Navigation Template Research Articles

Application of computer aided design 3D printed navigation template in Salter pelvic osteotomy for dislocation of hip joint in children

Objective To explore the feasibility of accurate localization for the acetabular direction in Salter pelvic osteotomy for the developmental dislocation of the hip joint in children by using computer aided design and 3D printing technique. Methods The clinical data of 12 patients of unilateral hip dislocation treated with Salter pelvic osteotomy by using 3D printed navigation template in Department of Orthopedics, Children′s Hospital of Nanjing Medical University From October 2016 to April 2017 were retrospectively analyzed.Among the 12 cases, there were 4 males and 8 females, 5 hips on the left and 7 hips on the right, aged 1.5 to 5.0 years old (mean 2.3 years old). According to the CT data, the models of the healthy hip joint were mirrored to the contralateral side by Mimics software.Computer-aided simulations of Salter pelvic osteotomy on models of the affected hip joints were performed.Then, the models of the affec-ted hip joint were rotated to the mirror models of the contralateral hip joint.The navigation templates were designed according to the exposed pelvic surface morphology during the operation.The navigation templates were printed by rapid prototyping technology to guide the operation.Preoperative and postoperative acetabular index (AI) and center edge angle (CEA) of affected side were compared to postoperative AI and CEA of contralateral side respectively. Results A method of making personalized navigation templates for Salter pelvic osteotomy was established in 12 children with developmental dislocation of the hip joint.The operation time ranged from 40.2 to 64.5 min, averaging (50.6±8.5) min.The intraoperative bleeding volume ranged from 35 to 60 mL, averaging 52 mL.No vascular and nerve injury was found in the postoperative examination, and no child had complications such as infection, residual foreign body of the guide plate and so on.There was significant difference in preoperative measurements regarding AI between the affected side [(38.4±2.8)°] and the contralateral side [(21.6±0.8)°](t=-18.77, P 0.05), there was no significant difference in postoperative measurements regarding CEA between the affected side[(21.2±2.6)°] and the contralateral side(t=-0.435, P>0.05). Conclusions The navigation template prepared by computer aided design and 3D printing technology has good accuracy, and is a new approach to accurate acetabular rotation in children with the developmental dislocation of the hip joint for Salter pelvic osteotomy. Key words: Dislocation of hip joint; Osteotomy; 3D printing

Application of three-level navigation template in surgery for hemivertebrae in adolescents

Objective . To assess efficacy and safety of using a three-level navigation template in the surgical treatment of congenital spinal deformities. Material and Methods . Three-level navigation templates were used in surgical treatment of four consecutively operated 10–17-year-old patients with congenital scoliosis associated with thoracic hemivertebrae. The correctness of screw position was evaluated according to CT data using a 2-mm increment method: class 0 – intraosseous screw position; class 1 – the screw extends beyond the pedicle cortex by less than 2 mm; class 2 – by 2–4 mm; and class 3 – by more than 4 mm. Preoperative DICOM data were processed with free software. The model of target zone and navigation template were 3D printed and used in surgery. Results . Four of 16 (25 %) pedicles were narrower than 4.35 mm and were estimated as difficult for implantation with a planned violation of the integrity of the endplate. Perforation of the outer cortical layer took place in all these cases, and screw position corresponded to class 2 only in pedicle width of 1.9 mm. In pedicles wider than 4.35 mm, 11 of 12 (91.7 %) screws were implanted intraosseously. One screw extended beyond the pedicle cortex by 0.8 mm (class 1). Conclusion . Three-level navigation template can be considered as an effective means of positioning transpedicular screws in secondarily changed segments adjacent to anomalous one and confounding implantation. Free software is sufficient for preparing 3D-model of target zone and navigation template, and such a model is a highly informative reference object that is convenient to use during the operation. A navigation template made using 3D printing does not require the use of expensive equipment, which can make surgery for congenital scoliosis more accessible.

