Computed Tomographic Evaluation of Adjacent Segment Motion after Ex Vivo Fusion of Equine Third and Fourth Cervical Vertebrae

Objective Surgical fusion of vertebral segments is a treatment option for horses with cervical stenotic myelopathy or cervical fracture.Degenerative disease affecting adjacent vertebral segments is a reported complication following surgical vertebral fusion in other species, termed adjacent segment disease. The aim of this study was to evaluate the impact of cervical vertebral fusion on the biomechanics of adjacent vertebral segments in the horse. Study Design Neck specimens of 12 horses were assessed using computed tomographic imaging. Range of motion (ROM) was determined by measuring the maximum sagittal flexion, extension and lateral bending between C2 and C5. C3/4 was subsequently fused using a standard locking compression plate and locking head screws and computed tomographic scans and ROM measurements were repeated. Results Prior to intervertebral fusion, a significant increase in ROM along the vertebral segments from cranial to caudal was observed. Range of motion measurements of C3/4 decreased significantly after fusion (p = 0.01).Range of motion of the adjacent segments (C2/3 and C4/5) did not change significantly after fusion. Conclusion Fusion of one cervical intervertebral joint did not affect the ROM of the adjacent vertebral segments. Further research investigating the implications of vertebral fusion on the intervertebral pressure in the equine patient is indicated.

Outcome of Ventral Fusion of Two or Three Cervical Vertebrae with a Locking Compression Plate for the Treatment of Cervical Stenotic Myelopathy in Eight Horses

Objectives It was recently shown that biomechanical stability achieved with a locking compression plate (LCP) for ventral cervical fusion in horses is similar to the commonly used Kerf cut cylinder. The advantages of the LCP system render it an interesting implant for this indication. The goal of this report was to describe surgical technique, complications and outcome of horses that underwent ventral fusion of two or three cervical vertebrae with an LCP. Methods Medical records of eight horses were reviewed for patient data, history, preoperative grade of ataxia, diagnostic imaging, surgical technique and complications. Follow-up information was obtained including clinical re-examination and radiographs whenever possible. Results Two (n = 5) or 3 (n = 3) cervical vertebrae were fused in a mixed population with a median age of 9 months, median weight of 330 kg and median grade of ataxia of 3/5. A narrow 4.5/5.0 LCP (n = 6), a broad 4.5/5.0 LCP (n = 1) and a human femur 4.5/5.0 LCP (n = 1) were applied. Two horses were re-operated due to implant loosening. Six patients developed a seroma. Long-term complications included ventral screw migration in four, spinal cord injury in one and plate breakage in two horses at 720 to 1116 days after surgery. Outcome was excellent in three, good in four, poor in one patient. Clinical Significance The use of an LCP for ventral cervical vertebral fusion is associated with good clinical results. However, a careful surgical technique is required to further reduce the complication rate.

Treatment of cervical stenotic myelopathy: a cost and outcome comparison of laminoplasty versus laminectomy and lateral mass fusion

