Computer assisted surgical anatomy mapping (CASAM) of the distal Posterior Interosseous Nerve (PIN) and its relation to the wrist arthroscopy portals: A cadaver study.

Introduction: The distal Posterior Interosseous Nerve (PIN) plays an important part in the sensory innervation of the wrist joint. Introduction of the arthroscopy portals during wrist arthroscopy might injure the PIN. The anatomic variation in the trajectory of the PIN and the proximity to the dorsal arthroscopy portals have not yet been fully explored. Materials and methods: Computer assisted surgical anatomy mapping (CASAM) is a technique to digitally compute and merge photographic images using anatomic landmarks and visualize variation in anatomy. A standard wrist arthroscopy procedure was carried out on eight cadaver forearms. CASAM was used to map the trajectory of the distal PIN and measure the distance to bony landmarks and the nearest wrist arthroscopy portals. Descriptive statistics were provided for anatomical measurements. Results: CASAM illustrated great variation in the PIN trajectories between the specimens. The mean distance from the PIN to Lister's tubercle was 9 â€‹mm (range 3-14, SD 3.9), the distance to the ulnar styloid was 27 â€‹mm (range 23-32, SD 3.3). None of the nerves showed signs of iatrogenic injury from placement of the arthroscopy portals. The 3-4 portal and the 6R portal were closest to the PIN with a respective mean distance of 9 â€‹mm (range 4-15, SD 3.8) and 19 â€‹mm (range 13-22, SD 3.2). Conclusion: CASAM demonstrated the importance of understanding nerve anatomy variations and offered insight into which arthroscopy portals are most likely to damage the distal PIN. However, we conclude that the overall risk of PIN injury from wrist arthroscopy is low due to the proximity to the portals.

Supinator to posterior interosseous nerve transfer to restore hand opening in brachial plexus and spinal cord injury: a systematic review and individual patient-data meta-analysis.

OBJECTIVE: Cervical spinal cord injury (SCI) and lower trunk brachial plexus injury (BPI) commonly result in hand paralysis. Although restoring hand function is complex and challenging to achieve, regaining volitional hand control drastically enhances functionality for these patients. The authors aimed to systematically review the outcomes of hand-opening function after supinator to posterior interosseous nerve (PIN) transfer. METHODS: A systematic literature review was performed according to the PRISMA guidelines. RESULTS: A total of 16 studies with 88 patients and 119 supinator to PIN transfers were included (87 transfers for SCI and 32 for BPI). In most studies, the time interval from injury to surgery was 6-12 months. Finger extension and thumb extension (Medical Research Council grade ≥ 3/5) recovered in 86.5% (103/119) and 78.1% (93/119) of cases, respectively, over a median follow-up of 19 months. The rates of recovery were similar for the SCI and BPI populations (finger extension, 87.3% in SCI and 84.3% in BPI; thumb extension, 75.8% in SCI and 84.3% in BPI). Type of injury (OR 1.05, 95% CI 0.17-6.4, p = 0.95), time from injury to surgery (OR 1.01, 95% CI 0.8-1.29, p = 0.88), and age (OR 0.97, 95% CI 0.90-1.06, p = 0.60) were not associated with odds of a successful outcome. Duration of follow-up was significantly associated with successful finger extension (OR 1.15, 95% CI 1.01-1.30, p = 0.026). No donor-associated supinator weakness was reported postoperatively given that patients had an intact bicep muscle preoperatively contributing to supination. CONCLUSIONS: Supinator to PIN transfer is a safe and effective procedure that can achieve successful restoration of digital extension in the SCI and BPI population at similar rates. Duration of follow-up was associated with superior outcomes, which was expected.

Vascularized posterior interosseous nerve graft for digital neurovascular bundle reconstruction.

