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(i) Irritable hip and septic arthritis of the hip
MINI-SYMPOSIUM: CHILDREN’S HIP PROBLEMS
(i) Irritable hip and septic arthritis of the hip
symptomatic and there is no risk of long-term adverse consequences. The clinical presentation is classically an acute onset of limp associated with a variable degree of restriction of the range of movement at the hip. There may be a prodromic illness, but there are no clinical signs to suggest ongoing sepsis. The original description of Lovett and Morse in 1892 - ‘‘.. short lived and ephemeral form of hip disease which presents at first the characteristics of common hip disease, but the symptoms of which disappear in a few months instead of continuing for years’’1 e though accurate, was aimed at distinguishing irritable hip from tuberculosis of the hip. The peak age of presentation (between 3 and 8 years of age) coincides with the peak age of presentation of Perthes’ disease, and non specific irritability of the hip may very well be the first clinical presentation of Perthes’ disease. However, Perthes’ disease is clearly distinct from transient synovitis, with the characteristic radiographic changes becoming evident with the passage of time. It is the differentiation from septic arthritis of the hip which is critical and more difficult.
M Padman BW Scott
Abstract Transient synovitis needs to be differentiated from septic arthritis of the hip when a child presents with features of an irritable hip. Although there is considerable overlap in the clinical presentation of the two conditions, the natural history, treatment strategy and potential range of outcomes are quite distinct. While transient synovitis is a self limiting condition, emergent surgical intervention in the form of arthrotomy and wash out of joint is the mainstay of treatment of septic arthritis. Clinical decision algorithms have been developed using a combination of clinical and laboratory parameters to help differentiate the two conditions.
Evaluation and treatment protocol Where the clinical picture is unequivocal, children with transient synovitis of the hip do not require further investigations apart from baseline haematological tests including inflammatory markers. If the clinical diagnosis is supported by the results of the blood investigations, no further imaging is required. However, the child needs to be brought back for a further review after 7 to 10 days and most emergency departments have a protocol wherein this follow up appointment can be arranged. The treatment during this period is based entirely on the level of symptoms, with activity modification and analgesics as required. There is some evidence that NSAID’s speed up the recovery process, but this is not conclusive. The earlier practice of complete bed rest and traction is not recommended at present. Further radiological investigations are indicated when the clinical picture is not well defined at the first presentation and/or if there is an element of overlap with the features of septic arthritis. Ultrasound examination of the hips is the preferred mode of imaging2e4 in order to a: detect the presence of an effusion, b: determine its characteristics in terms of size and echogenicity, c: exclude any evidence of osteomyelitis e for example a subperiosteal collection and d: to exclude soft tissue infection. Figure 1 illustrates the comparative ultrasound images of a normal hip and a hip with an effusion. Plain radiographs of the hip are more useful in the older child, although most emergency departments routinely use a frog leg lateral view along with the ultrasound evaluation of the hips at all ages. Radiological imaging and referral to the Orthopaedic clinic is also indicated when there is no resolution of symptoms at the follow up visit.
Keywords clinical algorithms; irritable hip; post septic sequelae; septic arthritis; transient synovitis
Introduction An acutely irritable hip in a child is very often a diagnostic challenge with a myriad of pathologies characterised by irritability of the hip as their first clinical presentation. The common causes are infection, transient synovitis, Perthes’ disease, slipped upper femoral epiphysis, trauma, inflammatory arthritis and tumours. An awareness of the natural history of these various conditions, including the age at presentation and the characteristic features, coupled with a careful history and thorough physical examination, will help narrow the differential diagnosis in the vast majority of cases. However, one can frequently be left with the crucial decision of having to differentiate quickly between transient synovitis and true infection around the hip (septic arthritis and osteomyelitis of the proximal femur). Despite a remarkable similarity between these two conditions at the time of presentation, it is imperative that they are differentiated at an early stage in view of the adverse consequences of delayed treatment of septic arthritis. Various diagnostic algorithms, using a combination of clinical and laboratory parameters, have been proposed to help differentiate these two conditions.
Transient synovitis Transient synovitis is a benign condition of non specific aetiology, which has a self-limiting course and often the diagnosis is established by exclusion of other pathologies. The treatment is
Septic arthritis of the hip Pathogenesis The hip joint is the second most frequent joint to be affected by infection after the knee joint, but the consequences of infection are much more dramatic. Bacteria enter the hip joint by either of two routes, either by the haematogenous route following bacteraemia, or by direct spread from an osteomyelitic focus within
M Padman FRCS(Tr & Orth) is a Specialist Registrar at Sheffield Children’s Hospital, UK. BW Scott FRCS(Orth) is a Consultant Orthopaedic Surgeon at Leeds General Infirmary, Leeds, UK.
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MINI-SYMPOSIUM: CHILDREN’S HIP PROBLEMS
Microbiology The causative organisms depend significantly on the age of presentation. Staphylococcus aureus remains the commonest organism across all age groups, responsible for 40 to 90% of all cases of musculoskeletal infection.9 Table 1 illustrates the pattern of microbial infection in the various age groups. With the widespread use of H1B vaccine, the incidence of Haemophilus influenzae infection has dramatically reduced. With the changing bacteriological pattern, unusual organisms like Kingella kingae are being recognised as responsible for an increasingly greater percentage of infections. K. kingae is a fastidious Gram negative bacillus, normally residing in the oropharynx of young children, but can become involved in musculoskeletal infection when it gains access to the bloodstream as an opportunistic pathogen. The increasing detection of K. kingae as the causative organism may be related to our greater understanding of how this organism can be isolated and cultured. Clinical features A child with septic arthritis of the hip presents with the systemic features of sepsis coupled with localised signs confined to the extremity in question. The systemic features may range from generalised irritability and pyrexia (temperature> 38.5 centigrade) to florid signs of septicaemia. The local symptoms are pseudoparalysis in the smaller child and a limp in the older, ambulant child. The clinical symptoms may be preceded by a non-specific prodromal illness or occasionally by trauma. The limb itself is held in a position of flexion, abduction and external rotation to accommodate the increased joint volume due to effusion. There is very little spontaneous movement of the extremity and any attempt to passively move the joint is resisted. The pelvis, including the sacroiliac joints and the lumbosacral spine, must be examined to exclude other foci of infection. A thorough systemic examination is necessary to identify any potential source of infection which may require input by other specialists.
