By definition, constrained total hip arthroplasty components include a mechanism that locks the prosthetic femoral head into a polyethylene acetabular component.. Constrained components
Trang 1Dislocation is one of the most
com-mon and distressing early
complica-tions of total hip arthroplasty The
reported incidence of dislocation
ranges from 0% to 10% after a
prima-ry arthroplasty and from 10% to 25%
after a revision arthroplasty A wide
variety of predisposing causes and
associated factors have been
suggest-ed.1,2 Pellicci et al3described the use
of a posterior approach and enhanced
soft-tissue repair in an attempt to
decrease the early incidence of
dislo-cation Nonsurgical treatment of the
initial dislocation with a cast or brace
is successful in approximately two
thirds of patients However, when
surgical treatment is required for
recurrent dislocation, satisfactory
results have been achieved in only
60% of hips using a wide variety of
techniques.1 Additionally, the chance
of success is even less when a precise etiology cannot be determined It is for these situations that constrained components have been considered
By definition, constrained total hip arthroplasty components include a mechanism that locks the prosthetic femoral head into a polyethylene acetabular component A thorough understanding of the design features
of constrained components in total hip arthroplasty, indications for their use, and results and complications is essential for the effective application
of this technique
Historical Perspective
The use of constrained total hip arthroplasty components has been limited.4 Sivash first reported on his
constrained prosthesis in 1963 in Moscow, at a conference on tubercu-losis of bones and joints.5 The Sivash prosthesis was a locked one-piece prosthesis, with the cup and head-neck components fabricated as a connected whole (Fig 1) The first components were fabricated of steel; they were later modified to include chrome-cobalt and titanium alloys The acetabular component was a threaded hemisphere made of a tita-nium alloy and was available in 51-, 57-, and 65-mm diameter sizes The femoral component had a chrome-cobalt head welded onto a titanium-alloy stem and was available in three sizes: 14-, 16-, and 18-mm proximal diameter The articulating surface was polyethylene Fixation was
Dr Lachiewicz is Professor, Department of Orthopaedics, University of North Carolina at Chapel Hill, Chapel Hill, NC Dr Kelley is Associate Professor, Department of Orthopaedics, University of North Carolina at Chapel Hill, Chapel Hill.
One or more of the authors or the departments with which they are affiliated have received something of value from a commercial or other party related directly or indirectly to the sub-ject of this article.
Reprint requests: Dr Lachiewicz, 242 Burnett-Womack Building, CB 7055, Chapel Hill, NC 27599.
Copyright 2002 by the American Academy of Orthopaedic Surgeons.
Abstract
The use of a constrained component may be appropriate for the surgical treatment of
recurrent dislocation due to soft-tissue insufficiency following a total hip arthroplasty.
Constrained components usually include a locking mechanism incorporated into the
polyethylene acetabular liner to keep the prosthetic femoral head in place Two
differ-ent prosthetic designs are available and have been approved by the U.S Food and
Drug Administration The S-ROM constrained component uses additional
polyeth-ylene in the rim, which deforms to more fully capture the femoral head and then is
held in place by a metal locking ring The Howmedica Osteonics constrained
compo-nent is a tripolar device; its bipolar compocompo-nent articulates with another polyethylene
liner These constrained components transfer hip forces that would otherwise lead to
dislocation to the locking mechanism, the liner-shell interface, or the bone-prosthesis
interface These forces may eventually contribute to failure of the component due to
loosening, dissociation, breakage, or recurrent dislocation Studies of these
compo-nents show a failure rate of 4% to 29% at relatively short-term follow-up.