Application of Personalized Navigation Templates to Oxford Single Condylar Replacement in a Chinese Population

The purpose of this study is to develop and validate a novel patient-specific navigational template for unicompartmental knee arthroplasty (UKA). A total of 120 patients who underwent UKA were randomized and divided into the conventional method and navigational template groups. In the navigational template group, patient-specific navigational templates were designed and used intraoperatively to assist 60 patients with UKA. Information on operation time and blood loss was recorded by an independent operating room nurse. After surgery, the positions of the prostheses were evaluated using X-rays. All navigation templates were found to fit its corresponding biomodel appropriately without any free movement. The navigational template exhibited significantly better accuracy than the conventional method. Statistically significant differences in the femoral prosthesis flip angle, femoral prosthesis flexion angle, and tibial plateau varus and valgus angle were observed between the two groups (p = 0.022, 0.042, 0.043, respectively). In addition, the mean operation time was statistically and significantly lower in the navigational template group than in the conventional group (p = 0.035). This study introduces a novel navigational template to UKA, the accuracy of which is proven by clinical operation. This is a Level III, therapeutic study.

Design and application of a novel patient-specific 3D printed drill navigational guiding template in percutaneous thoracolumbar pedicle screw fixation: A cadaveric study

The conventional surgical method of percutaneous pedicle screw fixation (PPSF) mainly uses X-ray fluoroscopy guidance to target the vertebral pedicle for screw placement. This study aimed to explore the feasibility of establishing a personalized drill guide template for PPSF based on a three-dimensional (3D) printing technique and to evaluate the accuracy and safety of the method for assisting screw insertion in cadaveric specimens. The T3-L3 trunk cadaveric specimens from six adults were subject to a computed tomography (CT) scan in the prone position. A three-dimensional model containing the back skin contour was reconstructed. A bilateral ideal pedicle screw in the T6-L1 segment was designed. Then, the reverse templates were designed. The two templates were fused and printed into an individualized guide template. PPSF was performed under the assistance of the guide template, and the CT scan was taken postoperatively to access the screw position. Ninety-six pedicle screws were successfully placed on the bilateral vertebral body of the T6-L1 segment with the assistance of a guide template. The guide plate was not loosened or displaced when operated by a single hand, and the operation time was 24.6 ± 7.9 s. The axial CT images after puncture indicated that in 96 puncture needles, 90 needles were grade I and 6 were grade II, with a puncture accuracy rate of 98.6%. In conclusion, an individualized PPSF navigation template was developed using Mimics software and 3D printing prototyping, which improved the accuracy of PPSF in cadaveric specimens.

Determination of optimal design of navigation templates for transpedicular implantation in the cervical and thoracic spine: results of cadaveric studies

Objective. To perform comparative analysis of safety and accuracy of pedicle screw placement in the cervical and thoracic vertebrae using custom-made 3D-printed navigation templates of various designs. Material and Methods . The study was performed on three cadaver preparations. A total of 60 pedicle screws were placed in C2–T4 using navigation templates of different designs. Three types of templates were used to install 20 screws in each group: monolateral templates in group A, bilateral templates in group B, and bilateral three-point templates supported by the spinous process in group C. The safety and accuracy of screw placement were evaluated by CT with following comparative evaluation. Results. Three-point templates (group C) demonstrated the highest implantation safety, only one screw (5 %) perforated pedicle’s wall with grade 1, 19 screws (95 %) were completely surrounded by bone tissue. In group A, three screws (15%) were placed with grade 1, two screws (10 %) with grade 2, and one screw (5 %) with grade 3. In group B, two screws (10 %) were placed with grade 1, and one screw (5 %) – with grade 2.The average deviation at the screw entry point was 5.0 ± 0.5 mm in group A, 1.7 ± 0.3 mm in group B, and 0.35 ± 0.05 mm in group C. The average deviation at the end point was 5.1 ± 0.7 mm in group A, 3.5 ± 0.6 mm in group B, and 0.53 ± 0.05 mm in group C. Differences between groups in terms of implantation safety and accuracy are statistically significant (p < 0.05). Conclusion. Bilateral three-point navigation templates supported by spinous process are recommended for pedicle screw placement in the cervical and thoracic spine.

