Paul W. Esposito
DEFINITION
Children with osteogenesis imperfecta (OI) and syndromes with congenital brittle bones sustain recurrent fractures and deformity, which cause chronic pain and limit their function.19,20
Multiple percutaneous osteotomies and percutaneous telescoping intramedullary nailing can improve comfort and function with lower morbidity than previously was possible.
The severity of bone disease, fracture incidence, degree of deformity, and functional level of the patient, as well as the patient's response to medical treatment, are more important in surgical decision-making than the specific diagnostic type of OI or brittle bone disease.
ANATOMY
There is broad variation in anatomic findings in the different types of OI and other brittle bone diseases that resemble it.
Some children have blue sclera, obvious dentinogenesis imperfecta, triangular facles, and ligamentous laxity, but this varies greatly, even within the same family, and many affected children have none of these findings.
The defining characteristics of children with OI are a varying degree of bone fragility, and recurrent fractures.
Progressive anterior bowing of the long bones is quite common, especially in children with moderate to severe involvement, even with early treatment with bisphosphonates (FIG 1).
Coxa vara, both apparent and true, can develop.8
PATHOGENESIS
OI is caused in the great majority of cases by dominant mutations in type I procollagen genes.
In the remaining cases, children may have brittle bone disease with a similar presentation and problems that are not caused by mutations in the type I procollagen genes.1,19
The flexors, such as the gastrocnemius muscles and hamstrings, contribute to the progressive bowing.
Secondary joint contractures may be seen as a result of the longstanding deformities.
NATURAL HISTORY
Historically, children with very severe OI, especially Sillence type II, rarely survived infancy, and children with types III and IV had severe disability secondary to recurrent fractures, bone pain, and deformities.24,25
Before bisphosphonate therapy was available, ambulation and even functional, comfortable sitting were difficult if not impossible for many children with severe forms of OI.
Even children with less severe forms of OI may have many significant fractures, which inhibit comfort, function, and quality of life.
Scoliosis and vertebral flexion fractures with secondary kyphosis are common.
Spondylolysis and spondylolisthesis are very common, especially in ambulatory children.
Progressive craniocervical abnormalities can occur and are not necessarily related to the overall severity of the OI.
PATIENT HISTORY AND PHYSICAL FINDINGS
Findings vary greatly depending on the type and severity of OI. In addition, findings on physical examination may change dramatically as children respond to treatment with bisphosphonates.
FIG 1 • A. Radiographs of an infant with moderately severe osteogenesis imperfecta (OI). B. At 16 months of age, bone strength is improved, but deformity does not remodel.
Possible physical findings include blue sclera, triangular face, dentinogenesis imperfecta, joint laxity, bowing of the arms and legs, and flattening of the skull, especially in infants with severe involvement, but these findings vary greatly even within the same family, and many of the children have none of these classic physical findings.
Flexible flat feet and externally rotated lower extremities are quite common.
A variety of presentations are possible, and children with subtle forms of OI may appear totally normal on physical examination, but present with multiple and recurrent fractures.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs are preferred as the initial study to evaluate children who have or may have OI.
Full-length radiographs of both legs on the same cassette from the hips to the ankles are ideal to assess areas of fractures and degree of deformity.
Radiographs of the lower extremity should be performed with the patellas directly anterior and also with the legs maximally externally rotated. This helps assess the severity of the disease, can help predict risk of fracture, and is useful in preoperative planning for osteotomies and instrumentation (FIG 2).
Standardized posteroanterior (PA) and lateral spine radiographs demonstrate spinal fractures, scoliosis and spondylolysis, and spondylolisthesis.
Bone density (dual x-ray absorptiometry [DEXA]) scans, although not perfect, can be useful in monitoring changes in bone density, using age-matched Z-scores and consistently using the same techniques and machine type. The DEXA scan alone, however, cannot be used for diagnosis, especially in infants, for whom no standardized validated Z-scores have been established.
