OEMs and suppliers see promise in the ability of manufacturing and software to expand the use of custom implants in orthopaedics. Multiple companies are focused on the custom market. This session provides the surgeon perspective on these devices. What are the benefits? When should and shouldn't they be used? Will the market take off?
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Current and Future Use of Custom Implants in Orthopaedic Surgery
1.
2. CURRENT AND FUTURE USE OF CUSTOM
IMPLANTS IN ORTHOPAEDIC SURGERY
OMTEC 2016 CHICAGO
P James Burn FRACS
Consultant Orthopaedic Surgeon
Canterbury District Health Board
Christchurch
New Zealand
pjamesburn@xtra.co.nz
3. DISCLOSURES:
• Founding shareholder of Ossis Ltd (NZ)
• Founding shareholder of Enztec Ltd (NZ)
• Receive royalties from the Enztec Stardrill
4. PERSONAL PRACTICE PROFILE
( NZ POPULATION 4 MILLION)
PrimaryTHR 2,000+
Last 1,000 cases 0% dislocation for PrimaryTHR post. approach
Revision rate 0.04 per 100 component years, with LIMA PF cup
(lowest on the NZJR)
RevisionTHR 300
PrimaryTKR 950 +
Primary UKR 400 +
RevisionTKR 97+
Custom hemi-pelvic replacements 3 + 1rev
+spine, foot and ankle and general orthopaedics.
CUSTOM ACETABULAR CASES 30
6. “ADDITIVE MANUFACTURE 1998” BEFORE
ACCESSIBLE SOFTWARE AND PRINTING
MY 3RD ITERATION TITANIUM HEMI-PELVIC
IMPLANTS WERE FABRICATED IN TITANIUM ALLOY
9. THE BIO-MODEL OF THE PELVIC DISSOCIATION AND IIIB
OUTLINE OF THE PROPOSED IMPLANT
Fracture line
through
posterior column
= 2 parts
THE NEED FOR CUSTOM IMPLANTS (HIP)
10. MRS MP 70YRS
SURGEONS: PCA / JB
TOTAL SURGICAL TIME REVISION ALL COMPONENTS: 2.3 HRS
DISCHARGED DAY 5 FULL WEIGHT BEARING
1ST GENERATION E-BEAM CUSTOM IMPLANT
dealing with bone loss and the dissociation: 2008
14. TOTAL NUMBER OF CASES USING EBM
ACETABULAR IMPLANTS = 102
Ossis Ltd, NZ and Med. Modelling / 3D Systems USA
NZ AND AUSTRALIAN MARKETS OF 24 MILLION
15. WHAT WOULDYOU PREFER TO USE
AS AN ORTHOPAEDIC SURGEON?
• Larger spherical cup
• Oblong cup
• Bone graft
• Autograft (not in revision cases)
• Allograft (banked femoral head)
• Allograft (Acetabular replacement)
• Synthetic Bone substitutes,TCP, DBM
• “Metal graft” substitution
• Cages/Rings
• Triflanged implants
INVENTORY COST!
16. OR A ONE-PIECE SOLUTIONTHAT IS
PATIENT PERFECT SPECIFIC!
17. A REAL PROBLEM AFTER 4 REVISION SURGERIES:
WHATTO DOWITHTHIS CASE?
22. MED MODELLING / OSSIS MESH
SEM PICTURE
THE MOST IMPORTANT “BIOLOGICAL” FEATURE
23. STRESS SHIELDING AND FATIGUE FAILURE
Too
stiff...stress
shielding
Too thin... broken
stem but the bone
stock was saved!!
