Gracilis Anatomy

Proximal Origin

• Site: a thin, flat aponeurosis from the body and inferior ramus of the pubis and the adjacent ischiopubic ramus, immediately lateral to the symphysis.
• Character: the origin is broad and membranous, only about 2-3 cm wide, and it lies superficial to adductor brevis and adductor magnus.
• Palpable landmark: the pubic tubercle is the reference point for all gracilis measurements. The muscle's leading edge is roughly a fingerbreadth lateral to it.

Course

• Descends vertically along the medial thigh, narrowing progressively — it is broad proximally and becomes a narrow strap by the mid-thigh.
• The muscle belly ends at approximately the junction of the middle and distal thirds of the thigh, giving way to a long, thin, round-to-flat tendon.
• The tendon passes behind the medial femoral condyle, then turns anteriorly around it to reach the tibia.

Distal Insertion

• Site: the superomedial surface of the tibia, as the middle tendon of the pes anserinus, roughly 2-3 cm distal to the medial joint line and medial to the tibial tuberosity.
• Layers at the pes (superficial to deep): sartorius fascia, gracilis, semitendinosus, then the pes anserine bursa, then the superficial MCL, then bone.
• Order at the tibia: gracilis lies proximal and anterior to semitendinosus at the insertion, which is why the gracilis is the first tendon encountered when the sartorial fascia is opened.

Harvestable Dimensions

• Tendon length: approximately 20-26 cm of usable tendon, shorter than semitendinosus.
• Muscle length: typically 35-45 cm of total muscle length in an adult; for free transfer a segment of 12-18 cm is usually taken, tailored to the excursion required.
• Doubled gracilis diameter: roughly 5-6 mm — insufficient alone for an ACL, which is why it is combined with semitendinosus.

Nerve Supply

• Nerve: the anterior division of the obturator nerve.
• Root values: L2, L3, L4 (predominantly L2 and L3).
• Course of the parent nerve: the obturator nerve arises from the lumbar plexus, descends along the medial border of psoas, crosses the pelvic brim behind the common iliac vessels, runs on the lateral pelvic wall, and exits through the obturator canal at the superolateral corner of the obturator foramen, dividing into anterior and posterior divisions around the adductor brevis.
• The anterior division runs anterior to adductor brevis and posterior to pectineus and adductor longus, supplying gracilis, adductor longus, adductor brevis and giving cutaneous branches to the medial thigh.
• The posterior division runs posterior to adductor brevis, supplying obturator externus and the adductor part of adductor magnus.

Motor Entry Point — the Number That Matters

• The gracilis branch enters the muscle on its deep (lateral) surface, in the proximal third, typically 8-12 cm distal to the pubic tubercle, and characteristically slightly proximal to and deep to the vascular pedicle.
• The branch enters as a single trunk in most specimens and can be traced proximally within the adductor compartment to yield 6-10 cm of dissectible nerve.
• Why this matters: for a functioning free muscle transfer the coaptation must be tension-free and outside the zone of injury. Taking the nerve long, by dissecting proximally toward the obturator canal, is what makes that possible.
• Intramuscular topography: the nerve divides within the muscle into branches running proximally and distally, which permits the muscle to be split longitudinally into independently innervated segments — the anatomical basis for splitting a gracilis for facial reanimation and for double free muscle transfer.

Testing and Denervation

• Isolated testing is unreliable because adductor longus, brevis and magnus dominate hip adduction. Gracilis is best inferred from the combination of adduction weakness with knee flexion weakness in a patient with intact hamstrings.
• Obturator neuropathy presents with medial thigh pain and paraesthesia, exercise-induced adductor pain (the classical sportsman's obturator neuropathy at the fascia over adductor brevis), and weakness of adduction.
• Iatrogenic obturator nerve injury is a recognised complication of pelvic surgery, acetabular fracture fixation through an anterior intrapelvic (modified Stoppa) approach, hip arthroscopy with excessive medial traction, and cement extrusion medially in acetabular arthroplasty.

The Dominant Pedicle

• Vessel: the adductor branch of the medial circumflex femoral artery, itself a branch of the profunda femoris artery (occasionally arising directly from the profunda or the femoral artery).
• Entry point: the deep (lateral) surface of the muscle, approximately 8-10 cm distal to the pubic tubercle, that is, in the proximal third of the muscle.
• Pedicle length: approximately 6-8 cm when dissected back to the profunda.
• Vessel calibre: artery 1.5-2.5 mm, with two venae comitantes typically 2-3 mm. These are comfortable calibres for microvascular anastomosis and are one reason the flap is so reliable.

Minor Pedicles

• One or two minor pedicles from the superficial femoral artery enter the middle and distal thirds of the muscle.
• Ligating them is part of the standard free harvest and does not compromise the muscle, because the dominant proximal pedicle perfuses the whole length.
• Mathes-Nahai type II — one dominant plus minor pedicles — the classification the examiner will ask for.

