The use of imageless navigation to quantify cutting error in total knee arthroplasty

Purpose Navigated total knee arthroplasty (TKA) improves implant alignment by providing feedback on resection parameters based on femoral and tibial cutting guide positions. However, saw blade thickness, deflection, and cutting guide motion may lead to final bone cuts differing from planned resections, potentially contributing to suboptimal component alignment. We used an imageless navigation device to intraoperatively quantify the magnitude of error between planned and actual resections, hypothesizing final bone cuts will differ from planned alignment. Materials and methods A retrospective study including 60 consecutive patients undergoing primary TKA using a novel imageless navigation device was conducted. Device measurements of resection parameters were obtained via attachment of optical trackers to femoral and tibial cutting guides prior to resection. Following resection, optical trackers were placed directly on the bone cut surface and measurements were recorded. Cutting guide and bone resection measurements of both femoral and tibial varus/valgus, femoral flexion, tibial slope angles, and both femoral and tibial medial and lateral resection depths were compared using a Student's t-test. Results Femoral cutting guide position differed from the actual cut by an average 0.6 ± 0.5° (p = 0.85) in the varus/valgus angle and 1.0 ± 1.0° (p = 0.003) in the flexion/extension angle. The difference between planned and actual cut measurements for medial and lateral femoral resection depth was 1.1 ± 1.1 mm (p = 0.32) and 1.2 ± 1.0 mm (p = 0.067), respectively. Planned cut measurements based on tibial guide position differed from the actual cut by an average of 0.9 ± 0.8° (p = 0.63) in the varus/valgus angle and 1.1 ± 1.0° (p = 0.95) in slope angle. Measurement of medial and lateral tibial resection depth differed by an average of 0.1 ± 1.8 mm (p = 0.78) and 0.2 ± 2.1 mm (p = 0.85), respectively. Conclusions Significant discrepancies between planned and actual femoral bone resection were demonstrated for flexion/extension angle, likely the result of cutting error. Our data highlights the importance of cut verification postresection to confirm planned resections are achieved, and suggests imageless navigation may be a source of feedback that would allow surgeons to intraoperatively adjust resections to achieve optimal implant alignment.

Appropriate determination of the surgical transepicondylar axis can be achieved following distal femur resection in navigation-assisted total knee arthroplasty

Background Many surgeons have determined the surgical transepicondylar axis (sTEA) after distal femur resection in total knee arthroplasty (TKA). However, in most navigation systems, the registration of the sTEA precedes the distal femur resection. This sequential difference can influence the accuracy of intraoperative determination for sTEA when considering the proximal location of the anatomical references for sTEA and the arthritic environment. We compared the accuracy and precision in determinations of the sTEA between before and after distal femur resection during navigation-assisted TKA. Methods Ninety TKAs with Attune posterior-stabilized prostheses were performed under imageless navigation. The sTEA was registered before distal femur resection, then reassessed and adjusted after distal resection. The femoral component was implanted finally according to the sTEA determined after distal femur resection. Computed tomography (CT) was performed postoperatively to analyze the true sTEA (the line connecting the tip of the lateral femoral epicondyle to the lowest point of the medial femoral epicondylar sulcus on axial CT images) and femoral component rotation (FCR) axis. The FCR angle after distal femur resection (FCRA-aR) was defined as the angle between the FCR axis and true sTEA on CT images. The FCR angle before distal resection (FCRA-bR) could be presumed to be the value of FCRA-aR minus the difference between the intraoperatively determined sTEAs before and after distal resection as indicated by the navigation system. It was considered that the FCRA-bR or FCRA-aR represented the differences between the sTEA determined before or after distal femur resection and the true sTEA, respectively. Results The FCRA-bR was −1.3 ± 2.4° and FCRA-aR was 0.3 ± 1.7° (p < 0.001). The range of FCRA-bR was from −6.6° to 4.1° and that of FCRA-aR was from −2.7° to 3.3°. The proportion of appropriate FCRA (≤ ±3°) was significantly higher after distal femur resection than that before resection (91.1% versus 70%; p < 0.001). Conclusions The FCR was more appropriate when the sTEA was determined after distal femur resection than before resection in navigation-assisted TKA. The reassessment and adjusted registration of sTEA after distal femur resection could improve the rotational alignment of the femoral component in navigation-assisted TKA. Level of evidence IV.

