Uncommon Anatomical Causes of Ulnar Compression: A Narrative Review.

OBJECTIVES: Some patients develop ulnar nerve compression due to rare anatomical variations or malformations. The aims of this review are to provide a comprehensive overview of anatomical structures and variations that can cause ulnar nerve compression and to evaluate treatment options. METHODS: Case reports and case series about rare cases of unusual ulnar nerve compression published from January 2000 until April 2022 were obtained from databases Embase, MEDLINE, and Web of Science. A total of 48 studies describing 64 patients were included in our study. RESULTS: The following structures have proven to cause ulnar nerve compression: anconeus epitrochlearis, accessory abductor digiti minimi, vascular anomalies, palmaris longus, fibrous bands, and flexor carpi ulnaris. All cases except one have had a surgical release of the ulnar nerve resulting in diminished symptoms or complete recovery at follow-up. CONCLUSIONS: In addition to considering common compression points, it is important to be aware that proximal compression symptoms, such as pain and a positive Tinel sign at the medial elbow, may be attributed to a hypertrophic AE or vascular anomaly. Distal compression symptoms encompass swelling, along with pain and a positive Tinel sign at the distal forearm. Various structures contributing to distal compression include an accessory abductor digiti minimi muscle, an accessory or anomalous palmaris longus muscle, or an accessory or hypertrophic flexor carpi ulnaris muscle. The occurrence of fibrous bands exhibits variability, manifesting in diverse locations across the arm.Level of Evidence: IV.

Ulnar Nerve Compression at the Elbow Secondary to Intramuscular Lipoma of the Flexor Carpi Ulnaris: A Case Report.

CASE: A 62-year-old right-hand-dominant woman presented with 1 year of persistent radiating pain, weakness, and paresthesias in her left forearm and hand. Electromyography findings were significant for ulnar neuropathy distal to the branch innervating the flexor carpi ulnaris (FCU), without superimposed cervical radiculopathy or other focal entrapment neuropathy. During open ulnar nerve neurolysis, an intramuscular lipoma was encountered within the FCU. Lipoma excision and cubital tunnel release with ulnar nerve transposition were performed with complete relief of neuropraxia. CONCLUSION: We demonstrate full neurologic recovery after intramuscular lipoma excision and cubital tunnel release. Although rare, anomalous anatomy and tissue overgrowth should remain on the differential for patients presenting with atypical neuropraxia.

Prospective outcome analysis of ulnar tunnel syndrome: Comparing traumatic versus non-traumatic etiologies.

BACKGROUND: Ulnar tunnel syndrome (UTS) is relatively uncommon compared to the carpal tunnel or cubital tunnel syndromes. Few reports dedicated to the functional outcomes after surgical intervention of the UTS exist. Herein we compare the outcomes of patients with UTS of different etiologies. METHODS: Patients diagnosed with UTS between 2016 and 2020 were recruited. Ulnar tunnel release was performed in all patients, along with other necessary osteosynthesis or reconstructive procedures in the traumatic group. Patients were followed-up every six months post-operatively. Outcomes measured include: objective evaluations, subjective questionnaires, records of clinical signs, and grading of the British Medical Research Council scale for intrinsic muscle strength. RESULTS: 21 patients were recruited, and favorable results were noted in all of them after surgery. Traumatic UTS patients had a worse initial presentation than the non-traumatic cases, but had a greater improvement after surgery and yielded outcomes comparable with those of the patients without trauma. Patients with aberrant muscles in their wrists had better outcomes in some objective measurements than those without aberrant muscles. CONCLUSIONS: Ulnar tunnel release improves the outcome of patients regardless of the etiology, especially in patients with trauma-induced UTS. Thus, a proper diagnosis of the UTS should be alerted in all patients encountering paresthesia in the ulnar digits, ulnar-sided pain, weakness of grip strength, or intrinsic weakness to ensure good outcomes.

Possible points of compression of the ulnar nerve: Tricks and traps that await clinicians from an anatomical point of view.

The ulnar nerve can be subject to numerous types of compression. The most common are cubital tunnel and ulnar tunnel syndromes, but there are many others with more uncommon etiologies. The existence of additional communicating branches, median nerve involvement, various types of injuries, and unusual anatomical variations can be a challenge for both diagnosis and treatment. This review presents a comprehensive depiction of ulnar nerve entrapment syndromes with particular reference to their anatomical background, risk factors, and clinical evaluation. Even common disorders can result from atypical morphological changes. It is important to be familiar with them as it is a key ability in daily medical practice.

Work-related risk factors for ulnar nerve entrapment in the Northern Finland Birth Cohort of 1966.

