Australas Radio1 1992; 36: 77-79
1
I
Acute Osteomyelitis: Early Diagnosis by Ultrasonography K. TANETA, S.K.MITTAL, S.K.MARYA, G. MEHROTRA, V.K. SHIV,S.K.BHARGAVA Department of Radiology & Imaging, University College of Medical Sciences & GTB Hospital Shahdara Delhi 95 India
I ABSTRACT
METHODS
A prospective study was carried out to evaluate the role of ultrasound in early detection of infections of bone. Presence of a hypoechoic collection adjacent to bone was considered highly suggestive of osteomyelitis whereas a hypoechoic collection away from the bone implied a soft tissue abscess. Cellulitis presented as increased subcutaneous thickness. Of the 31 patients clinically suspected to have osteomyelitis, and subjected to ultrasound, 25 were proven to be osteomyelitis at surgery or by subsequent radiological changes, 4 had soft tissue abscesses and the remaining 2 had cellulitis. Co-existent hip joint effusion was seen in 2 patients. It is felt that ultrasound is simple and non-invasive investigation, capable of detecting bone and soft tissue infections. INTRODUCTION Acute osteomyelitis is widely prevalent in the paediatric age group in India. To minimise morbidity, a high index of suspicion, early diagnosis and prompt treatment are essential. The bony changes of acute osteomyelitis are not appreciated in the early stages on plain X-rays. Bone scintigraphy is an established investigative aid for early diagnosis, as is magnetic resonance imaging. These modalities, however, are not widely and easily available in all situations. Though osseous structures are not well imaged by ultrasound, soft tissues, especially any fluid collection, are easily seen. Recent reports mention promising results with ultrasound of soft tissues and bones in the extremities (1). We present our preliminary experience with high resolution US in the diagnosis of acute osteomyelitis.
Ultrasonograms were performed with a Phillips 1550 scanner, using 4 MHZ transducer. Longitudinal and transverse scans of the involved area were obtained in order to delineate the extent of pathology. Comparison with the contralateral healthy side was made in all cases. Bone scintigraphy, CT and MRI were not performed, as the facilities were not available at our institution.
RESULTS Ultrasound examination was performed in 31 cases subsequently subjected to open surgical drainage. A hypoechoic area contiguous to cortical bone (Figure 1) was considered to indicate acute osteomyelitis (25 cases); whereas a hypoechoic area not immediately adjacent to bone, and with interposition of normal soft-tissue, (Figure 2) as soft tissue abscess (4 cases). Abscesses were treated with appropriate antibiotics and followed up with repeat ultrasound in order to confirm that resolution had occurred. Cortical irregularity (Figure 3) was definitely shown by ultrasound in 17 cases, and was doubtful in another 2. Defite periosteal elevation was seen only in 1 case. ' h o cases had increased subcutaneous tissue thickness which was considered to represent cellulitis (Figure 4). Co-existent pyogenic arthritis of the hip joint was present in 2 cases. Overall sensitivity was 100% with positive predectivity of 92%.
MATERIAL AND METHODS PATENTS Over a period of fourteen months, 3 1 children (1 to 11 years) with suspicion of acute infection of long bones, fever and local swelling, were subjected to radiography followed by ultrasonography. The children having obvious bony changes, namely periosteal reaction, were not a part of the study. All 31 patients were examined between 4th to 7th day of illness. Positive cases for osteomyelitis, on ultrasound, were subjected to surgery followed by appropriate antibiotic therapy.
Key words: Osteomyelitis ultrasonography Australasian Radiology, Vol. 36, No. I . February, 1992
FIGURE 1 - Acute osteomyelitis; Longitudinal and transverse scans; hypoechoic collection adjacent to bone. with conical irregularity.
Submitted for publication on: 13th February, 1991 Resubmitted for publication on:4th June, 1 9 9 1 Accepted for publication on: 5th July, 1991
77
K. TANHA er a1 Once clinical suspicion is aroused, plain radiographs are routinely obtained to assess the soft tissues and skeletal structures. The early changes on plain films include soft-tissue swelling and obliteration of fat planes (3). Soft tissue abnormalities can only be recognised on high quality films and are non-specific. Periosteal reaction and cortical destruction is only apparent later and usually after 1014 days of illness (3,6). Xeroradiography, radionuclide bone scan with Tc 99m and Gallium 67 citrate, and computed tomography have all been used to make an early diagnosis of osteomyelitis but with variable success. Most organisations in the third world counties do not have easy access to these modalities.
FIGURE 2 - Soft tissue abscess: Transverse and Longitudinal scan: Hypocchoic collection Seen away from bone, with interposition of soft tissue in between bone & collection.
