EXTERNAL FIXATION 0749-0712/93 $0.00 + .20
From the Limb Length Clinics, Gillette Children's Hospital, St. Paul; Shriner's Hospital for Crippled Children and Fairview Riverside Medical Center, Minneapolis; and University of Minnesota Medical School, Minneapolis, Minnesota
VOLUME 9 NUMBER 4 NOVEMBER 1993
THE GRADUAL CORRECTION
OF
FOREARM DEFORMITIES IN
MULTIPLE HEREDITARY
EXOSTOSES
Mark T. Dahl, MD
Pediatric forearm deformities may result from congenital, developmental, and posttraumatic conditions. When analyzing the potential for correcting a forearm deformity, its cause and its changing nature during growth must be considered. Length corrections of the upper extremity are indicated in fewer instances than in the lower extremity because moderate discrepancies in forearm length usually do not produce significant functional or cosmetic problems. Large length discrepancies and severe angular or articular deformities do result in functional and cosmetic problems. Small variations in length between the radius and ulna (i.e., multiple hereditary exostoses) or an absence of either bone (i.e., radial aplasia), also can result in disturbed function and cosmesis.
Significant progress in treating upper-extremity deformities has occurred with the introduction of Ilizarov methodology. Recent publications demonstrate how complicated cases, poorly treated by conventional techniques, can be corrected successfully and safely.(3,5,l4,l5) This report illustrates the combination of gradual mechanical distraction techniques (distraction histogenesis) with conventional osteotomies to restore forearm length, alignment, and joint position in multiple hereditary exostoses. Specifically, this communication has three goals: (1) to discuss the planning of pediatric forearm corrections, (2) to illustrate a hybrid circular fixation technique, and (3) to discuss a technique of gradual correction of forearm deformities associated with multiple hereditary exostoses.
A METHOD OF PLANNING
Etiology
The patient's history and
symptoms are considered in the context of the cause: congenital,
developmental, or acquired. Pain is identified by location, extent
(mild, moderate, or severe), and frequency. The cosmetic concerns
raised by the patient and family are carefully elicited because
they greatly influence the decisions made and the ultimate satisfaction
with the correction. It is usually necessary for the surgeon to
see the patient on several occasions to carefully analyze the
problems and address all the issues associated with the correction.
Furthermore, these progressive corrections require strict compliance
as treatment becomes a collaboration with the patient and family.
Preoperative patient education builds the foundation for this
collaboration. The complex technical information necessary to
understand the process of limb lengthening is best performed on
an incremental basis. For these reasons, no child at our clinic
undergoes a correction until members of the limb-length team,
child, and parents feel it is appropriate.
Function of the
Forearm
Functional activities
and limitations are analyzed by the surgeon and the upper-extremity
therapist. In cases involving very young children (infancy to
2 years), Bayley's scales of infant development are used.' For
older children, functional assessment forms are used before and
after correction. Adaptive mechanisms are noted, and the expected
function after correction is considered.
Radiographs
Bilateral, upper-extremity,
anteroposterior radiographs with the hands and elbows in anatomic
position, when possible, provide an optimal view for analysis.
A lateral radiograph of the forearm that includes the hand, wrist,
and elbow is obtained with an upper-extremity scanogram and bone
age film. Measurements of sitting and standing height are useful
in certain conditions of disproportionate
segment length (e.g., achondroplasia, multiple hereditary exostoses). Special studies such as radioactive bone scan, tomography, and magnetic resonance images are rarely necessary.
