Advice

Evidence review

Evidence review

Clinical and technical evidence

Regulatory bodies

There were 3 incidents identified in the US Food and Drug Administration (FDA) database: Manufacturer and User Device Facility Experience (MAUDE). None of the incidents resulted in any patient harm. In the first, which occurred in March 2012, the tip of the device broke off during drilling and could not be retrieved from the patient's pedicle. In the other 2 cases the device malfunctioned before the procedure was started. These events were in July 2009 and August 2010.

A search of the Medicines and Healthcare Products Regulatory Agency (MHRA) website revealed no manufacturer Field Safety Notices or Medical Device Alerts for this device.

Clinical evidence

Five studies on the PediGuard were identified, of which 1 in vitro study was excluded from further consideration.

The evidence comprises 2 randomised controlled trials, 1 non‑randomised controlled trial and a retrospective controlled study.

Randomised controlled trials

A study set in China by Bai et al. (2013) compared the PediGuard with a standard pedicle probe. The trial enrolled 42 people with adolescent idiopathic scoliosis, 20 of whom had the PediGuard and 22 of whom were considered a control group having a standard probe. In total, 694 screws were inserted: 362 in the PediGuard group and 332 in the control group. A statistically significant reduction in the number and duration of fluoroscopy shots was observed in the PediGuard group. The accuracy of screw placement also improved in the PediGuard group, with statistically significant improvement seen for screws inserted in the upper, middle and lower thoracic regions, but no statistical significance in the lower lumbar region. The time taken to place each screw showed a statistically significant reduction. A summary of these results is reported in tables 2 and 4.

Chaput et al. (2012) conducted a USA‑based study funded by the manufacturer of the PediGuard. The study compared pedicle screw placement using the PediGuard with a standard manual drilling method. A total of 78 screws were inserted in 18 people with a degenerative lumbar spine who were scheduled for posterior lumbar fusion. A single surgeon, who had prior PediGuard training on cadavers, used fluoroscopy guidance to place pedicle screws. Postoperative CT scans were used to assess pedicle perforation. The study demonstrated a 30% reduction in the number of fluoroscopy shots when using the PediGuard compared with standard manual drilling. There was no difference in the accuracy of pedicle screw placement using either technique, with each recording a single breach. A summary of these results is reported in tables 3 and 4.

Non-randomised controlled trials

Bolger et al. (2007) conducted a study to assess the PediGuard's ability to detect pedicle perforations. The study involved 9 centres and 11 surgeons in 5 European countries. It enrolled 97 people and involved the insertion of 571 pedicle screws. The study had 2 phases: phase 1 compared the diagnostic accuracy of the PediGuard with other detection methods (that were dependent upon the individual centre's protocol). Pedicle perforations were confirmed by postoperative CT. Phase 2 compared the diagnostic accuracy of the PediGuard with postoperative CT only. Overall, the study demonstrated that the PediGuard has a high level of diagnostic accuracy. A summary of these results is reported in table 5.

Retrospective controlled study

Ovadia et al. (2011) conducted a single‑centre study based in Israel. The authors compared the accuracy of pedicle screw placement by a single surgeon in children with scoliosis, who were split into 2 groups: in the first group, 1270 screws were inserted using a standard manual drilling method. In the second group, 1400 screws were inserted using the PediGuard. Neuromonitoring was performed to assess screw placement. Using the PediGuard statistically significantly reduced the number of clinically relevant malpositioned pedicle screws, measured by the number of neuromonitoring alarms. A summary of these results is reported in table 6.

Table 2 Overview of the Bai et al. (2013) randomised controlled trial

Study component

Description

Objectives/hypotheses

To compare the accuracy and time needed for pedicle screw placement between the PediGuard and the traditional free‑hand pedicle finder in thoracic and lumbar spine.

Study design

Randomised controlled trial.

Setting

A centre in China, no recruitment period specified. Patients followed‑up at 1 week for post‑operative CT.

