2).

Figure 2.

Schematic diagram of the application of the iliosacral screw fixation guide.

The outer end of the K‐wire was then connected to a drill and the front sharp point drilled about 4–5 mm into the bone. After it had been firmly fixed in the bone, the drill was removed, the K‐wire held firmly and the guide gently slid out toward its outer end along the K‐wire while the K‐wire remained in place.

Sixteen‐slice spiral CT scans were again performed and a 0.625 mm thick three‐dimensional reconstruction made. After the site of insertion and direction had been confirmed, the K‐wire was gradually inserted through the ilium and sacrum into the S₁ or S₂ vertebra and beyond the midline. A hollow drill was used to enlarge the hole and thread the K‐wire through. In accordance with the CT measurements, a hollow titanium alloy lag screw (diameter 7.3 mm, Synthes, Solothurn, Switzerland) of a suitable length was tightened along the K‐wire. By use of the pull‐out strength of the screw, the sacroiliac joint was reduced. In the process of screwing, the operator repeatedly asked the patients whether they had any numbness or radiating pain in their lower limbs.

CT scans and three‐dimensional reconstruction were then repeated once more to confirm whether the sacroiliac joint had been successfully reduced and the screw placed in the right position.

Results

The eight patients all had 8 AO hollow titanium alloy lag screws inserted. The total operation time, calculated from marking out the site of insertion to achieving the insertion and final confirmation by CT scans, lasted from 10 to 20 minutes (mean 14 minutes). All the operations were successful at the first attempt, requiring no readjustment of K‐wires. No numbness or radiating pain in the lower limbs occurred kduring the operations. No vascular or neurological complications occurred after surgery.

Discussion

Disadvantages of conventional percutaneous iliosacral screw fixation with computed tomography guidance

Iliosacral screw fixation is a common treatment for sacroiliac joint fracture‐dislocations and sacral fractures ¹ , ² , ³ . Currently, it is being applied more and more widely. Some doctors have used it for osteoplasty in advanced metastatic destruction of the iliosacral joint ¹¹ , and as a resuscitation adjunct for acute traumatic pelvic ring injuries with life‐threatening hemorrhage ¹² . For minor dislocations, sacroiliac joint fractures or dislocations that can be reduced by traction on the femoral condyle, percutaneous iliosacral screw fixation is generally preferred. It is true that percutaneous iliosacral screw fixation under CT guidance has many theoretical advantages, but we find that in practice the surgeon simply determines the K‐wire angle based on his own senses. This leads to some discrepancies between the actual insertion angle and the optimal angle as determined by CT preoperatively (Fig. 3). Consequently, the surgeon repeatedly adjusts the insertion angle. Therefore, the operation time is longer, the patient is subjected to extended radiation exposure and there is more trauma at the site of insertion. Besides, under local anesthesia, the patients are fully conscious. Repeated adjustments tend to intensify their emotional tension and psychological stress. Moreover, litigation tends to occur when there are any adverse events.

Figure 3.

Axial CT image showing a discrepancy between the actual inserted position and the optimal insertion route.

Advantages of using the guide

Our preliminary clinical trial shows that this technique can curtail the surgical time to about 14 minutes. The first case took the surgeon 20 minutes, starting from determination of the site of insertion on the body surface to the final confirmation of the screw position, owing to his lack of skill. As the surgeon has become more and more skillful, the surgical time is getting shorter and shorter. The shortest procedure has taken only 10 minutes, the mean time being 14 minutes. All the K‐wires have been implanted into their exact positions on the first attempt, requiring no readjustment of insertion points or angles. Hollow screw location has accorded with the preoperatively predetermined plan. No case has had any vascular or neurological complications.

From this initial clinical trial, we hold that the guide can help the surgeon to insert K‐wires accurately along the trajectory predetermined by the angle measured by CT before surgery, reduce readjustments of K‐wires, prevent discrepancies due to the operator's own judgment, shorten surgical time, lower patients’ exposure to radiation, promote operational accuracy, safety and simplicity and make percutaneous iliosacral screw fixation more minimally invasive. Besides, it not only aids in passing iliosacral screw from one side of the ilium via the sacrum to the other, is but also suitable for fixing several hollow screws in a narrow region. Finally, it is cost‐effective, an easy procedure to learn and suitable for most grassroots hospitals equipped with CT machines.

In the meantime, we must admit that our research has involved only a few cases. More clinical data and a prospective controlled study comparing it to conventional iliosacral screw fixation under CT guidance is required to confirm the guide's advantages.

Disclosure

The authors declare that they have no competing financial interests.