Anatomic Hip Center Research Articles

Reconstruction of rotation center in revision hip arthroplasty

Objective To discuss the feasibility of positioning the acetabular center,fixing acetabular implant correctly and reconstructing hip rotation center according to Harris fossa and the remaining anatomical markers of acetabular notch in revision hip arthroplasty.Methods Twenty-eight patients underwent revision hip arthroplasty from April 2007 to June 2009.Based on Paprosky type,3 cases with type Ⅰ were treated with biological fixed acetabular component;8 cases with ⅡA and ⅡB were reconstructed with using of morselized bone grafting and large diameter cemented acetabular prosthesis;17 cases with type ⅡC,ⅢA and ⅢB were treated with using of morselized bone grafting and fixation of acetabular reinforcement ring.Among them,5 patients with massive bone loss in acetabular wall were reconstructed with the use of the structural and morselized bone grafting.The center of the original acetabulum was believed to be in the lunate cartilage surface which was closed to Harris fossa.During the operation,the center was located in the site which was 25-28 mm above in line with perpendicular bisector of acetabular notch connecting line.The acetabular center was the point of positioning acetabular prosthesis (Ⅰ type) or making new acetabulum by impaction bone grafting.Acetabular reinforcement ring (Ⅱ,Ⅲ type) was fixed in accordance with proper transverse angle and anteversion angle.The vertical distance from hip rotation center to teardrop connection and the horizontal distance from hip rotation center to teardrop were measured on preoperative and postoperative radiograph.And the outcomes of reconstruction of rotation center were evaluated.Results The vertical distance was changed from (14.22±3.39) mm preoperatively to (32.64±4.51) mm postoperatively.The difference was statistically significant (t=3.65,P＜ 0.05).The horizontal distance was changed from (25.13±3.46)mm preoperatively to (32.87±4.73) mm postoperatively.The difference was statistically significant (t=2.72,P＜0.05).Conclusion Using residual Harris fossa and acetabular notch as the anatomical markers in revision hip arthroplasty,the restoration of the anatomical hip center has shown to be favorable. Key words: Arthroplasty,replacement,hip; Reoperation; Hip prosthesis

Cemented total hip arthroplasty with subtrochanteric femoral shortening transverse osteotomy for severely dislocated hips: outcome with a 3- to 10-year follow-up period

BackgroundTotal hip arthroplasty (THA) for the treatment of severe dislocation of the hip is a technically demanding procedure. In most previous reports, techniques and clinical outcomes using cementless prostheses are widely reported, but there have been few reports on the technique and outcomes using cemented prostheses. The purpose of this study was to evaluate the outcomes of a cemented THA with a simultaneous subtrochanteric femoral shortening transverse osteotomy in patients with Crowe type III or IV developmental dysplasia of the hip. MethodsWe retrospectively reviewed 15 hips in 11 patients who underwent cemented THA with subtrochanteric femoral shortening transverse osteotomy and with placement of the acetabular component at the level of the anatomic hip center. Patients were evaluated preoperatively and postoperatively with the Merle d'Aubigne and Postel hip score. Radiographic examination was performed to evaluate the level of the femoral osteotomy site, of the radiographic leg lengthening, and of bone union. ResultsThe clinical evaluation by the Merle d'Aubigne and Postel hip score was improved from 8.1 ± 2.5 preoperatively to 15.1 ± 1.3 at the time of final follow-up. Radiographic evidence of bone union at the osteotomy site appeared at more than 6 months after operation. Moreover, there were 3 (20%) nonunions that needed reoperation. No acetabular and femoral components exhibited radiological loosening at the time of final follow-up. In addition, one delayed union causing thigh pain was treated with low-intensity pulsed ultrasound that accelerated bone formation. ConclusionOur results in this study indicate that we should prevent instability at the transverse osteotomy site and an adequate intercalary cortical bone graft is needed to prevent nonunion in cemented THA combined with a subtrochanteric femoral shortening transverse osteotomy. We should apply this procedure with caution in patients, especially those who show less potential bone formation activity.

