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Purpose To investigate a computer-assisted technique for retrograde insertion of a percutaneous scaphoid screw and compare insertion time, accuracy, and radiation exposure to the traditional technique. We hypothesize that computer-assisted navigation of volar percutaneous scaphoid screw placement would improve accuracy, require less time, and diminish radiation exposure when compared to the traditional technique. Methods Ten matched pairs of cadaveric wrists were randomized to computer-assisted versus traditional volar percutaneous scaphoid screw placement. Time of the overall procedure, set-up time, time for ideal guide wire placement, and radiation time were recorded. Number of K-wire attempts was also recorded. Finally, accuracy of planned screw axis and actual screw axis were compared. Student's t -tests and rank sums were used to determine whether the differences in outcome variables between computer-assisted and traditional techniques was significant, with an alpha level of 0.05. Results Although the overall time of the 2 procedures and the set-up time were not different between the 2 groups, the time for placement of the K-wire was halved in the computer-assisted percutaneous scaphoid fixation group, and the number of K-wire attempts needed for accurate screw placement approached clinical significance. Although the radiation exposures for the individual components of set-up time and final check time were not different, the radiation exposures for global time of the procedure, K-wire placement, and screw placement were clinically significant. Conclusions Computer-assisted navigation of volar percutaneous scaphoid screw placement takes no more time that traditional methods and significantly reduces the amount of radiation exposure to the patient. Although not statistically significant, the technique reduced the number of incorrect passes of the K-wire, requiring a single attempt in 4 of the 5 specimens.

Technological progress in the electronics and computer fields has resulted in new methods of surgical aid. Indeed, several types of operations in orthopaedic or trauma surgery can now benefit from computer guidance systems. This relates, for example, to assistance in placing total hip or knee replacements, or again, in implementing difficult surgical procedures such as a peri-acetabular osteotomy (12, 20, 23, 31).

Aim: The aim of this prospective study was to evaluate the outcome of computer-guided flapless placement and immediate loading of four conical screw-type implants in the interforaminal region. Patients and methods: From May to August 2003, 25 consecutive patients (m : f=16 : 9) with edentulous mandibles were included in the study. After transmucosal drilling with computer-assisted navigation, four implants were placed in the interforaminal region. The lower dentures were converted and implants immediately loaded. Results: One-hundred implants were successfully placed. In two patients, all implants had to be submerged because of insufficient primary stability of one of the implants; another patient declined to receive immediate loading of implants after surgery and was lost to follow-up. During follow-up of the remaining 22 patients with 88 immediately loaded implants, loosening of four implants (4.5%) was seen in three patients. In these cases, immediate loading was terminated and all implants submerged; subsequently, two implants were lost in one patient, while the other two implants re-osseointegrated. The cumulative survival and success rates of immediately loaded implants were 97.7% after 2 years. Prosthetic success was 100%. Conclusion: Transmucosal computer-assisted placement and immediate loading of mandibular implants is a high-end approach to edentulism that provides excellent results while being minimally invasive.

Introduction Navigation in orthopaedic surgery is becoming more accepted as a means of improving and documenting accuracy. Yet, despite the improvements made, the road towards recognition of the capability and versatility of computer-assisted surgery has not always been smooth. Initially, navigation involved imagery, which utilized a localizer to calculate the geometry of the infrared reflective surfaces and light emitting diodes or tracking grids [1]. Image guided procedures utilized patient X-rays and fluoro-imaging obtained prior to or during a procedure as a guide for the physician. However, this was constrained by the necessity of direct, unobstructed line of sight. Both image-guided and imageless navigation systems require trackers to establish the position of the patient as movement occurs, whereas traditional imageless infrared (IR) navigation eliminates the need for fluoro-imaging while still requiring line-of-sight. Constraints on signal strength as well as a limited arc or azimuth of signal reception hinder its use. Additionally, IR accuracy is proportional to the separation between reflector markers, requiring expansive arrays, which are obtrusive to the surgical field and may injure soft tissue as movement of the extremity is performed. Due to problems including fixation, signal acquisition, soft tissue trauma, and operative constraints, a technology using a signal that does not require line-of-sight reception was desirable. An electromagnetic computer-assisted surgery (EM-CAS) system has this capability. Some of the first reports of the use of EM in surgery were in neurosurgical and ENT applications for cranial surgery [2,3]. Other applications of EM technology arose in cardiovascular surgery, where an electromagnetic field was used to guide ferrous-tipped catheters into tortuous vessels that were non-navigable by traditional catheterization techniques. These were tracked by fluoro-imaging yet had the distinction of reversing the role of EM to steer them rather than track them into extremely tight, convoluted vessels [4]. Part of the suspicion about EM technology for orthopaedic applications arises from concerns over the stability of the signal around metallic objects. However, with the advent of multiplex magnetic generators, known as localizers and receiver coils or trackers called dynamic reference frames (DRFs), much of the instability and signal inaccuracy is removed. Precision and accuracy is vastly improved to well beyond the industry standard of ±2 mm and ±2o of angulation. Achieving this level of accuracy allows EM tracking to have equivalent status as traditional line-of-sight IR navigation systems with the added benefit of soft tissue penetration.

