Navigation Template Research Articles

Comparative Analysis of Pedicle Screw Placement in Children with Congenital Scoliosis: Freehand Technique <i>(in vivo)<i> and Guide Templates <i>(in vitro)<i>

Objective. To evaluate accuracy between pedicle screw placement in vertebral bodies achieved in vivo with freehand techniques versus their placement in vertebrae plastic models achieved in vitro with the use of guide templates, in toddlers and preschool children with congenital kyphoscoliosis of the thoracolumbar transition and lumbar spine amid the vertebral malformation.Material and Methods. The research is based on a retrospective analysis of the results of treatment of 10 patients with congenital kyphoscoliosis of the thoracolumbar transition and lumbar spine amid the vertebral malformation. Age – from 2 years 2 months to 6 years 8 months old (mean 3 years 8 months old), gender – 6 boys, 4 girls. Based on the postoperative multi-slice spiral computed tomography (MSCT) of the spine, the pedicle screws placement accuracy of the correcting multi-support metalwork was evaluated. These patients constituted the 1st research group (in vivo group). The 2nd research group (in vitro group) was formed from 27 vertebrae plastic models with pedicle screws inserted in them with the use of guide templates. The placement accuracy of the installed pedicle support elements was assessed based on the S.D. Gertzbein et al. scale (1990).Results. In the 1st group, there were 52 pedicle screws placed. The screw placement accuracy according to the rate of misplacement, as follows: 53.8% in Grade 0, 25% in Grade I, 11.6% in Grade II, 9.6% in Grade III. The number of screws with the rate of misplacement in Grade 0 + Grade I was 41 (78.8%). In the 2nd group, there were 54 screws placed and slightly larger than the 1st group. The screw placement accuracy according to the rate of misplacement was 94.4% in Grade 0, 1.9% in Grade I, 3.7% in Grade II, respectively. The number of screws with the rate of misplacement in Grade 0 + Grade I was 52 (96.3%).Conclusions. Comparative analysis showed that the number of pedicle screws successfully placed in vertebrae plastic models in children with congenital deformities of the thoracolumbar transition and lumbar spine achieved with the use of guide templates was significantly higher than the number of screws successfully placed with freehand techniques (96.3% versus 80.8%, p = 0.011). The results obtained with method of navigation templates in vitro showed high precision and accuracy of pedicle screw placement which gives the prospect for using this type of navigation in clinical practice in toddlers with congenital scoliosis.

Accuracy of a 3-Dimensionally Printed Navigational Template for Localizing Small Pulmonary Nodules

Localization of small lung nodules are challenging because of the difficulty of nodule recognition during video-assisted thoracoscopic surgery. Using 3-dimensional (3-D) printing technology, a navigational template was recently created to assist percutaneous lung nodule localization; however, the efficacy and safety of this template have not yet been evaluated. To assess the noninferiority of the efficacy and safety of a 3-D-printed navigational template guide for localizing small peripheral lung nodules. This noninferiority randomized clinical trial conducted between October 2016 and October 2017 at Shanghai Pulmonary Hospital, Shanghai, China, compared the safety and precision of lung nodule localization using a template-guided approach vs the conventional computed tomography (CT)-guided approach. In total, 213 surgical candidates with small peripheral lung nodules (<2 cm) were recruited to undergo either CT- or template-guided lung nodule localization. An intention-to-treat analysis was conducted. Percutaneous lung nodule localization. The primary outcome was the accuracy of lung nodule localization (localizer deviation), and secondary outcomes were procedural duration, radiation dosage, and complication rate. Of the 200 patients randomized at a ratio of 1:1 to the template- and CT-guided groups, most were women (147 vs 53), body mass index ranged from 15.4 to 37.3, the mean (SD) nodule size was 9.7 (2.9) mm, and the mean distance between the outer edge of target nodule and the pleura was 7.8 (range, 0.0-43.9) mm. In total, 190 patients underwent either CT- or template-guided lung nodule localization and subsequent surgery. Among these patients, localizer deviation did not significantly differ between the template- and CT-guided groups (mean [SD], 8.7 [6.9] vs 9.6 [5.8] mm; P = .36). The mean (SD) procedural durations were 7.4 (3.2) minutes for the template-guided group and 9.5 (3.6) minutes for the CT-guided group (P < .001). The mean (SD) radiation dose was 229 (65) mGy × cm in the template-guided group and 313 (84) mGy × cm in CT-guided group (P < .001). The use of the 3-D-printed navigational template for localization of small peripheral lung nodules showed efficacy and safety that were not substantially worse than those for the CT-guided approach while significantly simplifying the localization procedure and decreasing patient radiation exposure. ClinicalTrials.gov identifier: NCT02952261.