Ultrasound images of hips. a Normal hip. b Hip with an effusion showing capsular distension, thickening and distortion of soft tissue planes due to oedema. Figure 1
that part of the metaphysis which is intra articular. The proximal femur, proximal humerus, distal lateral tibia and proximal radius all share the common anatomic characteristic of having part of their metaphysis within the joint.5 The synovium has a rich vascular network from where bacteria gain access to the joint through the highly permeable blood vessels. The clinical outcome is determined by the host response to the bacterial burden, which is influenced by the virulence of the organism and the local and systemic resistance of the host. The acute inflammatory response, mediated by polymorphonuclear leukocytes, results in an exudative reaction into the joint producing a tense effusion. Articular cartilage is destroyed by a combination of enzymatic degradation, mediated by the various proteolytic enzymes released during the inflammatory cascade and by the disruption of blood supply following thrombosis within the microcirculation and by the elevated intracapsular pressure.6 Animal studies have demonstrated the rapidity with which irreversible articular damage occurs7 and also the incomplete protection of articular cartilage with intravenous antibiotic treatment alone,8 hence the need for immediate surgical decompression and wash out of the joint as the mainstay of treatment. Delayed treatment of septic arthritis of the hip can cause significant problems as a consequence of damage to the physis or preosseous cartilage, ischaemia and avascular necrosis of the femoral epiphysis, spread of infection to involve the proximal femur and generalised sepsis.
ORTHOPAEDICS AND TRAUMA 23:3
Investigations The diagnosis of septic arthritis remains fundamentally a clinical one, based on a high index of suspicion and backed by appropriate investigations. The initial evaluation of a child with an irritable hip should include baseline haematological investigations; namely a total and differential white cell count (WCC), erythrocyte sedimentation rate (ESR) and C-reactive protein
Common organisms responsible for septic arthritis at various ages Age group
Commonest causative organisms
Neonate
Group B Streptococcus, Staph. aureus, Gram negative bacillus 1 monthe3 years Staph. aureus, Pneumococcus, Strep. pyogenes, (H. influenzae) 3 yearse12 years All of the above Adolescent Staph. aureus, N. gonorrhoeae Table 1
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(CRP). Typically the WCC is raised to> 12 000 cells per mm3 with a polymorphonuclear leukocystosis of 40e60%, the ESR is elevated to 50 mm per hour and the CRP is greater than 20. It is important to remember that the neonate may not show a significant elevation of the inflammatory markers due to the relative immaturity of their immune system. Blood cultures are positive in 40 to 60% of cases, and samples should be taken as part of the screening for sepsis before any antibiotics are administered. Ultrasound evaluation of the hips is a useful adjunct to identify an effusion within the hip where the clinical picture is not clear. The volume of fluid within the joint can be compared to the opposite side and the quality of the effusion can be assessed to see whether there is any debris, which would indicate an exudative reaction, and the presence of any subperiosteal collection detected.
joint. A follow up ultrasound scan is necessary to confirm that there is no residual instability before the harness is discontinued. The response to treatment is monitored clinically (temperature, spontaneous movement of the extremity and weight bearing) as well as with serial haematological investigations. Normalisation of the CRP level is the earliest laboratory parameter to indicate that the infective process is controlled and is a useful adjunct to determine the duration of antibiotic therapy. Controversy exists as to the total duration of antibiotic therapy as well as the optimum point for conversion from parenteral to oral antibiotics. Parenteral broad spectrum antibiotics are continued until formal culture and sensitivity results are obtained. Once switched to the appropriate antibiotics, as dictated by sensitivity results, the decision regarding the duration of antibiotic treatment is made based on several factors, including the virulence of the organism identified and the clinical response. A two to six week course is the standard regimen, with the longer duration reserved for more virulent organisms, protracted clinical course and when associated with concomitant osteomyelitis.10 Occasionally the clinical response to surgical drainage and antibiotic therapy is less than optimal, and when there is concern that there may be ongoing sepsis repeat ultrasound scans and Magnetic Resonance Imaging is indicated to exclude other foci of infection, especially within the pelvis.
The role of aspiration Evidence of pus on aspiration of the joint is diagnostic of suppurative arthritis, especially when done under ultrasound guidance.6,10 Diagnostic criteria have been established for confirmation of the diagnosis based on biochemical and cytological analysis of synovial fluid aspirate.11 However, the procedure is not well tolerated by the conscious child and therefore its routine use in clinical practice is limited. In practical terms, aspiration of the joint under fluoroscopic guidance is useful when done under anaesthesia before a formal arthrotomy, where there is a strong clinical suspicion of septic arthritis and the ultrasound evaluation has been either inconclusive or when facilities for sonography are unavailable.
Osteomyelitis of the proximal femur The clinical picture of osteomyelitis (Figure 2) is identical to septic arthritis, but for the absence of a hip effusion on ultrasound examination. Occasionally the ultrasound scan may show a subperiosteal collection and plain xrays may show an area of lucency in the proximal femoral metaphysis. The mainstay of treatment for osteomyelitis is antibiotic therapy, with the caveat that the total duration, as well as the duration of parenteral therapy, need to be more prolonged than for septic arthritis. The presence of concomitant osteomyelitis is a poor prognostic factor for the development of long term adverse sequelae.