Ultrasound has shown promising results in differentiating acute osteomyelitis from soft tissue abscess and cellulitis. Sonography of normal soft tissue reveals the muscle layer as hypoechoic with linear echogenic stiations between the layers (1, 2). Subcutaneous tissue may appear either echoic or hypoechoic. The cortex of the bone is seen as a dense echogenic line with a smooth surface (1). Vascular structures are recognisable by their characteristic pulsations and, if required, by Doppler waveform analysis. Under normal circumstances there is no fluid collection adjacent to bone. If anechoic or hypoechoic fluid collections are apparent, adjacent to bone or within soft tissues, infection should be suspected. The location of fluid with respect to bone is an important factor in differentiating acute osteomyelitis from soft tissue abscess.
FIGURE 3 - Acute Osteomyelitis; Longitudinal scans of diseased and healthy side respectively. Definite periostical elevation of fluid undermath.
Hypoechoic areas away from the bone were confirmed to be soft tissue abscesses by the good response to appropriate antibiotic therapy. Two cases of cellulitis were erroneously considered to be acute osteomyelitis before ultrasonograms demonstrated thickened, hypoechoic subcutaneous tissues (better appreciated on comparison with healthy, contralateral side) and no evidence of localised abscess. The lower echogenicity of the swollen tissues is probably due to a higher water content (13).
TABLE Ultrasound findings
No.
Hypoechoic area adjacent to cortical bone
25
Hypoechoic area away from cortical bone
4
Increase in thickness of subcutaneous tissue
2
Total no. of cases
31
FIGURE 4 - Cellulitis; transverse wans of diseased & healthy side. Increased soft-tissue thickness on the right side. no fluid collection. Specific findings of osteomyelitis on US
DISCUSSION Acute osteomyelitis is a common problem in developing counties, where poverty and lack of medical diagnostic facilities often lead to delayed diagnosis and improper treatment. 78
Cortical irregularity
14
Definite periostieal elevation
1
Coexistent hip joint effusion
2
Australasian Radiology, Vol. 36, No. 1 , February, I992
ACUTE OSTEOMYELITIS Concomitant hip joint effusion was seen as bulging of the articular capsule and was detected by ultrasound in two cases of suspected osteomyelitis. Pyogenic arthritis was confirmed by joint aspiration (12). Osteomyelitis was best demonstrated by sagittal scans, whilst abscesses and cellulitis were better seen on axial scans and with comparison with the healthy side.
4.
CONCLUSION
5.
Ultrasound has potential as a preliminary investigation, and a useful alternative to scintigraphy in clinically suspected acute osteomyelitis. It is quick, simple and noninvasive and aids in differentiating osteomyelitis from soft-tissue processes, at an early stage and in the absence of bony changes on plain films.
6.
Identification of periosteal elevation and abscess formation may be facilitated by employing high-resolution, small parts transducers.
9.
REFERENCES 1.
2. 3.
7. 8.
10. 11. 12. 13.
Austsalasian Radiolog!. Vn1.36. No. 1. Fehruar?. 1992
Abiri MM, Kirpekar M, Ablow RC. Osteomyelitis: detection with ultrasound (work in progress). Radiology 1988; 169 :795-797. Abiri MM, Kirpekar M, Ablow RC. Osteomyelitis: detection with ultrasound. Radiology 1989; 172 : 509-51 1. David R, Barron BJ. Madewell JE. Skeletal infections: acute osteomyelitis Rad. Clin. North America 1987; 25.6 : 1171-1202. Gilday DL. Problems in scintigraphic detection of osteomyelitis, Radiology 1980; 135 : 791. Gillespie WWJ, Nade S. Musculoskeletal infections, Melbourne: Blackwell Scientific Publications 1987; 152-153. Green NE. Edwards K. Bone and joint infections in children. Orthopaedic clinics of North America 1987; Vol. 18. No. 4 : 555576. Herman G, Rose JS. Computed tomography in bone and soft-tissues: pathology of extremities. J. Comput. Assisted Tcmiogr 1974; 3 : 5866. Kuhn JP, Berger PE. Computed tomographic diagnosis of osteomyelitis. Radiology 1979; 130 :503-505. Murray IPC. Bone scanning in child and young adult. Skeletal Radiology; 1980 5 :65-76. Raffi M, Firoomia H, Golibu C et al. Hematogemus osteomyelitis with fat-fluid level shown by CT.Radiology 1984; 153 : 493494. Ram PC, Martinez S , Korobkin M et al. CT detection of intraosseous gas: a new sign. AM Jour Roent 1987; 137 : 721-723. Shiv VK, Jain AK, Taneja K, Bhargava SK. Somgraphy of hip joint in infective arthritis. Journal of Canadian Association of Radiologists 1990.41 : 77-79. Yeh HC, Rabinowitz JG. Uluasonography of extremities and pelvic girdle and correlation with computed tomography. Radiology 1982: 143 : 519-525.