Cementless Modular Total Hip Arthroplasty with Subtrochanteric Shortening Osteotomy for Hips with Developmental Dysplasia

The purpose of this retrospective study was to analyze the functional and radiographic results of cementless, modular total hip arthroplasty combined with subtrochanteric osteotomy for the treatment of patients who had had Crowe Group-IV developmental dysplasia of the hip as a child. Twenty-five consecutive patients (thirty-three hips) who had previously had Crowe Group-IV developmental dysplasia of the hip were treated with a modular cementless prosthesis at a mean age of sixty years. The mean follow-up period was eight years (range, five to eleven years). The acetabular cup was placed in the position of the anatomical hip center in every patient. Subtrochanteric femoral shortening osteotomy was performed with use of a step-cut design. The mean Merle d'Aubigné and Postel hip score improved from 9 to 16 points (out of a maximum of 18 points). The mean limb-length discrepancy in seventeen patients with unilateral involvement was reduced from 5.1 cm (range, 3.7 to 6.5 cm) to 2.8 cm (range, 1.4 to 4.6 cm). Two patients had a positive Trendelenburg sign, and three had a slight limp at the time of the latest follow-up. No cases of nonunion or nerve palsy were encountered. Postoperative dislocations occurred in two hips. One hip showed progressive radiolucent lines around the proximal femoral sleeve within two years after the surgery, and this was followed by progressive stem subsidence. Only one femoral stem was revised. Cementless, modular total hip arthroplasty combined with subtrochanteric osteotomy for the treatment of patients with prior Crowe Group-IV developmental dysplasia of the hip resulted in satisfactory outcomes. Hips with poor bone quality and a developmentally short femoral neck present technical challenges with regard to achieving sufficient rotatory stability, following osteotomy, for osseointegration of the modular implants. Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Alignment of Computer-Assisted Total Knee Arthroplasty in Patients With Altered Hip Center

This study aimed to determine limb and component alignment after computer-assisted total knee arthroplasty in 30 patients (32 limbs) with an altered hip center due to a prior hip implant or deformed femoral head. There were no outliers greater than ±3° in the postoperative coronal alignment of the limb and the femoral component in relation to the altered hip center. Two limbs (8%) were more than ±3° for coronal alignment of the femoral component in relation to the anatomical hip center and 96% of limbs had less than 2° deviation in relation to the altered hip center. Computer-navigated total knee arthroplasty results in accurate restoration of lower limb and component alignment in patients with prior hip implants or deformed femoral heads where accurate restoration of alignment may be challenging due to altered hip center.

Porous Metal Augments: Big Hopes for Big Holes

The majority of acetabular defects can be reconstructed with a hemispherical acetabular component alone. However, severe bone loss encountered at the time of revision acetabular surgery can result in compromised initial fixation leading to component micromotion, failure of bone ingrowth, and mechanical failure. Porous acetabular augments offer a potential solution to enhance initial component fixation while maximizing the area for biologic ingrowth. Premanufactured metal augments can be placed independent of the acetabular component. This feature provides surgeons the flexibility to place the hemispherical acetabular component in the optimal orientation at the anatomic hip center. The augment is initially secured to the hemipelvis with multiple screws before it is then secured to the hemispherical acetabular component with the use of polymethylmethacrylate bone cement. The modularity of the augments effectively allows a custom implant to be designed intraoperatively. Porous acetabular augments offer the potential advantages of a nonresorbable material that can be inserted without extensive soft tissue stripping. Additionally, these metal augments do not carry the risk of disease transmission associated with bulk structural allograft and are manufactured in a variety of shapes and sizes. The early clinical and radiographic results of porous acetabular augments are promising, yet there remains a paucity of long-term data.