3D printing navigation template-guided percutaneous radiofrequency thermocoagulation for V2 trigeminal neuralgia treatment

This paper aimed to evaluate the effectiveness of the 3D printing puncture navigation template-guided percutaneous radiofrequency thermocoagulation for V2 trigeminal neuralgia treatment. A total of 52 patients with V2 trigeminal neuralgia were treated with radiofrequency thermocoagulation. A total of 32 patients were treated under the guidance of the 3D printing puncture navigation template (guide plate group), while 20 patients underwent puncture via pterygopalatine fossa routinely (routine treatment group). The puncture time, operation time, puncture success rate, and immediate postoperative pain were recorded. The degree of immediate postoperative pain was indicated by visual analogue scale (VAS). Barrow Neurological Institute (BNI) classification criteria were used to evaluate the efficacy, and the postoperative complications were observed. All patients were followed up for 1 year. The two groups showed significant decrease in VAS after the operation (P<0.05). The puncture and operation times of the guide plate group were significantly lower than those of the routine treatment group (P<0.05). The difference in terms of the clinical effects and recurrence rate between the two groups was insignificant (P>0.05). 3D printing puncture navigation template-guided radiofrequency thermocoagulation may increase the operation success rate and reduce complication incidence. Therefore, this technique possesses clinicalpromotionalvalue.

Comparison of the effect of navigation template assisted spinal pedicle fixation and traditional pedicle screw fixation:a Meta-analysis

To systematically evaluate the efficacy of rapid prototyping drill navigation template-assisted pedicle screw fixation and traditional anatomic landmark-based fixation in the treatment of spinal disease by accessing and searching some relevant literatures home and abroad. Randomized Controlled Trials (RCTs) and prospective case-control studies or retrospective case-control studies about rapid prototyping drill templates-assisted pedicle screw fixation and traditional anatomic landmark-based fixation for the treatment of spinal disease were searched electronically in PubMed, The Cochrane Library(Issue 5, 2017), Clinical Trial, Google Scholar, Web of Science, CNKI, Wanfang database and VIP database before June 2017. According to the inclusion and exclusion criteria, two researchers independently screened the literatures, and extracted the data. The methodological quality of randomized controlled trials were evaluated by the Cochrane Handbook, and prospective case-control studies and retrospective case-control studies were evaluated by the NOS scale. The outcomes were analyzed using RevMan 5.3 software provided by the Cochrane information management system. A total of 7 articles were included, including 2 RCTs, 1 prospective case-control study and 4 retrospective case-control studies. A total of 237 patients were implanted with 1 688 pedicle screws, including 898 screws in the navigation template group, 790 screws in the conventional method group. Meta-analysis results showed that there was significant difference in the excellent rate of screw implantation between navigation template group and conventional method group [OR=5.05, 95% CI(3.13, 8.16), P<0.000 01], there was significant difference in operative time, intraoperative blood loss for thoracolumbar surgery [WMD=-27.19, 95% CI(-38.21, -16.17), P<0.000 01; WMD=-100.82, 95% CI(-182.26, -19.37), P=0.02]. Compared with traditional pedicle screw fixation, navigation template spine pedicle screw fixation has better clinical effect, which can improve the excellent rate of screw placement, reduce the operation time and intraoperative bleeding.

Treatment of unstable pelvic fractures with sacroiliac screwing assisted by 3D printing technique in combination with front ring nail-rod system

