Aims. The aim of this retrospective study was to compare the correction achieved using a convex pedicle screw technique and a low implant density achieved using periapical concave-sided screws and a high implant density. We hypothesized that there would be no difference in outcome between the two techniques. Methods. We retrospectively analyzed a series of 51 patients with a thoracic adolescent idiopathic scoliosis. There were 26 patients in the convex pedicle screw group who had screws implanted periapically (Group 2) and a control group of 25 patients with bilateral pedicle screws (Group 1). The patients’ charts were reviewed and pre- and postoperative radiographs evaluated. Postoperative patient-reported outcome measures (PROMs) were recorded. Results. The number of implants (14.5 vs 17.1) and the implant density (1.5 vs 1.9) were significantly lower in Group 2 (p < 0.001). Operating time was 27 minutes shorter in Group 2 than in Group 1, with a mean of 217 minutes (SD 50.5; 120 to 346). The duration of surgery per instrumented vertebra was reduced by 19% in Group 2 (p = 0.011). No statistical difference was found in the postoperative Cobb angle, vertebral rotation, the relative correction achieved, or postoperative PROMs. Conclusion. Despite a lower implant density and achieving correction through a convex rod, surgical correction of the Cobb angle and vertebral body rotation was similar in both groups. Periapical pedicle screws and primary correction on the concave side do not seem to be mandatory in order to achieve good surgical results in idiopathic thoracic scoliosis. The operating time was shorter in the group with lower implant density. In conclusion, the technique provided good results and has the potential to reduce complications and costs. Cite this article: Bone Joint J 2021;103-B(3):536–541

Aims. The aim of this study was to compare the peak pull-out force (PPF) of pedicle-lengthening screws (PLS) and traditional pedicle screws (TPS) using instant and cyclic fatigue testing. Materials and Methods. A total of 60 lumbar vertebrae were divided into six groups: PLS submitted to instant pull-out and fatigue-resistance testing (groups A1 and A2, respectively), TPS submitted to instant pull-out and fatigue-resistance testing (groups B1 and B2, respectively) and PLS augmented with 2 ml polymethylmethacrylate, submitted to instant pull-out and fatigue-resistance testing (groups C1 and C2, respectively). The PPF and normalized PPF (PPFn) for bone mineral density (BMD) were compared within and between all groups. Results. In all groups, BMD was significantly correlated with PPF (r = 0.83, p < 0.001). The PPFn in A1 was significantly less than in B1 (p = 0.006) and C1 (p = 0.002). The PPFn of A2 was significantly less than in B2 (p < 0.001) and C2 (p < 0.001). The PPFn in A1, B1, and C1 was significantly greater than in A2 (p = 0.002), B2 (p = 0.027), and C2 (p = 0.003). There were no significant differences in PPFn between B1 and C1, or between B2 and C2. Conclusion. Pedicle lengthening screws with cement augmentation can provide the same fixation stability as traditional pedicle screws and may be a viable clinical option. Cite this article: Bone Joint J 2018;100-B:516–21

In patients with osteoporosis there is always a strong possibility that pedicle screws will loosen. This makes it difficult to select the appropriate osteoporotic patient for a spinal fusion. The purpose of this study was to determine the correlation between bone mineral density (BMD) and the magnitude of torque required to insert a pedicle screw. To accomplish this, 181 patients with degenerative disease of the lumbar spine were studied prospectively. Each underwent dual-energy x-ray absorptiometry (DEXA) and intra-operative measurement of the torque required to insert each pedicle screw. The levels of torque generated in patients with osteoporosis and osteopenia were significantly lower than those achieved in normal patients. Positive correlations were observed between BMD and T-value at the instrumented lumbar vertebrae, mean BMD and mean T-value of the lumbar vertebrae, and mean BMD and mean T-value of the proximal femur. The predictive torque (Nm) generated during pedicle screw insertion was [-0.127 + 1.62 × (BMD at the corresponding lumbar vertebrae)], as measured by linear regression analysis. The positive correlation between BMD and the maximum torque required to insert a pedicle screw suggests that pre-operative assessment of BMD may be useful in determining the ultimate strength of fixation of a device, as well as the number of levels that need to be fixed with pedicle screws in patients who are suspected of having osteoporosis

