Finite element analysis of locking screw assisted acetabular cup fixation / 中国组织工程研究

BACKGROUND: The main reason for the failure after total hip arthroplasty is aseptic loosening of the prosthesis. The traditional acetabular cup fixation method is still controversial in maintaining the initial stability of the acetabular cup. It is a new method that can be considered to further improve the fixation method of the acetabular cup to increase its stability. OBJECTIVE: To analyze the feasibility and superiority of locking screw assisted acetabular cup fixation. METHODS: The digital model of acetabular cup and screws were reconstructed and assembled by software Solidworks. The Von-Mises and shear stress of the acetabular cup and screw by three methods, including acetabular cup, acetabular cup with ordinary cancellous bone screw, and acetabular cup with locked cancellous bone screw, were compared. RESULTS AND CONCLUSION: (1) The finite element model of the established acetabular cup and screw had excellent geometric similarity and could be used for finite element analysis. (2) The acetabular cups with locking screws received less Von-Mises and shear stress than other methods. (3) The locking screws could bear higher stress than ordinary screws and effectively dispersed the shear stress of acetabular cups. (4) It is concluded that the combination of locking screws to fix the acetabular cup can effectively prevent the instability of the acetabular cup and the loosening of the prosthesis; it can better provide stability for the acetabular cup and the mechanical environment that the bone tissue grow in the later stage. The acetabular cups with locking screws have obvious advantages than other ordinary screw, which has the limited bearing capacity and low anti-acetabular cup shear force.

Three-dimensional model analysis of trabecular acetabular cup and solid acetabular CUP / 中国组织工程研究

BACKGROUND: Hip arthroplasty is most effective method to treat hip diseases such as femoral head necrosis, osteoarthritis, hip dysplasia and femoral neck fracture in the elderly. Therefore, it is necessary to study the biomechanical behaviors of hip arthroplasty. OBJECTIVE: To simulate the contact stress and Von Mise stress values and distributions of trabecular acetabular cup and solid acetabular cup by finite element analysis method, and to predict its effects on prosthesis and hip joint. METHODS: Two hip joint component models with different structures, trabecular acetabular cup and solid acetabular cup were designed in 3-Matic Research 11.0 software. The well-designed models were imported to Hypermesh 14.0 software to divide meshes and assign material properties. Finite element analysis software Abaqus 6.13 was used to simulate the stress values and distributions of both models. RESULTS AND CONCLUSION: The results of this study showed that the stress of the trabecular acetabular cup was scattered and distributed widely. The solid acetabular cup is prone to stress concentration, and the stress distribution is concentrated near the point of stress. Compared with the solid acetabular cup and the trabecular acetabular cup, the latter has larger contact area of stress distribution and more uniform stress distribution, which can reduce the wear between hip prostheses and the risk of aseptic loosening of hip prostheses.

Total Hip Arthroplasty: Past, Present, and Future. What Has Been Achieved? / 대한고관절학회지

In the 1960s, Sir John Charnley introduced to clinical practice his concept of low-friction total hip arthroplasty (THA). Although early designs were plagued by poor performance and even failure, there have been steady advances in implant designs, biomaterials, surgical techniques and an understanding of the biomechanical restoration of the hip; these advances have contributed to improvements in implant survival and clinical outcomes of THA in the past three decades. With improved wear resistance and mechanical reliability, a potential to last for at least 25 to 30 years are now available for THA. In this review, we focus on the evolution of THA and review current controversies and future directions of this procedure based on a single surgeon's 29-year of experience at a single institution.

