Magnetic resonance imaging of nonhealing pressure ulcers and myocutaneous flaps

1080

Magnetic Resonance Imaging of Nonhealing Pressure Ulcers and Myocutaneous Flaps Carolyn M. Ruan, MD, Eva Escobedo, MD, Scott Harrison, ABSTRACT. Ruan CM, Escobedo E, Harrison S, Goldstein B. Magnetic resonance imaging of nonhealing pressure ulcers and myocutaneous flaps. Arch Phys Med Rehabil 1998;79: 1080-8. Objective: To evaluate the use of magnetic resonance imaging (MRI) in making clinical decisions when assessing nonhealing pressure ulcers and nonhealing myocutaneous flaps for the presence of an abscess,osteomyelitis, sinus tracts, and Auid collections. Design: Retrospective review of patient charts and radiographic studies. Setting: Regional spinal cord injury center. Subjects: Twelve patients who had MRI as part of their evaluation for a nonhealing pressure ulcer or myocutaneous flap. Results: Seven patients had MRI for preoperative evaluation, four with a previous flap that had recurrent breakdown and three with a new grade III or IV ulcer. Five patients had MRI for postoperative evaluation of myocutaneous flaps with delayed healing. MRI was useful in identifying osteomyelitis in three patients and sinus tracts that required surgical revision in six patients. MRI was also used in two patients to assessthe size of fluid collections postoperatively in determining whether the patients should be mobilized after surgery. These chronic nonhealing wounds resulted in multiple admissions and lengthy hospital stays and required multiple surgical revisions. Patients who did poorly with healing or had repeated breakdown tended to have concurrent issues such as poor self care, increased age, increased time of spinal cord injury, poor nutrition, or other medical problems. Conclusion: Chronic nonhealing pressure ulcers and myocutaneous flaps can be difficult to treat and evaluate with conventional methods. There are multiple reasons for failure to heal. MRI can be a useful tool for identifying some of these factors including osteomyelitis, fluid collections, abcesses,and sinus tracts in the perioperative period. Identifying the appropriate patient populations and clinical indications for the optimal use of MRI should be subject of further study. 0 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation RESSURE ULCERS are often difficult to evaluate and P treat, particularly if the ulcer is chronic and nonhealing. Failure to identify underlying complications such as soft tissue From the Spinal Cord Injury Service (Dr. Goldstein) and Department of Radiology (Dr. Escobedo), VA Puget Sound Health Care System: and the Department of Rehabilitation Medicine (Drs. Rum, Goldstein) and Department of Radiology (Drs. Escobedo, Harrison), University of Washington Medical Center, Seattle, WA. Submitted for publication June 23,1997. Accepted in revised form October 1,1997. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprints are not available. 0 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation 0003-9993/98/7909-4553$3.00/O

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MD, Barry Goldstein, MD, PhD infection, osteomyelitis, abscess, sinus tract, fistula, septic arthritis, or squamous cell carcinoma can prevent normal healing and postpone proper treatment. In addition, age, nutrition, self-care, and concommitant medical problems should be considered. The diagnostic approach for a single pathologic entity in nonhealing ulcers is not always simple or straightforward. Chronic pressure ulcers are difficult to evaluate by physical examination alone. The methods used to identify the presence of infection, abcess, osteomyelitis, and sinus tracts in nonhealing ulcers have included plain film,’ sinogram, computed tomography (CT):,3 scintigraphic methods4s5 bone biopsy,4x6-9 and more recently, magnetic resonance imaging (MRI).iO The best method of evaluation, and the sensitivity and specificity of the various diagnostic tests, remain unsettled. Thus, there is no clear standard for the evaluation of nonhealing pressure ulcers to identify underlying complications when planning further treatment methods and possible surgery. We have become increasingly interested in diagnosis and treatment of complications of recurrent myocutaneous flap surgeries. Although myocutaneous flaps are recognized as a therapeutic option for grade III and IV pressure ulcers,11,12 failure of myocutaneous flaps is not uncommon. In the literature, rate of recurrent ulceration or complications after flap surgery has ranged from 5% to 36%.11-13Suture line dehiscience, often the most common flap complication, may occur in addition to infection, draining sinus, hematoma, or necrosis.10,12,13Long-term success is also a problem. Disa and colleagues12 reviewed 66 flaps and found that despite 80% successof definitive healing by discharge, 61% of the pressure ulcers had recurred within 1 year. Regarding surgical outcome, the question remains whether it is possible to develop diagnostic guidelines for evaluating nonhealing pressure ulcers that will guide clinical decisions in the perioperative period and optimize healing. Any type of guideline or algorithm would need to accommodate the heterogeneous nature of the types of complications that occur. The purpose of this study was to evaluate the use of MRI to assess nonhealing pressure ulcers and/or complicated myocutaneous flaps for the presence of infection, osteomyelitis, or sinus tracts. Two case reports are included to demonstrate the complexities involved in some of these cases.Finally, we propose that MRI is useful in evaluating complicated pressure ulcers in the perioperative period. MATERIALS AND METHODS This study involved a retrospective review of 12 patients from the Spinal Cord Injury Service at the Department of Veterans Affairs, Puget Sound Health Care System, who were admitted between March 1994 and August 1995 for a nonhealing pressure ulcer or flap breakdown. Patients were included if they had MRI as part of their diagnostic evaluation. Demographics and clinical data. Patient data included history, and physical examination of the pressure ulcer, age and duration of spinal cord injury (SCI) at time of ulcer, level of injury, American Spinal Injury Association (ASIA) classification, and previous history of surgical flaps or ulcers. Clinical

