Chest Wall Deformities

Question 1

Which of the following is the most common congenital chest wall deformity?

A. Pectus carinatum
B. Poland’s syndrome
C. Convex chest wall deformity
D. Pigeon chest
E. Pectus excavatum

Answer 1

ANSWER: E

COMMENTS: Pectus excavatum is the most common chest wall deformity in children, accounting for 88% of all chest wall deformities.

It is characterized by a concave chest wall deformity, with the sternum angled posteriorly toward the spine.

There is a male prevalence (3:1).

The defect may be present at birth but often becomes prominent during puberty due to rapid growth.

Symptoms can include dyspnea and exercise intolerance.

Surgical correction usually results in symptomatic relief, and there may be a slight improvement in pulmonary function tests.

Surgical repair will improve cosmetic appearance and the common psychosocial anxiety.

The Haller index should be calculated from an axial CT scan to determine the severity. It is the ratio of the widest transverse diameter within the ribs to the greatest length from the inner table of the sternum to the anterior surface of the vertebrae.

A ratio of >3.2 is considered as a severe defect.

Surgical repair may be performed with the open Ravitch procedure or with the minimally invasive Nuss procedure.

The Nuss procedure is currently favored due to less perioperative pain and smaller scars.

Pectus carinatum, also known as pigeon chest, is the next most common chest wall abnormality.

It is characterized by a protrusion of the sternum.

Management is initially nonsurgical with bracing. When worn appropriately, bracing can correct up to 75% of the deformities over time. However, noncompliance and discomfort are common.

Surgical correction is done via the open Ravitch proce- dure.

An osteotomy is made in the sternum, allowing it to be flattened to its normal position and contour.

Other congenital chest wall deformities exist, but are very rare.

Poland’s syndrome is characterized by the congenital absence of the pectoralis major, syndactyly, and occasionally missing ribs.

Question 2

What are the typical chest wall deformities?

Answer 2

The most common are the caved in sternum or pectus excavatum (PEX) and the protruding sternum or pectus carinatum (PC).

When these defects coexist in the same patient they are called mixed deformities.

Also, deformities may be asymmetric or part of a syndrome such as the Currarino Silverman syndrome, which is characterized by a congenital cardiac malformation and pectus arcuatum, a wide, non-articulated, short sternum.

(Pearls & Tricks in Pediatric Surgery)

Question 3

What are the demographic characteristics of pectus excavatum (PEX)?

Answer 3

The incidence of PEX has been traditionally described as 1 in 1000, and comprises 80% of all the pectus deformities.

However, and probably due to the rise of non-operative approaches to PC, there has been an increase in referrals of PC patients to pectus clinics in the last decades with a shift in the relative incidences in favor of PC resulting in a ratio of 1:1.

The sex distribution is predominantly male, with a 4:1 ratio.

A family history is common and connective tissue diseases are more frequently associated with pectus deformities.

(Pearls & Tricks in Pediatric Surgery)

Question 4

How is PEX classified?

Answer 4

PEX can be classified as typical and atypical.

The typical forms can be classified as localized or diffuse, shallow or deep, and as symmetric or asymmetric (Fig. 3.1).

The atypical forms include mixed deformities and the Poland syndrome.

(Pearls & Tricks in Pediatric Surgery)

Question 5

How is a patient with PEX studied?

Answer 5

The physical examination will provide information regarding the type of PEX and the probability of success with a non-surgical approach.

A vacuum bell connected to a vacuometer can predict how much pressure is necessary to correct the excavation and if the vacuum bell may be effective (Fig. 3.2).

We follow our patients with photos taken from 6 predetermined angles at diagnosis and follow-up.

In surgical candidates, a CT scan is performed to quantify the depth of the defect.

Physiologic testing may include stress echocardiography as well as a dynamic cardiac magnetic resonance imaging.

A history of metal allergy should be inquired and if uncertain, a nickel allergy test has to be performed to determine the patient will tolerate a steel bar. If not, a titanium bar will be needed.

We generally employ a 3D scanning system with virtual reconstruction for diagnosis and follow-up with a visual color-scale that varies according to its depth (Fig. 3.3).

(Pearls & Tricks in Pediatric Surgery)

Question 6

What indices are most commonly used to measure the severity of PEX?

