Biomechanical analysis by finite element method and evaluation of geometrical properties from two and three dimensional images of femur in the dog

Proximal femur bölgesi geometrisinin iyi anlaşılması, özellikle total kalça arthroplastisi uygulamalarında kemik-implant uyumunun değerlendirilmesi ve yeni tasarımlarının geliştirilebilmesinde önemlidir. Veteriner hekimlikte fonksiyonel ve morfolojik özelliğinden dolayı köpeklerin ortopedik hastalıklarında önemli bir yer tutan femur'a ve buna bağlı implant tasarımlarına ilişkin morfometrik çalışmalar yetersizdir. Bu çalışmada rutin olarak kullanılan röntgen ve son yıllarda yaygın olarak kullanılmaya başlanan üç boyutlu model görüntüleri ile elde edilen köpek proximal femur ölçümleri arasında farklılık olup olmadığının araştırılması amaçlanmıştır. Ayrıca, ülkemizde yaygın olarak yetiştirilen, art. coxae problemlerinin sık görüldüğü ve vücut konformasyonlarında da farklılık olan Alman çoban köpeği ve Kangal köpeği proximal femur geometrisinin ırklar arasında farklılık gösterip göstermediğinin ve olası geometrik farklılıkların proximal femur mekaniğinde değişikliklere neden olup olmadığının araştırılması amaçlanmıştır. Çalışmada 21 adet (11 adet Kangal Köpeği, 10 adet Alman Çoban Köpeği) köpeğe ait temizlenmiş femur kemikleri kullanılmıştır. Femur'ların öncelikle cranio-caudal, medio-lateral röntgen görüntüleri alınmış ve daha sonra üç boyutlu modellemede kullanılmak için bilgisayarlı tomografi ile kesit görüntüleri elde edilmiştir. Elde edilen bu kesit görüntüleri kullanılarak üç boyutlu katı model görüntüleri hazırlanmıştır. Bilgisayar ortamında üç boyutlu modellerde ve iki boyutlu görüntülerde proximal femur'a ilişkin morfometrik ölçümler alınmıştır. Ayrıca üç boyutlu femur modellerinde bilgisayar ortamında sonlu elemanlar yöntemi ile biyomekanik analiz simülasyonu yapılmıştır.Köpeklerde kalça protezi tasarımı açısından önemli olan morfometrik değerlere bakıldığında; yeniden şekillendirilen caput femoris'in yeri-pozisyonu ve protezin sap kısmının yerleşeceği proximal femur'un medullar kanal geometrisi hem röntgen görüntüleri hem de üç boyutlu kemik modelleri üzerinden değerlendirilmiş ve her iki yöntem ölçümleri arasında bazı farklılıklar bulunmuştur. Ancak tasarım açısından çok değerli olan inklinasyon açısı ve canal flare indeks değerlerinde yöntemler arası farklılık görülmemiştir. Bu sonuçlara göre, üç boyutlu ölçme yöntemi ile genel olarak amaç açısından daha geçerli bir geometrik değerlendirme yapılablise de, her iki yöntemin birlikte kullanılmasının değerlendirme kolaylığı sağlayabileceği düşünülmüştür. Protezin sap kısmının yerleşeceği medullar kanal şeklinde, kesit geometrisinde, isthmus bölgesinin yerinde Alman çoban ve Kangal köpeği ırkları arasında belirgin bir farklılık görülmemiştir. Bu hayvanlarda ortalama canal flare index değerleri medio-lateral yönlü olarak 2.44-2.64 arasında, cranio-caudal yönlü olarak 1.52-1.59 arasında tespit edilmiştir. Proximal isthmus pozisyon indexi 39.59-40.43 arasında, distal isthmus pozisyon indexi ise 42.84-46.54 arasında tespit edilmiştir. Caput femoris pozisyonuna ilişkin olarak ırklar arası farklılık gösteren inklinasyon açısı değerinin Alman çoban köpeğinde ortalama 145o, Kangal köpeğinde ortalama 149o olduğu dikkati çekmiştir. Bunun yanında caput femoris merkezinin anatomik eksene mesafesinin her iki ırkta da bir birbirine eşit olması nedeniyle ve inklinasyon açısı daha yüksek olan Kangal köpeğinde caput femoris'in oransal olarak proximale daha yakın olduğu tespit edilmiştir. Her ne kadar mekanik test simülasyonu sonucunda ırklar arasında bir farklılık bulunmamışsa da, morfometrik değerlendirmedeki bu farklılığın aynı tip protez kullanılması durumunda protez-kemik uyumunda beklenenin dışındaki bölgelerde ve farklı miktarlarda oluşabilecek yüklenmelere neden olabileceği ve bunun sonucunda postoperatif kırık ve benzeri sorunların riskini arttırabileceği düşünülmüştür.The understanding of the proximal femoral geometry is very important to develop of new prosthesis design and evaluate of bone-implant alignment on the total hip arthroplasty studies. The morphometric studies on dog femora are limited regarding implant design in veterinary medicine, although the femur is an important bone in dog orthopedics with functional and morphological properties. To investigate of differences on the measurements of canine proximal femora between the x-ray and three dimensional model images has aimed in this study. Second aim of this study has also investigated the differences on breed characteristics of geometrical and biomechanical properties of proximal femora between the German shepherd and Kangal dogs which have common hip problems and body conformation differences. The cleaned femora of 21 dogs (11 Anatolian shepherd dogs,10 German shepherd dogs) were used in this study. The X-ray images were obtained on cranio-caudal and medio-lateral positions. The sectional images were also obtained with computed tomography. The three-dimensional solid models were also created by using these images with computer. The some measurements were obtained from proximal femora both with computer-generated three-dimensional models and two-dimensional images. The biomechanical simulation with finite element method on three-dimensional models of femora was also generated. There were some differences on the measurements of position of femoral head and medullary canal of proximal femora between the x-ray and 3D methods. But, there were no differences between two methods at inclination angle and canal flare index which have more important data for designing of implant. The proximal femoral geometry may be evaluated more valid by three-dimensional measuring method, although the both methods may effective to this evaluation when used together. Beside, any difference was not observed on the shape of medullary canal and placement of isthmus region of the proximal femora between the Kangal and German shepherd dog. The mean values of canal flare index were observed 2.44-2.64 as medio-laterally, 1.52-1.59 as cranio-caudaly. The mean values of position of proximal and distal isthmus indices were also observed as 39.59-40.43 and 42.84-46.54, relatively. Related with femoral head position, there was an important diffirence between the inclination angle of Kangal and German Shepherd dogs. The mean angle was observed as 145o and 149o on German shepherd and Kangal dogs, relatively. In proportionally, the femoral head of Anatolian shepherd dog has located on more proximal than femoral head of German shepherd dog, but the distance between the center of femoral head and the anatomical axis of bone was similar in both breeds. There were no differences between the results of biomechanical simulations of dog breeds. However, the postoperative fracture risk may increase because of unexpected loads on different parts if the same type of prosthesis is used in different neck geometry