J Am Acad Orthop Surg 2002;10:233-238
The Use of Constrained Components
in Total Hip Arthroplasty
Paul F Lachiewicz, MD, and Scott S Kelley, MD
Trang 2either press-fit or cemented After
appropriate reaming of both surfaces,
the femoral component was
implant-ed, followed by impaction or
cement-ing of the locked-on acetabular
com-ponent Sivash reported its use in
200 cases, with 1- to 9-year follow-up
in 169 patients.5 The most common
indications were ankylosing
spondy-litis in 107 patients and tuberculous
arthritis in 56 patients Although
there was no detailed analysis of
results, Sivash reported that the
pros-thesis fractured in 13 hips
A modified Sivash prosthesis
with specially designed rasps was
described in 1974.6 A case report in
1981 described the successful use of
this modified prosthesis for recurrent dislocation and anecdotally
suggest-ed that cerebral palsy, Parkinson’s disease, and loss of hip muscula-ture were indications for its use.7
Although the prosthesis was used ex-tensively in Europe,8it was used only sporadically in the United States
Bryan and Reeve9 described a case of a patient with recurrent dis-location who was treated with this device Failure was eventually caused by fatigue fracture of the con-straining ring and severe polyethyl-ene wear and metal-metal abrasion
Koffman10 reported the use of three different designs of constrained com-ponents (including the Sivash) in five hips of four patients with spastic cerebral palsy The Sivash prosthesis was implanted in the only
ambulato-ry patient and failed because of dislocation and early acetabular loosening
Current Constrained Designs
Two constrained total hip arthro-plasty liner systems are presently approved by the U.S Food and Drug Administration (FDA) and have data published on results of their use They are the S-ROM con-strained acetabular liner (Poly-Dial;
DePuy Orthopaedics Warsaw, IN) and the Howmedica Osteonics con-strained acetabular liner (Stryker Howmedica Osteonics, Rutherford, NJ) Other constrained liners have been used in FDA trials or are in development
The S-ROM constrained acetabu-lar liner has been available since
1987 It was marketed under a Premarket Notification from the FDA To date, according to the com-pany, more than 6,000 have been implanted This constrained acetab-ular liner was designed for use with S-ROM metal shells The constraint
is derived from the addition of extra polyethylene in the rim, which
deforms to more fully capture the femoral head implant (Fig 2) In addition, a capture ring provides increased constraint The design of this component allows the head to dissociate from the liner before the forces dislodge the acetabular shell from the pelvic bone Cameron11
reported that the force required for withdrawal of this component is 60 inch-pounds and that the metal constraining ring increases the hold-ing power to 300 inch-pounds Lombardi et al12 reported that the metal ring provided a constraining force of more than 600 pounds with
a 32-mm head and 325 pounds with
a 28-mm head However, they found that the amount of leveraged torque required to pry the femoral head out of the liner was 150 lbs/in2 The optimal amount of torque required for removal of the femoral head from a constrained acetabular component is not known The S-ROM component, which is “dialed” into the acetabular shell, is currently available with an internal diameter
of 28 or 32 mm and with a standard rim or a 10° elevated rim The liner
is available to fit acetabular shells with an outer diameter of 48 mm to
68 mm and is fabricated of cross-linked polyethylene, with a mini-mum thickness of 5 mm The aver-age arc of motion (when used with
Figure 1 The one-piece Sivash constrained
component for total hip arthroplasty.
(Reprinted with permission from Amstutz
HC, Grigoris P: Metal on metal bearings in
hip arthroplasty Clin Orthop 1996;[329
suppl]:S11-S34.)
Figure 2 The S-ROM constrained
acetabu-lar liner with locking ring and correspond-ing uncemented metal shell (Reprinted with permission from Kaper BP, Bernini PM: Failure of a constrained acetabular prosthesis of a total hip arthroplasty: A
report of four cases J Bone Joint Surg Am
1998;80:561-565.)
