Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 https://doi.org/10.1186/s10195‑022‑00669‑0 SYSTEMATIC REVIEW Efficacy and safety of robotic spine surgery: systematic review and meta‑analysis Setefilla Luengo‑Matos1 , Luis María Sánchez‑Gómez1,2 , Ana Isabel Hijas‑Gómez1 , Esther Elena García‑Carpintero1,4* , Rafael Ballesteros‑Massó3 and Mar Polo‑deSantos1,2 Abstract Background: Robotic surgery (RS) may offer benefits compared with freehand/conventional surgery (FS) in the treat‑ ment of patients with spinal disease. The aim of this study was to evaluate the efficacy and safety of RS versus FS in spinal fusion. Methods: A systematic review and meta‑analysis was performed. Data analysis and risk of bias assessment were analysed using REVMAN V5.3. Results: We found 11 randomised clinical trials involving 817 patients (FS: 408, RS: 409). The main diagnosis was degenerative spine disease. SpineAssist, Renaissance (Mazor Robotics), Tianji Robot and TiRobot robots (TINAVI Medi‑ cal Technologies) were used. Pedicle screw placement within the safety zone (grades A + B according to the Gertz‑ bein and Robbins scale) ranged from 93% to 100% in FS versus 85–100% in RS (relative risk 1.01, 95% CI 1.00–1.03, p = 0.14). Regarding intervention time, the meta‑analysis showed a mean difference (MD) of 6.45 min (95% CI −13.59 to 26.49, p = 0.53). Mean hospital stay was MD of −0.36 days (95% CI −1.03 to 0.31, p = 0.30) with no differences between groups. Contradictory results were found regarding fluoroscopy time, although there seems to be a lower radiation dose in RS versus FS (p < 0.05). Regarding safety, the studies included surgical revision frequency. Conclusions: No conclusive results were found suggesting that there are benefits in using RS over FS for spinal fusion. Further research with adequate patient selection, robot type and quality‑of‑life variables is needed. Level of evidence: level 1. Keywords: Spine, Robotic surgery, Pedicle, Systematic review © The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. Introduction Spinal diseases are a major public health problem. They involve different processes of various aetiologies, although the most frequent are degenerative, closely linked to the ageing of the population [1]. The most seri- ous cases are associated with an increase in chronic- ity, deterioration in quality of life and reduction in the patient’s autonomy [2]. Their cost to the health system is high and has been rising in recent years [3]. The treatment of spinal diseases usually begins with a conservative approach aimed at the management of symptoms [1]. However, it is sometimes not effective, and these patients are candidates for surgical treatment [4]. The most common procedure is arthrodesis or spi- nal fusion. It consists of creating a bone bridge between two or more adjacent vertebrae by implanting bone tis- sue grafts or bone substitutes between the vertebrae to be fused [5]. The most commonly used instruments for fixation are pedicle screws and bars which, by stabilising the vertebral segments, facilitate the formation of bone tissue between these vertebral segments forming a solid mass [1]. Open Access Journal of Orthopaedics and Traumatology *Correspondence: esther.carpintero@cchs.csic.es 1 Health Technology Assessment Agency (Agencia de Evaluación de Tecnologías Sanitarias, AETS), Carlos III Institute of Health, Madrid, Spain Full list of author information is available at the end of the article Page 2 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 The traditional way of placing pedicle screws is by means of the “freehand technique”, conventional or manual (FS). The technique uses local anatomical ref- erences to identify the entrance to the pedicles and achieves good accuracy in screw placement [6]. On occasion, re-intervention is necessary owing to com- plications arising from malposition of the screws [7]. To improve the accuracy of screw insertion, new surgi- cal assistance devices have been incorporated such as fluoroscopy, navigation systems with intra-operative 3D fluoroscopy or, more recently, robots [6, 8, 9]. In general, robot-guided surgical procedures, prior to the operation, consist of of a computed tomography (CT) scan that allows for three-dimensional recon- struction, vertebra by vertebra, to assist in planning. The information from the CT scan is transferred to the robot in the operating room, which is fixed to the patient’s spine, allowing anatomical relationships and precision to be maintained at all times. It is the robot, moving along the vertebrae, that guides the approach for accurate and reliable implant placement [10]. The fundamental measure of efficacy to assess the outcome of the surgical procedure is the precision of the placement of the pedicle screws. The most com- monly used scale is the Gertzbein and Robbins scale, which classifies screw position into five grades, where the highest precision corresponds to grade A and the lowest precision corresponds to grade E [11]. In addition to the possible benefits of robotic surgery (RS) in terms of precision in the placement of pedicle screws, possible positive effects have been described in relation to surgical time, hospital stay or complica- tions [12]. However, some studies show non-conclusive results in favour of RS, and it is not clear whether