Inclusion/exclusion criteria

Inclusion:

  • AIS diagnosis, Lenke type 1‑V1

  • Spinal curve between 40–80º

Exclusion:

  • Non‑AIS patients

  • Spinal curve >80º

  • Body weight >80 kg

Primary outcomes

Primary:

  • Time needed to place a pedicle screw

  • Number of intraoperative fluoroscopy shots needed

  • Position of pedicle screw using CT imaging (1 week post‑operation):

    • grade 0 (no apparent violation of the pedicle)

    • grade 1 (<2 mm perforation of the pedicle, with 1 screw thread out of the pedicle)

    • grade 2 (between 2 mm and 4 mm of perforation of the pedicle, with half of the diameter of the screw outside of the pedicle)

    • grade 3 (>4 mm or complete perforation of the pedicle)

  • Rate of pedicle perforation (based upon graded system)

Secondary:

  • Inter‑observer and intra‑observer variability (50 CT scans evaluated at an 8‑week interval by 2 independent assessors)

Statistical methods

Descriptive statistics were used to present data in the form of mean and ranges. T‑test was used to compare time needed for pedicle screw placement and number of fluoroscopy shots. Pearson χ‑squared test was used to compare rates of pedicle perforation. Kappa agreement was used to assess inter‑ and intra‑observer reliability.

Significance level was not stated.

Participants

A total of 42 patients: Lenke type I=18; Lenke type II=8; Lenke type III=6; Lenke type IV=2; Lenke type V=4; and Lenke type VI=4.

Mean age=15±6.52 SD years (range, 10–18 years; median, 16 years).

Mean Cobb angle=55.3±7 SD (range, 45–78º), mean number of segments instrumented was 9±3 (range, 6–14).

ECD group: 20 patients; mean age=16.2±4.5 SD (range, 11–18 years); 4 male and 16 female; 362 pedicle screws placed.

NPF group: 22 patients; mean age=15.5±5.6 SD (range, 10–18 years); 5 male and 17 female; 332 pedicle screws placed.

Results

Average screw placement time reduced significantly in the ECD group (204±33 SD [range, 65–255 seconds]) compared with the NPF group (241± 61 SD [range, 72–367 seconds]), p=0.009.

The average number of fluoroscopy shots per case was significantly reduced in the ECD group (1.20±0.52 SD) compared with the NPF group (1.59±0.67 SD), p=0.040.

Screw perforation rates were significantly reduced in the ECD group (15/362=4.1%) compared with the NPF group (47/332=14.2%), p=0.001.

The number of screws successfully placed inside the pedicle (Grade 0) for the ECD group was 347/362 (95.9%) compared with 285/332 (85.8%) for the NPF group.

The number of screws fully inside the pedicle + screw perforating <2 mm (Grade 0+Grade 1) for the ECD group was 354/362(97.8%) compared with 292/332 (88%) for the NPF group.

Inter‑ (k=0.85) and intra‑observer (k=0.83) variability showed a good rate of agreement.

Conclusions

Using the PediGuard increases pedicle screw accuracy and reduces placement time and radiation in posterior AIS.

Abbreviations: AIS, adolescent idiopathic scoliosis; CT, computed tomography; SD, standard deviation; ECD, electronic conductivity device (PediGuard); NPF, normal pedicle finder.

Table 3 Overview of the Chaput et al. (2012) randomised controlled trial

Study component

Description

Objectives/hypotheses

To report the results of using the PediGuard to reduce radiation exposure while preparing the pilot hole for pedicle screw placement.

Study design

Randomised controlled trial.

Setting

USA‑based centre; no recruitment period specified.

Patients were followed‑up at discharge or their first outpatient follow‑up visit.

Inclusion/exclusion criteria

Inclusion: people diagnosed with a degenerative lumbar spine having a posterior spinal fusion.

No exclusion criteria were specified.

Primary outcomes

Primary:

  • Breach rate for either technique, as defined by ≥2 mm of screw encroaching into the epidural space.

