Purpose:The aim of this study was to compare the posterior tibial translation after ultracongruent (UC) and posterior-stabilized (PS) total knee arthroplasty (TKA) with two different UC with different heights in the anterior lip, and two different PS designs. This study also aimed to compare the range of motion (ROM) and outcomes scores after the use of these TKA models. It was hypothesised less posterior tibial translation after PS than after UC TKA, and less posterior tibial translation with a higher anterior lip in the UC insert than with a lower one.Methods: It was designed as a prospective randomized study of a group of 120 patients operated with a cemented TKA. In order to clarify the main purpose of the study, four groups were analysed using different polyethylene designs: Triathlon PS insert in group one, Triathlon UC insert in group two, U2 PS insert in group three and U2 UC insert in group four. One year after surgery, a forced posterior drawer with a Telos Stress applying 15 Kg of force posteriorly on the proximal tibia at 90° of knee flexion was analysed in the lateral radiograph. Limb alignment, tibial posterior slope and posterior condylar offset were also studied.Results: 30 patients were included in each group. The average age was 73 years. There were 72.2% female and 27.8% male patients. There were no significant differences in any demographic or radiographic studied variables, preoperative range of motion (ROM) or preoperative Knee Society Scores (KSS) among the different groups. One year after surgery, the average postoperative ROM and the postoperative KSS Knee and KSS Function scores improved in respect of the preoperative values in all the groups. There were no significant differences in the postoperative outcome scores among the different groups (p=n.s.). Postoperative alignment of the limb, tibial posterior slope and posterior condylar offset were similar in the 4 study groups (p=n.s.). The postoperative posterior tibial translation was different between groups: the PS groups (groups 1 and 3) showed significant inferior values (p<0.001) in respect of the UC groups (groups 2 and 4). There were no differences between both groups of PS models, but there was a significant increase in the posterior tibial translation of the Triathlon UC insert (11.2 mm SD 3.2) in respect of the U2 UC insert (6.1 mm SD 4.5) (p=0.004).Conclusions: UC inserts restrict the posterior tibial translation after TKA less than PS inserts, but a design with a high anterior lip in the polyethylene UC insert can better control the posterior tibial translation than an insert with a small anterior lip.

Recibido el 30 de julio de 2014; aceptado el 5 de mayo de 2015 Disponible en Internet el 23 de noviembre de 2015 PALABRAS CLAVE Hallux rigidus; Coughlin y Shurnas; Clasificación; ReproducibilidadResumen Existen diversas clasificaciones descritas en la literatura para los hallux rigidus. La clasificación de Coughlin y Shurnas es probablemente la más utilizada, empleándose tanto para la estadificación como para la decisión terapéutica. El objetivo de este estudio es evaluar su reproducibilidad a partir de su concordancia inter e intraobservador. Se obtuvo una muestra de 13 pacientes con diagnóstico de hallux rigidus (7 de ellos bilateral), sumando 20 casos. Se citó individualmente a todos los pacientes en consultas externas en 2 visitas separadas por 30 días. En cada visita fueron clasificados por los 3 observadores para los diferentes parámetros de la clasificación de Coughlin y Shurnas: arco de movilidad, radiología, clínica y en un grado final. Se realizó un estudio de correlación inter e intraobservador que resultó en una correlación buena o muy buena para los parámetros de arco de movilidad, radiología y grado final, encontrándose una pobre correlación para la clínica. En conclusión, la clasificación de Coughlin y Shurnas es reproducible para valorar la estadificación de los hallux rigidus.Abstract There are several classifications described in the literature for hallux rigidus. Coughlin and Shurnas classification system is probably the most widely used in this field, for both the staging and therapeutic decision. The objective of the present study was assessing the reproducibility of this classification system, based on the concordance between inter-and intraobserver. A sample of 20 cases was obtained based on 13 patients diagnosed with hallux rigidus (7 of them were bilateral). All patients were scheduled individually in outpatient services on 2 visits separated by 30 days. During each visit they were classified by 3 observers for the different parameters of Coughlin and Shurnas classification: range of motion, radiology, clinics, and finally in a final * Autor para correspondencia. Correo electrónico: xlizano@gmail.com (X. Lizano-Díez).http://dx.