Management of types III and IV acetabular deficiencies with the longitudinal oblong revision cup

The Journal of Arthroplasty Vol. 21 No. 6 2006

Management of Types III and IV Acetabular

Deficiencies With the Longitudinal Oblong

Revision Cup

Antonio Herrera, PhD, Angel Antonio Martınez, MD,Jorge Cuenca, MD, and Vicente Canales, MD

From the Service oUniversity Hospital, Z

Submitted June 1No benefits or fuReprint requests:

n815, 48B, 50008 Zan 2006 Elsevier I0883-5403/06/19doi:10.1016/j.arth

Abstract: Thirty-five longitudinal oblong revision (LOR) cups were used to

reconstruct 29 type III and 6 type IV acetabular defects. Intraoperatively, we

considered that cup contact was complete when we achieved a continuous contact

between the cup periphery and the acetabular rim. When there were areas with a

lack of contact, we considered that the contact was partial or incomplete. All patients

were followed up for 4 to 8 years (mean = 6.3 years). At the latest follow-up, 30 cups

were stable (85.8%) and 5 had migrated (14.2%). We found a significant relation

between incomplete cup contact with the acetabular rim and subsequent failure

( P = .042). The abduction angle was significantly increased in the group of unstable

cups ( P = .032) because of the migration of the acetabular component that became

more vertical. Pain, limp, use of walking aids, functional level, and limb-length

discrepancy significantly improved postoperatively ( P b .0001). The Harris hip score

improved from a mean preoperative score of 37 points to that of 79 points ( P b .01).

This implant showed satisfactory stability at early to midterm follow-up. Key words:

acetabular defect, hip arthroplasty, longitudinal oblong revision cup.

n 2006 Elsevier Inc. All rights reserved.

The reconstruction management of major acetabu-

lar bone defects remains a challenging problem in

revision total hip arthroplasty.

Standard porous-coated hemispherical cups have

provided excellent results in acetabula that have an

intact rim of bone [1-7].

Oversized hemispherical cups that convert a

deficient acetabulum into a hemisphere with an

intact rim of bone have also given good results [8].

However, if an acetabular defect is large, stan-

dard or oversized hemispherical cups may not

allow achieving enough stability. In such cases,

857

f Orthopedic and Trauma Surgery, Miguel Servetaragoza, Spain.4, 2004; accepted August 5, 2005.

nds were received in support of the study.Antonio Herrera, PhD, Avda Cesareo Aliertaragoza, Spain.nc. All rights reserved.06-0004$32.00/0.2005.08.026

several options for reconstruction have been used,

including structural bone grafting [9-12], impacted

morcellized cancellous bone grafting and cement

[13-15], antiprotrusio cages or reinforcement rings

[16-22], oblong [23-26] or bilobed [27-29] cups

inserted without cement, and stemmed cups [30].

The use of large structural allografts has not

given uniformly good results. The long-term fail-

ure rate reported has oscillated between 13% and

50% [9-12].

Antiprotrusio cages and reinforcement rings

have provided a midterm rate of success that has

oscillated between 80% and 90% [16-22].

Bilobed oblong porous-coated acetabular com-

ponents have been reported to have a midterm

loosening rate between 0% and 24% [27-29].

There are few reports about the use of oblong but

not bilobed porous-coated components. Early ex-

perience was very limited, with some short series

reported [24-26].

858 The Journal of Arthroplasty Vol. 21 No. 6 September 2006

A long series has been published by Kfster et al

[23], reporting a favorable midterm result in 98%

of cases.

A partially hydroxyapatite-coated stemmed ace-

tabular cup with morcellized allograft has been

used by Badhe and Howard [30] in the manage-

ment of severe acetabular deficiencies. Early results

have shown encouraging restoration of bone stock,

with no case of aseptic loosening.

The purpose of our study was to evaluate the

results of using a longitudinal oblong revision

(LOR) cup in the management of types III and IV

acetabular defects.

Materials and Methods

Patients

Between January 1995 and October 2000, 35 pa-

tients (22 men [63%] and 13 women [37%]) under-

went acetabular reconstruction using an LOR

component. Their mean age was 63.8 years (range =

36-79 years).

