3D-printed Patient-specific Guides Research Articles

Feline Shoulder Arthrodesis Using 3D-printed Patient-specific Guides.

This case series aims to explore the application of 3D-printed patient-specific guides (PSG) in feline shoulder arthrodesis, addressing the scarcity of literature on this procedure in cats. The primary objectives include assessing the feasibility, accuracy, and outcomes of the procedure in four feline cases. The study employed a retrospective analysis of cases involving feline shoulder arthrodesis performed using PSG. Surgical planning utilized CAD-based techniques, and 3D-printed guides were created for precise osteotomies and implant placement. Follow-ups included radiographic assessments, re-examinations, and owner-reported outcomes. Four feline cases with distinct shoulder issues were successfully treated using PSG. Postoperative management, radiographic evaluations, and long-term follow-ups revealed positive outcomes in terms of limb function and patient activity. The study demonstrates the potential of PSG in achieving accurate humeroscapular alignment in feline shoulder arthrodesis. This case series highlights the clinical significance of PSG in enhancing the precision of humeroscapular alignment during feline shoulder arthrodesis. The positive outcomes observed in various shoulder pathologies suggest that this technique could contribute to improved surgical outcomes.

Patient-Specific Distal Femoral Guides Optimize Cartilage Topography Matching in Osteochondral Allograft Transplantations

Background: Osteochondral allograft (OCA) transplantation is an important surgical technique for full-thickness chondral defects in the knee. For patients undergoing this procedure, topography matching between the donor and recipient sites is essential to limit premature wear of the OCA. Currently, there is no standardized process of donor and recipient graft matching. Purpose: To evaluate a novel topography matching technique for distal femoral condyle OCA transplantation using 3-dimensional (3D) laser scanning to create 3D-printed patient-specific instrumentation in a human cadaveric model. Study Design: Descriptive laboratory study. Methods: Human cadaveric distal femoral condyles (n = 12) underwent 3D laser scanning. An 18-mm circular osteochondral recipient defect was virtually created on the medial femoral condyle (MFC), and the position and orientation of the best topography-matched osteochondral graft from a paired donor lateral femoral condyle (LFC) were determined using an in silico analysis algorithm minimizing articular step-off distances between the edges of the graft and recipient defect. Distances between the entire surface of the OCA graft and the underneath surface of the MFC were evaluated as surface mismatch. Donor (LFC) and recipient (MFC) 3D-printed patient-specific guides were created based on 3D reconstructions of the scanned condyles. Through use of the guides, OCAs were harvested from the LFC and transplanted to the reamed recipient defect site (MFC). The post-OCA recipient condyles were laser scanned. The 360° articular step-off and cartilage topography mismatch were measured. Results: The mean cartilage step-off and graft surface mismatch for the in silico OCA transplant were 0.073 ± 0.029 mm (range, 0.005-0.113 mm) and 0.166 ± 0.039 mm (range, 0.120-0.243 mm), respectively. Comparatively, the cadaveric specimens postimplant had significantly larger step-off differences (0.173 ± 0.085 mm; range, 0.082-0.399 mm; P = .001) but equivalent graft surface topography matching (0.181 ± 0.080 mm; range, 0.087-0.396 mm; P = .678). All 12 OCA transplants had mean circumferential step-off differences less than a clinically significant cutoff of 0.5 mm. Conclusion: These findings suggest that the use of 3D-printed patient-specific guides for OCA transplantation has the ability to reliably optimize cartilage topography matching for LFC to MFC transplantation. This study demonstrated substantially lower step-off values compared with previous orthopaedic literature when also evaluating LFC to MFC transplantation. Using this novel technique in a model performing MFC to MFC transplantation has the potential to yield further enhanced results due to improved radii of curvature matching. Clinical Relevance: Topography-matched graft implantation for focal chondral defects of the knee in patients improves surface matching and has the potential to improve long-term outcomes. Efficient selection of the allograft also allows improved availability of the limited allograft sources.