The Results of Long-term Follow-up of Total Hip Arthroplasty Using Hydroxyapatite-coated Cups / 대한고관절학회지

PURPOSE: The aim of this study was to report the long-term outcome and the failure mechanism of cementless total hip arthroplasty (THA) using hydroxyapatite (HA)-coated acetabular cup. MATERIALS AND METHODS: From January 1992 to May 1994, a total of 123 consecutive cementless primary THAs were performed using a HA-coated acetabular cup with metal-on-polyethylene articulation. We retrospectively evaluated 66 hips available for follow-up at a mean 18.3 years (range, 10.4-23.6 years). The survival analysis was performed by the Kaplan-Meier method. We defined end point as any failure that required a reoperation of acetabular component. RESULTS: Thirty-nine of 66 hips (59.1%) were defined as a failure for progressive acetabular osteolysis or aseptic loosening of the cup. Acetabular osteolysis was observed in 47 hips (71.2%) and 33 hips (50.0%) were revised because of cup loosening. The Kaplan-Meier method showed the survival rate of the acetabular cup to be 46.3% at 15 years and 34.8% at 20 years for any failure that required a reoperation of acetabular component. CONCLUSION: The long-term survival rate of THA using HA-coated acetabular cup was unsatisfactory, and it was attributed to vulnerable property of HA coating and progressive osteolysis.

Navigated Acetabular Cup Fixation for Acetabular Deformity or Revision Total Hip Arthroplasty / 대한고관절학회지

PURPOSE: To evaluate the usefulness of navigated acetabular cup fixation for total hip arthroplasty in patients with acetabular deformity or revision total hip arthroplasty. MATERIALS AND METHODS: This study enrolled 28 patients with at least 12 months' follow-up. The safe zone of the acetabular cup was defined as 40degrees+/-10degreesin inclination and 15degrees+/-10degreesin anteversion. The authors used the navigation and radiographic data to determine whether the acetabular cup was located within the safe zone or not. To evaluate the clinical outcomes, preoperative and last follow-up Harris hip scores were checked, and the occurrence of complications was evaluated. RESULTS: According to the navigation data, the mean inclination and anteversion were 38.5degrees+/-4.7degrees(range, 32degrees-50degrees) and 16.6degrees+/-4.0degrees(range, 8degrees-23degrees), respectively. According to the radiographic data the mean inclination and anteversion were 40.5degrees+/-4.6degrees(range, 32degrees-50degrees) and 19.4degrees+/-4.2degrees(range, 8degrees-25degrees), respectively. In both cases, all values were within the safe zone. Harris hip score was improved in all patients from preoperative 52.3+/-14.4 points (range, 29-87 points) to 88.0+/-9.0 points (range, 65-99 points) at the last follow-up. There was no dislocation or loosening of both cases. CONCLUSION: Navigated acetabular cup fixation is a useful technique for total hip arthroplasty in patients with acetabular deformity or revision total hip arthroplasty because it prevents the malposition and related complications.

Liner Dissociation by Extrusion of the Acetabular Cup Fixation Screw after Total Hip Replacement: Two Cases Report / 대한고관절학회지

This is a report of 2 cases that showed dissociation of the acetabular cup liner by acetabular fixation screw among patients who underwent total hip replacement. Screws for fixation of the acetabular cup were used during the primary surgery in both cases. Each patient visited the out patient department complaining of pain and noise from the joint; radiologic finding revealed a collapse of the column shape bone graft area with dissociation of the acetabular cup liner. In both cases, during revision surgery, screw was extruded to the inner side of the acetabular cup, since it migrated superiorly. There has been no report of liner dissociation by extrusion of acetabular cup fixation screw after total hip replacement. Therefore, we report two cases of dissociation of the acetabular cup liner of hip arthroplasty, which occurred due to screw issues after total hip replacement with structural autogenous bone graft.