82 yr female
with worn PE
liner
82 yr male with
thigh pain
BIOLOGY NOT RESPECTED
24. CAUSES OF FAILURE OF IMPLANTS
PROBLEM
1. MODULUS MIS-MATCH
2. MAL-POSITION
3. FRICTION
4. WEAR PARTICLES
5. INFECTION
SOLUTIONS
1. MATERIALS AND STRUCTURE
2. EDUCATION and
INSTRUMENTATION
3. BETTERTRIBOLOGY
4. MATERIALS AND SURFACES
5. SURGICAL TECHNIQUE,
SURFACE COATINGS
25. RESPECT BIOLOGY AND ITS SOLUTIONS
DESIGNTHE IMPLANT TO “BLEND IN”
WITH MODULUS MATCHING
RESPECTTHE PRIMARY AND SECONDARY TRABECULAE
UNDERSTANDTHE SUBCHONDRAL BONE PLATE
UNDERSTANDTHE GROWTH PATTERN OF A LONG BONE
26. 3D PRINTING OF MATERIALS
THIS IS A TOOLTHAT CAN ADDRESSTHE
ANISOTROPIC REQUIREMENTS OF THE
IMPLANT TO MATCH BONE
THE METALLURGY OF PRINTED METALS MAY
NEED FURTHER IMPROVEMENT i.e. HIP
TREATMENT
27. WHY USE CUSTOM IMPLANTS:
ARE THEY FISCALLY VIABLE?
They reduce the inventory in revision and
complex primary: TRUE?
The dead stock sitting in hospitals is avoided
$$$$ : TRUE
The surgery is rehearsed during design:
Unexpected findings minimized: TRUE
Make primary implants more useable
in revision surgery: TRUE
29. WHO PAYS CURRENTLY IN N.Z.
PUBLIC HOSPITALS WITH PRIOR APPROVAL OF
SERVICE MANAGERS
PRIVATE INSURANCE COMPANIES,AGAIN PRIOR
APPROVAL AND EXPLANATION
30. DO THE OUTCOMES OF CUSTOMISED
IMPLANTS EXTRAPOLATE TO
STANDARD PROVEN IMPLANTS?
The “IdentiFit Hip” experience (milled stem)
?20% per annum failure, Dr J Hart,Australia
OPEN QUESTION
31. WHY CUSTOM IMPLANTS? A SMALL STEP
AFTER REQUIRED IMAGING ANYWAY!
The complexity is simplified:TRUE
(surgeon’s pulse < patient’s!)
32. PRE-OP PLANNING AND CT SCANNING
• Tray size would be known
• Augment thickness planned and
manufactured
• Bearing thickness still not predictable
• Saving on inventory required
33. Inventory required 3 thicknesses of hemi-
augments X 6 trays = 18 , or full size augments =
18: Grand total could be 36 parts
REVISION: 9/6/2016, CURRENT OFF THE SHELF
LCS AND AUGMENT OF IMPLANT, NOT BONE STOCK
37. CUSTOMISED PRIMARY IMPLANTS RATHER
THAN CUSTOM AUGMENTS
InTHR: easily “do-able” due to spherical bearings
(adjustable neck lengths etc.)
InTKR: Surface geometry critical for outcomes to be
predictable (PE does not adapt as menisci!)
In knees the soft tissue elasticity and balance is
variable, needing a range of sizes
InTrauma: specialised fixation plates
38. AM SPINAL IMPLANTS 2011
But still a range of heights per level needed
Indications: very small female.
40. INSERTION OPTIONS FOR
CUSTOM IMPLANTS
1. Standard instruments to give
standard “internal” cuts
2. Customised cutting blocks but accuracy can be
problematical (Oxford Knee 2/22 accurate in NZ
trial, Mr R Maxwell)
3. Robotic bone shaping using data files from the
implant: MAKO etc.
42. THE FUTURE
New biocompatible materials (polyimide
etc.)
“Plastic” knees
Custom implants incorporating
active surfaces
(antimicrobial and osteo-inductive)
Composite structures ( AM parts
and standard parts)
43. DESIGNS ARE INFINITE BUT A
CAUTIONARY NOTE…
RULES OF BIOLOGY CANNOT BE BROKEN…
Particulates, surface finishes, corrosion
THE REACTION OF LIVINGTISSUES
NEEDSTO CONSIDERED…
Osteolysis, ALVAL, toxicity of ion release,
impurities in and on implants
THE MATERIAL’S SPECIFIC ENGINEERING
PARAMETERS HAVETO BE ALLOWED FOR...
Fatigue resistance, loadings,
corrosion and valency, scratches