Drill Guides Research Articles

Accuracy of pin placement in the canine thoracolumbar spine using a free-hand probing technique versus 3D-printed patient-specific drill guides: An ex-vivo study.

To compare pin placement accuracy, intraoperative technique deviations, and duration of pin placement for pins placed by free-hand probing (FHP) or 3D-printed drill guide (3DPG) technique. Four greyhound cadavers. Computed tomography (CT) examinations from T6-sacrum were obtained for determination of optimal pin placement and 3DPG creation. Two 3.2/2.4-mm positive profile pins were inserted per vertebra, one left and one right from T7-L7 (FHP [n = 56]; 3DPG [n = 56]) by one surgeon and removed for repeat CT. Duration of pin placement and intraoperative deviations (unanticipated deviations from planned technique) were recorded. Pin tracts were graded by two blinded observers using modified Zdichavsky classification. Descriptive statistics were used. A total of 54/56 pins placed with 3DPGs were assigned grade I (optimal placement) compared with 49/56 pins using the FHP technique. A total of 2/56 pins placed with 3DPGs and 3/56 pins using the FHP technique were assigned grade IIa (partial medial violation). A total of 4/56 pins placed using the FHP technique were assigned grade IIIa (partial lateral violation). No pins were assigned grade IIb (full medial violation). Intraoperative technique deviations occurred with 6/56 pins placed using the FHP technique and no pins with 3DPGs. Overall, pins were placed faster (mean ± SD 2.6 [1.3] vs. 4.5 [1.8] min) with 3DPGs. Both techniques were accurate for placement of spinal fixation pins. The 3DPG technique may decrease intraoperative deviations and duration of pin placement. Both techniques allow accurate pin placement in the canine thoracolumbar spine. The FHP technique requires specific training and has learning curve, whereas 3DPG technique requires specific software and 3D printers.

Comparison of a Novel Static Computer-aided Surgical and Freehand Techniques for Osteotomy and Root-end Resection

IntroductionThis study compared the accuracy and efficiency of a novel static computer-aided surgical technique using a 3-dimensional (3D)-printed surgical guide (3D-SG) with a fully guided drill protocol (3D-SG FG) to the freehand (FH) osteotomy and root-end resection (RER). MethodsForty-six roots from 2 cadaver heads were divided into 2 groups: 3D-SG FG (n = 23) and FH (n = 23). Cone-beam computed tomographic scans were taken preoperatively and postoperatively. The endodontic microsurgery was planned in Blue Sky Bio software, and the 3D-SG was designed and 3D printed. The osteotomy and RER were conducted using a guided twist drill diameter of 2 mm and an ascending tapered drill with diameters of 2.8/3.2, 3.2/3.6, 3.8/4.2, and 4.2 mm with respective guided drill guides. Two-dimensional and three-dimensional virtual deviations and angular deflection were calculated. Linear osteotomy measures and root resection angle were obtained. The osteotomy and RER time and the number of mishaps were recorded. ResultsTwo-dimensional and three-dimensional accuracy deviations and angular deflection were lower in the 3D-SG FG protocol than in the FH technique (P < .05). The height, length, and depth of the osteotomy and root resection angle were less in the 3D-SG FG protocol than in the FH technique (P < .05). The osteotomy and RER time with the 3D-SG FG protocol were less than the FH method (P < .05). ConclusionsWithin the limitations of this cadaver-based study using denuded maxillary and mandibular jaws, 3D-SG FG protocol showed higher accuracy than FH osteotomy and RER. Moreover, the 3D-SG FG drill protocol significantly reduced the surgical time.

Custom-made 3D-printed porous metal acetabular composite component in revision hip arthroplasty with Paprosky type III acetabular defects: A case report.