Answer 6

The Haller index is the original measure, and it results from the ratio between the lateral distance and the anteroposterior distance between the sternum and the spine, calculated by means of a chest CT scan at the point of maximum sternal depth.

This index was not originally validated and it is highly variable depending on sex, symmetry, the shape of the thorax, and the respiration phase in which the study is acquired.

Nowadays, the Correction Index has received validation and is more precise to discriminate affected from non-affected subjects.

(Pearls & Tricks in Pediatric Surgery)

Question 7

What is the impact of PEX in the cardiopulmonary function?

Answer 7

In echocardiographic studies, functional alterations can be found such as ventricular dysfunction during exercise.

Employing dynamic cardiac magnetic resonance, 76% of the patients with PEX have shown some degree of right ventricular compression.

Recently, reports have demonstrated a relationship between sternal torsion and cardiac compression as well.

Normalization of cardiac function and structure has been reported after PEX repair.

More studies are currently underway.

(Pearls & Tricks in Pediatric Surgery)

Question 8

What strategies are there for the treatment of PEX?

Answer 8

There are operative and non-operative treatments for patients with PEX.

In most cases, chest wall flexibility determines whether surgery will be necessary to solve the deformity.

Chest wall flexibility can be determined manually or utilizing a vacuometer.

However, some patients have very dysplastic sternums or rib cages that may require an operation no matter the flexibility they may have.

(Pearls & Tricks in Pediatric Surgery)

Question 9

What is the non-operative treatment for PEX?

Answer 9

Since the first report in 2005, the use of a Vacuum Bell has become an option for patients with flexible rib cages [1].

This device is usually appropriate for patients under 11 years old with pectus depth less than 1.5 cm and with good compliance, who wear the device as many hours per day as possible.

It is noteworthy that an adjustment period of approximately 6 months of the presternal soft tissue is usually needed to avoid local lesions.

(Pearls & Tricks in Pediatric Surgery)

Question 10

In patients with an indication of surgery, what approaches can be used?

Answer 10

Donald Nuss reported the minimally invasive placement of a retrosternal bar in the ′90 s. While many variants are described, open resection of costal cartilages is rare today and is generally reserved for extremely asymmetric or mixed deformities.

(Pearls & Tricks in Pediatric Surgery)

Question 11

What safety measures should be applied during PEX surgery?

Answer 11

Thoracoscopic guidance is most commonly employed to decrease the possibility of undetected cardiac lacerations when introducing the tunnel dissector.

Upward traction on the sternum by vacuum bell or even a crane can be used (Fig. 3.4).

A subxiphoid finger can also be used to guide the bar and protect the heart [2].

(Pearls & Tricks in Pediatric Surgery)

Question 12

What is the role of cryoanalgesia in pain control of PEX?

Answer 12

Cryoanalgesia has recently become a promising strategy for pain control during and after PEX repair.

Thoracic cryoanalgesia consists of the transitory demyelination of the 3rd to the 7th intercostal nerves by the application of a cryoprobe for 2 minutes each at −70 degrees Celsius (Fig. 3.5).

Randomized trials have demonstrated that cryoanalgesia is superior to thoracic epidural and patient controlled analgesia in terms of length of stay and requirement of complementary opioids.

(Pearls & Tricks in Pediatric Surgery)

Question 13

How long does the bar stay in?

Answer 13

Usually 2.5–3 years.

Pearls & Tricks in Pediatric Surgery

Question 14

What complications may be found during follow-up?

Answer 14

Pneumothorax, pleural effusion, and metal allergy.

The more serious complications are bar infection and displacement of the implant.

The worst complications are related to cardiac or aortic injury during or after PEX repair.

(Pearls & Tricks in Pediatric Surgery)

Question 15

How is Pectus Carinatum (PC) classified?

Answer 15

PC is classified in chondrogladiolar and chondromanubrial types (Fig. 3.6).

If the protrusion involves the caudal third of the sternum, it is called chondrogladiolar, the most frequent variant.

The chondromanubrial type is a protrusion of the proximal segment of the sternum and frequently comprises a pectus arcuatum, an atypical variant consisting of a wide, short, unsegmented sternum.

If it is associated with a cardiac anomaly it is called Currarino Silverman Syndrome.

Also, PC may be classified in symmetrical, asymmetrical and mixed.

(Pearls & Tricks in Pediatric Surgery)

Question 16

How is a patient with PC studied?

