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Rheumatoid Arthritis Emedicine

Transient Synovitis: A Complete Review

Children with Transient Synovitis (TS) present with a constellation of symptoms referred to as Irritable Hip Syndrome. This syndrome may be the manifestation for a number of different underlying causes. Although TS is the mildest and most frequent diagnosis in the list of these causes, it serves only as a diagnosis of exclusion. A more thorough understanding of TS is imperative in order to confidently diagnose a patient with it, and, more importantly, to recognize its misdiagnosis earlier. WILL FIX REFERENCING SOON, ALL RELEVANT ARTICLES ARE CITED BELOW ~AN

INTRODUCTION

Transient Synovitis (TS), also known as Toxic Synovitis, is the most common cause of "Irritable Hip" in children and manifests as acute hip pain that usually results in temporary decreased mobility. Transient refers to the short-duration of the condition, usually lasting no more than a week, while Synovitis means that there is an inflammation of the Synovium (Synovial Membrane) - a lining of the bones inside the hip joint. While many etiologies of TS have been postulated, none have either substantially identified a particular cause, or shown to be representative of all patients presenting with TS.

Other Names

Although Transient Synovitis is the most common term to describe the condition many other names have been used to describe it. Some terms may be misnomers, however, remain in usage. These terms include:

Toxic SynovitisObservation HipCoxitis FugaxIrritable Hip (Syndrome)Hftschnupfens (German term)

BACKGROUND

Harding (1970) reviewed literature as far back as 1896, where he found what seems to be the first description of TS by Lovett and Morse. The pair described a "short-lived and ephemeral form of hip disease which presents at first characteristics of common hip disease, but the symptoms of which disappear in months instead of continuing for years". They believed the underlying cause to be related to some form of tuberculosis infection. In 1925, Todd hypothesized that trauma was the underlying cause of this condition. Subsequent researchers, including Fairbank (1926), Miller (1931), Butler (1933) and Finder (1936) all believed that an infection played a role in the etiology of TS. In 1952, an allergic hypersensitivity etiology was also proposed, this time by Edwards[4]. To this day, no etiological factor can be concretely associated with TS. However, an underlying infection of either viral or bacterial origin seems most likely.

ANATOMY & PATHOLOGY

*Gray's Anatomy of the Human Body

The hip joint is a synovial ball-and-socket joint; an articulation between the head of the femur (or Coxa) and the acetabulum of the hip. They are directly connected by the teres ligament and surrounded by the hip joint capsule (shown on the right). A number of studies have assessed the reaction of transient synovitis on the capsule. The consensus has been that there is an increased capsule size and increased effusion. However, whether the capsular size increase was as a result of effusion or independent of effusion was unlcear. Futami et al. found cartilage thickening in 2 of 36 patients with TS, which may also lead to increased capsular size[10], however, these findings have been contradicted by a more recent study (next paragraph). Robben et al. researched the effects of TS through the use of cadavers, healthy children and children with TS. Their aim was to analyze the effects of TS on the hip joint capsule. Their conclusion states that, "No measurable thickening of both layers (anterior and posterior) of the anterior joint capsule is present in transient synovitis. Therefore, enlargement of the anterior joint capsule in transient synovitis is caused solely by the presence of effusion"[17].

CLINICAL PRESENTATION

Children with TS present with a constellation of symptoms referred to as "Irritable Hip Syndrome". Irritable hip presents with a limp, or refusal to bear weight, and with the hip held in flexion, abduction, and external rotation[4][5]. This positioning is probably due to the fact that the patient feels most comfortable resting in such an orientation. Also, the movement of the affected hip is most likely to be limited, and therefore can be assessed during examination for verification; stretching of the joint will usually elicit pain in the affected hip.

