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BACKGROUND: Lacertus syndrome involves dynamic median nerve compression by the lacertus fibrosus, leading to sensory symptoms and loss of strength. Prevalence in the general population is unclear. OBJECTIVE: This study aimed to determine the prevalence of lacertus syndrome in the Belgian population and to evaluate the effectiveness of the exhaustion test combined with the scratch collapse test. METHODS: In a cross-sectional study from May 2023 to February 2024, 362 healthy individuals, aged 18 to 86 years underwent clinical examinations, including the scratch-collapse test and exhaustion test, to assess signs of lacertus syndrome. RESULTS: 11.3% of participants (95% CI: 8.2-15.1%) reported discomfort on lacertus fibrosus palpation. The scratch-collapse test at the lacertus fibrosus was positive in 7.2% of cases (95% CI: 4.8-10.4%), increasing to 25.7% (95% CI: 21.3-30.5%, p < 0.001) following the exhaustion test. There were no significant differences in gender, occupation, or hand dominance (all p > 0.05). Hagert's clinical triad and positive scratch-collapse test over the lacertus fibrosus were found in 2.21% (95% CI: 1.0-4.2%) of this general population after the exhaustion test. CONCLUSION: The prevalence of lacertus syndrome was 2.21% after the exhaustion test, and 0.83% before. The exhaustion test led to significant conversion of negative to positive scratch-collapse test from 7.2% to 25.7%. The exhaustion test enhanced the scratch-collapse test's diagnostic accuracy, revealing a spectrum of lacertus syndrome symptoms, from unnoticed mild cases to severe manifestations, and confirmed the importance of Hagert's clinical triad in diagnosing lacertus syndrome.

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Arterial entrapment syndrome (AES) at the elbow level is very rare. In cases of acute upper extremity ischaemia presenting in middle-aged patients with evident muscular hypertrophy, AES should always be included in the differential diagnosis. A thorough clinical examination should always follow, particularly when symptoms appear after reported strenuous upper extremity activity, and emergent surgical decompression is mandatory to avoid thrombotic complications in the affected arm in the future.

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Lacertus fibrosus syndrome is described as compression of the median nerve, which takes place beneath a layer of ligamentous tissue (lacertus fibrosus, also known as bicipital aponeurosis) slightly beyond the elbow joint. Both sexes can develop lacertus fibrosus syndrome, most often after the age of 35. The possible risk factors are repetition of movements, overwork, and manual work while the forearm is pronated. Lacertus fibrosus syndrome presents a distinct diagnostic challenge because it is a somewhat unknown and non-documented disease. Its symptoms are often mistaken for those of carpal tunnel syndrome, which complicates the differential diagnosis and management of the patient. All patients who report tingling, numbness, loss of strength, muscle loss, manual endurance, or dexterity should be investigated and tested for both carpal tunnel syndrome and lacertus syndrome. Here, a case of a 43-year-old woman is discussed, who presented with chief complaints of pain and tingling sensation in the left upper limb, which was associated with loss of thumb pinch grip. The pain was aggravated with elbow extension and relieved with rest. The patient underwent left elbow median nerve decompression and was discharged in steady condition. This case report highlights the accurate clinical presentation and surgical intervention for the syndrome, for which the outcome turned out to be satisfying.

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PURPOSE: In the literature, we find that patients with lacertus syndrome (LS), proximal median nerve compression at the elbow, present subjective improvement of thumb, and index flexion strength after lacertus fibrosus (LF) release. The aim of this study is to objectively evaluate the immediate change in intraoperative flexion strength after LF release. METHOD: We retrospectively reviewed prospectively collected data of a cohort of 24 patients with a double crush syndrome of the median nerve with no response to conservative treatment. All patients had surgery with LF and carpal tunnel release (CTR) under wide-awake local anaesthesia and no tourniquet (WALANT) and were evaluated intraoperatively with a dynamometer immediately before and after LF release. Flexor digitorum profundus of the second finger (FDP2) and Flexor pollicis longus (FPL) were tested in peak strength to failure. The primary outcome was the percentage of change in strength before and after the release in both assessed muscles. CTR was done after evaluating the change in flexor strength. RESULTS: A percentage of 79.2 women with an average age of 43.3 years. The average strength of FDP2 before LF release was 15.5 pounds (lbs.) (7.0 kg) (SD, 7.2 lbs (3.3 kg)) and 27.1 lbs. (12.2 kg) (SD, 7.1 lbs. (3.2 kg)) after LF release, which corresponds to a 96% (SD, 70%) change in strength (p=0.000). For FPL, the average pre-release strength was 17.7 lbs. (8.0kg) (SD, 4.8 lbs. (2.2 kg)) and 27.4 lbs. (12.4 kg) (SD, 5.2 lbs. (2.4 kg)) post-release, this corresponded to a 65% (SD, 38%) change in strength (p=0.000). CONCLUSIONS: Peak strength to failure in FDP2 and FPL has an immediate significant recovery after LF surgical release in patients with Lacertus syndrome. LEVEL OF EVIDENCE: IV, retrospective study.