The indications for LOR cup implantation were

aseptic loosening in 31 patients (88.6%), dysplasia

of the hip because of congenital subluxation that

caused a dysplastic hip with a defect in the superior

aspect of the acetabulum in 1 patient (3%), and

reimplantation after resection arthroplasty in

3 patients (8.6%).

The prerevision acetabular bone deficiency

was categorized according to the classification of

D’Antonio et al [31]. There were 29 type III (83%)

and 6 type IV (17%) defects. The follow-up period

ranged from 4 to 8 years (mean = 6.3 years), except

for the 2 cases that failed 1 year postoperatively and

required a new revision.

All cases were operated by the same group of

surgeons who used this cup. Other surgeons in our

center used other techniques, such as morcellized

cancellous bone grafting and cement as well as

reinforcement rings.

Revision Cup

The LOR cup (Allopro Sulzer, Winterthur, Swit-

zerland) consists of a titanium shell and a polyeth-

ylene inlay. It has an oblong shape with the

superoinferior dimension greater than the antero-

posterior dimension. The transverse diameter ranges

from 52 to 72 mm, in 4-mm steps. There are 2 shells

available for each transverse diameter, 1 elongated

by 6 mm and another 1 by 12 mm longitudinally.

Two rows of holes are arranged parallel to the outer

rim of the shell to take the titanium screws. The

polyethylene inlay has the articular surface central-

ly positioned in the 6-mm longitudinally elongated

sockets and central or 6 mm caudally displaced in

the 12-mm elongated sockets.

Operative Technique

A posterolateral approach was used in 28 cases

(80%) and an anterolateral approach was in

7 (20%). The acetabulum was prepared with

spherical reamers by which the longitudinal

dimension of the acetabulum was widened, re-

moving protrusions of the bony bed. The ante-

roposterior diameter of the acetabulum was

preserved. Defects were filled with bone chips in

all cases. Structural allografts were used in 2 cases.

Morcellized allograft was added in all cases. We

considered that cup contact was complete when

intraoperatively we achieved a continuous contact

between the cup periphery and the acetabular rim.

When there were areas with a lack of contact, we

considered that the contact was partial or incom-

plete. Cup contact with the acetabular rim was

considered complete in 30 cases (85.7%) and

partial in 5 (14.3%), with a lack of contact of

20% in 3 cases and of 30% in 2 cases in which

structural allograft was added. An average of

3.8 screws (range = 2-7) was used for fixation.

Usually the best screw fixation was obtained

superiorly, but additional stabilization can be

achieved by placing further screws in the pubis

and ischium. The polyethylene inlay had the

articular surface centrally positioned in 18 cases

(51.4%) and eccentrically in 17 (48.6%). Of the

35 hips, 19 had loose femoral components, which

were revised; 13 had well-fixed femoral compo-

nents (5 cemented and 8 cementless), which were

not revised; and 3 had a resection arthroplasty and

had no femoral component. Of the 19 hips in

which a femoral component was implanted, 8 were

implanted with an anatomical revision stem with

hydroxyapatite coating (Howmedica, Rutherford,

NJ) and 11 were with a straight revision stem with

hydroxyapatite coating (DePuy, Warsaw, Ind). A

28-mm head size was used in all the patients.

Postoperatively, protected weight bearing for

3 months with bilateral crutches was allowed,

except for patients with type IV defect, who were

advised non–weight bearing for 3 months.

Radiographic Assessment

Anteroposterior and lateral radiographs were

made before surgery and immediately after sur-

gery, at 3 months, at 6 months, at 1 year, and then

at 1-year intervals.

Fig. 1. Radiographic assessment. a indicates height of

the hip center; b, horizontal location of the hip center; c,

abduction angle; d, height of the cup.

The Longitudinal Oblong Revision Cup ! Herrera et al 859

Preoperatively, the following parameters were

measured (Fig. 1):

– the acetabular deficiency according to the classi-

fication of D’Antonio et al [31];

– the height of the hip center;

– the horizontal location of the hip center;

– the abduction angle measured from the horizon-

tal line through the inferior margin of both

teardrops to the line through the inferior limit

of the cup; and

– the height of the inferior edge of the cup, which

was the distance between the inferior edge of the

cup and the interteardrop line (a positive mea-

surement indicated that the caudal edge of the

cup was proximal to the line and a negative

measurement indicated that caudal edge of the

cup was distal to the line).

