Accuracy Of Patient-specific Instrumentation Research Articles

Effect of Preoperative Coronal Plane Alignment on Actual Versus Predicted Alignment Using Patient Specific Instrumentation in Total Ankle Replacement

Alignment in total ankle replacement is important for success and implant survival. Recently there has been the introduction and adoption of patient specific instrumentation for implantation in total ankle replacement. Current literature does not evaluate the effect of preoperative deformity on accuracy of patient specific instrumentation. A retrospective radiographic analysis was performed on 97 consecutive patients receiving total ankle replacement with patient specific instrumentation to assess the accuracy and reproducibility of the instrumentation. Subgroup analysis evaluated the effect of preoperative deformity. All surgeries were performed by fellowship trained foot and ankle surgeons without industry ties to the implants used. Preoperative and postoperative films were compared to plans based on computerized tomography scans to assess how closely the plan would be implemented in patients. Overall postoperative coronal plane alignment was within 2° of predicted in 87.6% (85 patients). Similarly, overall postoperative sagittal plane alignment was within 2° of predicted in 88.7% (86 patients). Tibial implant size was accurately predicted in 81.4% (79 patients), and talus implant size was correct in 75.3% (73 patients). Patients with preoperative varus deformity had a higher difference between predicted and actual postoperative alignment compared to valgus deformity (1.1° compared to 0.3°, p=0.02). A higher average procedure time was found in varus patients, and more adjunctive procedures were needed in patients with varus or valgus deformity, but these were not significant, p>0.5. Surgeons can expect a high degree of accuracy when using patient specific instrumentation overall, but less accurate in varus deformity.

Surgeon Dominated Design Can Improve the Accuracy of Patient-Specific Instruments in Kinematically Aligned TKA.

Precise bone resection is mandatory for kinematically aligned total knee arthroplasty (KA-TKA). This study is to investigate whether surgeon-dominated design can alter the accuracy of patient-specific instrumentation (PSI) in KA-TKA compared with the engineer design. A total of 24 patients (24 knees) who underwent KA-TKA in our institution were assigned to an engineer design group (10 knees) and surgeon design group (14 knees) chronologically. A novel portable medical-engineer interactive application can greatly enhance the surgeon’s participation in PSI design. The bone resection discrepancies were used to evaluate the accuracy of PSI in bone resection. The overall discrepancy of bone resection was reduced by surgeon-designed PSI compared to engineer-designed PSI by 0.33 mm. Surgeon-designed PSI seems to reduce the outliers in terms of relative discrepancies in bone resection as well, but it does not reach statistical significance. Moreover, surgeon-designed PSI could significantly improve the accuracy of PSI in the restoration of the joint line in terms of medial proximal tibial angle and mechanical lateral distal femoral angle. This study indicates that the dominance of surgeons in both PSI design and subsequent surgical operation should be emphasized in efforts to improve the accuracy of PSI.

The Accuracy of Patient-Specific Instrumentation with Laser Guidance in a Dynamic Total Hip Arthroplasty: A Radiological Evaluation.

The functional positioning of components in a total hip arthroplasty (THA) and its relationship with individual lumbopelvic kinematics and a patient’s anatomy are being extensively studied. Patient-specific kinematic planning could be a game-changer; however, it should be accurately delivered intraoperatively. The main purpose of this study was to verify the reliability and accuracy of a patient-specific instrumentation (PSI) and laser-guided technique to replicate preoperative dynamic planning. Thirty-six patients were prospectively enrolled and received dynamic hip preoperative planning based on three functional lateral spinopelvic X-rays and a low dose CT scan. Three-dimensional (3D) printed PSI guides and laser-guided instrumentation were used intraoperatively. The orientation of the components, osteotomy level and change in hip length and offset were measured on postoperative CT scans and compared with the planned preoperative values. The length of surgery was compared with that of a matched group of thirty-six patients who underwent a conventional THA. The mean absolute deviation from the planned inclination and anteversion was 3.9° and 4.4°, respectively. In 92% of cases, both the inclination and anteversion were within +/− 10° of the planned values. Regarding the osteotomy level, offset change and limb length change, the mean deviation was, respectively, 1.6 mm, 2.6 mm and 2 mm. No statistically significant difference was detected when comparing the planned values with the achieved values. The mean surgical time was 71.4 min in the PSI group and 60.4 min in the conventional THA group (p < 0.05). Patient-specific and laser-guided instrumentation is safe and accurately reproduces dynamic planning in terms of the orientation of the components, osteotomy level, leg length and offset. Moreover, the increase in surgical time is negligible.

