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

Accuracy analysis of CAS Stryker ADAPT® system for femoral trochanteric fracture using a fluoroscopic navigation system

Open access Accuracy analysis of computer-assisted surgery for femoral trochanteric fracture using a fluoroscopic navigation system: Stryker ADAPT® system, by Takai et al. Injury (2018).


ADAPT is a fluoroscopic computer-assisted surgery system which intraoperatively shows the distance from the tip of the screw to the surface of the femoral head, tip-to-head-surface distance (TSD), and the tip-apex distance (TAD) advocated by Baumgaertner et al. The study evaluated the accuracy of ADAPT.

Patients and Methods
A total of 55 patients operated with ADAPT between August 2016 and March 2017 were included as subjects. TSD and TAD were measured postoperatively using computed tomography (CT) and X-rays. The intraclass correlation coefficient (ICC) was checked in advance. The error was defined as the difference between postoperative and intraoperative measurement values of ADAPT. Summary statistics, root mean square errors (RMSEs), and correlations were evaluated.

ICC was 0.94 [95% CI: 0.90–0.96] in TSD and 0.99 [95% CI: 0.98–0.99] in TAD. The error was −0.35 mm (−1.83 mm to 1.12 mm) in TSD and +0.63 mm (−5.65 mm to 4.59 mm) in TAD. RMSE was 0.63 mm in TSD and 1.53 mm in TAD. Pearson’s correlation coefficient was 0.79 [95% CI: 0.66–0.87] in TSD and 0.83 [95% CI: 0.72–0.89] in TAD. There were no adverse events with ADAPT use.

ADAPT is highly accurate and useful in guiding surgeons in properly positioning the screws.

Virtual surgery simulation versus traditional approaches in training of residents in cervical pedicle screw placement


Virtual surgery simulation versus traditional approaches in training of residents in cervical pedicle screw placement, by Hou et al. Arch Orthop Trauma Surg (2018).


The cervical screw placement is one of the most difficult procedures in spine surgery, which often needs a long period of repeated practices and could cause screw placement-related complications. We performed this cadaver study to investigate the effectiveness of virtual surgical training system (VSTS) on cervical pedicle screw instrumentation for residents.

Materials and methods
A total of ten novice residents were randomly assigned to two groups: the simulation training (ST) group (n = 5) and control group (n = 5). The ST group received a surgical training of cervical pedicle screw placement on VSTS and the control group was given an introductory teaching session before cadaver test. Ten fresh adult spine specimens including 6 males and 4 females were collected, and were randomly allocated to the two groups. The bilateral C3–C6 pedicle screw instrumentation was performed in the specimens of the two groups, respectively. After instrumentation, screw positions of the two groups were evaluated by image examinations.

There was significantly statistical difference in screw penetration rates between the ST (10%) and control group (62.5%, P < 0.05). The acceptable rates of screws were 100 and 50% in the ST and control groups with significant difference between each other (P < 0.05). In addition, the average screw penetration distance in the ST group (1.12 ± 0.47 mm) was significantly lower than the control group (2.08 ± 0.39 mm, P < 0.05). Conclusions This study demonstrated that the VSTS as an advanced training tool exhibited promising effects on improving performance of novice residents in cervical pedicle screw placement compared with the traditional teaching methods.

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

Treatment of sagittal fracture of the zygomatic arch root assisted by surgical navigation technology

Published ahead of print: Treatment of Sagittal Fracture of the Zygomatic Arch Root Assisted by Surgical Navigation Technology, by Dai et al. Journal of Craniofacial Surgery (2018).


Sagittal fracture at the temporal root of the zygomatic arch often occurs as a part of zygomaticomaxillary fractures. The authors described the application of computer-assisted navigation in the lag screw insertion for the fixation of sagittal fracture at the temporal root of zygomatic arch. Using the presurgical planning of the computer-assisted navigation system, the trajectory of lag screw insertion was designed, and the insertion depth was calculated. In the presurgical planning, the trajectory of screw insertion was placed with an anterior inclination of 10° to 15° (mean: 12.24°), and the screw insertion depth was 9.0 to 12.0 mm (mean: 10.65 mm). In the operation, the screw insertion in the fixation of the sagittal fracture was performed under the guidance of navigation system according to the presurgical planning. The postoperative CT scan showed exact reduction and fixation of the sagittal fracture in all cases. Computer-assisted navigation is a useful tool for the lag screw insertion in the precise fixation of sagittal fracture at the temporal root of the zygomatic arch in complex zygomaticomaxillary fractures.

(A) In the presurgical planning, the entry point (red point) and trajectory of screw insertion (red line) were designed in the mirrored zygomatic arch root, and the calculated screw insertion depth (yellow line) was 10.1mm in this case. (B) Registered surgical motor used for screw hole drilling. (C) The sagittal fractures at the zygomatic arch root. (D) Screw hole drilling according to presurgical planning under computer-assisted navigation, and the long axis of drill (yellow line) coincided with the designed trajectory (red line) in the axial, sagittal, and coronal planes. (E) Screw hole drilling performed with guidance of the computer-assisted navigation system.