ICL 7 & 8ICL 7 & 8Acetabular Bone Loss Acetabular Bone Loss

During Revision Total Hip During Revision Total Hip Replacement:Replacement:

Preoperative Investigation Preoperative Investigation and Planningand Planning

David G. Campbell, BMDavid G. Campbell, BMBassam A. Masri, MD Bassam A. Masri, MD Donald S. Garbuz, MDDonald S. Garbuz, MDClive P. Duncan, MDClive P. Duncan, MD

INTRODUCTIONINTRODUCTION The prevalence of hip replacements has The prevalence of hip replacements has

increased dramatically, and thus, so increased dramatically, and thus, so have the number of revision total hip have the number of revision total hip arthroplasty. This may be the largest arthroplasty. This may be the largest iatrogenic orthopaedic problem of the iatrogenic orthopaedic problem of the late twentieth century.late twentieth century.

When planning a revision hip procedure, When planning a revision hip procedure, it is useful to consider the acetabular it is useful to consider the acetabular and femoral components independently.and femoral components independently.

GENERAL GENERAL CONSIDERATIONSCONSIDERATIONS

Prior to Prior to acetabular acetabular revision, it is revision, it is imperative to imperative to devise a devise a preoperative plan. preoperative plan. The following The following factors must be factors must be considered: considered:

PATIENT FACTORSPATIENT FACTORS Age: patients are usually a decade or Age: patients are usually a decade or

more older than at the primary operationmore older than at the primary operation– This results in diminished health and This results in diminished health and

physiologic reserve and a greater risk of physiologic reserve and a greater risk of perioperative morbidityperioperative morbidity

Local complications: increased following Local complications: increased following revision hip surgeryrevision hip surgery– Increased dislocation rates-2 or more times > Increased dislocation rates-2 or more times >

than primary arthroplastythan primary arthroplasty– Increased nerve palsies-aprox. 3 times > with Increased nerve palsies-aprox. 3 times > with

revision arthroplastyrevision arthroplasty

PATIENT FACTORS CONTPATIENT FACTORS CONT Previous skin incisions: these suggest Previous skin incisions: these suggest

the approach that was previously takenthe approach that was previously taken– Whenever possible the previous incision Whenever possible the previous incision

should be used to avoid wound edge should be used to avoid wound edge necrosis, although unlike the knee, this is necrosis, although unlike the knee, this is rarely a complication.rarely a complication.

Hip range of motion: this can be an Hip range of motion: this can be an important indicator of heterotopic bone important indicator of heterotopic bone formation and joint contractureformation and joint contracture

Limb length discrepancies: extensive Limb length discrepancies: extensive bone loss is often associated both with bone loss is often associated both with shortening of the limb and with shortening of the limb and with decreased femoral offset. This causes decreased femoral offset. This causes a short and stiff joint and is often a short and stiff joint and is often difficult to mobilize unless an extensive difficult to mobilize unless an extensive soft-tissue release is performed.soft-tissue release is performed.– A special approach may be necessary for A special approach may be necessary for

wider exposure of the pelvis and femur.wider exposure of the pelvis and femur.

Morrey-factors associated Morrey-factors associated with an increased hip with an increased hip

dislocationsdislocations Female sexFemale sex Revision surgeryRevision surgery Posterior approachPosterior approach Mobile hipsMobile hips Decreased femoral offsetDecreased femoral offset MOST IMPORTANT: Acetabular MOST IMPORTANT: Acetabular

orientationorientation

PREOPERATIVE PREOPERATIVE INVESTIGATIONS TO RULE INVESTIGATIONS TO RULE

OUT INFECTIONOUT INFECTION Severe loss of bone stock, particularly within a Severe loss of bone stock, particularly within a

short period of time, should raise the index of short period of time, should raise the index of suspicion for occult infection.suspicion for occult infection.

A careful history and physical should precede A careful history and physical should precede any tests.any tests.– Persistent pain, despite unremarkable radiographsPersistent pain, despite unremarkable radiographs– Question pt regarding recent infections, such as Question pt regarding recent infections, such as

skin infections or ulceration, UTIs, dental infectionsskin infections or ulceration, UTIs, dental infections

Initial tests should include ESR and C-reactive Initial tests should include ESR and C-reactive protein level- if both are normal, and the Hx and protein level- if both are normal, and the Hx and PE are not suggestive of infection, no further PE are not suggestive of infection, no further tests are necessary.tests are necessary.