Treatment Septic arthritis is a true emergency and the cornerstone of treatment is surgical drainage of the joint followed by copious irrigation. The hip joint is exposed through a mini bikini line incision, using the internervous plane between the tensor fascia lata and sartorius (modified Smith-Peterson approach). The capsule and pericapsular tissues may be oedematous as a consequence of the ongoing inflammation, which may distort tissue planes. Once the pericapsular soft tissues are cleared, the capsule is opened through a cruciate incision. Samples of fluid from the joint are taken at the first available opportunity and are sent for urgent Gram staining and microbiological analysis. To maximise the chances of isolating an organism, synovial fluid is injected into blood culture broths before sending to the lab. Empirical intravenous antibiotics are started as soon as specimens are obtained, based on the common patterns of microbiological isolation and sensitivities locally. It is helpful if advice is sought from the hospital microbiologist for the appropriate broad spectrum antibiotic, which would cover the common pathogens for the particular age group. The same anaesthetic sitting can be used for securing peripheral venous access (PICC line e peripherally inserted central catheter) for prolonged parenteral antibiotic therapy. The capsule and fascial layers are left open to facilitate continuous drainage of the joint, but the skin and subcutaneous layers can be closed. The neonate and the infant are at the greatest risk of developing subluxation or dislocation of the joint, and it may be necessary to immobilise the hip in a dynamic flexion-abduction brace (Pavlik harness) to maintain concentric reduction of the
ORTHOPAEDICS AND TRAUMA 23:3
Figure 2 Concomitant septic arthritis & proximal femoral osteomyelitis. Evidence of hip subluxation which needed Pavlik harness immobilisation. Periosteal reaction of proximal femur.
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MINI-SYMPOSIUM: CHILDREN’S HIP PROBLEMS
Sequelae of septic arthritis
Post septic sequelae and their possible mechanisms
The hip joint accounts for a substantial majority of poor outcomes when the adverse consequences following septic arthritis of all joints are assessed. The poor prognostic factors are: onset in a child under 6 months of age, delay in diagnosis by more than 4 days, concomitant proximal femoral osteomyelitis and infection with Staph. aureus.10,12,13 The catastrophic sequelae of delayed diagnosis of septic arthritis of the hip are a consequence of destruction of the articular hyaline cartilage and irreversible damage to the epiphysis, physis and metaphysis of the proximal femur and occasionally the triradiate cartilage of the acetabulum (Figure 3). The damage is brought about by a combination of enzymatic degradation, ischaemia and mechanical factors. Bacterial toxins, break down products of cells, proteolytic enzymes and inflammatory mediators (Interleukin-1) released as part of the inflammatory cascade all contribute to chondrolysis. Ischaemia to the preosseous cartilage is a consequence of septic emboli, endarteritis and mechanical factors. The mechanical factors that disrupt the subsynovial vasculature are capsular distension by the tense effusion and capsular stretching by the subluxing/dislocating femoral head. The various clinical and radiological sequelae of septic arthritis of the hip are listed in Table 2, along with their putative pathomechanisms. The sequelae were first classified by Hunka et al.14 on the basis of their radiological appearances, and several authors have attempted to devise reconstructive strategies to address the gross deformity and instability.15e18 The treatment strategies include conservative measures to maintain hip mobility in mild deformity, realignment proximal femoral osteotomies to correct varus/valgus deformities, pelvic osteotomies (Pemberton/Dega acetabuloplasties) to address acetabular dysplasia and instability, trochanteric distal transfer for abductor insufficiency plus the various measures to address the consequences of significant leg length discrepancy. Gross deformity and instability arising from a complete destruction of femoral head and neck (Hunka Type V hips) remain a challenge, and recent reports have indicated reasonable results with Pelvic Support Osteotomy along with Ilizarov hip reconstruction.19,20
Mechanism
Coxa magna
Transient disruption of the blood supply
Avascular necrosis of femoral head
Partial or total disruption of the blood supply
Acetabular dysplasia
Premature closure of the triradiate cartilage Persistent hip instability
Subluxation/Dislocation
Mechanical factorsecapsular distension
Abductor insufficiency/ Trochanteric overgrowth
Premature closure of proximal femoral physis
Coxa vara/coxa valga Torsional abnormalities
Asymmetric closure of the proximal femoral physis
Leg length discrepancy
Damage to the proximal femoral physis
Pseudoarthrosis of the femoral neck
Damage to the femoral neck and physis
Complete destruction of femoral head & neck
Damage to the preosseous cartilage and physis
Ankylosis of the hip
Natural consequence or following surgical treatment
Table 2
the hip, but have found considerable overlap between the two.21 Kocher et al.22 proposed a clinical prediction algorithm for differentiating between the two conditions, based on the retrospective evaluation of various clinical and laboratory features in children who presented to a tertiary centre with an irritable hip. Although several variables were found to differ significantly between the two groups, they also found that the overlap made it quite difficult to make the distinction based on individual variables alone. Four independent multivariate clinical predictors were evaluatedehistory of fever, non weight bearing, an Erythrocyte Sedimentation Rate (ESR) greater than 40 mm/hour and elevated White Cell Count of more than 12 000 cells per cubic millimetereas predictors for septic arthritis. The predictive values for a probable diagnosis of septic arthritis were 99.6% when all four variables were present, 93.1% in the presence of three variables, 40% for two variables and 3% for one variable. Subsequently, the authors validated the same four clinical variables in a prospective study within a different population although the predictive values were diminished (93% for all four variables, 72.8% for three variables).23 Although some investigators have found similar predictive values on prospective evaluation of the four variables plus C reactive protein,24 others have found the algorithm to be not
The differentiation between transient synovitis & septic arthritiseclinical diagnostic algorithms Clinicians have empirically used various parameters to establish clinical prediction rules that would help to objectively make a distinction between transient synovitis and septic arthritis of
Figure 3 Post septic sequelae.