Isolated Polyethylene Liner Exchange in a Revision Total Hip Arthroplasty

PURPOSE: To analyze the results of isolated exchange of polyethylene (PE) liners for treatment of wear and osteolysis around a well-fixed Harris-Galante (HG) cementless acetabular cup. MATERIALS AND METHODS: Thirty-three PE liner changes were performed without the removal of stably ingrown implants (33 hips of 32 patients). They were able to be followed for a mean period of 92 months. Clinically, the Harris hip score (HHS), pain evaluation, and complications were evaluated. Radiologically, the annual wear rate and the size of the osteolytic lesions were measured before the operation and the latest follow-up. The bone graft incorporation scale and the development of new osleolytic lesions were checked during the final follow-up. RESULTS: HHS improved to 89.3 at last follow-up. The size of the osteolysis was significantly reduced postoperatively. Bone graft incorporation scales were Grade I in 9 and Grade II in 14 cases. New osteolytic lesions have not developed at latest follow-up. As a complication, one case of dissociation of a liner and a periprosthetic fracture were noted. Annual wear rates during the same period were significantly reduced. There was no sign of alteration in stability of the PE liner. CONCLUSION: Exchange of a PE liner without removal of stable implants can be a good option for the treatment of wear and osteolysis around a stable cementless THA implant, even if the system has a weak locking mechanism, such as the HG cup. In these cases, under certain states with a higher risk of early failure in the locking mechanism, it would be better to select other revision procedures such as cup revision or cemented polyethylene liner fixation.

Revision Total Hip Arthroplasty of an Acetabular Cup with Acetabular Bone Defects

Recently, the incidence of revision total hip arthroplasty (THA) has increased following primary THA. Bone stock deficiency presents the major challenge in acetabular reconstruction during revision hip arthroplasty. The reasons for such acetabular defects include osteolysis, bone resportion following cup loosening, iatrogenic damage resulting from cup or cement removal during revision THA, and cup migration. The pre-operative assessment of acetabular bone stock, including the amount and location of pelvic osteolysis before revision surgery, is a critical preoperative preparation for the treatment of bone deficiency. In cases with mild acetabular defects, a variety of surgical options are available for treating. However, in cases with severe segmental, cavitary, or combined acetabular defects, controversies have existed so far about the most optimal treatment. Thereby, we tend to introduce the most commonly-adopted classification system of acetabular defects and management options using high hip center cups, oblong cups, structural allografts, morselized allografts with bipolar cups, morselized allografts with cementless cups, morselized allografts with acetabular reinforcement devices, and revisions with trabecular metal augmentations.

Cirugía de revisión acetabular utilizando un cotilo modular con superficie de metal trabecular de tantalio: resultados a corto plazo / Acetabular revision surgery using a modular acetabular cup coated with trabecular metal of tantalum: short term results

Objectives: To evaluate short-term clinical results of patients performed acetabular revision surgery using a Trabecular Tantalum coated modular acetabular cups. Materials and Methods: This is a retrospective and descriptive analysis of a serie of 32 consecutive patients (34 hips) with acetabular revision surgery (23 women, 9 men, mean age 70.7 years), mean follow-up 32 month (12-60). The Paprosky and the AAOS acetabular defects classifications were assessed. According to Paprosky acetabular defects classification, there were eleven type I, two IIA, three IIB, nine IIC, seven IIIA and two IIIB. According to AAOS acetabular defects classification there were thirteen patients with type 1, nine patients with type 2, ten type 3 and two type 4. The percentage of own acetabular bone in contact with the new cup was recorded for each patient at the time of surgery and was 45 percent (range from 20 to 80 percent), with 23 patients presenting less than 50 percent of bone contact (mean 35 percent). Postoperatively, osseous integration was radiographically assessed. Functional results were evaluated according to the Harris Hip Score (HSS). The complications related to the implant were also recorded. Results: In all radiographic assessments performed at 3, 6 and 12 month postoperatively an integrated cup without signs of migration or osteolysis was observed. Four patients (11.8 percent) presented recurrent hip dislocation that required a revision surgery without further cup revision. The final clinical assessment was performed at a mean of 26 month after surgery (12-60) with a mean HHS of 91.8 points. Conclusion: Trabecular tantalum coated modular acetabular cups in acetabular revision surgery shows good short term clinical results even with acetabular defects greater than 50 percent. No cup loosening was observed in these series.

