Version May 2024
INTRODUCTION — Infections of the bones and joints of the pelvis may arise hematogenously, secondary to trauma or surgery via direct inoculation of pathogens into bone, or via contiguous spread of infection from soft tissues within or outside the bony walls of the pelvis. These infections may manifest as pelvic osteomyelitis or septic arthritis with contiguous spread to the adjacent bony margins.
Issues related to pelvic osteomyelitis and septic arthritis of the two principle joints of the pelvis (the pubic symphysis and sacroiliac joint) will be reviewed here.
General issues related to the pathogenesis and classification of osteomyelitis and the clinical features of other types of osteomyelitis are discussed separately. (See "Nonvertebral osteomyelitis in adults: Clinical manifestations and diagnosis" and "Pathogenesis of osteomyelitis" and "Osteomyelitis associated with open fractures in adults".)
Nonsuppurative processes involving the sacroiliac joint are discussed separately. (See "Clinical manifestations of axial spondyloarthritis (ankylosing spondylitis and nonradiographic axial spondyloarthritis) in adults" and "Clinical manifestations and diagnosis of arthritis associated with inflammatory bowel disease and other gastrointestinal diseases".)
Clinical manifestations of osteomyelitis and septic arthritis are discussed separately. (See "Nonvertebral osteomyelitis in adults: Clinical manifestations and diagnosis" and "Septic arthritis in adults".)
EPIDEMIOLOGY — Among the bones within the pelvis, ischium is the bone most commonly associated with osteomyelitis.
Predisposing factors for pelvic osteomyelitis and pelvic septic arthritis include [1-6]:
●Bacteremia due to Staphylococcus aureus
●Bacteremia related to infection of intravascular catheters or other implanted devices
●Trauma (including athletic injuries, open fractures, and/or or instrumentation of the pelvic bones)
●Pressure ulcer(s) of the sacrum
●Obstetrical injuries or abortion
●Injection drug use
●Urogynecologic surgery, particularly involving procedures such as bladder suspension involving placement of bone anchors
●Other pelvic surgical procedures, including prostatectomy or transrectal prostate biopsy [7]
●Cardiac catheterization, especially when performed via the inguinal/femoral site
●Pelvic radiation, especially if complicated by osteoradionecrosis
●Spinal or anal surgery
●Epidural anesthesia
These risk factors may predispose to infection at one or several bony sites in the pelvis. As an example, pressure ulcers predominantly predispose to infections of the sacrum and adjacent portions of the ilium. Injection drug use, cardiac catheterization, and bacteremia have a propensity to cause infections of the pubis. Pelvic or urologic surgery can result in infection of the pubis as well as other sites such as the sacroiliac joint.
Rarely, infection arises spontaneously without an identifiable cause; such cases are likely complications of bacteremia that developed from an unrecognized site or event [8]. In some circumstances, it may be impossible to determine if trauma alone or trauma plus an incidental bacteremia led to the subsequent infection.
ANATOMY — The pelvic walls contain bone, ligaments, and muscles (figure 1). The bony pelvis consists of two hip bones (os coxae) that are joined in front by the pubic symphysis. The os coxae articulate posteriorly with the sacrum. The hip (coxal) bones consist of the ilium, the ischium, and the pubis. Both the pubis and ischium are further divided into their respective bodies and rami. The os coxae have been likened to a propeller with two oppositely bent blades with a central shaft (the acetabulum).
The pelvis contains two joints: the sacroiliac joint and the symphysis pubis. The sacroiliac joint is part synovial (one-third) and part cartilage (two-thirds); the symphysis pubis consists of cartilaginous layers on either side of an interpubic disk consisting of fibrocartilage. Fibrous ligaments such as the iliolumbar ligament further stabilize the bony pelvis.
The microanatomy of the blood supply of the symphysis pubis is controversial; there is evidence that blood vessels penetrate the dense connective tissue in rim of the fibrocartilage as well as the contiguous bones of the os coxae [9].
MICROBIOLOGY — Pathogens responsible for pelvic osteomyelitis vary depending on the pathogenesis of the infection. Hematogenous infections are commonly due to S. aureus (including methicillin-resistant S. aureus) [10], but almost any pathogen capable of causing primary or secondary bacteremia can cause a hematogenous infection in the bony pelvis [11]. Intravenous drug abusers who develop pubic osteomyelitis or septic sacroiliitis appear to have a higher propensity to have Pseudomonas aeruginosa as a causative pathogen [12]. Postoperative pelvic osteomyelitis infections and infections secondary to decubitus ulcers are commonly mixed infections due to bowel or perineal flora [13].
CLINICAL MANIFESTATIONS
Overview — Patients with acute sacroiliitis or pubic osteomyelitis may have fever and severe pain; however, many bony infections of the pelvis present subacutely with or without associated fever. Physical examination may be useful when predisposing causes such as pressure ulcers are present and patients have localized pain and tenderness over discrete sites such as the symphysis pubis or sacroiliac joints and inguinal region. In other cases, pain may be poorly localized or accompanied by other confusing symptoms such as antalgic gait, limp, hip or buttock pain, or inability to bear weight [14]. In patients with spinal cord injury, pain may be absent.
