Since PVP was first reported by Galibert in 1987 [20], it has been recommended as an effective minimally invasive treatment for painful OVCFs [21–23]. The standard approach to PVP is the bilateral transpedicular one. However, in recent years, unilateral puncture techniques such as the unipedicular or extrapedicular approach have been increasingly used, as they have the advantages of shorter operation time, lower X-ray exposure and better cost-effectiveness [24–26]. The optimal target location for unilateral PVP is one-third anterior and midline of the VB so that bone cement can diffuse to the unpunctured side, which balances the stress on the VB [19, 27]. Therefore, the unipedicular approach requires a more aggressive medial-inclination angle, which can lead to complications of facet joint damage, pedicle disruption and spinal-canal intrusion [13, 28]; meanwhile, the extrapedicular approach carries the risk of lumbar-artery injury [14–16]. In this study, we used the unilateral transforaminal approach to PVP for the treatment of OVCFs. We saw none of the above-mentioned complications, and operation time and X-ray radiation exposure were significantly lower than those in bilateral transpedicular PVP.
The intervertebral foramen is located between the deep arch of the inferior vertebral notch of the superior vertebra and the shallow arch of the superior vertebral notch of the inferior vertebra [29, 30]. The spinal root and vascular plexus course through the anterosuperior midportion of the foramen, immediately inferior to the upper pedicle [29, 31]. The skin entry point for the unilateral transforaminal approach is at the inferior endplate of the superior vertebra, at the inferior midportion of the foramen. Therefore, the unilateral transforaminal approach can anatomically avoid injuring the nerve root and vessel. The operation is performed under local anesthesia so that the patient can be asked about sensations of radiating pain, to avoid the risk of nerve root damage. In the process of puncturing the vertebral surface, the bone needle is placed above the superior notch of the pedicle to avoid injuring segmental vessels [14–16], and not beyond the medial margin of the ipsilateral pedicle, to avoid damaging the spinal cord and dura. In our study, we saw no complications of spinal-cord or nerve root injuries, hematomata or bone cement embolism, which further affirmed the safety of this method.
PVP involves the injection of bone cement into the VB to restore the rigidity and strength of the fractured vertebra, which on average, respectively, require cement fills of 16.2% and 29.8% [32]. Röder et al. recommend that at least 4.5 ml bone cement be injected to alleviate pain to a significant degree [33]. Besides cement volume, cement distribution is important to surgical effectiveness. When cement augmentation is limited to the punctured side of the VB only, the rigidity of the unpunctured side remains much weaker, which in turn leads to stress imbalance on the VB and subsequently induces compression and collapse of the weaker side. If cement augmentation crosses the midline, the rigidity of both sides increases to achieve biomechanical balance [2, 19]. Tan et al. and Zhang et al. both found that when bone cement can fully contact the upper and lower endplates, it can better reduce the risk of vertebral recompression and maintain the height of the VB [34, 35]. In our study, the volume of bone cement was 5.70 ± 0.86 ml in UTFA group and 5.82 ± 0.72 ml in BTPA group, with no statistically significant difference between the groups (P > 0.05); between-group distribution of bone cement did not differ significantly, either. Although cement was limited to the punctured side only in four cases of UTFA group, we were able to inject it during surgery via the contralateral transpedicular or transforaminal approach to obtain symmetrical distribution. VAS score and ODI in both groups were significantly decreased postsurgery versus presurgery (P < 0.05), with no significant differences in VAS score or ODI between the groups (P > 0.05). This meant that both unilateral transforaminal and bilateral transpedicular PVP, with similar clinical efficacies, could effectively relieve back pain and improve QoL.
In our study, the UTFA in PVP had the following advantages. First, as a unilateral puncture method, it could simplify the procedure while reducing operation time and X-ray radiation exposure. Second, as the puncture path was made in soft tissue, local anesthesia could reduce intraoperative pain more effectively than in the transpedicular approach. Third, the puncture direction and angle could be adjusted more widely to deliver the bone needle to one-third of the anterior middle region of the VB, which is not restricted by pedicles and is especially suitable for patients with abnormal or small pedicles.
The major limitation of our study was its retrospective design. Therefore, a randomized, controlled prospective study with long-term follow-up is required to confirm these results.