A laboratory comparison of computer navigation and individualized guides for distal radius osteotomy

Intraoral Condylectomy with 3D-Printed Cutting Guide versus with Surgical Navigation: An Accuracy and Effectiveness Comparison

This study compares the accuracy and effectiveness of our novel 3D-printed titanium cutting guides with intraoperative surgical navigation for performing intraoral condylectomy in patients with mandibular condylar osteochondroma (OC). A total of 21 patients with mandibular condylar OC underwent intraoral condylectomy with either 3D-printed cutting guides (cutting guide group) or with surgical navigation (navigation group). The condylectomy accuracy in the cutting guide group and navigation group was determined by analyzing the three-dimensional (3D) discrepancies between the postoperative computed tomography (CT) images and the preoperative virtual surgical plan (VSP). Moreover, the improvement of the mandibular symmetry in both groups was determined by evaluating the chin deviation, chin rotation and mandibular asymmetry index (AI). The superimposition of the condylar osteotomy area showed that the postoperative results were very close to the VSP in both groups. The mean 3D deviation and maximum 3D deviation between the planned condylectomy and the actual result were 1.20 ± 0.60 mm and 2.36 ± 0.51 mm in the cutting guide group, and 1.33 ± 0.76 mm and 4.27 ± 1.99 mm in the navigation group. Moreover, the facial symmetry was greatly improved in both groups, indicated by significantly decreased chin deviation, chin rotation and AI. In conclusion, our results show that both 3D-printed cutting-guide-assisted and surgical-navigation-assisted methods of intraoral condylectomy have high accuracy and efficiency, while using a cutting guide can generate a relatively higher surgical accuracy. Moreover, our cutting guides exhibit user-friendly features and simplicity, which represents a promising prospect in everyday clinical practice.

Application of Patient-Specific Instrumentation in a Dog Model with Antebrachial Growth Deformity Using a 3-D Phantom Bone Model

One of the most frequent bone deformities in dogs is antebrachial growth deformity (AGD), which results from malunion of the distal growth plates. The objective of the present study was to re-align the limbs, which can correct the length mismatch and reset the coherence of the joint with the aid of a 3-D phantom model for surgical preplanning. A 14-month-old, intact female Golden Retriever with an angular deformity of the left radius and ulna was selected for the study. The diagnosis was confirmed by orthogonal radiographs. Moreover, computed tomography (CT) scans revealed a multiplane deformity with valgus, procurator, and external rotation of the left radius. The pre-surgical planning started with the quantification of the angular deformity, followed by a simulated virtual osteotomy, and concluded with an in vitro rehearsal surgery on 3-D printed phantom bone models. In the operating room, prefabricated patient-specific instrumentation (PSI) was attached at the planned site of the radial bone surface for a precise closing wedge osteotomy. Then two locking plates were fixed routinely. Post-operative radiographs showed accurate correction of the deformity as we had planned. At 12 weeks post-operatively, the follow-up surveys revealed improved gait, weight-bearing, and progression of bone healing. Our PSI design, based on novel surgical planning, was steady yet straightforward during the osteotomy. The osteotomy was performed without difficulty since the PSI that pre-determined the sites and angles let the surgeon perform the antebrachial malformation surgery. This method of operation reduces stress on the operator and helps to improve accuracy, repeatability, and surgery time.

The effect of steam sterilization on different 3D printable materials for surgical use in veterinary medicine

Background

Different 3D-printed materials polyactic acid (PLA), polyamide (PA), polycarbonates (PC), acrylonitrile butadiene styrene (ABS) and GreenTEC Pro®^I have been considered for surgical templates, but there is a sparity of data about how these materials are affected by steam sterilization. The aim of the current study was to test if and how these materials change morphologically when high temperature, pressure and humidity are applied during the steam sterilization process. The overall aim is to create patient-specific sawing templates for performing corrective osteotomies. After the designing process, test-specimens with five different materials: PLA, PC, ABS, PA and GreenTEC Pro® were 3D-printed in two filling grades (30 and 100%). The FDM method was used for printing. After 3D-printing, the test-specimens were steam sterilized with a standard program lasting 20 min, at a temperature of 121 °C and a pressure of 2–3 bar. In order to measure the deviation of the printed model, we measured the individual test-specimens before and after steam sterilization using a sliding gauge.

Results

PC, PA and ABS showed great morphological deviations from the template after 3D-printing and steam sterilization (> 1%) respectively. ABS proved unsuitable for steam sterilization. PLA and GreenTEC Pro® demonstrated fewer morphological deviations both before and after sterilization. Therefore, we decided to perform a second test just with PLA and Green-TEC Pro® to find out which material has the highest stability and is probably able to be used for clinical application. The smallest deviations were found with the GreenTEC Pro® solid body. After autoclaving, the specimens showed a deviation from the planned body and remained below the 1% limit.