3D printed navigation template-guided minimally invasive percutaneous plate osteosynthesis for distal femoral fracture: A retrospective cohort study

ObjectiveTo evaluate functional and radiological outcomes in distal femoral fracture patients (distal femoral shaft fractures or metaphyseal fractures) receiving indirect reduction and internal fixation with the minimally invasive percutaneous plate osteosynthesis (MIPPO) assisted by 3D printing navigation templates. MethodsThis retrospective study included all adult (≥18 years) patients who underwent MIPPO for distal femoral fracture (AO32/33) at PLA 960 Hospital, Jinan, China between January 1, 2013 and December 31, 2016. 3D printed navigation templates were used to assist surgery. Functional assessment was performed using the Knee Society Score (KSS) and the Functional Knee Society Score (FKSS). Postoperative deformity was assessed with 3D-CT reconstruction using contralateral (non-fracture) side as the reference. ResultsA total of 54 patients underwent MIPPO for distal femoral fracture during the review period (34 and 20 for conventional and template-guided MIPPO, respectively). At 10–14 months, the KSS score was 160.6 ± 18.1 and 167.5 ± 17.2 in the conventional and template-guided MIPPO groups, respectively (p = 0.18). The FKSS was 77.6 ± 9.4 in the conventional MIPPO group vs. 81.0 ± 8.5 in the template-guided MIPPO group (p = 0.15). Femoral length difference was smaller in template-guided MIPPO group (3.31 ± 1.53 vs. 9.50 ± 4.49 mm in the control; p < 0.01). Template-guided MIPPO group also had smaller anatomic lateral distal femoral angle (aLDFA) difference (1.57° ± 0.72° vs. 3.89° ± 1.72° in the control; p < 0.01), anatomic posterior distal femoral angle (aPDFA) difference (1.95° ± 0.78° vs. 5.04° ± 1.78°; p < 0.01), and anteversion angle difference (2.52° ± 1.00° vs. 8.23° ± 4.07°; p < 0.01). The rate of length discrepancy (>20 mm), coronal angulation deformity (aLDFA difference >5°), sagittal angulation deformity (aPDFA difference >10°), and rotational malalignment (anteversion angle >10°) was 5.9%, 20.5%, 2.9%, and 32.4% in the control group. No patients in the template-guided MIPPO group had deformity of any type. ConclusionsMIPPO assisted by 3D printing navigation templates could practically improve surgical accuracy and eliminate postoperative rotational deformity in patients with distal femoral fractures.

A 3D-printed template for preparation of tibial tunnel in reconstruction of anterior cruciate ligament

Objective To evaluate the accuracy of a 3D-printed template used to assist the preparation of tibial tunnel in reconstruction of anterior cruciate ligament (ACL). Methods Twenty healthy adult cadaveric knees were scanned by computed tomography(CT) and magnetic resonance imaging (MRI). The knees were from 11 males and 9 females who had died at an average age of 36 years (range, from 27 to 68 years) and from 8 left and 12 right sides. Individualized 3D reconstruction models of the knee joint were established based on their imaging data. According to the anatomic footprints of the virtual tibial tunnel, 20 individualized navigation templates were designed and printed by 3D printing. The templates were used to assisst preparation of tibial tunnels in the ACL reconstruction for the 20 cadaveric knees. After operation, CT scanning was conducted again to compare the corresponding postitions between the preoperative virtual tunnel and the postoperative actual tunnel. The positions of the tibial tunnel were described by the Tsukada method. Results The ratio of the distance between the tunnel outlet center and the medial edge of the tibia to the distance between the median and lateral edges of the tibial plateau was 49.7%±2.1% for the preoperative virtual tibial tunnel and 48.8%±2.8% for the postoperative actural tunnel, showing no significant difference between them (t=1.971, P=0.063). The ratio of the distance between the tunnel outlet center and the anterior edge of the tibia to the distance between the anerior and posterior edges of the tibial plateau was 41.3%±1.3% for the preoperative virtual tibial tunnel and 40.3%±3.7% for the postoperative actural tunnel, showing no significant difference between them(t=1.494, P=0.152). Conclusion 3D printing can be used to design and manufacture a navigation template which can accurately assist preparation of tibial bone tunnel in ACL reconstruction. Key words: Knee joint; Anterior cruciate ligament; 3D printing technology; Template; Tibial bone tunnel

Accuracy of Computer-Guided Template-Based Implant Surgery: A Computed Tomography-Based Clinical Follow-Up Study.

