How robotic joint replacement works

In brief

• There is no universal robotic workflow: platforms differ in input data and tool control.
• The shared logic covers an anatomical model, plan, registration, joint assessment, guidance, bone preparation, placement and verification.
• The surgeon approves and may modify the plan; the device does not decide whether surgery is indicated.
• Accurate execution of a plan does not guarantee an individual clinical outcome.

1. Acquiring anatomical data

CT-based systems begin with computed tomography used to create a three-dimensional model. Imageless systems collect points and surfaces in theatre. Some platforms offer an image-based process using compatible radiographs. These labels describe the source of the model, not the degree of surgeon involvement.

2. Initial planning

The model supports identification of landmarks, proposed component size and position, bone preparation and alignment parameters. A CT-based workflow can provide a draft plan before surgery. An imageless plan emerges after intraoperative data collection. In either case, it is a working plan rather than an automated prescription.

3. Patient registration

The digital coordinates must be linked to the physical patient. The surgeon identifies landmarks or maps a surface, while optical tracking records bone position. For CT-based systems, registration matches the patient to the preoperative model; in an imageless system, it contributes to creating the model itself.

This stage is fundamental: digital precision is meaningful only if the physical-to-digital relationship is sound. The team checks registration quality and tracker stability.

4. Intraoperative assessment

The surgeon assesses limb position, range of motion and soft-tissue balance. Some systems display medial and lateral gaps at different joint positions. These measurements help show the consequences of a proposed change, but they do not select the strategy independently.

5. Approving or adapting the plan

The surgeon considers the digital values alongside anatomy, soft tissues, implant constraints and the goals of the procedure. Component position and resection parameters may be changed within the configuration’s capabilities. Responsibility for the accepted plan remains human.

6. Robotically guided bone preparation

Platform differences are most visible here. MAKO constrains a surgeon-directed tool within a haptic zone. CORI modulates the cutting action of a handheld burr near a software boundary. ROSA Knee positions a cut guide through which the surgeon operates a saw. VELYS constrains the saw plane. CUVIS can perform automated arm resection under surgeon control.

Automated motion is not autonomous judgement. A system follows an approved plan and requires setup, initiation, supervision and the ability to stop or adapt the process.

7. Component placement

After bone preparation, the surgeon performs trial assessment, confirms a compatible implant configuration and places the components. Robotic assistance at this stage varies by platform and procedure. Total Knee, Partial Knee and Hip functions cannot be treated as interchangeable without specific documentation.

8. Final verification

The team reassesses component position, stability, balance and available navigation measurements. Digital values supplement rather than replace clinical assessment. Postoperative care and rehabilitation remain important determinants of outcome.

Why systems differ

Platforms vary in CT requirements, model timing, registration, instrument design, software boundaries, supported joints and implant compatibility. Even applications within one product family can have distinct indications and workflows. The accurate question is therefore “how does this configuration work for this procedure?”

Does the robot operate by itself?

No. Automation varies, but clinical decisions and control remain with the surgical team.

Does imageless mean no imaging or visual data?

No. It means the workflow does not require a preoperative CT model; anatomy is captured intraoperatively.

Does closer agreement with the plan guarantee a better outcome?

No. It is a technical endpoint. Clinical benefit requires appropriately designed outcome research.

This material provides general information about the technology. It does not determine whether surgery is indicated or recommend a particular robotic system. Treatment options and methods depend on the diagnosis, anatomy, overall health, technology availability, and assessment by the surgical team. A robotic system is a surgeon-controlled tool; its technical capabilities alone do not guarantee a clinical outcome.