Mechanical Axis
Considerations
Orthopedic surgeons agree
on the reference points used when evaluating the mechanical axis
of the lower extremity.(11) No such agreement exists with reference
points and reference lines for the upper extremity. Standardized
reference points and reference lines are difficult to establish
in the upper extremity because of the paucity of biomechanical
and serial radiographic evaluations. General agreement exists
as to certain features: The relationship of the forearm to the
humerus is not collinear as in the lower extremity. Lines drawn
through the humeral epicondyles and shaft subtend an angle of
6° to 8°, and the proximal ulna is in 2° to 4°
of valgus with respect to the distal humerus, resulting in a carrying
angle of 8° to 12°. The radial neck is in 10° to 15°
of valgus relative to the radial shaft. The radial articular angle
(normally 15° to 30°) is the angle between the distal
radial articular surface and a line drawn perpendicular to the
radial shaft (Fig. 1). In the frontal plane, a palmer tilt of
10° exists at the distal radial articular surface. When relative
ulnar shortening exists, this distance can be measured from the
distal ulnar tip to the distal radial epiphysis at its ulnar border
(Fig. 1).
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This ulnar variance is considered negative when it is the ulna that is short. The carpal slip (normally £ 50%) is the percentage width of the lunate that falls ulnar to the longitudinal reference line (Fig. 1).
The apex of a bony deformity is defined by the intersection of lines drawn along the local anatomic axis of the bone. The true plane of a deformity describes the oblique plane in which a deformity exists, combining the frontal and sagittal plane magnitudes.
Problem List
The often daunting task
of planning a complicated multifocal correction usually leads
to the simple question, "Where do I start?" Ilizarov
advocates the creation of a problem list consisting of a detailed
compilation of the patient's current abnormalities and those that
may arise with correction or future growth. This list combines
features such as: the forearm length discrepancy, ulnar variance,
and the directions and magnitude of angulation. Other deformity
features may include: translation, rotation, bone loss, and contracture
or joint subluxation. The patient's age, the cause of their deformity,
neurovascular and psychological status, and the condition of the
soft tissues are also considered. Once complete, this list is
manually written on an overlay
tracing or computer digitization
of the radiograph. The overlay tracing is used as a worksheet
(Fig. 2).
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| PROBLEMS | 1. Diagnosis: Multiple Hereditary Exostoses |
| 2. distal ulnar osteophytes | |
| 3. 34° dorsolateral ulnar bow | |
| 4. 44° radial articular angle | |
| 5. 80% carpal slip | |
| 6. 2.3cm ulnar variance | |
| 7. radial head subluxation | |
| CORRECTION | 8. ring size 90mm |
| 9. wire/pin formula | |
Designing Fixation
The plane, magnitude,
and apex of the deformity are measured. Depending on the extent
of deformity correction and the size of the bones, a uniplanar
fixator or a hybrid circular fixator may be used. A uniplanar
fixator is selected when no angular deformity exists or when angulation
can be safely performed acutely, followed by gradual lengthening.
The hybrid circular fixator is used in cases that require gradual
multifocal or oblique plane corrections or if the wrist, hand,
or elbow require orthotic support.
Ring size is selected, allowing 1 cm of clearance for potential swelling. Fixator rings are drawn orthogonal to the deformed bone segments. Hinges, connecting rods, and motor rods are drawn in place based on the apices of the deformity. The worksheet is cut with a scissors at the proposed corticotomy site and the segments are angulated into the desired position through the hinge sites, thereby testing the correction plan. Pin and wire locations are preoperatively selected and illustrated on the worksheet.
The fixator is preassembled, and final adjustments are made on the basis of a preoperative fitting. This fitting also provides for further preoperative education and allows the patient and family familiarity with the device.
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TREATMENT MODELS
FOR MULTIPLE HEREDITARY EXOSTOSES
Multiple hereditary exostoses
is a condition characterized by abnormal metaphyseal bony prominences
capped with cartilage and associated with defective remodeling
and retardation of bone growth.(8)
Shapiro et al (13)
define forearm deformities of this condition as ulnar shortening,
radial bowing, ulnar deviation of the hand, radial head subluxation
or dislocation, and impinging osteochondromas. The radial articular
angle and carpal slip are often abnormal. The natural history
of untreated multiple hereditary exostoses is associated with
functional and cosmetic limitations (Fig. 3).
