Reply to Letter to the Editor: Preoperative Peripheral Nerve Blocks in Orthopaedic Trauma Surgery: A Guide to Diagnosis-Based Treatment

Abstract

T he Authors' Reply: We thank Smith et al and Pulos et al for their letter and continued discussion on our article: "Preoperative Peripheral Nerve Blocks in Orthopaedic Trauma Surgery: A Guide to Diagnosis-Based Treatment." 1 Their comments surrounding the use of peripheral nerve blocks (PNBs) in orthopaedic trauma highlight the paradox that some patients who stand to benefit from PNBs may be least often considered for it because of fear for missing or delaying the diagnosis of acute compartment syndrome (ACS). Our article highlights a gradation of recommendations for PNB use in different scenarios of clinical risk.The risk of compartment syndrome is 2% to 9% in tibia fractures 2 and 15% to 27% in high-energy tibia plateau fractures. 3 Smith et al refer to the retrospective study they are currently preparing for publication, with only two of 8,300 long bone fracture patients (0.02%) requiring fasciotomy for ACS in the setting of perioperative PNBs, which is not consistent with ACS incidence in the orthopaedic literature. It seems like either their practice comprises only very low-energy injuries, or there is a selection bias, which excludes high-risk patients.The timing of ACS is not necessarily predictable. Although most cases of ACS occur within 24 to 48 hours of injury, it can develop preoperatively, intraoperatively, or postoperatively. Significantly increased pain with passive stretch of specific compartment is commonly used to diagnose ACS; unfortunately, it is subjective. Moreover, the most objective sign to diagnose developing ACS is a neurologic deficit that usually starts with sensory and progresses to motor findings; therefore, a complete neurologic examination is critical. Smith et al bring up a very interesting point regarding the transmission of ischemic pain through the sympathetic nervous system, which should be unaffected by purely somatic PNBs. The risk, however, is that not all PNBs are purely somatic, which may confound the clinical examination. 4 In addition, their study was based on muscles in the gastrointestinal tract and the abdominal wall, 5 so it would be prudent to test this hypothesis in the appendicular skeleton. Furthermore, it is not only the masking of pain that confounds the clinical evaluation of compartment syndrome but also the masking of sensorimotor function. 6 Ischemia time of just 4 hours has been shown to lead to irreversible axonotmesis and 6 hours for irreversible necrosis. 7 Therefore, a timely physical examination that is monitored over time is crucial in the diagnosis of ACS, and inability to assess sensorimotor function due to PNBs that may last 8 to 18 hours eliminates these crucial data points. 8 A similar approach must be appreciated when evaluating injuries such as an acute distal radius fracture, where the development of acute carpal tunnel syndrome, which necessitates urgent carpal tunnel release, would be completely masked by PNBs. 9