Interventional procedure overview of minimally invasive fusionless posterior-approach surgery to correct idiopathic scoliosis in children and young people
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Evidence summary
Population and studies description
This interventional procedures overview is based on 90 patients from 2 retrospective case series (Floman 2020, Floman 2015), 1 retrospective cohort study (Floman 2021), and 1 prospective cohort study (Stadhouder 2021). There was some patient overlap between studies. This is a rapid review of the literature, and a flow chart of the complete selection process is shown in figure 1. This overview presents 4 studies as the key evidence in table 2 and table 3, and lists 2 other relevant studies in table 5.
The 4 studies included patients from Israel and the Netherlands. The recruitment period ranged from 2015 to 2021. Studies had a mean follow up between 2 to 3 years. Table 2 presents study details.
Study no. | First author, date country | Patients (male: female) | Age | Study design | Inclusion criteria | Intervention | Follow up |
|---|---|---|---|---|---|---|---|
1 | Floman Y 2020, Israel (multicentre study 2015 to 2016) | 22 (3:19) | 13 to 17 years | Retrospective case series (phase 3 design of the device) | Single AIS structural curve between 40° to 60°. Curve flexibility 30° or more. Risser grades 2 or above. Lenke type 1 or type 5 curves up to 60° that reduce on lateral bending views to 30° or less and kyphosis of 50° or less. | Posterior dynamic deformity correction (PDDC) device (ApiFix- MID-C system) PDDC surgery spanning 5-6 disc spaces. | Minimum 2-year follow-up (range 2 to 3 years). |
2 | Floman Y 2021 Israel (2015 to 2018) | 45 (4:41) | 11 to 17 years | Retrospective cohort study (multicentre, phase III design of the device) | Risser grades 0 to 5, with minimum 2-years of follow-up. indications for surgery: 40° to 60° curves, reduced on lateral bending views to 35° or less with kyphosis not exceeding 55°. Non-compliant braced patients or patients with Lenke 5 curves with Cobb angles 35° or above. | PDDC device (ApiFix- MID-C system) 35 with Lenke type 1 curves 10 Lenke type 5 curves. | Average 2.3 years follow-up (range 2 to 4 years) |
3 | Floman Y 2015, Israel | 3 (0:3) | 13 to 16 years | Case series | Preoperative thoracic curve of 43° to 53° Age 13 to 16 years Risser 1 to 4 | PDDC device (ApiFix- MID-C system) | 6 months to 2 years |
4 | Stadhouder A 2021, the Netherlands | 20 (1:19) | 12 to 17 years | Prospective cohort study (single centre, phase II design of the device) | Diagnosis of AIS Age 12 to 17 years Risser 1 to 4 Single structural curve (Lenke type 1 or 5) Major Cobb angle of 40° to 55° Reduction of the major curve to less than 35° on a supine lateral bending radiograph Apical vertebral rotation of less than 15° (Bunnell scoliometer) | PDDC device (ApiFix- MID-C system) phase 2 design FDA approved device Procedure done by single surgeon. Amount of distraction to achieve curve correction was based on surgeon assessment and was not standardised. Lenke type 1 (n=14) Type 5 (n=6) Risser stage mean 2.5 Vertebral spanning mean 5.1 | Mean 3.4 ±1.0 years Minimum 2 years. |
5 | FDA Submission Summary of Safety and Probable Benefit (SSPB) Template (fda.gov) August-December 2019 | Total: 252 Target population: 25 patients implanted with the HDE device version. Extended target population n=49 patients - combination of the target population (n=25) and patients (n=24) with 40 to 44 degree curves. | Target population: Mean age: 15.0 ±1.7 Range: 13 to 19 years | Retrospective analysis of studies outside US. Prospective, multi-centre, non-randomised open label clinical study (n=20) and additional data from other studies: post-market clinical studies (n=26), commercial use (n=197), special access (n=9). | Lenke type 1 or 5 curves Risser grade 2 or above Preoperative Cobb angle between 40 and 60° Flexible major curve – defined as lateral bending correction to 30 degrees or less. Thoracic kyphosis less than 55° | PDDC - MID-C system (phase I-III without extender component and phase IV with extender component) Older versions of the device were used in some procedures. | Up to 24 months |
Procedure technique
All studies were phase II and phase III design studies and used the first version of the device which is not currently in use. The company informed that the IFU has been updated with revised patient selection criteria and updated surgical technique.
Efficacy
Curve correction or improvement in curve
In a prospective cohort study of 20 patients with AIS who were treated with minimally invasive deformity correction without fusion, the device failed in 10 patients.In the remaining 10 patients with the implant in-situ the Cobb angles statistically significantly reduced at follow-up (mean major curve reduced from baseline 45.4° to 31.4° at 2 weeks and 31.4° at the time of the latest follow-up, p<0.001; mean minor curve from baseline 31.3° to 26.1 at 2 weeks and 24.2° at the time of the latest follow-up p=0.03; Stadhouder 2021).