Increases in the numbers of surgical procedures for primary total hip arthroplasty (THA) inevitably lead to increases in the requirements for revision THA. The achievement of long-term stability is difficult or impossible by conventional implants in patients with severe destruction of the acetabulum. This case report presents a successful treatment using a specific three-dimensional (3D)-printed porous titanium acetabular composite component without a flange in the management of Paprosky type IIIB acetabular defects. A 65-year-old female diagnosed with right hip prosthetic loosening with a huge acetabular defect presented to our hospital. We designed the 3D model of the pelvis and created an individualized 3D-printed porous titanium acetabular composite component for revision THA. The procedure was performed through a posterolateral approach, and the component was implanted in the defect and fixed with cup screws using the drill guides. At the last follow-up at 2years, the patient had a satisfactory hip joint function and no signs of loosening or other complications were found. The 3D-printed porous titanium acetabular composite component without a flange is showing promising clinical and radiological outcomes in the management of Paprosky type III acetabular defects.

Accuracy of CAD/CAM and 3D printing in the treatment of feline femoral neck fracture

The aim of this study was to investigate whether a CT scan provides accurate bone surface information for feline bone model development. The second part of study consisted of 3D printing of feline femoral bone models with and without femoral neck fractures (31-B1 and 31-B2 in AO VET classification), as well as the development and 3D printing of drill guides for treatment of femoral neck fractures. The study was carried out on eight models of femoral bones and four drill guides. Initially, trial models of the right and left femurs without neck fractures and trial drill guides were used. Radiographs showed that the use of the prototype guides made it possible to drill holes in the axes of the necks of the femurs. Then, after assessing the correct operation of the guides and improving their adhesion to the bone surface by smoothing the inner surfaces of the guide bases, final bone models without femoral neck fracture, models with fractures 31-B1 and 31-B2, and final drill guides were printed. All models featured a 2.7 × 30 mm positional cortical screw. Radiographs of the models, made after inserting screws, showed that the implants were placed as intended. Also in the longitudinal sections of the heads and necks of the femoral bones of the models without fractures, the implants were positioned in the intended places.

Fully Guided Synthetic Osteochondral Resurfacing of a Large Stifle OCD Lesion Using a Patient-Specific Implant and Drill Guides

AbstractSynthetic anatomical reconstruction of extensive, oval osteochondrosis dissecans (OCD) defects remains a challenge due to the ‘one shape fits all’ design of commercial round implants. This is further complicated by the inherent inaccuracy of free-hand implant positioning procedures. A 6-month-old German Shepherd presented with a 15 × 7.8 × 4.3 mm OCD defect at the lateral femoral condyle. A synthetic patient-specific implant (PSI) was designed, using the contralateral unaffected condyle as a template. Reaming of the implant bed was fully guided using a set of three-dimensional-printed drill guides. The implant, consisting of a titanium base and a polycarbonate urethane bearing surface, was press-fit into place. Temporary meniscal release of the cranial meniscal horn was repaired, followed by routine closure and postoperative care. The combination of PSI and matching drill guides resulted in an accurate restoration of the normal joint surface at the former defect area. At 6-week and 18-month follow-ups, mild joint effusion, unexpected soft tissue mineralization and a small joint mouse were present. No other complications were encountered, and the dog was clinically lameness-free. At 6 weeks and 6 months, computerized gait analysis documented increased loading of the affected limb from 36% preoperatively to 42 and 40%, on follow-up, respectively. Body weight distribution between both hindlimbs was nearly equal at the 6-month control with 1% difference in loading. Osteochondral resurfacing using a PSI appears to be a promising treatment option for large stifle OCD lesions in which other treatment modalities may not be eligible.

Low-cost 3D Modeling Software for Generating Patient-specific Drill Guide Templates for Cervical Pedicle Screw Insertion: An In Vitro Study

