A Sterile-freehand Reduction Technique for Corrective Osteotomy of Fixed Cervical Kyphosis

Sang-Hun Lee, MD; Ki-Tack Kim, MD; Kyung-Soo Suk, MD; Man-Ho Kim, MD; Dae-Hyun Park, MD; Kyu-Jin Kim, MD

Disclosures

Spine. 2012;37(26):2145-2150. 

In This Article

Discussion

Urist[6] reported the first case of corrective osteotomy for the cervical spine in 1958, an extension osteotomy similar to the Smith-Petersen osteotomy[7] of the lumbar spine. Simmons[2] and Simmons et al[3] reported the largest series of clinical outcomes after extension osteotomies in the seating position with local anesthesia and halo fixation. With the development of modern anesthesia, neuromonitoring,[1,8] and internal fixation,[8] cervical spine osteotomy in the prone position[1] -using strong internal fixation and somatosensory-evoked potential and/or MEP monitoring under general anesthesia[9] -is considered a standard procedure in many reports.

The osteotomy technique has advanced continuously as well. The conventional extension osteotomy has the largest number of reports and cases.[1,2,8,10–13] These articles reported excellent clinical outcomes but a non-negligible rate of complications as a result of the loss of correction and related neurological complications. In 2002, El Saghir and Boehm[14] reported that corrective osteotomy consists of posterior osteotomy after an anterior release. Mummaneni et al[15] reported a similar anterior-posterior-anterior 540° procedure to allow for safer correction with structural stability. Most recently, a closing osteotomy technique using the pedicle subtraction procedure for the cervical spine was reported by Tokala et al[5] in 2007.

Similar to PSO on the thoracolumbar spine, PSO on the cervical spine has the advantages of structural stability and a wider cancellous contact surface for bony union over the extension-type osteotomy. However, there are few reports on outcomes of PSO for the cervical spine.[5,16] In the present study, we used PSO in most of the cases. All cases showed solid union with no loss of reduction or complications. More studies with a larger number of cases are needed to demonstrate the effectiveness and safety of PSO for the cervical spine.

After complete release of the bony structure using either the extension-type or closing-type procedure, the spinal column is extremely unstable. Thus, the safe reduction of the deformity is the most critical step for a successful corrective osteotomy. Especially in AS patients, the bone of the vertebral body is usually weak, whereas the anterior cortex is stronger for complete ossification of the anterior longitudinal ligament. Subluxation of the spinal column with a fracture could occur with uncontrolled, sudden forceful correction and may cause catastrophic neurological complications.

Since the gradual reduction over a week using a turnbuckle and halo vest in the first report of cervical osteotomy by Urist,[6] various methods to ensure safe reduction have been reported. In 1996, Shimizu et al[17] reported a sequential tightening technique using sublaminar wires after initial wire fixation of a prebent rectangular loop rod on the occiput and thoracic spine. In 1999, Mehdian et al[12] described a controlled-reduction technique using a temporary malleable rod. Reduction techniques using Ilizarov distraction with a halo vest,[18] the elevator mechanism of the Jackson operating table,[19] and a hinged rod system[11] have also been reported, but the numbers of these cases are small and the techniques not yet standardized.

Of all the reduction techniques, intraoperative manual reduction is the most basic and the most commonly reported for both extension- and closing-type osteotomies. In the conventional "unscrubbed-scrubbed" manual reduction in the prone position,[5,11,12,15,20] the operator and an assistant should be "unscrubbed" and move to the cranial side of the patient. Next, the assistant releases the clamp while the operator holds the clamp or a halo ring. After manual reduction of the deformity by an operator outside the surgical field, the assistant retightens the clamp while another assistant monitors impingement of the spinal dura and nerve root. This procedure may need to be repeated multiple times to obtain the desired correction angle. The disadvantages of conventional manual reduction are that (1) the operator cannot monitor the surgical field closely during the reduction procedure, even using transparent surgical drapes; (2) it is inconvenient for the operator to control the force and direction because the force of correction is applied from outside the surgical field, whereas the lever point is located within the surgical field; (3) multiple steps are necessary to release and retighten of the clamp. However, the clamp holding the extremely unstable cervical spine is not freely movable in 3 dimensions; and (4) the assistants are unlikely to be familiar with cervical osteotomy, because it is not a frequently performed procedure.

In the SF reduction technique used in the present study, traction was applied within the sterile surgical field with a freely movable rope, and thus the inconvenient step of multiple releases and retightening of the clamp from outside the surgical field is avoided. This technique does not require any other special instruments or devices and relies less on skilled assistants compared with the conventional reduction technique. In addition, the force and point of the lever of the reduction are all located within the surgical field, allowing for more stable reduction. Most of all, the operator can control the power, speed, and direction of reduction simultaneously and under close visual observation of the osteotomy gap within the surgical field. Thus, the SF reduction technique makes gradual controlled reduction and 3D corrections possible, not only for deformities of the sagittal plane but also for coronal and axial plane deformities. Last, craniocervical alignment can be easily assessed intraoperatively, as the whole head is included within the surgical field.

We used the Gardener-Wells tongs instead of a halo ring in this technique. Although a halo ring provides multiple-level fixation point and better stability by itself, it would be more uncomfortable to include the larger ring within the sterile field and to support head by the horseshoe headrest frame. In addition, Gardner-Wells tongs are simple, bucket-handle shaped, and it is easier to control the direction and degree of correction with the surgeon's dominant hand. A shortcoming of the SF reduction technique would be a wider range of shaving than conventional procedure. All patients in this study were informed of the purposes and risks of the osteotomy, and agreed on the entire-head shaving. Although it could not be a critical problem, some patients may have aversion to this. Recent cases of the authors, which are not included in this study, could be performed with preservation of their bangs. It could be a better option for this problem.

For PSO, successful safe reduction was possible using SF reduction techniques in the present study. However, for extension osteotomy or in cases where the vertebra has a hypertrophied strong anterior wall, there still might be a risk of uncontrolled fracture or translation, even using this technique. The combined usage of a malleable rod or a hinged rod system as described in previous reports may decrease the risk of neurological complications.

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