Multilevel anterior cervical corpectomy and fibular allograft fusion for

J Neurosurg 86:990–997, 1997

Multilevel anterior cervical corpectomy and fibular allograft fusion for cervical myelopathy R. LOCH MACDONALD, M.D., PH.D., F.R.C.S.(C), MICHAEL G. FEHLINGS, M.D., PH.D., F.R.C.S.(C), CHARLES H. TATOR, M.D., PH.D., F.R.C.S.(C), ANDRES LOZANO, M.D., PH.D., F.R.C.S.(C), J. ROSS FLEMING, M.D., F.R.C.S.(C), FRED GENTILI, M.D., F.R.C.S.(C), MARK BERNSTEIN, M.D., F.R.C.S.(C), M. CHRIS WALLACE, M.D., F.R.C.S.(C), AND RONALD R. TASKER, M.D., F.R.C.S.(C) Section of Neurosurgery, University of Chicago Medical Center, Chicago, Illinois; and Division of Neurosurgery, The Toronto Hospital, University of Toronto, Toronto, Canada U This study was conducted to determine the safety and efficacy of multilevel anterior cervical corpectomy and stabilization using fibular allograft in patients with cervical myelopathy. Thirty-six patients underwent this procedure for cervical myelopathy caused by spondylosis (20 patients), ossified posterior longitudinal ligament (four patients), trauma (one patient), or a combination of lesions (11 patients). The mean age (6 standard deviation) of the patients was 58 6 10 years and 30 of the patients were men. The mean duration of symptoms before surgery was 30 6 6 months and 11 patients had undergone previous surgery. Prior to surgery, the mean Nurick grade of the myelopathy was 3.1 6 1.4. Seventeen patients also had cervicobrachial pain. Four vertebrae were removed in six patients, three in 19, and two in 11 patients. Instrumentation was used in 15 cases. The operative mortality rate was 3% (one patient) and two patients died 2 months postoperatively. Postoperative complications included early graft displacement requiring reoperation (three patients), transient dysphagia (two patients), cerebrospinal fluid leak treated by lumbar drainage (three patients), myocardial infarction (two patients), and late graft fracture (one patient). One patient developed transient worsening of myelopathy and three developed new, temporary radiculopathies. All patients achieved stable bone union and the mean Nurick grade at an average of 31 6 20 months (range 0–79 months) postoperatively was 2.4 6 1.6 (p , 0.05, t-test). Cervicobrachial pain improved in 10 (59%) of the 17 patients who had preoperative pain and myelopathy improved at least one grade in 17 patients (47%; p , 0.05). Twenty-six surviving patients (72%) were followed for more than 24 months and stable, osseous union occurred in 97%. These results show that extensive, multilevel anterior decompression and stabilization using fibular allograft can be achieved with a perioperative mortality and major morbidity rate of 22% and with significant improvement in pain and myelopathy.

KEY WORDS • cervical spine • myelopathy • spondylosis • corpectomy • spinal cord

ATIENTS with cervical spondylosis, ossification of the posterior longitudinal ligament (OPLL), a combination of these diseases, or occasionally trauma, may have spinal cord compression that extends over multiple levels. Surgical options in these cases include decompression and stabilization at the level that is most affected, laminectomy or laminoplasty, anterior discectomies at multiple levels, or multilevel anterior corpectomies.1,2,8,12,16,24 Stabilization may be achieved using iliac crest or fibula autograft or allograft with or without instrumentation.3,6,17,22,23 There are few reports of the outcomes in patients undergoing multilevel anterior corpectomies and stabilization using fibular allograft.6 In this study we reviewed the cases of 36 patients who underwent this procedure for a variety of pathological conditions. The goals were to determine the efficacy of the procedure, the rate of complications, and the time it takes for the fibular graft to attain

P

990

osseous union. An additional goal was to determine if there were factors that could be used to predict postoperative complications such as delayed neurological worsening and displacement, nonunion, or fracture of the graft. Clinical Material and Methods Patient Population

