Posterior interosseous neuropathy: distinguishing from a proximal radial neuropathy

The posterior interosseous nerve is the terminal motor branch of the radial nerve that innervates the extensor carpi ulnaris and the extensors of the thumb and fingers. We describe a case of a posterior interosseous neuropathy presenting with the typical ‘finger drop’ and partial ‘wrist drop’. We focus on the clinical signs that distinguish it from a more proximal radial neuropathy, clarified by nerve conduction studies and needle electromyography. Multimodal imaging of the forearm did not identify a compressive lesion. Persistent symptoms prompted surgical exploration 5 years after initial onset. It identified compression of the posterior interosseous nerve in the region of the arcade of Frohse and leash of Henry. The sites were decompressed and concurrent salvage secondary reconstructive tendon transfers were required in view of the severe axonal loss with minimal chance of functional reinnervation.

Supinator to Posterior Interosseous Nerve Transfer for Restoration of Finger Extension

BACKGROUND Cervical spinal cord injuries result in a severe loss of function and independence. The primary goal for these patients is the restoration of hand function. Nerve transfers have recently become a powerful intervention to restore the ability to grasp and release objects. The supinator muscle, although a suboptimal tendon transfer donor, serves as an ideal distal nerve donor for reconstructive strategies of the hand. This transfer is also applicable to lower brachial plexus injuries. OBJECTIVE To describe the supinator to posterior interosseous nerve transfer with the goal of restoring finger extension following spinal cord or lower brachial plexus injury. METHODS Nerve branches to the supinator muscle are transferred to the posterior interosseous nerve supplying the finger extensor muscles in the forearm. RESULTS The supinator to posterior interosseous nerve transfer is effective in restoring finger extension following spinal cord or lower brachial plexus injury. CONCLUSION This procedure represents an optimal nerve transfer as the donor nerve is adjacent to the target nerve and its associated muscles. The supinator muscle is innervated by the C5-6 nerve roots and is often available in cases of cervical SCI and injuries of the lower brachial plexus. Additionally, supination function is retained by supination action of the biceps muscle.

Posterior interosseous nerve entrapment by intramuscular lipoma arising from the supinator muscle - a case report

Background: Lipomas are benign, slow-growing tumors frequently subcutaneous and asymptomatic, intramuscular lipoma constituting a rare subtype. However, a lipoma occurring nearby the proximal radius may cause posterior interosseous nerve (PIN) entrapment. Case presentation: We described an uncommon case of a 45-year-old-man with a history of progressive, painless proximal right (dominant) forearm swelling for 4 months associated with PIN entrapment syndrome, presenting as fingers extension weakness. Intramuscular lipoma was observed in the supinator muscle in the magnetic resonance imaging (MRI). Lipoma surgical excision and release of the PIN through proximal forearm direct anterior approach was performed. Results: The histopathological examination confirmed the diagnosis of benign intramuscular lipoma. The follow-up of the patient showed full recovery within three months postoperatively. Discussion: Intramuscular lipoma is rare; however, it could originate from supinator muscle in the forearm, presenting with vague pain and could lead to compression of nearby neurovascular structures such as the PIN. Clinical evaluation and imaging studies, especially MRI, are crucial for diagnosis. If neural compression is evident, surgical resection is mandatory. Conclusion: Intramuscular lipoma entrapping PIN is rare and requires early clinical diagnosis confirmed by imaging and neurophysiological studies, surgical excision being the method of choice for optimum functional outcomes.

Posterior Interosseous Nerve Graft: Utilizing External Landmarks and Anthropometric Ratios to Predict Available Length for Digital Nerve Reconstruction in a Cadaveric Study

Objective: In digital nerve defects that require grafting, autografts remain the efficacious option. The sensory posterior interosseous nerve (PIN) is an ideal choice as it is of similar caliber to digital nerves and leaves no donor morbidity upon resection. However, a finite length of harvestable PIN exists, and considerable variations of this length have been reported in the literature. There exists no predictive model to estimate this length. We sought to determine a method to accurately predict the available length of PIN based on individual patient anthropometry. Methods: A cadaveric dissection study was performed in a fresh tissue laboratory. The length of the sensory branch of the PIN and various anthropometric measurements were made in respect to surface anatomy of the ulna to develop a predictable ratio for available PIN donor graft. Results: A total of 16 specimens were obtained. On average the length of the PIN was 5.7 cm (range: 3.3-9. cm) and the length of the ulna was 25.7 cm (range: 23.5-30.6 cm). The ratio of PIN to ulnar length was 0.222 ( r = 0.4651). Using one-fifth the length of the ulna, the mean predicted length of the PIN was 5.14 cm (range: 4.7-6.1 cm). On univariate analysis, there was no significant difference between the measured and predicted PIN length ( P = .249). Conclusion: An anthropometric ratio predicated on reproducible surface anatomy of the ulna is a useful tool in predicting the sensory PIN length. Such a prediction may be a useful in guiding patient discussions concerning surgical options for digital nerve reconstruction.