Objetivo: Evaluar los resultados clínicos a corto plazo de pacientes sometidos a cirugía de revisión acetabular utilizando cotilos modulares con superficie de metal trabecular de tantalio. Material y Métodos: Estudio retrospectivo-descriptivo de una serie consecutiva de 32 pacientes (34 caderas) sometidos a cirugía de revisión acetabular (23 mujeres, 9 hombres, edad promedio 70,7 años), seguimiento promedio 32 meses (12-60). Se clasifican los defectos acetabulares de acuerdo ala clasificación de Paprosky y de la AAOS. Según la clasificación de Paprosky de los defectos acetabulares, 11 pacientes tenían categoría I, 2 categoría IIA, 3 categoría IIB, 9 categoría IIC, 7 categoría IIIA y 2 categoría IIIB. Según la clasificación de la AAOS, 13 pacientes correspondieron a nivel 1, 9 pacientes a nivel 2, 10 a nivel 3 y 2 a nivel 4. Se registra el porcentaje de hueso propio acetabular en contacto con el nuevo cotilo de cada paciente que fue en promedio 45 por ciento (20-80 por ciento), presentándose en 23 caderas un porcentaje < 50 por ciento, el cual fue en promedio 35 por ciento. En el postoperatorio se evalúa la integración ósea mediante radiografías de pelvis. Se evalúan los resultados funcionales mediante el HHS (Harris Hip Score) y las complicaciones postoperatorias relacionadas con el implante. Resultados: En todas las radiografías postoperatorias realizadas a los 3, 6 y 12 meses se evidenciaba el cotilo integrado, sin signos de migración ni osteolisis. Cuatro pacientes (11,8 por ciento) presentaron luxaciones recidivantes de cadera, las cuales requirieron de una cirugía de revisión sin recambio del cotilo. La última evaluación clínica fue en promedio 26 meses tras la cirugía (12-60 meses) constatándose un HHS promedio de 91,8 puntos. Conclusión: El uso de cotilos modulares con revestimiento de metal trabecular de tantalio en cirugías de revisión acetabular presenta buenos resultados clínicos a corto plazo incluso en defectos óseos acetabulares superiores...

Análisis experimental del desgaste entre UHMWPE y acero inoxidable 316l empleados en la manufactura de prótesis coxofemorales / Experimental wear analysis of UHMWPE and stainless 316l used in the manufacturing of coxofemoral prosthesis

La causa más común de falla en prótesis coxofemorales es el aflojamiento entre los componentes que conforman el sistema, de manera específica la copa acetabular y la cabeza femoral. En esta investigación se presenta un análisis tribológico del desgaste en los componentes mencionados, ya que cuando las superficies en contacto se desgastan, la funcionalidad mecánica del sistema se compromete, debido al cambio de geometría de los mismos, dando como resultado un juego mecánico entre la copa y la cabeza. Los materiales considerados en este estudio son el polietileno de ultra elevado peso molecular (UHMWPE, por sus siglas en inglés) para la copa acetabular, y acero inoxidable 316L para la cabeza femoral. Esta combinación de materiales representa hoy en día la recomendación más usual por parte de los cirujanos para pacientes de la tercera edad. La tasa anual de desgaste se determinó de manera experimental y se cuantificó la cantidad de material desprendido durante el contacto. Se establecieron las condiciones de carga de forma analítica, considerando las que actúan sobre la cabeza femoral a lo largo del área de desgaste durante la marcha humana. Posteriormente, se realizó el análisis experimental de desgaste utilizando una máquina tribológica de configuración perno-sobre-disco (pin-on-disk), diseñada de manera específica para este estudio. Las pruebas para determinar la pérdida volumétrica de los componentes se realizaron bajo tres condiciones de operación: en seco, lubricada con agua destilada y lubricada con suero bovino. El marco experimental considerado consistió en pernos de UHMWPE sobre discos de acero inoxidable 316l simulando el desgaste equivalente a diez años de uso de la prótesis. Finalmente, de los resultados obtenidos se puede establecer que el desgaste y la cantidad de partículas desprendidas disminuyen considerablemente cuando se utiliza suero bovino como lubricante para replicar las condiciones reales de operación del sistema...

