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Isolated revision acetabuloplasty using a porous-coated cementless acetabular component without removal of a well-fixed femoral component
The Journal of Arthroplasty Vol. 12 No. 7 1997
Isolated Revision Acetabuloplasty Using a Porous-coated Cementless Acetabular C o m p o n e n t W i t h o u t R e m o v a l of a Well-fixed Femoral Component A 3- to 9-Year Follow-up Study Joseph T. Moskal, MD,* Olumide A. Danisa, MD,-I- and Christopher I. Shaffrey, MD~-$
Abstract: The results of isolated acetabular revision performed in 31 patients (32 hips) were monitored for between 3 and 9 years. All femoral components were well fixed and not removed or revised at the time of index surgery. There were 4 hips with little or no acetabular bony defect, 2 hips with pure segmental defects (type I), 10 hips with cavitary defects (type II), 15 with combined segmental cavitary defects (type III), and 1 with pelvic discontinuity (type IV). All revision acetabular implants were cementless, using a porous-coated hemispheric cup with or without bone-graft. There were four grade I reconstructions, 16 grade II reconstructions, and 12 grade III reconstructions. At final follow-up evaluation 94% of the cups were judged to be stable. Two hips required a second revision acetabuloplasty because of loss of fixation of the cup. The 2 repeat revisions were also done without removal of the femoral component. One acetabular component had evidence of rotational migration, which stabilized and remained nonprogressive. There were no cases of femoral component radiographic or clinical failure. The mean pre and postoperative hip scores were 44 and 83, respectively. The pre- and postoperative pain scores were 12 and 42, respectively. The findings of this study suggest that isolated acetabular revision, using a cementless porous-coated hemispheric cup, can be successfully performed without removing or revising a well-fixed femoral stem and not compromise the final outcome. K e y w o r d s : Revision acetabuloplasty, loose acetabular component, well-fixed femoral component, arthroplasty.
A p p r o x i m a t e l y 1 5 % of r e v i s i o n h i p a r t h r o p l a s t y is p e r f o r m e d for i s o l a t e d f a i l u r e of t h e a c e t a b u l a r c o m p o n e n t [ I ] . T h e c o m p l e x i t y of a c e t a b u l a r revi-
sion depends largely on the reconstruction required to r e s t o r e n o r m a l a n a t o m y d u e to a c e t a b u l a r b o n e loss [ 2 - 6 ] . F e m o r a l c o m p o n e n t r e m o v a l h a s b e e n recommended to p r o v i d e a d e q u a t e acetabular e x p o s u r e i n cases in w h i c h a s i g n i f i c a n t r e c o n s t r u c t i o n n e e d s to b e p e r f o r m e d [ 7 - 1 1 ] . C o m p a r e d with isolated revision acetabuloplasty, however, c o m b i n e d f e m o r a l a n d a c e t a b u l a r r e v i s i o n is a s s o c i a t e d w i t h i n c r e a s e d c o m p l i c a t i o n rate, s u r g i c a l t i m e , b l o o d loss, a n d cost [7,11]. T h e l o n g - t e r m r e s u l t s of r e v i s i o n f e m o r a l a r t h r o p l a s t y a r e clinically i n f e r i o r to f e m o r a l c o m p o n e n t s of p r i m a r y
From the *Roanoke Orthopaedic Center, Roanoke; ]-University of Virginia, Charlottesville; and ~Naval Medical Center, Portsmouth, Virginia. The views expressed in this article are those of the authors a n d do n o t reflect the official policy or position of the D e p a r t m e n t of the Navy, U.S. D e p a r t m e n t of Defense, or t h e U.S. g o v e r n m e n t . Reprint requests: Joseph T. Moskal, MD, Roanoke Orthopaedic Center, 4064 Postal Drive, SW, Roanoke, VA 24018.
© 1997 Churchill Livingstone Inc.
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total hip arthroplasty (THA); therefore, maintaining the original well-fixed femoral prosthesis w o u l d be a theoretic advantage if it did not compromise the revision acetabuloplasty [5,10-15]. The purpose ot this study was to determine w h e t h e r revision of an isolated failed acetabular c o m p o n e n t w i t h o u t the removal of a well-fixed femoral stem can be successfully performed even w h e n complex acetabular reconstruction is required and not compromise the ultimate outcome. The status of the femoral components was also analyzed to determine if the processes that cause acetabular loosening result in a higher than expected femoral comp o n e n t failure rate in the retained prostheses.
Materials and Methods All patients w h o had revision hip arthroplasty were identified from a prospectively developed database of all primary and revision THAs performed by the senior a u t h o r (J.T.M.). From December 1987 to December 1993, 171 consecutive revision THAs were performed in 159 patients, and 31 patients with 32 hips requiring only revision of the acetabular c o m p o n e n t were identified. Criteria for inclusion in the study were aseptic loosening and malposition of a previously cemented or uncem e n t e d acetabular c o m p o n e n t with a well-fixed femoral prosthesis. The average time from revision acetabuloplasty to the latest follow-up examination was 58 m o n t h s (range, 3 6 - 1 1 4 months). The average patient age was 66 years (range, 29-87 years). There were 20 w o m e n and 11 men. The preoperative diagnosis was aseptic loosening in 31 cases and malposition of the acetabular c o m p o n e n t in 1 hip. Eighteen hips had c e m e n t e d acetabular components 10 of which were all polyethylene, and 8 were metal backed. All cemented components were revised for aseptic loosening. F o u r t e e n acetabular components were not cemented (12 porous coated, 1 hydroxyapatite coated, and I threaded). Thirteen of the n o n c e m e n t e d c o m p o n e n t s were revised for aseptic loosening and 1 was malpositioned. There were 21 monolithic (monoblock) femoral c o m p o n e n t s with a fixed h e a d size and neck length and 11 c o m p o n e n t s that had a m o d u l a r femoral head with a Morse taper. The monolithic femoral c o m p o n e n t s were fixed with c e m e n t in 17 hips and porous coating in 4 hips. The modular femoral c o m p o n e n t s used biologic fixation in 7 (6 with porous coating and 1 with hydroxyapatite coating) and c e m e n t in 4. All u n c e m e n t e d femoral components were d e t e r m i n e d to be osteointegrated and stable before surgery by the radiographic criteria
described by Engh et al. ]16]. All c e m e n t e d femoral c o m p o n e n t s were n o t e d to be well fixed and had no radiographic evidence of loosening, using the criteria of Harris and McGann {17]. The group averaged 1.52 surgical procedures (range, 1-4), 1.21 previous arthroplasties (range, 1-3) performed prior to the index arthroplasty, and a 9-year survival (range, 1-18 years) of the current femoral prosthesis at time of revision acetabular surgery. The goals of surgery were to restore normal biomechanics and acetabular b o n y integrity and to provide c o n t a i n m e n t of the acetabular c o m p o n e n t with secure fixation. To e n h a n c e bone ingrowth, attempts were made to maximize h o s t - b o n e contact and achieve rigid stability of the porous acetabular implant. Rigid graft fixation, alignment of lag screws and graft trabeculae in the weight-bearing axis, and the concept of positioning the allograft u n d e r a viable bed were followed at the time of surgery to e n h a n c e fixation and longevity [18]. Leg-length discrepancy was improved by returning the hip center of rotation to an anatomic position with monolithic femoral c o m p o n e n t s and a combination of returning the hip center of rotation to an anatomic position and altering neck length in modular c o m p o n e n t s w h e n necessary. The modified direct lateral approach was used in 20 hips [I9]. In the remaining cases, the trochanteric slide [20] (7), transtrochanteric (4), and triradiate [2 l] (1) approaches were used. Patients with significant ilioischial structural deficiency requiring posterior c o l u m n bone-grafting and plating were a p p r o a c h e d via posterior transtrochanteric or trochanteric slide exposure [20] (Fig. 1). The modified direct lateral approach was used for patients with bone stock deficiencies in the posterior wall, superior dome, and central portions of the acetabu l u m [19] (Fig. 2). An extensile exposure, such as the triradiate approach, was used for pelvic dissociation [21 ]. Routine anteroposterior radiographs of the pelvis and proximal femurs and a true lateral radiograph of the hip were obtained and reviewed before surgery, immediately after surgery, and at yearly intervals. The prosthetic components and acetabular defects were evaluated using radiographic criteria previously described [16,17,22-26]. W h e n indicated, Judet views were used to provide additional information. Zonal analysis was used to determine location, size, and progression of radiolucent lines and osteolysis of the bone-implant interface of the acetabulum [24]. Cup angle and the distance from the acetabular c o m p o n e n t to Kohler's line and the teardrop were measured and compared on serial radiographs [27,28]. Linear migration of the acetab-
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Fig. 1. Radiographs of the hip of a 78-year-old woman with a failed cementless cup, 3 years after a total hip arthroplastg for traumatic osteoarthritis secondary to an associated posterior column and posterior wall acetabular fracture, initially treated without surgery. (A, B) Preoperative radiographs suggest an ilioischial deficiency, type III. The femoral component is a N-inch porous-coated stem with a modular head that appears stable and well fixed with bony ingrowth. (C) Six years after revision acetabuloplasty, a grade III reconstruction with structural allograft fixed to host ilium and ischiurn, using a pelvic reconstruction plate and interfragmentary screw fixation, was performed via a trochanteric slide approach.