Conclusion

Steam sterilization causes morphological deviations in 3D printed objects. GreenTEC Pro® seems to be a suitable material for clinical use, not only for intraoperative use, but also for precise modeling. Microbiological examination, as well as biomechanical tests, should be performed to further assess whether intraoperative use is possible.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03065-8.

3D-printed saw guides for lower arm osteotomy, a comparison between a synthetic CT and CT-based workflow

BACKGROUND

Three-dimensional (3D)-printed saw guides are frequently used to optimize osteotomy results and are usually designed based on computed tomography (CT), despite the radiation burden, as radiation-less alternatives like magnetic resonance imaging (MRI) have inferior bone visualization capabilities. This study investigated the usability of MR-based synthetic-CT (sCT), a novel radiation-less bone visualization technique for 3D planning and design of patient-specific saw guides.

METHODS

Eight human cadaveric lower arms (mean age: 78y) received MRI and CT scans as well as high-resolution micro-CT. From the MRI scans, sCT were generated using a conditional generative adversarial network. Digital 3D bone surface models based on the sCT and general CT were compared to the surface model from the micro-CT that was used as ground truth for image resolution. From both the sCT and CT digital bone models saw guides were designed and 3D-printed in nylon for one proximal and one distal bone position for each radius and ulna. Six blinded observers placed these saw guides as accurately as possible on dissected bones. The position of each guide was assessed by optical 3D-scanning of each bone with positioned saw guide and compared to the preplanning. Eight placement errors were evaluated: three translational errors (along each axis), three rotational errors (around each axis), a total translation (∆T) and a total rotation error (∆R).

RESULTS

Surface models derived from micro-CT were on average smaller than sCT and CT-based models with average differences of 0.27 ± 0.30 mm for sCT and 0.24 ± 0.12 mm for CT. No statistically significant positioning differences on the bones were found between sCT- and CT-based saw guides for any axis specific translational or rotational errors nor between the ∆T (p = .284) and ∆R (p = .216). On Bland-Altman plots, the ∆T and ∆R limits of agreement (LoA) were within the inter-observer variability LoA.

CONCLUSIONS

This research showed a similar error for sCT and CT digital surface models when comparing to ground truth micro-CT models. Additionally, the saw guide study showed equivalent CT- and sCT-based saw guide placement errors. Therefore, MRI-based synthetic CT is a promising radiation-less alternative to CT for the creation of patient-specific osteotomy surgical saw guides.

A modified intrafocal pinning technique with three-dimensional planning to facilitate volar plating in dorsally comminuted AO/OTA C2 and C3 distal radius fractures

Backgrounds

Theaim of this study was to assess the efficacy of a modified intrafocal pinningtechnique with three-dimensional (3D) planning to facilitate volar plating in dorsally comminuted intra-articular distal radius fractures.

Methods

Intotal 35 AO/OTA type C2 and C3 fractures were finally included.The 3D digital model of the fracture was reconstructed based on preoperative computedtomographic (CT) images, with the displacement of the comminuted dorsalfragment and the intra-articular fragment analyzed for preoperative planning. During operation, amodified intrafocal pinning technique was applied percutaneously from thedorsal aspect of the radius to reduce the collapsed intra-articular fragmentfollowing volar plating. Adequate reduction was confirmed in all of patientsconsidering radial height, radial inclination and volar tilt in postoperativeradiographs.

Results

No significant fracture re-displacement wasobserved in most of the cases during a mean follow-up period of 17.4 months, exceptfor two patients withthe C3 fracture. All of the patients achieved adequate clinicalROMs at 12 months postoperatively, with a mean DASH score of 12.0. Most of the patients achievedan excellent (n = 21) or good (n = 12) Gartland and Werley wrist score.

Conclusions

Ourmodified intrafocal pinning technique with 3D planning contributes to a satisfactoryclinical and radiological outcome in dorsally comminuted intra-articular distalradius fractures fixed with a volar locking plate.

Trialregistration

Notapplicable because the design of the study is retrospective.

Corrective Osteotomy of Upper Extremity Malunions Using Three-Dimensional Planning and Patient-Specific Surgical Guides: Recent Advances and Perspectives

Malunions of the upper extremity can result in severe functional problems and increase the risk of osteoarthritis. The surgical reconstruction of complex malunions can be technically challenging. Recent advances in computer-assisted orthopedic surgery provide an innovative solution for complex three-dimensional (3-D) reconstructions. This study aims to evaluate the clinical applicability of 3-D computer-assisted planning and surgery for upper extremity malunions. Hence, we provide a summary of evidence on this topic and highlight recent advances in this field. Further, we provide a practical implementation of this therapeutic approach based on three cases of malunited forearm fractures treated with corrective osteotomy using preoperative three-dimensional simulation and patient-specific surgical guides. All three cases, one female (56 years old) and two males (18 and 26 years old), had painful restrictions in range of motion (ROM) due to forearm malunions and took part in clinical and radiologic assessments. Postoperative evaluation of patient outcomes showed a substantial increase in range of motion, reduction of preoperatively reported pain, and an overall improvement of patients' satisfaction. The therapeutic approach used in these cases resulted in an excellent anatomical and functional reconstruction and was assessed as precise, safe, and reliable. Based on current evidence and our results, the 3-D preoperative planning technique could be the new gold standard in the treatment of complex upper extremity malunions in the future.