INTRODUCTION: Despite the progress in microsurgery in recent decades, neurovascular bundle defects during ring finger injuries still pose challenges for the surgeon. Usually, a reversed venous graft and a non-vascularized nerve graft are utilized to reconstruct this defect. One of the most common challenges encountered when using a venous graft is the caliber mismatch between the graft and the digital arterial ends. The use of an arterialized nerve graft (neurovascular graft) is poorly described and could represent an attractive reconstructive option. CASE PRESENTATION: We present the case of a 36-year-old manual worker, a non-smoker, with no significant medical or surgical comorbidities, who presented a ring avulsion type trauma, leading to the amputation of the third left finger at the distal interphalangeal joint and avulsion of the circumferential skin at the level of the middle and proximal phalanges (Urbaniak III). The patient presented a neurovascular bundle defect of 3 cm, reconstructed by the vascularized posterior interosseous nerve graft along the distal perforator of the dorsal branch of the anterior interosseous artery serving both as an interpositional arterial conduit and as a nerve graft. The results of postoperative nerve regeneration at three years are satisfactory, with the patient demonstrating a two-point discrimination measured at 6 mm. CONCLUSION: Simultaneous digital artery and nerve reconstruction using a neurovascular flap is very appealing to the hand surgeon as it offers several advantages over traditional methods, particularly the ideal diameter match between the digital arteries and the distal perforator of the dorsal branch of the anterior interosseous artery.

Anterior Congenital Radial Head Dislocation in an Adult with Associated Posterior Interosseous Nerve Palsy.

Introduction: Anterior congenital radial head dislocation (CRHD) is a rare abnormality that is less commonly seen in the adult population. Most of the time, adult-onset symptoms are due to the prolonged dislocation of the radiocapitellar joint that has been present since birth. One of the possible complications of having a prolonged radial head dislocation is the presence of neuropathies such as posterior interosseous nerve (PIN) palsy. There has been, however, no literature published regarding the relationship of CRHD with PIN palsy. Case Report: We here report a 66-year-old male incidentally diagnosed with anterior CRHD with concomitant PIN palsy after acquiring a fracture of the lateral humeral condyle. Open reduction internal fixation of the lateral condyle was done along with decompression of the said nerve. PIN palsy was completely recovered 2 months after surgery. Conclusion: Surgeons must be aware that PIN palsies can occur in the presence of a chronic radial head dislocation, even if asymptomatic. Prompt nerve decompression as well as removal of the mechanical block is pertinent to avoid the perilous effects of an irreversible PIN palsy.

Neurovascular crossing patterns between leash of Henry and deep branch of radial nerve: implications for neurointervention and diagnostic imaging.

OBJECTIVE: To detail the neurovascular crossing patterns between the leash of Henry (LoH) and the deep branch of the radial nerve (DBRN) in supination and pronation of the forearm, using imaging methods with anatomic correlation. MATERIALS AND METHODS: This cross-sectional study was performed ex vivo with HRUS and MRI with anatomic correlation on 6 samples and in vivo with HRUS with Doppler on 55 participants scanned bilaterally. The in vivo participants were enrolled over a 6-month period. The crossing patterns between the LoH and DBRN were assessed ex vivo and in vivo. Additional morphological features of the DBRN, LoH, and fat plane were assessed in vivo only. Biometric features of the participants were recorded. Statistical analyses were performed using Shapiro-Wilk, parametric and non-parametric tests. RESULTS: The most common neurovascular crossing pattern was the ascending branch of the radial recurrent artery (RRAab) crossing below (ex vivo: 83.3%, in vivo: 85.3%) and the muscular branch crossing above (ex vivo: 100%, in vivo: 63.2% %) the DBRN. Both the deep and superficial surfaces of the DBRN exhibited an intimate relationship with the vessels of the LoH. A positive correlation between vessel diameter and anthropometric factors was observed. In addition, the muscular branch exhibited a significantly smaller diameter than the RRAab. CONCLUSION: Our study detailed the relationship between the LoH and the DBRN and highlighted the high incidence of vessel crossing above the DBRN at the level of the muscular branch. Knowledge of neurovascular crossings is crucial for understanding neurovascular entrapment syndromes and planning interventional procedures to reduce vascular complications.

Nomenclature of the radial nerve: distinguishing between the deep branch of the radial nerve and the posterior interosseous nerve.

To address an inconsistency in the nomenclature of the anatomy and compressive syndromes of the deep branch of the radial nerve, we advocate for a single compression syndrome that presents along a spectrum from pain to posterior interosseous nerve palsy.

Clinical, Electrodiagnostic, and Ultrasound Findings in 87 Patients With Finger Drop.

