Transcript Cables, Plates & Grafts

Cables, Plates & Onlay Allografts
Mark Ashworth
Torbay Hospital
Cables, Plates & Onlay Allografts
• Guide you through the ‘menu’
• Discuss the merits of the various ‘dishes’
• Perhaps make a recommendation or two
• Set the scene for the ‘main course’ to follow
Cables
Cables
• Current indications
– Prophylactically
• Increased hoop stress resistance (Tsiridis, 2003)
– Temporary
• Stabilisation pending plate, strut, THR insertion
– Definitive
• Simple periprosthetic # - alone
•
– Calcar splits on insertion
– B1 spiral #
Complex periprosthetic # - with other devices
– Plates, mesh, impaction or strut graft….
• Contra-indications
– Transverse/short oblique periprosthetic #
(poor torsion/bending rigidity)
Cables
a – Stainless Steel wire
Knot twist
Symmetrical
Wire
twist
wrap
• Knot Strength
– Thicker wire = stronger knots (Wilson 1985)
– >2 twists = NO increase in strength (Schultz 1985)
Square knot
& tuck
AO loop
AO Loop
– Double loop knot strength > square knot > twist (Roe, 1997 & 2002)
– Simple twist easily untwists with little tension (Meyer 2003)
– Knot twist 100000 cycle fatigue stronger>twist
(Bostrom 1994)
Double loop
Cables
b - Multi filament
• Cable material
–
–
–
Zimmer & Biomet - Stainless steel, cobalt chrome & titanium
De puy - Stainless steel 1.8mm
Dall Miles - Stainless steel & Cr Co Mo (vitallium)
• Cable strength
– Fatigue
– cables superior to SS wire (Weiss 1996)
– Ultimate strength – 1 cable > 1 wire (Carls 1997); but 1 cable = 2 wires
– Chrome cobalt
> stainless steel
• Cable cost
– Double loop cerclage ~10x less £££££ than cables
(Ritter 2006)
(Liu 1997)
Cables
c - Nylon
• Nylon core, UHMWPe sheath (Ti/Al/V clasp - some Cr Co)
• Contraindication if can catch on mesh or plate edge (Kinamed)
• Elastic energy stored after initial relaxation
– Iso-elastic cable maintains continuous compressive forces
= initial compression of cerclage wires
– Compensates for # movement & decreased risk of cable slip
Cables
c - Nylon
• Ultimate strength
Cerclage Type
Ultimate Tensile Strength
Nylon SuperCable
1000N
Stainless steel wire
280 - 600N
Titanium alloy cable
1000 - 1840N
Cobalt-chrome alloy cable
1200 - 2800N
Cables
c - Nylon
• Fatigue strength
Cerclage Type
Cyclic Load
Cycles to Failure
Nylon SuperCable
400N
No failures @ 1 million cycles
Stainless steel wire
140-320N
100,000 cycles
Titanium alloy cable
40 – 200 N
100,000 – 1 million cycles
Cobalt-chrome alloy cable
80 – 200 N
100,000 – 1 million cycles
Breakage in cabling systems are generally fatigue failure not tensile failures
Plates
Plates
• “2B or not 2B, that is the question”
– Lindahl 2006 Swedish register 245 cases-
• Single plate ORIF higher risk of failure with B1#
• #’s were probably un-recognised B2 (revision best)
– Prosthesis considered loose until proven otherwise
– Infer…..’ no place for fixing #, then later revising stem ‘
Plates
a.
b.
c.
Non locked
Locked
Cable plate systems
–
Dall Miles 1983
Plates
a- Non Locking plates
•
Ogden (1978) - Proximal cables, distal screws
–
Plate & screws (in vitro) > Ogden > 2 struts > cabled plate
–
Clinical results = 80% good/union
•
Standard plate –
–
–
All Screws
90 : 90 plating = best biomechanics
Soft tissue strip++
90% union with broad DCP
Old 2006 Rx
Plates
a- Non Locking plates
•
Old 2006
•
MIPPO B1 #
–
–
–
–
–
95 % union ( no bone graft/strut)
Long plate for proximal screw fixation
+/- cerclage wires
Their technique = Haddad 2002 results

used strut allograft or strut & plate
Indirect ORIF 1 lateral plate no bone graft
 ~12/52 86% union
 100% (Abhaykumar 2000, Ricci 2005)
 Adjuvant bone graft not always necessary
(Ricci 2007)
Plates
b- Locking plates
•
Stiffer than Ogden, & fail by lat cortex fracture
•
Conventional outermost screw reduces stress riser & significantly
increased strength (Bottlang 2009)
•
90:90 construct (plate or strut)
–
–
–
(Fulkerson 2006)
(Talbot 2008)
Stiffer than 1 plate
Locking screws give no mechanical advantage over conventional screws
No cable loosening after 100,000 cycles
Plates
b- Locking plates
• C# & B1#
– 100% union
• LCP
• MIPPO
– 90% union
• LCP
• LISS technique difficult but fewer complications than
traditional fixation
– Better results IF combined with struts
Plates
c- Cable plates
• B1 #
–
–
–
–
100% union 4/12
85% union
57% union, cabled Dall Miles – ‘consider strut or long stem’
40% successful union, ‘avoid in varus stem’
• Avoid if retaining a stem in varus
• Threaded pin cerclage better than cerclage plate wrap
Sit in screw head
Plates
Screw angles
• DCP
D
– Offset hole 4mm on broad BUT not narrow plate
– 250 & 70 screw angle
d
Plates
Screw angles
• DCP
– Offset hole 4mm on broad BUT not narrow plate
– 250 & 70 screw angle
