Cables, Plates & Onlay Cables, Plates & Onlay AllograftsAllografts

Mark AshworthMark Ashworth

Torbay HospitalTorbay Hospital

Cables, Plates & Onlay Cables, Plates & Onlay AllograftsAllografts

• Guide you through the ‘menu’Guide you through the ‘menu’

• Discuss the merits of the various ‘dishes’Discuss the merits of the various ‘dishes’

• Perhaps make a recommendation or twoPerhaps make a recommendation or two

• Set the scene for the ‘main course’ to Set the scene for the ‘main course’ to followfollow

CablesCables

CablesCables

• 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 Cables a – Stainless Steel wirea – Stainless Steel wire• Knot Strength

– Thicker wire = stronger knots (Wilson 1985)

– >2 twists = NO increase in strength (Schultz 1985)

– Double loop knot strength > square knot > twist (Roe, 1997 & 2002)

– Simple twist easily untwists with little tension ((Meyer 2003)

– Knot twistKnot twist 100000 cycle fatigue stronger>twist (Bostrom 1994)

Knot twist

AO Loop

Double loop

Square knot AO loop & tuck

Symmetrical Wire

twist wrap

Cables Cables b - Multi filamentb - 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 (Liu 1997)

– Chrome cobalt > stainless steel

• Cable cost– Double loop cerclage ~10x less £££££ than cables (Ritter 2006)

Cables Cables c - Nylonc - 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 Cables c - Nylonc - Nylon• Ultimate strength

Cerclage TypeCerclage Type Ultimate Tensile StrengthUltimate Tensile Strength

NylonNylon SuperCable SuperCable 1000N1000N

Stainless steel wireStainless steel wire 280 - 600N280 - 600N

Titanium alloy cableTitanium alloy cable 1000 - 1840N1000 - 1840N

Cobalt-chrome alloy cableCobalt-chrome alloy cable 1200 - 2800N1200 - 2800N

Cables Cables c - Nylonc - Nylon• Fatigue strength

Breakage in cabling systems are generally fatigue failure not tensile failures

Cerclage TypeCerclage Type Cyclic LoadCyclic Load Cycles to FailureCycles to Failure

NylonNylon SuperCable SuperCable 400N400N No failures @ 1 million cyclesNo failures @ 1 million cycles

Stainless steel wireStainless steel wire 140-320N140-320N 100,000 cycles100,000 cycles

Titanium alloy cableTitanium alloy cable 40 – 200 N40 – 200 N 100,000 – 1 million cycles100,000 – 1 million cycles

Cobalt-chrome alloy cableCobalt-chrome alloy cable 80 – 200 N80 – 200 N 100,000 – 1 million cycles100,000 – 1 million cycles

PlatesPlates

PlatesPlates

•“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 ‘

PlatesPlates

a.a. Non locked Non locked

b.b. LockedLocked

c.c. Cable plate systemsCable plate systems– Dall Miles 1983Dall Miles 1983

PlatesPlatesa- Non Locking platesa- 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

PlatesPlatesa- Non Locking platesa- Non Locking plates• Old 2006

– 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

• MIPPO B1 #– 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)

Old 2006 Old 2006 RxRx

PlatesPlatesb- Locking platesb- Locking plates• Stiffer than Ogden, & fail by lat cortex fracture (Fulkerson 2006)

• Conventional outermost screw reduces stress riser & significantly increased strength (Bottlang 2009)

• 90:90 construct (plate or strut) (Talbot 2008)

– Stiffer than 1 plate– Locking screws give no mechanical advantage over conventional

screws– No cable loosening after 100,000 cycles

PlatesPlatesb- Locking platesb- Locking plates• C# & B1#

– 100% union • LCP

• MIPPO

– 90% union • LCP

• LISS technique difficult but fewer complications than traditional fixation

– BetterBetter results IF combined with struts

PlatesPlatesc- Cable platesc- 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

PlatesPlatesScrew anglesScrew angles• DCP DCP

– Offset hole 4mm on broad BUT not narrow plateOffset hole 4mm on broad BUT not narrow plate– 25250 0 & 7& 70 0 screw anglescrew angle

D d

PlatesPlatesScrew anglesScrew angles• DCP DCP

– Offset hole 4mm on broad BUT not narrow plateOffset hole 4mm on broad BUT not narrow plate– 252500 && 7 700 screw anglescrew angle

• LC-DCP LC-DCP – 80800 0 & 14& 140 0 screw angle, 4mm offsetscrew angle, 4mm offset

D

PlatesPlatesScrew anglesScrew angles• DCP DCP

– Offset hole 4mm on broad BUT not narrow plateOffset hole 4mm on broad BUT not narrow plate– 252500 & & 7700 screw anglescrew angle

• LC-DCP LC-DCP – 808000 & & 141400 screw angle, 4mm offsetscrew angle, 4mm offset

• Locking CPLocking CP– 505000 (<DCP) and 14 (<DCP) and 1400 non locked screw angle non locked screw angle– 4mm offset4mm offset

PlatesPlatesScrew anglesScrew angles• DCP DCP

– Offset hole 4mm on broad BUT not narrow plateOffset hole 4mm on broad BUT not narrow plate– 252500 & & 7700 screw anglescrew angle

• LC-DCP LC-DCP – 808000 & & 141400 screw angle, 4mm offsetscrew angle, 4mm offset

• Locking CPLocking CP– 505000 (<DCP) and (<DCP) and 141400 non locked screw angle, 4mm non locked screw angle, 4mm

offsetoffset

• Kinamed Supercable– 57570 0 & 16& 160 0 nonnon locked screw angle, 4mm offsetlocked screw angle, 4mm offset– Curved plates (match femur)Curved plates (match femur)

160

570

D+

PlatesPlates

• MennenMennen

PlatesPlates

• MennenMennen– Ahuja 2002 75% complication rateAhuja 2002 75% complication rate

– Noorda 2002 Noorda 2002 mechanical failure 31% and non-union mechanical failure 31% and non-union

28%28%

Onlay Allograft Onlay Allograft

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 AllograftOnlay AllograftTechniqueTechnique• 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 AllograftOnlay AllograftBiology of unionBiology 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 AllograftOnlay AllograftBiology of unionBiology 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 AllograftOnlay AllograftBio-mechanicsBio-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 AllograftOnlay AllograftResultsResults• 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 YouThank You