The Geometry of the Trochlear Groove

Background In the natural and prosthetic knees the position, shape, and orientation of the trochlea groove are three of the key determinants of function and dysfunction, yet the rules governing these three features remain elusive. Questions/Purpose The aim was to define the three-dimensional geometry of the femoral trochlea and its relation to the tibiofemoral joint in terms of angles and distances. Methods Forty CT scans of femurs of healthy patients were analyzed using custom-designed imaging software. After aligning the femur using various axes, the locations and orientations of the groove and the trochlear axis were examined in relation to the conventional axes of the femur. Results The trochlear groove was circular and positioned laterally in relation to the mechanical, anatomic, and transcondylar axes of the femur; it was not aligned with any of these axes. We have defined the trochlear axis as a line joining the centers of two spheres fitted to the trochlear surfaces lateral and medial to the trochlear groove. When viewed after aligning the femur to this new axis, the trochlear groove appeared more linear than when other methods of orientation were used. Conclusions Our study shows the importance of reliable femoral orientation when reporting the shape of the trochlear groove

The structural properties of the lateral retinaculum and capsular complex of the knee

Although lateral retinacular releases are not uncommon, there is very little scientific knowledge about the properties of these tissues, on which to base a rationale for the surgery. We hypothesised that we could identify specific tissue bands and measure their structural properties. Eight fresh-frozen knees were dissected, and the lateral soft tissues prepared into three distinct structures: a broad tissue band linking the iliotibial band (ITB) to the patella, and two capsular ligaments: patellofemoral and patellomeniscal. These were individually tensile tested to failure by gripping the patella in a vice jaw and the soft tissues in a freezing clamp. Results: the ITB–patellar band was strongest, at a mean of 582 N, and stiffest, at 97 N/mm. The patellofemoral ligament failed at 172 N with 16 N/mm stiffness; the patellomeniscal ligament failed at 85 N, with 13 N/mm stiffness. These structural properties suggest that most of the load in-vivo is transmitted to the patella by the transverse fibres that originate from the ITB

Live (green) and dead (red) cells on hMSC treated with different concentration of gadolinium.

<p>White small arrows indicate dead cells. The number of dead cells increased by increasing the SACC blocker concentration.</p

Effect of gadolinium on strain-induced decrease in DNA counts.

<p>The cells were fixed and DNA stained by Hoechst (blue). (A) The nuclei of the cells were visualized using confocal microscope and counted. (B) In the presence of Gd³⁺, 8% + 1 Hz for 72 h significantly decreased DNA count. The result was expressed as a mean ± 1 SD for five randomly selected fields in 3 independent experiments. Statistical significance (<i>p</i> < 0.05) was represented by asterisk which was compared to unstrained group with gadolinium treated. S-: no mechanical stimulation; S+: cyclic stretching applied; B+: with SACC inhibitor, gadolinium.</p

Immunostaining and immunofluorescence images of unstained and strained hMSCs cultured with or without gadolinium.

<p>The cells were stained with immunostaining antibody collagen I and collagen III. Immunofluorescence antibody was used as a method to access fibronectin and N-cadherin. Cells were stained with Hoechst (blue) to reveal the nucleus, and the images were merged with the corresponding fibronectin or N-cadherin (green). The direction of uniaxial strain is indicated as red arrow. S-: no mechanical stimulation; S+: cyclic stretching applied; B-: no gadolinium; B+: with SACC inhibitor, gadolinium.</p

mRNA expression of apoptosis genes subjected to cyclic tensile loading at 1 Hz and 8% at different duration of stretching.

<p>The expression level of each gene was normalized with the level of housekeeping gene. The value of fold change was presented as ratio of strained group to unstrained group, where both groups treated with gadolinium. Statistical significance (<i>p</i> < 0.05) was represented by asterisk which compared to unstrained group (indicated as 0). N = 6, n = 3. Error bar = ± 1 SEM.</p

Effects of different gadolinium concentration on hMSCs.

<p>Morphological changes of hMSCs cell culture after 72 hours incubation of gadolinium. By increasing the gadolinium concentration, small vesicles were observed (probably apoptotic bodies) as well as cell detachment (the yellow arrow).</p

The apoptosis genes of interest were determined in this study.

<p>The apoptosis genes of interest were determined in this study.</p

Morphology of hMSCs after treated with gadolinium.

<p>The unstrained cells and strained cells at 1 Hz, 8%, at different duration of stretching exposure, with or without using 20 μM gadolinium, respectively. The direction of uniaxial strain is indicated as red arrow.</p

Effect of uniaxial stretching on mRNA expression of tenogenic markers in hMSCs, which were performed at 1 Hz + 8% in different duration of mechanical stimulate.

<p>(A) Tenogenic differentiation of hMSCs is triggered by mechanical stimulation. Fold changes of expression were measured by normalizing the relative expressions with the corresponding control groups (unstrained groups). Statistical significance (<i>p</i> < 0.05) was represented by asterisk which compared to unstrained. (B) Tenogenic lineage genes expression was influenced after adding SACC blocker, Gd³⁺ to the strained cells. The value of fold change was presented as ratio of strained group treated with gadolinium to strained group without gadolinium. Statistical significance (<i>p</i> < 0.05) was represented by asterisk which was compared to strained group without treatment (indicated as 0). N = 6, n = 3. Error bar = ± 1 SD.</p