Conservative Femoral Stem Revision

The Journal of Arthroplasty Vol. 24 No. 3 2009

Conservative Femoral Stem Revision Avoiding Therapeutic Escalation Alban Pinaroli, MD,* Frédéric Lavoie, MD, MSc, FRCSC,y Jean-Claude Cartillier, MD,z Philippe Neyret, MD,* and Tarik Ait Si Selmi, MD*

Abstract: A conservative approach to femoral revision is assessed. We report on 41 femoral revisions using an extensively coated hydroxyapatite primary femoral stem. Clinical, operative, and radiological data were gathered. Harris hip scores increased from 65/100 to 90/100 at the minimal follow-up of 1 year (P b .05). All stems showed signs of osseous integration. No significant migration was measured. No patient had to be reoperated because of problems related to the stem. Good results are reported for femoral revision with Paprosky type I and II bone defects with no significant difference between the 2 subgroups, hereby proving that conservative femoral revision is a reasonable treatment alternative. Reproducible results with such a technique may bring surgeons to be more aggressive when noticing early signs of femoral loosening. Key words: revision hip arthroplasty, femoral stem revision, primary intention stem, metaphyseal fixation, hydroxyapatite coating, bone loss. © 2009 Elsevier Inc. All rights reserved.

Revision total hip arthroplasty (RTHA) is a currently evolving issue because the annual number of such procedures is increasing [1-5]. It represents a significant socioeconomic burden [6], mainly because of the complexity of the surgical act [7-9]. Surgeon experience also plays a key role. On the femoral side, the objective is to replace the initial stem by another with a “fixation as proximal as possible and as distal as necessary” [10]. This concept implies using long stems, with or without bone grafting, in case of significant bone defects.

Numerous surgical methods involving various techniques have been proposed: - Cementless long femoral stems [5,11-18], sometimes with a hydroxyapatite coating [12,19], sometimes with distal locking [20,21]; - Cemented reconstruction stems [22]; - Cementless stem-allograft composite [23]; - Morcellized allograft combined with short cemented stem [7,9,24-26]. For us, these options constitute a therapeutic escalation, that is, a complexification of surgical treatment related to the sometimes unnecessary use of long stems as well as cement. This path could be avoided by the use of first intention implants with an osteoconductive coating, hereby allowing bone stock reconstitution by the bone itself [27]. In this study, we present a series of femoral component revisions using a forged titanium, quadrangular, and press-fit femoral stem entirely coated with hydroxyapatite (Corail, Depuy, Johnson & Johnson, Leeds, UK). This stem has proven its value in primary hip arthroplasties [28-32]. The objectives of the study are to evaluate if this implant

From the *Orthopedic Surgery Department, Centre Livet, Hôpital de la Croix-Rousse, Caluire, France; yOrthopedic Surgery Department, Hôpital Notre-Dame, Centre Hospitalier de l'Université de Montréal, Montréal, Canada; and zOrthopedic Surgery Department, Clinique Eugène André, Lyon, France. Submitted May 23, 2007; accepted December 3, 2007. No benefits or funds were received in support of the study. Frédéric Lavoie would like to thank the Société Française de Chirurgie Orthopédique et Traumatologique for their financial support during his fellowship year in France. Reprint requests: Tarik Ait Si Selmi, MD, Centre Livet, Hôpital de la Croix-Rousse, 8 rue de Margnolles, 69300 Caluire, France. © 2009 Elsevier Inc. All rights reserved. 0883-5403/07/2403-0006$36.00/0 doi:10.1016/j.arth.2007.12.002

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366 The Journal of Arthroplasty Vol. 24 No. 3 April 2009 can be a good choice for revision surgery and, if so, to determine when it should be used, specifically regarding the amount of femoral bone loss.

Material and Methods This retrospective study is based on 41 femoral component revisions using the Corail stem performed between 1989 and 2005 on 38 patients (17 men, 21 women, 25 left hips, 16 right hips, 3 bilateral). This component revision was always the first one. The mean age at revision surgery was 62 years (range, 2882), whereas the average delay between the 2 operations was 115 months (range, 1-348). Thirty revisions were performed because of aseptic loosening: 8 isolated acetabular loosenings, 5 isolated femoral loosenings (including 2 fractured stems), and 17 combined acetabular and femoral loosenings. In the 8 isolated acetabular loosenings, the femoral component was exchanged either for exposure purposes (monoblock stem) or to allow use of a different bearing surface (Morse taper compatibility) (Fig. 1). Six revisions were performed because of deep infection, 4 times as a 2-stage procedure and twice as a single-stage procedure. Two revisions were done after a fracture of the femoral prosthetic neck. Finally, for 3 cases, the reason for revision was a mechanical problem: one iliopsoas impingement, one 15 mm leg lengthening associated with hip pain, and one patient with subjective hip instability symptoms for whom significant pistoning was observed clinically and radiographically. All 3 hips had a decreased femoral offset. Before the revision procedure, a clinical examination was performed, and the Harris hip score was