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factors that could influence healing included other medical problems, nutritional status, compliance with pressure relief, and prolonged sitting for more than 8 hours a day. Other clinical data and decisions included use of preoperative or perioperative antibiotics, type of surgical procedure or surgical debridement of bone, and postoperative complications. The decision of whether to advance a patient to sitting was also evaluated. In our institution, mobilization usually begins 3 weeks postoperatively when the patient is taken off a Clinatron bed and gradually increases sitting time by a scheduled protocol. MRZ. A total of 18 pelvic MRI examinations of nonhealing wounds in 12 patients were obtained from March 18, 1994 to August 8, 1995. Initial MRI was obtained during different times in the perioperative period. The first seven patients were evaluated preoperatively; four patients with a history of myocutaneous flap surgery from a previous admission had a recurrent grade II to IV ulcer in the region of the flap, and three patients with a new grade IV pressure ulcer had no prior history of surgery. Two of the seven patients who had preoperative MRI also had follow-up MRI in the postoperative period. The other five patients had a myocutaneous flap surgery during this study period and were evaluated by MRI for delayed healing of the flap. Four of the five patients who had initial MRI for delayed healing in the postoperative period also had follow-up MRI. MRI was performed with a 1.5 Tesla Gyroscan unita A short tau inversion recovery (STIR) (TR 2000, TE 20, TI 160) sequence in the coronal plane, and fast-spin echo T2-weighted (TR 4000-4600, TE 160) sequence in the axial plane was obtained on every patient. A Tl-weighted (TR 500-720, TE 12-18) axial sequence was obtained in all but four of the studies. Additional sequences included axial fat-suppressed Tl-weighted (TR 500-720, TE 12-180) images after intravenous injection of 20mL gadopentetate dimeglumine,b performed in 10 of the studies, and axial STIR (TR 2000, TE 20, TI 160) images performed in 6 of the studies. MRZ data. On MRI, the following were evaluated: the size and depth of pressure ulcers; the presence and extent of sinus tracts, fluid collections, or abscesses; associated soft tissue inflammation (cellulitis); and osteomyelitis of the adjacent bone. On MRI, pressure ulcers were defined as an area of skin and adjacent subcutaneous defect, with underlying focal low signal intensity on Tl-weighted images and corresponding high signal intensity on T2-weighted and STIR images. Ill-defined areas of abnormal low signal intensity on Tl-weighted images with corresponding high signal intensity on T-2 weighted and STIR images within soft tissues adjacent to the pressure ulcer were classified as cellulitis. Fluid collections were diagnosed when homogeneous, well-defined areas of low signal intensity on Tl-weighted images with high signal intensity on T2weighted and STIR images were seen. Abscesses and sterile fluid collections could not always be differentiated. However, the presence of a thickened, irregular capsule of low signal intensity on Tl- and T2-weighted images surrounding the fluid, with rim enhancement of this capsule after intravenous gadapentetate dimeglumine (gadolinium) injection, was considered diagnostic of an abscess.A sinus tract was defined on MRI by a linear signal abnormality, low on Tl-weighted and high on T2-weighted and STIR images, extending from a pressure ulcer or myocutaneous flap margin. Enhancement of the walls of the tract after gadolinium administration was considered diagnostic. Criteria for osteomyelitis on MRI included low signal intensity on Tl-weighted images with corresponding high signal intensity on T2-weighted or STIR images within the bone marrow, with or without obvious cortical bone destruc-

