Abductor Biomechanics Clinically Impact the Total Hip Arthroplasty Dislocation Rate: A Prospective Long-Term Study.

BACKGROUND: Factors related to the patient, implant, and surgery have been associated to the rate of dislocation for total hip arthroplasty (THA). We ask if the position of the cup and the reconstruction of the abductor mechanism actually lower the THA dislocation rate. METHODS: We evaluated 1318 patients (1414 hips) undergoing cementless THA between 1992 and 2012. All THAs had a 28- or a 32-mm femoral head size. Hip reconstruction was radiologically assessed evaluating cup position and the hip rotation center according to Ranawat. The reconstruction of the abductor mechanism was measured using 2 variables: the lever arm distance and the height of the greater trochanter. RESULTS: There were 38 dislocations (2.7%). After controlling the relevant confounding variables, such as demographic and implant data, multivariate regression analysis showed that the most important factors associated with dislocation were a greater distance to the anatomic hip rotation center and hips outside 2 safe windows for cup position (acetabular inclination and version angles) and abductor mechanism (lever arm distance and height of the greater trochanter). CONCLUSION: A proper reconstruction of the hip is essential to decrease the risk of dislocation after primary THA. The weakness of the abductor muscles of the hip may be one of the most important causes for dislocation.

THA revisions using impaction allografting with mesh is durable for medial but not lateral acetabular defects.

BACKGROUND: Most acetabular revisions are managed with cementless hemispherical or elliptical metal implants relying on bone ingrowth. Nonetheless, loss of acetabular bone stock and inability to achieve secure component fixation represent challenges in the setting of revision total hip arthroplasty. Impaction bone grafting (IBG) using allograft represents one option for treatment of this problem. However, cup migration and bone graft resorption are limitations when IBG is used for large segmental defects, and the precise role of IBG as well as the use of mesh (and the kinds of defects for which mesh does not work well) in this setting remains unknown. QUESTIONS/PURPOSES: We therefore evaluated patients undergoing acetabular revision surgery using IBG and a cemented cup in large bone defects to determine (1) the frequency with which the hip center could be restored in hips with Paprosky 3A and 3B defects and in hips with or without the use of metallic mesh during surgery; (2) survivorship of IBG acetabular-revision reconstructions in patients with severe Paprosky 3A and 3B defects; and (3) risk factors for failure of the reconstruction, including the use of mesh and defect severity (3A versus 3B). METHODS: Between 1997 and 2009, we performed 226 acetabular revisions using IBG. During that time, indications for using IBG in this setting included Paprosky 3A and 3B defects without pelvic discontinuity. Of these, 204 (90.2%) were available for followup at a minimum of 5 years (mean, 10 years; range, 5-17 years). There were 100 hips with an intraoperative bone defect of Paprosky 3A and 104 with a 3B. Medial or rim acetabular uncontained defects were treated with medial and/or lateral metallic mesh in 142 hips. We determined the postoperative radiological cup position and acetabular reconstruction of the hip center according to Ranawat in both groups. We assessed the appearance of cup loosening and the possible risk factors with regression analysis. RESULTS: Mean postoperative acetabular abduction angle and vertical, horizontal, and hip rotation center distances improved (p < 0.001 in all parameters). Nine hips showed radiological loosening in the group with bone defect 3A and 16 in Group 3B. The survival rate for loosening at 15 years was 83% (95% confidence interval [CI], 71%-95%) for Group 3A and 73% (95% CI, 60%-84%) for Group 3B (p = 0.04). The survivorship for loosening when using mesh or not at 15 years was: no mesh 89% (95% CI, 74%-99%), medial mesh 85% (95% CI, 72%-97%), lateral mesh 80% (95% CI, 67%-91%), and medial and lateral meshes 54% (95% CI, 31%-76%) (p = 0.008). After controlling the most relevant confounding variables we found that the most important factor associated with loosening was lateral mesh use (p = 0.008; hazard ratio, 2.942; 95% CI, 1.328-6.516). CONCLUSIONS: IBG provides an improvement in reconstruction of the hip rotation center in acetabular revision surgery. Although results are good for contained or medial large defects, hips with a rim or lateral segmental defect may need other options for reconstruction of these challenging surgeries. LEVEL OF EVIDENCE: Level III, therapeutic study.