The aim of this clinical study was to analyze the accuracy of computer-guided implant surgery. Assisted by computed tomography (CT)-based planning software and navigational templates, 16 patients successfully received 26 dental implants. Each implant parameter (a-d) was calculated based on superimposed preoperative and postoperative cone beam CT scans: (a) deviation at entry point; (b) deviation at apex; (c) angular deviation; and (d) depth deviation. Mean central deviation at implant entry point and apex was 0.91 mm (standard error [SE] = 0.11 mm; 95% confidence interval [CI]: 0.69-1.13) and 1.22 mm (SE = 0.11 mm; 95% CI: 0.99-1.45), respectively. Mean angulation deviation was 4.11 degrees (SE = 0.52 degrees; 95% CI: 3.04-5.17) and the average depth deviation was 0.65 mm (SE = 0.11 mm; 95% CI: 0.42-0.87). For the total number of implants placed, the maximum error was 2.34 mm at entry point, 2.71 mm at apex, 9.44 degrees in angular deviation, and 2.00 mm in depth deviation. Great accuracy was reached even in advanced cases with prior bone augmentation and complex traumas. This leads to the conclusion that particularly in advanced cases, computer-guided implantation can be beneficial.

Gait analysis after total knee arthroplasty assisted by three-dimensional printing navigation template

To explore the gait trajectory characteristics of patients after total knee arthroplasty (TKA) assisted by three-dimensional (3D) printing navigation template. Twenty female patients (20 knees) with knee osteoarthritis who were treated with TKA assisted by 3D printing navigation template between February 2017 and February 2018 were selected as the 3D printing group. The patients were 50-69 years old, with an average age of 57.2 years. The disease duration was 4-7 years, with an average of 5.6 years. The osteoarthritis was classified as Kellgren-Lawrence Ⅲ level in 5 cases and Ⅳ level in 15 cases. The preoperative hip-knee-ankle angle (HKA) was (170.8±5.6)°. All patients were varus deformity. According to age and affected side, 20 healthy female volunteers were selected as the control group. The volunteers were 51-70 years old, with an average age of 56.7 years. Preoperative HKA was (178.8±0.6)°. There was significant difference in HKA between the two groups ( P>0.05). The HKA, Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and visual analogue scale (VAS) scores of the 3D printing group before and after operation were compared. At 6 months after operation, the gait trajectory characteristics of 3D printing group and control group were analyzed by Vicon gait capture system. The kinematics parameters included velocity, cadence, stride length, maximum knee flexion angle (stance), minimum knee flexion angle (stance), maximum knee flexion angle (swing), mean hip rotation angle (stance), mean ankle rotation angle (stance). The incisions of 3D printing group healed by first intention, with no complications. All patients were followed up 7-12 months (mean, 9.0 months). The WOMAC and VAS scores at 6 months after operation were significant lower than those before operation ( P<0.05). The HKA was (178.8±0.8)° at 4 weeks after operation and the difference was significant when compared with that before operation ( t=39.203, P=0.000). The position of the prosthesis was good. The femoral posterior condyle osteotomy line, surgical transepicondylar axis, and patella transverse line were parallel, varus deformity was corrected, and lower limb alignment was restored to neutral position. Gait analysis at 6 months after operation showed that the differences in all kinematics parameters between the two groups were significant ( P<0.05). Assisted by 3D printing navigation template, TKA can alleviate pain symptoms and correct deformity, with satisfactory early effectiveness. Compared with healthy people, the early postoperative gait of the patients were characterized by decreasing velocity, cadence, stride length, knee flexion range, and increasing compensatory hip and ankle rotation range.

Navigation template for vertebral pedicle passage in transpedicular screw fixation

Transpedicular screw fixation is the most established means to stabilize the spine. Present study evaluates personalized navigation templates application for vertebral pedicle passage. Navigation templates were used for inserting 35 transpedicular screws in 5 patients with spinal deformity (age 2–16). Each patient underwent computed tomography preoperatively. Acquired data was processed into a virtual 3d-model of target zone. Life size virtual pedicular probes were placed onto transpedicular trajectories determined on multiplanar cross-sections of the model. Navigation template was created by modification and union of geometric primitives. Target zone model and navigation template were made with PLA by 3D-printer. In surgery the template was placed on skeletonized posterior surface of appropriate vertebrae. After confirmation of template stability trajectories were passed to a depth of 20 mm through guiding tubes by pedicular probe. Resulting channels were controlled with ball tip feeler, and the full depth trajectories were made by free hand technique. Postoperatively screws placement accuracy was assessed by plain X-rays in each patient. Two patients (16 screws) also underwent computed tomography. In these patients screw placement accuracy was assessed by system based on 2 mm breach increments. 15 screws (93. 7%) were fully contained within the pedicle (grade 0), 1 screw breached external cortex of the pedicle by 0. 8 mm (grade 1). Efficacy and safety of navigation template for transpedicular screws insertion was demonstrated.

