Pectineus Anatomy

Origin

• Pectineal line (pecten pubis) on the superior surface of the superior pubic ramus — the sharp ridge running from the pubic tubercle to the iliopubic eminence.
• The adjacent bone anterior to the pectineal line, and the pectineal fascia.
• The pectineal (Cooper's) ligament — the thickened periosteum along the pectineal line — is closely related and is the structure used for fixation in some hernia repairs.

Insertion

• The pectineal line of the femur, a vertical ridge on the posterior surface of the femur running from the lesser trochanter to the upper end of the linea aspera.
• The muscle therefore passes posteriorly and laterally from the pubis to the back of the proximal femur, wrapping around the anteromedial aspect of the hip.

Shape and plane

• Flat and quadrilateral, roughly 5-8 cm wide in its middle portion.
• Occupies the most anterior and most superior position of the adductor group, in the same coronal plane as (and immediately anterior to) the hip joint capsule.
• Its medial border abuts the adductor longus; its lateral border abuts the iliopsoas at the iliopectineal groove, which is the point where the femoral vessels lie.

Named landmarks and measurements

Dual supply — the defining feature

1. Obturator nerve, anterior division (L2, L3, L4)

• The obturator nerve arises from the anterior divisions of the ventral rami of L2, L3 and L4, descends on the medial border of the psoas, crosses the pelvic brim behind the common iliac vessels, runs along the lateral pelvic wall above the obturator vessels, and leaves the pelvis through the obturator canal at the upper part of the obturator foramen.
• It divides into anterior and posterior divisions, classically within or just distal to the obturator canal, separated by the upper border of the obturator externus and then by the adductor brevis.
• The anterior division descends anterior to the adductor brevis and posterior to the pectineus and adductor longus, supplying adductor longus, adductor brevis, gracilis and pectineus, and giving the cutaneous branch to the medial thigh and an articular branch to the hip.

2. Femoral nerve branch

• A branch from the femoral nerve (often from the nerve to iliopsoas, or directly from the main trunk before or just after it passes beneath the inguinal ligament) enters the anterior surface of the pectineus.
• Accessory obturator nerve, present in a minority of individuals, arises from L3 and L4, passes over the superior pubic ramus rather than through the obturator canal, and supplies the pectineus and sometimes the hip joint.

Motor entry points

• Obturator (anterior division) branches enter the posterior surface of the muscle in its proximal half — that is, from the deep side.
• The femoral nerve branch enters the anterior surface, usually in the proximal third close to the lateral border.
• Practical consequence: the muscle can be partially denervated from either side, and a purely medial dissection that divides the obturator branches leaves the femoral supply intact.

Practical consequences

• Obturator nerve block for transurethral bladder surgery (to prevent the adductor jerk) and for chronic adductor spasticity blocks the obturator supply but not the femoral branch, so a residual adductor twitch may persist — a genuine clinical observation.
• Selective obturator neurectomy for spastic adduction reduces but does not abolish adduction for the same reason, and this should be explained before the procedure.
• Electromyography of the pectineus is not routine; the diagnostic value lies in recognising the pattern of preserved versus lost adduction.

Root-value cross-check

• Hip adduction = L2/L3/L4 (obturator).
• Medial thigh sensation is obturator (a small patch on the distal medial thigh); the anteromedial thigh is femoral (medial and intermediate cutaneous nerves of the thigh) and the medial leg is saphenous.
• Weak adduction with medial thigh numbness localises to the obturator nerve; add quadriceps weakness and the lesion is proximal (lumbar plexus, L2-L4 roots, or a retroperitoneal process such as haematoma, abscess, or tumour).

Supply

• Medial circumflex femoral artery (MCFA) — the dominant supply, and the reason the pectineus matters surgically. The MCFA arises from the profunda femoris (occasionally directly from the femoral artery), passes posteriorly between the pectineus and the psoas major, then continues between the obturator externus and the quadratus femoris to reach the posterior hip.
• Obturator artery — its anterior and posterior branches supply the proximal muscle; the anterior branch also gives the acetabular branch which runs in the ligamentum teres.
• Muscular branches of the profunda femoris and, proximally, the inferior epigastric or external iliac territory via anastomoses.
• Venous drainage to the profunda femoris vein and to the obturator veins.

The vascular fact that matters

• The MCFA is the principal blood supply to the femoral head in the adult, via its deep branch and the terminal retinacular (lateral epiphyseal) vessels entering the head at the posterosuperior head-neck junction.
• Its course takes it immediately deep and posterior to the pectineus and adductor brevis in the proximal medial thigh. Any medial approach to the hip therefore places the MCFA at risk, and injury causes avascular necrosis of the femoral head.
• In the medial (Ludloff) approach for developmental dysplasia of the hip, the MCFA is the structure whose injury has been implicated in the reported rates of avascular necrosis after medial open reduction.

