Low back pain is one of the leading causes of disability and lost productivity worldwide, with an increase in disability-adjusted life years of nearly 19% from 2005 to 2015 (1). Percutaneous imaging-guided infiltrations represent one of the recommended options for minimally invasive treatment of low back pain (2–4), with computed tomography (CT) guidance used in many centers. In particular, spinal stenosis, neural foraminal stenosis, and lumbovertebral pain syndrome are commonly treated with steroid injections into the affected area (4). Accuracy of needle placement is a critical step for the success of CT image-guided percutaneous interventions as inaccurate needle placement can lead to loss of time, unwarranted radiation exposure, adverse events, or treatment failures (3).

Needle placement is most often performed with the free-hand method whereby translation from the planned needle angle to the actual needle insertion angle is estimated by the operator and confirmed via a series of control scans. Thus, success is dependent on the visuospatial abilities and experience of the physician. In particular, if an out-of-axial plane trajectory (double oblique) is required to achieve the best access route, needle guidance can be challenging as needle orientation becomes difficult to assess in axial control images. In these cases, CT navigation guidance systems have been shown to be helpful (3). However, many CT navigation guidance systems are impractical due to their expense, bulk, or added time required for setup (5).

A recently introduced navigation tool, the Cube Navigation System, has shown high accuracy in an in vitro study (6) and promising initial clinical results (7). Additionally, its relatively small size and ease of use seem to address some of the problems with other CT navigation systems. We describe our first clinical experiences using the Cube Navigation System on patients in whom a double-oblique access route was necessary.

See Table 2 for summary of results. Mean patient age was 69 ± 13 years (range 58–82 years; all female). One patient (Pat. 2) had a history of clinically nonsuccessive decompressive surgery. In two patients (Pat. 2 and 3), fluoroscopy-guided interventions had been attempted in the referring department, albeit unsuccessfully. One patient (Pat. 5) had previous periradicular infiltrations at the level of the epidural infiltration, not performed at our institution, and not successful.

Technical success was obtained in all cases, and there were no reported adverse events. The mean procedure time to reach the target from the time point of the planning scan with the cube was 15 ± 7 (10–22) min. An average of 2 ± 1 control scans were used to reach the final target. In one patient, the first control scan required a correction of needle path after first introduction of needle as the needle path was slightly misaligned. For that, the Puncture Cube was left in place on the patient but collapsed (the upper plate was brought down to the lower plate), allowing for a slight adjustment of the needle angulation.

Two patients experienced rapid pain reduction, immediately after the infiltration (Pat. 1 and 3), while two patients experienced delayed yet sustained pain reduction (Pat. 4 and 5), and the final patient experienced a transient and incomplete effect.

In this small series of patients, the Cube Navigation System showed to be a promising guidance tool for percutaneous double-oblique CT-guided interventions. Needle placement proved overall to be highly accurate: in only one of the five punctures, initial needle position was slightly incorrect, most likely due to a breathing artifact. Time required for correct needle placement was well within the range when compared with the literature (7) and, in fact, the variability of procedure time appeared to be lower than that of the free-hand method from our experience. This has the potential to improve scheduling efficiency through improved estimations of procedure time.

From the patient's perspective, we assume a benefit concerning patient comfort. Usually, intervention areas with complex access routes require multiple needle corrections. In the current study, this was largely avoided. Additionally, some patients who might otherwise be considered unsuitable for the procedure due to anatomical considerations indeed may be eligible for interventional treatment using this system. In our experience, the Cube Navigation System does not add discomfort or extra time to the procedure and poses no additional risks, while potentially improving puncture accuracy and availability of treatment.

Practically speaking, the Cube Navigation System was implemented easily in the clinical routine, as only a connection from the CT modality to the Cube Navigation System software had to be installed. The lack of any space-occupying hardware equipment, as required with optical, electromagnetic, or laser systems (8–12), in the CT examination room can be regarded as an advantage to other navigation systems. Furthermore, the Puncture Cube can be used with needles of up to 18 G making it a viable option for many injections. This has promising implications for future research.

There are some limitations to the Puncture Cube. Unlike other navigation systems, larger needles cannot be used. Collapsing the cube after the initial puncture for needle correction is possible and was found necessary in one of our cases. However, it would be of advantage to have the option to remove the Puncture Cube after needle introduction completely, as otherwise the lower plate remains fixed to the patient and the scope of possible needle correction is limited. Attachment of the cube to the body by the self-adhesive tape pre-mounted on the Puncture Cube was stable at the level of the lower spine. However, at locations other than the thorax and lower back, which have essentially a plane surface, fixation might be more challenging.

Double-oblique punctures with the Cube Navigation System in this initial case series of complex access routes at the lumbar spine were accurate, and the procedure was time efficient. Prospective and comparative studies with larger patient samples for different indications and access routes are warranted for evaluation of this system.

The current case series included a limited number of patients and indications and was retrospective. While a strength of this approach is the ability to understand how the Puncture Cube performs in a limited clinical context, further studies with larger numbers of patients that are ideally prospective and comparing the Cube Navigation System to the free-hand method are necessary and planned for the future.