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tion. High signal intensity enhancement after intravenous injection of gadolinium in those cases in which contrast was administered heightened the suspicion for infection. Other diagnostic studies. Charts were reviewed for white blood cell count (WBC), erythrocyte sedimentation rate (ESR), sinograms, and CT and nuclear medicine studies (bone scan, labelled leukocyte scan) when available. Outcome data. Patient outcome data included number of hospital days and hospital admissions for pressure ulcer treatment, and number and types of surgeries. The status of the patients’ skin was also reported at discharge and at follow-up 1 year and after 2 years. RESULTS The patients’ ages ranged from 23 to 67 years, with the majority being older (mean 45 years), and having a SC1 for a longer duration (mean 16 years). All 12 patients had a cervical or high thoracic level of injury and were either ASIA classification A or B. Five of 12 (42%) had flaps before being involved in this study period. A chart review was performed to determine if patients sat for prolonged periods of time (longer than 8 hours a day) or if they were compliant with pressure relief. Eight patients were noncompliant in either prolonged sitting and/or pressure release. Five patients had medical problems that may have influenced healing, including diabetes mellitus, peripheral vascular disease, coronary artery disease, and poor nutrition. None of the patients had renal disease or impaired immune function (table 1). MRI examinations were obtained during different times in the patients’ hospital courses and were used to evaluate different clinical situations. To discuss MRI use for a certain clinical situation, these patients were divided into two groups. The first seven patients had MRI preoperatively to evaluate either a recurrent pressure ulcer that developed in an area where the patient had previous flap surgery (cases 1 through 4) or to evaluate a new nonhealing pressure ulcer (cases 5 through 7) (table 2). In this group of patients that had preoperative MRI, three had findings of osteomyelitis (cases 1, 5, and 6). All three underwent bony debridement or osteotomy in addition to flap surgery. Postoperative MRI was obtained in case 1 before mobilization because of his previous history of recurrent breakdown. This showed a decrease in the previous fluid collection and he was mobilized without further breakdown. Case 6 continued to have local skin breakdown despite follow-up MRI that showed no evidence of osteomyelitis. He later required a hip disarticulation because of a lack of viable skin, but still did not heal. Preoperative MRI was used in three other patients in this group (cases2,3, and 4) to further evaluate nonhealing margins of flaps from a previous admission. In all three cases, a sinus tract was detected to be more extensive by MRI than by physical examination alone, resulting in surgical revision of their nonhealing flaps. With prolonged nonhealing, case 2 required a second flap surgery and finally healed. The other two patients continued to have chronic nonhealing openings along the flap margin. Both were elderly and had been injured for more than 20 years. Case 7 in the preoperative MRI group had an uneventful course; his MRI showed no evidence of wound infection, abscess, or osteomyelitis. He underwent a tensor fascia lata (TLF) myocutaneous flap and healed without complications. This 23-year-old patient had been injured for 1 year. MRI was used postoperatively in five other patients (cases8 through 12) who had prolonged healing after a myocutaneous flap procedure despite local wound care and bedrest. MRI was used postoperatively to evaluate possible underlying complicaArch

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Table SCI CaS3

Level

ASIA

1: Demographics

Previous Flaps

Years

A

8

Yes

No

c5 Tl

A A

8 42

Yes

Yes

No

c5 T4

B A

22 15

Yes (9)* Yes

No Yes

PVD,CAD NIDDM

C6 T7

A A

35

Yes Yes

Yes No No

c5 T6

A A

Yes No

Yes No

IDDM

1 24

No

CAD

c5 c5

A B

c5

A

67 59 40 55 23 63 44 37 51 50

12

PVD, peripheral vascular diabetes mellitus. flap surgeries.

16 8 8

Yes

No No Yes

19 disease;

coronary

artery

Table Ulcer Characteristics

Case

7

Preoperative MRI Findings

Clinical

Osteomyelitis

TFL flap

Sinus

tract

Bony

Ischium* Grade II

Sinus

tract

Debride

lschium* Grade IV Ischium”

Sinus

tract

Rectus

Sinus

tract

Conservative healing

Grade II lschium Grade IV Greater trochanter Grade IV Greater trochanter Grade

Small

Bony debridemen

No osteomyelitis

TFL flap

IV

N/A, not applicable (MRI flap from prior admission.

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flap

Gluteal flap Osteotomy TFL flap

abcesses

not done).

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Healed

old flap

Yes NIDDM,

NIDDM,PVD

non-insulin-dependent

diabetes

mellitus;

IDDM,

MRI Postoperative MRI Findings

Outcome

debridement

Osteomyelitis Fluid collection Osteomyelitis

Abbreviation: * Previous

Phys

revision

Yes

down. Follow-up MRI showed a remaining fluid collection and a sinus tract where a Jackson-Pratt drain had been placed. Despite a second surgical revision, the flap never successfully healed. Eleven of 12 caseshad normal WBC and ESR throughout the perioperative period. The 1 patient who had an elevated ESR of 95mm/h also had an MRI that was interpreted as osteomyelitis (case 6). Other radiographic methods were reviewed when available. For the three cases of osteomyelitis diagnosed by MRI, findings on CT, bone scan, and WBC scan were consistent with findings shown by MRI (table 4). Nonhealing pressure ulcers and failed flaps resulted in multiple surgeries, hospital admissions, and lengthy hospital stays (table 5). The average number of total hospital days was 215 (range, 131 to 347). Half of the patients required 2 to 3 admissions secondary to flap failure or recurrent ulcer breakdown. Two patients were discharged from the hospital unhealed, to attempt further conservative healing at home. However, they were still not healed at 1 year. An additional 2 of the 12 were not healed 1 year after follow-up. By 2 years after follow-up, 6 of 12 patients had recurrent skin breakdown.