All patients who underwent corpectomies involving two or more vertebral bodies and implantation of fibula allografts at the Toronto Hospital between 1988 and 1992 were included. Thirty-six patients were identified and all medical records and radiographs were reviewed. Data were collected on patient demographics, diagnosis, prior surgical treatment for cervical spine disease, history and physical examination findings prior to surgery, occupational status, and neuroradiological presentation. Details J. Neurosurg. / Volume 86 / June, 1997

Fibular strut grafting on duration of surgery, levels decompressed and fused, length of the bone graft, blood loss, evoked potentials, instrumentation used, and intraoperative complications were obtained from operative records. Operative Procedure

The indications for surgery were progressive myelopathy with spinal cord compression documented on computerized tomography (CT) myelography or magnetic resonance (MR) imaging. Instability or pain was present in some cases but was not a primary indication for surgery. Traction was not used to try to reduce deformities in patients with postlaminectomy kyphosis because of the limited reduction that can be obtained and because of the risk of neurological deterioration. The preoperative plan was to perform surgery in all patients placed in a halo head ring with 5-lb traction while using somatosensory evoked potential monitoring. The surgical procedure was similar to that described by Saunders, et al.,20 and was performed through a longitudinal incision along the anterior border of the sternocleidomastoid muscle. A right-sided approach was used unless there had been extensive previous surgery on that side, in which case the spine was approached from the left side. After obtaining a radiograph to confirm the levels to be removed, the operating microscope was brought in and the corpectomies were performed using rongeurs and an air drill. The osteophytes and the posterior vertebral body cortices were removed using a diamond burr drill and/or 1- or 2-mm bone punches. The corpectomy was at least 15 mm wide. In all cases of OPLL and in most cases of cervical spondylosis, the posterior longitudinal ligament was removed using sharp dissection. Following decompression, a 5- to 7-mm-deep hole, approximately 1 cm in diameter, was drilled into the upper and lower vertebrae with respect to the corpectomies to accept the bone graft. A piece of fibular allograft was fashioned with rounded ends and seated deeply into the upper and lower vertebrae under traction. The bone graft did not project anteriorly, as with some techniques.1 For the duration of this study, cervical reconstruction plates longer than 55 mm were unavailable. In some cases, an anterior cervical plate was applied spanning the fusion or at the upper and/or lower end of the fusion. Thirty-five patients were then placed in external halo fixation for 3 months. Follow-Up Evaluation

The patients were followed clinically and radiographically with plain and dynamic cervical spine films at 3 and 6 months and then every 6 months postoperatively. Indications for CT scanning or MR imaging were progression of neurological symptoms and signs, inability to determine osseous union of the graft from plain radiographs, or a complication of graft placement such as displacement or fracture. For assessment of fusion, postoperative flexion–extension radiographs obtained at 3- to 6-month intervals were reviewed. The individual reviewing the radiographs was blinded to the time after surgery when the radiographs were obtained. Other criteria were then judged by comparing radiographs across time. J. Neurosurg. / Volume 86 / June, 1997

TABLE 1 Nurick’s functional classification of myelopathy Grade

0 1 2 3 4 5

Condition

signs or symptoms of root involvement; no evidence of spinal cord disease signs of spinal cord disease; no difficulty walking slight difficulty walking; fully employed difficulty walking that prevents fulltime employment or ability to do all housework; not requiring ambulatory aids ability to walk w/ help or w/ aid of cane or walker chairbound or bedridden

Definitions and Endpoints

Myelopathy was graded according to Nurick’s grading system18 (Table 1). Osseous union of the graft was defined as complete bridging of the trabeculae between the bone graft and the adjacent vertebral body.4 Instability was defined as more than 5˚ of angulation observed using flexion–extension views.29 Displacement of the graft was present if there was more than 2 mm of displacement at either end of the graft as assessed by a comparison of intraoperative or immediate postoperative films and subsequent films.6,29 Collapse was defined as a more than 2mm loss of height of the graft or as a penetration of the graft into the upper or lower vertebral body (“telescoping”). Kyphosis was defined as greater than 5˚ of angulation developing postoperatively. Collapse and kyphosis were also assessed by a comparison of intraoperative or immediate postoperative films and subsequent films. Fibrous union was judged to be present when there was no instability or displacement of the graft and also no osseous union. A pseudoarthrosis was present when there was instability and no osseous union.29 For statistical analysis, the superior and inferior ends of the bone graft were assessed independently so that there were 72 fusion sites in the 36 patients. Statistical Analysis

