(BQ) Part 2 book "Bone and joint imaging" presents the following contents: Infectious diseases, traumatic diseases, internal derangement of joints, thermal, iatrogenic, nutritional, and neurogenic diseases, tumors and tumor like diseases, congenital diseases, diseases of soft tissue and muscle,...
Infectious Diseases XIV SECTION CHAPTER 53 Osteomyelitis, Septic Arthritis, and Soft Tissue Infection: Mechanisms and Situations SUMMARY OF KEY FEATURES A thorough understanding of regional anatomy is fundamental to the accurate interpretation of clinical, radiographic, and pathologic characteristics of infections of bone, joint, and soft tissue In most persons with such infections, a specific mechanism of contamination can be recognized; infection may be derived from hematogenous seeding, spread from a contiguous source, direct implantation, or operative contamination The radiographic findings of osteomyelitis (including abscess, involucrum, and sequestration), septic arthritis (including joint space loss and marginal and central osseous erosions), and soft tissue suppuration (including swelling, radiolucent streaks, and periostitis) are generally delayed for a variable period after the clinical onset of infection Other diagnostic techniques, including scintigraphy and magnetic resonance imaging, allow an accurate diagnosis at an earlier stage of the process INTRODUCTION Infection of bone, joint, and soft tissue is a common and disturbing problem that often represents a diagnostic and therapeutic challenge Early diagnosis is imperative because it allows prompt treatment, which can prevent many of the dreaded complications TERMINOLOGY Ostemyelitis implies an infection of bone and marrow It most commonly results from bacterial infections, although fungi, parasites, and viruses can infect the bone and the marrow Infective (suppurative) osteitis indicates contamination of the bone cortex Infective osteitis can occur as an isolated phenomenon or, more frequently, as a concomitant to osteomyelitis Infective (suppurative) periostitis implies contamination of the periosteal cloak that surrounds the bone In this situation, a subperiosteal accumulation of organisms frequently leads to infective osteitis and osteomyelitis Soft tissue infection indicates contamination of cutaneous, subcutaneous, muscular, fascial, tendinous, ligamentous, or bursal structures This may be seen as an isolated condition or as a complication of periosteal, osseous, marrow, or articular infection Articular infection implies a septic process of the joint itself Septic arthritis can occur as an isolated condition that may soon spread to the neighboring bone or as a complication of adjacent osteomyelitis or soft tissue infection A sequestrum represents a segment of necrotic bone that is separated from living bone by granulation tissue Sequestra may reside in the marrow for protracted periods, harboring living organisms that have the capability of evoking an acute flare-up of the infection An involucrum denotes a layer of living bone that has formed about the dead bone It can surround and eventually merge with the parent bone Cloaca is an opening in the involucrum through which granulation tissue and sequestra can be discharged Sinuses are tracts leading to the skin surface from the bone A bone abscess (Brodie’s abscess) is a sharply delineated focus of infection It is of variable size, can occur at single or multiple locations, and represents a site of active infection It is lined by granulation tissue and frequently is surrounded by eburnated bone Garré’s sclerosing osteomyelitis is a sclerotic, nonpurulent form of osteomyelitis Although this term is applied carelessly to any form of osteomyelitis with severe osseous eburnation, it should be reserved for those cases in which intense proliferation of the periosteum leads to bony deposition and in which no necrosis or purulent exudate and little granulation tissue are present The clinical stages of osteomyelitis are frequently designated acute, subacute, and chronic This does not imply that definitive divisions exist between one stage and another, nor does it signify that all cases of osteomyelitis progress through each of these phases The relatively abrupt onset of clinical symptoms and signs during the initial stage of infection is a clear indication of the acute osteomyelitic phase; if this acute phase passes without complete elimination of infection, subacute or chronic osteomyelitis can become apparent