Oxford® Partial Knee

Michael O. Williams, M.D., F.A.A.O.S.

Oxford Partial Knee Replacement

The Oxford partial knee replacement is indicated for treatment of anteromedial osteoarthritis of the knee. This arthritis involves primarily the medial compartment of the knee with joint space narrowing seen on X-rays. The lateral compartment and patella are usually not arthritic in this condition. The Oxford differs from other partial knees in that it has a mobile UHMWPE bearing which duplicates normal knee kinematics.

Arthritis

• Defined as inflammation of the joint

• Number one cause of disability inthe United States1

• More than 100 different types • Two primary types– Rheumatoid– Osteoarthritis

Rheumatoid Arthritis

• Inflammatory• Diagnosed at younger ages than osteoarthritis• Can affect multiple joints at one time• Excess synovial fluid• Cartilage destruction

Osteoarthritis

• Degenerative joint disease• Most common form of arthritis• Wear and tear condition• Develops over time– Overuse, injury or repetitive movement – Developmental disorders

• Results in pain, stiffness

Symptoms of Osteoarthritis2

• Pain• Stiffness• Grating or “catching”

sensation during jointmovement

• Bony growths at the margins of affected joints

X-Rays

• Helps determine severity of joint damage• Cannot see cartilage on an X-ray• Space on normal X-ray is healthy cartilage

Healthy X-ray

• Space shows healthy cartilage

Osteoarthritis X-ray

• Joint space narrowing• Abnormal bone formation– “spurs”

• Joint deformity– Bowleg– Knock-knee

• A manageable, treatable condition

When to Consider Joint Replacement

• Conservative non-operative treatments fail to provide adequate pain relief

• Diminished quality of life• Diminished joint function

Joint Replacement

• Also called “arthroplasty”• Implants to resurface damaged bone and

cartilage• Metal alloy and durable plastic• Traditional vs. min. invasive with Oxford®

Partial Knee

Traditional Total Knee Replacement

• Resurfaces damaged cartilage on:– End of femur– Top of tibia– Back of patella

• Incision between six and eight inches long

Primary Knee Components

Femoral Component

Polyethylene Bearing

Tibial Tray

Minimally Invasive Knee Replacement

• Potential advantages to traditional knee replacement– Healthy muscles and tissues preserved • May be through a shorter incision

– Less blood loss– Less tissue damage

• Not all patients are candidates

Minimally Invasive vs. Traditional Incisions

Traditional Incision

Minimally Invasive Incision

Minimally Invasive Partial Knee Replacement

• Replaces one compartment of the knee• Knee cartilage resurfaced– Metal alloy and polyethylene (plastic) components

• Instrumentation for minimally invasive technique to help preserve healthy tissue

Oxford Partial Knee Components

Femoral Component

PolyethyleneBearing

Tibial Tray

Oxford® Partial Knee Animation

Oxford® Partial Knee Implant

• Only mobile-bearing partial knee in U.S.– Mobile plastic bearing moves with knee

motions– Mobile bearing helps limit forces to

help avoid loosening4,5

• One clinical study yielded a 94% success rate at 10 years and an 89% success rate at 20 years6

• There is no specific expected survivorship for joint replacement

Examples of Potential Complications of Total Joint Replacement,

Any of Which Can Lead to Revision Surgery

• Infection• Blood clots• Implant breakage• Malalignment• Wear• Loosening• Dislocation• No implant will last forever

Complications Affecting Outcome & Longevity

• Malalignment of implants - Very dependent on surgical technique and

surgeon’s skill level - Can be prevented with Signature cutting

blocks and guides

Signature ™ Personalized Patient Care

Signature ™ System

• Patient-specific femoral and tibial positioning guides (not implanted) used for instrument placement to remove damaged bone and cartilage

• Developed from MRI Scan• Allows for personalized instrumentation for

implant positioning

Before Surgery

• Traditional– X-rays to plan

implant size

• Signature™ System– MRI Scan to plan

surgery• Digital, interactive

planning software– Plans implant size and

placement before surgery

Pre-op MRI/CT Scan

• About 20 minutes for MRI scan

• Scan of hip, knee and ankle

• Head stays outside of machine MRI

The Surgical Procedure

• Signature– Patient-specific Guides• Unique to every patient• Placed directly on bone/cartilage• Position pins for cut blocks• Cut blocks guide removal of damaged bone and

cartilage

Surgical Instrumentation

Signature™ SystemTraditional

Signature™ System Benefits

• Does not invade the bone canal• Fewer surgical instruments than traditional

partial knee replacement• Allows for personalized instrumentation for

placement of the Oxford® Partial Knee implant• Reduces the incidence of malaligned

components do to surgeon error• Implant alignment optimized for that patient

Value of Joint Replacement

• Total joint replacement can save an individual as much as $68,000 (total knee replacement) to $180,000 (total hip replacement) in medical costs over the life of the average total joint recipient as compared to non surgical ‐treatment.4,5

Success of Total Joint Replacement

• Every year, over 1,000,000 people in the United States have joint replacement

• Joint replacement treats debilitating pain and deformity from various forms of arthritis

Closing

• A proper diagnosis from an orthopedic surgeon can help identify cause of joint pain

• Many conservative treatments available• Arthritis can be treated• New surgical treatments also now available

with joint replacement implants with improved function and longevity

References

1. Centers for Disease Control and Prevention http://www.cdc.gov/chronicdisease/resources/publications/AAG/arthritis.htm

2. The Arthritis Foundation http://www.arthritis.org/rheumatoid-arthritis.php 3. Vanguard Complete Knee System Package Insert http://www.biomet.com/orthopedics/getFile.cfm?id=2171&rt=inline 4. Argenson, J. et al. Polyethylene Wear in Meniscal Knee Replacement. A One to Nine-year Retrieval Analysis of the Oxford

Knee. Journal of Bone and Joint Surgery [Br]. 74 B:228–32, 1992.5. Psychoyios, V. et al. Wear of Congruent Meniscal Bearings in Unicompartmental Knee Arthroplasty—A Retrieval Study of

16 Specimens. Journal of Bone and Joint Surgery [Br]. 80-B:976–82,1998.6. Price, A. and Svard, U. A Second Decade Lifetable Survival Analysis of the Oxford Unicompartmental Knee Arthroplasty.

Clinical Orthopaedics and Related Research. Published Online 13 August 20107. AAOS. http://orthoinfo.aaos.org/topic.cfm?topic=A002338. Chang RW, Pellissier, JM, Hazen GB, “A Cost effective Analysis of Total Hip Arthroplasty for Osteoarthritis of the Hip,” ‐

Journal of the American Medical Association (JAMA), Vol. 275, No.11, 1996, pp. 858 865. (Figures apply to average 60 ‐year old patient and adjusted for inflation.)

Questions

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