The most common cause of failure in coxofemoral prostheses is the loosening between the components of the system, namely the acetabular cup and the femoral head. In this work a tribologic analysis of wear suffered in the components is presented, due to when the surfaces in contact are worn, the mechanical function of the system is compromised as the wearing implies a change in the geometry of the components, thus in their dimensions, resulting on a looseness between the cup and the head. The materials considered in this study are Ultra High Molecular Weight Polyethylene (UHMWPE) for the cup and 316L Stainless Steel for the femoral head, which represent the surgeons choice for elderly patients. The annual wearing rate between these components was experimentally determined, as well as the amount of debris produced during contact. Firstly, the loading conditions were determined analytically considering those acting on the femoral head taking into consideration the wearing area during human walk. Secondly, the experimental analysis consisted in wearing tests using a tribology pin-on-disk machine, specifically built for this study. The tests to determine the volumetric loss of the components were performed under three different operational conditions: dry, lubricated with bovine serum and lubricated with destilated water. The experimental set up consisted on UHMWPE pins and 316L Stainless steel discs simulating the equivalent wear of ten years of usage of the prostheses. Lastly, the obtained results proved that using the bovine serum as lubricant the wear and debris of the components was significantly reduced when compared with other cases, being the dry scenario where more damage was produced. It is important to point out that the bovine serum was chosen to simulate the synovial fluid in which the system is embedded.

Effectiveness of a Pre-Operative Lateral Decubitus Position Radiologic Examination Using a Goniometer and Rod in THRA

PURPOSE: For inserting an acetabular cup with the correct inclination angle, we checked the pelvic tilts using the lateral decubitus position X-ray and a goniometer and pointer. The accuracy of the cup inclination at the targeted angles was evaluated after insertion of the cup at an adjusted angle with using a goniometer and pointer. MATERIALS AND METHODS: Between January 2008 and December 2009, 56 hips in 50 patients who underwent total hip replacement arthroplasty (THRA) were enrolled. The mean age at the time of surgery was 63.8 years. There were 31 male patients (36 hips) and 19 female patients (20 hips). The preoperative diagnoses included osteonecrosis of the femoral head in 27 hips, secondary osteoarthritis in 10 hips and femoral neck fracture in 14 hips. The preoperative pelvic tilts were evaluated according to the lateral decubitus position X-ray with using a goniometer and pointer. The target inclination angle was 40degrees for 27 hips that underwent ceramic-on-ceramic THRA. The target inclination angle was 45degrees for the 29 hips that underwent ceramic-on-polyethylene THRA. The inclination of the cup was evaluated after inserting the acetabular cup at the adjusted angle using a goniometer and pointer. RESULTS: The mean inclination angle of the acetabular cup was 39.3degrees for the ceramic-on-ceramic THRA and 44.4degrees for the ceramic-on-polyethylene THRA. There were no significant differences between the 40degrees and 45degrees (P=0.059, P=0.071). CONCLUSION: The pelvic tilt can be evaluated by checking the lateral decubitus X-ray with a goniometer and pointer. Insertion of an acetabular cup at the adjusted angle could be a credible method for reducing the variability of cup inclination.

Cemented Total Hip Replacement Arthroplasty

The use of cement in total hip replacement arthroplasty has long controversial. However, since the 1980s, osteolysis has occurred with high frequency in cementless total hip replacement arthroplasty, and has been a significant cause for loosening. Recently, a cemented femoral stem has been frequently used because of improvements in cement techniques, materials for joint arthroplasty, design, etc. Also, the use of an acetabular cup with cement seems desirable where indications are for a revision procedure or where there is an aged patient with severe osteoporosis, and where the patient requires a broad bone graft due to an acetabular bone defect. The purpose of this article was (i) to review how to fix an acetabular cup with cement and a femoral stem in current hip replacement arthroplasty procedures and (ii) to review possible directions for further development.

