JL. Lerat, C. Falaise LYON - France EFORT Congress (June 2001- Rhodes) The results of cementless cups (HAP or Ti) with additional divergent pegs and acetabular reconstruction with graft in failed THA The concept of “migration en bloc” (1993) JL. Lerat, C. Falaise LYON - France EFORT Congress (June 2001- Rhodes)

Special Cup with pegs for revision 1st model : «Spring» ( 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

Material 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

Acetabular reconstruction } 93 % Iliac crest autograft : 85 Bone from reaming : 33 Opposite femoral head : 1 Simple prolongation of the posterior incision

Acetabular reconstruction } 93 % 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 } 38 % Iliac crest is grafted : 38 cases

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) Easy cases : graft into the holes, sufficient contact of the cup with the host bone

Paprosky : Type II (n = 63) A (n = 20) B (n = 22) C (n = 21) The cup may be stabilised between the 2 columns Press-fitting the acetabular component is often possible 1 iliac crest is sufficient

Paprosky : Type II (n = 63) - 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 III (n = 32) III A (n = 22) III B (n = 10) Massive bone graft is necessary for the reconstruction of : - the centre - the columns - the roof

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 pegs 2 - Spongious autograft is placed on the HAP coating 3 - The bone block is then fitted on the cup by 1 or 2 pegs (or 1 adjusting srew) inside outside

The use of screws is not recommended usualy 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

Stability of the implants Press-fit alone : 45 Stability attained by the use of pegs : 83 The divergent pegs bring a complementary stability to cup

Stability of the implants 6 years The stabilisation of the cup is obtained with graft incorporation and remodelling under load-bearing conditions

Weight load-bearing Immediate (partial) : 25 4 to 6 weeks : 48 2 to 3 months : 55

Complications 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)

Operation Cup + stem 75 cases Cup alone 53 cases Blood loss : 1075 ml ± 883 (100-4500) Drainage : 650 ml ± 365 (20-1900) Op time : 192 min ± 60 (90-345) Cup alone 53 cases Blood loss : 645 ml ± 534 (200-3400) Drainage : 555 ml ± 293 (20-1170) Op time : 160 min ± 38 (90-300)

Diameter of the cups Cases Removed cups : 49.6 mm + cement New cups :

Removed cups : 49.6 mm + cement New cups : 55.9 mm Cement Bone graft The mean diameter of the new cups increases, but the cement is replaced by bone graft Cement Bone graft

Evaluation Radiographic measurements Functional value 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 16.4 ± 2 / 18 Postel-Merle d’Aubigné score (18 pts) 16.4 ± 2 / 18 Excellent : 69 Good : 29 Fair: 10 Poor : 1 Impossible to estimate : 27 The results are also influenced by the status of the femur

Results The results are good for the 3 types of Paprosky

Results Complete healing : 94 Pain at the iliac crest : 3 Poor active abduction : 22

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 measurements 1) 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(a) = Rp/Rc a = 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 6 index (3 longitudinal, 3 transversal) Longitudinal L1 - 2

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

Computerised measurements Inclination and anteversion of the cups 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

Computerised measurements Position of the cup / U ligne Position of the cup / U 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 Post op 6 months Stable after 1 year

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

Postop 1 year 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 Consequences of migation when using screws = wear or screw fracture

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

Failed revision Successfull revision Only 3 pegs with 6 pegs 5 cups placed with screws failed and they had been revised with a similar cup with pegs Failed revision Successfull revision Only 3 pegs with 6 pegs + 5 years

5 years 5 ans

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

What can we do for large defects « type 4 » ? Failure of a 1rst revision using a cemented ring (Kerboul) Protrusio (6 years later)

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 Ti-6Al-7Nb Protasul TM Cementless and metal on metal

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

heads + 80 cc of morsellised bone graft 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

4 years Failure of other kinds of revision rings

Op. 5 4 previous operations Op. 2 Op. 3 Op. 4 1 iliac crest + 1 femoral head Face + 5 ans

Op. 5 1 iliac crest + 1 femoral head 7 years Op. 5 1 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

Polyethylene must be replaced by better materials Alumina on alumina Alumine - alumine Alumine - polyéthylène Metal on metal Zircone - zircone

- Ti-6Al-7Nb Protasul Cup with pegs 2d generation (Cedior-Sulzer) - Ti-6Al-7Nb Protasul - 7 pegs - Metal / metal (metasul) 54 cases (since 6/2000)

11 months Follow-up < 1 year

Conclusions 10 m 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

Conclusions 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