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Inertial Navigation Technology

The Navbit Sprint system uses an inertial navigation system and a novel method of registration of the patient which does not rely on anatomical landmarks.

Introduction

Navbit Sprint Inertial Navigation System

Computer navigation can be used in Total Hip Arthroplasty (THA) to improve the accuracy of the acetabular cup component orientation 1-5. The Navbit® Sprint system is a palm-sized navigation device which provides the surgeon with a real-time measure of the orientation of the acetabular cup. The Navbit Sprint is small and accurate through its novel navigation system and registration process.

The Navbit Sprint system uses an inertial navigation system and a novel method of registration of the patient which does not rely on anatomical landmarks.

Inertial navigation system

Navigation System

Many existing imageless systems use optical navigation 6, 7. In contrast, the Navbit sprint uses an inertial measurement system, including gyroscopes and accelerometers. The device provides the surgeon with real-time radiographic 8 inclination and anteversion angles of the acetabular cup, shown in Figure 1.

Figure 1: Navbit Sprint Device

Registration Method

Patient registration provides a reference frame for calculating the orientation of the acetabular component. Such a reference frame is necessary for an imageless navigation system. Most existing imageless hip navigation systems use registration methods that rely on the surgeon locating anatomical landmarks9-15. The difficulty of locating these landmarks contributes to inaccuracies in navigation 10. In contrast, the Navbit Sprint System uses the patient’s position on the table during registration (see Figure 2), which is relatively easy to achieve.

Figure 2: Patient is Aligned with the Table During Registration

Note: Lateral and supine patient position

Once the patient is correctly aligned. The functional reference system is defined as three reference axes. For the patient positioned supine these are the anteroposterior axis, longitudinal axis, and transverse axis. For the patient positioned laterally these are the transverse axis, longitudinal axis, and anteroposterior axis.

To establish the reference planes the device guides the surgeon in a sequence of tilting the operating table. This sequence enables the device to define a functional pelvic reference system (see Figure 3). The radiographic inclination and anteversion angles are then calculated relative to this coordinate system (see Figures 4a and 4b).

Figure 3: Functional Pelvic Reference System

Note: The sagittal plane, coronal plane, and transverse plane are established.

Figure 4a: Calculation of Angles of Acetabular Cup – Inclination

Note: From Harrison, Thomson, Cutts, Rowe, Riches 16. α is radiographic inclination. Radiographic inclination is the angle between the longitudinal axis and the acetabular axis when this is projected onto the coronal plane8.

 

Figure 4b: Calculation of Angles of Acetabular Cup – Anteversion

Note: θ is radiographic anteversion. Radiographic anteversion is the angle between the acetabular axis and the coronal plane8.

Innovative technology

Conclusion

The Navbit Sprint system uses a novel navigation system and a novel method of registration of the patient.

References

  1. Gandhi R, Marchie A, Farrokhyar F, Mahomed N. Computer navigation in total hip replacement: a meta-analysis. Int Orthop. 2009;33(3):593-597.

  2. Agarwal S, Eckhard L, Walter WL, et al. The Use of Computer Navigation in Total Hip Arthroplasty Is Associated with a Reduced Rate of Revision for Dislocation: A Study of 6,912 Navigated THA Procedures from the Australian Orthopaedic Association National Joint Replacement Registry. J Bone Joint Surg Am. 2021.

  3. Xu K, Li Y-m, Zhang H-f, Wang C-g, Xu Y-q, Li Z-j. Computer navigation in total hip arthroplasty: A meta-analysis of randomized controlled trials. Int J Surg. 2014;12(5):528-533.

  4. Li Y-L, Jia J, Wu Q, Ning G-Z, Wu Q-L, Feng S-Q. Evidence-based computer-navigated total hip arthroplasty: an updated analysis of randomized controlled trials. Eur J Orthop Surg Traumatol. 2014;24(4):531-538.

  5. Bohl DD, Nolte MT, Ong K, Lau E, Calkins TE, Della Valle CJ. Computer-Assisted Navigation Is Associated with Reductions in the Rates of Dislocation and Acetabular Component Revision Following Primary Total Hip Arthroplasty. J Bone Joint Surg Am. 2019;101(3):250-256.

  6. Paprosky WG, Muir JM. Intellijoint HIP(®): a 3D mini-optical navigation tool for improving intraoperative accuracy during total hip arthroplasty. Med Devices (Auckl). 2016;9:401-408.

  7. Elfring R, de la Fuente M, Radermacher K. Assessment of optical localizer accuracy for computer aided surgery systems. Comput Aided Surg. 2010;15(1-3):1-12.

  8. Murray DW. The definition and measurement of acetabular orientation. Journal of Bone & Joint Surgery. 1993;75(2):228-232.

  9. Gurgel HMCP, Croci ATP, Cabrita HABAP, Vicente JRNP, Leonhardt MC, Rodrigues JC. Acetabular Component Positioning in Total Hip Arthroplasty With and Without a Computer-Assisted System: A Prospective, Randomized and Controlled Study. J Arthroplasty. 2014;29(1):167-171.

  10. Davis ET, Schubert M, Wegner M, Haimerl M. A new method of registration in navigated hip arthroplasty without the need to register the anterior pelvic plane. J Arthroplasty. 2015;30(1):55-60.

  11. Lass R, Kubista B, Olischar B, Frantal S, Windhager R, Giurea A. Total Hip Arthroplasty Using Imageless Computer-Assisted Hip Navigation A Prospective Randomized Study. J Arthroplasty. 2014;29(4):786-791.

  12. Sendtner E, Schuster T, Wörner M, Kalteis T, Grifka J, Renkawitz T. Accuracy of acetabular cup placement in computer-assisted, minimally-invasive THR in a lateral decubitus position. Int Orthop. 2011;35(6):809-815.

  13. Wan Z, Malik A, Jaramaz B, Chao L, Dorr LD. Imaging and Navigation Measurement of Acetabular Component Position in THA. Clin Orthop Relat Res. 2009;467(1):32-42.

  14. Cross MB, Schwarzkopf R, Miller TT, Bogner EA, Muir JM, Vigdorchik JM. Improving registration accuracy during total hip arthroplasty: a cadaver study of a new, 3-D mini-optical navigation system. Hip Int. 2018;28(1):33-39.

  15. Feng JE, Anoushiravani AA, Eftekhary N, Wiznia D, Schwarzkopf R, Vigdorchik JM. Techniques for Optimizing Acetabular Component Positioning in Total Hip Arthroplasty: Defining a Patient-Specific Functional Safe Zone. JBJS Rev. 2019;7(2):e5.

  16. Harrison CL, Thomson AI, Cutts S, Rowe PJ, Riches PE. Research Synthesis of Recommended Acetabular Cup Orientations for Total Hip Arthroplasty. The Journal of Arthroplasty. 2014;29(2):377-382.

Further Reading

Inertial Navigation Technology

The Navbit Sprint system uses an inertial navigation system and a novel method of registration of the patient which does not rely on anatomical landmarks.

Read more

Allowing for Pelvic Tilt in Supine Total Hip Arthroplasty (THA)

Using an adjusted intraoperative target, an estimated 99.7% of patients will be within ±10° of both the inclination and anteversion targets.

Read more

Accuracy During Surgery

The Navbit Sprint is highly accurate in a surgical setting, quickly providing the surgeon with measurements they can trust.

Read more