2: Use of Preoperative

Decision

Greater trochanter* Grade IV

disease;

Poor Nutrition

Yes Yes No

Yes

CAD,

tions that could be preventing successful healing (table 3). All of the MRI studies showed evidence of sinus tract, abscess, or fluid collection that often resulted in surgical intervention or influenced whether a patient would be mobilized. For example, MRI in case 8 showed enhancement along the flap margin, and the patient was kept on bed rest an additional 3 weeks. Follow-up MRI showed a decrease in the enhancement of the flap margin. The patient was subsequently mobilized without further breakdown. In contrast, case 9 had a fluid collection identified by MRI in the postoperative period. The patient was mobilized despite the MRI findings and then developed a wound dehiscence. Follow-up MRI showed a new sinus tract in the original area where the fluid collection had been. As a result, the patient had debridement of the sinus tract and a new flap that healed successfully. The last three patients (cases 10, 11, and 12) underwent flap revisions because of the extent of the sinus tracts seen on MRI. A second postoperative MRI examination in Case 10 showed a decrease in the fluid collection seen on his previous MRI. He was mobilized and had no further breakdown. Case 11 also had no further breakdown after flap revision. The last patient (case 12) continued to have break-

6

Problems

T4

Abbreviations: insulin-dependent * Nine previous

5

Yes

Medical

47

9 10 11

4

PresSWe Release

46

8

3

Prolonged Sitting

2 3

6 7

2

Ruan

1

4 5

1

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Decreased

fluid

Clinical

Decision

Mobilize

Outcome

Successful sitting

collection Continued

N/A

Gracillis

nonhealing Flap necrosis

N/A

Rectus

N/A

Flap

N/A

Flap revision

Continued breakdown Healed

No osteomyelitis

Hip disarticulation Flap revision

Continued breakdown

Continued breakdown Dehiscience Continued breakdown

It Healed

N/A

flap take-down

revision

Healed Continued breakdown

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Table

8

lschium S/P biceps

9 IO

Postoperative MRI Findings

Ulcer/Flap Characteristics

Case

lschium S/P rectus

Enhancement along flap

flap

margin Seroma Sinus

11

Sinus

12

S/P TFL flap Sacral

Fluid

Abbreviations:

3: Use of Postoperative

Clinical

Decision

Continue

bedrest

flap

tract

abcess

tract collection

S/P, status

post;

N/A,

MRI Use

4: Other

WBC

ESR 25

Premobilization

8,700 4,700

2 3 4

Preoperative Preoperative Preoperative

9,200 N/A 8,900

8 62 70

5 6

Preoperative Preoperative

7,600 N/A

43 95

N/A

4

7

Postoperative Preoperative

5,900 10,700 N/A

35 19 30

Preoperative

8

Postoperative Premobilization

9

Postoperative

6,500

11

(1) Preoperative

N/A

N/A 28 40 15 24

Postoperative

11

Premobilization Postoperative

6,800 6,300 8,000

12

Postoperative

N/A

(1) Postoperative

Flap

8,000

as number N/A,

Clinical Decision

in flap

Mobilize

tract

Healed

Decreased

Debridement Revise with

revision

Healed

collection N/A

gracilis flap Flap revision

Breakdown

N/A

not applicable

(MRI

not done);

Studies

CT

Bone Scan

WBC Scan

(+)OM

(+)OM

(+)OM

Fistulogram Yes

(+)OM

JP drain Fluid

Gracilis

Outcome Successful sitting

flap

Healed

JP, Jackson-Pratt

Case

Number of Surgeries*

as millimeters

-

tract

Flap

revision

Continued breakdown

Total Hospital Days

5: Outcome

Total Hospital Admissions

Healed at Discharge

1

2

196

2 3 4

2 2

135 147

3 1 1

1 2

260 260

4 1

2 1

324 131

1 1

Yes Yes Yes

1 2 2

199 135 210

1 3 3

Yes Yes Yes

2 3

240 347

2 2

Yes No

5 6

9 IO 11 ESR reported

-

drain.

