Latissimus Dorsi Anatomy

The latissimus dorsi is the broadest muscle in the body, a fan of fibres converging from the lower half of the trunk onto a short flat tendon at the front of the humerus. Its functional role — adduction, extension and internal rotation — is entirely duplicated by the pectoralis major, teres major and subscapularis, which is precisely why it is the most expendable large muscle available and the most heavily used donor in reconstructive surgery.

Three surgical identities dominate examination discussion. It is the transfer of choice for an irreparable posterosuperior rotator cuff tear in a younger patient. It is the workhorse flap for reconstruction of the chest wall, breast, head and neck, and limbs, either pedicled or free. And in brachial plexus birth palsy it is one of the internal rotators whose unopposed pull produces a fixed internal rotation contracture and progressive glenoid dysplasia — the same muscle that later becomes the solution when it is released and transferred.

Actions by plane

• Adduction of the humerus, powerfully and through a long arc.
• Extension of the humerus from a flexed position.
• Internal (medial) rotation of the humerus.
• Depression of the shoulder girdle, drawing the whole shoulder downward and backward.
• Trunk elevation with a fixed arm: during climbing, crutch walking and wheelchair transfers, the latissimus pulls the trunk toward the fixed arm. This is the action that matters when counselling a wheelchair user about donor morbidity.
• Accessory respiration: it contributes to forced expiration and coughing, and the scapular slip contributes to scapular depression and downward rotation.

Mechanical characteristics that make it a good donor

• Long fibres and generous excursion. Unlike the short, stiff teres major, the latissimus has a long parallel-fibred architecture and a large excursion, which is what allows it to be routed around the humerus and still reach the greater tuberosity.
• Single long pedicle. A 6 to 16 cm pedicle of adequate calibre with a wide arc of rotation.
• Functional redundancy. Its actions are duplicated by pectoralis major, teres major and subscapularis, so most patients report no functional loss after harvest.
• The trade-off is that its excursion comes with relatively modest force per unit cross-section compared with a pennate muscle, and after transfer the tendon must be tensioned carefully to place the muscle on the correct part of its length-tension curve.

Synergists and antagonists

• Synergists: teres major and pectoralis major (adduction, extension, internal rotation), subscapularis (internal rotation), posterior deltoid (extension), long head of triceps (extension).
• Antagonists: deltoid and supraspinatus (abduction), infraspinatus and teres minor (external rotation), trapezius and serratus anterior (shoulder girdle elevation).

Palpation and positioning

• Ask the patient to place the hand on the hip and press inward, or to cough. The posterior axillary fold becomes prominent and the broad sheet of latissimus can be traced from the fold down and medially toward the iliac crest.
• The anterior (lateral) border is the key surgical landmark and is marked pre-operatively with the patient standing and adducting against resistance; the flap skin paddle and the descending vascular branch are planned relative to it.
• The inferior angle of the scapula is palpated to identify the scapular slip and to orient the superior extent of a flap.

Named tests and clinical assessment

Radial nerve injury

• Mechanism: blind dissection inferior to the tendon insertions at harvest, or traction while routing the transfer.
• Consequence: wrist drop and loss of thumb and finger extension in a patient operated on for shoulder weakness — a catastrophic and entirely avoidable outcome.
• Avoidance: abduct and externally rotate the arm, release under direct vision, and never sweep blindly.

Axillary nerve injury

• Mechanism: proximal mobilisation into the quadrangular space, or forceful passage of the tendon beneath the deltoid.
• Consequence: deltoid loss, which removes both active elevation and the option of a subsequent reverse arthroplasty.
• Avoidance: create the subdeltoid tunnel bluntly under palpation and confirm it is free before pulling the tendon.

Pedicle compromise and flap loss

• Mechanism: injury to the thoracodorsal artery during harvest, kinking as the flap is inset, compression by a tight tunnel, or previous axillary surgery having already damaged the pedicle.
• Avoidance: dissect the pedicle to the subscapular trunk to gain length, preserve the serratus branch where possible for retrograde perfusion, avoid tension and kinking at inset, and always take a history of previous axillary surgery or irradiation.
• Recognition: monitor the flap clinically and with implantable Doppler where available; early re-exploration salvages a thrombosed anastomosis.

Donor site morbidity

• Seroma is the commonest complication of latissimus harvest, particularly with wide pedicled dissection. Quilting sutures to obliterate the dead space and prolonged drainage reduce, but do not eliminate, it.
• Functional loss is usually negligible in ambulant patients because the actions are duplicated. It is not negligible in wheelchair users, crutch users, climbers, rowers and swimmers, who depend on latissimus for transfers and propulsion. Counsel these groups explicitly and consider a split harvest.
• Loss of the posterior axillary fold contour and a long visible scar.
• Shoulder stiffness from prolonged immobilisation after a transfer.

Failure of a transfer

• Insufficient subscapularis is the dominant predictor of failure, shown clearly in long-term series.
• Tensioning error: tensioning in internal rotation leaves the transfer slack and functionless.
• Rupture of the transfer at the tuberosity, particularly if active use begins too early.
• Failure of motor re-education: the patient must learn to fire an internal rotator as an external rotator. Without a structured programme with biofeedback, a technically perfect transfer produces no functional gain.