Background. Instrumented posterior cervical spine surgery (IPCSS) can be conducted using screws inserted through the pedicles of the vertebra. A safe IPCSS method uses 3D-printing to produce templates that will serve as drill guides for screw placement.Objectives. This study describes the generation of 3D-printed drill guides using low-cost general purpose 3D modeling software and the comparison of screw insertion accuracy scores against the traditional landmark method and guides created using commercial grade software.Methods. Twenty-five (25) subaxial pedicles of five cadaveric spines were selected and scanned using computedtomography (CT). A digital reconstruction of the five cadaveric spines were created based on the CT DICOM data. A low-cost 3D modeling software, Rhinoceros 3D, was utilized for trajectory planning and generation of a patientspecific drill template using the digital reconstruction. The templates were then fabricated in ABS plastic using a fused deposition modeling (FDM) 3D printer. Insertion of cervical pedicle screws on the cadaveric spines was done by an orthopedic resident using the 3D printed guides. Postoperative CT scans were obtained, and placement accuracy of the screws were scored by two assessors utilizing a four-point rating system. Screws in correct placement were scored Grade 0 while misplaced screws with neurovascular damage were given a score of Grade 3.Results. Accuracy scores for the 3D-printed drill guides were 52% for assessor 1 and 44% for assessor 2. Forassessor 1, screw placement in C3, C6, and C7 received the highest scores. For assessor 2, the highest scores were achieved in C3 and C7. The hybrid method of Bundoc et al. achieved scores of 94% while 3D printed guides utilizing commercial software like Materialise Mimics, Geomagic Freeform, or UG Imageware achieved scores of 80-100%. The traditional landmark method had scores ranging from 12% to 94% depending on the skill of the surgeon.Conclusion. Commercial medical 3D image-based engineering software has high acquisition costs that might be beyond the reach of most institutions. A sub-$1000 general purpose 3D modeling software can be used to create drill templates. Several factors were identified in the design and fabrication of the template that can be addressed to increase accuracy. Trajectory planning can also be improved by automating the process. The researchers recommend further studies in these areas specially in the context of developing 3D printing as a support service for surgical operations in the Philippines.

Minimally invasive plate osteosynthesis of femoral fractures with 3D-printed bone models and custom surgical guides: A cadaveric study in dogs.

Assess the accuracy and efficiency of reduction provided by application of plates precontoured to 3-dimensional (3D)-printed femoral bone models using a custom fracture reduction system (FRS) or intramedullary pin (IMP) to facilitate femoral minimally invasive plate osteosynthesis (MIPO) in dogs. Experimental cadaveric study. Seven dog cadavers. Virtual 3D femoral models were created using computed tomographic images. Simulated, virtual mid-diaphyseal femoral fractures were created and reduced. Reduced femoral models were 3D-printed and a plate was contoured. Custom drill guides for plate screw placement were designed and 3D-printed for the FRS. Mid-diaphyseal simulated comminuted fractures were created in cadavers, and fractures were aligned using FRS or IMP and stabilized with the precontoured plates. Number of fluoroscopic images acquired per procedure and surgical duration were recorded. Computed tomographic scans were repeated to assess femoral length and alignment. Compared to the preoperative virtual plan, median change in femoral length and frontal, sagittal, and axial alignment was less than 3 mm, 2°, 3°, and 3° postoperatively, respectively, in both reduction groups. There was no difference in length or alignment between reduction groups (P > .05). During FRS, fewer fluoroscopic images were taken (P=.001), however, surgical duration was longer than IMP procedures (P=.011). Femoral alignment was accurate when using plates precontoured to 3D printed models, regardless of reduction method. Accurate plate contouring using anatomically accurate models may improve fracture reduction accuracy during MIPO applications. Custom surgical guides may reduce fluoroscopy use associated with MIPO.

Thoracolumbar Spinal Stabilization with Three Dimensional-Printed Drill Guides and Pre-Contoured Polyaxial Bone Plates.

The aim of this study was to report new preoperative and intraoperative techniques performed for canine thoracic or lumbar spine kyphosis stabilization using three-dimensional-printed patient-specific drill guides, polyaxial titanium bone plates and drill stops, and to determine the accuracy of screw placement using these techniques. Retrospective study, five client-owned dogs. Three-dimensional-printed patient-specific drill guides and drill stops allowed safe drilling and screw placement in all of the cases, with (i) 84% of the screws graded as I (ideal placement) and 16% as IIa, IIIa or IIIb according to the modified Zdichavsky classification (partial penetration of medial pedicle wall, partial penetration of lateral pedicle wall and full penetration of lateral pedicle wall respectively), (ii) mean mediolateral deviation of ± 4.06 degrees (standard deviation: 8.21 degrees) compared to planned trajectories and (iii) variation in screw depth of ± 2.29mm (standard deviation: 3.07mm) compared to planned depth. We believe that the techniques presented here for thoracic spinal stabilization in dogs show promise; they allowed safe placement of screws along planned trajectories and depth; they also removed the need to use polymethylmethacrylate, while the use of titanium offers the possibility to repeat magnetic resonance imaging in these cases with chronic spinal conditions.

