There should be 1 to 2 cm of space between the halo and the head. The halo is attached to a rope, which can be run over a pulley and attached to weights or an adjustable tension device, such as a simple spring scale. The orthopaedic surgeon either directly supervises or carries out knot tying at the ends of the rope to ensure their security. Tying the rope around a carabiner allows easy manipulation of the hook without having to adjust or retie knots. Because substantial amounts of weight may be used for prolonged periods, the strength of the knots is critical to avoid slipping. Our protocol encourages the use of bowline or figure-of-8 follow-through knots to ensure adequate strength for prolonged traction (Figure 3). The use of a magnetic safety mechanism that runs inline with the traction has been described and can be released in the event of a sudden increase in traction force, such as in a transportation accident.20
The patient is allowed to become accustomed to the halo before traction is placed. Traction is initiated with 5 lb (2.3 kg) of weight beginning on the day following halo placement, with increases of 2 lb (0.9 kg) daily. The goal is to achieve a traction of 50% body weight and to maintain traction for approximately 2 weeks. We recommend maintaining a log of when and how much weight is added, the patient’s tolerance of the additional weight, and neurologic examination findings. Neurologic checks, including checks of the cranial nerves, are also repeated every 8 hours by trained nursing staff.
Traction is maintained as much as possible, although nurses are permitted to remove traction as needed for toileting, movement, or patient intolerance. Customized wheelchairs and walkers are used to maintain traction during daily activities (Figures 4 and 5). When the patient is supine, the head of the bed is elevated to 45° to prevent the patient from being pulled proximally (Figure 6). Traction is intended to be used at night but may be removed for comfort, if needed. No well-defined protocol for radiographic surveillance exists, but at a minimum, we recommend obtaining PA and lateral radiographs of the spine in traction after the maximum weight has been added and before the planned definitive spinal fusion. Traction can be continued during the definitive surgical procedure. In our experience, only approximately 15 lb (6.8 kg) is necessary to maintain the correction intraoperatively.
Preoperative Halo-femoral Traction
HFT is another option for preoperative traction. Similar to HGT, HFT is done before definitive posterior instrumentation and fusion, and a preceding anterior spinal release may or may not have been done before traction. Qiu et al21 reported on their HFT technique, which included anterior spinal release. Two days after the anterior spinal release, HFT was initiated with a weight of 2 lb (0.9 kg), increasing 2 to 3 lb (0.9 to 1.4 kg) per day until 33% to 50% of body weight was reached. Traction was maintained for a minimum of 12 hours per day and decreased by 50% during sleep. For patients with idiopathic scoliosis, the major curve was corrected an average of 39% at the end of traction, whereas pretraction side bending radiographs showed an average correction of only 24%. Similarly, for patients with congenital scoliosis, preoperative bending radiographs showed an average correction of 22%, and post-HFT radiographs showed an average correction of 35%. Although HGT is transferrable to devices, such as wheelchairs and walkers, HFT is not transferrable and requires continuous bed rest while traction is in place. The patient’s limited mobility during traction may increase the potential for complications (eg, pressure ulcers, pulmonary issues). This limitation also results in more frequent removal of traction during the day, thus limiting the duration of traction before the definitive posterior fusion. For these reasons, preoperative HGT has been more popular than preoperative HFT.
The same complications associated with HGT are associated with HFT. In addition, brachial plexus palsy has been associated with HFT. Qiu et al21 reported on four patients in whom brachial plexus palsy developed during preoperative HFT after an anterior spinal release. All four patients had complete return of function within 2 months.
Intraoperative Halo-femoral Traction
Large spinal deformities, especially those caused by underlying neuromuscular disorders or severe lumbar scoliosis, can present the additional challenge of pelvic obliquity. Pelvic obliquity leads to inappropriate sitting posture and recalcitrant pressure sores. Improvement of pelvic obliquity is key to an optimal outcome but achieving improvement can be challenging. Intraoperative HFT can be a useful adjunct for improved correction of pelvic obliquity (Figure 7).