Trang 3an S-ROM femoral component) is
reported to be 88° with a 28-mm
head and 98° with a 32-mm head.12
This arc of motion is probably less
when an elevated rim liner is
com-bined with a “skirted” modular
femoral head component
The Howmedica Osteonics
con-strained acetabular liner was
intro-duced as a custom component in
198813 and was marketed under a
Premarket Approval from the FDA,
until recently converted to a class II
device This component is basically
a tripolar device (Fig 3): a
polyeth-ylene inner liner is covered with a
polished cobalt-chrome shell; the
shell articulates with another
poly-ethylene liner (the outer bearing),
which is inserted into a standard
noncemented acetabular shell The
inner liner accepts a 22-, 26-, or
28-mm femoral head and has a locking
ring identical to the ring in a bipolar
prosthesis
Some authors have suggested that
the constrained acetabular liner can
be cemented into a well-fixed
acetab-ular shell or into an acetabulum
pre-pared for cement fixation.14The
Howmedica Osteonics constrained
acetabular liner has been cemented
into both an acetabular shell of
another manufacturer and into an
acetabulum prepared for cement
fix-ation.14 If the former technique is
used, the surgeon should carefully consider preoperatively if this con-strained liner will fit The smallest acetabular shell into which this liner could be safely cemented is probably
52 mm According to the manufac-turer, the total range of motion is 72°
when it is used with 50- to 54-mm outer acetabular shells, 82° with a
56-mm shell, and 84° with 58- to 74-56-mm shells The two polyethylene articu-lating surfaces have a thickness rang-ing from 5.2 to 7.7 mm for the inner bearing and from 4.3 to 10.4 mm for the outer bearing The polyethylene thickness varies based on femoral head size and acetabular shell diam-eter The pullout strengths of the three segments of this tripolar liner have not been reported
Indications
The use of a constrained acetabular component in total hip arthroplasty
is indicated for recurrent dislocation
of the hip due to soft-tissue insuffi-ciency (capsular or abductor muscu-lature) that is not amenable to repair
or augmentation If the abductor mechanism has been resected, then reconstruction with a constrained system may be required Soft-tissue laxity (not insufficiency) due to short-ening of the prosthetic hip may be
treated by lengthening the femoral neck and/or lateralizing the acetabu-lar component or liner Component malposition, loosening, or wear should be treated by revision of one
or both components Dislocation re-sulting from impingement of bone or
a “skirted” femoral head against an elevated-rim acetabular liner should not routinely be treated by a con-strained component Bone impinge-ment can be treated by bone resection and impingement of the femoral head by revision of the head, liner,
or acetabular component Acute avulsion of a greater trochanteric osteotomy or fracture of the greater trochanter should be treated by sur-gical repair and/or advancement However, recurrent dislocation due
to a chronic nonunion of the greater trochanter, with severe and irrepara-ble loss of abductor muscle function, may be an indication for use of the constrained component Recurrent dislocation associated with a large mismatch between the femoral head size and the outer acetabular compo-nent diameter, as reported by Kelley
et al,15should be treated by revision
to a larger head and corresponding acetabular liner, if possible
Late (>1 to 2 years postopera-tively) recurrent dislocation, which may be associated with weight loss, decrease in muscle mass, and/or chronic disease (cancer, rheumatoid arthritis) without component malpo-sition, is extremely difficult to treat The constrained component may be
a reasonable option in patients with these conditions When late disloca-tion is associated with an acute or chronic infection, the treatment is complex, must be individualized, and may involve the use of a con-strained component
Contraindications for the use of constrained components include acute dislocation, dislocation due to component loosening or malposi-tion, insufficient acetabular bone structure, acute infection, skeletal immaturity, and neurologic
spas-Outer bearing (UHMWPE)
Inner bearing shell (CoCr)
Acetabular shell
Inner bearing (UHMWPE) Bipolar retaining
ring (UHMWPE)
Figure 3 A, The Howmedica Osteonics constrained acetabular liner B, Schematic showing
the tripolar nature UHMWPE = ultra-high-molecular-weight polyethylene, CoCr =
cobalt-chrome (Adapted with permission from Stryker Howmedica Osteonics, Rutherford, NJ.)