3D planning and patient specific instrumentation for intraarticular corrective osteotomy of trapeziometacarpal-, metacarpal and finger joints

BackgroundIntra-articular malunions of the finger can lead to deformity and loss of function and can be treated with intra-articular corrective osteotomies. The aim of this study was to evaluate radiographic joint congruency, feasibility and functional outcome of three-dimensional (3D) printed patient-specific instrumentation (PSI) for corrective osteotomies at the trapeziometacarpal and finger joints.MethodsComputer-tomography (CT) scans were acquired preoperatively for standard 3D planning, which was followed by calculation of cutting planes and the design of individualized bone surface contact drilling, sawing and reposition guides. Follow-up CT scans and clinical examinations (range of motion, grip strength) were performed. Postoperative complications were documented and patient-reported outcome measurements were assessed (Single Assessment Numeric Evaluation (SANE) score, brief Michigan Hand Questionnaire (MHQ)).ResultsTen patients (mean age 28.4 ± 12.8,range 13.8–51.3) years) were included with a mean follow-up of 21 ± 18 (3–59) months including seven osteotomies at the trapeziometacarpal or metacarpophalangeal joints and three at the proximal interphalangeal joint (PIP). All radiographic follow-up examinations showed the planned correction with good joint congruency and regular osseous consolidation. At the latest follow-up, the range of motion (ROM) increased and the average grip strength recovered to the level of the contralateral side. No postoperative complication was detected. The mean SANE score improved from 44 ± 23 (0–70) to 82 ± 12 (60–90) after a mean of 72 ± 20 (44–114) months. The mean postoperative brief MHQ was 92 ± 8 (71–98).ConclusionThe use of 3D PSI in treating intra-articular malunions at the trapeziometacarpal and finger joints restored articular congruency accurately. ROM and grip strength improved postoperatively comparable to the healthy contralateral side and patient-reported outcome measures improved after medium-term follow-up.

Early experience of wafer-free Le Fort I osteotomy with patient-specific implants in cleft lip and palate patients

The use of virtual surgical planning and patient-specific saw and drill guides combined with customized osteosynthesis is becoming a gold standard in orthognathic surgery. The aim of this study is to report preliminary results of the use of virtual surgical planning and the wafer-free PSI technique in cleft patients. Patient-specific saw and drill guides combined with milled patient-specific 3D titanium alloy implants were used in reposition and fixation in Le Fort I osteotomy of 12 cleft patients. Surgical information was retrieved from hospital records. Pre- and post-operative lateral cephalograms were analyzed. In 10 of 12 cases, the implants fitted as planned to predesigned drill holes and bone contours with high precision. In one patient, the mobilization of the maxilla was too demanding for virtually planned advancement, and the implants could not be used. In another patient, PSI fitting was impaired due to an insufficient mobilization of maxilla and tension on PSI fixation with screws. After the surgery, the mean advancement of the anterior maxilla (point A) of all patients was 5.8mm horizontally (range 2.7-10.1) and -3.1mm vertically (range -9.2 to 3.4). Skeletal relationships of the maxilla and mandible could be corrected successfully in all patients except for the one whose PSI could not be used. Virtual surgical planning combined with PSI is a possible useful clinical adjunct for the correction of maxillary hypoplasia in cleft patients. Large maxillary advancements and scarring may be cause problems for desired advancement and for the use of implants.