ORTHOPAEDICS AND TRAUMA 23:3
Clinical/Radiological abnormality
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MINI-SYMPOSIUM: CHILDREN’S HIP PROBLEMS
13 Gillespie R. Septic arthritis of childhood. Clin Orthop Relat Res 1973; 96: 152e9. 14 Hunka L, Said SE, MacKenzie DA, Rogala EJ, Cruess RL. Classification and surgical management of the severe sequelae of septic hips in children. Clin Orthop Relat Res 1982; 171: 30e6. 15 Choi IH, Pizzutillo PD, Bowen JR, Dragann R, Malhis T. Sequelae and reconstruction after septic arthritis of the hip in infants. J Bone Joint Surg Am 1990; 72-A(8): 1150e65. 16 Choi IH, Shin YW, Vhung CY, Cho TJ, Yoo WJ, Lee DY. Surgical treatment of the severe sequelae of infantile septic arthritis of the hip. Clin Orthop Relat Res 2005; 434: 102e9. 17 Forlin E, Milani C. Sequelae of septic arthritis of the hip in children: a new classification and a review of 41 hips. J Pediatr Orthop. 2008; 28(5): 524e8. 18 Wada A, Fujii T, Takamura K, Yanagida H, Urano N, Surijamorn P. Operative reconstuction of the severe sequelae of infantile septic arthritis of the hip. J Pediatr Orthop 2007; 27(8): 910e4. 19 Rozbruch SR, Paley D, Bhave A, Herzenberg JE. Ilizarov hip reconstruction for the late sequelae of infantile hip infection. J Bone Joint Surg Am 2005; 87-A(5): 1007e18. 20 Pafilas D, Nayagam S. The pelvic support osteotomy: Indications and preoperative planning. Strategies Trauma Limb Reconstr 2008; 3: 83e92. 21 Del Beccaro MA, Champoux AN, Bockers T, Mendelman PM. Septic arthritis versus transient synovitis of the hip: the value of screening laboratory tests. Ann Emerg Med 1992; 21(12): 1418e22. 22 Kocher MS, Zurakowski D, Kasser JR. Differentiation between septic arthritis and transient synovitis of the hip in children: an evidencebased clinical prediction algorithm. J Bone Joint Surg Am 1999; 81-A(12): 1662e70. 23 Kocher MS, Mandiga R, Zurakowski D, Barnewolt C, Kasser JR. Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. J Bone Joint Surg Am 2004; 86-A(8): 1629e35. 24 Caird MS, Flynn JM, Leung YL, Millman JE, D’Italia JG, Dormans JP. Factors distinguishing septic arthritis from transient synovitis of the hip in children. A prospective study. J Bone Joint Surg Am 2006; 88-A(6): 1251e7. 25 Luhmann SJ, Jones A, Schootman M, Gordon JE, Schoenecker PL, Luhmann JD. Differentiation between septic arthritis and transient synovitis of the hip in children with clinical prediction algorithms. J Bone Joint Surg Am 2004; 86-A(5): 956e62.
useful in distinguishing between transient synovitis and septic arthritis with predictive values as low as 59% even with the presence of four variables.25
Conclusion The diagnosis of septic arthritis of the hip fundamentally remains a clinical one despite the development of various clinical diagnostic algorithms. Laboratory and imaging studies are useful adjuncts to support the clinical decision. A
REFERENCES 1 Lovett RW, Morse JL. A transient or ephemeral form of hip-disease, with a report of cases. Boston Med Surg J 1892; 127: 161e3. 2 Bickerstaff DR, Neal LM, Booth AJ, Brennan PO, Bell MJ. Ultrasound examination of the irritable hip. J Bone Joint Surg Br 1990; 72-B(4): 549e53. 3 Zieger MM, Dorr U, Schulz RD. Ultrasonography of hip joint effusions. Skeletal Radiol 1987; 16(8): 607e11. 4 Hill SA, MacLarnon JC, Nag D. Ultrasound-guided aspiration for transient synovitis of the hip. J Bone Joint Surg Br 1990; 72-B(5): 852e3. 5 Dormans JP, Drummond DS. Pediatric hematogenous osteomyelitis: new trends in presentation, diagnosis and treatment. J Am Acad Orthop Surg 1994; 2(6): 333e41. 6 McCarthy JJ, Dormans JP, Kozin SH, Pizzutillo PD. Musculoskeletal infections in children. Basic treatment principles and recent advancements. J Bone Joint Surg Am 2004; 86-A(4): 850e63. 7 Daniel D, Akeson W, Amiel D, Ryder M, Boyer J. Lavage of septic joints in rabbits: effects of chondrolysis. J Bone Joint Surg Am 1976; 58-A(3): 393e5. 8 Smith RL, Schurman DJ, Kajiyama G, Mell M, Gilkerson E. The effect of antibiotics on the destruction of cartilage in experimental infectious arthritis. J Bone Joint Surg Am 1987; 69-A(7): 1063e8. 9 Morrissy RT, Weinstein SL, eds. Lovell and Winter’s Pediatric Orthopaedics. 6th edn., No. 1. Lippincott Williams & Wilkins; 2006. 10 Sucato DJ, Schwend RM, Gillespie R. Septic arthritis of the hip in children. J Am Acad Orthop Surg 1997; 5(5): 249e60. 11 Nade S. Acute septic arthritis in infancy and childhood. J Bone Joint Surg Br 1983; 65-B(3): 234e41. 12 Jackson MA, Nelson JD. Etiology and medical management of acute suppurative bone and joint infections in pediatric patients. J Pediatr Orthop 1982; 2(3): 313e23.