A retrospective case series of 22 patients AIS curves (with a single curve between 40° and 60°, Risser grades 2 or above, 13 with Lenke type 1 curves and 9 with type 5 curves) who had minimally invasive deformity correction without fusion (spanning 5-6 disc levels) reported that curve correction was achieved at 2 to 3 years follow-up. The mean major curve significantly improved from 47° (range 40 to 55°) preoperatively to 25° (46% correction, p<0.05) at 2-year follow up. A satisfactory result (defined as the mean final Cobb angle of the major curve 30° or less at final follow-up) was achieved in 82% (18/22) of patients. The mean minor curve also significantly reduced from 27° to 17° (average 35% correction, p<0.05). The trunk shift was corrected by 1.5 cm (range 0.4 to 4.3 cm) (Floman 2020).
A retrospective cohort study of 45 patients with moderate AIS treated with minimally invasive deformity correction without fusion who had a minimum 2-year follow up reported that the major Cobb angle, of either Lenke type 1 or 5 curve reduced from baseline and was similar among the 3 groups in varying skeletal maturity stages at final follow-up (Risser 0 to 1 stage group from 47.6° to 26.4°; Risser 2 to 3 from 46° to 20.4°; and Risser 4 to 5 from 41.5°to 26.2° respectively) (Floman 2021).
The FDA clinical evaluation reported that the probable benefit (defined as Cobb angle less than or equal to 35 degrees and no curve progression at 12 and 24 months compared to baseline) in the target population (n=25) was 75% (9/12). Probable benefit success rate of 85% (22/26) at 12 months and 90% (18/20) at 24 months was reported in the extended target group. Mean major curve correction at 24 months (n=8) was 28° (range 19 to 37°) compared to baseline (mean 49°, range 45 to 59°) in the target population. The mean improvement was 43% (range 20 to 58%) (FDA 2019).
Change in kyphotic or lordotic curves
The prospective cohort study of 20 patients with AIS who were treated with minimally invasive deformity correction without fusion reported that in the 10 patients with implant in-situ no statistically significant changes were observed from baseline at latest follow-up in lumbar lordosis (baseline 17.6° to 22.5°, p=0.987), thoracic kyphosis (55.4° to 55.4°, p=0.183) and in the scoliometer rotation measures (10.3 to 8.8, p=0.100) (Stadhouder 2021).
In the retrospective case series of 22 patients with AIS who had minimally invasive deformity correction without fusion, at 2 to 3 years follow-up, for patients with Lenke type 1 patterns, the mean 2D thoracic kyphosis statistically significantly increased from 24° preoperatively to 27° (p<0.05). For patients with Lenke type 5 curves, the mean lumbar lordosis statistically significantly reduced from 47° preoperatively to 42° at final follow-up (p<0.05) (Floman 2020).
The retrospective cohort study of 45 patients with moderate AIS treated with minimally invasive deformity correction without fusion who had a minimum 2-year follow up reported that thoracic kyphosis increased on average by 7° in the Lenke 1 curves while lumbar lordosis decreased by 4° in the Lenke 5 curves at 2-year follow up (Floman 2021).
Coronal plane wedging of the apical vertebra
The retrospective cohort study of 45 patients with moderate AIS treated with minimally invasive deformity correction without fusion who had a minimum 2-year follow up reported that preoperative coronal plane wedging of the apical vertebra was reduced after surgery in the overall cohort (from 7.4° to 5.7°, p<0.05). A subgroup analysis among the 3 groups in varying skeletal maturity stages at final follow-up showed a significant reduction in vertebral wedging (Risser 0 to 1 stage group [n=16] reduced from 9.5° to 5.4°; Risser 2 to 3 group [n=15] reduced from 7.7° to 7.0°; and Risser 4 to 5 group [n=14] reduced from 4.8° to 4.7° respectively) (Floman 2021).
Patient reported outcome measures
The prospective cohort study of 20 patients reported that in the 10 patients with the implant in-situ, the mean preoperative SRS-22 questionnaire score improved statistically significantly at 2-year follow up (from 2.6 ± 0.4 at baseline to 4.3 ± 0.4, p<0.0001). Scores for all individual domains (pain, function, self-image, mental health and satisfaction with management also changed statistically significantly (p<0.001) (Stadhouder 2021).
