No conflicts OUTLINE Unicompartmental Joint Resurfacing Decision - - PowerPoint PPT Presentation

No conflicts

OUTLINE

• Unicompartmental Joint

Resurfacing –

– Decision Making

• Onlay Arthroplasty
• Patient Specific Jigs and

Implants

– Accuracy – Results

• Alternative Techniques

– Robotics, Mobile bearing, Legacy tech

Biologic or Prosthetic Resurfacing ????

Key decision making point

• Multifactoral decision

– Lesion/Cartilage nearby – Patient Factors – Age (biological) – Comorbidities – Joint Status – Resources

Transitional thinking from biologics to prosthetics

• Once progress in

resurfacing algorithm from bio to prosthetic need conceptual framework

• 1. Inlay

2.Onlay

• 3. Bone sacrificing

(traditional TKA)

Why Consider Resurfacing?

• 1. Need for bridging or intermediary procedure in

younger patients

• 2. Preserve healthy anatomy in older patients
• Increased burden of US TKA --- 4M with TKA, 1.5M between 50-

69 yrs – Weinstein, JBJS March, 2013

• 15% of total knee patients have severe or extreme persistent

pain three to four years post op. – Wylde V, Pain 2011  19% of middle aged patients were entirely satisfied with the

• utcome of their total knee replacement

 Bourne et al., Clin Orthop Relat Res 2010

Onlay Knee Resurfacing using Patient Specific Jigs and Implants

Theoretical advantages

• Line-to-line bone conformity of components to bone
• Can preop AND intraop manipulate/correct

malalignment and malangulation

• Minimize bone resections, no resection distal femur
• Simplify and speed procedure, potentially more

predictable outcomes

• Facilitate optimal load transfer to cortical bone,

possible/theoretical greater longevity

• Lesser bone cuts AND better fit, theoretically longer

lasting, facilitate easier and/or fewer revisions

Onlay Resurfacing Arthroplasty with Patient Specific Jigs & Implants Practical:

• Digitize limb, including size

and alignment PRE-OP

– MRI or CT

• Avoid intraop “fiddling”
• Why not preserve

subchondral bone????

Onlay Resurfacing with Patient Specific Implants & Jigs

• Implants and Jigs 3D

printed

• More accurate fit may

increase longevity

• Accommodate

morphologic variability, “odd sizes and shapes”

Patient Specific UKA Implants and Jigs Fit Better

• Patient-specific implants vs off-the-shelf implants
• Greater cortical rim surface area coverage
• 77% v. 43% medially
• 60% v. 37% laterally

Patient Specific Jigs and Implants ONLY good Lateral Side Option

• Tibial fit was much better in patient specific vs

legacy implants

– 1.0 mm mismatch vs 3.3mm mismatch p<.01

• Survivorship at mean 36 mos 97% vs 85%

• 31 patients with medial OA (27 medial knee osteoarthritis,

4 osteonecrosis)

• Mean age 60 years. Minimum follow-up 17 months.
• One aseptic loosening needed exchange; one acute late-onset infection
• No further revisions/reoperations or complications.
• X-rays showed an ideal fit of the implant with less than 2 mm subsidence
• r overhang in all cases.
• VAS changed from 6.51 preoperatively to 1.11 postoperatively.
• KSS (Knee Society Score) improved from 111.23 preoperatively to 180.61

postoperatively

• Functional KSS improved from mean 60.39 to 94.51.

Tibial Component Sizing - Onlay

Does size matter? Implication of mismatch

• Overhang of tibial tray by

>3mm occurred in 9% of Oxford UKR in series n=160

• 5 yrs post op, this group

had significantly worse Oxford Knee Scores (p=.0001) than those without overhang

• Don’t want to undersize

tray either, risk subsidence

• Chau R, Gulati A, Pandit H, Beard DJ, Price AJ,

Dodd CAF, Gill HS, Murray DW: Tibial component

• verhang following unicompartmental knee

replacement - does it matter? Knee 2009, Vol. 16, pp. 310 - 313.

Excellent Fit and Alignment

• Accuracy of Implant Match:

– Mean: 0mm AP, 1mm Med-Lat

• Slope maintained

– 5 degree pre op slope unchanged

• WB Fem-Tib alignment corrected

– Mean preop 7 degrees varus – Mean postop 1 degree varus

Patient Specific

Onlay Resurfacing

Residual cartilage subjacent to implant removed

Holes for implant pegs and cement interdigitation

Mobile Bearing… really????

• Disadvantages

– Huge bone resection – Poor fit – Non anatomic

• Advantages

– NHS formulary – 35+ year history

• VCR, pagers, cassettes

You’ve got to be kidding…..

• Robot costs >1M $
• Implants are off the

shelf

• Marked intraop

complexity

• A “work-around” for

Patient Specific Jig and Implant IP

For those of you that still think the robot is the way to go…..

Patient Specific Jigs and Implants are the only way to go….

• Simpler
• Faster
• More Accurate
• Less Cost
• Longer Lasting
• BETTER

Thank You phildavidsonmd@gmail.com davidsonorthopedics.com