The phrase "constitute the backbone" is a correct and usable phrase in written English.
You can use it to describe something that is the most important or significant supporting element of something else. For example, "The ideals of justice and equality constitute the backbone of this nation."
His 17 string quartets constitute the backbone of the repertory.
The moments of transition, in which something changes, constitute the backbone of all of us.
Jeep assembly lines will remain in operation in the United States and will constitute the backbone of the brand.
Such tribal groups are among India's most marginalized citizens and constitute the backbone of the Maoist insurgency in the eastern middle of the country.
All of the opening source evidence since the last round of counter-revolutionary street protests suggests that there has been no particular strengthening of the urban and merchant forces who constitute the backbone of "reform" in Iran.
Mr. Kim, 74, is a man whose life has been so packed with high drama that its details could easily constitute the backbone of two or three life stories, with plenty of intriguing loose ends left over.
These manifolds constitute the backbones of bursting patterns in a neuronal model.
Highly connected (hub) nodes constitute the backbones of a network structure.
As Mr. Chávez was arriving, Mr. da Silva was addressing a conference of Argentine and Brazilian business leaders, telling them that the strategic alliance between their countries constituted "the backbone" of South America.
With government soldiers, he consults contacts in small villages, using connections from his youth on the coast among Alawites, the minority sect of Mr. Assad, which constitutes the backbone of the army.
The weak rule of his semiblind father had allowed usurpation by the amīrs, or chiefs, of the Turkmen tribes, who had brought the Ṣafavid to power and still constituted the backbone of Ṣafavid military strength.