Object Cervical stenotic myelopathy due to spondylosis or ossification of the posterior longitudinal ligament is often treated with laminoplasty or cervical laminectomy (with fusion). The goal of this study was to compare outcomes, radiographic results, complications, and implant costs associated with these 2 treatments. Methods The authors analyzed the records of 56 patients (age range 42–81 years) who were surgically treated for cervical stenosis. Of this group, 30 underwent laminoplasty and 26 underwent laminectomy with fusion. Patients who had cervical kyphosis or spondylolisthesis were excluded. An average of 4 levels were instrumented in the laminoplasty group and 5 levels in the fusion group (p < 0.01). Forty-two percent of the fusions crossed the cervicothoracic junction, but no laminoplasty instrumentation crossed the cervicothoracic junction, and it only reached C-7 in one-third of the cases. Preoperative and postoperative Nurick grades and modified Japanese Orthopaedic Association (mJOA) scores were obtained. Outcomes were also assessed with neck pain visual analog scale (VAS) scores and the Odom outcome criteria. Postoperative length of stay, complications, and implant costs were calculated. Results The mean duration of follow-up, average patient age, and length of hospital stay were similar for both groups. The mean Nurick scores were also similar in the 2 groups and improved an average of 1.4 points in both (p < 0.01 for preoperative-postoperative comparison in each group). The mean mJOA scores improved 2.7 points in laminoplasty patients and 2.8 points in fusion patients (p < 0.01 for each group). The mean VAS scores for neck pain did not change significantly in the laminoplasty cohort (3.2 ± 2.8 [SD] preoperatively vs 3.4 ± 2.6 postoperatively, p = 0.50). In the fusion cohort, the mean VAS scores improved from 5.8 ± 3.2 to 3.0 ± 2.3 (p < 0.01). Excellent or good Odom outcomes were observed in 76.7% of the patients in the laminoplasty cohort and 80.8% of those in the fusion cohort (p = 0.71). In the fusion group, complications were twice as common and implant costs were nearly 3 times as high as in the laminoplasty group. When cases involving fusions crossing the cervicothoracic junction were excluded, analysis showed similar complication rates in the 2 groups. Conclusions Patients treated with laminoplasty and patients treated with laminectomy and fusion had similar improvements in Nurick scores, mJOA scores, and Odom outcomes. Patients who underwent fusion typically had higher preoperative neck pain scores, but their neck pain improved significantly after surgery. There was no significant change in the neck pain scores of patients treated with laminoplasty. Our series suggests cervical fusion significantly reduces neck pain in patients with stenotic myelopathy, but that the cost of the implant and rate of reoperation are greater than in laminoplasty.

Laminoplasty outcomes: is there a difference between patients with degenerative stenosis and those with ossification of the posterior longitudinal ligament?

Object Two common causes of cervical myelopathy include degenerative stenosis and ossification of the posterior longitudinal ligament (OPLL). It has been postulated that patients with OPLL have more complications and worse outcomes than those with degenerative stenosis. The authors sought to compare the surgical results of laminoplasty in the treatment of cervical stenosis with myelopathy due to either degenerative changes or segmental OPLL. Methods The authors conducted a retrospective review of 40 instrumented laminoplasty cases performed at a single institution over a 4-year period to treat cervical myelopathy without kyphosis. Twelve of these patients had degenerative cervical stenotic myelopathy ([CSM]; degenerative group), and the remaining 28 had segmental OPLL (OPLL group). The 2 groups had statistically similar demographic characteristics and number of treated levels (mean 3.9 surgically treated levels; p > 0.05). The authors collected perioperative and follow-up data, including radiographic results. Results The overall clinical follow-up rate was 88%, and the mean clinical follow-up duration was 16.4 months. The mean radiographic follow-up rate was 83%, and the mean length of radiographic follow-up was 9.3 months. There were no significant differences in the estimated blood loss (EBL) or length of hospital stay (LOS) between the groups (p > 0.05). The mean EBL and LOS for the degenerative group were 206 ml and 3.7 days, respectively. The mean EBL and LOS for the OPLL group were 155 ml and 4 days, respectively. There was a statistically significant improvement of more than one grade in the Nurick score for both groups following surgery (p < 0.05). The Nurick score improvement was not statistically different between the groups (p > 0.05). The visual analog scale (VAS) neck pain scores were similar between groups pre- and postoperatively (p > 0.05). The complication rates were not statistically different between groups either (p > 0.05). Radiographically, both groups lost extension range of motion (ROM) following laminoplasty, but this change was not statistically significant (p > 0.05). Conclusions Patients with CSM due to either degenerative disease or segmental OPLL have similar perioperative results and neurological outcomes with laminoplasty. The VAS neck pain scores did not improve significantly with laminoplasty for either group. Laminoplasty may limit extension ROM.