Objective To explore the clinical efficacy of 3D printing technique in assisting sacroiliac screwing in combination with front ring nail-rod system for treatment of unstable pelvic fractures. Methods From July 2015 to June 2017, 3D printing technique was used to assist the sacroiliac screwing in combination with front ring nail-rod system for 16 patients with unstable pelvic fracture at Orthopaedic Center, The Fourth People's Hospital of Zigong. They were 9 males and 7 females, aged from 19 to 60 years (average, 39.8 years). By the Tile classification, 5 cases were type B1, 6 type B2, 3 type B3 and 2 type C. Their operation duration, bleeding, fluoroscopy frequency, incision length, postoperative fracture reduction, success rate of sacroiliac screwing, accuracy of sacroiliac screwing, perioperative complications, weight-bearing exercise time, fracture healing time and the Majeed scores at the last follow-up were documented. Results All the 3D models and navigation templates were successfully designed and printed. Surgery succeeded in all the patients. Follow-ups ranged from 6 to 18 months, averaging 13.3 months. The bleeding ranged from 100 to 250 mL, averaging 162.4 mL; the operation duration ranged from 60 to 120 min, averaging 73.2 min; the intra-operative fluoroscopy frequency ranged from 13 to 31 times, averaging 17.4 times; the incision length ranged from 16 to 32 cm, averaging 21.1 cm. All the incisions healed by the first intention and all the fractures obtained osseous union after 90 to 120 d (average, 102.3 d). No significant complications like neurovascular injury or pulmonary embolism happened. The weight-bearing exercise time ranged from 25 to 40 d, averaging 31.5 d. According to the Matta imaging scores, the reduction was rated as excellent in 12 cases and good in 4. Altogether 28 screws were inserted with a success rate of 100%. Compared with the preoperative simulated screwing, the actual screwing angle deviated postoperatively by 0.12°±0.32°, the X axis by 0.36±1.24 mm, the Y axis by 0.36±1.24 mm and the Z axis by 0.22±1.26 mm, showing no statistically significant difference between the actual 3D deviations and the test value of 0 (P>0.05). Conclusion In the treatment of unstable pelvic fractures, 3D printing technique can be used in preoperative preparation of the connecting rod in the front ring nail-rod system to assist the sacroiliac screwing, significantly shortening the operation duration, reducing bleeding, ensuring safe and accurate screwing, and facilitating functional recovery. Key words: Pelvis; Fracture fixation, internal; Bone nails; 3D printing technique

Virtual Surgical Planning Assisted Management for Three-Dimensional Dentomaxillofacial Deformities.

Treatment of 3-dimensional dentomaxillofacial deformities remains a significant clinical challenge. This retrospective study aims to present the modalities of management for complex 3-dimensional dentomaxillofacial deformities with the assistance of virtual surgical planning (VSP) and 3-dimensional printed navigation templates. Ten patients diagnosed with complex 3-dimensional dentomaxillofacial deformities received treatment of combined orthodontics and orthognathic surgery. Various surgical techniques as well as bone graft and distraction osteogenesis were used under the guidance of VSP and 3-dimensional printed navigation templates according to the characteristics of each patient. Follow-up included clinical examination and studies of spiral computed tomography preoperatively and for an average of 12 months postoperatively. The clinical outcomes of patients showed that VSP was successfully transferred to actual surgery in all the 10 patients. Three-dimensional dentomaxillofacial deformities were corrected significantly. Satisfactory profiles and occlusion were achieved. The management of 3-dimensional dentomaxillofacial deformities required comprehensive consideration and detailed surgical planning. Virtual surgical planning serves as a reliable assistance in the management of 3-dimensional dentomaxillofacial deformities.

Design of a 3D navigation template to guide the screw trajectory in spine: a step-by-step approach using Mimics and 3-Matic software.

Rapid development of 3D printing techniques has led to the design of navigation templates to assist with accurate insertion of pedicle screws in last decades. However, there are still without the precise step-by-step methods to design 3D navigation templates from computed tomography (CT) images. Our present article provides a detailed protocol to allow the readers or researchers to obtain the 3D navigation template easily, and assist with pedicle screw insertion in their future research and surgery. Using 3D navigation template-assisted pedicle screw fixation in spine surgery is low cost and can decrease the radiation exposure to both patients and surgeons.

One-Stage treatment for maxillofacial asymmetry with orthognathic and contouring surgery using virtual surgical planning and 3D-printed surgical templates

Asymmetry is one of the most common maxillofacial deformities. One-stage treatment for maxillofacial asymmetry with orthognathic and contouring surgery has been rarely reported. This retrospective study aims to investigate the feasibility of simultaneous orthognathic and facial bone contouring surgery with the help of virtual surgical planning and 3D-printed navigation templates for facial asymmetry. From January 2012 to December 2015, 51 patients diagnosed with maxillofacial asymmetry received treatment of combined orthognathic and contouring surgery under the guidance of virtual surgical planning and 3D-printed templates. Photographs and measurements were taken before and after operation to evaluate the effectiveness of the treatment. Photographs and cephalometric analysis showed the asymmetry was effectively corrected. All patients were satisfied with the aesthetic results. This study suggested the clinical feasibility of simultaneous orthognathic and contouring surgery for the treatment of maxillofacial asymmetry. Virtual surgical planning and 3D-printed surgical templates enable the surgeons to plan and carry out the procedure more predictably and achieve satisfactory outcomes.