The Geometry of the Proximal Femoral Medullary Canal in German Shepherd and Kangal Dogs

The proximal femur has morphological variability that is related to its functional and biomechanical properties. Therefore, researchers have long been interested in these variations especially associated with the femoral implant design and implantation in total hip arthroplasty. The positions of the femoral head and the geometrical variations in the medullary canal are evaluated in particular to understand the proximal femoral morphology. The position of head or neck of the dog has already been studied in detail. There are incomplete data to evaluate variations in the geometry of the medullary canal of proximal femur in dog. Proximal femoral morphology of the medullary canal has been evaluated only at the coronal plane in dog studies using plain radiography. The morphometric data on the sagittal plane are also need to innovations in femoral implants. The purpose of this study is to indicate the detailed geometric data about proximal femoral canal of dog using three-dimensional morphometric methods to provide a database for the orthopedic studies. The effect of the breed with different pelvic limb conformation was also studied in this study. The cleaned femora from 16 German shepherd and 16 Kangal dogs were used. The three-dimensional images were reconstructed from the computed tomographic images. The femoral length, the anteversion angle and neck angles, the isthmus position and the widths on medio-lateral and cranio-caudal directions of the cross-sections of proximal femur were measured. The cortico-medullary indices, the isthmus position index and the canal flare indices were also calculated to detailed investigation of medullary canal of the proximal femur. According to our study results, it must be considered in stem design that the level of the isthmus might change in response to different conformations of the dog breeds, whilst the flare indices are similar in the dogs. The flare of the medullary canal was firstly evaluated with the cranio-caudal diameters on the three-dimensional images in this study. The cortico-medullary index shows some variation between the dog breeds across the levels and the directions of the cross-sections of the proximal femur. Nowadays, three-dimensional images can be acquired and morphometric measurements can be done easily by tomography in a lot of veterinary clinics. The data from three-dimensional morphometric analysis may contribute to the optimization of the design and preoperative selection of femoral implants by surgeons

Foraminal index on the dog femora

Damages of the main nutrient artery during the fractures may lead to poor repair or bone infarcts. Therefore, knowledge about the localization and number of nutrient foramina of bones is important in some surgical procedures such as bone implants, fracture repair, bone grafts. Foraminal index is calculated as dividing the distance between proximal end of the bone and nutrient foramen to the total bone length. One hundred and twelve femora of the 56 mature dogs were used in this study. The general morphometric parameters of femur; the total length, the cranio-caudal and medio-lateral diameters of mid-femur were taken. The numbers of the primary and secondary nutrient foramina were determined and the foraminal index was calculated. One foramen nutricium was determined at the 88 bones while two foramen at the 24 bones. The mean foraminal index was 36.4%, between ranges of 31.8% - 55.1% in dog femora. Statistical difference of foraminal index was not determined between male and female dog femora. These data may be valuable for surgeons in cases of total hip arthroplasty, intramedullary pin, and external fixation and also on evaluating period of fracture repair after surgery