7 8 Abcess

Successful sitting

Table

Yes

Mobilize

The patient did well until 4 months later when an area again opened up at the inferior margin of the flap. Examination revealed a large, grade IV, undermined ulcer with foul-smelling, yellow discharge located over the right greater trochanter, along the margin of the previous flap. Initial evaluation included a WBC of 8,7OO/pL and ESR of 2.5&n/h. The suspicion for continued underlying infection and/or osteomyelitis was high because the patient had breakdown of his flap again. He underwent an extensive evaluation including bone scan, WBC scan, fistulogram, and MRI. The MRI (fig 1) showed high signal intensity at the site of the previous intramedullary rod within the proximal femur. The focal high signal intensity in the greater tuberosity of the right femur was consistent with osteomyelitis. There was also a high signal within the soft tissues adjacent to the tuberosity, continuous with the medullary canal, consistent with a sinus tract traversing the subcutaneous tissue to the skin. The area of osteomyelitis was further substantiated by a WBC scan and bone scan. A fistulogram was used to determine possible joint involvement. This demonstrated a 3cm X Scm cavity adjacent to the greater trochanter but no communication with the joint. The patient had surgery for debridement of the right proximal femur and a right TFL flap revision. Postoperatively, he was treated with intravenous oxacillin for 6 weeks. Because of all of the previous complications, MRI was done 3 weeks postoperatively to rule out any residual osteomyelitis or fluid collection before mobilizing the patient. MRI showed a marked decrease in the fluid collection previously seen, and the patient was mobilized per protocol. The patient was discharged 3 months

(6)OM

(-)OM

fluid

collection

(+DM (-DM

per microliter;

not applicable.

flap

margin

(2) WBC reported per hour. Abbreviations:

Decrease defect Sinus

(2) IO

healing

Dehiscience

inflammation

Table

1

Follow-Up MRI Findings

Mobilization

CASE STUDY 1 This patient was a 44-year-old man with T4 complete paraplegia since 1985. Because of a grade IV ulcer over his right greater trochanter, he had a TFL myocutaneous flap in August 1993. His hospital course was prolonged because he developed a chronic wound at the inferior flap margin. After an extended period of bedrest, the flap healed and the patient was discharged to home. He was rehospitalized 7 months later for an opening at the inferior margin of the flap with a lo-cm tract that undermined the flap. Because of concern for osteomyelitis, he underwent removal of an old intramedullary rod, femur debridement, and TFL flap revision. Intraoperative cultures of the wound and bony fragments were positive for Staphylococcus aureus. He was subsequently treated with antibiotics for 4 weeks. Because of an opened area at the inferior flap margin that would not heal, the patient required a split thickness skin graft. He was finally discharged 2 months later with healed skin.

Case

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flap

Pilonidal cyst S/P gluteal flap lschium

S/P gluteal

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during

current

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Yes Yes No Yes

Healed at 1 Year

Healed at >2 Years

Yes

Yes

Yes No No

No No No

Yes No

Yes No

Yes Yes Yes

Yes Yes No

Yes Yes

Yes

No

Yes No

period.

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Fig 1. (A) Coronal STIR MRI showing high signal-intensity site of previous intramedullary rod within the proximal femur (small arrows). There is focal high-signal intensity in the greater tuberosity of the right femur (large arrow) compared with the left, consistent with osteomyelitis. Note the abnormal high signal within the soft tissues adjacent to the tuberosity, continuous with the medullary canal, and with a sinus tract traversing the subcutaneous tissue to the skin (curved arrows). (B) Axial Tl-weighted fat-suppressed MRI after intravenous contrast administration demonstrates a focal low signalintensity cavity corresponding to a portion of the air-containing sinus tract (filled arrow), surrounded by a large area of high signal-intensity enhancement, consistent with active inflammation. Note the high signal within the greater tuberosity of the right femur (curved arrow), highly suspicious for osteomyelitis.

later with fully healed skin. Two years later his flap remained intact. This patient’s course is summarized in figure 2. CASE STUDY 5 This patient was a 40-year-old man with T4 paraplegia since 1977. He developed a pressure ulcer over the left ischium MRl Femoml M nail flap Brcakdow~ removed & debrided BE&dOWIl + 0steamyeMis 7194 1l/93 3/18/94 9194 I I I I I I I I I Home TFL R&mitted Split thickness Readmitted 5194 to hospital skingaft s/94 m 4/94 S/93 3194

flap

Fig 2. Timeline

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1 events.

79, September

lvm M fluid collection 1l/94 I I I FQIVJI HOIlK debridement 11/94 TFL revision IO/94

IM, intramedullary.

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Fig 3. (A) Axial contrast-enhanced CT of the lower pelvis showing rim-enhancing fluid collection (arrow) abutting the left ischial tuberosity, consistent with abscess formation. (B) Same CT image as A, using bone detail, showing erosion of the cortical margin and development of sclerosis in the medullary space of the ischial tuberosity (arrow) adjacent to the soft tissue abscess, consistent with osteomyelitis.