Skin Territory

• A skin paddle can be raised over the proximal third of the muscle, based on musculocutaneous perforators from the dominant pedicle, usually within 8-12 cm of the pubic tubercle.
• The distal skin over the muscle is not reliably perfused — a common cause of partial flap loss when an over-long skin paddle is designed.
• This is why a myocutaneous gracilis flap has a proximally sited, relatively small paddle, and why a monitoring skin island is placed proximally.

Vascular Consequences of Tendon Harvest

• Tendon-only harvest divides the distal tendon and its small distal vessels; the muscle belly retains its dominant proximal pedicle and remains fully viable.
• Harvesting the tendon does not preclude later use of the muscle as a flap, although scarring makes the dissection harder — a point worth remembering when both procedures might be needed in the same patient.

Medial Thigh

• Superficial (medial): skin, subcutaneous fat, the great saphenous vein running just anterior to the muscle in the distal thigh, and the deep fascia. Gracilis is the most superficial adductor, so it is the first muscle encountered on a medial thigh approach.
• Deep (lateral): adductor brevis and adductor magnus proximally; the sartorius crosses superficial to it anteriorly in the distal thigh.
• Anterior: adductor longus proximally, then sartorius distally.
• Posterior: adductor magnus and, further posteriorly, semimembranosus.
• The plane that matters: the interval between the posterior border of adductor longus and the anterior border of gracilis leads directly to the anterior division of the obturator nerve on the front of adductor brevis. This is the interval used for obturator neurectomy and for exposing the nerve in a gracilis harvest.

At the Knee

• The gracilis tendon passes posterior to the medial femoral condyle, superficial to the superficial MCL, and turns anteriorly to the pes.
• Immediately superficial: the sartorial fascia and, within or deep to it, the infrapatellar branch of the saphenous nerve running transversely.
• Immediately deep and posterior: the semitendinosus tendon and, beyond it, the medial head of gastrocnemius.
• Fascial expansions: like semitendinosus, gracilis gives fascial expansions — to the crural fascia and, less constantly, to the medial gastrocnemius fascia. They must be released before stripping.

Structures at Risk

• Obturator nerve and its anterior division — during proximal dissection and during any medial thigh or pelvic procedure.
• Great saphenous vein — subcutaneous, immediately anterior to the muscle in the distal thigh.
• Saphenous nerve and its infrapatellar branch — at the pes.
• Medial circumflex femoral artery and profunda femoris — during proximal pedicle dissection.
• The adductor canal contents (femoral artery, vein, saphenous nerve, nerve to vastus medialis) — deep and anterior, protected by adductor longus and sartorius but reachable if the dissection strays anteriorly.

As a Free Tendon Graft

• ACL reconstruction: combined with semitendinosus as the classic four-strand hamstring graft. Doubled gracilis alone is only 5-6 mm and is never adequate on its own.
• MPFL reconstruction: the standard graft in most units. A doubled gracilis is more than strong enough — the native MPFL fails at around 200 N, whereas a doubled gracilis is several times stronger, so graft strength is never the limiting factor. Tunnel position and tension are.
• MCL and posteromedial corner, posterolateral corner, PCL augmentation and multiligament reconstruction.
• Hand and wrist: ligament reconstruction where a longer graft than the palmaris longus is required.
• Ankle and foot: lateral ligament, spring ligament and deltoid reconstruction; peroneal and tibialis posterior tendon reconstruction.
• Acromioclavicular joint reconstruction and coracoclavicular ligament reconstruction.

Harvest Technique

1. Position: supine, hip flexed, abducted and externally rotated, knee flexed 90 degrees (figure-of-four).
2. Incision: a 2-3 cm oblique incision over the pes, roughly 2-3 fingerbreadths distal to the medial joint line, oriented parallel to the infrapatellar branch of the saphenous nerve.
3. Identify the sartorial fascia; the gracilis is the more proximal and thinner cord palpable through it, semitendinosus the more distal and thicker.
4. Incise the fascia along the superior border of the gracilis, deliver the tendon with a right-angled clamp, and whip-stitch it.
5. Release the fascial expansions and the dense investing fascia on the deep surface with firm distal traction, sharply and under direct vision. The gracilis has fewer and less substantial accessory attachments than the semitendinosus, whose accessory insertion was found in 77 per cent of cadaveric knees, but they still misdirect a stripper.
6. Detach the tibial insertion subperiosteally, then advance the closed-loop stripper coaxially with steady traction. Never force it.
7. Prepare and measure the graft; close the sartorial fascia.

Practical Notes

• The gracilis strips more easily than the semitendinosus because it has fewer accessory bands — but the same discipline applies.
• Sparing the gracilis is increasingly favoured in young patients, using a quadrupled or quintupled semitendinosus alone, to preserve a future graft source and to reduce donor deficit.
• Regeneration cannot be assumed. In a two-year MRI study, both the semitendinosus and gracilis had regenerated in only 35 per cent of patients, and donor muscle loss was greater where the tendon had not regenerated — another argument for sparing the gracilis where the semitendinosus alone will suffice.

