Shape Matched Surgery

What is Shape-Matched Surgery?

Shape-matched surgery refers to shape-matched knee or hip replacement surgery in which the components used in knee/hip replacement surgery are specifically matched to the patient's unique knee/hip anatomy. This technique is often associated with patient-specific instrumentation (PSI) or patient-specific cutting guides.

Knee and hip replacement surgery involves replacing the worn-out bone and cartilage lining your knee/hip joint with new artificial joint parts (prostheses) made of metal, plastic, or ceramic.

In traditional knee/hip replacement surgery, surgeons typically use standard-sized implants and instruments. However, in shape-matched knee/hip surgery, advanced imaging techniques such as MRI or CT scans are used to create a personalised, 3D model of the patient's knee/hip joint. This allows for the creation of custom-made cutting guides or implants that match the unique anatomy of the patient's knee/hip.

The goal of shape-matched surgery is to enhance the precision and accuracy of the surgery, potentially improving the overall outcome and reducing complications. By tailoring the surgical approach to the individual patient, surgeons aim to achieve better alignment, stability, and function after knee/hip replacement.

Indications for Shape-Matched Surgery

Some of the common scenarios where shape-matched surgery may be considered include:

• Complex Anatomy: Patients with complex knee/hip anatomy, unusual shapes, or deformities may benefit from shape-matched surgery. This approach allows for a more personalised and precise fit of the implants.
• Revision Surgeries: In cases where a patient is undergoing a revision knee/hip surgery (a second or subsequent knee/hip replacement), the anatomy may be altered from the previous surgery. Shape-matched techniques can help address these changes.
• Alignment Corrections: Patients with specific alignment issues or deformities in the knee/hip may benefit from shape-matched surgery, as the personalised guides and implants can be designed to correct alignment more accurately.
• Customisation for Implants: Shape-matched surgery is often considered when a more customised fit for the knee/hip implant is desired. This is particularly relevant in patients with non-standard anatomy or those who may not be well-suited for off-the-shelf implants.
• Improved Precision: Surgeons may opt for shape-matched techniques to enhance the precision of the surgery, potentially reducing the risk of complications and improving overall outcomes.

Preparation for Shape-Matched Surgery

The preoperative preparation for shape-matched surgery is similar to traditional knee/hip replacement procedures. But contrary to traditional knee/hip replacement techniques, the shaped matched surgical approach utilises a series of CT scans or MRI to generate a 3D model of the patient’s knee or hip anatomy, which helps to design personalised cutting guides or instruments to match the patient's specific anatomy. These guides are created to assist the surgeon in making precise cuts during the surgery. Based on the preoperative planning and analysis, the surgeon selects implants that are best suited to the patient's anatomy.

Additional pre-surgery preparation may involve the following steps:

• A thorough history and physical examination
• Routine diagnostic tests such as blood work and urinalysis
• Informing your doctor about medications or supplements you are taking
• Informing about allergies to any medications, anaesthesia, or latex (which can be found in surgical gloves)
• Disclosing any recent illnesses or other medical conditions, which may impact the surgery
• Refraining from some medications such as blood thinners and supplements, if contraindicated for the procedure
• Refraining from solids or liquids at least 8 hours prior to surgery
• Arranging for someone to drive you home following surgery
• Signing an informed consent form after the pros and cons of the surgery have been explained

Procedure for Shape-Matched Surgery

Shape-matched surgery involves several steps to customise the surgery based on the patient's unique joint anatomy. In general, the procedure involves the following steps:

• The patient is positioned on the operating table, and anaesthesia is administered to ensure you are unconscious and pain-free during the surgery.
• A surgical incision is made to access the knee or hip joint.
• The surgeon carefully moves and prepares the soft tissues around the knee or hip to expose the joint.
• The personalised cutting guides or instruments are positioned on the bone surfaces based on the preoperative planning. These guides serve as templates for making precise cuts in the bone to accommodate the knee or hip implant.
• Using the customised guides, the surgeon makes the necessary bone cuts to prepare the joint for the implant.
• The chosen knee or hip implant components (such as the acetabular, femoral, tibial, and patellar components) are then carefully inserted and secured into the prepared bone surfaces.
• The surgeon closes the incision with sutures or staples, and the wound is dressed.

Postoperative Care and Recovery

In general, postoperative care instructions and recovery after shape-matched surgery may involve the following steps:

• You will be moved to the recovery area where the medical staff will closely monitor your vital signs to ensure stability.
• You may experience pain, swelling, and discomfort in the treated area. Pain and anti-inflammatory medications are provided as needed to address these.
• You are advised to keep your leg elevated above the heart level for a defined period while resting to prevent swelling and pain.
• You will be placed on assistive devices such as crutches for the first few weeks to facilitate movement with instructions on restricted weight-bearing.
• Instructions on surgical site care and bathing will be provided to keep the wound clean and dry.
• You are advised on activity modifications, including restrictions on heavy lifting, strenuous exercises or activities, and specific movements, to protect the healing joint.
• An individualised physical therapy regimen will be designed to help strengthen your joint muscles and optimise joint function.
• You should be able to resume your normal activities in a couple of months but with certain activity restrictions.

Risks and Complications

Shaped-matched surgery is a relatively safe procedure; however, as with any surgery, there are risks and complications that can occur, such as:

• Bleeding
• Infection
• Joint pain/stiffness
• Blood clots (deep vein thrombosis or pulmonary embolism)
• Allergic/anaesthetic reactions
• Nerve or blood vessel damage
• Implant malposition
• Delayed healing

Benefits

Compared to traditional surgery, shape-matched surgery offers several potential benefits such as:

• Precision and customisation
• Improved accuracy in bone cuts
• Reduced blood loss
• Faster recovery
• Minimal soft tissue trauma
• Improved alignment and stability
• Reduced wear and tear of implants
• Improved patient satisfaction