Joint Replacement Surgery

Total Hip Replacement

Total hip replacement (THR) is a commonly performed surgical procedure for a damaged hip joint. It is one of the most successful surgical procedures in all medical fields in terms of improving quality of life. 

Causes of hip damage that might require total hip replacement include conditions such as arthritis, avascular necrosis, and congenital hip conditions. It is also an excellent treatment option for certain hip fractures.

Implants vary in terms of the type of metal, the bearing surfaces (moving parts), and the mechanism of fixation to bone. The most suitable implant will vary from one patient to the next, depending on factors such as joint pathology, bone density, and dislocation risk.

In most cases a metal socket and a metal stem (thigh bone component) is used. The bearing surface usually consists of a polyethylene (plastic) liner that fits in the socket and a ceramic or metal ball that fits on the stem.

In some cases, particularly for hip fractures, bone cement is used for fixation of implants to bone. When cementless implants are used, a very tight initial fit of the implant in bone allows for bone to heal onto the implant. This process is called osteo-integration and ensures a physiological bond between bone and implant.  

There are various different surgical approaches that can be used for total hip replacement. Dr. Reid prefers the posterior approach. In the majority of hip replacements, the less invasive piriformis-sparing posterior approach is used. In revision and other complex cases, Dr. Reid utilises a more extensile posterior approach.  

Total Knee Replacement and Partial Knee Replacement

The majority of knee replacements are performed for osteoarthritis (OA). Primary osteoarthritis is a degenerative joint condition with no underlying cause. Secondary OA occurs when there is an underlying cause such as trauma, infection, or inflammatory arthritis.

Damaged cartilage and underlying bone is removed during the procedure and replaced with prosthetic implants.

Most knee replacements consist of 3 components: A metal femoral (thigh bone) component, a metal tibial (shin bone) component, and a polyethylene (plastic) insert. In some cases, a polyethylene component is also used to resurface the patella (knee cap).

Total Knee Replacement (TKR)

In most cases of severe knee OA, there is damage to the cartilage in each of the three compartments of the knee. A TKR is a resurfacing of the entire knee joint surface of the femur (thigh bone) and tibia (shin bone). The patella (knee cap) is often left un-resurfaced.

Partial Knee Replacement 

A medial uni-compartmental knee replacement (UKR), a lateral UKR, or a patellofemoral replacement can be considered in cases where there is severe arthritis of one compartment of the knee with relative preservation of the rest of the knee. The advantage of partial knee replacement is that intact, well-functioning cartilage and cruciate ligaments can be retained, while replacing damaged cartilage causing pain and functional deficit. 

Robotics in joint replacement surgery – click here for more information.

Surgical procedures other than joint replacement

Below is a discussion of non-joint replacement surgical options for the hip and knee, specifically in cases of arthritis. 

Arthroscopy

Arthroscopy is often called “key-hole surgery” because only small incisions are required to place a lens and other endoscopic instruments in a joint. Arthroscopy allows the surgeon to assess the condition of cartilage, ligaments and other relevant structures such as the menisci or labrum. These structures can also be assessed accurately on MRI scan and arthroscopy is no longer performed purely as a diagnostic procedure.

Damaged ligaments, menisci or labrum can be repaired or reconstructed in certain cases. Loose bodies or fragments of meniscus or cartilage can be removed.

Ligament repair or reconstruction

In cases of acute knee ligament injury, surgical repair of affected ligaments might be required. In some cases, ligament repair is not possible or is not likely to succeed and ligament reconstruction might be required.

Cases of instability in combination with arthritis might need special consideration. Management usually depends on the severity of arthritis. If the arthritis is severe enough to warrant a joint replacement, the procedure itself might address the instability at the same time. In rare cases of severe arthritis and severe instability, ligament reconstruction could be combined with joint replacement or more constrained implants might be required to address both problems. 

Osteochondral grafting

In cases of focal loss of cartilage in weight-bearing areas it is possible to harvest cartilage (and the underlying bone) from non- weight bearing regions and to transplant the graft into the damaged region. This option can be considered in cases of cartilage loss due to injury. It is not effective for loss of cartilage due to arthritis.

Micro fracture

A less invasive option than osteochondral grafting for focal loss of cartilage is micro fracture. Small holes are drilled into the exposed bone in an area of full thickness cartilage loss. This triggers the healing process and a scar of fibrocartilage is formed. Micro fracture is only effective if there is good cartilage articulating with the affected side and it is not effective at all if there is bone-on-bone loss of cartilage. 

Osteotomy

Angular or rotational deformity of a bone or joint can be corrected with a surgical procedure.

In cases of arthritis, osteotomy is generally performed for one of two reasons; offloading the affected part of the joint (and placing more load on a healthier part of the joint) or correcting an extra-articular deformity (deformity outside of the joint) to allow for a less complicated joint replacement.