The transition from acute to subacute and chronic osteomyelitis may indicate that therapeutic measures have been inadequate OSTEOMYELITIS Routes of Contamination Osseous (and articular) structures can be contaminated by four principal routes: Hematogenous spread of infection Infection can reach the bone (or joint) via the bloodstream Spread from a contiguous source of infection Infection can extend into the bone (or joint) from an adjacent contaminated site Cutaneous, sinus, and dental infections are three important sources of extraskeletal infective foci 713 714 Section XIV Infectious Diseases Direct implantation Direct implantation of infectious material into the bone (or joint) may occur following puncture or penetrating injuries Postoperative infection Postoperative infection may occur via direct implantation, spread from a contiguous septic focus, or hematogenous contamination of the bone (or joint) Hematogenous Infection Bacteremia Bacteria usually enter the blood vessels (or the lymphatics and then the blood vessels) by direct extension from extravascular sites of infection, which include the genitourinary, gastrointestinal, biliary, and respiratory systems; the skin and soft tissue; and other structures In some instances, no primary source of infection is identifiable Bacteremia is often transient and totally asymptomatic; however, in some cases, prominent clinical manifestations may occur A single pathogenic organism is usually responsible for hematogenous osteomyelitis In neonates and infants, Staphylococcus aureus, group B streptococcus, and Escherichia coli are the bone isolates recovered most frequently In children older than year of age, S aureus, Streptococcus pyogenes, and Haemophilus influenzae are responsible for most cases of hematogenous osteomyelitis In those older than years, staphylococci are the major pathogens in this disease, as the prevalence of osteomyelitis related to H influenzae decreases Gram-negative organisms assume importance as pathogens in bone and joint infections in adults and in intravenous drug abusers A recent surgical procedure or concurrent soft tissue infection is frequently associated with staphylococcal septicemia and osteomyelitis; disorders of the gastrointestinal or genitourinary tract may initiate a gram-negative septicemia; and an acute or chronic respiratory infection is important in the pathogenesis of tuberculous, fungal, and pneumococcal osteomyelitis Blood cultures are positive in approximately 50% of patients with acute hematogenous osteomyelitis General Clinical Features Childhood osteomyelitis can be associated with a sudden onset of high fever, a toxic state, and local signs of inflammation, although this presentation is not uniform Indeed, as many as 50% of children have vague complaints, including local pain of to months’ duration with minimal if any temperature elevation In infants, hematogenous osteomyelitis often leads to less dramatic findings, including pain, swelling, and an unwillingness to move the affected bones The adult form of hematogenous osteomyelitis may have a more insidious onset, with a relatively longer period between the appearance of symptoms and signs and accurate diagnosis In all age groups, the prior administration of antibiotics for treatment of the febrile state can attenuate or alter the clinical (and imaging) manifestations of the bone infection Single or multiple bones can be infected; involvement of multiple osseous sites appears to be particularly common in infants In the younger age group, the long tubular bones of the extremities are especially vulnerable; in adults, hematogenous osteomyelitis is encountered more frequently in the axial skeleton Vascular Anatomy The vascular supply of a tubular bone is derived from several points of arterial inflow, which become complicated sinusoidal networks within the bone (Fig 53–1) One or two diaphyseal nutrient arteries pierce the cortex and divide into ascending and descending branches As they extend to the ends of the bones, they branch repeatedly, becoming finer channels, and are joined by the terminals of metaphyseal and epiphyseal arteries The metaphyseal arteries originate from neighboring systemic vessels, whereas the epiphyseal arteries arise from periarticular vascular arcades The arteries within the bone marrow form a series of cortical branches that connect with the fenestrated capillaries of the haversian systems At the bony surface, the cortical capillaries form