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Talar osteochondral lesions (OCLs) lead to progressive stages of talar destruction. Core decompression with cancellous bone grafting (CBG) is a common treatment for Berndt and Harty stages II and III. However, in a subset of patients, talar revascularization may fail. Surgical angiogenesis using vascularized medial femoral condyle (MFC) autografts may improve on these outcomes. These 2 treatment strategies were directly compared via a prospective preliminary randomized trial including 20 participants with talar core decompression followed by either cancellous (CBG group, n = 10) or vascularized MFC (MFC group, n = 10) bone grafting. Outcome analysis was performed with visual analog scale (VAS), American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, Lower Extremity Functional Scale (LEFS), and contrast-enhanced magnetic resonance imaging (MRI) scans. At 12 months of follow-up, the mean VAS score was reduced from 6.6 ± 2.5 preoperatively to 4 ± 1.9 in the CBG group and from 5.2 ± 2.9 preoperatively to 1 ± 1.1 in the MFC group (p.001). The LEFS improved from 53.4 ± 13.1 to 62.6 ± 16.2 CBG and from 53 ± 9.3 to 72.4 ± 7.4 MFC (p = .114). AOFAS improved from 71 ± 12.1 to 84.1 ± 12.5 in CBG and from 70.5 ± 7.4 to 95.1 ± 4.8 in MFC (p = .019). The MRI scans in the CBG group demonstrated 9 partial malperfusions and 1 hypervascularized bone graft, whereas the MFC group had 8 well-vascularized grafts incorporated into the talus and 1 partial malperfusion. Vascularized MFC autografts provide superior pain relief along with improvement of physical function in patients with talar OCL stage II and III compared with CBG. To confirm these promising results, further multicenter randomized controlled trials are required.

Purpose To compare and evaluate knee laxity and functional outcomes between autologous bone graft and silicate-substituted calcium phosphate (Si-CaP) in the treatment of tunnel defects in 2-stage revision anterior cruciate ligament reconstruction (ACLR). Methods This prospective, randomized controlled trial was conducted between 2012 and 2015 with a total of 40 patients who underwent 2-stage revision ACLR. The tunnels were filled with autologous iliac crest cancellous bone graft in 20 patients (control group) and with Si-CaP in the other 20 patients (intervention group). After a minimum follow-up period of 2 years, functional outcomes were assessed by KT-1000 arthrometry (side-to-side [STS] difference), the Tegner score, the Lysholm score, and the International Knee Documentation Committee score. Results A total of 37 patients (follow-up rate, 92.5%) with an average age of 31 years were followed up for 3.4 years (range, 2.2-5.5 years). The KT-1000 measurement did not show any STS difference between the bone graft group (0.9 ± 1.5 mm) and the Si-CaP group (0.7 ± 2.0 mm) (P = .731). One patient in the intervention group (5%) had an STS difference greater than 5 mm. Both groups showed significant improvements in the Tegner score, Lysholm score, and International Knee Documentation Committee score from preoperative assessment to final follow-up (P ≤ .002), without any difference between the 2 groups (P ≥ .396). Complications requiring revision occurred in 4 control patients (22%) and in 2 patients in the intervention group (11%) (P = .660). No complications in relation to Si-CaP were observed. Conclusions Equivalent knee laxity and clinical function outcomes were noted 3 years after surgery in both groups of patients. Si-CaP bone substitute is therefore a safe alternative to autologous bone graft for 2-stage ACLR. Level of Evidence Level I, prospective, randomized controlled clinical trial.

Revision surgery after failed primary anterior cruciate ligament reconstruction is technically demanding. In cases in which the tunnels of the primary anterior cruciate ligament reconstruction are widened to greater than 10 mm and/or are incorrectly positioned, a 2-stage procedure enables restoration of bone stock and thus free placement of the tunnels during the revision. The gold standard for tunnel augmentation is an autologous iliac crest cancellous bone graft. However, harvesting the graft is associated with high morbidity. This article describes an alternative method for managing bone deficiencies using the synthetic bone graft substitute silicate-substituted calcium phosphate.