Accuracy of Axis Drill Guides in the Cases of Atlantoaxial Instabilities Associated With High-Riding Vertebral Arteries, Narrow Pedicles, and Complex Deformities: Comparison of 3 Fixation Methods

The current study's objective was to contrast the accuracy of C2 navigation template-assisted versus free-hand pedicle and/or pars screw fixation in high-risk cases where a high-riding vertebral artery or narrow pedicle and complex deformities were associated. In our hospital, CT data of 30 subjects with pathology on C0-1-2, who had risk factors for VA injury, that were complex cervical deformities, atlantoaxial instabilities with narrow C2 pedicle and/or HRVA variations were retrospectively reviewed. Using CAD software and desktop printer we printed three sets of high cervical models per case. We divided them into three groups using three different C2 screw fixation techniques: the free hand pars screw fixation group, the free hand pedicle screw fixation group, and the navigation template-assisted pedicle screw fixation group. After 180 screw placements were finished, the parts underwent a CT scan. Then the breach rates on postoperative scans were measured. Our results stated that the accurate placement rate is not noticeably different between navigation template-assisted and free hand pedicle screws, where the HRVA and narrow pedicles associated, but was better in navigational template group with complex deformities. Pars screws were found to be superior in terms of accuracy. The current study suggests that navigational template assisted pedicle screws are risky for high-risk individuals with abnormal anatomy, such as those with a high-riding vertebral artery, a narrow pedicle, and complex abnormalities, and alternative C2 pars screws may be a reliable option for such individuals.

Preoperative templating in orthopaedic fracture surgery: The past, present and future

Preoperative planning in orthopaedic fracture surgery corroborates with the goal of establishing the best possible surgical result and ensuring a functioning limb for the patient. From placing sketches on overhead projector paper and measuring lengths from anatomical landmarks, ways of preoperative planning have evolved rapidly over the last 100 years. Today, preoperative planning includes methods such as advanced 3-Dimensional (3D) printed models and software programs incorporating entire libraries of osteosynthesis materials that can be shaped and rotated to fit a patient's specific anatomy. Relevant literature was evaluated to review the development of preoperative templating from the past and present, in order to assess its impact on the future of osteosynthesis.We identified studies on 3D-imaging, computer-assisted systems, and 3D-printed fractured bones and drill guides. The use of some of these systems resulted in a reduction in operation time, blood loss, perioperative fluoroscopy and hospital stay, as well as better placement of osteosynthesis material. Only few studies have identified differences in patient morbidity and mortality. Future techniques of preoperative templating are on the rise and the potential is vast. The cost-effectiveness and usefulness of certain methods need to be evaluated further, but the benefit of preoperative templating has the potential of being revolutionary, with the possibility of radical advances within orthopaedic surgery.

Accuracy of a patient-specific 3D-printed drill guide for placement of bicortical screws in atlantoaxial ventral stabilization in dogs.

Atlantoaxial instability (AAI) in dogs refers to abnormal motion at the C1–C2 articulation due to congenital or developmental anomalies. Surgical treatment options for AAI include dorsal and ventral stabilization techniques. Ventral stabilization techniques commonly utilize transarticular and vertebral body screws or pins. However, accurate screw insertion into the vertebrae of C1 and C2 is difficult because of the narrow safety corridors. This study included 10 mixed dogs, 1 Pomeranian, and 1 Shih-Tzu cadaver. All dogs weighed <10 kg. Each specimen was scanned using computed tomography (CT) from the head to the 7th cervical vertebrae. This study used 12 bone models and 6 patient-specific drill guides. Bone models were made using CT images and drill guides were created through a CAD (computer-aided design) program. A total of six cortical screws were used for each specimen. Two screws were placed at each of the C1, C2 cranial, and C2 caudal positions. Postoperative CT images of the cervical region were obtained. The degree of cortex breaching and angle and bicortical status of each screw was evaluated. The number of screws that did not penetrate the vertebral canal was higher in the guided group (33/36, 92%) than in the control group (20/36, 56%) (P = 0.003). The screw angles were more similar to the reference angle compared to the control group. The number of bicortically applied screws in the control group was 28/36 (78%) compared to 34/36 (94%) in the guided group. Differences between the preoperative plan and the length of the applied screw at the C1 and C2 caudal positions were determined by comparing the screw lengths in the guide group. The study results demonstrated that the use of a patient-specific 3D-printed drill guide for AAI ventral stabilization can improve the accuracy of the surgery. The use of rehearsal using bone models and a drilling guide may improve screw insertion accuracy.

Cochlear implant positioning and fixation using 3D-printed patient specific surgical guides; a cadaveric study.