• LC-DCP
– 800 & 140 screw angle, 4mm offset
D
Plates
Screw angles
• DCP
– Offset hole 4mm on broad BUT not narrow plate
– 250 & 70 screw angle
• LC-DCP
– 800 & 140 screw angle, 4mm offset
• Locking CP
– 500 (<DCP) and 140 non locked screw angle
– 4mm offset
Plates
Screw angles
• DCP
– Offset hole 4mm on broad BUT not narrow plate
– 250 & 70 screw angle
• LC-DCP
– 800 & 140 screw angle, 4mm offset
• Locking CP
– 500 (<DCP) and 140 non locked screw angle, 4mm offset
• Kinamed Supercable
– 570 & 160 non locked screw angle, 4mm offset
– Curved plates (match femur)
D+
570
160
Plates
• Mennen
Plates
• Mennen
– Ahuja 2002 75% complication rate
– Noorda 2002 mechanical failure 31% and non-union 28%
Onlay Allograft
Onlay Allograft
• Current indications
– Restore bone loss
• Uncontained non-circumferential defects
– As a ‘Plate’
• Reinforce bone loss areas & bypass stress risers
• Fix periprosthetic fractures
• Stabilize bulk allograft : host junctions
Onlay Allograft
Technique
• 1st description
– Penenberg & Chandler 1989
• Chandler 1998
– Struts ½ diameter of shaft
– Med & lat placement, contour to fit shaft
– To avoid stress riser plate/allograft should be staggered &
bypass # by 2 diameters
– Avoid linea aspera to protect blood supply
– Keep periosteum for blood supply
– Cables x 6 minimum
• Bradey 1999
–
1/
3
diameter @ 90:90 anterior & lat
• Preserves b.s from linea aspera & reduced stripping
Onlay Allograft
Biology of union
• Bone resorption
– Variable rounding off & scalloping by 6 months
• Bridging
– Partial at 8/12 , completed by 1 yr
• Partial revascularisation
– 20% by 5 years
– Diffuse loss of radiodensity & changed trabecular pattern
• Remodelling
– Of the graft & host femur
Onlay Allograft
Biology of union
• Union rate
– Improves if rigid fixation
– 11-20% fail -infection, rejection, fracture, non union
• Union speed/quality
– Auto graft
- better quality union but not faster
– Osteogenic protein 1 - faster healing & better quality
– BMP2
- faster healing & better quality
• Immune response
– Reduces osteoinduction
– Freezing reduces antigenicity
Onlay Allograft
Bio-mechanics
• Bone strength
– Freezing > freezing & irradiation > freeze drying
– Dead bone > repaired bone (resorption)………
– Allograft fractures increase around 2-4 years
• Stress shielding in vitro
– Plate > strut
Onlay Allograft
Results
• Plate & strut better than strut alone
– 90 - 95% union, strut alone
– 95% union, 1 plate 1 strut
– 98% union, struts +/- plate
My Recommendations:-
My Recommendations:• Wire
–
–
Temporary use – thickness & knot type is unimportant
Definitive use – if run out of cables simple B1 or C# (with great caution)
My Recommendations:• Wire
–
–
Temporary use – thickness & knot type is unimportant
Definitive use – if run out of cables simple B1 or C# (with great caution)
• Cables
–
–
MUCH better than wire, but best used with plates
Nylon cables have some theoretical advantages in more complex # pattern
• movement compensation; but costs more
My Recommendations:• Wire
–
–
Temporary use – thickness & knot type is unimportant
Definitive use – if run out of cables simple B1 or C# (with great caution)
• Cables
–
–
MUCH better than wire, but best used with plates
Nylon cables have some theoretical advantages in more complex # pattern
• movement compensation; but costs more
• Plates
–
–
–
–
Cabled plates good enough
Broad plates with all screws (offset screw holes) are better
Locked plates best
MIPPO difficult but results worth the effort
My Recommendations:• Wire
–
–
Temporary use – thickness & knot type is unimportant
Definitive use – if run out of cables simple B1 or C# (with great caution)
• Cables
–
–
MUCH better than wire, but best used with plates
Nylon cables have some theoretical advantages in more complex # pattern
• movement compensation; but costs more
• Plates
–
–
–
–
Cabled plates good enough
Broad plates with all screws (offset screw holes) are better
Locked plates best
MIPPO difficult but results worth the effort
• Strut graft
–
Almost as good as locked plates clinically
My Recommendations:• Wire
–
–
Temporary use – thickness & knot type is unimportant
Definitive use – if run out of cables simple B1 or C# (with great caution)
• Cables
–
–
MUCH better than wire, but best used with plates
Nylon cables have some theoretical advantages in more complex # pattern
• movement compensation; but costs more
• Plates
–
–
–
–
Cabled plates good enough
Broad plates with all screws (offset screw holes) are better
Locked plates best
MIPPO difficult but results worth the effort
• Strut graft
–
Almost as good as locked plates clinically
90:90 configuration,
although stronger
bio-mechanically,
clinically probably
not necessary.
Thank You