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(i) Irritable hip and septic arthritis of the hip
symptomatic and there is no risk of long-term adverse consequences. The clinical presentation is classically an acute onset of limp associated with a variable degree of restriction of the range of movement at the hip. There may be a prodromic illness, but there are no clinical signs to suggest ongoing sepsis. The original description of Lovett and Morse in 1892 - ‘‘.. short lived and ephemeral form of hip disease which presents at first the characteristics of common hip disease, but the symptoms of which disappear in a few months instead of continuing for years’’1 e though accurate, was aimed at distinguishing irritable hip from tuberculosis of the hip. The peak age of presentation (between 3 and 8 years of age) coincides with the peak age of presentation of Perthes’ disease, and non specific irritability of the hip may very well be the first clinical presentation of Perthes’ disease. However, Perthes’ disease is clearly distinct from transient synovitis, with the characteristic radiographic changes becoming evident with the passage of time. It is the differentiation from septic arthritis of the hip which is critical and more difficult.
M Padman BW Scott
Abstract Transient synovitis needs to be differentiated from septic arthritis of the hip when a child presents with features of an irritable hip. Although there is considerable overlap in the clinical presentation of the two conditions, the natural history, treatment strategy and potential range of outcomes are quite distinct. While transient synovitis is a self limiting condition, emergent surgical intervention in the form of arthrotomy and wash out of joint is the mainstay of treatment of septic arthritis. Clinical decision algorithms have been developed using a combination of clinical and laboratory parameters to help differentiate the two conditions.
Evaluation and treatment protocol Where the clinical picture is unequivocal, children with transient synovitis of the hip do not require further investigations apart from baseline haematological tests including inflammatory markers. If the clinical diagnosis is supported by the results of the blood investigations, no further imaging is required. However, the child needs to be brought back for a further review after 7 to 10 days and most emergency departments have a protocol wherein this follow up appointment can be arranged. The treatment during this period is based entirely on the level of symptoms, with activity modification and analgesics as required. There is some evidence that NSAID’s speed up the recovery process, but this is not conclusive. The earlier practice of complete bed rest and traction is not recommended at present. Further radiological investigations are indicated when the clinical picture is not well defined at the first presentation and/or if there is an element of overlap with the features of septic arthritis. Ultrasound examination of the hips is the preferred mode of imaging2e4 in order to a: detect the presence of an effusion, b: determine its characteristics in terms of size and echogenicity, c: exclude any evidence of osteomyelitis e for example a subperiosteal collection and d: to exclude soft tissue infection. Figure 1 illustrates the comparative ultrasound images of a normal hip and a hip with an effusion. Plain radiographs of the hip are more useful in the older child, although most emergency departments routinely use a frog leg lateral view along with the ultrasound evaluation of the hips at all ages. Radiological imaging and referral to the Orthopaedic clinic is also indicated when there is no resolution of symptoms at the follow up visit.
Keywords clinical algorithms; irritable hip; post septic sequelae; septic arthritis; transient synovitis
Introduction An acutely irritable hip in a child is very often a diagnostic challenge with a myriad of pathologies characterised by irritability of the hip as their first clinical presentation. The common causes are infection, transient synovitis, Perthes’ disease, slipped upper femoral epiphysis, trauma, inflammatory arthritis and tumours. An awareness of the natural history of these various conditions, including the age at presentation and the characteristic features, coupled with a careful history and thorough physical examination, will help narrow the differential diagnosis in the vast majority of cases. However, one can frequently be left with the crucial decision of having to differentiate quickly between transient synovitis and true infection around the hip (septic arthritis and osteomyelitis of the proximal femur). Despite a remarkable similarity between these two conditions at the time of presentation, it is imperative that they are differentiated at an early stage in view of the adverse consequences of delayed treatment of septic arthritis. Various diagnostic algorithms, using a combination of clinical and laboratory parameters, have been proposed to help differentiate these two conditions.
Transient synovitis Transient synovitis is a benign condition of non specific aetiology, which has a self-limiting course and often the diagnosis is established by exclusion of other pathologies. The treatment is
Septic arthritis of the hip Pathogenesis The hip joint is the second most frequent joint to be affected by infection after the knee joint, but the consequences of infection are much more dramatic. Bacteria enter the hip joint by either of two routes, either by the haematogenous route following bacteraemia, or by direct spread from an osteomyelitic focus within
M Padman FRCS(Tr & Orth) is a Specialist Registrar at Sheffield Children’s Hospital, UK. BW Scott FRCS(Orth) is a Consultant Orthopaedic Surgeon at Leeds General Infirmary, Leeds, UK.
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Microbiology The causative organisms depend significantly on the age of presentation. Staphylococcus aureus remains the commonest organism across all age groups, responsible for 40 to 90% of all cases of musculoskeletal infection.9 Table 1 illustrates the pattern of microbial infection in the various age groups. With the widespread use of H1B vaccine, the incidence of Haemophilus influenzae infection has dramatically reduced. With the changing bacteriological pattern, unusual organisms like Kingella kingae are being recognised as responsible for an increasingly greater percentage of infections. K. kingae is a fastidious Gram negative bacillus, normally residing in the oropharynx of young children, but can become involved in musculoskeletal infection when it gains access to the bloodstream as an opportunistic pathogen. The increasing detection of K. kingae as the causative organism may be related to our greater understanding of how this organism can be isolated and cultured. Clinical features A child with septic arthritis of the hip presents with the systemic features of sepsis coupled with localised signs confined to the extremity in question. The systemic features may range from generalised irritability and pyrexia (temperature> 38.5 centigrade) to florid signs of septicaemia. The local symptoms are pseudoparalysis in the smaller child and a limp in the older, ambulant child. The clinical symptoms may be preceded by a non-specific prodromal illness or occasionally by trauma. The limb itself is held in a position of flexion, abduction and external rotation to accommodate the increased joint volume due to effusion. There is very little spontaneous movement of the extremity and any attempt to passively move the joint is resisted. The pelvis, including the sacroiliac joints and the lumbosacral spine, must be examined to exclude other foci of infection. A thorough systemic examination is necessary to identify any potential source of infection which may require input by other specialists.