ular c o m p o n e n t was defined as a c h a n g e in direct i o n - e i t h e r medial, superior, or a c o m b i n a t i o n of b o t h [28]. Rotational m i g r a t i o n was defined as a c h a n g e in theta angle. P o r o u s - c o a t e d h e m i s p h e r i c cups w e r e placed in all cases at t h e time of revision acetabuloplasty. The a v e r a g e a c e t a b u l a r c o m p o n e n t i m p l a n t e d at the time of s u r g e r y w a s 61 m m (range, 5 2 - 7 4 ) . Prior to April I 9 8 9 , the a c e t a b u l u m w a s p r e p a r e d to o b t a i n line-to-line fit to t h e s a m e size as t h e o u t e r shell of the c o m p o n e n t . Five a c e t a b u l a r c o m p o n e n t s w i t h peg fixation w e r e u s e d in 5 hips a n d 2 spherical c o m p o n e n t s t h a t w e r e s u p p l e m e n t e d w i t h ,;crew
fixation w e r e i m p l a n t e d in 2 hips. Since M a y 1989, the a c e t a b u l u m has b e e n p r e p a r e d b y c o n c e n t r i c r e a m i n g using a spherical cup in 25 hips u n d e r r e a m e d b y 2 - 4 m m . E i g h t e e n of the 25 i n v o l v e d use of 1-3 6 . 5 - m m cancellous screws to supplem e n t the initial fixation of the acetabular c o m p o n e n t . S e v e n of the acetabular c o m p o n e n t s w e r e n o t t h o u g h t to require a n y a d j u v a n t screw fixation, a l l o w i n g use of a solid acetabular shell w i t h o u t a n y holes in it. S u p p l e m e n t a l screw fixation w a s u s e d o n l y if o n m a n u a l testing, by m a n i p u l a tion of the acetabular trial, m o t i o n w a s detected. All screws w e r e carefully placed into the safe zones
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Fig. 2. Radiographs of the hip of a 70-year-old woman with aseptic loosening of a cemented acetabular component. (A) Preoperative radiograph demonstrates a contained type II combined segmental cavitary defect, located superiorly. The femoral component is monolithic with a cemented stem, which is not loose. (B) Five-year postoperative radiograph demonstrating a grade II reconstruction using morsellized filler allograft, performed via a modified direct lateral approach.
of Wasielewski et al. [20]. Absence of any m o t i o n was felt to correspond to intrinsic press-fit stability, and no screws were used in that situation. After surgery, all patients received 48 hours of intravenous antibiotics. Patients were m a i n t a i n e d on warfarin (Coumadin) for t h r o m b o e m b o l i c prophylaxis for 6 weeks after surgery, unless there was a prior history of a t h r o m b o e m b o l i c event; in that event, a 12-week period of anticoagulation was performed. Patients were restricted to t o e - t o u c h weight bearing for the first 6 weeks and gradually advanced to full weight bearing. The patients were evaluated after surgery at 2 weeks, 6 weeks, 3 months, 6 months, and yearly thereafter. Clinical evaluations including d e t e r m i n a t i o n of leg-length inequality, function, range of motion, and the Harris hip score [20] were p e r f o r m e d at each yearly follow-up examination. All radiographs were evaluated for heterotopic ossification [23]. No patients were lost to follow-up evaluation. Two patients (2 hips) died during the follow-up period from causes unrelated to the index hip surgery. Data from the yearly follow-up evaluations preceding the deaths were i n d u d e d in the study.
Results The A m e r i c a n A c a d e m y of Orthopaedic Surgeons (AAOS) C o m m i t t e e o n the Hip classification
of acetabular deficiencies was used (Table 1) [22]. There w e r e 4 hips that had little or no b o n e defect, 2 p u r e segmental defects (type I), 10 cavitary defects (type II), 15 c o m b i n e d segmental cavitary defects (type III), and 1 pelvic discontinuity (type IV). The grading system popularized by Borden and G r e e n k y [31] and H u n g e r f o r d et al. [32] (Table 2) was used to quantitate the m a g n i t u d e of the defect as it relates to the degree and quality of fixation w i t h i n host bone. There were 4 grade I reconstructions, 16 grade II reconstructions, 10 of w h i c h h a d cavitary defects, and 6 c o m b i n e d segm e n t a l cavitary defects. Twelve hips h a d a grade
Table 1. Classification of Acetabular Deficiencies Type I: segmental deficiencies Peripheral Superior Anterior Posterior Central (medial wall absent) Type II: cavitary deficiencies Peripheral Superior Anterior Posterior Central (medial wall intact) Type III: combined deficiencies Type IV: pelvic discontinuity Type V: crthrodesis (From D'Antonio et al. [22], with permission.)
Isolated Revision Acetabuloplasty Table 2. Grading System Grade I Complete prosthetic host-bone contact No bone-graft required Grade II Incomplete prosthetic host-bone contact Prosthesis stable on host bone Filler graft may be added Grade III Incomplete prosthetic host-bone contact Prosthesis is not stable in host bone Structural bone-graft required to stabilize the prosthesis (From D'Antonio [3], with permission.)