because of prolonged sitting. He was treated in a nursing home for 5 months with bedrest and local wound care. He went home with a grade II ulcer and attemped to achieve definitive healing with bedrest in the prone position without success for an additional 5 months. The patient was admitted and placed in a Clinatron bed. Wet-to-dry dressing changes were used to clean the wound locally. The patient had an initial ESR of 43mm/b. There was a high index of suspicion for osteomyelitis. Workup included CT (fig 3) and MRI (fig 4) of the pelvis that showed findings consistent with osteomyelitis of the left ischium. The patient initially refused surgery. He was treated with intravenous antibiotics and local wound care for 3 months without successful healing. He subsequently underwent a gluteal rotation flap and ischial osteotomy. Pathologic diagnosis of bony fragments at the time of surgery revealed focal marrow fibrosis, focal bone formation, and no evidence of active osteomyelitis. One month later, the surgical wound broke down and there was purulent drainage. The flap was revised and the patient was placed on antibiotics for another month. For the next 5 months, he had multiple episodes of skin breakdown that required bedrest. Finally, the patient progressed through the sitting protocol. His skin was fully healed at discharge 20 months after

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Fig 4. (A) Coronal STIR MRI through the posterior bony pelvis, obtained 1 week after CT, shows abnormal high (bright) signal-intensity within the marrow of the left ischial tuberosity (large arrow) compared with the normal low (dark) signal-intensity of the tuberosity on the right. Ill-defined high signal-intensity (small arrows), consistent with fluid or active inflammation, is seen within the soft tissues surrounding this area and the greater tuberosity of the femur. (B) Axial TZ-weighted MRI just below the level of the ischial tuberosities shows intermediate signal intensity surrounded by a thick, irregular, low signal-intensity periphery within the subcutaneous tissue of the gluteal region (arrows). This is consistent with a central abscess with a thick fibrotic capsule. (C) Axial T2-weighted MRI at the level of the ischial tuberosities. The abscess cavity can be seen adjacent to the left ischial tuberosity (arrows). (D) Corresponding Tl-weighted fat-suppressed MRI after contrast administration demonstrates a large amount of high signal-intensity enhancement surrounding the ischial tuberosity. The intensity of this bright signal obscures the abscess seen on the TZ-weighted images. However, compared with other MRI sequences, it is more sensitive in detecting inflammation, as is demonstrated by the much larger extent of surrounding high signal abnormality. High signal within the ischial tuberosity is consistent with osteomyelitis (arrow). The bright signal seen midline and anterior represents the normal corpora cavernosa.

the initial admission and 1 year later. The patient developed a stage IV ulcer in the same location 2 years later. This patient’s course is summarized in figure 5. DISCUSSION Staggering costs and human suffering result from chronic pressure ulcers.i4.15In the population of patients with SCI, for example, reports of pressure ulcer incidence have been as high as 85% in some centers. The average cost of treatment for a single pressure ulcer treatment has been estimated to be from 14+ months tedrest I-II

bm Flap + astwmyelius revision 12/30/94 417194 I -1 -iv antibiotics- I -multiple breakdoansI Admitted GbIkd 12114194 flap & 0ste0t0my 3/17/95

Fig 5. Timeline

of case 5 events.

iv, intravenous.

Discharged 813l/94 I

$30,000 to $120,000.16-18 The total annual cost of treating pressure ulcers in the United States has been estimated to be approximately $3 billion. l9 These tremendous costs reflect, in part, recurrent pressure ulcers and failure of conventional therapies. One of the great difficulties in this area is the lack of standards to guide clinical decisions. Evaluating complications of pressure sores by physical exam alone is problematic. Osteomyelitis is an excellent casein point. Darouiche and colleagues2o found that two skilled physicians had only 56% accuracy when clinically evaluating underlying osteomyelitis in pressure ulcers. In addition, they found that WBC, ESR, and radiologic findings were unhelpful. Darouiche’s group20 and others6,7,ghave suggested that a definitive diagnosis of osteomyelitis in pressure ulcers should come from pathologic diagnosis of a bone biopsy. Yet, bone biopsy is not without problems either. Percutaneous needle biopsy may be limited by failing to adequately sample infected bone.6x7.9 Others have suggested that bone osteotomy is more accurate.4s Arch

