The humerus intertubercular sulcus, also known as the bicipital groove, is a significant anatomical feature of the proximal humerus. It plays a crucial role in the anatomy and function of the shoulder, serving as a passageway for important neurovascular structures and providing attachment points for key muscles. Understanding the detailed anatomy of this sulcus is essential for clinicians, radiologists, and students of anatomy, especially when diagnosing shoulder injuries or planning surgical interventions. This article provides a comprehensive overview of the humerus intertubercular sulcus, including its anatomy, clinical significance, and related structures.
Anatomical Overview of the Humerus Intertubercular Sulcus
Location and General Description
The humerus intertubercular sulcus is a deep groove located on the anterior aspect of the proximal humerus. It runs longitudinally between the greater and lesser tubercles, which are bony prominences on the proximal end of the humerus. The sulcus extends from the surgical neck of the humerus downward toward the diaphysis.
The groove's primary function is to serve as a pathway for the long head of the biceps brachii muscle, along with accompanying neurovascular structures, making it a vital anatomical landmark.
Structural Features
The intertubercular sulcus exhibits the following features:
- Medial lip: Bounded superiorly by the crest of the lesser tubercle.
- Lateral lip: Bounded inferiorly by the crest of the greater tubercle.
- Floor: Formed by the long head of the biceps tendon, which traverses the groove.
- Roof: Covered by a synovial membrane that lines the shoulder joint capsule.
The sulcus is deep enough to accommodate the long head of the biceps brachii, which is held in place by the transverse humeral ligament, preventing it from slipping out of the groove during shoulder movements.
Associated Structures and Attachments
Muscles Involved
The primary muscle associated with the intertubercular sulcus is:
- Long head of biceps brachii: Runs within the sulcus, attaching proximally to the supraglenoid tubercle of the scapula and distally to the radial tuberosity.
Other muscles related to the proximal humerus and shoulder joint include:
- Supraspinatus, infraspinatus, subscapularis, teres minor: These rotator cuff muscles attach to the tubercles and stabilize the shoulder joint.
Neurovascular Structures
The axillary nerve and posterior humeral circumflex artery are the primary neurovascular elements that pass through or near the intertubercular sulcus:
- Axillary nerve: Provides motor innervation to the deltoid and teres minor muscles and sensory supply to the skin over the deltoid.
- Posterior humeral circumflex artery: Supplies blood to the deltoid muscle, shoulder joint, and surrounding tissues.
These structures are vulnerable during surgical procedures involving the proximal humerus or shoulder dislocations.
Clinical Significance of the Humerus Intertubercular Sulcus
Shoulder Dislocations and Fractures
Dislocations of the shoulder often involve the humeral head slipping out of the glenoid cavity, which can sometimes lead to fractures of the tubercles or the proximal humerus. Fractures involving the intertubercular sulcus may affect the biceps tendon or neurovascular structures passing through the groove.
- Biceps tendon injuries: Rupture or tenodesis of the long head of the biceps can occur in this region.
- Fractures: Greater tubercle fractures are common, and involvement of the intertubercular sulcus can complicate healing or lead to impingement syndromes.
Rotator Cuff Pathologies
Since the rotator cuff tendons attach near the tubercles, injuries or degenerative changes in these tendons can impact the sulcus region. For example:
- Calcific tendinitis can cause impingement within the groove.
- Rotator cuff tears may be associated with tubercle fractures or bursal inflammation.
Surgical Interventions
Understanding the anatomy of the humerus intertubercular sulcus is vital during surgical procedures like:
- Biceps tenodesis: Fixation of the long head of the biceps tendon in the groove.
- Fracture fixation: Using plates or screws near the proximal humerus.
- Shoulder arthroscopy: Navigating around neurovascular structures passing through the sulcus.
Injury to the axillary nerve or posterior humeral circumflex artery during surgery can lead to complications such as deltoid paralysis or hemorrhage.
Radiological Evaluation of the Intertubercular Sulcus
Imaging Techniques
The intertubercular sulcus can be evaluated using various imaging modalities:
- Plain radiographs: Anteroposterior (AP) and lateral views can reveal fractures, dislocations, or bony anomalies.
