Approach to the Posterior Lateral Thorax for Excision of Ribs

After scoliosis surgery has been completed, portions of the ribs on the posterolateral aspect of the rib cage may have to be resected to flatten out a hump caused by ribs that still protrude.

Position of the Patient

Place the patient prone on the operating table. Position bolsters longitudinally on either side of the patient from the anterior superior iliac spine to the shoulders to allow room for chest expansion (see Fig. 6-101).

Landmarks and Incision

Landmarks

The best landmarks are the prominent ribs, usually on the right posterior thoracic region. They may be so distorted that they produce a “razorback” deformity.

Incision

The standard incision for scoliosis surgery, the longitudinal midline incision, also is used for the removal of ribs (see Fig. 6-102).

Internervous Plane

The internervous plane lies between the trapezius and latissimus dorsi muscles. The trapezius is innervated by the spinal accessory nerve and the latissimus dorsi is innervated by the long thoracodorsal nerve. The deeper muscle, the iliocostalis portion of the sacrospinalis, is innervated segmentally and, therefore, is not denervated when it is split longitudinally.

Superficial Surgical Dissection

With retractors, lift the skin and its thick subcutaneous tissue. Free them from the underlying fascia and retract them laterally. Center the dissection over the most prominent, or apical, rib. Extend it laterally to at least 12 cm from the midline, and then proximally and distally to expose all the deformed ribs (Fig. 6-112).

Intermediate Surgical Dissection

The fibers of the trapezius muscle run obliquely downward toward the midline as far as the spinous process of T12. Identify this muscle by its rolled, lateral free border. Dissect along the lateral border and retract the muscle medially. The medial portion of the fibers of the latissimus dorsi muscle and its aponeurosis run almost perpendicular to and under the trapezius muscle; it takes origin from the lower six thoracic spinous processes, as well as from the lumbodorsal fascia. Dissect the muscle free with cautery and retract it laterally (see Fig. 6-112).

Deep Surgical Dissection

Below the retracted trapezius and latissimus dorsi muscles lies the iliocostalis, a longitudinal muscle with flattened tendons in its musculature that insert into the lower borders of the ribs. Split the iliocostalis muscle longitudinally over each of the deformed portions of the ribs that are being removed, then dissect and retract it medially and laterally in line with the ribs (Fig. 6-113).

Incise the periosteum along the posterior aspect of the rib in the rib’s own plane. Use an Alexander dissector to push the split periosteum to the upper and lower borders of the rib. With the special end of the dissector, strip the intercostal muscles off the upper end of the rib in a medial to lateral direction in the angle formed by the intersection of the external intercostal muscles and the rib. Then, strip the intercostal muscles from the lower end of the rib in a lateral to medial direction, remaining in the angle formed by the origin of the external intercostal muscle and the rib to discourage bleeding. By keeping the dissection in a subperiosteal location, the neurovascular bundle, which will have been freed from the lower border of the rib with the intercostal muscles, will be avoided (Fig. 6-114).

Before continuing, have the anesthesiologist stop the patient’s breathing so that the visceral pleura can fall away from the rib, minimizing the danger to the pleura during anterior dissection. When the ribs have been uncovered completely, begin to resect them.

Dangers

The neurovascular bundle lies along the lower edge of the rib in the neurovascular groove. Unless the dissection is kept in a subperiosteal location, it may be cut inadvertently during the resection and the intercostal vessels will have to be cauterized, causing possible segmental chest wall numbness (see Fig. 6-114, inset).

Violating the pleura may result in a pneumothorax. If that happens, plan to insert a chest tube immediately after the wound is closed, while the patient is still in the operating room.

Connecting the midline wound with that of the rib resection may cause a hemothorax, with blood flowing from the area of the spinal fusion into the lung. If the two areas of dissection are connected, be prepared to insert a chest tube to drain the blood.

The skin may adhere to the cut ends of the ribs, causing unsightly dimpling. To prevent this, take a thick subcutaneous layer with the skin and, during closure, suture the fascia of the trapezius muscle to that of the latissimus dorsi muscle.

Figure 6-112 Retract the rolled lateral border of the trapezius muscle medially to expose the thin, aponeurotic medial portion of the latissimus dorsi. Incise the aponeurotic medial portion of the latissimus dorsi perpendicular to its fibers.

Figure 6-113 Retract the latissimus dorsi laterally and the trapezius medially to expose the underlying iliocostalis muscle. Incise the muscle longitudinally, parallel to its fibers.

Figure 6-114 Dissect and retract the iliocostalis muscles laterally and medially from their insertion to expose the posterior aspect of the ribs. Incise the periosteum over the rib. Push the split periosteum to the upper and lower borders of the rib. With a special dissector, strip the intercostal muscles off the borders of the rib as well as anteriorly.

How to Enlarge the Approach

Local Measures

Continue subcutaneous dissection further laterally, proximally, and distally to ensure a complete view of the distorted ribs.

Occasionally, in more proximal rib resections, the lower portion of the rhomboid major muscle may have to be dissected to expose the rib area more fully. Distally, the muscular belly of the iliocostalis muscle may have to be split as it splits from the sacrospinalis muscle.

Extensile Measures

This incision cannot be extended; deciding which ribs to remove depends on the size and extent of the rib hump.

Special Points

When removing ribs, resect each one from the point just lateral to its maximum deformity to the most medial end, without removing its head and neck. The lateral portion of the resected rib will drop forward, reducing the rib hump, but the medial portion, held rigidly in place by the costotransverse and costovertebral ligaments, will not move. That is why the rib should be resected as medially as possible. Otherwise, the medial end of the rib will continue to stick out posteriorly, causing continued deformity.

The removal of more than four ribs may cause a sympathetic effusion of a lung field. If this occurs, insert a chest tube to drain the fluid.

Treat the cut ends of the ribs with bone wax to prevent continued oozing of blood. The wax does not prevent the ribs from regenerating.

The resected portions of the ribs can be cut into small, matchsticksized pieces and used as graft material in a midline spine fusion.

If the vertebral body has rotated up under the rib, resecting the ribs will not produce a significant reduction in the rib hump deformity.