Total Hip Arthroplasty with Shortening Subtrochanteric Osteotomy in Crowe Type-IV Developmental Dysplasia

When surgeons perform total hip arthroplasty for hips with a high dislocation related to developmental dysplasia of the hip, obtaining long-term stable implant fixation and optimizing patient function remain challenges. The purpose of this paper was to evaluate the results of cementless arthroplasty with a simultaneous subtrochanteric shortening osteotomy in a group of patients with Crowe type-IV developmental dysplasia of the hip. In a retrospective study, we evaluated the results and complications of twenty-eight consecutive primary cementless total hip arthroplasties in twenty-four patients (twenty women and four men), all of whom had Crowe type-IV developmental dysplasia of the hip. The arthroplasty was performed in combination with a subtrochanteric shortening osteotomy and with placement of the acetabular component at the level of the anatomic hip center. The patients were evaluated at a mean of 4.8 years postoperatively. The mean Harris hip score increased from 43 points preoperatively to 89 points at the time of final follow-up (p < 0.01). Twelve (43%) of the twenty-eight hips had an early or late complication or a reoperation. Two (7%) of the twenty-eight subtrochanteric osteotomies were followed by nonunion. There was one instance of isolated loosening of the femoral stem. One acetabular component loosened, and one acetabular liner disengaged. Four hips dislocated postoperatively. All remaining components were well-fixed at the time of the last radiographic follow-up. No sciatic neurapraxic injuries were identified. Cementless total hip arthroplasty combined with a subtrochanteric femoral shortening osteotomy in patients with a high hip dislocation secondary to developmental dysplasia was associated with high rates of successful fixation of the implants and healing of the osteotomy site and a mean postoperative Harris hip score of 89 points. The complication rate, however, was substantially higher than that associated with primary total hip arthroplasty in patients with degenerative arthritis.

Revisionsendoprothetik

Approximately 18,000 hip revision procedures of the acetabular component are performed annually in Germany with rising incidence. The aims of acetabular revision are reconstruction of the anatomic hip center, reconstruction of bone stock, cement-free primary stability of the revision implant in autochthonous bone and permanent secondary integration.Precise planning of the revision surgery is necessary with analysis and classification of the bone defects and reconstruction following a concise therapeutic concept. Cup loosening without bone loss as well as segmental bone defects can usually be reconstructed with standard implants. Cavity defects, especially the common craniolateral defects, require the implantation of oval cups or augments to achieve anatomic reconstruction of the hip center. Combined segmental and cavity defects can be reconstructed using oval cups with craniolateral plates, whereas acetabular discontinuity requires stable fixation within the iliac wing by means of an intramedullary stem combined with an extramedullary plate. Middle and long term survival greater than 90% can be realized with the use of this therapeutic concept.

Cementless Total Hip Arthroplasty with Subtrochanteric Transverse Shortening Osteotomy for Severely Dysplastic or Dislocated Hips

Total hip arthroplasty in dislocated developmental hip dysplasia is a complex, technically demanding procedure with high complication rates. Anatomic abnormalities and the young age of the patients influence the results. Restoration of the anatomic hip center often requires shortening of the femur in order to avoid over-stretching of neurovascular structures. We performed cementless total hip arthroplasty with subtrochanteric transverse osteotomy on 44 hips in 31 patients. There were 29 female and 2 male patients. The average age at the time of the operation was 43.2 (range, 22-63 years) and the mean follow up period was 62 months (range, 24-96 months). Harris hip scores improved from 36.2 to 81.2 with good and excellent results in 79.5% of the patients. We stabilized the osteotomy line with low contact plates and screws primarily on 10 hips when rotational stability was in doubt. In the other hips, good initial rotational stability was obtained by the femoral component. However, we observed 5 nonunions in patients whose osteotomies were not stabilized with plates. These patients were later treated successfully with internal fixation and autogenous bone grafting. The osteotomies healed at a mean time of 4 months (range, 2.5-14 months). Postoperatively two dislocations, one acetabular component displacement under the structural bone autograft and two superficial infections were seen. There were no cases of symptomatic loosening, deep infection, or neurovascular injury. Subtrochanteric transverse osteotomy is a versatile, relatively easy and reliable method for shortening the femur when performing cementless total hip arthroplasty in hip dysplasia cases. This technique makes it possible to implant standard sized cementless femoral stems. When necessary, tortional stability may further be augmented with a plate and screws.

