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

Etiology of chest wounds:

• Radiation 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).
• Pectus Excavatum: 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.

Reconstruction of chest wounds: radiation wounds must be treated with vascularized tissue.

• Omental flaps: good for midline (sternal chest wounds)
• Pectoralis flaps: supplied by the thoracoacromial vessels (dominant), internal mammary perforators, and the lateral thoracic artery (lateral thoracic artery is dominant in 6% of patients)
• Good for anterior chest wall 
• Unliteral will not cover central sternal wounds alone
• Latissimus flaps: based on the thoracodorsal vessels, good for anterior chest wall
• Type V Mathes and Nahai flap (one dominant and multiple segmental pedicles)
• Covers large defects, does not reach for sternal wounds
• Posterolateral thoracotomy makes this flap unreliable due to unknown pedicle status
• Serratus flaps: good for posterior chest wounds
• Rectus flap: based off of the superficial inferior epigastric. This is often ligated ipsilaterally with radical resections, or not a good choice in the setting of radiation (remember the SIEA is a continuation of the internal mammary artery).
• May use contralateral rectus or abdominal based flap for anterior and central chest wall reconstruction
• Rib reconstruction: used for defects larger than 5cm or with 4 consecutive ribs. 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.
• If the question stem states the patient has loss of thoracic compliance there is no need for skeletal reconstruction
• Anterior and posterior defects are tolerated more than lateral.
• Buzz words to watch out for: CABG with internal mammary harvest, wide excisions from breast cancer or debridement (local obliteration of vessels- IE internal mammary), radiation to the breast (ipsilateral internal mammary not intact).
• Remember the rectus flap is based off the superficial system which is a continuation of the internal mammary system! Not intact if internal mammary has been sacrificed.

Complications

• Cardiac tamponade: presents as beck’s triad (hypotension, elevated venous pressure with jugular distention, muffled heart sounds)
• Treatment is decompression (make sure to listen to the patients’ heart sounds to confirm!)

Gynecomastia: male breast enlargement

• Etiology: May be due to excess circulating estrogen, decreased androgens, or deficiency in androgen receptors. In older men it is commonly due to excessive aromatization of androgens to estrogens.
• Pseudogynecomastia is distinguished by gynecomastia by physical exam where palpation reveals soft fatty breast with no glandular or periareolar tissue. This is often seen in overweight patients.
• Grade 1- minimal breast hypertrophy without ptosis
• Grade 2- moderate hypertrophy without ptosis
• Grade 3- severe hypertrophy with moderate ptosis 
• Grade 4- severe hypertrophy with severe ptosis
• Prior to treatment for gynecomastia should perform examination of scrotum and testes to rule out any testicular masses, as well as measurement of beta HCG.
• Treatment is based on degree of breast enlargement and ptosis. Liposuction is effective for mild to moderate gynecomastia without ptosis. Direct peri areolar excision and subcutaneous mastectomy for patients without ptosis or mild ptosis. Patients with severe ptosis may benefit from mastectomy and free nipple graft.
• If there is a significant glandular component it is important to complete a subtotal glandular resection (liposuction does not address this).
• If patient is pubertal should observe for 6 months -1 year prior to surgical intervention.
• Medication induced gynecomastia: from medications like leurpolide can cause gynecomastia and mastodynia (breast tenderness).

Abdominal Wall Reconstruction

Abdominal Wall Pathology

• Desmoid type fibromatosis: rare, locally infiltrative mesenchymal neoplasm found in young adults. Does not metastasize but can have aggressive local course.
• Treatment 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.

Component Release

• 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.
• Can perform a perforator-sparing component separation which spares the peri-umbilical perforators.
• 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 transversalis muscle
• Can include transversus abdominus release (TAR) to provide further mobility and preserve innervation of the rectus muscle 

Hernia Repair

• Recurrence rates are lowest when primary fascial closure of the abdominal wall is reinforced with mesh placement as an underlay.
• Bridging mesh repair is associated with the highest rates of recurrence.
• Overlay technique: higher rates of recurrence than underlay
• Rives-Stoppa (underlay): sublay mesh placed between the rectus muscle and the posterior sheath and has a 3-6% recurrence (lowest overall) .
• Typically dissection is carried only to the semilunaris- can release internal oblique or transversus to extend dissection (internal oblique will disrupt muscular innervation).
• For large fascial defects with sufficient skin, bilateral component separation with interposition mesh (either biologic versus nonbiologic) should be placed followed by skin closure.
• If there is insufficient skin then tissue expansion, local tissue rearrangement, or distant flaps need to be considered

Hernia Mesh

• Nonbiologic
• Biologic: used for contaminated wound beds and provide an intact extracellular matrix and support tissue regeneration, more resistant to infection.
• Degraded over time by collagenase, which accounts for higher recurrence rates and abdominal bulge.
• Higher cost
• Ventral hernia working group recommends use of biologic mesh in contaminated fields, infected mesh and septic dehiscence.

Risks of Recurrence

• Highest predictor of recurrence is whether the fascia can be closed over the hernia defect (bridged versus underlay).

Pediatric Abdominal Wall

• Omphalocele: midline partial thickness abdominal wall defect covered by a membrane of amnion and peritoneum occurring within the umbilical ring and containing abdominal contents
• Associated with elevated maternal serum alpha fetoprotein
• Associated with chromosomal abnormalities
• Gastroschisis: full thickness paraumbilical abdominal wall defect associated with eviscerated bowel
• Associated with elevated maternal serum alpha fetoprotein 
• Treatment is 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.

Complications of Abdominal Wall Reconstruction

• Abdominal compartment syndrome: develops after rapid increase in intra-abdominal pressure
• Mechanisms: vascular compression, elevation of diaphragm and direct organ compression can lead to multiple organ failure
• Vascular compression leads to decreased flow through IVC and increase in renal vascular resistance, decreased preload, increase in systemic afterload

Miscellaneous

• Myelomeningocele: involves dorsal herniation of the meninges and spinal cord through vertebrae. This is often diagnosed prenatally by elevated maternal serum alphafetoprotein and ultrasonography.
• Treatment to repair with NSU and soft tissue coverage (PSU) with infection prevention from bacterial meningitis being the primary goal.
• Occurs in first 24-48 hours of life
• Method of reconstruction includes local fascial flap and skin advancement flap (such as paraspinous fascial flaps).
• Abdominoperineal resections (APR): best treated with rectus abdominus myocutaneous flap
• This includes posterior vaginal defects.
• Poland Syndrome: absence pectoralis and breast hypoplasia, axillary webbing
• Can also have rib and cartilage hypoplasia, ipsilateral brachysyndactyly 
• Primitive cell that failed to develop was mesoderm derivative
• Renal Failure: 
• Pre-renal: causes include hypovolemia, cardiac failure, sepsis
• On examination UA is normal
• BUN: serum creatinine is 20:1
• Urinary sodium is less than 20meq/L
• Urine osmolality is higher than 500 mOsmol/kg
• FENA (fractional excretion of sodium (FENa) is <1%
• Intrinsic: causes include disorders of renal parenchyma, acute tubular necrosis, glomerular disease
• Normal BUN: serum creatinine
• Urine osmols <350
• Abnormal UA
• Post-renal: causes include renal vein occlusion and urinary tract obstruction
• Elevated BUN: serum creatinine 
• FENA >1%
• Normal UA