Data were coded and entered into a computer. Uni- and multivariate statistical analysis, one-way analysis of variance, and linear regression were used to determine whether there were variables that would predict postoperative Nurick grade or displacement or nonunion of the bone graft. Data are presented as means 6 standard deviation. The level of significance was established at p , 0.05. Results Clinical Results

There were 30 men and six women in the study with an overall mean age of 58 6 10 years (Table 2). The mean preoperative Nurick grade was 3.1 6 1.4 and this improved significantly to 2.4 6 1.6 (p , 0.05) at a mean follow-up time of 31 6 20 months (Table 2). The Nurick grades of 15 patients did not change after surgery, whereas seven patients improved one grade, 10 patients improved two or more grades, and four patients deteriorated by one or more grades (Table 3). Deterioration in Nurick 991

R. L. Macdonald, et al. TABLE 2 Demographic and clinical characteristics of 36 patients who underwent multilevel cervical decompression and fibular allograft fusion

TABLE 4 Characteristics of surgery in 36 patients who underwent multilevel cervical decompression and fibular allograft fusion Characteristic

Characteristic

No. of Patients

mean age in yrs (range) sex ratio mean preop Nurick grade (range) mean duration of symptoms (range) prior surgery laminectomy discectomy total diagnosis spondylotic myelopathy OPLL spondylosis & OPLL trauma spondylosis & trauma

58 6 10 (22–75) 30 M:6 F 3.1 6 1.4 (1–5) 30 6 6 mos (1 day–120 mos) 3 8 11 20 4 5 1 6

grade was due to development of symptomatic lumbar spinal stenosis in two patients and hip osteoarthritis in one patient. These changes made patients unable to work or unable to ambulate without an aid, thus decreasing their Nurick grade by one grade in each case. One patient with severe cervical spondylosis progressively deteriorated from Grade 1 to Grade 4 at 6 months follow-up review. Neuroradiological investigations showed adequate spinal cord decompression. The patient was subsequently lost to follow up. Patients with severe myelopathy could improve substantially, although recovery took up to 2 years to occur. Six (38%) of 16 patients who had Nurick Grades 4 or 5 before surgery improved more than one grade. It was observed, however, that a statistically significant predictor of postoperative Nurick grade was the patient’s preoperative grade (r2 = 0.53, p , 0.0001). There was also a significant relationship between worsening Nurick grade and shorter duration of preoperative symptoms (r2 = 0.14, p , 0.05). This relationship persisted even after excluding patients suffering from trauma who presented acutely with severe myelopathy. Diagnoses included cervical spondylotic myelopathy (20 patients), OPLL (four patients), trauma (one patient), trauma and spondylosis (six patients), and spondylosis plus OPLL (five patients) (Table 2). Eleven patients had

TABLE 3 Changes between preoperative and postoperative Nurick grades of myelopathy assessed a mean of 29 months postoperatively Postop Nurick Grade (no. of patients) Preop Nurick Grade

0

1

2

3

4

5

Total

0 1 2 3 4 5 total

0 3 2 1 0 0 6

0 1 2 1 1 0 5

0 0 4 0 1 2 7

0 0 2 2 2 2 8

0 1 0 1 4 0 6

0 0 0 0 0 4 4

0 5 10 5 8 8 36

992

Value

vertebral bodies removed (no. of patients) 2 3 4 mean 6 SD (range) length of graft in mm (mean 6 SD [range]) duration of surgery in hrs (mean 6 SD [range]) instrumentation (no. of patients) blood loss in ml (mean 6 SD [range])