Prosthetic Accuracy Depends on the Design of Patient-Specific Instrumentation: Results of a Retrospective Study Using Three-Dimensional Imaging.

To determine accuracy of patient-specific instrumentation (PSI), the preoperative three-dimensional (3D) plan should be superimposed on the postoperative 3D image to compare prosthetic alignment. We aimed to compare prosthetic alignment on a preoperative 3D computed tomography (CT) plan and postoperative 3D-CT image, and evaluate the accuracy of PSI during total knee arthroplasty (TKA). Thirty consecutive knees (30 patients) who underwent TKA using PSI were retrospectively evaluated. The preoperative plan was prepared using 3D CT acquisitions of the hip, knee, and ankle joints. The postoperative 3D CT image obtained 1 week after surgery was superimposed onto the preoperative 3D plan using computer software. Differences in prosthetic alignment between the preoperative and postoperative images were measured using six parameters: coronal, sagittal, and axial alignments of femoral and tibial prostheses. Differences in prosthetic alignment greater than 3 degrees were considered outliers. Two observers performed all measurements. All parameters were repeatedly measured over a 4-week interval. This measurement method's intraobserver and interobserver reliabilities were more than 0.81 (very good). For the femoral and tibial prostheses, absolute differences between the preoperative and postoperative 3D CT images were significantly larger in the sagittal than in the coronal and axial planes (p < 0.001). The outlier rate for the sagittal alignment of femoral and tibial prostheses was significantly higher than that for the alignment of coronal and axial planes (p < 0.001). However, there were no significant differences in the range of motion (ROM) before and after TKA when comparing cases with and without outliers in the sagittal plane. Even though the present study did not reveal any issues with the ROM that depended on the presence of an outlier, accurate verification of prosthetic alignment for individual PSI models may be necessary because the designs, referenced images, and accuracy are different in each model.

Accuracy of three dimensional-planned patient-specific instrumentation in femoral and tibial rotational osteotomy for patellofemoral instability.

Patellofemoral instability can be caused by tibial or femoral torsional deformity. Established surgical treatment options are rotational osteotomies, but the transfer from pre-operative planning to surgical execution can be challenging. Patient-specific instruments (PSI) are proofed to be helpful tools in realignment surgery. However, accuracy of PSI in femoral and tibial rotational osteotomies remains still unknown. Goal of the present study was to evaluate the accuracy of PSI in femoral and tibial rotational osteotomies in a patient population suffering from patellofemoral instability. All patients that underwent femoral or tibial rotational osteotomy using PSI in case of patellofemoral instability from October 2015 until April 2019 in our clinic were included. Twelve knees with twelve supracondylar femoral and seven supratuberositary tibial rotational osteotomies could be included. Accuracy of the correction was assessed using pre- and post-operative CT scans based on conventional measurements and, in 3D, based on 3D bone models of the respective patients. CT measurements revealed an absolute difference between planned and achieved rotation of 4.8° ± 3.1° for femoral and 7.9° ± 3.7° for tibial rotational osteotomies without significant difference (p = 0.069). Regarding 3D assessment, a significant difference could be observed for the residual error between femoral and tibial rotational osteotomies in the 3D angle (p = 0.014) with a higher accuracy for the femoral side. The application of PSI for femoral and tibial rotational osteotomy is a safe surgical treatment option. Accuracy for femoral rotational osteotomies is higher compared with tibial rotational osteotomies using PSI.