Rapid prototyping navigation template assisted cervical screw implantation:a review

The cervical screw fixation has been used widely in the clinic setting due to the high fusion rate, immediate fixation of the surgical segment and good correction of the deformity. However, owing to the variation of anatomical structures and the narrow pedicle screws, it's rather difficult to implant the screws through traditional methods. The perforation rate of the screw is high, which can cause serious complications such as neurovascular injury. In recent years, rapid prototyping navigation templates have been reported in the appilication to assist cervical screw placement for improving the accuracy of screw placement. In this paper, we reviewed and summarized published literatures about navigation template assisted cervical screw implantation in the past 20 years, systematically introduced the methods of producing and using of navigation templates, the development of design concept and the status of application in cervical spine surgery. To date, relevant clinical and cadaveric studies confirm that the use of rapid prototyping navigation template assisted cervical screw placement in cervical surgery can reduce screw perforation rate, intraoperative ionizing radiation injury and operation time, which is worth applying in the clinical practice. However, specific clinical effects of different design types of navigation templates are not well summarized. As a result, more clinical and cadaveric studies comparing the accuracy and safety of navigation templates of different design types are needed to help clinicians select the appropriate navigation template for surgery.

Precise orthormorphia of tibial angulation deformity and shortening deformity by using digital technology combined with circular external fixator

To evaluate the effectiveness of precise orthormorphia of tibial angulation deformity and shortening deformity by using digital technology combined with external fixator. Twenty-six cases of tibial angulation deformity combined with shortening deformity were treated between June 2012 and August 2016, including 12 males and 14 females aged from 1 to 19 years with an average age of 16.5 years. There were 6 cases of congenital patella pseudoarthrosis, 1 case of fibrous dysplasia of femur and tibia, 3 cases of limb shortening deformity caused by infantile paralysis, 16 cases of fracture malunion. Limb shortening was 1.5-9.5 cm (mean, 6.2 cm) before operation. The deformity from three-dimensional perspective was analysed by digital technology, the surgical procedures of lengthening and osteotomy was simulated, the navigation templates were completed with computer aided design (CAD) and three-dimensional printing, and the external fixator was used to assist the lengthening of the tibia. X-ray films were regularly reviewed after operation to observe the new bone remolding, limb lengthening, load bearing line of lower limb, and recurrences of angulation. All the patients were followed up 14-48 months (mean, 18.8 months). There was only 1 case of superficial pin site infection which was cured with oral antibiotics and pin site care with mild disinfectants, and no complication such as bone nonunion, equines deformity, or vascular nerve injury occurred. The deformity of tibia and load bearing line of lower limb had been completely recovered according to postoperative X-ray films at 1 week. All the cases achieved perfect limb length as with preoperative design. The bone mineralization time was 12-20 weeks (mean, 11.6 weeks), the external fixator removal time was 18-26 weeks (mean, 14.9 weeks), and the healing index was 21-78 d/cm (mean, 63.4 d/cm). The postoperative flexion range of the injured limb was 15° less than the unaffected extremity in 1 case, and the situation was improved significantly after some physical manipulation and exercise, who completed the limb lengthening and achieved the expected effectiveness finally. Precise orthormorphia of tibial deformity by using digital technology, and limb lengthening with the aid of external fixator can achieve good effectiveness with good reliability, invasiveness, and precision.

