Distraction Osteogenesis of Multiple Ribs for the Treatment of Acquired Thoracic DystrophyMerisa L. Piper, MD, Lawrence Delrosario, MD, William Y. Hoffman, MD

Division of Plastic and Reconstructive Surgery, Department

of Surgery, University of California, San Francisco, San

Francisco, California

Dr Piper coordinated and supervised data

collection; Drs Piper and Delrosario assisted

in writing the initial manuscript; Drs Piper and

Hoffman reviewed and revised the manuscript; Dr

Delrosario performed the initial data collection;

Dr Hoffman conceptualized and designed the

technique; and all authors approved the fi nal

manuscript as submitted and agree to be

accountable for all aspects of the work.

DOI: 10.1542/peds.2015-2053

Accepted for publication Nov 20, 2015

Address correspondence to William Hoffman, MD,

Division of Plastic Surgery, University of California,

San Francisco, 505 Parnassus Ave, Suite M593, San

Francisco, CA 94143. E-mail: william.hoffman@ucsf.

edu

PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online,

1098-4275).

Copyright © 2016 by the American Academy of

Pediatrics

FINANCIAL DISCLOSURE: The authors have

indicated they have no fi nancial relationships

relevant to this article to disclose.

FUNDING: No external funding.

POTENTIAL CONFLICT OF INTEREST: The authors

have indicated they have no potential confl icts of

interest to disclose.

Surgical correction of pectus

excavatum has evolved to be less

invasive and cause less morbidity.1,2

Nevertheless, it is still associated

with a variety of complications. A

hypoplastic, abnormally developed

thorax has been described in

patients after repair by the open

Ravitch technique or other modified

open repair techniques on young

children.3–5 The proposed etiology of

this thoracic dystrophy is decreased

longitudinal rib growth resulting from

extensive resection of rib cartilage and

injury to the costochondral junction

in young patients during repair.4,5

The disruption of the cartilage growth

plate limits the growth and proper

development of the chest wall. This

results in decreased thoracic volume

and may cause restricted pulmonary

function and cardiac compression.3,5,6

The optimal treatment approach to

increase thoracic volume by surgical

intervention has been controversial

and must accommodate chest wall

expansion as children continue to

grow.7–13

Distraction osteogenesis, first

presented by Codivilla in 1905 and

revisited by Ilizarov starting in the

1950s,14 describes the phenomenon

in which separation and gentle

traction of skeletal elements

leads to metabolic activation and

eventual bone formation between

the separated skeletal elements.15,16

Distraction osteogenesis has been

used in a wide variety of orthopedic

and craniomaxillofacial applications,

particularly after traumatic injury or

from congenital deformities. Here, we

present the case of a 17-year-old boy

with symptomatic acquired thoracic

dystrophy after repair of pectus

excavatum who was successfully

treated with distraction osteogenesis.

abstractAcquired thoracic dystrophy is a complication associated with early open

repair of pectus excavatum resulting from extensive cartilage resection.

The condition can cause serious functional and physiologic impairments,

including cardiac compression and restrictive pulmonary function.

We describe a 17-year-old boy with acquired thoracic dystrophy after

Ravitch repair of pectus excavatum during infancy, whom we treated

with distraction osteogenesis. The patient had a marked deformity of the

chest wall and general hypoplasia of the central portion of the ribcage,

with resultant symptomatic dyspnea on exertion and reduced pulmonary

function. After osteotomies and distraction osteogenesis of bilateral

ribs 4–8 using customized distraction devices, he had improved thoracic

contour, resolution of dyspnea, and decreased restrictive pulmonary

symptoms. This case suggests that distraction osteogenesis, already used

extensively in craniomaxillofacial and orthopedic surgery, may be a novel

method for management of this condition.

CASE REPORTPEDIATRICS Volume 137 , number 3 , March 2016 :e 20152053

To cite: Piper ML, Delrosario L, Hoffman WY.

Distraction Osteogenesis of Multiple Ribs for

the Treatment of Acquired Thoracic Dystrophy.

Pediatrics. 2016;137(3):e20152053

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PIPER et al

PATIENT DESCRIPTION

The patient initially presented to the

plastic surgery service at University

of California, San Francisco, at

age 11 years for consultation for

arrested sternal growth after a

Ravitch repair of pectus excavatum

at age 2. This deficient growth led

to inadequate bony protection of

the heart and upper abdominal

viscera. Because a short sternum is

not typical with this condition, we

speculate that it is related to the

early age of his initial surgery and

presumed devascularization of the

sternum. He subsequently underwent

methyl methacrylate chest wall

reconstruction with rectus abdominis

muscle coverage to address the

hypoplastic sternum and complex

chest wall deformity. However, he

returned after a hiatus of several

years with a marked deformity of his

chest wall and general hypoplasia of

the central portion of the ribcage (Fig

1). He had symptomatic dyspnea on

exertion, was unable to participate in

sports, which negatively impacted his

self-esteem, and was self-conscious of

his appearance. Pulmonary function

tests revealed a 50% reduction in

vital capacity and forced expiratory

volume. After extensive discussions

with our pediatric pulmonology

and pediatric surgery colleagues,

we decided to pursue bilateral

distraction osteogenesis of ribs 4–8

when the patient was 17 years old to

increase his overall thoracic volume.