A 3D printed cast for minimally invasive transfer of distal radius osteotomy: a cadaver study

Purpose

In corrective osteotomy of the distal radius, patient-specific 3D printed surgical guides or optical navigation systems are often used to navigate the surgical saw. The purpose of this cadaver study is to present and evaluate a novel cast-based guiding system to transfer the virtually planned corrective osteotomy of the distal radius.

Methods

We developed a cast-based guiding system composed of a cast featuring two drilling slots as well as an external cutting guide that was used to orient the surgical saw for osteotomy in the preoperatively planned position. The device was tested on five cadaver specimens with different body fat percentages. A repositioning experiment was performed to assess the precision of replacing an arm in the cast. Accuracy and precision of drilling and cutting using the proposed cast-based guiding system were evaluated using the same five cadaver arms. CT imaging was used to quantify the positioning errors in 3D.

Results

For normal-weight cadavers, the resulting total translation and rotation repositioning errors were ± 2 mm and ± 2°. Across the five performed surgeries, the median accuracy and Inter Quartile Ranges (IQR) of pre-operatively planned drilling trajectories were 4.3° (IQR = 2.4°) and 3.1 mm (IQR = 4.9 mm). Median rotational and translational errors in transferring the pre-operatively planned osteotomy plane were and 3.9° (IQR = 4.5°) and 2.6 mm (IQR = 4.2 mm), respectively.

Conclusion

For normal weight arm specimens, navigation of corrective osteotomy via a cast-based guide resulted in transfer errors comparable to those using invasive surgical guides. The promising positioning capabilities justify further investigating whether the method could ultimately be used in a clinical setting, which could especially be of interest when used with less invasive osteosynthesis material.

Use of Hausdorff Distance and Computer Modelling to Evaluate Virtual Surgical Plans with Three-Dimensional Printed Guides against Freehand Techniques for Navicular Bone Repair in Equine Orthopaedics

OBJECTIVE

 The aim of this study was to evaluate the surgical execution of a virtual surgical plan (VSP) with three-dimensional (3D) guides against a freehand approach in the equine navicular bone using an automated in silico computer analysis technique.

STUDY DESIGN

 Eight pairs of cadaveric forelimb specimens of adult horses were used in an ex vivo experimental study design with in silico modelling. Limbs received either a 3.5 mm cortical screw according to a VSP or using an aiming device. Using computed tomography and computer segmentation, a comparison was made between the executed screw and the planned screw using the Hausdorff distance (HD).

RESULTS

 Navicular bone mean HD registration error was -0.06 ± 0.29 mm. The VSP with 3D printing demonstrated significantly superior accuracy with a mean deviation of 1.19 ± 0.42 mm compared with aiming device group (3.53 ± 1.24 mm, p = 0.0018). The VSP group was 5.0 times more likely to result in a mean aberration of less than 1.0 mm (95% confidence interval, 0.62-33.4). A 3.5 mm screw with an optimal entry point can have a maximum deviation angle of 3.23 ± 0.07, 2.70 ± 0.06 and 2.37 ± 0.10 degrees in a proximal, dorsal and palmar direction respectively, prior to violating one of the cortical surfaces.

CONCLUSION

 Procedures performed using the 3D guides have a high degree of accuracy, with minimal mean deviations (<1 mm and <1 degree) of a VSP compared with those using the conventional aiming device. The use of VSP and the HD for evaluation of orthopaedic surgeries and outcome measures shows promise for simplifying and improving surgical accuracy.

The efficacy of 3D printing-assisted surgery in treating distal radius fractures: systematic review and meta-analysis

Aim: To compare the efficacy of 3D printing-assisted surgery with routine surgery in the treatment of distal radius fractures to evaluate whether 3D printing technology has more advantages. Materials & methods: To retrieve all published studies that compared the efficacy of 3D printing-assisted surgery with routine surgery for distal radius fractures. Operation time, frequency of intraoperative fluoroscopy, blood loss and other outcomes were assessed. Results: The results suggested that 3D printing-assisted surgery was better than routine surgery in the fields of operation time, frequency of intraoperative fluoroscopy, and blood loss. Conclusion: In the treatment of distal radius fractures, 3D printing-assisted surgery may be superior to routine surgery.

