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SCIENTIFIC ARTICLE
The next generation of telescoping rod (Bailey-Dubow) helped to eliminate this by increasing the interval to reoperation by nearly double the time (2.5 to 5 years); however, it suffered to dissociation and migration necessitating further surgery. The that is rigidly attached to the rod resulting in a marked decrease in revision surgery.52 The Fassier-Duval rod has a threaded tip frequently in the lower extremity as opening of the ankle joint can be avoided.26 Complications of rodding include extrusion, migration, iatrogenic physeal injury, nonunion, infection, and rotational deformity.51,54 Use of these rods in conjunction with mobility improvements, and easier self-care.55
Implant selection depends on growth patterns and bone diameter with expandable rods being preferred because they splint the bone along their entire length. In general, the largest diameter used.52 In situations where the boney diameter can be larger than the largest available telescoping rod (i.e. femur), dual Rush rods have been described as an acceptable alternative technique.54 In some patients, the opposite problem can occur with a medullary diameter too narrow to accept the smallest telescoping rod without creating a longitudinal split in the bone. In such instances Kirschner wires may be used. Alternatively, the bone may be deliberately split longitudinally, followed by securing the ends
of the rod into the epiphysis, and then re-approximating the split pieces to the rod. These fragments can be sutured together and bone graft may be used to augment healing.26
The widespread use of bisphosphonates at increasingly earlier ages has led to a decrement in the magnitude overall thus facilitating minimally invasive rod insertion. Fluoroscopic guidance can be used to determine the level of osteotomy and boney exposure occurs only at these levels thus preserving blood supply, periosteum, and cortical thickness.56
It should be noted that coxa vara (femoral neck-shaft angle
< 110 degrees) occurs in approximately 10 percent of patients with OI resulting in gait impairment. Deformity correction can be achieved at the time of intramedullary device implantation by passing the rod from the piriformis and out of the lateral cortex of the femur just below the greater trochanter.32
Deformities of the upper extremity are less common and much better tolerated by OI patients. Surgical indications are less well
function such as wheelchair use and interference with activities of daily living.57
Although the effect of spinal deformity on pulmonary functional capacity remains unknown, some authors recommend spinal fuse progression.33 With improvements in BMD as a result of screws can be employed. Luque instrumentation is also an acceptable method of correction.58
FUTURE DIRECTIONS
One area of current research in the treatment of OI focuses on bone marrow transplantation (mesenchymal stem cells). The stem cells to differentiate into functional mesenchymal cells with resultant normal collagen synthesis.59,60 Currently there are only sporadic case series with positive preliminary data.61 Another area of research is gene therapy in the form of antisense suppression therapy. This modality attempts to decrease or silence the mutated allele in order to decrease the severity of OI.62-64 Major limitations for the diseased allele as well as stability.28
The use of a nickel-titanium alloy called nitinol for the use of OI fractures is underway due to the metal’s “memory” properties. to bend bones toward the original shape of the nitinol wires with hopes that these principles can be used in boney deformities seen in OI.65
CONTRIBUTING AUTHORS
■ KAYVON R. GOLSHANI, MD is an Orthopaedic Surgery Resident at Georgetown University Hospital in Washington, DC.
■ MERYL R. LUDWIG, MD is an Orthopaedic Surgery Resident at Georgetown University Hospital in Washington, DC.
■ PETER L. COHN, MD is an Orthopaedic Surgery Resident at Georgetown University Hospital in Washington, DC.
■ RICHARD KRUSE, MD is a Pediatric Orthopaedic Surgeon
at Nemours/Alfred I. duPont Hospital for Children in Wilmington, Del.
Del Med J | June 2016 | Vol. 88 | No. 6
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