Trang 4ticity Neurologic spasticity may
seem to be an attractive indication
for the use of this component, but
Root et al,16in reporting the results of
total hip arthroplasty without
con-strained components performed in
patients with cerebral palsy, found
that only 2 of 15 patients had a
recur-rent dislocation, and both had
com-ponent malposition
The prophylactic use of
con-strained components in primary or
revision total hip arthroplasty is
con-troversial Because good data are
lacking, constrained acetabular liners
should not be used routinely in these
situations Larger femoral head
sizes, femoral necks with greater
length and offset, and/or elevated
rim liners are better choices
Results and Complications
Theoretically, constrained acetabular
components should transfer the
forces that would otherwise lead to
dislocation to the locking
mecha-nism, the liner-shell interface,
or the prosthesis (or
bone-cement) interface If the hip center is
shifted laterally, which may occur
with either of the two available
con-strained components, these forces
may be increased The reported
results of constrained components
have demonstrated four types of
fail-ure: loosening of the acetabular
component;12dissociation of the
con-strained liner from the shell (with
redislocation)17,18 (Fig 4); material
failure (breakage) or disengagement
of the constraining ring (with or
without redislocation)17,19 (Fig 5);
and dissociation of a modular
femoral head from its neck.20 An
additional potential mode of failure
is excessive wear of a thin
acetabu-lar liner interface
According to information
avail-able from the manufacturer, the
S-ROM constrained acetabular liner
has a low rate of
dissociation-dislocation in the more than 6,000
implanted since 1987 However, a careful clinical review of these cases has not been performed, and there are relatively few published data on the component
Lombardi et al12reported a retro-spective review of 57 S-ROM con-strained acetabular liners implanted
in 55 patients Six were used in primary arthroplasties and 51 in revision arthroplasties Of these, however, only 31 were done for dis-location, and of those, 13 patients had experienced multiple disloca-tions (average, 2.7; range, 2 to 5) Al-though the clinical follow-up period for the entire groupwas relatively short (mean, 30.2 months), two patients experienced early definite radiographic loosening of the ace-tabular component with screw breakage and migration Five of 55 patients (9%) experienced failure due
to redislocation at a mean of 2.5 months (range, 1 to 9 months) post-operatively Three of these five patients had undergone the proce-dure because of recurrent disloca-tion, and thus the failure rate of the constrained component for this indi-cation was 23% (3 of 13) Open reduction was necessary when a dis-location of this constrained compo-nent occurred
Anderson et al17 reported the results of S-ROM constrained acetabular liners in 21 patients, 18 of whom had experienced recurrent dislocation At a mean follow-up of
31 months (range, 24 to 64 months),
15 patients (71%) reported no fur-ther dislocations However, six patients (29%) reported eight redis-locations at a mean of 10 months postoperatively (range, 1 to 30 months) In four cases, the polyeth-ylene liner (still securely fixed to the femoral head) was levered out of the metal shell; in two failures, the femoral head pulled out of the liner;
and in two other dislocations, the metal retaining ring disengaged from the polyethylene liner In all six patients with redislocations, the
preoperative diagnosis was recur-rent dislocation, for a failure rate of 33% However, no loosening of the
19 porous-coated acetabular compo-nents was reported in this study Fisher and Kiley18 reported two cases of failure of the S-ROM com-ponent One occurred 9 months postoperatively and was due to fail-ure of the retaining ring and poly-ethylene wear; the other occurred 5 months postoperatively, with both loosening of the metal shell and pullout of the polyethylene liner from the shell following a traumatic event Of 51 hips in which the S-ROM constrained component was used, either for recurrent dislocation
or in extensive revisions, there were
5 failures—3 redislocations and 2 dissociations (10% failure)—and all required open reduction or revision
of the component.18
Of 12 patients managed with the S-ROM component at their institu-tion, Kaper and Bernini19reported
Figure 4 Radiograph showing the S-ROM
constrained polyethylene component dislo-cated from the metal shell Probably there is also loosening of the acetabular shell (Reprinted with permission from Anderson
MJ, Murray WR, Skinner HB: Constrained
acetabular components J Arthroplasty
1994;9:17-23.)