Answer 16

The evaluation of a patient with PC consists of a physical examination with medical photography destined for diagnosis and follow up.

CT scans or X-rays are reserved for special cases in which association with skeletal malformations are suspected.

In the last years, 3D scanning has become a relevant, radiation-free tool for the workup of chest wall malformations.

We perform 3D scans in all patients with PC at the moment of initial diagnosis, during, and after corrective treatments (Fig. 3.7).

(Pearls & Tricks in Pediatric Surgery)

Question 17

What is the impact of PC in the health of patients?

Answer 17

PC is not an isolated protrusion of a segment of the sternum. Rather, PC consists of a dysplastic rib cage as a whole with posterior asymmetry, disproportionate shoulders, sternal rotation, chondro-costal anomalies, and scoliosis and kyphosis.

No cardiopulmonary anomalies are associated.

However, the psychosocial impact of PC includes shame, shyness, anguish, anxiety, depression, difficulties with social interactions and sports.

(Pearls & Tricks in Pediatric Surgery)

Question 18

What is the non-operative treatment for PC?

Answer 18

Bracing is the treatment of choice for most patients. In 2008, we developed and reported the usefulness of a dynamic compressor and a pressure measuring device for this purpose (Fig. 3.8).

This device provided objectivity to the amount of pressure to be applied to the chest to correct the protrusion for the first time (pressure of initial correction) and how much pressure to be applied during the different stages of treatment (pressure of treatment).

(Pearls & Tricks in Pediatric Surgery)

Question 19

How are patients with dynamic compression systems followed-up?

Answer 19

A scheme of gradual increase of pressure of compression is determined. At first, the pressure of initial correction is determined to set up a goal. Then, the first stage of adjustment with a lower pressure begins for 6 months to avoid soft tissue lesions.

As the treatment advances, the chest becomes more elastic and this is evident by a drop in the pressure of correction. Thus, the pressure of treatment and the time of use can be gradually increased as shown in Table 3.1.

(Pearls & Tricks in Pediatric Surgery)

Question 20

What is the advantage of measuring the pressure of compression while bracing?

Answer 20

There are two advantages: the elasticity of the chest can be determined precisely at diagnosis determining the pressure of initial correction, and damage to the soft tissues can be prevented by avoiding excessive compression initially.

(Pearls & Tricks in Pediatric Surgery)

Question 21

What prognostic factors favor success in cases treated with dynamic compression systems?

Answer 21

A lower initial pressure of correction and younger age have been associated with improved results, probably due to a higher chest wall flexibility.

A longer duration of brace therapy is another variable associated with a good outcome and one of the most important limiting factors of success is the lack of compliance among teenagers.

(Pearls & Tricks in Pediatric Surgery)

Question 22

In patients with an indication of surgery, for pectus deformities, what approaches can be used?

Answer 22

Both open and minimally invasive surgeries are used. Open techniques involve resecting costal cartilages with sternal osteotomies (Ravitch procedure).

(Pearls & Tricks in Pediatric Surgery)

Question 23

What minimally invasive techniques are there for the operative treatment of PC?

Answer 23

Minimally invasive techniques for PC can be classified in resective and non-resective.

Thoracoscopic resective approaches have been described but since Abramson reported the Reverse-Nuss procedure [4], most PC with an indication of surgery have been resolved with non-resective operations.

These last operations aim to remodel the chest wall by means of the introduction of a pre-sternal implant through a subcutaneous tunnel.

This implant is stabilized to the ribs by a metal device fixed with wire.

There have been several modifications to this technique like the Yüksel technique [5] with a special design of implants and lateral stabilizers depending on the characteristics of the deformity and the Zip-back technique with pre-molded implants, the intraoperative use of a sternal compressor, and the avoidance of lateral stabilizers by employing polymer zip-ties to fix the implants to the ribs (Fig. 3.9).

All these modifications are intended to avoid displacement and complications at the time of bar removal.

For asymmetrical PC, Park and Kim have described the Sandwich technique which consists in the utilization of an internal and external bar thus treating at the same time carinatum and excavatum deformities.

(Pearls & Tricks in Pediatric Surgery)

Question 24

How is postoperative follow up done for pectus deformities and what complications should be closely looked for?

Answer 24

The patient is seen at one and two weeks postoperatively, at 1, 2, 4, 6 months and then yearly.