Several surgical procedures have been described and used to treat multiple hereditary exostoses, including excision of osteochondromas, ulnar lengthening, radial hemiepiphyseodesis, closing wedge osteotomy of the distal radius, open reduction of the radial head, and excision of the radial head.8,10,l2 The experience gained from performing these procedures has taught us that early and aggressive treatment is indicated to prevent disability.
Ulnar Lengthening
A variety of techniques
for ulnar lengthening in patients with multiple hereditary exostoses
have been described.(8,10,l2,l5) Transverse osteotomy with immediate lengthening
stabilized by iliac crest bone graft and internal fixation or
immediate lengthening using a step-cut technique are limited to
0.5 to 1.5 cm of lengthening. Gradual lengthening by Wagner's
technique requires multiple operations to interpose bone graft
into the distraction defect.(l7)
Pritchett (l2)
describes ten ulnar lengthenings in eight patients with multiple
hereditary exostoses. Four of these cases involved bone grafting
and plating, and six lengthenings in five patients were treated
with distraction osteogenesis. Unilateral fixation may provide
an excellent environment for new bone formation. Application and
postoperative care is relatively straightforward, and good patient
tolerance exists (Fig. 4); however, the adjustability of unilateral
fixators in certain periarticular applications is limited because
pin size and pin spread may be too great for a child's ulna. Regardless
of the type of external fixator selected, it is clear that ulnar
lengthening by means of distraction osteogenesis predictably produces
new bone without the need for secondary bone grafting.
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| Figure 4. This 10-year-old boy underwent ulnar lengthening with uniplanar external fixation. Note the unrestricted elbow flexion. | Figure 5. This patient has restricted elbow flexion because two full rings were used. |
Lengthening of the forearm with the classic Ilizarov technique,
using transfixing wires, results in a high rate of serious complications.
Of 13 corrections reported by Villa et al, (l5)
4 involved either temporary radial nerve palsies or sympathetic
dystrophy. Circular fixation has the added disadvantage of a steep
learning curve for the surgeon and staff.(6)
It also involves considerable bulk, limiting the patient's comfort
and function during the correction (Fig. 5).
Hybrid fixation of the forearm, using transverse Ilizarov wires opposed at 90° to half pins, avoids damage to muscle compartments and neurovascular structures yet allows versatility in angular correction and lengthening (Fig. 6).
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Excision of Osteochondromas
Indications for excision of osteochondromas
include pain, cosmetic prominence, and neural impingement. The
tethering role of ulnar osteochondromas is disputed, (2) and
excision to prevent progression of deformity has not been shown
to be effective. Excision, in combination with lengthening, should
be considered if ulnar lengthening will create secondary impingement.
Ulnar Angular Correction
Ulnar bowing usually exists in a dorsoradial plane. The true plane of the deformity can be defined, and correction of the angular deformity can be combined with lengthening, using techniques of distraction osteogenesis. The apex of the deformity then becomes the site for angular correction and subsequent lengthening.
Radial Angular
Correction
Hemiepiphyseal stapling has been shown to improve the radial articular angle and the clinical appearance of the wrist and wrist motion but also can be unpredictable and further shorten an already shortened limb.(8,12) Irani and Petrucelli (10) describe performing subtraction osteotomy of the radius with internal fixation with a plate preceding ulnar lengthening by 1 year. This measure has the obvious disadvantage of multiple surgeries. As an alternative, a closing wedge osteotomy of the radius with K-wire fixation is performed in conjunction with ulnar lengthening. This measure also simplifies treatment by allowing the gradual correction of only one bone.
Radial Head Reduction
Long-standing radial head
dislocation causes clinical deformity, limits motion, and may
be associated with elbow or wrist pain. Conventional open reduction
techniques are unpredictable and may lead to further pain and
stiffness.(4) Prichett (12) reports improvement of radial head stability
in five of six patients who had preoperative instability. This
instability most likely results from partial reduction of the
radial head. Villa et al (15) report gradual reduction in a congenitally
dislocated radial head by secondarily transfixing the ulna to
the radius and applying gradual traction on the dislocated radial
head. A subsequent closed reduction of the dislocated radial head,
using an Ilizarov olive wire for lateral traction, has been described.