11 19 6 2.9 6 0.7 (2–4) 72 6 16 (42–105) 7.9 6 2.5 (4–18) 15 660 6 610 (100–3000)

undergone previous surgery, which included three laminectomies and eight discectomies. Neck and upper limb pain were prominent symptoms in 17 patients (49%, excluding one patient with acute trauma). This pain improved postoperatively in 10 patients (59%). The mean number of vertebral bodies resected was 2.9 6 0.7, with two vertebral bodies resected in 11 patients (31%), three in 19 patients (53%), and four in six patients (17%) (Table 4). Evoked potential recordings were obtained in 27 cases. There was no change in neurological condition in two patients who had intraoperative changes in their evoked potentials, and adequate recordings could not be obtained and recording was abandoned in the patient who awoke from surgery with increased myelopathy. The average hospital stay was 27 6 22 days. Radiographic Outcome

Evidence for osseous union of the graft appeared approximately 5 months after surgery (Table 5 and Figs. 1–3). There was a progressive increase in osseous union over time so that by 24 months postoperatively, 96% of the grafts assessed had osseous union at both ends. Pseudoarthrosis was present in some cases at 3 to 6 months and at 9 to 18 months, although fibrous or osseous union occurred at subsequent follow-up review. There was TABLE 5 Postoperative radiographic findings in 36 patients who underwent multilevel cervical decompression and fibular allograft fusion Feature

3–6 Mos Postop

9–18 Mos Postop

$24 Mos Postop

no. of patients osseous union superior inferior fibrous union superior inferior pseudarthrosis superior inferior displacement superior inferior collapse kyphosis

31

15

26

0 4

9 6

26 25

27 22

4 7

0 1

4 5

2 0

0 0

2 4 0 1

0 1 0 1

0 2 2 2

J. Neurosurg. / Volume 86 / June, 1997

Fibular strut grafting TABLE 6 Postoperative complications in 36 patients who underwent multilevel cervical decompression and fibular allograft fusion* Complication

acute surgical transient C-5 radiculopathy transient increased myelopathy recurrent laryngeal nerve palsy vertebral artery injury dysphagia graft displacement cerebrospinal fluid leak esophageal injury acute medical deep vein thrombosis myocardial infarction reintubation pneumonia sepsis gastrointestinal hemorrhage death delayed increased myelopathy graft displacement new deafferentation pain graft fracture skull penetration by halo pin death

No. of Patients

3 1 4 1 2 3 3 1 2 2 3 2 1 1 1 4 2 2 1 1 2

FIG. 2. Magnetic resonance image obtained 6 months after a three-level corpectomy of C4–6 and stabilization using fibula allograft in a 41-year-old patient with multilevel cervical spondylosis and two traumatic cervical spine injuries. The MR image, obtained to follow the posttraumatic syrinx, shows an adequate decompression with bulging of the thecal sac into the decompression site.

* Acute = within 30 days of surgery; delayed = more than 30 days postoperatively.

early displacement of the graft at the upper or lower end in four patients (11%). At 24 months there was telescoping of the graft into the lower vertebra in two cases. This was associated with osseous union in one case and fibrous union in the other case. The only factor that could be used to predict whether a graft complication would develop, such as displacement, telescoping, or fracture, was the number of vertebral bodies that were removed (analysis of variance, p , 0.05). Graft complications were more likely to occur with longer decompressions. Although instrumentation was used in 15

cases, two grafts that became displaced had instrumentation, and displacement was associated with screw pullout. One patient was not placed in external halo fixation after surgery; however, acute displacement of the graft prompted reoperation and subsequent placement in external halo fixation. Complications of the Surgery

Twenty patients (56%) developed 30 complications or died within 30 days of surgery (Table 6). The most common neurological change was a C-5 radiculopathy that was transient (less than 3 months in duration) in all cases.

