Transient osteoporosis of the hip is a rare cause of hip pain, affecting mainly healthy middle-aged men and sometimes women in the third trimester of pregnancy. In women in most of the times affects the left hip. Aetiology is unknown although some conditions as altered neurology, endocrine dysfunction or vascular and metabolic problems may be considered as cause.

The hallmark is its self-limiting nature and usually is improving with 9-12 months and occasionally is affecting the opposite hip but not at the same time and if this will occur it will be some years down the line.

In the differential diagnosis has to be included any inflammatory arthritis of the hip, including infection, AVN, stress fracture of the femoral neck, synovial disorders and neoplasia.

MRI would be the best investigation and this can show decreased signal intensity of bone marrow on T1 and increased signal on T2. Joint effusions may be present on T2.

Bone marrow oedema can also be seen in hip osteoarthritis and traumatic fractures of the hip but there we have secondary findings as presence of osteophytes narrowing of joint or fracture line is present. The plain films do not show any deformity of the femoral head. In cases of any inflammation of the hip (RA, OA, etc.), plain radiographs show loss of the joint space.

In AVN radiographs do not show usually effusion and the head according to the stage may be deformed as it is gradually collapsing but clinically the pain is in the groin something that Transient Osteoporosis usually does not have, as it may be present also in the trochanderic region as it is a diffused pain. There is no presence of high temperature and despite that there is limitation of the hip movements this is not the same as in an infective joint.

A repeat MRI in 3 months will show the improvement of the hip.

So really the detailed history, clinical examination and radiological pictures with a team including a musculoskeletal radiologist can make the diagnosis.

I see around 1 New case alternate month, in my fairly busy practice. High index of suspicion and awareness about this entity is important to reach to an early diagnosis

This is so amazing as according to available literature say  that in Asia the condition is not so common 

Absolutely not true. George, can you please give a reference to this statement?

Hi Raju

Here is the paper that says that Transient osteoporosis of hip is rare in Asia

Diwanji SR, Cho YJ, Xin ZF, Yoon TR (2008) Conservative treatment for transient osteoporosis of the hip in middle aged women. Singapore Med J; 49 (1) : 17 - 21

Thank you

Fully agree with the answer given by George...

This is a very nice question indeed. I am sure that a higher degree of awareness among orthopaedic surgeons is needed as far as the differential diagnosis of this strange and little known  condition (TOH) from AVN is concerned.

 I am sure that there are still  some patients with TOH who are misdiagnosed with stage 1 AVN, and therefore subjected to core decompression (forage) in a benevolent strive to prevent further necrosis with collapse.

To the above colleagues’ opinions (MRI shows a diffuse oedema with an extent exceeding the amount in AVN and little evidence of focal changes),  I would add that bone scanning  may also be used showing  in TOH uniformly increased uptake at the affected femoral head extending down into the femoral neck and intertrochanteric region.

 One should also look for elevated alkaline phosphatase and ESR which is not typical for the early stages of AVN but may be found in TOH.

Thanks Panayot for your valuable inputs

Prior to MRI, Bone scan was possible the investigation that it was helpful. With the recent awareness the patients have and the new regulations about irradiation this investigation fell to the oblivion and it is not in use any more. CT scan can show the fracture line in case that the differential diagnosis is an un-displaced subcapital fracture, but this information may be taken (partly) from the MRI. A lot of investigators try CRP levels and potential alkaline phosphatase is used, but ESR, again, unfortunately and to me opinion wrongly, is not in use any more in the majority of the Hospital labs.

One of the most characertistic MRI finding is a diffuse blow out bright appearance on T2 images

George, now I have to oppose your opinion. In my practice the bone scanning did not fall to "the oblivion" because one of the differential diagnoses in an acute onset of severe pain in the hip, pelvis, proxinmal femur (as in TOH) is a metastatic process of unknown origin. Whole body scintigraphy is done to exclude other affected places. It is not specific, but very sensitive. ESR testing may not be wrong, classical tests are classical having proved the test of time. Anyway, I thank you for the information that the labs in your country do not use ESR.

Regards  

Panayot I agree with you on the subject that in some areas of the world investigations are thriving where in other places are not. The reasons for that  are patients institutions and guidelines of organisations that are placing the framework in which doctors are practicing. I am not disagreeing with you about bone scanning but this practice in the place of my work will be strongly questioned and opposed even by the radiologists who have every right to stop you and advice for the investigation that their association proposed. 

George, I understand the situation you describe. Certainly, there are some obstacles evertwhere. In any case this discussion is carried out to find some reasonable points to diagnose TOH and to avoid unnecessary operations (core decompression) for patients who in fact do not suffer of AVN. Unfortunately, this happens and the pseudoresults are excellent.

Regards  

Good discussion on this interesting topic

Bone scanning and the possibility of the lack of its use as diagnostic tool I think that it is not an obstacle to TOH diagnosis as MRI is safer for the patients and very informative.

The misdiagnosis and pseudo-excellent results are the result of potential overlook of the doctors during consultation time which is removing the TOH for the differential diagnosis plan.

The classical features of TOH are:

1. Sudden onset of hip pain. Symptoms are out of propotion to signs.

2. Non destructive and self limiting clinical condition.

3. Conservative treatment often succeeds.

4. MRI is the diagnostic modality of choice.

Dear Raju 

I agree with you entirely. 

I also agree with Dr. Vaishya.

Classical MRI images of TOH

Classic picture. Thank you for sharing 

The diagnosis of osteoporosis of the proximal femur can be supplied only by DEXA or MSCT. Of course it is not for pregnant women