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PURPOSE: Lacertus syndrome is defined as proximal median nerve entrapment at the lacertus fibrosus. We aimed to analyze change in pinch strengths in patients who underwent median nerve release at the lacertus fibrosus under WALANT (wide-awake local anesthesia, no tourniquet). METHODS: Pinch strength was measured with a pinch gauge. Subjective DASH score and pain, numbness in the operated extremity and satisfaction on visual analog scales were analyzed before and 6 weeks after surgery. RESULTS: There were 32 patients. Median nerve release under the lacertus fibrosus elicited statistically significant increases in tip-to-tip, lateral and tripod pinch strength at postoperative week 6. Improvements in DASH score, pain and paresthesia were also statistically significant. CONCLUSIONS: For lacertus syndrome treatment, mini-incision release of the lacertus fibrosus under WALANT was satisfactory and increased pinch strength significatively. LEVEL OF EVIDENCE: Therapeutic, Level IV - Case series.

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BACKGROUND: Unconscious bias of the clinician favors the diagnosis of carpal tunnel syndrome (CTS) in patients with median paresthesia. We hypothesized that more patients in this cohort would be diagnosed with proximal median nerve entrapment (PMNE) by strengthening our cognitive awareness of this alternative diagnosis. We also hypothesized that patients with PMNE may be successfully treated with surgical release of the lacertus fibrosus (LF). METHODS: In this retrospective study, cases of median nerve decompression at the carpal tunnel and in the proximal forearm for the 2-year periods before and after adopting strategies to mitigate cognitive bias for CTS were enumerated. Patients diagnosed with PMNE and treated by LF release under local anesthesia were evaluated to determine surgical outcome at minimum 2-year follow-up. Primary outcome measures were changes in preoperative median paresthesia and proximal median-innervated muscle strength. RESULTS: There was a statistically significant increase in PMNE cases identified after our heightened surveillance was initiated (z = 3.433, P < .001). In 10 of 12 cases, the patient had previous ipsilateral open carpal tunnel release (CTR) but experienced recurrent median paresthesia. In 8 cases evaluated an average of 5 years after LF release, there was improvement in median paresthesia and resolution of median-innervated muscle weakness. CONCLUSIONS: Owing to cognitive bias, some patients with PMNE may be misdiagnosed with CTS. All patients with median paresthesia, particularly those with persistent or recurrent symptoms after CTR, should be assessed for PMNE. Surgical release limited to the LF may be an effective treatment for PMNE.

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PURPOSE: The lacertus fibrosus (or bicipital aponeurosis) is a potential site of proximal median neuropathy at the elbow. Lacertus syndrome with motor and/or sensory symptoms has been addressed with a minimally invasive surgical lacertus release. This study evaluates if a lacertus release alters the maximal perineural pressure (Pmax) of the median nerve at the level of the lacertus fibrosus during elbow flexion. METHODS: Seven upper limbs from four fresh cadavers were included. Perineural pressure of the median nerve at the level of the lacertus fibrosus was measured continuously during automated elbow flexions by the biceps brachii muscle. RESULTS: The mean Pmax before the lacertus release was significantly different than the mean Pmax after the lacertus release (669.15 mmHg vs 77.01 mmHg, p = 0.0180). The mean Pmax after the lacertus release decreased with an average 81.41%. CONCLUSION: A simple surgical release of the lacertus fibrosus significantly decreases the maximal perineural pressure of the median nerve at the level of the lacertus fibrosus during elbow flexion.

