Influence of the quality of intraoperative fluoroscopic images on the spatial positioning accuracy of a CAOS system

Influence of the quality of intraoperative fluoroscopic images on the spatial positioning accuracy of a CAOS system, by Wang et al. MRCAS (2018) e1898.


Spatial positioning accuracy is a key issue in a computer-assisted orthopaedic surgery (CAOS) system. Since intraoperative fluoroscopic images are one of the most important input data to the CAOS system, the quality of these images should have a significant influence on the accuracy of the CAOS system. But the regularities and mechanism of the influence of the quality of intraoperative images on the accuracy of a CAOS system have yet to be studied.Two typical spatial positioning methods – a C-arm calibration-based method and a bi-planar positioning method – are used to study the influence of different image quality parameters, such as resolution, distortion, contrast and signal-to-noise ratio, on positioning accuracy. The error propagation rules of image error in different spatial positioning methods are analyzed by the Monte Carlo method.Correlation analysis showed that resolution and distortion had a significant influence on spatial positioning accuracy. In addition the C-arm calibration-based method was more sensitive to image distortion, while the bi-planar positioning method was more susceptible to image resolution. The image contrast and signal-to-noise ratio have no significant influence on the spatial positioning accuracy. The result of Monte Carlo analysis proved that generally the bi-planar positioning method was more sensitive to image quality than the C-arm calibration-based method.The quality of intraoperative fluoroscopic images is a key issue in the spatial positioning accuracy of a CAOS system. Although the 2 typical positioning methods have very similar mathematical principles, they showed different sensitivities to different image quality parameters. The result of this research may help to create a realistic standard for intraoperative fluoroscopic images for CAOS systems.

Computer-assisted surgery prevents complications during peri-acetabular osteotomy


Computer-assisted surgery prevents complications during peri-acetabular osteotomy, Hayashi, S., Hashimoto, S., Matsumoto, T. et al. International Orthopaedics (SICOT) (2018).


The aim of study is to evaluate the accuracy of a navigation system during curved peri-acetabular osteotomy (CPO).

Forty-seven patients (53 hips) with hip dysplasia were enrolled and underwent CPO with or without navigation during surgery. Clinical and radiographical evaluations were performed and compared between the navigation group and non-navigation group, post-operatively.

The clinical outcomes were not significantly different between the navigation and non-navigation groups. Furthermore, post-operative reorientation of the acetabular fragment was similar between the navigation and non-navigation groups. However, the discrepancy between the pre-operative planning line and post-operative osteotomy line was significantly improved in the navigation group compared with that in the non-navigation group (p < 0.05). Further, the complication rate was significantly improved in the navigation group (p < 0.001). Conclusion The accuracy of the osteotomy’s position was significantly improved by using the navigation. Therefore, the use of navigation during peri-acetabular osteotomy can avoid complications.

The measurement of the distance between the 100-mm radius sphere line that was determined during pre-operative planning and the post-operative iliac bone surface (the error distance) on the a coronal and b axial planes. a The error distance outside the pelvis on the coronal plane (50–45.5 mm= 4.5 mm). b The error of the distance inside the pelvis on the axial plane (57.8–50 mm= 7.8 mm)

Total knee arthroplasties from the origin to navigation: history, rationale, indications

Review article Total knee arthroplasties from the origin to navigation: history, rationale, indications, Saragaglia, Rubens-Duval, Gaillot, et al. International Orthopaedics (SICOT) (2018).


Since the early 1970s, total knee arthroplasties have undergone many changes in both their design and their surgical instrumentation. It soon became apparent that to improve prosthesis durability, it was essential to have instruments which allowed them to be fitted reliably and consistently. Despite increasingly sophisticated surgical techniques, preoperative objectives were only met in 75% of cases, which led to the development, in the early 1990s, in Grenoble (France), of computer-assisted orthopaedic surgery for knee prosthesis implantation. In the early 2000s, many navigation systems emerged, some including pre-operative imagery (“CT-based”), others using intra-operative imagery (“fluoroscopy-based”), and yet others with no imagery at all (“imageless”), which soon became the navigation “gold standard”. They use an optoelectronic tracker, markers which are fixed solidly to the bones and instruments, and a navigation workstation (computer), with a control system (e.g. pedal). Despite numerous studies demonstrating the benefit of computer navigation in meeting preoperative objectives, such systems have not yet achieved the success they warrant, for various reasons we will be covering in this article. If the latest navigation systems prove to be as effective as the older systems, they should give this type of technology a well-deserved boost.

Distal femoral cutting guide, fitted with marker

Guided pelvic resections in tumor surgery


Guided Pelvic Resections in Tumor Surgery, Alexander, John, H.; Mayerson, Joel, L.; Scharschmidt, Thomas, J. Techniques in Orthopaedics (Publish Ahead of Print)


Primary bone sarcoma of the pelvis is one of the more challenging pathologies treated by orthopedic oncologists. In particular, their anatomic complexity contributes to delays in diagnosis and high rates of positive margins with associated high rates of local recurrence, all contributing to poor outcomes in this patient population. Computer-assisted surgery in the form of navigation and patient-specific instrumentation has shown promise in other fields of orthopedics. Intuitively, in an effort to improve tumor resections and improve oncologic outcomes, surgeons have been working to apply these advances to orthopedic oncology. Early studies have demonstrated benefits from guided pelvic resections, with studies demonstrating improved resection accuracy, fewer positive margins and decreased rates of local recurrence. Although these techniques are promising and will likely become an essential tool for orthopedic oncologist, surgeons must understand the limitations and costs associated with each technology before blind adoption.