Postoperatively, evaluation included the same

parameters except for the acetabular defect. We

classified the stability of the cups at the latest

radiographic evaluation as (1) stable, when there

was no definite migration, no continuous radiolu-

cent line wider than 2 mm at the bone-cup

interface, no radiolucency adjacent to screws, and

no breakage or back out of screws; (2) probably

unstable, when there was no definite migration but

there was breakage or migration of screws or

a continuous periacetabular radiolucent line

wider than 2 mm; (3) unstable, when there was

definite migration (N48 of change in the abduction

angle or N4 mm of medial or superior movement of

the cup).

Clinical Evaluation

Several parameters were assessed preoperatively

and at the latest follow-up evaluation: the Harris

hip score, the pain, the limp, the use of walking

aids, the functional level, and the limp-length

discrepancy.

Patient satisfaction was subjectively measured by

asking the following 3 questions:

Has the operation increased function and daily

activity?

Has the operation decreased hip pain?

Are you satisfied with the result of the operation?

Statistical Methods

Statistical analysis was performed with the

Wilcoxon signed rank test, Fisher’s Exact test, or

2-tailed unpaired Student’s t test.

Results

Of the 35 patients, 1 died, in whom the cup was

stable, after the 5-year control. All patients had a

full clinical and radiographic follow-up.

Radiographic findings

The following radiographic findings were noted:

– The preoperative average height of the hip

center was 37.9 mm (range = 18-82 mm). The

postoperative average height of the hip center was

28.6 mm (range = 12-51 mm). The hip center was

lowered an average of 9 mm (range = 4-30 mm).

– The preoperative average horizontal location of

the hip center was 40.4 mm (range = 28-71 mm).

The postoperative average horizontal location of

the hip center was 35.6 mm (range = 22-58 mm).

This location was an average of 4.7 mm (range =

0-14 mm) medial to the preoperative position.

860 The Journal of Arthroplasty Vol. 21 No. 6 September 2006

– The preoperative average abduction angle was

55.78 (range = 208-1148). The postoperative

average abduction angle was 49.28 (range =

308-728). The abduction angle was decreased an

average of 6.48 (range = 08-428).– The preoperative average location of the inferior

edge of the cup was 9.3 mm (range = �7 to

42 mm). The postoperative average location of

the inferior edge of the cup was �2.4 mm

(range = �13 to 26 mm). This edge went down

an average of 11 mm (range = 0-18 mm).

– At the latest follow-up, 30 cups were stable

(85.8%; Fig. 2A-C) and 5 components (14.2%)

were unstable. These 5 components needed a

revision. Of these cups, 2 failed 1 year after

surgery (Fig. 3A-C) and 3 did 4 years postoper-

Fig. 2. A, Anteroposterior radiograph of the pelvis of a 63-ye

12 years previously. B, The type III acetabular defect was revise

after the revision.

atively. In addition, 4 of these unstable compo-

nents had been implanted in type III defects and

1 was in a type IV defect.

The abduction angle was significantly increased in

the group of unstable cups ( P = .032) because of the

migration of the acetabular component that became

more vertical. There was a statistically significant

relation between incomplete cup contact with the

acetabular rim and subsequent failure ( P = .047).

We did not find significant differences between

the groups of stable and unstable cups respect to

patient age, patient body weight, number of screws

used for stabilization, acetabular deficiency, post-

operative height of the hip center, postoperative

horizontal location of the hip center, postoperative

ar-old woman who had had a right total hip arthroplasty

d using an LOR component. C, The cup was stable 5 years

Fig. 3. A, Anteroposterior radiograph of a 72-year-old

woman who had had a right total hip arthroplasty

14 years previously. B, The type IV acetabular defect

was revised using an LOR component and morcellized

bone graft. C, The cup was loose 1 year postoperatively.

The Longitudinal Oblong Revision Cup ! Herrera et al 861

height of the inferior edge of the cup, and use of

central or eccentric polyethylene.

Clinical findings

The following clinical findings were noted:

– The mean preoperative Harris hip score was

37 points (range = 7.5-80 points). The mean

hip score at the latest follow-up was 79 points

(range = 42-94 points). The improvement was

statistically significant ( P b .01).