the use of the robot would justify its incorporation into clinical practice, given its high acquisition and mainte- nance costs [3, 13]. The aim of this systematic review is to analyse the efficacy and safety of RS treatment versus conventional FS in the placement of screws in patients undergoing spinal surgery. Methods We performed a systematic review in accordance with PRISMA guidelines [14], with the methods of the anal- yses and inclusion criteria being specified in advance and documented in a protocol. We searched Med- Line, EMBASE, Cochrane Library and other databases of health technology assessment agencies. The search period was until April 2019, and was updated until April 2021. A manual review of the bibliographic references of the documents found was also carried out. The search strategy did not include restrictions on study size. The selection of relevant studies was based on the Population–Intervention–Comparator–Outcome-Study Design (PICOS) criteria (Table  1). Studies in English, French and Spanish were included. Studies that failed to meet the PICOS criteria or provide assessable data related to the selected outcome measures were excluded. Similarly, we excluded studies that were duplicated or outdated by subsequent studies by the same institution. The identification, selection, review, data extraction and assessment of the evidence of studies was carried out by two independent reviewers, with any discrepancies being resolved by consensus, and a third reviewer being consulted in case of disagreement. Tables were prepared detailing the studies included and excluded in the review, justifying the cause of exclusion (available to the reader). Meta-analyses were carried out in relation to the accu- racy of the placement of the pedicle screws, the duration of the intervention, and the hospital stay in FS and RS, using the random effects model to take into account the heterogeneity among the studies. The degree of heteroge- neity was assessed using graphic and statistical methods (χ2 statistic and I2 inconsistency index). Relative risk (RR) and mean difference (MD) were used as relative measures of effect and presented graphically in the corresponding forest plots, with their 95% CIs. A funnel plot was used to assess the presence of publication bias, interpreting a symmetrical inverted V-shaped graph as a demonstration that there is probably no publication bias. Data analysis was carried out using REVMAN V5.3 [15], which uses the Cochrane risk of bias assessment tool for RCTs [16]. We used the GRADE methodology to assess the quality of the evidence [17]. Table 1 Inclusion criteria according to the PICOS scheme Population Patients of any age and sex with any pathology of the spine Intervention Robot‑assisted surgery for the placement of pedicle screws in spinal operations Comparator Any other type of surgery for the placement of pedicle screws in spine surgery Outcomes Any measure related to the efficacy and safety of the use of the robot. Studies assessing economic, organisational, ethical, legal or implementation aspects of the technology were also included Study design Randomised controlled trials (RCTs), SRs and/or meta‑analyses, HTA reports, Clinical Practice Guidelines Page 3 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 Similarly, an internal quality assessment was performed using the checklist developed within the framework of the Spanish Network of Health Technologies Assess- ments Agencies (RedETS), and an external review by a specialist in Orthopaedic Surgery. Results Our electronic search identified 118 articles. After screening the title/abstracts, we retrieved the full text of 30 references, of which 21 were excluded. We included nine studies that analysed spinal arthrodesis with FS versus RS [13, 18–25]. Two of the included studies cor- respond to the same trial [22, 24]; the second study [24] provided additional data on the quality of life of patients 1 year after the intervention. The update of the literature search identified two further studies [26, 27] (Fig. 1 Study flow diagram). Trials were published between 2013 and 2020. The trials were performed in Germany [18, 19], China [13, 20, 23, 25–27] and Korea [21, 22, 24]. One trial declared that they received industry help (equipment loan) [22, 24], while the other trials received no funding. Participants A total of 817 participants were analysed, 408 undergo- ing FS and 409 with RS. The mean age ranged from 49 to 67.9 years (FS: 49.5–67.9 years; RS: 49–67.6 years). In five studies, the percentage of female patients operated on, in both FS and RS, was higher (FS: 51.3–73.3%; RS: 52.2– 70.0%) [13, 18, 21, 25, 27], while in four other studies no differences were observed or the percentage was slightly lower [19, 20, 22, 23]. The main diagnosis was degenera- tive spine disease in most studies, and two studies also included traumatic pathology [13, 23] (Table 2). Fig. 1 Study flow diagram Page 4 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 Surgical characteristics In both FS and RS, the most common surgical approach was the posterior approach [13, 21, 22, 25]. The total number of screws placed, including pedicle screws and other cervical screws, ranged from 22 to 584 in FS and from 23 to 532 in RS. Only one study included the average number of pedicle screws used