- Magnetic Resonance Imaging (MRI): Offers detailed visualization of soft tissues such as tendons and neurovascular structures.
- Computed Tomography (CT): Provides precise bony detail, useful in complex fractures.
Common Radiological Findings
- Fracture lines along the tubercles or within the sulcus.
- Bony spurs or osteophytes that may impinge on the bicipital groove.
- Tendon calcifications or tears within the groove.
- Displacement of the humeral head in dislocation cases.
Variations and Anomalies
While the intertubercular sulcus is typically consistent in structure, some variations can occur:
- Accessory bicipital grooves: Rarely, an additional groove may be present, which can complicate surgical procedures.
- Bony spurs or osteophytes: Common in osteoarthritic changes, potentially narrowing the groove and causing impingement.
- Congenital anomalies: Such as hypoplasia or duplication of tubercles, affecting the sulcus anatomy.
Summary
The humerus intertubercular sulcus is a vital anatomical feature that serves as a conduit for essential neurovascular structures and a site for muscle attachment. Its anatomy and variations have significant clinical implications, especially in shoulder injuries, rotator cuff pathologies, and surgical procedures. Proper understanding of this structure enhances diagnostic accuracy, surgical planning, and treatment outcomes.
Key Points to Remember:
- Located between the greater and lesser tubercles on the proximal humerus.
- Houses the long head of the biceps brachii tendon.
- Passageway for the axillary nerve and posterior humeral circumflex artery.
- Common site for fractures, dislocations, and tendinous injuries.
- Important in surgical interventions like biceps tenodesis and fracture fixation.
A thorough grasp of the humerus intertubercular sulcus's anatomy and its clinical relevance is indispensable for healthcare professionals involved in treating shoulder injuries or performing shoulder surgeries.
Frequently Asked Questions
What is the humerus intertubercular sulcus and where is it located?
The humerus intertubercular sulcus, also known as the bicipital groove, is a deep groove located on the anterior surface of the proximal humerus between the greater and lesser tubercles. It serves as a passage for the tendon of the long head of the biceps brachii muscle.
What structures pass through the intertubercular sulcus of the humerus?
The intertubercular sulcus transmits the tendon of the long head of the biceps brachii, along with the ascending branch of the anterior circumflex humeral artery and the cephalic vein.
How does the intertubercular sulcus relate to shoulder joint stability?
The sulcus provides a pathway for tendons and vessels, and its structure helps maintain the position of the long head of the biceps tendon within the shoulder joint, contributing to shoulder stability and movement.
What are common clinical conditions associated with the intertubercular sulcus?
Conditions such as biceps tendinitis, tears of the long head of the biceps tendon, and bicipital groove fractures are associated with the intertubercular sulcus, often presenting with pain and limited shoulder movement.
How can the intertubercular sulcus be identified during an imaging study?
On X-ray or MRI images, the intertubercular sulcus appears as a distinct groove on the proximal humerus, often used as a landmark for locating the biceps tendon and assessing pathologies.
What is the significance of the intertubercular sulcus in humeral fractures?
Fractures involving the humeral head or tubercles can disrupt the groove, affecting the passage of the biceps tendon and potentially leading to functional impairments or deformities such as a 'surgical neck fracture.'
Are there any variations in the anatomy of the humerus intertubercular sulcus?
Yes, anatomical variations can include differences in depth, width, and shape of the sulcus, which may influence the susceptibility to certain injuries or the approach during surgical procedures.
What surgical procedures involve the humerus intertubercular sulcus?
Procedures such as biceps tenodesis, shoulder arthroscopy, and fracture fixation often require identification or manipulation of the intertubercular sulcus to access the biceps tendon or stabilize the proximal humerus.
How does the intertubercular sulcus develop embryologically?
Embryologically, the sulcus develops as part of the ossification and growth processes of the proximal humerus, with the tubercles forming around the area where the biceps tendon and associated vessels are anchored during development.