BACKGROUND: The inability to extend the fingers at the metacarpophalangeal and interphalangeal joints leads to finger drop. While wrist drop and foot drop are well recognized, the causes of finger drop are poorly understood. AIMS: This study describes the clinical, electrodiagnostic (EDX), and ultrasound (US) features in patients with finger drop. MATERIALS AND METHODS: This is a retrospective study of 87 patients presenting with finger drop and referred for EDX studies during the past 10 years. We analyzed the clinical picture, EDX data, and US findings. The patients were categorized into global (all five digits) or partial (limited to 1-4 digits) finger drop. RESULTS: Fifty-six (64%) patients had global finger drop, while 31 (36%) had partial finger drop. The frequent cause of finger drop was Parsonage-Turner syndrome (PTS) (29 [33%]), followed by trauma (23 [26%]), cervical radiculopathy (16 [18%]), extensor tendon rupture (four [4%]), and compression/entrapment (two [2%]). In 13 (15%) patients, no cause was identified. A total of 13/16 (81%) patients with cervical radiculopathy and four of the patients with tendon rupture had partial finger drop, while 52/64 (81%) with posterior interosseous nerve (PIN) neuropathy had global finger drop. Of the 16 patients who experienced cervical radiculopathy as the cause of the finger drop, 15 patients had C7 and C8 radiculopathy and one patient had C7 radiculopathy. EDX studies of patients with PTS revealed partial axon loss in 18 (62%) patients, conduction block in eight (28%), and total axon loss in four (14%). Enlarged fascicles were observed by US in 40% of patients with PTS. EDX studies of patients who sustained iatrogenic nerve injury causing finger drop demonstrated total axon loss in six (46%) patients, partial axon loss in four (31%), demyelination in two (15%), and conduction block in two (15%). CONCLUSIONS: PIN neuropathy is the most common cause of finger drop, however, lesser-known causes such as cervical radiculopathy and extensor tendon rupture should also be considered. Global finger drop is suggestive of PIN neuropathy, while partial finger drop occurs more often in cervical radiculopathy and tendon rupture. EDX and US studies provide valuable information for localizing the lesion site and may reveal the cause of the finger drop.

Neglected posterior interosseous nerve injury.

Posterior interosseous nerve (PIN) injury is uncommon due to its anatomically deep location. We report a neglected, rare case of PIN injury presenting the loss of extension of thumb, index, and small fingers with weakness of thumb abduction in a 49-year-old male patient. The patient sustained a penetrating injury to his right forearm caused by a kitchen knife that was repaired primarily through an emergency surgery under general anesthesia. During the regular follow-up on the 52nd postoperative day, the patient presented 20° of extension lags in the right thumb and index finger and 30° in the small finger. Wrist extension was intact, and there was no sensory deficit. We explored the wound and traced the PIN completely, identifying a club-shaped neuroma formation at the proximal cut end of the PIN. Delayed nerve repair was performed with a double-strip cable graft. Hand surgeons should be aware of the probable PIN injury in certain situations of forearm-penetrating injury and perform proper preoperative physical examination to rule out neurovascular deficits. Careful exploration and immediate repair of severe PIN are mandatory, even in emergency situations.

Imaging characteristics of posterior interosseous nerve syndrome.

Posterior interosseous nerve syndrome (PINs) is a rare nerve compression syndrome that affects the deep branch of the radial nerve in the supinator muscle region. In this article, we aimed to report a case of a 58-year-old male who had clinical symptoms, electromyographic, ultrasound, and MRI features suggestive of PINs due to compressing the arcade of Frohse. He subsequently underwent surgical correlation at our hospital, and the clinical symptoms were improved significantly.

Posterior Interosseous Neuropathy Related to a Loose Distal Biceps Cortical Button: A Case Series.

Posterior interosseous nerve (PIN) injury is an uncommon yet debilitating complication following distal bicep tendon repair. There are case reports of acute intraoperative PIN injury related to retractor placement, drill trajectory, and nerve incarceration. We report three cases of delayed PIN neuropathy in the setting of a loose cortical button. All patients had resolution of their pain with removal of the cortical button and decompression of the radial tunnel. The purpose of this case series is to: 1) highlight the possibility of a loose cortical bicep button as the cause of proximal forearm pain and PIN neuropathy in the early or late postoperative timeframe; and 2) emphasize the importance of proper surgical technique and use of intraoperative fluoroscopy to assure the cortical button is well-fixed and flush with the radial shaft. .

TREATMENT OF IRRECOVERABLE RADIAL NERVE PALSY USING THE MODIFIED MERLE D'AUBIGNÉ TENDON TRANSFER METHOD.