Computer assisted surgery (CAS) has been applied more often within the last years. Multiple aspects of CAS have been important in orthopaedic and trauma surgery such as pre-operative planning, intraoperative imaging and navigation. In total four different methods of navigation within CAS exist. While imageless navigation is used more regularly in osteotomy, 3D-based navigation is applied in trauma surgery more commonly. CAS uses infrared signals sent from markers attached to the patient and the instruments which are detected by a camera and processed by a connected computer. The aim of CAS is a visual support during complex surgical procedures leading to an improvement of the operational result. The enhancement of the visualization permits surgical procedures with low soft tissue impairment especially in crucial anatomical regions. Hence CAS together with minimal invasive procedures and an improvement of digital imaging has the option to optimize surgical procedures. However there exist limitations to the application of CAS in trauma care which have to be considered.

Purpose To evaluate the histologic and radiographic outcomes of using silicate-substituted calcium phosphate (Si-CaP) as bone graft substitute for the augmentation of tunnel defects in 2-stage revision anterior cruciate ligament (ACL) reconstruction. Methods Forty patients undergoing 2-stage revision ACL reconstruction were included in a prospective, randomized controlled clinical trial between 2012 and 2015. The inclusion criteria were tunnel diameter of the tibial and/or femoral tunnel of 10 mm or greater after failed ACL reconstruction. Twenty patients received autologous bone from the iliac crest and 20 patients received Si-CaP as a bone graft substitute for tunnel grafting at the first-stage procedure. Punch biopsy specimens of the augmented tunnels were taken at the second-stage procedure, and histologic examination included quantitative analysis of the area of immature bone formation, lamellar bone, and bone marrow. Radiographic analysis included determination of the filling rates of the tunnels on postoperative computed tomography scans. Results Forty patients with a mean age of 32 years (standard deviation [SD], 11.0 years) were analyzed. Histologic examination of the tunnels filled with Si-CaP showed that 15% (SD, 14%) of the area was covered with immature bone formation, 41% (SD, 10%) with well-organized lamellar bone, and 44% (SD, 8%) with bone marrow. In the control group (autologous bone), 58% (SD, 3%) of the area was covered with well-organized lamellar bone and 42% (SD, 3%) with bone marrow. Quantitative evaluation of the postoperative computed tomography scans showed a trend of better filling rates in patients with Si-CaP for the tibial tunnel (86% [SD, 17%] vs 78% [SD, 14%]; P = .131). Intraoperatively, Si-CaP was completely integrated into the original bone tunnel providing good stability for tunnel placement and tendon graft fixation comparable to autologous bone. Conclusions Si-CaP as bone graft substitute for tunnel augmentation in 2-stage revision ACL reconstruction shows good histologic, radiographic, and intraoperative integration comparable to autologous bone. Level of Evidence Level I, prospective randomized controlled trial.

Background: The intraoperative assessment of the articular surface in displaced intra-articular distal tibia fractures can be challenging using conventional fluoroscopy. The aim of the study was to determine the frequency and the method of intraoperative corrections of fracture reductions or implant placements during open reduction, internal fixation by using cone beam computed tomography (CT) after conventional fluoroscopy. Methods: Displaced intra-articular distal tibia fractures were retrospectively analyzed from August 2001 until December 2011. The fractures were classified according to the standards of the AO/OTA as type B or C and treated with open reduction and internal plate fixation. After primary reduction using conventional fluoroscopy, an additional cone beam CT scan was used to determine the alignment of the joint line and the implant position. The number of intraoperative revisions of the primary reduction due to the use of cone beam CT was analyzed. Results: A total of 143 patients with an intra-articular tibial plafond fracture were included in the analysis. In 43 patients (30%), an intraoperative correction was performed after the cone beam CT scan. In 34 (24%) of these cases, intraoperative correction was required because of inadequate joint line reduction. Nine (6%) corrections were required as a result of a malposition of the implant. The revision rate did not differ by fracture classification. Conclusion: Despite its acceptance as the standard method of imaging, intraoperative conventional fluoroscopy for the assessment of implant positioning and fracture reduction of tibial plafond fractures is limited. The intraoperative utilization of cone beam CT provided additional information for the surgeon to detect insufficient reduction or implant malposition. Level of Evidence: Level III, retrospective comparative series.