If the ESR and/or CRP are elevated, further tests If the ESR and/or CRP are elevated, further tests are indicated.are indicated.– A hip joint aspiration, with the pt off ABX for at least A hip joint aspiration, with the pt off ABX for at least

4 weeks, should then be performed. If the aspiration 4 weeks, should then be performed. If the aspiration is negative, and the suspicion remains high, it should is negative, and the suspicion remains high, it should then be repeated under arthrography or ultrasound. then be repeated under arthrography or ultrasound.

Other tests include various nuclear Other tests include various nuclear scans and if all remain inconclusive, scans and if all remain inconclusive, however, the suspicion remains high, a however, the suspicion remains high, a frozen intraoperative tissue section can frozen intraoperative tissue section can be obtained prior to revision surgery.be obtained prior to revision surgery.

If all of these remain negative the If all of these remain negative the surgeon can then proceed with the surgeon can then proceed with the revision total hip arthroplasty.revision total hip arthroplasty.

ANATOMY AND ANATOMY AND RADIOLOGIC EVALUATION RADIOLOGIC EVALUATION

OF THE ACETABULUMOF THE ACETABULUM– The hemipelvis can be thought of as an The hemipelvis can be thought of as an

inverted “Y”, with the limbs of the letter “Y” inverted “Y”, with the limbs of the letter “Y” representing the anterior and posterior representing the anterior and posterior columns straddling the acetabulum.columns straddling the acetabulum.

– The acetabulum can be divided into 4 regions:The acetabulum can be divided into 4 regions: The roof and superior rimThe roof and superior rim The posterior column and posterior rimThe posterior column and posterior rim The anterior column and anterior rimThe anterior column and anterior rim The medial wallThe medial wall

RADIOGRAPHSRADIOGRAPHS Judet views best Judet views best

enhance the enhance the acetabulum, they acetabulum, they include:include:– Iliac obliqueIliac oblique

posterior columnposterior column anterior rimanterior rim

– Obturator obliqueObturator oblique anterior columnanterior column posterior rimposterior rim

The acetabular tear figure The acetabular tear figure is a constant reference of is a constant reference of the medial acetabular wall the medial acetabular wall and is best evaluated by a and is best evaluated by a standard A/P radiograph.standard A/P radiograph.

Despite best efforts, Despite best efforts, however, this assessment however, this assessment may not be entirely may not be entirely accurate, and the surgeon accurate, and the surgeon has to be prepared to deal has to be prepared to deal with more severe bone with more severe bone defects at the time of defects at the time of surgery.surgery.

CLASSIFICATION OF CLASSIFICATION OF ACETABULAR BONE ACETABULAR BONE

DEFICIENCYDEFICIENCY The AAOS currently The AAOS currently

recommends the descriptive recommends the descriptive classification of D’Antonio.classification of D’Antonio.

Two basic categories are used: Two basic categories are used: segmental and cavitary segmental and cavitary– Segmental-any complete loss of Segmental-any complete loss of

bone in the supporting bone in the supporting hemispheric structure of the hemispheric structure of the acetabulum.acetabulum.

– Cavitary-localized volumetric loss Cavitary-localized volumetric loss of bone that does not disrupt the of bone that does not disrupt the acetabular rim.acetabular rim.

ENGH AND GLASSMAN ENGH AND GLASSMAN MODIFICATION OF THE MODIFICATION OF THE AAOS CLASSIFICATIONAAOS CLASSIFICATION

The modified The modified classification is classification is simpler and consists simpler and consists of three categories:of three categories:– Type I-mildType I-mild– TypeII-moderateTypeII-moderate– Type III-severe*Type III-severe*

*Protrusio acetabuli *Protrusio acetabuli and pelvic discontinuity and pelvic discontinuity are subcategories of are subcategories of type III bone losstype III bone loss

CHANDLER AND CHANDLER AND PENENBERG PENENBERG

CLASSIFICATIONCLASSIFICATION This classification This classification

is based upon the is based upon the anatomic division anatomic division of the acetabulum of the acetabulum into a superior into a superior wall, anterior and wall, anterior and posterior posterior columns, and a columns, and a medial wall.medial wall.