Instrumentation of hypoplastic pedicles with patient-specific guides

PurposeHypoplastic pedicles of the thoracolumbar spine (<5 mm diameter) are often found in syndromic deformities of the spine and pose a challenge in pedicle screw instrumentation. 3D-printed patient-specific guides might help overcome anatomical difficulties when instrumenting pedicles with screws, thereby reducing the necessity for less effective fixation methods such as hooks or sublaminar wires. In this study, the surgical feasibility and clinical outcome of patients with hypoplastic pedicles following pedicle screw instrumentation with 3D-printed patient-specific guides were assessed.MethodsHypoplastic pedicles were identified on preoperative computed tomography (CT) scans in six patients undergoing posterior spinal fusion surgery between 2017 and 2020. Based on these preoperative CT scans, patient-specific guides were produced to help with screw instrumentation of these thin pedicles. Postoperatively, pedicle-screw-related complications or revisions were analyzed.Results93/105 (88.6%) pedicle screws placed with patient-specific guides were instrumented. 62/93 (66.7%) of these instrumented pedicles were defined as hypoplastic with a mean width of 3.07 mm (SD ±0.98 mm, 95% CI [2.82–3.32]). Overall, 6 complications in the 62 hypoplastic pedicles (9.7%) were observed and included intraoperatively managed 4 cerebrospinal fluid leaks, 1 pneumothorax and 1 delayed revision due to 2 lumbar screws (2/62, 3.3%) impinging the L3 nerve root causing a painful radiculopathy. The mean follow-up time was 26.7 (SD ±11.7) months. Complications were only noted when the pedicle-width-to-screw-diameter ratio measured less than 0.62.ConclusionPatient-specific 3D-printed guides can aid in challenging instrumentation of hypoplastic pedicles in the thoracolumbar spine, especially if the pedicle-width-to-screw-diameter ratio is greater than 0.62.

Poster 130: Accuracy of Distal Femoral Condyle Osteochondral Allograft Transplantation Using Patient Specific Instrumentation

Objectives: As a surgical treatment option for cartilage defects in the knee, osteochondral allograft (OCA) transplantation reconstructs the damaged area with a fully formed articular hyaline cartilage/osseous unit. For patients undergoing this procedure, topography matching between the donor and recipient sites is essential to limit premature wear of the OCA. To help prevent graft failure, the surgeon must precisely reconstruct the original anatomic curvature of the articular surface. For this to be successful, the graft needs to be chosen and harvested from the correct location on the donor femoral condyle, and then placed correctly on the recipient condyle during surgery to minimize step-off relative to the surrounding cartilage. Currently, the process of donor and recipient graft matching as well as intra-operative techniques to match these surfaces are fairly rudimentary and require significant experience from the treating surgeon. The purpose of this study is to evaluate a novel topography matching technique for distal femoral condyle OCA transplantation using three-dimensional (3D) laser scanning to create 3D printed patient-specific instrumentation in a human cadaveric model. Methods: Twelve cadaveric knees were dissected to isolate the distal femoral condyles (DFC) with cartilage intact and then 3D laser scanned. An 18-mm circular osteochondral recipient defect was virtually created on the medial femoral condyle (MFC) and the position and orientation of the best topography matched osteochondral graft from a paired donor lateral femoral condyle (LFC) was determined using an in-silico analysis algorithm minimizing articular step-off (Figure 1). Donor (LFC) and recipient (MFC) 3D-printed patient-specific guides were created based on 3D reconstructions of the scanned condyles. Using the guides, OCAs were harvested from the previously defined best-match position on the LFC and transplanted to the reamed recipient defect site (MFC) (Figure 2). The post-OCA recipient condyles were laser scanned. The 360-degree articular step-off and cartilage mismatch topography were calculated by a point-to-surface distance calculation algorithm and compared to the in-silico result. Results: The in-silico cartilage step-off and graft perimeter mismatch for the virtual OCA transplant was 0.073 ± 0.029 mm (range: 0.005-0.113 mm) and 0.166 ± 0.039 mm (range: 0.120-0.243 mm), respectively. Comparatively, our cadaveric specimens post-implant had significantly larger step-off differences (0.173 ± 0.085 mm, range: 0.082-0.399 mm, P = 0.001) but equivalent surface topography matching (0.181 ± 0.080 mm, range: 0.087-0.396 mm, P = 0.678). Conclusions: This novel technique for OCA articular step-off and topography matching demonstrated the ability to optimize cartilage topography matching for LFC to MFC transplantation. Despite a larger mean step-off in the cadaveric specimens compared to the ideal in-silico model, our study demonstrated substantially lower mismatch values compared to previous orthopedic literature evaluating LFC to MFC transplantation that reported means of 0.48 mm for articular step-off (range: 0.335-0.738 mm) and 0.63 mm for surface area mismatch (range: 0.349-1.461 mm). It should be noted that clinically, surgeons performing OCA for the femoral condyles will preferentially select the ipsilateral condyle from the donor to take a plug for the recipient, as this will generally allow for optimal surface matching. Our results show better mismatch values than prior work using this contralateral technique, and even the maximum step-off distance in our cadaveric model fell well below the 0.5 cm –1.0 cm maximum step-off values assigned to be clinically significant by prior studies evaluating ipsilateral OCA transplantations. Using this novel technique in a model performing MFC to MFC transplantation would likely yield further enhanced results due to improved radii of curvature matching. Improving upon topography matched graft implantation for focal chondral defects of the knee in young patients will improve surface matching and associated long-term outcomes. Additionally, efficient selection of the allograft using patient-specific guides would also improve availability of the limited allograft sources and reduce surgical time.