Closed reduction of a dislocated radial head with an olive wire
and percutaneous radial neck osteotomy has also been described
(personal communication, Dr. Paley, MD). Despite these technical
options, I have avoided any direct reduction of chronically dislocated
or dysplastic joints because stiffness and pain may result.
Gradual improvement in radial head position is achieved by proceeding with the ulnar lengthening and by applying traction on the radius directly through the interosseous membrane or indirectly through the carpus by distal ulnar engagement. A1ternatively, a distal radioulnar transfixing wire, added after the ulnar variance is corrected, may then provide traction on the radius.
SURGICAL TECHNIQUES
The treatment plan described
is designed to simultaneously manage all the deformity features
that can be predictably corrected in children with multiple hereditary
exostoses. The procedure consists of an excision of impinging
osteochondromas,
a closing wedge osteotomy of the radius with K-wire fixation, and the application of an ulnar external fixator with gradual ulnar lengthening.
Accessory Surgery
Removal of osteochondromas,
epiphysiodesis, and soft-tissue releases are performed at the
same operation but before fixator application and corticotomies.
Radial Osteotomy
A conventional closing
wedge osteotomy of the radius is used for acute angular correction
in the following circumstances: (1) when ulnar deviation of the
wrist is present, (2) if the radial articular angle exceeds 35°,
or (3) if the carpal slip is 3 60%. This "subtraction osteotomy"
is performed subperiosteally, leaving the far cortex, periosteum,
and soft-tissue envelope intact as a hinge. Percutaneously crossed
K-wires, augmented with a postoperative volar splint, is sufficient
fixation for children (Fig. 7). The Kirschner wires can be removed
in the clinic, 5 to 6 weeks after surgery, when the osteotomy
has healed.
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| Figure 7. A volar splint supports the radial osteotomy and wrist. | Figure 8. A proximal half ring allows full elbow flexion during treatment. |
Hybrid Fixation
The preassembled fixator,
consisting of one half ring placed proximally and one full ring
placed distally, is mounted to the limb with fluoroscopic guidance
(Fig. 8). The attachment to the bone is completed with a hybrid
formula individualized for each deformity. If angular correction
is to precede lengthening, temporary hinge and motor mountings
can be created with additional plates on the half ring. Ulnar
fixation consists of proximal and distal reference wires, placed
transversely to avoid neurovascular structures (Fig. 9). Each
wire is opposed at a 60°- to 90°-crossing angle with a
3-mm titanium half pin placed through the subcutaneous border
of the ulna. Careful attention to safe zones of fixation is necessary. (9)
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The wire and pin are separated by a distance of 1 to 2 cm, depending
on the size of the bone segment. Stability should be increased
for the larger patient by increasing pin and wire diameter, number,
and spread.
Ulnar Corticotomy
The preferred level of
ulnar corticotomy for lengthening is the proximal metaphysis,
just distal to the coronoid process (Fig. 10). Good vascular supply
and the large cross sectional area provide for excellent regenerate
bone. If deformity correction is to be achieved, the apex of the
deformity is selected as the site of corticotomy and lengthening.
Prior to corticotomy, the frame is destabilized by temporarily
removing the hinges or motor rods. A 1- to 2-cm longitudinal incision
is made along the subcutaneous border of the ulna. A limited,
subperiosteal exposure avoids stripping the radial side of periosteum.
A drill-corticotomy technique using a 2-mm drill bit and a small
osteotome or cortitome cuts the ulnar, volar, and dorsal cortices.
The far cortex is cracked by gentle angulation. The periosteum
is repaired and the corticotomy reduced by reattachment of hinges
or motor rods.
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Compression is applied across the corticotomy site to minimize postoperative discomfort. Distraction begins 3 to 5 days after surgery, at a rate of 0.25 mm every 8 hours and is altered on the basis of radiographic monitoring of bone production.