connections with overlying periosteal plexuses, which themselves are derived from the arteries of the neighboring muscles and soft tissues The cortices of the tubular bones derive nutrition from both the periosteal and the medullary circulatory systems The central arterioles drain into a thin-walled venous sinus, which subsequently unites with veins that retrace the course of the nutrient arteries, piercing the cortex at various points and joining larger and larger venous channels Joints receive blood vessels from periarterial plexuses that pierce the capsule to form a vascular plexus in the deeper part of the synovial membrane The blood vessels of the synovial membrane terminate at the articular margins as looped anastomoses (circulus articularis vasculosus) The epiphysis and the adjacent synovium share a common blood supply The radiographic and pathologic features of osteomyelitis differ in children, infants, and adults, related in large part to peculiarities of the vascular anatomy of the tubular bones in each age group (Fig 53–2; Table 53–1) Childhood Pattern Between the age of approximately year and the time when the open cartilaginous growth plates fuse, a childhood vascular pattern can be recognized in the ends of the tubular bones (see Fig 53–2A) In the metaphysis, the vessels turn in acute loops to join large sinusoidal veins, which occupy the intramedullary portion of the metaphysis; here, the blood flow is slow and turbulent The epiphyseal blood supply is distinct from that on the metaphyseal aspect of the plate This anatomic characteristic explains the peculiar predilection of hematogenous osteomyelitis to affect metaphyses and equivalent locations in children Infantile Pattern A fetal vascular arrangement may persist in some tubular bones up to the age of year (see Fig 53–2B) Some vessels at the surface of the metaphysis penetrate the preexisting growth plate, ramifying in the epiphysis This arrangement affords a vascular connection between the metaphysis and epiphysis and explains the frequency of epiphyseal and articular infection in infants 715 Chapter 53 Osteomyelitis, Septic Arthritis, and Soft Tissue Infection: Mechanisms and Situations A C B Figure 53–2 Normal vascular patterns of tubular bone, based on age A, In the child, the capillaries of the metaphysis turn sharply, without violating the open growth plate B, In the infant, some metaphyseal vessels may penetrate or extend around the open growth plate, ramifying in the epiphysis C, In the adult, with closure of the growth plate, a vascular connection between the metaphysis and epiphysis can be recognized Adult Pattern With narrowing and closing of the physeal growth plate, metaphyseal vessels progressively reestablish a vascular connection between the metaphysis and the epiphysis (see Fig 53–2C) Blood within the nutrient vessels can then reach the surface of the epiphysis through large anastomosing channels Age-Related Patterns The development of hematogenous osteomyelitis varies according to age-related characteristics of the bones (Fig 53–3; Table 53–2) Childhood In childhood hematogenous osteomyelitis, the metaphyseal location is related to (1) the peculiar anatomy of the vascular tree, (2) the inability of vessels to penetrate the open physeal plate, (3) the slow rate of blood flow in this region, (4) a decrease in phagocytic ability of neighboring macrophages, or (5) secondary thrombosis of the nutrient artery Primary involvement of an epiphysis or secondary extension across the physis to an epiphysis is encountered rarely Inflammation in the adjacent bone of the metaphysis is characterized by vascular engorgement, edema, cellular response, and abscess formation Transudates extend from Figure 53–1 Normal osseous circulation to a growing tubular bone Nutrient arteries (1) pierce the diaphyseal cortex and divide into descending and ascending (2) branches These latter vessels continue to divide, becoming fine channels (3) as they approach the end of the bone They are joined by metaphyseal vessels (4) and, in the subepiphyseal (growth) plate region, form a series of end-arterial loops (5) The venous sinuses extend from the metaphyseal region toward the diaphysis, uniting with other venous structures (6) and eventually piercing the cortex as a large venous channel (7) At the ends of the bone, nutrient arteries of the epiphysis (8) branch into finer structures, passing into the subchondral region At this site, arterial loops (9) are again