Ultrasound images of hips. a Normal hip. b Hip with an effusion showing capsular distension, thickening and distortion of soft tissue planes due to oedema. Figure 1
that part of the metaphysis which is intra articular. The proximal femur, proximal humerus, distal lateral tibia and proximal radius all share the common anatomic characteristic of having part of their metaphysis within the joint.5 The synovium has a rich vascular network from where bacteria gain access to the joint through the highly permeable blood vessels. The clinical outcome is determined by the host response to the bacterial burden, which is influenced by the virulence of the organism and the local and systemic resistance of the host. The acute inflammatory response, mediated by polymorphonuclear leukocytes, results in an exudative reaction into the joint producing a tense effusion. Articular cartilage is destroyed by a combination of enzymatic degradation, mediated by the various proteolytic enzymes released during the inflammatory cascade and by the disruption of blood supply following thrombosis within the microcirculation and by the elevated intracapsular pressure.6 Animal studies have demonstrated the rapidity with which irreversible articular damage occurs7 and also the incomplete protection of articular cartilage with intravenous antibiotic treatment alone,8 hence the need for immediate surgical decompression and wash out of the joint as the mainstay of treatment. Delayed treatment of septic arthritis of the hip can cause significant problems as a consequence of damage to the physis or preosseous cartilage, ischaemia and avascular necrosis of the femoral epiphysis, spread of infection to involve the proximal femur and generalised sepsis.
ORTHOPAEDICS AND TRAUMA 23:3
Investigations The diagnosis of septic arthritis remains fundamentally a clinical one, based on a high index of suspicion and backed by appropriate investigations. The initial evaluation of a child with an irritable hip should include baseline haematological investigations; namely a total and differential white cell count (WCC), erythrocyte sedimentation rate (ESR) and C-reactive protein
Common organisms responsible for septic arthritis at various ages Age group
Commonest causative organisms
Neonate
Group B Streptococcus, Staph. aureus, Gram negative bacillus 1 monthe3 years Staph. aureus, Pneumococcus, Strep. pyogenes, (H. influenzae) 3 yearse12 years All of the above Adolescent Staph. aureus, N. gonorrhoeae Table 1
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MINI-SYMPOSIUM: CHILDREN’S HIP PROBLEMS
(CRP). Typically the WCC is raised to> 12 000 cells per mm3 with a polymorphonuclear leukocystosis of 40e60%, the ESR is elevated to 50 mm per hour and the CRP is greater than 20. It is important to remember that the neonate may not show a significant elevation of the inflammatory markers due to the relative immaturity of their immune system. Blood cultures are positive in 40 to 60% of cases, and samples should be taken as part of the screening for sepsis before any antibiotics are administered. Ultrasound evaluation of the hips is a useful adjunct to identify an effusion within the hip where the clinical picture is not clear. The volume of fluid within the joint can be compared to the opposite side and the quality of the effusion can be assessed to see whether there is any debris, which would indicate an exudative reaction, and the presence of any subperiosteal collection detected.
joint. A follow up ultrasound scan is necessary to confirm that there is no residual instability before the harness is discontinued. The response to treatment is monitored clinically (temperature, spontaneous movement of the extremity and weight bearing) as well as with serial haematological investigations. Normalisation of the CRP level is the earliest laboratory parameter to indicate that the infective process is controlled and is a useful adjunct to determine the duration of antibiotic therapy. Controversy exists as to the total duration of antibiotic therapy as well as the optimum point for conversion from parenteral to oral antibiotics. Parenteral broad spectrum antibiotics are continued until formal culture and sensitivity results are obtained. Once switched to the appropriate antibiotics, as dictated by sensitivity results, the decision regarding the duration of antibiotic treatment is made based on several factors, including the virulence of the organism identified and the clinical response. A two to six week course is the standard regimen, with the longer duration reserved for more virulent organisms, protracted clinical course and when associated with concomitant osteomyelitis.10 Occasionally the clinical response to surgical drainage and antibiotic therapy is less than optimal, and when there is concern that there may be ongoing sepsis repeat ultrasound scans and Magnetic Resonance Imaging is indicated to exclude other foci of infection, especially within the pelvis.
The role of aspiration Evidence of pus on aspiration of the joint is diagnostic of suppurative arthritis, especially when done under ultrasound guidance.6,10 Diagnostic criteria have been established for confirmation of the diagnosis based on biochemical and cytological analysis of synovial fluid aspirate.11 However, the procedure is not well tolerated by the conscious child and therefore its routine use in clinical practice is limited. In practical terms, aspiration of the joint under fluoroscopic guidance is useful when done under anaesthesia before a formal arthrotomy, where there is a strong clinical suspicion of septic arthritis and the ultrasound evaluation has been either inconclusive or when facilities for sonography are unavailable.
Osteomyelitis of the proximal femur The clinical picture of osteomyelitis (Figure 2) is identical to septic arthritis, but for the absence of a hip effusion on ultrasound examination. Occasionally the ultrasound scan may show a subperiosteal collection and plain xrays may show an area of lucency in the proximal femoral metaphysis. The mainstay of treatment for osteomyelitis is antibiotic therapy, with the caveat that the total duration, as well as the duration of parenteral therapy, need to be more prolonged than for septic arthritis. The presence of concomitant osteomyelitis is a poor prognostic factor for the development of long term adverse sequelae.