III reconstruction, 9 of w h i c h h a d c o m b i n e d segm e n t a l cavitary defects, 2 p u r e s e g m e n t a l defects, a n d 1 pelvic discontinuity. Two hips (6%) required a second revision acetabuloplasty during the r e p o r t e d period because of loss of fixation of the acetabular c o m p o n e n t . B o t h h a d a grade III reconstruction w h e r e the i m p l a n t was d e p e n d e n t on the b o n e - g r a f t for structural support. Intraoperative inspection s h o w e d incorporation of b o n e - g r a f t (although no biopsy was obtained) a n d loss of prosthetic fixation without evidence of graft failure. Each case was re,wised to a larger-diameter i n g r o w t h socket w i t h a d j u v a n t screw fixation w i t h o u t the n e e d for additional b o n e - g r a f t , resulting in a grade II reconstruction at the time of rerevision (Fig. 3). The intervals b e t w e e n the i n d e x a n d repeat revisions w e r e 14 and 48 m o n t h s , respectively. The original allograft united to host bone, was structurally intact, a n d restored h o s t - b o n e stock. This facilitated the s u b s e q u e n t revision by simplifying the reconstruction on the previous revision and permitting stable initia] fixation w i t h o u t further bone-grafting. The 2 repeat revisions w e r e also done w i t h o u t r e m o v a l of the femoral components, which r e m a i n e d well fixed. At the m o s t recent evaluation, all c o m p o n e n t s were radiographically s h o w n to be stable and the patients clinically asymptomatic, at a m e a n of 43 m o n t h s (36 and 50 months) after repeat acetabular revision. Twenty (63%) acetabular components had adjunctive screw fixation w i t h an average of 2.1 screws (range, 1-3 screws). The only screw breakage, migration, or associated radiolucencies w e r e in the 2 cups requiring rerevision. Isolated radiolucent lines w e r e present in the acetabular zones, in 9 % of cases in zone 1, 15% in zone 2, a n d 35 % in zone 3. No radiolucencies w e r e evident in 32% of the hips. In 2 of the 32 acetabular c o m p o n e n t s , 2 of the 3 zones w e r e inw)lved. There was 1 c o n t i n u o u s line in all 3 zones {24]. All radiolucencies w e r e nonprogressive a n d less tlhan 2 m m . In addition, at final follow-up e x a m i n a t i o n ,
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no hip had evidence of periacetabular osteolysis. Only 1 acetabular c o m p o n e n t h a d d o c u m e n t e d rotational migration at 22 m o n t h s , w h i c h b e c a m e stable w i t h o u t a n y further progression over a subsequent 5-year follow-up period. Radiographic analysis of the femoral c o m p o n e n t s revealed that those using biologic fixation all r e m a i n e d osseointegrated a n d stable w i t h endosteal spot welds [15]. There w e r e no circumferential radiolucencies (lines) or subsidence {16]. One c e m e n t e d femoral c o m p o n e n t at 77 m o n t h s f r o m the index surgery s h o w e d a radiolucent zone at the b o n e - c e m e n t interface that was not present on i m m e d i a t e postoperative or previous follow-up radiographs. At 98 m o n t h s after surgery, despite a good clinical result (a Harris hip score of 86 points), radiographs d e m o n s t r a t e d progression and m e t the criteria established by Harris and M c G a n n for possible loosening of the femoral c o m p o n e n t {17]. The r e m a i n i n g c e m e n t e d femoral c o m p o n e n t s w e r e stable and solidly fixed. None s h o w e d evidence of definite loosening (radiographic evidence of migration of the c o m p o n e n t or the cement) or probable loosening (a complete radiolucent zone) [17]. The m e a n pre- and postoperative Harris hip scores w e r e 44 a n d 83, respectively. The pre- and postoperative p a i n scores w e r e 14 a n d 42, respectively. There was a n overall incidence of heterotopic ossification of 54%; class I, 32%; class II, 24%; class III, 7%; class IV, 0 % [23]. Leg-length inequality averaged 14 m m (range, 0-40) before a n d 3 m m (range, 0-12) after surgery. There was 1 clinical deep vein thrombosis despite the routine use of perioperative warfarin, but there w e r e no d o c u m e n t e d cases of p u l m o n a r y embolization. There w e r e n o dislocations, n e r v e palsies, early or late infections, intraoperative fractures, or cases requiring f e m o r a l c o m p o n e n t r e m o v a l to facilitate surgical exposure.
Discussion Different m e c h a n i s m s of failure for t h e f e m oral a n d a c e t a b u l a r c o m p o n e n t s h a v e b e e n f o u n d [ 2 , 3 , 1 1 , 3 3 - 3 5 ] . Clinically, this correlates to different failure rates a n d inevitably leads to situations w h e r e only the acetabular c o m p o n e n t has loosened [35-39]. At the time of acetabular revision, there is almost always some f o r m of acetabular b o n e loss present, a n d m a n a g i n g acetabular defects can be challenging [2-6]. The difficulty in reconstructing the a c e t a b u l u m to a near-anatomic condition is d e p e n d e n t on the extent and location of b o n e loss. An anatomic reconstruction provides support for the cup and helps in restoring leg length.
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Fig. 3. Radiographs of the hip of a 64-year-old w o m a n with aseptic loosening of a c e m e n t e d a l l - p o l y e t h y l e n e cup. (A) Preoperative radiograph demonstrating a severe acetabular protrusio and a type III combined segmental cavitary deficiency. The femur has a cemented monolithic well-fixed component. (B) Immediate postoperative radiograph after a grade III reconstruction, using both structural and morsellized allograft. To restore normal biomechanics and place the hip center in the normal anatomic location, morsellized graft was first packed against the residual fibrous m e m b r a n e of the protrused medial wall as outlined by the arrows, followed by a structural allograft. (C) Fourteen months after revision acetabuloplasty, radiograph shows breakage of screws, with failure and migration of cup. (D) Three years after repeat revision acetabuloplasty using a larger-diameter cup with 1 adjuvant screw. No additional bone-graft was necessary, as the allograft from the index surgery was incorporated, allowing a grade II reconstruction. Radiographic assessm e n t shows graft united to host bone, with evidence of trabecular bridging and remodeling of the medial wall.
R e m o v a l of t h e f e m o r a l c o m p o n e n t h a s b e e n reco m m e n d e d to p r o v i d e a d e q u a t e a c e t a b u l a r e x p o s u r e to p e r m i t a p p r o p r i a t e r e c o n s t r u c t i o n [ 7 - 1 1 ] . Revision acetabular component surgery without r e m o v a l of t h e f e m o r a l c o m p o n e n t has the
p o t e n t i a l a d v a n t a g e of r e d u c i n g t h e t i o n s a s s o c i a t e d w i t h r e m o v a l of a femoral component but may restrict e x p o s u r e , r e s u l t i n g i n p e r f o r m a n c e of quate reconstruction.
complicawell-fixed acetabular an inade-
Isolated Revision Acetabuloplasty
Over a 6-year period, we reported on 32 hips on which an isolated cementless revision acetabuloplasty had b e e n p e r f o r m e d out of a total of 171 revision hip arthroplasties. This I 8 % incidence is in accordance with the 15 % of revision THAs ~-hat do not require revising the femoral c o m p o n e n t [1 ]. Reported benefits of concomitant femoral stem removal for isolated acetabular loosening include the ability to provide superior exposure and more satisfactorily address instability or leg-length inequality by adjusting femoral component position, neck length, or head size {7,8, I 1]. Such potential benefits must be weighed against the associated short- and long-term complications. The rate of intraoperative femoral perforation or fracture during femoral revision has been reported as high as 21% {11,40,41]. There are also the hazards of increased operating time and blood loss. In addition, the long-term results of revised femoral components have been clinically inferior to those of the femoral components of primary THA [8,10,1 I-15]. The "tap out-tap in" technique has been descrf.bed in which the femoral c o m p o n e n t is r e m o v e d and t h e n reinserted, with or w i t h o u t additional cement, into the original cement mantle [7,11,42,43]. The use of ultrasound tools to assist in removal of the femoral c o m p o n e n t and create surface modifications within the original c e m e n t mantle has been described [8]. This allows recementing of a femoral c o