Aims and Objectives: The goal of the study was to describe the short time results of our new surgical technique of arthroscopic Button-to-Button fixation for acute tibial posterior cruciate ligament (PCL) avulsion fractures. Concerning clinical and radiographic outcomes, and complication rates. Materials and Methods: This prospective study includes patients with an acute tibial avulsion fracture of the PCL. The reduction and fixation was performed all arthroscopic, reduction and suture fixation by Tight Rope ABS and 2 ABS Buttons (Fa. Arthrex). Indication for image-proven displaced tibial PCL avulsion fractures with posterior knee instability of grade II or higher. The mean follow-up period was 6 months. Follow-up assessment included clinical assessment, functional scores, and radiographic evaluation. Results: First Results showed that Patients had better range of motion compared to Patients with an open technique. The postoperative physiotherapy was not limited by the dorsal approach. We have seen no leck of extension after 6 months due to all arthroscopic technique. All fractures achieved union. We have seen no procedure connected complications like wound infections, Button dislocations or nonunions. Conclusion: Treatment of tibial PCL avulsion fractures by all arthroscopic Button-to-Button fixation seems to be a successful technique. The benefit with an stable fixation without a dorsal approach helps the postoperative treatment and avoids soft tissue problems , especially limitations of the extension due to Arthrofibrosis and dorsal scar formation. Intermediate and long term results have to prove the clinical results.

The biomechanically and anatomically correct placement of hip prostheses components is the main challenge in revision hip arthroplasty. The orientation of the cup and stem with the restoration of leg length, offset and hip centre is hampered by the defect situations frequently present. In primary hip arthroplasty, it has been demonstrated that the components can be accurately positioned using computer-navigated procedures. However, such procedures could also be of considerable benefit in revision hip arthroplasty. Systems that not only detect anatomical landmarks using pointers but also use image data for referencing may provide a possible solution for the defect situation. Literature about navigation in revision arthroplasty is very rare. This article comprises general considerations on this subject and presents our experience and possible clinical applications.

Background Acute unstable syndesmotic ankle injuries are treated primarily by reduction and stabilization with a syndesmotic screw. Examination with fluoroscopy or standard radiographs may not provide reliable information about the quality of the reduction. There is evidence that intraoperative three-dimensional imaging can demonstrate a large proportion of malreductions. The aim of this study was to determine whether intraoperative three-dimensional imaging improves the detection of inadequate positioning of the distal aspect of the fibula in the tibiofibular incisura after syndesmotic screw insertion compared with the findings on standard intraoperative fluoroscopy. Methods Of 2286 ankle fractures treated operatively from August 2001 to February 2011, 251 consecutive cases (11%) were identified in a retrospective chart review. All had an unstable syndesmosis and underwent syndesmosis stabilization on the basis of an intraoperative hook test. After fluoroscopy, an intraoperative three-dimensional scan was performed. The result of this scan was documented by the surgeon and analyzed retrospectively with regard to the incidence and nature of the need for intraoperative revisions. Results The intraoperative three-dimensional scan altered the surgical outcome in eighty-two ankles (32.7%). In most ankles (seventy-seven; 30.7%), the reduction was improved, with the most common improvement being the alignment of the fibula in the tibiofibular incisura in sixty-four patients (25.5%) followed by correction of the fracture reduction in thirteen patients (5.2%). The other five alterations involved implant corrections. The most common malpositions requiring correction after insertion of a positioning screw, with or without additional fixation, were anterior displacement and internal rotation of the distal aspect of the fibula. Conclusions Following open reduction and internal fixation of an ankle fracture, the correct position of the syndesmosis cannot be evaluated reliably with use of conventional radiographs or intraoperative fluoroscopy. In view of the high proportion of positive findings in this study, we believe that any treatment of a syndesmotic injury should include intraoperative three-dimensional imaging or at least a postoperative computed tomography scan.