Modular Cementless Total Hip Arthroplasty with Subtrochanteric Shortening Osteotomy in Patients with High Hip Dislocation

Purpose: The purpose of this study was to report on the results of performing modular cementless total hip arthroplasty with a simultaneous subtrochanteric shortening osteotomy in patients with high hip dislocation. Materials and Methods: We evaluated 23 patients (24 hips) with high hip dislocation and who had undergone total hip arthroplasty using a proximally modular cementless stem in combination with a subtrochanteric shortening osteotomy in order to place the acetabular cup at the level of the anatomic hip center between May 1996 and June 2008. There were 6 males and 17 females with a mean age of 44 years. The mean duration of follow-up was 5.6 years. Results: The mean Harris hip score improved from 53 points preoperatively to 88 points at the time of final followup (P<0.001), and there were good or excellent results in 21 hips (87.5%). There was one instance of isolated loosening of the acetabular component. With the exception of one hip requiring revision surgery at 12 years postoperatively because of polyethylene wear and cup loosening, all the remaining components were well-fixed at the time of the last follow-up. A total of 4 hips (17%) had complications during follow-up; one dislocation, two transient femoral nerve palsies and one nonunion of the subtrochanteric osteotomy site. Conclusion: Modular cementless total hip arthroplasty with a subtrochanteric shortening osteotomy in patients with high hip dislocation was associated with excellent clinical outcomes while it minimized additional fixation of the osteotomy site.

Restoration of the Center of Rotation in Revision Total Hip Arthroplasty

We measured the change of the center of hip rotation after the revision of acetabular loosening using an acetabular reconstruction ring and an impaction allogenic bone grafting. Thirty-five revision total hip arthroplasties were performed. The average follow-up was 3.8 years. Horizontal distance was changed from 34.01 ± 10 mm preoperatively to 41.07 ± 6 mm at the latest follow-up. Vertical distance was changed from 32.06 ± 9 mm preoperatively to 20.21 ± 7 mm at the latest follow-up. The Harris hip score was improved from an average of 47 in the preoperative period to 86 at the final follow-up. The restoration of the anatomical hip center has shown to be favorable in terms of functional and radiologic evaluation in total hip revision.

Total Hip Arthroplasty with Shortening Subtrochanteric Osteotomy in Crowe Type-IV Developmental Dysplasia

When surgeons perform total hip arthroplasty for hips with a high dislocation related to developmental dysplasia of the hip, obtaining long-term stable implant fixation and optimizing patient function remain challenges. The purpose of this paper was to evaluate the results of cementless arthroplasty with a simultaneous subtrochanteric shortening osteotomy in a group of patients with Crowe type-IV developmental dysplasia of the hip. In a retrospective study, we evaluated the results and complications of twenty-eight consecutive primary cementless total hip arthroplasties in twenty-four patients (twenty women and four men), all of whom had Crowe type-IV developmental dysplasia of the hip. The arthroplasty was performed in combination with a subtrochanteric shortening osteotomy and with placement of the acetabular component at the level of the anatomic hip center. The patients were evaluated at a mean of 4.8 years postoperatively. The mean Harris hip score increased from 43 points preoperatively to 89 points at the time of final follow-up (p < 0.01). Twelve (43%) of the twenty-eight hips had an early or late complication or a reoperation. Two (7%) of the twenty-eight subtrochanteric osteotomies were followed by nonunion. There was one instance of isolated loosening of the femoral stem. One acetabular component loosened, and one acetabular liner disengaged. Four hips dislocated postoperatively. All remaining components were well-fixed at the time of the last radiographic follow-up. No sciatic neurapraxic injuries were identified. Cementless total hip arthroplasty combined with a subtrochanteric femoral shortening osteotomy in patients with a high hip dislocation secondary to developmental dysplasia was associated with high rates of successful fixation of the implants and healing of the osteotomy site and a mean postoperative Harris hip score of 89 points. The complication rate, however, was substantially higher than that associated with primary total hip arthroplasty in patients with degenerative arthritis.

