If you took a poll of all adults who have had a radial head fracture, stiffness would probably be the number one lingering postoperative problem. There are a number of different possible reasons for this complication starting with the hardware used to hold it together. If the pins or screws come loose and start to back out, they can block motion. Some hardware may be in its proper place but prominent causing the same mechanical problems.
Noncompliance with the rehab program is certainly one reason some patients don’t get their motion and function back. But it doesn’t sound like this is the case for you. Even the most compliant patients can end up with stiffness if the joint capsule (soft tissues around the joint) tighten up or contract. Other changes in the soft tissues such as heterotopic ossification (bone forming in the muscles) can account for stiffness weeks to months later.
The best way to find out what is going on is to re-visit your surgeon. You may need some imaging studies (X-rays and/or CT scans) to determine the cause. But a physical examination may also reveal the underlying problem. If the soft tissues are stiff but the joint still has a little bounce or spring to it, then a splint may be helpful. But if the joint is blocked and has no “give” to it at all, then another surgery may be needed.
Even if you have to have a second (revision) surgical procedure, good results are still possible. The surgeon may just remove the radial head and replace it with a spacer so you have normal forearm and elbow motion. Elbow joint replacements are available but this option is saved for last if and when nothing else works.
Make a follow-up appointment with your surgeon sooner than later. Early follow-up may yield better results before the soft tissues become so stiff they can’t respond to treatment. Be prepared for some additional rehab and exercises but with your hard work and diligence, it’s likely you can expect a good result!