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Functional and radiological outcome in patients undergoing three level corpectomy for multi-level cervical spondylotic myelopathy and ossified posterior longitudinal ligament
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.173654
Background: To review our experience with patients undergoing 3 level cervical central corpectomy (CC) with un-instrumented fibular autograft fusion. Keywords: Cervical; corpectomy; fibula; myelopathy; uninstrumented
Surgical management of patients with long segment (greater than [>] 2 vertebral levels) multi-level cervical spondylotic myelopathy (CSM) or ossified posterior longitudinal ligament (OPLL) is challenging, especially if there is an associated cervical kyphosis. These patients mandate a ventral decompressive surgical procedure and a complex reconstruction of the cervical spine.[1],[2],[3],[4],[5],[6],[7],[8] Surgical outcomes following central corpectomy (CC) in this group of patients may differ from those with a shorter segment of compression.[9],[10] It is generally perceived that the outcomes are worse in this group of patients with an increase in surgical morbidity and a higher incidence of graft related complications. Hence, some authors have advocated avoidance of >2 level CC.[11],[12] We have been routinely using uninstrumented CC for multi-level CSM and OPLL for the past two decades. We reviewed our experience with patients undergoing a 3 level CC.
Patient population We performed a retrospective analysis of all patients who underwent a three level CC for CSM or OPLL in the period 2002-2010. All patients were operated upon by the senior author (VR). This study was approved by the Institutional Review Board of our institution (IRB Min no: 9443). There were 33 patients who underwent a three level CC, out of a total of 401 CC performed in our department during the same period (8.2%). Out of these patients, 31 were male (93.9%) and 2 were female (6.1%) patients. The mean age at presentation was 52.0 years (range, 32 to 65 years). There was a preceding history of trauma in 3 patients (9.1%). All but one patient had features of myelopathy on presentation and there were 4 patients who had radicular pain in their upper limbs. 28 patients had sensory symptoms in the form of limb paresthesias and numbness, and 18 patients had complaints of urinary urgency. Neck pain was not a common symptom, and was present in only 7 of the patients. The mean duration of symptoms was 23.4 months (nearly two years), varying from as low as 2 months to as long as 120 months. The functional status of all these patients was classified according to the Nurick grading scale,[13] and ranged from 0 (only radiculopathy) to grade 5 (bed ridden), with a mean preoperative Nurick grade of 3.55. All patients underwent a three level CC with an autologous fibular graft without the use of any instrumentation. Thirty two of the 33 patients underwent a C4-6 corpectomy while one patient underwent a C5-7 corpectomy. In 19 patients (57.6%), the cervical cord compression was due to an ossified posterior longitudinal ligament, whereas the remaining patients either had a thickened posterior longitudinal ligament or vertebral body osteophytes causing cord compression. Surgical technique Patients were positioned supine with the head in skull traction and the neck in extension with a rolled up sheet under the shoulder. A longitudinal skin incision was made on the right side of the neck along the anterior border of the sternocleidomastoid. The prevertebral space was reached and the required disc spaces were identified with the help of intraoperative fluoroscopy. The intervening discoidectomies were done and the central 16 mm of the vertebral bodies were removed using rongeurs and drills. The posterior longitudinal ligament was excised in all patients. In some patients with OPLL densely adherent to the dura, the central part was “floated” off by sectioning it from the lateral, caudal and cranial parts of the OPLL. Mortises were made in the upper and lower vertebral bodies, and a fibular bone graft (obtained from the patient by the orthopedic surgeons during the same surgery) was fashioned to fit into the corpectomy defect. In the postoperative period, all patients were fitted with a Philadelphia cervical collar. The initial 10 patients were mobilized out of bed one week after surgery. But the later 23 patients were mobilized immediately after surgery. They were asked to wear the collar for six months postoperatively. Radiographic evaluation Plain lateral radiographs of the cervical spine were obtained in the preoperative period, in the immediate postoperative period (prior to discharge from the hospital) and at follow up. The following parameters were assessed on these radiographs:
Follow up Clinical follow up was obtained for 29 patients (follow up rate 87.9%) with an average duration of follow up of 65.1 months (12 to 138 months). This was achieved through out-patient consultation, letters and telephonic interviews. However, as our patients were from far flung regions of the country and could not attend our clinic for the follow up, we had radiological follow up for only 20 patients (60.6%). The Nurick grade of patients was re-assessed at follow up, and if there was a change in grade of 1 or more, it was considered as significant improvement. Statistical methods Data were entered into an Excel spreadsheet (Microsoft Inc.) and analyzed using IBM SPSS statistics, version 20 (IBM Inc.). Student's t test was used to compare means. A P < 0.05 was considered to be significant.
