The document discusses the use and future potential of custom implants in orthopaedic surgery, highlighting their benefits in reducing inventory costs and improving surgical outcomes through personalized design. It emphasizes the importance of collaboration between surgeons and engineers, the need for better materials, and adherence to biological principles to avoid implant failures. Additionally, it notes the increasing viability of custom implants due to advancements in 3D printing technology and the continuous evolution of implant designs.

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

5. DESIGNING CONSIDERATIONS
Requirement of an experienced surgeon/engineer
with an engineer with clinical experience
EngineerSurgeon

6. “ADDITIVE MANUFACTURE 1998” BEFORE
ACCESSIBLE SOFTWARE AND PRINTING
MY 3RD ITERATION TITANIUM HEMI-PELVIC
IMPLANTS WERE FABRICATED IN TITANIUM ALLOY

7. CUSTOM ACETABULAR CASES:
N=102
IMPLANTED IN:
NEW ZEALAND AND AUSTRALIA
MANUFACTURED BY:
OSSIS LTD, NZ
In conjunction with
MED. MODELLING/3D SYSTEMS, USA

8. 2ND CASE:
THE PROBLEM

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

11. FINAL ASSEMBLY:
COMPLETEWITH HARD ON HARD BEARING
SURGICALTIMEWITH STEM REVISION 2.3 HRS
02/04/08 26/04/2010

12. SEVERE RHEUMATOID :
FEMALE AGED 57

13. BILATERAL CUSTOM ACETABULAE
5YRS POST -OP
8 MONTHS
POST-OP
Cheaper overall, full weigh-bearing, therefore cost-effective

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?

18. THE EBMTi ALLOY AUGMENT:
PRIMARY KNEE AND STEM (2008)

19. A HUGE CAVITY BUT A GOOD SOLUTION

20. 7YRS POST-OP :
GREAT ONTHE FEMORAL SIDE

21. INTERFACES
ARE
EXCELLENT
POORER
INTERFACES
ON TIBIAL SIDE

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

28. CUSTOM
DOES NOT EQUAL
CUSTOMIZABLE
(Descriptive and Legal
Regulatory processes, N.Z.)

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

34. AN INFECTEDTKR REFERRED
AFTER 8 MONTHS WITH A SPACER

35. 3YRS POST OP LEFT KNEE

36. OTHER USES

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.

39. PATIENT EXPECTATIONS:
STRESS SHEILDING

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.

41. SILVER COATEDTITANIUM IMPLANT 1999
FOR FEMORAL OSTEOMYELITIS
COURTESY PJ BURN
Enztec Ltd NZ
Yes it
works!

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

44. THANKYOU FROM NEW ZEALAND