NaviFast 6D for Limb Length Measurement During Total Hip Arthroplasty

This was a multicenter, controlled, open-label, non-randomized clinical investigation of the NaviFast 6D orthopedic miniature measuring arm in patients undergoing primary total hip arthroplasty.

NaviFast 6D is an active, invasive surgical medical device with a measuring function. The device consists of pelvic and femoral fixation elements, an articulated measuring arm with motion sensors, and a microprocessor unit with a display. It is intended for professional use by orthopedic surgeons during total hip arthroplasty to provide intraoperative information on changes in lower limb length and hip offset relative to the pre-implantation state.

During the procedure, fixation elements were attached to the pelvis and femur using cannulated screws. The measuring arm connected the two fixation elements and recorded relative displacement in six degrees of freedom. A baseline measurement was taken before implantation. After preparation of the acetabulum and femur and placement of trial components, the measuring arm was used again to assess the change in limb length and offset. The surgeon could then consider these measurements before final implantation.

The clinical investigation was conducted in two phases. Phase I focused on verification of device functionality, safety, usability, optimization of the measurement procedure, and comparison of NaviFast 6D measurements with reference radiographic measurements. During Phase I, surgical decisions were based on standard clinical assessment rather than on the device measurements. Phase II evaluated use of the final device configuration in clinical practice, with surgeons allowed to use NaviFast 6D measurements when selecting implant components, unless clinical assessment contradicted the measurement.

The primary objective of Phase I was to determine the accuracy of NaviFast 6D measurements of limb length change and hip offset compared with radiographic reference measurements. The primary objective of Phase II was to compare postoperative leg length discrepancy in patients treated with NaviFast 6D with a control group treated using conventional clinical assessment only.

Secondary objectives included assessment of the accuracy of the radiographic reference measurement method using the LLDcalc.com software, estimation of the additional operative time associated with use of NaviFast 6D, and identification and classification of adverse events or device deficiencies associated with use of the measuring arm.

The study population consisted of adult patients undergoing primary total hip arthroplasty. Patients were enrolled at participating clinical centers in Poland. The overall study period covered recruitment, surgical procedures, and postoperative observation from May 9, 2023 to August 30, 2024.

Inclusion criteria

• Patients scheduled for primary total hip arthroplasty.
• Male or female patients.
• Age 20 to 85 years.
• No previous surgical procedures in the affected hip joint.
• Ability and willingness to provide informed consent for participation in the clinical investigation.

Exclusion criteria

• Lack of informed consent to participate in the clinical investigation.
• Pregnancy.
• Femoral neck fracture.
• Pertrochanteric femoral fracture.
• Pseudarthrosis of the femoral neck.
• Traumatic or post-traumatic changes of the proximal femur or acetabular region.
• Bone neoplasm.
• Bone infection.
• Advanced osteoporosis.