The preoperative computed tomography and magnetic resonance imaging were utilized to create a virtual resection plane and representative 3-dimensional model (3D Systems, Rock Hills, SC). A, Preoperative virtual 3-dimensional model of the sacral-based chondrosarcoma with the associated resection planes and planned postresection defect. B, Virtual representation of 3D-printed resection guides and their intraoperative placement. C, Stereolithographic 3D-printed pelvic model (3D Systems, Rock Hills, SC) made from a photopolymer resin with patient-specific sacral mass, vascular anatomy, and resection planes.

Mid-term Survivorship and patient satisfaction of robotic-arm assisted medial unicompartmental knee arthroplasty

Mid-term Survivorship and Patient Satisfaction of Robotic-Arm Assisted Medial Unicompartmental Knee Arthroplasty: A Multicenter Study by Kleeblad et al., Arthroplasty (2018), in press, accepted manuscript.

Studies have showed improved accuracy of lower leg alignment, precise component position, and soft-tissue balance with robotic-assisted unicompartmental knee arthroplasty (UKA). No studies, however, have assessed the effect on mid-term survivorship. Therefore, the purpose of this prospective multicenter study was to determine mid-tem survivorship, modes of failure, and satisfaction of robotic-assisted medial UKA.

473 consecutive patients (528 knees) underwent robotic-arm assisted medial UKA surgery at four separate institutions between March 2009 and December 2011. All patients received a fixed-bearing metal-backed onlay tibial component. Each patient was contacted at minimum five-year follow-up and asked a series of questions to determine survival and satisfaction. Kaplan-Meier method was used to determine survivorship.

Data was collected for 384 patients (432 knees) with mean follow-up of 5.7 years (5.0 – 7.7). The follow-up rate was 81.2%. In total, 13 revisions were performed, of which 11 knees were converted to TKA and in two cases one UKA component was revised, resulting in 97% survivorship. The mean time to revision was 2.27 years. The most common failure mode was aseptic loosening (7/13). Fourteen reoperations were reported. Of all unrevised patients, 91% was either very satisfied or satisfied with their knee function.

Robotic-arm assisted medial UKA showed high survivorship and satisfaction at mid-term follow-up in this prospective multicenter study. However, in spite of the robotic technique, early fixation failure remains the primary cause for revision with cemented implants. Comparative studies are necessary to confirm these findings and compare to conventional implanted UKA and TKA.

New system of computer-assisted navigation leading to reduction in operating time in uncemented total hip replacement

A new system of computer-assisted navigation leading to reduction in operating time in uncemented total hip replacement in a matched population by Chaudhry, Ismail, and Davis, European Journal of Orthopaedic Surgery & Traumatology (2018).


Computer-assisted navigation techniques are used to optimise component placement and alignment in total hip replacement. It has developed in the last 10 years but despite its advantages only 0.3% of all total hip replacements in England and Wales are done using computer navigation. One of the reasons for this is that computer-assisted technology increases operative time. A new method of pelvic registration has been developed without the need to register the anterior pelvic plane (BrainLab hip 6.0) which has shown to improve the accuracy of THR. The purpose of this study was to find out if the new method reduces the operating time. This was a retrospective analysis of comparing operating time in computer navigated primary uncemented total hip replacement using two methods of registration. Group 1 included 128 cases that were performed using BrainLab versions 2.1-5.1. This version relied on the acquisition of the anterior pelvic plane for registration. Group 2 included 128 cases that were performed using the newest navigation software, BrainLab hip 6.0 (registration possible with the patient in the lateral decubitus position). The operating time was 65.79 (40–98) minutes using the old method of registration and was 50.87 (33–74) minutes using the new method of registration. This difference was statistically significant. The body mass index (BMI) was comparable in both groups. The study supports the use of new method of registration in improving the operating time in computer navigated primary uncemented total hip replacements.

Current role of computer navigation in total knee arthroplasty (review)


Current Role of Computer Navigation in Total Knee Arthroplasty, by Christopher W. Jones and Seth A. Jerabek, AAHKS Symposium (Accepted manuscript, in press).


Computer-assisted surgical (CAS) navigation has been developed with the aim of improving the accuracy and precision of total knee arthroplasty (TKA) component positioning and therefore overall limb alignment. The historical goal of knee arthroplasty has been to restore the mechanical alignment of the lower limb by aligning the femoral and tibial components perpendicular to the mechanical axis of the femur and tibia. Despite over four decades of TKA component development and nearly two decades of interest in CAS, the fundamental question remains; does the alignment goal and/or the method of achieving that goal affect the outcome of the TKA in terms of patient reported outcome measures and/or overall survivorship? The quest for reliable and reproducible achievement of the intra-operative alignment goal has been the primary motivator for the introduction, development and refinement of CAS navigation. Numerous proprietary systems now exist and rapid technological advancements in computer processing power are stimulating further development of robotic surgical systems. Three categories of CAS can be defined; image-based large console navigation; imageless large-console navigation and more recently, accelerometer based hand-held navigation systems have been developed.

A review of the current literature demonstrates that there are enough well-designed studies to conclude that both large-console CAS and handheld navigation systems improve the accuracy and precision of component alignment in TKA. However, missing from the evidence base, other than the subgroup analysis provided by the AOANJRR, are any conclusive demonstrations of a clinical superiority in terms of improved patient reported outcome measures and/or decreased cumulative revision rates in the long term. Few authors would argue that accuracy of alignment is a goal to ignore, therefore in the absence of clinical evidence, many of the arguments against the use of large console CAS navigation centre on the prohibitive cost of the systems. The utilization of low-cost, handheld CAS navigation systems may therefore bridge this important gap and over time, further clinical evidence may emerge