Treatment Septic arthritis is a true emergency and the cornerstone of treatment is surgical drainage of the joint followed by copious irrigation. The hip joint is exposed through a mini bikini line incision, using the internervous plane between the tensor fascia lata and sartorius (modified Smith-Peterson approach). The capsule and pericapsular tissues may be oedematous as a consequence of the ongoing inflammation, which may distort tissue planes. Once the pericapsular soft tissues are cleared, the capsule is opened through a cruciate incision. Samples of fluid from the joint are taken at the first available opportunity and are sent for urgent Gram staining and microbiological analysis. To maximise the chances of isolating an organism, synovial fluid is injected into blood culture broths before sending to the lab. Empirical intravenous antibiotics are started as soon as specimens are obtained, based on the common patterns of microbiological isolation and sensitivities locally. It is helpful if advice is sought from the hospital microbiologist for the appropriate broad spectrum antibiotic, which would cover the common pathogens for the particular age group. The same anaesthetic sitting can be used for securing peripheral venous access (PICC line e peripherally inserted central catheter) for prolonged parenteral antibiotic therapy. The capsule and fascial layers are left open to facilitate continuous drainage of the joint, but the skin and subcutaneous layers can be closed. The neonate and the infant are at the greatest risk of developing subluxation or dislocation of the joint, and it may be necessary to immobilise the hip in a dynamic flexion-abduction brace (Pavlik harness) to maintain concentric reduction of the
ORTHOPAEDICS AND TRAUMA 23:3
Figure 2 Concomitant septic arthritis & proximal femoral osteomyelitis. Evidence of hip subluxation which needed Pavlik harness immobilisation. Periosteal reaction of proximal femur.
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MINI-SYMPOSIUM: CHILDREN’S HIP PROBLEMS
Sequelae of septic arthritis
Post septic sequelae and their possible mechanisms
The hip joint accounts for a substantial majority of poor outcomes when the adverse consequences following septic arthritis of all joints are assessed. The poor prognostic factors are: onset in a child under 6 months of age, delay in diagnosis by more than 4 days, concomitant proximal femoral osteomyelitis and infection with Staph. aureus.10,12,13 The catastrophic sequelae of delayed diagnosis of septic arthritis of the hip are a consequence of destruction of the articular hyaline cartilage and irreversible damage to the epiphysis, physis and metaphysis of the proximal femur and occasionally the triradiate cartilage of the acetabulum (Figure 3). The damage is brought about by a combination of enzymatic degradation, ischaemia and mechanical factors. Bacterial toxins, break down products of cells, proteolytic enzymes and inflammatory mediators (Interleukin-1) released as part of the inflammatory cascade all contribute to chondrolysis. Ischaemia to the preosseous cartilage is a consequence of septic emboli, endarteritis and mechanical factors. The mechanical factors that disrupt the subsynovial vasculature are capsular distension by the tense effusion and capsular stretching by the subluxing/dislocating femoral head. The various clinical and radiological sequelae of septic arthritis of the hip are listed in Table 2, along with their putative pathomechanisms. The sequelae were first classified by Hunka et al.14 on the basis of their radiological appearances, and several authors have attempted to devise reconstructive strategies to address the gross deformity and instability.15e18 The treatment strategies include conservative measures to maintain hip mobility in mild deformity, realignment proximal femoral osteotomies to correct varus/valgus deformities, pelvic osteotomies (Pemberton/Dega acetabuloplasties) to address acetabular dysplasia and instability, trochanteric distal transfer for abductor insufficiency plus the various measures to address the consequences of significant leg length discrepancy. Gross deformity and instability arising from a complete destruction of femoral head and neck (Hunka Type V hips) remain a challenge, and recent reports have indicated reasonable results with Pelvic Support Osteotomy along with Ilizarov hip reconstruction.19,20
Mechanism
Coxa magna
Transient disruption of the blood supply
Avascular necrosis of femoral head
Partial or total disruption of the blood supply
Acetabular dysplasia
Premature closure of the triradiate cartilage Persistent hip instability
Subluxation/Dislocation
Mechanical factorsecapsular distension
Abductor insufficiency/ Trochanteric overgrowth
Premature closure of proximal femoral physis
Coxa vara/coxa valga Torsional abnormalities
Asymmetric closure of the proximal femoral physis
Leg length discrepancy
Damage to the proximal femoral physis
Pseudoarthrosis of the femoral neck
Damage to the femoral neck and physis
Complete destruction of femoral head & neck
Damage to the preosseous cartilage and physis
Ankylosis of the hip
Natural consequence or following surgical treatment
Table 2
the hip, but have found considerable overlap between the two.21 Kocher et al.22 proposed a clinical prediction algorithm for differentiating between the two conditions, based on the retrospective evaluation of various clinical and laboratory features in children who presented to a tertiary centre with an irritable hip. Although several variables were found to differ significantly between the two groups, they also found that the overlap made it quite difficult to make the distinction based on individual variables alone. Four independent multivariate clinical predictors were evaluatedehistory of fever, non weight bearing, an Erythrocyte Sedimentation Rate (ESR) greater than 40 mm/hour and elevated White Cell Count of more than 12 000 cells per cubic millimetereas predictors for septic arthritis. The predictive values for a probable diagnosis of septic arthritis were 99.6% when all four variables were present, 93.1% in the presence of three variables, 40% for two variables and 3% for one variable. Subsequently, the authors validated the same four clinical variables in a prospective study within a different population although the predictive values were diminished (93% for all four variables, 72.8% for three variables).23 Although some investigators have found similar predictive values on prospective evaluation of the four variables plus C reactive protein,24 others have found the algorithm to be not
The differentiation between transient synovitis & septic arthritiseclinical diagnostic algorithms Clinicians have empirically used various parameters to establish clinical prediction rules that would help to objectively make a distinction between transient synovitis and septic arthritis of
Figure 3 Post septic sequelae.
