a technique of occipital spine

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SPINE Volume 26, Number 7, pp 8258292001, Lippincott Williams & Wilkins, Inc.

A Technique of Occipitocervical Arthrodesis inChildren Using Autologous Rib Grafts

Max W. Cohen, MD, Denis S. Drummond, MD, John M. Flynn, MD, Stephan G. Pill, MS, PT,

and John P. Dormans, MD

Study Design. Description of an operative technique

with an illustrative case report.

Objectives. The technique is presented to provide an

alternative to iliac crest graft procedures for achieving

occipitocervical fusion in children. This technique is par-

ticularly useful in children with instability after extensive

decompression or laminectomy and in children with a

large protuberant occiput.

Summary of Background Data. The majority of tech-

niques previously described for occipitocervical fusion in

children rely on corticocancellous iliac crest autograft.

Results generally have been promising; however, it can

be difficult to harvest enough graft to span large defects

after extensive decompression or to contour an iliac crestgraft to a protuberant occiput. Structural rib autograft is

superior in terms of availability and its unique and mod-

ifiable contour. Theoretical benefits of rib graft include

superior strength and lower donor site morbidity.

Methods. The surgical technique is described. A case

of a 2-year-old boy with Downs syndrome and myelop-

athy secondary to cervical instability is reviewed.

Results. The patient underwent occipitocervical arth-

rodesis using the technique described. The child made a

full neurologic recovery, and at the 2-years follow-up

evaluation, the graft had incorporated and the spine was

stable.

Conclusion. A technique of occipitocervical arthrode-

sis in children is described using autologous rib graft.

This procedure was designed to span large defects or todeal with a large protuberant occiput; however, it is also

useful for less demanding cases and may offer several

advantages compared with procedures relying on iliac

crest graft. [Key words: atlanto-occipital joint, arthrodesis,

child Downs syndrome, ribs spinal fusion] Spine 2001;26:

825829

Occipitocervical fusion is rarely done in children, but it isoccasionally indicated in the pediatric patient with cer-vical instability caused by a variety of congenital or ac-quired conditions. Several techniques have been de-

scribed, most using corticocancellous graft harvestedfrom the iliac crest. Fixation of the graft generally hasbeen accomplished with rigid wiring or heavy suturecombined with various methods of postoperative immo-bilization.2,3,5,7,8,14 Results generally have been favor-able; however, these techniques are not always applica-ble when the arthrodesis must span multiple levels

brought about by extensive laminectomy or decompres-sion. In addition, some patients have a difficult-shaped

occiput rendering a relatively straight iliac crest graftsuboptimal. This report describes a technique for occipi-tocervical fusion using autologous rib grafts, specificallydesigned for spanning large defects and for patients witha large or odd-shaped skull. The rib is an ideal structuralmaterial for these difficult cases. The shape of the graftcan be modified by the choice of rib and by moving theresection from the flatter posterior to the more curvedanterior portion of the rib. Childrens ribs are quite plas-tic and can be molded after harvest to fine-tune the lor-dotic contour of the graft. This should be limited to avoidcompromising the structural integrity of the rib. Theunique and modifiable shape of rib allows optimal con-tact between the graft and recipient bed. In contrast toiliac crest graft, procurement can be accomplishedthrough a single surgical field. Finally, rib is strong,readily available, provides low donor site morbidity, andregenerates rapidly in children.

Operative Technique

After intubation in the supine position, a halo ring is applied.

Subsequently, the patient is carefully positioned prone, and thehalo is secured to the operating table using the Mayfield posi-

tioning frame. The alignment of the occiput and cervical spineis confirmed with a lateral radiograph. The positioning, halo

application, reduction, and all subsequent surgery is performed

with somatosensory and motor-evoked potential monitoring.

The posterior thorax is included in the surgical field for harvestof the autogenous rib graft. The exposure extends from the

occiput to the second cervical vertebra or to the first vertebra

that is both below the level of instability and that has an intactposterior arch. Particular care is taken to limit the lateral dis-

section to avoid damage to the vertebral arteries.

