Hi. A year ago I got a wrist x-ray by my orthodontist and he told me that I had 3 to 6 inches of growth left. He showed me that I still have cartilage in my growth plate in my fingers and that the bones in my wrist hadn't fused, but that was a year ago. However I haven't grown any since. My Tanner Stage is 4.5. I was wondering if my orthodontist was wrong or I just haven't reached my 3 to 6 inches of growth yet. I am currently 15 years old. Also, does that growth include the lengthening of the spinal cord? Please explain the process to me. Thank you very much.
The wrist x-ray is considered to be the most accurate method of judging whether an adolescent will continue to grow. The x-ray is compared to a series of x-rays which show each of the stages of development. There is a good description and pictures of this in an article on Computerized Bone Age Estimation.
The bone age only shows how far a person has developed and the potential for further development. It can't directly state how much more you will grow in height. Normally this bone age is feed into a formula similar to the second one used in on the Adult Height Predictor to provide a fourth variable that improves the accuracy of the estimate. Interestingly, as a height predictor, the bone age only improves the accuracy a little bit. Most doctors use a table, which given a person's bone age, sex, and current height, tells them what a typical healthy person can expect to see -- but not what will happen.
A year ago, the x-ray showed that your bones' growth plates had not fused, so you still had the potential to grow further. Now, a year later you are in Tanner Stage 4 and haven't seen any growth. Generally once you reach stage four, you only have a few more inches to go. Your growth spurt is done and you are basically getting a few more inches as the body winds down from the growth spurt. Most of the dramatic growth that comes in stage three is from your leg bones getting longer. In stage four most of the growth comes from you spine getting larger. But a lot of growth in stage four appears as your shoulders get wider.
The stages of growth are described in "What Is Happening to Me?" and details are given in the series of pages at the bottom of the Tanner Stage Calculator for Boys. The links for stage 4 and stage 5 are here.
As best that I can tell without seeing you, you are basically done with your upward growth. There is a possibility that you might grow a bit more, but it will be well less than an inch.