m p o n e n t into a stable c e m e n t mantle. These a f o r e m e n t i o n e d techniques are indicated only in carefully selected cases in which the c e m e n t e d femoral prosthesis is a s m o o t h stem and there is no radiographic or clinical evidence of loosening. Only 37% (12) of the hips in this study qualified for use of these techniques; however, these techniques are not applicable for c o n t e m p o r a r y femoral components, such as c e m e n t e d t e x t u r e d or precoated stems and those stabilized by biologic ingrowth, which accounted for 63% (20) of the hips studied. In our study, all 32 hips u n d e r w e n t revision acetabuloplasty w i t h o u t removal of the femoral stem because it was s h o w n to be stable and well fixed both radiographically and clinically at the time the index surgery was performed. The surgical approach used was determined before surgery, based on the type of acetabular defect {22]. The presence of the femoral c o m p o n e n t did not influence the selection of the surgical approach. A modified direct lateral approach was predominantly used in this series [19]. In cases in which additional exposure was needed, other specific surgical approaches were used. At the latest follow-up examination (at a m e a n of 58 months), 30 of the acetabular c o m p o n e n t s
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inserted at the index surgery were judged to be stable (94%), with no additional operation necessary. In 4 cases, a grade I reconstruction was performed; no bone-graft was used. Demonstrable evidence of acetabular b o n e loss was n o t e d in the remaining 28 of 32 hips undergoing acetabular revision. There were 16 grade II reconstructions in which morselfized filter graft was used: 10 of these had cavitary defects, and 6 had a combined segmental cavitary defect. In 12 cases, grade III reconstructions were performed, 9 with combined segmental cavitary defects, 2 with pure segmental defects, and 1 with pelvic discontinuity. Thus, 37% of our patients u n d e r w e n t structural allografting to stabilize their prostheses. It is from this high-risk group that repeat revision surgery was n e e d e d in 2 hips. In both hips, aseptic loosening of the acetabuIar c o m p o n e n t was noted, at 14 and 48 months, respectively, after index acetabuloplasty. The graft at the time of repeat acetabuloplasty was found to be grossly incorporated. No further structural allografting was performed. This facilitated the repeat revisions, which at the most recent follow-up examinations at 36 and 50 months, respectively, continue to be successful. The original allografl in both hips was used in the n e w reconstruction. Each hip was rerevised with a large-diameter porouscoated implant with adjuvant screw fixation, a grade II reconstruction. The 2 repeat revisions were also done without removing the femoral components, which remained well fixed. Although these cases represented clinical failures, incorporation of the allograft used in the initial reconstruction restored bone stock and simplified the second revision surgery. Some authors consider restoring bone stock the major goal of complex revision acetabuloplasty, and in grade III reconstructions a two-stage revision acetabuloplasty m a y be required [4,26,44]. At 22 months, I cup demonstrated rotational migration, which stabilized and remained nonprogressive over a 5-year follow-up periods. At the time of surgery, the patient had a grade II reconstruction, and it was thought that the combination of an intact rim and the achievement of a stable press-fit with the hemispheric Porous-coated c o m p o n e n t obviated the need for supplemental screw fixation. Despite a good clinical result, early rotational migration of the cup might have been prevented by using screws for immediate adjunctive stability. No hip in this study required revision because of femoral loosening. In 1 patient, at 8 years after the index revision acetabuloplasty, there was radiographic evidence of the cemented femoral component's being possibly loose, but it was asymptomatic [I7]. All other femoral components remain well
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fixed, with no other potential or pending revisions. Femoral c o m p o n e n t s have been f o u n d to loosen at a linear rate until 10 years. After 10 years, however, the rates plateau [30-39]. In this series, the femoral c o m p o n e n t s had been in place 1-18 years prior to the index revision acetabuloplasty. Since that time, the femoral c o m p o n e n t s have remained well fixed an additional 3-9 years. In light of the inferior results achieved with revision femoral c o m p o n e n t surgery compared with primary surgery, maintaining the original femoral c o m p o n e n t w h e n solidly fixed has significant advantages [8,10,11-15]. The study group as a whole enjoyed symptomatic relief and functional i m p r o v e m e n t after revision acetabuloplasty. Harris hip scores increased by a m e a n of 39 points, while the pain scores increased by 28 points. Prior to acetabular revision, the m e a n leglength inequality measured 14 mm. After surgery, the m e a n leg-length discrepancy was 3 mm. Only 11 of 32 hips (34%) had a modular femoral head allowing additional adjustment of the leg length at the time of surgery. The remaining 66% of the hips had a monolithic femoral component, with a fixed head size and neck length. In 1 patient, a deep vein thrombosis was diagnosed despite postoperative warfarin prophylaxis: the patient was successfully treated with a 6 - m o n t h course of full anticoagulation. There were no clinical cases of p u l m o n a r y embolization, dislocation, nerve palsy, or infection. Revision acetabuloplasty using a cementless hemispheric acetabular c o m p o n e n t , with or without bone-grafting, has h a d good mid- to l o n g - t e r m success [ 4 - 6 , 1 0 , 2 6 - 2 8 , 4 5 - 4 9 ] . The results of our study compare favorably with these reports, thus suggesting that revision acetabuloplasty can be perf o r m e d w i t h o u t r e m o v i n g or revising a stable, well-fixed femoral c o m p o n e n t , and not c o m p r o mise the final outcome.
References 1. Harris WH: Modularity is unnecessary in primary femoral THA but has some advantages in primary acetabular THA. J Arthroplasty 11:334, 1996 2. Schmalzried TE Kwong CM, Jasty M e t al: The mechanism of loosening of cemented acetabular components in total hip arthroplasty. Clin Orthop 274:60, 1992 3. D'Antonio JA: Acetabular reconstruction in revision total hip arthroplasty. Semin Arthroplasty 6:45, 1995 4. Garbuz D, Morsi E, Gross AE: Revision of the acetabular component of a total hip arthroplasty with a massive structural allograft: study with a minimum five-year follow-up. J Bone Joint Surg 78A:693, 1996
5. Paprofsky WG, Perona PG, Lawrence JM: Acetabular defect classification and surgical reconstruction in revision arthroplasty: a six year follow-up evaluation. J Arthroplasty 9:33, I994 6. Morsi E, Garbuz D, Gross AE: Revision total hip arthroplasty with shelf bulk allografts: a long term follow-up study. J Arthroplasty 11:86, 1996 7. Barrack RE, Folgueras AJ: Revision total hip arthroplasty: the femoral component. J Am Acad Orthop Surg 3:79, 1995 8. McCallum JD, Hozack W J: Recementing a femoral component into a stable cement mantle using ultrasound tools. Clin Orthop 319:232, I995 9. Heekin RD, Engh CA, Vinh T: Morselized allograft in acetabular reconstruction post mortem retrieval analysis. Clin Orthop 319:184, 1995 I0. Silverton CD, Rosenberg AG, Sheinkop MB et al: Revision total hip arthroplasty using a cementless acetabular component technique and results. Clin Orthop 319:201, 1995 11. Nabors ED, Liebelt R, Mattingly DA, Bierbaum BE: Removal and reinsertion of cemented femoral components during acetabular revision. J Arthroplasty II:146, 1996 12. Amstutz HC, MA SM, Jinnah RH, Mal L: Revision of aseptic loose total hip arthroplasties. Clin Orthop 170:21, 1982 13. Callaghan J J, Salvati EA, Pellici PM et al: Results of revision for mechanical failure after cemented total hip replacement, 1979 to 1982: a two to five year follow-up. J Bone Joint Surg 67A:1074, 1985 14. Hunter GA, Welsh RE Cameron HU, Bailey WH: The results of revision of total hip arthroplasty. J Bone Joint Surg 61B:419, 1979 15. Jasty M, Harris WH: Salvage total hip reconstruction in patients with major acetabular bone deficiency using structural femoral head allografts. J Bone Joint Surg 72B:63, 1990 16. Engh CA, Massin P, Suthers KE: Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop 257:107, 1990 17. Harris WI-I, McGann WH: Loosening of the femoral component after use of the medullary-plug technique: follow-up note with a minimum five-year follow-up. J Bone Joint Surg 68A:1064, i986 18. Chandler HE Penenberg BL: Bone stock deficiency. In total hip replacement: classification and management. Slack, Thorofare, NJ, 1989 19. Moskal, JT, Mann JW: A modified direct lateral approach for primary hip and revision total hip arthroplasty: a prospective analysis of 453 cases. J Arthroplasty 11:255, 1996 20. Glassman A, Engh C, Bobyn J: A technique of extensile for total hip arthroplasty. J Arthroplasty 2:11, 1987 21. Krackow KA, Steinman H, Cohen BT et al: Clinical experience with a triradiate exposure of the hip for difficult total hip arthroplasty. J Arthroplasty 3:267, 1988
