the results of cementless cups (hap or ti) with additional divergent pegs and acetabular...

The results of cementless cups (HAP or Ti) The results of cementless cups (HAP or Ti) with additional divergent pegs with additional divergent pegs

and acetabular reconstruction with graft and acetabular reconstruction with graft in failed THAin failed THA

The concept of “migration en bloc”The concept of “migration en bloc”

(1993)(1993)

JL. Lerat, C. FalaiseJL. Lerat, C. Falaise

LYON - France LYON - France

EFORT Congress (June 2001- Rhodes)EFORT Congress (June 2001- Rhodes)

Special Cup with pegs for revision Special Cup with pegs for revision 1st model : «Spring» «Spring» ( Landanger-Depuy 1993 - 2000 )( Landanger-Depuy 1993 - 2000 ) Special Cup with pegs for revision Special Cup with pegs for revision

1st model : «Spring» «Spring» ( Landanger-Depuy 1993 - 2000 )( Landanger-Depuy 1993 - 2000 )

• Metallic cup ( Ti ). Hydroxyapatite coating

• 6 holes for 6 pegs fixed with the cup by threading

• Alumine on polyethylene

1rst model (alumine on polyethylene) : 128 cases

6 divergent pegs bring usually a good primary stability

: 10 and 15 mm (in the majority of the cases)

or 20, 25, 30 mm

The most frequent cause of revision is cemented cups with bone defects

corresponding to the amount of cement: 91 cases

Revision of non-cemented cups : 29 cases

Revision of cemented acetabular rings previously used for revision : 4 cases

128 acetabular revisions (11 infected)

• 75 complete revisions

• Previous operations : 1 to 8• Previous surgery : 9.8 ± 5 years

• Females : 88• Mean age : 64.4 ± 11 Ys• Mean follow-up : 4.6 y ± 1.7 (1 to 7 y)

• One surgeon, one technique

Material

Acetabular reconstructionAcetabular reconstruction

Simple prolongation of the posterior incisionSimple prolongation of the posterior incision

• Iliac crest autograft : 85• Bone from reaming : 33 • Opposite femoral head : 1

} } 93 %93 %

Acetabular reconstruction Acetabular reconstruction

• Iliac crest autograft : 85• Bone from reaming : 33 • Opposite femoral head : 1

• + Allograft :

1 femoral head : 43

2 femoral heads : 4

3 femoral heads : 2

• + bone substitute : 6

Iliac crest is grafted : 38 cases

} } 93 %93 %

}} 38 %38 %

Prolongation of the posterior approach toward the posterior iliac crest

Prolongation of the posterior approach toward the posterior iliac crest

Preservation of the vascularisation and inervation of the muscle

Prolongation of the posterior approach toward the posterior iliac crest

Preservation of the vascularisation and inervation of the muscle

Prolongation of the posterior approach toward the posterior iliac crest

Preservation of the vascularisation and inervation of the muscle

Paprosky : Type I (n = 31)Paprosky : Type I (n = 31)

Easy cases : graft into the holes, sufficient contact of the

cup with the host bone

Paprosky : Type II (n = 63)Paprosky : Type II (n = 63)

• The cup may be stabilised between the 2 columns

• Press-fitting the acetabular component is often possible

• 1 iliac crest is sufficient

A (n = 20) B (n = 22) C (n = 21)

- Autograft into the holes and for the roof reconstruction- Bone is impacted with the « trial cup »- Stabilisation by press-fitting the cup between the 2 columns + 6 pegs

Paprosky : Type II (n = 63)Paprosky : Type II (n = 63)

Massive bone graft is necessary for the reconstruction of :

- the centre

- the columns

- the roof

Paprosky :Paprosky : Type III (n = 32)Type III (n = 32)

III A III A (n = 22) (n = 22) III B III B (n = 10)(n = 10)

The reconstruction of a column is made after the cup has been fixed to the host bone and to the graft

1 - Fixation of the component with pegs2 - Spongious autograft is placed on the HAP coating3 - The bone block is then fitted on the cup by 1 or 2 pegs

(or 1 adjusting srew) inside outside

Adjusting screws may be used to fit the graft against the cup

Or for the primary stabilisation of the cup

It is recommended to replace the screws by pegs for definitive fixation

The use of screws is not recommended usualy

Stability of the implantsStability of the implants

• Press-fit alone : 45

• Stability attained by the use of pegs : 83

The divergent pegs bring a complementary stability to cup

6 years

The stabilisation of the cup is obtained with graft incorporation

and remodelling under load-bearing conditions

Stability of the implantsStability of the implants

Immediate (partial) : 25

4 to 6 weeks : 48

2 to 3 months : 55

Weight load-bearingWeight load-bearing

ComplicationsComplications

• Dislocations (2 first months) : 9• Trochanteric non-unions : 6

(4 had previous non-unions)• Ossifications : 1• Infections : 3 (recurrence for 3 of 11 previous infections)