– Pain before the operation was severe in 23 hips

(65.7%) and moderate in 12 (34.3%). At the

time of the latest follow-up, 16 hips (45.7%)

were pain free, 14 (40%) were mildly painful,

2 (5.7%) were moderately painful, and 3 (8.5%)

were severely painful. Overall, pain had signifi-

cantly decreased postoperatively ( P b .0001). Of

the 5 patients who had a loose acetabular

component, 2 had moderate pain and the other

3 had severe pain.

– Preoperatively, 29 patients (82.9%) had a severe

limp and 6 (17.1%) had a moderate limp. At the

latest postoperative follow-up, 11 patients

(31.4%) had no limp, 19 (54.2%) had a moder-

ate limp, and 5 (14.2%) had a severe limp.

Overall, limp had significantly decreased postop-

eratively ( P b .0001).

– Preoperatively, 33 patients (94.3%) needed full-

time support and 2 (5.7%) needed a cane for

long walks. At the latest postoperative follow-up,

8 patients (22.9%) did not need assistive devices

to walk, 19 (54.3%) used a cane on long walks,

and 8 (22.9%) needed full-time support. Overall,

the need for walking aids had significantly

decreased postoperatively ( P b .0001).

– Preoperatively, 4 patients (11.4%) could walk

4 to 6 blocks, 10 (28.6%) could walk 2 to

3 blocks, and 21 (60%) could walk indoors only.

At the latest follow-up, 10 patients (28.6%)

could walk an unlimited distance, 18 (51.4%)

could walk 4 to 6 blocks, 3 (8.6%) could walk 2 to

3 blocks, and 4 (11.4%) could walk indoors only.

Overall, functional level had significantly in-

creased postoperatively ( P b .0001).

– The average preoperative limb-length discre-

pancy was 1.8 cm shorter on the involved side

(range = 0-6.3 cm). Ten patients (28.6%) had a

discrepancy of 1 cm or less, 11 (31.4%) had a

difference between 1 and 2 cm, and 14 (40%)

had a difference of more than 2 cm. The average

postoperative discrepancy was 0.5 cm. Thirty

patients (85.7%) had a discrepancy of 1 cm or

less, 3 (8.6%) had a difference between 1 and

2 cm, and 2 (5.7%) had a difference of more than

2 cm. The average improvement was 1.3 cm

(range = 0-4.8 cm). This improvement was

statistically significant ( P b .0001).

– Of the patients, 30 (85.7%) were satisfied with

the result of the operation, 32 (91.4%) had

improved function and daily activity, and

32 (91.4%) had less pain as compared with their

pain before the operation.

862 The Journal of Arthroplasty Vol. 21 No. 6 September 2006

Complications

There were 3 intraoperative femoral fractures

around the tip of the stem that were treated with

internal fixation.

A total of 3 patients had sciatic nerve palsies, 1

of which resolved completely and 2 persisted,

consequently requiring the patients to use an

ankle-foot orthosis.

There were 2 cases of deep venous thrombosis,

2 cases of late femoral fractures (1 of them treated

surgically and the other with rest and a thigh

orthosis), 2 cases of early dislocation that had no

additional dislocation after an initial closed reduc-

tion, 1 case of late dislocation that did not recur

after closed reduction, and 4 cases of heterotopic

ossifications that caused a moderate limitation of

joint mobility.

A total of 5 patients required cup revision because

of cup failure, 2 of them 1 year after surgery and the

3 remaining 4 years postoperatively.

There was one case of superficial wound in-

fection that was treated by debridement and anti-

biotic therapy.

There was no case of pulmonary embolism.

Discussion

Several technical approaches have been used to

overcome the difficulties in revising failed acetab-

ular components.

Minor defects can usually be managed with

standard implants. In larger defects, there are

several alternatives. The use of structural allog-

rafts is controversial. The failure rate has ranged

from 13% to 47%, and acetabular failure has in-

creased significantly with longer follow-up eva-

luation [9-12].

Acetabular reconstruction with impacted morcel-

lized cancellous bone autograft and a cemented cup

has been proven to provide a good long-term

result, with a survival rate of 94% [13-15].