evident, some of which pierce the subchondral bone plate before turning to enter the venous sinusoid and venous channels of the epiphysis (10) At the bony surface, cortical capillaries (11) form connections with overlying periosteal plexuses (12) Note that in the growing child, distinct epiphyseal and metaphyseal arteries can be distinguished on either side of the cartilaginous growth plate Anastomoses between these vessels either not occur or are infrequent TABLE 53–1 Vascular Patterns of Tubular Bones Pattern Age (yr) Characteristics Infantile 0–1* Childhood 1–16† Adult >16 Diaphyseal and metaphyseal vessels may perforate open growth plate Diaphyseal and metaphyseal vessels not penetrate open growth plate Diaphyseal and metaphyseal vessels penetrate closed growth plate *Upper age limit depends on specific local anatomic variation in the appearance and growth of the ossification center † Upper age limit is related to the time at which the open growth plate closes 716 Section XIV Infectious Diseases periosteum produces single or multiple layers of bone (i.e., periostitis) and eventually lays down bone in the form of an involucrum Infection may penetrate the periosteal membrane, producing cloacae (Fig 53–4) Childhood hematogenous osteomyelitis is not confined to tubular bones In flat or irregular bones such as the calcaneus, clavicle, and bones of the pelvis, childhood osteomyelitis may show a predilection for metaphysealequivalent osseous locations adjacent to an apophyseal cartilaginous plate and epiphyseal-equivalent locations adjacent to articular cartilage B A C Figure 53–3 Sites of hematogenous osteomyelitis of tubular bone, based on age A, In the child, a metaphyseal focus is frequent From this site, cortical penetration can result in a subperiosteal abscess in locations where the growth plate is extra-articular (1) or in a septic joint in locations where the growth plate is intra-articular (2) B, In the infant, a metaphyseal focus may be complicated by epiphyseal extension, owing to the vascular anatomy in this age group C, In the adult, a subchondral focus in an epiphysis is not unusual, owing to the vascular anatomy in this age group the marrow to the adjacent cortex A rise in intramedullary pressure, caused by the presence of inflammatory and edematous tissue confined by the rigid cortical columns of bone, encourages the extension of infected fluid by way of haversian and Volkmann’s canals The inflammatory process soon reaches the outer surface of the cortex and abscesses develop, lifting the periosteum and disrupting the periosteal blood supply to the external cortical surface Elevation of the periosteum is prominent in the immature skeleton because of its relatively loose attachment to the subjacent bone The elevated Infancy In infants, because some of the vessels in the metaphysis penetrate the growth plate, a suppurative process of the metaphysis may extend into the epiphysis (Fig 53–5) Epiphyseal infection can then result in articular contamination and damage to the cells on the epiphyseal side of the growth cartilage, leading to arrest or disorganization of growth and maturation Articular involvement is also facilitated by the frequent localization of infantile osteomyelitis to the ends of bones in which the growth plate is intra-articular (e.g., hip) Adulthood Unique manifestations of hematogenous osteomyelitis are seen in adults (see Table 53–2) The disease in the mature skeleton does not commonly localize in the tubular bones; hematogenous osteomyelitis of the spine, pelvis, and small bones is more common in adult patients In cases in which involvement of tubular bones is evident, the free communication of the metaphyseal and epiphyseal vessels through the closed growth plate allows infection to localize in the subchondral (beneath the articular cartilage) regions of the bone (Fig 53–6) Joint contamination can complicate this epiphyseal location The firm attachment of the periosteum to the cortex in adults resists displacement; therefore, subperiosteal abscess formation, extensive periostitis, and involucrum formation are relatively unusual in this age group Extensive sequestration is not a common feature In adults, infection violates and disrupts the cortex itself, producing atrophy and osseous weakening, and predisposes the bone to pathologic fracture TABLE 53–2 Hematogenous Osteomyelitis of Tubular Bones Aspect Infant Child Adult Localization Metaphyseal with epiphyseal extension Common Common