The child's clinical course with regard to incidence of fracture and pain is a much more reliable indicator of successful medical treatment than a specific Z-score.
FIG 2 • Typical bowing deformity of the femurs and tibias caused by pre-existing deformity and recurrent fractures, accentuated by the pull of the flexors, including the hamstrings and gastrocnemius–soleus complex. Note sclerosis in the medullary canal of the right tibia.
DIFFERENTIAL DIAGNOSIS
Child abuse
Metabolic bone disease (eg, hypo- and hyperphosphatasia, rickets)
Idiopathic juvenile osteoporosis
NONOPERATIVE MANAGEMENT
Early diagnosis and treatment with bisphosphonates has significantly improved the lives of children with OI. This treatment positively alters the mechanical properties of their bones, decreases their fracture rate and pain, and enhances their psychomotor development.22
This improvement in bone density and strength often allows them to function at levels that previously were not possible by decreasing their bone fragility and pain.2,5,10,13
Surgical treatment for these children is now possible, whereas previously in many cases no surgical options existed because of the severity of their bone disease.
It has been suggested that treatment with pamidronate may be related to delayed healing of osteotomies—but not fractures—in children with OI.16,18
It remains unclear whether the incidence of delayed healing will decrease with lower doses of pamidronate.21
Casting, splinting, and bracing for many children with OI should be short-term temporizing measures only, because residual deformities will not remodel, and osteoporosis is worsened by prolonged immobilization.
SURGICAL MANAGEMENT
Intramedullary fixation of long bones in children with OI required extensive soft tissue disruption with traditional techniques.26
Insertion of telescoping and nontelescoping rods still requires extensive exposure and arthrotomies for insertion, and the reoperation rate is high.3–5,8,9,28,29
Improved surgical treatment has been made possible by the development of percutaneous techniques,14,15,23 as well as modification of existing nails and development of new nails for fixation, both telescoping7,8,11,12,27 and nontelescoping.9,11,14,23,28
Principles of Surgical Treatment
Primary indications for surgical treatment include recurrent fractures, pain, and deformity.
These approaches should be considered as children begin attempting to stand or crawl.
There is no advantage to waiting until the child is older.
Surgical treatment should be considered in acute fracture with deformity, even with less severe OI (FIG 3A, B).
Correct deformity and axial alignment.
Residual bowing does not correct with growth and predictably leads to further fracture.
As many involved, symptomatic bones should be corrected at one setting as can be safely accomplished.
Minimize soft tissue dissection and trauma.
Percutaneous technique provides more stability, less scarring, and earlier healing.
Minimize immobilization.
Light splints only
Early weight bearing and motion as symptoms allow
The role of bracing for long bones is not proven, and bracing may inhibit function.
FIG 3 • A,B. Plating of the proximal femur in a young child with progressive bowing pain and recurrent fractures at the end of the plate. C. An 8-year-old child treated with an adult nail with lateral migration distally, coxa vara, and proximal growth inhibition. D. The same child treated with the Fassier-Duval nail and valgus osteotomy 6 months postoperatively.
Use telescoping intramedullary devices whenever possible.
Use relatively small, flexible nails to share stress.
Rigid nails may lead to disappearing bone (FIG 3C, D).
Do not remove nails electively.
Plating predictably leads to stress reaction.
Indications in forearm are more limited.
Fixation in the forearm is less predictable, and has higher risks and rate of complications.
Instrumentation and bone quality are not optimal.
Such fixation should be considered only when comfort, motion, and function are significantly limited by deformity.
Preoperative Planning
The keys to surgical success are careful selection of children with adequate bone strength and density, and availability of an experienced team and appropriate equipment (FIG 4A).
Templates must be used to ensure that every appropriate size and type of device is available (FIG 4B).
FIG 4 • A. Fassier-Duval instrumentation tray. B. Templates for Fassier-Duval nail. (B: Courtesy of Pega Medical, Inc, Montreal, Canada.)
FIG 5 • Common severe anterior and lateral femoral bowing.