Use of 3D-Printed Patient Specific Guides in Osteotomies around the Knee

High tibial osteotomies are challenging procedures that have traditionally implemented two-dimensional planning (2D) for a complex three-dimensional surgery (3D). In an effort to improve the accuracy and precision of the technique, there has been a growing interest in the use of patient specific instrumentation (PSI). The implementation of PSI in osteotomies has demonstrated consistent and reliable results in the correction of the hip-knee-ankle angle, proximal tibial angle, and the posterior tibial slope. Initial clinical studies describing the implementation of this technology have reported superior accuracy in both the coronal and sagittal planes as compared to free-hand techniques. Additionally, these studies reported a fast surgeon learning curve, short operative times, and minimal fluoroscopy exposure. The senior author's preferred closing wedge HTO technique utilizes a patient specific cutting guide with osteotomy fixation provided by an extra-cortical titanium alloy locking plate. This technique is designed to provide reliable and accurate HTOs while minimizing the risk of major complications such as hinge fractures on the contralateral cortex.

Custom-made 3D printed patient specific guides (PSG) improves component axial alignment in total knee arthroplasty (TKA)

BackgroundUsage of Patient Specific Instrumentation (PSI) or Patient Specific Guides (PSG) in TKA has evolved rapidly in the past decade. Restoration of Mechanical axis in TKA is vital to achieve good functional outcome and long term implant survival. We carried out a comparative study to assess the efficacy of PSG in achieving neutral axial alignment and its impact on early functional outcomes compared to Conventional Instrumentation (CI). MethodsPatients eligible as per study design (n = 100) undergoing TKA were randomized and divided in two equal groups which were matched in baseline demographics and clinical profile. All the patients in the PSG group (n = 50) and conventional instrumentation (CI) group (n = 50) underwent TKA with same implant. Pre-operative CT scans done as per specified protocol to acquire image data for 3D printing PSG. Duration of surgery and post-operative Hip-Knee-Ankle (HKA) angles achieved in the two groups was compared. Post-operative functional outcomes were assessed using WOMAC scores. ResultsThere was statistically significant difference in the mean post-operative axial alignment achieved between the two groups (p = 0.041). Outliers (180 ± 3 deg) of HKA angle were more in the CI Group (p = 0.007). There was no difference in functional outcomes between the two groups at one year. Duration of surgery was significantly less in PSG Group (p < 0.001). Conclusion3D printed PSG are superior in achieving neutral HKA axis as compared to CI in TKA. Better axial alignment of TKA components does not correlate with better patient reported functional outcomes. PSG use significantly reduces surgical time.

