Total knee replacement

Question 1

What are the materials for the Biomedtrix total knee replacement system?

Answer 1

Femoral component: cobalt chromium.
Tibial component: UHMW polyethylene.

Semiconstrained system.

Question 2

Is the Biomedtrix total knee replacement system cemented or cementless?

Answer 2

The femoral component is press-fit, while the tibial component is cemented (although a cementless base plate is also available).

Question 3

What are the most common causes of failure following total knee replacement?

Answer 3

Collateral ligament disruption, infection, aseptic loosening.

Question 4

Name the displayed implant.

Answer 4

Question 5

What are indications for total knee replacement?

Answer 5

Severe OA secondary to cruciate ligament deficiency, osteochondrosis, intra-articular fractures, patellar luxation, chronic infection, collateral ligament injury, and distal femoral or proximal tibial deformities.

Question 6

What are contraindications for total knee replacement?

Answer 6

Infection (implant removal should be performed at least 6 weeks prior to surgery), metastatic neoplasia, concurrent systemic illness, neurologic disease, loss of an effective extensor mechanism.

Question 7

In instances of concurrent angular limb deformity, should correction occur at the time of total knee replacement or prior?

Answer 7

Ideally prior to give the soft tissues time to adjust. Concurrent repair may result in failure of the collateral ligament(s) and luxation.

Question 8

Describe the procedure for total knee replacement.

Answer 8

Question 9

What is the angulation of the tibial component of the total knee replacement in the frontal and sagittal planes?

Answer 9

Frontal: 90 degrees to the mechanical axis of the tibia.
Sagittal: 6 degree slope to mirror current CCLR recommendations.

The femoral component is placed to match the tibial component.

Question 10

What is the risk associated with excessive removal of bone at the time of total knee replacement?

Answer 10

Subsequent laxity of the collateral ligaments and increased risk of luxation (semiconstrained device). Removal of not enough bone is associated with potential collateral ligament rupture.

Question 11

What are the most significant intraoperative complications associated with total knee replacement?

Answer 11

Damage to the collateral ligaments or patellar ligament, femoral or tibial fracture, hemorrhage.

Question 12

What are some post-operative complications associated with total knee replacement?

Answer 12

1. Implant wear. Adhesive wear with delamination of the UHMW polyethylene component is the predominant form for wear in total knee replacements.
2. Aseptic loosening secondary to wear debris.
3. Chronic joint instability (errors of 3 degrees can alter load transfer).
4. Limited range of motion.
5. Infection (Staphylococcus is the most frequent isolate).

Question 13

What are options for treatment of total knee implant luxation secondary to collateral ligament instability?

Answer 13

Use of a custom made constrained or hinged device.

Question 14

What are the treatment options for an infected total knee replacement?

Answer 14

1. Chronic medical management.
2. Surgical debridement with retention of the implants.
3. Revision procedures to remove and replace the implants.
4. Arthrodesis.
5. Amputation.