Intraoperative measurement of acetabular component position using imageless navigation during revision total hip arthroplasty

Background: Acetabular component malposition is a major cause of dislocation following total hip arthroplasty (THA). Intellijoint HIP is an imageless navigation tool that has been shown to provide accurate intraoperative measurement of cup position during primary THA without substantially increasing operative time. However, its accuracy in revision THA has not been evaluated. This study therefore aims to assess the accuracy of Intellijoint HIP in measuring cup inclination and anteversion in comparison with computed tomography (CT) during revision THA. Methods: Intellijoint HIP was used to measure the position of the preexisting cup in 53 consecutive patients undergoing revision THA between December 2018 and February 2020. Two authors blinded to the intraoperative navigation measurements also independently measured cup position using preoperative CT according to Murray’s radiographic definitions. Pearson correlation coefficients with 95% confidence intervals (CIs), paired t tests and Bland–Altman plots were used to assess agreement between navigation- and CT-measured cup position. Statistical analysis was performed using GraphPad Prism, with p values less than 0.05 indicating statistical significance. Results: There was excellent agreement between navigation and CT measurements for both cup inclination (r = 0.89, 95% CI 0.81–0.93) and anteversion (r = 0.93, 95% CI 0.88–0.96), with the mean absolute difference being 5.2º (standard deviation [SD] 4.0º) for inclination and 4.8º (SD 5.4º) for anteversion. The navigation measurement was within 10º of the radiographic measurement in 47 of 53 (88.7%) cases for inclination and 46 of 53 (86.8%) cases for anteversion. Conclusion: Imageless navigation demonstrated excellent correlation and agreement with CT measurements for both inclination and anteversion over a wide range of acetabular component positions.

Validity of intraoperative imageless navigation (Naviswiss) for component positioning accuracy in primary total hip arthroplasty: protocol for a prospective observational cohort study in a single-surgeon practice

IntroductionOptimal outcomes in total hip arthroplasty (THA) are dependent on appropriate placement of femoral and acetabular components, with technological advances providing a platform for guiding component placement to reduce the risk of malpositioned components during surgery. This study will validate the intraoperative data captured using a handheld imageless THA navigation system against postoperative measurements of acetabular inclination, acetabular version, leg length and femoral offset on CT radiographs.Methods and analysisThis is a prospective observational cohort study conducted within a single-centre, single-surgeon private practice. Data will be collected for 35 consecutive patients (>18 years) undergoing elective THA surgery, from the research registry established at the surgeon’s practice. The primary outcome is the agreement between intraoperative component positioning data captured by the navigation system compared with postoperative measurements using CT. A total of ten CT scans will be reassessed for interobserver and intraobserver reliability. The influence of patient and surgical factors on the accuracy of component position will also be examined with multivariable linear regression.Ethics and disseminationEthics approval for this study was provided through a certified ethics committee (Bellberry HREC approval number 2017-07-499). The results of this study will be disseminated through peer-reviewed journals and conference presentations.Trial RegistrationAustralian and New Zealand Clinical Trials Registry (ANZCTR) Trial ID: ACTRN12620000089932.

Periacetabular osteotomy using an imageless computer-assisted navigation system: a new surgical technique

Periacetabular osteotomy (PAO) is an effective surgical treatment for hip dysplasia. The goal of PAO is to reorient the acetabulum to improve joint stability, lessen contact stresses and slow the development of hip arthrosis. During PAO, the acetabulum is repositioned to adequately cover the femoral head. PAO preserves the weight-bearing posterior column of the pelvis, maintains the acetabular blood supply and retains the hip abductor musculature. The surgical technique needed to perform PAO is technically demanding, with correct repositioning of the acetabulum the most important—and challenging—aspect of the procedure. Imageless navigation has proven useful in other technically challenging surgeries, although its use in PAO has not yet been investigated. We have modified the standard technique for PAO to include the use of an imageless navigation system to confirm acetabular fragment position following osteotomy. Here, we describe the surgical technique and discuss the potential of this modified technique to improve patient-related outcomes.

Peak Active Hip Flexion Following Navigated Total Hip Arthroplasty.

The importance of accurate cup positioning during total hip arthroplasty (THA) to minimise post- operative complications has been well defined. However it remains unclear if following navigated THA there is a relationship between the active range of movement, the inclination and anteversion of the implant, and the theoretical range of movement as measured intra-operatively using imageless navigation. Fifteen male patients undergoing primary THA using the Orthopilot (Aesculap AG, Tuttlingen, Germany) imageless navigation system were recruited. The Orthopilot system flexion value was recorded. Three months post-THA patients underwent 3D biomechanical analysis (Vicon Motion Systems, Oxford, UK) during which patients performed a standing active hip flexion movement and a sitting task. Inclination and anteversion calculated according to Pradhan’s formula were taken from post-operative radiographs. There was no observed correlation with the theoretical hip flexion and the standing peak active or sitting peak hip flexion values in this series. However, Orthopilot flexion considers only the interaction of the implant components and not the soft tissues surrounding the hip joint which may limit clinical flexion. There does not appear to be any relationship between the inclination and anteversion angles and the range of movement observed post- operatively during a standing active hip flexion task and sitting task. It was observed that peak active hip flexion between the operated and non-operated limbs was not significantly different at three months, which indicates a good level of symmetry at this time point.