Effects of a contoured articular prosthetic device on tibiofemoral peak contact pressure: a biomechanical study

Many middle-aged patients are affected by localized cartilage defects that are neither appropriate for primary, nor repeat biological repair methods, nor for conventional arthroplasty. This in vitro study aims to determine the peak contact pressure in the tibiofemoral joint with a partial femoral resurfacing device (HemiCAP®, Arthrosurface Inc., Franklin, MA, USA). Peak contact pressure was determined in eight fresh-frozen cadaveric specimens using a Tekscan sensor placed in the medial compartment above the menisci. A closed loop robotic knee simulator was used to test each knee in static stance positions (5°/15°/30°/45°) with body weight ground reaction force (GRF), 30° flexion with twice the body weight (2tBW) GRF and dynamic knee-bending cycles with body weight GRF. The ground reaction force was adjusted to the living body weight of the cadaver donor and maintained throughout all cycles. Each specimen was tested under four different conditions: Untreated, flush HemiCAP® implantation, 1-mm proud implantation and 20-mm defect. A paired sampled t test to compare means (significance, P ≤ 0.05) was used for statistical analysis. On average, no statistically significant differences were found in any testing condition comparing the normal knee with flush device implantation. With the 1-mm proud implant, statistically significant increase of peak contact pressures of 217% (5° stance), 99% (dynamic knee bending) and 90% (30° stance with 2tBW) compared to the untreated condition was seen. No significant increase of peak contact pressure was evaluated with the 20-mm defect. The data suggests that resurfacing with the HemiCAP® does not lead to increased peak contact pressure with flush implantation. However, elevated implantation results in increased peak contact pressure and might be biomechanically disadvantageous in an in vivo application

Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing

<p>Abstract</p> <p>Background</p> <p>Up to date, no information exists about the intra-articular temperature changes of the knee related to activity and ambient temperature.</p> <p>Methods</p> <p>In 6 healthy males, a probe for intra-articular measurement was inserted into the notch of the right knee. Each subject was jogging on a treadmill in a closed room at 19°C room temperature and skiing in a ski resort at -3°C outside temperature for 60 minutes. In both conditions, temperatures were measured every fifteen minutes intra-articulary and at the skin surface of the knee. A possible influence on joint function and laxity was evaluated before and after activity. Statistical analysis of intra-articular and skin temperatures was done using nonparametric Wilcoxon's sign rank sum test and Mann-Whitney's-U-Test.</p> <p>Results</p> <p>Median intra-articular temperatures increased from 31.4°C before activity by 2.1°C, 4°C, 5.8°C and 6.1°C after 15, 30, 45 and 60 min of jogging (all p ≤ 0.05). Median intra-articular temperatures dropped from 32.2°C before activity by 0.5°C, 1.9°C, 3.6°C and 1.1°C after 15, 30, 45 and 60 min of skiing (all n.s.). After 60 minutes of skiing (jogging), the median intra-articular temperature was 19.6% (8.7%) higher than the skin surface temperature at the knee. Joint function and laxity appeared not to be different before and after activity within both groups.</p> <p>Conclusion</p> <p>This study demonstrates different changes of intra-articular and skin temperatures during sports in jogging and alpine skiing and suggests that changes are related to activity and ambient temperature.</p

Morphologic and histologic comparison between the patella and hamstring tendons grafts: A descriptive and Anatomic study

Purpose: Morphologic and histologic comparison of patella and hamstring tendon grafts. Methods: Hamstring tendons (semitendinosus and gracilis) and patellar tendons were taken from 20 cadaveric knees and were investigated by using light and electron microscopy, immunohistochemistry, and morphometry. The thickness of collagen fibrils, fibril/interstitum ratio, density of blood vessels, density of fibroblasts, and distribution of the collagen fibrils were analyzed. Results: The sernitendinosus and gracilis tendons provide 20% and 30% more fibril/interstitum ratio compared with the patella tendon (P =.0056 and .0028). Also, the density of fibroblasts was 50% and 35% more (P =.0061 and .0050). No differences regarding the thickness of the collagen fibrils, density of blood vessels, and distribution of the fibrils were found. Conclusions: Both semitendinous and gracilis tendons provide significantly more density of collagen fibrils as well as density of fibroblasts in comparison with patellar tendons. These findings provide a potential advantage of the hamstrings group on better remodelling and regeneration of the tissue. Clinical Relevance: These grafts have been used as autografts for anterior cruciate ligament reconstruction. Despite the interest on these tendons, their microscopic structure has not been sufficiently investigated yet

Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing-0

Jogging group. No significant changes were observed in the skiing group.<p><b>Copyright information:</b></p><p>Taken from "Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing"</p><p>http://www.biomedcentral.com/1471-2474/9/46</p><p>BMC Musculoskeletal Disorders 2008;9():46-46.</p><p>Published online 11 Apr 2008</p><p>PMCID:PMC2330048.</p><p></p

Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing-2

Jogging group. No significant changes were observed in the skiing group.<p><b>Copyright information:</b></p><p>Taken from "Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing"</p><p>http://www.biomedcentral.com/1471-2474/9/46</p><p>BMC Musculoskeletal Disorders 2008;9():46-46.</p><p>Published online 11 Apr 2008</p><p>PMCID:PMC2330048.</p><p></p

Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing-1

jogging group. No significant changes were observed in the skiing group.<p><b>Copyright information:</b></p><p>Taken from "Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing"</p><p>http://www.biomedcentral.com/1471-2474/9/46</p><p>BMC Musculoskeletal Disorders 2008;9():46-46.</p><p>Published online 11 Apr 2008</p><p>PMCID:PMC2330048.</p><p></p

Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing-3

jogging group. No significant changes were observed in the skiing group.<p><b>Copyright information:</b></p><p>Taken from "Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing"</p><p>http://www.biomedcentral.com/1471-2474/9/46</p><p>BMC Musculoskeletal Disorders 2008;9():46-46.</p><p>Published online 11 Apr 2008</p><p>PMCID:PMC2330048.</p><p></p