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We compared, via a computational model, the biomechanical performance of reamed versus unreamed intramedullary tibial nails to treat fractures in three different locations: proximal, mid-diaphyseal, and distal. Two finite element models were analyzed for the two nail types and the three kinds of fractures. Several biomechanical variables were determined: interfragmentary strains in the fracture site, von Mises stresses in nails and bolts, and strain distributions in the tibia and fibula. Although good mechanical stabilization was achieved in all the simulated fractures, the best results were obtained in the proximal fracture for the unreamed nail and in the mid-diaphyseal and distal fractures for the reamed nail. The interlocking bolts, in general, were subjected to higher stresses in the unreamed tibial nail than in the reamed one; thus the former stabilization technique is more likely to fail due to fatigue.

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.

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 deterioration. We found that with the best mechanical conditions and with the same materials, the prosthesis design determines a different periprosthetic bone remodeling.

The main objective of this work is the evaluation, by means of the finite element method (FEM) of the mechanical stability and long-term microstructural modifications in bone induced to three different kinds of fractures of the distal femur by three types of implants: the Condyle Plate, the less invasive stabilization system plate (LISS) and the distal femur nail (DFN). The displacement and the stress distributions both in bone and implants and the internal bone remodelling process after fracture and fixation are obtained and analysed by computational simulation. The main conclusions of this work are that distal femoral fractures can be treated correctly with the Condyle Plate, the LISS plate and the DFN. The stresses both in LISS and DFN implant are high especially around the screws. When respect to remodelling, the LISS produces an important resorption in the fractured region, while the other two implants do not strongly modify bone tissue microstructure.

The ongoing debate surrounding the surgical treatment of trochanteric hip fractures, particularly unstable fractures, has led to continuous changes in the design of well-established implants and to the development of new ones. The goal of this paper was to use a finite element simulation to compare the biomechanical behaviour of two intramedullary implants most often used at the University Hospital of Zaragoza: the standard Gamma nail (Howmedica) and the proximal femoral nail (PFN, Stratec). The main focus was on the displacements of the fracture focus and the stress distributions along the femur and the implant. Both nails produced an important redistribution of stress in the bone tissue, but the redistribution of peak stress was higher for the Gamma nail. On the other hand, with PFN there were smaller displacements at the fracture site. Finally, under the same workload, the Gamma nail supported higher stresses than the PFN.

Objective: The finite element method (FEM) was used to evaluate the short-term mechanical stability of trochanteric fractures treated by two types of implants: the Gamma" nail (Howmedica) and the Dynamic Hip Screw, DHS" (Synthes)., Methods: The displacement and stress distributions of bone and implants were computed using a complete 3D FE model., Results: The main conclusion is that proximal stable femoral fractures can be treated correctly with the Gamma Nail and DHS. For unstable fractures, the Gamma Nail achieves good stabilization but DHS is insufficient and requires a static screw due to the lack of torsional stiffness. Both extramedullary and intramedullary systems were found to distort the load transmission with respect to the anatomic pattern, so they both have biomechanical limitations in the long-term. (Hip International 2004; 14: 18-23)NO PDF AVAILABLE!

The authors present a series of 25 patients with Lisfranc fracture-dislocation who were treated by reduction (open or closed) and stabilization with Kirschner wiring. Minimum follow-up was two years. The dislocations were divided based on the Quenu and Kuss classification system. Nonsurgical reduction was possible in 17 patients. Neither the type of dislocation nor the type of reduction influenced the results in progression in our series. Nonetheless, long-term functional results were better when the quality of the reduction was excellent.

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The aim of the present article is to ascertain the differences between two surgical treatments commonly used in displaced radial neck fractures in children. We report the retrospective results of 20 displaced radial neck fractures with > 30 degrees of tilt (Judet grades 3-4) in children aged between 7 and 14 years treated with closed intramedullary pinning according to the Metaizeau technique (6 cases) or with arthrotomy and pinning (14 cases). Sex distribution was 14 girls and 6 boy. The average follow-up was 43 months. We found no relationship between delay in the surgical treatment and functional results. On the other hand, a relationship between residual final tilt and poorer functional results appears. The Metaizeau technique produced better results and fewer complications than arthrotomy and pinning, and, in our opinion, is the treatment of choice in this type of fracture.