Common Common Not common Not common Metaphyseal Epiphyseal Common Common Not common Common Not common Variable Not common Not common Common Not common Common* Common Involucrum Sequestrum Joint involvement Soft tissue abscess Pathologic fracture Sinus tracts *In neglected cases Chapter 53 Osteomyelitis, Septic Arthritis, and Soft Tissue Infection: Mechanisms and Situations 717 Figure 53–4 Hematogenous osteomyelitis of tubular bone in a child A, Sequential steps in the initiation and progression of infection: 1, a metaphyseal focus is common; 2, the infection spreads laterally, reaching and invading the cortical bone; 3, cortical penetration is associated with subperiosteal extension and elevation of the periosteal membrane; 4, subperiosteal bone formation leads to an involucrum or shell of new bone; 5, the involucrum may become massive with continued infection B, Lytic metaphyseal focus in the femur is readily apparent It extends to the growth cartilage (causative organism is Staphylococcus) A B 718 Section XIV Infectious Diseases Figure 53–5 Hematogenous osteomyelitis of tubular bone in an infant In this infant with acute staphylococcal osteomyelitis, metaphyseal and epiphyseal involvement of the distal end of the femur is associated with periostitis and articular involvement Radiographic and Pathologic Abnormalities Acute Hematogenous Osteomyelitis The pathologic changes associated with acute hematogenous pyogenic osteomyelitis are described in Table 53–3 Radiographic evidence of significant osseous destruction is delayed for a period of days to weeks Nevertheless, initial and subtle radiographic changes in the soft tissues may appear within days after bacterial contamination of bone, although radiographically evident bone destruction and periostitis can be delayed for to weeks Eventually, large destructive lesions become evident on the radiograph In children, these lesions appear as enlarging, poorly defined lucent shadows of the metaphysis, surrounded by varying amounts of eburnation; the lucent lesions extend to the growth plate and, on rare occasions, may violate it In addition, destruction progresses horizontally, reaching the cortex, and periostitis follows In infants, the epiphyses are unossified or only partially ossified, making radiographic recognition of epiphyseal destruction extremely difficult Metaphyseal lucent lesions, periostitis, and joint effusion are helpful radiographic clues In adults, soft tissue alterations are more difficult to detect on radiographic examination Epiphyseal, metaphyseal, and diaphyseal osseous destruction creates radiolucent areas of varying size, which are associated with mild periostitis Cortical resorption can be identified as Figure 53–6 Hematogenous osteomyelitis of tubular bone in an adult Epiphyseal localization is not infrequent in this age group Observe the lytic lesion (abscess), with surrounding sclerosis extending to the subchondral bone plate (arrows) Metaphyseal and diaphyseal sclerosis is evident The elongated shape of the lesion is typical of infection (causative organism is Staphylococcus) endosteal scalloping, intracortical lucent regions or tunneling, and poorly defined subperiosteal bony defects Subacute and Chronic Hematogenous Osteomyelitis Brodie’s Abscess Single or multiple radiolucent abscesses may be evident during subacute or chronic stages of osteomyelitis These abscesses are now defined as circumscribed lesions showing a predilection for (but not confined to) the ends of tubular bones; they are found characteristically in subacute pyogenic osteomyelitis and are usually of staphylococcal origin It has been suggested that bone abscesses develop when an infective organism has a reduced virulence or when the host demonstrates increased resistance to infection Brodie’s abscesses are especially common in children, more typically in boys In this age group, they appear in the metaphysis, particularly that of the distal or proximal portion of the tibia In young children and infants, Brodie’s abscesses may occur in epiphyses Radiographs outline radiolucent areas with adjacent sclerosis (Fig 53–7) This lucent region is commonly located in the metaphysis, where it may connect with the Chapter 53 Osteomyelitis, Septic Arthritis, and Soft Tissue Infection: Mechanisms and Situations 719 TABLE 53–3 Hematogenous Osteomyelitis: Radiographic-Pathologic Correlation Pathologic Abnormality Radiographic Abnormality Vascular changes and edema of soft tissues