ACETABULAR RECONSTRUCTIONWITH ALLOGRAFTS, METALLIC ARMATURE

AND CEMENTED PROSTHESIS

TECHNIQUE AND LONG TERM OUTCOME

M. Kerboull

In the early 70’s, 5 years after we started using a metal-metal prosthesis (Mc Kee-Merle d’Aubigné) we had to deal with a high rate of acetabular loosenings

At 2 y. 10 %

At 10 y. 32 %

These loosenings were sometimes associated with

severe acetabular bone loss.

After some unsuccessful

attempts, filling the bone loss with

cement or a big socket it seemed

to us that

bony reconstruction with bone was absolutely necessary.

Because a great amount of bone was needed, the use of allografts was indispensable and in 1974 we

reactivated our bone bank which existedsince 1955 to fill it with femoral heads resected

during THR.

COCHIN BONE BANK

• 1955: PRESERVATION OF MASSIVE BONES

(femur, tibia, humerus) used for bone reconstruction in tumor surgery

• 1974: PRESERVATION OF FEMORAL HEADS• 1985: PRESERVATION OF MASSIVE BONES

sterilized by gamma radiation

---> Every year

350 femoral heads

80 massive bones

10.74 06.75

Sometimes, it was possible to repair a wide destroyed acetabulum witha big head without any metallic fixation

12.73 01.74

But the existence, not so rare, of a pelvic discontinuity forced us tofind a metallic device to secure the fracture

We have had since 1970 a hemispheric cross with 4 arms which was used, in the position of a St Andrew’s cross, with the branches bended on the acetabular rim, as an antiprotrusio cage.

1974 PRE-OP 1975 1 y PO

In 1974, to secure a pelvic discontinuity, I used this device, one branch bended in a hook inserted under the teardrop, the opposite screwed to the iliac bone, the others cut at an adequate length. This osteosynthesis, associated with autogenous graft to fill the bone defect, led to bone union within a year

1976 2 y PO 2000 26 y PO

1 year later, a prosthesis was implanted leaving the armature in place.At 26 y. PO, despite a fracture of the hook which occurred 3 y PO, a polyethylene wear of more than 7 mm without osteolysis, the cemented fixation of the socket is still strong and the function of the hip satisfactory.

In 1976, this hemispheric cross shaped stainless steel armature, with 4 branches, an inferior hook an a superior flange with 4 screw holes was manufactured by Howmedica.

It was more rigid and suitable, unique and symmetrical, of medium size.

FIRST ARMATURE 1976

It allowed a strong, fixation of a pelvic discontinuity and kept in place the grafts coming from a femoral head shaped into cubes and slices to exactly repair the bone defect.

PRE-OP

8 m PO

This reconstruction seemed strong enough to implant a prosthesis atthe same time.

In 1984 this armature became asymmetrical with an anterior branch shorter than the posterior to avoid any contact with the psoas tendon and give the opening plane an anteversion of 15°

1984

It also became multiple and there are now a right and a left series of 6 sizes

For sockets from 40 to 60 mm in outside diameter

It acts as a guide and a reinforcement for bone reconstruction

First intended to secure a pelvic discontinuity, this device has been

systematically used for 35 years every time a bone reconstruction was necessary

ACETABULAR METALLIC ARMATUREHEMISPHERIC CROSS

• STIFF enough to ensure a strong fixation of a pelvic discontinuity

• OPEN, flexible enough not to change the elasticity of the acetabulum

• Automatically provides the artificial hip with the right anatomic centre

• Partially unloads the grafts during their incorporation

PRINCIPLES OF SURGICAL TECHNIQUE

To restore normal anatomic conditions

-Acetabular cavity of normal size in an anatomic position- The choice of the armature to be implanted is guided by two references :

. A healthy controlateral hip, or a radiograph of the homolateral hip before it was destroyed.

. If these references are missing, the size of the bony cavity in its inferior part must be taken into account, knowing that after bone reconstruction, the anterior, posterior and medial walls must be at least 7 mm thick.