Trang 5failure in four In two, the
constrain-ing rconstrain-ing had fractured, and in the
other two, the liner had pulled out of
the metal acetabular shell Because
two of the failures involved an
ele-vated-rim constrained liner, these
authors suggested that the use of that
liner may contribute to a lever-out
mechanism
McPherson et al21 recently
de-scribed a new technique that resulted
in the successful closed reduction of a
dislocated S-ROM constrained liner
in three medically compromised
patients With the patient under
gen-eral anesthesia and using
fluoroscop-ic guidance, the femoral head was
perched into the opening of the
acetabular component With the leg
positioned in 40° of abduction and
30° of flexion, a minimum of three
people using a “bear hug” maneuver
of the hip and pelvis apply a
contin-ued axial compressive force for at
least 90 to 120 seconds, until an
audi-ble and palpaaudi-ble clunk of reduction
has occurred No complications were reported, but all three patients later had revision or resection
arthroplas-ty The advantage of this technique is the ability to delay revision surgery until conditions (the patient’s health and the availability of equipment and personnel) are more favorable
Because of wide variation in series size and in indications for surgery, little information beyond anecdotal case reports can be gleaned from the four series reviewing the use of S-ROM constrained components.12,17-19
However, the reported rate of failure
or redislocation is high (9% to 33%)
There is even less published experience with the Howmedica Osteonics constrained acetabular liner, in part because its use was ini-tially restricted to two medical cen-ters Goetz et al14reported the use of this acetabular liner for recurrent dis-location in 56 hips Forty-six con-strained components were inserted without cement, and 10 were inserted with cement (four of these were cemented into acetabular shells of another manufacturer) The 38 patients (39 hips) still living at the time of the report had been followed for a mean of 5.3 years (range, 3 to 8 years), and the deceased 16 patients had been followed for a mean of 2.3 years (range, 1 to 81 months) One patient was lost to follow-up Only two patients (4%) experienced failure described as “recurrent dislocation.”
However, in one patient, the acetabu-lar shell (with screws) pulled out of the pelvis, and in the other, the cemented constrained component dissociated from a well-fixed shell
Seven hips (13%) required revision surgery in the follow-up period, including four for infection and one for acetabular component loosening
Radiographic analysis was per-formed for 38 hips with a minimum 2-year follow-up There was acetabu-lar osteolysis in 2 of 27 hips (7%) treated with a new acetabular shell and a new constrained liner, both in-serted without cement There was
also definite loosening of 2 of 34 uncemented acetabular components (6%) and 2 of 33 uncemented femoral components (6%)
Goetz et al14emphasized that, because the primary goal of these revisions was a stable hip, the patients and surgeons were willing to accept the increased risk of polyethylene wear, osteolysis, and component loos-ening It also should be emphasized that these patients were
predominant-ly elderpredominant-ly, debilitated women with a mean age of 71 years There are no published reports on the use of this constrained component in younger or active patients, in whom an even higher rate of failure of fixation would be expected
Summary
Constrained components should be used judiciously for the surgical treatment of recurrent dislocation of the hip The ideal patient is an
elder-ly, low-demand patient with recur-rent dislocation despite well-fixed and properly positioned compo-nents The etiology of these dislocations is usually soft-tissue (capsule or musculature)
insufficien-cy around the prosthetic hip joint These components should be consid-ered for use only when other options are exhausted and only when bipolar arthroplasty, resection arthroplasty,
or a constrained acetabular liner remains For the two presently avail-able constrained hip components, the rates of failure, including redislo-cation, dissociation of the liner from the acetabular shell, and loosening of the acetabular shell, are reported to
be from 4% to 29% at short-term follow-up Based on the limited published data regarding these con-strained components, prophylactic use of these components is not presently recommended because of the danger of excessive wear of thin polyethylene, breakage, and acceler-ated loosening of components
Figure 5 Radiograph showing the
con-straining ring displaced from the S-ROM
polyethylene component (Reprinted with
permission from Anderson MJ, Murray
WR, Skinner HB: Constrained acetabular
components J Arthroplasty 1994;9:17-23.)