A high-speed drill is used to make four burr holes through

both cortices of the occiput. The holes are aligned transverselywith two on each side of the midline and are placed caudal to

the transverse sinuses. A strong osseous bridge is left between

each pair of holes (Figure 1a). The area to be spanned by the rib

graft is evaluated for both overall length and sagittal contour.The caudal extent of the arthrodesis is determined by the pres-

ence or absence of a previous laminectomy, congenital anom-

alies, or the level of the instability.The graft harvest is accomplished through an oblique inci-

sion is made over the rib intended for harvest. The specific rib

as well as the portion of it to be harvested is determined by the

length and the optimal shape required to span the plannedarthrodesis (Figure 1b). The muscles of the posterior chest wall

are split in line with the incision down onto the thoracic cage.

From the Division of Orthopaedic Surgery, Childrens Hospital of Phil-adelphia, Philadelphia, Pennsylvania.Acknowledgment date: February 8, 2000.First revision date: May 10, 2000.Acceptance date: June 23, 2000.Device status category: 1.Conflict of interest category: 12.

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The periosteum overlying the rib is incised and circumferen-tially dissected and elevated. The graft is removed by cutting itproximally and distally with a rib cutter. Adequate rib shouldbe harvested so that enough is available for both structural andmoralized graft. After the graft harvest, the exposed pleura isinspected, and its integrity is confirmed. The wound is floodedwith irrigation fluid, and the lungs are hyperinflated. If no airleaks are observed, the wound is closed in layers. If there hasbeen an inadvertent injury to the pleura, this is repaired, and a

decision is made concerning the need for thoracostomydrainage.Two full-thickness structural grafts are precisely contoured

to the shape of the required arthrodesis site. On each side of themidline, 16-gauge wire is passed under the strong osseousbridge between burr holes. The wires are secured for later fix-ation of the graft. Alternatively, braided cable can be used inplace of wire. For patients who are very small or who have thinbone of poor quality, #5 Mersilene suture can be used to de-crease the risk of the wire or cable cutting out. Distal purchaseis accomplished with wire, cable, or suture passed under thelamina of the caudal vertebra, one on each side of the midline.The structural grafts then are positioned in the arthrodesis siteand, under radiographic control, secured into place by subse-quently twisting andcutting the previously placed wires (Figure1c). Reduction and alignment of the occiput and spine can becontrolled by positioning of the head with the halo frame, byadjusting the contour of the graft, and, to a lesser extent, byappropriate tightening of the wires. After acceptable alignmenthas been confirmed, moralized rib autograft is packed into thearthrodesis site, and the wound is closed in layers. The Halovest is applied and maintained for 812 weeks after surgery. Achest radiograph is taken in the recovery room to detect anoccult pneumothorax.

Case Report

The patient is 2-year-old boy with Downs syndrome who wasadmitted to the hospital with a 24-hour history of being unable

to walk or move his upper extremities. Three months before

admission, he experienced a minor trauma and developed a

torticollis to the right that resolved. He also was noted to have

a decrease in his ability to walk and use his upper extremities

during the past 2 months. On presentation, he had a marked

quadriparesis and was unable to move his extremities against

gravity. Respiratory efforts were noted to be weak. Radio-

graphs of the cervical spine revealed marked atlantoaxial sub-

luxation with a decrease in the space available for the cord

(Figure 2a). Magnetic resonance imaging again demonstratedsubluxation of C1 on C2 with compression and edema of the

spinal cord at this level (Figure 2b). The MRIwas repeated with

mild extension of the cervical spine, and the subluxation was

noted to reduce, relieving the cord compression. He was started

on Dexamethasone (4 mg IV every 6 hours) to control spinal

cord edema and electively intubated for hypoventilation and an

increasing PCO2. A halo vest was applied in slight extension,

and reduction of C1 on C2 was verified with a lateral radio-

graph. He was monitored in the intensive care unit and main-tained on ventilator support and intravenous steroids. Defini-

tive surgical intervention was delayed to allow for reduction in

spinal cord edema.

Five days after admission, he was taken to the operatingroom for an occipitocervical fusion using the technique de-

scribed above (Figure 2c, 2d). The decision to extend the arth-

rodesis to the occiput was made because of the high complica-tion rate reported with posterior cervical arthrodesis in

children with Downs syndrome.10 In addition, Tredwell et al13

have demonstrated the common occurrence of atlantooccipital

instability along with atlantoaxial instability in this patientpopulation. The patient was extubated 9 days after the arthro-

desis, and the halo vest was discontinued at 10 weeks when

there was radiographic evidence of fusion. The child made a

full neurologic recovery, and at the 2-year follow-up evalua-tion, the graft had incorporated, and the spine was stable in

flexion and extension.