Computer-assisted total knee arthroplasty has been gaining popularity given the proposed benefits of increased accuracy of the femoral and tibial cuts, quantitative feedback on soft tissue balancing, and the potential for performing the procedure through smaller incisions with decreased soft tissue trauma. Most navigation systems require femoral and tibial threaded pin insertion for placement of guidance trackers, which when removed leave behind defects in the bone that may act as stress risers. We present 2 cases of a femoral fracture through a previous pin site where a guidance tracker had been placed for computer-assisted total knee arthroplasty. Both patients were informed that data concerning the cases would be submitted for publication. To our knowledge, this complication has not previously been reported for this procedure.

Endovascular therapy provides a minimally invasive solution for the treatment of brain aneurysms. Interventional neuroradiologists navigate microcathers, platinum coils and stents from the femoral artery to treat the pathological target vessel under fluoroscopic guidance. The procedure involves a clinically significant radiation dose to the patient and the clinical team. We have developed a multi-modality navigation platform providing real-time visualization of the position of endovascular tools without radiation exposure. The system integrates magnetic tracking of surgical devices, and 3D visualization of their position inside a reconstructed model of the vasculature. Preliminary phantom tests have demonstrated an accuracy of 3.8 mm. By merging imaging and localization data, this prototype can provide 3D real-time navigation in brain arteries.

The incidental acquisition of spatial orientation knowledge when using a pedestrian navigation assistance system for wayfinding was compared to incidental learning during map-based wayfinding. First-time visitors to a real environment (a zoo) took a guided tour. In the navigation assistance conditions, users were provided with direction information and view-based pictures of the current intersection at each decision point, presented on a hand-held computer. In the map-based condition, participants derived route segments from a map (each segment comprising three or four intersections), and then walked the partial routes from memory. After walking, unexpected tests on route memory and survey knowledge were administered. Navigation assistance users showed good route knowledge and poor survey knowledge. In contrast, map users showed better survey knowledge and nearly perfect route knowledge. Variations of information presentation within navigation assistance conditions (auditory vs. visual direction command, additional presentation of allocentric spatial information) was not effective. Results are explained with an active encoding principle. Only information that is actually encoded, transformed, and/or memorized during the primary wayfinding activity, is incidentally learned. Since navigation assistance systems do not require users to encode, transform, and memorize spatial information, the spatial orientation knowledge of navigation assistance users is poor.

Computer-aided surgical navigation technology is commonly used in craniomaxillofacial surgery. It offers substantial improvement regarding esthetic and functional aspects in a range of surgical procedures. Based on augmented reality principles, where the real operative site is merged with computer generated graphic information, computer-aided navigation systems were employed, among other procedures, in dental implantology, arthroscopy of the temporomandibular joint, osteotomies, distraction osteogenesis, image guided biopsies and removals of foreign bodies. The decision to perform a procedure with or without computer-aided intraoperative navigation depends on the expected benefit to the procedure as well as on the technical expenditure necessary to achieve that goal. This paper comprises the experience gained in 12 years of research, development and routine clinical application. One hundred and fifty-eight operations with successful application of surgical navigation technology--divided into five groups--are evaluated regarding the criteria "medical benefit" and "technical expenditure" necessary to perform these procedures. Our results indicate that the medical benefit is likely to outweight the expenditure of technology with few exceptions (calvaria transplant, resection of the temporal bone, reconstruction of the orbital floor). Especially in dental implantology, specialized software reduces time and additional costs necessary to plan and perform procedures with computer-aided surgical navigation.