A Novel Drill Navigation Template Combines Preoperative Simulation in Expansive Open-Door Laminoplasty

To evaluate the effects of preoperative simulation based on patient-specific vertebral models, and computer-assisted designed drill navigation templates in expansive open-door laminoplasty (EOLP). We retrospectively analyzed 18 consecutive patients who underwent EOLP, 11 patients (45 vertebrae) were treated with traditional EOLP (traditional group) and 7 patients (28 vertebrae) were treated with EOLP aided by the drill navigation template and preoperative simulation (template group). We assessed the operation time, intraoperative blood loss, hospitalization expenses, visual analog scale (VAS), Japanese orthopedic association (JOA), neck disability index (NDI), Pavlov's ratio, laminoplasty opening size (LOS), hinge fracture rate and trough positions. The operation time of template group (98.6 ± 13.0 minutes) was significantly shorter (P < 0.05) than that of traditional group (125.4 ± 13.2 minutes). Both groups achieved similar hospitalization expenses and significant improvement in VAS, JOA score, NDI, and Pavlov ratio. The postoperative hinge fracture rate of template group (0%; 0/28) was significantly lower (P < 0.05) than that of traditional group (11.1%, 5/45). In template group, all the troughs (56/56 [100%]; 28/28 on the hinge side and 28/28 on the open side), while in traditional group, only 72.2% (65/90; 31/45 on the hinge side and 34/45 on the hinge side) of the troughs were at the proper hinge position. Drill navigation template and preoperative simulations in EOLP are technically feasible. With the help of templates and preoperative simulation, shorten operation time, accurate trough positioning, decrease incidence of hinge fracture and could be acquired. This technique should be further studied and affirmed in clinical applications.

Clinical study of three-dimensional printed navigation template assisted Ludloff osteotomy in treatment of moderate and severe hallux valgus

To explore the effectiveness and advantage of three-dimensional (3D) printed navigation templates assisted Ludloff osteotomy in treatment of moderate and severe hallux valgus. Between April 2013 and February 2015, 28 patients (28 feet) with moderate and severe hallux valgus who underwent Ludloff osteotomy were randomly divided into 2 groups ( n=14). In group A, the patients were treated with Ludloff osteotomy assissted with a 3D printed navigation template. In group B, the patients were treated with traditional Ludloff osteotomy. There was no significant difference in gender, age, affected side, and clinical classification between 2 groups ( P>0.05). The operation time and intraoperative blood loss were recorded. The ankle function of the foot at preoperation, immediate after operation, and last follow-up were assessed by the American Orthopedic Foot and Ankle Society (AOFAS) score. Besides, the X-ray film were taken to assess the hallux valgus angle (HVA), intermetatarsal angle (IMA), and the first metatarsal length shortening. All patients were followed up 18-40 months (mean, 26.4 months). The operation time and intraoperative blood loss in group A were significantly less than those in group B ( P<0.05). The HVA, IMA, and AOFAS scores in groups A and B at immediate after operaton and last follow-up were sinificantly improved when compared with preoperative values ( P<0.05); but no significant difference was found between at immediate after operation and at last follow-up ( P>0.05). No significant difference was found in HVA and IMA between group A and group B at difference time points ( P>0.05). There were significant differences in AOFAS score and the first metatarsal length shortening at immediate after operation and at last follow-up between 2 groups ( P<0.05). Except 1 case of metastatic metatarsalgia in group B, there was no other operative complications in both groups. 3D printed navigation template assisted Ludloff osteotomy can provide accurate preoperative planning and intraoperative osteotomy. It is an ideal method for moderate and severe hallux valgus.

Short-term effectiveness of total knee arthroplasty assisted by three-dimensional printing osteotomy navigation template