Infection in medullary space with hyperemia, edema, abscess formation, and trabecular destruction Infection in haversian and Volkmann’s canals of cortex Subperiosteal abscess formation with lifting of the periosteum and bone formation Infectious penetration of periosteum with soft tissue abscess formation Localized cortical and medullary abscesses Soft tissue swelling with obliteration of tissue planes Osteoporosis, bone lysis Deprivation of blood supply to cortex due to thrombosis of metaphyseal vessels and interruption of periosteal vessels, cortical necrosis External migration of dead pieces of cortex with breakdown of skin and subcutaneous tissue Increasing lysis, cortical lucency Periostitis, involucrum formation Soft tissue swelling, mass formation, obliteration of tissue planes Single or multiple radiolucent cortical or medullary lesions with surrounding sclerosis Sequestration Figure 53–7 Brodie’s abscess: radiographic abnormalities Sinus tracts Lateral radiograph outlines a typical appearance of an abscess of the distal end of the tibia caused by staphylococci Observe the elongated radiolucent lesion, with surrounding sclerosis extending to the closing growth plate (arrows) The channellike shape of the lesion is important in the accurate diagnosis of this condition growth plate by a tortuous channel Radiographic detection of this channel is important; identification of a metaphyseal defect connected to the growth plate by such a tract ensures the diagnosis of osteomyelitis In the diaphysis, the radiolucent abscess cavity may be located in central or subcortical areas of the spongiosa or in the cortex itself and may contain a central sequestrum In an epiphysis, a circular, well-defined osteolytic lesion is seen, which, in the immature skeleton, may border on the chondro-osseous junction or on the physis, where it may extend into the metaphysis When an abscess is located in the cortex, its radiographic appearance, consisting of a lucent lesion with surrounding sclerosis and periostitis, simulates that of an osteoid osteoma or stress fracture A rounded radiolucent lesion without calcification is characteristic of a cortical abscess; a circular lucent area with or without calcification that is smaller than cm is more typical of an osteoid osteoma; and a linear lucent shadow without calcification is characteristic of a stress fracture In any skeletal location, computed tomography (CT) or magnetic resonance (MR) imaging can be used to better assess the extent of the abscess and any signs of its reactivation (Fig 53–8) One or more areas of osseous necrosis are commonly situated in the medullary aspect of a tubular bone (sequestration is less prominent in flat bones), where they create radiodense bony spicules (Fig 53–9) The sequestrum frequently is marginated sharply, surrounded by granulation tissue Sequestra may extrude through cortical breaks, extending into the adjacent soft tissues, where they eventually may be discharged through draining sinuses Sequestration During the course of hematogenous osteomyelitis, cortical sequestration may become evident In most cases of osteomyelitis and septic arthritis arising from such a contiguous source, soft tissue infections are Sclerosing Osteomyelitis In the subacute and chronic stages of osteomyelitis, considerable periosteal bone formation can surround the altered cortex, and an increased number and size of spongy trabeculae can reappear in the affected marrow, leading to considerable radiodensity and contour irregularity of the affected bone (Fig 53–10) Cystic changes may occur within the sclerotic area, but sequestra are uncommon At any site, the radiographic findings of sclerosing osteomyelitis resemble those of osteoid osteoma, fibrous dysplasia, and Ewing’s sarcoma Infection from a Contiguous Source General Clinical Features 720 Section XIV Infectious Diseases Figure 53–8 Brodie’s abscess: radiographic abnormalities Tibial metaphyseal involvement in a 19-year-old woman Routine radiograph shows a metaphyseal radiolucent lesion (arrow) with a medial channel (arrowheads) (Courtesy of M Mitchell, MD, Halifax, Nova Scotia, Canada.) implicated The importance of osteomyelitis of the mandible and maxilla in persons with poor dental hygiene and of the frontal portion of the skull and face in persons with chronic sinusitis is undeniable Soft tissue infections that lead to bone and joint contamination are frequent after trauma, animal and human bites, puncture