Duration of surgery The mean duration of surgery was 3.2 hours (range, 2.5 hours to 4 hours). Complications Five out of 33 patients (15.2%) had an intraoperative CSF leak. These were managed using fascial grafts and gelatin sponge as well as lumbar subarachnoid drains as described in a previous publication.[14] There were no other major intraoperative complications. Four patients had transient dysphagia postoperatively. Two of these patients had significant increase in the prevertebral shadow, which subsided with administration of steroids. One patient developed dyspnea and another patient developed respiratory arrest and subsequently pneumonia, requiring a tracheostomy. The patient later recovered and the tracheostomy was closed. Two patients developed a C5 radicular involvement postoperatively, with one complaining of sensory loss over the C5 dermatome, and another developing a mild shoulder abduction weakness. Both these patients improved symptomatically during their stay in the hospital. There were no mortalities and no instances of graft extrusion in our series. Cervical alignment and fusion There was no preoperative radiograph available for one patient. Of the remaining, 21 patients (65.6%) had a lordotic cervical spine on the preoperative radiographs, while 7 patients had a straight cervical spine and 4 patients (12.5%) had a kyphotic cervical spine. Of the 20 patients for whom we had radiological follow up, 9 patients had a lordotic cervical spine curvature, and 9 and 2 patients had straight and kyphotic cervical spines, respectively. The follow up cervical spine curvatures of these patients are shown in [Table 1].
The table shows that 5 out of 12 patients (41.7%) developed straightening of a lordotic spine, but no patient with a preoperative lordotic spine developed kyphosis postoperatively. Of the 5 patients with a preoperative straight spine with follow up imaging, the curvature became lordotic in one patient (20%), remained straight in 3 (60%), while in one patient (20%) it became kyphotic. The average segmental curvature of the cervical spine preoperatively was 11.400 ± 8.980 and in the immediate postoperative period was 4.260 ± 6.660 (difference of 7.140). On follow up radiographs (20 patients), the mean difference of the segmental curvature was 3.600. According to Carman et al.,[15] to reflect a true change in the segmental curvature, the change should be more than 100 [Figure 2] and [Figure 3].
The average graft height in the immediate postoperative period was 87.15 mm (±16.90 mm), and the mean reduction in graft height at the follow up visit was 5.70 mm (±7.30 mm). Out of the 20 patients who had a follow up radiograph available, fusion of the fibular graft occurred in 18 patients, thus giving a fusion rate of 90%. Follow up magnetic resonance imaging (MRI) Follow up MRIs were obtained in 13 out of 33 patients (39.4%). In all these patients, there was good decompression of the cord [Figure 4] and [Figure 5].
Functional outcome The mean preoperative Nurick grade was 3.55 and the mean follow-up Nurick grade was 2.42 (P = 0.0001). In calculation of the mean follow-up Nurick grade, we used the baseline-observation-carried-forward (BOCF) approach.[16] Hence in patients lost to follow up, we considered the follow-up Nurick grade to be same as their preoperative Nurick grade, thus giving a more accurate reflection of the treatment outcome. There were 5 patients who did not have any improvement in their Nurick score, although their neurological symptoms had improved. There was one patient who had deterioration in his Nurick grade from 3 to 4, but that was due to bilateral hip replacement that the patient underwent 2 years after our operation, thus requiring the support of a walking stick. Hence overall, there was no clinical deterioration documented in any of our patients. A comparison of the preoperative and follow up Nurick grades of the patients is summarized in [Table 2].
Most patients had improvement in their motor symptoms, with persistence of sensory symptoms. Also neck pain was documented in five patients at follow up, with one of them complaining of mild restriction of neck movements.
Strategies for long level decompression There have been a few studies published on long level corpectomies for CSM.[4],[9],[17],[18],[19],[20],[21] Saunders et al.,[20] documented a series of 4 level uninstrumented corpectomy. Fibular autografts [21] or even allografts [22] have been shown to be an effective means of long level arthrodesis in such surgeries. [Table 3] summarizes the outcomes in >2 level corpectomy published in literature.