per operation with a mean of 4.7 screws in FS versus 4.3 in RS [21]. Another study specified the diameter of the screws (6.5 and 5.5  mm) [22]. The single segment (two adjacent Table 2 Summary of patient characteristics BMI body mass index, SD standard deviation * Median Patients (N) Age (years) (mean ± SD) Sex n (%) BMI (kg/m2) (mean ± SD) Diagnosis Symptom length (months) (mean ± SD) Women Men Ringel [18] Freehand 30 67* 18 (66.0) 12 (40.0) 28* Indication for lumbosacral stabilisa‑ tion – Robot 30 68* 16 (53.3) 14 (46.4) 26* Roser [19] Freehand 10 – – – Degenerative lumbar instability – Robot 18 – – – Hyun [21] Freehand 30 66.8 ± 8.9 22 (73.3) 8 (26.7) 25.8 ± 3.3 Degenerative lumbar disorder – Robot 30 66.5 ± 8.1 21 (70.0) 9 (30.0) 24.7 ± 2.6 Kim [22] Freehand 41 66.0 ± 8.6 19 (46.3) 22 (53.7) 25.3 Lumbar spinal stenosis 13.1 ± 8.2 Robot 37 65.4 ± 10.4 18 (48.6) 19 (51.4) 25.9 12.5 ± 9.3 Tian [20] Freehand 17 – – – – – – Robot 23 – – – – Wang [23] Freehand 15 43* 7 (46.7) 8 (53.3) – Polytrauma – Robot 15 36* 5 (33.3) 10 (66.7) – Feng [25] Freehand 40 67.9 ± 7.3 27 (67.5) 13 (32.5) 25.6 ± 3.5 Degenerative disk disease: 19 Degenerative spondylolisthesis: 12 Spondilolytic listhesis: 5 Degenerative scoliosis: 4 – Robot 40 67.6 ± 6.5 28 (70.0) 12 (30.0) 25.0 ± 4.5 Degenerative disk disease: 20 Degenerative spondylolisthesis: 10 Spondilolytic listhesis: 7 Degenerative scoliosis: 3 Han [13] Freehand 119 56.1 ± 13.4 61 (51.3) 58 (48.7) 24.9 ± 2.9 Degenerative pathology: 84 Traumatic pathology: 35 – Robot 115 54.6 ± 11.3 60 (52.2) 55 (47.8) 25.7 ± 4.1 Degenerative pathology: 74 Traumatic pathology: 41 Fan [26] Freehand 66 49.5 (39,59) 27 (40.9) 39(59.1) 24.47 ± 3.94 – Robot 61 49 (34.5,57.5) 18 (29.5) 43(70.5) 23.65 ± 4.10 – Feng [27] Freehand 40 64.22 ± 6.19 25(62.5) 15(37.5) – Lumbar spinal stenosis: 21 Degenerative spondylolisthesis: 14 Lumbar instability: 5 Robot 40 63.45 ± 4.56 24(60) 16(40) – Lumbar spinal stenosis: 19 Degenerative spondylolisthesis: 18 Lumbar instability: 3 Page 5 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 vertebrae) was the most common arthrodesis in both FS and RS [19, 21–23]. The most frequent level of arthro- desis was lumbar [13, 18, 19, 21, 22, 25, 27]. The robots used were the SpineAssist Surgical Guidance Robot [18, 19] and the Renaissance Surgical Guidance Robot [21, 22] from Mazor Robotics; the TiRoboT [13, 20, 23, 25, 27] and Tianji Robot, only in the cervical region, from TINAVI Medical Technologies [26] (Table 3). Risk of bias in included studies Random sequence generation, allocation conceal- ment, blinding of participants and personnel, blinding of outcome assessment and others were judged as at an unclear/high risk of bias in most of studies. Incomplete outcome data and selective reporting were judged as at a low risk of reporting bias (Fig. 2 Risk of bias included studies). No publication bias was identified. Certainly of evidence The certainty of the evidence has been rated as low or very low owing to the high risk of bias observed in the studies and the high heterogeneity observed with I2 val- ues ranging between 34% and 93% (Table  4). For some outcomes, the quality of evidence has been downgraded for imprecision due to the small size of the samples analysed. Effects of intervention The main efficacy and operation-related outcomes are listed in Table  4; the other outcomes and the quality of evidence can be found in the supplementary material (Additional file 1). Precision of pedicle screw placement was evaluated using the Gertzbein and Robbins scale [11] in most of the studies [13, 18–22, 25–27] and according to the criteria of Gras et al. [28] in one study [23]. Accord- ing to the Gertzbein and Robbins scale, the maximum precision (grade A) was obtained in 68.0–98.3% of the screws placed by FS and in 56.0–98.6% by RS. The meta- analysis of nine studies [13, 18–22, 25–27] did not show superiority of RS over FS (RR 1.06, 95% CI 1.01–1.07, p = 0.02, I2 = 87%). Accuracy of pedicle screw placement within the safety zone (grades A + B) was 93.0–100% in FS and 85.0–100% in RS, with no statistically significant difference between RS and FS (RR 1.01, 95% CI 1.00–1.03, p = 0.14). Only Ringel et  al. [18] described favourable results for RS versus FS. There was marked heterogene- ity among these nine studies, and a randomised method was used (I2 = 81%; p < 0.00001) (Fig.  3 Results of meta- analysis). According to the criteria of Gras et al. [28], the accuracy in screw placement was “excellent” in 72.7% of the cases with FS and in 100% with RS [23]. Only two studies evaluated the screw mean distance from the proximal facet, ranging from 2.7 ± 1.6  mm to 4.6 ± 0.6  mm in FS and 5.2 ± 2.1 to 5.8 ± 1.7  mm in RS (p < 0.01) [18, 19]. Four studies reported that the most common deviation was lateral (70.6% in FS and 34.2% in RS) [18, 20–22]. Additionally, four studies described intra-operative blood loss as a secondary outcome, with a variability between 254.7 and 165 ml for RS and 356.2 and 217 ml for FS [13, 25–27]. The use of RS was characterised by a lower radiation dose required in the intervention compared with FS, according to the findings of four studies [13, 19, 21, 25]. Other secondary outcomes included intervention- related times. Among them, the mean total fluoroscopy time did not differ significantly between