We reviewed 212 consecutive patients with adolescent idiopathic scoliosis who underwent posterior spinal arthrodesis using all pedicle screw instrumentation in terms of clinical, radiological and Scoliosis Research Society (SRS)-22 outcomes. In Group 1 (51 patients), the correction was performed over two rods using bilateral segmental pedicle screws. In Group 2 (161 patients), the correction was performed over one rod using unilateral segmental pedicle screws with the second. rod providing stability of the construct through two-level screw fixation at proximal and distal ends. The mean age at surgery was 14.8 years in both groups. Comparison between groups showed no significant differences with regard to age and Risser grade at surgery, pre- and post-operative scoliosis angle, coronal Cobb correction, length of hospital stay and SRS scores. Correction of upper thoracic curves was significantly better in Group 1 (p = 0.02). Increased surgical time and intra-operative blood loss was recorded in Group 1 (p < 0.001 and p = 0.04, respectively). The implant cost was reduced by mean 35% in Group 2 due to the lesser number of pedicle screws. Unilateral and bilateral pedicle screw techniques have both achieved excellent deformity correction in adolescent patients with idiopathic scoliosis, which was maintained at two-year follow-up. This has been associated with high patient satisfaction and low complication rates

Aims. The aim of this study was to evaluate whether, after correction of an adolescent idiopathic scoliosis (AIS), leaving out the subfascial drain gives results that are no worse than using a drain in terms of total blood loss, drop in haemoglobin level, and opioid consumption. Methods. Adolescents (aged between 10 and 21 years) with an idiopathic scoliosis (major curve ≥ 45°) were eligible for inclusion in this randomized controlled noninferiority trial (n = 125). A total of 90 adolescents who had undergone segmental pedicle screw instrumentation were randomized into no-drain or drain groups at the time of wound closure using the sealed envelope technique (1:1). The primary outcome was a drop in the haemoglobin level during first three postoperative days. Secondary outcomes were 48-hour postoperative oxycodone consumption and surgical complications. Results. All 90 patients were included in the primary outcome analysis (no drain = 43; drain = 47). The mean total postoperative blood loss (intraoperative and drain output) was significantly higher in the group with a subfascial drain than in the no-drain group (1,008 ml (SD 520) vs 631 ml (SD 518); p < 0.001). The drop in haemoglobin level did not differ between the study groups over the postoperative timepoints (p = 0.290). The 48-hour opioid consumption was significantly higher in the no-drain group (2.0 mg/kg (SD 0.9) vs 1.4 (SD 0.6); p = 0.005). Two patients in the no-drain and one patient in the drain group developed a surgical site infection. Conclusion. Leaving the subfascial drain out after pedicle screw instrumentation for AIS is not associated with higher postoperative haemoglobin levels. Patients treated without a subfascial drain needed 30% more opioids during the first 48 hours than those who had a drain. Cite this article: Bone Joint J 2022;104-B(9):1067–1072

We compared the clinical, radiological and quality-of-life outcomes between hybrid and total pedicle screw instrumentation in patients undergoing surgery for neuromuscular scoliosis. A matched comparison using prospectively collected data was undertaken. A total of 66 patients underwent posterior or anteroposterior correction and fusion with hybrid (n = 33, mean age at surgery 15.8 years (9.10 to 19.6)) or total pedicle screw instrumentation (n = 33, mean age 14.7 years (7.0 to 20.7)) with a minimum follow-up of two years. The major curve pre-operatively was a mean of 87° (. sd. 29, 25° to 141°) and 81° (. sd. 18, 47° to 116°) in the hybrid and total pedicle screw groups, respectively (p = 0.29) and at a minimum of two years it was 33° (. sd. 20; 2° to 87°) and 20° (. sd. 12; 1° to 55°), respectively (p = 0.0016). The mean correction of the major curve was 59% (41% to 88%) in the hybrid and 75% (43% to 99%) in the total pedicle screw groups at two-year follow-up (p = 0.0011). The mean operating time was 7.45 hours (. sd. 2.18) and 6.04 hours (. sd. 1.71) in the hybrid and total pedicle screw groups, respectively (p = 0.001), and the mean intra-operative blood loss was 3760 ml (. sd.  2790) and 1785 ml (. sd. 1110), respectively (p = 0.001). Total pedicle screw instrumentation provided shorter operating times, less blood loss and better correction of the major curve compared with hybrid constructs in patients undergoing surgery for neuromuscular scoliosis