This chapter will describe the technique of the posterior mini-incision of average 8 cm length. Sixty percent or more of total hip replacements in the United States are performed through the posterior approach. Therefore, it only makes sense that the majority of surgeons will need to initially learn to perform MIS THR through a posterior approach. Most will not go beyond this approach to an intermuscular one because the posterior mini-incision operation satisfies the needs of most patients. Gait studies have always shown better function post-operatively, at least in the first 6 months, in patients with a posterior rather than an anterior approach [1].

Computer assisted navigation and biomechanical modeling have made surgical simulation a new domain of research in the last decade. One possible operation that could benefit from this progress is the Anterior Cruciate Ligament (ACL) reconstruction. During this operation, the anterior cruciate ligament graft has to be placed in such a way that it is isometric during a flexion-extension and in traction when the leg is in extension. That is to say two constraints : a geometrical one and a physical one. We present a CT-Free navigation system that solves both these constraints in real-time and intra-operatively. With the combined solution, the surgeon will be able to know per-operatively if the graft placement will lead to a robust and effective reconstruction or not.

New evolving technology usually lacks sufficient data indicating clear advantages to conventional methods. We, therefore, performed a five-center study in order to demonstrate the consistency and superiority of the OrthoPilot navigation system in TKA.

Computer assisted navigation and biomechanical modeling have made surgical simulation a new domain of research in the last decade. In this paper, we focus on assisting the surgeon to manage anterior cruciate ligament (ACL) reconstruction. During this operation, the ACL graft has to be placed in such a way that it is isometric during a flexion-extension and in traction when the leg is in extension. That is to say, two constraints: a geometrical one and a physical one. We present a CT-Free system that solves both these constraints in real-time and intra-operatively. The geometrical constraint is solved by Aesculap's OrthoPilot system while a deformable model is used to solve the physical one. With our combined solution, the surgeon will be able to know intra-operatively if the graft placement will lead to robust and effective reconstruction or otherwise.

Summary Computer-assisted navigation shall reliably guide the surgeon to a planned target position. Various medical image modalities are required for a safe diagnosis and intervention planning. For treatment forms like LITT, therapy simulation should be part of a planning scenario. In soft tissues, the intervention usually will render preoperative images inappropriate if tissue shifts occur. In these cases intraoperative images are necessary to show the current state, to update the preoperative data, and to register preoperative images to the current situation. The update is an iterative process triggered by situational changes during the ongoing intervention. This paper presents our concept of iterative multimodal navigation that has been implemented in the LOCALITE Navigator for interventional MR and ultrasound.

In this paper we describe a surgical navigation system named HipNav (Hip-Navigation) for THR and KneeNav (Knee-Navigation) for TKR with an emphasis on using these systems as a real time intraoperative measurement tool (these enabling technologies are the surgical toolbox of the future). This approach will permit the direct comparison of patient outcomes with measurable surgical techniques.

The value of intraoperative computer navigation during total knee arthroplasty has been debated for more than a decade. Despite substantial research, contradictory results and reservations about the cost and efficacy of the technology have contributed to the failure of computer navigation to become the accepted standard for establishing limb alignment during knee replacement surgery. In their paper, Zhang and colleagues report the results of a well-designed, prospective, randomized study that was conducted to compare the short-term clinical and radiographic results of total knee arthroplasty performed with computer navigation with the results of total knee arthroplasty performed with conventional mechanical instruments. The authors attempted to control for as many variables as possible by studying patients with bilateral knee arthritis who were undergoing simultaneous bilateral knee replacement. For each patient, both the order of the surgery and the knee that was assigned to the computer-navigation group were selected by randomization. During the follow-up period, the clinician, radiologist, and patient were blinded with regard to the type of procedure that had been performed on each knee. The outcomes recorded included overall limb alignment on full-length radiographs; various parameters of prosthetic positioning on both standard radiographs and …