FIG. 1. Left: Lateral radiograph obtained immediately postoperatively, showing a fibular strut graft extending from C-2 to C-6. Center: Postoperative radiograph, obtained 2 years later, displaying complete incorporation of the graft with ossification along the anterior aspects of the vertebral bodies. Right: A CT myelogram, obtained because the patient developed increasing pyramidal tract dysfunction, showing that there is adequate decompression of the cord. The patient was found to have lacunar cerebral infarctions.


993

R. L. Macdonald, et al.

FIG. 3. Left: Magnetic resonance image obtained in a 53-year-old patient presenting with progressive numb, tingling hands. It was not recognized that the low signal intensity posterior to the C-3 and C-4 vertebral bodies represented OPLL. Center: A CT scan showing the OPLL. The scan was obtained after an anterior cervical discectomy and fusion at C4–5 failed to relieve her symptoms. The patient underwent anterior corpectomies at C3–5 and the inferior part of the C-2, followed by a fibula strut graft and instrumentation. At the time this procedure was performed, long cervical reconstruction plates were unavailable. Accordingly, a buttress plate was used at the caudal end of the construct. Right: Immediate postoperative radiograph showing the instrumentation. The patient made substantial improvement and the graft progressed to osseous union.

Acute increases in myelopathy, recurrent laryngeal nerve palsy, vertebral artery injury, and dysphagia did not result in permanent morbidity. Cerebrospinal fluid leaks were managed using lumbar drainage and pseudomeningoceles did not develop. The one case of esophageal injury was partial thickness and did not cause morbidity. Three grafts became displaced within days of the surgery and the patients required reoperation. One patient with gastrointestinal bleeding required a laparotomy. One patient died due to cerebral venous sinus thrombosis 2 days postoperatively. Seven delayed complications occurred in six patients (17%) and two patients died due to medical complications 2 months postoperatively. Two patients developed new disabling postoperative pain that had characteristics of deafferentation pain, one in the upper limb and one in the lower limb. One patient who had a graft placed between C-3 and C-7 had plates that were placed across the lower and upper ends of the graft but did not span the entire graft. In this case the graft fractured between the plates 1 year postoperatively, requiring the patient to undergo a posterior fusion. Serial radiographs in two patients who had undergone two- or four-level vertebrectomies, during which the lower ends of the grafts were buttressed by plates, showed progressive anterior displacement of the graft and plate. Osseous fusion occurred in one case and surgery was required in the other case. Overall, surgical mortality or permanent major morbidity occurred in eight patients (22%). Discussion Multilevel anterior corpectomies and fibular allograft fusion were associated with significant improvement in a consecutive series of 36 patients with relatively severe myelopathy, as evidenced by their poor overall Nurick grade and by their having had previous surgeries. This was associated with a 22% incidence of mortality and major morbidity. Fusion of the graft took up to 24 months 994

to occur, during which time approximately 15% of the grafts showed some displacement. Longer decompressions and grafts were more likely to be associated with displacement, fracture, or telescoping into the vertebral body. Previous Studies

There are reports in the literature with which to compare these results, although all of these focus on patients undergoing corpectomies and fusion with autografts (Table 7).1–3,5,9–11,14,19,20,22,23,25,26,28 Previous reports also differ in the degree of preoperative neurological deficit, the number of levels decompressed, and the type of graft used. Among the 227 cases that were reported in detail, two vertebral bodies were removed in 136 cases (60%), three in 80 cases (35%), and four in 11 cases (5%). Autografts were used in all cases and were obtained from the iliac crest in 116 patients (51%), the fibula in 25 (11%), the tibia in three (1%), and from unspecified sources in 83 patients (37%). One hundred sixty-one patients (71%) had cervical spondylotic myelopathy, 26 had OPLL (11%), seven (3%) had a combination of these diseases, 17 (7%) had postlaminectomy kyphosis, 13 (6%) had trauma, and three (2%) had other conditions. The fusion was supplemented with instrumentation in 36 patients (16%). The complication rates in these series ranged from 3 to 48% with an overall average of 31%. Surgical mortality was less than 1%. Improvement in myelopathy occurred in approximately 50 to 60% of patients, which is similar to the rate observed in this study. Our review of the literature indicates that the rate of graft complications increases as the number of levels decompressed increases and as the number of patients with previous procedures, particularly laminectomy, increases. This series confirms the first of these findings. There was one case of vertebral artery injury in this series, which occurred in a patient who had undergone prior surgery and a lateral subluxation and rotation of the cervical spine that J. Neurosurg. / Volume 86 / June, 1997