We undertook a retrospective study investigating the accuracy and safety of percutaneous pedicle screws placed under fluoroscopic guidance in the lumbosacral junction and lumbar spine. The CT scans of patients were chosen from two centres: European patients from University Medical Center Hamburg-Eppendorf, Germany, and Asian patients from the University of Malaya, Malaysia. Screw perforations were classified into grades 0, 1, 2 and 3. A total of 880 percutaneous pedicle screws from 203 patients were analysed: 614 screws from 144 European patients and 266 screws from 59 Asian patients. The mean age of the patients was 58.8 years (16 to 91) and there were 103 men and 100 women. The total rate of perforation was 9.9% (87 screws) with 7.4% grade 1, 2.0% grade 2 and 0.5% grade 3 perforations. The rate of perforation in Europeans was 10.4% and in Asians was 8.6%, with no significant difference between the two (p = 0.42). The rate of perforation was the highest in S1 (19.4%) followed by L5 (14.9%). The accuracy and safety of percutaneous pedicle screw placement are comparable to those cited in the literature for the open method of pedicle screw placement. Greater caution must be taken during the insertion of L5 and S1 percutaneous pedicle screws owing to their more angulated pedicles, the anatomical variations in their vertebral bodies and the morphology of the spinal canal at this location. Cite this article: Bone Joint J 2015; 97-B:1111–17

Aims. We present the results of correcting a double or triple curve adolescent idiopathic scoliosis using a convex segmental pedicle screw technique. Patients and Methods. We reviewed 191 patients with a mean age at surgery of 15 years (11 to 23.3). Pedicle screws were placed at the convexity of each curve. Concave screws were inserted at one or two cephalad levels and two caudal levels. The mean operating time was 183 minutes (132 to 276) and the mean blood loss 0.22% of the total blood volume (0.08% to 0.4%). Multimodal monitoring remained stable throughout the operation. The mean hospital stay was 6.8 days (5 to 15). Results. The mean post-operative follow-up was 5.8 years (2.5 to 9.5). There were no neurological complications, deep wound infection, obvious nonunion or need for revision surgery. Upper thoracic scoliosis was corrected by a mean 68.2% (38% to 48%, p < 0.001). Main thoracic scoliosis was corrected by a mean 71% (43.5% to 8.9%, p < 0.001). Lumbar scoliosis was corrected by a mean 72.3% (41% to 90%, p < 0.001). No patient lost more than 3° of correction at follow-up. The thoracic kyphosis improved by 13.1° (-21° to 49°, p < 0.001); the lumbar lordosis remained unchanged (p = 0.58). Coronal imbalance was corrected by a mean 98% (0% to 100%, p < 0.001). Sagittal imbalance was corrected by a mean 96% (20% to 100%, p < 0.001). The Scoliosis Research Society Outcomes Questionnaire score improved from a mean 3.6 to 4.6 (2.4 to 4, p < 0.001); patient satisfaction was a mean 4.9 (4.8 to 5). . Conclusions. This technique carries low neurological and vascular risks because the screws are placed in the pedicles of the convex side of the curve, away from the spinal cord, cauda equina and the aorta. A low implant density (pedicle screw density 1.2, when a density of 2 represents placement of pedicle screws bilaterally at every instrumented segment) achieved satisfactory correction of the scoliosis, an improved thoracic kyphosis and normal global sagittal balance. Both patient satisfaction and functional outcomes were excellent. Cite this article: Bone Joint J 2017;99-B:1080–7