Trang 61 Morrey BF: Difficult complications
after hip joint replacement: Dislocation.
Clin Orthop 1997;344:179-187.
2 Paterno SA, Lachiewicz PF, Kelley SS:
The influence of patient-related factors
and the position of the acetabular
com-ponent on the rate of dislocation after
total hip replacement J Bone Joint Surg
Am 1997;79:1202-1210.
3 Pellicci PM, Bostrom M, Poss R:
Pos-terior approach to total hip replacement
using enhanced posterior soft tissue
repair Clin Orthop 1998;355:224-228.
4 Schneider PG: Total replacement
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Chapchal G (ed): Arthroplasty of the
Hip Stuttgart, Germany: G Thieme,
1973, pp 113-167.
5 Sivash KM: The development of a
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from a partial joint replacement
Re-constr Surg Traumatol 1969;11:53-62.
6 Russin LA, Russin MA: Abstract: A
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Russin-modified Sivash prostheses: 100 cases.
41st Annual Meeting Proceedings, Dallas,
Texas Chicago, IL: American Academy
of Orthopaedic Surgeons, 1974, p 119.
7 Russin LA, Sonni A: Indications for
the use of a constrained THR
prosthe-sis Orthop Rev 1981;10:81-84.
8 Radulovic B, Kenig I, Radovanovic M:
Indications for Sivash type total hip
prosthesis, in Charnley J (ed): Low
Friction Arthroplasty of the Hip: Theory and Practice Berlin, Germany:
Springer-Verlag, 1979, pp 74-81.
9 Bryan WJ, Reeve RE: Dislocation and failure of an articulated total hip
replacement: A case report Orthopedics
1986;9:1113-1115.
10 Koffman M: Proximal femoral resec-tion or total hip replacement in
severe-ly disabled cerebral-spastic patients.
Orthop Clin North Am 1981;12:91-100.
11 Cameron HU: Use of a constrained acetabular component in revision hip
surgery Contemp Orthop 1991;23:481-484.
12 Lombardi AV Jr, Mallory TH, Kraus
TJ, Vaughn BK: Preliminary report on the S-ROM constraining acetabular insert: A retrospective clinical
experi-ence Orthopedics 1991;14:297-303.
13 Goetz DD, Capello WN, Callaghan JJ, Brown TD, Johnston RC: Salvage of total hip instability with a constrained
acetabular component Clin Orthop
1998;355:171-181.
14 Goetz DD, Capello WN, Callaghan JJ, Brown TD, Johnston RC: Salvage of a recurrently dislocating total hip pros-thesis with use of a constrained acetabular component: A retrospective
analysis of fifty-six cases J Bone Joint
Surg Am 1998;80:502-509.
15 Kelley SS, Lachiewicz PF, Hickman
JM, Paterno SM: Relationship of femoral head and acetabular size to
the prevalence of dislocation Clin
Orthop 1998;355:163-170.
16 Root L, Goss JR, Mendes J: The treat-ment of painful hip in cerebral palsy
by total hip replacement or hip
arthro-desis J Bone Joint Surg Am 1986;68:
590-598.
17 Anderson MJ, Murray WR, Skinner HB: Constrained acetabular
compo-nents J Arthroplasty 1994;9:17-23.
18 Fisher DA, Kiley K: Constrained
acetab-ular cup disassembly J Arthroplasty
1994;9:325-329.
19 Kaper BP, Bernini PM: Failure of a con-strained acetabular prosthesis of a total hip arthroplasty: A report of four cases.
J Bone Joint Surg Am 1998;80:561-565.
20 Namba RS, Van der Reis WL: Femoral head and neck dissociation after a total hip arthroplasty with a constrained
acetabular liner Orthopedics 2000;23:
489-491.
21 McPherson EJ, Costigan WM, Gerhardt
MB, Norris LR: Closed reduction of dislocated total hip with S-ROM constrained acetabular component
J Arthroplasty 1999;14:882-885.