Application of patient-specific 3D navigation templates for pedicle screw fixation of subaxial and upper thoracic vertebrae

Objective. To analyze the safety and accuracy of pedicle screw placement in the subaxial cervical and upper thoracic spine using patient-specific 3D navigation templates.Material and Methods. The study included 16 patients who underwent transpedicular implantation of screws in the subaxial cervical and upper thoracic vertebrae using patient-specific 3D navigation templates. A total of 88 screws were installed. All patients underwent preoperative CT angiography to assess visualization of the vertebral artery. Customized vertebral models and navigation templates were created using 3D printing technology. Models and templates were sterilized and used during surgery. The results of screw implantation, as well as the safety and accuracy of the placement, were assessed by postoperative CT.Results. The average deviation from the planned trajectory was 1.8 ± 0.9 mm. Deviation was estimated as class 1 (&lt;2 mm) for 57 (64.77 %) screws, class 2 (2–4 mm) for 29 (32.95 %), and class 3 for two (2.27 %). The safety of screw implantation of grade 0 (the screw is completely inside the bone structure) was in 79 (89.77 %) cases, of grade 1 (&lt;50 % of the screw diameter perforates the bone) – in 5 (5.68 %), and of grade 3 – in 2 (2.27 %).Conclusion. Using 3D navigation templates is an affordable and safe method of installing pedicle screws in the cervical and upper thoracic spine. The method can be used as an alternative to intraoperative CT navigation.

The influence of triple pelvic osteotomy on the spine-pelvis ratios in children with dysplastic subluxation of the hip

Introduction. Triple pelvic osteotomy is an effective surgical treatment for dysplastic subluxation of the hip in children aged above 12 years. However, modern studies did not assess the indicators of spine-pelvis ratios, sagittal profile of the spine in children with dysplastic subluxation of the hip following surgical treatment, and possibility of change on these values during the operation.&#x0D; Aim. This study aimed to evaluate the effectiveness of the improved technique of performing triple pelvic osteotomy on children with dysplastic subluxation of the hip.&#x0D; Materials and methods. We analyzed the x-ray images and surgical treatment of 35 female patients (44 hip joints) aged 13 to 18 years with dysplastic subluxation of the hip between 2016 and 2018. The patients were divided into two groups: the main group consisted of 20 patients (25 hip joints) who underwent surgical treatment that had taken into account the state of sagittal spine-pelvis ratios according to the improved method using personalized navigation templates, and the control group consisted of 15 patients (19 hip joints) who received surgical treatment according to the generally accepted method.&#x0D; Results. In addition to the typical clinical and radiological abnormalities of the dysplastic subluxation of the hip in 90% of patients in both groups, there were changes in the sagittal balance in the form of excessive pelvic anteversion and lumbar hyperlordosis. One year postoperatively, patients in the main group showed significant changes (p &lt; 0.05) in the state of sagittal spine-pelvis ratios in the form of a decrease in the pelvic base angle, which led to the achievement of the average values of the angle of inclination of the sacral slope (SS) and the value of global lumbar lordosis. On the other hand, these radiological parameters in patients in the control group remained within the preoperative values.&#x0D; Conclusion. The improved technique of triple pelvic osteotomy provides conditions for the reduction of pelvic anteversion and restoration of the sagittal profile of the spine (p &lt; 0.05). The use of personalized navigation templates allows for the most accurate multiplane correction of the acetabulum. It is necessary to include a specialized x-ray examination in the preoperative planning to assess the state of sagittal spine-pelvis ratios.

Three-Dimensionally Printed Template for Percutaneous Localization of Multiple Lung Nodules

When multiple target lung nodules exist, the computed tomography (CT)-guided percutaneous localization procedure becomes complicated. In this study, a three-dimensional (3D)-printed template was designed that could guide hook wire localization of multiple lung nodules. The pilot study aimed for preliminary validation of the feasibility of template-guided localization for multiple lesions. Patients with multiple lung nodules (<2 cm) and who were scheduled for surgical resection were recruited for participation in this study. After securing their preadmission CT images, the study investigators reconstructed a 3D thorax model from which they designed a digital model as a navigational template. A physical template was then printed for guiding the percutaneous localization of lung nodules. The localization accuracy was evaluated on the basis of the deviation between the localizer and the nodule. From April 2018 to November 2018, the study enrolled 16 patients with 34 lung nodules. All noduleswere successfully localized under template guidance, with a median procedural time of 10.0minutes(interquartile range [IQR], 8.5-12.6 minutes) anda median radiation exposure of 235 mGy • cm(IQR, 195-254 mGy • cm). The median deviation fromthe hookwires and nodule centers was 9.0 mm (IQR, 6.2-11.8 mm). Except for2 cases of pneumothorax without needfor furtherintervention, no complications occurred. Navigational templates built using 3D printing may serve as an effective approach for facilitating localization of multiple lung nodules.