The long duration of surgery and consequently, the prolonged retraction of soft tissues in the neck has been one of the factors leading to the avoidance of long constructs. The prolonged retraction sometimes leads to an increase in the prevertebral swelling, which may or may not present clinically as dyspnea or dysphagia, requiring the use of steroids. This swelling has been found to be maximum at C2 level in patients undergoing corpectomy, and was maximal on the third or fourth postoperative day.[25] At the level of the corpectomy, the swelling was found to be maximum on the fifth postoperative day.[25] As a pre-emptive measure, elective ventilation for 24 hours has been proposed in the postoperative period.[26] Edwards et al.,[11] suggested that long level laminoplasty was a better option than corpectomy for multi-level CSM. Others have suggested a “hybrid” CC wherein a CC is combined with an adjacent cervical discoidectomy and fusion. This would avoid the use of a long construct and its attendant problems.[27],[28],[29] Some surgeons prefer to do a posterior fusion in all patients undergoing >2 level CC.[30],[31] They believe that this would prevent acute graft extrusion. Acute graft extrusion Chances of acute graft extrusion are higher in longer level corpectomies. Wang et al.,[12] have shown graft displacement rates of 4.2% with one level corpectomy, 5.3% with two level corpectomy, 9.9% with three level corpectomy and 16.7% with four level corpectomy. Macdonald et al.,[19] analyzed a total of 36 patients undergoing multilevel cervical corpectomy and fibular allograft fusion. Their rate of graft migration was 11%, and the only predictive factor for it was the number of vertebral bodies involved. A rare complication of fibular grafting is a delayed fibular fracture,[32] which is primarily due to an osteoporotic bone allograft used from a common source. We have not come across any such complication in our experience. Titanium prostheses have been compared with fibular grafts for long level corpectomies, and have been shown to have less operative time and lower rate of dislodgement in the immediate postoperative period.[33] However, they have been associated with higher rates of reoperation. Graft fusion In an analysis of 126 patients undergoing multilevel discectomy and vertebrectomy,[34] the non-union rates were found to be 27% for autografts and 41% for the fibular allografts. Much higher fusion rates have been shown for strut grafts than multiple interbody grafting hence proving that the long level corpectomy is a better option than multilevel discectomy and fusion.[35] The median time for fusion of these grafts ranges from 85 to 90 days on an average, and it has been shown that the cephalad end fuses before the caudal end.[19] In our series, the fusion rate was 90%, which is comparable to the rates published in literature. Ikinega et al.,[24] published a case series of long level corpectomies with fibular grafts, using a one-screw technique and had a fusion rate of 85.1%. Postoperative sagittal alignment In a review of two and three level corpectomies with uninstrumented fusion using a fibular graft, a subsidence of 6-7 mm was seen, producing a loss of height rather than a kyphotic angulation.[36] A certain amount of settling is an integral part of a successful arthrodesis. Kyphotic changes at the fused segment may occur in patients undergoing one and two level corpectomies; however, this does not affect the functional outcome of these patients.[37] In our series, the mean difference in the segmental angle was 3.600 at follow up, which was not considered as a significant kyphotic change.[15] Functional outcome In CSM/OPLL patients, most studies have shown an overall improvement in the mean Nurick grade of patients undergoing CC.[8],[11],[13],[19],[23] Saunders et al.,[20] retrospectively analyzed 31 patients with CSM undergoing a four-level CC, and found an improvement of 1 Nurick grade or more in 80% of the patients. However in their study, they documented an overall morbidity rate of 38.7%, with the graft associated complication rate of 10%. In our series, we noted an overall improvement in the mean Nurick grade by 1.13, which was of statistical significance. There was improvement in the functional status of patients who presented with a poor Nurick score initially (Nurick 4 or 5), with 9 out of 14 such patients (64.3%) returning to full time employment. Limitations The limitations of this study were its retrospective design, invariably leading to a loss of follow- up for a few patients as well as variable follow-up durations. Appropriate radiographs were not available for a few patients included in the study, both preoperatively as well as on follow-up.
From our experience, we conclude that the three level un-instrumented corpectomy is a relatively safe surgery if performed by experienced surgeons. The surgical time is relatively short (average 3.2 hours). It avoids the additional morbidity associated with instrumentation or 360 degree fusion. Finally, it is economical as it avoids the financial burden of instrumentation. There was a significant improvement in the functional status of our patients, as shown by an improvement in the mean Nurick grade from 3.55 to 2.42. We have achieved a fusion rate of 90% with a transient morbidity rate of 28.6% and no permanent morbidity or mortality. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]
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