Aims. We aimed to retrospectively assess the accuracy and safety of CT navigated pedicle screws and to compare accuracy in the cervical and thoracic spine (C2-T8) with (COMB) and without (POST) prior anterior surgery (anterior cervical discectomy or corpectomy and fusion with ventral plating: ACDF/ACCF). Patients and Methods. A total of 592 pedicle screws, which were used in 107 consecutively operated patients (210 COMB, 382 POST), were analysed. The accuracy of positioning was determined according to the classification of Gertzbein and Robbins on post-operative CT scans. Results. High accuracy was achieved in 524 screws (88.5%), 192 (87.7%) in the cervical spine and 332 (89%) in the thoracic spine, respectively. The results in the two surgical groups were compared and a logistic regression mixed model was performed to analyse the risk of low accuracy. Significantly lower accuracy was found in the COMB group with 82.9% versus 91.6% in the POST group (p = 0.036). There were no neurological complications, but two vertebral artery lesions were recorded. Three patients underwent revision surgery for malpositioning of a screw. Although the risk of malpositioning of a screw after primary anterior surgery was estimated to be 2.4-times higher than with posterior surgery alone, the overall rates of complication and revision were low. Conclusion. We therefore conclude that CT navigated pedicle screws can be positioned safely although greater caution must be taken in patients who have previously undergone anterior surgery. Cite this article: Bone Joint J 2017;99-B:1373–80

We examined the radiographs from a prospective clinical study of fixation by pedicle screws and those from an experimental study in a sheep model. In the clinical study, instruments were removed from 21 patients after implantation for 11 to 16 months and the extraction torques of the screws were recorded. A structured protocol was used for the radiological examinations. In the experimental study, loaded pedicle screw instrumentations were implanted in the sheep for six or 12 weeks. After radiological examination the pull-out resistance and the histological characteristics were studied. In the clinical study, all screws with radiolucent zones had a significantly reduced mean extraction torque compared with screws without radiolucent zones (16 ± 10 Ncm v 403 ± 220 Ncm; p < 0.0001). In the experimental study the mean maximum pull-out resistance for the screws with radiolucent zones was significantly lower than for those with no radiolucency (243 ± 156 N v 2214 ± 578 N; p = 0.0006) and the mean bone-to-screw contact was reduced for screws with zones compared with those without zones (8 ± 9% v 55 ± 29%; p = 0.0002). Our findings showed that all screws with radiolucent zones had low extraction torques or low pull-out resistance. A radiolucent zone is a good indicator of loosening of a pedicle screw

We investigated the effects of hydroxyapatite (HA) coating on the purchase of pedicle screws. A total of 23 consecutive patients undergoing lumbar fusion was randomly assigned to one of three treatment groups. The first received uncoated stainless-steel screws, the second screws which were partly coated with HA, and the third screws which were fully coated. The insertion torque was recorded. After 11 to 16 months, 21 screws had been extracted. The extraction torque was recorded. Radiographs were taken to assess fusion and to detect loosening of the screws. At removal, the extraction torques exceeded the upper limit of the torque wrench (600 Ncm) for many HA-coated screws. The calculated mean extraction torque was 29 ± 36 Ncm for the uncoated group, 447 ± 114 Ncm for the partly-coated group and 574 ± 52 Ncm for the fully-coated group. There were significant differences between all three groups (p < 0.001). There were more radiolucent zones surrounding the uncoated screws than the HA-coated screws (p < 0.001). HA coating of pedicle screws resulted in improved fixation with reduced risk of loosening of the screws

Computer-assisted frameless stereotactic image guidance allows precise preoperative planning and intraoperative localisation of the image. It has been developed and tested in the laboratory. We evaluated the efficacy, clinical results and complications of placement of a pedicle screw in the lumbar spine using this technique. A total of 62 patients (28 men, 34 women) had lumbar decompression and spinal fusion with segmental pedicle screws. Postoperative CT scans were taken of 35 patients to investigate the placement of 330 screws. None showed penetration of the medial or inferior wall of a pedicle. Registration was carried out 66 times. The number of fiducial points used on each registration averaged 5.8 (4 to 7) The mean registration error was 0.75 mm (0.32 to 1.72). This technique provides a safe and reliable guide for placement of transpedicular screws in the lumbar spine

