Lateral Mass Screw Fixation in the Cervical Spine: Introducing a New Technique

Study Design

This was designed as a randomized double blind study to compare the classical Magerl technique of insertion of lateral mass screws with the authors’ technique. The observations regarding length, outcome, and radiology was done by a group blinded to the technique used.

Purpose

The present study was designed with the objective of identifying the optimal technique for introducing the lateral mass screws that uses the maximum possible dimension of the lateral mass.

Overview of Literature

Lateral mass screw fixation is a common surgery that is performed in the cervical spine. Various modifications for the procedure have been described, such as changes in the entry point, angulation of the screws, and modifications in the exit point. These do not allow the insertion of longer screws that can give more purchase on the bone.

Methods

From January 1, 2009 to December 31, 2018, 176 patients who were scheduled to undergo lateral mass screw fixation were enrolled. They were randomized into two groups; we inserted lateral mass screws using our new technique for one group and by using the classical Magerl technique for the other group. Intraoperative measurements were used to assess the bone-screw interface length. Postoperative radiography and postoperative computed tomography were performed to assess the trajectory of the screws.

Results

Total 88 patients were included in the study group, including 68 men. The control group included 65 men. The most common indication for surgery was cervical spondylotic myelopathy. The average bi-cortical length that was measured intraoperatively was 19.9 mm in the study group and 16.3 mm in the control group. This was significantly different from the average lengths of screws in the control group.

Conclusions

The trajectory that involves an entry point as close as possible to the posterior inferior medial angle of the lateral mass cuboid and traverses a distance of about 20 mm to obtain a bi-cortical purchase in the diagonally opposite angle may provide a much better and firmer bony purchase in the lateral mass than conventional points of entry and trajectories.

Neurological recovery in patients of old healed tubercular rigid kyphosis with myelopathy treated with transpedicular decancellation osteotomy

PURPOSE

The purpose of the study was to find out if transpedicular decancellation osteotomy (TDO) is recommendable for neurological recovery in patients with myelopathy due to tubercular rigid kyphosis. We have analyzed the pattern of recovery seen after the surgery and also made an effort to correlate the neurological recovery with preoperative clinical and radiological features.

METHODS

The clinical parameters used were (1) ASIA impairment scale for motor and sensory function, (2) sphincter dysfunction score, (3) time duration from the onset of myelopathy till the date of surgery, and (4) SRS 30 outcomes questionnaire. Radiological parameters used were (1) Cobb's angle in standing/sitting radiographs, (2) levels of gibbus, (3) cord changes in sagittal T2 MRI images, and (4) percentage of cord compression. Assessment was done preoperatively and at 1 month, 3 months, 6 months, 1 year and at 2 years postoperatively.

RESULTS

Seventeen patients were included. The follow-up period was 2 years. We had one patient in ASIA A, nine patients in ASIA C and seven patients in ASIA D. Four patients with ASIA C presented with mild sphincter disturbance (score 2) and one presented with severe disturbance (score 1). The ASIA A patient had complete retention (score 0). The ASIA impairment scale improved after surgery, with maximum improvement at 3 months and improvement continuing up to 6 months. 16 (94 %) patients had improvement in lower limb function and 5 (83 %) patients had improvement of sphincter function. 94 % patients had neurological recovery after the operation. The neurological recovery reached a plateau at 6 months with no significant improvement in the further follow-up. Preoperative MRI changes, cord compression and duration from onset of myelopathy to day of surgery were not predictive of the final neurological outcome after surgery.

CONCLUSION

TDO gives good results in delayed onset neurological deficits in caries spine with rigid kyphosis. At least, one grade improvement in the neurological status of patients with ASIA C and ASIA D can be expected. Maximum improvement in the neurology is seen in the first 3 months and up to 6 months from the date of surgery, without much improvement thereafter. Level of evidence Level IV.

Posterior scoliosis correction for adolescent idiopathic scoliosis using side-opening pedicle screw-rod system utilizing the axial translation technique

BACKGROUND

Though adequate literature is present depicting the results of pedicle screw-rod instrumentation using top loading systems for correction of adolescent idiopathic scoliosis (AIS), using the rod rotation technique, few published data is available regarding side loading systems used for a similar purpose. We report a retrospective study of a cohort of patients with strict inclusion criteria who underwent surgical correction of AIS with side-opening pedicle screw-rod posterior instrumentation using the axial translation technique of curve correction to assess the efficacy of side opening system for scoliosis correction with regards to patient satisfaction, Cobb's angle correction and spinal balance.

MATERIALS AND METHODS

Clinical and radiological outcomes were measured in 14 consecutive patients (3 males, 11 females) with an average age of 14.0 years (range 9 to 23 years). They were followed up for an average period of 13.0 months (range - 2.2 to 28.5). All patients underwent posterior instrumentation only with pedicle screws used as anchor points. Hybrid constructs using hooks/wires or curves requiring anterior release were excluded from the study. All levels were not instrumented - more screws were put on the concavity and in the peri-apical region. Radiological evaluation was done by whole spine standing AP, lateral radiograms preoperatively and 1, 3, 6 and12 months after surgery. Cobb's angles were measured and the spinal balance was noted. Clinical evaluation was done by SRS questionnaire. The complications were documented.

RESULTS

The mean preoperative Cobb's angle was 58.35 degrees (range - 44 to 72 degrees ), which came down postoperatively to 23.45 degrees (range - 10 to 38 degrees ) signifying a mean correction of 59.57% (range - 26.92 to 76.17%). Clinical outcomes were evaluated using the SRS - 30 questionnaires. The values of mean pre- and postoperative scores are 3.68 and 4.18, showing an improvement of 0.5 points. Other than one patient of superficial wound infection, which healed with antibiotics, there was no major complication. No patient had neurological deterioration.

CONCLUSION

Side-opening spinal instrumentation systems, using the axial translation technique, achieved good clinical and radiological outcome for patients of AIS.

Purification and characterization of Borrelia burgdorferi from feeding nymphal ticks (Ixodes scapularis)

Here we describe a protocol for purifying Borrelia burgdorferi from feeding ticks by velocity centrifugation and Percoll density gradient centrifugation. The purified spirochetes were motile and 10- to 20-fold purer than the bacteria in crude tick homogenates. The purified bacteria were present in sufficient quantity for protein and gene expression studies. In comparison to culture-grown bacteria, tick-borne spirochetes had several proteins that were upregulated and a few that were downregulated. When the levels of B. burgdorferi outer surface proteins OspA and OspC were measured, OspC protein and mRNA levels were lower in cultured bacteria than in bacteria purified from ticks. Although differences in OspA mRNA levels were observed between cultured and tick-borne bacteria, no differences were observed at the protein level. These experiments demonstrate that tick-transmitted borreliae display a gene expression and antigen profile different from that of spirochetes cultured in vitro.