Radiographs can be used to estimate length and diameter of nails as well as to determine osteotomy sites (FIG 5).
Measuring the Fassier-Duval Nail
The distance from the greater trochanter to the distal femoral physis can be used to estimate the length of the female nail.
The female nail should be approximately 1 cm shorter than this distance.
Digital software and templates to determine length and diameter of the nails are available.
Angular correction can also be estimated on digital radiographs, but they can be deceiving because of the multiplanar nature of the angulation.
The female nail can be cut preoperatively, but I prefer to cut the female nail intraoperatively, after the osteotomies are completed.
Positioning
For fractures and deformities of the tibia and femur, the patient is placed in the semilateral position with an axillary roll and a long, padded posterior roll near the edge of the radiolucent table.
The leg can be gently rotated from the anteroposterior (AP) to the lateral position with the C-arm positioned on the opposite side of the table (FIG 6).
Only one leg can be prepped at a time especially if both the femur and tibia are being treated at the same surgical setting.
Bilateral tibial surgery can be done supine, but not femoral surgery.
FIG 6 • Positioning for lower extremity surgery.
Approach
For the femur, a 1.5-cm vertical incision is made, starting at the tip of the greater trochanter and extending proximally (FIG 7A).
The fascia of the abductors is then incised, exposing the white greater trochanter (FIG 7B).
The tibia is approached through a medial peripatellar incision, bluntly dissecting behind the patellar tendon when possible without disrupting the synovium. If necessary, an arthrotomy can be used to expose the starting point for the tibial nail just anterior to the tibial spines.
The humerus is approached through a small deltoid-splitting incision to expose the greater tuberosity.
FIG 7 • A. 1.5-cm incision proximal to the greater trochanter. B. Greater trochanter exposed.
TECHNIQUES
APPROACHES TO OSTEOGENESIS IMPERFECTA
Percutaneous Osteotomy With Intramedullary Telescoping FassierDuval Nail
The percutaneous technique described in this section is as described by Fassier and Duval7,8,17 with only minor technical variations.
The open technique, which is not described in this chapter, is performed the same way, with the following exceptions:
A larger incision at the osteotomy or fracture site
Retrograde guidewire placement and reaming of the proximal fragment
Passing the wire into the distal femur under direct vision
Guidewire Placement and Osteotomies in the Femur
Short and long guidewires are available, depending on the length of the femur.
Ideally, the tip of the guidewire is placed just medial to the center of the greater trochanter.
It may be difficult to visualize the greater trochanter in small children with poor bone density, and the insertion point may be necessarily in the piriformis fossa to avoid overreaming of the lateral cortex and to allow a straight line of advance to the femoral canal.
Avascular necrosis has not been demonstrated in children in whom this technique has been used.
The relation between the entrance point and use of the nail and the development of coxa vara is not clearly defined at this point1 (TECH FIG 1A).
The wire is then advanced to the first osteotomy site.
In many cases it is necessary to angle the wire markedly, both anteriorly and laterally, at first because of the very common severe anterior and lateral bowing of the femur in the subtrochanteric region.
Osteotomy sites are marked on the skin after visualization with the C-arm, based on preoperative templating and intraoperative visualization (TECH FIG 1B).
A 1-cm incision is made directly over the anterior lateral apex of the deformity.
Blunt dissection then is performed with a hemostat down to the periosteum (TECH FIG 1C).
The periosteum is incised longitudinally with a small osteotome, which is then rotated 90 degrees (TECH FIG 1D).
An incomplete osteotomy is performed while stability of the leg is maintained manually. The osteotomy is completed with gentle manual pressure, the guidewire is extended to the next osteotomy site, and the process is continued until all deformities are corrected.
The guidewire is then passed into the distal femur (TECH FIG 1E).
Use of a longer guidewire can help to avoid capturing the guidewire in the reamer.
A subtle flexion deformity often is present distally, in both the femur and tibia, that is not always apparent on the preoperative radiographs and that will cause the nail to go too far anteriorly.