calculated [33]. Preoperative radiological workup included an antero posterior (AP) view of the pelvis (weight bearing when possible) and AP and lateral view of the affected hip. We were then able to detect radiolucent lines and score the amount of bone loss according to the Paprosky classification [2,3]. Primary femoral stems were used in all cases (Corail, Depuy, Johnson & Johnson). It is a forged titanium alloy stem extensively coated with 155 μm of hydroxyapatite. It has a metaphyseal double taper and does not rely on diaphyseal fixation for stability. Coxa vara implants (neck shaft angle of 125° vs 135°) as well as high-offset implants (7 mm lateralization) are available for all stem sizes. Collared stems were used in all cases except when a high-offset stem was used because collared highoffset stems are not available for this implant. When available, the authors prefer collared stems because they feel these prevent stem migration. Surgeries were performed by 1 of 2 surgeons (T.A. and J.C.C.). Recorded data included the approach used, the type of implants removed, and the ease of extraction including the use of special extraction techniques. Bone loss was reassessed after component removal, again according to Paprosky. Type and size of the applied components were noted, as well as the use of bone grafting. Peroperative complications were detailed. The postoperative regimen included low-molecular-weight-heparin prophylactic therapy for 45 days. Weight bearing as tolerated was usually prescribed; otherwise, the reason was recorded. All patients were seen in an outpatient clinic between 6 and 8 weeks postoperatively, and then after 1 year. At the last follow-up (average, 30.4 months;

Fig. 1. Preoperative AP (A) and lateral (B) views of a loosened polyethylene cemented cup in a 30-year-old man. The monoblock cemented Charnley stem was well fixed but was removed for exposition purposes and to allow use of a hard on hard bearing surface. Femoral bone stock was good after stem removal. Good fixation was achieved with a primary intention Corail stem as seen on the postoperative AP view (C). Cancellous allograft was used to fill bone defects.

Conservative Femoral Stem Revision  Pinaroli et al

range, 12-120), the Harris hip score was calculated. Complications and repeat surgeries were recorded. An AP x-ray of the pelvis was systematically obtained in the immediate postoperative period, whereas the AP view of the pelvis as well as the AP and frog-leg lateral views of the operated hip was obtained at each follow-up visit. The magnification coefficient was always 1.2. Implant integration was assessed and recorded [34]. The vertical distance between the center of the prosthetic femoral head and the apex of the lesser trochanter was measured by an independent examiner on the immediate postoperative AP pelvis view and the same view at the last follow-up, providing an evaluation of femoral component migration. Student t test was performed on pre- and postoperative Harris hip scores and on the vertical position of the femoral component to detect significant differences with a P value of .05.

Results Revision Procedure A posterolateral approach was used for all cases except one for which an anterolateral approach was chosen. The removed femoral components were all first intention implants: 26 smooth cemented stems, 14 cementless hydroxyapatitecoated stems, and 1 cementless screwed stem. Stem removal was relatively straightforward for 33 (80.5%) cases, but special extraction techniques were necessary for 8 (19.5%) patients: 1 extended trochanteric osteotomy (fractured cemented stem), 2 linea aspera osteoclasies (1 cementless screwed stem and 1 cementless hydroxyapatite-coated stem), and 1 cortical window (large cement plug). A mechanical cement extractor (EMC, Depuy, Johnson & Johnson) was used in 4 cases. This device is made of an external frame rigidly fixed to the femur with 8-mm pins. The frame guides an aggressive drill that allows accurate removal of the distal cement plug. After extraction of the loosened femoral components (including 5 of the infected prosthesis, n = 27), the amount of bone loss was graded as type I for 12, type II for 14, and type IIIa for 1. Bone loss was minimal after extraction of the well-fixed stems. Peroperative events included 2 femoral fractures (both while using the mechanical cement extractor) and 1 weakening of the greater trochanter during extraction of a cementless hydroxyapatite-coated stem. Cerclage wires were used to fix the peroperative fractures, the preoperative fracture, and the extended trochanteric osteotomy, also to strengthen