Several clinical aspects of pelvic osteomyelitis and septic arthritis warrant special emphasis [11,13,15-18]:
●There may be a long interval between a precipitating cause (such as trauma or surgery) and the onset of pelvic osteomyelitis, and fever may be absent. These factors may contribute to diagnostic delay.
●Patients with pubic osteomyelitis initially develop an infection of the pubic symphysis that later produces osteomyelitis in adjacent pubic rami. Such patients characteristically have severe pelvic pain associated with point tenderness overlying the symphysis pubis. They usually also have difficulty walking and manifest a characteristic wide-based waddling gait.
●Patients with pyogenic sacroiliitis and secondary pelvic osteomyelitis may have vague poorly localized pain or pain in the buttock or hip. However, focal tenderness on exam is usually present with pressure or percussion over the sacroiliac region [19].
●Patients with pelvic osteomyelitis may develop abscesses in soft tissues adjacent to the bony pelvis or infection may dissect into areas that are quite distant from the site of bony involvement. For example, pubic osteomyelitis can lead to bilateral abscesses in the adductor muscles of the thigh [17].
Osteitis pubis — Osteitis pubis is an idiopathic postoperative complication of suprapubic cystotomy. Patients with this condition have bony destruction of the margins of the symphysis pubis, severe pelvic pain, and a characteristic wide-based waddling gait [20]. Osteitis pubis has been recognized as a complication of a wide range of urologic and gynecologic surgical procedures. It has been described in association with pregnancy, hernia repairs, pyelonephritis, and presumed trauma in athletes [10,13]. Sinus tracts, a characteristic manifestation of osteomyelitis, have been described in some patients. Fever is usually absent.
The pathogenesis of osteitis pubis is uncertain. Possible etiologies include infection, mechanical trauma to the symphysis, local vascular damage, or reflex sympathetic dystrophy. Some experts believe that all cases of osteitis pubis are secondary to infection (eg, that osteitis pubis is synonymous with pubic osteomyelitis) [13]. Others believe that pubic osteomyelitis and osteitis pubis are separate conditions (ie, that osteitis pubis is not an infectious disease) [21]. Even though this controversy remains unresolved, the possibility of infection (osteomyelitis) should be carefully assessed in every patient with presumed osteitis pubis. (See "Osteitis pubis".)
Sacral osteomyelitis — Most commonly, sacral osteomyelitis arises from contiguous spread of infection from deep (stage IV) pressure ulcers. It may also arise as a complication of open or laparoscopic pelvic surgery [22,23], following pelvic radiation, spinal or anal surgery, after penetrating trauma such as a gunshot wound, or in the setting of sacral fracture or epidural anesthesia [24]. (See "Infectious complications of pressure-induced skin and soft tissue injury", section on 'Clinical features'.)
DIAGNOSIS — Culture and/or histopathologic examination of a bone biopsy are required in order to make a definitive diagnosis of osteomyelitis. In general, rates of culture positivity are higher when cultures are obtained at the time of surgical debridement. The utility of percutaneous bone biopsy in the setting of pelvic osteomyelitis is controversial; some centers report a low yield of cultures from such procedures. As an example, in one report including 35 biopsies of the pelvis, a pathogen was identified in only 17 percent of cases [25].
Compatible symptoms in the setting of relevant risk factors, together with positive blood cultures and radiographic evidence of osteomyelitis, may also be diagnostic. Aspiration and cultures of pus obtained from abscesses that are contiguous to bony pelvic abnormalities may supplant the need for bone biopsy in some cases. (See "Nonvertebral osteomyelitis in adults: Clinical manifestations and diagnosis", section on 'Diagnosis'.)
White blood counts, erythrocyte sedimentation rate, and measurement of C-reactive protein levels may provide clues to the presence of an infectious process in the bony pelvis. However, these tests lack specificity in distinguishing bony infection from other noninfectious conditions such as seronegative spondyloarthropathies.
Plain radiography is not sensitive for detecting osteomyelitis, although it may be useful to exclude other causes of pain such as tumor or fractures. Computed tomography (CT) is more sensitive than plain radiography in detecting pelvic osteomyelitis, pyogenic sacroiliitis, or early pubic osteomyelitis but is less sensitive than magnetic resonance imaging (MRI). CT or ultrasound may be useful in detecting soft tissue swelling and abscess formation in contiguous soft tissues, particularly when aspiration or drainage procedures are planned. (See "Approach to imaging modalities in the setting of suspected nonvertebral osteomyelitis".)
MRI is the most sensitive radiographic modality for detection of pelvic osteomyelitis. Marrow abnormalities typical of osteomyelitis may be detected by MRI before lytic or other typical changes of osteomyelitis appear. (See "Approach to imaging modalities in the setting of suspected nonvertebral osteomyelitis" and "Infectious complications of pressure-induced skin and soft tissue injury", section on 'Radiologic imaging'.)