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The utility of radiologic methods for diagnosing pathologic processes underlying pressure ulcers remains controversial. Many groups have compared radiographic techniques for accuracy in diagnosing underlying osteomyelitis in pressure sores. This has included use of conventional radiography, nuclear medicine, CT, and MRI. Conventional radiography may be normal in early osteomyelitis and changes in plain film often do not show up until 14 days into the disease.21 In identifying osteomyelitis under pressure sores, plain films should not be used alone because heterotopic ossification or sclerotic bones changes may be misleading.g,20,21Lewis and colleagues8 reported the combination of plain film, WBC, and ESR, when one test is positive, as the best noninvasive workup (sensitivity 89%, specificity 88%) but believed bone biopsy was a more definitive diagnosis. Nuclear medicine techniques used to identify osteomyelitis include bone scans with technetium 99 (9gmT~),gallium 67 (67Ga) scans, ‘and leukocyte scans labeled with indium 111 (“‘In). A cumulative review by Schauwecker5 showed that the three phase ggmTcbone scan had a high sensitivity (94%) and specificity (95%) for osteomyelitis when reviewing studies of adults with normal radiographs. However, bone scan was considered to be much less specific when there was increased bone remodeling (33%), overlying cellulitis, or septic arthritis (60% to 70%), conditions often present when evaluating pressure ulcers.67Ga-citrate scans had an 81% sensitivity and and an even lower specificity (67%). Gallium is not specific for infection and may be positive in increased bone remodelling or neuropathic changes in bone. Leukocyte-labeled “lIn scans have been found to be more effective than ‘j7Ga-citrate for diagnosing osteomyelitis, with specificity and sensitivity of 88% and 85%, respectively. When suspected osteomyelitis is superimposed on a disease that may cause bone remodeling, a combined “‘In-labeled leukocytePgmTc bone scan is recommended in non-marrow-containing skeleton to further improve specificity.5 The results of using these nuclear medicine techniques for evaluating osteomyelitis and pressure sores have been variable. Thornhill-James and colleagues9 found a poor correlation of diagnosing osteomyelitis by technetium and gallium scans. Bone and gallium scans were positive for osteomyelitis in all ulcer sites that were positive by needle biopsy except one. However, scans were also positive in 45% of histopathologic sites that were negative for osteomyelitis. This group also emphasized that negative scansessentially ruled out osteomyelitis, although many of the negative sites by bone and gallium scan were not biopsied. In contrast, Burdge and Gribble4 reported three patients with negative technetium bone scans in pressure sores with histologically proven osteomyelitis obtained by surgical biopsy. Lewis and colleagues* found that g9mTcbone scans had a sensitivity and specificity of 64% and 57%, respectively, when compared with pathological examination of bone osteotomy. CT have been used to effectively evaluate soft tissue and bone in the pelvic region for suspected osteomyelitis and pelvic abcess.‘” Despite increased cost and patient limitations, MRI has largely replaced CT for evaluating osteomyelitis because it has better resolution in distinguishing between soft tissue and bone, is more sensitive to marrow edema, and has the advantage of being multiplanar.5~22~23 Combined results of 11 studies that used MRI to diagnose osteomyelitis in a variety of settings had a sensitivity of 95% and specificity of 88%.s Erdman and colleaguesz2 compared histopathologic results with MRI for diagnosing osteomyelitis

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and found a sensitivity of 98% and specificity of 78%. MRI should be used with caution in situations that can mimic osteomyelitis in which there is increased water content of the bone marrow. This may occur in septic joints, tumors, fractures, or sickle cell infarctions.21,22,24,25 Use of contrast agents such as gadolinium may help to differentiate reactive edema and infection or distinguish abscess from surrounding cellulitis/ myositis but does not always distinguish between infectious and noninfectious inflammatory conditions.21,23,26 MRI has been used in the management of diabetic foot infections for detecting the presence and extent of osteomyelitis.27,28Only one study has been done to look at the utility of MRI and gluteal decubitus ulcers in patients with SCI. MRI was used to identify soft tissue changes, fluid collections, heterotopic ossification, and bone marrow edema indicating acute or chronic osteomyelitis. lo This study was limited to MRI findings of pressure ulcers, but no specifics were given regarding clinical decision making or outcomes for individual patients. In the current study, MRI was used to evaluate pressure ulcers and myocutaneous flaps in the perioperative setting for detecting sinus tracts, fluid collections, abcesses,associated soft tissue inflammation, and osteomyelitis. Because this patient population had significantly different clinical situations and a high number of poor outcomes, other contributing factors such as self-care, age, years with XI, and concommitant medical problems were explored. Three patients (cases 1, 5, and 6) had nonhealing pressure ulcers that were highly suspicous for underlying osteomyelitis. On initial evaluation, physical exam revealed large grade IV ulcers with exposed bone in cases 5 and 6. Case 1 had a long, draining sinus tract and its extent was difficult to determine by physical exam alone. WBC and ESR were unremarkable except for the elevated ESR in case6. Osteomyelitis was detected in all three patients with a combination of MRI, CT scan, and bone scan in case 1; MRI and CT scan in case 5; and MRI and bone scan in case6. MRI was useful not only in identifying the extent of the bony changes consistent with osteomyelitis as seen on bone scan or CT but also in determining the involvement of soft tissue structures for the presence of inflammation, sinus tracts, abcesses, or fluid collections. For example, in case 1 MRI revealed a large air filled sinus tract with a large area of surrounding inflammation (fig 1). These findings prompted treatment, including extensive soft tissue and bony debridement and 6 weeks of intravenous antibiotics postoperatively. In case 5, CT revealed abcessformation (fig 3A) and osteomyelitis (fig 3B). MRI also showed osteomyelitis of the left ischial tuberosity (fig 4A) and abcess formation (fig 4B and 4C). Using Tl-weighted fat-supressed images (fig 4D) showed a greater extent of surrounding inflammation as compared with CT or other MRI sequences. In the three casesof osteomyelitis, CT and/or bone scan were obtained to verify the MRI findings of osteomyelitis. Because of the retrospective nature of this study, it is not possible to separate how the patients would have been managed if only MRI versus one of the other studies had been obtained. MRI provided a more detailed evaluation of soft tissue findings of abcess and sinus tract formation in cases 1 and 5. Both of these patients underwent extensive soft tissue debridement in addition to osteotomy during their flap surgeries and ultimately healed successfully. MRI was also used for evaluating flaps that had nonhealing margins or sinus tracts. This is a particularly interesting problem when one considers how healing of a sinus tract is followed over time. At regular intervals, patients were exam-