Symptoms

Hip pain usually presents only on one side or joint but can be referred down to the knee joint as well[6]. Bilateral involvement has also been reported[7], however, due to its rare occurrence and lack of reporting, an estimated incidence compared to that of unilateral TS is difficult to evaluate. According to Turek's Orthopedics, however, unilateral involvement accounts for 95% of cases[8]. Other common clinical presentation of TS also include a child's reluctance to walk or bear weight, joint stiffness and a mild fever. While these symptoms may be interpreted as fairly unique, they are unfortunately not enough for a diagnosis. Other conditions such as septic arthritis, and Perths disease may present with identical symptoms, however, lead to detrimentally different outcomes. Therefore, when one is presented with the signs and symptoms of an "Irritable Hip" one must consider the possibility of other conditions before considering TS. TS is simply a diagnosis of exclusion, and even when it is diagnosed, a follow up visit to a physician should be scheduled to verify the diagnosis.

Imaging

A number of researchers have searched for characteristic manifestations of TS on various imaging techniques. Although the use of radiographs (X-rays), ultrasonography (USG), and MRI can be applied, limited information can be obtained for a diagnosis of TS[6][9][10]. X-Rays show no abnormality, but aid in the exclusion of other conditions[6][11]. USG can be used to determine whether joint effusion is present, however, it cannot aid in the differentiation between TS and other problems[9][12]. On the contrary to USG, (Lee Sang Kwon et al, 1999) it has been suggested that TS can be differentiated from septic arthritis using specific MRI imaging techniques[9], however, whether it is feasible to use MRI on every child presenting with an "irritable hip" needs to be further evaluated.

PREDISPOSING FACTORS

Age

The age group mainly affected by TS varies on the study. As a result of this, it would be more appropriate to simply state that children under the age of 15 are almost exclusively affected[1][6][7][13]. Although it is rare for children under 2 to be diagnosed with TS, one study documented a child as young as 6 weeks to show symptoms[11]. Furthermore, a number of cases in literature report the same presentation and symptomatology in adults. One case report presented a patient as old as 70 years of age[2].

Sex

Current research on the gender distribution of TS, presents a 2-3 times more frequent occurrence amongst boys over girls[1][14]. Most studies on TS also carry an approximate 2-3:1 ratio of boys to girls most likely as a result of the higher incidence in boys [7][13][15]. However, one should note that practically all data on incidence and gender distribution were conducted by European countries and therefore, this may not be a precise reflection of its presentation in the rest of the world.

Previous TS Episode

Children with a previous episode of TS are more likely to experience a recurrence when compared to children who have no history of TS[1][13]. One large study showed that the chance of recurrence in children with a previous episode was increased 20 fold[1]. Moreover, a review of other studies have shown a risk of recurrence between 0-17%[13]. The wide range may be explained by a number of factors; the most important of which is whether patients returned to seek medical attention. Patients (or their guardians) with prior episodes already know of the self-limiting course of TS as well as its likely short-duration, and therefore may be reluctant to return to their physician when encountering similar symptoms. This could explain the under-reported number of relapses in studies that sought medical records as a means of calculating recurrences. Therefore, while it is not known exactly how likely it will be to have a relapse of TS after a previous episode, studies have shown there to be an increased incidence.
In one study of 39 patients (Uziel et al. 2006), recurrences were most common within the first year after the initial episode (27/39, 69%). Five (13%) children had a recurrence during the second year and 7 (18%) children had later recurrence. The same hip was affected in 25 (64%) of the children[13].
Taking into consideration that a viral infections may be the precipitating cause, this would also then suggest that a recurrence of TS may be depended on a similar infection to have occurred prior to, or along with it. However, as mentioned below, the support for an infection to be the precipitating cause prior to an onset of TS needs to be further substantiated.

Infection?

Many sources indicate that it is a common finding to have an infection, in particular upper respiratory infection, proceeding the onset of TS. However, this has not been confirmed through scientific literature. The basis of this connection may have been erroneously passed through clinical teaching, or to the contrary, scientific evidence for such an association may simply have been not been able to "proof" such a relationship. Regardless of the facts, information on whether an infection preceded the onset of TS does not effect the outcome of the condition which remains self-limited, and more importantly, is not necessary for diagnosing TS. Various sources indicate that TS is often proceeded or accompanied by viral infections, however, these studies have indicated possible associations with these infections and only for a fraction of cases[1][6][7][17]. Furthermore, many studies have used the term "Irritable Hip" and associated it with viral infections; however, "Irritable Hip" does not exclusively lead to TS and the term is not interchangeable. This leads to misleading information if the final diagnosis was not confirmed to be TS.
Viruses Although upper respiratory viral infections are commonly stated as possible etiologies of TS [1][18], this has not been fully substantiated. While some researchers have suggested that indications of an etiological association exists[7][18], studies that have searched for evidence of this have not been successful[6][19]. One study evaluated the serological markers for Parvovirus B19 and Herpes Virus 6 in patients with TS, however, neither were concluded to be linked to its cause[20].
Bacterial Specific serological investigation of patients for streptococci and staphylococci found no relationship and did not support a bacterial etiology. The first hypothesis of a relationship between bacterial infection and TS found was by Fairbank in 1926 who suggested that in many cases there was a subacute or chronic infection of the joint due to a mild strain of staphylococci[6].