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the femur after the cortical window and one of the linea aspera osteoclasies. Endofemoral preparation was done using primary compaction broaches. More aggressive broaches were used in some cases to stimulate the cortices, mostly after the removal of cemented stems. Corail femoral implants were used in all cases as stated previously. Stem sizes are displayed in Table 1. In a range of available sizes going from 8 to 20, a size less than 12 was used for 15 hips. An alumina ceramic surface bearing was used in 30 cases, the rest being polyethylene on metal. A highoffset stem was used in 6 cases: 3 times to correct a mechanical problem and 3 times to match the morphology of the previous stem. Large diameter femoral heads were used in 9 cases (three 32-mm heads and six 36-mm heads). In 6 cases metaphyseal defects were filled with either bone substitutes or cancellous allograft. Postoperative weight bearing was delayed for 6 weeks in 23 cases. The reason was related to the femur 10 times: 5 times because of femoral osteosynthesis, 4 times because of femoral bone grafting, and once after single-stage revision for sepsis. For the remaining 13 cases, weight bearing was delayed because of acetabular bone grafting. Clinical Follow-Up Three patients (3 hips, 7.3%) were lost to followup. The remaining 35 patients (39 hips, 92.7%) were last seen 30.4 months after revision surgery (range, 12-120). The average Harris hip score was 65/100 preoperatively (range, 9-100) and increased to 90/100 at last follow-up (range, 50-100) (P b .05). Separate analysis of the Harris hip score was done for 3 subgroups: Paprosky type I bone defects (n = 12), Paprosky type II bone defects (n = 14), and femoral stems that were well fixed at revision surgery (n = 14). Comparisons between groups showed no statistically significant difference for the preoperative Table 1. Distribution of Implanted Stems' Size Stem Size 9 10 11 12 13 14 15 16 17 18

No. of Subjects 2 6 7 8 6 4 2 4 0 2

368 The Journal of Arthroplasty Vol. 24 No. 3 April 2009 score, the last follow-up score, as well as for the difference between the preoperative and last followup scores (P N .05). Some patients had complications: one experienced multiple dislocation episodes (2.4%) and was reoperated in another center where the acetabular component was replaced. Another experienced a single dislocation episode 2 months after revision surgery (2.4%): it was reduced in closed fashion and never recurred. One patient presented a superficial wound infection that was treated conservatively (2.4%). There was no deep infection in the series. A patient was reoperated after 4 years because of aseptic loosening of the acetabular component (2.4%): only this component was changed as the femoral stem was well fixed. No patient had to be reoperated because of problems related to the femoral stem. Radiological Follow-Up At the last follow-up, all femoral stems showed signs of osseous integration (Fig. 2). Femoral fractures, cortical windows, osteoclasies, and trochanteric osteotomies all healed. No significant migration of the stems could be detected between postoperative radiographs and those at last followup. The difference between the 2 measurements was never superior to 5 mm. No migration difference was seen between the 3 bone defect subgroups.

Discussion In this study, we report good results for a group of 41 hip arthroplasty revisions using a primary

intention femoral stem. The average length of follow-up (30 months) is comparable to other series [7,24,35,36]. We showed a significant increase of the Harris hip score from 65 preoperatively to 90 at the latest follow-up, similar to the series of Mahoney et al [25] (from 44 to 90/100) and better than other series [8,12,18,21,24,35-38] for which the Harris score varies between 78 and 86/100 at last followup. This difference could be explained, at least partially, by the avoidance in our series of long cementless stems, which can cause thigh pain and proximal stress shielding in 10% to 24% of cases [15,16,18,38]. The radiological follow-up showed no significant stem migration and bony integration of all the femoral stems. This may be related in part to the hydroxyapatite coating as stated by many authors [12,16,37,39]. This type of coating has been said to be appropriate for revision after an infection [40] and could lead to a better healing of trochanteric osteotomies [41]. The design of the stem must also be considered because it determines the strength of the primary fixation: its horizontal ridges and double-taper shape make it stable vertically, whereas its quadrangular cross-section provides rotational stability. When taking osseous integration and absence of revision as criteria for success, our success rate for the femoral stem is 100% at the average follow-up of 30 months. This rate compares favorably to those of other femoral revision techniques like long cementless stems (92%–98%) [8,14,16,18,19,21,38], modular stems (97% at 3.5 years) [42], impaction grafting (70%–97%) [7,25], and, mostly, cemented reconstruction stems (83% at 3.5 years) [22].

Fig. 2. Ten-year follow-up AP (A) and lateral (B) views of the same patient as Figure 1 showing bony integration of the stem and no migration.

