Table 2. Surgical modifications that were implemented in MIRPE across the years.

Surgical modification	Study	Description
Forced sternal elevation
Crane technique	Park et al. (81), 2008, Kelly et al. (63), 2022	A percutaneous wire is passed through the bony tissue of the sternum and the wire is connected to a table-mounted crane system. This alleviates pressure on the hinge points which prevents tearing/stripping of intercostal muscles. The bar displacement rate, major complication rates and reoperation rates all decreased after implementing this new approach
Two Langenbeck handheld retractors	Tedde et al. (82), 2012	Incision made in the intercostal space adjacent to the sternum at the deepest portion of the defect. Enters the hemithorax from the left side first, position 1st retractor at the hinge point, followed by entering the right hemithorax to introduce a camera and 2nd retractor allowing safe retrosternal instrumentation
Horseshoe-shaped sternal elevator	Takagi et al. (83), 2012	No extra skin incision is needed for the elevator, its usage enlarges the retrosternal space for safer passage of thoracoscopically guided introducer and allows visualization of substernal tunneling
Vacuum bell	Haecker et al. (84), 2012	Vacuum Bell is placed on the defect and suction is initiated to reduce defect. Applicable only to young and elastic chest wall defects
Subxiphoid incision/sternal lift + anchor	Johnson et al. (85), 2013	A subxiphoid incision is made and a retractor is placed under the sternum to assist with elevation of sternum
		Subxiphoid incision allows access to create a plane between the posterior sternum and pericardium. Lift is inserted beneath the sternum, allowing sternal elevation and locked in place by anchor
Bone clamp and Rultract retractor	Jaroszewski et al. (79), 2014	Incisions made either parallel or perpendicular to sternum, tips of bone clamp placed into anterior table of the sternum and attached to the cable coming off a table mounted Rultract retractor. This reduces risk of intercostal muscles stripping and reduces stress on intercostal spaces during bars insertion and rotation
T-fastener suture technique	Kim et al. (86), 2014	Chest incisions are made lateral to the sternum, sutures are delivered outside the lateral chest and tied to a metal plate with 3 holes. T-fastener sutures are used to elevate the anterior chest from both sides of the sternum by tying them to a crank attached to a cross bar. No specialized equipment is required (metal plate commonly used in orthopedic practice), no incisions need to be made (needle holes created require no suture closures), and no fracture or tear occur to anterior chest. Metal plate must be retrieved at the end which presents difficulty after bars are positioned
Bar stabilization technique
Five-point fixation (multipoint suture fixation MPF), stabilizers, CFT and HP, and bridge technique	Park et al. (78), 2004, (81), 2008, (87), 2011, (88,89), 2015	MPF offered bar fixation to upper and lower ribs at the ends of the bar and a fifth wire at the hinge point medially with all sutures done through a single incision on each side. Attachment of stabilizers to both ends of the pectus bar to prevent bar flipping. CFT holds the bar to a rib by hooking it with a metal blade. HP reinforced the hinge points (the entrance points of the bar to the thoracic cavity) with a metal plate. Combining HP and CFT in adults: after bars insertion lifts the chest wall depression, both bar ends were fixed together by bridge plates and screws which enhances stability of the bars and eliminates need for suturing
Third point of fixation	Hebra et al. (73), 2006	Alongside crossbars/lateral stabilizers, a third point of fixation consisting of absorbable suture is placed around the bar and around an anterior rib next to the right side of the sternum
Medial stabilizers and multiple PDS sutures	Pilegaard et al. (90), 2008, Pio et al. (91), 2016	Stabilizer placed closer to the entrance of the bar into the thoracic cavity, thereby decreasing the risk of rotation/displacement as the stabilizer functions as a hinge
Unilateral stabilizer and multiple PDS sutures	Kelly et al. (92), 2010	Attaching a metal stabilizer on the left and placing multiple pericostal PDS sutures around the bar and underlying ribs
FiberWire multiple points fixations of bars circumferentially and bilaterally	McMahon et al. (75), 2014	Multipoint fixation with FiberWire that are secured around ribs (lateral and medial), fixation on both sides of the bar, and utilizes the bar’s lateral holes to minimize lateral dislocation
Figure-of-eight FiberWire reinforcement, FiberWire multipoint fixation and sternal fixation	Jaroszewski et al. (72), 2016	“Hammock” Figure-of-Eight FiberWire tie that incorporates the rib above and below the interspace that the bar will be placed in to reinforce and prevent lateral posterior bar migration and intercostal muscle stripping. FiberWire multipoint fixation around ribs and bars medial and lateral, sternal holes drilled for suture that incorporates bar and sternal bone for medial fixation
Stabilizer secured with wire/FiberWire + several pericostal PDS sutures	Nuss et al. (17), 1998	Stabilizer is attached and secured to the bar with non-absorbable sutures on the left side + multiple PDS sutures placed around the bar and the underlying rib on the right side
Bars configuration
Compound	Park et al. (78), 2004, Yoon et al. (93), 2010	The compound bar presents a concept of exaggerated convexity in the center of the bar, with a smaller central arc between the hinge point and adjoining at either side by two larger arcs. The smaller central arc makes the bar convex enough to elevate the depression and the larger lateral arcs can adjust the width of the bar easily to fit the size of the chest
Multiple bars	Nuss (94), 2008, Pilegaard et al. (90), 2008, Nagaso et al. (95), 2010, Stanfill et al. (96), 2012	Using 2 bars have been implemented by surgeons treating adults with Pex to fully correct the deformity and decrease rate of recurrence/requirement of revision. Multiple bars allow for better distribution of pressure (decreasing risk of bar migration) and may also decrease the pain
	Jaroszewski et al. (72), 2016	>40% of patients required 3 bars to fully correct the deformity
New steel bar	Li et al. (97), 2015	Introduced new steel bar through bilateral thoracic minimally invasive incisions using a thoracoscope for guidance. The bar was installed or removed by pushing and pulling without flipping it
Cross bar technique	Park et al. (98), 2016, Sayan et al. (99), 2021	Cross bars cover the promontory of the depression and the whole anterior chest wall (including lateral parts) by avoiding hinge compressions and residual depressions
Introducer bar complex	Wang et al. (100), 2021	New kind of steel bar curved according to normal structure of the human anterior chest wall and includes 15 different specifications. One end designed to connect to introducer/stabilizer. Connecting the bar to the stabilizer creates the introducer-bar complex which doesn’t require rotation or turning, it is pushed in our pulled out
Thoracoscopy
Unilateral thoracoscopy	Croitoru et al. (101), 2002	Direct visualization of the mediastinal structures using right thoracoscopy via an additional small incision for thoracoscopic observation in the right pleural cavity under insufflation of CO2 made the procedure much safer
Bilateral thoracoscopy	Cheng et al. (102), 2008	The modified bilateral thoracoscopy is utilized via the wound made for bar insertion without extra incisions for the thoracoscope. It allows for excellent visualization over each pleural cavity. It could eliminate the risk of cardiopulmonary injuries as it allows direct bilateral inspection of mediastinum and facilitate mediastinal dissection
Pectoscopy	Park et al. (74), 2010	A specially designed video-scope approach to guide the introducer or the pectus clamp as it is passed through the mediastinum

MIRPE, minimally invasive repair for pectus excavatum; MPF, multipoint fixation; CFT, claw fixator; HP, hinge plate; PDS, polydioxanone; Pex, pectus excavatum.