An Easy and Economical Way to Produce a Three-Dimensional Bone Phantom in a Dog with Antebrachial Deformities

Simple Summary

Accurate planning, for corrective surgeries in case of bone cutting, is necessary to obtain a precise coordination of the skeleton and to achieve the owner’s satisfaction. The present experiment displays a simple and cost-effective technique for surgical planning, utilizing a 3-D bone phantom model in a dog with foreleg deformity.

Abstract

3-D surgical planning for restorative osteotomy is costly and time-consuming because surgeons need to be helped from commercial companies to get 3-D printed bones. However, practitioners can save time and keep the cost to a minimum by utilizing free software and establishing their 3-D printers locally. Surgical planning for the corrective osteotomy of antebrachial growth deformities (AGD) is challenging for several reasons (the nature of the biapical or multiapical conformational abnormalities and lack of a reference value for the specific breed). Pre-operative planning challenges include: a definite description of the position of the center of rotation of angulation (CORA) and proper positioning of the osteotomies applicable to the CORA. In the present study, we demonstrated an accurate and reproducible bone-cutting technique using patient-specific instrumentations (PSI) 3-D technology. The results of the location precision showed that, by using PSIs, the surgeons were able to accurately replicate preoperative resection planning. PSI results also indicate that PSI technology provides a smaller standard deviation than the freehand method. PSI technology performed in the distal radial angular deformity may provide good cutting accuracy. In conclusion, the PSI technology may improve bone-cutting accuracy during corrective osteotomy by providing clinically acceptable margins.

The Use of Virtual Planning and Patient-specific Guides to Correct Complex Deformities of the Foot and Ankle

This article provides an overview regarding the virtual planning and precise execution of corrective osteotomies around the foot and ankle. Based on 3-dimensional data obtained from CT scans, surgeons are able to create a virtual plan of how to correct a complex deformity. This plan is transferred into the production of true patient-specific guides, designed to perform a specific surgical intervention. The authors have extensive experience with this technique and were involved in the development of the method. The current article provides an overview regarding the virtual planning and precise execution of corrective osteotomies around the foot and ankle.

Application of 3D printed osteotomy guide plate-assisted total knee arthroplasty in treatment of valgus knee deformity

INTRODUCTION

To analyze the application of 3D printed osteotomy guide plate-assisted total knee arthroplasty (TKA) for valgus knee deformity.

METHODS

The clinical data of 20 patients with valgus knee deformity admitted to our hospital from April 2012 to April 2017 were collected and analyzed. According to the treatment method, these patients were divided into two groups: 3D printed osteotomy guide plate-assisted TKA (combined treatment group, n = 10) and TKA (treatment group, n = 10). The operation time, intraoperative bleeding volume, postoperative mean femorotibial angle (MFTA), and Knee Society Score (KSS) of the two groups were statistically analyzed.

RESULTS

Compared with the treatment group, the operation time was significantly shorter (P < 0.05), the intraoperative blood loss and postoperative MFTA were significantly decreased (P < 0.05), and the clinical and functional scores were significantly increased (P < 0.05) in the combined treatment group.

CONCLUSION

3D printed osteotomy guide plate-assisted TKA for valgus knee deformity is more effective than TKA alone.

Application of computer-assisted navigation in mandibular angle osteotomy

Objective

To compare the effectiveness, accuracy, and surgical safety of a navigation technique with those of a traditional technique for intraoperative mandibular angle osteotomy.

Methods

Forty-three postsurgical patients with mandibular angle hypertrophy who were admitted to our Department from June 2014 to June 2017 were retrospectively reviewed. Of these patients, 23 underwent mandibular angle osteotomy using computer-assisted navigation (navigation group), and 20 underwent osteotomy using a traditional technique (traditional group). Postoperative computed tomography images were analyzed by three-dimensional software. Each patient’s facial proportion indices were measured using Mimics 19.0 software, and statistical comparisons and analyses were performed preoperatively and postoperatively.

Results

The postoperative facial contour morphology and facial proportion were improved in both groups; the navigation group showed greater improvement. The difference between the predicted and postoperative values was smaller in the navigation group than traditional group. The postoperative shape of the mandibular angle sample was similar to the preoperative predicted shape in the navigation group. No complications occurred in the navigation group, but paresthesia occurred in 17% of patients in the traditional group.

Conclusions

Mandibular angle osteotomy aided with computer-assisted navigation is more effective, accurate, and safe than the traditional technique and represents a promising clinical approach.

Accuracy of patient-specific three-dimensional-printed osteotomy and reduction guides for distal femoral osteotomy in dogs with medial patella luxation

OBJECTIVE

To compare precorrectional and postcorrectional femoral alignment following distal femoral osteotomy using patient-specific 3-dimensional (3D)-printed osteotomy and reduction guides in vivo and ex vivo.