FS and RS in the two studies that analysed this outcome [13, 19]. The mean operating time ranged from 118.2 to 230.6 min for FS and from 138.9 to 208.5  min for RS (MD 6.45  min, 95% CI −13.59 to 26.49, p = 0.53), with a high heteroge- neity among the studies (I2 = 74%). Pedicle screw place- ment time ranged from 27.8 ± 87.0 to 32.3 ± 10.5  min in the FS group versus 27.6 ± 8.6 min to 35.2 ± 11.3 min in the RS group [19, 25]. The mean and median plan- ning time required in RS was 20 ± 5.3 min [19] and 7.8– 24 min, respectively [18, 23]. According to the results of four studies [13, 18, 21, 25], the average time spent in hospital ranged from 5.0 to 9.4  days in FS and from 4.8 to 7.0  days in RS (MD −0.36  days, 95% CI −1.03–0.31, p = 0.30). There was moderate heterogeneity between studies (I2 = 62%; p = 0.07), with only one study showing statistically sig- nificant differences with a shorter time spent in hospital in the RS group [21]. Four studies incorporated clinical results after a fol- low-up period ranging from 6.0 to 16.3 months on aver- age [21, 22, 24, 27]. Improvements in both low back and lower limb pain measured with the EVA scale, quality of life measured with the SF-36, and disability measured with the Oswestry Disability Index (ODI) were described in both the FS and the RS groups, with significant differ- ences between RS and FS in the ODI index alone in one study [24]. Security Eight studies collected information on the need for surgi- cal revision to assess screw placement [13, 18, 20–23, 25, 26]. The number of surgical revisions ranged from 0 to 2 in FS and from 0 to 10 in RS; one of the studies described a significantly lower number of surgical revisions in the FS group than in the RS group (1 revision in 152 screws versus 10 in 146 screws; p < 0.05) [18]. No study reported on technical failures of the procedure or cases of death. Two studies described other adverse events, such as wound infection [26, 27], although no difference in infec- tions rates between groups was observed. Other adverse Page 6 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 Table 3 Surgery characteristics a Number of patients b Number of pedicle screws c These data include all types of cervical screw: number of lateral mass screws, 117 (69 for freehand and 48 for robot procedure); number of odontoid screws, 38 (21 for freehand and 17 for robot); number of Magerl screws, 60 (25 for freehand and 35 for robot); number of pedicle screws, 175 (89 for freehand and 86 for robot) Approach Decompression Total pedicle screws (n) Fusion level (percentage of patients) Vertebral level Robot One segment n (%) Two segment n (%) Ringel [18] Freehand – If needed 152 14 (46, 7)a 16 (53, 3)a L2: 8 L3: 30 L4: 52 L5: 52 S1: 10 – Robot If needed 146 17 (56, 7)a 13 (43, 3)a L2: 8 L3: 24 L4: 50 L5: 48 S1: 16 SpineAssist Roser [19] Freehand Posterolateral Yes 40 10 (100)a – Lumbar – Robot – – 72 18 (100)a – Lumbar SpineAssist Hyun [21] Freehand Posterior – 140 20 (66, 7)a 10 (33, 3)a Lumbar – Robot Posterior If needed 130 25 (83, 3)a 5 (16, 7)a Lumbar Renaissance Kim [22] Freehand Posterior Yes 172 37 (90, 2)a 4 (9, 8)a L2–3: 2 – Robot Posterior Yes 158 32 (86, 5)a 5 (13, 5)a L2–3: 3 Renaissance Tian [20] Freehand – – 88 – – – – Robot – – 102 – – – TiRobot Wang [23] Freehand – – 22 22 (100)b 0 S1: 13 S2: 9 – Robot – – 23 19 (82, 6)b 4 (17, 4)b S1: 13 S2: 10 TiRobot Feng [25] Freehand Posterior If needed 225 – – L2: 18 L3: 49 L4: 78 L5: 80 – Robot Posterior If needed 202 – – L2: 18 L3: 48 L4: 80 L5: 64 TiRobot Han [13] Freehand Posterior If needed 584 – – Thoracic and lumbar – Robot Posterior – 532 – – Thoracic and lumbar TiRobot Fan [26] Freehand – If needed 204c – – Cervical Tianji Robot Robot – If needed 186c – – Cervical Feng [27] Freehand Posterior – 174 – – Lumbar TiRobot Robot – – 170 – – Lumbar Page 7 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 events were three cases of post-operative cerebrospinal fluid fistula headache, one case of vertebral artery injury without symptom and one case of weakness in the left hip flexor in the FS group [26, 27]. Other outcomes of interest No studies on cost or cost-effectiveness were found. One study described that the price of the Renaissance system, including hardware and installation cost, was $550,000 in 2018, not including disposables and implants (about $1500 per case); in addition, the system’s maintenance costs should be considered [2]. No studies assessed organisational, ethical, legal or implementation aspects of the technology. Discussion The present study aims to determine the efficacy and safety of RS versus FS in spinal fusion. Eleven clini- cal trials that respond to the objective of our research were analysed. We found that in both FS and RS the socio-demographic characteristics of the patients were similar. The most common surgical approach was poste- rior, the most frequent arthrodesis was monosegmentary and the most frequent location was at the lumbar level. We have not found sufficient information on whether the cases operated on with RS were minimally invasive or open surgery. The robot seemed to benefit minimally invasive surgery by guiding the surgeon to the precise location without the need for anatomical visualisation [21, 29]. In cases in which open surgery with visualisation of the surgical field is