Fluoroscopy is the most common tool for the intraoperative control of long-bone fracture reduction. Limitations of this technology include high radiation exposure for the patient and the surgical team, limited visual field, distorted images, and cumbersome verification of image updating. Fluoroscopy-based navigation systems partially address these limitations by allowing fluoroscopic images to be used for real-time surgical localization and instrument tracking. Existing fluoroscopy-based navigation systems are still limited as far as the virtual representation of true surgical reality is concerned. This article, for the first time, presents a reality-enhanced virtual fluoroscopy with radiation-free updates of in situ surgical fluoroscopic images to control metaphyseal fracture reduction. A virtual fluoroscopy is created using the projection properties of the fluoroscope; it allows the display of detailed three-dimensional (3D) geometric models of surgical tools and implants superimposed on the X-ray images. Starting from multiple registered fluoroscopy images, a virtual 3D cylinder model for each principal bone fragment is constructed. This spatial cylinder model not only supplies a 3D image of the fracture, but also allows effective fragment projection recovery from the fluoroscopic images and enables radiation-free updates of in situ surgical fluoroscopic images by non-linear interpolation and warping algorithms. Initial clinical experience was gained during four tibia fracture fixations that were treated by LISS (Less Invasive Stabilization System) osteosynthesis. In the cases operated on, after primary image acquisition, the image intensifier was replaced by the virtual reality system. In all cases, the procedure including fracture reduction and LISS osteosynthesis was performed entirely in virtual reality. A significant disadvantage was the unfamiliar operation of this prototype software and the need for an additional operator for the navigation system.

After experimental and preclinical evaluation of a CT-free image guided surgical navigation system for acetabular cup placement, the system was introduced into clinical routine. The computation of the angular orientation of the cup is based on reference coordinates from the anterior pelvic plane concept. A hybrid strategy for pelvic landmark acquisition has been introduced, involving percutaneous pointer-based digitization with the noninvasive bi-planar landmark reconstruction using multiple registered fluoroscopy images. From January 2001 to October 2003, a total of 236 consecutive patients (mean age 66 years, 144 male, 92 female, 124 left and 112 right hip joints) were operated on with the hybrid CT-free navigation system. During each operation, the angular orientation of the inserted implant was recorded. To determine the placement accuracy of the acetabular components, the first 50 consecutive patients underwent a CT scan 7-10 days postoperatively to analyze the cup position relative to the anterior pelvic plane. This procedure was done blinded and with commercial planning software. There was no significant learning curve observed for the use of the system. Mean values for postoperative inclination read 42 degrees (SD 3.6, range (37-49)) and anteversion 21 degrees (SD 3.9, range (10-28)). The resulting system accuracy, ie, the difference between intraoperatively calculated cup orientation and postoperatively measured implant position shows a maximum error of 5 degrees for the inclination (mean 1.5 degrees, SD 1.1) and 6 degrees for the anteversion (mean 2.4 degrees, SD 1.3). An accuracy of better than 5 degrees inclination and 6 degrees anteversion was achieved under clinical conditions, which implies that there is no significant difference in performance from the established CT-based navigation methods. Image-guided CT-free cup navigation provides a reliable solution for future total hip arthroplasty (THA).

Die Ruptur des hinteren Kreuzbands stellt auch in der heutigen Zeit noch eine grose Herausforderung an den behandelnden Chirurgen. Wahrend Rupturen des vorderen Kreuzbands in der Behandlung relativ einheitliche Standards erhalten haben, ist das Behandlungsspektrums des hinteren Kreuzbands wesentlich breiter. Von konservativer Therapie uber primare und fruhsekundare Nahtrefixation bis hin zum primaren oder sekundaren Ersatz werden alle Verfahren als Therapie der Wahl beschrieben. Dennoch finden sich in allen Studien nur geringe Fallzahlen, sodass die Aussagen zu den einzelnen Verfahren schwer interpretierbar und in der Regel nicht vergleichbar sind. Die konservative Behandlung des HKB ist aufgrund der guten Vaskularisation moglich und kann zu stabilen Ausheilungen fuhren, dies gilt ebenso fur die Behandlung mit augmentierter Naht. Wesentlich grosere Probleme als bei VKB bestehen beim HKB-Ersatz durch die vorgegebene Anatomie mit verschiedenen Faserbundeln und das daraus abgeleitete unterschiedliche Isometrieverhalten. Als Rekonstruktionsverfahren werden Ersatzplastiken mit Patella-, Quadrizeps-, Semitendinosus- und/oder Grazilissehne in Einzel- und Doppelbundeltechnik favorisiert.