In the retrospective case series of 22 patients, the mean preoperative SRS-22 questionnaire score improved statistically significantly at 2-year follow up (from 2.74 ± 0.3 at baseline to 4.31 ± 0.4, p<0.0001). Also, the mean preoperative self-image score change was statistically significant (3.14 ± 0.39 versus 4.03 ± 0.41), but it did not meet the MICD of 0.98. Scores for other domains (pain, activity, and mental health) did not change significantly. Patient satisfaction assessed by a questionnaire (score range 1 to 5) showed high satisfaction scores for general satisfaction with the procedure (4.8 out of 5), the fact they would they choose the procedure again (4.8/ out of 5), and they would recommend it to a friend (4.8 out of 5) (Floman 2020).
In the FDA submission, the prospective study of 20 patients reported consistent improvement across SRS-22 questionnaire scores from baseline up to 2 years for all 5 domains (intensity of pain, self-image, function or activity, mental health, and satisfaction from treatment). FDA data also indicated overall patient satisfaction on an unvalidated survey of 18 patients. (FDA submission 2019).
Safety
Revision surgery and device failure
In the prospective case series of 20 patients, 11 adverse events needing revision or removal of the device were reported in 50% (10/20) of patients at an average 21 months after surgery. High complication rates led to the premature termination of this study.
Osteolysis of 1 of the pedicle screws was reported in 6 cases. Revision was done in 3 and the device was removed in 4 (including 1 who had a revision).
Device failure (breakage of the pedicle screw in 1, failure of the ratchet mechanism in 1 and breakage of a screw and the device in 1). The implant was removed in 1 patient and posterior fusion was done in 2 patients.
Pain without abnormal radiographic findings (n=2); the implant was removed in 1 at the patient's request.
Culture specimens were obtained during 9 revision procedures, 6 of which were positive for Cutibacterium acnes (formerly known as Proprionibacterium acnes).
Macroscopic and microscopic metal particles were observed in all patients who had revision, around the ratchet and ball-and-socket joints. (Stadhouder 2021).
Revision surgery was done in 18% (4/22) of patients because of nut loosening (n=2), pedicle screw backup (n=1), and device ratchet malfunction (n=1) in the retrospective case series of 22 patients. Nut loosening occurred in 2 patients in the early postoperative period and this was attributed to insufficient torque while tightening the nuts. Rachet malfunction occurred 3 years after surgery. The implant was removed in this patient but was retained in the remaining 3 patients. (Floman 2020).
Revision surgery was done in 9% (4/45) of patients because of nut loosening (n=1), pedicle screw misplacement (n=1), device rachet malfunction (n=1) and partial screw pull-out (n=1) in the retrospective cohort study of 45 patients. Re-instrumentation with the implant was done in 3 patients and conversion to VBT was done in 1 patient (Floman 2021).
The FDA submission reported that the overall reoperation rate was 18% (45/252) for all patients and 12% for both the target population (3/25) and expanded target population (6/49) with preoperative curve 40° to 60°. The mean postoperative timepoint of reoperation was 13 months. Reoperation reasons include: nut loosening (n=5), misplaced screws or migration (n=9), insufficient curve correction (n=8), screw pull-out (n=5), infection (n=8), screw fracture (n=1), rod fracture (n=2) screw dislocation from rod (n=2), unexpected rod movement (n=1), pain (n=1), additional device distraction (n=1), extender misalignment (n=1) and unspecified device failure (n=1). (FDA submission 2019).
Anecdotal and theoretical adverse events
Expert advice was sought from consultants who have been nominated or ratified by their professional Society or Royal College. They were asked if they knew of any other adverse events for this procedure that they had heard about (anecdotal), which were not reported in the literature. They were also asked if they thought there were other adverse events that might possibly occur, even if they have never happened (theoretical).
They listed no anecdotal adverse events or theoretical adverse events.
Three professional expert questionnaire for this procedure were submitted. Find full details of what the professional experts said about the procedure in the specialist advice questionnaires for this procedure.
Validity and generalisability
Authors of the Floman papers made substantial contribution to design of the device.
Different versions of the ApiFix device (phase 2 and 3 design without the extender component) were used in the studies. There are no published studies with the current version of the device (phase IV MID-C System with an Extender component).
Recruitment to the Stadhouder prospective study was terminated early due to high failure rates, so the analysis was based on a small cohort.
Stadhouter 2021 suggests that the identified curve reduction occurs shortly after the treatment. Further study of the device's benefit throughout its deployment would be beneficial. The presence of metal debris at revision may indicate possible wear debris problems.
Amount of distraction to achieve curve correction is based on surgeon assessment and was not standardised.
Sample sizes were relatively small across papers and the analyses did not include any patients from the UK.
Although some variation was observed, similar inclusion criteria were present across studies which are pertinent to this indication.
Most studies had a mean follow-up between 2 to 3 years so there is a need for long-term outcomes.
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