Chest Wall Reconstruction

• Physiology of breathing
• Tidal volume: volume of air that is moved into or out of the lungs during quiet breathing
• Vital Capacity: volume of air expired after the deepest inspiration
• Residual Volume: volume of air remaining after maximal exhalation
• Dead space volume: the amount of air inhaled that does not take part in gas exchange

• Congenital Chest Wall: 
• Pectus Excavatum: chest wall “caved in” is the most common congenital chest wall deformity and is more common in males
• Treatment includes minimally invasive procedures (intrathoracic retrosternal support bars) between the ages of 6-12 (mid adolescence)
• Reinsertion of correction bar is not always successful in correcting post-adolescent patients since bones have ossified
• Treat recurrence of female patients (with no respiratory issues) with implantation including augmentation and customized silicone elastomer for the sternal defect

• Etiology of Chest Wall wounds: 
• Radiation: This can cause long standing ulcers and osteonecrosis (like after breast cancer). 
• Treatment includes biopsy of the ulcer first, followed by excision of all radiation-damaged tissue (including rib).
• Primary Cancer: ex breast cancer with invasion into the chest wall or chest wall sarcoma
• Cardiac surgery with sternotomy 

• Reconstruction of chest wounds: radiation wounds must be treated with vascularized tissue
• Pedicled Flaps: 
• Pectoralis flaps:
• Arterial Innervation:  Mathes and Nahai type V flap (one dominant and multiple minor pedicles). Supplied by the thoracoacromial vessels (dominant), internal mammary perforators, and the lateral thoracic artery (lateral thoracic artery is dominant in 6% of patients).
• Variations: Pectoralis flaps may be used most commonly as rotation advancement flaps based on the thoracoacromial vessels or  turnover flaps based on the IMAs
• Use: anterior chest wall wound – rotation advancement flaps are good for anterior chest wall, however a unilateral flap will not cover central sternal wounds alone

• Latissimus flaps: based on the thoracodorsal vessels, good for anterior chest wall
• Arterial Supply: Type V Mathes and Nahai flap (one dominant and multiple segmental pedicles), Supplied by the thoracodorsal vessels (primary) and lumbar and posterior intercostal vessles 
• Use: Covers large defects of the anterior chest wall but will not reach sternal wounds
• Notes: History of posterolateral thoracotomy makes this flap unreliable because the thoracic surgeons can injury the thoracodorsal in their approach 

• Serratus flaps: 
• Arterial supply: serratus branch from the subscapular artery 
• Use: good for posterior chest wounds

• Omental flaps: 
• Arterial supply: These are based on the gastroepiploic arteries.  
• Use: good for midline (sternal chest wounds)
• Downsides: subxiphoid hernia due to needed fascial defect 

• Rectus flap:
• Arterial supply: superior epigastric artery. These are a continuation of the IMAs therefore they may be damaged in the setting of a radical resection, cardiac surgery and radiation to the chest. 

• Free flap-based reconstruction: 
• Based on the defect size however larger flaps such as ALT or DIEPs are often needed if you need something larger than local flaps can cover

• Rib reconstruction: 
• Indications: 
• Used for defects larger than 5cm or with 4 consecutive ribs. 
• NOT  a hard/fast rule
• Anterior and posterior defects are tolerated more than lateral defects 
• Often radiation to the chest wall can cause fibrosis and loss of respiratory efficiency- less paradoxical motion with rib resections which can tolerate more resection. Therefore these patients often don’t need rib reconstruction 

Abdominal Wall Reconstruction

• Regional Anatomy: 
• The central abdominal wall is composed of seven layers 

• Skin
• subcutaneous fat
• Scarpas fascia (which provides the strength layer at the time of closure)
• subscarpal layer
• the anterior rectus sheath
• rectus abdominis muscles
• posterior rectus sheath

• Regional Muscles: There are 4 paired muscle groups that make up the abdominal wall including the rectus abdominis centrally and the external oblique, internal oblique and trasversus abdominis laterally. 
• Linea Alba: 
• Definition: The aponeurotic portions of the oblique muscles and transversus make up the anterior and posterior rectus sheaths which come together in the midline called the linea alba.
• With weight gain and pregnancy there can be a separation of the rectus muscles at the linea alba called rectus diastasis which is not a hernia but can cause a midline bulge. 