Computer-Guided Arthrocentesis Using Patient-Specific Guides: A Novel Protocol for Treatment of Internal Derangement of the Temporomandibular Joint

The aim of the present study was to evaluate the accuracy of 3-dimensionally (3D) printed patient-specific guides (PSGs) to direct the passage of inlet and outlet needles into the superior joint spaces of the temporomandibular joint (TMJ) in preparation for arthrocentesis. The present study included 10 patients with 14 TMJs with anterior disc displacement with reduction. A 3D PSG was designed for each patient to lead the inlet and outlet needles into the superior joint space of the TMJ. The PSGs were implemented, and their accuracy for guiding the needles into the superior joint space was assessed. Both arthroscopic verification and clinical evaluation revealed that direct access to all the predetermined anatomic locations inside the TMJs had been obtained, except for 1 case, during which the patient had failed to maintain the maximum mouth opening during computed tomography scanning. The virtual computer-initiated PSGs were beneficial for directing the passage of the needles into the superior joint space.

Pedicle screw insertion with patient-specific 3D-printed guides based on low-dose CT scan is more accurate than free-hand technique in spine deformity patients: a prospective, randomized clinical trial.

Screw misplacement incidence can be as high as 15-30% in spine deformity surgery, with possible devastating consequences. Some technical solutions to prevent misplacement require expensive devices. MySpineTM comprises a low-dose CT scan of the patient's spine to build a virtual model of the spine to plan the screw trajectories and a 3D-printed patient-specific guide system to prepare the screw trajectories and to implant the screws in the vertebrae in order to increase reproducibility and safety of the implants. The aim of this open-label, single-center, prospective randomized clinical trial with independent evaluation of outcomes was to compare the accuracy of free-hand insertion of pedicle screws to MySpineTM 3D-printed patient-specific guides. Twenty-nine patients undergoing surgical correction for spinal deformity were randomized to Group A (pedicle screws implantation with MySpineTM) or Group B (free-hand implantation). Group A received 297 pedicle screws, and Group B 243 screws. Forty-three screws in Group A crossed over to free-hand implantation. Screw position was graded according to Gertzbein in grades 0, A, B or C, with grades 0 or A considered as "safe area." Total fluoroscopy dose and time were compared in six patients of each group. Comparing the two study groups, we observed a statistically significant difference between the two groups (p < 0.05), with 96.1% of screws in the "safe area" in Group A versus a 82.9% in Group B. Group-A patients had a mean effective dose of 0.23mSv compared to 0.82mSv in Group B. Patient-specific, 3D-printed pedicle screw guides increase safety in a wide spectrum of deformity conditions. In addition, the total radiation dose is reduced, even considering the need of a low-dose preoperative CT for surgical planning. I. These slides can be retrieved under Electronic Supplementary Material.

3D-printed Patient-specific Guides for Hip Arthroplasty.

Surgeons and engineers constantly search for methods to improve the surgical positioning of implants used for joint arthroplasty. Rapid prototyping is being used to develop patient-specific instrumentation (PSI) and has already been successfully translated into large-scale clinical use for knee arthroplasty. PSI has been used in shoulder arthroplasty; however, it is not yet known whether PSI provides improved accuracy and outcomes compared with conventional methods in either shoulder arthroplasty or knee arthroplasty. In the hip, PSI has been limited to the positioning of custom-manufactured implants and a small number of surgeons testing the emerging solutions from different manufacturers. Early results indicate consistent accurate positioning of implants with the use of PSI in hip arthroplasty but with added costs and uncertain effect on clinical outcomes.

3D-Printed Patient-Specific ACL Femoral Tunnel Guide from MRI.