Regional differences between US and Europe in radiological osteoarthritis and self assessed quality of life in patients undergoing total hip arthroplasty surgery.

Precise indications for THA remain unclear and regional differences might exist in selecting patients for surgery. In this study we investigate radiological OA grade and self-reported quality of life in 909 patients undergoing THA in 16 centers across US and Europe. Patients in US were younger and had higher BMI. More patients with mild Tönnis OA grade underwent surgery in the US compared to Europe. Patients in the US had significantly higher pain VAS and significantly lower SF-36 Physical, while having significantly higher EQ-VAS scores preoperatively. Patient demographics and disease severity according to radiological OA grade and self-reported survey scores vary between the United States and Europe. This knowledge can be used in the interpretation of US and European based studies on outcome following THA.

Increase of cortical bone after a cementless long stem in periprosthetic fractures.

BACKGROUND: Healing and functional recovery have been reported using an extensively porous-coated stem in Vancouver B2 and B3 periprosthetic fractures; however, loss of cortical bone has been observed when using these stems in revision surgery for aseptic loosening. However, it is unclear whether this bone loss influences subsequent loosening. QUESTION/PURPOSES: We analyze the healing fracture rate and whether the radiographic changes observed around and extensively porous-coated stem used for periprosthetic fractures affect function or loosening. METHODS: We retrospectively reviewed 35 patients with periprosthetic fractures (20 Vancouver B2 and 15 Vancouver B3). Patients' mean age at surgery was 80 years (range, 51-86 years). No cortical struts were used in this series. We evaluated radiographs for signs of loosening or subsidence. The cortical index and the femoral cortical width were measured at different levels on the immediate pre- and postoperative radiographs and at different periods of followup. The minimum followup was 3 years (mean, 8.3 years; range, 3-17 years). RESULTS: All fractures had healed, and all stems were clinically and radiographically stable at the end of followup. Nineteen hips showed nonprogressive radiographic subsidence during the first 3 postoperative months without clinical consequences. The cortical index and the lateral and medial cortical thickness increased over time. Increase of femoral cortex thicknesses was greater in cases with moderate preoperative osteoporosis and in cases with stems less than 16 mm in thickness. CONCLUSIONS: Our data suggest an extensively porous-coated stem for Vancouver B2 and B3 periprosthetic fractures leads to a high rate of union and stable fixation. Cortical index and lateral cortex thickness increased in these patients with periprosthetic fractures. Patients with moderate osteoporosis and those using thin stems showed a major increase in femoral cortex thickness over time.

Cup press fit in uncemented THA depends on sex, acetabular shape, and surgical technique.

BACKGROUND: Uncemented press-fit cups provide bone fixation in primary THA, but the use of screws is sometimes necessary to achieve primary stability of the socket. However, it is unclear whether and when screws should be used. QUESTION/PURPOSES: We analyzed the factors related to screw use with a press-fit uncemented cup and assessed whether screw use is associated with the same rates of loosening and revision as a press-fit technique. METHODS: We retrospectively reviewed 248 patients who underwent THA using the same prosthetic design. Eighty-eight hips had screws to achieve primary cup fixation (Group 1), and 189 did not (Group 2). Mean age was 50 years (range, 14-73 years). We analyzed factors related to the patient, acetabular type, and reconstruction of the rotation center of the hip. Minimum followup was 5 years (mean, 8.9 years; range, 5-12 years). RESULTS: We found higher screw use in women, patients with less physical activity, Acetabular Types A or C, and a distance from the center of the prosthetic femoral head to the normal center of rotation of more than 3 mm. There were four revisions in Group 1 and five in Group 2. Eight hips had radiographic loosening in Group 1 and nine in Group 2. Cups with a postoperative abduction angle of more than 50° had a higher risk for loosening. CONCLUSIONS: Press fit was achieved less frequently in women and patients with Acetabular Types A or C and less physical activity; a closer distance to the normal center of rotation decreased screw use. Screw use to augment fixation achieved survival similar to that of a press-fit cup. LEVEL OF EVIDENCE: Level II, prognostic study. See Instructions for Authors for a complete description of levels of evidence.

Alumina-on-alumina THA in patients with juvenile idiopathic arthritis: a 5-year followup study.