The Finite Element Method (FEM) can be used to analyze very complex geometries, such as the pelvis, and complicated constitutive behaviors, such as the heterogeneous, nonlinear, and anisotropic behavior of bone tissue or the noncompression, nonbending character of ligaments. Here, FEM was used to simulate the mechanical ability of several external and internal fixations that stabilize pelvic ring disruptions. A customized pelvic fracture analysis was performed by computer simulation to determine the best fixation method for each individual treatment. The stability of open-book fractures with external fixations at either the iliac crests or the pelvic equator was similar, and increased greatly when they were used in combination. However, external fixations did not effectively stabilize rotationally and vertically unstable fractures. Adequate stabilization was only achieved using an internal pubis fixation with two sacroiliac screws.

Synovial chondromatosis is an uncommon lesion, characterised by cartilaginous and osseous metaplasia of the joint synovium. It usually involves a large joint and rarely occurs in the hand. A case of tenosynovial chondromatosis of the third finger is reported.

Nora's tumor, also known as bizarre paraosteal osteochondromatous proliferation, is an exophytic outgrowth from the cortical surface that consists of a mixture of bone, cartilage, and fibrous tissue. It is a benign lesion with atypical microscopic features and a tendency to recur. Nora reported 35 cases emerging from the bones of the hands and feet. The largest published series is of 65 cases, with 17 lesions involving the long bones. With this exception, most authors report isolated cases. Age range from 8 to 74 years but most patients are between 20 and 35 years of age, and with the lesion affecting males and females in equal proportions. Usually the presenting symptoMs are due to bony mass, with a variable growth rate (months-years), and infrequent pain. In 15-20% of the cases there was trauma in the patient history: nevertheless, Fechner and Mills report no association with trauma. Radiography shows a calcified, rounded mass emerging directly from the surface of the bone. Isotope bone scans show intense tracer uptake in the lesion. With time, the appearance progresses to the more characteristic mature bone architecture.

We studied the effect of implantation of self-reinforced polyglycolic acid (SR-PGA) screws through the greater trochanter in rabbits. 15 rabbits aged 10 weeks had an SR-PGA screw inserted through the left trochanter physis. A similar drilling was made through the right greater trochanter without screw implantation. The animals were assigned to 3 groups of 5, and were killed after 1, 2 or 3 months. Radiographs of both femurs were obtained monthly and the articulo-trochanteric distance and the neck-shaft angle were measured. After killing the animals, a histological study was performed. The drilling on the right trochanter generated a bony bridge in all the animals. The SR-PGA screws did not give rise to an epiphysiodesis. The progressive peripheral degradation of the implants gave rise to the formation of only modest bridges, which were smaller in size than those observed in the control trochanter. Our findings suggest that absorbable PGA screws implanted through a growth plate cause only minor bone formation and no epiphyseodesis.

We have carried out an experimental investigation of lesions of the intervertebral disc produced by flexion, lateral bending and rotational forces in an attempt to produce disc herniations. Adult Wistar rats were divided into 4 groups: control and posterior, lateral and rotational herniation. There were 10 rats in each group. The tail between the 5th and 8th vertebral segments was used. A Kirschner wire was inserted into each of 2 adjacent vertebrae and the movement produced had an apex which was anterior or lateral depending on the group involved. Variables such as rupture of the annulus, the cellularity of the nucleus pulposus and the site of the lesion in the disc were studied histologically. The height of the disc, the protrusion, the thickness, and the surfaces of the annulus fibrosus and the nucleus pulposus were measured. In every case we found a nuclear displacement which did not become a protrusion. The surface parameters and the cellularity of the nucleus pulposus are most useful indicators and should be included in any study examining the disc after the injection of substances for treatment.