Subtrochanteric shortening with overlapping femoral resection in total hip arthroplasty for Crowe type IV adult dislocation of the hip

To summarize the surgical technique and clinical outcomes of subtrochanteric shortening with overlapping femoral resection in primary total hip arthroplasty (THA) for Crowe type IV adult dislocation of the hip (ADH). From January 2000 to December 2005, 12 patients with ADH (15 hips) were treated with primary cementless hip arthroplasty using the method of subtrochanteric shortening with overlapping femoral resection. There were three male and nine female patients (nine unilateral and three bilateral hips) with an average age of 56 years (range, 41-75). Subtrochanteric shortening with overlapping femoral resection and 'V' shaped derotational osteotomy were performed in all cases without soft tissue cutting release. Proximal femoral shaft splitting was performed as an adjunct in 10 hips. The mean follow-up time was 6 years (range, 3-8). There were no infections, nonunion, malunion, dislocation or nerve injury of traction. Postoperative X-ray films showed that the acetabular cups were placed in anatomical position with 95% coverage of the acetabulum. Furthermore, initial stability of the femoral stem fixation was satisfactory and all osteotomies healed in 10-15 weeks. The Harris hip score had improved from 25-32 to 88-98 at one year after surgery (P < 0.01). All acetabular and femoral components were judged to be osteointegrated and well-fixed during follow-up. No components have needed revision. Subtrochanteric shortening osteotomy is a safe and predictable method for restoring the anatomic hip center in Crowe type IV ADH. The clinical outcomes of treating Crowe type IV ADH with THA were satisfactory.

Type III Acetabular Defect Revision With Bilobed Components

Combined segmental and cavitary deficiencies of the acetabulum (American Academy of Orthopaedic Surgeons Type III) are a difficult problem that revision arthroplasty surgeons must tackle with increasing frequency. Porous-coated bilobed acetabular components are a reconstruction option that allows for increased host bone-prosthesis contact with restoration of the anatomic hip center without the use of a structural bone graft. Eleven consecutive Type III acetabular defects in 11 patients were revised with a porous-coated bilobed cup without a structural bone graft between January 1999 and January 2001 and prospectively followed. Average Harris hip scores improved from 36 preoperatively to 85 postoperatively. Radiographic analysis showed improvement in the average vertical displacement of the hip center. Average leg length discrepancies decreased from 34 mm preoperatively to 7 mm postoperatively. There have been no revisions performed or planned. Porous-coated bilobed acetabular components can provide good clinical and radiographic results at intermediate followup for treatment of Type III acetabular deficiencies. Bilobed components offer a viable option for reconstruction of Type III defects without the use of a structural bone graft or cement while maximizing the host bone-implant contact and restoring the native hip center. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Type III Acetabular Defect Revision With Bilobed Components

Combined segmental and cavitary deficiencies of the acetabulum (American Academy of Orthopaedic Surgeons Type III) are a difficult problem that revision arthroplasty surgeons must tackle with increasing frequency. Porous-coated bilobed acetabular components are a reconstruction option that allows for increased host bone-prosthesis contact with restoration of the anatomic hip center without the use of a structural bone graft. Eleven consecutive Type III acetabular defects in 11 patients were revised with a porous-coated bilobed cup without a structural bone graft between January 1999 and January 2001 and prospectively followed. Average Harris hip scores improved from 36 preoperatively to 85 postoperatively. Radiographic analysis showed improvement in the average vertical displacement of the hip center. Average leg length discrepancies decreased from 34 mm preoperatively to 7 mm postoperatively. There have been no revisions performed or planned. Porous-coated bilobed acetabular components can provide good clinical and radiographic results at intermediate followup for treatment of Type III acetabular deficiencies. Bilobed components offer a viable option for reconstruction of Type III defects without the use of a structural bone graft or cement while maximizing the host bone-implant contact and restoring the native hip center. Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Erfordert die transverse Osteotomie bei der subtrochantären Femurverkürzungsosteotomie in der Hüftprothesenimplantation hoher Dysplasiekoxarthrosen eine additive Osteosynthese? Kurzfristige Erfahrung bei 7 Hüften mit kongenitaler Luxation