Postoperative Care
A multidisciplinary limb-length
team is assembled and trained to manage the education and the
postoperative care of these patients. Key team members include
pediatric orthopedic nurses, physical therapists, occupational
therapists, orthopedic physician's assistants, orthotists, psychologists,
social workers, and child life specialists. Planning the deformity
correction, designing the fixation and performing the surgery,
which are all critical to success, are only preparatory for the
"reshaping process" that occurs during a period of months.
Hospitalization usually last 2 to 4 days; however, if the patient
has special needs that preclude early discharge (i.e., orthotic,
physical therapy), hospitalization can last 2 to 4 weeks.
During the immediate postoperative period, the patients are encouraged to use their digits, elbow, and upper extremity. Postoperative analgesia is administered parenterally for 1 day and orally for 7 to 14 days. Children should need little or no narcotic medication after 7 to 14 days.
Lengthening begins 3 to 5 days after surgery at the rate of 0.25 mm every 8 hours unless an acute intraoperative angular correction has taken place. In these instances, lengthening is delayed for 1 to 2 weeks because greater disruption of local blood supply requires a longer latency period.
Weekly clinic visits occur during the distraction phase, with radiographs taken to assess the nature,
pattern, and size of regenerate bone formation. The rate and rhythm should be increased for abundant bone formation extending beyond the limits of the cortex and should be decreased for thin, irregular, or incomplete bone formation. An irregular pattern of bone regenerate implies frame instability, which must be remedied promptly. Proximal and distal joints should be inspected carefully, both clinically and radiographically, for signs of luxation. Axis alignment also should be assessed.
With each visit to the clinic, patients are carefully queried in regard to pain, its amount and frequency, and its location. Sudden increases in pain, particularly if it results in a call for narcotic medication that was not previously being taken, signifies a disturbance in the limb and requires prompt evaluation. Articular function is examined by the surgeon and hand therapist. Strengthening exercises are emphasized, and orthotics are fabricated as necessary. Pin and wire sites are inspected at each visit, and the patient and parents are carefully instructed on the proper care of these sites. Routine pin and wire care consists of normal saline cleansing once weekly with an immobilizing foam dressing at the site. After distraction is complete, many patients choose to leave the pin and wire sites exposed without dressings. The protocol is adjusted to include a daily cleansing with half strength hydrogen peroxide if signs and symptoms of inflammation or infection develop. Oral antibiotic therapy is also administered for 1 week. Patients are instructed to notify us promptly if these changes do not alleviate the signs of sepsis.
Neurologic symptoms, however unusual, require prompt attention. A neurologic symptom should result in discontinuation of the lengthening for 2 to 3 days. Neurologic signs require reversal of the lengthening until a prompt examination can be conducted. The lengthening can resume after examination reveals no neurologic deficit and any symptoms have subsided.
Expected outpatient modifications may include conversion of an angular correction to a lengthening correction. Some examples of unexpected outpatient modifications include correction of an axis deviation, exchange of a chronically infected pin, or repair of a broken wire.
Timing fixator removal can be difficult. The fixator is worn two times the length of distraction plus 2 to 4 more weeks. When the radiograph demonstrates corticalization of bone in 3 of 4 cortices and the appropriate static fixation has occurred, the connections between the rings or clamps are loosened to passively dynamize the regenerate bone. If no pain develops at the lengthening site within a 1-week interval, the fixator can be removed on an outpatient basis. Uniplanar fixators can easily be removed without anesthesia, even in children. Fixators with transfixion wires and titanium pins are generally removed on an outpatient basis under
light anesthesia. Once removed, a short arm cast is applied for 3 to 4 weeks. Follow-up examinations after fixator removal occur twice annually to check for recurrent deformity.