TL 18051 - Accuracy of patient-specific instrumentation in total ankle arthroplasty

Introduction: Correct positioning of implants in total ankle arthroplasty (TAA) is a key step to ensure the longevity of the prosthesis. Patient-specific instrumentation (PSI) via preoperative computed tomography for TAA was developed and made available through PROPHECY (Wright Medical, Memphis, TN). The purpose of this study was to compare the use of PSI with the standard referencing guide (SRG) in regard to the accuracy of tibial implant positioning, operative time, and fluoroscopy time. Methods: A retrospective analysis of 99 patients who underwent a primary TAA with the INFINITY prosthesis (Wright Medical, Memphis, TN) was performed. Patients were divided in two groups based on the type of instrumentation used during the TAA (75 in the PSI - PROPHECY group vs 24 in the SRG group). Results: Tibial implant positioning was similar between groups. In the coronal plane, the absolute deviation of the tibial implant was 1.7 ± 1.4 degrees for the SRG and 1.6 ± 1.2 degrees for PSI (P = 0.710). In the sagittal plane, the absolute alignment deviation of the tibial implant was 1.8 ± 1.4 degrees for the SRG and 1.9 ± 1.5 degrees for PSI (P = 0.675). Operative time (P = 0.040) and fluoroscopy time (P &lt; 0.001) were significantly decreased in the PSI group. The PSI preoperative plan report correctly predicted the implant size in 73% of cases for the tibial component and in only 51% of cases for the talar component. Conclusions: PSI provided similar tibial component alignment to standard instrumentation while decreasing the operative and fluoroscopy time. However, PSI preoperative plan reports were poor predictors of implant sizing. Therefore, the final decision should always be based on the surgeon’s experience to prevent errors in implant sizing and positioning.

Design improvement in patient-specific instrumentation for total knee arthroplasty improved the accuracy of the tibial prosthetic alignment in the coronal and axial planes.

The accuracy of patient-specific instrumentation (PSI) in total knee arthroplasty (TKA) is still controversial, especially in the tibial prosthesis. It was hypothesized that the design modification of PSI improved the tibial prosthetic alignment and reduced the associated complications. The aim of this study was to compare the accuracy of a conventional PSI with that of a newly designed PSI for total knee arthroplasty (TKA) using a new three-dimensional (3D) measurement method. Thirty TKAs each using the conventional and newly designed PSIs were studied. The postoperative 3D-computed tomography (3D CT) image was superimposed on the preoperative 3D CT plan. The absolute differences in the tibial prosthetic alignment between the preoperative and postoperative 3D CT images were directly measured in the coronal, sagittal, and axial planes. Knees in which the difference in the prosthetic alignment was > 3° were considered deviations. The new PSI showed less mean absolute differences and lower rate of deviations than the conventional PSI in the coronal and axial planes (p = 0.045 and p = 0.004, respectively). The deviations (> 3°) of the tibial prosthesis using the conventional PSI were 27, 30, and 63% and of those using the new PSI were 0, 20, and 20% in the coronal, sagittal, and axial planes, respectively. This is the first report to evaluate the effect of improvement in PSI design on the postoperative alignment using 3D method, and it clearly showed that the modification significantly improved the accuracy of alignment and reduced the deviations. Therapeutic study, case-control study, Level III.

