The current study attempted to validate a modified preprocedural ultrasound-assisted technique by suggesting needle insertion angles in elderly patients with hip fractures. In comparison with the landmark-guided technique, the ultrasound-assisted technique had a higher first-pass and first-attempt success rate, fewer needle passes and insertion attempts, and a shorter puncture time; this improved the efficacy of CSE anesthesia, as well as patient satisfaction.
CSE anesthesia was applied to reduce the dose of local anesthetic in spinal anesthesia; this lowered the risk of unstable hemodynamic conditions among the elderly patients, who had a high prevalence of underlying diseases. Epidural cathetering was applied to ensure an adequate block level during the surgery, and maintenance of postoperative analgesia [33]. No differences in patient baseline characteristics were found between the two study groups. Compared with previous studies[23, 24], the subjects in the current study had a higher mean age and lower lumbar curvature ability; furthermore, patients with scoliosis were also included. Thus, puncture was relatively more difficult in the present study.
The results observed in the ultrasound group can be attributed to several reasons. First, accurately measured insertion angles provided a better needle trajectory. Previous studies have suggested 10–15° medial and cephalad angles during the puncture [27]. However, in practice, these angulations are estimated based on personal judgment. The present study provided personalized insertion angles and used an aseptic protractor to guide the puncture. The results (Table 3) showed that for most cases (70%), the actual cephalad angle discrepancies were within 5°. Indeed, the first pass was also achieved in these cases. For the medial angle, 80% of the cases showed a discrepancy within 5°. These results demonstrated that the suggested angles could provide reasonable guidance. Second, for elderly patients with hip fractures, limitations associated with patient positioning may have led to a narrow interlaminar space. Previous studies have often placed the posterior and anterior complex at the center of the screen, and identified the needle insertion point by skin-marking the midpoint of the probe at that time [23, 28], thereby resulting in a relatively limited operating space (Fig. 3). The current study placed the upper edge of the inferior lamina at the center of the screen to obtain a lower needle insertion point and a larger cephalad angle, resulting in a wider operating space for the puncture (Fig. 3). Third, ultrasonography could have indicated the most suitable interlaminar space for puncture, based upon the variation in individual anatomic characteristics.
In the current study, a successful first pass was not always accomplished. In most circumstances, this was because of bony contact, most frequently with the inferior laminar. Therefore, needle redirection and more needle passes were needed for a successful puncture. In five cases, the actual cephalad angle exceeded the maximum suggested angle (∠α) measured by the ultrasound image; this may have been explained by the deviation of the insertion point. If the marked needle insertion point was lower than the ideal point, the needle encountered the inferior laminar, and a larger cephalad angle was needed.
Relative to similar studies involving elderly patients [23, 24], the first-pass success rate in the ultrasound group was higher than that reported in a study conducted by Park et al. [23], and a higher first-attempt rate was achieved compared with that reported in a study conducted by Geng et al. [24]. These results may have been possibly due to the use of the modified ultrasound-assisted technique, which provided a more accurate guidance for the needle trajectory, resulting in a lower number of needle redirections. However, an undesirable result was a lower first-attempt success rate relative to values reported in previous studies [23]. This was possibly due to the patients in the current study having a higher average age, as well as the difficulties experienced with positioning as a result of their hip fracture.
Although the differences in adverse reactions and postoperative complications were not statistically significant between the two groups, unintentional dural puncture occurred in three cases, possibly because the degenerative disc disease, ligament calcification, and stenosis of the spinal canal in elderly patients made it difficult to identify the tissue layer and control the force to perform the procedure [34]. Two cases in the landmark group required the use of alternative techniques, indicating that the variability of performance in the landmark group was relatively large compared with the ultrasound group. No patients in either group required conversion to general anesthesia; this may have been due to the high level of experience of the senior anesthetists, who were able to achieve success with two different interlaminar spaces or an alternative technique, in the event of initial failure.
Compared to PSO views, fewer ultrasound images of good quality were obtained from the TM views; this concurred with the results of previous studies [24, 28]. The moderate and poor images may have been due to the calcification of the supraspinous and interspinous ligaments, as well as facet joint hypertrophy [8, 15, 28].
While there has been an increasing trend in the use of real-time ultrasound guidance [35–38], this technique may not have been suitable for the current study, due to the limitations in the operator’s dominant hand in the PSO view [38], and the poor quality of the ultrasound image in the TM view [36].
The current study had some limitations. First, due to the nature of the study design, only the patients were blinded during the CSE anesthesia procedure. Second, measurement error was inevitable, even though the suggested cephalad and medial angles were measured by the same operator. Finally, in some cases, inaccuracy in the needle insertion point was unavoidable, as elderly patients often have loose and mobile skin.