Last updated on May 13 2025
Description
Hallux Valgus (HV) is a condition characterized by a deformity at the base of the big toe. In certain mild instances of bunion formation, surgical intervention may be limited to the removal of the bony prominence associated with the bunion.
To determine the appropriate surgical approach, it is essential to assess whether the metatarsal bone requires cutting and realignment. This decision is based on measuring the angle between the first and second metatarsals. A normal angle is typically around 9° to 10°. If the measured angle is 13° or greater, it is likely that the metatarsal will need to be cut and realigned to correct the deformity effectively.
Requirements
This procedure can be performed using a computed tomography (CT) scan, which provides a detailed 3D model of the foot anatomy. Additionally, a conventional radiograph (CR) may be used, offering a clear 2D representation of the metatarsal alignment.
Measurements
The following measurements are obtained during the procedure:
2D
- Hallux Valgus Angle (HVA): This angle represents the relationship between the longitudinal axes of the first metatarsal bone and the first proximal phalanx, providing crucial information about the alignment of the big toe.
- Intermetatarsal Angle (IMA): This angle is defined as the measure between the longitudinal axes of the first and second metatarsals, providing important insights into the alignment and spacing of the bones in the foot.
- Distal Metatarsal Articular Angle (DMAA): This angle is formed by the tangent line at the distal articular surface of the first metatarsal and the line that is perpendicular to the longitudinal axis of the same metatarsal.
- Proximal Metatarsal Articular Angle (PMAA): The angle formed by the line tangent to the proximal articular surface of the first metatarsal and the line that is perpendicular to the longitudinal axis of the first metatarsal;
- Distal Articular Set Angle (DASA): The angle formed by the line that is perpendicular to the proximal articular surface and the longitudinal bisection of the hallux's proximal phalanx.
- Frontal Plane Angle (FPA)
3D
- Hallux Valgus Angle (HVA): This angle represents the relationship between the longitudinal axes of the first metatarsal bone and the first proximal phalanx, providing crucial information about the alignment of the big toe.
- Intermetatarsal Angle (IMA): This angle is defined as the measure between the longitudinal axes of the first and second metatarsals, providing important insights into the alignment and spacing of the bones in the foot.
- Foot width (FW): The measurement of foot width is defined as the distance from the medial edge of the first metatarsal head to the lateral edge of the fifth metatarsal head.
- Space Between Metatarsal Heads (Metatarsal distances): The measurement of the gap between the outer edge of the first metatarsal and the inner surface of the second metatarsal.
- Sesamoid Complex Angle (SCA): The angle measured from the midpoint of the sesamoid complex line to the reference point on the floor.
- Distal Metatarsal Articular Angle (DMAA): This angle is formed by the tangent line at the distal articular surface of the first metatarsal and the line that is perpendicular to the longitudinal axis of the same metatarsal.
- Proximal Metatarsal Articular Angle (PMAA): The angle formed by the line tangent to the proximal articular surface of the first metatarsal and the line that is perpendicular to the longitudinal axis of the first metatarsal;
- Distal Articular Set Angle (DASA): The angle formed by the line that is perpendicular to the proximal articular surface and the longitudinal bisection of the hallux's proximal phalanx.
- Frontal Plane Angle (FPA).
- Space Between Metatarsal Heads (Min. Possible Gap): The measurement representing the gap between the outer edge of the first metatarsal and the inner surface of the second metatarsal.
How to perform
Pre-op stage
- Validate landmarks and consult measurements
Upon creating the case and uploading the image, the system will automatically place all relevant landmarks, allowing you to view the pre-operative values of each measurement.
If necessary, you can refine the position of these landmarks. Simply click on "Edit landmarks," make the required adjustments, and then save your changes by selecting "Save." The measurements will be updated accordingly, enabling you to continue to the next step by clicking “Approve.”
Note: To reposition the landmarks, simply hover your cursor over the desired landmark and use the left mouse button to adjust each handle to the most appropriate location.
Plan stage
- Deformity correction
PeekMed web features adjustable sliders that allow for precise modifications to the frontal plane rotation correction and intermetatarsal angle correction during HVL procedure. These adjustments play a crucial role in customizing the patient-matched VAC guide, ensuring optimal alignment and correction of the deformity.
- Template selection and positioning (CT only)
Upon the approval of the procedure, you will proceed to the templating stage. Here, you can select the manufacturer of your choice. If only one manufacturer is available, it will be automatically selected for you.
During the template configuration phase, you have the flexibility to adjust the properties of the selected template(s) and reposition them as needed.
To finalize the plan, it is essential to click on "Approve plan" and confirm the action in the dialog box that appears.
Export stage
The final stage of the planning process involves the Export step. At this point, you can download a comprehensive PDF report that encapsulates all the planning information, ensuring you have a thorough record of the procedures and measurements taken.