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The bicipital aponeurosis (BA) is the distal aponeurosis of the biceps brachii which usually covers the median nerve (MN), and the brachial artery (BrA) and sometimes causes compression of these structures. Since these situations are rarely reported in the literature, BA frequently does not come to mind as a cause of such compression. Therefore, the diagnosis may be delayed. In this study, we aimed to investigate the morphometry of BA and its relationship with the surrounding neurovascular structures and to draw attention to BA as a structure that can cause entrapment of the MN and rarely, the BrA. We examined the MRIs of the elbow of 279 patients (107 women, 172 men) aged between 18 and 72 years. We measured the thickness, length and width of BA, and investigated the anatomical relationship between BA, BrA, and MN. The respective median thickness, width, and length of BA were 0.7 (0.4-1.8 mm), 18.0 (6.0-34.0 mm), and 32.0 (18.0-50.0 mm), respectively. In all sections examined, the BA covered the BrA and MN, and was located immediately anterior to the BrA. In 225 (80.6%) of 279 MRIs, the BrA was located anterior to the MN and posterior to the BA. In the remaining 54 (19.4%) MRIs, the MN was located anterior to the BrA and posterior to the BA. The respective median thickness, width, and length of the BA were 0.7 mm, 18.0 mm, and 32.0 mm, respectively. It covered the BrA and MN and was located immediately anterior to the BrA. The BA sometimes causes compression syndromes of these structures, therefore, for physicians, it is important to understand the anatomy of the BA.

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BACKGROUND: The biceps brachii (BB) muscle is one of the three muscles located in the anterior compartment of the arm. Its insertion consists of two parts. The first part - main tendon - attached in the radial tuberosity and the second part - lacertus fibrosus (LF) - in the fascia of the forearm flexors. The intention of research was to reveal the morphological diversity of the insertion of this muscle. Thanks to the results of this work, have been created a classification of the distal attachment of BB. The results of that research can be used to further develop surgical procedures in the given region. MATERIALS AND METHODS: Eighty (40 left, and 40 right, 42 female, 38 male) upper limbs fixed in 10% formalin solution were examined. RESULTS: We observed three types of the insertion of the BB. Type I was characterised by a single tendon and occurred most frequently in 78.75% of the examined limbs. The second most common type was type II which was characterised by a double tendon and was observed in 13.75% of all the limbs. The last and least common was type III which was characterised by three tendons and occurred in 7.5% of the examined limbs. Additionally, the type of LF was analysed. In 8 (10%) specimens it was absent, i.e. in 2 specimens with type II insertion and 6 specimens with type III (p = 0.0001). Therefore, it may be deduced that type III BB insertion tendon predisposes to LF deficiency. CONCLUSIONS: The BB tendon is characterised by high morphological variability. The new classification proposes three types of distal attachment: type I - one tendon; type II - two separated band-shaped tendons; type III - three separated band-shaped tendons. The presence of type III BB tendon predisposes to a lack of LF.

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BACKGROUND: Chronic tendon retraction subsequent to distal biceps tendon rupture significantly increases repair difficulty and potential for tendon grafting. Biceps tendons that appear short or absent with magnetic resonance imaging (MRI) or that cannot be readily identified at surgery may erroneously be classified as irreparable. These apparent "absent" biceps tendons may actually be retracted and curled up inside the muscle, visually resembling the head-neck of a turtle retracted inside its shell (the "turtle neck sign"). When located, these tendons could be unfolded and repaired primarily. This type of tendon retraction seems to be associated with high-degree ruptures and larcertus fibrosus tears. PURPOSE: To test the hypothesis that tendon retractions with a turtle neck sign on MRI are more associated with high-degree ruptures and larcertus fibrosus tears versus tendon tears with simple linear retraction. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Retracted distal biceps tendon ruptures on sagittal MRI were categorized as linear retraction or curled-up (turtle neck) retraction. Retraction length, injury severity, and lacertus fibrosus tears were analyzed. RESULTS: The authors retrospectively analyzed the patient records of 85 consecutive traumatic distal biceps tendon ruptures from 2003 to 2019; the final study cohort was 37 patients. Injury-to-surgery timing was as follows: <3 weeks, 43% (16 cases); 3 weeks to 3 months, 32% (12 cases); and >3 months, 24% (9 cases). Overall, 19 patients had linear retraction <7 cm (mean, 3.3 ± 1.9 cm) and 18 patients had a turtle neck retraction ≥7 cm (mean, 9.1 ± 1.6 cm). The injury-to-surgery time (median [± interquartile range]) was 27 days (±90 days) in the linear retraction group and 23 days (±65 days) in the turtle neck retraction group. The turtle neck retraction group had a significantly higher occurrence of abnormal hook test findings, complete distal biceps tendon rupture, and lacertus fibrosus tears compared with the linear retraction group (100% vs 58%, 100% vs 68%, and 100% vs 37%, respectively; P ≤ .02). However, significant repairability differences were not found. CONCLUSION: Highly retracted distal biceps turtle neck sign tendon ruptures occur frequently in association with high-degree ruptures and lacertus fibrosus tears. The presence of a turtle neck retraction did not affect reparability. Surgeons should be aware of this curled-up retraction to avoid mistaking it for an absent tendon or a muscle-tendon disruption.

