# Presentation: 096728

## Imaging Assessment of Diabetic Foot Infections

- Regina Alivisatos, MD
- Medical Officer
- DSPIDPs

## Introduction

**Patients with osteomyelitis should be identified**
**in order to ensure**
**the most appropriate course of treatment**
**a homogenous clinical trials population**
**7 – 14% of enrolled subjects found to have**
**osteomyelitis**
**excluded from the PP populations**
**failures in the ITT analysis**

## WHY?

**Decreasing size of the PP populations that may be distributed unequally **
**Inaccurate assessment of the true efficacy for one or both of the treatment arms**
**Database size insufficient to draw conclusions about a drugs efficacy in CSST infections or in the diabetic foot subset**

## Applications to Date

| Diagnostic Procedure | Applications
*done at investigator’s discretion |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  | A | B | C | D | E | F | G |
| X/R |  |  |  | X* | X* | X* | X | X* |
| Bone Scan |  |  |  |  |  |  |  | X* |
| In Scan |  |  |  |  |  |  |  | X* |
| MRI |  |  |  |  |  |  |  | X* |
| Probe |  |  |  |  |  | X |  |  |
| Bone biopsy |  |  |  |  |  |  |  | X* |
| Unknown |  | X | X |  |  |  |  |  |

## Complications

**Determination of infection complicated because of superimposed neuropathic osteoarthropathy and peripheral vascular disease**
**Neuropathic disease can lead to f/x, deformity, bone production, and hyperemia which can mimic infection on MRI and scanning increasing the false positives**
**Peripheral vascular disease can prevent contrast material or tracer from reaching site of concern and lead to false negatives**

## Diagnosis - osteomyelitis

**Presence of osteomyelitis impacts on failure rate of soft tissue infections**
**“****gold standard” is bone histology and culture through non-infected tissue**

## Procedures

**1) Plain films**
**2) Radionuclide or ****Scintigraphic imaging**
**Triple Phase Bone Scan (TPBS)**
**Gallium Scan**
**Indium-111 Leukocyte Scan**
**3) Magnetic Resonance Imaging (MRI)**
**4) Probe to Bone**

## Procedures

**1) ****Plain films**
**2) Radionuclide or ****Scintigraphic imaging**
**Triple Phase Bone Scan (TPBS)**
**Gallium Scan**
**Indium-111 Leukocyte Scan**
**3) Magnetic Resonance Imaging (MRI)**
**4) Probe to Bone**

## X-Ray

**Initial screening tool:**
**Easily obtained, relatively inexpensive and provides anatomical information**
**Demineralization, periosteal reaction, bony destruction: (the classic triad)**
**Appear after 30 – 50% of bone destroyed and can take as much as 2 weeks to appear**
**Found in other conditions such as fracture or deformity**
**Sensitivity and specificity approximately 54% and 80%**

## Procedures

**1) Plain films**
**2) ****Radionuclide or ****Scintigraphic imaging**
**Triple Phase Bone Scan (TPBS)**
**Gallium Scan**
**Indium-111 Leukocyte Scan**
**3) Magnetic Resonance Imaging (MRI)**
**4) Probe to Bone**

## Three-phase bone scintigraphy (TPBS)

**Highly sensitive since positive as early as 24 hours after onset**
** **
**Focal hyperperfusion, hyperemia, bony uptake**
** **
**Can also be seen in fractures, neuropathic joints and longstanding cellulitis decreasing specificity**
**Fourth phase (24 hour image) enhances specificity**
**Concurrent TPBS with IN111 scanning optimal**

## TPBS

**Literature review of 20 reports of 1,166 patients (method of confirmation of osteomyelitis diagnosis not specified)**
**In patients w/o prior bone changes: 94% sensitive and 85% specific for osteomyelitis**
**In patients with complicating conditions: 95% sensitive, 33% specific**.
-     Schauwecker et al; The scintigraphic diagnosis of osteomyelitis. AJR 1992; 158(1):9-18

## Gallium Scanning	

**Must be performed with a TPBS**
**Diagnostic criteria include**
**  ****gallium uptake exceeds TPBS scan uptake**
**  ****gallium and TPBS scan results are discordant**
**Sensitivity 81% and specificity 69%**
**Cost of gallium scan AND TPBS may exceed cost of a single more sensitive and specific test such as an Indium scan or an MRI**
-        Schauwecker et al. AJR 158; 9 - 18, January 1992