Effectiveness analysis of three-dimensional printing assisted surgery for unstable pelvic fracture

To evaluate the effectiveness of three-dimensional (3D) printing assisted internal fixation for unstable pelvic fractures. The clinical data of 28 patients with unstable pelvic fractures admitted between March 2015 and December 2017 were retrospectively analyzed. The patients were divided into two groups according to different surgical methods. Eighteen cases in the control group were treated with traditional anterior and posterior open reduction and internal fixation with plate; 10 cases in the observation group were treated with 3D printing technology to make pelvic models and assist in shaping the subcutaneous steel plates of the anterior ring. Sacroiliac screw navigation template was designed and printed to assist posterior ring sacroiliac screw fixation. There was no significant difference between the two groups in gender composition, age, cause of injury, fracture type, and time interval from injury to surgery ( P>0.05). The operation time, intraoperative blood loss, intraoperative fluoroscopy times, incision length, waiting time for weight-bearing exercise, and fracture healing time were recorded and compared between the two groups. Majeed score was used to evaluate the function at last follow-up. At immediate after operation, the reduction was evaluated according to Matta imaging scoring criteria, and the success of sacroiliac joint screw implantation in the observation group was evaluated. The deviation of screw entry point and direction between postoperative screws and preoperative simulated screws were compared in the observation group. All the operation was successfully completed, and all patients were followed up 6-18 months (mean, 14.4 months). In the control group, 1 case had wound infection and 2 cases had deep vein thrombosis. No serious complication such as important blood vessels, and nerve injury and pulmonary embolism occurred in other patients in the two groups. No screw pulling out or steel plate breaking occurred. The operation time, intraoperative blood loss, fluoroscopy times, incision length, and waiting time for weight-bearing exercise of the control group were significantly more than those of the observation group ( P<0.05); there was no significant difference in fracture healing time between the two groups ( t=0.12, P=0.90). There was no significant difference in reduction quality between the two groups at immediate after operation ( Z=-1.05, P=0.30); Majeed score of the observation group was significantly better than that of the control group at last follow-up ( Z=-2.42, P=0.02). The success rate of sacroiliac joint screw implantation in the observation group reached category Ⅰ. In the observation group, the deviation angle of the direction of the screw path between the postoperative screw and the preoperative simulated screw implant was (0.09±0.22)°, and the deviation values of the entry points on the X, Y, and Z axes were (0.13±0.63), (0.14±0.58), (0.15±0.53) mm, respectively. There was no significant difference when compared with those before the operation (all values were 0) ( P>0.05). Computer design combined with 3D printing technology to make personalized pelvic model and navigation template applied to unstable pelvic fractures, is helpful to accurately place sacroiliac screw, reduce the operation time, intraoperative blood loss, and the fluoroscopy times, has good waiting time for weight-bearing exercise and function, and it is an optional surgical treatment for unstable fractures.

3D printed navigation template assists pedicle lag-screw placement for atypical Hangman’s fracture