We prospectively studied the use of intercostal EMG monitoring as an indicator of the accuracy of the placement of pedicle screws in the thoracic spine. We investigated 95 thoracic pedicles in 17 patients. Before insertion of the screw, the surgeon recorded his assessment of the integrity of the pedicle track. We then stimulated the track using a K-wire pedicle probe connected to a constant current stimulator. A compound muscle action potential (CMAP) was recorded from the appropriate intercostal or abdominal muscles. Postoperative CT was performed to establish the position of the screw. The stimulus intensity required to evoke a muscle response was correlated with the position of the screw on the CT scan. There were eight unrecognised breaches of the pedicle. Using 7.0 mA as a threshold, the sensitivity of EMG was 0.50 in detecting a breached pedicle and the specificity was 0.83. Thoracic pedicle screws were accurately placed in more than 90% of patients. EMG monitoring did not significantly improve the reliability of placement of the screw

The purpose of this study was to evaluate and compare the effect of short segment pedicle screw instrumentation and an intermediate screw (SSPI+IS) on the radiological outcome of type A thoracolumbar fractures, as judged by the load-sharing classification, percentage canal area reduction and remodelling. . We retrospectively evaluated 39 patients who had undergone hyperlordotic SSPI+IS for an AO-Magerl Type-A thoracolumbar fracture. Their mean age was 35.1 (16 to 60) and the mean follow-up was 22.9 months (12 to 36). There were 26 men and 13 women in the study group. In total, 18 patients had a load-sharing classification score of seven and 21 a score of six. All radiographs and CT scans were evaluated for sagittal index, anterior body height compression (%ABC), spinal canal area and encroachment. There were no significant differences between the low and high score groups with respect to age, duration of follow-up, pre-operative sagittal index or pre-operative anterior body height compression (p = 0.217, 0.104, 0.104, and 0.109 respectively). The mean pre-operative sagittal index was 19.6° (12° to 28°) which was corrected to -1.8° (-5° to 3°) post-operatively and 2.4° (0° to 8°) at final follow-up (p = 0.835 for sagittal deformity). No patient needed revision for loss of correction or failure of instrumentation. Hyperlordotic reduction and short segment pedicle screw instrumentation and an intermediate screw is a safe and effective method of treating burst fractures of the thoracolumbar spine. It gives excellent radiological results with a very low rate of failure regardless of whether the fractures have a high or low load-sharing classification score. Cite this article: Bone Joint J 2014;96-B:541–7

Percutaneous placement of pedicle screws is a well-established technique, however, no studies have compared percutaneous and open placement of screws in the thoracic spine. The aim of this cadaveric study was to compare the accuracy and safety of these techniques at the thoracic spinal level. A total of 288 screws were inserted in 16 (eight cadavers, 144 screws in percutaneous and eight cadavers, 144 screws in open). Pedicle perforations and fractures were documented subsequent to wide laminectomy followed by skeletalisation of the vertebrae. The perforations were classified as grade 0: no perforation, grade 1: < 2 mm perforation, grade 2: 2 mm to 4 mm perforation and grade 3: > 4 mm perforation. In the percutaneous group, the perforation rate was 11.1% with 15 (10.4%) grade 1 and one (0.7%) grade 2 perforations. In the open group, the perforation rate was 8.3% (12 screws) and all were grade 1. This difference was not significant (p = 0.45). There were 19 (13.2%) pedicle fractures in the percutaneous group and 21 (14.6%) in the open group (p = 0.73). In summary, the safety of percutaneous fluoroscopy-guided pedicle screw placement in the thoracic spine between T4 and T12 is similar to that of the conventional open technique. Cite this article: Bone Joint J 2015;97-B:1555–61