wounds, irradiation, burns, and decubitus or pressure ulcers in paralyzed or immobilized patients A General Radiographic and Pathologic Features Whereas the direction of contamination in hematogenous osteomyelitis is from the bone outward into the soft tissue, the direction of contamination in osteomyelitis resulting from adjacent sepsis is from the soft tissues inward into the bone (or joint) (Table 53–4; Fig 53–11) Periosteal bone formation is commonly the initial radiographic manifestation of osteomyelitis After traumatic initiation of soft tissue infection, periostitis may appear early in response to injury and may not reflect actual bone infection With further accumulation of pus, subperiosteal resorption of bone and cortical disruption ensue As infection gains access to the spongiosa, it may spread in the marrow, producing lytic osseous defects on the radiograph Specific Locations Hand Three distinct routes are available to organisms that become lodged in the soft tissues of the hand; infection may disseminate via tendon sheaths, fascial planes, or lymphatics (Fig 53–12) Infective digital tenosynovitis can result from a puncture wound, particularly in a flexor crease of the finger, where skin and sheath are intimately related A sheath infection may perforate into an adjacent bone or joint in the finger; the most characteristic site of such extension is the proximal interphalangeal articulations and adjacent middle phalanx (Fig 53–13) The B Figure 53–9 Chronic osteomyelitis: sequestration A, In this radiograph of a femur, chronic osteomyelitis is associated with several radiodense, sharply marginated foci (arrows) within lucent cavities that contain granulation tissue B, CT scanning identifies sequestered bone (arrow) metacarpophalangeal joints are altered less commonly Such tenosynovitis causes exquisite tenderness over the course of the sheath, a semiflexed position of the finger, severe pain on extension of the finger, and fusiform swelling of the digit Infections in the fascial planes of the hand are numerous but result in joint or bone alterations less frequently than those in the synovial sheaths Lymphangitis may result from superficial injuries In intense cases, complications may include tenosynovitis, septicemia, osteomyelitis, and septic arthritis Chapter 53 Osteomyelitis, Septic Arthritis, and Soft Tissue Infection: Mechanisms and Situations Figure 53–10 Chronic sclerosing osteomyelitis Chronic osteomyelitis can be associated with considerable new bone formation In this patient, a cortical abscess contains a sequestrum (arrow) and is surrounded by sclerosis (arrowheads) The appearance is reminiscent of that of an osteoid osteoma 721 Foot The plantar aspect of the foot is especially vulnerable to soft tissue infection Foreign bodies, puncture wounds, or skin ulceration from weight bearing can represent the portal of entry for various organisms In a diabetic patient, soft tissue breakdown over certain pressure points (e.g., metatarsal heads, calcaneus) leads to infection that is combined with vascular and neurologic abnormalities Puncture wounds of the plantar aspect of the foot can lead to osteomyelitis and septic arthritis (Fig 53–16) The infective organisms can vary, but gram-negative agents such as Pseudomonas aeruginosa are frequently implicated; this is not surprising, because these organisms are usually found in the soil and may be normal inhabitants of skin Typically, local pain and swelling appear within days after a puncture wound, although radiographs usually are normal at this time After a delay of to weeks, the radiographs reveal typical abnormalities of osteomyelitis or septic arthritis Osteomyelitis of the os calcis is a recognized complication of repeated heel punctures in neonates The clinical, radiographic, and pathologic characteristics of osteomyelitis (and septic arthritis) complicating foot infections in diabetic patients are modified by the associated problems of these persons, including vascular insufficiency and neurologic deficit The radiographic picture usually reveals significant soft tissue swelling and mottled osteolysis (Fig 53–17) Osteosclerosis, fragmentation, periostitis, and soft tissue gas may be seen In some diabetic patients with foot infections complicated by osteomyelitis, findings can simulate those of diabetic neuropathic osteoarthropathy, and differentiation of neurologic and infectious processes can be difficult In fact, both infection and neuropathic osteoarthropathy of