Cementless Total Hip Arthroplasty for Osteonecrosis of the Femoral Head: A Follow-up Study for 10+ Years

PURPOSE: The aim of this study was to assess the outcome of cementless total hip arthroplasty (THA) in cases of osteonecrosis of the femoral head. MATERIALS AND METHODS: We studied long-term outcomes for 54 patients (72 hips). Mean duration of follow-up was 13.5 years. Clinical outcomes were evaluated by the Harris Hip Score. Radiographic evaluation from the preoperative and follow-up periods included assessment of the fixation of the femoral and acetabular components, polyethylene wear, osteolysis, and radiolucent line. RESULTS: The mean Harris Hip Score improved from a preoperative value of 51.9 points to 89.4 at final follow-up. Regarding the femoral components, there was radiographic evidence of stable bony ingrowth in 69 hips, stable fibrous ingrowth in 2 hips and unstable fixation in 1 hip. There was a radiolucent line of less than 1 mm in 7 hips, and femoral osteolysis in 27 hips. Regarding the acetabular components, there was radiographic evidence of stable fixation in 68 hips, unstable fixation in 4 hips, and osteolysis in 39 hips. There was a significant correlation between (i) failure of components and (ii) femoral osteolysis, acetabular osteolysis, polyethylene thickness, linear wear rate per year, or total linear wear. CONCLUSION: The findings of this study show favorable long term results, both clinical and radiographic, using cementless total hip replacement arthroplasties. However, the revision rates for the Harris-Galante acetabular components were high. Wear of the load? weight? bearing surface continues to limit the long-term success rate of THA, and improved design of the acetabular components should be considered.

Analysis of Failure Cause of Acetabular Components Among Total Hip Replacement Arthroplasties Using RB Wagner Acetabular Cup

PURPOSE: The purpose of this study was to analyze the cause of failure of acetabular component cases after metal-on-metal primary total hip arthroplasty using RB Wagner acetabular cup. MATERIALS AND METHODS: Between January 1993 and January 2005, we retrospectively studied failure cause of 27 patients who underwent acetabular revision surgery among 468 consecutive cementless total hip arthroplasties using RB Wagner acetabular component. The duration of primary arthroplasty to revision ranged from 5.1 years to 11.5 years (mean 9.2 years). The clinical evaluation was performed using preoperative and last follow-up modified Harris hip scores. The radiological evaluation was performed in terms of the stability, such as inclination, anteversion, cup size, acetabular bone coverage, osteolysis, radiolucency and gap. RESULTS: The average Harris hip scores was 49.6 preoperatively and 91.3 at the most recent follow-up. In revision cases, the score was 41.2 to 51.7. Among 468 cases, 27 patients underwent revision surgery (7%, 27/468) and there was no osseointegration in all cases. The radiological evaluation in revision cases revealed inclination (46.04+/-5.328, p=0.0031), anteversion (14.14+/-2.95, p=0.584), cup size (54 mm+/-2.5, p=0.042) and acetabular bone coverage (67.9%+/-4.77, p=0.003). Focusing on the relation between disease entities, there was relatively high risk in patients with hip dysplasia (Fisher's exact test, p=0.0095). CONCLUSION: Although Wagner acetabular cup relatively showed as high survival rate as 93%, failure rate is significantly high in dysplastic hip patients.

Are Portable Imaging Intraoperative Radiographs Helpful for Assessing Adequate Acetabular Cup Positioning in Total Hip Arthroplasty?