Figure 1. A, Four burr-holes are placed into the occiput in transverse alignment, with two on each side of the midline, leaving a strong

osseous bridge between the two holes of each pair. B, Cranially,16-gauge wire is passed through each burr hole pair. Caudally, wires arepassed under the lamina on each side of the midline at the second cervical vertebra or at the first vertebra that is both below the levelof instability and that has an intact posterior arch. The rib graft is secured into place by twisting the wires.

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Discussion

The authors of the present study have previously re-ported on 16 consecutive children who underwent anoccipitocervical arthrodesis using autologous iliac crestgraft.2 Since reporting on these patients, the authors have

performed approximately 20 additional procedures us-

ing the same technique. Results have been promising;however, on several younger patients it was difficult to

obtain enough graft material. In infants, the iliac crest isrelatively small in comparison to the head and spine. Whenmultiple levels must be spanned after extensive decompres-

sion, there can be a shortage of iliac crest graft.

Figure 2. A, Boy with Downssyndrome and myelopathy. Lat-eral radiograph demonstratingsubluxation of C1 on C2. B, Post-

operative lateral radiograph afterreduction and occiput to C2 fu-sion using autologous rib graft. C,Lateral radiograph taken 2 yearsafter surgery demonstrating in-corporation of rib grafts.

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Iliac crest graft also can be suboptimal in patients witha large protuberant occiput. Hydrocephalus, for exam-ple, can alter the relation of the occiput to the cervicalvertebrae, placing the spine relatively anterior to theback of the skull (Figure 3). If a relatively straight iliaccrest graft is fixed proximally to the occiput and distally

to the caudal vertebra, the intervening segments of thespine will lie at a distance from the graft. Rib has uniquecurvature that can be customized to allow optimal con-tact with the recipient bed. This is accomplished by se-lecting a rib with an appropriate contour, by moving theresection from the flatter posterior portion to the morecurved anterior portion of the rib.

Autogenous rib has several practical and theoreticaladvantages over iliac crest as a graft for occipitocervicalfusion. Rib provides an abundant source of material, andit regenerates rapidly in children. Procurement is predict-able because rib can easily be resected en bloc, resultingin a more reliable corticocancellous structure comparedwith grafts taken from the iliac crest. Grafts applied tothe occipitocervical junction are subjected to multiplanarloads including flexionextension, axial rotation, andlateral bending.16 The circumferentially intact cortex ofrib makes it better suited to withstand these multiplanarloads.

A major limitation of iliac crest graft is donor sitemorbidity, the incidence of which exceeds 25% in someseries.1,9,12 The principle objection to using rib as a graftsource has been the potential for serous donor site mor-bidity, including pneumothorax and intercostal neural-gia. Whitaker et al15 reported a high rate of pneumotho-

rax complicating rib harvest used for craniofacial

reconstruction in a multi-institutional review. This num-ber approached 30% at some participating centers. Lau-rie et al6 reported on a similar patient population with a9% incidence of this complication. These investigatorsalso reported a 6.8% incidence of persistent dysestheticchest pain. Several small subsequent series reported a 3%and 0% incidence of pneumothorax and no cases ofchronic chest wall pain.4,11 Typically, the authors of the

present study have not experienced complications fromrib harvest, even when multiple ribs are removed in sco-liosis patients after thoracoplasty. Recently, Sawin et al9

reviewed a heterogenous group of 600 patients undergo-ing cervical spine fusion. Three hundred patients under-went rib harvest and posterior cervical arthrodesis. Theremaining patients underwent iliac crest harvest (248 foran anterior cervical arthrodesis and 52 for posterior ar-throdesis). The rib harvest group had a 3.7% complica-tion rate and 0% incidence of pneumothorax or chestwall pain. Iliac crest morbidity occurred in 25.3% of thepatients in this group. Fusion occurred in 98% of the rib

graft and 94% of the posterior iliac crest constructs,leading these authors to conclude that autogenous rib issuperior to iliac crest for posterior cervical arthrodesis interms of donor site morbidity and rate of osseous union.

