The skeletal scintigraphy

Especially in the diagnosis of prosthetic loosening the bone scintigraphy can help – however, there is an important temporal aspect:

1. Increased activity immediately after implantation

In the first 12 to 18 months after prosthesis implantation, a skeletal scintigraphy always shows increased accumulation around the implant.
Why?

• After the prosthesis is implanted, the bone reacts to the trauma caused by the surgery.
• Repair processes are taking place: bone remodeling (so-called "bone remodeling") and reaction to the new mechanical stress.
• In addition, micro-movements occur between bone and prosthesis until the final healing is completed.

➡️ Result: Skeletal scintigraphy is almost always positive during this time – even if there is no loosening.

This means:
👉 Increased scintigraphic activity in the first 1 to 1.5 years is not specific for prosthetic loosening.

2. Risk of misinterpretation (false-positive findings)

If scintigraphy were performed during this period, there would be a high risk of:

• False-positive findings: Normal healing or remodeling processes are incorrectly interpreted as loosening.
• Unnecessary interventions: Based on a false diagnosis, unnecessary revision surgeries could be performed.

Example:
A patient has mild pain 10 months after hip replacement implantation. A scintigraphy shows enrichment. Without considering the healing process, loosening could be incorrectly assumed – however, the finding is completely normal for this phase.

3. Time point after 1.5 years - why this period?

After about 15–18 months:

• Has the remodeling activity largely normalized.
• The bone-implant interaction stabilizes.
• If increased enrichment persists, this is now actually indicative of pathological processes (e.g. loosening, infection).

➡️ From this point on, bone scintigraphy has a significantly higher specificity and informative value for:

• Loosening (aseptic or septic)
• Implant loosening due to infection or mechanical instability
• Bone damage or osteolysis

In short:
👉 Only after about 1.5 years can scintigraphy reliably distinguish a true loosening from normal remodeling processes.

4. Current scientific consensus

Studies and guidelines (e.g. from the German Society for Orthopaedics and Trauma Surgery, DGOU) therefore recommend:

• No skeletal scintigraphy for loosening diagnosis within the first 12-18 months after primary implantation of a hip TEP or a knee TEP.
• Instead, during this period: Clinical examination, conventional X-ray diagnostics, possibly puncture if infection is suspected.

5. Alternative diagnostics in the first 18 months

If a loosening of a hip prosthesis or knee prosthesis is suspected early (e.g. with persistent pain, fever, functional limitations), the following should be used preferentially:

• Conventional X-ray (direct signs such as loosening of the prosthesis or osteolysis)
• CT (high-resolution diagnostics, implant loosening test)
• Aspiration (to differentiate between septic and aseptic loosening)
• Laboratory values (CRP, leukocyte count)

Only if these methods remain unclear and the complaints persist, should scintigraphy be considered after approximately 18 months.

Conclusion: Bone scintigraphy in case of suspected prosthetic loosening is usually only useful after 1.5 years!

Bone scintigraphy is a valuable diagnostic tool when there is suspicion of loosening of a hip or knee prosthesis . However, the right timing must be observed:
In the first 12 to 18 months after implantation , the findings are often falsified by normal healing and remodeling processes, making interpretation difficult and prone to errors.

Only after about 1.5 years after the operation does the bone scintigraphy provide meaningful indications of an actual loosening or a possible infection.
Therefore, it is crucial to resort to classical diagnostic methods such as clinical examination, radiographic diagnostics, and, if necessary, joint aspiration early on.

A targeted, temporally sensible scintigraphy can then contribute decisively to diagnosing a prosthesis loosening safely and setting the course for a successful therapy.

Note:
 Before 1.5 years → Scintigraphy hardly usable due to normal healing.
 After 1.5 years → Meaningful tool if loosening is suspected.