EBM Series: Traumatic Arthrotomy
The Case
A 30-year-old male presents to the emergency department after an accident at work. He works as a logger, and while cutting down a tree, he accidentally cut along his knee with a chainsaw. The patient is hemodynamically stable, bleeding is controlled, and he denies other trauma. He has an 8cm linear laceration extending horizontally across the knee. He has limited range of motion secondary to pain.
What are the next best steps in approaching the workup of this patient?
Traumatic Arthrotomy (TA): Background
Definition
TA occurs when there is violation of a joint space from an overlying soft tissue injury. Violation of the sterile joint capsule exposes the joint space to microbes which predisposes to deep infection and significant morbidity with potential mortality if left untreated.
Figure 2. Knee Anatomy
Source: Atlanta Osteoarthritis Center
Epidemiology
Occurs most commonly in mid-twenty to early thirty-year-old men
Common mechanisms: MVA, GSW
Knee is the most commonly affected joint (53 to 91% of all TA presentations)
Can occur at any joint including the shoulder, elbow, wrist, hip, ankle, hands, and feet
TA increases the risk of septic arthritis and is considered an emergent surgical condition
Incidence of concurrent fracture: 24% to 55%; infection rate: 0% to 11.8% [1]
Clinical Signs
Peri-articular laceration
Limited ROM
Synvoial fluid extravasation
Open fracture
Severe: Neurovascular deficit, hemodynamic instability
Morbidity
Prior to antibiotics, septic arthritis occurred in up to 100% of traumatic arthrotomies
Since development of novel diagnostic techniques and appropriate treatment, the rate of septic arthritis after a traumatic arthrotomy is less than 5% [1]
Septic arthritis carries 15% mortality even when appropriately diagnosed and treated in the hospital
Irreversible decrease in joint function rate between 25 and 50%
Delayed debridement leads to worse pain, limp, range of motion, and joint instability [2]
Diagnostic Approach
For decades, the gold standard for the emergency department diagnosis of TA involved the Saline Load Test (SLT). While this approach (with or without the addition of methylene blue) has been more extensively studied, and generally carries favorable testing characteristics, more recent studies suggest that a CT scan may have a higher diagnostic yield, is less operator-dependent, and may be more tolerable for patients.
SLT Technique
The SLT involves injecting sterile saline into a joint where a penetrating articular injury is suspected. The site of injection is judiciously chosen to avoid the periarticular wound. Extravasation of saline from the joint represents a positive test. Failure of extravasation is defined as a negative SLT and classically implies an intact joint capsule [3].
No single study has comprehensively assessed the SLT's efficacy in detecting open wounds across various joints. Existing literature predominantly concentrates on the knee joint, leaving other joints inadequately explored.
Additionally, there is no consensus regarding the optimal amount of saline to inject to yield a reliable result. The most comprehensive data suggests that within the knee joint volumes ranging from 155 to 194 mL can provide a sensitivity of 95%,[4,5], while a volume of 175 mL has been shown to provide a sensitivity of 99% [4]. A proposed explanation of the wide range of reliable volumes is the heterogeneous sizes of lacerations included in the studies [3].
Regarding other joints, a study involving ankle SLT found a sensitivity ranging from 95% to 99% using 30 mL of saline [6]. A study of elbow SLT demonstrated a 95% sensitivity of SLTs employing 40 mL of saline combined with methylene blue dye [7].
Notably, SLT can lead to iatrogenic injury from increased joint pressure leading to decreased blood flow, injury of surrounding structures if the needle is improperly placed, and disturbance of an intact joint [8,9]. Further, it can lead to increased pain for patients [8].
Table 1: Adequate proposed volumes for SLT by joint
Methylene Blue
Only one study to date has compared whether the addition of methylene blue improves the reliability of SLT. While it is intuitive to anticipate that its addition would increase diagnostic yield, the study found no statistically significant difference between SLT regardless of the addition of methylene blue [10]. Notably, however, many providers still prefer its addition as it has not been shown to cause harm [7, 11].
CT Scan
While SLT is still considered a relatively reliable diagnostic modality for TA, recent research suggests that CT scans have several advantages. For instance, a study compared the accuracy of SLT and CT scans and found CT outperformed SLT with a sensitivity and specificity of 100% (compared to a sensitivity of 92%) [12].
The inter-operator reliability, lack of potential for iatrogenic injury, and the patient satisfaction impact of obtaining a CT scan compared to SLT to assess for TA has already led to a change of practice for many providers. Further research is necessary to ensure this data is reliable and safe to employ as standard of care.
Clinical Practice Guideline
While the literature on the diagnostic approach to TA is heterogeneous and largely inconclusive, I have proposed a Clinical Practice Guideline that attempts to address these inadequacies while applying the best available data.
Figure 3: Proposed Clinical Practice Guideline to the Suspected Traumatic Arthrotomy
Case Continued
Our patient’s exam was concerning for a penetrating joint injury. We first obtained an XR’s of the knee which did not show a fracture and was inconclusive regarding joint penetration. A CT of the knee was then obtained (below) showing air along the joint space, prompting an orthopedic consult, IV antibiotics, and the patient was made NPO. He was taken the next morning for washout without any functional deficits at 6 months.
Take Home Points
Suspect TA with peri-articular lacerations
Most commonly occurs in knee joints of young adult men
Carries significant morbidity and potential mortality if unaddressed
CT appears adequately sensitive and specific enough to identify the majority of TA
If CT is negative, and there is still a concern for TA, it is reasonable to perform a SLT
AUTHORED BY: NICK DIMEO, MD, PGY3
FACULTY EDITING BY: NIK SEKOULOPOULOS, MD
References
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