Chest x-rays are done by 1 week, 1 month, 4 months, and then yearly.

The implant is removed at 2 or 3 years postoperatively and a 3D scan is done in the immediate preoperative month.

Complications include metal allergy, pleural effusion, foreign body reaction, wound infection, and bar displacement.

(Pearls & Tricks in Pediatric Surgery)

Question 25

What are the future directions in the evolution of diagnosis and treatment of chest wall deformities?

Answer 25

Defining the cardiopulmonary impact of PEX in the long term is one of the most interesting challenges in the field. In the evolution of the treatment of chest wall deformities, the development of 3D based implants are the next step. (Pearls & Tricks in Pediatric Surgery)

Question 26

What is the rationale for the use of internal bracing for pectus excavatum?

Answer 26

1. Malleability of the chest: Children have a soft and malleable chest. In young children, the chest is so soft that even minor respiratory obstruction can cause severe sternal retraction. Trauma rarely causes rib fractures and flail chest because the chest is so soft and malleable. Thus, the American Heart Association recommends “using only two fingers” when performing cardiac resuscitation in young children and “only one hand in older children” for fear of crushing the heart. 2. Chest reconfiguration: In middle-aged and older adults, a barrel-shaped chest configuration develops in response to chronic obstructive respiratory diseases such as emphysema. If older adults are able to reconfigure the chest wall, children and teenagers should be able to remodel as well, especially with the increased malleability of their anterior chest wall. 3. Bracing: The role of braces and serial casting in successfully correcting skeletal anomalies such as scoliosis, clubfoot, and maxillomandibular malocclusion by orthopedic and orthodontic surgeons is well established. The anterior chest wall, being even more malleable than the previously mentioned skeletal structures, is ideally suited for this type of correction.

Question 27

A young female who has always been shy about participating in sports because of her body appearance presents to the plastic surgeon. She states that ever since she was a child, her right upper arm and breast were not well developed compared to the left side. She denies any major functional ability but feels very conscious that her right breast is much smaller than the left breast. Examination reveals that she has marked hypoplasia of the right upper chest and breast and has upper limb abnormalities. The chest x-ray reveals ipsilateral hyperlucent hemithorax. In this particular disorder, which of the following muscles is rarely affected? Choices: 1. External oblique 2. Supraspinatus 3. Pectoralis minor 4. Innermost intercostal

Answer 27

Answer: 4 - Innermost intercostal Explanations: • The classic ipsilateral features of Poland syndrome include (1) absence of the sternal head of the pectoralis major muscle, (2) hypo-plasia or aplasia of breast or nipple (athelia), and (3) deficiency of subcutaneous fat and axillary hair. •The individual may also have abnormalities of the rib cage and upper extremity anomalies, including a short upper arm, forearm, or fingers (brachysymphalangism). • Muscles that are often hypoplastic or aplastic include the serratus, external oblique, pectoralis minor, latissimus dorsi, infraspinatus, and supraspinatus muscles. •The condition, even though it may appear drastic, has very little functional disability and is benign. The majority of individuals seek treatment only to enhance cosmesis.

Question 28

A young female who has always been shy about participating in sports because of her body appearance presents to the plastic surgeon. She states that ever since she was a child, her right upper arm and breast were not well developed compared to the left side. She denies any major functional ability but feels very conscious that her right breast is much smaller than the left breast. Examination reveals that she has marked hypoplasia of the right upper chest and breast and has upper limb abnormalities. The chest x-ray reveals ipsilateral hyperlucent hemithorax. In this particular disorder, which of the following muscles is rarely affected? Choices: 1. External oblique 2. Supraspinatus 3. Pectoralis minor 4. Innermost intercostal

Answer 28

Answer: 4 - Innermost intercostal Explanations: • The classic ipsilateral features of Poland syndrome include (1) absence of the sternal head of the pectoralis major muscle, (2) hypo-plasia or aplasia of breast or nipple (athelia), and (3) deficiency of subcutaneous fat and axillary hair. •The individual may also have abnormalities of the rib cage and upper extremity anomalies, including a short upper arm, forearm, or fingers (brachysymphalangism). • Muscles that are often hypoplastic or aplastic include the serratus, external oblique, pectoralis minor, latissimus dorsi, infraspinatus, and supraspinatus muscles. •The condition, even though it may appear drastic, has very little functional disability and is benign. The majority of individuals seek treatment only to enhance cosmesis.