2 (13), 3 (4)

2 (3), 3 (4)

30

10

14

17

7

Boni, et al., 1984

Yonenobu, et al., 1985

Hanai, et al., 1986

Bernard & Whitecloud, 1987 Brown, et al., 1988

37

8 13

Saunders, et al., 1991

Seifert & Stolke, 1991 Herman & Sonntag, 1994

* Approximate. † After graft displacement.

21

2 (7), 3 (1) 2 (11), 3 (2)

2 (15), 3 (22)

2 (3), 3 (6), 4 (2) 2 (14), 3 (7)

2 (12), 3 (13), 4 (1)

26

11

2 (2), 3 (5)

7

Zdeblick & Bohlman, 1989 Okada, et al., 1991

Tippets & Apfelbaum, 1988 Kojima, et al., 1989

2 (2), 3 (6), 4 (7) 2 (20), 3 (9), 4 (1) 2

15

2

2 2 (7), 4 (1)

3 8

No. of Levels (no. of cases)

Cattell & Clark, 1967 Whitecloud & LaRocca, 1976 Hanai, et al., 1982

Authors & Year

No. of Cases

iliac crest or fibula iliac crest or fibula unspecified autograft iliac crest iliac crest

fibula or iliac crest fibula or tibia iliac crest

fibula

iliac crest

iliac crest

iliac crest

iliac crest

tibia fibula

Type of Bone Graft

53* 57 6 15

64*

58*

48 6 19

57 6 7

cervical spondylotic myelopathy postlaminectomy kyphosis

cervical spondylotic myelopathy

cervical spondylotic myelopathy (6), trauma (1) swan neck (1), neck pain (2), myelopathy (4) cervical spondylotic myelopathy (8), OPLL (11), cervical spondylotic myelopathy & OPLL (7) cervical spondylotic myelopathy (8), trauma (2), tumor (1) cervical spondylotic myelopathy

51 6 15 50 6 17



cervical spondylotic myelopathy, trauma cervical spondylotic myelopathy

postlaminectomy kyphosis cervical spondylotic myelopathy (7), trauma (1) OPLL

Diagnosis (no. of cases)

not stated

55*

56 6 9

17–75

55 6 7

12 6 1 44 6 12

Patient Age (yrs)

0 13

0

0

9

2*

3*

1

0

0

0

0

0

0 1

8 13

0

0

0

0

7

7

0

0

0

1†

0

0 0

InstruPrior mentaSurgery tion (no. of (no. of cases) cases)

6 mos–13 yrs

not stated

17 6 17 17 6 7*

Follow Up (mos)

18% 38%

48%*

22%*

27%

24%

20%*

57%

5%*

21 (8–46) 28 6 9

2–5 yrs

49 (28–70)

27 6 11

not stated

1–15 mos

15 (3–24)

32 (12–89)

30% non- 30* (12–88) union 3%* 36*

28%*

20%

0% 35%*

Complications

Outcome

all fused, myelopathy better in 74%* 23% stable, 77% neurologically improved

Japanese Orthopedic Association score increased from 7 6 2 to 14 6 3 postop 58% cured, 15% failures

preop Nurick Grade 4 6 1 improved to 1 6 2

preop Nurick Grade 3 6 1 improved to 2 6 1

no fusion failures

all patients improved

Japanese Orthopedic Association score increased from 8 6 2 to 14 6 3 postop Japanese Orthopedic Association score increased from 9 6 3 to 14 6 1 postop preop Nurick Grade 3 6 1 improved to 2 6 2

all improved, stable union 1 graft displaced, reoperated; myelopathy improved in all cases 1 excellent, 8 good, 6 fair/good; bone union not reported 92%* good/moderate, 8% poor