STUDY DESIGN

Prospective study.

SAMPLE POPULATION

Ten client-owned dogs and matching 3D-printed plastic bone models.

METHODS

Distal femoral osteotomy was performed via a standard approach using osteotomy and reduction guides developed with computer-aided design software prior to 3D-printing. Femoral osteotomy and reduction was also performed on 3D-printed models of each femur with identical reprinted guides. Femoral varus angle (FVA) and femoral torsion angle (FTA) were measured on postoperative computed tomographic images by 3 observers.

RESULTS

In vivo, the mean difference between target and achieved postoperative was 2.29° (±2.29°, P = .0076) for the FVA, and 1.67° (±2.08°, P = .300) for the FTA. Ex vivo, the mean difference between target and achieved postoperative was 0.29° (±1.50°, P = .813) for the FVA, and -2.33° (±3.21°, P = .336) for the FTA. Intraobserver intraclass correlation coefficients (ICC; 0.736-0.998) and interobserver ICC (0.829 to 0.996) were consistent with an excellent agreement.

CONCLUSION

Use of 3D-printed osteotomy and reduction guides allowed accurate correction of FTA in vivo and both FVA and FTA ex vivo.

CLINICAL SIGNIFICANCE

Use of 3D-printed osteotomy and reduction guides may improve the accuracy of correction of femoral alignment but warrant further evaluation of surgical time, perioperative complications, and patient outcomes compared with conventional techniques.

Improving accuracy of opening-wedge osteotomies of distal radius using a patient-specific ramp-guide technique

BACKGROUND

Opening-wedge osteotomies of the distal radius, performed with three-dimensional printed patient-specific instruments, are a promising technique for accurate correction of malunions. Nevertheless, reports of residual malalignments and discrepancies in the plate and screw position from the planned fixation exist. Consequently, we developed a patient-specific ramp-guide technique, combining navigation of plate positioning, osteotomy cutting, and reduction. The aim of this study is to compare the accuracy of navigation of three-dimensional planned opening-wedge osteotomies, using a ramp-guide, over state-of-the-art guide techniques relying solely on pre-drilled holes.

METHODS

A retrospective analysis was carried out on opening-wedge osteotomies of the distal radius, performed between May 2016 and April 2017, with patient-specific instruments. Eight patients were identified in which a ramp-guide for the distal plate fixation was used. We compared the reduction accuracy with a control group of seven patients, where the reduction was performed with pre-drilled screw holes placed with the patient-specific instruments. The navigation accuracy was assessed by comparing the preoperative plans with the postoperative segmented, computed tomography scans. The accuracy was expressed using a 3D angle and in measurements of all six degrees of freedom (3 translations, 3 rotations), with respect to an anatomical coordinate system.

RESULTS

The duration of the surgery of the ramp-guide group was significantly shorter compared to the control group. Significantly less rotational and translational residual malalignment error was observed in the open-wedged osteotomies, where patient-specific instruments with ramp-guides were used. On average, a residual rotational malalignment error of 2.0° (± 2.2°) and a translational malalignment error of 0.6 mm (± 0.2 mm) was observed in the ramp-guide group, as compared to the 4.2° (± 15.0°) and 1.0 mm (± 0.4 mm) error in the control group. The used plate was not significantly positioned more accurately, but significantly fewer screws (15.6%) were misaligned in the distal fragment compared to the control group (51.9%).

CONCLUSION

The use of the presented ramp-guide technique in opening-wedge osteotomies is improving reduction accuracy, screw position, and surgical duration, compared to the existing patient-specific instrument based navigation methods.

Accuracy and Early Clinical Outcome of 3-Dimensional Planned and Guided Single-Cut Osteotomies of Malunited Forearm Bones

PURPOSE

To investigate the reduction accuracy of 3-dimensional planned single-cut osteotomies (SCOTs) of the forearm that were performed using patient-specific guides.

METHODS

A retrospective analysis of SCOTs performed between 2012 and 2014 was performed. Ten patients (age, 15-59 years) with 6 malunions of the ulna and 6 malunions of the radius were identified. The reduction accuracy was assessed by comparing the 3-dimensional preoperative plan of each osteotomy with the superimposed bone model extracted from postoperative computed tomography data. The difference was assessed by 3-dimensional angle and in all 6 degrees of freedom (3 translations, 3 rotations) with respect to an anatomical coordinate system. Wrist range of motion and grip strength was assessed after a mean of 16.7 months and compared with the preoperative measurements.