Question 29

Regarding child breast, which of the following statements is not correct? A. Polythelia is an accessory breast. B. Amastia is an absence of breast. C. Mastitis neomatorum is an infectious condition. D. Premature thelarche is breast enlargement in girls under 8 years of age. E. Macromastia refers to large but histologically normal breast.

Answer 29

A Polythelia is a supernumery nipple. Polymastia is referred to as accessory breast. Syed/MCQ

Question 30

Regarding pectus excavatum, all of the following are correct except: A. It is protrusion deformity of chest. B. Aetiology is unknown. C. Severity is assessed by anteroposterior diameter of chest. D. Pulmonary function is evaluated by radio nucleotide scan. E. It is associated with scoliosis.

Answer 30

A Pectus excavatum is posterior depression of sternum and lower costal cartilage. Syed/MCQ

Question 31

The following are all features of Poland syndrome except: A. Syndactyly B. Absence of ribs C. Athelia or amastia D. Absence of axillary hairs E. Absence of latissimus dorsi muscle

Answer 31

E Absence of latissimus dorsi muscle is not a feature of Poland syndrome. Absence of pectoralis major or minor muscle is a feature of Poland syndrome. Syed/MCQ

Question 32

Regarding pectus excavatum, which one of the following statements is false? A. Male-to-female ratio is 3:1. B. Among musculoskeletal deformities, scoliosis is the most common. C. Marfan syndrome is commonly seen. D. Diagnosis is made in the first year of life in the majority of cases. E. The vast majority of patients do not have symptoms.

Answer 32

C Marfan syndrome occurs infrequently, less than 1 per cent of patients. Syed/MCQ

Question 33

Thoracoscopy should be used: A from the right side only B from the left side only C from both sides D never E any of the above, at the discretion of the surgeon.

Answer 33

E The use of the thoracoscope has decreased the incidence of intraoperative collateral structure injury. The decision to use the thoracoscope on the left or right side is up to the surgeon. Even bilateral thoracoscopy is reasonable and actually recommended in cases of severe pectus excavatum, redo Nuss’s procedure, or if visualisation from one side is inadequate. Although some advocate not using thoracoscopy, we have found it very helpful and it definitely makes the dissection safer. SPSE 1

Question 34

The best age to repair pectus excavatum using the minimally invasive technique is: A 3–6 years B 7–10 years C 11–14 years D 15–20 years E 21 and over.

Answer 34

C Repair of pectus excavatum prior to pubescence is not ideal because of the fact that most patients will outgrow the bar as they go through puberty. Repair of pectus excavatum after puberty is not ideal because the patient’s chest begins to develop less compliance. Watching the patient’s growth trajectory during the ages 11–14 years will typically allow for a time frame that is more optimal for pectus repair via the minimally invasive technique. SPSE 1

Question 35

It is easier to correct pectus excavatum before the child reaches puberty because: A the psychological effects of the chest wall deformity will be prevented B the patient will require only one bar C the rib and cartilage structures are more pliable D the pectus bar is smaller and easier to bend into position E the patient has no physiologic benefit until after puberty.

Answer 35

C Prior to puberty the cartilage of the anterior rib cage as well as the bone of the lateral and posterior rib cage is more pliable. Changes in the density of the bony rib cage and ossification of the cartilaginous rib cage result in a much stiffer chest after puberty and into adulthood. SPSE 1

Question 36

Additional equipment kept immediately available in the cardiothoracic OR includes all except: A sternoscopy tray B sternal saw C sternal retractors D vascular clamps E suction.

Answer 36

A Although the risk of cardiac injury is low, preparation for the steps that follow are of vital importance to improve the chances of patient survival. If a cardiac injury is recognised during introduction of the stabiliser, the first step is to leave the introducer in place and then call for assistance. Having the sternoscopy tray in the room will prevent this from being a source of delayed treatment. SPSE 1

Question 37

The pectus bar may be removed as an outpatient procedure after a minimum of _____ years? A 1 B 2 C 3 D 4 E 5

Answer 37

B Long-term assessment of pectus excavatum repair has been classified into four categories: excellent, good, fair or failed. An excellent repair is defined as a patient with no evidence of recurrence and resolution of associated symptoms. More patients fall into the excellent and good categories when the bar is left in place 24 months or longer. SPSE 1

Question 38

Pad placement for defibrillation in patients with a pectus bar should be: A posterior/mid-axillary B bilateral anterior C anterior/mid-axillary D anterior/posterior E bilateral axillary.

