CASE OF THE WEEK – “Case of systemic lupus erythematosus (SLE) with severe low back pain radiating to both the gluteal regions & whole body and hybrid SPECT CT bone scintigraphy showing elevated Sacroiliac Joint Uptake Ratios (Sacroilitis) & clinically occult bilateral avascular necrosis of both the femoral heads (Case report) )” by Dr. Shekhar Shikare, Consultant, Nuclear Medicine, Dr. Bobby Jose, HOD & Specialist, Neurosurgery & Clinical Administrator, Dr. Milind Raje, Consultant, Radiology and Dr. Deepak Bhatia, Specialist, Orthopaedic Surgery at NMC Royal Hospital Sharjah

CASE OF THE WEEK – “Case of systemic lupus erythematosus (SLE) with severe low back pain radiating to both the gluteal regions & whole body and hybrid SPECT CT bone scintigraphy showing elevated Sacroiliac Joint Uptake Ratios (Sacroilitis) & clinically occult bilateral avascular necrosis of both the femoral heads (Case report) )”  by Dr. Shekhar Shikare, Consultant, Nuclear Medicine, Dr. Bobby Jose, HOD & Specialist, Neurosurgery & Clinical Administrator, Dr. Milind Raje, Consultant, Radiology and Dr. Deepak Bhatia, Specialist, Orthopaedic Surgery at NMC Royal Hospital Sharjah

Introduction

Avascular necrosis (AVN) is a major cause of morbidity in SLE. Since its first description by Dubois and Cozen in 1960, AVN has been increasingly reported in SLE patients. The prevalence rate of AVN in SLE varies widely and ranges from 2.8% to 40%.Several factors have been associated with the development of osteonecrosis in SLE but corticosteroid therapy has been the most consistent association.

It has been reported that many factors such as thromboembolism, fat embolism, thrombophilia, hypo fibrinolysis, intramedullary hemorrhage, vasculitis and increased bone marrow pressure are related to corticosteroid-induced osteonecrosis. Sacroiliac joint radiographs and radionuclide elevated sacroiliac joint uptake ratios found unilaterally/bilaterally in SLE active patients and mild sacroiliac joint sclerosis and erosions were detected on underlying CT images reflects synovitis and patient can have inflammatory arthritis in these joints.

If elevated ratios are seen in patients with active disease, it is a nonspecific finding and probably due to lupus synovitis. If the ratios are elevated in the absence of active lupus, another cause must be found for the sacroiliac joint abnormality.

Technetium-99m methylene diphosphonate (99mTc-MDP) bone scintigraphy is one of the most commonly performed nuclear medicine studies. It is highly sensitive in detection of different benign and malignant bone pathologies.

Hybrid SPECT/CT provides both anatomical and metabolic information. CT component is helpful in localization and characterization of increased osteoblastic CT scan added to SPECT can detect subtle collapse of the femoral head, which may not be easily visible on plain radiographs. In addition, morphological imaging may detect other underlying pain generators, which may explain the symptoms.

As osteonecrosis (ON) is an evolving process, the appearance on bone scan depends on the stage of the disease. In the acute phase of ON, no radiotracer is delivered to the bone tissue. Therefore, initially for 7-10 d after the event, ON generally appears on bone imaging as a photopenic area. After 1–3-week, increased radiotracer uptake is seen in a subchondral distribution due to osteoblastic activity at the reactive interface around the necrotic segment.

In chronic processes like steroid induced ON, typical cold lesion may not be identified, and scintigraphy usually demonstrates increased tracer localization due to micro collapse and repair.

Case

44 years old gentleman is a known case of Systemic lupus erythematosus (SLE) under high doses of prednisolone. Presented with the severe low back pain radiating to both the gluteal region.

Clinically it was suspected that he is having sacroiliitis and hence referred for Whole body and hybrid SPECT CT bone scintigraphy.

Biochemical parameters

Creatine phosphokinase 195 U/L (46-171), CRP 6 mg/L (<10), ESR 23 mm/1st hr (0.15)

X RAYS Both Hip Joints

Mild degenerative changes seen in both hip and Sacro iliac joint.

