Growth plates, also known as physes or epiphyseal plates, are cartilage structures found in the developing skeletons of children and adolescents. These cartilaginous zones are responsible for the longitudinal lengthening of bones, determining the final height and size of the skeletal structure. In the spine, growth occurs across multiple points within the individual vertebral segments. Understanding the timeline of spinal growth plate closure is important because it marks the end of skeletal growth. Closure involves the cartilage being gradually replaced by solid bone (ossification), which is fundamental to achieving adult skeletal maturity.
Anatomy of Spinal Growth Plates
Growth of the vertebral bodies, which form the main column of the spine, occurs primarily at two distinct locations within each segment. The first location is the superior and inferior vertebral endplates. These are thin layers of hyaline cartilage separating the vertebral body from the adjacent intervertebral discs. These endplates drive the increase in the vertical height of the vertebral body, functioning similarly to growth plates in long bones.
The second structure is the ring apophysis, a circular rim of cartilage located around the periphery of the upper and lower surfaces of the vertebral body. The ring apophysis does not contribute significantly to the longitudinal lengthening of the spine. Its purpose is to provide a firm anchor point for the outermost fibers of the intervertebral disc, contributing to the structural integrity and width of the mature vertebra.
Predicting Skeletal Maturity and Closure Timing
Closure of spinal growth plates, which signifies the end of trunk growth, is a gradual process occurring during the mid-to-late teenage years. Skeletal maturity is typically reached earlier in females, often between ages 13 and 15, and in males between 15 and 17 years old. The ring apophysis completes its fusion to the vertebral body over a wider range, generally from the late teens into the early twenties.
Doctors assess skeletal maturity and remaining spinal growth potential using indirect indicators, primarily the Risser sign. The Risser sign evaluates the progressive ossification of the iliac crest apophysis, a pelvic growth center that matures at a similar rate to the vertebral growth plates. This assessment uses a scale from 0 to 5 as a visual proxy for the spine’s readiness for growth cessation.
A Risser stage of 0 indicates no visible ossification center on the iliac crest, signifying significant remaining growth. Stages 1 through 4 track the gradual progression of ossification across the iliac crest. Risser 4 indicates full ossification but no fusion to the pelvis. Risser 5 represents the complete fusion of the iliac apophysis to the ilium, which signals that the spine has reached skeletal maturity and longitudinal growth has ceased. The rate of progression can be rapid during the peak growth spurt, with Risser 3 and 4 signaling the definite slowing of growth.
Medical Significance of Spinal Growth Plate Closure
The timing of spinal growth plate closure is highly significant in clinical medicine, relating to final adult height and the management of spinal deformities. Closure establishes the maximum attainable standing and sitting height. Once the physes have fused to solid bone, no further longitudinal growth of the vertebral column is possible.
For patients with progressive spinal conditions like adolescent idiopathic scoliosis, closure timing dictates the course of treatment. The risk of a spinal curve worsening dramatically decreases once the spine is skeletally mature. While a curve may still progress minimally in adulthood, the rapid progression seen during the adolescent growth spurt ceases after Risser 5 is achieved.
This information is used for decisions regarding bracing and surgical intervention. Doctors may discontinue bracing once a patient reaches skeletal maturity, as the brace is no longer needed to guide growth. Surgical procedures involving spinal fusion are often timed to coincide with the end of growth to prevent a complication known as the crankshaft phenomenon. This occurs when continued growth after a fusion surgery leads to a worsening of the deformity.