Conservative Femoral Stem Revision  Pinaroli et al

The good results of the Paprosky type II bone defects subgroup, similar to those of the Paprosky I and well-fixed stems subgroups, support the idea that using a first intention femoral stem in the context of metaphyseal bone loss is a reasonable alternative (Fig. 3). In their 10- to 16-year review of hip revision arthroplasties using the Corail stem, Reikeras and Gunderson [19] used a primary intention stem for 18 femoral revisions out of 66, all of those presenting Paprosky type I or II femoral

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defects: no loosening or significant migration was observed, also supporting the idea of using a primary intention stem for Paprosky type II defects. The first advantage of this approach compared with diaphyseal-fitting stems is the simplicity of the procedure because diaphyseal reaming is not required, leading to a preservation of the bone stock. This point is reinforced by the fact that largediameter stems are used in many diaphyseal-fitting stem series: 19 mm in average (18–22) for

Fig. 3. Preoperative AP (A) and lateral (B) views of a 41-year-old man presenting a loosening of a screwed acetabular cup as well as femoral osteolysis in the greater trochanter area associated with thigh pain. A linea aspera osteoclasy was necessary to remove the screwed stem. After stem removal, the mainly metaphyseal bone defects were classified as Paprosky type II. Stem revision was performed using a primary intention Corail stem and cancellous allograft filling of bone defects. As seen on the postoperative AP view (C), cerclage wiring of the osteoclasy was not deemed necessary. Four-year follow-up AP (D) and lateral (E) views show the bony integration of the stem.

370 The Journal of Arthroplasty Vol. 24 No. 3 April 2009 Sotereanos et al [21] and 17 mm (15–20) for Crawford et al [12]. Furthermore, a stem with a size inferior to 12 mm was used in 15 (37%) cases of the present series, whereas the smallest size of stems in the diaphyseal-fitting system we used (Kar, Depuy, Johnson & Johnson) is 12 mm; hence, iatrogenic bone loss would have occurred had a diaphyseal-fitting stem been used. Such diaphyseal reaming in the context of large cementless stems may explain the high peroperative femoral fracture rates reported by different authors: 9% for Isaack et al [43], 10% for Trikha et al [18], 13% for Nadaud et al [38], up to 24% for Morgan et al [26], and even 50% for Mulliken et al [5]. Raman et al [16] report 6% of peroperative fissures. The risk of femoral fissuring is present even with cementless primary intention stems [37], although we did not experience this complication in our series. This may be due in part to the shape of the proximal stem, which is unlikely to cause a fracture of the greater trochanter because of its low profile lateral shoulder. Our 3 fractures occurred during cement removal (2) or when extracting the stem (1). In our view, the biggest advantage of primary intention stems over revision stems is the avoidance of therapeutic escalation or more specifically iatrogenic therapeutic escalation. Because diaphyseal reaming is not performed and because metaphyseal stress shielding does not occur [44], femoral bone stock is preserved, making an eventual femoral revision easier. This argument has been evoked in favor of femoral resurfacing arthroplasty [45], although our results show that early stage bone defects can be successfully addressed with a straightforward procedure and primary intention femoral implants. This tends to prove that the difficulty in revision hip arthroplasty does not lie on the femoral side, at least when no extensive bone defect is present, hereby weakening one of the main arguments of resurfacing proponents. Furthermore, the good results presented here imply that the revision of a loosened femoral component should be carried out as soon as the diagnostic is made, again in the perspective of avoiding therapeutic escalation, as a relatively simple procedure can be done in the initial stages of loosening but would be ill-advised after osteolysis has progressed. This conservative approach to revision hip arthroplasty is only possible if a regular long-term radiological follow-up is made. The last advantage of using primary intention stems for femoral revision is related to the size, friction couple, varus angle, and offset options they offer, which are superior to those offered by most revision implant systems. As the importance of femoral offset is stressed by many authors in the