Background: Irrecoverable radial nerve palsy (RNP) leads to the inability to extend the wrist and fingers and significant reduction in grip strength. The aim was to assess the outcomes of treating non-recovering motor RNP using the modified Merle d'Aubigné tendon transfer method. Materials and Methods: A descriptive prospective study involved 33 patients between January 2017 and March 2019. Results: Males constituted the majority (32/33 cases, 97%). The ratio of radial nerve and posterior interosseous nerve injuries was nearly equivalent (16/17). The mean extension range of the wrist was 48.6° ± 14.9° during finger extension and 30.9° ± 14.4° during finger flexion. The mean flexion range of the wrist was 34.8° ± 15.8° during finger extension and 42.6° ± 14.8° during finger flexion. 93.9% of patients achieved full finger extension when the wrist joint was extended beyond 10°. The mean angulation range of the index finger was 55.3° ± 7.4°. The Kapanji score achieved was 8.4 ± 1.2. The achieved grip strength was 65.4% compared to the unaffected side. The surgery did not induce radial deviation deformities of the wrist joint. 32/33 patients were satisfied with the surgical outcomes. 31/33 patients returned to their previous professions. 93.9% of patients achieved very good and good results, while 6.1% achieved fair results. Conclusion: Treating irrecoverable radial nerve palsy using the modified Merle d'Aubigné tendon transfer method yields very good results. The utilization of the pronator teres for wrist extensor transfer and the flexor carpi radialis for finger extensor transfer is appropriate and contributes to limiting wrist joint radial deviation deformities. This modified technique has been researched and recommended by various authors worldwide.

Anconeus Muscle Transfer to Correct or Prevent Wrist Radial Deviation in Radial and Posterior Interosseous Nerve Injuries.

PURPOSE: Wrist radial deviation is a possible complication of tendon transfer for restoration of wrist extension in cases of radial nerve paralysis. In posterior interosseous nerve (PIN) injury, this is because of the imbalance caused by the intact extensor carpi radialis longus and paralysis of the extensor carpi ulnaris (ECU). This deformity may also occur following transfer of the pronator teres (PT) to the extensor carpi radialis brevis (ECRB) for radial nerve palsy. To address wrist radial deviation, we propose transferring the anconeus muscle, extended by the intermuscular septum between the ECU and the flexor carpi ulnaris (FCU), to the ECU tendon. METHODS: Through an incision over the ulna, the intermuscular septum between the ECU and FCU is harvested at the level of the periosteum and left attached to the anconeus proximally. The anconeus muscle is then released from the ulna, and the intramuscular septum extension is sutured to the ECU tendon under maximal tension. Anconeus muscle transfer was performed on two patients to correct chronic wrist radial deviation following PT to ECRB tendon transfer for radial nerve injury, as well as on two patients with PIN paralysis. In four patients, transfer was performed in addition to standard tendon transfers for radial nerve paralysis to prevent radial wrist deviation deformity. RESULTS: Wrist radial deviation was corrected or prevented in all but one patient at an average follow-up of 10 months. Patients with PIN lesions and those who had anconeus transfer concomitantly with radial nerve tendon transfers were capable of active ulnar deviation. No patient experienced elbow extension weakness, pain, or instability. CONCLUSIONS: Anconeus muscle transfer extended by intermuscular septum presents a viable alternative for addressing radial deviation of the wrist in cases of PIN nerve lesions or following PT to ECRB tendon transfer in radial nerve paralysis. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

Neuralgic Amyotrophy and Hourglass Nerve Constriction/Nerve Torsion: Two Sides of the Same Coin? A Clinical Review.

Neuralgic amyotrophy, also called Parsonage-Turner syndrome, in its classic presentation is a brachial plexopathy or a multifocal neuropathy, involving mainly motor nerves of the upper limb with a monophasic course. Recently, a new radiological entity was described, the hourglass constriction, which is characterized by a very focal constriction of a nerve, or part of it, usually associated with nerve thickening proximally and distally to the constriction. Another condition, which is similar from a radiological point of view to hourglass constriction, is nerve torsion. The pathophysiology of neuralgic amyotrophy, hourglass constriction and nerve torsion is still poorly understood, and a generic role of inflammation is proposed for all these conditions. It is now widely accepted that nerve imaging is necessary in identifying hourglass constrictions/nerve torsion pre-surgically in patients with an acute mononeuropathy/plexopathy. Ultrasound and MRI are useful tools for diagnosis, and they are consistent with intraoperative findings. The prognosis is generally favorable after surgery, with a high rate of good motor recovery.