  • The number of intraoperative fluoroscopy shots required with each technique.

Statistical methods

Descriptive statistics were used to present data in the form of mean, ranges, SD and percentages. Fisher's exact test was used to compare breach rates between the techniques. The ANOVA test was used to compare the number of fluoroscopy shots between the techniques.

Significance level was not stated.

Participants

18 patients; mean age= 55±12 SD years.

Two groups with a total of 78 screws inserted; PediGuard, n=39 screws inserted and standard, n=39 screws inserted.

Results

One breach was recorded in each group. There was no significant difference in breach rate between the 2 groups (97.5% for each group), p=1.000.

The total number of fluoroscopy shots in the PediGuard group was 202, compared with 293 used in the standard group (30% reduction).

A significant difference was demonstrated in the mean number of fluoroscopy shots: PediGuard=5.2 (range, 0–15 and 3.30 SD) compared with standard=7.5 (range, 2–17 and 3.60 SD), p<0.0001.

Conclusions

The use of the PediGuard reduced the number of fluoroscopy shots by 30% compared with a standard drilling probe and this reduction of radiation occurred while maintaining a 97.5% accurate, safe screw placement.

Abbreviations: ANOVA, analysis of variance; n, number; SD, standard deviation.

Table 4 Summary of the randomised controlled trials

PediGuard

Standard manual insertion

Analysis

Bai et al. (2013)

Design

Randomised

n=362

n=332

Efficacy

n=362

n=332

Primary outcome: number of pedicle breaches

15/362 (4.1%)

47/332 (14.2%)

p=0.001

Selected secondary outcomes

Time needed to insert a pedicle screw

Mean 204±33 SD (range, 65–255) seconds

Mean 241± 61 SD (range, 72–367) seconds

p=0.009

Number of fluoroscopy shots needed per screw

Mean 1.20±0.52 SD

Mean 1.59±0.67 SD

p=0.040

Safety

n=42

n=42

Patients reporting serious adverse events

Not reported

Not reported

Neurovascular involvement

0

0

Revision surgery

0

0

Chaput et al. (2012)

Design

Randomised

n=39

n=39

Efficacy

n=39

n=39

Primary outcome: number of fluoroscopy shots needed using each technique

Median 5.2±3.30 SD (range, 0–15)

Median 7.5±3.60 SD (range, 2–17)

p<0.0001

Selected secondary outcomes

Successful pedicle screw insertion (or <2mm breach)

38/39

38/39

p=1.000

Unsuccessful pedicle screw insertion, ≥2mm breach

1/39

1/39

Safety

n=18

n=18

Patients reporting serious adverse events

Not reported

Not reported

Neurological deficit following surgery

0

0

Radiculopathy following surgery

0

0

Abbreviations: SD, standard deviation.

Table 5 Overview of the Bolger et al. (2007) study

Study component

Description

Objectives/hypotheses

To assess the diagnostic accuracy of the PediGuard in detecting pedicle perforation in comparison with other standard methods.

Study design

Multicentre, prospective, biphasic study.

Setting

Five European centres.

Recruitment was between September 2002 and September 2004.

No follow‑up period was reported.

Inclusion/exclusion criteria

No inclusion or exclusion criteria were reported.

Primary outcomes

Primary:

  • The ability of the device to detect pedicle breaches against other available methods of detection.

Phase 1:

  • Pedicle screws placed using PediGuard in addition to the surgeon's usual method of guidance (for example: tactile feel, mechanical probing, fluoroscopy, CT scans, EMG, SEEP, computer assisted navigation; depending on their availability in each centre).

  • Post‑operative CT was to assess accuracy.

Phase 2:

  • Pedicle screws placed using the PediGuard only.

  • Post‑operative CT was to assess accuracy.

Statistical methods

Data were presented as actual values and percentages.

Significance level was not stated.

Participants

97 patients in 9 centres.

