Partial Knee Replacement: An Overview
Over the course of their lifetimes, approximately one in five
Americans will develop knee arthritis. Fortunately, a wide range of
nonsurgical and surgical techniques are available to address the discomfort and
disability that can accompany this condition. Partial knee replacement is a
surgical treatment option that replaces (or resurfaces) only the damaged
portion of the knee while conserving knee ligaments and unaffected cartilage.
Patients with unicompartmental knee arthritis have cartilage degeneration in only
one section or compartment of the knee. In cases where nonsurgical techniques
do not provide sufficient symptom relief, surgeons can remove damaged cartilage
and bone in the diseased area only, while preserving the ligaments that help
support the knee joint.
A prosthesis—which
may also be called an implant—takes the place of the damaged area of the knee,
leaving the other compartments intact. Partial knee replacement
surgery may also be referred to as partial knee resurfacing, unicondylar knee
surgery, unicondylar knee replacement, or unicondylar knee arthroplasty. Over
the past 15 years, improvements in surgical techniques and instrumentation have
made partial knee replacement a viable option for a growing number of patients;
in fact, recent data suggests that anywhere from 10 to 15% of all patients
with osteoarthritis of the knee may be eligible for the procedure.
Understanding Unicompartmental Knee Arthritis
Arthritis
of the knee may
occur in any one of the three compartments that make up the knee joint. The
inner ormedial compartment of the knee and the outer or lateral
compartment of the
knee are formed by the articulation (or joining) of the lowest part of the
thighbone (femur) and the highest part of the shinbone (the
tibia). The third
compartment of the knee is formed by the kneecap (patella) and the front part of the femur. This
is referred to as the patellofemoral
joint.
The medial compartment is
the most frequent site of osteoarthritis of the knee, with the disease occurring
less frequently in the lateral compartment. (Arthritis that is confined to
the patellofemoral compartment of the knee is rare.)
![]() |
Medial compartment osteoarthritis |
![]() |
Medial compartment osteoarthritis |
Who Can Benefit from Partial Knee Replacement?
Partial knee replacement is appropriate for patients with
arthritis that is confined to a single compartment of the knee and is generally
restricted to patients who are not morbidly obese. The surgery is not appropriate for
patients with marked stiffness in the knee or those with a significant angular
deformity. Intact ligaments are generally a requirement for a partial
knee replacement. Patients with rheumatoid
arthritis are
not candidates for partial knee solutions since inflammatory-type arthritis
typically involves the entire joint. Additional considerations are evaluated on
a case-by-case basis with the surgeon and patient determining together whether
partial knee replacement is the best treatment option. Selecting the right
patient is considered one of the most important steps to ensuring a good
functional outcome and longevity for a partial knee replacement.
What Happens during Partial Knee Replacement?
During
partial knee replacement, the orthopedic surgeon makes a small incision to gain
access to the affected compartment of the knee. He or she gently moves
supporting structures of the knee out of the way and removes damaged cartilage
and bone tissue from the surfaces of the tibia and the femur in the arthritic
area. The surgeon then prepares these surfaces for insertion of the prosthesis
components which are specifically sized to the patient’s joint. Cement is used
to secure these components. All surrounding structures and tissues are restored
to their anatomic position and the incision is closed. Following animation may
give you a good idea about the procedure - View
animation
Depending on which
compartment is affected and whether the patient’s anterior
cruciate ligament (ACL)
is intact, the surgeon will use either a unicondylar fixed bearing knee
replacement—the most commonly used prosthesis—or a mobile bearing unicondylar knee
replacement. These prostheses are made of plastic and metal
components.
![]() |
Fixed bearing unicondylar knee replacement |
![]() |
Fixed bearing unicondylar knee replacement |
Some surgeons apply
computer-assisted techniques and robotic tools to partial knee replacement. This
technology allows the surgeon to create and manipulate a 3D image of the patient’s
knee in advance of surgery, a process that allows for highly precise removal of
damaged tissue and refined positioning of the prosthesis during the actual
procedure.
![]() |
Mobile bearing unicondylar knee replacement |
![]() |
Mobile bearing unicondylar knee replacement |
Patients undergoing partial knee replacement surgery are usually
given regional anesthesia, which numbs the lower half of the body and allows
the patient to remain awake during the procedure. Throughout partial knee
replacement surgery, patients are carefully monitored to minimize the risk of
complications. Patients who have been properly screened for the procedure can
expect to experience a low level of complications and a rapid recovery.
However, as with other types of knee surgery, in a small percentage of cases,
revision surgeries are required. Results obtained with revision surgery may not
be as good as those achieved with primary surgery.
Recovering from Partial Knee Replacement Surgery
Following surgery, most
patients undergoing partial knee replacement can expect to spend one to two
nights in the hospital. Most patients are able to walk with assistance, or
independently, on the same day as their surgery. Typically, the patient is
given a cane within a week of surgery to allow for increased independence and
begins outpatient rehabilitation. Patients are often finished taking narcotic-type
pain medication within four weeks post-surgery. Partial knee replacement
usually involves minimal blood loss and is associated with a low rate of
complications; most patients can expect to be back to their daily activities
within three to six weeks. Many patients find that after undergoing physical
rehabilitation, they are able to return to sports such as golf, within six to
ten weeks.
Setting the Stage for a Successful Outcome: Surgery at HSS
Partial knee replacement is
widely recognized as a technically demanding surgery. As demonstrated in the
scientific literature, data shows that choosing an orthopedic surgeon and
institution with extensive experience with this procedure can help ensure a
good result. In fact, at high-volume institutions like Hospital for
Special Surgery (HSS), in well-selected patients, surgeons achieve the same longevity
for partial knee replacement as that reported for total
knee replacement. “It’s important to understand that partial knee replacement is
a challenging procedure to perform,” says Michael
M. Alexiades, MD, Attending Orthopedic Surgeon at HSS. “At HSS, we collect data
on partial knee replacement patients on an ongoing basis. This allows us to
continuously refine screening and surgical techniques to achieve predictable
results and the best outcome possible” says Michael
M. Alexiades, MD.
Published at - hss.edu
Published at - hss.edu
No comments:
Post a Comment