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BACKGROUND: Chronic distal biceps tendon ruptures may require tendon graft augmentation secondary to tendon attrition or retraction. The lacertus fibrosus is a local, cost-effective graft that can be used to supplement reconstruction. PURPOSE: To compare the biomechanical strength of distal biceps tendon repairs with and without lacertus fibrosus augmentation in a tendon-deficient cadaveric model. STUDY DESIGN: Controlled laboratory study. METHODS: Sixteen fresh-frozen matched cadaveric pairs of elbows were randomized into 2 groups: (1) standard distal biceps tendon repair and (2) tendon-deficient (50% step cut) repair with lacertus fibrosus augmentation. All repairs were completed using an oval bone trough and 2 double-loaded No. 2 braided nonabsorbable sutures in a locked Krackow fashion tied over a lateral bone bridge. For the lacertus augmentation group, the lacertus was wrapped circumferentially in a tubular fashion around the tendon to restore the native size and incorporated into the Krackow suture. All specimens underwent cyclic loading and then were loaded to failure. Displacement, stiffness, load to failure, and mode of failure were recorded. RESULTS: The standard repair and lacertus augmentation groups had similar displacements on cyclic loading (1.66 ± 0.62 vs 1.62 ± 0.58 mm, respectively; P = .894). The stiffness was significantly greater for the standard repair group (21.3 ± 2.5 vs 18.5 ± 3.5 N/mm; P = .044). Both groups provided excellent mean peak load to failure strengths, despite the standard repair group having significantly greater strength (462.4 ± 140.5 vs 377.3 ± 101.1 N; P = .022). The primary mode of failure in the standard repair group was fracture at the bone bridge (n = 5/8) compared with suture pullout (n = 4/8) in the lacertus augmentation group. CONCLUSION: Lacertus fibrosus augmentation of a tendon-deficient biceps repair was less stiff and had lower mean load to failure compared with repair of the native tendon in this cadaveric model, but these values remained biomechanically acceptable above critical thresholds. Consequently, lacertus fibrosus augmentation is a viable option for chronic distal biceps tendon ruptures with tendon attrition. CLINICAL RELEVANCE: Chronic distal biceps tendon ruptures may require autograft or allograft reconstruction secondary to tendon scarring, shortening, attrition, and degeneration. The lacertus fibrosus is a cost-effective and low-morbidity local autograft that can be used to augment repairs.

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PURPOSE: The lacertus fibrosus (LF) is involved in various surgeries. However, the biomechanical contribution of the LF remains unclear. The aim of this study was to determine the role of the lacertus fibrosus on the elbow and forearm kinematics and on the biceps brachii muscle lever arms. METHODS: This biomechanical study was performed on seven fresh-frozen upper limbs of cadavers. Elbow flexion, forearm supination, and biceps brachii muscle lever arms were analyzed in the intact conditions (I) and after superficial (R) and deep part (R2) of the lacertus fibrosus release, respectively. RESULTS: Elbow flexion shows a significant difference (p < 0.0001) between I, R, R2. Abduction/adduction shows a significant difference between I-R (p < 0.0001) and I-R2 (p < 0.0001). Supination does not show a significant difference in mean maximum amplitude, but between 40 and 70%, there are significant differences. There is a significant mean decrease of lever arm in flexion (28%) and supination (50%) after superficial and deep part of the lacertus fibrosus release. CONCLUSION: The results of this study show that the lacertus fibrosus increases the lever arm during flexion and supination. It limits the flexion and abduction of the elbow and supination of the forearm. Lacertus fibrosus maintains the rhythmicity between the elbow flexion and supination of the forearm. LEVEL OF EVIDENCE: Basic science study, biomechanics.