PAPROSKY PAPROSKY CLASSIFICATIONCLASSIFICATION

This system is designed to assess failed total hip This system is designed to assess failed total hip replacementsreplacements

The main parameters that are assessed are:The main parameters that are assessed are:– 1. the degree of superior migration of the cup- >2cm or not1. the degree of superior migration of the cup- >2cm or not– 2. lysis of the ischium-which is indicative of column bone loss2. lysis of the ischium-which is indicative of column bone loss– 3. the integrity of Kohler’s line-determines if anteromedial 3. the integrity of Kohler’s line-determines if anteromedial

portion can support a prosthesisportion can support a prosthesis– 4. the presence or absence of a teardrop-indicating whether 4. the presence or absence of a teardrop-indicating whether

the inferomedial is able to allow osteointegration of a porous-the inferomedial is able to allow osteointegration of a porous-coated component.coated component.

PAPROSKY PAPROSKY CLASSIFICATIONCLASSIFICATION

Three different Three different types of defects types of defects divided into divided into subcategories:subcategories:

PREOPERATIVE PLANNINGPREOPERATIVE PLANNING It is important to be aware of the It is important to be aware of the

limitations of assessing the bone limitations of assessing the bone deficiency preoperatively.deficiency preoperatively.

Frequently, the bone deficiency Frequently, the bone deficiency encountered after component removal is encountered after component removal is more extensive than suggested by more extensive than suggested by preoperative imaging, and it is preoperative imaging, and it is recommended that the surgical plan recommended that the surgical plan include a strategy to manage an include a strategy to manage an unexpectedly larger deficiency.unexpectedly larger deficiency.

Following radiographic assessment of Following radiographic assessment of bone deficiency, the degree of bone loss bone deficiency, the degree of bone loss is classified and the reconstruction is is classified and the reconstruction is planned with reference to 5 important planned with reference to 5 important questions:questions:– 1. Is there sufficient host bone to allow a 1. Is there sufficient host bone to allow a

standard acetabular component to achieve standard acetabular component to achieve stability and restore the center of rotation, stability and restore the center of rotation, with or without morcellized bone grafting but with or without morcellized bone grafting but without structural grafting?without structural grafting?

– 2. Is there segmental acetabular deficiency 2. Is there segmental acetabular deficiency that will require augmentation with that will require augmentation with structural allograft, or can a high hip center structural allograft, or can a high hip center be accepted?be accepted?

– 3. Is the bone loss so severe that stable cup 3. Is the bone loss so severe that stable cup support and fixation will not be achieved by support and fixation will not be achieved by a simple segmental bone graft alone?a simple segmental bone graft alone?

– 4. Is there pelvic discontinuity?4. Is there pelvic discontinuity?– 5. What is the best surgical approach for 5. What is the best surgical approach for

this procedure?this procedure?

CONCLUSIONSCONCLUSIONS With adequate preoperative planning, the surgeon With adequate preoperative planning, the surgeon

should have an assessment of the preoperative should have an assessment of the preoperative deficiencies associated with acetabular revision, deficiencies associated with acetabular revision, including general patient factors and anatomic including general patient factors and anatomic deficiencies that will require attention during the deficiencies that will require attention during the reconstruction.reconstruction.

It is imperative to have a comprehensive It is imperative to have a comprehensive assessment of these factors, particularly the nature assessment of these factors, particularly the nature of the bone deficiency.of the bone deficiency.

This will help predict potential problems and This will help predict potential problems and complications before discovering them complications before discovering them intraoperatively.intraoperatively.

REVISION ARTHROPLASTY REVISION ARTHROPLASTY OF THE ACETABULUM IN OF THE ACETABULUM IN ASSOCIATION WITH LOSS ASSOCIATION WITH LOSS

OF BONE STOCKOF BONE STOCK

Allan E. Gross, MDAllan E. Gross, MDClive P. Duncan, MDClive P. Duncan, MDDonald Garbuz, MDDonald Garbuz, MD

Elsayed Morsi Z. Mohamed, MBBCH, Elsayed Morsi Z. Mohamed, MBBCH, MSMS

INTRODUCTIONINTRODUCTION The goals of revision arthroplasty The goals of revision arthroplasty

of the hip are to relieve pain and to of the hip are to relieve pain and to improve function. These goals can improve function. These goals can be accomplished by insertion of a be accomplished by insertion of a new implant with stable fixation of new implant with stable fixation of the interface and restoration (or at the interface and restoration (or at least near restoration) of the least near restoration) of the anatomy.anatomy.