Trauma?

Trauma has been considered as a possible etiology of TS, however, findings are not suggestive of it contributing to its occurence[6].

DIAGNOSIS

Diagnosing TS can be challenging. The fact that no known etiology has been confirmed has resulted in the utilization of clinical symptoms and experience as principle methods by which TS is diagnosed. Recent studies have focused on specific clinical parameters that may be useful in combination in the diangosis of TS.Most of the focus has been on differentiating between TS and septic arthritis. The reason for this, is not only explained by their similar presentation but also because neither are excluded from X-rays. Radiographic imaging is most likely to be the first medical investigation and is able to exclude other conditions such as a fracture or Slipped Upper Femoral Epiphysis (Slipped Capital Femoral Epiphysis). Kocher's Protocol (1999) focused on the following clinical parameters: Presence of fever, Weight-bearing ability, ESR (Erythrocyte Sedimentation Rate), and serum white blood cell count. Other more recent papers have proposed the use of CRP (C-Reactive Protein) rather than ESR. While the efficacy of Kocher's protocol has been both supported and disputed by subsequent papers, it serves as a tool in the diagnosis of TS.

DIFFERENTIAL DIAGNOSIS

When a patient presents with symptoms of an Irritable Hip the following other conditions need to be excluded before considering a diagnosis of TS.
Septic Arthritis
Legg-Calv-Perthes disease (Avascular Necrosis of the Femoral Head)
Osteomyelitis
Bone fracture
Developmental Dysplasia of the Hip (DDH)
Juvenile Idiopathic Arthritis (JIA) or Juvenile Rheumatoid Arthritis (JRA)
Slipped Upper Femoral Epiphysis (Slipped Capital Femoral Epiphysis)
Gonococcal Arthritis or Non-Gonococcal Arthritis (e.g. Lyme Arthritis)
Neoplastic Disease

The above differential diagnosis was adapted from "The limping child: epidemiology, assessment and outcome" (reference 7 below).

PROGNOSIS

The course of TS is mild; It may last only a few days, but in some cases can take a little longer to resolve. While the Etiology of TS has not yet been established, it is known that increased synovial effusion occurs in the hip joint. This has led earlier research to propose a possible link between TS and an increased risk in Legg-Calv-Perthes disease (Avascular Necrosis of the Femoral Head), however, newer studies have disputed these findings by finding no such correlation[21]. The basis of this link was probably as a result of the idea that increased effusion may increase intracapsular pressure and as a result decrease arterial perfusion pressure leading to avascular necrosis of the femoral head.

TREATMENT

Since TS is a mild and self-limiting condition[6][7], treatment is not usually necessary. However, in some cases pain may be a significant factor which led to the child's visit to the physician and therefore can be managed with NSAIDs (Non-Steroidal Anti-inflammatory Drugs) such as ibuprofen[3]. The efficacy of ibuprofen in reducing the average number of days with symptoms in TS was assessed by a randomized placebo-controlled triple-blind study published in 2002. The findings of the study suggested that ibuprofen decreases the average number of symptoms of TS from 4.5 days in the placebo group to 2 days with ibuprofen[3].
Although the study suggests that treatment is an effective way to reduce symptoms of TS it should be used cautiously. The analgesic effects of NSAIDs may mask a more severe underlying condition that was wrongly diagnosed as TS. As a diagnosis of exclusion, TS should therefore be clearly evident before considering treatment with NSAIDs.

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19 Dec 2011 at 3:06pm

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