OPERATIVE TECHNIQUE

After the patient was positioned

supine with arms extended, lazy-S

incisions were made bilaterally over

the anterior axillary line. The serratus

anterior was divided in 3 locations to

permit access to the ribs of interest. A

small incision was made at the lower

border of each rib to dissect a small

periosteal pocket, permitting us to

divide the rib while maintaining the

periosteum as a sleeve to promote

osteogenesis. Osteotomies of bilateral

ribs 4–8 were performed by using a

reciprocating saw.

The 10 rib distractors used were

custom manufactured by KLS Martin

(Jacksonville, FL), based on a design

originally used for placement on

metacarpals. They were chosen

over midface distractors because of

their increased rigidity; the custom

manufacturing extended their length

to 3 cm. The distraction device was

placed across the osteotomy gap in

a supraperiosteal position, using 4

screws (2-mm diameter, 11-mm total

length) on each side. The activating

rods were brought out anteriorly

through small separate skin incisions.

All distractors were placed in a

similar fashion with the exception

of the fourth rib on the patient’s

right side. The fourth rib was located

slightly inferior to the third rib and

pectoralis muscle, and consequently

the activating rod would not

reach the skin. An osteotomy was

performed on the right fourth rib but

no distractor was placed, with the

expectation that it would follow the

distraction of the other four ribs on

that side. After excellent fixation of

all devices was obtained, muscle and

soft tissue were closed in a layered

fashion (Fig 2).

After a latency period of 5 days,

distraction began at a frequency

of twice a day, for 1 mm of total

daily lengthening for each of the

9 distractors. The patient was

discharged on postoperative day 9,

and the family continued distraction

at home until the total distraction

distance of 3 cm was achieved. Two

e2

FIGURE 1Three-dimensional reconstruction of patient’s thoracic cavity before distraction osteogenesis. Note the constricted appearance of ribs 4–8. Upper left, anterior view of chest wall. Upper right, coronal view of chest wall. Bottom left, left lateral view of chest wall. Bottom right, right lateral view of chest wall.

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PEDIATRICS Volume 137 , number 3 , March 2016

months after discharge, the patient

returned to the operating room

for removal of the activator rods

to minimize the risk of ascending

infection. A computed tomography

scan was obtained before removal

to evaluate the ossification and

distraction length (Fig 3). Seven

months later, the distraction

devices were removed during a

third operation once computed

tomography documented sufficient

bone growth (Fig 4).

OUTCOME

One month after the activator rods

were removed, the patient underwent

pulmonary function analysis (Table

1). Compared with levels from 9

months preoperatively, his forced

vital capacity increased from 53% to

67% of predicted, forced expiratory

volume increased from 55% to 63%

of predicted, vital capacity increased

from 50% to 67% of predicted, and

total lung capacity increased from

70% to 80% of predicted. At his most

recent follow-up visit 4 years later,

although he remains asymptomatic

without dyspnea, his forced vital

capacity was 57%, forced expiratory

volume was 59%, vital capacity was

55%, and total lung capacity was 61%.

All measurements were still higher

than preoperative values, except for

the total lung capacity, but to a lesser

degree.

We calculated lung volumes pre- and

postoperatively based on computed

tomography. Before expansion,

the left lung volume was 2.44 L

and the right was 2.92 L (5.36 L

total). Six months after removal of

the distractor devices, the left lung

volume was 2.72 L and the right was

3.48 L (6.20 L total). This reflects a

16% increase in overall lung volume.

The patient had no early or late

postoperative complications. He

was initially seen monthly, and now

is seen on an annual basis. At his

most recent postoperative visit, the

patient still had a mild hourglass

deformity of the chest wall. This is

exaggerated by the abrupt end of the

pectoralis muscles (Fig 5). However,

the patient reported no restrictive

pulmonary symptoms, such as

exertional dyspnea or cough. He rides

a bike without shortness of breath

and has no pain. Overall, he is pleased

with his functional and aesthetic

outcomes.

DISCUSSION

Acquired thoracic deformity can

be a significant cause of morbidity

after early open repair of pectus

excavatum, resulting in cardiac

compression and restrictive

pulmonary function. In this case

e3

FIGURE 2A, Implantation of a distractor underneath the rib periosteum, before coverage with a periosteal sleeve. B, Distractor device, manufactured by KLS Martin. C, Activator rods protruding through skin along the anterior axillary line.