TABLE 7 Summary of reports of multilevel anterior vertebrectomy and autograft fusion for cervical myelopathy*

Fibular strut grafting

995

R. L. Macdonald, et al. distorted the anatomy. Attempts at wider decompressions may increase the risk of this complication but it is believed that the decompression must be at least as wide as the spinal cord, although data are not provided in the present report to support this assumption. Another graft complication was telescoping of the hard, cortical bone fibula into the cancellous bone of the vertebral body above or below. This may be avoided by not drilling through the endplate of the vertebral body, although this results in less fixation of the graft unless internal fixation with screws in the graft itself is used. Care must be used when drilling and placing screws in the fibula because of the tendency of the brittle cortical bone to fracture. Anterior Versus Posterior Approach

Current surgical results of anterior decompressive surgery appear to improve on the natural history of cervical spondylosis.1–3,5,9–11,14,19,20,22,23,25,26,28 Good and excellent results also have been reported for posterior approaches for myelopathy caused by multilevel cervical spondylosis or OPLL and a retrospective review of 269 patients undergoing operation by various approaches did not find that one approach was superior to another.12 Prospective randomized and long-range studies have been proposed to compare anterior and posterior approaches, as well as nonoperative management, before definitive conclusions can be reached.20,24 The variable natural histories, pathologies, and pathogeneses will require that many patients be studied before we can draw meaningful conclusions. The present results cannot be used to recommend any specific approach over another but they do indicate what can be achieved. Type of Graft

The advantages of using autograft are that vascularization and ossification may occur more rapidly than when using allograft, based on studies in experimental animals.4,6,21,27,29 The disadvantages of allograft include theoretical concerns about immunological reaction to the graft and an increased risk of infection. The use of allograft avoids the incidence of graft-site morbidity and mortality, which occur in up to 29% of cases; allograft yields uniformly strong cortical and cancellous bone in a great variety of shapes and sizes; allograft reduces postoperative pain; and it shortens operative time.4,7,15,21,27,29 For single-level anterior cervical spine surgery, there is no appreciable difference in fusion rates using allograft or autograft.4,21,27 There is less information available with which to compare the use of allograft and autograft in multilevel corpectomies. The results of this study suggest that fusion rates are as high as with autograft, although the time it takes for fusion to occur (approximately 2 years) is longer and the rate of graft complications may be higher. Fernyhough, et al.,6 compared 67 patients who underwent multilevel discectomy and fusion using fibula autograft with 59 patients undergoing the same procedure but with fusion with fibula allograft. Complete corpectomies were not performed and the patients were placed in a hard collar for 12 weeks after surgery. After a mean follow-up period of 83 months, pseudarthrosis occurred in 25% of 996

the patients with autograft and in 36% of the patients with allograft. Nonunion was more likely to occur with the increasing number of levels fused. The authors recommended adding a posterior fusion or using more rigid external fixation to increase the rate of union. Another option is to use anterior instrumentation or a vascularized autograft.3,11,13,17,22,23 Indications for Instrumentation