Isolated Revision Acetabuloplasty 22. D'Antonio JA, Capello WN, Borden LS et al: Classification and m a n a g e m e n t of acetabular abnormalities in total hip arthroplasty. Clin Orthop 243:126, 1989 23. Brooker AF, B o w e r m a n JW, Robinson RA et al: Ectopic ossification following total hip replacement: incidence and a m e t h o d of classification. J Bone Joint Surg 55A:1629, 1973 24. DeLee JG, Charnley J: Radiological demarcation of cemented sockets in total hip replacement. Clin Orthop 121:20, 1976 25. Gruen TA, McNeice GM, Amstutz HC: "Modes of failure" of cemented stem-type femoral components: a radiographic analysis of loosening. Clin Orthop 141:17, 1979 26. Lawrence JM, Engh CA, Macalino GE, Laura GR: Outcome of revision hip arthroplasty done without cement. J Bone Joint Surg 76A:965, 1994 27. Padgett DE, Kull L, Rosenberg A et al: Revision of the acetabular component without cement after total hip arthroplasty: three to six year follow-up. J Bone Joint Surg 75A:663, 1993 28. Dorr LD, Wan Z: Ten years of experience with porous acetabular components for revision surgery. Clin Orthop 319:191, 1995 29. Wasjelewski RC, Cooperstein LA, Kruger ME Rubash HE: Acetabular a n a t o m y and transacetabular fixation of screws in total hip arthroplasty. J Bone Joint Surg 72A:501, 1990 30. Harris WH: Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a n e w m e t h o d of result evaluation. J Bone Joint Surg 51A:737, 1969 31. Borden LS, Greenky SS: The difficult primary total hip replacement: acetabular problems, p. 1007. In Steinberg ME (ed): The hip and its disorders. WB Saunders, Philadelphia, 1991 32. Hungerford DS, Krackow KA, Lennox DW: The PCA primary and revision hip systems. In fitzgerald R (ed): N o n - c e m e n t e d total hip arthroplasty. Lippincott-Raven, New York, 1988 33. Maloney WJ, Jasty MJ, Burke DW et al: Biomechanical and histologic investigation of cemented total hip arthroplasties. Clin Orthop 249:129, 1989 34. Petrera P, Rubash HE: Revision total hip arthroplasty: the acetabular component. J A m Acad Orthop Surg 3:15, 1995 35. Jasty M, Maloney WJ, Bragdon CR et al: Histomorphological studies of the long-term skeletal responses
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to well fixed cemented femoral components. J Bone Joint Surg 72A:1220, 1990 Sutherland CS, Wilde AH, Borden LS, Marks KE: A ten year follow-up of one h u n d r e d consecutive Mueller curved stem total hip arthroplasty. J Bone Joint Surg 64A:970, 1982 Stauffer RN: Ten-year follow-up study of total hip replacement. J Bone Joint Surg 64A:983, 1982 Mulroy RD Jr, Harris WH: The effect of improved cementing techniques on component loosening in total hip replacement. J Bone Joint Surg 72B:757, 1990 Mulroy WE Estok DM, Harris WH: Total hip arthroplasty with use of so-called second-generation cementing technique. J Bone Joint Surg 77A:1845, 1995 Christiansen CM, Seger BM, Schultz RB: Management of intraoperative femur fractures associated with revision hip arthroplasty. Clin Orthop 248:177, 1989 Turner RH, Mattingly DA, Scheller A: Femoral revision arthroplasty using a long-stem femoral component: clinical and radiographic analysis. J Arthroplasty 2:247, 1987 Archibald DAA, Protherae K, Stother IG, Campbell A: A simple technique for acetabular revision: brief report. J Bone Joint Surg 70B:838, 1988 Lieberman JR, Moeckel BH, Evans BG et al: Cement-within-cement revision hip arthroplasty. J Bone Joint Surg 75B:869, 1993 Pollock FH, Whiteside LA: The fate of massive allografts in total hip acetabular revision surgery. J Arthroplasty 7:271, 1992 Engh CA, Glassman AH, Griffin WL, Mayer JG: Results of cementless revision for failed cemented total hip arthroplasty. Clin Orthop 235:91, 1988 Lachiewiez PE Hussamy OD: Revision of the acetabulum without cement with use of the Harris-Galante porous-coated implant. J Bone Joint Surg 76A:1834, 1994 Paprosky WG, Magnus RE: Principles of bone grafting in revision total hip arthroplasty: acetabular technique. Clin Orthop 298:147, 1994 Morsi E, Garbuz D, Gross AE: Total hip arthroplasty with shelf grafts using u n c e m e n t e d cups: a longterm follow-up study. J Arthroplasty 11:81, 1996 Tanzer M, Drucker D, Jasty M e t al: Revision of the acetabular component with an u n c e m e n t e d Harris-Galante porous-coated prosthesis. J Bone Joint Surg 74A:987, 1992
Isolated Revision Acetabuloplasty Using a Porous-coated Cementless Acetabular C o m p o n e n t W i t h o u t R e m o v a l of a Well-fixed Femoral Component A 3- to 9-Year Follow-up Study Joseph T. Moskal, MD,* Olumide A. Danisa, MD,-I- and Christopher I. Shaffrey, MD~-$
Abstract: The results of isolated acetabular revision performed in 31 patients (32 hips) were monitored for between 3 and 9 years. All femoral components were well fixed and not removed or revised at the time of index surgery. There were 4 hips with little or no acetabular bony defect, 2 hips with pure segmental defects (type I), 10 hips with cavitary defects (type II), 15 with combined segmental cavitary defects (type III), and 1 with pelvic discontinuity (type IV). All revision acetabular implants were cementless, using a porous-coated hemispheric cup with or without bone-graft. There were four grade I reconstructions, 16 grade II reconstructions, and 12 grade III reconstructions. At final follow-up evaluation 94% of the cups were judged to be stable. Two hips required a second revision acetabuloplasty because of loss of fixation of the cup. The 2 repeat revisions were also done without removal of the femoral component. One acetabular component had evidence of rotational migration, which stabilized and remained nonprogressive. There were no cases of femoral component radiographic or clinical failure. The mean pre and postoperative hip scores were 44 and 83, respectively. The pre- and postoperative pain scores were 12 and 42, respectively. The findings of this study suggest that isolated acetabular revision, using a cementless porous-coated hemispheric cup, can be successfully performed without removing or revising a well-fixed femoral stem and not compromise the final outcome. K e y w o r d s : Revision acetabuloplasty, loose acetabular component, well-fixed femoral component, arthroplasty.
A p p r o x i m a t e l y 1 5 % of r e v i s i o n h i p a r t h r o p l a s t y is p e r f o r m e d for i s o l a t e d f a i l u r e of t h e a c e t a b u l a r c o m p o n e n t [ I ] . T h e c o m p l e x i t y of a c e t a b u l a r revi-
sion depends largely on the reconstruction required to r e s t o r e n o r m a l a n a t o m y d u e to a c e t a b u l a r b o n e loss [ 2 - 6 ] . F e m o r a l c o m p o n e n t r e m o v a l h a s b e e n recommended to p r o v i d e a d e q u a t e acetabular e x p o s u r e i n cases in w h i c h a s i g n i f i c a n t r e c o n s t r u c t i o n n e e d s to b e p e r f o r m e d [ 7 - 1 1 ] . C o m p a r e d with isolated revision acetabuloplasty, however, c o m b i n e d f e m o r a l a n d a c e t a b u l a r r e v i s i o n is a s s o c i a t e d w i t h i n c r e a s e d c o m p l i c a t i o n rate, s u r g i c a l t i m e , b l o o d loss, a n d cost [7,11]. T h e l o n g - t e r m r e s u l t s of r e v i s i o n f e m o r a l a r t h r o p l a s t y a r e clinically i n f e r i o r to f e m o r a l c o m p o n e n t s of p r i m a r y
From the *Roanoke Orthopaedic Center, Roanoke; ]-University of Virginia, Charlottesville; and ~Naval Medical Center, Portsmouth, Virginia. The views expressed in this article are those of the authors a n d do n o t reflect the official policy or position of the D e p a r t m e n t of the Navy, U.S. D e p a r t m e n t of Defense, or t h e U.S. g o v e r n m e n t . Reprint requests: Joseph T. Moskal, MD, Roanoke Orthopaedic Center, 4064 Postal Drive, SW, Roanoke, VA 24018.