Background:Traditional ACL reconstruction with non-anatomic techniques can demonstrate unsatisfactory long-term outcomes with regards instability and the degenerative knee changes observed with these results. Anatomic ACL reconstruction attempts to closely reproduce the patient's individual anatomic characteristics with the aim of restoring knee kinematics, in order to improve patient short and long-term outcomes. We designed an arthroscopic, patient-specific, ACL femoral tunnel guide to aid anatomical placement of the ACL graft within the femoral tunnel.Methods:The guide design was based on MRI scan of the subject's uninjured contralateral knee, identifying the femoral footprint and its anatomical position relative to the borders of the femoral articular cartilage. Image processing software was used to create a 3D computer aided design which was subsequently exported to a 3D-printing service.Results:Transparent acrylic based photopolymer, PA220 plastic and 316L stainless steel patient-specific ACL femoral tunnel guides were created; the models produced were accurate with no statistical difference in size and positioning of the center of the ACL femoral footprint guide to MRI (p=0.344, p=0.189, p=0.233 respectively). The guides aim to provide accurate marking of the starting point of the femoral tunnel in arthroscopic ACL reconstruction.Conclusion:This study serves as a proof of concept for the accurate creation of 3D-printed patient-specific guides for the anatomical placement of the femoral tunnel during ACL reconstruction.

Corrective Osteotomies of Phalangeal and Metacarpal Malunions Using Patient-Specific Guides: CT-Based Evaluation of the Reduction Accuracy.

Surgical planning of corrective osteotomies is traditionally based on conventional radiographs and clinical findings. In the past 10 years, 3-dimensional (3D) preoperative planning approaches with patient-specific guides have been developed. However, the application of this technology to posttraumatic deformities of the metacarpals and phalangeal bones has not yet been investigated. Our goal was to evaluate the feasibility of the surgical application to the latter and to evaluate the extent and precision of correction. We present results of 6 patients (8 osteotomies) treated with phalangeal or metacarpal corrective osteotomy. Deformities were located in the third ray in 1, fourth ray in 3, and fifth ray in 4 cases. Six malunited metacarpal bones (1 intra-articular) and 2 deformed proximal phalanges were treated. Computer-based 3D preoperative planning using the contralateral hand as a template allowed the production of 3D-printed patient-specific guides that were used intraoperatively for navigation. The precision of the reduction was assessed using pre- and postoperative computed tomography by comparing the postoperative bone model with the preoperatively simulated osteotomy. Range of motion and grip strength were documented pre- and postoperatively. The mean follow-up time was 6 months (range: 5-11 months). Rotational deformity was reduced from a mean of 10.0° (range: 7.2°-19.3°) preoperatively to 2.3° (range: 0.7°-3.7°) postoperatively, and translational incongruency decreased from a mean of 1.4 mm (range: 0.7-2.8 mm) to 0.4 mm (range: 0.1-0.9 mm). Preliminary results indicate that a precise reduction for corrective osteotomies of metacarpal and phalangeal bones can be achieved by using 3D planning and patient-specific guides.

Corrective limb osteotomy using patient specific 3D-printed guides: A technical note

We describe the step-by-step process of a corrective osteotomy using 3D printed patient specific guides. Before surgery, bilateral computed tomography (CT) scans are made to plan correction in the affected limb. The digital pre-planning defines the location of the K-wires, drill holes, and the osteotomy site(s). Subsequently, a 3D printed patient specific guide is applied, which indicates the exact position of these drill holes and the osteotomies. This increases the accuracy of the surgery by means of patient specific fit of the guide. During surgery an incision is made and the guide is applied on the bone, which allows the surgeon to perform a very precise osteotomy. Next, the bone is reduced either directly using the plate and marked drill holes, or indirectly using a second reduction guide. In the latter case, the previously drilled K-wires are used to adequately position the reduction guide. Fixation of the bone fragments using plating osteosynthesis finalizes the process. Although this technique has its specific limitations, it might serve as a powerful tool in the treatment of malunion of both articular and nonarticular fractures of the limb.