Verletzungen des kindlichen Skeletts finden sich im Krankengut von spezialisierten traumatologischen Zentren in hoher Zahl. Insbesondere Verletzungen des Kniegelenks und ihre Folgen werden haufig unterschatzt. Die klinische Untersuchung und Bild gebende Diagnostik konnen das wahre Ausmas der Kniebinnenschadigung haufig nicht ausreichend sicher vorhersagen. Orientierend am Leitsymptom Hamarthros finden sich in uberwiegender Zahl intraartikulare Lasionen, die eine operative Intervention erforderlich machen. 121 Kinder und Jugendliche unter 18 Jahren wurden im Zeitraum vom 1.1.2000–31.10.2001 an der BG-Unfallklinik Ludwigshafen aufgrund von Kniegelenkverletzungen operiert. Es dominierten die Verletzungen der Kreuzbander und Patellaluxationen. In dieser Arbeit werden die Versorgungsprinzipien an unserer Klinik dargestellt und mit der aktuellen Literatur verglichen.

Background: In about 25% of cases, reduction of acute unstable syndesmotic injuries and stabilization with syndesmotic screws leads to an inadequate reduction. Conventional fluoroscopy does not provide reliable information about the reduction outcome. However, use of intraoperative 3D imaging can be more accurate. The purpose of this study was to identify predictors of inadequate reduction so that the need for intra- or postoperative 3D imaging could be assessed. Our hypothesis was that complex injuries of the syndesmosis present a higher risk of malreduction than simpler ankle fractures. Methods: From August 2001 to February 2011, 251 unstable syndesmotic injuries were treated from a total of 2286 ankle fractures. In 61 of these cases, malreduction of the fibula into the fibular notch was detected by intraoperative 3D imaging. The influence of all possible concomitant and combination injuries of the ankle joint, surgeon’s experience, and potential implant-related effects was analyzed. Results: Thirty-seven Weber C fractures (60.7%), 13 Maisonneuve fractures (21.3%), 10 Weber B fractures (16.4%), and 1 syndesmotic injury without fracture (1.6%) were included. In 14 cases (23%) there was involvement of the posterior malleolus, in 10 cases of the medial malleolus (16.4%), and in 12 cases both (19.7%). The Weber C fractures included 10 bimalleolar fractures with involvement of the posterior malleolus. In neither this combination nor in any other possible injury configuration was it possible to identify a statistically significant correlation with malreduction of the fibula into the fibular notch. The surgeon’s experience or an implant-related effect had no detectable influence either. Conclusion: Based on the factors studied, it is not possible to conclude whether a patient has an increased risk of malreduction. Therefore we still recommend verifying all reduction outcomes by intraoperative 3D imaging or postoperative computed tomography. Level of Evidence: Level III, retrospective comparative study.

Background: Displaced intra-articular calcaneal fractures are frequently treated by open reduction and internal fixation. The usual intraoperative monitoring by means of fluoroscopy does not always provide complete intraoperative information for the surgeon. The aims of this study were to analyze the percentage of patients for whom intraoperative three-dimensional imaging leads to intraoperative revision and whether the avoidance of an intra-articular step or gap influences the clinical outcome. Methods: From August 2001 to June 2009, 377 consecutive, operatively treated calcaneal fractures were identified in a retrospective chart review. The results of the intraoperative three-dimensional scans were analyzed for the rate of and the reason for intraoperative revision. For the clinical evaluation, all patients with Sanders type-II and III fractures who were seen from October 2002 to January 2006 were included. When the outer shape of the calcaneus was successfully restored, the fractures were divided into two groups according to the reduction outcome for all joint surfaces (a step-off or gap of