Reinforcement rings and structural or morcel-

lized bone graft have been used successfully to

manage severe segmental or combined defects

where there is limited host bone available to

provide cup support [16-22]. Reported failure rates

have oscillated between 10% and 50%. The best

results have been obtained in cavitary deficiencies;

the worst, in combined defects.

Cementless acetabular components have been

used with satisfactory results [1-7], but their

problem is that it is not possible to obtain a good

fixation in large defects without using allografts.

The best results have been obtained in hips with

a bone defect of less than 30%; the worst, when the

bone defect was greater than 50% and a structural

bone graft was used to stabilize the prosthesis [2].

Large hemispherical cementless components

fixed with screws have been used successfully in

large defects [8], but the complication rate was

high (dislocation, late infection, trochanteric

osteotomy nonunion).

An important problem in revision arthroplasty is

that when we try to convert an oblong defect to a

hemisphere to insert an uncemented hemispheric

component, usually of extra large size, the required

reaming can damage the bone stock of the anterior

and posterior columns of the acetabulum. An

alternative option of reconstruction that avoids

large allografts or excessive reaming is the use of

porous-coated oblong acetabular implants. There

are 2 types of oblong cups: the bilobed oblong

acetabular component and the LOR cup.

The theoretical advantages of these cups are an

increased surface contact area between the porous

component and native host acetabular bone,

the avoidance of structural bone grafts, and the

potential to normalize the center of rotation. The

main disadvantage is the lack of bone stock

restoration. There are few published clinical results

about these cups.

Bilobed oblong acetabular cups have been used

by several authors [27-29]. DeBoer and Christie

[29] and Berry et al [27] reported good results at

early to midterm follow-up. They recommend this

implant for large superolateral bone deficiencies.

Chen et al [28] reported an early rate of loosening

of 24%. They believe that this device is indicated in

an oblong-shaped acetabular defect, with an intact

medial wall of the acetabulum, when a surgeon

wants to correct an elevated hip center.

Longitudinal oblong revision cups have been

used by Sutherland [24-26] and by Kfster et al

[23]. Initial series were very small [24-26]. The

largest series was published by Kfster et al [23],

who reported favorable results in 98 acetabular

revisions at midterm follow-up, with a success

rate of 98%. In this series, there were 21%

segmental deficiencies, 42% cavitary defects, 32%

combined defects, and 5% pelvic discontinuities.

This could explain these excellent results, because

the primary stability of the cup usually is very

good in segmental or cavitary defects. In our

series, the LOR cup was used in types III and IV

defects. Our loosening rate was higher than that

of Kfster et al [23], but they reported that all cup

migrations observed in their series occurred in

major defects.

The Longitudinal Oblong Revision Cup ! Herrera et al 863

We think that the LOR socket is suitable to be

used in types III and IV defects. In type IV defects,

the possibility of obtaining fixation with screws

in the ilium, pubis, and ischium allows achieving

an acceptable stabilization of the pelvic discontinu-

ity. Owing to the oblong shape of the defect, the

form of this cup allows better contact with the

remaining bone and loads distribution than if it

were hemispherical. However, we think that the

stability of the reconstruction could be improved by

treating pelvic discontinuities with plate fixation

before reconstructing the defect with the LOR cup

in type IV defects.

Oblong cups are designed to restore the position

of the hip center. In our series, we did not find

a significant relationship between the postoperative

height of the hip center and the outcome. We

found that an increased postoperative abduction

angle and an incomplete contact of the cup with the

acetabular rim significantly worsened the outcome.

Schutzer and Harris [32] have recommended using

a high hip center technique by means of a standard

small hemispherical cup screwed high on the ilium

to bypass the acetabular defect and gain stability on

healthy host bone. However, Yoder et al [33] noted

that cups placed in a nonanatomical, superolateral

position had a significantly higher femoral compo-

nent loosening rate compared with those placed in

an anatomical position.

The midterm clinical and radiographic results

using the LOR cup in our series of patients with

types III and IV defects have been encouraging. The

longitudinal oblong form of the cup obviates the

need for bulky structural allografts to fill the

superior defect or the need for excessive reaming

to obtain a hemispheric acetabulum. The initial

anchorage of the implant was achieved by means of

the contact of the cup with the acetabular rim and

the added screw fixation.

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