Objectives To evaluate the 3D printed navigation template used to assist axis pedicle lag-screw placement in the treatment of atypical Hangman’s fracture (AHF). Methods From May 2015 to January 2017, 12 patients with AHF were treated at Department of Orthopedics, The Fourth People’s Hospital of Zigong.In their operation, the axis pedicle lag-screw placement was assisted by a 3D printed navigation template.They were 8 men and 4 women, aged from 27 to 53 years (average, 45.6 years).There were 7 cases of type Ⅰ, 4 cases type Ⅱ and one case of type ⅡA according to the Levine-Edwards classifi-cation.There were 2 cases of grade D and 12 cases of grade E according to the assessment of America Spinal Injury Association (ASIA).Their preoperative and postoperative neck pain was evaluated by visual analogue scale (VAS); their preoperative and postoperative ranges of cervical motion were recorded and compared.To evaluate the postoperative safety of screws, the insertion point, position within the pedicle, axial angle and sagittal angle of the screws and maximum fracture displacement were compared between actual operation and simulative operation. Results A total of 12 guide plates were designed and printed; a total of 24 lag-screws were placed.All patients underwent surgery uneventfully.They were followed up for 12 to 20 months, with an average of 14.7 months.Two patients with ASIA grade D recovered to ASIA grade E at the last follow-up.All patients showed a significant improvement in neck pain.Their VAS score at 5 days after surgery (5.86±2.02) was significantly lower than their preoperative score (8.29±1.88) (P 0.05).Their postoperative X-ray and CT images showed that the dislocation was all corrected.The last follow-up showed no obvious vertebral in-stability, screw breakage or loosening.Postoperative CT showed that the 24 screws had been located com-pletely in the pedicle (grade 0), indicating that the screw placement was 100% accurate.The postoperative deviation at insertion point (0.70±0.78 mm), deviation within the pedicle (1.3±0.82 mm), axial angle (8.26°±0.88°) and sagittal angle (22.62°±0.86°) of the screws showed no significant differences from the preoperative simulative data (P>0.05).There was a significant difference in the maximum fracture dis-placement between the preoperative data (3.94±0.38 mm) and the postoperative data (2.21±0.39 mm) (P<0.05). Conclusion The 3D printed navigation template can be used to better assist axis pedicle lag-screw placement in the treatment of AHF, because it ensures safe screw placement, leading to good re-duction and fixation and precise match with the preoperative plan. Key words: Axis; Fracture; Fractures fixation, internal; Bone screw; 3D printing tech-nology

Design and basic research on accuracy of a novel individualized three-dimensional printed navigation template in atlantoaxial pedicle screw placement.

ObjectiveTo design and evaluate the accuracy of a novel navigation template suitable for posterior cervical screw placement surgery by using 3D printing technology to improve the existing guiding template design.MethodsThe researchers (including spine surgeons and technicians) used CT to perform thin-slice scanning on 12 cases of normal upper cervical vertebral specimens and defined the screw channels that were completely located in the pedicle without penetrating the cortex as ideal screw channels, then designed the ideal channel of the upper cervical vertebral (atlantoaxial) pedicle screw by computer software which was regarded as the preset values, and recorded the screw entrance point, transverse angle and sagittal angle of the ideal channel. Then, researchers designed the novel navigation templates for placement pedicle screw according to the ideal screw channel preset values and manufactured them with one for every single vertebra by 3D printer. A senior spine surgeon performed the posterior surgery to implant pedicle screw on the specimens by the novel navigation templates, then performed CT thin-slice scanning on the specimens again after removing the screws, and reconstructed the actual screws channel by computer software, recorded the screw entrance point, transverse angle and sagittal angle of the actual channels which were defined as the actual values and evaluated them according to Kawaguchi’s pedicle screw evaluation standard finally. The differences between the preoperative preset values of ideal screw channel and the postoperative actual values of actual screw channel were compared by a nonparametric paired rank test.Results48 screws were placed on 12 cases of upper cervical vertebral specimens in total. It showed that the grade 0, I, II, III channels in this study were 47, 1, 0, 0, respectively. The grade 0 channels accounted for 97.92% of the total number of channels. There was no significant difference with regard to the screw entrance point, the transverse angle, and the sagittal angle between the preoperative preset values of ideal screw channels and the postoperative actual values of actual screw channels.ConclusionTo implant pedicle screw assisted with the novel individually navigation template designed by 3D printed in the posterior cervical surgery can improve accuracy of pedicle screw placement and safety of the surgery.

Preliminary application of 3D printing navigation template in the screw insertion of the suprapubic fracture