DIFFERENTIAL DIAGNOSIS — Pelvic bone and joint infections can be difficult to distinguish from other mimics. For example, pubic osteomyelitis may rarely be confused with spermatic cord torsion [26]. Chronic recurrent multifocal osteomyelitis, a rare condition of unknown etiology that most often affects long bones, can affect the bony pelvis in rare cases, particularly in children and adolescents [27]. Postradiation changes, healing fractures, and a variety of pathological problems involving the hip can also be mimics of pelvic osteomyelitis. Obturator pyomyositis can rarely mimic pelvic osteomyelitis as well as lead to secondary osteomyelitis of the ischio-pubic bones [28,29].
TREATMENT — Treatment of pelvic osteomyelitis consists of debridement of infected or necrotic tissues, in conjunction with antimicrobial therapy directed at the causative pathogens. (See "Nonvertebral osteomyelitis in adults: Clinical manifestations and diagnosis" and "Osteomyelitis associated with open fractures in adults" and "Nonvertebral osteomyelitis in adults: Treatment" and "Infectious complications of pressure-induced skin and soft tissue injury", section on 'Management of osteomyelitis'.)
In general, pelvic osteomyelitis associated with sacral decubitus ulcer(s) requires surgical debridement for cure [6]. Often, tissue reconstruction is required following debridement and antimicrobial therapy [30,31]. In some circumstances, definitive debridement of advanced osteomyelitis associated with adjacent sacral decubitus ulcers is not be possible. For some cases, hemicorporectomy has been performed; morbidity and mortality in such cases is high [32].
For patients with osteomyelitis involving the ilium, acetabulum, or ischium, thorough debridement may be difficult because of the proximity of overlying or adjacent structures such as the sacral plexus, and/or because of difficult access for areas deep within the pelvis. In addition, debridement of the symphysis pubis may be associated with subsequent instability and gait problems.
For cases in which definitive debridement is not feasible, a long course of intravenous antibiotics (eg, six to eight weeks) may be sufficient for cure [19]. Successful management of pubic osteomyelitis have been managed with antimicrobial therapy without extensive debridement (after needle biopsy demonstrated a causative pathogen) has been described [13,33,34].
Selection of antibiotic therapy should be guided by bone cultures obtained via open biopsy or aspiration. For cases in which such microbiology data is not available, empiric antibiotic therapy should include activity against staphylococci, gram-negative bacilli, and anaerobes. Reasonable regimens include vancomycin in combination with a third- or fourth-generation cephalosporin (such as ceftriaxone, ceftazidime, or cefepime) and metronidazole. An alternative regimen consists of vancomycin in combination with a carbapenem.
The optimal duration of antibiotic therapy for treatment of pelvic osteomyelitis is uncertain. Most experts favor continuing antimicrobial therapy at least until debrided bone has been covered by vascularized soft tissue, which is usually at least six weeks from the last debridement.
OUTCOMES — Risk factors for treatment failure include fistula, malignancy, polymicrobial infection, and resistant organisms [35]. In one review including 61 patients with chronic osteomyelitis who underwent surgical debridement, the recurrence rate was 11.5 percent [31]. In another retrospective cohort study including 61 patients with pelvic osteomyelitis associated with pressure ulcer who underwent debridement and flap coverage with antimicrobial therapy for 20 weeks, the rate of treatment failure was 23 percent [36].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Osteomyelitis and prosthetic joint infection in adults".)
SUMMARY
●Pelvic osteomyelitis may arise hematogenously, secondary to trauma or surgery via direct inoculation of pathogens into bone, or via contiguous spread of infection from soft tissues within or outside the bony walls of the pelvis. (See 'Introduction' above.)
●Predisposing factors for pelvic osteomyelitis include bacteremia related to infection of implanted devices, trauma, pressure ulcers, pelvic or urologic surgery, obstetrical procedures, and intravenous drug abuse. (See 'Epidemiology' above.)
●There may be a long interval between a precipitating cause (such as trauma or surgery) and the onset of pelvic osteomyelitis, and fever may be absent. (See 'Clinical manifestations' above.)
●Osteitis pubis consists of bony destruction of the margins of the symphysis pubis, severe pelvic pain, and a characteristic wide-based waddling gait. Fever is usually absent. Osteitis pubis may occur as a result of infection or noninfectious causes. (See 'Osteitis pubis' above.)
●Culture and/or histopathological examination of a bone biopsy are required in order to make a definitive diagnosis of osteomyelitis. Magnetic resonance imaging (MRI) is the most sensitive radiographic modality for detection of pelvic osteomyelitis. (See 'Treatment' above.)
●Treatment of pelvic osteomyelitis consists of debridement of infected or necrotic tissues and a long course of antimicrobial therapy directed at the causative pathogens. In some cases, thorough debridement may be anatomically difficult and/or may result in instability and secondary gait problems. In such cases, a long course of antimicrobial therapy without extensive debridement may be sufficient. Pelvic osteomyelitis due to sacral decubitus ulcer generally requires surgical debridement for cure. (See 'Treatment' above.)
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