Effect of Tibial Plateau Leveling Osteotomy on Mechanical Tibial Axis Shift in Dogs: Two-Dimensional Bone Study in Sagittal Plane

To determine the tibial axis shift (TAS), change in tibial plateau angle (TPA), and the position of the tibial articular surface after tibial plateau leveling osteotomy (TPLO) simulation in the tibiae of dogs, tibias of 91 dogs from 23 dif- ferent breeds were used. The TPA, tibial length, midshaft width, medial tibial condyle length, and distances between the tibial axis (TA) and cranial-most point of the medial condyle were measured on the tibial images. After simulated TPLO, all measurements were retaken. Paired t-tests were used to compare pre- and postoperative variables. Pear- son correlation analysis was conducted to assess whether the difference between pre- and postoperative TAS was re- lated to tibial length, tibial width, medial condyle length, and/or the degree of TPA rotation. The results showed that TPLO shifted the cranial-most point of the medial condyle caudally and distally, and the caudal-most point caudally and proximally. These shifts resulted in significant differences between pre- and postoperative distances between the TA and the cranial-most point and its percentage to the medial condyle length. It is concluded that the TPLO led to caudal TAS and altered the position of the articular surface of the medial condyle with respect to the distal part of the tibia

Proximal and distal alignment of normal canine femurs: A morphometric analysis

Many researchers are interested in femoral conformation because most orthopaedic problems of the long bones occur in the femur and its joints. The neck-shaft (NSA) and the anteversion (AVA) angles are good predictors for understanding the orientation of the proximal end of the femur. The varus (aLDFA) and procurvatum (CDFA) angles have also been used to understand the orientation of the distal end of the femur. The purposes of this study were to investigate the relationship between the proximal and distal angles of the femur and to compare the distal femoral angles in male and female dogs in order to investigate the sexual dimorphism. The measurements of normal CDFAs, which have not been previously reported, may also provide a database of canine distal femoral morphology

The Effect of Ozone on Bone Strenght in Animal Model of Rheumatoid Arthritis

Objective: Periarticular and systemic osteoporosis are more common in rheumatoid arthritis (RA) than normal population. In this study, we aimed to investigate the effectiveness of ozone on bone strength in Freund’s complete adjuvant (FCA) arthritis, which is considered as the animal model for RA. Materials and Methods: In this study, 28 male Wistar rats were used. Saline was injected into the hindpaws of 14 rats, and Freund’s complete adjuvant was injected into the hindpaws of the other 14 rats, subcutaneously. At the end of two weeks, 40 µg/ml ozone was administered intraperitoneally to 7 of the rats in each group for 6 times totally within duration of three weeks. At the 6th week, serum interleukin-1 (IL-1), IL-6 and tumor necrosis factor-alpha (TNF-α) levels were measured. Right femurs were separated for 3-point flexure test. Results: TNF-α levels of FCA arthritis were significantly higher than that of the control group (p0.05). Serum levels of IL-1 and IL-6 were not statistically significant among all groups (p>0.05). Maximum force and moment of inertia tended to increase in FCA arthritis-ozone group compare to the FCA arthritis group (p>0.05). The stiffness and toughness were similar in the all groups (p>0.05). Conclusion: To the best of our knowledge, this is the first study in which the effects of ozone on bone strength of RA were investigated. It is determined that ozone is not effective enough, but not harmful on bone strength of FCA arthritis. It is clear that further studies are required with ozone treatment and its use in RA when administrated in different doses and time courses

Rotational deformities of the long bones can be corrected with rotationally guided growth during the growth phase: A study in rabbits

Background and purpose — Coronal and sagittal plane long bone deformities can be corrected with guided growth, whereas transverse plane rotational deformities require osteotomy and internal or external fixation. We investigated whether rotational changes can be introduced with the plating technique. Methods — 45 rabbits (6 weeks old) were divided into 3 groups. The unoperated right tibia was used as control. In groups 1 and 3, two plates were placed obliquely to the long axis and in different directions. In group 2, a sham operation was performed with screws. Animals in groups 1 and 2 were followed for 4 weeks. In group 3 the implants were removed 4 weeks after the operation to observe rebound effect, and the animals were followed for another 4 weeks. The tibial torsion was assessed on computed tomography (CT). External rotation was accepted as a negative value. Results — In group 1, mean torsion was −20° (SD 7.9) in the right tibia and −2.9° (SD 7.2) in the left tibia (p < 0.001). In group 2, mean torsion was −23° (SD 4.9) in the right tibia and −26° (SD 6.5) in the left tibia (p = 0.2). In group 3, mean torsion was −21° (SD 6.3) in the right tibia and −9.5° (SD 5.3) in the left tibia (p < 0.001). Intergroup evaluation for left torsion showed a significant difference between group 2 and the other groups (p < 0.001). When the rebound effect was evaluated, there was no statistically significant difference between groups 1 and 3 (p = 0.08). Interpretation — A rotational change was attained with this technique. Although a rebound effect was seen after implant removal, it did not reach statistical significance. The final rotational change remained constant