Accuracy of patient-specific instrumentation in total ankle arthroplasty: A comparative study

BackgroundPatient-specific instrumentation (PSI) for TAA is a novel technology with several potential benefits. The primary goal of this study was to compare the use of PSI with the standard referencing guide (SRG) in regards to accuracy of tibial implant positioning. Operative time, fluoroscopy time and accuracy of PSI preoperative reports were also evaluated. MethodsA retrospective analysis of 99 patients who underwent a primary TAA with the INFINITY prosthesis (Wright Medical, Memphis, TN) was performed. Patients were divided in two groups based on the type of instrumentation used during the TAA (75 in the PSI group vs 24 in the SRG group). There was no significant difference between groups in regards to age at the time of surgery (P=0.122), sex (P=0.138), number of concomitant procedures performed during surgery (P=0.567) and etiology (P=0.841). However, preoperative deformity was significantly smaller in the PSI group (P=0.002). ResultsTibial implant positioning was similar between groups. In the coronal plane, the absolute deviation of the tibial implant from the intended alignment was 1.7±1.4° for the SRG and 1.6±1.2° for PSI (P=0.710). In the sagittal plane, the absolute alignment deviation of the tibial implant was 1.8±1.4° for the SRG and 1.9±1.5° for PSI (P=0.675). Operative time (167 vs 190min, P=0.040) and fluoroscopy time (85 vs 158s, P<0.001) were significantly decreased in the PSI group. The PSI preoperative plan report correctly predicted the implant size in 73% of cases for the tibial component and in 51% of cases for the talar component. ConclusionsPSI provided similar tibial component alignment as standard instrumentation. Additionally, PSI preoperative plan reports were poor predictors of implant sizing. Therefore, the final decision should always be based on surgeon’s experience in order to prevent errors in implant sizing and positioning. Level of evidenceLevel III, retrospective comparative study.

Patient-specific instrumentation for total shoulder arthroplasty: not as accurate as it would seem

There is an increasing body of literature suggesting that the use of patient-specific instrumentation (PSI) in total shoulder arthroplasty (TSA) results in improved positioning of the glenoid component. The aim of this in vivo study was to assess the accuracy of PSI of the glenoid component in TSA in a consecutive series at a single center. Eleven consecutive TSAs (7 TSAs and 4 reverse TSAs) were performed using custom-made patient-specific positioning guides for the glenoid component. Each patient had preoperative computed tomography scans and guides produced to allow 0° of glenoid inclination and version in anatomic TSAs and 10° of inferior inclination for reverse TSAs. Postoperative computed tomography imaging was performed to determine accuracy of component implantation. Patients were observed to the 1-year mark. For the conventional TSA group, the mean version was measured at 8° ± 10° retroversion and 1° ± 4° inclination. For reverse TSAs, mean version was 10° ± 10° retroversion and -1° ± 5° inclination. There were 5 cases classified as outliers in terms of version (>10° anteversion or retroversion). We had a mean correction of version of 22° ± 9° and 17° ± 9° in inclination compared with preoperative measurements. Our results suggest that the in vivo accuracy of PSI-guided glenoid positioning is not as successful as suggested in the literature.

Novel alignment measurement technique for total knee arthroplasty using patient specific instrumentation.

This study was designed to evaluate the true accuracy of patient specific instrumentation (PSI) for total knee arthroplasty (TKA) using a new 3D measurement method. Consecutive 21 patients (30 knees) who underwent TKA using computed tomography (CT)-based PSI were retrospectively evaluated. Mean patient age was 69.2years (62 to 77). The postoperative three-dimensional (3D) CT image were superimposed onto the preoperative 3D CT plan and measured the absolute difference in the prosthetic alignment using six parameters: coronal, sagittal, and axial alignment of the femoral and tibial prostheses. Cases in which the difference in the prosthetic alignment was greater than 3° were considered outliers. For the femoral prosthesis, mean absolute differences between the preoperative 3D CT plan and postoperative 3D CT image were not significantly different and the rates of outliers were 10.0, 33.3, 23.3% in the coronal, sagittal, and axial planes. For the tibial prosthesis, mean absolute differences were significantly larger in the axial plane than in the coronal and sagittal planes (p < 0.001) and the rates of outliers were 23.3, 36.7, 63.3% in the coronal, sagittal, and axial planes. The rates of outliers for the axial alignment of tibial prosthesis were significantly higher than for the other five planes (p = 0.006). The rotation of the tibial prosthesis with CT-based PSI was less accurate in the axial plane than in the other five planes.

