UKA Manual Versus UKA MAKO Robotic

Total knee arthroplasty (TKA) is known to have excellent long-term survivorship and clinical
success in the management of degenerative joint disease, and remains the primary treatment
for patients with bi- or tri-compartmental osteoarthritis. However, the patient population
seeking knee arthroplasty is evolving, with patients being younger and more demanding on
their prostheses (1). Recent investigations have highlighted that there remains a high
incidence of residual symptoms including grinding/popping/clicking, swelling, and
difficulties getting in and out of a car and chair, and 16% of patients remain "unsatisfied"
following TKA (1).

Medial unicompartmental knee arthroplasty (UKA) remains a viable alternative to total knee
arthroplasty in patients presenting with isolated, medial compartment osteoarthritis of the
knee. Its use has increased in popularity in the United States, as the number of UKA
performed over the last decade has increased by 30%(1). Proposed benefits of UKA include a
smaller incision, less blood loss as well as shorter recovery time to functional level. Other
benefits of UKAs include improved knee range of motion and better restoration of the knee
kinematics (2, 5). These benefits are attributed to the less invasive nature of the procedure
with preservation of the anterior and posterior cruciate ligaments, and minimal bony
resections.

Unfortunately, historically the survival rate of UKA has been poor, with several reports
demonstrating a survival rate of only 65-70% at 7-10 year follow-up (8, 9). These
historically poor results have been attributed to instrumentation that was difficult to use,
poor indications for the surgical procedure, and inadequate implant designs. More recent
reports have shown 10-year survival rates ranging from 91% to 98% using both mobile-bearing
and fixed-bearing UKA designs (7, 10-12). Mobile bearing UKA have a 92% survival rate at 20
years (5). However, the vast majority of these studies were performed at high-volume centers,
and national joint registries have continued to demonstrate an increased rate of early
failure and decreased survivorship of UKA versus TKA(13).

Recently, robotic-assisted UKA has been introduced to improve the accuracy of implant
positioning (4). As implant positioning including alignment and translation in the coronal
and sagittal planes and implant sizing are critical for success after UKA, the addition of
robotic-assistance theoretically can improve radiographic alignment and clinical outcomes.

Currently, the most common robotic guidance system used in UKA is the Robotic Arm Interactive
Orthopedic System (RIO; MAKO Surgical; Ft. Lauderdale, FLA). The purposes of this
investigation is to 1) retrospectively review the radiographic and clinical outcomes of
medial UKA using conventional techniques performed at our institution and 2) prospectively
assess the learning curve, radiographic, and clinical outcomes of use of the RIO system as it
is incorporated into our clinical practice.

Inclusion Criteria:

- All patients who receive a robotic arm assisted UKA using the RIO navigation system
will be prospectively included. All patients who have received a medial fixed or
mobile UKA performed by surgeons in the Joint Preservation, Resurfacing, and
Replacement Service at Washington University will be retrospectively reviewed. Also,
all TKAs from a pervious study (IRB 201308057) performed by surgeons in the Joint
Preservation, Resurfacing, and Replacement Service at Washington University will be
retrospectively reviewed as well.

- Patient is willing and able to comply with postoperative follow-up requirements
and self-evaluations

- Patient is willing to sign an IRB approved informed consent

- Patient is at least 18 years of age

Exclusion Criteria:

- • Patient has a BMI < 40

- Patient is skeletally immature

- Patient has an active infection or suspected infection in or about the joint

- Bone stock that is inadequate to support fixation of the prosthesis

- Neuromuscular disorders, muscular atrophy or vascular deficiency in the affected
limb rendering the procedure unjustified.

- Patients with mental or neurological conditions which may be incapable of
following instructions.

- Blood supply limitations

- Collateral ligament insufficiency.

- Patients with prior HTOs or Unis.

- Patients requiring bilateral knee arthroplasty.