If there is no loss of bone stock, the anatomy If there is no loss of bone stock, the anatomy may be restored by simply inserting a new may be restored by simply inserting a new implant. If there is loss of bone it should be implant. If there is loss of bone it should be categorized as a contained or uncontained categorized as a contained or uncontained defect and dealt with accordingly.defect and dealt with accordingly.

Contained, or cavitary, defects are more Contained, or cavitary, defects are more easily dealt with because the skeleton, while easily dealt with because the skeleton, while weakened, is basically intact.weakened, is basically intact.

Uncontained, or segmental, defects are more Uncontained, or segmental, defects are more of a challenge.of a challenge.

Revision of the acetabular side of a Revision of the acetabular side of a total hip arthroplasty requires that total hip arthroplasty requires that considerable resources, including a considerable resources, including a variety of implants and banked bone, variety of implants and banked bone, be available to the treating surgeon; be available to the treating surgeon; that the surgeon be well versed in the that the surgeon be well versed in the use of comprehensive surgical use of comprehensive surgical exposures and the potential exposures and the potential complications.complications.

PRINCIPLES OF BONE PRINCIPLES OF BONE GRAFTINGGRAFTING

The treatment of bone defects on the The treatment of bone defects on the acetabular side of an arthroplasty ranges acetabular side of an arthroplasty ranges from morcellized bone graft to large from morcellized bone graft to large structural grafts.structural grafts.

Bone grafts can be classified as Bone grafts can be classified as heterogenous grafts (bone from another heterogenous grafts (bone from another species), allografts (bone from the same species), allografts (bone from the same species), and autogenous grafts (bone from species), and autogenous grafts (bone from another part of the same individual).another part of the same individual).

TYPES OF BONE GRAFTSTYPES OF BONE GRAFTS Autogenous grafts have the advantage of Autogenous grafts have the advantage of

being nonimmunogenic and, being the being nonimmunogenic and, being the best at inducing new bone formation.best at inducing new bone formation.

Their main disadvantage are that the Their main disadvantage are that the supply of available bone is limited and supply of available bone is limited and that the strength, shape, and form of the that the strength, shape, and form of the graft usually cannot duplicate those of graft usually cannot duplicate those of the bone that originally was present at the bone that originally was present at the site of the deficit.the site of the deficit.

Allografts, in contrast, are available in large Allografts, in contrast, are available in large quantity, have very good initial strength, and quantity, have very good initial strength, and can be shaped to fit almost any deficit. can be shaped to fit almost any deficit.

However, they are expensive, immunogenic, However, they are expensive, immunogenic, and not as effective as autogenous grafts at and not as effective as autogenous grafts at inducing new-bone formation. inducing new-bone formation.

Allograft bone can be classified as morcellized Allograft bone can be classified as morcellized or structural, depending on how it is used.or structural, depending on how it is used.

MORCELLIZED BONEMORCELLIZED BONE Morcellized bone (fragments of cancellous Morcellized bone (fragments of cancellous

bone ranging from 5-10 mm in diameter) is bone ranging from 5-10 mm in diameter) is used as a filler scaffold in contained defects. used as a filler scaffold in contained defects. It can undergo revascularization and It can undergo revascularization and remolding, and it strengthens with time.remolding, and it strengthens with time.

It is designed to be inserted without cement, It is designed to be inserted without cement, at least 50% of the cup to make contact with at least 50% of the cup to make contact with host bone and screws will probably be host bone and screws will probably be necessary for fixation.necessary for fixation.

If it is not possible for at least 50% If it is not possible for at least 50% of the cup to make contact with of the cup to make contact with host bone, then a roof-host bone, then a roof-reinforcement ring and a cup that reinforcement ring and a cup that is designed to be inserted with is designed to be inserted with cement.cement.