Denervation of the graft

• A transfer whose thoracodorsal nerve is injured, or a flap harvested from a side with previous axillary node clearance, becomes a passive tenodesis rather than a functioning muscle. Confirm contraction pre-operatively.

Related pages. The muscle it travels with: Teres Major Anatomy is transferred alongside it in birth palsy and torn alongside it in throwers — see Latissimus Dorsi and Teres Major Rupture.

Pathology and clinical roles

Grading and imaging

• MRI identifies the tendon at the floor of the bicipital groove, anterior to teres major, and demonstrates rupture, retraction and fatty change. Muscle quality on MRI is assessed before transfer.
• Imaging in birth palsy: ultrasound in infants avoids anaesthesia and assesses head subluxation dynamically; MRI is used to grade glenoid version and morphology.
• Angiographic or duplex assessment of the thoracodorsal pedicle is used selectively before free flap transfer, particularly where there has been previous axillary surgery, irradiation or trauma.
• Denervation appears as diffuse muscle oedema-like signal followed by fatty replacement, uniform across the belly.

Latissimus dorsi transfer for irreparable posterosuperior cuff tear

Flap surgery

• Pedicled myocutaneous flap on the thoracodorsal pedicle: the standard reconstruction for the breast after mastectomy, for chest wall defects, for head and neck reconstruction, and for coverage of the shoulder, axilla and proximal arm. Its arc of rotation reaches the head and the mid-chest.
• Free flap: the workhorse muscle free flap. Its long pedicle, adequate calibre, large surface area and reliable anatomy make it the standard choice for large defects of the lower limb, the scalp and complex wounds anywhere.
• Functional free muscle transfer: with microvascular anastomosis and coaptation of the thoracodorsal nerve to a recipient motor nerve, the latissimus is used to restore elbow flexion in brachial plexus reconstruction, and in facial reanimation.
• Split or segmental flap: because the pedicle divides into descending and transverse branches, half the muscle can be taken while the other half remains innervated and perfused — reducing donor morbidity.
• Reverse (turnover) flap: based on the paraspinous perforators, reaching midline lumbar and lower thoracic defects. This is the practical expression of the Mathes-Nahai Type V pattern.
• Latissimus dorsi transfer for elbow flexion (bipolar transfer): the whole muscle is moved on its pedicle to the anterior arm to substitute for an absent biceps.

Other uses and landmarks

• L'Episcopo and Hoffer transfers in brachial plexus birth palsy, and the modified L'Episcopo combined with reverse arthroplasty in adults with combined loss of elevation and external rotation.
• The lumbar triangle of Petit and the auscultatory triangle are defined by its borders and appear regularly in anatomy vivas.
• The anterior border guides thoracotomy incisions and is preserved in a muscle-sparing thoracotomy specifically to keep the flap option available.

Anatomical variation across populations

• The scapular slip from the inferior angle is present in roughly half of individuals in cadaveric series, with variation between populations. Its presence matters at flap harvest and explains why strong latissimus contraction can rotate the scapula.
• The axillary arch (Langer's arch), a muscular slip crossing the axilla from latissimus to pectoralis major, the coracoid or the conjoined tendon, is described with reported prevalence differences across populations. It can compress the axillary neurovascular bundle, confuse axillary node dissection, and be mistaken for a mass.
• The branching pattern of the thoracodorsal artery varies, particularly the level at which the serratus branch and the intramuscular division arise, which is the basis for planning split flaps and must be confirmed intra-operatively rather than assumed.
• The point at which the thoracodorsal nerve enters the muscle also varies, affecting the arc of rotation achievable in a functional transfer.

Side-by-side guidance

Registry and outcome signals

• Tendon transfers about the shoulder are low-volume procedures and are not captured by national joint registries; the evidence base is long-term institutional series. The consistent signal across those series is that pain relief is the most reliable outcome, functional gain is more variable, and subscapularis integrity dominates the result.
• Breast reconstruction registries and national audits capture latissimus flap use in reasonable volume. Seroma is consistently the commonest donor complication, and total flap loss with a pedicled latissimus is rare.
• Brachial plexus birth palsy outcomes are tracked through specialist multidisciplinary networks rather than registries. The consistent message is that early recognition of the internal rotation contracture and rebalancing before fixed glenoid dysplasia develops determines long-term shoulder function.
• Reverse arthroplasty volumes in national registries continue to grow, and in many settings a reverse has replaced tendon transfer for older patients who would previously have had a latissimus transfer.

High-resource versus limited-resource practice

• Well-resourced settings: microvascular free tissue transfer, arthroscopically assisted latissimus transfer, MRI for muscle quality grading, and implantable Doppler flap monitoring.
• Limited-resource settings: the pedicled latissimus flap is one of the most valuable operations available anywhere, requiring no microsurgical equipment and covering an enormous range of defects. Similarly, latissimus and teres major transfer for birth palsy needs no implants and changes a lever rather than replacing a joint.
• The single universally applicable step costs nothing: ask about previous axillary surgery and confirm latissimus contraction clinically before planning any operation that depends on this muscle.