Ulnar nerve entrapment (UNE) is the second most common entrapment neuropathy in the upper extremity. The aetiology of UNE is multifactorial and is still not fully understood. The aim of the study was to identify occupational risk factors for UNE and to determine whether smoking modifies the effects of work-related factors on UNE. The study population consisted of the Northern Finland Birth Cohort of 1966 (NFBC1966). In total, 6325 individuals active in working life participated at baseline in 1997. Occupational risk factors were evaluated by a questionnaire at baseline. The data on hospitalizations due to UNE were obtained from the Care Register for Health Care between 1997 and 2018. The incidence rate of hospitalization due to UNE was 47.6 cases per 100,000 person-years. After adjusting for confounders, entrepreneurs (Hazard ratio (HR) = 3.68, 95% CI 1.20-11.27), smokers (HR = 2.51, 95% CI 1.43-4.41), workers exposed to temperature changes (HR = 1.72, 95% CI 1.00-2.93), workers with physically demanding jobs (HR = 3.02, 95% CI 1.39-6.58), and workers exposed to hand vibration (HR = 1.94, 95% CI 1.00-3.77) were at an increased risk of hospitalization for UNE. Exposure to work requiring arm elevation increased the risk of hospitalization due to UNE among smokers (HR = 2.62, 95% CI 1.13-6.07), but not among non-smokers. Work-related exposure to vibration and temperature changes, and physically demanding work increase the risk of hospitalization for UNE. Smoking may potentiate the adverse effects of work-related factors on UNE.

Isolated compression of the ulnar motor branch due to carpal joint ganglia: clinical series, surgical technique and postoperative outcomes.

The entrapment of the ulnar nerve in Guyon's canal (GC) is a well-known wrist canalicular syndrome which is usually followed by a gradual combination of both sensitive and motor symptomatology. However, GC nerve compression could also cause a pure hand motor dysfunction. This condition, less frequent than the classic Guyon's syndrome, can be difficult to diagnose. Authors report a case series of eight patients affected by isolated compression of the ulnar nerve motor branch, due to piso-triquetrum or triquetro-hamate joint ganglia. Surgical technique and postoperative outcomes are discussed in this paper. The isolated compression of the ulnar nerve motor branch is a very rare clinical condition which is often linked to several causes. The rarity of the pathology is probably due to lack of knowledge and therefore to the difficulty in formulating a correct diagnosis. Surgical treatment appears to be decisive in most cases, although late diagnosis often leads to incomplete functional recovery.

An accessory abductor digiti minimi as possible risk factor of the median and ulnar nerves compression / Músculo abductor digiti minimi accesorio como posible factor de riesgo de la compresión de los nervios mediano y ulnar

SUMMARY: During routine dissection of a left upper limb of a 68-year-old male human cadaver, an unusual muscle was observed originating from the radius and flexor retinaculum, and continued in the hypothenar region with the muscle belly of the abductor digiti minimi. We checked that it was an accessory abductor digiti minimi (ADM). Its muscular belly was in close relation to the median and ulnar nerves. We review the literature regarding such muscle variations and discuss the potential for compression of the median and ulnar nerves. Although the accessory ADM is usually asymptomatic and only rarely results in nerve compression, it should be taken into account by surgeons when establishing a differential diagnosis in the compression neuropathies of the median and ulnar nerves. An ultrasound scanning can help establish the differential diagnosis.

RESUMEN: Durante la disección de rutina de un miembro superior izquierdo de un cadáver humano masculino de 68 años, se observó un músculo inusual que se originaba en el radio y el retináculo flexor del carpo, y continuuaba en la región hipotenar con el vientre muscular del abductor digiti minimi manus. Verificamos que se trataba del músculo abductor digiti minimi accessorius (ADMA). Su vientre muscular se encontraba en estrecha relación con los nervios mediano y ulnar. Revisamos la literatura sobre variaciones musculares y discutimos la potencial compresión de los nervios mediano y ulnar. Aunque el ADMA suele ser asintomático y rara vez produce compresión nerviosa, los cirujanos deben tenerlo en cuenta al establecer un diagnóstico diferencial en las neuropatías de compresión de los nervios mediano y ulnar. Una ecografía puede ayudar a establecer el diagnóstico diferencial.

Ulnar tunnel syndrome: pathoanatomy, clinical features and management.

Ulnar tunnel syndrome is compression of the ulnar nerve at the level of the wrist within Guyon's canal. It is most commonly caused by a ganglion cyst but may also be secondary to fractures, inflammatory conditions, neoplasm, vascular anomalies, aberrant musculature or a combination of these. Assessment should include a detailed history focusing on duration, site and progression of symptoms. The level of compression can be estimated clinically on examination by assessing motor and sensory changes in the hand. Investigations are used to confirm diagnosis or to clarify the underlying cause. X-rays and computed tomography can be used to exclude fractures. Ultrasound is used to diagnose ganglion cysts and vascular anomalies, and can localise the level of compression. Nerve conduction studies can be used to support the diagnosis and look for proximal compression. Mild symptoms can be managed non-operatively. Surgical exploration and decompression is the gold standard treatment for neuro-compressive causes with largely good outcomes.