RESULTS

On average, the 12 SCOTs demonstrated excellent accuracy of the reduction with respect to rotation (ie, pronation/supination, 4.9°; flexion/extension, 1.7°; ulnar/radial angulation, 2.0°) and translation (ie, proximal/distal, 0.8 mm; radial/ulnar, 0.8 mm; dorsal/palmar, 0.8 mm). A mean residual 3-dimensional angle of 5.8° (SD, 3.6°) was measured after surgery. All 6 patients operated on for reasons of a reduced range of motion demonstrated improved symptoms and increased movement (from 20° to 80°). In the patients with unstable/painful distal radioulnar joint, 3 were totally free of complaints and 1 patient showed residual pain during sports.

CONCLUSIONS

A SCOT combined with patient-specific guides is an accurate and reliable technique to restore normal anatomy in multiplanar deformities of the forearm.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Positioning error of custom 3D-printed surgical guides for the radius: influence of fitting location and guide design

PURPOSE

Utilization of 3D-printed patient-specific surgical guides is a promising navigation approach for orthopedic surgery. However, navigation errors can arise if the guide is not correctly positioned at the planned bone location, compromising the surgical outcome. Quantitative measurements of guide positioning errors are rarely reported and have never been related to guide design and underlying bone anatomy. In this study, the positioning accuracy of a standard and an extended guide design with lateral extension is evaluated at different fitting locations (distal, mid-shaft and proximal) on the volar side of the radius.

METHODS

Four operators placed the surgical guides on 3D-printed radius models obtained from the CT scans of six patients. For each radius model, every operator positioned two guide designs on the three fitting locations. The residual positioning error was quantified with a CT-based image analysis method in terms of the mean target registration error (mTRE), total translation error ([Formula: see text]) and total rotation error ([Formula: see text]) by comparing the actual guide position with the preoperatively planned position. Three generalized linear regression models were constructed to evaluate if the fitting location and the guide design affected mTRE, [Formula: see text] and [Formula: see text].

RESULTS

mTRE, [Formula: see text] and [Formula: see text] were significantly higher for mid-shaft guides ([Formula: see text]) compared to distal guides. The guide extension significantly improved the target registration and translational accuracy in all the volar radius locations ([Formula: see text]). However, in the mid-shaft region, the guide extension yielded an increased total rotational error ([Formula: see text]).

CONCLUSION

Our study demonstrates that positioning accuracy depends on the fitting location and on the guide design. In distal and proximal radial regions, the accuracy of guides with lateral extension is higher than standard guides and is therefore recommended for future use.

[Effectiveness of total knee arthroplasty using three-dimensional printing technology for knee osteoarthritis accompanied with extra-articular deformity]

Objective

To evaluate the effectiveness of total knee arthroplasty (TKA) using three-dimensional (3D) printing technology for knee osteoarthritis (KOA) accompanied with extra-articular deformity.

Methods

Between March 2013 and December 2015, 15 patients (18 knees) with extra-articular deformity and KOA underwent TKA. There were 6 males (6 knees) and 9 females (12 knees), aged 55-70 years (mean, 60.2 years). The mean disease duration was 10.8 years (range, 7-15 years). The unilateral knee was involved in 12 cases and bilateral knees in 3 cases. The clinical score was 57.44±1.06 and the functional score was 60.88±1.26 of Knee Society Score (KSS). The range of motion of the knee joint was (72.22±0.18)°. The deviation of mechanical axis of lower limb was (18.89±0.92)° preoperatively. There were 8 cases (10 knees) with extra-articular femoral deformity, 5 cases (5 knees) with extra-articular tibial deformity, and 2 cases (3 knees) with extra-articular femoral and tibial deformities. Bone models and the navigation templates were printed and the operation plans were designed using 3D printing technology. The right knee joint prostheses were chosen.

Results

The operation time was 65-100 minutes (mean, 75.6 minutes). The bleeding volume was 50-150 mL (mean, 90.2 mL). There was no poor incision healing, infection, or deep venous thrombosis after operation. All patients were followed up 12- 30 months (mean, 22 months). Prostheses were located in the right place, and no sign of loosening or subsidence was observed by X-ray examination. At last follow-up, the deviation of mechanical axis of lower limb was (2.00±0.29)°, showing significant difference when compared with preoperative one ( t=13.120, P=0.007). The KSS clinical score was 87.50±0.88 and function score was 81.94±1.41, showing significant differences when compared with preoperative ones ( t=27.553, P=0.000; t=35.551, P=0.000). The range of motion of knee was (101.94±1.42)°, showing significant difference when compared with preoperative one ( t=31.633, P=0.000).

Conclusion

For KOA accompanied with extra-articular deformity, TKA using 3D printing technology has advantages such as individualized treatment, reducing the difficulty of operation, and achieving the satisfactory function.

