The spine doesn’t react very positively to stretching but what about other cartilagenous regions?  In one post, we discovered that articular cartilage can undergo endochondral ossification and can undergo grow in size.

A big question is whether articular can contribute to height:

The use of knee height to estimate maximum stature in elderly Chinese.

“In a study of 247 (130 men and 117 women) adult ethnic Chinese living in Melbourne, Australia, we tested the hypothesis that knee height is independent of age{thus that articular cartilage degeneration would not affect knee height} and attempted to devise an equation for the estimation of maximum stature (MS) in the this elderly group (aged 65 yrs) of this population. Anthropometric indices, including body weight, stature, arm-span, and knee height were twice measured using standard methods. In both men and women, the younger adults were taller and had a greater arm-span than their elderly counterparts: however, there was no difference in knee height or body weight between the two groups. Knee height was not associated with age, while stature and arm-span{But arm span would be affected by articular cartilage too only} correlated negatively with age.  Knee height provides for a valid estimate of MS during early adulthood than arm-span. Knee height is independent of age and does not appear to decreased over time, in spite of an expected cohort effect in this population. Arm-span, however, appears to change with a cohort as well as with age. Thus, there is a place in a life-time nutritional assessment of the aged to measure both arm-span as an index of cohort status and knee height for an individual’s maximum achieved stature.”

According to Figure 1, the knee height measurement would incorporate the articular cartiage regions of the ankle and the knee.  There was a negative correlation between age and knee height it was just not statistically significant.  Interestingly arm span decreased more than overall stature despite discs not being a factor.

Micromechanical response of articular cartilage to tensile load measured using nonlinear microscopy.

“This work investigates the inhomogeneous distribution of strain in loaded AC by tracking the movement and morphological changes of individual chondrocytes using point pattern matching and Bayesian modeling.”

“Articular cartilage (AC) is a connective tissue found at the ends of articulating bones within the synovial joints of mammals. Healthy AC is composed primarily of a gel of hydrophilic proteoglycan molecules and interstitial fluid, constrained by a dense network of collagen fibres.”

“Tensile loading reveals the interconnectivity of the fibrous protein networks, and facilitates continuity of load transmission through the matrix”

“As well as resisting shear load associated with joint articulation, the superficial zone also provides a strain-limiting surface that restricts bulging close to regions that experience high compressive load.”

“Ridges in the surface of bovine AC that appeared as the tissue was stretched, and attributed these to protruding collagen fibres. Although these were slightly thinner than those found in the present investigation, the size difference could be associated with width contraction under load and the resolution limitations of the camera. The thick palmar cartilage showed regions of blurred and filamented signal near the surface, and filamented patterns throughout the middle and deep zones. Dorsal and cortical ridge samples showed patches of high intensity and varying signal orientation in the middle zone, which are possibly leaves of collagen overlapping at different angles. In the deep zone, images contained streaks of high signal intensity, which are unlikely to be due to tangentially aligned collagen. It is possible that these patterns arise from the interweaving in the horizontal plane of the predominantly perpendicular fibres. Chondrocytes (which appear dark under PLM) are arranged in columns perpendicular to the underlying bone, and regular spacing of these columns may cause the surrounding matrix to appear filamented when viewed en face.”

“Cartilage is thickest in regions that experience the least compressive load”

“The average cellular strain values of 2% in the long axis and −5% in short axis indicate that the cells experienced a mean in-plane compressive force and that ellipticity increased despite an outward force being applied to the sample. This overall compressive strain was not significantly different to that of the surrounding matrix, despite the low mechanical stiffness of chondrocytes”

Epiphysiodesis involves either removing the growth plate or taking it and modifying it before reinsertion.  Prophylactic Fixation involves inserting a metal into the bone.  A cannulated screw has a hollow central shaft.

Persisting Growth After Prophylactic Single-Screw Epiphysiodesis in Upper Femoral Epiphysis.

