Neglected patellar tendon rupture: a case of reconstruction without quadriceps lengthening

Neglected rupture of the patellar tendon is a rare, can be easily missed in a group of patients. We present a 24 year old, male patient who sustained right femoral diaphyseal and tibial plateau fractures and a patellar tendon rupture following a motor vehicle accident. The fractures were treated by open reduction internal fixation but the patellar tendon rupture was missed and the diagnosis was delayed by 7 months. Patella was migrated proximally. It was moved distally to the original location and neglected patellar tendon rupture treated successfully with modified Ecker technique. Neither preoperative traction nor additional intraoperative procedures were performed to relocate the patella to its anatomic position in the extended knee and good functional result was achieved with intensive rehabilitation

Response of Sheep Chondrocytes to Changes in Substrate Stiffness from 2 to 20 Pa: Effect of Cell Passaging

Aim: The influence of culture substrate stiffness (in the kPa range) on chondrocyte behavior has been described. Here we describe the response to variations in substrate stiffness in a soft range (2–20 Pa), as it may play a role in understanding cartilage physiopathology. Methods: We developed a system for cell culture in substrates with different elastic moduli using collagen hydrogels and evaluated chondrocytes after 2, 4, and 7 days in monolayer and three-dimensional (3D) cultures. Experiments were performed in normoxia and hypoxia in order to describe the effect of a low oxygen environment on chondrocytes. Finally, we also evaluated if dedifferentiated cells preserve the capacity for mechanosensing. Results: Chondrocytes showed less proliferating activity when cultured in monolayer in the more compliant substrates. Expression of the cartilage markers Aggrecan (Acan), type II collagen (Col2a1), and Sox9 was upregulated in the less stiff gels (both in monolayer and in 3D culture). Stiffer gels induced an organization of the actin cytoskeleton that correlated with the loss of a chondrocyte phenotype. When cells were cultured in hypoxia, we observed changes in the cellular response that were mediated by HIF-1α. Results in 3D hypoxia cultures were opposite to those found in normoxia, but remained unchanged in monolayer hypoxic experiments. Similar results were found for dedifferentiated cells. Conclusions: Chondrocytes respond differently according to the stiffness of the substrate. This response depends greatly on the oxygen environment and on whether the chondrocyte is embedded or grown onto the hydrogel, since mechanosensing capacity was not lost with cell expansion