TECH FIG 1 • A. Guidewire placed through the greater trochanter to the site of the first osteotomy. B. Localization for osteotomy. Reaming can be done at the site of the osteotomy to stabilize the proximal segment. C. A 1-cm incision is made over the apex of the osteotomy, and the soft tissues are spread to the periosteum. D. The osteotome is rotated and the osteotomy completed. Gentle manual traction and use of a lever such as a padded mallet will help to gently align and complete the osteotomy site. E. Guidewire in the distal femur.
Reaming and Placement of the Male Nail
The reamers are 0.25 to 0.35 mm larger than the corresponding nails.
The canal is reamed over the guidewire down to the distal femoral metaphysis, approximately 1 cm proximal to the physis in the center-center position on both AP and lateral radiographs (TECH FIG 2A).
The guidewire is removed to insert the male nail driver and nail after verifying the distal male nail thread length, while maintaining traction manually.
Avoid bending the rod and driver, to prevent impingement and damage to the nail.
The nail and driver cannot be used to forcefully manipulate the osteotomy or fracture site.
The nail and driver are passed to the center-center position in the distal metaphysis (TECH FIG 2B, C).
If the male nail requires redirection, it should be retracted slowly, while maintaining a gentle counterclockwise screwing motion to prevent dislodgment of the driver from the wing of the nail, which is not locked in the male nail driver (TECH FIG 2D).
On occasion, it may be necessary to remove the male nail and repeat the process.
Varus and valgus malalignment can be corrected with a distal osteotomy and correct placement of the nail in the center-center position in the distal femur.
Correct positioning is checked using AP and lateral views with the C-arm just before passing the male nail across the center-center position of the physis.
The threads are gently screwed into the epiphysis until the rounded portion of the rod located just proximal to the threads is bridging the physis.
Multiple transgressions of the physis are to be avoided.
The rod pusher is then placed into the cannulated portion of the male nail driver, and a sharp backward blow is made on the T handle. The C-arm verifies that the male nail is still engaged in the epiphysis (TECH FIG 2E).
Cutting and Insertion of the Female Nail
To measure the length of the female rod intraoperatively, it is placed with the threaded portion just at the top of the ossified greater trochanter with C-arm verification using a metal marking device distally approximately 1 cm above the physis (TECH FIG 3A).
The appropriate length of the female nail is verified with the C-arm, as previously discussed.
The female nail is covered with K-Y Jelly (Johnson & Johnson, New Brunswick, NJ) then cut with a diamondtip burr and cooled with sterile saline.
The cannulated portion must be checked to ensure that no metal will impinge on the male nail to prevent it from lengthening and that any metal shards are rinsed off (TECH FIG 3B, C).
The male nail driver is then removed, and the female nail is placed over the male nail.
The female nail is then screwed into the greater trochanter with the T-handle screwdriver until just a few threads are engaging the bony portion of the greater trochanter, and the upper part of the female nail is just palpable above the greater trochanter (TECH FIG 3D).
If the female nail is too shallow, it will back out, but if it is too deep, it is more likely to become overgrown and ultimately reside in the femoral canal.
TECH FIG 2 • A. The guidewire and reamer must be extended to the distal metaphysis in the central position on both the AP and lateral planes. The reamer can easily bind on the guidewire and be pushed distally. B,C. The male nail is then inserted to the center-center position at the distal metaphysis. At this point, valgus, varus, and distal flexion can be corrected. D. The male nail is not locked in the driver. E.Disengaging the male rod driver.
TECH FIG 3 • A. Measuring the female rod. B,C. Intraoperative cutting and trimming of the female nail. D. The female threads are shown just barely engaging the bones of the greater trochanter to mitigate overgrowth of the trochanter. E,F. Distal placement of the male nail driver and nail in the center-center position is mandatory. The threads engage the epiphysis of the distal femur, with the rounded, smooth portion traversing the physis.