required, the robot would provide fewer advantages [29]. The robots used are essentially two: first and second generation from Mazor Robotics ([18, 19, 21, 22] and TiRobot [13, 20, 23, 25, 27]. However, there are other dif- ferent types of robots on the market, and the technologi- cal development of these devices is evolving rapidly. It is expected that the new generations of robots are designed to have fewer limitations and greater ease of use [3, 19, 29]. Selecting the type of robot is important since the Fig. 2 Risk of bias in included studies Page 8 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 results can vary according to the type of robot used or the system of navigation chosen [3]. Precision in the placement of the pedicle screws is described as the fundamental goal to achieve in spinal fusion surgery [8]. To measure precision, the Gertzbein and Robbins scale is used [11], although the studies did not detail how the information was collected. Maximum precision (grade A) or the placement of pedicle screws within the safety zone (grades A + B) was achieved in a high percentage of cases in both FS and RS. The results of the meta-analysis show a result slightly in favour of FS. However, the studies show great heterogeneity, so these results should be treated with caution. Some problems concerning lack of precision in RS were attributed to the system of fixation of the robot to the patient’s spine [18]. The literature has shown contradictory results regard- ing accuracy of RS. There are studies that observe a clear superiority of RS over FS [30, 31], while others observe no differences between groups [32, 33]. However, a high heterogeneity is also noted between studies. In addition to accuracy, the studies analysed other vari- ables related to screw placement, such as distance of the screw to the articular facet, screw deflection at the entry point and at the exit point, and invasion of the articular surface. The information collected in the studies was het- erogeneous and limited, and it was not possible to ade- quately evaluate the results. Other important outcomes included intra-operative blood loss, and radiation and fluoroscopy dose and time. Blood loss was higher in the FS group than in the RS group, although data were limited. This may be attrib- uted to the fact that open FS usually involves greater soft tissue trauma with consequent blood loss, while RS is usually minimally invasive [21]. In cases where RS is performed openly, blood loss is also greater than in cases where a minimally invasive procedure is used [13]. In relation to radiation dose, understood as the cumu- lative fluoroscopy dose required for screw insertion [21], most studies showed that the dose was higher in the FS group than in the RS group, although the units of meas- urement used were different between studies. In the case of FS, the surgeon may continuously adjust the position of the screws during the procedure, resulting in a higher radiation exposure than occurs in minimally invasive SR. Owing to the associated radiation risk to the operating room staff and to the patient [13, 29], the lower radia- tion exposure is considered a relevant factor in favour of RS [21]. Regarding fluoroscopy time, the results are not clearly in favour of one or the other type of intervention, since the data are scarce. Nor was it possible to evaluate whether fluoroscopy time is decreased with repeated use of the robot [6]. We found that most of the studies analysed the relation- ship between the type of intervention and intervention time, and hospital stay. The meta-analysis did not show a significant difference in operating time between groups. For some authors, the screw placement time could be reduced with the help of the robot, and this represented Table 4 Main findings of studies included in meta‑analysis MD mean difference, RR risk ratio a Assessed with: Gertzbein and Robbins scale b Measurements were made in different units: µSv, mSv and mGy Patient (studies) Surgical events (events/total) Risk ratio/mean difference (95% CI) Overall certainty of evidence Freehand Robot Accuracy of pedicle screw placementa Grade A (maximum accuracy) 3477 (9 RCTs) 1515/1779 1566/1698 RR 1.06 (1.01–1.11) p = 0.02 (I2 = 87%) Very low Grades A + B, safety zone 3477 (9 RCTs) 1706/1779 1665/1698 RR 1.06 (1.01–1.11) p = 0.14 (I2 = 81%) Very low Proximal facet violation 1716 (3 RCTs) 26/896 0/820 RR 0.07 (0.01–0.40) p = 0.003 (I2 = 0% Low Intra‑operative blood loss (ml) 394 (3 RCTs) 199 195 MD −68.12 (−109.24 to 27.01) p = 0.001 (I2 = 34)% Very low Radiation dose (standard mean difference)b 402 (4 RCTs) 203 199 MD −1.31 (−2.02 to −0.60) p = 0.0003 (I2 = 87%) Very low Fluoroscopic time (min) 262 (2 RCTS) 50 58 MD −3.00 (−28.01 to 22.00) p = 0.81 (I2 = 93%) Very low Total screw placement time (min) 108 (2 RCTs) 50 58 MD 0.84 (−10.93 to 12.61) p = 0.89 (I2 = 89%) Very low Operating time (min) 492 (5 RCTs) 247 245 MD 6.45 (−13.59 to 26.49) p = 0.53 (I2 = 74%) Low Length of hospital stay (days) 374 (3 RCTs) 189 185 MD −0.36 (−1.03 to 0.31) p = 0.30 (I2 = 62%) Very low Page 9 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 Fig. 3 Results of meta‑analysis Page 10 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 a quarter of the total intervention time [12, 25]. The data found in the studies were