BACKGROUND: THA is a concern in juvenile idiopathic arthritis (JIA) owing to patients' youth, poor bone stock, and small physical size. QUESTIONS/PURPOSES: We asked whether (1) uncemented alumina-on-alumina THAs have good clinical and radiographic results at midterm followup in young patients with inflammatory arthritis and end-stage hip disease secondary to JIA, and (2) the anatomic center of rotation of the hip could be reconstructed in patients with acetabular protrusion. We also assessed the rate of surgical complications. PATIENTS AND METHODS: We retrospectively reviewed 31 alumina-on-alumina THAs in 21 patients with a mean age of 30.9 years (range, 14-48 years). Minimum followup until the time of revision of any component or the latest evaluation was 16 months. For nonrevised cases, the minimum followup was 60 months (range, 60-108 months). Acetabular protrusion was mild in 17 hips (Group 1) and moderate-severe in 14 (Group 2). Bone autograft was used to reconstruct the acetabulum in Group 2. Acetabular reconstruction was evaluated according to Ranawat et al. RESULTS: One cup was revised owing to aseptic loosening at 16 months; the remaining hips showed good clinical and radiographic results. The mean postoperative horizontal distance and the distance between the center of the head of the prosthesis and the true center of the femoral head improved in Group 2. There were no complications related to alumina. CONCLUSIONS: Although THA is a technically demanding procedure in patients with JIA, uncemented alumina-on-alumina THA provides pain relief and improves quality of life. In patients with acetabular protrusion, bone grafts enable anatomic cup positioning. Continued followup will be required to determine whether the alumina-on-alumina bearings in patients with JIA result in less osteolysis and loosening. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Ceramic-on-ceramic cementless total hip arthroplasty in patients aged 40 years or under: Do preoperative conditions affect long-term results?

INTRODUCTION: Underlying diseases, bone deformities and polyethylene wear affect outcome in young patients undergoing total hip arthroplasty (THA). These issues are not widely confirmed for ceramic - on-ceramic THA, particularly regarding cup fixation. Therefore, we did a retrospective long-term investigation on a large population of cementless ceramic-on-ceramic THA in patients aged 40 years or younger aiming to analyze: 1) the complication rate; 2) clinical results; and 3) survival for cup loosening with regard to their preoperative conditions. HYPOTHESIS: Cup loosening could be related to preoperative diagnosis in young patients with a cementless ceramic-on-ceramic THA. PATIENTS AND METHODS: Two hundred and seven hips in 171 patients (97 men and 74 women) underwent a cementless ceramic-on-ceramic THA at a mean age of 31.6±6.8 years. The most frequent diagnoses were avascular necrosis (AVN) of the femoral head (74 hips), pediatric hip diseases (35 hips), severe congenital hip dysplasia (CHD) (31 hips), juvenile rheumatoid arthritis (30 hips) and mild CHD (26 hips). The prosthesis included a press-fit metal backed cup with a hydroxyapatite coating and a macrotexture surface on either the equatorial region (93 cups) or the entire surface of the shell (114 cups). Ceramics were made of pure alumina and had a femoral head size of 28 (60 hips) or 32mm (147 hips). In all cases same the straight cementless tapered stem was inserted. RESULTS: There were three early dislocations, one requiring cup revision No hip was revised due to infection, ceramic fracture, or femoral component loosening. Eight cups were revised for aseptic loosening (3,8%). The mean preoperative Harris Hip score was 52.8±6.2 and 93.4±6.9 at the end of follow-up. It was better in AVN (95.7±2.3) and worst in severe CHD (88.8±11.8) (p=0.001). If the end-point was cup aseptic loosening, the survival rate at 17 years was 95.1% (95% CI: 91.3-98.9), 100% for AVN and post-traumatic arthritis, and 86.8% (95% CI: 74.9-98.7) for severe CHD. CONCLUSIONS: Despite diagnoses frequently causing technical difficulties at the surgery, outcome of cementless ceramic-on-ceramic THA in patients under the age of 40 years is satisfactory over ten years of follow up. Cup aseptic loosening was the main cause of failure and appears more related to the initial hip diseases than the age of the patient. LEVEL OF EVIDENCE: III; retrospective comparative study.

Impaction bone grafting in hip re-revision surgery.