Hypothenar Hammer Syndrome with Ulnar Nerve Neuropathy.

Hypothenar hammer syndrome is a rare medical condition that is usually associated with repetitive hand trauma. In this article, we delineate the importance of the nerve conduction velocity study to help determine objectively whether neuropathy is significant to the point that surgical means should be considered in absence of obvious ischemic change.

Revision Total Wrist Arthroplasty Due to Polyethylene Wear, Metallosis-Induced Carpal Tunnel Syndrome, Distal Ulnar Impingement, and Fourth Carpometacarpal Joint Pain: Case Report and Pitfalls to Avoid.

Background: Total wrist arthroplasty (TWA) is indicated to alleviate pain secondary to arthritis while preserving wrist motion. Despite vigilant measures, TWAs are susceptible to complications. The current case illustrates an array of preventable complications which are addressed through operative technique in a revision setting. Case presentation: The patient was a 72-year-old man who presented with chronic pain at the fourth carpometacarpal joint (CMCJ) and distal radioulnar joint with paresthesias in the median nerve distribution. Surgery was undertaken to address the following complications secondary to a previous TWA: impingement of the native distal ulna on the prosthesis, carpal tunnel due to metallosis and polyethylene synovitis, loose carpal component, and prominent screw at the fourth CMCJ. Surgical correction included open carpal tunnel release with extensive flexor tenosynovectomy, distal ulna resection and implant arthroplasty with shortening, revision of carpal component with bone grafting, and shortening of the ulnar screw to avoid crossing the fourth CMCJ. Within 6 months of the procedure, the patient reported resolution of neuropathic symptoms and pain-free motion of the wrist. Discussion: Preventable complications associated with TWA are individually highlighted. In addition, we compare and contrast our approach and surgical technique to current reported literature. Overall, we provide education and guidance to avoid possible TWA pitfalls. Conclusion: With this case report, we hope to increase TWA knowledge with emphasis on the requirements of judicious patient selection, preoperative planning, meticulous surgical technique, and complication awareness for subsequent optimization of wrist function, stability, and durability.

Bilateral reversed palmaris longus muscle: a case report and systematic literature review.

PURPOSE: We present a case of a bilateral reversed palmaris longus muscle and a systematic review of the literature on this anatomical variation. METHODS: Routine dissection of a 90-year-old male cadaver revealed a rare bilateral reversed palmaris longus. This was documented photographically, and length and relation to anatomical landmarks were recorded. This finding stimulated a systematic review of the literature on the reversed palmaris longus variation, from which measurements were collated and statistical analysis performed to determine the prevalence, average length, relationship to side and sex, and to discuss its clinical and evolutionary implications. RESULTS: The average length of the muscle belly and tendon of reversed palmaris longus was 135 mm and 126 mm, respectively. Statistical analysis revealed no disparity in presentation due to sex and side; however, bilateral reversed palmaris longus has only been reported in males. A high proportion (70.8%) of reversed palmaris longus were discovered in the right upper limb compared to the left. CONCLUSION: Variations in palmaris longus are purported to be as a result of phylogenetic regression. Clinically, patients with this variant may present with pain or swelling of the distal forearm, often as a result of intense physical exertion related to occupation or sport. Clinicians should be aware of this muscle variant as its presence could lead to confusion during tendon allograft harvesting procedures in reconstructive and tendon grafting surgery.

Unusual olecranon mass with ulnar nerve compressive neuropathy caused by a haemophilic pseudotumour.

A 55-year-old man with a history of haemophilia A and bilateral haemophilic arthropathy of the elbows presented with an enlarging left elbow mass and worsening paresthesias in the ulnar distribution of the left hand. The mass, originally thought to be olecranon bursitis and treated as such, was found to be due to a haemophilic pseudotumour. The patient underwent successful excision of the haemophilic pseudotumour with concomitant ulnar nerve decompression and had sustained resolution of the pseudotumour and symptoms at 10 years of follow-up. This case demonstrates the need for consideration of haemophilic pseudotumour in the differential diagnosis for olecranon masses and cubital tunnel compressive neuropathy in patients with haemophilia, and highlights the viability of surgical excision as a therapeutic option for the treatment of haemophilic pseudotumours in the elbow.

Smoking is associated with ulnar nerve entrapment: a birth cohort study.