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PURPOSE: The importance of an intact lacertus fibrosus in distal biceps tendon injury is uncertain. This study aimed to assess long-term outcome following distal biceps tendon repair with focus on the significance of the lacertus fibrosus. METHODS: Thirty-six patients surgically treated for primary distal biceps tendon rupture were identified. Medical records were reviewed for patient demographics in addition to surgery-related data. All patients underwent a targeted clinical examination to assess elbow function and they completed a patient reported questionnaire. Radiographs were obtained at time of follow-up and evaluated for the presence of osteoarthritis (OA) and heterotopic ossification (HO). RESULTS: All patients were male. Median age at injury was 48 years (34-69) and median time of follow-up of was 71 months (23-165). All patients presented functional range of motion in the elbow. Median flexion strength was 76 Nm (45-135) (median 99% of uninjured side; range 66-128) with intact lacertus fibrosus and 70 Nm (43-124) (88%, 62-114) with torn lacertus fibrosus. Median supination strength was 6 Nm (3-11) (86%, range 36-144) with intact lacertus fibrosus and 8 Nm (3-17) (67%, 28-118) with torn lacertus fibrosus. No signs of OA were revealed, but three patients had major HO of which one patient had minor limitations in range of elbow motion. CONCLUSION: An intact lacertus fibrosus contributes to elbow strength and should be preserved in distal biceps tendon repair. LEVEL OF EVIDENCE: III.

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BACKGROUND: The bicipital aponeurosis (BA) can often be torn concomitantly with a distal biceps tendon (DBT) rupture. Its repair, although recommended by some, has not commonly been addressed during the surgical management of DBT ruptures, and to date, surgical repair of the BA with DBT repair has not been evaluated clinically. PURPOSE: To utilize subjective and objective outcome measures to examine the safety and efficacy of 2-incision DBT repair with and without repair of the BA in patients with a DBT rupture. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Demographic and surgical data were reviewed retrospectively. Patients returned to the clinic to complete subjective outcome measures and objective measurements of range of motion, strength, and biceps contour. All patients were evaluated at least 1 year after surgical treatment. RESULTS: Data from 24 male patients with a DBT rupture were used for the analysis; 13 (54%) underwent concomitant DBT and BA repair, and 11 (46%) underwent isolated DBT repair. There were no complications at 1 year in either group. The DBT + BA repair group returned to recreational activities faster (77% within 6 months and 100% within 1 year) than the isolated DBT repair group (36% within 6 months, 91% within 1 year, and 100% after more than 2 years) (P = .05). There was a trend toward better Patient-Rated Elbow Evaluation pain scores in the DBT + BA repair group than in the isolated DBT repair group (1.2 vs 5.3, respectively; P = .18). A trend also emerged toward closer return to subjective preinjury strength (77% vs 44%, respectively; P = .14). No significant difference emerged in patient satisfaction with the biceps contour, subjective scores on functional activities and disability, or objective measurements of strength, contour, and range of motion. CONCLUSION: This pilot study suggests that repair of the BA in conjunction with DBT repair leads to a faster return to recreational activities compared with isolated DBT repair. Also noted was a trend toward subjectively improved pain and greater perceived strength, after DBT + BA repair, although this was not statistically significant. Further investigation with a larger population is required to better elucidate these potential differences.

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OBJECTIVE: To establish a high-resolution US technique that enables a systematic morphometric examination of the three components that form the distal biceps brachii tendinous complex; the internal bicipital aponeurosis, the distal biceps brachii tendon and the external bicipital aponeurosis (also known as lacertus fibrosus). MATERIALS AND METHODS: Fifty cryopreserved cadaver body donor elbows were dissected to obtain morphometric reference values and to establish reliable landmarks for the US examination. Then, a systematic US technique was designed and validated by a one-to-one US/dissection analysis of 11 cryopreserved cadaver body donor elbows. Finally, the systematic US technique was carried out in 44 healthy volunteers and morphometric parameters were compared to those obtained in the first part of the study. RESULTS: Mean dissection reference values: internal bicipital aponeurosis width 39.61 mm (10.02 SD) and thickness 0.75 mm (0.24 SD), distal biceps brachii tendon width 8.38 mm (1.87 SD) and thickness 2.73 mm (0.69 SD), external bicipital aponeurosis width 11.17 mm (5.84 SD) and thickness 0.85 mm (0.28 SD). One-to-one US/dissection correlation was overall good (intraclass correlation coefficient 0.876, p < 0.0001). When comparing volunteer US/dissection measurements, significant differences were encountered in all measures except for internal bicipital aponeurosis width. However, the overall magnitude of such significant differences was < 0.7 mm. CONCLUSIONS: Using the systematics hereby proposed, high-resolution US is reliable for the morphometric assessment of the distal biceps brachii tendinous complex. The external bicipital aponeurosis is morphometrically the most variable structure.