ORTHOPAEDICS AND TRAUMA 23:3
Clinical/Radiological abnormality
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MINI-SYMPOSIUM: CHILDREN’S HIP PROBLEMS
13 Gillespie R. Septic arthritis of childhood. Clin Orthop Relat Res 1973; 96: 152e9. 14 Hunka L, Said SE, MacKenzie DA, Rogala EJ, Cruess RL. Classification and surgical management of the severe sequelae of septic hips in children. Clin Orthop Relat Res 1982; 171: 30e6. 15 Choi IH, Pizzutillo PD, Bowen JR, Dragann R, Malhis T. Sequelae and reconstruction after septic arthritis of the hip in infants. J Bone Joint Surg Am 1990; 72-A(8): 1150e65. 16 Choi IH, Shin YW, Vhung CY, Cho TJ, Yoo WJ, Lee DY. Surgical treatment of the severe sequelae of infantile septic arthritis of the hip. Clin Orthop Relat Res 2005; 434: 102e9. 17 Forlin E, Milani C. Sequelae of septic arthritis of the hip in children: a new classification and a review of 41 hips. J Pediatr Orthop. 2008; 28(5): 524e8. 18 Wada A, Fujii T, Takamura K, Yanagida H, Urano N, Surijamorn P. Operative reconstuction of the severe sequelae of infantile septic arthritis of the hip. J Pediatr Orthop 2007; 27(8): 910e4. 19 Rozbruch SR, Paley D, Bhave A, Herzenberg JE. Ilizarov hip reconstruction for the late sequelae of infantile hip infection. J Bone Joint Surg Am 2005; 87-A(5): 1007e18. 20 Pafilas D, Nayagam S. The pelvic support osteotomy: Indications and preoperative planning. Strategies Trauma Limb Reconstr 2008; 3: 83e92. 21 Del Beccaro MA, Champoux AN, Bockers T, Mendelman PM. Septic arthritis versus transient synovitis of the hip: the value of screening laboratory tests. Ann Emerg Med 1992; 21(12): 1418e22. 22 Kocher MS, Zurakowski D, Kasser JR. Differentiation between septic arthritis and transient synovitis of the hip in children: an evidencebased clinical prediction algorithm. J Bone Joint Surg Am 1999; 81-A(12): 1662e70. 23 Kocher MS, Mandiga R, Zurakowski D, Barnewolt C, Kasser JR. Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. J Bone Joint Surg Am 2004; 86-A(8): 1629e35. 24 Caird MS, Flynn JM, Leung YL, Millman JE, D’Italia JG, Dormans JP. Factors distinguishing septic arthritis from transient synovitis of the hip in children. A prospective study. J Bone Joint Surg Am 2006; 88-A(6): 1251e7. 25 Luhmann SJ, Jones A, Schootman M, Gordon JE, Schoenecker PL, Luhmann JD. Differentiation between septic arthritis and transient synovitis of the hip in children with clinical prediction algorithms. J Bone Joint Surg Am 2004; 86-A(5): 956e62.
useful in distinguishing between transient synovitis and septic arthritis with predictive values as low as 59% even with the presence of four variables.25
Conclusion The diagnosis of septic arthritis of the hip fundamentally remains a clinical one despite the development of various clinical diagnostic algorithms. Laboratory and imaging studies are useful adjuncts to support the clinical decision. A
REFERENCES 1 Lovett RW, Morse JL. A transient or ephemeral form of hip-disease, with a report of cases. Boston Med Surg J 1892; 127: 161e3. 2 Bickerstaff DR, Neal LM, Booth AJ, Brennan PO, Bell MJ. Ultrasound examination of the irritable hip. J Bone Joint Surg Br 1990; 72-B(4): 549e53. 3 Zieger MM, Dorr U, Schulz RD. Ultrasonography of hip joint effusions. Skeletal Radiol 1987; 16(8): 607e11. 4 Hill SA, MacLarnon JC, Nag D. Ultrasound-guided aspiration for transient synovitis of the hip. J Bone Joint Surg Br 1990; 72-B(5): 852e3. 5 Dormans JP, Drummond DS. Pediatric hematogenous osteomyelitis: new trends in presentation, diagnosis and treatment. J Am Acad Orthop Surg 1994; 2(6): 333e41. 6 McCarthy JJ, Dormans JP, Kozin SH, Pizzutillo PD. Musculoskeletal infections in children. Basic treatment principles and recent advancements. J Bone Joint Surg Am 2004; 86-A(4): 850e63. 7 Daniel D, Akeson W, Amiel D, Ryder M, Boyer J. Lavage of septic joints in rabbits: effects of chondrolysis. J Bone Joint Surg Am 1976; 58-A(3): 393e5. 8 Smith RL, Schurman DJ, Kajiyama G, Mell M, Gilkerson E. The effect of antibiotics on the destruction of cartilage in experimental infectious arthritis. J Bone Joint Surg Am 1987; 69-A(7): 1063e8. 9 Morrissy RT, Weinstein SL, eds. Lovell and Winter’s Pediatric Orthopaedics. 6th edn., No. 1. Lippincott Williams & Wilkins; 2006. 10 Sucato DJ, Schwend RM, Gillespie R. Septic arthritis of the hip in children. J Am Acad Orthop Surg 1997; 5(5): 249e60. 11 Nade S. Acute septic arthritis in infancy and childhood. J Bone Joint Surg Br 1983; 65-B(3): 234e41. 12 Jackson MA, Nelson JD. Etiology and medical management of acute suppurative bone and joint infections in pediatric patients. J Pediatr Orthop 1982; 2(3): 313e23.
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