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total hip arthroplasty (THA); therefore, maintaining the original well-fixed femoral prosthesis w o u l d be a theoretic advantage if it did not compromise the revision acetabuloplasty [5,10-15]. The purpose ot this study was to determine w h e t h e r revision of an isolated failed acetabular c o m p o n e n t w i t h o u t the removal of a well-fixed femoral stem can be successfully performed even w h e n complex acetabular reconstruction is required and not compromise the ultimate outcome. The status of the femoral components was also analyzed to determine if the processes that cause acetabular loosening result in a higher than expected femoral comp o n e n t failure rate in the retained prostheses.
Materials and Methods All patients w h o had revision hip arthroplasty were identified from a prospectively developed database of all primary and revision THAs performed by the senior a u t h o r (J.T.M.). From December 1987 to December 1993, 171 consecutive revision THAs were performed in 159 patients, and 31 patients with 32 hips requiring only revision of the acetabular c o m p o n e n t were identified. Criteria for inclusion in the study were aseptic loosening and malposition of a previously cemented or uncem e n t e d acetabular c o m p o n e n t with a well-fixed femoral prosthesis. The average time from revision acetabuloplasty to the latest follow-up examination was 58 m o n t h s (range, 3 6 - 1 1 4 months). The average patient age was 66 years (range, 29-87 years). There were 20 w o m e n and 11 men. The preoperative diagnosis was aseptic loosening in 31 cases and malposition of the acetabular c o m p o n e n t in 1 hip. Eighteen hips had c e m e n t e d acetabular components 10 of which were all polyethylene, and 8 were metal backed. All cemented components were revised for aseptic loosening. F o u r t e e n acetabular components were not cemented (12 porous coated, 1 hydroxyapatite coated, and I threaded). Thirteen of the n o n c e m e n t e d c o m p o n e n t s were revised for aseptic loosening and 1 was malpositioned. There were 21 monolithic (monoblock) femoral c o m p o n e n t s with a fixed h e a d size and neck length and 11 c o m p o n e n t s that had a m o d u l a r femoral head with a Morse taper. The monolithic femoral c o m p o n e n t s were fixed with c e m e n t in 17 hips and porous coating in 4 hips. The modular femoral c o m p o n e n t s used biologic fixation in 7 (6 with porous coating and 1 with hydroxyapatite coating) and c e m e n t in 4. All u n c e m e n t e d femoral components were d e t e r m i n e d to be osteointegrated and stable before surgery by the radiographic criteria
described by Engh et al. ]16]. All c e m e n t e d femoral c o m p o n e n t s were n o t e d to be well fixed and had no radiographic evidence of loosening, using the criteria of Harris and McGann {17]. The group averaged 1.52 surgical procedures (range, 1-4), 1.21 previous arthroplasties (range, 1-3) performed prior to the index arthroplasty, and a 9-year survival (range, 1-18 years) of the current femoral prosthesis at time of revision acetabular surgery. The goals of surgery were to restore normal biomechanics and acetabular b o n y integrity and to provide c o n t a i n m e n t of the acetabular c o m p o n e n t with secure fixation. To e n h a n c e bone ingrowth, attempts were made to maximize h o s t - b o n e contact and achieve rigid stability of the porous acetabular implant. Rigid graft fixation, alignment of lag screws and graft trabeculae in the weight-bearing axis, and the concept of positioning the allograft u n d e r a viable bed were followed at the time of surgery to e n h a n c e fixation and longevity [18]. Leg-length discrepancy was improved by returning the hip center of rotation to an anatomic position with monolithic femoral c o m p o n e n t s and a combination of returning the hip center of rotation to an anatomic position and altering neck length in modular c o m p o n e n t s w h e n necessary. The modified direct lateral approach was used in 20 hips [I9]. In the remaining cases, the trochanteric slide [20] (7), transtrochanteric (4), and triradiate [2 l] (1) approaches were used. Patients with significant ilioischial structural deficiency requiring posterior c o l u m n bone-grafting and plating were a p p r o a c h e d via posterior transtrochanteric or trochanteric slide exposure [20] (Fig. 1). The modified direct lateral approach was used for patients with bone stock deficiencies in the posterior wall, superior dome, and central portions of the acetabu l u m [19] (Fig. 2). An extensile exposure, such as the triradiate approach, was used for pelvic dissociation [21 ]. Routine anteroposterior radiographs of the pelvis and proximal femurs and a true lateral radiograph of the hip were obtained and reviewed before surgery, immediately after surgery, and at yearly intervals. The prosthetic components and acetabular defects were evaluated using radiographic criteria previously described [16,17,22-26]. W h e n indicated, Judet views were used to provide additional information. Zonal analysis was used to determine location, size, and progression of radiolucent lines and osteolysis of the bone-implant interface of the acetabulum [24]. Cup angle and the distance from the acetabular c o m p o n e n t to Kohler's line and the teardrop were measured and compared on serial radiographs [27,28]. Linear migration of the acetab-
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Fig. 1. Radiographs of the hip of a 78-year-old woman with a failed cementless cup, 3 years after a total hip arthroplastg for traumatic osteoarthritis secondary to an associated posterior column and posterior wall acetabular fracture, initially treated without surgery. (A, B) Preoperative radiographs suggest an ilioischial deficiency, type III. The femoral component is a N-inch porous-coated stem with a modular head that appears stable and well fixed with bony ingrowth. (C) Six years after revision acetabuloplasty, a grade III reconstruction with structural allograft fixed to host ilium and ischiurn, using a pelvic reconstruction plate and interfragmentary screw fixation, was performed via a trochanteric slide approach.
ular c o m p o n e n t was defined as a c h a n g e in direct i o n - e i t h e r medial, superior, or a c o m b i n a t i o n of b o t h [28]. Rotational m i g r a t i o n was defined as a c h a n g e in theta angle. P o r o u s - c o a t e d h e m i s p h e r i c cups w e r e placed in all cases at t h e time of revision acetabuloplasty. The a v e r a g e a c e t a b u l a r c o m p o n e n t i m p l a n t e d at the time of s u r g e r y w a s 61 m m (range, 5 2 - 7 4 ) . Prior to April I 9 8 9 , the a c e t a b u l u m w a s p r e p a r e d to o b t a i n line-to-line fit to t h e s a m e size as t h e o u t e r shell of the c o m p o n e n t . Five a c e t a b u l a r c o m p o n e n t s w i t h peg fixation w e r e u s e d in 5 hips a n d 2 spherical c o m p o n e n t s t h a t w e r e s u p p l e m e n t e d w i t h ,;crew
fixation w e r e i m p l a n t e d in 2 hips. Since M a y 1989, the a c e t a b u l u m has b e e n p r e p a r e d b y c o n c e n t r i c r e a m i n g using a spherical cup in 25 hips u n d e r r e a m e d b y 2 - 4 m m . E i g h t e e n of the 25 i n v o l v e d use of 1-3 6 . 5 - m m cancellous screws to supplem e n t the initial fixation of the acetabular c o m p o n e n t . S e v e n of the acetabular c o m p o n e n t s w e r e n o t t h o u g h t to require a n y a d j u v a n t screw fixation, a l l o w i n g use of a solid acetabular shell w i t h o u t a n y holes in it. S u p p l e m e n t a l screw fixation w a s u s e d o n l y if o n m a n u a l testing, by m a n i p u l a tion of the acetabular trial, m o t i o n w a s detected. All screws w e r e carefully placed into the safe zones
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Fig. 2. Radiographs of the hip of a 70-year-old woman with aseptic loosening of a cemented acetabular component. (A) Preoperative radiograph demonstrates a contained type II combined segmental cavitary defect, located superiorly. The femoral component is monolithic with a cemented stem, which is not loose. (B) Five-year postoperative radiograph demonstrating a grade II reconstruction using morsellized filler allograft, performed via a modified direct lateral approach.
of Wasielewski et al. [20]. Absence of any m o t i o n was felt to correspond to intrinsic press-fit stability, and no screws were used in that situation. After surgery, all patients received 48 hours of intravenous antibiotics. Patients were m a i n t a i n e d on warfarin (Coumadin) for t h r o m b o e m b o l i c prophylaxis for 6 weeks after surgery, unless there was a prior history of a t h r o m b o e m b o l i c event; in that event, a 12-week period of anticoagulation was performed. Patients were restricted to t o e - t o u c h weight bearing for the first 6 weeks and gradually advanced to full weight bearing. The patients were evaluated after surgery at 2 weeks, 6 weeks, 3 months, 6 months, and yearly thereafter. Clinical evaluations including d e t e r m i n a t i o n of leg-length inequality, function, range of motion, and the Harris hip score [20] were p e r f o r m e d at each yearly follow-up examination. All radiographs were evaluated for heterotopic ossification [23]. No patients were lost to follow-up evaluation. Two patients (2 hips) died during the follow-up period from causes unrelated to the index hip surgery. Data from the yearly follow-up evaluations preceding the deaths were i n d u d e d in the study.