Aims. Loosening of pedicle screws is a major complication of posterior spinal stabilisation, especially in the osteoporotic spine. Our aim was to evaluate the effect of cement augmentation compared with extended dorsal instrumentation on the stability of posterior spinal fixation. Materials and Methods. A total of 12 osteoporotic human cadaveric spines (T11-L3) were randomised by bone mineral density into two groups and instrumented with pedicle screws: group I (SHORT) separated T12 or L2 and group II (EXTENDED) specimen consisting of T11/12 to L2/3. Screws were augmented with cement unilaterally in each vertebra. Fatigue testing was performed using a cranial-caudal sinusoidal, cyclic (1.0 Hz) load with stepwise increasing peak force. Results. Augmentation showed no significant increase in the mean cycles to failure and fatigue force (SHORT p = 0.067; EXTENDED p = 0.239). Extending the instrumentation resulted in a significantly increased number of cycles to failure and a significantly higher fatigue force compared with the SHORT instrumentation (EXTENDED non-augmented + 76%, p < 0.001; EXTENDED augmented + 87%, p < 0.001). Conclusion. The stabilising effect of cement augmentation of pedicle screws might not be as beneficial as expected from biomechanical pull-out tests. Lengthening the dorsal instrumentation results in a much higher increase of stability during fatigue testing in the osteoporotic spine compared with cement augmentation. Cite this article: Bone Joint J 2016;98-B:1099–1105

With the identification of literature shortfalls on the techniques employed in intraoperative navigated (ION) spinal surgery, we outline a number of measures which have been synthesised into a coherent operative technique. These include positioning, dissection, management of the reference frame, the grip, the angle of attack, the drill, the template, the pedicle screw, the wire, and navigated intrathecal analgesia. Optimizing techniques to improve accuracy allow an overall reduction of the repetition of the surgical steps with its associated productivity benefits including time, cost, radiation, and safety. Cite this article: Bone Joint J 2020;102-B(3):371–375

In a prospective observational study we compared the two-year outcome of lumbar fusion by a simple technique using translaminar screws (n = 57) with a more extensive method using transforaminal lumbar interbody fusion and pedicular screw fixation (n = 63) in consecutive patients with degenerative disease of the lumbar spine. Outcome was assessed using the validated multidimensional Core Outcome Measures Index. Blood loss and operating time were significantly lower in the translaminar screw group (p < 0.01). The complication rates were similar in each group (2% to 4%). In all, 91% of the patients returned their questionnaire at two-years. The groups did not differ in Core Outcome Measures Index score reduction, 3.6 (sd 2.5) (translaminar screws) vs 4.0 (sd 2.8) (transforaminal lumbar interbody fusion) (p = 0.39); ‘good’ global outcomes, 78% (translaminar screws) vs 78% (transforaminal lumbar interbody fusion) (p = 0.99) or satisfaction with treatment, 82% (translaminar screws) vs 86% (transforaminal lumbar interbody fusion) (p = 0.52).

The two fusion techniques differed markedly in their extent and the cost of the implants, but were associated with almost identical patient-orientated outcomes.

Extensive three-point stabilisation is not always required to achieve satisfactory patient-orientated results at two years.

Aims. The aim of this study was to assess the accuracy of pedicle screw placement, as well as intraoperative factors, radiation exposure, and complication rates in adult patients with degenerative disorders of the thoracic and lumbar spines who have undergone robotic-navigated spinal surgery using a contemporary system. Methods. The authors reviewed the prospectively collected data on 196 adult patients who had pedicle screws implanted with robot-navigated assistance (RNA) using the Mazor X Stealth system between June 2019 and March 2022. Pedicle screws were implanted by one experienced spinal surgeon after completion of a learning period. The accuracy of pedicle screw placement was determined using intraoperative 3D fluoroscopy. Results. A total of 1,123 pedicle screws were implanted: 1,001 screws (89%) were placed robotically, 63 (6%) were converted from robotic placement to a freehand technique, and 59 (5%) were planned to be implanted freehand. Of the robotically placed screws, 942 screws (94%) were determined to be Gertzbein and Robbins grade A with median deviation of 0.8 mm (interquartile range 0.4 to 1.6). Skive events were noted with 20 pedicle screws (1.8%). No adverse clinical sequelae were noted in the 90-day follow-up. The mean fluoroscopic exposure per screw was 4.9 seconds (SD 3.8). Conclusion. RNA is highly accurate and reliable, with a low rate of abandonment once mastered. No adverse clinical sequelae occurred after implanting a large series of pedicle screws using the latest generation of RNA. Understanding of patient-specific anatomical features and the real-time intraoperative identification of risk factors for suboptimal screw placement have the potential to improve accuracy further. Cite this article: Bone Joint J 2023;105-B(5):543–550