Case Examples
To illustrate the variety
of deformities encountered in patients with multiple hereditary
exostoses, two cases are presented. The first is of an 11year-old
boy who complained of elbow pain, deformity, and a dorsally prominent
distal radial osteochondroma (Fig. 11). The child's mother, who
had bilateral radial head dislocations and proration contractures,
was particularly concerned about preventing progression of the
deformity. Excision of the radial osteochondroma, radial osteotomy,
and gradual ulnar lengthening was performed. Wrist function, cosmetic
appearance, and radioulnar motion was improved. The correction
was complicated by temporary extrinsic finger flexor tightness
and a loss of 15° of terminal elbow extension.
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The second case involved an 8-year-old boy with multiple hereditary exostoses who complained of wrist pain, dysfunction, and deformity (Fig. 12). The deformity features included negative ulnar variance of 2.5 cm, distal ulnar osteochondromata, ulnar angulation of 40°, radial articular angle of 38° and carpal slip of 75%. Progressive ulnar deviation of the hand and a prominent, chronically dislocated radial head were present. A two-ring circular fixator was designed and preassembled to address the deformities. Radial subtraction osteotomy and acute ulnar angular correction with hybrid ulnar fixation were performed followed by a gradual ulnar lengthening and partial radial head reduction. The fixator was worn 22 weeks, followed by 3 weeks in a short arm cast. Negative ulnar variance recurred at 4 mm per year, making it necessary to retreat the patient at 12 years of age.
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RESULTS
The results are summarized
in Tables 1 and 2. Cases 2 and 3 are
the same patient with case 3 representing the second treatment,
4 years after the initial correction (Fig. 13). All patients and
parents reported satisfaction with the appearance of the corrected
limbs. Six of seven patients considered the result excellent.
One patient had loss of motion,
therefore the result of the
correction was rated good. Appearance of the wrist improved in
all cases. Functional improvement was present in four of seven
cases. The radial head position on the radiograph improved in
three of seven cases. Ulnar length gains ranged from 1.6 to 5.5
cm, with fixator durahon ranging from 14 to 26 weeks. Radial articular
angle improved to normal range in six of seven cases. The one
case that did not show improvement in radial articular angle was
not treated with a radial osteotomy.
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COMPLICATIONS
Complications were considered
minor, serious, or severe and occurred in four of seven (57%)
corrections. Inflammation in three of seven cases (43%) and flexor
tightness in three of seven cases (43%) were considered minor
because they resolved without significant intervention. Permanent
loss of motion was considered serious and occurred in three of
seven corrections (43%). No severe complications occurred (i.e.,
malunion, nonunion, fracture, neurologic injury, or deep infection).
No secondary admissions or surgeries were necessary other than
outpatient fixator removal.
Pin- and wire-site inflammation is the most frequent complication occurring in lower extremity lengthenings.7 This finding is in contrast to the relatively infrequent occurrence in this series in which three of seven patients (43%) had one temporary superficial infection requiring antibiotics. Several variables may explain this result: the status of the upper extremity as not bearing weight, the careful selection of wire and pin sites in the "hybrid" technique, fewer pin and wire sites, and the smaller pin and wire caliber used in these pediatric forearms.
Extrinsic finger flexor tightness occurred in three of seven corrections (43%), resolving with the use of dynamic sling and orthotic support.
Loss of motion of more than 10° occurred in three of seven corrections (43%). Loss of forearm rotation was particularly severe in case number seven, when a bulbous distal ulnar osteochondroma impinged against the distal radius as the ulna was lengthened. This impingement could be prevented by removing potentially impinging osteochondromas at the beginning of correction or even 1 year prior to instituting the lengthening.
Negative ulnar variance recurred in all cases at an average rate of 4 mm per year. Recurrence is diminished by over lengthening the ulna, however this is limited by the contact made between the distal ulnar epiphysis and carpus at the extremes of lengthening (Table 2).
SUMMARY
Careful preoperative planning,
fixator selection and design, surgical technique, and sustained
follow-up care are essential for successful gradual correction
of pediatric forearm deformities. The sequence of planning gradual
deformity correction can be created by establishing a problem
list and using this as the basis for design of the gradual correction.
