His most important work is "The Treatment of Deformities of the Spine, or, The Correction of Lateral Curvature", published in 1876. This book was a seminal work on scoliosis, providing a detailed description of the condition and its treatment. It was widely acclaimed and translated into several languages.
Other works by Posselt include:
* "The Treatment of Club-Foot" (1876)
* "The American Hand-Book of the Treatment of Club-Foot" (1884)
* "The American Hand-Book of the Treatment of Lateral Curvature of the Spine" (1884)
* "The American Hand-Book of the Treatment of Deformities of the Spine" (1892)
Posselt was a pioneer in the field of orthopedic surgery, and his work was influential in shaping the understanding and treatment of spinal deformities and clubfoot.