Unless a spine surgeon knows how to consistently create a dry operative field they should seek another professional endeavor. It is simply not possible to perform technically demanding, microsurgical, spine procedures without controlling hemorrhage. The primary means of accomplishing this relate to patient positioning. Once the patient is appropriately and safely positioned (protection of face and extremities) the next challenge is where to make the incision. Spine marking and intra-operative imaging serve well for this purpose. After the incision has been made the surgeon needs to continue maintaining a dry operative field. The differentiation of anatomic structures and their adequate visualization then require appropriate magnification and illumination by the surgeon in order to exercise their hard-earned skills.
Patient positioning is the first step in achieving a dry operative field for lumbar spine surgery. The key is to reduce pressure on the patient’s abdomen and thus decrease systemic venous pressure with attendant decrease in hemorrhage. The first knee-chest devices developed did the job but often caused pressure related facial sores, peripheral nerve palsies, etc. and did not allow for bi-plane x-ray monitoring. The more advanced positioning tables allow for even morbidly obese patients to be operated upon without being subject to significant abdominal compression.
A GPS system for anatomic localization does not yet exist for spine surgeons. For routine operative procedures localization is important and can be accomplished by a number of different approaches:
Pre-operative spine marking–
This technique (preferred by the Editor) is performed prior to surgery under fluoroscopic control. A visible dye such as lymphazurin or methylene blue is injected into the dermis as well as the tip of a dorsal process. The illustration on the left shows a needle tip above the red dot on the L5 dorsal process. At surgery (middle image) dye can be seen both in the skin and on the tip of a dorsal process. The value of this technique varies with the patient’s anatomy, the technique of the radiographer, and the characteristics of the dye. Under direct x-ray control a metallic marker needle can also be inserted into a spine location and left until surgery. This is not commonly used because it is usually uncomfortable for the patient
Spine Marking Advantages
- Relatively easy to perform.
- Performed before surgery.
- Intra-operative spine marking performed general anesthesia.
- Intra-operative spine marking may add 15-30min to surgery.
Spine Marking Disadvantages:
Patient may experience an allergic reaction to dye. Surgeon may also have to perform intra-operative marking.
Operative observation and marking–
Under direct x-ray control metallic markers, such as needles, can be placed by the surgeon. In the image above a bent 18 gauge spinal needle has been placed in the disc interspace as a means of localization.
Operative Marking Advantages:
- The most reliable marking procedure.
Operative Marking Disadvantages:
- The risks of surgery increase with the length of anesthesia.
- Waiting for a x-ray can add significant time (and cost) to surgery.
When all is said and done it is important to perform surgery at the level intended.
The lowering of systemic venous pressure by proper positioning combined with the optimization of arterial pressure by the anesthesiologist represents the first step in achieving adequate hemostasis. Once the incision is made the control of bleeding must be effective to decrease overall blood loss and allow for a dry operative field. Adequate and safe spinal surgery requires a dry operative field.
In 1928 physicist W. T. Bovie first developed a clinical electrosurgical unit for the purpose of cautery (at the request of Harvey Cushing). It functioned by a spark gap generator and was referred to as monopolar because the current field was between the surgical instrument and a grounding pad placed on the patient. A significant advance in controlled focal coagulation and microsurgical technique was the development, in 1955 of bipolar coagulation by Leonard Malis. Shown above is a modern bipolar surgical forcep designed to avoid tissue charring. Less well known than cautery are adjuvant techniques such as the local utilization of powdered gelfoam and thrombin mixtures. These combinations create pastes which can be topically applied through a syringe to the area of need. Care must be exercised in applying this mixture to cancellous bone so as not to promote emboli.