Corona mortis — the related vascular trap

• An anastomotic vessel between the obturator and external iliac (or inferior epigastric) systems, crossing the superior pubic ramus behind the pectineus origin, typically within about 3-6 cm lateral to the symphysis pubis.
• Present in a substantial proportion of individuals (venous more often than arterial).
• Relevance: torrential and difficult-to-control bleeding during anterior pelvic (Stoppa, ilioinguinal) approaches, acetabular fracture fixation and pelvic ring surgery. Identify and ligate deliberately.

Anterior (superficial) to pectineus

• Femoral artery, femoral vein and femoral canal contents — the pectineus forms the floor on which the vessels lie in the iliopectineal groove.
• Deep inguinal lymph nodes in the femoral canal.
• Pectineal fascia and, more superficially, the fascia lata and cribriform fascia over the saphenous opening.
• Great saphenous vein joining the femoral vein at the saphenofemoral junction, roughly 3-4 cm below the pubic tubercle.
• Femoral nerve lies lateral, on the iliopsoas rather than on the pectineus.

Posterior (deep) to pectineus

• Anterior division of the obturator nerve — descending on the anterior surface of the adductor brevis, therefore deep to the pectineus.
• Adductor brevis, and behind it the posterior division of the obturator nerve and the adductor magnus.
• Obturator externus and the hip joint capsule proximally.
• Medial circumflex femoral artery passing posteriorly between the pectineus and the psoas.

Lateral

• Iliopsoas, with the iliopectineal groove between them carrying the femoral vessels.
• Hip joint capsule and the iliopsoas bursa.

Medial

• Adductor longus — the pectineus is immediately lateral and slightly deeper.

Structures at risk in the pectineus territory

The medial (Ludloff) approach to the hip

Purpose: direct access to the inferomedial hip capsule, the transverse acetabular ligament and the psoas tendon — the structures blocking reduction in a dislocated hip. Principally used for open reduction of developmental dysplasia of the hip in the infant, and occasionally for psoas release, biopsy of a medial lesion, or removal of a medially placed foreign body.

Positioning and incision

• Supine with the hip flexed, abducted and externally rotated (the frog-leg position) to bring the medial structures forward.
• Incision: a transverse or longitudinal incision over the adductor longus, beginning roughly 1-2 cm distal to the pubic tubercle and extending distally and posteriorly for 4-6 cm.

Interval — the part that matters

• Ludloff's original interval: between adductor longus and gracilis superficially, then between adductor brevis and adductor magnus deeply. This is the classic description.
• The Ferguson modification: between adductor longus and adductor brevis, that is anterior to the adductor brevis.
• Why the distinction matters: the anterior division of the obturator nerve lies anterior to adductor brevis, and the posterior division lies posterior to it. The medial circumflex femoral artery lies posteriorly, deep to the pectineus and adductor brevis. Working anterior to adductor brevis keeps the surgeon away from the posterior division of the obturator nerve and, critically, further from the medial circumflex femoral artery.
• The pectineus is the anterior boundary of the working corridor; it is retracted anteriorly (or partially released) and it protects the femoral vessels lying on its anterior surface.

Sequence

1. Identify and, if required, tenotomise the adductor longus close to its origin.
2. Develop the interval anterior to the adductor brevis.
3. Identify the anterior division of the obturator nerve on the anterior surface of adductor brevis and protect it.
4. Retract the pectineus anteriorly, protecting the femoral vessels.
5. Identify and release the iliopsoas tendon at the level of the lesser trochanter — a major block to reduction.
6. Perform the capsulotomy, excise the ligamentum teres and the pulvinar, and divide the transverse acetabular ligament to allow reduction.

Advantages and disadvantages

Adductor release in cerebral palsy hip surveillance

Context

• Hip displacement is common in cerebral palsy and its prevalence rises steeply with GMFCS level, approaching a high proportion of non-ambulant children (GMFCS IV-V). It is initially painless, which is why radiographic surveillance rather than symptom-driven review is the standard of care.
• Migration percentage (Reimers index) on a standardised AP pelvis with the legs in neutral is the measurement used: the proportion of the femoral head width lateral to Perkins' line.
• Surveillance schedules are stratified by GMFCS level, with more frequent radiographs for higher levels. The aim is to detect displacement while soft-tissue surgery can still work.

Indications for soft-tissue release

• A young child (typically under about 6-8 years) with a migration percentage of roughly 30-50 percent, reduced passive abduction, and a still-adequate acetabulum.
• The goal is prevention of progressive displacement and dislocation, plus improvement in seating, hygiene and comfort.

Technique and sequence

1. Adductor longus tenotomy — the primary release, performed close to the pubic origin.
2. Gracilis release — commonly added, and the reason abduction should be assessed with the knee both flexed and extended.
3. Adductor brevis partial release — added if abduction remains restricted.
4. Pectineus release — the deepest and most anterior structure, released last and only if needed, with the obturator nerve and the medial circumflex femoral artery immediately behind it.
5. Iliopsoas lengthening at the pelvic brim (intramuscular psoas lengthening) rather than a tenotomy at the lesser trochanter, to preserve hip flexion power in an ambulant child.
6. Target: approximately 40-45 degrees of abduction per side intraoperatively.

