Belen Seral

The best methods to manage tibial bone defects following total knee arthroplasty remain under debate. Different fixation systems exist to help surgeons reconstruct knee osseous bone loss (such as tantalum cones, cement, modular metal augments, autografts, allografts and porous metaphyseal sleeves) However, the effects of the various solutions on the long-term outcome remain unknown. In the present work, a bone remodeling mathematical model was used to predict bone remodeling after total knee arthroplasty (TKA) revision. Five different types of prostheses were analyzed: one with a straight stem; two with offset stems, with and without supplements; and two with sleeves, with and without stems. Alterations in tibia bone density distribution and implant Von Mises stresses were quantified. In all cases, the bone density decreased in the proximal epiphysis and medullary channels, and an increase in bone density was predicted in the diaphysis and around stem tips. The highest bone resorpti...

Dislocation is a serious complication in total hip replacement (THR). An inadequate range of movement (ROM) can lead to impingement of the prosthesis neck on the acetabular cup; furthermore, the initiation of subluxation and dislocation may occur. The objective of this study was to generate a parametric three-dimensional finite element (FE) model capable of predicting the dislocation stability for various positions of the prosthetic head, neck, and cup under various activities. Three femoral head sizes (28, 32, and 36 mm) were simulated. Nine acetabular placement positions (abduction angles of 25°, 40° and 60° combined with anteversion angles of 0°, 15° and 25°) were analyzed. The ROM and maximum resisting moment (RM) until dislocation were evaluated based on the stress distribution in the acetabulum component. The analysis allowed for the definition of a "safe zone" of movement for impingement and dislocation avoidance in THR: an abduction angle of 40°-60° and anteversion...

Resumen.—En la evolución de un paciente sometido a un trasplante hepático existe una importante morbilidad con complicaciones musculosqueléticas, especialmente debido a la osteopenia que sufren con fracturas patológicas y necrosis avasculares. Es un tema im-portante puesto que son pacientes jóvenes, que se encuentran sometidos a quimioterapia inmunosupresora intensiva. Además no existe una terapia profiláctica efectiva ni trata-miento de las complicaciones. Presentamos el caso de un niño de 16 años de edad al que se le realizó un trasplante hepático en 1994 y en uno de sus múltiples ingresos refería una lumbalgia aguda con una hipercifosis dorsolumbar. Se ha realizado una revisión de la li-teratura, estudiando los posibles mecanismos etiopatogénicos implicados en el desarrollo de las fracturas vertebrales tras un trasplante hepático. OSTEOPENIC VERTEBRAL FRACTURES AFTER LIVER TRANSPLANTATION Summary.—Orthotopic liver transplantation has greatly improved the survival of pa-tients wit...

Resumen.—La fagocitosis de las partículas de polietileno (PE) liberadas de los implantes pro­ tésicos es efectuada por células macrofágicas. En este trabajo estudiamos con microscopía elec­ trónica de transmisión las alteraciones intracelulares inducidas por las partículas de PE. Se han tomado muestras de la interfase situada entre el cotilo de PE y su lecho óseo en 8 casos de re­ cambio de cotilo que habían sido tratados mediante artroplastia total de cadera con cotilo de po­ lietileno roscado de Endler y que habían desarrollado migración por osteólisis. Se han identifica­ do como componentes del tejido granulomatoso reactivo al PE los siguientes componentes: ma- crófagos polinucleados, macrófagos mononucleados, linfocitos, fibroblastos y células endoteliales capilares. Hemos observado depósitos de PE extracelulares en gran cantidad alternando con fi­ bras de colágeno. La microscopía electrónica de transmisión permite identificar macrófagos acti­ vados con gran producción de vesícu...

It is our belief that this is the first histologically documented case of popliteal cyst secondary to early failure of a cementless knee prosthesis, that occurred after 4 years. The walls of the cyst presented with granulomatous reaction to polyethylene particles. In prosthetic reimplantation successive to excision of the cyst we observed a recurrence of cysts and osteointegration of the prosthetic components, that made reimplantation difficult. Histological assessment of the synovial tissue, periprosthetic tissue and underlying bone showed granulomatous reaction to polyethylene debris. A "tumor" in a patient that has a knee prosthesis can be caused by implant failure. In cases of early failure wear forms large particles and their migration at the bone-prosthesis interface may be obstructed and thus cause a different biological response. If reimplantation is necessary osteointegration of the implants may make surgery difficult.

Remodeling periprosthetic femoral bone after total hip arthroplasty has been studied extensively. Finite element (FE) analysis, together with mathematical remodeling theories, has predicted that femoral bone-mineral density decreases proximally after total hip arthroplasty. There is significant controversy concerning the clinical consequences of bone remodeling such as the reduction in bone strength, the possibility of a cement mantle fracture, the aseptic loosening of the implant, or the appearance of a periprosthetic fracture, which could threaten the survival of the hip prosthesis. The status of periprosthetic bone stock is an important concern when total hip arthroplasty revision is undertaken. This study was conducted to evaluate the periprosthetic bone-mineral density evolution following primary total hip arthroplasty by FE analysis. We compared two cemented stems with different designs: the Exeter and the SHP to study the phenomenon of femoral stress shielding and bone cement...

... Pubmed 11. Palanca D, Albareda J, Seral F. Subcapital stress fracture of the femoral neck after total knee arthroplasty. ... J Biomech 1998; 31:753-7. Pubmed. Seral García, B a ; Cegoñino Banzo, J a ; García Aznar, JM a ; Doblaré Castellano, M a ; Seral Iñigo, F a. ... Brown, David L. ...

Debonding of the stem-cement interface and damage accumulation in the cement mantle are basic events that contribute to the long-term failure of cemented hip reconstructions. In this work, a numerical study with these two processes coupled is presented. On the one hand, debonding of the stem-cement interface was simulated by means of a cohesive surface theory that was implemented into an interface finite element. This interface model includes a tensile-shear behavior law, the fatigue failure of the interface, and the friction evolution between both surfaces. On the other hand, damage accumulation in the cement was formulated through the theory of continuum damage mechanics, considering cement damage due to tension, creep under compression, crack closure effects, non-linear damage accumulation and cement residual stresses appearing during polymerisation. This methodology was applied to simulate and compare the degradation process of the cement and stem-cement interface in four different concepts of design: Exeter, Charnley, Elite Plus and ABG II stems. As the actual mechanical properties of the surface of each specific prosthesis are not known, we assumed the same for all of them, distinguishing between polished and matt surfaces. With this assumption, the predicted results showed that the debonding process is very different for each implant depending on the stem geometry. Lower cement deterioration was obtained for the Exeter and ABG II stems, while the lowest stem-cement interface debonding was produced in the Exeter and the Elite Plus stems.