99m Tc-MDP Whole Body and hybrid SPECT CT Bone Scan

It shows

A) Abnormally increased tracer uptakes in both the S.I joints as compared to rest of the joints (figure 1 & 2)

QUNATITATIVE S.I. JOINT RATIOS (figure 2 & 3)
Right S.I. joint ratio 1.83 (1.05-1.36)
Left S.I. Joint ratio 1.83 (1.05-1.36)

A) Abnormally increased tracer uptakes seen in both the femoral heads
(figure 4, 5 & 6)

Left hip- Abnormal in-homogeneously increased tracer uptakes seen peripherally with central cold area in the femoral head.

Right hip- Abnormal in-homogeneously increased tracer uptakes peripherally with cold area antero-laterally in the femoral head.

INCREASED TRACER UPTAKES & ELEVATED S.I. JOINT UPTAKE RATIOS IN BOTH THE S.I. JOINTS AND UNDERLYING CT IMAGES SHOWING MAINTAINED JOINT CAVITY , ARTICULAR SURFACES ARE SMOOTH WITH SCLEROSIS ON THE ILIAL SIDE OF THE JOINT SUPERIOOLRY (LT>RT), FAVORS SACRO-ILITIS.

BOTH THE HIP FINDINGS AS DESCRIBED ABOVE AND UNDERLYING CT IMAGES SHOWING MULTIPLE LYTIC AREAS IN BOTH THE FEMORAL HEADS WITH IRREGULAR SCLEROTIC

MARGINS, FAVORS OSTEONECROSIS OF BOTH THE FEMORAL HEADS AND THE SCAN PATTERN WISE, IT LOOKS LIKE IN REPARATIVE PHASE.

Subsequently (2-3 months later) developed severe bilateral hip pain radiating from the groin down to both the knees.

O/E unable to walk more than five minutes without severe pain and severe pain on flexion, adduction and rotation.

Bilateral MRI Hip confirmed severe avascular necrosis of both the femoral heads.

Procedure

Patient underwent core decompression combined with bone graft of right hip first (more symptomatic) and later on underwent similar procedure on the left hip.

Follow up MRI HIP

Evidence of core decompression involving both femoral heads with surgical tract in the femur.

Altered morphology and signal intensity of the femoral heads on both sides representing advanced avascular necrosis. This involves more than 50% of the surface. The left side shows more prominent changes with fluid like signal is representing bone cysts. The superior surface shows irregularity and reduced joint cavity. On the left side, edema is seen extending into the femoral neck region. Effusion is seen in the hip joint capsules. The alignment is maintained.


Figure 1 99mTc MDP whole body images

Figure 2 99mTc MDP of S.I joint shows elevated S.I. joint uptake ratios
Right S.I. joint ratio 1.83 (1.05-1.36) and Left S.I. Joint ratio 1.83 (1.05-1.36)

Figure 3 99mTc MDP . hybrid SPECT CT images of S.I. jonits showing increased tracer uptakes on either sides.
Figure 4 CT images of S.I joint shows slerosis on the ilieal side (left>right)
Figure 5 99mTc MDP hybrid SPECT CT images of hips shows Abnormally increased tracer uptakes seen in both the femoral heads.
Right hip- Abnormal in-homogeneously increased tracer uptakes peripherally with cold area antero-laterally in the femoral head.
Left hip- Abnormal in-homogeneously increased tracer uptakes seen peripherally with central cold area in the femoral head.
Figure 6 CT images of hips shows multiple lytic areas in both the femoral heads with irregular sclerotic margins ? early infarct
Hybrid SPECT CT images favors early osteonecrosis of both the femoral heads (left >right).

Discussion

Although MRI is considered the diagnostic modality of choice in patients with femoral head ON, bone scan remains a valid alternative with fractured femoral neck with a metallic fixation device. Moreover, it is also helpful when involvement of multiple sites is suspected in patients with risk factors such as sickle cell disease.