Error range in proximal femoral osteotomy using computer tomography-based navigation

PURPOSE  : The purpose of this preliminary study was to determine the error range compared with preoperative plans in proximal femoral osteotomy conducted using a computed tomography (CT)-based navigation system. METHODS  : Four patients (four hips) underwent transtrochanteric rotational osteotomy (TRO), and three patients (four hips) underwent curved varus osteotomy (CVO) using CT-based navigation. Volume registration of pre- and postoperative CT was performed for error assessment. RESULTS  : In TRO, the mean osteotomy angle error was [Formula: see text] (range [Formula: see text]) in the valgus direction and [Formula: see text] (range [Formula: see text]) in the retroversion direction. The mean osteotomy position error, with the femoral head side as positive, was -0.4 mm (range -1.4 to 0 mm). The bone fragment rotational movement error was [Formula: see text] (range [Formula: see text]). In CVO, the mean osteotomy position error, with the femoral head side as positive, was -0.2 mm (range -2.0 to 1.7 mm) at the level of the lesser trochanter and 0.8 mm (range 0-3.2 mm) at the level of the greater trochanter. Bone fragment varus accuracy was [Formula: see text] (range [Formula: see text]). CONCLUSIONS  : In proximal femoral osteotomy using CT-based navigation, the angle error of osteotomy was within [Formula: see text] and the positional error was within 4 mm. The rotational movement error of the proximal fragment was within [Formula: see text]. These margins of error should be considered in preoperative planning. To improve surgical accuracy, it would be necessary to develop a computer-assisted device which can track the osteotomized fragment.

Patient-specific 3D models aid planning for triplane proximal femoral osteotomy in slipped capital femoral epiphysis

PURPOSE

Slipped capital femoral epiphysis (SCFE) can result in a complex three-dimensional (3D) deformity of the proximal femur. A three-plane proximal femoral osteotomy (TPFO) has been described to improve hip mechanics. The purpose of this study was to evaluate the benefits of using 3D print technology to aid in surgical planning.

PATIENTS AND METHODS

Fifteen children treated with TPFO for symptomatic proximal femoral deformity due to SCFE were included in this study. Ten patients were treated by a single surgeon with (model group, n = 5) or without (no-model group, n = 5) a 3D model for pre-operative planning, and compared with patients treated by two senior partners without the use of a model (senior group, n = 5) to evaluate for a learning curve. Peri-operative data including patient body mass index (BMI), surgical time and fluoroscopy time were recorded.

RESULTS

Children in all three groups had similar BMIs at the time of the TPFO. Post-operative radiographic parameters were equally improved in all three groups. On average, surgical time decreased by 45 minutes and 38 minutes, and fluoroscopy time decreased by 50% and 25%, in the model group compared with the no-model and senior groups, respectively.

CONCLUSIONS

Patient-specific 3D models aid in surgical planning for complex 3D orthopaedic deformities by enabling practice of osteotomies. Results suggest that 3D models may decrease surgical time and fluoroscopy time while allowing for similar deformity correction. These models may be especially useful to overcome steep learning curves for complex procedures or in trainee education through mock surgical procedures.

Bilateral shoulder arthrodesis in a Pekinese using three-dimensional printed patient-specific osteotomy and reduction guides

OBJECTIVE

To report the use of computer-aided design software for virtual surgical planning and design of three-dimensional printed patient-specific osteotomy and reduction guides for facilitation of bilateral shoulder arthrodesis in a dog.

METHODS

A three-year-old male entire Pekinese was presented unable to walk due to bilateral severe medial shoulder instability. Computed tomographic data was processed to yield three-dimensional mesh representations of the humeri and scapulae which could be manipulated in computer-aided design software. Key virtual surgical planning steps included joint realignment, osteotomies of the glenoid and humeral head, and reduction. Virtual osteotomy and reduction guides were designed, three-dimensionally printed, and used intra-operatively.

RESULTS

Appropriate alignment, reduction and fixation of the humeri and scapulae were achieved bilaterally. The patient regained the ability to walk unassisted after two weeks and was subsequently able to exercise normally without lameness.

CLINICAL SIGNIFICANCE

Patient-specific, three-dimensional printed osteotomy and reduction guides facilitated accurate bilateral shoulder arthrodeses.

Patient-Specific Orthopaedic Implants

Patient-specific orthopaedic implants are emerging as a clinically promising treatment option for a growing number of conditions to better match an individual's anatomy. Patient-specific implant (PSI) technology aims to reduce overall procedural costs, minimize surgical time, and maximize patient outcomes by achieving better biomechanical implant fit. With this commercially-available technology, computed tomography or magnetic resonance images can be used in conjunction with specialized computer programs to create preoperative patient-specific surgical plans and to develop custom cutting guides from 3-D reconstructed images of patient anatomy. Surgeons can then place these temporary guides or "jigs" during the procedure, allowing them to better recreate the exact resections of the computer-generated surgical plan. Over the past decade, patient-specific implants have seen increased use in orthopaedics and they have been widely indicated in total knee arthroplasty, total hip arthroplasty, and corrective osteotomies. Patient-specific implants have also been explored for use in total shoulder arthroplasty and spinal surgery. Despite their increasing popularity, significant support for PSI use in orthopaedics has been lacking in the literature and it is currently uncertain whether the theoretical biomechanical advantages of patient-specific orthopaedic implants carry true advantages in surgical outcomes when compared to standard procedures. The purpose of this review was to assess the current status of patient-specific orthopaedic implants, to explore their future direction, and to summarize any comparative published studies that measure definitive surgical characteristics of patient-specific orthopaedic implant use such as patient outcomes, biomechanical implant alignment, surgical cost, patient blood loss, or patient recovery.