Curettage and filling with acrylic cement in the treatment of para-articular giant cell tumor (GCT) has multiple advantages as compared to other methods; nonetheless, the possibility of progression in arthrosis is still a drawback. The literature does not report long-term functional results when this method was used. Four cases are presented with a mean long-term follow-up of 13.5 years (minimum 11, maximum 18). Clinical results, evaluated by the Enneking system (18), were excellent, and there were no radiological modifications, so that we believe that this is the method to choose for Campanacci stage I and II GCT (1), and in some stage III cases, as joint function is not compromised in time.

The adherence of Staphylococcus aureus to biomaterials used in orthopaedic surgery (polymethylmethacrylate, fresh bone, steel and titanium alloys) and to glass was studied in vitro at 1, 2, 6, 24 and 48 h of incubation. Nonslime-producing strains (72, 80 and 510) and slime-producing variants of these strains were used. An automated and fast method of ATP-bioluminiscence was applied to determine bacterial viability. The lowest adherence corresponded to polymethylmethacrylate and bone, and the highest to metals. Significant adherence was detected in all cases after 6 h and was strain dependent, being lowest for strain 72. In most cases, adherence of nonslime-producing variants was not significant compared with controls, and slime-producing were more adherent than nonslime-producing variants. These differences were maximal at 6 h or 48 h, depending on the strain and the material. The findings suggest that the appearance of slime-producing cells within a given nonslime-producing bacterial population may jeopardise postoperative immune systems and antibiotic efficacy as a consequence of biofilm formation on implants and prostheses.

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.

A case of giant cell tumor localized in the proximal end of the right tibia, initially treated by simple curettage is described. After 11 years there was local recurrence, confirmed anatomopathologically, observed during wide resection and reconstruction by arthroplasty plus homoplastic grafting. After a few months there were metastatic lesions in the left parietooccipital and right retroorbitary area. Biopsy of the parietooccipital lesion showed giant cells in a sarcomatous stroma. The patient died after several attempts at chemotherapy. Even if only sporadic cases have been described of late recurrences and of extrapulmonary metastases for giant cell tumors, the case presented here is exceptionally rare. The factors that influence recurrence of these tumors and their ability to metastasize is discussed.

A retrospective review of complications with the gamma nail has been carried out in 152 patients with stable and unstable pertrochanteric fractures. Operative complications occurred in 10 patients. Screws penetrated the femoral neck in 3, immediate varus was associated with a short screw in 2, diaphyseal fractures occurred at the site of the distal screws in 3 and comminuted femoral fractures in 2. Fifteen patients (10.5%) died in hospital. At follow up, pseudarthrosis was present in 2 cases and fractures of the femoral shaft in 4. The incidence of complications could be reduced by using of shorter nails, less valgus angulation and by not introducing distal screws unless essential.

Although total knee arthroplasty is a valuable surgical technique, complications and problems do occur. Associated stress fracture of the femoral neck is relatively rare and we have only found eleven relevant reports. In this paper we present a case of bilateral total knee arthroplasty where three months after the second replacement, and without significant injury, the patient suffered a femoral neck fracture in the limb which had received the first new knee joint.

A series of 260 noncemented total hip arthroplasties with a titanium alloy stem and fixation by the Zweymüller press-fit and an Endler polyethylene threaded cup was reviewed in detail. The minimum follow-up period was 48 months and the maximum 72 months, with an average of 60 months. A scale from zero to five points was applied to evaluate pain, mobility, and motion for a total possible accumulation of 15 points. The global results of the different etiologic groups (arthrosis, femoral head necrosis, rheumatoid arthritis, and subcapital hip fractures) have been very good and good (12-15 points) in 67.5% of the cases and fairly good and bad in 32.3%. These results have been better in femoral head necrosis than in arthrosis or rheumatoid arthritis, but not as good in subcapital hip fractures. The age groups below 60 had better results than the above 60 groups. The Singh index higher than 3 was correlated with better-than-average results. The polyethylene cup migrated horizontally (more than 4 mm) in 7.6% of the cases and vertically (more than 5 mm) in 10%. The non-evolutionary cortical remodelation of the femur does not influence the results. Prosthetic stem sinking less than 4 mm has been found in 62% of the cases, from 4 to 9 mm in 21%, and greater than 9 mm in 6%. No alterations with clinical consequences attributable to stress-shielding have been detected.