To develop and validate the optimal design and evaluate accuracy of individualized 3D- printed surgical guides for cochlear implantation. Positioning and fixation of the cochlear implant (CI) are commonly performed free hand. Applications of 3-dimensional (3D) technology now allow us to make patient specific, bone supported surgical guides, to aid CI surgeons with precise placement and drilling out the bony well which accommodates the receiver/stimulator device of the CI. Cone beam CT (CBCT) scans were acquired from temporal bones in 9 cadaveric heads (18 ears), followed by virtual planning of the CI position. Surgical, bone-supported drilling guides were designed to conduct a minimally invasive procedure and were 3D-printed. Fixation screws were used to keep the guide in place in predetermined bone areas. Specimens were implanted with 3 different CI models. After implantation, CBCT scans of the implanted specimens were performed. Accuracy of CI placement was assessed by comparing the 3D models of the planned and implanted CI's by calculating the translational and rotational deviations. Median translational deviations of placement in the X- and Y-axis were within the predetermined clinically relevant deviation range (< 3 mm per axis); median translational deviation in the Z-axis was 3.41 mm. Median rotational deviations of placement for X-, Y- and Z-rotation were 5.50°, 4.58° and 3.71°, respectively. This study resulted in the first 3D-printed, patient- and CI- model specific surgical guide for positioning during cochlear implantation. The next step for the development and evaluation of this surgical guide will be to evaluate the method in clinical practice.

Accuracy of Lumbosacral Pedicle Screw Placement in Dogs: A Novel 3D Printed Patient-Specific Drill Guide versus Freehand Technique in Novice and Expert Surgeons.

The aim of this study was to compare the accuracy of pedicle screw placement at the canine lumbosacral junction using a novel unilateral three-dimensional printed patient-specific guide (3D-PSG) versus a freehand drilling technique. Additionally, accuracy of screw placement between a novice and an experienced surgeon was determined. Preoperative computed tomography images from 20 lumbosacral cadaveric specimens were used to design a novel unilateral 3D-PSG for the L7 and sacral vertebrae which was printed in acryl-nitrile butadiene styrene plastic. A novice and an expert surgeon each placed 3.5mm cortical screws in 10 cadavers; on the left using the unilateral 3D-PSG and by the freehand (anatomic landmark) technique on the right. Sixty screws were placed using the unilateral 3D-PSG and 60 using the freehand technique. There was no statistical difference in accuracy for the comparison between methods performed by the expert (p = 0.679) and novice (p = 0.761) surgeon, nor between an expert and novice surgeon overall (p = 0.923). Unexpectedly, the use of a unilateral 3D-PSG increased variability for the expert surgeon in our study (p = 0.0314). Using a novel unilateral 3D-PSG did not improve the accuracy of screw placement for lumbosacral stabilization by a novice surgeon compared with an expert surgeon in lumbar spine surgery. This may reflect a suboptimal PSG design.

Accuracy of guide wire placement for femoral neck stabilization using 3D printed drill guides

BackgroundThe goal of stabilization of the femoral neck is to limit morbidity and mortality from fracture. Of three potential methods of fixation, (three percutaneous screws, the Synthes Femoral Neck System, and a dynamic hip screw), each requires guide wire positioning of the implant(s) in the femoral neck and head. Consistent and accurate positioning of these systems is paramount to reduce surgical times, stabilize fractures effectively, and reduce complications. To help expedite surgery and achieve ideal implant positioning in the geriatric population, we have developed and validated a surgical planning methodology using 3D modelling and printing technology.MethodsUsing image processing software, 3D surgical models were generated placing guide wires in a virtual model of an osteoporotic proximal femur sawbone. Three unique drill guides were created to achieve the optimal position for implant placement for each of the three different implant systems, and the guides were 3D printed. Subsequently, a trauma fellowship trained orthopedic surgeon used the 3D printed guides to position 2.8 mm diameter drill bit tipped guide wires into five osteoporotic sawbones for each of the three systems (fifteen sawbones total). Computed Tomography (CT) scans were then taken of each of the sawbones with the implants in place. 3D model renderings of the CT scans were created using image processing techniques and the displacement and angular deviations at guide wire entry to the optimal sawbone model were measured.ResultsAcross all three percutaneous screw guide wires, the average displacement was 3.19 ± 0.12 mm and the average angular deviation was 4.10 ± 0.17o. The Femoral Neck System guide wires had an average displacement of 1.59 ± 0.18 mm and average angular deviation of 2.81 ± 0.64o. The Dynamic Hip Screw had an average displacement of 1.03 ± 0.19 mm and average angular deviation of 2.59 ± 0.39o.ConclusionThe use of custom 3D printed drill guides to assist with the positioning of guide wires proved to be accurate for each of the three types of surgical strategies. Guides which are used to place more than 1 guide wire may have lower positional accuracy, as the guide may shift during multiple wire insertions. We believe that personalized point of care drill guides provide an accurate intraoperative method for positioning implants into the femoral neck.

