Let's start stitching the arm to the female model's body in 3D Studio MAX ( 3ds max ). Merge the scene containing the arm to our current scene (head and body combined). The process is similar to that we have done while combining the head with the body in 3D Studio MAX ( 3ds max ). Scale and align the arm with the body as shown in the figure and Attach both the spline cages as done previously.

Now that you have attached both the spline cages together in 3D Studio MAX ( 3ds max ), snap the corresponding vertices after turning on 3D snap (Don't forget to check vertex in 3D snap settings). After you snap the vertices properly, weld the vertices together in 3D Studio MAX ( 3ds max ). Refer the figure for better clarity.