insufficient to draw a conclu- sion in this regard. On the other hand, the mean hospital stay was similar in both intervention groups, despite the fact that the minimally invasive approach of SR would be expected to favour a shorter duration of hospitalisation [21]. Other efficacy outcomes, such as the ODI estimate, showed a superior improvement in the index after SR compared with after FS. On the other hand, the evalu- ation of efficacy indicators in relation to disability or quality of life was limited. We consider that, taking into account that arthrodesis essentially seeks to improve patients’ quality of life, the collection and analysis of these types of variables should be strengthened in future studies [4]. In relation to the safety of the technology, the studies reported the number of surgical revisions that had to be performed to assess the adequate placement of the screws, with similar results in both intervention groups, with no information on associated deaths. Only two stud- ies reported on adverse events, which included mainly wound infections and post-operative cerebrospinal fluid fistula headache, without significant difference between groups. However, it would be necessary to establish a procedure for maintaining the sterility of the robots [26]. Although the robot may provide advantages, it would not replace the surgeon’s knowledge of the surgical anatomy and ability to handle unforeseen events during the opera- tion [29]. In assessing the results of this study, it is relevant to point out the importance of the learning curve in SR. The number of interventions required for the proper use of the first generation of the Mazor robot was estimated at 25, although new generations of robots may require a shorter learning time [29]. The two studies included that evaluated the learning curve showed contradictory results [18, 21]. It is essential that interventions be per- formed by experienced professionals [6]. We should keep in mind that our study focuses on the results of spinal fusion with FS versus SR. However, there are other surgical assistance procedures that have shown good results in terms of accuracy and safety [8]. One of the studies included in our review incorporated navigator-guided surgery in addition to FS and SR in the comparative analysis [19]. The study, which analysed nine patients, found similar screw placement accuracy results in the three intervention groups. Additionally, a retro- spective study comparing SR with new generations of robots versus navigator-guided surgery with 3D tomog- raphy revealed that both procedures are safe and accu- rate. However, the robot required shorter fluoroscopy time, shorter screw placement time and shorter hospital stay. The authors stated that the results should be verified in future studies [12]. From an economic point of view, we have not found any studies on the cost of the technology or the profit- ability of the procedure. However, the price of the robot is high, with a high acquisition and maintenance cost [3]. Some authors argue that it may be time and resource consuming [19], although others suggest that the intro- duction of the technology could be reasonable in first- world healthcare systems [2]. One way to improve the cost-effectiveness of the robot would be to increase its indications. In this sense, some types of robots such as the TiRobot can be used in different anatomical loca- tions, both in open surgery and in minimally invasive surgery, which could provide advantages [13]. We found no information regarding other organisational, ethical, legal or implementation aspects. However, some of the outcome variables collected in relation to efficacy, such as time of surgery or radiation dose required, may be related to these aspects. We would like to point out the limitations of this study. The results may change depending on the search strat- egy chosen and the inclusion and exclusion criteria con- sidered. Several sources of heterogeneity were observed among the studies, including the main cause of diag- nosis, the type and use of the robot, and the outcomes analysed. On the other hand, first-generation robots and second-generation robots, analysed by the included stud- ies, did not have integrated navigation and independent instrument navigation. Recent spine robots have a fully integrated navigation platform, allowing for real-time instrument tracking and pedicle screw placement with- out guidewires [34]. The data collected varied across studies; sometimes, the data were scarce and sometimes the units of measurement were different, so it is not pos- sible to properly assess these findings. In addition, the risk of bias was difficult to define in most of the studies. Bias assessment reported using funnel plots should be interpreted with caution, since the number of studies was not sufficient according to the recommendations (ten or more included studies). Nevertheless, a comprehensive and systematic search of multiple databases and informa- tion sources was performed to reduce the potential for publication bias. It is important to emphasise that progress is currently being made in the development of robots, with the aim of improving existing limitations, facilitating their use and achieving maximum benefits in terms of precision and safety [29]. The use of robotic assistance