Does Implant Design Influence the Accuracy of Patient Specific Instrumentation in Total Knee Arthroplasty?

PSI software adjusts preoperative planning to accommodate differences in implant design. Such adjustments may influence the accuracy of intraoperative jig placement, bone resection, or component placement. Our purpose was to determine whether implant design influences PSI accuracy. 96 and 123 PSI TKA were performed by a single surgeon using two different implant systems and identical PSI software. Femoral coronal alignment outliers were greater for Implant 1 (23.9% Implant 1 vs. 13.4% Implant 2; P=0.050). Tibial coronal alignment outliers were greater for Implant 2 (10.9% Implant 1 vs. 22.7% Implant 2; P=0.025). There was no difference in overall mechanical axes. Differences in implant design can influence bone resection and component alignment. PSI software rationale must align with surgeons’ intraoperative goals.

Reliability of Templating with Patient-Specific Instrumentation in Total Knee Arthroplasty

Magnetic resonance imaging (MRI) or computed tomography-based patient-specific instrumentation (PSI) may allow for reliable alignment and fewer outliers when compared with conventionally instrumented total knee arthroplasty (TKA). However, some authors have suggested that frequent intraoperative surgeon-directed changes may still be required. This study evaluated the accuracy of PSI to predict component sizing and alignment during TKA. A total of 84 patients (89 knees) who underwent a TKA using a PSI system were evaluated. An MRI-based preoperative plan of every knee was provided and approved by the surgeons. This demonstrated the proposed prosthetic component alignment, as well as the femoral, tibial, and bearing insert component size and position. Intraoperative changes to these components were prospectively recorded and compared with the computerized preoperative plan. Major changes were defined as any changes in femoral or tibial resection, size, and position of the components. Minor changes were defined as any change in the size of the polyethylene bearing insert. The preoperative plan was able to correctly predict the size of the implanted tibial and femoral component in 93 and 95.5% of the cases, respectively. Thirteen major intraoperative changes were made. In one knee, the proposed femoral resection was not acceptable (because of the presence of significant amount of osteophytes) and was abandoned in favor of a manual extramedullary guide. In another patient, the proposed femoral and tibial components were upsized. In two other patients, the femoral components were downsized, in four patients, the tibial components were downsized, and in another patient, it was upsized. There were also 16 minor changes, which included 2-mm upsizing of the polyethylene liner in 13 knees and 4-mm upsizing in 3 knees. Surgical experience is necessary to recognize improper component size, incorrect surgical resection, or nonideal alignment when performing TKA using PSI. The authors believe that the design and manufacture of PSI combined with a comprehensive templating resulted in excellent intraoperative concordance of the preoperative plan at the default settings with minimal changes.

Image-based Evaluation of Patient Specific Instrument Attachment in TKA

Patient specific instruments (PSI) system has been attracting considerable attention for navigation-free surgical operation of total knee arthroplasty (TKA). PSI is a jig which guides a cutting section of the femoral or the tibia bones where TKA implant is attached to ensure accurate and reproducible surgery, and is prepared for a specific patient. However, another problem has been raised because the attachment of PSI will cause errors of TKA guidance. This paper proposes a novel system to evaluate the accuracy of attaching PSI during TKA operation using cone-beam CT. The system acquires 3-D sectional images of PSI attached to knee, and evaluates the attachment accuracy by means of image registration techniques with computer-aided design (CAD). It calculates the position and the angle of guidance pin, and compares with the preoperative planning. The system has been applied to three subjects which had been operated TKA with PSI. The results produced 3- D renderings of the attached PSI and of the planned PSI, and calculated angle differences between the attached and the planned guidance pin. By using them, we can evaluate the attachment accuracy of PSI, and also evaluate the implanting accuracy of TKA.