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Subclinical Peroneal Nerve Entrapment may be an Under-recognized Cause of Falls in Hospitalized Patients
Louis H. Poppler, MD1, Anchal Bansal, BS1, Andrew Groves, BS1, Gina Sacks, BS1, Kristen Davidge, MD2, Susan E. Mackinnon, MD1.
1Washington University in St. Louis School of Medicine, St. Louis, MO, USA, 2Hospital for Sick Children, Toronto, ON, Canada.
PURPOSE: Falls are a major cause of morbidity and mortality, costing the United States $30 billion in 2010. Compression of the peroneal nerve at the fibular neck is a known cause of foot drop that can lead to tripping and falling. We hypothesize that sub-clinical or early entrapment of the peroneal nerve can cause tripping, stumbling and falling. Additionally, peri- and post-operative positioning, along with other surgical factors are known causes of peripheral neuropathies. We hypothesize that lengthy surgery and ICU stays may increase the risk of peroneal neuropathy and thereby increase a patient’s likelihood to fall. Early intervention could be a major opportunity to prevent falls in this population.
METHODS: Aim 1 - A prospective cross-sectional study examined 100 randomly selected patients identified at moderate or high fall risk on four medical floors with high falls frequency. Medical co-morbidities, tripping and falls histories, and the Activities-specific Balance Confidence (ABC) Scale were collected. Medical Research Council (MRC) strength testing of ankle dorsi- and plantar-flexion, inversion and eversion, and provocative testing (Tinel’s test and Scratch Collapse (SC) Test) were performed to assess for signs of peroneal neuropathy. Aim 2 - 50 elective cardiac surgery patients were prospectively examined for peroneal neuropathy (as in Aim 1) at a pre-operative anesthesia visit and then again after discharge from the Cardiac ICU. Data on anesthesia time, ICU stay, and surgery type were collected. Weakness of dorsiflexion/eversion, provocative tests, and a history of falls were correlated using odds ratios and chi-squared test. In aim 2, frequency of weakness and positive provocative tests before and after surgery were correlated with operative time and ICU stay.
RESULTS: Aim 1 - 100 patients, mean age 53.0 ± 13.1, 59% female were examined. 42% had at least one positive provocative sign and 38% had weakness of the peroneal nerve. A positive Tinel’s, SC or both were all significantly (p<0.05) associated with peroneal nerve weakness (Odds ratio 4.8, 2.8 and 8.0 respectively). Patient’s with a positive Tinel’s were 3.8x more likely to have falls in the last year (p=0.009) and patients with both provocative signs were 4.4x more likely to trip or stumble frequently (p=0.008). Aim 2 - 27 patients enrolled, mean age 67.2 ± 15.1, 35.7% female. 32% of pre-operative patients had a provocative sign. 63% of post op patients have a provocative sign. 48% of patients gained at least one provocative sign.
CONCLUSION: This study suggests that peroneal neuropathy is common among hospitalized patients identified as high-risk for falls. Positive provocative tests for peroneal neuropathy in this population were also significantly correlated with a recent history of falls, suggesting that peroneal neuropathy may be a contributor to outpatient falls. Furthermore, subclinical peroneal neuropathy was present in approximately 1/3 of patients undergoing elective cardiac surgery. The observed increase in the proportion of patients with clinical evidence of peroneal neuropathy postoperatively suggests that prolonged surgery and ICU stays may contribute to the development of subclinical peroneal neuropathy.
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