the midfoot and forefoot frequently coexist in diabetic patients Pelvis Soft tissue breakdown that occurs in debilitated persons who maintain a single position for long periods is referred to as a pressure sore, decubitus ulcer, or bedsore Although other sites (e.g., heels) may be affected, most pressure sores develop about the pelvis, TABLE 53–4 Figure 53–11 Diagrammatic representation of the sequential steps of osteomyelitis resulting from a contiguous contaminated source 1, Initially, a soft tissue focus of infection is apparent Occasionally, such a focus can irritate the underlying bone, producing periostitis without definite invasion of the cortex 2, The infection subsequently invades the cortex, spreading via haversian and Volkmann’s canals 3, Finally, the medullary bone and marrow spaces are affected A felon results from infection in the terminal pulp space Bone involvement is not infrequent in neglected cases because of the close proximity of the terminal phalanx (Fig 53–14) Subcuticular abscesses of the nail fold are termed paronychia On rare occasions, osseous destruction of a terminal phalanx may be evident (Fig 53–15) Osteomyelitis Due to Spread from a Contiguous Source of Infection: Radiographic-Pathologic Correlation Pathologic Abnormality Radiographic Abnormality Soft tissue contamination and abscess formation Soft tissue swelling, mass formation, obliteration of tissue planes Periostitis Infectious invasion of the periosteum with lifting of the membrane and bone formation Subperiosteal abscess formation and cortical invasion Infection in haversian and Volkmann’s canals of cortex Contamination and spread in marrow Cortical erosion Cortical lucency and destruction Bone lysis 722 Section XIV Infectious Diseases Figure 53–12 Spread of infection in the hand: available anatomic pathways A, Drawing demonstrates the relationships of the tendon sheaths, bursae, and fascial planes (thenar space, midpalmar space) B, Drawing of a section through the metacarpal bones outlines two spaces—the midpalmar and thenar spaces— separated by a septum and located above the digital flexor tendon sheaths Note the close relationship between the sheath of the index finger and the thenar space and between the sheaths of the third, fourth, and fifth fingers and the midpalmar space (From Resnick D: Osteomyelitis and septic arthritis complicating hand injuries and infections: Pathogenesis of roentgenographic abnormalities J Can Assoc Radiol 27:21, 1976.) especially near the sacrum, ischial tuberosities, trochanteric regions, and buttocks Local soft tissue infection and bacteremia are commonly associated with decubitus ulcers Osteomyelitis is observed most commonly in the Figure 53–13 Spread of infection in the hand: digital flexor tenosynovitis After a neglected puncture wound, a 45-year-old woman developed tenosynovitis and osteomyelitis Note the soft tissue swelling, particularly along the volar surface of the proximal phalanx (open arrow); the semiflexed position of the finger; and extensive permeative osseous destruction, with pathologic fracture (solid arrow) of the proximal phalanx (From Resnick D: Osteomyelitis and septic arthritis complicating hand injuries and infections: Pathogenesis of roentgenographic abnormalities J Can Assoc Radiol 27:21, 1976.) innominate bones and proximal portions of the femora, areas subjacent to sites of skin breakdown, and is related to spread from a contiguous contaminated source The accurate diagnosis of osteomyelitis complicating pressure sores is difficult, owing to a number of other conditions that may become evident in immobilized or paralyzed patients Pressure-related changes in bone are not infrequent, leading to flattening and sclerosis of bony Figure 53–14 Spread of infection in the hand: felon An infection in the pulp space has produced considerable soft tissue swelling (open arrows) Extension into the tuft and diaphysis of the terminal phalanx is apparent (solid arrows) Shrapnel from a previous injury can be seen (From Resnick D: Osteomyelitis and septic arthritis complicating hand injuries and infections: Pathogenesis of roentgenographic abnormalities J Can Assoc Radiol 27:21, 1976.) 1442 Section XXII Miscellaneous Diseases TABLE 82–6 SAPHO Syndrome Disorder Typical Age at Onset Pustulosis Palmaris et Plantaris Anterior Chest Wall Involvement Chronic recurrent multifocal osteomyelitis Sternocostoclavicular hyperostosis Pustulotic arthro-osteitis First decades of life Evident in