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PURPOSE: We established a detailed sonographic approach to the bicipital aponeurosis (BA), because different pathologies of this, sometimes underestimated, structure are associated with vascular, neural and muscular lesions; emphasizing its further implementation in routine clinical examinations. METHODS: The BA of 100 volunteers, in sitting position with the elbow lying on a suitable table, was investigated. Patients were aged between 18 and 28 with no history of distal biceps injury. Examination was performed using an 18-6 MHz linear transducer (LA435; system MyLab25 by Esaote, Genoa, Italy) utilizing the highest frequency, scanned in two planes (longitudinal and transverse view). In each proband, scanning was done with and without isometric contraction of the biceps brachii muscle. RESULTS: The BA was characterized by two clearly distinguishable white lines enveloping a hypoechoic band. In all longitudinal images (plane 1), the lacertus fibrosus was clearly seen arising from the biceps muscle belly, the biceps tendon or the myotendinous junction, respectively. In transverse images (plane 2) the BA spanned the brachial artery and the median nerve in all subjects. In almost all probands (97/100), the BA was best distinguishable during isometric contraction of the biceps muscle. CONCLUSION: With the described sonographic approach, it should be feasible to detect alterations and unusual ruptures of the BA. Therefore, we suggest additional BA scanning during clinical examinations of several pathologies, not only for BA augmentation procedures in distal biceps tendon tears.

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BACKGROUND: Repair of distal biceps tendon ruptures has become widely accepted. Unfortunately, care of retracted-degenerated injuries remains a challenge for orthopedic surgeons. Complication rates appear to increase when surgery is performed in chronic cases compared to those operated acutely. Multiple techniques for chronic reconstruction with the use of grafts have been described. Recently Morrey, from the Mayo Clinic, proposed a direct anatomic repair of retracted distal biceps tendon ruptures in extreme flexion (60°-90°) to avoid grafting. MATERIALS AND METHODS: The authors propose and describe a new surgical technique using the lacertus fibrosus (LF) as augmentation-elongation for retracted-degenerated distal biceps tendon tears. We present four cases with chronic ruptures with 2-year follow-up. The mean age was 45 years old (33-51), the time of surgery was 13 weeks (4-24) after the trauma, dominant arm was involved in two cases. RESULTS: The mean MEPS was 95/100 at 2-year follow-up. With this technique we increase the length of the tendon up to 2.5 cm. The major complication in our study was transient sensitive radial nerve paresthesia. We did not have any hardware mobilization or muscular herniation. CONCLUSION: With this study we want to present our experience in the treatment of retracted distal biceps tendon tear with lacertus fibrosus augmentation. Our surgical technique is an effective and cheap option for chronic-retracted distal biceps tendon lesions. Recovery time is quicker, and integration is faster due to the use of an autologous vascularized graft. Preoperative ultrasound scan is mandatory in order to evaluate LF integrity, thickness and size.

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BACKGROUND: Poor positioning of patients can result in devastating permanent neurologic deficits. We describe a previously unreported cause of median nerve compression that we have termed the brachialis syndrome, associated with patient positioning that results in permanent median nerve damage. METHODS: We identified this condition affecting 6 median nerves. All patients underwent surgical decompression of the proximal median nerve at the level of the antecubital fossa. RESULTS: Five patients presented with symptoms of median nerve compression; 6 affected median nerves manifested brachialis syndrome after a lengthy index surgery. Every patient had a similar presentation characterized by a mixed sensory and motor deficit. Average time to symptom presentation postoperatively was 1 hour. Two patients had delayed time to decompression, one of 25 days and one of 92 days. In the additional patients, the average time to decompression was 19.7 hours. At median nerve decompression, the brachialis was found to have varying degrees of muscle necrosis. In the patients whose decompression was delayed, there was only partial neurologic recovery at follow-up to 1 year. In the patients expeditiously decompressed, full neurologic recovery occurred in 1 to 14 days. CONCLUSIONS: This is the first description of the brachialis syndrome. During surgery, arms were placed into full extension, compressing the brachialis against the trochlea. The brachialis reliably developed necrosis, resulting in swelling, compressing the median nerve against the lacertus fibrosus. Two patients with delayed decompression had poor neurologic outcomes. This supports modification of patient positioning, postoperative vigilance, and timely surgical management of brachialis syndrome.

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