ULTRASOUND DIAGNOSIS OF BONY NERVE ENTRAPMENT: CASE SERIES AND LITERATURE REVIEW CARMEN ERRA, MD, 1 GIUSEPPE GRANATA, MD, 2 GIOVANNA LIOTTA, MD, 3,4 SIMON PODNAR, MD, DSc, 5 MAURO GIANNINI, MD, 6 HANI KUSHLAF, MB, BCh, 7 LISA D. HOBSON-WEBB, MD, 7 FRASER J. LEVERSEDGE, MD, 8 CARLO MARTINOLI, MD, PhD, 9 and LUCA PADUA, MD, PhD 1,2 1 Don Carlo Gnocchi Foundation, Piazzale Morandi 6, Milan, Italy 2 Department of Neurosciences, Institute of Neurology, Catholic University of Sacred Heart, Rome, Italy 3 Ospedale degli Infermi, Rivoli, Turin, Italy 4 Department of Neuroscience, University of Messina, Messina, Italy 5 Institute of Clinical Neurophysiology, Division of Neurology, University Medical Centre, Ljubljana, Slovenia 6 Policlinico Casilino, Rome, Italy 7 Department of Neurology, Duke University Medical Center, Durham, North Carolina, USA 8 Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina, USA 9 Radiology Department, DISC, Universit a di Genova, Genova, Italy Accepted 6 March 2013 ABSTRACT: Introduction: Nerve entrapment due to osseous callus formation is a rare complication after bone fracture. Elec- trodiagnostic studies and routine radiographic imaging often fail to demonstrate the pathology. The diagnosis is difficult and is often made incidentally upon surgical exploration. Nerve ultra- sonography has not been used routinely to assess such lesions. Methods: We report 5 cases of nerve entrapment in os- seous callus after fractures that occurred in 2011 and 2012. The diagnosis was made by ultrasound (US). We then per- formed a review of the relevant literature. Conclusions: US is becoming an invaluable tool for diagnosing peripheral nerve entrapments. The current cases suggest that nerve US should be strongly considered as an adjunctive diagnostic tool for nerve palsies developing after trauma. Muscle Nerve 48: 445–450, 2013 Nerve palsies developing weeks or months after a trauma are diagnostically challenging. Physicians may incorrectly attribute the palsy to the trauma or subsequent surgery and be unaware of the role of posttraumatic or postsurgical posture. Nerve entrapment due to osseous callus formation is a rare complication after bone fractures. The diag- nosis is usually made incidentally during surgical exploration and cannot be made through routine imaging or electrodiagnostic (EDx) testing. Ultrasound (US) is a sensitive technique for studying peripheral nerves. It can identify unex- pected causes of nerve damage and provide ana- tomical information to supplement clinical and electrophysiological examinations. 1,2 It is particu- larly helpful in examination of traumatic nerve injury, permitting more exact localization of injury and demonstration of nerve continuity. We describe 5 patients with bone fractures and delayed nerve palsies due to nerve entrapment within the healed fracture site. Although EDx test- ing revealed the extent of nerve dysfunction, the diagnosis was made by US. We also performed a lit- erature review to search for similar cases. CASE REPORTS Patients presented for evaluation at our labora- tories in 2011 and 2012. All testing was performed as part of routine medical care. Patient 1. A 45-year-old man presented with pro- gressive left hand weakness and sensory loss. Physi- cal examination revealed left elbow ankylosis, atrophy and weakness of the first dorsal interosse- ous and intrinsic muscles of the hand, and hypes- thesia of the fourth and fifth fingers. Four months earlier he had a traumatic left olecranon epiphy- seal fracture, which was treated surgically soon after the injury. The left ulnar sensory nerve action potential (SNAP) was absent. Ulnar motor nerve conduction studies, recorded from the first dorsal interosseous and abductor digiti minimi muscles, showed reduced compound motor action potential (CMAP) amplitudes. There was also marked slowing of con- duction velocity (6 m/s) and conduction block (from 1 to 0.3 mV) across the elbow. Motor conduc- tion velocity was normal in the arm and forearm. On initial US examination, the left ulnar nerve was not visible distal to the elbow. After further evalua- tion, the nerve was identified entering an hypere- choic tunnel (the osseous callus; Fig. 1A). Distal to this structure, the ulnar nerve was again visible (Fig. 1A), appearing hypoechoic and enlarged (cross-sectional area 16 mm 2 ). X-ray of the elbow showed the presence of callus, but no other abnormalities were seen (Fig. 1B). The patient then underwent surgical exploration, which confirmed that the ulnar nerve had been encased Abbreviations: 3D-CT, 3-dimensional computerized tomography; CMAP, compound motor action potential; EDx, electrodiagnostic; EMG, electro- myography; SNAP, sensory nerve action potential; US, ultrasound Key words: bony nerve entrapment; bony tunnel; delayed nerve palsy; nerve ultrasound; osseous callus Correspondence to: C. Erra; e-mail: carmen.erra@hotmail.it V C 2013 Wiley Periodicals, Inc. Published online 27 July 2013 in Wiley Online Library (wileyonlinelibrary. com). DOI 10.1002/mus.23845 Bony Tunnel and Nerve US MUSCLE & NERVE September 2013 445