Patient-specific Surgical Guides Research Articles

Rapid prototyping for patient-specific surgical orthopaedics guides: A systematic literature review.

There has been a lot of hype surrounding the advantages to be gained from rapid prototyping processes in a number of fields, including medicine. Our literature review aims objectively to assess how effective patient-specific surgical guides manufactured using rapid prototyping are in a number of orthopaedic surgical applications. To this end, we carried out a systematic review to identify and analyse clinical and experimental literature studies in which rapid prototyping patient-specific surgical guides are used, focusing especially on those that entail quantifiable outcomes and, at the same time, providing details on the guides' design and type of manufacturing process. Here, it should be mentioned that in this field there are not yet medium- or long-term data, and no information on revisions. In the reviewed studies, the reported positive opinions on the use of rapid prototyping patient-specific surgical guides relate to the following main advantages: reduction in operating times, low costs and improvements in the accuracy of surgical interventions thanks to guides' personalisation. However, disadvantages and sources of errors which can cause patient-specific surgical guide failures are as well discussed by authors. Stereolithography is the main rapid prototyping process employed in these applications although fused deposition modelling or selective laser sintering processes can also satisfy the requirements of these applications in terms of material properties, manufacturing accuracy and construction time. Another of our findings was that individualised drill guides for spinal surgery are currently the favourite candidates for manufacture using rapid prototyping. Other emerging applications relate to complex orthopaedic surgery of the extremities: the forearm and foot. Several procedures such as osteotomies for radius malunions or tarsal coalition could become standard, thanks to the significant assistance provided by rapid prototyping patient-specific surgical guides in planning and performing such operations.

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

BackgroundComputer 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.MethodsFourteen 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.ResultsOn 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.ConclusionsThe 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.

Docking Robustness of Patient Specific Surgical Guides for Joint Replacement Surgery

In joint replacement surgery, patient specific surgical guides (PSSGs) are used for accurate alignment of implant components. PSSGs are designed preoperatively to have a geometric fit with the patient's bone such that the incorporated guidance for drilling and cutting is instantly aligned. The surgeon keeps the PSSG in position with a pushing force, and it is essential that this position is maintained while drilling or cutting. Hence, the influence of the location and direction of the pushing force should be minimal. The extent that the pushing force may vary is what we refer to as docking robustness. In this article, we present a docking robustness framework comprising the following quantitative measures and graphical tool. Contact efficiency ηc is used for the quantification of the selected bone–guide contact. Guide efficiency ηg is used for the quantification of the whole guide including an application surface whereon the surgeon can push. Robustness maps are used to find a robust location for the application surface based on gradient colors. Robustness R is a measure indicating what angular deviation is minimally allowed at the worst point on the application surface. The robustness framework is utilized in an optimization of PSSG dimensions for the distal femur. This optimization shows that 12 contacts already result in a relatively high contact efficiency of 0.74 ± 0.02 (where the maximum of 1.00 is obtained when the guide is designed for full bone–guide contact). Six contacts seem to be insufficient as the obtained contact efficiency is only 0.18 ± 0.02.

MyHip: supporting planning and surgical guidance for a better total hip arthroplasty : A pilot study.

Total hip arthroplasty (THA) aims to restore patient mobility by providing a pain-free and stable artificial joint. A successful THA depends on the planning and its execution during surgery. Both tasks rely on the experience of the surgeon to understand the complex biomechanical behavior of the hip. We investigate the hypothesis that a computer-assisted solution for THA effectively supports the preparation and execution of the planning. We devised MyHip as a computer-assisted framework for THA. The framework provides pre-operative planning based on medical imaging and optical motion capture to optimally select and position the implant. The planning considers the morphology and range of motion of the patient's hip to reduce the risk of impingements and joint instability. The framework also provides intra-operative support based on patient-specific surgical guides. We performed a post-operative analysis on three patients who underwent THA. Based on post-operative radiological images, we reconstructed a patient-specific model of the prosthetic hip to compare planned and effective positioning of the implants. When the guides were used, we measured non-significant variations of planned executions such as bone cutting. Moreover, patients' hip motions were acquired and used in a dynamic simulation of the prosthetic hip. Conflicts prone to implant failure, such as impingements or subluxations, were not detected. The results show that MyHip provides a promising computer assistance for THA. The results of the dynamic simulation highlighted the quality of the surgery and especially of its planning. The planning was properly executed since non-significant variations were detected during the radiological analysis.

Virtual 3D planning and patient specific surgical guides for osteotomies around the knee

We have investigated the benefits of patient specific instrument guides, applied to osteotomies around the knee. Single, dual and triple planar osteotomies were performed on tibias or femurs in 14 subjects. In all patients, a detailed pre-operative plan was prepared based upon full leg standing radiographic and CT scan information. The planned level of the osteotomy and open wedge resection was relayed to the surgery by virtue of a patient specific guide developed from the images. The mean deviation between the planned wedge angle and the executed wedge angle was 0° (-1 to 1, sd 0.71) in the coronal plane and 0.3° (-0.9 to 3, sd 1.14) in the sagittal plane. The mean deviation between the planned hip, knee, ankle angle (HKA) on full leg standing radiograph and the post-operative HKA was 0.3° (-1 to 2, sd 0.75). It is concluded that this is a feasible and valuable concept from the standpoint of pre-operative software based planning, surgical application and geometrical accuracy of outcome.

Validation of patient specific surgical guides in total hip arthroplasty.