Cup + stem 75 casesCup + stem 75 cases• Blood loss : 1075 ml ± 883 (100-4500)

• Drainage : 650 ml ± 365 (20-1900)

• Op time : 192 min ± 60 (90-345)

Cup alone 53 casesCup alone 53 cases• Blood loss : 645 ml ± 534 (200-3400)• Drainage : 555 ml ± 293 (20-1170)

• Op time : 160 min ± 38 (90-300)

OperationOperation

Diameter of the cups

0

5

10

15

20

25

30

38 42 46 50 54 58 62

cupule enlevée

cupule "Spring"

Diameter of the cupsDiameter of the cups

CasesCases

Removed cups :Removed cups :

49.6 mm49.6 mm + cement+ cement

New cups :New cups :

55.9 mm55.9 mm

The mean diameter of the new cups increases, but the cement is replaced by bone graft

Cement Bone graft

Removed cups :Removed cups :

49.6 mm49.6 mm + cement+ cement

New cups :New cups :

55.9 mm55.9 mm

EvaluationEvaluation

Radiographic measurements• Incorporation /radio lucent line

• Stability in the 3 planes

- Numerised X-rays

- Precise measurements

(special software : “MetrOs” C. Falaise)

Functional value• PMA Score (Postel - Merle d'Aubigné)

• Lost for follow-up : 3

• Deceased : 8

• Revisions : 11• Loosening : 9• Infection : 2

• Patients reviewed : 102

Results

• Excellent : 69 • Good : 29 • Fair: 10 • Poor : 1

• Impossible to estimate : 27

Postel-Merle d’Aubigné score (18 pts)Postel-Merle d’Aubigné score (18 pts)

16.4 ± 2 / 1816.4 ± 2 / 18

The results are also influenced by the status of the femur

Type I Type 2 A Type 2 B Type 2 C Type 3 A Type 3 B

Excellent 16 15 11 10 4 0Good 7 3 7 8 3 0Fair 4 0 2 1 1 1Poor 1 0 0 0 0 0

The results are good for the 3 types of Paprosky

Results

• Complete healing : 94

• Pain at the iliac crest : 3

• Poor active abduction : 22

Results

Radio lucencies

• None : 87.7 %

• Zone I : 3.3

• Zone II : 1.6

• Zone III : 3.3

• Zone I,II : 0.8

• Zone II,III : 1.6

• Zone I,II,III : 1.6

Radiological results manual measurements

(Failed cases included)

• 86 % of the implants are stable at visual examination no migration, no radio-lucent line

• Vertical migration

2 to 6 mm : 3

> 6 mm : 5• Medial migration

2 to 4 mm : 2

> 4 mm : 7 • Verticalisation : 5.5 %

Important displacement : 7 cases

Revised by the same cup : 5

Computerised measurements

• Scanner Vidar• Definition : 150 Dot per inch• Selection 1 Pixel : 0.17 mm• Special software «MètrOs» (C. FALAISE)

• Navigation into the image with magnification

• Adjustment of the luminosity and contrast

• Scale adapted to the size of the implants

• Geometric constructions and calculation of index automatically

• « EBRA » method (Krismer - Innsbruck)– 6 index (3 longitudinal, 3 transversal)– 11 measurements– Accuracy : 0.7 mm

Computerised measurements Scale adapted to the size of the implants

Computerised measurements1) Ascension (1st measurement)

Computerised measurements Ascension (2d measurement)

Computerised measurements 2) Lateralisation 1

Computerised measurements Lateralisation 2

Computerised measurements 3) Inclination

Computerised measurements 4) Version

sin() = Rp/Rc= sin-1(Rp/Rc)

« EBRA » method

• Krismer et coll. 1995 (Innsbruck) • Control of mistakes due to incidence variations• Comparability of 2 films by measuring the position of constant

anatomical landmarks • Difference in size = Comparability Index

• For an index limited to 3 mm, the precision is ± 0.7 mm for the

experimental model and ± 1 mm in clinical study

Comparability of 2 films by measuring the position of constant anatomical landmarks

Longitudinal L1 - 2

6 index (3 longitudinal, 3 transversal)

Longitudinal L2 - 3

Comparability of 2 films by measuring the position of constant anatomical landmarks

6 index (3 longitudinal, 3 transversal)

Transversal M1 - 2

Comparability of 2 films by measuring the position of constant anatomical landmarks

6 index (3 longitudinal, 3 transversal)

Transversal M 2 - 3

Comparability of 2 films by measuring the position of constant anatomical landmarks

6 index (3 longitudinal, 3 transversal)