In a study of 40 patients with neuromuscular scoliosis who underwent posterior final fusion with extension of fixation to the pelvis, 20 patients had intraoperative HFT,10 which was set up after the induction of anesthesia. Each halo was held with four pins tightened with 6 to 8 lb (2.7 to 3.6 kg) of torque. A heavy Kirschner wire was placed through the distal femur on the side with the elevated hemipelvis. After prone positioning in the standard fashion, 15 lb (6.8 kg) of traction was applied to the halo. Femoral traction was then gradually increased to an average of 25 lb (11.3 kg) until the pelvis became level. Outcomes of this study include a 78% correction of pelvic obliquity in the HFT group compared with a 52% correction in the control group (P = 0.001). Similarly, Huang and Lenke11 presented a case of severe pelvic obliquity treated with intraoperative HFT in which good correction of the deformity was achieved.
Hamzaoglu et al12 reported on 15 patients with thoracic scoliosis >100° treated with intraoperative HFT and posterior-only instrumentation. This review differs from earlier reviews in that HFT was not specifically used for correction of pelvic obliquity. The protocol involved obtaining a preoperative traction radiograph while the patient was under anesthesia. If the curve corrected to ≤60°, the authors proceeded with posterior-only instrumentation and fusion. The average improvement of the major thoracic curve was 51%. If the curve did not adequately correct, they proceeded with wide facet resection and posterior release.
The aforementioned studies of intraoperative HFT report no traction-related complications. Because the traction is short-term, complications associated with preoperative traction, such as pin-site infection or loosening, should be less common. Barsoum et al13 reported on an adult patient treated with 5 lb (2.3 kg) of traction applied via Gardner-Wells tongs who experienced a postoperative cranial nerve VI palsy. At 6-month follow-up, this neurologic deficit had completely resolved.
Temporary Internal Distraction of the Spine
TID involves placing fixation points at the top and bottom of stiff curves and using spinal instrumentation to distract the spine, similar to the techniques used for growing rod constructs. Because of the prolonged hospital stay and potential complications associated with HGT and HFT, these options may not be acceptable for all patients. TID may be an option when external traction is contraindicated. TID can also be used as part of a single-stage procedure as an adjunct to other corrective measures.
In a study of 10 patients with large, stiff curves in whom HGT was contraindicated, 6 patients had an initial anterior release, and 4 did not.22 Temporary posterior distraction instrumentation was used in all patients who then returned to the operating room at an average of 2.4 weeks for definitive fusion. Six patients had more than one distraction procedure during the treatment. Buchowski et al22 reported that the average curve correction was 53% (range, 39% to 79%), which was better than their pretraction bending radiograph correction. This also compared favorably with the reported outcomes of HGT and HFT. No neurologic or infectious complications were noted. In a study of 11 patients with severe and rigid scoliosis treated with TID, Hu et al23 reported a 53% improvement in the major Cobb angle, and the forced expiratory volume in 1 second improved from 61.4% to 71.3%. The authors also noted no neurologic or infectious complications.
Our technique for TID is similar to the technique described by Buchowski et al.22 Standard prone positioning is used, as for any posterior spinal procedure. Neuromonitoring is always used and is an especially important measure during the distraction procedure. A midline skin incision is made and subperiosteal dissection is done to expose the desired anchor points. Infralaminar or subpedicle hooks are placed for cephalad fixation. It is important not to place these hooks at the desired levels for final fusion because some plowing through the bone can occur. The ribs may also be used for cephalad anchor points. Caudal anchor points are commonly downgoing laminar hooks, lumbar pedicle screws at two adjacent levels, or fixation to the pelvis. These anchor points frequently loosen during the distraction; thus, they should not be used as final anchor points during fusion. If iliac screws are used, they should be placed so that new screws can be positioned just distal to them during the definitive procedure. Several rod constructs can be used. The simplest construct is composed of one rod for the cephalad anchors and one for the caudal anchors (Figure 8). These rods can be connected via a side-to-side connector. Once the rods are in place and distraction is applied, wide posterior releases are done at each rigid level of deformity. Sequential increases in distraction are then done to take advantage of the viscoelastic properties of the spine and to obtain maximal distraction. The wound is closed per surgeon preference, and patients are mobilized postoperatively without bracing or casting. Typically, at least 1 week of TID is allowed before definitive fusion is performed. A longer period of distraction can be done but is not likely to impart better correction. At the time of definitive fusion, the temporary implant is removed, and final instrumentation is placed.
TID can also be used in a single-stage fashion. The distraction construct is placed as early as possible during the procedure to obtain distraction while other parts of the procedure are completed. The construct can then be sequentially lengthened until final instrumentation is placed. The TID construct is then removed before closure, eliminating the need for a second procedure.