Background Pedicle screw misplacement is relatively common, with reported rates ranging up to 42%. Although computer-assisted image guidance (CaIG) has been shown to improve accuracy in open spinal surgery, its use in minimally invasive procedures has not been as well evaluated. We present our technique and review the results from a cohort of patients who underwent minimally invasive lumbar pedicle screw placement utilizing the O-arm imaging unit in conjunction with the StealthStation Treon System. Methods A retrospective review of patients who underwent minimally invasive pedicle screw fixation with CaIG was performed. Eleven consecutive patients were identified and all were included. Nine patients underwent a single-level transforaminal lumbar interbody fusion. Two patients underwent multi-level fusion. Inaccurate pedicle screw placement was determined by postoperative computed tomography (CT) and graded as 0-2, 2-4, 4-6, or 6-8 mm. Results A total of 52 screws were placed. Forty screws were inserted in eight patients who had postoperative CT, and a misplacement rate of 7.5% was noted including one lateral and two medial breaches. All breaches were graded as 0-2 mm and were asymptomatic. In the remaining three patients, post-instrumentation O-arm imaging did not demonstrate pedicle screw misplacement. Conclusion Although this initial study evaluates a relatively small number of patients, minimally invasive pedicle screw fixation utilizing the O-arm and StealthStation for CaIG appears to be safe and accurate.

o. (group A) and patients with varus deformity＞20° (group B). T he P FC S igma implants were used in both groups. The mechanical axis and implant position were measured by 2 observers according to the reontgenographic evaluation system of the American Knee S ociety. Resul ts : There was no significant difference in α, β, δ angle and mechanical axis between group I and II. There was a significant difference in the γ angle between group I and II (p＜0.05). There was a significant difference in the α and β angle and mechanical axis between group IA and IB (p＜0.05). There was a significant difference in the α angle and mechanical axis between group IIA and IIB (p＜0.05). There was a positive correlation between the measured angle by the respective observers in all groups (p＜0.05). Concl u si o n: P atients with a preoperative varus deformity＞20

Purpose: This study assessed the accuracy of the alignment of the lower extremity and the position of the components in a total knee arthroplasty (TKA), which was performed using a computer-assisted navigation system. Materials and Methods: This study reviewed 40 TKA using a manual alignment system (group A) and 36 TKA using the Orthopilot ® 4.0 navigation system (group B). The radiographs taken 2 months after surgery were used to measure the femoro-tibial angle, the mechanical axis deviation, and the inclination of the femoral and tibial component. A value within the optimum±3° was defined as an ‘acceptable’ and a value over the optimum±3° was befined as an ‘outlier’. Results: The coronal inclination of the femoral component to the anatomical femoral axis showed outliers in 13 knees in group A and 1 knee in group B. The coronal inclination of the femoral component to the mechanical axis revealed 17 and 2 outliers in each group, respectively. The coronal inclination of the tibial component and sagittal inclination of femoral component showed no significant differences between two groups, but the sagittal inclination of tibial component showed 16 and no outlier in each group, respectively. Concerning the femoro-tibial angle, there were 9 outliers in group A and 2 outliers in group B. The mechanical axis deviation showed 9 and 2 outliers in groups A and B, respectively. Conclusion: The navigation system helped to produce more ‘acceptable’ and less ‘outlier’ results than the manual alignment system. The alignment of the lower extremity after a TKA can be achieved more accurately using the navigation system.

Objectives To introduce a computer-assisted navigation system and to evaluate its application in pediatric sinusonasal surgery. Methods A commercially available wireless passive marker system that allows the calibration and tracking of virtually any instrument was adapted to children and used during pediatric endoscopic sinusonasal surgery. Results The headset localizer that was initially used in computed tomographic scanning was not well accepted by children. Correlation of the preoperative computed tomographic scan to the actual patient was made possible by a laser device. Setup time was able to be decreased from an initial 20 minutes to 3 minutes. The average recording accuracy was 1.1 mm. The advantages of the system became apparent as experience increased in cases involving sinus polyposis, choanal atresia, nasopharyngeal fibroma removal, tumor biopsy, and minimally invasive maxillary, frontal, and sphenoidal surgery. Conclusions The computer-assisted navigation system was used first as a control system and then, as experience increased, as a true surgical guide. Indications for its use also increased. Pediatric intranasal surgery was performed using 2 complementary guides: an endoscopic view and a computed tomographic view of the instrument's position.