Compression of the posterior interosseous nerve secondary to a synovial cyst: Case report and review of the literature.

INTRODUCTION AND IMPORTANCE: Posterior interosseous nerve syndrome secondary to compression by a synovial cyst at the elbow is a rare and often unrecognized pathology. Early management relies on complete neurolysis to achieve satisfactory functional recovery. Increasing awareness among the orthopedics will help in the early diagnosis of the disease and in the initiation of early and proper treatment. CASE PRESENTATION: In this article, we report the case of a 32-year-old patient with posterior interosseous nerve syndrome secondary to compression by a synovial cyst of the elbow. Surgical management combined with post-operative rehabilitation resulted in indolence with good functional recovery. CLINICAL DISCUSSION: Posterior interosseous nerve syndrome secondary to compression by a synovial cyst at the elbow is a rare entity. Anatomically, the deep branch of the radial nerve or posterior interosseous nerve passes through the Fröhse's arch or arch of the supinator muscle at the elbow, then travels between the two heads of this muscle. Several anatomical structures may compress the NIOP. Clinically, it presents as paralysis or paresis of the extensor muscles of the fingers and the abductor muscle of the thumb. Limitation of the ulnar extensor carpi may be responsible for radial deviation of the carpus in some cases. MRI is the radiological examination of choice. Electromyography plays a contributory role in diagnosis prior to surgical exploration. Surgical excision is the treatment of choice. It may be combined with radial neurolysis for better recovery. Progression after surgical treatment is generally favourable. CONCLUSION: Ignorance of posterior interosseous nerve palsy syndrome frequently leads to misdiagnosis. Early management relies on complete neurolysis to achieve satisfactory functional recovery.

Location of the posterior interosseous nerve in relation to common lateral approaches to the elbow.

PURPOSE: The risk of posterior interosseous nerve (PIN) injury during surgical approaches to the lateral elbow varies depending on the chosen approach, level of dissection, and rotational position of the forearm. Previous studies evaluated the trajectory of the PIN in specific surgical applications to reduce iatrogenic nerve injuries. The goal of this study is to examine the location of the PIN using common lateral approaches with varying forearm rotation. METHODS: The Kaplan, extensor digitorum communis (EDC) split, and Kocher approaches were performed on 18 cadaveric upper extremity specimens. Measurements were recorded with a digital caliper from the radiocapitellar (RC) joint and the lateral epicondyle to the point where the PIN crosses the approach in full supination, neutral, and full pronation with the elbow at 90°. The ratio of the nerve's location in relation to the entire length of the radius was also evaluated to account for different-sized specimens. RESULTS: The PIN was not encountered in the Kocher interval. For Kaplan and EDC split, with the forearm in full supination, the mean distance from the lateral epicondyle to the PIN was 52.0 ± 6.1 mm and 59.1 ± 5.5 mm, respectively, and the mean distance from the RC joint to the PIN was 34.7 ± 5.5 mm and 39.3 ± 4.7 mm, respectively; with the forearm in full pronation, the mean distance from the lateral epicondyle to the PIN was 63.3 ± 9.7 mm and 71.4 ± 8.3 mm, respectively, and the mean distance from the RC joint to the PIN was 44.2 ± 7.7 mm and 51.1 ± 8.7 mm, respectively. CONCLUSIONS: The PIN is closer to the lateral epicondyle and RC joint in the Kaplan than EDC split approach and is not encountered during the Kocher approach. The PIN was not encountered within 26 mm from the RC joint and 39 mm from the lateral epicondyle in any approach and forearm position and is generally safe from iatrogenic injury within these distances.

Distal biceps tendon rupture: a comprehensive overview.

Distal biceps tendon (DBT) is a relatively rare injury mainly occurring in middle-aged men while in eccentric biceps muscle contraction. Clinical appearance with proximal avulsion of the muscle and specific clinical tests are most of the time sufficient for diagnosing DBT, but if needed ultrasonography and MRI, most often in FABS view, can be used to ensure diagnosis of DBT and partial DBT. Surgical anatomical reinsertion has shown to be a successful method of treatment, although conservative treatment can be initiated in older patients. Two different approaches are described in literature: single- and double-incision techniques with different fixation methods proving to have similarly good results. Major complications of surgical intervention are posterior interosseous nerve palsy and symptomatic heterotropic ossification. Overall outcome of surgical intervention has shown high subjective satisfaction with slight weakness in flexion and supination but mostly without loss in range of motion.