To investigate the short-term effectiveness of total knee arthroplasty (TKA) assisted by three-dimensional (3D) printing osteotomy navigation template. A retrospective study was performed on 60 patients with osteoarthritis bewteen January 2016 and June 2017. Thirty cases underwent TKA assisted by 3D printing osteotomy navigation template (3D printing group) and 30 cases underwent the conventional TKA (conventional TKA group). There was no significant difference in gender, age, body mass index, surgical side, and disease duration between 2 groups ( P>0.05). The operation time, the pre- and post-operative hemoglobin values, the amount of drainage, the Hospital for Special Surgery (HSS) score and Knee Society Score (KSS) of knee joint before operation and at 3 months after operation were observed. And 6 freedom degrees of knee (the varus and valgus angle, the internal and external rotation angle, the antero-posterior displacement, the proximal-distal displacement, the flexion and extension angle, and the internal and external displacement) before operation and at 3 months after operation were recorded by Opti-Knee (the knee 3D motion analysis system). The values of 2 groups were compared with 30 healthy adults (<60 years). The operation time was shorter in 3D printing group than that in conventional TKA group ( t=5.833， P=0.000). The hemoglobin values at 1 and 3 days after operation were higher in 3D printing group than those in conventional TKA group ( P<0.05). The amount of drainage was less in 3D printing group than that in conventional TKA group ( t=5.468， P=0.000). All patients were followed up 6-9 months (mean, 7.3 months). There was no significant difference in pre- and post-operative HSS score and KSS clinical score between 2 groups ( P>0.05). There was no significant difference in preoperative KSS function score between 2 groups ( P>0.05), but the KSS function score of 3D printing group at 3 months after operation was higher than that of conventional TKA group ( P<0.05). Before operation, the varus and valgus angle, the internal and external rotation angle, the antero-posterior displacement, the proximal-distal displacement of 3D printing group and conventional TKA group were larger than that of the healthy adults ( P<0.05); there was no significant difference in the flexion and extension angle and the internal and external displacement between 2 groups and healthy adults ( P>0.05). At 3 months after operation, compared with healthy adults, the varus and valgus angle of conventional TKA group was increased, the flexion and extension angle of conventional TKA group was decreased ( P<0.05); the proximal-distal displacement and the internal and external displacement of 2 groups were decreased ( P<0.05); there was no significant difference in other freedom degrees between groups ( P>0.05). No sign of prosthesis loosening was observed by X-ray examination. Compared with the traditional TKA, TKA assisted by the 3D printing osteotomy navigation template had such advantages as shorter operation time, less postoperative blood loss, and well postoperative recovery.

Digital analysis and certification of osseous pathway for anterograde screwing in acetabular posterior column

Objective To analyze and determine the optimal osseous pathway for anterograde screwing in the acetabulum posterior column. Methods Recruited for this study were 40 healthy adult volunteers, 20 males and 20 females, aged from 18 to 56 years (average, 34.6 years). Firstly, their abdomen CT scanning images were transformed into Materialise Mimics Innovation Suite 16.0 software to obtain the 3D reconstruction images of the pelvis (.stl file). The Imageware 12.0 software (EDS, USA) was used to produce the optimal osseous pathway for anterograde screwing in the acetabulum posterior column. The diameter and length of the pathway were measured and statistically analyzed. Secondly, after 10 adult fresh pelvic specimens were scanned, the optimal osseous pathway for anterograde screwing in the acetabulum posterior column was determined in the same way as the above. A navigation template for anterograde screwing in the acetabular posterior column was manufactured. The screwing in the posterior column of the acetabulum was conducted using Kirschner wire with the aid of the navigation template. Imaging evaluation was performed after fixation. Results The projection of the safe zone in the acetabular posterior column was irregularly triangle; there were no significant differences regarding the projection size between different ages (P>0.05). The maximum diameter and the maximum length of the left optimal pathway in males were respectively 22.37±1.42 mm and 131.27±3.63 mm, and those of the right optimal pathway in males respectively 23.16±1.39 mm and 129.23±3.27 mm. The maximum diameter and the maximum length of the left optimal pathway in females were respectively 17.58±1.83 mm and 112.56±2.77 mm, and those of the right optimal pathway in females respectively 16.92±1.66 mm and 114.41±2.98 mm. There were no significant differences between the left and right sides for the same item in the same gender (P>0.05).There were significant differences between males and females for the same item in the same side (P<0.05). No penetration into the cortex or the hip joint happened. Conclusion The optimal osseous pathway for anterograde screwing in the acetabulum posterior column can be determined by digital techniques, leading to a simple and safe procedure for the treatment of fractures of the acetabular posterior column. Key words: Acetabulum; Fractures, bone; Fracture fixation, internal; Bone nails; Imaging, three-dimensional

S2 alar-iliac screwing assisted by an individualized navigation template

Objective To evaluate the accuracy and feasibility of S2 alar-iliac screwing assisted by an individualized navigation template in clinic. Methods Five patients underwent S2 alar-iliac screwing from March 2015 to July 2017. They were 2 men and 3 women, aged from 41 to 61 years (average, 54.8 years). After their preoperative CT scan data of the pelvis were used for 3D reconstruction, their individualized navigation templates were designed, 3D printed and used to assist the implantation of S2 alar-iliac screws. After operation, their postoperative CT data were reviewed and reconstructed using software Mimics. The caudal angulation on the sagittal plane (sagittal angle, SA), lateral angulation on the transverse plane (transverse angle, TA), horizontal distance to the median sacral crest (horizontal distance, HD), and vertical distance to the first posterior sacral foramen's inferior margin (vertical distance, VD) of the screws were measured and compared with the corresponding values in the preoperative design. Results In the 5 patients, altogether 10 S2 alar-iliac screws were implanted through the sacroiliac joint without piercing the iliac bone cortex. There were no significant differences between the preoperative design and postoperative measurements in terms of SA (32.22°±5.57° versus 31.95°±5.78°), TA (42.59°±4.55° versus 42.21°±5.29°), HD (5.04±0.40 mm versus 5.00±0.41 mm) or VD (19.58±1.49 mm versus 19.54±1.12 mm) (P>0.05). Conclusion In the adult pelvic fixation, the S2 alar-iliac screwing can be assisted by an individualized navigation template to achieve high accuracy in implantation. Key words: Pelvis; Sacroiliac joint; Pelvimetry; 3D printing technology; Navigation template