521 pedicle screws were placed in total; phase 1=147 and phase 2=374.

No further patient characteristics were reported.

Results

Phase 1 (147 pedicle screws inserted):

  • 23/147 (16%) confirmed breaches on postoperative CT scanning.

  • 10/23 (43%) breaches detected by the surgeon's own method.

  • 22/23 (96%) breaches detected by the PediGuard.

  • 1 false‑negative result using the PediGuard (99% negative predictive value).

  • 1 false‑positive result using the PediGuard (96% positive predictive value).

  • 96% specificity.

  • 99% sensitivity.

Phase 2 (374 pedicle screws inserted):

  • 41/374 (11%) confirmed breaches on postoperative CT scanning.

  • 41/41 (100%) breaches detected by the PediGuard.

  • 3 false‑positive results using the PediGuard (93% positive predictive value).

  • 0 false‑negative results using the PediGuard.

  • 100% specificity.

  • 99% sensitivity.

  • 41 (11%) confirmed breaches on postoperative CT scanning.

Conclusions

This device offers a simple, safe and sensitive method of detecting pedicle breach during routine drilling of the pedicle.

Abbreviations; CT, computed tomography; EMG, electromyography; SEEP, somatosensory evoked potentials.

Table 6 Overview of the Ovadia et al. (2011) retrospective, controlled clinical study

Study component

Description

Objectives/hypotheses

To evaluate the contribution of an ECD (PediGuard) to the safety of thoracic and lumbar pedicle screw placement in a large group of people with scoliosis, of diverse aetiologies.

Study design

Retrospective, controlled clinical study.

Setting

Single centre based in Israel.

This study recruited patients between 2003 and 2009.

No follow‑up period was reported.

Inclusion/exclusion criteria

Inclusion:

  • Scoliosis diagnosis

  • Received spinal deformity correction surgery

No exclusion criteria were reported.

Primary outcomes

The number of clinically relevant malpositioned pedicle screws, measured by intra‑operative neuromonitoring.

Statistical methods

Descriptive statistics were used to present data in the form of mean and SD. Fisher's exact test was used to compare the rate of abnormal neuromonitoring events within each group. The statistical comparison used the number of screws as the unit of analysis.

Significance level was not stated.

Participants

A total of 248 people with scoliosis were studied in the following groups:

Group 1: pedicle screws inserted with standard manual hand drilling n=150.

97 women (64.7%) and 53 men (35.3%); mean age 13.68±3.8 SD years.

23 congenital scoliosis (15.6%); 80 idiopathic scoliosis (53.1%); 47 other(31.3%); preoperative Cobb angle, 73.3±21.3°SD; postoperative Cobb angle, 29.2±13.2°SD; Cobb angle correction, 60.2%.

Group 2: pedicle screws inserted with the use of ECD (PediGuard) n=98.

73 women (74.5%) and 25 men (25.5%); mean age, 14.35±2.9 SD years.

10 congenital scoliosis (10.2%); 61 idiopathic scoliosis (62.2%); 27 other (27.6%); preoperative Cobb angle, 69.8±16.2°SD; postoperative Cobb angle, 24±9.7°SD; Cobb angle correction, 65.6%.

The 2 study groups were matched by age, sex, scoliosis aetiology, Cobb angle, and surgical criteria.

Results

Group 1 had a total of 1270 pedicle screws, mean number of screws/procedure=8.5.

Group 2 had a total of 1400 pedicle screws, mean number of screws/procedure=14.

A significant reduction in number of neuromonitoring alarms was demonstrated using the PediGuard.

Group 2: 3 procedures (3%) compared with Group 1: 10 procedures (6.6%) where the PediGuard was not used (p=0.048).

Nine of the 13 monitoring alarms (69%) were associated with implantation adjacent to the apex of the spinal curve.

Conclusions

The use of an ECD significantly reduced the incidence of clinically relevant malpositioned screws in a variety of scoliosis patients, thereby increasing the safety of pedicle screw implantation.