79
1
I
Acute Osteomyelitis: Early Diagnosis by Ultrasonography K. TANETA, S.K.MITTAL, S.K.MARYA, G. MEHROTRA, V.K. SHIV,S.K.BHARGAVA Department of Radiology & Imaging, University College of Medical Sciences & GTB Hospital Shahdara Delhi 95 India
I ABSTRACT
METHODS
A prospective study was carried out to evaluate the role of ultrasound in early detection of infections of bone. Presence of a hypoechoic collection adjacent to bone was considered highly suggestive of osteomyelitis whereas a hypoechoic collection away from the bone implied a soft tissue abscess. Cellulitis presented as increased subcutaneous thickness. Of the 31 patients clinically suspected to have osteomyelitis, and subjected to ultrasound, 25 were proven to be osteomyelitis at surgery or by subsequent radiological changes, 4 had soft tissue abscesses and the remaining 2 had cellulitis. Co-existent hip joint effusion was seen in 2 patients. It is felt that ultrasound is simple and non-invasive investigation, capable of detecting bone and soft tissue infections. INTRODUCTION Acute osteomyelitis is widely prevalent in the paediatric age group in India. To minimise morbidity, a high index of suspicion, early diagnosis and prompt treatment are essential. The bony changes of acute osteomyelitis are not appreciated in the early stages on plain X-rays. Bone scintigraphy is an established investigative aid for early diagnosis, as is magnetic resonance imaging. These modalities, however, are not widely and easily available in all situations. Though osseous structures are not well imaged by ultrasound, soft tissues, especially any fluid collection, are easily seen. Recent reports mention promising results with ultrasound of soft tissues and bones in the extremities (1). We present our preliminary experience with high resolution US in the diagnosis of acute osteomyelitis.
Ultrasonograms were performed with a Phillips 1550 scanner, using 4 MHZ transducer. Longitudinal and transverse scans of the involved area were obtained in order to delineate the extent of pathology. Comparison with the contralateral healthy side was made in all cases. Bone scintigraphy, CT and MRI were not performed, as the facilities were not available at our institution.
RESULTS Ultrasound examination was performed in 31 cases subsequently subjected to open surgical drainage. A hypoechoic area contiguous to cortical bone (Figure 1) was considered to indicate acute osteomyelitis (25 cases); whereas a hypoechoic area not immediately adjacent to bone, and with interposition of normal soft-tissue, (Figure 2) as soft tissue abscess (4 cases). Abscesses were treated with appropriate antibiotics and followed up with repeat ultrasound in order to confirm that resolution had occurred. Cortical irregularity (Figure 3) was definitely shown by ultrasound in 17 cases, and was doubtful in another 2. Defite periosteal elevation was seen only in 1 case. ' h o cases had increased subcutaneous tissue thickness which was considered to represent cellulitis (Figure 4). Co-existent pyogenic arthritis of the hip joint was present in 2 cases. Overall sensitivity was 100% with positive predectivity of 92%.
MATERIAL AND METHODS PATENTS Over a period of fourteen months, 3 1 children (1 to 11 years) with suspicion of acute infection of long bones, fever and local swelling, were subjected to radiography followed by ultrasonography. The children having obvious bony changes, namely periosteal reaction, were not a part of the study. All 31 patients were examined between 4th to 7th day of illness. Positive cases for osteomyelitis, on ultrasound, were subjected to surgery followed by appropriate antibiotic therapy.
Key words: Osteomyelitis ultrasonography Australasian Radiology, Vol. 36, No. I . February, 1992
FIGURE 1 - Acute osteomyelitis; Longitudinal and transverse scans; hypoechoic collection adjacent to bone. with conical irregularity.
Submitted for publication on: 13th February, 1991 Resubmitted for publication on:4th June, 1 9 9 1 Accepted for publication on: 5th July, 1991
77
K. TANHA er a1 Once clinical suspicion is aroused, plain radiographs are routinely obtained to assess the soft tissues and skeletal structures. The early changes on plain films include soft-tissue swelling and obliteration of fat planes (3). Soft tissue abnormalities can only be recognised on high quality films and are non-specific. Periosteal reaction and cortical destruction is only apparent later and usually after 1014 days of illness (3,6). Xeroradiography, radionuclide bone scan with Tc 99m and Gallium 67 citrate, and computed tomography have all been used to make an early diagnosis of osteomyelitis but with variable success. Most organisations in the third world counties do not have easy access to these modalities.
FIGURE 2 - Soft tissue abscess: Transverse and Longitudinal scan: Hypocchoic collection Seen away from bone, with interposition of soft tissue in between bone & collection.