STRUCTURAL GRAFTSSTRUCTURAL GRAFTS The advantages of structural grafts include the The advantages of structural grafts include the

potential to restore the anatomy and to provide potential to restore the anatomy and to provide structural support for the implantstructural support for the implant

Disadvantages include revascularization and Disadvantages include revascularization and remolding that can lead to resorption, collapse, or remolding that can lead to resorption, collapse, or both, and often weaken with time.both, and often weaken with time.

A structural graft is indicated for the treatment of an A structural graft is indicated for the treatment of an uncontained defect when it is necessary to restore the uncontained defect when it is necessary to restore the anatomy and limb length and provide support for the anatomy and limb length and provide support for the implant.implant.

SIMULATED STRUCTURAL SIMULATED STRUCTURAL GRAFTGRAFT

This term is used when bone from This term is used when bone from another anatomic region and is another anatomic region and is shaped to fit the deficit.shaped to fit the deficit.– e.g.-the distal aspect of the femur can e.g.-the distal aspect of the femur can

be sculpted to duplicate an be sculpted to duplicate an acetabulum, or a femoral head can be acetabulum, or a femoral head can be sculpted to the desired shape.sculpted to the desired shape.

ANATOMIC STRUCTURAL ANATOMIC STRUCTURAL GRAFTGRAFT

This term is used when the bone is This term is used when the bone is from the same anatomic part as from the same anatomic part as that being duplicated.that being duplicated.– e.g.-an acetabular allograft can be e.g.-an acetabular allograft can be

used, in whole or in part, to replace used, in whole or in part, to replace an acetabular defect.an acetabular defect.

– These grafts have been found easier These grafts have been found easier to shape than simulated grafts.to shape than simulated grafts.

STRUCTURAL ALLOGRAFTSSTRUCTURAL ALLOGRAFTS These grafts may fail because of These grafts may fail because of

resorption or fragmentation. It is resorption or fragmentation. It is therefore important to use an implant therefore important to use an implant that extends from host bone to host that extends from host bone to host bone, thereby bridging and protecting bone, thereby bridging and protecting the graft.the graft.

It is important to use morcellized It is important to use morcellized autogenous graft for bone grafting of autogenous graft for bone grafting of the host bone-allograft junctions.the host bone-allograft junctions.

CLASSIFICATION OF BONE CLASSIFICATION OF BONE DEFECTSDEFECTS

Gross et al developed a Gross et al developed a simple, functional system simple, functional system for the classification of for the classification of bone defects associated bone defects associated with loose hip implants.with loose hip implants.

These defects can usually These defects can usually be classified by plain be classified by plain radiograph but the final radiograph but the final decision depends of decision depends of intraoperative findings.intraoperative findings.

SURGICAL TECHNIQUESURGICAL TECHNIQUE Approach-a contained defect can be Approach-a contained defect can be

reconstructed through a reconstructed through a conventional approach.conventional approach.

For a structural defect, it is preferred For a structural defect, it is preferred to have access to the anterior and to have access to the anterior and posterior columns; therefore, a posterior columns; therefore, a transtrochanteric approach or transtrochanteric approach or trochanteric slide is implemented.trochanteric slide is implemented.

The acetabulum is prepared after The acetabulum is prepared after the hip has been dislocated. the hip has been dislocated.

After the cement and the After the cement and the component are removed, the component are removed, the defect is defined whether it is defect is defined whether it is cavitary or segmental and then cavitary or segmental and then which type of reconstruction is which type of reconstruction is necessary.necessary.

TYPE-I DEFECTSTYPE-I DEFECTS Morcellized bone is Morcellized bone is

compacted into the compacted into the cavitary defect by reverse cavitary defect by reverse reaming. A porous-coated reaming. A porous-coated implant can be inserted implant can be inserted without cement if it is without cement if it is possible for at least 50% of possible for at least 50% of the cup to make contact the cup to make contact with host bone. Screws are with host bone. Screws are usually needed for fixation.usually needed for fixation.