Abbreviations: ECD, electronic conductivity device; SD, standard deviation.

Recent and ongoing studies

One ongoing clinical trial has been identified relating to the PediGuard:

  • NCT00549627: Evaluation of the PediGuard for Pedicle Screw Insertion. Patient recruitment was suspended in February 2009.

The manufacturer has stated that it will be starting a prospective randomised trial using the cannulated PediGuard in 2015. Also, the manufacturer indicated that a prospective, randomized trial set in Brazil completed in early 2015. This study investigated the use of the PediGuard in people with diminished bone mineral density.

Costs and resource consequences

Approximately 11,350 finished consultant episodes were reported in the Hospital Episodes Statistics 2012–13 (HSCIC 2013) for spinal surgery involving fusion or instrumentation (V36–V46, V66). According to the manufacturer, since its introduction the PediGuard has been used in 35,000 procedures worldwide and is currently being used at 3 NHS centres.

Use of the PediGuard would not require any changes in the way that current services are organised or delivered. No other additional facilities or technologies are needed alongside the technology.

No published evidence on resource consequences of the PediGuard was identified in the systematic review of evidence.

Strengths and limitations of the evidence

Of the 2 randomised controlled trials, only Chaput et al. (2012) reported their randomisation method. This was done by alternating between the 2 methods of drilling pedicle pilot holes. The use of an intrapatient randomisation scheme ensures that all confounding factors are equally distributed in both groups. It is unclear how the randomisation methods may have influenced the outcomes of Bai et al. (2013). Additionally, although Ovadia et al. (2011) was a retrospective controlled trial, the 2 study groups were matched by a number of factors including: age, sex, scoliosis aetiology, Cobb angle and surgical criteria. Matching ensures that the 2 groups are as homogenous as is practicable. This limits the impact of confounding factors on the results and, therefore, reduces selection bias.

None of the included studies reported a sample size calculation. Consequently it is unclear if the studies were adequately powered to detect any differences in the primary and secondary outcomes.

The operators could not be blinded to the intervention and control groups in either of the randomised controlled trials. Although this may introduce performance bias, this limitation is common in studies involving medical devices.

In surgical procedures, another source of potential performance bias is the surgeon's training to use the device, and the duration of the learning curve associated with the procedure. Only Chaput et al. (2012) stated that cadaveric training was undertaken by the sole user in this study who also had previous experience with using the PediGuard in previous clinical cases. In addition, Ovadia et al. (2011) reported that the surgeon involved with the study was an experienced senior spine specialist. None of the other studies reported whether the investigators had undergone prior training with the device, nor did they report the investigators' level of prior experience.

Although 3 studies reported the PediGuard's effect on pedicle perforations, there was variability in the grading system each used. Bai et al. (2013) used a 4‑grade system, while Chaput et al. (2012) used a 2‑grade system to assess pedicle perforations. However, in both studies the same definition of perforation was used, with up to 2 mm of screw perforating the vertebral cortex considered as acceptable. Bolger et al. (2007) did not report on their definition of pedicle perforation or how it was measured. Furthermore, the authors state that 'other methods of detection' were used as a comparison to the PediGuard. It may be difficult to directly compare outcomes from phase 1 of the study by Bolger et al. (2007) if many unspecified methods of detection were used.

The number of fluoroscopy shots, as recorded by both Bai et al. (2013) and Chaput et al. (2012), is an objective measurement but it is not a direct measure of radiation exposure. A more appropriate outcome measure may have been the effective dose (measured in Sieverts).

Although 3 types of the PediGuard exist, each of which is available in various sizes, none of the studies states which PediGuard tool was used and the reasons for its selection.

The study by Chaput et al. (2013) was funded by the manufacturer and the lead author of Bolger et al. (2007) is listed by SpineGuard as an original co‑inventor of the PediGuard. This has the potential for introducing bias in the reporting of outcomes.