After cleaning the destroyed acetabulum, the selected device is put in place, the hookunder the inferior marginnear the ischium.Then the device is tiltedat 45°. This movementshould not tend to ejectthe hook from the teardrop. If it does, three possible causes must be explored: 1) The acetabular device is too large, try a smaller one. 2) The medial wall just above the teardrop is too thick, thin it down

with a rongeur or a gouge until the hook stays in the right position.

3) The inferior acetabular margin is destroyed by a polyethylene granuloma. It should be repaired with an allograft fragment before inserting the hook.

When there is major structural defect of the roof, the superior flange does not come into contact with bone. One must not place the device more vertical neither open it nor bend the flange to adapt it to the bone loss. On the contrary, the acetabular armature should be used as a guide to evaluate the size and location of bone defect as well as the shape and dimension of the allograft fragments needed to achieve bone reconstruction.

If there is a defect of the inferior margin, more or less extended to the medial wall, it is first repaired with a bone fragment of the adequate size and shape, wedged in between the edges of the defect to give the hook a solid grasp.

Then, the roof bone loss is filled with a bulky graft, if possible unique. This fragment is carefully shaped with the trabeculae properly oriented so that it can resist the pressure stresses in the bearing area. The superior part made convex accurately fits the dome, its inferior part made concave matches the convexity of the device. The flange of the device lies on its lateral part made of subchondral bone.

Two screws then fix the flange to the iliac bone, the first, the inferior screw, pass the graft through a reamed hole, directed up and back, to put the armature under tension and bites the sound bone near the sacro iliac joint. A second, usually anterior, is needed to stabilize the armature.

Anterior and posterior walls are repaired by embedding slice grafts between the remaining wall bone and branches of the armature. Cavitary defects of pubic bone and ischium, as well as the gaps between structural grafts are filled with impacted cancellous bone.

When there is a pelvic discontinuity with a wide gap, it is advisable to close it. This can be done easily using the armature, the hook inserted under the teardrop, a Steinman pin obliquely introduced through a screw hole. A lever movement of the Steinman pin brings the separate bones in contact. The reduction of the fracture is then secured with 2 or 3 screws and bone reconstruction done by wedging slice fragments between bone and branches of the armature.

When the reconstruction is achieved, a socket of adequate size is cemented into this restored and armed bony cavity.

- On a AP x-rays of the hip, the armature appears in a strict lateral view

- Obturator hook in close contact with the teardrop

- Screws directed up and back, bite the sound bone near the sacro iliac joint

You can find details of this technique in Surgical Techniques in Orthopaedics and Traumatology.This technique, we have been using for 35 years, have allowed us to cope with all the cases encountered on over 2000 in the Orthopaedic Department of Hospital Cochin Paris, and for myself on 700 cases.

SOME EXAMPLES

PRE-OP 1 m PO

In this case a major bone loss of the roof and a pelvic discontinuity.

Bony restoration has beendone with a unique bulkyfragment.

PRE-OP

Here, a Beechtol prosthesis in a big protrusion.

X-rays at 9 y. PO

PRE-OP

The same patient, the controlateralside, severe bone defect

But a simpler restoration.The result a 8 y. PO

PRE-OP

Third consecutive failure,with severe acetabular bone loss

X-rays, 3 y. PO

PRE OP

Here a cementless prosthesisin a high position

PO 4 m

Restoration of a wide superiordefect and implantation of the socket in an anatomic position.

PRE-OP

A big bone loss with a completedestruction of the roof, the innerwall and inferior acetabularmargin

Restoration of the inner wallwith a wide and thick sliceof femoral head.X-rays at 1 y. PO

GRAFT

CONSOLIDATION

1 m PO 6 m PO

Union of the grafts, together and with the host bone, has been obtained within 1 year, as it is shown in this case where demarcation between graft and host bone has disappeared 6 months after the operation.

PRE-OP

1 m PO

In this other case, where 3 fragments were used.

1 y PO

4 y PO

Consolidation is obvious at 1 y. PO

And perfect at 4 y. PO

PRE-OP 1 m PO

Here, two big superposed fragments were used to fill a wide superior defect.

