20.1 Introduction

The surgical management of progressive adolescent idiopathic scoliosis (AIS) aims to safely halt the progression of the spinal deformity and improve the spinal alignment and balance while preserving as much of the native spine as possible. The surgery often results in improved cosmesis, which is commonly of great importance to the patient and family. ¹ The presence of an asymmetric posterior rib prominence, or “rib hump,” is a common reason for dissatisfaction in appearance. In 1983, Howard Steel was keenly aware of this when he reported on the first large series of patients who underwent thoracoplasty in the setting of scoliosis surgery. Steel highlighted that the procedure not only produced significant cosmetic improvement but also obviated the need for an iliac crest bone graft and its associated donor site morbidity. ² Although Steel demonstrated great promise and potential in the thoracoplasty procedure, scoliosis surgeons were slow to adopt the technique because of reluctance to disrupt the chest wall.

The two predominant causes of the asymmetric posterior rib prominence found in AIS are the inherent rib cage asymmetry and the rotational deformity found in the apical vertebrae, resulting in a posterior translation of the subsequently rotated attached ribs. Therefore, derotation of the vertebrae during scoliosis corrections attenuates the rib prominence. Unfortunately, earlier deformity correction techniques, such as those utilizing nonsegmental hooks and Harrington rods, did not attempt to derotate the spine. Deformity correction was obtained by distraction of the posterior column, which primarily improved the coronal aspect of the deformity but did not significantly improve the posterior rib prominence. ^{3 , 4 , 5} When Yves Cotrel and Jean Dubousset popularized their instrumentation and deformity correction techniques in the mid-to-late 1980s, there was great hope that the utilization of segmental hooks and rod derotation would significantly reduce the rib prominence. Several studies reported that vertebral derotation could be achieved with the Cotrel–Dubousset (C-D) instrumentation. ^{6 , 7} Nonetheless, Harvey et al ⁸ demonstrated that although C-D instrumentation combined with derotation maneuvers often produced satisfactory cosmetic results, it was not as predictable as surgery in patients who also underwent thoracoplasty.

Following the era of C-D instrumentation, there were subsequent variations in the surgical approach to scoliosis surgery, such as the thoracoscopic anterior release of the apical intervertebral disc and anterior spinal instrumentation. The ability to manipulate the anterior column of the spine offered the potential for increased control of the deformity with the need for fewer fusion levels. However, thoracoplasty continued to be performed with well-documented benefits. In these circumstances, open internal thoracoplasty and video-assisted thoracoplasty were frequently utilized. ^{9 , 10 , 11 , 12}

In 1995, Suk et al ¹³ described the use of pedicle screws in the thoracic spine for the management of idiopathic scoliosis. There was great apprehension among scoliosis surgeons to adopt this practice due to concerns regarding the potential dangers of placing pedicle screws in the middle and upper thoracic spine. Later studies demonstrated a promising safety profile for the procedure. ¹⁴ Pedicle screws provided rigid, segmental three-column fixation. This combination allows for improved deformity correction in the coronal, sagittal, and axial planes. ^{15 , 16} In fact, larger coronal deformities could be successfully managed without the need for an anterior procedure. ^{17 , 18} Furthermore, thoracic pedicle screws offered superior axial plane control through direct vertebral body derotation. ¹⁹ The marked improvement in the overall deformity correction with the use of pedicle screws led to a clinical equipoise regarding whether thoracoplasty still offered a meaningful benefit. ²⁰ To that end, subsequent work demonstrated that even with pedicle screw instrumentation and direct vertebral body derotation, the addition of thoracoplasty resulted in significantly improved correction of rib prominence. ^{21 , 22}

It is currently debated whether thoracoplasty causes a clinically significant decline in pulmonary function. ^{23 , 24 , 25 , 26 , 27 , 28} Newton et al ²⁶ found a higher likelihood of having a measurable decrease in pulmonary function testing (PFT) when a thoracoplasty was added to an instrumented posterior spinal fusion. However, several subsequent studies have found a mild short-term diminution in PFT, with the return to baseline by 3 to 24 months. ^{24 , 27} Other surgeons contend that modifications in the surgical technique can reduce the incidence of any postoperative pulmonary changes or complications. ²⁹

20.2 Indications

There is no universally accepted set of indications to perform a thoracoplasty in the setting of idiopathic scoliosis surgery using an all-pedicle-screw construct. Harvey et al ⁸ developed a set of indications for thoracoplasty when using C-D instrumentation, which included rib prominence greater than 15 degrees, curve magnitude greater than 60 degrees, curve flexibility less than 20%, or intraoperative curve correction less than 50%. Despite using all-pedicle-screw constructs, some surgeons consider these factors in their decision-making. The senior author (H.L.S.) routinely performs a thoracoplasty in conjunction with an all-pedicle-screw construct. The decision to perform a thoracoplasty is not based on the specific curve magnitude or flexibility but, instead, the preoperative clinical appearance of the deformity. For this reason, thoracoplasty may be performed for the treatment of thoracolumbar curves as well.

