Costochondral Graft
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Direct answer
A costochondral graft is autogenous rib harvested with its cartilage cap — typically from the fifth to seventh rib — and used to rebuild the mandibular condyle or ramus, above all in growing children with ankylosis, condylar absence or post-traumatic loss. Its unique selling point is the cartilaginous growth centre: the transferred costochondral junction can grow with the child, which no alloplastic joint can do. The graft is fixed to the mandibular ramus with wires or miniplates, the cartilage cap seated in the glenoid fossa as a new condyle. Its celebrated weakness is unpredictable growth — overgrowth, undergrowth or lateral drift — and donor-site morbidity includes pneumothorax, pain and chest wall deformity.
What you must remember
- Indication profile: TMJ ankylosis release in a growing child (Kaban protocol reconstruction step), congenital condylar absence as in hemifacial microsomia, post-traumatic or post-tumour condyle-ramus loss in the young; adults more often receive alloplastic joints or other autogenous options.
- Harvest geometry: the graft is taken at the costochondral junction, commonly the fifth, sixth or seventh rib, preserving a cartilage cap of roughly 5-10 mm — an oversized cap overgrows, an undersized one resorbs.
- Why cartilage matters: the costochondral junction carries the rib's growth plate, giving the graft translational growth potential matched to the child's remaining facial growth.
- Fixation: the bony end is adapted to the ramus with miniplates or stainless steel wires; contact must be rigid and intimate, since micromotion resorbs the graft.
- Unpredictable growth is the signature complication: overgrowth creating asymmetry and open bite, undergrowth, and lateral bowing of the new "condyle" — reasons for years of follow-up.
- Donor-site discipline: close over a water-seal check or perform a Valsalva to exclude pneumothorax before closure; chest pain and reduced ventilation demand a chest radiograph.
- Alternative vocabulary: temporalis interposition plus graft in ankylosis; free fibula flap for adult segmental defects; alloplastic total joint prostheses after growth completion.
Harvesting and placing the graft
Picture the ankylosis release described in theatre: the gap is made, temporalis interposed, and the ramus is short. A submammary incision exposes the fifth or sixth rib at the costochondral junction; the perichondrium is incised with care — scoring through the junction can split the growth plate — and the rib is cut laterally with a oscillating saw, leaving about 5-8 mm of cartilage medially. The pleura is inspected, the wound flooded with saline while the anaesthetist performs a Valsalva manoeuvre, and absence of bubbles excludes pneumothorax before layered closure. The graft is then carved: bone to bone, it is mortised to the mandibular ramus remnant and fixed with two miniplates or a wire, while the cartilage cap is shaped into a smooth condylar head seated against the interposed temporalis in the fossa. The new joint must be freely mobile on the table. The child wakes to early physiotherapy, and returns yearly, because the real result is measured over a decade of facial growth — an overgrowing graft may need later reduction, and a resorbing one re-grafting. This long negotiation with growth is precisely why the graft is reserved for children, whereas adults with ankylosis receive gap arthroplasty with interposition alone or a prosthetic joint.
Where the viva marks are hidden
The first hidden mark is the cap size: "how much cartilage do you leave?" — about 5-10 mm is the quoted compromise between overgrowth and resorption, and candidates who say "as much as possible" have never read the follow-up literature. The second is the pneumothorax check, asked as "what do you do before closing the chest wound?" The third is the philosophical question: why not a prosthesis in a child? — because no implant grows and repeated replacements in a growing face are untenable. Examiners also enjoy "which rib and why" — the fifth to seventh offer length, straight geometry and a junction suitable for a condyle. Finally, the overgrowth answer must be honest: growth of a costochondral graft cannot be predicted, only monitored.
Frequently asked questions
Why is a costochondral graft preferred in children with TMJ ankylosis?
The costochondral junction carries a growth centre, so the reconstructed condyle can grow with the child — something no alloplastic joint replicates.
Which rib is harvested and how much cartilage is kept?
Commonly the fifth to seventh rib at the costochondral junction, retaining a cartilage cap of roughly 5-10 mm to balance growth potential against overgrowth.
What is the most important long-term complication?
Unpredictable growth — overgrowth, undergrowth or lateral drift of the grafted condyle — demanding years of facial growth monitoring.
How is pneumothorax excluded during harvest?
The donor bed is flooded with saline while a Valsalva manoeuvre is performed; escaping air bubbles indicate pleural breach, and a postoperative chest radiograph is routine.
How is the graft fixed to the mandible?
The bony end is rigidly fixed to the ramus with miniplates or wires, the cartilage cap acting as the new condylar head in the glenoid fossa.