18 m PO

3 y PO

X-rays at 18 months PO And 3 y. PO

GRAFT REMODELLING

1 m PO 2 y PO

Bone remodelling, which began at 2 years, proceded for 5 to 6 years in the bearing zone

4 y PO 7 y PO

As shown by this X-rays 4 y. PO And 7 y. PO

PRE-OP

1 m PO

2 y PO

As well as in the inner wall where at 2 y. PO remodelling is obvious

These radiological pictures strongly suggest that grafts are biologically and mechanically incorporated.

RADIOLOGICAL PICTURES

LONG TERM

At long term, there has been, up to now, no serious problem

PRE-OP

8 y PO

A case at 8 years with a beautiful bone remodelling

PRE-OP

1 y PO

Another, with the steps of bone remodelling.

At 6 y. PO And 10 y. PO

PRE-OP 19 y PO

A pelvic discontinuity Its result a 19 y. PO

PRE-OP

20 y PO

Another At 20 y. PO

PRE-OP1 m PO

On the left hipProgressive remodelling of the graft at 1 m. PO

10 y PO 18 y PO

PRE-OP

1 m PO

2 y PO

Right hip, same patientAcetabular protrusion

Partial resorption of a too thick graft fragment

10 y PO 18 y PO

And bone remodelling at 10 y PO

And 18 y. PO

RESULTS

Long term outcome of the technique was published 10 years ago in Clinical Orthopaedics and Related Research

MATERIAL

• 53 PATIENTS: 48 women, 5 men

• MEAN AGE: 58 years

• OPERATED ON FROM 1976 to 1986

• 60 ACETABULAR RECONSTRUCTIONS

• CONTINUOUS SERIES

• ONE SURGEON

• CHARNLEY-KERBOULL PROSTHESIS

MATERIAL

It was, most of the time, a failure of THR more often metal-polyethylene than metal-metal and for nearly 50 % a recurrent failure:

1 to 3 (near 1.7)

60 MECHANICAL ACETABULAR LOOSENINGS 4 Double cups

56 THR- Metal-Metal: 8- Metal-Polyethylene: 48

ACETABULAR DEFICIENCY

CLASSIFICATION

AAOS TYPE III 48 TYPE IV 12

SOFCOT TYPE III 48 TYPE IV 12

PAPROSKY TYPE III A 23 TYPE III B 37

FOLLOW-UP

They all had physical and radiologic examination at6 weeks, 3 months, 6 months, 1 year and every 2 years

Average follow up of the

Entire series 60 12.4 y. (5 to 24)

Deceased 8 (10 hips) (4 to 18 y. PO)

Lost 0

COMPLICATIONS

• 1 trochanteric non union• 1 deep veinous thrombosis (DVT)• 1 extensive haematoma (debrided)• 1 peroneal palsy• 0 infection• 0 dislocation

CLINICAL RESULTS(D’Aubigné score. max 18)

GLOBAL FUNCTION

BEFORE AFTER

11.7 17.7

EXCELLENT (18) 44

V. GOOD (17) 8

GOOD (16) 1

FAIR (15) 5

POOR (14) 2

BAD (13) 0

5380 %

RADIOLOGICAL RESULTS

SUCCESSES 57No graft resorptionNo acetabular loosening

FAILURES 3 (5 %)Graft lysis due to polyethylene wear (This is

different from early resorption which is extremely rare and occurs when the patient has developed antibodies against HLA of the graft)

Graft resorption led to break of armature or screws and socket loosening

2 were revised with the same technique and were successful 7

and 10 y. PO

10.86 1 y PO 10.88 3 y PO

This is one of them The first change was a breakof the armature at 3 y.

10.93 8 y PO 10.94 1 y PR

5 y. later graft resorption was complete, the device broken in 3 parts and the acetabular component loose

This case was revised with the same technique. Here the X-rays at 1 y. PO

X-rays at 7 y. PO

One could not be revised because of poor cardio vascular conditions

SURVIVAL CURVE(Acetabular component loosening as end point)

CONCLUSION

With a 92 % survival rate of the cemented fixation of the acetabular component at 16 y. and despite these few failures this technique can be regarded as reliable, even at long term.