Ulnar nerve entrapment is the second most common compression neuropathy of the upper extremity. It has been associated with smoking in cross-sectional studies. Our aim was to study whether smoking is associated with ulnar nerve entrapment. The study population consisted of the Northern Finland Birth Cohort 1966 participants, who attended the 31-year follow-up in 1997 (N = 8,716). Information on smoking, body mass index (BMI), long-term illnesses, and socio-economic status were recorded at baseline in 1997. Data on hospitalizations due to ulnar nerve entrapment neuropathies was obtained from the Care Register for Health Care, 1997-2016. Hazard ratios (HR) with 95% confidence intervals (CI) and population attributable risk (PAR) were calculated adjusted for gender, BMI and socio-economic status. 66 patients were diagnosed with ulnar nerve entrapment in the follow-up 1997-2016. Before the age of 31 years, smoking ≤10 pack years associated with more than doubled (HR = 2.57, 95% CI = 1.29-5.15) and smoking >10 pack years with more than five-folded (HR = 5.61, 95% CI = 2.80-11.23) risk for ulnar nerve entrapment compared to non-smokers in the adjusted analyses. Adjusted PAR for smoking (reference of no smoking) was 53.6%. In our study, smoking associated with increased risk for ulnar nerve entrapment, accounting for considerable proportion of increased risk.

Ulnar nerve entrapment in Guyon's canal caused by a ganglion cyst: two case reports and review of the literature.

In this article, two cases of ulnar nerve neuropathy in Guyon's canal caused by a ganglion cyst are reported. A review of the literature found 73 cases reported in 35 articles of ulnar neuropathy at the wrist secondary to a ganglion cyst. We investigated the pathogenesis of ganglion cysts, which are separated as extraneural and intraneural. At this anatomical area, there are a variety of clinical factors that can also lead to ulnar nerve compression such us trauma, fracture of the hamate's hook, arterial thrombosis, tumors and other anatomical variations. The symptoms may include weakness, paresthesia, numbness and atrophy of hypothenar muscles. Except the careful clinical assessment, magnetic resonance imaging, ultrasound and electrophysiological control are useful tools regarding our differential diagnosis. The treatment of this clinical condition is surgical. We consider that instant surgical decompression is of the essence and enables postoperatively total recovery. LEVEL OF EVIDENCE: Level III.

Hypothenar hammer syndrome: A case of a late complication after surgery.

Hypothenar hammer syndrome is a rare condition secondary to ulnar artery damage in Guyon's canal, affecting mainly those exposed to repeated palm trauma. Surgery is discussed in cases of severe symptoms that are resistant to conservative treatment, and/or when anatomical lesions with high embolism potential are discovered during imaging exams. Resection of the pathological zone with revascularization by autologous vein graft is the best option. We report the case of a 60-year-old patient who had a recurrence of symptoms more than 10 years after this type of surgical treatment was performed. There was an aneurysmal thrombosed vein graft with extensive thrombus from the ulnar artery upstream to Guyon's canal to the superficial palmar arch. Finger revascularization was provided by the superficial branch of the radial artery and the presence of a collateral vascular supply. This late complication was responsible for compression of the ulnar nerve in Guyon's canal. A new surgery was performed to resect the thrombosed zone, including the vein graft, without vascular reconstruction due to the good vascularization of all the fingers, and to release the ulnar nerve at the wrist. The postoperative course was uneventful with the disappearance of pain and sensory-motor deficits. Good finger vascularization was confirmed by imaging at 3 months postoperative; nerve conduction was normal at 6 months on electroneuromyography.

Isolated Compression of the Ulnar Nerve Motor Branch: A Case Series With 3 Unique Etiologies.

BACKGROUND: Although ulnar neuropathies are commonly encountered, isolated involvement of the motor branch is exceedingly rare. Previous reports of this entity describe compression as the deep motor branch passes through the piso-hamate hiatus and the adductor pollicis hiatus. This case series described 3 cases of motor branch compression due to unique etiologies which resolved after surgery. METHODS: A retrospective chart review identified patients with compression of the ulnar nerve motor branch. From these patients, 3 were selected with a unique etiology for compression. Patient demographics, objective and subjective findings, and pathology identified during surgery were recorded and analyzed. RESULTS: Eight patients had compression of the ulnar nerve motor branch and 3 unique etiologies were selected; an intraneural ganglion, a constricting leash of vessels, and a series of compressing fibrous bands. All required surgery, and each patient had full resolution of symptoms by 1 year postoperatively. DISCUSSION: Patients presenting with complaints of weakness with a positive Froment and Egawa signs but a negative Wartenberg sign and no sensory complaints can be a diagnostic dilemma. Compression of the ulnar nerve motor branch must be considered, and here we present 3 unique cases. Activity modification in those presenting early may be curative, although many ultimately require surgery. In the cases presented here, all patients experienced full resolution of their symptoms by 1 year after surgery.