Ultrasound visualization of an underestimated structure: the bicipital aponeurosis

Lacertus syndrome: recent advances

Lacertus syndrome consists in proximal median nerve entrapment with median nerve compression at the lacertus fibrosus, causing hand weakness and fatigue, forearm pain and occasional numbness. Recent advances emphasized the importance of clinical examination, due to limitations in electromyographic diagnosis and delayed diagnosis. The Hagert clinical triad, lacertus notch sign, lacertus antagonist test and taping help accurate diagnosis. Non-operative treatment should be tried; and surgical techniques, whether open or ultrasound-guided under WALANT (wide-awake, local anesthesia, no tourniquet) show promising outcomes. Improved awareness, accurate diagnosis and innovative treatments enhance patient care for this challenging condition.

Gender differences on effects of forearm rotation on compressive stiffness of flexor carpi ulnaris during submaximal handgrip contractions

Little is known about gender differences in stiffness of forearm muscles during voluntary actions. This study aimed to investigate the effect of forearm rotation on flexor carpi ulnaris (FCU) stiffness in men and women during submaximal handgrip contractions. During a single session, measurements were made on 20 young participants (9 females). Two positions of the forearm were compared in random order with the elbow flexed 90 degrees: (i) neutral position and (ii) maximal supination. In each position, participants performed two submaximal handgrip contractions at 25% and 50% of maximal voluntary contraction, while compressive stiffness was collected using a hand myometer (MyotonPRO). A mixed repeated measurement ANOVA was applied to assess the interaction between gender, forearm position, and contraction intensity. The FCU stiffness is affected by handgrip contraction intensity (p < 0.001), gender (p < 0.001), BMI (p = 0.009), and forearm rotation (p = 0.007). Only the gender factor was found to have significant interaction with forearm rotation (p = 0.037). Men's FCU was stiffer than women's in both positions and contraction intensities (p < 0.05). Only in men a significant increase in FCU stiffness was observed when comparing contraction intensities at both forearm positions (p < 0.05), as well as when the forearm was rotated from neutral to supine at both intensities (p < 0.05). In conclusion, FCU stiffness during handgrip contraction differed significantly between men and women. Women have fewer stiffness changes in FCU when performing different levels of handgrip contraction. We also observed that only men increased FCU stiffness by changing the forearm position from neutral to supine position for both handgrip intensities.

Ultrasound exploration of the elbow: A user-friendly approach

Ultrasound is a strong diagnostic and therapeutic tool for the elbow joint. Existing guidelines and protocols list relevant structures to be scanned but lack some logical connection and intermediate exploration manoeuvres to link each step, which we consider crucial from an operator's perspective that aims to be efficient in regular clinical practice. We present thirteen steps that are described in detail and accompanied by forty-seven ultrasound images, logically linked in what we believe is the best balance between detail and a real-world applicable protocol to perform an ultrasound of the elbow joint.

Effect of lacertus fibrosus release on perineural pressure of the median nerve at the elbow: a cadaveric study

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.

Percutaneous Ultrasound-Guided Release of the Lacertus Fibrosus for Median Nerve Entrapment at the Elbow

PURPOSE

The aim of this technical note is to present a microinvasive percutaneous ultrasound-guided release of the lacertus fibrosus of the biceps brachii for pronator syndrome, i.e., entrapment of the median nerve at the elbow.

METHODS

Fifteen consecutive patients were included. Patients showed isolated pronator syndrome including pain plus reduced strength of specific median nerve innervated muscles. The release was performed in a non-operating interventional room under wide-awake local anesthesia no tourniquet (WALANT). It was conducted superficial to the pronator teres with in-plane ultrasound guidance. The recovery of strength was first assessed peroperatively, and then systematic visits at postoperative weeks 1 and 4 included assessments of both strength and pain.

RESULTS

Procedures were comfortably completed with no immediate surgical or anesthetic complication. Muscle strength returned immediately and persisted at postoperative visits. Visual analog scores for pain reduced from 6.2 to 2.5 and 0.6 at weeks 1 and 4, respectively. All working patients were able to perform in their professional activities at week 1. The millimetric skin incision healed with no hypertrophic scar tissue. A small hematoma occurred at week 1 and resorbed spontaneously. No other delayed complication was observed. The procedure appeared effective with improved invasiveness compared to existing techniques. Real-time monitoring with ultrasound may improve the safety. The technique could be regarded as a new ultrasound-guided alternative to surgery.

CONCLUSION

Performed superficial to the pronator teres muscle under WALANT anesthesia, the microinvasive percutaneous ultrasound-guided release of the lacertus fibrosus may be an effective treatment of pronator syndrome.

Distal biceps tendon ruptures: more efficient diagnostics for a better outcome

Distal biceps tendon ruptures are a rare pathology, but can have significant functional repercussions. Rapid, accurate diagnosis and treatment are essential for a favorable prognosis. During the diagnostic process of distal biceps tendon ruptures, several problems can emerge. An answer to the following clinical questions is given based on an extensive literature review. - Which clinical tests are the most sensitive/ specific for clinical examination? - Can ultrasound evaluation of the distal biceps tendon be optimized? - Is ultrasound an equivalent alternative to MRI in the diagnosis of distal biceps tendon injuries? An extensive literature search was conducted through Pubmed and Embase. The search strategy was developed systematically in the Medline data- base (PubMed interface), using medical subject headings as well as free text words. A standardized clinical examination of the distal biceps tendon consisting of the Hook test, the Passive Forearm Pronation Test and the Biceps Crease Interval test has a high accuracy for correct diagnosis of full-thickness ruptures. Furthermore, Cobra sign, Supinator view and Pronator view give an additional value to the standard ultrasound examination of the distal biceps tendon. Finally, ultrasound can be considered a trustworthy and cost-effective alternative to MRI in evaluation of distal biceps tendon ruptures.

Ultrasonography, Microcomputed Tomography, and Macroscopic Preparation in an Anatomical Study of the Thoracic Limb of the Golden-Headed Lion Tamarin (Leontopithecus chrysomelas)

The aim of this study was to evaluate the normal anatomy of the forearm of the golden-headed lion tamarin (Leontopithecus chrysomelas) using microcomputed tomography (micro-CT) and ultrasonography (US) and then compare the results with the results of a gross anatomy dissection of the forearm. The results of the US examination of the musculoskeletal system of the tamarin forearm were not satisfactory. US imaging enabled observation of the shape of the soft tissue and the size of muscle groups; however, we distinguished more muscles by traditional methods. In addition, in the dissection study, the assessment of the muscles was easier. Examination of the forearm bones using micro-CT provided a complete picture of the bones in this part of the body and was less time-consuming than traditional methods. Imaging allows the anatomy to be represented as a 3D image. However, some methods are not accurate; as in our study, US did not allow a complete assessment of the forearm musculature.

An intact lacertus fibrosus improves strength after reinsertion of the distal biceps tendon

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.

High-resolution ultrasound in the assessment of the distal biceps brachii tendinous complex

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.