TYPE-I DEFECTS CONT.TYPE-I DEFECTS CONT. If it is not possible for at least 50% If it is not possible for at least 50%

of the cup to make contact with of the cup to make contact with bleeding host bone, a roof-bleeding host bone, a roof-reinforcement ring is impacted reinforcement ring is impacted superomedially and is held with 2 superomedially and is held with 2 or 3 cancellous bone screws that or 3 cancellous bone screws that are directed into the dome. the are directed into the dome. the cup is then cemented into the ring.cup is then cemented into the ring.

TYPE-IIA DEFECTSTYPE-IIA DEFECTS Structural acetabular Structural acetabular

allografts are used for the allografts are used for the treatment of type-IIA treatment of type-IIA segmental defects, which segmental defects, which involve <50% of the involve <50% of the acetabulum.acetabulum.

Because at least 50% of Because at least 50% of the cup will be in contact the cup will be in contact with host bone, the cup with host bone, the cup can be inserted with or can be inserted with or without cement.without cement.

TYPE-IIB DEFECTSTYPE-IIB DEFECTS Type-IIB segmental Type-IIB segmental

defects involve at least defects involve at least 50% of the acetabulum, 50% of the acetabulum, and may be associated and may be associated with pelvic discontinuity.with pelvic discontinuity.

An acetabular allograft An acetabular allograft involving at least 50% of involving at least 50% of the acetabulum is the acetabulum is fashioned to fit the defect fashioned to fit the defect with 6.5mm cancellous with 6.5mm cancellous screws.screws.

TYPE-IIB DEFECTS CONT.TYPE-IIB DEFECTS CONT. Cavitary defects are filled with Cavitary defects are filled with

morcellized bone and a Burch-morcellized bone and a Burch-Schneider reconstruction ring Schneider reconstruction ring extends from the ilium to the extends from the ilium to the ischium used to protect the graft.ischium used to protect the graft.

If fixation of the screws is not If fixation of the screws is not adequate, the cup must be adequate, the cup must be inserted with cement.inserted with cement.

OVERVIEWOVERVIEW In summary, cavitary defects are In summary, cavitary defects are

treated with impacted, morcellized treated with impacted, morcellized allograft bone. If at least 50% of the allograft bone. If at least 50% of the cup will be in contact with host bone, cup will be in contact with host bone, the cup can be inserted without cement the cup can be inserted without cement with screw fixation.with screw fixation.

Otherwise, a roof-reinforcement ring Otherwise, a roof-reinforcement ring should be used and inserted with should be used and inserted with cement.cement.

OVERVIEW CONT.OVERVIEW CONT. If a segmental defect cannot be treated by If a segmental defect cannot be treated by

placement of the cup at a high hip center, a placement of the cup at a high hip center, a structural allograft is used.structural allograft is used.

It is attempted to make contact between at It is attempted to make contact between at least 50% of the cup and host bone so that a least 50% of the cup and host bone so that a minor column or shelf graft can be used.minor column or shelf graft can be used.

If it is not possible, a major column graft is If it is not possible, a major column graft is used. Under these circumstances, the graft used. Under these circumstances, the graft should be protected with a reconstruction ring should be protected with a reconstruction ring and the cup should be cemented.and the cup should be cemented.

RESULTSRESULTS Success was defined as an increase of at Success was defined as an increase of at

least 20 points in the Harris hip score, a least 20 points in the Harris hip score, a stable cup, and no need for an additional stable cup, and no need for an additional operation.operation.– Hips revised with morcellized grafts only had Hips revised with morcellized grafts only had

a 90% success ratea 90% success rate– Hips revised with a minor column had an 86% Hips revised with a minor column had an 86%

success ratesuccess rate– Use of major column allograft had a 55% Use of major column allograft had a 55%

success ratesuccess rate

CONCLUSIONSCONCLUSIONS The use of morcellized bone grafts for the The use of morcellized bone grafts for the

treatment of cavitary defects and structural treatment of cavitary defects and structural grafts that support <50% of the cup provide grafts that support <50% of the cup provide reproducible, encouraging results.reproducible, encouraging results.

Structural grafts that support >50% of the cup Structural grafts that support >50% of the cup are associated with a more guarded prognosis.are associated with a more guarded prognosis.

It is imperative that techniques be developed to It is imperative that techniques be developed to improve the performance of large grafts rather improve the performance of large grafts rather than abandon their use.than abandon their use.