Computer-assisted oblique single-cut rotation osteotomy to reduce a multidirectional tibia deformity: case report

The correction of multiplanar deformity is challenging. We describe preoperative 3-D planning and treatment of a complex tibia malunion using an oblique single-cut rotation osteotomy to correct deformity parameters in the sagittal, coronal and transverse plane. At 5 years postoperatively, the patient ambulates without pain with a well-aligned leg.

The production of digital and printed resources from multiple modalities using visualization and three-dimensional printing techniques

PURPOSE

Virtual digital resources and printed models have become indispensable tools for medical training and surgical planning. Nevertheless, printed models of soft tissue organs are still challenging to reproduce. This study adopts open source packages and a low-cost desktop 3D printer to convert multiple modalities of medical images to digital resources (volume rendering images and digital models) and lifelike printed models, which are useful to enhance our understanding of the geometric structure and complex spatial nature of anatomical organs.

MATERIALS AND METHODS

Neuroimaging technologies such as CT, CTA, MRI, and TOF-MRA collect serial medical images. The procedures for producing digital resources can be divided into volume rendering and medical image reconstruction. To verify the accuracy of reconstruction, this study presents qualitative and quantitative assessments. Subsequently, digital models are archived as stereolithography format files and imported to the bundled software of the 3D printer. The printed models are produced using polylactide filament materials.

RESULTS

We have successfully converted multiple modalities of medical images to digital resources and printed models for both hard organs (cranial base and tooth) and soft tissue organs (brain, blood vessels of the brain, the heart chambers and vessel lumen, and pituitary tumor). Multiple digital resources and printed models were provided to illustrate the anatomical relationship between organs and complicated surrounding structures. Three-dimensional printing (3DP) is a powerful tool to produce lifelike and tangible models.

CONCLUSIONS

We present an available and cost-effective method for producing both digital resources and printed models. The choice of modality in medical images and the processing approach is important when reproducing soft tissue organs models. The accuracy of the printed model is determined by the quality of organ models and 3DP. With the ongoing improvement of printing techniques and the variety of materials available, 3DP will become an indispensable tool in medical training and surgical planning.

Three-dimensional postoperative accuracy of extra-articular forearm osteotomies using CT-scan based patient-specific surgical guides

BACKGROUND

Computer assisted corrective osteotomy of the diaphyseal forearm and the distal radius based on computer simulation and patient-specific guides has been described as a promising technique for accurate reconstruction of forearm deformities. Thereby, the intraoperative use of patient-specific drill and cutting guides facilitate the transfer of the preoperative plan to the surgery. However, the difference between planned and performed reduction is difficult to assess with conventional radiographs. The aim of this study was to evaluate the accuracy of this surgical technique based on postoperative three-dimensional (3D) computed tomography (CT) data.

METHODS

Fourteen patients (mean age 23.2 (range, 12-58) years) with an extra-articular deformity of the forearm had undergone computer assisted corrective osteotomy with the healthy anatomy of the contralateral uninjured side as a reconstruction template. 3D bone surface models of the pathological and contralateral side were created from CT data for the computer simulation. Patient-specific drill and cutting guides including the preoperative planned screw direction of the angular-stable locking plates and the osteotomy planes were used for the intraoperative realization of the preoperative plan. There were seven opening wedge osteotomies and nine closing wedge (or single-cut) osteotomies performed. Eight-ten weeks postoperatively CT scans were obtained to assess bony consolidation and additionally used to generate a 3D model of the forearm. The simulated osteotomies- preoperative bone models with simulated correction - and the performed osteotomies - postoperative bone models - were analyzed for residual differences in 3D alignment.

RESULTS

On average, a significant higher residual rotational deformity was observed in opening wedge osteotomies (8.30° ± 5.35°) compared to closing wedge osteotomies (3.47° ± 1.09°). The average residual translation was comparable small in both groups, i.e., below 1.5 mm and 1.1 mm for opening and closing wedge osteotomies, respectively.

CONCLUSIONS

The technique demonstrated high accuracy in performing closing wedge (or single-cut) osteotomies. However, for opening wedge osteotomies with extensive lengthening, probably due to the fact that precise reduction was difficult to achieve or maintain, the final corrections were less accurate.