AIMS: Bone stock restoration of acetabular bone defects using impaction bone grafting (IBG) in total hip arthroplasty may facilitate future re-revision in the event of failure of the reconstruction. We hypothesized that the acetabular bone defect during re-revision surgery after IBG was smaller than during the previous revision surgery. The clinical and radiological results of re-revisions with repeated use of IBG were also analyzed. METHODS: In a series of 382 acetabular revisions using IBG and a cemented component, 45 hips (45 patients) that had failed due to aseptic loosening were re-revised between 1992 and 2016. Acetabular bone defects graded according to Paprosky during the first and the re-revision surgery were compared. Clinical and radiological findings were analyzed over time. Survival analysis was performed using a competing risk analysis. RESULTS: Intraoperative bone defect during the initial revision included 19 Paprosky type IIIA and 29 Paprosky type IIIB hips; at re-revision, seven hips were Paprosky type II, 27 type IIIA and 11 were type IIIB (p = 0.020). The mean preoperative Harris Hip Score was 45.4 (SD 6.4), becoming 80.7 (SD 12.7) at the final follow-up. In all, 12 hips showed radiological migration of the acetabular component, and three required further revision surgery. The nine-year cumulative failure incidence (nine patients at risk) of the acetabular component for further revision surgery was 9.6% (95% confidence interval (CI) 2.9 to 21.0) for any cause, and 7.5% (95% CI 1.9 to 18.5) for aseptic loosening. Hips with a greater hip height had a higher risk for radiological migration (odds ratio 1.09, 95% CI 1.02 to 1.17; p = 0.008). CONCLUSION: Bone stock restoration can be obtained using IBG in revision hip surgery. This technique is also useful in re-revision surgery; however, a better surgical technique including a closer distance to hip rotation centre could decrease the risk of radiological migration of the acetabular component. A longer follow-up is required to assess potential fixation deterioration. Cite this article: Bone Joint J 2021;103-B(3):492-499.

Wear of hip prostheses increases serum IGFBP-1 levels in patients with aseptic loosening.

The biological mechanisms involved in aseptic loosening include inflammation-associated and bone resorption-associated processes. Coordinated cellular actions result in biochemical imbalances with devastating consequences for the joint. Given that this condition is not known for showing systemic signs, we investigated whether circulating levels of inflammation-related proteins are altered in patients with aseptic loosening. Our study included 37 patients who underwent revision surgery due to hip osteolysis and aseptic loosening and 31 patients who underwent primary total hip arthroplasty. Using antibody arrays, we evaluated the serum levels of 320 proteins in four patients from each group. The results showed differences in insulin-like growth factor-binding protein 1 (IGFBP-1) concentrations, which we then quantified using enzyme-linked immunosorbent assay tests in all study patients. The results confirmed that serum IGFBP-1 concentrations were higher in the revision surgery patients than in the hip arthroplasty patients. In vitro studies showed that exposure of human osteoblasts to titanium particles induced an IGFBP-1 release that further increased when exposure to particles was performed in media conditioned by human M1 macrophages. These findings suggest that elevated serum IGFBP-1 levels in patients with aseptic loosening can arise from increased local IGFBP-1 production in the inflammatory environment of the periprosthetic bed.

The survival and fate of acetabular reconstruction with impaction grafting for large defects.

BACKGROUND: Impaction bone grafting has been used for acetabular reconstruction in revision surgery. However, most series do not establish differences in survival in revisions with differing severity of bone loss. QUESTIONS/PURPOSES: We therefore determined (1) the survival rate for rerevision associated with varying degrees of bone loss; (2) the frequency with which bone graft resorption occurred; and (3) whether the reconstruction restored the anatomic center of rotation of the hip. METHODS: We retrospectively reviewed 165 patients (181 hips) who underwent rerevision for major bone loss. Using the classification of Paprosky et al. 98 hips had a Grade 3A defect and 83 a Grade 3B. We determined survival rates for revision and graft resorption. Cup position was determined measuring vertical and horizontal positions and the distance from the center of the prosthetic femoral head to the normal center of rotation of the hip in both groups according to Ranawat. The minimum followup until rerevision or the latest evaluation was 0.3 years months (mean, 7.5 years; range, 0.3-17.7 years). RESULTS: The survival rate for revision at 8 years was 84% (95% confidence interval: 61-100) for Grade 3A and 82% (95% confidence interval: 68-100) for Grade 3B. Twelve hips were rerevised. Seventeen grafts showed bone resorption. Acetabular cup position was anatomically restored in both Grades 3A and 3B. CONCLUSIONS: The midterm results for impacted bone allograft and cemented all-polyethylene cups were similar in both Grade 3A and Grade 3B hips. Acetabular reconstruction allows anatomic positioning of the cups and is associated with a low rate of rerevision.