“Prophylactic fixation of the contralateral hip in cases of slipped upper femoral epiphysis is controversial. Using a single-cannulated screw has been widely accepted. Differing reports exist on the occurrence of persisting growth after prophylactic epiphysiodesis. The aim of this study was to evaluate the presence of persisting growth of the upper femoral epiphysis after prophylactic fixation.
From 2006 until 2009, 11 children underwent prophylactic pinning using a single-cannulated 6.5-mm cancellous screw. Time to fusion, persisting growth, and overgrowing of the screw were measured on plain radiographs taken postoperatively and at least after the growth plate was fused.
All patients except 1 (91%) showed a persisting growth of the epiphysis, and in 2 cases a hardware replacement was necessary. The mean increase of the femoral neck length was 8.2% (SEM 1.46%). Mean follow-up was 37 months (range, 12 to 49 mo). All patients had a Risser sign grade 0 at the time of surgery, and equal or less than grade 3, when the growth plate was fused{Riser 5 equals cessation of growth}.
Prophylactic fixation using a single-cannulated cancellous screw showed in our series growth persistence was the rule and in some cases the physeal overgrowth necessitates a hardware replacement.”

“After placing the guidewire under fluoroscopic guidance in a central position and drilling with a 5.0-mm drill just over the proximal femoral growth plate, the insertion of the 6.5-mm cannulated cancellous screw was carried out through a 0.5-inch incision.”

“The mean increase of femoral neck length at the time of physeal closure in patients without further surgeries was 8.6%, 7.5% in the 16mm threaded group and 10% in the 32mm threaded group.”<-The bigger the screw the larger the overgrowth.

Maybe placing a screw in adult bone will also cause a length increase?

 Insulin-Like Growth Factor I (IGF-1) Ec/Mechano Growth Factor – A Splice Variant of IGF-1 within the Growth Plate

“Human insulin-like growth factor 1 Ec (IGF-1Ec), also called mechano growth factor (MGF), is a splice variant of insulin-like growth factor 1 (IGF-1), which has been shown in vitro as well as in vivo to induce growth and hypertrophy in mechanically stimulated or damaged muscle. Growth, hypertrophy and responses to mechanical stimulation are important reactions of cartilaginous tissues, especially those in growth plates.  We wanted to ascertain if MGF is expressed in growth plate cartilage and if it influences proliferation of chondrocytes, as it does in musculoskeletal tissues. MGF expression was analyzed in growth plate and control tissue samples from piglets aged 3 to 6 weeks. Furthermore, growth plate chondrocyte cell culture was used to evaluate the effects of the MGF peptide on proliferation. MGF is expressed in considerable amounts in the tissues evaluated. We found the MGF peptide to be primarily located in the cytoplasm, and in some instances, it was also found in the nucleus of the cells. Addition of MGF peptides was not associated with growth plate chondrocyte proliferation.”

“IGF-1 and MGF are up-regulated in exercised and damaged skeletal muscle, probably inducing muscle growth and hypertrophy. MGF has been shown to stimulate proliferation and suppress differentiation, while IGF-1 also supported differentiation”

“Cyclic stretching of osteoblasts enhanced cell proliferation and induced expression of Mgf on the mRNA level. MGF has been observed to inhibit osteoblast differentiation and mineralization in osteoblast cell culture medium”

“Injecting MGF into [a] bone defect gap for 5 consecutive days resulted in accelerated bone healing”

“Comparison of mRNA expression revealed that the Mgf fraction of total Igf1 ratios varied between the tissues examined ranging from 8% in muscle to 31% in Ranvier’s groove “<-So MGF and IGF-1 correlates between muscle, bone, and cartilage tissue.

“Igf1 and Mgf expressions were lower in the proliferative zone than in the resting and hypertrophic zones”

“[No] statistically significant effects of the MGF peptides on the proliferation of monolayer growth plate chondrocytes in concentrations ranging from 0.1 to 500 ng/ml. Differences between concentrations could be detected when growth plate explants were treated with IGF-1 alone”

“In contrast to mature IGF-1, MGF has been reported to activate ERK1/2 without influencing Akt phosphorylation”