Results The A m e r i c a n A c a d e m y of Orthopaedic Surgeons (AAOS) C o m m i t t e e o n the Hip classification
of acetabular deficiencies was used (Table 1) [22]. There w e r e 4 hips that had little or no b o n e defect, 2 p u r e segmental defects (type I), 10 cavitary defects (type II), 15 c o m b i n e d segmental cavitary defects (type III), and 1 pelvic discontinuity (type IV). The grading system popularized by Borden and G r e e n k y [31] and H u n g e r f o r d et al. [32] (Table 2) was used to quantitate the m a g n i t u d e of the defect as it relates to the degree and quality of fixation w i t h i n host bone. There were 4 grade I reconstructions, 16 grade II reconstructions, 10 of w h i c h h a d cavitary defects, and 6 c o m b i n e d segm e n t a l cavitary defects. Twelve hips h a d a grade
Table 1. Classification of Acetabular Deficiencies Type I: segmental deficiencies Peripheral Superior Anterior Posterior Central (medial wall absent) Type II: cavitary deficiencies Peripheral Superior Anterior Posterior Central (medial wall intact) Type III: combined deficiencies Type IV: pelvic discontinuity Type V: crthrodesis (From D'Antonio et al. [22], with permission.)
Isolated Revision Acetabuloplasty Table 2. Grading System Grade I Complete prosthetic host-bone contact No bone-graft required Grade II Incomplete prosthetic host-bone contact Prosthesis stable on host bone Filler graft may be added Grade III Incomplete prosthetic host-bone contact Prosthesis is not stable in host bone Structural bone-graft required to stabilize the prosthesis (From D'Antonio [3], with permission.)
III reconstruction, 9 of w h i c h h a d c o m b i n e d segm e n t a l cavitary defects, 2 p u r e s e g m e n t a l defects, a n d 1 pelvic discontinuity. Two hips (6%) required a second revision acetabuloplasty during the r e p o r t e d period because of loss of fixation of the acetabular c o m p o n e n t . B o t h h a d a grade III reconstruction w h e r e the i m p l a n t was d e p e n d e n t on the b o n e - g r a f t for structural support. Intraoperative inspection s h o w e d incorporation of b o n e - g r a f t (although no biopsy was obtained) a n d loss of prosthetic fixation without evidence of graft failure. Each case was re,wised to a larger-diameter i n g r o w t h socket w i t h a d j u v a n t screw fixation w i t h o u t the n e e d for additional b o n e - g r a f t , resulting in a grade II reconstruction at the time of rerevision (Fig. 3). The intervals b e t w e e n the i n d e x a n d repeat revisions w e r e 14 and 48 m o n t h s , respectively. The original allograft united to host bone, was structurally intact, a n d restored h o s t - b o n e stock. This facilitated the s u b s e q u e n t revision by simplifying the reconstruction on the previous revision and permitting stable initia] fixation w i t h o u t further bone-grafting. The 2 repeat revisions w e r e also done w i t h o u t r e m o v a l of the femoral components, which r e m a i n e d well fixed. At the m o s t recent evaluation, all c o m p o n e n t s were radiographically s h o w n to be stable and the patients clinically asymptomatic, at a m e a n of 43 m o n t h s (36 and 50 months) after repeat acetabular revision. Twenty (63%) acetabular components had adjunctive screw fixation w i t h an average of 2.1 screws (range, 1-3 screws). The only screw breakage, migration, or associated radiolucencies w e r e in the 2 cups requiring rerevision. Isolated radiolucent lines w e r e present in the acetabular zones, in 9 % of cases in zone 1, 15% in zone 2, a n d 35 % in zone 3. No radiolucencies w e r e evident in 32% of the hips. In 2 of the 32 acetabular c o m p o n e n t s , 2 of the 3 zones w e r e inw)lved. There was 1 c o n t i n u o u s line in all 3 zones {24]. All radiolucencies w e r e nonprogressive a n d less tlhan 2 m m . In addition, at final follow-up e x a m i n a t i o n ,
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no hip had evidence of periacetabular osteolysis. Only 1 acetabular c o m p o n e n t h a d d o c u m e n t e d rotational migration at 22 m o n t h s , w h i c h b e c a m e stable w i t h o u t a n y further progression over a subsequent 5-year follow-up period. Radiographic analysis of the femoral c o m p o n e n t s revealed that those using biologic fixation all r e m a i n e d osseointegrated a n d stable w i t h endosteal spot welds [15]. There w e r e no circumferential radiolucencies (lines) or subsidence {16]. One c e m e n t e d femoral c o m p o n e n t at 77 m o n t h s f r o m the index surgery s h o w e d a radiolucent zone at the b o n e - c e m e n t interface that was not present on i m m e d i a t e postoperative or previous follow-up radiographs. At 98 m o n t h s after surgery, despite a good clinical result (a Harris hip score of 86 points), radiographs d e m o n s t r a t e d progression and m e t the criteria established by Harris and M c G a n n for possible loosening of the femoral c o m p o n e n t {17]. The r e m a i n i n g c e m e n t e d femoral c o m p o n e n t s w e r e stable and solidly fixed. None s h o w e d evidence of definite loosening (radiographic evidence of migration of the c o m p o n e n t or the cement) or probable loosening (a complete radiolucent zone) [17]. The m e a n pre- and postoperative Harris hip scores w e r e 44 a n d 83, respectively. The pre- and postoperative p a i n scores w e r e 14 a n d 42, respectively. There was a n overall incidence of heterotopic ossification of 54%; class I, 32%; class II, 24%; class III, 7%; class IV, 0 % [23]. Leg-length inequality averaged 14 m m (range, 0-40) before a n d 3 m m (range, 0-12) after surgery. There was 1 clinical deep vein thrombosis despite the routine use of perioperative warfarin, but there w e r e no d o c u m e n t e d cases of p u l m o n a r y embolization. There w e r e n o dislocations, n e r v e palsies, early or late infections, intraoperative fractures, or cases requiring f e m o r a l c o m p o n e n t r e m o v a l to facilitate surgical exposure.
Discussion Different m e c h a n i s m s of failure for t h e f e m oral a n d a c e t a b u l a r c o m p o n e n t s h a v e b e e n f o u n d [ 2 , 3 , 1 1 , 3 3 - 3 5 ] . Clinically, this correlates to different failure rates a n d inevitably leads to situations w h e r e only the acetabular c o m p o n e n t has loosened [35-39]. At the time of acetabular revision, there is almost always some f o r m of acetabular b o n e loss present, a n d m a n a g i n g acetabular defects can be challenging [2-6]. The difficulty in reconstructing the a c e t a b u l u m to a near-anatomic condition is d e p e n d e n t on the extent and location of b o n e loss. An anatomic reconstruction provides support for the cup and helps in restoring leg length.