The Accuracy of Patient-Specific Spinal Drill Guides Is Non-Inferior to Computer-Assisted Surgery: The Results of a Split-Spine Randomized Controlled Trial.

In recent years, patient-specific spinal drill guides (3DPGs) have gained widespread popularity. Several studies have shown that the accuracy of screw insertion with these guides is superior to that obtained using the freehand insertion technique, but there are no studies that make a comparison with computer-assisted surgery (CAS). The aim of this study was to determine whether the accuracy of insertion of spinal screws using 3DPGs is non-inferior to insertion via CAS. A randomized controlled split-spine study was performed in which 3DPG and CAS were randomly assigned to the left or right sides of the spines of patients undergoing fixation surgery. The 3D measured accuracy of screw insertion was the primary study outcome parameter. Sixty screws inserted in 10 patients who completed the study protocol were used for the non-inferiority analysis. The non-inferiority of 3DPG was demonstrated for entry-point accuracy, as the upper margin of the 95% CI (−1.01 mm–0.49 mm) for the difference between the means did not cross the predetermined non-inferiority margin of 1 mm (p < 0.05). We also demonstrated non-inferiority of 3D angular accuracy (p < 0.05), with a 95% CI for the true difference of −2.30°–1.35°, not crossing the predetermined non-inferiority margin of 3° (p < 0.05). The results of this randomized controlled trial (RCT) showed that 3DPGs provide a non-inferior alternative to CAS in terms of screw insertion accuracy and have considerable potential as a navigational technique in spinal fixation.

Generating patient-matched 3D-printed pedicle screw and laminectomy drill guides from Cone Beam CT images: Studies in ovine and porcine cadavers.

BackgroundThe emergence of robotic Cone Beam Computed Tomography (CBCT) imaging systems in trauma departments has enabled 3D anatomical assessment of musculoskeletal injuries, supplementing conventional 2D fluoroscopic imaging for examination, diagnosis, and treatment planning. To date, the primary focus has been on trauma sites in the extremities.PurposeTo determine if CBCT images can be used during the treatment planning process in spinal instrumentation and laminectomy procedures, allowing accurate 3D‐printed pedicle screw and laminectomy drill guides to be generated for the cervical and thoracic spine.MethodsThe accuracy of drill guides generated from CBCT images was assessed using animal cadavers (ovine and porcine). Preoperative scans were acquired using a robotic CBCT C‐arm system, the Siemens ARTIS pheno (Siemens Healthcare, GmbH, Germany). The CBCT images were imported into 3D‐Slicer version 4.10.2 (www.slicer.org) where vertebral models and specific guides were developed and subsequently 3D‐printed. In the ovine cadaver, 11 pedicle screw guides from the T1–T5 and T7–T12 vertebra and six laminectomy guides from the C2–C7 vertebra were planned and printed. In the porcine cadaver, nine pedicle screw guides from the C3–T4 vertebra were planned and printed. For the pedicle screw guides, accuracy was assessed by three observers according to pedicle breach via the Gertzbein–Robbins grading system as well as measured mean axial and sagittal screw error via postoperative CBCT and CT scans. For the laminectomies, the guides were designed to leave 1 mm of lamina. The average thickness of the lamina at the mid‐point was used to assess the accuracy of the guides, measured via postoperative CBCT and CT scans from three observers. For all measurements, the intraclass correlation coefficient (ICC) was calculated to determine observer reliability.ResultsCompared with the planned screw angles for both the ovine and porcine procedures (n = 32), the mean axial and sagittal screw error measured on the postoperative CBCT scans from three observers were 3.9 ± 1.9° and 1.8 ± 0.8°, respectively. The ICC among the observes was 0.855 and 0.849 for the axial and sagittal measurements, respectively, indicating good reliability. In the ovine cadaver, directly comparing the measured axial and sagittal screw angle of the visible screws (n = 14) in the postoperative CBCT and conventional CT scans from three observers revealed an average difference 1.9 ± 1.0° in axial angle and 1.8 ± 1.0° in the sagittal angle. The average thickness of the lamina at the middle of each vertebra, as measured on‐screen in the postoperative CBCT scans by three observes was 1.6 ± 0.2 mm. The ICC among observers was 0.693, indicating moderate reliability. No lamina breaches were observed in the postoperative images.ConclusionHere, CBCT images have been used to generate accurate 3D‐printed pedicle screw and laminectomy drill guides for use in the cervical and thoracic spine. The results demonstrate sufficient precision compared with those previously reported, generated from standard preoperative CT and MRI scans, potentially expanding the treatment planning capabilities of robotic CBCT imaging systems in trauma departments and operating rooms.