Background Palliative irreversible electroporation of pancreatic adenocarcinomas is rapidly gaining in interest since a large proportion of these patients cannot be radically resected. Methods This is a description of a minimally invasive approach to irreversible electroporation of pancreatic tumors using computer-assisted navigation, laparoscopy and laparoscopic ultrasound to correctly guide electrodes into the tissue. Results The procedure is presented. Conclusion Minimally invasive irreversible electroporation of pancreatic tumors through computer-assisted navigation of needles during laparoscopy is a feasible and accurate approach. Electronic supplementary material The online version of this article (doi:10.1007/s00464-016-5173-6) contains supplementary material, which is available to authorized users.

Summary Introduction The goal of this observational study is to measure the physiological laxity of a knee, supposedly normal in the coronal plane, at 0 and 90° of flexion with a navigation system that can be used during total knee replacement. Hypothesis The physiological laxity measured by this navigation system is different from the results already published using other measurement devices. Materials and methods Twenty patients consecutively operated on for an isolated anterior cruciate ligament injury were selected. Medial and lateral laxities at 0 and 90° of knee flexion were measured by the navigation system during cruciate replacement. Results The mean medial laxity in extension was 3.6 ± 1.2°. The mean lateral laxity in extension was 4.1 ± 1.9°. The mean medial laxity at 90° of flexion was 2.1 ± 1.2°. The mean lateral laxity at 90° of flexion was 3.7 ± 1.2°. The medial and lateral laxities in extension were not asymmetric. The medial and lateral laxities at 90° of flexion were asymmetric. Medial laxities in extension and at 90° of flexion were asymmetric. Lateral laxities in extension and at 90° of flexion were not asymmetric. Discussion The data collected in our study suggest, during total knee replacement, the following tolerable ligamentous balance: medial and lateral laxities in extension about 3°, medial laxity at 90° of flexion about 2°, and lateral laxity at 90° of flexion about 4°. Level of evidence Level IV. Prospective study.

Introduction The causes of failure of anterior cruciate ligament (ACL) reconstruction mainly involve incorrect tunnel positioning. There is no intraoperative tool allowing the surgeon to test graft biomechanics and to confirm that the new graft is in an optimal position. Hypothesis Control is improved with computer assisted navigation. Material and methods In this retrospective study, revision ACL reconstruction was performed with a new autologous graft in a continuous series of 52 failed ACL reconstructions. A computer assisted navigation system was used intraoperatively in all knees. Evaluation with this system confirmed the position of old and new tunnels as well as intraoperative laxity. Results Evaluation of tunnel position based on traditional radiological criteria found in the literature significantly underestimated graft biomechanics: 69% of the cases presented with unfavorable graft ansiometry (mean: 13 ± 2.2 mm) while the correct position of the tibial tunnel was identified in 64% of cases on radiography and the femoral tunnel in 48%. All new grafts were optimally positioned by the computer assisted navigation system with a mean isometery of 3.2 (±0.7) mm. Comparative pre- and postoperative evaluation of laxity showed a statistically significant improvement (P

As many as 175,000 anterior cruciate ligament (ACL) reconstructions are performed annually in the United States at a cost > $1 billion. Estimates of the rate of revision surgery are as high as 10%-20%, potentially resulting in as many as 35,000 revisions a year. In addition, errors that are not obvious at short-term or mid-term follow-up may have significant long-term effects in young patients. Studies have demonstrated that the majority of revisions are related to technical errors, primarily tunnel placement. Computer-aided navigation systems provide enhanced precision in tunnel placement and may reduce the rate of revision surgery. Computer-aided systems can provide valuable data on rotational and translational laxity of the knee.