• Arcuate line:
• Definition: horizontal line at the inferior 3^rd of the rectus muscle at which the rectus sheath becomes exclusively anterior
• Above the arcuate line the posterior rectus sheath is from the aponeuroses of the internal oblique and transversus oblique 
• Below the arcuate line, those aponeuroses lie anterior to the rectus muscle and only the transversalis fascia and peritoneum lie posteriorly, ie there is no posterior sheath

• Hernia Repair
• Definition: defect in the abdominal fascia that allows intra-abdominal contents to herniate out of the 
• Repair: 
• Fascial Closure: 
• Anterior Component Separation: performed by making an incision longitudinally in the external oblique aponeurosis, just lateral to the semilunaris (only cut fascia not muscle!).
• This allows for advancement of myofascial complex (rectus, internal oblique, transversalis)
• Intercostal nerves that supply the anterior abdominal wall run between the internal oblique and transversalis muscle and are not divided.
• Advancement: 4cm (unilaterally) for epigastric, 10cm at the waist (umbilicus), 4cm at the suprapubic areas. Smallest area of advancements is subxiphoid and subcostal
• Posterior Component Separation: divides posterior rectus sheath and begins with a vertical incision 0.5cm medial to the linea semilunaris and continues laterally in the avascular plane posterior to the transversus abdominus muscle 
• Can include transversus abdominus release (TAR) to provide further mobility and preserve innervation of the rectus muscle 

• Mesh Hernia Repair: 
• Overall: Recurrence rates are lowest when primary fascial closure of the abdominal wall is reinforced with mesh. 
• Location: 
• Underlay or Rives-Stoppa: sublay mesh placed between the rectus muscle and the posterior sheath and has a 3-6% recurrence (lowest overall). 
• Bridging mesh:  associated with the highest rates of recurrence.
• Overlay technique: higher rates of recurrence than underlay
• Type of Mesh: 
• Nonbiologic
• Biologic: recommended for use in contaminated fields. It provides an intact extracellular matrix and support tissue regeneration. 
• It is degraded over time by collagenase, which prevents chronic infections but also accounts for higher recurrence rates and abdominal bulge. 
• Higher cost

• Large fascial defects: 
• Fascial defects with sufficient skin:  bilateral component separation with interposition mesh (biologic versus nonbiologic) should be placed followed by skin closure.
• Fascial defects with insufficient skin: tissue expansion, local tissue rearrangement, or distant flaps need to be considered

Other Abdominal Wall Pathology

• Desmoid type fibromatosis: 
• Definition: rare, locally infiltrative mesenchymal neoplasm found in young adults. Does not metastasize but can have aggressive local course
• Treatment:
• Resection:  includes radical resection with wide margins (usually contains frozens to ensure negative margins)
• Reconstruction should include contralateral anterior component separation and bridging mesh placement, primary skin closure. May use pedicled flaps (ALT or rectus femoris), but should use mesh in addition

Pediatric  Chest / Abdominal Wall / (and some back) 

• Pediatric Abdominal Wall Congenital Defects
• Omphalocele: 
• Definition: midline partial thickness abdominal wall defect covered by a membrane of amnion and peritoneum occurring within the umbilical ring and containing abdominal contents
• Prenatal diagnosis: elevated maternal serum alpha fetoprotein
• Associated with chromosomal abnormalities and associated cardiac defects

• Gastroschisis: 
• Definition: full thickness paraumbilical abdominal wall defect associated with eviscerated bowel
• Prenatal diagnosis: Associated with elevated maternal serum alpha fetoprotein 
• Treatment of both: aimed at primary closure or silo placement with reduction and eventual primary abdominal closure. Can use anterior component separation to achieve closure for bulges or defects <5cm; once it is >5cm should consider tissue expanders and flap advancement.

• Myelomeningocele: 
• Definition: Involves dorsal herniation of the meninges and spinal cord through vertebrae. This is often diagnosed prenatally by elevated maternal serum alpha-fetoprotein and ultrasonography
• Treatment:  
• Timing: 
• repair with NSU and soft tissue coverage (PSU) with infection prevention from bacterial meningitis being the primary goal within the 1^st 48 hours of life. 
• There are some trials about prenatal repair within the 2^nd trimester but later 3^rd trimester prenatal repair has been shown not to be beneficial
• Method of reconstruction:
• local fasciocutanous flaps and skin advancement flap

 

• Poland Syndrome 
• Definition: Absence pectoralis and breast hypoplasia, axillary webbing, concave chest wall. Can also have rib and cartilage hypoplasia, ipsilateral brachysyndactyly (shortened and/or webbed digits)
• Cause: Primitive cell that failed to develop was mesoderm derivative
• Thorax, breast, nipple-areola complex (TBN classification)
• Degree of abnormality T1-4; B1-2; N1-3
• Thorax
• T1: absence of all or part of pectoralis
• T2: T1 + pectus excavatum or carinatum
• T3: T1 + rib aplasia (usually 3 and 4)
• T4: T1 + T2 + T3
• Breast
• B1: hypoplastic breast
• B2: breast aplasia (amastia)
• Nipple-areola complex
• N1: hypoplastic NAC less than 2 cm displaced
• N2: hypoplastic NAC more than 2 cm displaced
• N3: athelia