Three-Dimensional Guided Zygomatic Implant Placement after Maxillectomy.

Zygomatic implants are used in patients with maxillary defects to improve the retention and stability of obturator prostheses, thereby securing good oral function. Prosthetic-driven placement of zygomatic implants is even difficult for experienced surgeons, and with a free-hand approach, deviation from the preplanned implant positions is inevitable, thereby impeding immediate implant-retained obturation. A novel, digitalized workflow of surgical planning was used in 10 patients. Maxillectomy was performed with 3D-printed cutting, and drill guides were used for subsequent placement of zygomatic implants with immediate placement of implant-retained obturator prosthesis. The outcome parameters were the accuracy of implant positioning and the prosthetic fit of the obturator prosthesis in this one-stage procedure. Zygomatic implants (n = 28) were placed with good accuracy (mean deviation 1.73 ± 0.57 mm and 2.97 ± 1.38° 3D angle deviation), and in all cases, the obturator prosthesis fitted as pre-operatively planned. The 3D accuracy of the abutment positions was 1.58 ± 1.66 mm. The accuracy of the abutment position in the occlusal plane was 2.21 ± 1.33 mm, with a height accuracy of 1.32 ± 1.57 mm. This feasibility study shows that the application of these novel designed 3D-printed surgical guides results in predictable zygomatic implant placement and provides the possibility of immediate prosthetic rehabilitation in head and neck oncology patients after maxillectomy.

The Feasibility of Creating Image-Based Patient-Specific Drill Guides for the Atlantoaxial Instabilities Using Open-Source CAD Software and Desktop 3D Printers

C1/2 cervical pedicle screw fixation is a well-known procedure for treating severely damaged and unstable C1/2 fractures. On the other hand, C1/C2 screw fixation is not safe and can lead to potentially disastrous consequences. The importance of personalized 3-dimensional (3D) printed navigational guides in avoiding these consequences cannot be overstated. We retrospectively reviewed the neuroimaging data of 16 patients who had undergone fixation for treatment of C1/2 diseases. We created patient-specific C1/2 models and drill guide models using open-source 3D editing software and a desktop 3D printer. The drill guides were then placed over the respective vertebrae models and fixated with 3.5-mm screws. Following fixation, the parts were scanned with a thin-slice (01mm) computed tomography scan, and the screw trajectories in the transverse and sagittal planes were measured at each level. Of the total of 62 screws, 58 were type I (93.54%), 4 were type II (6.45%), and no screws were type III. The results showed that there was no significant deviation in the screw trajectories and the accuracy of the drill guides was 93.54%. In our study, type I and type II screws were deemed acceptable, and the acceptable rates of C1/2 screw fixation were 100%. In this preclinical study, we demonstrated that it is possible to create patient-specific pedicle drill guides using open-source editing software and a commercially available desktop polylactic acid printer, resulting in high accuracy rates in pedicle screw placement in C1/2 patient models.