Total hip arthroplasty for high developmental hip dislocations should restore the anatomic hip centre by implanting the acetabular cup in the true acetabulum. The normalisation of the position of the hip may require femoral shortening to avoid the risk of neurological traction injury. In this study group a subtrochanteric transverse shortening with a cement-free stem (Alloclassic-SL) with a rectangular square diameter was used to secure rotation stability. With this technique seven primary hip arthroplasties were performed in Crowe grade types III and IV. The age at time of operation averaged 41.7 years (range: 29 to 64 years). Average follow-up was 18 months. An average subtrochanteric resection of 4.2 cm (range: 3 to 5 cm) by a transverse subtrochanteric osteotomy without external fixation was performed. There was one symptomatic stem loosening 15 months postoperatively. The average Harris hip score preoperatively of 43 points (range: 29 to 61 points) improved to a mean of 77 points (range: 66 to 90 points) at the time of follow-up. The hemispherical cups were implanted in all cases at the place of the original acetabular site. Meanwhile, there was no loosening on the acetabular side. All transverse osteotomies healed with evidence of union at the osteotomy site. At the last follow-up six of the seven Alloclassic-SL stems presented a secondary osseointegration. The subtrochanteric transverse shortening osteotomy in total hip arthroplasty is a safe and predictable method for restoring the anatomic centre in high development hip dislocation. The intramedullary stability will be secured by the distal rotation stability of the inherent cross-sectional geometry of this stem design without external stabilisation. A Z-shaped osteotomy of the subtrochanteric shortening or additional augmentation with allograft struts and cables is not necessary.

Determination of the rotational center of the hip

We introduce a new method to determine the anatomic rotation center of the hip. In total, 214 healthy hip joints were examined and statistically analyzed. As a reference point we used the intersection between Koehler's line and a line between the upper rims of the two foramina obturatoria. In relation to the reference point the anatomic hip center is localized 7.7% in vertical direction and 17.4% in horizontal direction for male individuals and 7.75 and 15.4% for female individuals, respectively. Those data were referred to the pelvic height. Our data can be used to determine the anatomic hip center in an easy and reliable way, not only for preoperative planning but also for retrospective investigations.

Acetabular Anatomy and Transacetabular Screw Fixation at the High Hip Center

A quadrant system that defines the safe acetabular locations for screw placement exists for the anatomic hip center. We wanted to develop a similar system for the high hip center. The purposes of our study were to identify the anatomic structures at risk during placement of transacetabular screws in the high hip center, to identify maximum bone depth for screw purchase, and to determine if a high hip center quadrant system could be validated to guide placement of screws during acetabular arthroplasty. For this cadaver study of nine pelves, an acetabulum was reamed superiorly into the high hip center a distance equal to (1/2) of the native acetabular diameter. Screws exiting the acetabular bone by 15 mm were inserted before a computed tomography scan and a precise anatomic dissection were done. Structures at risk of penetration by screws include the external iliac vessels, the obturator nerve and vessels, the superior gluteal nerve and vessels, and the sciatic nerve. We found that a quadrant system at the high hip center can demarcate safe zones for screw placement. At the high hip center, only the peripheral (1/2) of the posterior quadrants are safe for screw placement.