## Indium scanning

**Best sensitivity, specificity, and cost compromise in patients with and without prior bone abnormalities**
**Issue of practicality of labeling WBCs and later images**
**Does not accumulate at sites that are not infected**
**Compilation of sensitivity and specificity for 142 diabetic subjects from 5 studies showed sensitivity of 88.6% and specificity of 84%**
- Schauwecker et al. AJR 158; 9 - 18, January 1992

## Procedures

**1) Plain films**
**2) Radionuclide or ****Scintigraphic imaging**
**Triple Phase Bone Scan (TPBS)**
**Gallium Scan**
**Indium-111 Leukocyte Scan**
**3) ****Magnetic Resonance Imaging (MRI)**
**4) Probe to Bone**

## MRI: High-tech, high cost?

**Decreased marrow signal intensity on T1-weighted images and increased signal intensity on T2-wighted images with marrow enhancement after injection of contrast**
**Associated findings of soft tissue mass, cortical destruction, sequestrum formation and sinus tracts with ulceration increase diagnostic certainty**
**Good anatomical detail**
**Sensitivity and specificity comparable to that of Indium scan**
**Review of 129 diabetics showed MRI sensitivity of 86% and specificity of 84%**
-     American College of Radiology: Imaging diagnosis of Osteomyelitis in patients with DM/Appropriateness Criteria, 1999

## MRI continued

**62 feet in 59 patients with suspected osteomyelitis were prospectively evaluated (27 with DM, 35 w/o)**
**In DM sensitivity 82%, specificity 80%**
**In non-DM: sensitivity 89%, specificity 94%**
**Accuracy increased with contrast-enhanced studies (89%) vs.78%**
**Cost savings initially because test is more rapid**
**Competitively priced compared with combination of TPBS and Indium or with gallium**
**Allows good delineation of surgical field**
-      Morrison, WB et al, Radiology; Aug 1995:196:557-64

## TPBS with In-111-labeled WBC scintigraphy in the examination of the feet in diabetic patients: Results of Published Reports

| Author | Year | # patients | Sensitivity | Specificity |
| --- | --- | --- | --- | --- |
|  | Seabold 
1993 | 16 | 80% | 55% |
| TPBS
+
 IN-111 WBC Scan | Larcos
1991 | 51 | 79% | 78% |
|  | Jacobson
1991 | 45* | 73% | 91% |
|  | Keenan
1989 | 39 | 100% | 79% |
|  | Schauweker
1988 | 35 | 100% | 89% |
|  | Maurer
1986 | 13 | 75% | 89% |
| MRI | 1999 | 129 | 86% | 84% |

## Procedures

**1) Plain films**
**2) Radionuclide or ****Scintigraphic imaging**
**Triple Phase Bone Scan (TPBS)**
**Gallium Scan**
**Indium-111 Leukocyte Scan**
**3) Magnetic Resonance Imaging (MRI)**
**4) ****Probe to Bone**

## Probe

**75 subjects with 76 ulcers from one center**
**Osteomyelitis diagnosed in 50 (66%), excluded in 26 **
**Confirmation based on histologic examination**
**culture data not analyzed as cultures were taken from base of infected ulcer**
**if bone biopsy not done, diagnosis was based on radiographic tests or surgeons finding of purulent nonviable bone**
**Bone probed in 36 of 50 with contiguous osteomyelitis and in 4 of 26 w/o osteomyelitis**
**Sensitivity 66%, specificity 85%, positive predictive value 89%, negative 56%**
**Conclusion: Palpation of bone strongly correlated with presence osteo. Probing included in initial assessment of diabetics with infected ulcers. Specialized imaging studies not necessary if positive**
-      Grayson et al JAMA 1995 Mar 1;273(9):721-3

## Cost

| Procedure | Cost (1994) |
| --- | --- |
| Plain Film | $120 |
| TPBS | $550 |
| Gallium Scan | $1000 |
| Indium Scan | $1000 |
| MRI | $1000 |

## ConclusionWhich procedure?