20.3 Operative Technique

The patient is positioned prone and a complete subperiosteal dissection of the spine is performed. On the convex side of the deformity, most prominent ribs involved are identified, usually four to five ribs. All distal ribs contributing to the posterior prominence are included, as these can become more clinically noticeable once proximal rib segments are removed. A combination of blunt dissection and electrocautery is used to develop the plane beneath the thoracolumbar fascia and above the erector spinae muscles (Fig. 20‑1). Care should be taken to preserve bridging nerves when encountered. With blunt dissection, a plane is developed between the iliocostalis muscle (laterally) and the longissimus muscle (medially). Through this muscle plane, the dorsal apex of the rib prominence is identified. Electrocautery is used to incise the periosteum in line with the rib, approximately 1 cm lateral and 2 to 3 cm medial to the dorsal apex of the prominence (Fig. 20‑2). The periosteum is peeled cranially and caudally using a dry sponge or an Alexander dissector. This process is continued around the ventral aspect of the rib. A Doyen retractor can be used for this purpose (Fig. 20‑3). Particular care should be taken to protect the neurovascular bundle inferiorly and the pleura ventrally. A rib cutter is carefully passed around the rib from inferior to superior to help avoid inadvertent trauma to the intercostal neurovascular bundle (Fig. 20‑4). The lateral rib cut is made first. The rib is then secured with a clamp, and then the medial cut is made. There is no need to disrupt the costotransverse articulation, given that the apex of the rib prominence is usually located sufficiently lateral to this joint (Fig. 20‑5). The residual rib segment located medial to the thoracoplasty site is rarely noticeable after derotation of the vertebra. Careful inspection of the thoracoplasty site should be performed at this time. There is usually mild cancellous bone bleeding from the cut ends of the rib, which seldom needs to be addressed. When excessive cancellous bone bleeding is encountered, absorbable bone wax may be used. Vascular bleeding should be managed by tamponade or bipolar cauterization. Violations of the pleura are treated with a chest tube. However, a chest tube is not placed prophylactically. The ends of the ribs are left free in the periosteal sleeve. The thoracolumbar fascia is then reapproximated to the erector spinae muscles and closed with a running, self-locking, no. 0 polydioxanone suture. A running no. 0 polyglactin (910) may also be used. The rib segments are processed in a bone mill and used as an autologous bone graft (Fig. 20‑6 and Fig. 20‑7). No form of orthosis is required postoperatively. Radiographic evidence of rib reconstitution usually occurs after approximately 3 months, and remodeling follows (Fig. 20‑8).

20.4 Complications

In addition to the possible pulmonary function effects previously discussed in this chapter, thoracoplasty has several other well-described potential complications. ^{2 , 8 , 21 , 24 , 29 , 30} Pleural violation is one of the most common intraoperative complications. Historically, the incidence has been reported to be approximately 5%; nonetheless, this is inevitably affected by patient- and technique-related factors. ⁸ If a significant pleural rupture is caused, attempting to repair is not recommended. Instead, a chest tube should be placed through the pleural defect. Mismanagement of a pleural violation may lead to a hemothorax or pneumothorax.

In the postoperative period, the discovery of a pleural effusion is not uncommon. At times, this may represent a pleural violation that was not appreciated intraoperatively. More frequently, it is caused by generalized irritation of the pleura. For the vast majority of cases, radiographic observation and clinical correlation is all that is required. However, in situations where the effusion continues to expand, a thoracentesis may be necessary. If a thoracentesis fails to resolve the problem, the placement of a chest tube is indicated.

Intercostal neuralgia can occur after thoracoplasty. It is usually transient, but longer-lasting symptoms have been described. ³⁰ Preservation of the periosteum when exposing the rib and careful protection of the intercostal neurovascular bundle should reduce the occurrence of this complication.