TOTAL HIP ARTHROPLASTY WITH CEMENT AND WITHOUT ACETABULAR BONE GRAFT FOR SEVERE HIP DYSPLASIA

We previously evaluated a cohort of fifty-three patients with severe hip dysplasia (Crowe Type-II, III, or IV subluxation) who underwent a total of sixty-six Charnley total hip arthroplasties. The acetabular component was placed at the anatomic hip center, the superolateral defect was filled with cement, and no bone-grafting was used to supplement the acetabular wall. All but one patient, who was lost to follow-up, were followed until death or for a minimum of twenty years. Radiographic and functional follow-up data were collected prospectively. This retrospective review included twenty-four patients (thirty-four hips) who were alive at a minimum of twenty years following the surgery. Fourteen (22%) of the sixty-five hips underwent revision of a component, with eleven of the revisions performed because of aseptic loosening. Eight of those eleven hips underwent revision because of acetabular loosening alone; two, because of femoral loosening alone; and one, because of loosening of both components. The combined prevalence of revision because of aseptic loosening of the acetabular component and radiographic evidence of failure of the acetabular component was 28% (eighteen hips). With the numbers available, the need for acetabular revision was not associated with the percentage of cement coverage (p = 0.362) or the Crowe classification (p = 0.159). At a minimum of twenty years postoperatively, the survivorship of the acetabular component was 86% ± 8% with revision because of aseptic loosening as the end point and 82% ± 10% with revision because of aseptic loosening or radiographic evidence of loosening as the end point. The results that we evaluated at a minimum of twenty years after use of this technique can be compared with the results of other techniques in studies with similar long-term follow-up periods. Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Total Hip Arthroplasty with Cement and without Acetabular Bone Graft for Severe Hip Dysplasia

We previously evaluated a cohort of fifty-three patients with severe hip dysplasia (Crowe Type-II, III, or IV subluxation) who underwent a total of sixty-six Charnley total hip arthroplasties. The acetabular component was placed at the anatomic hip center, the superolateral defect was filled with cement, and no bone-grafting was used to supplement the acetabular wall. All but one patient, who was lost to follow-up, were followed until death or for a minimum of twenty years. Radiographic and functional follow-up data were collected prospectively. This retrospective review included twenty-four patients (thirty-four hips) who were alive at a minimum of twenty years following the surgery. Fourteen (22%) of the sixty-five hips underwent revision of a component, with eleven of the revisions performed because of aseptic loosening. Eight of those eleven hips underwent revision because of acetabular loosening alone; two, because of femoral loosening alone; and one, because of loosening of both components. The combined prevalence of revision because of aseptic loosening of the acetabular component and radiographic evidence of failure of the acetabular component was 28% (eighteen hips). With the numbers available, the need for acetabular revision was not associated with the percentage of cement coverage (p = 0.362) or the Crowe classification (p = 0.159). At a minimum of twenty years postoperatively, the survivorship of the acetabular component was 86% +/- 8% with revision because of aseptic loosening as the end point and 82% +/- 10% with revision because of aseptic loosening or radiographic evidence of loosening as the end point. The results that we evaluated at a minimum of twenty years after use of this technique can be compared with the results of other techniques in studies with similar long-term follow-up periods.

The high hip center.

Revision of a failed acetabular component presents many challenges to the arthroplasty surgeon. The goal in most cases should be to reconstruct the acetabulum by positioning the hip center as close as possible to the anatomic hip center. However, severe acetabular bone stock deficiency and distorted acetabular anatomy often preclude placement of the acetabular component at the true anatomic hip center. In these cases, many options exist for reconstruction of the acetabulum, including placement of the cup superiorly at a high hip center. Although biomechanical studies have shown that superolateral placement of the hip center may lead to increased moments and forces across the hip (leading to potentially higher rates of loosening), superior only displacement of the hip center does not seem to adversely affect the forces about the hip. Proximal placement of the hip center facilitates contact between intact, viable host bone and the acetabular implant, thereby reducing the need for structural bone grafts, and increasing the chances for stable bony ingrowth. With proper patient selection and meticulous surgical technique, the high hip center can be a useful technique for reconstruction of the deficient acetabulum in the patient with a loose acetabular component after total hip arthroplasty.