in spinal inter- ventions is particularly relevant, as precision is crucial and the device can be adapted to limited surgical access. In this regard, new generations of cervical spine robots have been specifically designed to enable percutaneous Page 11 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 interventions in the area with promising results [19]. Only one included study analysed the efficacy and safety of cervical spine robots, showing outcomes superior to those of FS [26], with screw deviation < 1  mm, which is considered to be the optimal expected accuracy for a sur- gical navigation system [35]. On the other hand, the devi- ation observed in this study is lower than that observed in other studies [13, 20, 26]. Ideally, and contributing to improving its efficacy, the extension of the use of robotic assistance to other types of interventions, and not exclu- sively for the spine, should be considered. The aim would be to assist different procedures, providing a common benefit between different surgical disciplines [19]. Conclusion The present study found no significant differences between FS and RS with respect to the primary outcome, accuracy of pedicle screw placement. It was not pos- sible to adequately assess the results of other variables related to screw placement, such as distance of screws to the articular facet, screw deviation or invasion of the articular surface, as data are still scarce and the method of data collection differed from one study to another. No clear results were found in favour of one or the other type of intervention in terms of safety, total operative time, pedicle screw placement time or hospital stay. Surgical intervention time was shorter in the FS group than in the RS group, although the data are limited and the results should be interpreted with caution. Information on cumulative fluoroscopy dose required for screw insertion and fluoroscopy time was equally scarce. The studies showed heterogeneity in the patients oper- ated on, in the type and use of the robot, and in the results evaluated, and are not free of possible biases. It is essential to perform new studies with an adequate selection of patients, type of robot, and comparator, including additional clinical and quality-of-life variables. Supplementary Information The online version contains supplementary material available at https:// doi. org/ 10. 1186/ s10195‑ 022‑ 00669‑0. Additional file 1. Table GRADE‑Summary of findings. Author contributions S.L.M. has contributed to the design, selection of studies, analysis, report writing and manuscript review. L.M.S.G. has contributed to the design and manuscript review. A.I.H.G. has contributed to analysis, report writing and manuscript review. E.E.G.C. has contributed to information retrieval, report writing and manuscript review. R.B.‑M. has contributed to report writing and manuscript review. M.P.‑S. has contributed to the design, selection of studies, analysis, report writing and manuscript review. All authors read and approved the final manuscript. Funding This research received no specific grant from any funding agency, commercial or not‑for‑profit sectors. Availability of data and materials Data available in supplementary material. Declarations Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors have no conflicts of interest to declare that are relevant to the content of this article. Author details 1 Health Technology Assessment Agency (Agencia de Evaluación de Tec‑ nologías Sanitarias, AETS), Carlos III Institute of Health, Madrid, Spain. 2 Research Network on Chronicity, Primary Care and Health Promotion (RICAPPS), Madrid, Spain. 3 Servicio de Traumatología, Hospital Quirónsalud Sur, Alcorcón, Spain. 4 Consejo Superior de Investigaciones Científicas, Madrid, Spain. Received: 21 June 2021 Accepted: 24 September 2022 References 1. Australian Safety and Efficacy Register of New Interventional Procedures‑ Surgical (ASERNIP‑S). SpineAssist miniature robotic positioning device. Camberra, Australia; 2010. 2. Fiani B, Quadri SA, Farooqui M, Cathel A, Berman B, Noel J et al (2018) Impact of robot‑assisted spine surgery on health care quality and neuro‑ surgical economics: a systemic review. Neurosurg Rev. https:// doi. org/ 10. 1007/ s10143‑ 018‑ 0971‑z 3. Siccoli A, Klukowska AM, Schröder ML, Staartjes VE (2019) A systematic review and meta‑analysis of perioperative parameters in robot‑guided, navigated, and freehand thoracolumbar pedicle screw instrumentation. World Neurosurg. https:// doi. org/ 10. 1016/j. wneu. 2019. 03. 