In this series, instrumentation was used when the surgeon had the impression at surgery that the graft was not solid and was at risk for displacement or when the patient underwent repeated surgery because the graft had become displaced or fractured. The use of instrumentation to supplement suboptimal graft placement could have contributed to the pullout of two plates. Another factor was the lordotic curve of the cervical spine, which resulted in the superior surface of the lower vertebra sloping anteriorly, creating a force vector that could contribute to the inferior end of the graft displacing anteriorly. Clearly, the use of plates and screws reduces but does not eliminate graft complications.3 There may be an increased risk of infection, and late complications include screw pullout. Screw pullout occurred in 5% of 20 patients undergoing surgery for postlaminectomy kyphosis, a situation in which the risk may be higher.11 In this study, fracture of the graft at the ends or at the junction of plates across the upper and lower ends of the graft was also observed. The patients reviewed in this report underwent surgery before the widespread availability of long anterior cervical plates and before we had extensive experience using this instrumentation. The use of instrumentation is believed to decrease the risk of graft complications and to obviate the need for temporary external fixation in cases in which the posterior column is intact. We currently use internal fixation in preference to a halo ring and vest for patients who undergo multilevel corpectomies, although the options should be discussed with the patient preoperatively. In patients with posterior column instability as a result of prior laminectomy who are at higher risk of anterior instrumentation failure, supplementing anterior plates with posterior internal fixation with lateral mass plates at either the same or a second operation has been considered or a halo vest can be used. There are recent reports of adequate fusion in such patients using only anterior instrumentation.11 Conclusions The results of this series and the analysis of previously reported series shows that two-, three-, or four-level corpectomies using fibular allograft fusion and halo ring and vest external fixation results in improvement in cervical myelopathy in 47% of cases and carries an approximately 22% risk of perioperative mortality and morbidity. Although it is believed that the decompression must be at least as wide as the spinal cord (approximately 14 mm), care must be taken to avoid injury to the vertebral artery. The risk of complications increases with the increasing length of the decompression and in patients who have undergone previous procedures. Current techniques for anterior internal fixation can usually obviate the need for J. Neurosurg. / Volume 86 / June, 1997

Fibular strut grafting a halo ring and vest, although they are still associated with a small risk of graft complications. In the presence of a laminectomy, consideration may be given to additional fixation using a halo ring and vest or to posterior internal fixation placed either at the same surgery or subsequently. References 1. Bernard TN Jr, Whitecloud TS III: Cervical spondylotic myelopathy and myeloradiculopathy. Anterior decompression and stabilization with autogenous fibula strut graft. Clin Orthop 221:149–160, 1987 2. Boni M, Cherubino P, Denaro V, et al: Multiple subtotal somatectomy. Technique and evaluation of a series of 39 cases. Spine 9:358–362, 1984 3. Brown JA, Havel P, Ebraheim N, et al: Cervical stabilization by plate and bone fusion. Spine 13:236–240, 1988 4. Brown MD, Malinin TI, Davis PB: A roentgenographic evaluation of frozen allografts versus autografts in anterior cervical spine fusions. Clin Orthop 119:231–236, 1976 5. Cattell HS, Clark GL Jr: Cervical kyphosis and instability following multiple laminectomies in children. J Bone Joint Surg (Am) 49:713–720, 1967 6. Fernyhough JC, White JI, LaRocca H: Fusion rates in multilevel cervical spondylosis comparing allograft fibula with autograft fibula in 126 patients. Spine 16:S561–S564, 1991 7. Gore DR, Sepic SB: Anterior cervical fusion for degenerated or protruded discs. A review of one hundred forty-six patients. Spine 9:667–671, 1984 8. Goto S, Mochizuki M, Kita T, et al: Anterior surgery in four consecutive technical phases for cervical spondylotic myelopathy. Spine 18:1968–1973, 1993 9. Hanai K, Fujiyoshi F, Kamei K: Subtotal vertebrectomy and spinal fusion for cervical spondylotic myelopathy. Spine 11: 310–315, 1986 10. Hanai K, Inouye Y, Kawai K, et al: Anterior decompression for myelopathy resulting from ossification of the posterior longitudinal ligament. J Bone Joint Surg (Br) 64:561–564, 1982 11. Herman JM, Sonntag VKH: Cervical corpectomy and plate fixation for postlaminectomy kyphosis. J Neurosurg 80:963–970, 1994 12. Hukuda S, Mochizuki T, Ogata M, et al: Operations for cervical spondylotic myelopathy. A comparison of the results of anterior and posterior procedures. J Bone Joint Surg (Br) 67: 609–615, 1985 13. Kaneda K, Kurakami C, Minami A: Free vascularized fibular strut graft in the treatment of kyphosis. Spine 13:1273–1277, 1988 14. Kojima T, Waga S, Kubo Y, et al: Anterior cervical vertebrectomy and interbody fusion for multi-level spondylosis and ossification of the posterior longitudinal ligament. Neurosurgery 24:864–872, 1989


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