Viewing limb length and deformity correction as a "process,"
rather than a procedure, is of value. Using a hybrid fixation
formula that combines half pins with wires can minimize the potential
for neurovascular injury. The combination of radial osteotomy,
excision of osteochondromas, and gradual ulnar lengthening by
distraction osteogenesis improves forearm appearance and function
in most patients with multiple hereditary exostoses.
Author's Perspective
There is great promise
for orthopedic reconstruction through distraction osteogenesis.
Based on many successes in 250 corrections, I have enthusiasm
for future applications. Along with this enthusiasm, however,
comes a sense of humility because these problems are quite difficult
to manage.
Special courses, tutorials, and visits with other surgeons are of value. When visiting another facility, surgeons generally focus on surgical technique; however, this is one area of orthopedics where patient care is crucial and observation in the clinics of experienced surgeons in addition to the operating room should be done. Additionally, the surgeon should establish a highly committed team to assist in the care of these patients. Furthermore, accurate documentation and the willingness to share success and failures are important in these evolving methodologies.
After careful analysis of the patient's condition, function, and the mechanical features of the deformity, the surgeon should allow liberal use of the imagination to create the best correction possible. Finally, realistic expectations, practical technical limits, and a full understanding of a patient's expectations should provide the means for establishing realistic goals.
ACKNOWLEDGMENT
The author thanks Jorie LePlavy for assisting in the preparation of this manuscript.
References
1. Bayley N: The Bayley Scales of Infant Development. Institute of Human Development, University of California, Berkeley. San Antonio, Texas, The Psychological Corporation, 1969
2. Burgess RC, Cates H: Deformities of the forearm in patients who have multiple cartilaginous exostoses. J Bone Joint Surgery [Am] 75(1):13-18, 1993
3. Carroll NC: Half-pin skeletal fixation in children. Bull Hosp Jt Dis Orthop Inst 51(1):88-92, 1991
4. Cooney WP: Contractures of the elbow. In Morrey BF (ed): The Elbow and Its Disorders, ed 2. Philadelphia, W. B. Sanders Co, 1993
5. Cooney WP, Dahl MT: Radial aplasia and distraction lengthening. Advances in Orthopaedic Surgery 16(3):150-161 1992
6. Dahl M, Gulli B, Berg T, et al: Complications of limb lengthening: A learning curve. submitted
7. Dahl M, Moore DP: Tibial llizarov wire site sequelae: A prospective bacteriologic study. submitted
8. Fogel GR, McElfresh EC, Peterson HA: Management of deformities of the forearm in multiple hereditary osteochondromas. J Bone Joint Surgery lam] 66(5):670-680, 1984
9. Green SA: Complications of External Skeletal Fixation. Springfield, Illinois, Charles C. Thomas, 1991, p 12
10. Irani RN, Petrucelli RC: Ulnar lengthening for negative ulnar variance in hereditary multiple osteochondromas. J Pediatr Orthop Part B 1:143-147,1993
11. Paley D, Tetsworth K: Mechanical axis deviation of the lower limbs: Preoperative planning of uniapical angular deformities of the tibia and femur. Clin Orthop 280:48-64, 1992
12. Pritchett JW: Lengthening the ulna in patients with hereditary multiple exostoses. J Bone Joint Surgery [Br] August, 1986
13. Shapiro F, Simon S, Glimcher M: Hereditary multiple exostoses. J Bone Joint Surgery [Am] 61:815-824,1979
14. Tetsworth K, Krome J, Paley D: Lengthening and deformity correction of the upper extremity by the llizarov technique. Orthop Clin North Am 22(4):689-713, 1991
15. Villa A, Paley D, Catagni MA, et al: Lengthening of the forearm by the llizarov technique. Clin Orthop 250:125-137, 1990
16. Wagner H: Operative lengthening of the femur. Clin Orthop 136:125, 1978
Address reprint requests to
Mark T. Dahl, MD
Minnesota Limb Length Center
606 South 24th Avenue #119
Minneapolis, MN 55454