196 4. Martinez Férez IM, Molina Linde JM, Villegas Portero R (2009) Estándares de uso adecuado de la artrodesis vertebral. Agencia de Evaluación de Tecnologías Sanitarias de Andalucía, Sevilla 5. Ballesteros Massó R, Gómez Barrena E, Bonsfills García N, González Diaz R, García Lázaro FJ, Moreno Martínez J et al (2012) Artrodesis. Columna toracolumbar. Marban, Madrid 6. Ghasem A, Sharma A, Greif DN, Alam M, Maaieh MA (2018) The arrival of robotics in spine surgery: a review of the literature. Spine 43(23):1670–7 7. Fuster S, Vega A, Barrios G, Urdaneta I, Ojeda O, Macchia M et al (2010) Fiabilidad del navegador en la colocación de tornillos pediculares tora‑ columbares. Neurocirugía 21:306–311 8. Kochanski RB, Lombardi JM, Laratta JL, Lehman RA, O’Toole JE (2019) Image‑guided navigation and robotics in spine surgery. Neurosurgery 84(6):1179–1189 9. Pescador D, Rendón D, Blanco J, González R, Martín J, Cano‑Gala C et al (2016) Navegación O‑arm en cirugía vertebral para casos complejos. Acta Ortop Mex 30:100–104 10. Salud Digital https:// www. consa lud. es/ salud igital/. Accessed 11 June 2021 11. Gertzbein SD, Robbins SE (1990) Accuracy of pedicular screw placement in vivo. Spine 15(1):11–4 12. Khan A, Meyers JE, Yavorek S, O’Connor TE, Siasios I, Mullin JP et al (2019) Comparing next‑generation robotic technology with 3‑dimensional computed tomography navigation technology for the insertion of poste‑ rior pedicle screws. World Neurosurg 123:e474–e481 13. Han X, Tian W, Liu Y, Liu B, He D, Sun Y et al (2019) Safety and accuracy of robot‑assisted versus fluoroscopy‑assisted pedicle screw insertion in Page 12 of 12Luengo‑Matos et al. Journal of Orthopaedics and Traumatology (2022) 23:49 thoracolumbar spinal surgery: a prospective randomized controlled trial. J Neurosurg Spine 30(5):615–622 14. Moher D, Liberati A, Tetzlaff J, Altman DG (2009) Preferred reporting items for systematic reviews and meta‑analyses: the PRISMA statement. PLoS Med 6(7):e1000097 15. The Cochrane Collaboration. Review Manager (RevMan)[computer program]. Version 5.4. 2020. 16. Higgins JPT, Altman DG, Gøtzsche PC, Jüni P, Moher D, Oxman AD et al (2011) The Cochrane Collaboration’s tool for assessing risk of bias in randomised trials. BMJ 343:d5928 17. Atkins D, Best D, Briss PA, Eccles M, Falck‑Ytter Y, Flottorp S et al (2004) Grading quality of evidence and strength of recommendations. BMJ 328(7454):1490 18. Ringel F, Stuer C, Reinke A, Preuss A, Behr M, Auer F et al (2012) Accuracy of robot‑assisted placement of lumbar and sacral pedicle screws: a prospective randomized comparison to conventional freehand screw implantation. Spine 37(8):E496‑501 19. Roser F, Tatagiba M, Maier G (2013) Spinal robotics: current applications and future perspectives. Neurosurgery 72(Suppl 1):12–18 20. Tian W (2016) Robot‑assisted posterior C1–2 transarticular screw fixation for atlantoaxial instability: a case report. Spine 41(19):B2–B5 21. Hyun SJ, Kim KJ, Jahng TA, Kim HJ (2017) Minimally invasive robotic ver‑ sus open fluoroscopic‑guided spinal instrumented fusions: a randomized controlled trial. Spine 42(6):353–358 22. Kim HJ, Jung WI, Chang BS, Lee CK, Kang KT, Yeom JS (2017) A prospec‑ tive, randomized, controlled trial of robot‑assisted vs freehand pedicle screw fixation in spine surgery. Int J Med Robot. 13(3):e1779 23. Wang J‑Q, Wang Y, Feng Y, Han W, Su Y‑G, Liu W‑Y et al (2017) Percutane‑ ous sacroiliac screw placement: a prospective randomized comparison of robot‑assisted navigation procedures with a conventional technique. Chin Med J (Engl) 130(21):2527–2534 24. Kim HJ, Kang KT, Chun HJ, Hwang JS, Chang BS, Lee CK et al (2018) Comparative study of 1‑year clinical and radiological outcomes using robot‑assisted pedicle screw fixation and freehand technique in posterior lumbar interbody fusion: a prospective, randomized controlled trial. Int J Med Robot 14(4):e1917 25. Feng S, Tian W, Sun Y, Liu Y, Wei Y (2019) Effect of robot‑assisted surgery on lumbar pedicle screw internal fixation in patients with osteoporosis. World Neurosurg 125:e1057–e1062 26. Fan M, Liu Y, He D, Han X, Zhao J, Duan F et al (2020) Improved accuracy of cervical spinal surgery with robot‑assisted screw insertion: a prospec‑ tive, randomized controlled study. Spine 45(5):285–291 27. Feng S, Tian W, Wei Y (2020) Clinical effects of oblique lateral interbody fusion by conventional open versus percutaneous robot‑assisted mini‑ mally invasive pedicle screw placement in elderly patients. Orthop Surg 12(1):86–93 28. Gras F, Marintschev I, Wilharm A, Klos K, Mückley T, Hofmann GO (2010) 2D‑fluoroscopic navigated percutaneous screw fixation of pelvic ring injuries—a case series. BMC Musculoskelet Disord 11:153 29. Molliqaj G, Schatlo B, Alaid A, Solomiichuk V, Rohde V, Schaller K et al (2017) Accuracy of robot‑guided versus freehand fluoroscopy‑assisted pedicle screw insertion in thoracolumbar spinal surgery. Neurosurg Focus 42(5):E14 30. Fatima N, Massaad E, Hadzipasic M, Shankar GM, Shin JH (2021) Safety and accuracy of robot‑assisted placement of pedicle screws compared to conventional free‑hand technique: a systematic review and meta‑analy‑ sis. Spine J 21(2):181–192 31. Xu ZJ, Han PF, Wu ZZ, Zhao B, Wang YF (2020) Robot‑assisted and fluoroscopy‑guided pedicle screw placement: a meta‑analysis. Chin J Tissue Eng Res 24(18):2932–2938 32. Li W, Li G, Chen W, Cong L (2020) The safety and accuracy of robot‑ assisted pedicle screw internal fixation for spine disease: a meta‑analysis. Bone Jt Res 9(10):653–666 33. Peng YN, Tsai LC, Hsu HC, Kao CH (2020) Accuracy of robot‑assisted versus conventional freehand pedicle screw placement in spine surgery: a systematic review and meta‑analysis of randomized controlled trials. Ann Transl Med 8(13):824 34. Alluri RK, Avrumova F, Sivaganesan A, Vaishnav AS, Lebl DR, Qureshi SA (2021) Overview of robotic technology in spine surgery. HSS J 17(3):308–316 35. Phillips R (2007) The accuracy of surgical navigation for orthopaedic surgery. Curr Orthop 21(3):180–192 Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in pub‑ lished maps and institutional affiliations.