Preparation and Assessment of an Individualized Navigation Template for Lower Cervical Anterior Transpedicular Screw Insertion Using a Three-Dimensional Printing Technique.

Prospective trial. To establish an individualized navigation template for safe and accurate insertion of lower cervical anterior transpedicular screw (ATPS) based on a three-dimensional (3D) printing technique. Conventional screw insertion manually under fluoroscopy easily leading to deviation of ATPS screw channel, cervical instrumentation procedures demand the need for a precise technique for screw placement. Twenty adult cervical spine specimens (10 men and 10 women, with a mean age of 50.29 ± 6.98) were selected for computed tomography pre- and postoperatively. A 3D lower cervical spine model was reconstructed using Mimics software to measure the screw-related parameters and generate a reverse template with optimal screw channel as well as a prototype using 3D printing. Assisted by the navigation template, bilateral ATPS were inserted into the cadavers. The mean outer width and height of pedicle were 5.31 ± 1.23 and 6.78 ± 1.10 mm, respectively. The average length, sagittal, and axial angles of the optimal screw channel obtained through the optimal entry point were 36.34 ± 4.39 mm, 40.67° ± 5.10°, and 93.7° ± 7.96°, respectively. The adjustable safe ranges of sagittal and axial angles were 3.89° ± 1.13° and 5.64° ± 0.97°, respectively. The axial and sagittal accuracies of the 200 screws were 99.5% and 97%, respectively. The average deviations of the actual entry point and the preset opening in the X, Y, and Z axes were 0.39 ± 0.43, 0.21 ± 0.41, and 0.29 ± 0.14 mm, respectively (P > 0.05). An individualized ATPS navigation template was developed using Mimics software and 3D printing prototyping, based on computed tomography, for highly accurate screw insertion. 4.

Application of individualized navigation template in the location of femoral and tibial prosthesis in Oxford single condylar replacement

Objective To investigate the accuracy of the positioning of the prosthesis of the femur and tibia by the individual navigation template assisted Oxford unicompartmental arthroplasty and to evaluate of the value of navigation template in unicompartmental arthroplasty. Methods Twenty cadaveric legs were randomly divided into two groups (n=10), group 1 for navigation template and 2 for conventional method. A CT scan was performed preoperatively on the lower limb for navigational group. Geomagic software was used to process the CT data. A navigational template was constructed as the inverse of the distal femur and proximal tibia surface with an osteotomy gap. Two drills were used to define the rotational alignment of the femur in the computer. The navigational templates were produced using a rapid prototyping (RP) technique to assist UKA. The traditional method group was guided by the tibial extramedullary localization and the femoral intramedullary localization for the osteotomy and prosthesis placement. Both groups were performed according to the same standard. The position of the single condyle was evaluated by the anteroposterior X-ray films of the knee joint. The vertical relationship between the osteotomy surface and its mechanical axis was evaluated by CT. The parallel relationship between the central placement of femoral prosthesis and the posterior femoral cortex was also evaluated. Results The navigation template was close to the femoral condyle and tibial plateau without obvious movement. The mean operative duration of the navigation template group were 50.75±2.3 min and the traditional method group were 58.57±1.5 min (P>0.05). The postoperative femoral prosthesis flip angles of the navigation template group and the traditional group were 2.5°±-0.65° and -7.8°±3.26° respectively (P<0.05). The femoral prosthesis flexion angles were -2.9°±4.18° and-6.5°±4.25° (P<0.05), and the tibial prosthesis varus and valgus angles were -1.5°±0.50° and -5.8°±3.15° respectively (P<0.05). The tibial implant posterior inclination angles were 4.50°±1.55°and 3.05°±3.63° respectively (P<0.05). The average angles between navigational group distal femoral osteotomy surface and mechanical shaft were 89.5°±2.3° (range 87.5°-91.8°). The average angle between the proximal tibial resected surface and the mechanical axis was 90.3°±0.5° (range 89.4°-90.7°). There were 17 specimens of central column of femoral prosthesis parallel with the posterior femoral cortex. However, the angle of remaining 3 samples were less than 5°. In the traditional method group, the osteotomy surface and its mechanical axis were all angled. The deviation of distal femur distal surface in 7 specimens from the mechanical axis was larger than 10°, while that in 5 specimens was larger than 5°. Conclusion The navigation template can improve the accuracy of the femoral prosthesis localization, orientation and tibial prosthesis implants in the direction of valgus and valgus. However, there was no significant effect on the tibial prosthesis in the direction of posterior inclination. Key words: Arthroplasty, replacement, knee; Computer-aided design; Imaging, three-dimensional