FIGURE 3Three-dimensional reconstruction of patient’s thoracic cavity 5 months after osteotomies of ribs 4–8 and placement of rib distractors. This computed tomography scan was obtained 3 months after complete distraction. Upper left, anterior view of chest wall. Upper right, coronal view of chest wall. Bottom left, left lateral view of chest wall. Bottom right, right lateral view of chest wall.

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PIPER et al

report, we present a novel method

for managing this complication using

distraction osteogenesis, a technique

often used in craniomaxillofacial and

orthopedic surgery. The particularly

challenging aspect of this case was to

attempt distraction with the constant

respiratory movement of the ribs.

The distractors proved capable of

maintaining fixation under these

conditions and allowing for new bone

formation. The success of distraction

osteogenesis in restructuring the

thoracic cavity acts as a proof of

principle that this technique may be

used in a broader scope to treat other

acquired and congenital thoracic

conditions.

However, as with all surgical

procedures, this procedure has

drawbacks. First, it requires 3

separate surgeries: distractor

placement, activator rod removal,

and distractor removal. This means

3 episodes of general anesthesia,

potential hospitalizations, and

periods of postoperative recovery.

Second, this technique is painful

during the distraction process, as

well as after the 3 surgeries. Third,

the distractor devices are expensive,

∼$5000 per piece, although we did

receive a bulk discount. Finally,

there is bilateral scarring, which

may be unsightly. However, the

alternative surgical options also have

drawbacks. Sternal split with rib

graft placement improves pulmonary

function, but leaves the intrathoracic

organs vulnerable to injury and does

not adequately address cosmetic

concerns.13 A vertical expandable

prosthetic titanium rib requires a

large incision, has minimal benefit in

children older than 8 years, and can

cause significant tension on the soft

tissues, leading to erosion.7 Risks of

anterior chest wall reconstruction

with release and elevation of

the sternum include supporting

retrosternal bar migration, migration

and exposure of the rib grafts and

sternal wires, and difficulty in

e4

FIGURE 4Three-dimensional reconstruction of patient’s thoracic cavity 6 months after removal of distractor devices, demonstrating adequate ossifi cation of ribs 4–8 bilaterally. Upper left, anterior view of chest wall. Upper right, coronal view of chest wall. Bottom left, left lateral view of chest wall. Bottom right, right lateral view of chest wall.

TABLE 1 Pulmonary Function Test Results at 9 Months Preoperatively, 1 Month After Ribs Fully

Distracted, and 4 Years After Removal of the Distractor Devices

Test Preoperative, % 1 mo postoperative, % 4 y postoperative, %

Forced vital capacity 53 67 57

Forced expiratory volume 55 63 59

Vital capacity 50 67 55

Total lung capacity 70 80 61

Values are expressed as age-adjusted percentages of predicted values.

FIGURE 5A, Anterior view of the patient’s chest wall before distraction osteogenesis. B, Anterior view of the patient’s chest wall 4 years after distraction osteogenesis completed; note the abrupt end of the pectoralis muscles. C, Appearance of scarring 4 years after distraction osteogenesis completed; lazy-S scar from rib access and punctate scars from distractor rods.

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PEDIATRICS Volume 137 , number 3 , March 2016

controlling hemorrhage as the sternum

is separated from scar tissue.17

Despite the drawbacks, our

patient had substantial functional

and aesthetic improvement, as

evidenced by higher levels in his

pulmonary function tests, increased

lung volumes, and greater self-

esteem. His pulmonary function

never normalized, however, and

in fact declined over time after

initial postoperative improvement.

Although this was suboptimal, he

remains asymptomatic. The decline

may indicate additional growth of

the patient without commensurate

growth of the chest wall. Therefore,

there may be a theoretical benefit

to performing this operation when

the patient is younger, so that the

ribs and lungs may continue to grow

together. We believe this outcome

could also be improved by increasing

the length of distraction, and propose

to do this in future cases or even to

perform distraction at 2 points in

the rib (for example, anterior and

posterior axillary lines). In addition,

a device that follows the curvature

of the ribs could improve both the

aesthetic, as well as the functional,

outcome. Overall, the symmetry of

this patient’s chest wall has remained

stable over 4 years despite continued

growth and skeletal maturity.

Distraction osteogenesis may provide

a safe and effective alternative for

surgical management of acquired

thoracic dystrophy.

ACKNOWLEDGMENTS

Thank you to Pamela Derish for her

review of the manuscript. Thank you

also to Dr. Brian Haas for his assistance

with calculating lung volumes.

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