According to lots of researches, many complications have been reported due to the disadvantages of the traditional posterior approach position, such as postoperative visual loss (POVL), skin necrosis, venous air embolism, etc[3, 6]. These complications may have serious consequences to the patients, but researchers have only sporadically attempted to modify the traditional prone surgical position.
Improper pressure over the eyeballs and facial skin for long time is a common cause of visual loss and skin necrosis. Several studies have discussed postoperative vision loss due to prone position[3]. They conclude that the inappropriate pressure from the horseshoe headrest led to direct pressure over the eyeball, which may cause intraocular pressure and visual loss[7, 8]. In addition, there have been many documented cases of facial pressure sores and ischemic orbital compartment relate to prone position and horseshoe headrest[3]. It has been reported that the long-term localized pressure on the face in the prone position is on average below 30 mmHg but can be higher than 50 mmHg in certain areas, such as the chin and forehead above the supraorbital ridge, which may cause facial edema and pressure sores[9–11].
According to our experience, surgeons may need intraoperative readjustment of patients’ position for a better surgical field. The traditional prone position has no fixation of the patients’ head, body and operating table, so it is impossible to ensure the stability of patients when adjusting the operating table and traction direction during the operation, which may lead to respiratory passage compression and asphyxia. Additionally, Kadam AB et al.[2] proposed a modified prone position for posterior cervical spine surgeries using cervical tong for traction and two lateral brace attachments on an operating table, which can avoid localized pressure over the eyeballs and face skin associated with horseshoe headrest. However, this modified prone position has an inability to intraoperatively readjust the position and tilt the table beyond 30° to either side.
Immobilization by a cervical collar to protect the patient from secondary damage is a standard procedure in cervical spine trauma patients[12, 13]. However, more studies have pointed out that applying a cervical collar in general will cause immense three-dimensional movement, and extrication collars can result in abnormal movement within the upper cervical spine in the presence of a severe injury[14–16]. We believe that an absolute restriction of the cervical spine cannot be only achieved by the cervical collar during preoperative positioning and may cause secondary dislocation in those with spinal cord injury, especially in the presence of a dissociative injury[17].
The BSPST position has more advantages in protecting facial skin and eyes from skin necrosis and ocular complications with the use of protective macromolecular material. The body-shape plaster bed can decrease the vertical direct pressure by distributing pressure equally across the facial skin, and the round head holder has no direct contact with patients’ eyes. In our analysis of the traditional and BSPST positions, we identified ten patients (47.8%) with postoperative complications in the traditional position group and three patients (8.3%) with postoperative complications in the BSPST group (p = 0.004). This result showed that the incidence of postoperative complications was relatively high when cervical spine surgery incorporated a traditional prone surgical position compared with the BSPST prone surgical position.
As for the adjustment of the surgical position, the BSPST position can maintain a stable position even when the table exceeds 35° to either side. Additionally, the traction direction can be intraoperatively adjusted to expose of the operation fields for obese and short-neck patients. This method also allows patients to be stably positioned in the reverse Trendelenburg’s position (see Additional file 3), which can reduce venous congestion and bleeding as well as reduce orbital pressure to diminish the occurrence of postoperative vision loss[6, 18]. It was obvious in our research that only one patient in the traditional position group but 20 patients in the BSPST group provided surgeon comfort levels of 1 and 2 (p < 0.01), and intraoperative blood loss in the BSPST position group was significantly less than that in the traditional position group (p = 0.003). These results indicated that the BSPST position may provide the surgeons with a more comfortable surgical position and reduce intraoperative blood loss.
To maintain safety during the preoperative positioning, the surgeon and assistants can create a situation in which the patient and body-shape plaster bed stay together so that the patients’ head, whole cervical spine and body can turn around at the same time by using the body-shape plaster bed. The BSPST position also facilitated easy access to the anesthesia tube, which could be removed from either side below the body-shape plaster bed (Figs. 1, 2 and Additional file 2).
Intraoperative radiography is necessary for spine surgery, especially cervical spine surgery, and it can help surgeons to conform surgical segments and guide as well as conform pedicle screw placement[19]. However, anterior-posterior interoperative radiography is unavailable in traditional position because of the material of the headrest, which may create difficulties to the surgeons (Figs. 2 and 5). The BSPST position system is X-ray penetrable, easy to assemble and inexpensive, and can be acceptable for patients in many hospitals in developing countries compared with other innovations of prone position for cervical spine surgeries[20–22].
The positioning time was 16.250 ± 6.835 min in the BSPST group and 15.960 ± 6.832 min in the traditional group, which were not significantly different (p = 0.144). Although cervical tong application may appear to require additional time, it is a relatively quick procedure, and the time consumed is well compensated by the reduced time required to reduce skin necrosis and ocular complications. In addition, the BSPST position can be used in not only cervical spine fracture surgeries but also other posterior cervical spine surgeries.
All techniques have downsides, and there are still several limitations of this study and the BSPST position. First, retrospective results from a single center should be prospectively verified by multicenter and randomized controlled studies. Second, the patient sample was relatively small, and the follow-up was relatively short in this study. Besides, this position is not available for advanced deformity patients and has some disadvantages directly related to the prone position. In addition, the measurement of the C7SP-EOP angle may show significant deviations in obese patients due to thick fat tissue around the neck and back. Finally, further studies are required to conclusively establish the efficacy and safety of the BSPST position to put it into use and improve upon it.