context of revision of loosened components, it is mainly with regard to postoperative stability [35,46,47]. Offset problems as the main cause for THA revision are rarely reported [48], although in our series decreased femoral offset justified the revision procedure, at least in part. This highlights the importance of restoring the anatomy of the hip with arthroplasty, including offset as well as length. This is especially true when operating younger individuals with high activity level, knowing that such patients are increasingly common. For some patients, such goal may not be reachable with revision stems due to unavailability of an implant with the right characteristics. Conservative femoral revision requires a careful surgical technique to be successful. After exposure of the hip joint—either using the same approach as used for the first surgery or systematically using a particular approach like the posterolateral approach as was the case for most of our series—extraction of the femoral stem is carried out, aiming to remove as little bone as possible [49]. Accessory procedures may be necessary like a cortical window at the level of the cement plug (30% of cases for Raman et al [16], but only 1 case out of 26 cemented stems in our series) or an extended trochanteric osteotomy [21,37]. Such procedures were used only rarely in our series because we were able to perform stem and cement removal for most of the cases by using thin osteotomes inserted in a proximal to distal fashion. We only experienced one case of greater trochanter weakening using this technique, our 2 peroperative femoral fracture cases being secondary to the use of the mechanical cement extractor. A significant learning curve is associated with this tool for it to be safe and efficient, leading us to think that performing an extended trochanteric osteotomy instead may be a better option. We performed 2 linea aspera osteoclasies, one of them to extract a screwed stem. This technique is interesting because it is simple and poses few risks for the femur. Once the previous femoral component and/or cement are completely removed, the amount of bone loss is assessed. The final decision regarding the implant to be used is based on this assessment rather than on preoperative imaging as the two can differ significantly. Many classifications are based on the amount of metaphyseal and diaphyseal bone loss (classifications of the American Association of Orthopaedic Surgery; Paprosky), whereas others are based on the amount of healthy bone still present under the lesser trochanter [13]. For our study, we used the Paprosky classification because it is widely recognized and treatment algorithms are based on it [2,3]. Use of primary intention femoral

Conservative Femoral Stem Revision  Pinaroli et al

components for Paprosky type I defects is an accepted option because the metaphyseal bone is relatively intact, making the situation similar to a first intention hip arthroplasty. Some poor results have been reported when using proximally porouscoated cementless femoral stems for RTHA [5,5052], leading to widespread use of distal fixation for most RTHA cases [12,53,54]. The initial poor results of primary intention femoral stems for RTHA may have been related to suboptimal initial prosthesis stability or to poor patient selection because good midterm results were recently published by Kelly et al [37] using a proximally hydroxy apatite (HA)coated primary femoral stem for selected revision cases. Similarly, we report excellent clinical and radiological results with the use of a primary fully HA-coated femoral stem for Paprosky type II bone defects, comparable to those of Paprosky type I defects, hereby reinforcing the acceptability of this therapeutic approach. Based on our results, it seems that a stem with a diaphyseal extension as proposed by Kelly et al [37] is not mandatory. Avoidance of diaphyseal reaming is viewed by the authors as a key aspect of conservative femoral revision. Although in our series a conservative femoral revision was successfully performed for one case with a Paprosky type IIIa defect, we cannot recommend this conduct routinely. Indeed, worse results can be expected due to the diaphyseal extension of bone lysis. In that context, distal fixation may be preferable as is the case for more severe defects [21,38]. Potential study limitations include the length of follow-up and the limited amount of data on the acetabulum. Given that mechanical failure of cementless stems usually occurs during the first 5 years following revision [15], it seems likely that stems showing signs of osseous integration will remain stable in the long term. In addition, longterm clinical experience with this implant has shown that loosening of integrated stems is unlikely [19,31,32]. Hence, we feel that a minimal follow-up of 1 year as is the case in this study is acceptable because all the stems are radiographically integrated at the last follow-up. Our focus on the femur may have introduced a bias on the reported Harris hip scores because it is influenced by both components of the hip joint. Indeed, one may argue that the improvement in the score is attributable to the revision of the acetabular component, especially for cases with acetabular loosening but a well-fixed femoral component (8 cases). Because our objective was to show that revision of the femoral component with a primary implant leads to good clinical

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results, our view is that the improvement in the Harris score found in this study could only have been lessened because of acetabular problems. This is reinforced by the fact that most of our complications occurred on the acetabular side, but the Harris score at the last follow-up is nevertheless excellent.

Conclusion Conservative femoral revision is a valuable goal because it allows the preservation of bone stock should another revision be necessary. This may become even more important as hip arthroplasty is increasingly performed on young and active patients. The use, for femoral revision, of a hydroxyapatite-coated femoral stem that has proven its value in primary hip arthroplasty appears as a good way of reaching this goal based on the results of our series. In addition to its bone-preserving characteristics, this approach involves a relatively simple operative procedure that allows the surgeon to choose the friction couple and offset best suited for each patient. We stress that this conduct may only be applicable to patients with femoral bone loss limited to the metaphysis and that more severe damage should be addressed with distal fixation. Nonetheless, given the advantages of conservative femoral revision and its paucity of complications, it may become common practice to revise a femoral component as soon as signs of loosening are noticed, hereby avoiding osteolysis progression as a conservative procedure may then be impossible. For that to happen, regular long-term radiological follow-up is necessary.

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