The validation of patient-specific surgical guides (PSGs) by their design and the comparison of planned and actual PSG setting in total hip arthroplasty (THA) have not previously been reported. The errors between preoperative planning and computed tomography (CT)-based PSG setting (E1), and between preoperative planning and implantation (E2) were evaluated using CT in 16 fresh cadaveric hips. E2 was significantly smaller with the wide-base-contact resurfacing-THA PSG than with the narrow-base-contact type (P<0.05). E1/E2 of the wide-base-contact neck-cut PSG was 1.6±0.7°/2.4±1.1° for the coronal plane and 1.2±0.8 mm/0.7±0.5mm for the medial neck-cut height. E1/E2 of the wide-base-contact cup-impaction PSG was 1.0±0.9°/3.4±1.9° for inclination and 1.7±1.1°/6.6±4.4° for anteversion. The wide-base-contact PSG in resurfacing-THA and the PSG for neck-cut in THA could be applied clinically. Although cup-impaction PSG setting was acceptable, errors were made due to the impaction process during cup implantation.

Corrective Osteotomies in Malunions of the Distal Radius, Using Preoperative 3-Dimensional Computer Planning and Patient-Specific Surgical Guides: Level 4 Evidence

Corrective Osteotomies in Malunions of the Distal Radius, Using Preoperative 3-Dimensional Computer Planning and Patient-Specific Surgical Guides: Level 4 Evidence

Shaping Patient Specific Surgical Guides for Arthroplasty to Obtain High Docking Robustness

Patient specific surgical guides (PSSGs) are used in joint replacement surgery to simplify the surgical process and to increase the accuracy in alignment of implant components with respect to the bone. Each PSSG is fabricated patient specifically and fits only in the planned position on the joint surface by the matching shape. During surgery, the surgeon holds the PSSG in the planned position and the incorporated guidance is used in making the essential cuts to fit the implant components. The shape of the PSSG determines its docking robustness (i.e., the range of forces that the surgeon may apply without losing the planned position). Minimal contact between the PSSG and the joint surface is desired, as this decreases the likelihood of interposition with undetected tissues. No analytical method is known from literature where the PSSG shape can be optimized to have high docking robustness and minimal bone-guide contact. Our objective is to develop and validate such an analytical method. The methods of motion restraint, moment labeling and wrench space—applied in robotic grasping and workpart fixturing—are employed in the creation of this new method. The theoretic approach is utilized in an example by optimizing the PSSG shape for one joint surface step-by-step. The PSSGs that arise from these optimization steps are validated with physical experiments. The following design tools for the analytical method are introduced. The optimal location for bone-guide contact and the application surface where the surgeon may push can be found graphically, respectively, by the use of the wrench space map and the application angle map. A quantitative analysis can be conducted using the complementary wrench space metrics and the robustness metric R. Utilization of the analytical method with an example joint surface shows that the PSSG's shape can be optimized. Experimental validation shows that the standard deviation of the error between the measured and calculated angular limits in the docking force is only 0.7 deg. The analytical method provides valid results and thus can be used for the design of PSSGs.

Preoperative analysis of the stability of fit of a patient-specific surgical guide

Although the use of patient-specific surgical guides has gained popularity over the past decade, little research has been done to examine in an objective and qualitative way the fit of such instruments. In this study, we have developed a model to predict the stability of a guide designed to fit on a supporting bone surface, thereby providing feedback on the translational and rotational stability of the device. The method was validated by comparing different guide designs with respect to their stability on the contact surface and comparing these results to those measured with a set of experiments. This validation experiment indicates that our stability model can be used to predict the stability of the fit of a surgical guide during the preoperative design process.

Computer-assisted versus non-computer-assisted preoperative planning of corrective osteotomy for extra-articular distal radius malunions: a randomized controlled trial

BackgroundMalunion is the most common complication of distal radius fracture. It has previously been demonstrated that there is a correlation between the quality of anatomical correction and overall wrist function. However, surgical correction can be difficult because of the often complex anatomy associated with this condition. Computer assisted surgical planning, combined with patient-specific surgical guides, has the potential to improve pre-operative understanding of patient anatomy as well as intra-operative accuracy. For patients with malunion of the distal radius fracture, this technology could significantly improve clinical outcomes that largely depend on the quality of restoration of normal anatomy. Therefore, the objective of this study is to compare patient outcomes after corrective osteotomy for distal radius malunion with and without preoperative computer-assisted planning and peri-operative patient-specific surgical guides.Methods/DesignThis study is a multi-center randomized controlled trial of conventional planning versus computer-assisted planning for surgical correction of distal radius malunion. Adult patients with extra-articular malunion of the distal radius will be invited to enroll in our study. After providing informed consent, subjects will be randomized to two groups: one group will receive corrective surgery with conventional preoperative planning, while the other will receive corrective surgery with computer-assisted pre-operative planning and peri-operative patient specific surgical guides. In the computer-assisted planning group, a CT scan of the affected forearm as well as the normal, contralateral forearm will be obtained. The images will be used to construct a 3D anatomical model of the defect and patient-specific surgical guides will be manufactured. Outcome will be measured by DASH and PRWE scores, grip strength, radiographic measurements, and patient satisfaction at 3, 6, and 12 months postoperatively.DiscussionComputer-assisted surgical planning, combined with patient-specific surgical guides, is a powerful new technology that has the potential to improve the accuracy and consistency of orthopaedic surgery. To date, the role of this technology in upper extremity surgery has not been adequately investigated, and it is unclear whether its use provides any significant clinical benefit over traditional preoperative imaging protocols. Our study will represent the first randomized controlled trial investigating the use of computer assisted surgery in corrective osteotomy for distal radius malunions.Trial registrationNCT01193010