Brachial Plexus Reconstruction

• Indication: restoration of elbow flexion, and in the Doi double free muscle technique also finger flexion and extension, after a complete (C5-T1) brachial plexus avulsion or in a late presentation where the native biceps has undergone irreversible motor endplate loss (generally beyond 12 months from injury, since a denervated muscle cannot be usefully reinnervated after that window).
• Why a free muscle rather than a nerve transfer: a nerve transfer requires a viable target muscle. Beyond about a year, the biceps has fibrosed and no nerve transfer will work. A functioning free muscle transfer brings its own muscle, so the time limit no longer applies.

Donor Nerves for Neurotisation

Technique for Elbow Flexion

• Recipient vessels: the thoracoacromial or thoracodorsal vessels, or the brachial artery with an end-to-side anastomosis and a venous anastomosis to a comitans or the cephalic vein.
• Proximal fixation: the muscle origin is secured to the clavicle, second rib or coracoid — a fixed proximal anchor is essential or the muscle has nothing to pull against.
• Distal fixation: the tendon is woven into the biceps tendon, or in the Doi double transfer routed further to the finger flexors.
• Tension: set by restoring the in-situ marking-suture intervals with the elbow flexed.
• Timeline: first contraction at 3-6 months; plateau function at 18-24 months; realistic goal is MRC grade M3-M4 elbow flexion.

Facial Reanimation

• Indication: long-standing facial paralysis (generally beyond 18-24 months), congenital facial palsy including Möbius syndrome, and after ablative surgery where the facial nerve has been sacrificed.
• Two-stage classical technique: stage one, a cross-face sural nerve graft from selected buccal branches of the contralateral, normal facial nerve, tunnelled across the upper lip and banked in the paralysed cheek. Stage two, 9-12 months later once an advancing Tinel confirms axonal arrival, a free gracilis segment is transferred and coapted to the banked graft.
• Single-stage alternative: free gracilis neurotised by the ipsilateral masseteric nerve, giving a stronger and faster but initially non-spontaneous smile. Some units perform a dual innervation technique combining both.
• Anatomy of the inset: only a slip of gracilis (3-4 cm wide) is taken, based on the dominant pedicle. It is anchored proximally to the zygomatic arch and preauricular fascia and distally to the modiolus and the orbicularis oris at the oral commissure, along the vector of the contralateral smile (typically 30-45 degrees above the horizontal).
• Recipient vessels: the facial artery and vein, or the superficial temporal vessels.
• Outcomes: first movement at 4-6 months, maturation over 1-2 years, with commissure excursion measured in millimetres as the outcome metric.

Pedicled Gracilis Flap

• Based on the same dominant proximal pedicle, the muscle can be rotated locally for perineal, vaginal, anal sphincter (dynamic graciloplasty), ischial pressure sore and groin reconstruction.
• Its arc of rotation reaches the perineum, ischium and the contralateral groin, but not the knee — for knee and proximal tibial cover the gastrocnemius is the flap of choice.

Adductor-Related Groin Pain

• Gracilis is part of the adductor group implicated in the Doha agreement category of adductor-related groin pain: pain at the adductor origin reproduced by resisted adduction.
• Gracilis-specific presentation: pain at the pubic origin that is worse with the knee extended (biarticular stretch) and relieved by knee flexion.
• Gracilis syndrome: a described entity of chronic pain and a fibrous, stenosed musculotendinous origin, occasionally requiring release. It is uncommon and should be a diagnosis of exclusion.
• Management: load management, progressive adductor strengthening (the Copenhagen adduction exercise programme), and correction of the kicking or skating mechanics that provoke it.

Avulsion and Strain

• Musculotendinous strain of the gracilis occurs in kicking sports and gymnastics, typically at the proximal musculotendinous junction.
• Distal avulsion at the pes is very rare and is managed non-operatively.
• Apophyseal avulsion of the ischiopubic ramus in adolescents involves the gracilis and adductor origins; radiographs make the diagnosis and management is almost always non-operative.

Obturator Neuropathy

• Sportsman's obturator neuropathy: entrapment of the anterior division by fascia over adductor brevis, producing exercise-induced medial thigh pain and adductor weakness in Australian-rules footballers and other kicking athletes. Treated by fascial release where conservative measures fail.
• Obturator hernia: compression of the nerve in the obturator canal producing the Howship-Romberg sign — medial thigh and knee pain provoked by hip extension, abduction and internal rotation, relieved by flexion. Classically an elderly, thin woman with bowel obstruction; a surgical emergency.
• Iatrogenic: pelvic and gynaecological surgery, anterior intrapelvic acetabular approaches, medial cement extrusion in hip arthroplasty, and hip arthroscopy traction.

Pes Anserine Bursitis

• The bursa lies deep to all three pes tendons and superficial to the superficial MCL, roughly 4-5 cm distal to the medial joint line. Gracilis is one of the three tendons overlying it.
• Presentation, discriminators and management as for semitendinosus — the key point is that the tenderness is distal and anterior to the joint line, not on it.