The technique described in this report was designed todeal with a difficult-shaped skull or to span laminectomydefects in children requiring occipitocervical arthrodesis.The procedure also should be useful in less demandingsituations and may offer several advantages comparedwith iliac crest procedures in terms of donor site morbid-ity, graft strength, and rate of fusion.

Key Points

Rib has a unique and modifiable contour thatmakes it ideal for posterior occipitocervical arthro-desis in children. Rib is strong, readily available, and provides lowdonor site morbidity. Structural rib graft is particularly useful whenspanning large laminectomy defects or to deal witha protuberant occiput in children requiring occipi-tocervical arthrodesis.

References

1. Banwart JC, Asher MA, Hassanein RS. Iliac crest bone graft harvest donor

site morbidity. A statistical evaluation. Spine 1995;20:105560.

2. Dormans JP, Drummond DS, Sutton LN, et al. Occipitocervical arthrodesis

in children. A new technique and analysis of results. J Bone Joint Surg 1995;

77A:123440.

3. Georgopoulos G, Pizzutillo PD, Lee MS. Occipitoatlantal instability in chil-

dren. A report of five cases and review of the literature. J Bone Joint Surg

1987;69A:42936.

4. Kline RM, Wolfe S. Complications associated with the harvesting of cranial

bone grafts. Plast Reconstr Surg 1995;95:513.

5. Koop SE,WinterRB, Lonstein JE.The surgical treatmentof instability of the

upper part of thecervical spine in children andadolescents. J Bone Joint Surg

1984;66A:40311.

6. Laurie SW, Kaban LB, Mulliken JB, et al. Donor-site morbidity after har-

vesting rib and iliac bone. Plast Reconstr Surg 1984;73:9338.

Figure 3. Adolescent girl with spina bifida, controlled hydroceph-alus, and spinal stenosis of the upper cervical spine. Because ofprogressive myelopathy, extensive decompression and arthrode-

sis was done from the occiput to C4. Structural rib graft was usedto span the protuberant occiput and the extensive laminectomydefects. Lateral radiograph 1 year after surgery showing incorpo-ration of the rib grafts. Heavy suture was used to secure the graftsbecause of the patients poor bone quality.

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7. Letts M, Slutsky D. Occipitocervical arthrodesis in children. J Bone Joint

Surg 1990;72A:116670.

8. Rodgers WB, Coran DL, Emans JB, et al. Occipitocervical fusions in chil-

dren.Retrospective analysis and technical considerations. Clin Orthop 1999;

364:12533.

9. Sawin PD, Traynelis VC, Menezes AH. A comparative analysis of fusion

rates anddonor-site morbidityfor autogeneic riband iliac crest bone graftsin

posterior cervical fusions. J Neurosurg 1998;88:25565.

10. Segal LS, Drummond DS, Zanotti RM, et al. Complications of posterior

arthrodesis of the cervical spine in patients who have Downs syndrome.

J Bone Joint Surg 1991;73A:154754.

11. Skouteris CA, Sotereanos GC. Donor site morbidity following harvest ofautogenous rib grafts. J Oral Maxillofac Surg 1989;47:80812.

12. Summers BN, Eisenstein SM. Donor site pain from the ilium: a complication

of lumbar spine fusion. J Bone Joint Surg 1989;71B:67780.

13. TredwellSJ, Newman DE, Lockitch G. Instability of the upper cervical spine

in Downs syndrome. J Pediatr Orthop 1990;10:6026.

14. Wertheim SB, Bohlman HH. Occipitocervical fusion. Indications,technique,

and long-term results in 13 patients. J Bone Joint Surg 1987;69A:8336.

15. Whitaker LA,MunroIR, SalyerKE, Jetal. Combined reportof problems and

complications in 793 craniofacial operations. Plast Reconstr Surg 1979;64:

198203.

16. White AA, Panjabi MM. The clinical biomechanics of the occipitoatlanto-

axial complex. Orthop Clin North Am 1978;9:86778.

Address reprint requests to

Denis S. Drummond, MDDivision of Orthopaedic Surgery

Childrens Hospital of Philadelphia2nd Floor Wood Building

34th and Civic Center BlvdPhiladelphia, PA 19104

829Occipitocervical Arthrodesis Using Rib Grafts Cohen et al

a technique of occipital spine

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