The female nail is checked distally to be sure there is some space between its distal end and the wing of the male nail, to ensure that the male nail is not driven distally into the joint either acutely or with impaction of the osteotomy with weight bearing (TECH FIG 3E, F).
The male nail can be cut either with a front-biting heavy wire cutter or with the male nail cutters in the FD set.
Cutting the male nail approximately 1 cm above the top of the female nail rarely causes persistent symptoms and allows for more growth.
The probe is used to ensure that the cut male nail is smooth and not bent, which would prevent telescoping.
Occasionally, the diamond-tipped burr may be necessary to smooth the end of the male nail, but the soft tissues must be protected from debris and injury.
Coxa Vara
If true coxa vara is present, it should be corrected at the same sitting by combining this femoral nail technique with the valgus osteotomy described by Fassier and Glorieux8 (TECH FIG 4).
Revision
When a rod system requires revision after maximal telescoping, it usually can be retrieved through just a proximal incision.
A guidewire is placed in the greater trochanter and into the cannulated portion of the female nail under fluoroscopic control.
Specialized female and male retrievers, as shown, allow for intramedullary retrieval (TECH FIG 5).
TECH FIG 4 • Valgus osteotomy in conjunction with Fassier-Duval nailing to correct coxa vara. The lateral cortex is placed in the canal.
TECH FIG 5 • A. Female rod retriever. B. Male nail rod retriever. (Courtesy of Pega Medical, Inc, Montreal, Canada.)
Open osteotomy, cutting the rod and removing the segments, may be necessary to retrieve a broken or bent nail or one that has migrated laterally and distally. The male nail also may be retrieved with an arthroscopic alligator clamp after the female nail is removed.
Tibial Technique
Nails from the small-bone set are used. These have a somewhat shorter female-threaded portion to avoid extension of the threads across the proximal tibial epiphysis.
Injury to the anterior horn of the medial meniscus is avoided with arthrotomy if necessary.
A 0.62-inch K-wire or awl is placed just lateral to the anterior horn of the medial meniscus, and just anterior to the tibial spine in the non–weight-bearing surface. A soft tissue protector is helpful in directing the guidewire.
This usually places the wire in the midportion of the tibial epiphysis on the AP view and at the junction of the anterior and middle thirds on the lateral view.
With the knee kept flexed in excess of 90 degrees, the guidewire is passed into the center position of the proximal metaphysis and shaft.
Typically, the wire tends to go posteriorly and laterally so that the wire driver must be directed anteriorly and usually slightly medially.
Alternatively, the wire can be manually pushed into the epiphysis if this provides better control and visualization with the C-arm.
Avoid repetitive injury to the physis by checking the direction of the wire with the C-arm while it is still in the proximal tibial epiphysis. The guide pin can be advanced either with manual pressure on the pin or using a drill.
While maintaining hip and knee flexion, the lateral radiograph can be done by simply abducting and externally rotating the leg.
The guidewire is drilled down to the site of the first osteotomy, which often is the midto distal portion of the shaft of the tibia, although bowing of the proximal tibia also may be present.
To perform the tibial osteotomy, a 1.5-cm incision is made. The periosteum is visualized and partially elevated. Multiple osteotomies may be necessary (TECH FIG 6A).
A pure closed technique is more hazardous in the tibia.
When the medullary canal is obliterated by recurrent fracture and bowing, retrograde drilling is required to establish a medullary canal at the osteotomy site.
TECH FIG 6 • A. Incisions to correct multiple tibial deformities. B,C. Correct placement of the distal male nail after complete correction of anterolateral bowing. D,E. Correct proximal tibial nail placement.
The guidewire is then passed beyond the osteotomy.
Ideally, the entrance point to the distal tibial epiphysis is slightly posterior on the lateral view and slightly lateral on the AP view. This helps to avoid the tendency to valgus and anterior cut-out.
Closed osteoclysis of the fibula often can be performed with minimal force after the first osteotomy, especially in younger children, but open osteotomy may be necessary.
The reamer is passed down to the distal metaphysis while maintaining the knee in flexion at all times.