Total hip arthroplasty after acetabular fracture: does initial treatment make any difference to the outcome? A 5- to 23-year follow-up with clinical and radiological analysis.

PURPOSE: To determine if initial treatment affects the outcome of total hip arthroplasty (THA) after acetabular fracture. METHODS: 49 patients (49 hips) initially treated non-operatively followed some months later by THA in conjunction with acetabular reconstruction (Group 1) and 29 patients (29 hips) who had undergone THA after a previous osteosynthesis (Group 2) were assessed. The mean follow-up was 11.7 (range 5-23) years. RESULTS: 3 acetabular components were revised for aseptic loosening in Group 1 and 2 in Group 2. The survival rate for cup loosening at 16 years was 90.6% (95% confidence interval [CI], 78.1-100) for Group 1 and 94.1% (95% CI, 86.5-100) for Group 2 (p = 0.76). There were 2 sciatic palsies in Group 2 after osteosynthesis. The mean preoperative clinical score and postoperative range of mobility were better in Group 1. There were more heterotopic ossifications in Group 2. CONCLUSION: Despite the good results found in both groups, THA after previous osteosynthesis for acetabular fractures had more complications than a primary THA in conjunction with acetabular reconstruction.

Oral antibiotics are effective for highly resistant hip arthroplasty infections.

Infected arthroplasties reportedly have a lower eradication rate when caused by highly resistant and/or polymicrobial isolates and in these patients most authors recommend intravenous antibiotics. We asked whether two-stage revision with interim oral antibiotics could eradicate these infections. We prospectively followed 36 patients (mean age, 71.8 years) with late hip arthroplasty infections. Combinations of oral antibiotics were prescribed according to cultures, biofilm, and intracellular effectiveness. The minimum followup was 1 year (mean, 4.4 years; range, 1-12 years). We presumed eradication in the absence of clinical, serologic, and radiographic signs of infection. Infection was eradicated in all 13 patients with highly resistant bacteria who completed a two-stage protocol (10 with methicillin-resistant Staphylococci) and in eight of 11 patients treated with only the first stage (and six of nine with methicillin-resistant Staphylococci). Infection was eradicated in six of six patients with polymicrobial isolates (of sensitive and/or resistant bacteria) who completed a two-stage protocol and in five of seven with polymicrobial isolates treated with only the first surgery. The Harris hip score averaged 88.1 (range, 70-98) in patients who underwent reimplantation and 56.8 (range, 32-76) in patients who underwent resection arthroplasty. Long cycles of combined oral antibiotics plus a two-stage surgical exchange appear a promising alternative for infections by highly resistant bacteria, methicillin-resistant Staphylococci, and polymicrobial infections.

Alumina-on-alumina total hip arthroplasty in young patients: diagnosis is more important than age.

Total hip arthroplasty (THA) in young patients has a high loosening rate, due in part to acetabular deformities that may compromise bone fixation and polyethylene wear. We therefore asked whether wear or osteolysis and loosening differ in patients under 40 years of age with alumina-on-alumina THA compared to those who are older. We prospectively followed 56 patients (63 hips) younger than 40 years (Group 1) and 247 patients (274 hips) older than 40 (Group 2) who had an alumina-on-alumina THA. The minimum followup was 4 years (mean, 5.6 years; range, 4-9 years). The two groups differed in various features: there were no patients with primary osteoarthritis in Group 1 and they had worse preoperative function and range of mobility, while weight, activity level, and implant size were greater in Group 2. The survival rate for cup loosening at 80 months postsurgery was 90.8% (95% confidence interval, 82.9-98.6%) for Group 1 and 96.5% (95% confidence interval, 94.2-98.7%) for Group 2. Cup loosening was less frequent with primary osteoarthritis than with severe developmental dysplasia of the hip. Although an alumina-on-alumina THA provided similar midterm survival and radiographic loosening in both age groups, the preoperative diagnosis seems more important than age for outcome. Continued followup will be required to determine if the alumina-on-alumina bearings in young patients result less risk of osteolysis and loosening.

