TAR and Component Separation

Component separation gains advancement of the abdominal wall muscles by dividing a musculo-aponeurotic plane instead of forcing the suture. TAR (transversus abdominis release) is its posterior evolution: it preserves the intercostal nerves and creates a wide retromuscular pocket for the mesh.

In wide midline defects the rectus muscles are retracted towards the flanks and direct suture would be too tense: the answer is to move the tissues, not stretch them. Component separation, described by Ramirez in 1990, exploits the ability of the lateral abdominal wall muscles to slide over one another to bring the recti back to the centre.

Anterior separation (Ramirez)

In the original technique wide subcutaneous flaps are raised and the external oblique aponeurosis is divided about 2 cm lateral to the semilunar lines: this gains a medial advancement that can reach 4–5 cm per side at the umbilical level. The price is the extensive subcutaneous undermining, with a non-negligible risk of flap ischaemia and seromas.

TAR: the posterior separation (Novitsky)

In 2012 Novitsky proposed reaching the same result from the posterior plane: after a retromuscular dissection conducted as in the Rives-Stoppa technique, the transversus abdominis muscle is divided medially to the intercostal nerves, accessing the preperitoneal plane. The lateral wall stays innervated and vascularised, no skin flaps are raised and the pocket for the mesh extends well beyond the semilunar lines.

In detail: once the retromuscular dissection is completed as far as the semilunar line — where the posterior sheath thins out — the sheath is incised by a few millimetres at its lateral edge, exposing the fibres of the transversus abdominis. The muscle is divided along its whole height, from the costal margin to below the arcuate line, staying medial to the intercostal neurovascular bundles running between the internal oblique and the transversus: this is the step that preserves the innervation of the wall. The posterior sheath, with the peritoneum, can then slide towards the midline; the pocket extends upwards to the diaphragm, downwards to the Retzius space and laterally to the psoas muscles, on both sides.

The result is a bilateral advancement that allows the midline to be closed without tension even in wide defects, with the mesh in the sublay position covering the entire pocket: the working plane is the same as Rives-Stoppa, simply wider. In Novitsky's 2016 outcome series, surgical site events were 18% and infections 9%, with a mean stay of 6 days — figures that improved further with experience in subsequent series.

The Madrid modification (García-Ureña)

The Madrid group led by Miguel Ángel García-Ureña proposed a substantial modification of TAR, formalised in 2024 as the Madrid posterior component separation (Madrid PCS). The main anatomical difference: the transversus abdominis muscle is not divided. Instead, a lateral release of the posterior rectus sheath is performed, incised 0.5–1 cm medial to the semilunar line, in a down-to-up direction, entering the preperitoneal plane from the Bogros space below the arcuate line.

The other two distinctive points are the cranial preservation of the posterior sheath at its chondrocostal insertion — the medial incision stops 7–8 cm below the xiphoid, sparing the diaphragmatic fibres inserting there and the medial terminal branches of the T7–T9 intercostal nerves — and, in the subxiphoid region, the switch from the preperitoneal to the pre-transversalis and pre-diaphragmatic planes, which reduces the risk of peritoneal tears. For the authors themselves these differences place it halfway between Novitsky's TAR and Heniford's preperitoneal repair: so much so that they propose classifying it as a posterior rectus sheath release rather than a TAR.

The reconstruction follows the Madrid APPROACH: the posterior wall is closed with a slowly absorbable monofilament, reinforced with a bioabsorbable mesh, and above it a very large large-pore polypropylene mesh (up to 50×50 cm) fixed only to Cooper's ligaments — Stoppa's "giant reinforcement of the visceral sac" applied to the midline. In the multicentre 2015–2023 series (223 patients, highly complex defects: about half redo surgery, 80% VHWG grade 2–3) the recurrence rate was 1.9% at a mean follow-up of about 24 months. Since 2018 the protocol has included preoperative botulinum toxin for defects over 9 cm and progressive preoperative pneumoperitoneum in loss of domain.

When it is needed

Critical points of the technique

The division of the transversus must stay medial to the intercostal neurovascular bundles: dividing too far laterally denervates the wall and defeats the principle of dynamic reconstruction. The posterior plane must be reconstructed without tension and the mesh — placed in the retromuscular plane — must cover the entire dissected area, because every uncovered zone is a possible site of recurrence.

Sources