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Custom Halo Superstructure Applied Preoperatively to Craniopagus Conjoined Twins: A Case Report

Nicole Parent-Weiss, CO, OTR, FAAOP
Bruce Phillips

ABSTRACT

Craniopagus twinning is a condition that occurs when twins are born physically joined at the skull. It is an extremely rare occurrence and has rarely required orthotic intervention. This case report documents a custom design of orthosis to facilitate a unique and challenging goal of combining both motion limitation and selective mobility with adequate preoperative pressure relief. Craniopagus twins presented with a clinical need for pressure relief to the cranial area during a 5-month period of preoperative surgical separation skin expander placement. A custom halo superstructure/vest system was constructed from three-dimensional computed tomography-generated 3D models of the twins' torsos and heads. The challenge became the dynamic fit of the final orthosis to provide a balance of adequate pressure relief with preservation of the children's existing mobility. Although limited success was achieved with this intricate design, it provides a prime example of the possibilities of standard orthosis design modification and the possibilities that exist along with the importance of hands-on evaluation and continual re-evaluation for true clinical success. (J Prosthet Orthot. 2006; 18:120–123.)

Craniopagus twinning is a condition that occurs when twins are born physically joined at the skull. It is an extremely rare condition, with an incidence of 1 in 2.5 million births.¹ Twin boys from a small town south of Cairo were affected by this condition in which they were born fused at their skulls ( Figure 1 ). They lived the first 6months of their lives in Egypt under the care of Dr. Nasser Abdel-Al and the University of Cairo Medical Center. Consultation for evaluation of the possibility of surgical separation was obtained through Dr. Kenneth Salyer at Medical City Dallas Hospital. At the age of 16 months, the twins were transported to Dallas. The World Craniofacial Foundation, a nonprofit corporation founded by Dr. Salyer dedicated to helping children obtain craniofacial surgery, funded the trip and organized the doctor's volunteer efforts.

EVALUATION AND PROCEDURAL PROTOCOL

Multiple medical tests were conducted by the team of craniofacial and neurological surgeons in the evaluation of the twins' surgical separation. The determination was made that the twins had distinctly separate brains, with an overlap of only 10% of their brain tissue. Further magnetic resonance imaging and computed tomography (CT) scans revealed that many of the vascular structures were dependent, posing a challenging situation for the surgeons. After extensive evaluation, the first step toward separation was skin expander placement to allow stretching of the tissue to cover the defect that would arise once separation occurred. A low-air-loss bed (KinAir MedSurg, KCI USA, San Antonio, TX) was used during the time the tissue expanders would be in place. A custom device needed to be developed to prevent undue pressure on the fragile skin expanders and allow maximum protection during the 5 months the twins needed to allow the skin to stretch. The skin expanders were surgically placed on the twins' foreheads and on their legs and were filled with saline routinely to increase the size, thereby stretching the skin. Air mattresses were used to decrease pressure while they were lying down. The mobility level (rolling and sitting up head to head) of the twins was a concern during this phase of the procedure. Although their mobility was limited by their physical connection, they were able to move in several different ways. The goal was to retain as much of this learned mobility as possible. A specially adapted vest was designed to continue to allow the twins their limited mobility while ensuring protection of the skin expanders. This case study highlights a novel application for the orthotics and prosthetics field and underscores the need for the discipline to consider non-traditional applications.

ORTHOSIS DESIGN

The twins were evaluated in Dallas, Texas. The goal was to create a device that minimized pressure on the skin expanders without excessive limitation of existing mobility. It was a long-distance team approach, with clinicians from Medical City, Dallas Hospital (Dallas, Texas), engineering representatives from Medical Modeling, LLC (Golden, CO), KCI USA, Inc. (San Antonio, Texas), and orthotists and technicians from the acute care division at the University of Michigan (Ann Arbor). The process began with the receipt of a CT-generated three-dimensional (3D) model of the twins in their conjoined state, created by Medical Modeling, LLC ( Figure 2 ). This 3D model was wrapped with fiberglass to create a negative impression, taking care to preserve the details in the original model. Especially important to preserve was the orientation of each twin's face and torso. The negative fiberglass mold was removed from the 3D model and filled with plaster to create a positive impression with which to create an orthosis. The motion limitations required in the orthosis design included limiting cervical flexion and extension to prevent the head coming in contact with the bed, which could lead to resultant friction or pressure. Cervical rotation did not require limitation and was left free motion in the orthosis design. However, head support was necessary to support both twins' heads as they would essentially be floating above the air mattress on which they would lie. With the understanding that the halo cervicothoracic orthosis (halo CTO) is the most stable form of cervical immobilization,² a halo system was selected as the framework, with adaptations as necessary to allow motion that would not be detrimental to the integrity of the skin expander.