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Fig. 3. Radiographs of the hip of a 64-year-old w o m a n with aseptic loosening of a c e m e n t e d a l l - p o l y e t h y l e n e cup. (A) Preoperative radiograph demonstrating a severe acetabular protrusio and a type III combined segmental cavitary deficiency. The femur has a cemented monolithic well-fixed component. (B) Immediate postoperative radiograph after a grade III reconstruction, using both structural and morsellized allograft. To restore normal biomechanics and place the hip center in the normal anatomic location, morsellized graft was first packed against the residual fibrous m e m b r a n e of the protrused medial wall as outlined by the arrows, followed by a structural allograft. (C) Fourteen months after revision acetabuloplasty, radiograph shows breakage of screws, with failure and migration of cup. (D) Three years after repeat revision acetabuloplasty using a larger-diameter cup with 1 adjuvant screw. No additional bone-graft was necessary, as the allograft from the index surgery was incorporated, allowing a grade II reconstruction. Radiographic assessm e n t shows graft united to host bone, with evidence of trabecular bridging and remodeling of the medial wall.
R e m o v a l of t h e f e m o r a l c o m p o n e n t h a s b e e n reco m m e n d e d to p r o v i d e a d e q u a t e a c e t a b u l a r e x p o s u r e to p e r m i t a p p r o p r i a t e r e c o n s t r u c t i o n [ 7 - 1 1 ] . Revision acetabular component surgery without r e m o v a l of t h e f e m o r a l c o m p o n e n t has the
p o t e n t i a l a d v a n t a g e of r e d u c i n g t h e t i o n s a s s o c i a t e d w i t h r e m o v a l of a femoral component but may restrict e x p o s u r e , r e s u l t i n g i n p e r f o r m a n c e of quate reconstruction.
complicawell-fixed acetabular an inade-
Isolated Revision Acetabuloplasty
Over a 6-year period, we reported on 32 hips on which an isolated cementless revision acetabuloplasty had b e e n p e r f o r m e d out of a total of 171 revision hip arthroplasties. This I 8 % incidence is in accordance with the 15 % of revision THAs ~-hat do not require revising the femoral c o m p o n e n t [1 ]. Reported benefits of concomitant femoral stem removal for isolated acetabular loosening include the ability to provide superior exposure and more satisfactorily address instability or leg-length inequality by adjusting femoral component position, neck length, or head size {7,8, I 1]. Such potential benefits must be weighed against the associated short- and long-term complications. The rate of intraoperative femoral perforation or fracture during femoral revision has been reported as high as 21% {11,40,41]. There are also the hazards of increased operating time and blood loss. In addition, the long-term results of revised femoral components have been clinically inferior to those of the femoral components of primary THA [8,10,1 I-15]. The "tap out-tap in" technique has been descrf.bed in which the femoral c o m p o n e n t is r e m o v e d and t h e n reinserted, with or w i t h o u t additional cement, into the original cement mantle [7,11,42,43]. The use of ultrasound tools to assist in removal of the femoral c o m p o n e n t and create surface modifications within the original c e m e n t mantle has been described [8]. This allows recementing of a femoral c o m p o n e n t into a stable c e m e n t mantle. These a f o r e m e n t i o n e d techniques are indicated only in carefully selected cases in which the c e m e n t e d femoral prosthesis is a s m o o t h stem and there is no radiographic or clinical evidence of loosening. Only 37% (12) of the hips in this study qualified for use of these techniques; however, these techniques are not applicable for c o n t e m p o r a r y femoral components, such as c e m e n t e d t e x t u r e d or precoated stems and those stabilized by biologic ingrowth, which accounted for 63% (20) of the hips studied. In our study, all 32 hips u n d e r w e n t revision acetabuloplasty w i t h o u t removal of the femoral stem because it was s h o w n to be stable and well fixed both radiographically and clinically at the time the index surgery was performed. The surgical approach used was determined before surgery, based on the type of acetabular defect {22]. The presence of the femoral c o m p o n e n t did not influence the selection of the surgical approach. A modified direct lateral approach was predominantly used in this series [19]. In cases in which additional exposure was needed, other specific surgical approaches were used. At the latest follow-up examination (at a m e a n of 58 months), 30 of the acetabular c o m p o n e n t s
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inserted at the index surgery were judged to be stable (94%), with no additional operation necessary. In 4 cases, a grade I reconstruction was performed; no bone-graft was used. Demonstrable evidence of acetabular b o n e loss was n o t e d in the remaining 28 of 32 hips undergoing acetabular revision. There were 16 grade II reconstructions in which morselfized filter graft was used: 10 of these had cavitary defects, and 6 had a combined segmental cavitary defect. In 12 cases, grade III reconstructions were performed, 9 with combined segmental cavitary defects, 2 with pure segmental defects, and 1 with pelvic discontinuity. Thus, 37% of our patients u n d e r w e n t structural allografting to stabilize their prostheses. It is from this high-risk group that repeat revision surgery was n e e d e d in 2 hips. In both hips, aseptic loosening of the acetabuIar c o m p o n e n t was noted, at 14 and 48 months, respectively, after index acetabuloplasty. The graft at the time of repeat acetabuloplasty was found to be grossly incorporated. No further structural allografting was performed. This facilitated the repeat revisions, which at the most recent follow-up examinations at 36 and 50 months, respectively, continue to be successful. The original allografl in both hips was used in the n e w reconstruction. Each hip was rerevised with a large-diameter porouscoated implant with adjuvant screw fixation, a grade II reconstruction. The 2 repeat revisions were also done without removing the femoral components, which remained well fixed. Although these cases represented clinical failures, incorporation of the allograft used in the initial reconstruction restored bone stock and simplified the second revision surgery. Some authors consider restoring bone stock the major goal of complex revision acetabuloplasty, and in grade III reconstructions a two-stage revision acetabuloplasty m a y be required [4,26,44]. At 22 months, I cup demonstrated rotational migration, which stabilized and remained nonprogressive over a 5-year follow-up periods. At the time of surgery, the patient had a grade II reconstruction, and it was thought that the combination of an intact rim and the achievement of a stable press-fit with the hemispheric Porous-coated c o m p o n e n t obviated the need for supplemental screw fixation. Despite a good clinical result, early rotational migration of the cup might have been prevented by using screws for immediate adjunctive stability. No hip in this study required revision because of femoral loosening. In 1 patient, at 8 years after the index revision acetabuloplasty, there was radiographic evidence of the cemented femoral component's being possibly loose, but it was asymptomatic [I7]. All other femoral components remain well
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fixed, with no other potential or pending revisions. Femoral c o m p o n e n t s have been f o u n d to loosen at a linear rate until 10 years. After 10 years, however, the rates plateau [30-39]. In this series, the femoral c o m p o n e n t s had been in place 1-18 years prior to the index revision acetabuloplasty. Since that time, the femoral c o m p o n e n t s have remained well fixed an additional 3-9 years. In light of the inferior results achieved with revision femoral c o m p o n e n t surgery compared with primary surgery, maintaining the original femoral c o m p o n e n t w h e n solidly fixed has significant advantages [8,10,11-15]. The study group as a whole enjoyed symptomatic relief and functional i m p r o v e m e n t after revision acetabuloplasty. Harris hip scores increased by a m e a n of 39 points, while the pain scores increased by 28 points. Prior to acetabular revision, the m e a n leglength inequality measured 14 mm. After surgery, the m e a n leg-length discrepancy was 3 mm. Only 11 of 32 hips (34%) had a modular femoral head allowing additional adjustment of the leg length at the time of surgery. The remaining 66% of the hips had a monolithic femoral component, with a fixed head size and neck length. In 1 patient, a deep vein thrombosis was diagnosed despite postoperative warfarin prophylaxis: the patient was successfully treated with a 6 - m o n t h course of full anticoagulation. There were no clinical cases of p u l m o n a r y embolization, dislocation, nerve palsy, or infection. Revision acetabuloplasty using a cementless hemispheric acetabular c o m p o n e n t , with or without bone-grafting, has h a d good mid- to l o n g - t e r m success [ 4 - 6 , 1 0 , 2 6 - 2 8 , 4 5 - 4 9 ] . The results of our study compare favorably with these reports, thus suggesting that revision acetabuloplasty can be perf o r m e d w i t h o u t r e m o v i n g or revising a stable, well-fixed femoral c o m p o n e n t , and not c o m p r o mise the final outcome.
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