Interbody fusion cages were developed as a stand-alone device to augment arthrodesis via the anterior approach. Their introduction caused resurgence in interbody fusion for degenerative disorders. Cages have demonstrated their ability to function as load-sharing devices and to adequately fixate the spine and increase segmental stiffness thus achieves acceptable fusion rates [5].
Some surgeons have reported poor outcomes and fusion rates secondary to a high rate of cage subsidence and pseudoarthrosis. They believed that this phenomenon occurred as a result of insufficient fixation power of cage alone. Allowing postoperative micro-motions to continuously occur between the contact surfaces of the cage and vertebra, these continuous micro-motions prevent the induction of bone fusion [6]. Internal fixation using anterior cervical plate (ACP) has been developed in order to enhance the stability provided by the intervertebral cages, to help prevent graft dislodgement, and ultimately to promote mature bony fusion of the spinal segment. Some authors reported lesser graft dislocations or collapse and higher fusion rates after ACDF with internal fixation compared with ACDF alone [7].
In postoperative results in our study, there was a statistically significant relief of cervical pain after surgery in both groups (P < 0.05) but no significant difference between the two groups (P = 0.64). In Hwang and colleagues [8] series, he showed similar results in both groups.
In our study, brachialgia was significantly improved after surgery in both groups (P < 0.01 in both groups). In Liu and colleagues [9] series, the mean post-operative VAS arm pain score was significantly improved compared with preoperative score.
We assessed patient satisfaction using Odom’s criteria of outcome grading. In group A, 36.8% of patients had excellent recovery, 31.6% had good recovery, 15.8% had fair recovery, and 15.8% had poor recovery. In group B, 42.9% had excellent recovery, 21.4% had good recovery, 2 patients 14.3% had fair recovery, and 21.4% of patients had poor recovery.
In Uribe and colleagues [10] series, 83.3% of patients had excellent recovery, 14.3% had good recovery, 2.34% had fair recovery, and no patients had poor recovery among 42 non-plated patients. In the study by Wang and colleagues [7], 28.1% had excellent recovery, 50.9% had good recovery, 15.8% had fair recovery, and 5.2% of patients had poor recovery among 57 plated patients.
At 1-year follow-up examination, we achieved 78.9% fusion rate in group A and 85.7% in group B. In Hwang and colleagues [8] series, the rate of fusion at 1-year follow-up was 90.6% in 32 non-plated patients and 91.7% in 24 plated patients. Criteria of fusion included detection of presence of bone formation between the cage and vertebral endplates, also through lack of motion in the postoperative dynamic X-rays.
Cervical plate fixation, however, is not free from complications and morbidity. Significantly higher complication rate was reported in patients managed by anterior cervical plate than patients managed by interbody fusion cages alone. After surgery, we reported adverse effects such as transient dysphagia which was the most common complication. It occurred in 10 (52.6%) of group A patients and in 12 (85.7%) of group B patients. Dysphagia was probably more accentuated in group B patients due to longer duration of surgery and traction on the esophagus. Dysphagia was mild in all these patients and lasted only for few days. Dogan and colleagues [11] mentioned in his series that transient dysphagia occurred in 5 (22.7%) of 22 non-plated patients while Song and colleagues [12] reported dysphagia in 4 (9.3%) of 43 plated patients.
In our study, transient hoarseness of voice occurred in two (10.5%) of group A patients and in four (28.6%) of group B patients. The hoarseness lasted only for few days in all cases and resolved spontaneously. Cage subsidence occurred in five (26.3%) of group A patients and in two (14.3%) of group B patients in this study. Subsidence was referred to loss of height as ≥ 3 mm of the direct postoperative intervertebral height compared to the intervertebral one or presence of pseudoarthrosis at the follow-up radiographs. In all these patients, the subsidence occurred within the first 3 months but no further progression was demonstrated on follow-up radiographs 12 months after surgery and the subsidence did not produce any symptoms in these cases without recurring nerve root compression and required no further management. In other series, rate of subsidence was 32.3% in the stand-alone cage group as compared to 9.7% in the cage and plate group [13].
In Erol and colleagues [14] cohorts, subsidence of cages was measured by any decrease in the disc space narrowing of at least 3 mm. They assumed that subsidence in cervical stand-alone interbody cage fusion is a major problem and additional stabilization is necessary to avoid this problem [15]. Thus due to cage subsidence, the foraminal height decrease, loss of segmental lordosis, and cervical spine instability can lead to adjacent segment degeneration [16].
To minimize the risk of subsidence, the surgeon should avoid aggressive removal of the bony end-plate; the best is to remove parts of the end plate to promote fusion and to leave other parts intact to minimize subsidence. Proper size of the cage should be used as a larger cage size will increase the possibility of subsidence. Also, avoidance of overdistraction and forceful implantation reduces the risk of subsidence [17].
In our study, 2 patients (14.3%) in group B developed instrumentation failure in the form of loosening of a plate and screw with no clinical problems or neurological complications and were managed conservatively. There were no cases of plate or screw fracture. This coincides with the results of Song and colleagues [18] series in which 3 (14.3%) of 21 patients developed instrumentation failure in the form of loosening of a plate and screw.