Objective To introduce the method of using hollow pull screw insertion for the suprapubic fracture with 3D printing navigation template and to evaluate its clinical effect. Methods From March 2016 to August 2017, eighteen cases of suprapubic ramus fractures treated with hollow lag screw fixation in the Department of Orthopedics of Yanan University Affiliated Hospital were retrospectively collected was collected.Before operation, the thin slice CT scan of pelvis was used to get raw data, and the mimics17.0 software was used to reconstruction the model, to design and make the personalized navigation template assisting the suprapubic fractures surgery.The navigation template was printed out pre-operatively, and the nail was inserted via the assisted by the template intra-operatively.After the operation, the fracture reduction was evaluated by Matta imaging scores and the pelvis function was evaluated by Majeed scores. Results All the operations were successfully completed.The Matta scores were excellent in 11 cases, good in 6 cases, and fair in 1 case.The Majeed scores were excellent in 13 cases, good in 3 cases, and fair in 2 cases. Conclusion 3D Printing navigation template assisted the placement of the hollow screw on the suprapubic fracture could provide personalized treatment, reduce the difficulty of operation and satisfy the clinical effect. Key words: 3D printing navigation template; suprapubic fracture; Retrospectively study

Accuracy analysis and clinical application of the progressive navigation template system to assist atlas-axial pedicle screw placement

To investigate the accuracy of progressive three-dimensional navigation template system (abbreviated as progressive template) to assist atlas-axial pedicle screw placement. The clinical data of 33 patients with atlas-axial posterior internal fixation surgery between May 2015 and May 2017 were retrospectively analyzed. According to the different methods of auxiliary screw placement, the patients were divided into trial group (19 cases, screw placement assisted by progressive template) and control group (14 cases, screw placement assisted by single navigation template system, abbreviated as initial navigation template). There was no significant difference in gender, age, cause of injury, damage segments, damage types, and preoperative Frankel classification between the two groups ( P>0.05). The operation time and intraoperative blood loss of the two groups were compared. The safety of screw placement was evaluated on postoperative CT by using the method from Kawaguchi et al, the deviation of screw insertion point were calculated, the angular deviation of the nailing on coordinate systems XOZ, XOY, YOZ were calculated according to Peng's method. All patients completed the operation successfully; the operation time and intraoperative blood loss in the trial group were significantly less than those in the control group ( t=-2.360, P=0.022; t=-3.006, P=0.004). All patients were followed up 12-40 months (mean, 25.3 months). There was no significant vascular injury or nerve injury aggravation. Postoperative immediate X-ray film and CT showed the dislocation was corrected. Postoperative immediate CT showed that all 76 screws were of grade 0 in the trial group, and the safety of screw placement was 100%; 51 screws were of grade 0, 3 of gradeⅠ, and 2 of gradeⅡ in the control group, and the safety of screw placement was 91.1%; there was significant difference in safety of screw placement between the two groups ( χ2=7.050, P=0.030). The screw insertion point deviation and angular deviation of the nailing on XOY and YOZ planes in the trial group were significantly less than those in the control group ( P<0.05). There was no significant difference in angular deviation of the nailing on XOZ between the two groups ( t=1.060, P=0.290). Compared with the initial navigation template, the progressive navigation template assisting atlas-axial pedicle screw placement to treat atlas-axial fracture with dislocation, can reduce operation time and intraoperative blood loss, improve the safety of screw placement, and match the preoperative design more accurately.

Design and Application of Individualized, 3-Dimensional-Printed Navigation Template for Placing Cortical Bone Trajectory Screws in Middle-Upper Thoracic Spine: Cadaver Research Study

To evaluate the safety and accuracy of use of a 3-dimensional printed navigation template in the placement of a cortical bone trajectory (CBT) screw in the middle-upper thoracic spine. Ten human cadavers were included in the study. Sixty CBT screws were placed on 1 side, using the free-hand technique, and 60 CBT screws were placed on the other side, using the navigation template that was designed and printed using data from 10 cadavers. The safety and accuracy of use of the CBT screws were directly evaluated by radiography and computed tomography. Computed tomography revealed that 2 and 3 of 60 screws, placed using the navigation template, were broken in the medial or lateral areas and in the superior or inferior pedicle wall, respectively. Furthermore, 8 screws were broken in the medial or lateral areas and 11 screws were broken in the superior or inferior pedicle wall when the free-hand technique was used. Radiography revealed that 3 screws in zone I, 55 screws in zone II, and 2 screws in zone III were placed using the navigation template. Furthermore, 7 screws in zone I, 45 screws in zone II, and 8 screws in zone III were placed using the free-hand technique. In this cadaver study, insertion of the CBT screws in the middle-upper thoracic spine with the assistance of the navigation template was safe and convenient.

3D打印阻挡钉导航模板在胫骨骨折髓内钉闭合复位内固定术的临床应用

3D打印阻挡钉导航模板在胫骨骨折髓内钉闭合复位内固定术的临床应用