Ultrasound has shown promising results in differentiating acute osteomyelitis from soft tissue abscess and cellulitis. Sonography of normal soft tissue reveals the muscle layer as hypoechoic with linear echogenic stiations between the layers (1, 2). Subcutaneous tissue may appear either echoic or hypoechoic. The cortex of the bone is seen as a dense echogenic line with a smooth surface (1). Vascular structures are recognisable by their characteristic pulsations and, if required, by Doppler waveform analysis. Under normal circumstances there is no fluid collection adjacent to bone. If anechoic or hypoechoic fluid collections are apparent, adjacent to bone or within soft tissues, infection should be suspected. The location of fluid with respect to bone is an important factor in differentiating acute osteomyelitis from soft tissue abscess.
FIGURE 3 - Acute Osteomyelitis; Longitudinal scans of diseased and healthy side respectively. Definite periostical elevation of fluid undermath.
Hypoechoic areas away from the bone were confirmed to be soft tissue abscesses by the good response to appropriate antibiotic therapy. Two cases of cellulitis were erroneously considered to be acute osteomyelitis before ultrasonograms demonstrated thickened, hypoechoic subcutaneous tissues (better appreciated on comparison with healthy, contralateral side) and no evidence of localised abscess. The lower echogenicity of the swollen tissues is probably due to a higher water content (13).
TABLE Ultrasound findings
No.
Hypoechoic area adjacent to cortical bone
25
Hypoechoic area away from cortical bone
4
Increase in thickness of subcutaneous tissue
2
Total no. of cases
31
FIGURE 4 - Cellulitis; transverse wans of diseased & healthy side. Increased soft-tissue thickness on the right side. no fluid collection. Specific findings of osteomyelitis on US
DISCUSSION Acute osteomyelitis is a common problem in developing counties, where poverty and lack of medical diagnostic facilities often lead to delayed diagnosis and improper treatment. 78
Cortical irregularity
14
Definite periostieal elevation
1
Coexistent hip joint effusion
2
Australasian Radiology, Vol. 36, No. 1 , February, I992
ACUTE OSTEOMYELITIS Concomitant hip joint effusion was seen as bulging of the articular capsule and was detected by ultrasound in two cases of suspected osteomyelitis. Pyogenic arthritis was confirmed by joint aspiration (12). Osteomyelitis was best demonstrated by sagittal scans, whilst abscesses and cellulitis were better seen on axial scans and with comparison with the healthy side.
4.
CONCLUSION
5.
Ultrasound has potential as a preliminary investigation, and a useful alternative to scintigraphy in clinically suspected acute osteomyelitis. It is quick, simple and noninvasive and aids in differentiating osteomyelitis from soft-tissue processes, at an early stage and in the absence of bony changes on plain films.
6.
Identification of periosteal elevation and abscess formation may be facilitated by employing high-resolution, small parts transducers.
9.
REFERENCES 1.
2. 3.
7. 8.
10. 11. 12. 13.
Austsalasian Radiolog!. Vn1.36. No. 1. Fehruar?. 1992
Abiri MM, Kirpekar M, Ablow RC. Osteomyelitis: detection with ultrasound (work in progress). Radiology 1988; 169 :795-797. Abiri MM, Kirpekar M, Ablow RC. Osteomyelitis: detection with ultrasound. Radiology 1989; 172 : 509-51 1. David R, Barron BJ. Madewell JE. Skeletal infections: acute osteomyelitis Rad. Clin. North America 1987; 25.6 : 1171-1202. Gilday DL. Problems in scintigraphic detection of osteomyelitis, Radiology 1980; 135 : 791. Gillespie WWJ, Nade S. Musculoskeletal infections, Melbourne: Blackwell Scientific Publications 1987; 152-153. Green NE. Edwards K. Bone and joint infections in children. Orthopaedic clinics of North America 1987; Vol. 18. No. 4 : 555576. Herman G, Rose JS. Computed tomography in bone and soft-tissues: pathology of extremities. J. Comput. Assisted Tcmiogr 1974; 3 : 5866. Kuhn JP, Berger PE. Computed tomographic diagnosis of osteomyelitis. Radiology 1979; 130 :503-505. Murray IPC. Bone scanning in child and young adult. Skeletal Radiology; 1980 5 :65-76. Raffi M, Firoomia H, Golibu C et al. Hematogemus osteomyelitis with fat-fluid level shown by CT.Radiology 1984; 153 : 493494. Ram PC, Martinez S , Korobkin M et al. CT detection of intraosseous gas: a new sign. AM Jour Roent 1987; 137 : 721-723. Shiv VK, Jain AK, Taneja K, Bhargava SK. Somgraphy of hip joint in infective arthritis. Journal of Canadian Association of Radiologists 1990.41 : 77-79. Yeh HC, Rabinowitz JG. Uluasonography of extremities and pelvic girdle and correlation with computed tomography. Radiology 1982: 143 : 519-525.
79