Proximal Femoral Bone Regeneration After an Uncemented Hydroxyapatite-coated Long-stem in Revision Hip Surgery.

BACKGROUND: Bone remodelling with lateral femoral cortex thinning is a major concern after extensively porous-coated long-stem in revision surgery. Extensive hydroxyapatite coated long-stems were introduced to improve osseointegration, but bone remodelling changes have not been quantified. OBJECTIVE: The question of whether bone remodelling changes from extensive hydroxyapatite-coated long stems influence the durability of femoral revision, clinical outcome is assessed in follow-up radiographs. METHODS: Uncemented straight monoblock hydroxyapatite-coated long-stems used in revision hip surgery for aseptic loosening were assessed in a consecutive series of 64 hips (60 patients). Mean follow-up was 8.6 years and the mean age at surgery was 70 years (27-91). The pre-operative bone defect was classified according to Paprosky. Cortical struts were not used in this series. Cortical index and femoral cortical width were measured at three different levels at different periods. RESULTS: Four patients with pain under level 4 due to stem loosening needed an exchange surgery of their femoral component, but two patients rejected re-surgery. The cumulative probability of not having aseptic loosening was 91.2% (95% confidence interval 73.5-96.9) at 10 years according to Kaplan and Meier. Twenty-seven of 35 osteolytic lesions had disappeared or decreased at the last follow-up. The thickness of the lateral and medial cortex increased over the course of the study at different levels. Increases of femoral cortex thickness were greater in men and in cases with mild bone defects. CONCLUSION: Although clinical outcome of the hydroxyapatite-coated long stem in revision surgery is good but not outstanding, most osteolytic lesions heal and the femoral cortex thickness increases at different levels.

Total Hip Arthroplasty with Use of the Cementless Zweymüller Alloclassic System: A Concise Follow-up, at a Minimum of 25 Years, of a Previous Report.

We previously reported the 10 to 13-year follow-up results for 104 total hip replacements with the Zweymüller Alloclassic stem and a threaded cup in 94 patients. The present study is a clinical and radiographic outcome update after a minimum follow-up of 25 years. Four patients (4 hips) were lost and 46 patients (50 hips) died, leaving 44 patients (50 hips) available for follow-up. Since our previous report, 7 cups and 2 stems were revised. At 20 years, the probability of survival of any component was 84.1% (95% confidence interval [CI], 73.91% to 94.29%) and the cumulative probability of not having stem loosening was 95.9% (95% CI, 95.51% to 96.29%). We observed proximal femoral osteolysis in 15 hips (30%), cortical hypertrophy in 21 hips (42%), and proximal femoral osteopenia in 30 hips (60%). The Zweymüller Alloclassic stem continues to provide excellent results after extended follow-up. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Factores de riesgo de luxación en una serie de 2732 prótesis totales de cadera / Risk Factors for Dislocation in a Series of 2732 Total Hip Replacements

Introducción: La luxación de la prótesis total de cadera puede afectar los resultados del implante, la calidad de vida del paciente, y el costo del proceso. Su etiología es multifactorial. Objetivos: Identificar posibles factores de riesgo relacionados con la aparición de luxación en prótesis total de cadera en una serie de casos. Métodos: En una serie de 2732 prótesis total de cadera, en la que hubo 92 luxaciones (3,4 por ciento), se compararon factores relacionados con el paciente, el implante, y la técnica quirúrgica uilizada en el Hospital La Paz-IDIPaz de Madrid entre los años 2000 y 2016. Se utilizó el análisis de regresión para la significación de dichos factores. Resultados: De las 92 luxaciones, 62 fueron tratadas de manera conservadora (67,4 por ciento) y 30 pacientes precisaron de cirugía de revisión (32,6 por ciento). El estudio multivariado mostró significación estadística en los siguientes factores de riesgo: estado de la columna lumbar (p < 0,001), y una pobre reconstrucción del centro de rotación de la cadera (p= 0,035), y cúpulas posicionadas fuera de las ventanas de Lewinnek (p < 0,001) y del mecanismo abductor (p < 0,001) en relación con la técnica quirúrgica. No hubo factores significativos en relación con el tipo de implante, diámetro de la cabeza femoral o par de fricción. Conclusiones: La patología lumbar aumenta el riesgo de luxación en la prótesis total de cadera. Una adecuada reconstrucción de la cadera, que incluya la posición de la cúpula y el centro de rotación de la cadera, así como del mecanismo abductor ayudaría a mejorar la tasa de inestabilidad(AU)

