The flexor carpi radialisbrevis muscle - an anomaly in forearm musculature: a review article

The prevalence and distribution of the flexor carpi radialis brevis muscle in the Turkish population

The flexor carpi radialis brevis (FCRB) is a very rare anomalous muscle that is usually asymptomatic but may cause various pathologies, such as radial-sided wrist pain. The aim of this study was to determine the prevalence of FCRB in the Turkish population, its location, and sex differences. Forearm, wrist, and hand magnetic resonance images of 849 individuals aged 18-65 years were retrospectively evaluated in this study. The survey found an FCRB prevalence of 4%, with a prevalence of 3.6% among women and of 4.7% among men. However, the difference between the sexes was not statistically significant (p = 0.629). The origin of all 34 FCRBs identified was the distal third of the anterior aspect of the radius; the insertion site of 28 was the second metacarpal bone, whereas that of the remaining 6 was the os trapezium. In conclusion, the data of this study report the prevalence of FCRB for the first time in the Turkish population, which will contribute to radiological and surgical evaluations in the region and help in early and accurate diagnosis of various pathological conditions that may be caused by FCRB.

Surgical Exposure Technique for Volar Locking Plate Fixation of Distal Radius Fractures in Patients with Flexor Carpi Radialis Brevis Muscle Anomaly

The flexor carpi radialis brevis (FCRB) muscle, considered a rare anomaly, is not well known among orthopedic surgeons. The indications for volar locking plates to treat distal radius fractures have recently expanded, and, as a result, encounters with the FCRB are becoming more common. However, few studies have described how to retract an FCRB. Here, we describe seven of 264 patients with FCRB who underwent surgery for distal radius fractures. In one case, the retracted FCRB interfered with the internal fixation. The presented cases demonstrate that the radial retraction of an FCRB with a large muscle belly enables favorable exposure of the distal radius.

Morphological and functional assessment of the flexor carpi radialis brevis using conventional ultrasound and elastography

PURPOSE

The flexor carpi radialis brevis (FCRB) is a supernumerary musculotendinous structure of the wrist that has been the focus of some interest in the last decade. While its anatomy is well known, its in vivo function remains unknown as it has never been studied.

METHODS

Eleven cases of FCRB underwent a multimodal ultrasound consisting of B-mode, color Doppler and shear wave elastography.

RESULTS

A pennate shape was observed in all cases and the mean value of the cross-sectional area was 0.8 cm² (SD 0.3 cm²). Young's modulus was significantly (p < 0.01) different between the resting position and active flexion or passive extension.

CONCLUSION

Our study demonstrates that the FCRB shows biomechanics of a typical skeletal muscle and is voluntarily controlled by flexing the wrist. Absent in other vertebrate taxa, the FCRB probably plays a role in active stability of the wrist in Human.

Prevalence of Flexor Carpi Radialis Brevis in Chinese Patients with Volar Wrist Plating Performed for Distal Radius Fracture

Background: Volar locking plates were increasing popular as treatment of distal radius fractures. Various distal forearm anatomical variants were encountered during surgery. Flexor carpi radialis brevis (FCRB) was one of the most common and relevant anatomical variants because of its close proximity to fracture site. Methods: This is a retrospective single-centre study. In a 3.5-year period from March 2015 to August 2018, 133 patients who suffered from distal radius fracture requiring volar wrist plating were identified. Operation records and clinical photos were reviewed. All patients were followed up for at least 1 year. Any complications were recorded. Results: 9 patients with FCRB variant were identified. The prevalence was 6.8%. Hypoplastic pronator quadratus were found in 5 cases out of the 9 cases. None of these cases had any neurovascular injuries. No complications were noted during follow-up at 1 year. Conclusions: In Chinese population with volar locking plate done for distal radius fracture, the prevalence of flexor carpi radialis brevis was 6.8%. Surgeons should be aware of the possibility of FCRB variant.

Volar Locking Plate Fixation of Distal Radius Fracture with a Flexor Carpi Radialis Brevis and a Hypoplastic Pronator Quadratus

Introduction:

Recently, distal radius fracture (DRF) has been treated with internal fixation using volar locking plates and several reports describing patients with a flexor carpi radialis brevis (FCRB) appeared. However, no studies have so far investigated the location of the FCRB relative to the volar locking plate.

Case Report:

We herein report three cases of DRF with an FCRB. Two patients had a bilateral FCRB, and an FCRB was detected in 5 of 174 limbs (2.9%). In all cases, the FCRB had a muscle belly and was retracted to the radial side and volar plate fixation was performed without difficulty. The pronator quadratus (PQ) under the FCRB was thin. In one case, the PQ was hypoplastic and restoration was impossible. The distance from the plate to the FCRB and that from the plate to the flexor pollicis longus (FPL) tendon were examined postoperatively using ultrasound. In the case in which the PQ could not be restored, the FPL tendon was located close to the plate and the FCRB was in contact with the plate.

Conclusion:

As volar locking plate fixation of a DRF with an FCRB and a hypoplastic PQ may cause the restoration of the PQ impossible, the operation should be performed more carefully and follow-up is necessary to avoid post-operative FPL tendon injury and FCRB tendinopathy due to friction with the plate.

Flexor carpi radialis brevis: a rare accessory muscle presenting as an intersection syndrome of the wrist

The flexor carpi radialis brevis (FCRB) is a rare accessory muscle of the forearm and wrist. It is typically asymptomatic, but has been discovered either incidentally during cadaveric studies or at the time of surgery in patients with distal forearm injury. Rarely, the FCRB muscle is associated with pain. We report a patient with wrist pain related to intersection between the tendon of the FCRB muscle and the tendon of the flexor carpi radialis (FCR) muscle, with an associated longitudinal split tear of the FCR tendon, documented by magnetic resonance imaging (MRI). To our knowledge, this is only the second report in the English literature of this intersection syndrome.

Anatomic Variations of the Flexor Carpi Radialis Brevis: A Report of Five Cases

The flexor carpi radialis brevis (FCRB) is a rare, anomalous musculotendinous structure of the wrist. Here, we report five cases of FCRB in a consecutive series of 123 distal radius fractures that were repaired by using volar locking plates.

Flexor carpi radialis tendon ultrasound pictorial essay

Disorders of the flexor carpi radialis tendon (FCRt) are often missed even though they are a relatively frequent cause of volar radial wrist pain. They can manifest as tenosynovitis, tendinopathy, synovial sheath cysts with or without scaphoid-trapezoid-trapezium (STT) joint pathology, and partial or complete rupture. Because FCRt disorders often present with non-specific symptoms and a non-diagnostic clinical examination, imaging is often necessary for accurate evaluation and therapeutic planning. Conventional radiography provides good visualization of the neighboring bones and joints, as well as rare intratendinous calcifications. MRI enables evaluation of the FCRt and adjacent anatomical structures with excellent tissue resolution. In comparison, ultrasound (US) evaluation of the FCRt is less commonly described in the radiology literature, despite its affordability, exquisite soft tissue resolution, and the advantages of quick, dynamic diagnostic imaging. This pictorial essay describes and demonstrates the normal anatomy of the FCRt, its US examination technique and normal US appearance, and US findings of clinically relevant FCRt disorders.