Obturator neurectomy — a historical caution

• Anterior branch obturator neurectomy was formerly combined with adductor release. It is now generally avoided or limited, because a complete neurectomy can produce an abduction contracture — the opposite deformity, which is functionally worse for seating and for perineal care.
• Note also that neurectomy cannot abolish adduction because the pectineus retains its femoral supply and the ischiocondylar adductor magnus its sciatic supply.

When soft-tissue release will not suffice

• Migration percentage greater than about 50-60 percent, an established acetabular deficiency, marked coxa valga and femoral anteversion, or an older child.
• Then the operation is a varus derotation osteotomy of the proximal femur combined with a pelvic osteotomy (Dega, San Diego shelf-type, or Pemberton), with open reduction and capsulorrhaphy as required, and adductor release performed as part of the same procedure.
• Salvage for the painful dislocated hip in a non-ambulant adolescent: proximal femoral resection (Castle or McHale procedure), valgus osteotomy, or arthroplasty in selected cases — all with limited and variable outcomes, which is precisely the argument for effective surveillance.

Adductor release in the adult

• Adductor spasticity after stroke, brain injury or spinal cord injury causing scissoring, hygiene problems or difficulty with catheterisation: obturator nerve block (diagnostic and therapeutic), botulinum toxin to the adductor group, then adductor tenotomy with or without limited obturator neurectomy for a fixed problem.
• Adductor contracture before total hip arthroplasty in a long-standing arthritic or ankylosed hip: adductor tenotomy may be required to allow positioning and dislocation. Do it before the arthrotomy so that the limb can be manipulated freely.

Obturator neuropathy

• Causes: pelvic surgery (particularly gynaecological and urological), pelvic fracture and acetabular fracture fixation, obstetric compression during labour, tumour or lymphadenopathy, an obturator hernia, pelvic haematoma, and in athletes a fascial entrapment at the exit from the obturator canal.
• Presentation: exercise-induced medial thigh pain with weakness of adduction, and a small patch of altered sensation on the distal medial thigh. In the athlete the pain begins after minutes of exertion and settles with rest.
• Investigation: MRI of the pelvis to exclude a mass or hernia; electromyography of the adductors showing denervation is the most useful test, sometimes only after exercise provocation; diagnostic obturator nerve block.
• Treatment: address the cause. For fascial entrapment in the athlete, surgical release of the fascia over the short adductor at the obturator exit has been reported to be effective, with return to sport.

Groin pain — the pectineus contribution

• The Doha agreement classifies longstanding and acute groin pain in athletes into adductor-related, iliopsoas-related, inguinal-related, pubic-related and hip-related entities, plus other causes. The value of the framework is that it forces anatomical localisation and acknowledges that entities coexist.
• Isolated pectineus injury is uncommon and rarely diagnosed clinically; on MRI, pectineus oedema is often seen alongside adductor and pubic symphyseal changes in the athlete with pubic-related groin pain, and in that setting it should be interpreted as part of the wider pattern rather than as an isolated lesion.
• Pectineus strain does occur, typically with a forced abduction and external rotation mechanism, and presents with deep proximal medial groin pain and pain on resisted adduction in hip flexion.

Obturator hernia

• Herniation through the obturator canal, classically in an elderly, thin, multiparous woman, presenting with small bowel obstruction.
• Howship-Romberg sign: medial thigh pain on hip extension, adduction and internal rotation, caused by compression of the obturator nerve by the hernia.
• Hannington-Kiff sign: absent adductor reflex on the affected side with a preserved patellar reflex.
• Diagnosis: CT. Treatment: surgical repair, usually urgently.
• Orthopaedic relevance: it is a cause of medial thigh and knee pain that will be missed if the differential stops at the musculoskeletal system.

Femoral hernia and the pectineal ligament

• The femoral canal is bounded anteriorly by the inguinal ligament, posteriorly by the pectineal ligament (Cooper's ligament) on the pectineal line, medially by the lacunar ligament and laterally by the femoral vein.
• A femoral hernia passes through the femoral ring into the canal and can present as a lump inferolateral to the pubic tubercle (in contrast to an inguinal hernia, which is superomedial).
• The pectineal ligament is the fixation point used in the McVay repair and is closely applied to the pectineus origin.

Heterotopic ossification and myositis ossificans

• Heterotopic ossification in the adductor group and pectineus occurs after acetabular fracture surgery, hip arthroplasty, head and spinal cord injury, and can bridge the pubis to the femur, producing a fixed adduction deformity.
• Management: prophylaxis in high-risk patients; excision only when mature, with recurrence prophylaxis.

Read this section knowing what it is. Pectineus has almost no primary literature of its own: there is no trial of pectineus release, no cadaveric series devoted to it, no outcome study naming it. Every paper below is therefore a context paper - it defines the vessel the muscle guards, the approach that divides it, the operation it is added to, or the nerve it shares. Each card's limitation opens by saying what that paper does not contain. That is a fair basis for teaching a landmark muscle; it is not a basis for claiming any of these studies measured anything about pectineus itself.