Das Standardvorgehen bei der Behandlung von Calcaneusfrakturen ist eine Osteosynthese. Mit Hilfe der intraoperativen Bildgebung wie dem mobilen C-Bogen CT kann der Chirurg das Repositionsergebnis noch im Operationssaal verifizieren und wenn notig korrigieren. Die Mobilitat des C-Bogen CT hat jedoch zur Folge, dass Informationen uber die Orientierung des Patienten zum Gerat verloren gehen. Dadurch kann keine Standard-Ausrichtung der dreidimensionalen Daten an die Anatomie erfolgen. Eine manuelle Einstellung des Volumendatensatzes durch den Chirurgen ist damit unabdingbar. Dies ist ein zeitaufwendiger Schritt und kann bei einer unprazisen Einstellung zu Fehlern bei der Beurteilung der Daten fuhren. In diesem Paper stellen wir zwei automatische Methoden zur Einstellung der Standard-Ebenen auf mobilen C-Bogen CT Daten vor. Die automatischen Methoden rekonstruieren die Standard-Ebenen in zwei Schritten: als Erstes werden SURF-Keypoints (2D und neu eingefuhrte Pseudo-3D-Punkte) fur das Bildvolumen berechnet, in einem zweiten Schritt wird eine Atlas-Punktwolke auf diese Merkmale registriert und die Parameter der Standard-Ebenen transformiert. Die Genauigkeit unserer Methoden wurde an 51 klinischen mobilen C-Bogen CT Bildern mit manuell eingestellten Standard-Ebenen evaluiert. Die Referenzdaten wurden von drei Chirurgen mit unterschiedlichem Erfahrungsstand erstellt. Die durchschnittlich benotigte Zeit der Experten (46 s) unterscheidet sich von der des fortgeschrittenen Benutzers (55 s) um neun Sekunden. Die Berechnungszeit des 2D-Surf Ansatzes betragt 10 Sekunden und liefert bei 88% der Ebenen der Referenzdaten eine korrkte Einstellung. Der Pseudo-3D Ansatz liefert die besten Ergebnisse mit einer Genauigkeit von 91% und einer Berechnungszeit von nur 8 Sekunden.

Tibial shaft fracture is one of the most common types of bone fracture in young patients. In this prospective clinical cohort study, we investigated the effects of cigarette smoking on the clinical, functional, psychosocial and occupational outcomes after isolated lower-leg fracture. We examined 85 patients, including 61 men and 24 women, with a collective mean age of 46 years (range: 18-84 years). Thirty-nine patients had never smoked (G1) and 45 patients were current or previous smokers (G2). The G2 group displayed a significantly increased risk for delayed union or nonunion (G1=3 patients, G2=18 patients; P=0.0007) and increased time required for fracture healing (mean times: G1=11.9 weeks, G2=17.4 weeks; p=0.003) and a markedly increased time out of work (mean times: G1=16.1 weeks, G2=21.5 weeks; p=0.1177 (not significant)). The 18 negatively affected patients in G2 displayed a significant increase in the time required for fracture healing and time out of work (26 weeks (p=0.02) and 31 weeks (p=0.03), respectively). G2 group members had a 3- to 18-fold higher risk of impaired bone healing. The mean Short Form 36 (SF-36) was similar in both groups. The physical-function scores were G1=49.6 and G2=48.6; the mental scores were G1=52.7 and G2=52.8. These findings indicate that smoking significantly increases the risk of impaired fracture healing, which has clinical and occupational consequences for the affected patients. Based on our data, we developed a score to estimate the individual risk of impaired fracture healing. These types of patients must be informed and closely monitored to determine the need for timely re-intervention with additional therapy, such as BMP s or ultrasound.

High tibial dome osteotomy is a well accepted but technically demanding surgical procedure. Common complications include postoperative malalignment of either under- or over-correction, pin penetration of the tibial plateau, and damage to the tibial dorsal neurovascular structures. In order to address all these problems, we developed a CT-free intraoperative planning and navigation system based on SurgiGATE system (Praxim-Medivision, La Tronche, France). Following acquisition of fluoroscopic images and registration of anatomic landmarks, a patient specific coordinate system is established. The deformity is measured intraoperatively and the surgical procedure is planned interactively. The osteotomy and deformity correction are performed under navigational guidance. The system holds the promise to improve the accuracy, reliability, and safety of this surgical procedure.

High tibial osteotomy is a widely accepted treatment for unicompartmental osteoarthritis of the knee and other lower extremity deformities, particularly in young and active patients. However, it is generally recognized as a technically demanding procedure. The lack of intraoperative control of the mechanical axis of the affected limb often results in postoperative malalignments, which is one of the main reasons for poor long-term results. Moreover, inaccurate osteotomies, such as insufficient or excessive bone cut, or incorrect orientation of the chisel or saw blade, have been observed. A computer assisted intraoperative planning and navigation system is therefore proposed in order to address these technical problems. During operation, fluoroscopic images are acquired and anatomical landmarks are digitized; a patient-specific coordinate system is established accordingly. After the three-dimensional measurement of the deformity and interactive planning of the osteotomy plane, the deformity is corrected under navigational guidance. The proposed system has been successfully introduced into the clinical practice of surgery after encouraging laboratory evaluations, with results affirming that it is safe and accurate.