**3. Results**

Operative fixation was performed at an average of 10.4 (range, 4–22) days after patients were appropriately resuscitated and optimized for surgery. Seven patients had multiple fractures, including spine, forearm, tibial, and ankle fractures. Two patients sustained various chest traumas, such as flail chest, pneumo-/hemothorax, and multiple rib fractures. Two patients sustained a liver injury that required emergency intervention.

Overall, 16 of the 19 patients underwent surgery via the anterior approach alone, whereas three patients required additional posterior fixation through a separate posterior approach. The mean operation time was 208.6 min (range, 150–290). Primary bone union was achieved in all cases at an average of 17.3 (range, 15–20) weeks. The quality of reduction assessed by Matta's criteria at the final follow-up was excellent, good, and poor in 10, 8, and 1 patients, respectively. Notably, all patients achieved excellent or good functional outcomes with a median Merle d'Aubigné score of 16.6 (range, 15–18), except for two patients.

These two patients (10.5%) underwent hip arthroplasty at 5 and 11 months postoperatively, respectively. One patient had a severe femoral head impaction at the time of injury, and osteonecrosis of the femoral head, followed by secondary arthritis, was found to be rapidly progressing. The other patient sustained severe comminution of the acetabular cartilage. Although the postoperative reduction status was relatively satisfactory, joint space narrowing gradually progressed and osteoarthritis eventually developed with complaints of severe pain.

Complications caused by continuous traction, such as nerve or vascular damage, pin site problems, or pressure sore, were not observed in any case.

## **4. Discussion**

Reduction is the first and most important step in acetabular surgery. Intraoperative traction is essential to neutralize the deforming force that caused the fracture, and it facilitates the reduction. Various intraoperative traction methods have been described in the relevant literature, including the use of a surgical assistant to provide intermittent manual traction, an external fixator, a fracture table, or an on-table frame [7]. A skilled assistant can apply manual traction, but the assistant can easily be exhausted, and the need for additional operating room personnel is another drawback. Moreover, a previous study reported that the major disadvantage of using a radiolucent table is the need for manual traction; thus, it requires a minimum of two or three assistants [10]. In addition, it is difficult for a human to apply a constant force throughout the operation. In contrast, the benefit of using the fracture table is that constant and precise traction can be maintained indefinitely, although an additional surgical assistant is still required to operate the table. However, the design of the fracture table limits certain movements of the extremity and interferes with certain fluoroscopic views [11–13]. Notably, an on-table frame can be used for this purpose, but force vectors are two-dimensional [5]. Moreover, external fixators or distractors can be used, although traction is most commonly provided along a single defined vector in these techniques [3–6]. In contrast, the method described in our study does not require additional personnel, and the number of assistants can be decreased. Before using limb positioner traction, our surgical team for a pelvic-acetabular fracture usually consisted of one surgeon and three assistants, whereas two assistants are sufficient after using this method. In addition, it is easily adjustable and can be manipulated in multiple vectors simultaneously. An additional advantage is that the distraction direction, which facilitates fracture reduction, can be adjusted and maintained and, if necessary, easily changed during the operation. Similarly, compared with other table attachments that offer only leg movement, a particular advantage of the limb positioner is that the leg can be manipulated in rotation and flexion/extension while engaged [7]. In addition to having complete freedom of leg position when initially applying traction, it is easy to adjust it as often as preferred. Furthermore, since most centers performing limb surgery are generally furnished with a limb positioner, it is also considered to be cost effective to use this as a traction device in this respect.

The Spider Limb Positioner is a pneumatic arm with three fully articulated joints that uses compressed air or nitrogen to facilitate its static locking mechanisms. It was classically used for shoulder arthroscopic procedures. The foot pedal allows the surgeon to control the limb during surgery and is the means by which pressurized air or nitrogen is supplied to the pneumatic arm. Notably, the foot pedal unlocks the three joints simultaneously, allowing the repositioning of the limb in an infinite number of positions while maintaining a sterile field [8]. Additionally, the limb can be connected to and disconnected from the limb positioner while maintaining a sterile field throughout the procedure. Owing to the limb positioner's unique ability to allow infinite positional adjustments in three dimensions, we aimed to use it for intraoperative traction. Furthermore, the limb positioner can support a maximum of 22.3 kg (50 lbs) [8], which is believed to provide sufficient strength for traction.

In a previous study of both-column acetabular fracture, the hip joint was congruent in 94.7% after surgery, which is comparable to our result [2]. However, they experienced 8.9% of iatrogenic nerve injuries and 60.7% of patients had the mean Merle d'Aubigné score of 15, and 25.8% of the patients diagnosed a joint failure, which is somewhat inferior to ours. The operation time in the current study was also relatively shorter than described in previous

studies [2,14,15]. It is believed that this is because the operation can be performed while maintaining stable traction with the limb positioner, without repetitive actions for reduction.

To the best of our knowledge, no case series has described the use of a limb positioner as a reduction tool with clinical and radiological outcomes in both-column fractures of the acetabulum with adequate follow-up, although a previous case report described the technique of lateral traction for reduction of the medialized femoral head using a limb positioner [7]. Although intraoperative traction using a limb positioner may not have a significant effect on the clinical and radiological outcome, it is considered to be true that the surgical procedure can be convenient and efficient.

This study has some limitations. First, the study used a retrospective design and a small cohort size. Second, the unconventional use of a limb positioner for traction purposes is not authorized. However, considering that this is a novel attempt to introduce the limb positioner in acetabular fracture surgery, we believe that it deserves attention as it can provide acetabular surgeons with a new reliable traction technique. In addition, this can be a reasonable and safe alternative technique to maintain intraoperative traction when operating both-column fractures of the acetabulum.