Despite advances in surgical techniques and instrumentation, current intra-operative estimations of acetabular version in total hip arthroplasty are of limited accuracy. In the present study, two experienced orthopedic surgeons compared intra-operatively measured (using portable imaging) anteversions and vertical inclinations of acetabular components with those measured using standardized radiographs post-operatively in 40 patients. Of the all vertical inclinations measured from intra-operative radiographs, 72.5% (n=29) were within +/-2degrees, and 97.5% (n=39) were within +/-5degrees of those determined using post-operative radiographs, and for anteversion, 52.5% (n=21) were within +/-2degrees, and 97.5% (n=39) were within +/-5degrees. Post-operative radiographs demonstrated that 90.0% (n=36) of vertical inclinations and anteversions were within the adequate zone. Obviously, our method has its limitations, but the authors conclude that the method described in this article better allows surgeons to verify acetabular version intra-operatively. In particular, the described method is suitable in cases with a deformed acetabular anatomy and difficult revision surgery.

Acetabular Revision Using Uncemented Acetabular Cup

PURPOSE: The purpose of this study is to evaluate the clinical and radiological results of revision total hip arthroplasty with using impacted bone grafts and uncemented acetabular cups on the acetabulum with bone defects. MATERIALS AND METHODS: From June 1990 to March 2006, 131 revision total hip arthroplasties using an uncemented acetabular cup and impacted bone graft, were performed in 124 patients. The average follow-up period was 66 months. The clinical results were evaluated with the Harris hip score. The radiological results included the period of graft incorporation, the rate of resorption, the migration and the change of inclination of the cup. The failure rate and 13 year survival rate were analyzed. RESULTS: The Harris hip scores were 51.8 preoperatively and 82.5 postoperatively. The period of incorporation was a mean of 6.38 month. Most cases showed a resorption rate below 10%. The mean migrations of the acetabular cup were 1.37 mm superiorly and 1.20 mm medially. The mean change of inclination was 1.24 degrees. There were 5 re-revision surgeries. The failure rate was 3.8%. The survival rate of the revision that was done due to loosening was 94.9% at 13 years. CONCLUSION: Acetabular revision arthroplasty with bone grafts, and an uncemented cup is recommendable as it achieves favorable outcomes in terms of rapid incorporation of the grafted bone and stable fixation of the cup.

Acetabular Reconstruction with Impacted Morselized Allograft, Wire Mesh and Cemented Acetabular Cup in Severe Acetabular Bone Defect

PURPOSE: This study evaluated the clinical and radiographic results of an acetabular reconstruction with an impacted morselized allograft and wire mesh in revision total hip arthroplasty. MATERIALS AND METHODS: This study examined 21 cases of acetabular revisions involving 20 patients with a severe acetabular bone defect managed with an impacted morselized allograft, wire mesh and cemented acetabular cup between February 2000 and June 2003. The mean follow up period was 31.7 months. Clinically, the Harris hip score was evaluated. The radiographic parameters included bony incorporation between the host bone and allograft, the change in cup inclination, acetabular cup migration, radiolucency around the cup and loosening. RESULTS: The mean Harris hip score was improved from a preoperative 54.1 to 91.9 at the last follow up. Radiological incorporation between the host bone and allograft was achieved after an average 11.4 months after surgery. The mean change in cup inclination was 1.9 degrees, and the mean medial and superior migration was 3.93 mm and 4.41 mm respectively. The majority of these radiological changes occurred within 6 months after surgery. One case of Brooker grade I heterotopic ossification and one case of acetabular cup loosening was observed but there was no re-revision or complications, such as infection and dislocation. CONCLUSION: In a severe acetabular bone stock deficiency that cannot be reconstructed with a cementless acetabular cup, an acetabular reconstruction with an impacted morselized allograft, wire mesh and cemented acetabular cup showed good results in this short term follow up study.