Introduction: The dislocation of the total hip replacement can affect the results of the implant, the quality of life of the patient, and the cost of the process. Its etiology is multifactorial. Objectives: To identify possible risk factors related to the appearance of dislocation in total hip replacement in a series of cases. Methods: In a series of 2732 total hip prostheses, in which there were 92 dislocations (3.4percent), factors related to the patient, the implant, and the surgical technique used at La Paz-IDIPaz Hospital in Madrid were compared, from 2000 to 2016. Regression analysis was used for the significance of these factors. Results: Out of 92 dislocations, 62 were treated conservatively (67.4 percent) and 30 patients required revision surgery (32.6 pecent). The multivariate study showed statistical significance in the following risk factors: state of the lumbar spine (p <0.001), and poor reconstruction of the center of rotation of the hip (p = 0.035), and domes positioned outside Lewinnek windows (p <0.001) and the abductor mechanism (p <0.001) in relation to the surgical technique. There were no significant factors in relation to the type of implant, diameter of the femoral head or friction torque. Conclusions: Lumbar pathology increases the risk of dislocation in total hip replacement. Proper hip reconstruction, including the position of the dome and the center of rotation of the hip, as well as the abductor mechanism, would help to improve the rate of instability(AU)

Total hip arthroplasty with use of the cementless Zweymüller Alloclassic system. A ten to thirteen-year follow-up study.

BACKGROUND: The Zweymüller Alloclassic total hip arthroplasty system is widely used, although few intermediate-term studies have been published. The purpose of the present study was to evaluate the clinical and radiographic results of this system after ten years. METHODS: One hundred and twenty-four consecutive primary total hip arthroplasties were performed with the Zweymüller Alloclassic cementless system at our institution between February 1988 and March 1991, and 104 hips (ninety-four patients) were retrospectively reviewed after a minimum duration of follow-up of ten years. The mean age of the patients at the time of the arthroplasty was 62.3 years (range, twenty-five to seventy-seven years). The mean duration of follow-up was 11.3 years. Standard radiographs were made for all patients immediately after the operation, at six and twelve months, and annually thereafter for at least ten years. Cox multivariate regression analysis was performed to assess the influence of various factors on survival of the implant. RESULTS: The cumulative probability of not having a revision of any prosthetic component for any reason was 94.1% (95% confidence interval, 91.9% to 96.3%) at twelve years in the best-case scenario and 85.3% (95% confidence interval, 82.1% to 88.5%) at twelve years in the worst-case scenario for the entire series of 124 hips. Among the 104 hips in the follow-up study, three acetabular components and no stems were revised. Two hips had level-4 pain according to the system of Merle D'Aubigné and Postel. Seven acetabular components (7%) were loose at twelve years, and all stems had radiographic evidence of stable fixation. Acetabular cup loosening was related to a vertical cup angle (p = 0.0008, Student t test), acetabular wear of > or =1 mm (p = 0.001, Fisher exact test), and a 32-mm femoral head (p = 0.001, Fisher exact test). Although femoral osteolysis was seen in eighteen hips (17%) at twelve years, all osteolytic cavities were proximal and focal. CONCLUSIONS: The Zweymüller Alloclassic prosthesis, particularly its femoral stem, demonstrated good results and durable fixation at a minimum of ten years of follow-up.

Bone defect determines acetabular revision surgery.

Cup revision can be a highly complex operation depending on the bone defect. In acetabular defects of less than 30% (Paprosky types 1 and 2), porous hemispherical cementless cups fixed with screws give good results. Modern trabecular metal designs improve these good results. Morsellised allografts are useful for filling cavitary defects. In acetabular defects greater than 30% (Paprosky types 3A and 3B), impacted morsellised allografts with a cemented cup technique produce good results. Difficult cases with pelvic discontinuity require reconstruction of the acetabulum with acetabular plates or large cup-cages to solve these difficult problems.