A modified double-halo vest system consisting of two interconnected superstructures and two modified custom-molded vests was constructed. The plastic vests were fabricated from thermoplastic (polyethylene) and molded over the positive plaster models ( Figure 3 ). During the fabrication process, spacers were used to allow room for removable sheepskin liners for pressure relief and growth adjustment. No ring or pins were used, and the only connections from vest to vest were modified superstructures connecting to one another via an additional adjustable transverse bar connection. An additional transverse bar was connected via standard universal clamps on the halo system to allow bypass of the typical connection to the ring ( Figure 4 ). The uprights that extended from the anterior and posterior section of each vest were adjustable for height and angle to allow for the twins' weight as they sank into the low-air-loss bed. Therefore, adjustability existed at the vest joints, both anteriorly and posteriorly, as well as at the universal clamps on the top and bottom transverse bar. This connection allowed increased space around the head and variable amounts of height so the twins could be lifted off the bed in coordination with the increasing size of the expanders.

The vest system was designed to be used in conjunction with the low-air-loss bed to decrease interface pressure on the skin expanders during the twins' time in bed ( Figure 5 ). The KinAir MedSurg low-air-loss bed would be necessary to allow the halo superstructure to sink lower relative to the head position. Using the device without the low-air-loss bed would unfortunately produce an unnatural position, making it unclear whether the twins would be able to tolerate its use. An additional roll bar was added to both sides of the framework ( Figure 6 ) to allow rolling side to side with momentum generated by the twins. This was reported to be a motion the twins were capable of without the device, and the goal was to continue to allow this freedom of motion. Although each head needed to be supported from falling into excessive extension, rotation motion did not need to be immobilized. Each twin, in coordinated motion, was able to turn his head to the side, and it would not be desirable to limit this. Therefore, a free rotation component was used to attach the posterior head supports. A round bar stock was connected to each head support and also connected to the posterior superior aspect of each vest in which free rotation could occur. The only approximation difficult to build into the design was the amount of space needed to prevent pressure posteriorly on the skin expanders. These head supports were made to be removable if pressure did occur ( Figure 7 ).

DISCUSSION

The adapted halo device was never used functionally for the twins because of the limitations. Therefore, considering the very limited functional use of the described device to provide pressure relief to the skin expanders during the 5-month time frame, an alternative device was constructed and used more successfully. This alternative device consisted of a modified air vest to allow elevation of the torso with subsequent relief over the precarious areas of skin while positioned on the low-air-loss bed ( Figure 8 ).

The custom halo was designed and constructed without the orthotist or orthotic technicians ever seeing the twins in person. As with any custom orthosis design, patient evaluation is vital to design formation, final fitting, and adjustment. The 3D CT-generated model provided an invaluable tool to fabricate a device that fit anatomically; however, challenges arose in making adjustments to accommodate the unique movement patterns in which these twins functioned. One unanticipated development was the twins' ability to extricate themselves from the vests despite what seemed initially a close intimate fit.

The custom halo's use only on the low-air-loss bed also served as an ultimate limitation to its functional use.

Use of the halo vests required a surface that allowed the superstructure to sink lower so the twins were not suspended above the surface. These custom halos could not be used on a flat surface, such as a mat or floor.

Dynamic motion of a patient, or in this case two patients, requires detailed hands-on evaluation with subsequent reevaluation and allowance for modification and adjustment. The halo is a proven device to achieve cervical immobilization.² The extremely adjustable components can, with creative design, allow not only immobilization but also a combination of immobilization with limited mobility. Clinical creativity is required to achieve this goal.

This case presented a unique opportunity to work with a referral source not generally seen in the orthotics and prosthetics (O&P) community. It also demonstrates the need for the O&P field to expand its realm of design possibilities to areas that may not ordinarily be considered. The purpose of this report is to increase awareness among O&P practitioners that the possibilities of our current designs and the unique modifications to those designs offer unlimited opportunities in nontraditional applications.

ACKNOWLEDGMENTS

Creative designs of this magnitude involve the contributions of many people. The authors particularly thank James Evans, RTPO, Nancy Evans, RTPO, ROA, and Thomas Lucas, ROA; the University of Michigan Orthotics & Prosthetics Center; and Dupuy Spine.

Correspondence to:Nicole Parent-Weiss, CO, OTR, FAAOP, University of Michigan Orthotics & Prosthetics, 1500 East Medical Center Drive, Box 0784, Ann Arbor, MI 48109; e-mail: .

NICOLE PARENT-WEISS, CO, OTR, FAAOP, is affiliated with the University of Michigan Orthotics & Prosthetics, Ann Arbor, Michigan.

BRUCE PHILLIPS is affiliated with KCI USA, San Antonio, Texas.

References:

1. Campbell S. Separation of craniopagus twins: the Brisbane experience. Child Nerv Syst 2004;20(8 –9):601–606.
2. Johnson R, Hart D, Simmons E, et al. Cervical orthoses: a study comparing their effectiveness in restricting cervical motion in normal subjects. J Bone Joint Surg Am 1977;59:332–339.