Intraoperative Imaging to Monitor the Alignment of Acetabular Cup for Total Hip Replacement Arthroplasty

PURPOSE: This study examined intraoperative imaging to monitor the alignment of the acetabular cup for total hip replacement arthroplasty (THRA) using C-arm fluoroscopy and to increase the accuracy of THRA prosthetic fixation. MATERIALS AND METHODS: From March 2004 to April 2007, 54 patients underwent THRA monitored by the imaging. 40degreesinclination and a 15degreesanteversion angle was considered to be ideal. The items compared included the alignment of the acetabular cup and the follow up rates of the hip dislocation. RESULTS: There was one case of hip dislocation. The mean inclination angle of the acetabular component was 39.9degreeswith a standard deviation of 3.038. The mean anteversion angle of the acetabular component was 14.9degreeswith a standard deviation of 1.398. The mean difference examination and variance in the anteversion angle showed a significant result.(P<0.05) CONCLUSION: Intraoperative imaging increases the alignment accuracy of the acetabular cup and helps stabilize the prosthesis.

Total Hip Arthroplasty with Hydroxyapatite-Coated Cementless Acetabular Cup : Minimum 10-Year Follow-up Result / 대한정형외과학회잡지

PURPOSE: We report on minimum 10-year follow-up results of total hip arthroplasties with hydroxyapatite (HA)-coated cementless acetabular cups. MATERIALS AND METHODS: From January 1992 to October 1994, we performed one-hundred eight primary total hip replacements in ninety-seven patients using HA-coated cementless acetabular cup. Eighty-four cases in seventy-seven patients were followed-up for a minimum of 10 years. RESULTS: The mean Harris score was 54.7 (range, 0 to 77.2) points preoperatively and 88.5 (range, 27.1 to 100) points at the most recent follow-up. Revision procedures were required on twenty-eight (33.3%) hips. Thirteen (15.5%) cups were revised because of loosening. Seven (9.5%) hips among the eight that revealed excessive polyethylene wear and osteolysis were revised and one hip is waiting for the revision procedure. In seven (8.3%) cases, only a polyethylene liner exchange was performed because of excessive liner wear without osteolysis. The mean linear polyethylene wear was 2.74 mm. The mean linear wear rate was 0.28 mm per year and the corresponding estimate of volumetric wear was 1689.15 mm3. The mean linear polyethylene wear and linear wear rate in revised hips was 3.05 mm and 0.33 mm per year, respectively. The estimated volumetric wear in the revised group was 1882.27 mm3. CONCLUSION: HA-coated cementless acetabular cup (Atoll(R)) demonstrated a high rate of loosening and poor results in wear and osteolysis. Further studies are needed to promote the design of acetabular cups and the technique of HA coating.

Risk Factors of Dislocation Occurring after Acetabular Component Revision

Purpose: To analyze the causes and to prevent dislocations of the hip joint that occur in patients who underwent revisions of total hip arthroplasties by changing only the polyethylene liners and femoral heads, subsequent to primary total hip arthroplasties. Materials and Methods: We evaluated 28 patients who underwent acetabular component revisions of total hip arthroplasties subsequent to primary total hip arthroplasties. The average age of the patients was 55 years old and all 28 patients had operations through the posterolateral approach. In 17 of the cases, the acetabular cups, polyethylene liners, and femoral heads were changed; in 10 cases, just the polyethylene liners and femoral heads were changed; and in 1 case, only the polyethylene liner was changed. Results: We observed 7 cases of hip dislocations that occurred among a total of 28 cases after revisions of total hip arthroplasties. In all 7 cases, the polyethylene liners and femoral heads were changed, but not the acetabular cups. In additional, in all 7 cases of dislocation, the patients were non-compliant and started weight-bearing prematurely after revisions of the total hip arthroplasties Conclusion: We observed new dislocations in the 7 cases in which the polyethylene liners and femoral heads were changed. The main reasons were inadequate soft tissue tension and hip joint laxity. Therefore, it is necessary to increase the neck length, use elevated rim polyethylene liners, readjust the acetabular cups to their optimal positions, and apply hip abduction braces to patients early after revision of total hip arthroplasties in order to lessen the danger of dislocations.