Reaming should be done slowly, with frequent stops at the apex of the angular deformity. This bone typically is quite dense in response to recurrent fractures.
Extending the knee while the reamer is in place can impinge and injure the femoral condyles.
The male nail is either cut after determining the length with the C-arm before placement into the tibia, which is my preferred technique, or inserted, removed, and then cut after the appropriate length is determined (TECH FIG 6B, C).
There is a small hole in the distal male nail to allow interlocking with a small wire, which is then bent over into the epiphysis. I have not used this technique and have concerns about migration and retrieval of the wire with growth.
The female nail is cut to length in the same manner as for the femoral technique, and inserted until the threaded portion is fully seated into the epiphysis.
It usually is visible just a few millimeters deep to the articular cartilage, even when the C-arm suggests that it is protruding into the joint (TECH FIG 6D, E).
The male nail cannot be left protruding into the joint, because it will injure the trochlear cartilage.
Humeral Nailing
The deltoid is spread in line with its fibers through a 1.5-cm incision, and the greater tuberosity is exposed.
The guidewire is drilled down into the shaft.
Typically, the diaphyseal deformity involves the midto distal shaft of the humerus when the guidewire is passed to the apex of angular deformity.
If a proximal deformity is present, an open or percutaneous osteotomy can be considered.
A distal anterolateral approach is used, and the radial nerve is identified and protected before the distal osteotomy is done.
The guidewires are then drilled down into the ossified capitellum after correction of the varus and anterior bowing.
The canal is then reamed to the size of the female nail down to the distal metaphysis.
The male nail is then placed down into the capitellum, which commonly leaves a slight amount of varus, which is well tolerated (TECH FIG 7A).
In older children, the nail can be placed into the superior segment of the ossified central trochlea, which allows better correction of the distal varus.
The small-bone female nail is used, cut to appropriate length before insertion. The upper end of the female nail should be deep to the articular cartilage to avoid impingement. This is verified by placing the shoulder through full range of motion (TECH FIG 7B–C).
TECH FIG 7 • A,B. AP and lateral male nail in capitellum. C.Female nail appears to be protruding but is actually deep to the articular cartilage and is not causing impingement. D. Two years postop. Note telescoping of nail. There is no clinical impingement.
POSTOPERATIVE CARE
Postoperative immobilization can be accomplished safely with lightweight radiolucent fiberglass wrapped under the foot to resist equinus and avoid heel pressure.
The splint can be extended up to the buttocks to support the femur, and loosely overwrapped with an elastic wrap.
Rarely, a percutaneous tendo Achilles tenotomy will be required.
Floor activities can be increased whenever the child is comfortable.
Weight bearing can begin in water approximately 4 weeks after the osteotomies achieve early healing and rotational control.
Gentle passive range of motion of the hips, knees, and ankles can begin as soon as the child is comfortable.
Hip, knee, ankle, and foot orthoses are a time-honored treatment and are used postoperatively in many centers.
Their effectiveness in avoiding recurrent fractures and deformity has not been demonstrated, however, and we do not use them in our center.
Many of the children are significantly more mobile without these orthoses, and healing is not impaired.
I prefer to limit use of orthoses to only those children with significant soft tissue laxity in the feet such that support is required for stability.
OUTCOMES
Improved comfort, a decreased rate of fracture, and an increased activity level are achieved in most children.
Long-term monitoring of these patients and constant improvement in instrumentation are necessary to ensure optimal development, comfort, and function in this patient population.
Revisions are still necessary as the children outgrow or damage the rods, but the instrumentation allows for a less traumatic experience for the patient and surgeon.
COMPLICATIONS
Complications include failure of telescoping of the rod, overgrowth of the greater trochanter, bending and breakage of the rods, as well as delayed union and nonunion.
Treatment for symptomatic complications of the rod is revision.
Fractures can occur even with satisfactory alignment, but recovery is typically rapid and requires short-term restriction of activities rather than long-term immobilization.
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