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ined by measuring the length of a cotton-tipped applicator that was inserted into the wound to determine if the tract was healing. The questionable accuracy of this method for wound evaluation ultimately prompted us to obtain MRIs. This was done preoperatively to assessthe need for surgical intervention (cases 2, 3, and 4) or postoperatively to better define the underlying pathology of a nonhealing myocutaneous flap (cases 10 and 11). MRI revealed sinus tracts that were much larger than suggested by physical exam alone and identified inflammation or abcessformation in the surrounding tissue. These MRI findings prompted surgical revision of a previous flap (cases 2, 4, and 10) or a surgical revision using an alternative myocutaneous flap (cases3 and 11). MRI was also helpful in identifying fluid collections. In case 9, a patient was found by MRI to have an irregular fluid collection under his myocutaneous flap that was not detectable by physical examination. He was subsequently progressed to a seating protocol because the flap was essentially intact. However, during the seating program, new breakdown of the flap occurred. Repeat MRI showed a gas-containing sinus tract that had developed in place of the previous fluid collection. The patient went on to have sinus tract debridement and a second flap that resulted in definitive healing. Despite surgical intervention or prolonging a patient’s bedrest because of MRI findings, there was still a high failure rate of healing. Fifty percent of all cases had breakdown within 2 years of discharge. In addition to MRI findings of osteomyelitis or sinus tract, multiple factors were probably relevant to the high failure rate, including underlying medical problems, nutrition, and compliance of skin care. The two patients that never healed had multiple medical problems, were over 50 years old and had SC1 for more than 19 years. The two patients that had skin breakdown within the first year were diabetic, injured more for than 20 years and over the age of 55. Of the six patients that did not have recurrent skin breakdown, five were injured less than 10 years and had no other medical problems. The sixth patient that did well was 63 years old, injured for 24 years, and had coronary artery disease. Because of the high number of poor outcomes it is difficult to optimally determine the diagnostic capabilities of MRI. In addition, identifying an optimal patient population when considering the diagnostic utility of MRI would be helpful. The patients that had better outcomes did not have as many contributing factors for failure. In those patients, MRI often prompted surgical intervention that resulted in healing. Another limitation to this study was the highly variable clinical course for each patient. Because this was a retrospective study, there was no standard protocol for using MRI. Patients also had multiple admissions and multiple surgeries, with MRI done at different times. Because of the clinical variation, a control population of patients with nonhealing pressure ulcers that did not have MRI was not available to compare hospital course and outcomes. Prospective studies are necessary to identify optimal patient populations, timing, and indications of MRI when evaluating nonhealing pressure ulcers. CONCLUSION Chronic nonhealing pressure ulcers can be difficult to evaluate and treat with conventional methods alone. MRI was useful in identifying osteomyelitis, fluid collections, abcesses, and sinus tracts that often required surgical revision for successful healing. MRI may also be used to evaluate skin or flap integrity in complicated healing courses before mobilization to prevent breakdown from an underlying hematoma, fluid

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collection, or sinus tract. Controlled prospective studies are needed to further evaluate the utility of MRI in assessing nonhealing pressure ulcers and myocutaneous flaps with the hope of improving diagnostic efficacy for optimal treatment and outcome. References

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25. Tehranzadeh J, Wang F, Mesgarzadeh M. Magnetic resonance imaging of osteomyelitis. Crit Rev Diagnostic Imaging 1992;33: 495-534. 26. Hopkins K, Li K, Bergman G. Gadolinium-DPTA-enhanced magnetic resonance imaging of musculoskeletal infectious processes. Skeletal Radio1 1995;24:325-30. 27. Yuh W, Corson J, Baraniewski H, Rezai K, Shamma AR, Kathol MH, et al. Osteomyelitis of the foot in diabetic patients: evaluation with plain film, 99Tc-MDP bone scintigraphy, and MR imaging. AJR Am J Roentgen01 1989;152:795-800.

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28. Cook T, Rahim N, Simpson H, Galland R. Magnetic resonance imaging in the management of diabetic foot infection. Br J Surg 1996;83:245-8. Suppliers a. Philips Medical Systems Inc., 710 Bridgeport Ave., Shelton, CT 06484-4708. b. Magnevist; Berlex Laboratories Inc., 300 Fairfield Road, Wayne, NJ 07470-7358.