Treatment of posterior interosseous nerve entrapment syndrome with ultrasound-guided hydrodissection: A case report.

BACKGROUND: Posterior interosseous nerve (PIN) entrapment syndrome is one of the causes of weakness and pain of the arm muscles, which is prone to missed diagnosis and misdiagnosis in clinic practice. This paper reports a case of PIN entrapment syndrome, with PIN injury indicated by electrophysiology. Musculoskeletal ultrasound was applied to identify that the entrapment point was located at the inlet of the Frohse arch and the outlet of the supinator muscle. Treatment with ultrasound-guided nerve hydrodissection was performed on the entrapment point, which significantly improved the symptoms. Ultrasound-guided nerve hydrodissection is an effective therapeutic method for PIN entrapment syndrome. CASE SUMMARY: A male patient, 35 years old, worked as an automobile mechanic. He felt slightly weak extension activity of his right fingers 2 years ago but sought no treatment. Later, the symptoms gradually became aggravated and led to finger drop, particularly severe in the right middle finger, accompanied by supination weakness of the right forearm. Neural electrophysiological examination showed that the patient had partial PIN injury of the right radius. Musculoskeletal ultrasound examination indicated PIN entrapment at the inlet of the Frohse arch and the outlet of the supinator muscle. Therefore, PIN entrapment syndrome was diagnosed. After treatment with ultrasound-guided nerve hydrodissection around the entrapment point, the dorsiflexion weakness of the right hand was significantly improved compared with before treatment. CONCLUSION: Ultrasound-guided hydrodissection is efficacious for PIN entrapment syndrome, with high clinical value and great application prospects.

Retrospective Study on the Risk of Nerve Injury After Distal Biceps Tendon Repair Using Cortical Button.

BACKGROUND: Distal biceps tendon ruptures are relatively rare injuries that typically require surgical intervention to restore flexion and supination strength. Concerns have been raised regarding the risk of nerve injuries, particularly the posterior interosseous nerve (PIN), associated with the use of cortical buttons in distal biceps repair. This study aimed to estimate the incidence of PIN injury as well as injuries to the lateral cutaneous nerve of the forearm and superficial branch of the radial nerve following distal biceps repair using cortical buttons. METHODS: A retrospective review was conducted on all patients who underwent distal biceps repair with cortical buttons at a district general hospital between January 2014 and May 2022. Patient data, including age, gender, time from injury to surgery, type of procedure, and postoperative nerve injuries, were collected. The incidence of nerve injuries was analyzed, and the outcomes were assessed during postoperative follow-up visits. RESULTS: Ninety-six male patients were included in the study, with an average age of 45.6 years. The average time from injury to surgery was 22.6 days. All patients underwent primary repair except for two patients who underwent reconstruction with hamstring grafts. None of the patients experienced a PIN injury. However, 16 patients (16.7%) developed lateral cutaneous nerve injuries of the forearm, and three patients (3.1%) had superficial radial nerve injuries. CONCLUSION: Our study, encompassing a large cohort of patients over an eight-year period, demonstrates the safety of distal biceps repair using cortical buttons with regard to PIN nerve injury. However, there were incidences of lateral cutaneous nerve of the forearm and superficial radial nerve injuries, consistent with previous studies.

An unusual cause of posterior interosseous nerve palsy and contribution of ultrasonography to electromyography in a patient with neurofibroma.

Neurofibroma, a benign peripheral nerve sheath tumor, represents a rare cause of posterior interosseous nerve syndrome. Electrodiagnostic studies may not identify the exact site of nerve compression, a possible lesion that compresses the nerve and do not provide information about the morphological changes. Ultrasound is a cost-effective, practical modality that provides the opportunity for dynamic tracking in the peripheral nerves, and it is widely considered as the initial imaging modality for peripheral nerves. Herein, we report a case of posterior interosseous nerve palsy in a 13-year-old boy with neurofibroma of posterior interosseous nerve diagnosed with ultrasound. The benefit of ultrasound in localizing and determining the etiology of the posterior interosseous nerve palsy is emphasized in this case report. A meticulous ultrasound examination is recommended in suspected peripheral nerve lesions, regardless of the results of electrophysiological and imaging modalities.