Post-op

Inclination : 49° ± 7,5

Anteversion : 17.1° ± 9.9

Follow-up : 4 years

Inclination : 48.7° ± 9.8

Anteversion : 19.5° ± 12.4

Inclination and anteversion of the cups

Computerised measurements

Computerised measurements

Vertical  plane

M - 1SD M + 1SD M + 2SD

Male 12 16.5 ± 4 21 25.5lowering Normal Ascension +

Female 11 16.1 ± 4 21 25

Horizontal plane

M - 1SD M + 1SD

Male 26 31 ± 5 36

Medial Normal Lateral

Female 21 25 ± 4 30

Position of the cup / U

Position of the cup / U ligne

Hip centre correct : 43 %

Migrations

Migrations = 45 % with computerised measurements

= 14 % visual method (migrations > 3mm)

Literature : maxi 9 %

Callaghan 9 % 4 years (JBJS 1985)

Kavanagh 9 % 4.5 years (JBJS 1985)

EBRA is the best method to detect migrations

(except RSA : roentgen stereophotogrammetry)

Ilchmann T. J. Arthroplasty 1992

Post op 6 months Stable after 1 year

1 example of verticalisation and ascencion

Stable Migration Total

type 1 15.1 9.2 24.4

type 2A 9.2 5.9 15.1

type 2B 10.9 5.0 16.0

type 2C 9.2 7.6 16.8

type 3A 7.6 10.9 18.5

type 3B 3.4 5.0 8.4

Consequences of migation when using screws = wear or screw fracture

The stability of a cup is achieved by bone remodeling.

We consider that a small migration is a normal phenomena

(proved by computerised measurements)

Postop 1 year

Mobility between the cup and the screws has consequences :

Impression in the polyethylene

±  metallic wear 

± fractures of the screws

The concept of “migration en bloc”The concept of “migration en bloc”

The pegs tend to limit the migration of the cup but should this occur, The pegs tend to limit the migration of the cup but should this occur, they migrate together in the same directionthey migrate together in the same direction

Failed revision Successfull revision Only 3 pegs with 6 pegs

+ 5 years

5 cups placed with screws failed and they had been

revised with a similar cup with pegs

5 ans

5 years

5 years

6 years

13 infected cases

Two-steps revision

3 recurences of infection finally healed

The limits of this cup

Type 4

Destruction of the roof and 2 columns

+ destruction of inferior bone

Failure of a 1rst revision using a cemented ring (Kerboul) Protrusio (6 years later)

What can we do for large defects « type 4 » ?

Granuloma + cement

The host bone and the cancellous bone graft cannot find any possibility of ingrowht on

this surface

Wagner’s acetabular ring for revision and massive bone graft

Cementless and metal on metal

Ti-6Al-7Nb Protasul TM

A part of a femoral head is placed in the defect

Cortico-spongious blocks to reconstruct the columns and the roof

Spongious morsellised bone (auto and allo graft) cover the precedent graft

The Wagner ’s ring is impacted and fixed with screws

Acetabular reconstruction with 3 femoral

heads + 80 cc of morsellised bone graft

The new Wagner’s ring (for type 4)

2 advantages : cementless ( Ti coating for bony integration )

and metal on metal

1 drawback : Migration is bound to happen ( problem with the screws)

pegs for future ??

Some examples of « Spring » cup

Failure of other kinds of revision rings

Failure of other kinds of revision rings

4 years

4 previous operations

Op. 2Op. 2 Op. 3Op. 3 Op. 4 Op. 4

Op. 5Op. 51 iliac crest +1 iliac crest +

1 femoral head1 femoral head

Face + 5 ans

7 years

Op. 5Op. 5 1 iliac crest + 1 femoral head1 iliac crest + 1 femoral head

The polyethylene debris are responsible for the loosening of the THA

Foreign bodies Granulomas

Acetabular reconstruction is often associated with femoral problems

Polyethylene and metal-back must be eradicated

Alumine - polyéthylèneAlumine - alumine

Zircone - zircone

Alumina on alumina

Metal on metal

Polyethylene must be replaced by better materials

Cup with pegs 2d generation (Cedior-Sulzer)

- Ti-6Al-7Nb Protasul

- 7 pegs- Metal / metal (metasul)

54 cases (since 6/2000)

Follow-up < 1 year

11 months

• Incorporation-stability of the cup :

success rate : 96 % in types 1,2,3(follow-up : 1 to 7 years)

• Restoration of bony structures :

autograft ++ or auto + allograft

ConclusionsConclusions

10 m

• Usefulness of non cemented cups (HAP or Ti)

• Interest of the pegs fixed to the cup

• Pegs are preferable to screws

• Pegs do not interfere with small migration during

osteo-integration

ConclusionsConclusionsConclusionsConclusions