Towards the end of the 1940s Hepworth was captivated by the dramatic theme of the operating theater resulting in a figurative series of works known as the 'hospital drawings.' Having met the orthopedic surgeon Norman Capener in 1944, she was invited by him to witness an operation in November 1947. She recalled, "in about the middle of 1947, a suggestion was made to me that I might watch an operation in a hospital, I expected I should dislike it; but from the moment when I entered the operating theatre I became completely absorbed by two things: first, the extraordinary beauty of purpose and co-ordination between human beings all dedicated to the saving of life, and the way that unity of idea and purpose dictated a perfection of concentration, movement and gesture; and secondly by the way this special grace (grace of mind and body) induced a spontaneous space composition, an articulated and animated kind of abstract sculpture very close to what I had been seeking in my own work" (quoted in Barbara Hepworth: Carvings and Drawings, London, 1952, facing pl. 92).
Hepworth produced a number of highly finished works, both on paper and on board, which reveal the intensity of her interest in this subject matter. Hepworth not only perceived the correlation between the movement and tools of a surgeon and her own methods as a sculptor, but to her it also represented the realization of coordinated human interaction. As Chris Stephens remarks, "She noticed how the harmony of their work resulted in the harmonious disposition of the surgeons and nurses, and it was this instinctive, unconscious spatial arrangement, symbolic of cooperative activity, that she sought to communicate through the composition of the pictures" (in Barbara Hepworth Centenary, London, 2003, p. 99).
In the present work Astragaloid (which refers to a type of ankle operation), firmly executed lines and cross-hatching are applied to a panel prepared with a glazed ground. The interrelation of the figures and their remarkable volume and mass are characteristic of this group of works. Referring to the 'hospital drawings,' J.P. Hodin observes, "It is of interest to note the tension between these representational drawings and the abstract sculptures produced at the same time. We feel that here is the key to the understanding of her working method, which is that of a constant interchange of outward observation and inner reflection" (in Barbara Hepworth, Neuchâtel, 1961, p. 21).