Occipital Condyle Screw Placement Using an Individualized Navigation Template Based on Three-Dimensional Printing

Occipital Condyle Screw Placement Using an Individualized Navigation Template Based on Three-Dimensional Printing

Accurate placement of cervical pedicle screws using 3D-printed navigational templates : Animproved technique with continuous image registration.

Accurate placement of cervical pedicle screws remains asurgical challenge. This study aimed to test the feasibility of using anovel three-dimensional (3D-)printed navigational template to overcome this challenge. Cervical spines were scanned using computed tomography (CT). A3D model of the cervical spines was created. The screw trajectory was designed to pass through the central axis of the pedicle. Thereafter, anavigational template was designed by removing the soft tissue from the bony surface in the 3D model. A3D printer was used to print the navigational template. The screws were then placed in the cadavers following CT scanning. The 3D model of the designed trajectory and the placed screws were registered. The coordinates of the entry and exit points of the designed trajectory and the actual trajectory were recorded. The numbers of qualified points that met the different degrees of accuracy were compared using aχ2 test. Atotal of 158screws were placed. Five screws breached the pedicle cortex with adistance <2 mm. There was no significant difference between the pre- and postoperative entry points with adegree of accuracy≥1.7 mm (P= 0.131). Meanwhile, there was no significant difference between the pre- and postoperative exit points with degrees of accuracy≥6.4 mm (P= 0.071). Anavigational template can be designed by removing the soft tissue from the bony surface in aCT-generated 3D model. This guiding tool may effectively prevent intraoperative drifting and accurately places cervical pedicle screws.

Clinical Application of Atlantoaxial Pedicle Screw Placement Assisted by a Modified 3D-Printed Navigation Template

OBJECTIVES:To investigate the primary clinical value of atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template.METHODS:We retrospectively analyzed the cases of 17 patients treated from June 2015 to September 2016 with atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template. All procedures were performed prior to surgery, including thin-slice CT scanning, medical image sampling and computerized 3D modeling of the atlantoaxial joint, optimal pedicle screw trajectory determination, and anatomical trait acquisition for the atlantoaxial pedicle, spinous process of the axis, vertebral lamina and posterior lateral mass, and design of a reverse template. During surgery, a navigation template was tightly attached to the atlantoaxial joint to assist in pedicle screw placement. Surgeons subsequently used an electric drill to remove the template through a guide channel and then placed the atlantoaxial pedicle screw. Observed indexes included the VAS score, JOA improvement rate, surgery duration, and blood loss.RESULTS:Surgery was successful in all 17 patients, with an average operation duration of 106±25 min and an average blood loss of 220±125 ml. Three days postoperatively, the VAS score decreased from 6.42±2.21 to 3.15±1.26. Six months postoperatively, the score decreased to 2.05±1.56. The postoperative JOA score increased significantly from 7.68±2.51 to 11.65±2.72 3 d after surgery and to 13.65±2.57 after 6 months. Sixty-eight pedicle screws were inserted successfully, with 34 in the atlas and 34 in the axis. According to the Kawaguchi standard, 66 screws were in grade 0 (97.06%), and 2 were in grade 1 (2.94%). The pre- and postoperative transverse and sagittal screw angles showed no significant differences.CONCLUSIONS:Atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template is worth recommending due to the improved accuracy in screw placement, improved patient safety and beneficial clinical effects.