Answer 38

D Placement of the defibrillator in the typical recommended sites of the chest wall may result in ineffective delivery of energy to the heart because of the energy taking the path of least resistance along the bar. For this reason, in order to optimise delivery of energy to the myocardium, pad placement should be such that one pad is placed on the anterior thorax and one on the posterior thorax. SPSE 1

Question 39

Bar removal is facilitated by: A palpating the ends of the bar B reviewing chest X-ray preoperatively if bar cannot be palpated C fluoroscopy during surgery if needed D opening both incisions if needed E all of the above.

Answer 39

E Bar removal can be a complicated matter with significant complications if not done correctly. Knowing exactly where the bar is, is critical and imaging may be necessary if significant calcifications have developed. Counterbending the bar to straighten, by opening both incisions, is the safest method, to minimise the bar pulling on any tissue or organ on removal. SPSE 1

Question 40

Bar infection may require: A short-term high-dose antibiotic therapy B long-term preventive maintenance antibiotic therapy C incision drainage and packing of the wound D bar removal after failed conservative therapy E all of the above.

Answer 40

E Bar infection should be rare and occurs <2.5% of the time. Appropriate sterile technique and use of antibiotics minimises the risk of infection. When an infection occurs aggressive treatment can often save the bar. This includes long-term antibiotics, incision and drainage and use of wound-closure devices. Complete blood count, erythrocyte sedimentation, and C-reactive protein are useful inflammatory markers to use in determining duration of therapy. Repeat course of antibiotics has been able to preserve the bar when repeat infection occurs. Testing for metal allergy is also warranted for any ‘atypical’ wound issue. SPSE 1

Question 41

Stabilisers and polydioxanone (PDS) sutures placed around the ribs and the bar have reduced the incidence of bar displacement from 15% to: A 12% B 10% C 5% D <2% E 0%.

Answer 41

D Bar displacement is the most common complication associated with Nuss’s procedure. Various modifications over the last 20 years have significantly decreased the incidence. Generally one stabiliser per bar is recommended since bilateral stabilisers did not change the incidence and can lead to rib compression in those patients who are actively growing. The use of PDS around the ribs and the liberal use of two bars have greatly decreased the incidence of bar displacement. If the bar rotates less than 10–15 degrees and still provides the same support it can be observed without reoperating. Slight rotation within 1 month of surgery may be best treated by adding a second bar or resecuring. SPSE 1

Question 42

When planning to place two bars, do all except: A place introducer in easiest location first B elevate sternum while passing second introducer through deepest defect C make sure at least one bar is under the sternum D make sure both bars are under the sternum E put stabilisers on opposite sides.

Answer 42

D The use of 2 bars has significantly increased in the last 10 years. Their use is increased in older patients >16 years with stiff chests, saucer-shaped defects, asymmetrical pectus patients, sterna torsion, recurrent pectus excavatum patients, and those patients with marfan’s syndrome or similar phenotype. When placing two bars it is easier to place the more superior bar first since this will be an easier dissection. It is frequently helpful to leave the first introducer in place to facilitate dissecting the second tunnel. It is imperative that at least one bar is fully under the sternum, but the second bar does not necessarily need to be under the sternum if the defect is low. SPSE 1

Question 43

Techniques to avoid pericardial injury include all except: A maintaining dissection immediately adjacent to the posterior sternum B turning up pulse oximeter volume while passing the introducer C use of a thoracoscope D dissection predominantly in an anterior to posterior direction E reviewing pre-op CT scan for sternal torsion/anatomy.

Answer 43

B Any hole in the pericardium may lead to post-pericardiotomy syndrome. This can easily be treated with non-steroidal anti-inflammatory drugs. Although a hole should be avoided it is sometimes impossible not to have it occur if there are a lot of adhesions. The bar should NEVER be allowed to go through the pericardium since this may lead to cardiac rupture at time of removal. Thoracoscopy is invaluable in avoiding this injury and more importantly recognising it if it occurs and allowing repositioning of the bar outside the pericardium. SPSE 1