Hu et al23 described a different technique for TID using minimally invasive incisions only at the levels required for the anchor points. The authors did not perform subperiosteal dissection. They placed two pedicle screws at the cephalad and caudal levels of the major Cobb angle and placed a rod in each set of screws, connected by a side-to-side crosslink. They recommended the use of an orthosis after surgery and allowed up to 15 weeks of distraction before performing definitive fusion.
Anterior Spinal Release
Traditionally, an anterior spinal release with or without anterior fusion was combined with posterior surgery to achieve maximum correction of large, stiff deformities. The separate procedures could be done the same day or in a staged fashion. As mentioned earlier, many patients who had preoperative or intraoperative traction also had an initial anterior spinal release. In these situations, anterior release is meant to improve the flexibility of the spine, increase the efficacy of the traction, improve the final correction achieved, and create greater surface area for healing bone to fuse.
In a review of 24 patients treated with an anterior spinal release (with or without a concomitant posterior release) and application of 5 lb (2.3 kg) of HFT before definitive posterior fusion, Mehlman et al14 reported that the final traction radiographs demonstrated an average 59% correction. This was a statistically significant improvement compared with the best preoperative bending radiographs. Final postoperative correction was an average of 70%.
Several studies have questioned the efficacy of adding an anterior spinal release to deformity correction protocols. Keeler et al15 compared two groups of patients with nonambulatory neuromuscular scoliosis. One group underwent anterior and posterior surgery, and the other underwent posterior-only surgery for correction of the deformities. Both groups had intraoperative HFT. The group treated with posterior-only surgery had significantly shorter surgical time, less blood loss, a decreased need for postoperative intubations, and few postoperative pulmonary complications than did the group treated with anterior and posterior surgery. The authors found no difference between the two groups with regard to final Cobb angles, percentage of corrections, or sagittal balance. Zhang et al24 reported on 29 patients with idiopathic scoliotic curves >100°; 12 patients had an anterior spinal release followed by 2 weeks of HFT and posterior fusion, and 17 had posterior-only surgery with intraoperative HFT and a wide posterior release. The authors found no significant difference in final curve correction between the two groups. In their report on patients who underwent TID to correct severe scoliosis, Buchowski et al22 noted that there was no difference in curve correction between those patients who had an initial anterior spinal release and those who did not.
Anterior spinal release can be performed as an open or a video-assisted procedure. Typically, the apex and adjacent vertebra of the major curve are exposed from the convex side. Anterior structures, including the anterior longitudinal ligament, intervertebral disks, and vertebral end plates, are excised. Mehlman et al14 recommended achieving an approximately 250° arc of release extending from the near-side rib head to the far-side posterolateral body. Autogenous or allograft bone graft can then be placed within the disk spaces to obtain fusion.
Complications related to anterior spinal release typically are related to the increased surgical time and blood loss associated with the procedure. Keeler et al15 found that pneumonia, prolonged postoperative intubation, coagulopathy, and hypotension requiring vasopressors were more commonly associated with anterior spinal releases than with posterior-only fusion. The authors also reported that one case of superior mesenteric artery syndrome occurred in the anterior release group.
Large, stiff spinal deformities in children present many treatment challenges. Preoperative HGT is a safe and efficacious method for improving deformity correction that has largely replaced HFT because it is associated with less morbidity and allows patient mobilization in a wheelchair or walker without removal of traction. Protocols for HGT and HFT should include proper cranial halo placement, appropriate knot tying, setups for traction wheelchairs and walkers to allow mobility, incremental increases in traction weight, frequent neurologic examinations, and radiographic imaging to assess goals before the definitive procedure. Intraoperative HFT can help reduce pelvic obliquity and help obtain correction of spinal curvatures. TID is an option when external traction is not feasible. Although this method does not allow for an incremental increase in traction force without a return to the operating room, it does not require a prolonged hospital stay and may prevent some of the complications related to the use of external traction devices. Surgical release of anterior spinal structures may increase the flexibility of the spine before initiating traction, but several studies have questioned the efficacy of anterior spinal release for management of large, stiff spinal deformities. When the appropriate protocols are followed, each of these techniques can be a useful tool to safely improve patient outcomes.
References printed in bold type are those published within the past 5 years.
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Keywords:© 2017 by American Academy of Orthopaedic Surgeons
scoliosis; stiff spinal deformity; traction; anterior spinal release; halo-gravity traction; halo-femoral traction; temporary internal distraction