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Fig. 10.1 Frequency range
for most high-frequency
electrosurgical devices
U. Vieweg
50 Hz
Mains
current
10 kHz 550 kHz
Electrosurgery
neuromuscular
stimulation
needle electrodes perfused with saline solution (e.g.
Elektrotom HITT 106, Integra LifeSciences)
• High-frequency-induced thermotherapy of facet joints,
for example, with high-frequency currents supplied
through insulated needles specially positioned within the
tissue (e.g. MultiGen RF generator, Stryker)
10.4 Manufacturers ofHigh-Frequency
Electrosurgical Generators
The manufacturers of high-frequency electrosurgical generators are the Aaron Medical Industries, adeor Medical
Technologies GmbH, Aesculap AG, Elliquence, Ellman
International, Erbe Elektromedizin GmbH, Gyrus ENT,
Integra LifeSciences, MEGADYNE Medical Products,
Naeem Jee Corporation, PEAK Surgical, Schuco, Söring
GmbH and Stryker Valleylab.
10.5 Basic Physical Principles [1–5]
When a current is passed through the tissue, the cell liquid
expands, and the cell explodes and evaporates, which causes
the cutting or coagulation effect. Three effects are important
when the body is subjected to an electric current: the Faraday
effect, the electrolytic effect and the thermal effect. Nerve
and muscle cells can be stimulated electrically. In the human
1550 kHz 54–800 MHz
No
AM radio
FM radio
tissue, the stimulation effect is greatest with an alternating
current of approximately 100Hz. This effect decreases with
increasing frequency, thus losing its damaging, or even lifethreatening, action.
With high-frequency alternating currents, electrolysis and
nerve stimulation occur only to a very small extent. According
to Joule’s law, the heat ΔQ produced per tissue volume ΔV is
directly proportional to the resistivity ρ of the tissue and the
square of the current density j, ΔQ = ρ⋅j2⋅ΔV⋅Δt. Current
densities of j= 1–6A/cm2 are usual. The body tissue has a
higher electrical resistance than the metal cutting electrode.
The ow of current therefore heats up the surrounding tissue
but not the electrode. The effect is particularly strong close to
the operating electrode because the whole current ows
through a very small cross-sectional area of the tissue. At the
neutral electrode, the returning current is spread out over a
large area and thus causes only slight heating of the tissue.
The degree of tissue heating caused by an electric current
depends on the following factors: the current density, the
resistivity of the tissue and the length of time for which current is applied.
The following variables inuence the effect exerted on the
tissue: power setting, size of electrode, time, manipulation of
electrode, type of the tissue, waveform and eschar. The
smaller the electrode, the greater is the current density.
Consequently, the same tissue effect can be achieved with a
smaller electrode, even though the power setting is reduced.
At any given setting, the longer the generator is activated, the
TV
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67
Fig. 10.2 Illustration of the
effects of the two
electrosurgical processes—
coagulation and incision—on
the tissue (coagulation:
energy dried out by heatcoagulated cell; incision: high
energy density, uid
evaporates, cell expands, cell
explodes) [6]
Coagulation
Incision
High
energy density
Energy
Coagulated cell
Drying out
from heat
Exploded
cell
Cell expands by
evaporating
more heat is produced. The greater the heat, the farther it will
travel to the adjacent tissue (thermal spread). Tissues vary
widely in resistance. Eschar is relatively high in resistance to
current. Keeping electrodes clean and free of eschar will
enhance performance by maintaining lower resistance within
the surgical circuit.
10.6 Eect ofHigh-Frequency Current
The surgical effects of high-frequency currents can be
divided into two main groups: cutting and coagulation [1, 3,
5–7]. Cutting severs the tissue, while coagulation dries the
tissue out.
• Coagulation is the clotting of protein with reduction of
volume and loss of water (see Fig.10.2). Coagulation can
be divided into deep and surface coagulation or into desiccation and fulguration (see Fig. 10.3). Desiccation
refers to coagulation induced using an inserted needle
electrode (contact coagulation). Fulguration or spray
coagulation refers to surface carbonisation or surface
coagulation caused by spark discharge from an electrode
held close to the tissue (non-contact coagulation). The
intra- and extracellular uid is evaporated by sparks emitted from the tip of the electrode which is held a few millimetres from the tissue and moved over it. The main
difference between fulguration and desiccation is that fulguration does not involve contact between the tissue and
the electrode. This effect is primarily used when sealing
the tissue over a large surface. The depth of coagulation
depends on the strength of the current used. If a large current is used, carbonisation occurs, and eschar forms which
inhibits the spread of the heat to a greater depth. When the
electrode is subsequently removed, the burnt tissue is
removed as well because it sticks to the electrode tip.
However, if a small current and a long duration of action
are selected, the tissue around the electrode, down to a
depth slightly greater than the diameter of the electrode, is
vaporised. Coagulation can also be divided into the following categories depending on the qualities of the current used:
Soft coagulation (<190V): In this case, no spark or arc of
light occurs, and no unwanted cutting is caused.
Carbonisation is prevented.
Forced coagulation (up to 2.35kV peak): Arcs of light are
produced in order to reach a greater coagulation depth. In
the process, carbonisation cannot be avoided. Ball
electrodes with a small surface area are usually used for
this purpose.
Spray coagulation (up to 8kV peak): In spray coagulation, long and powerful arcs of light are produced which
heat the tissue both exogenously and endogenously. In
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U. Vieweg
Fig. 10.3 Illustration of the
effects of the two
electrosurgical processes—
coagulation and incision—
and their subgroups (pure cut,
blend cut, desiccation,
fulguration) [6]
Pure (smooth)
Incision
this process, no spark or arc of light occurs, and no
unwanted cutting is caused.
• Incision involves cutting of the tissue with high-frequency
current and electrodes with a small surface area. Explosive
evaporation of cellular uids at the site of the cut severs
the tissue and coagulates it at the cut edges (see Fig.10.2).
Incisions are divided into pure cuts and blend cuts (see
Fig.10.3). A pure or smooth incision (cut) exerts as little
lateral haemostatic effect as possible.
10.7 Electrode Congurations
Modern, high-frequency electrosurgical devices transfer
electrical energy to the human tissue via a treatment electrode (in a bipolar or monopolar conguration) that remains
cool (see Table10.1). In the bipolar conguration, the voltage is applied to the tissue using special forceps of which one
tine is connected to one pole of the generator and the other
tine is connected to the other pole of the generator. When a
piece of tissue is held with the forceps, a high-frequency
electric current ows between the tines, heating the intervening tissue. In monopolar electrosurgery, the active electrode
is in the surgical site. The patient’s return electrode is
attached somewhere else on the patient. The current must
ow through the patient to the patient’s return electrode. In
the monopolar conguration, the patient is in contact with
the return electrode, a relatively large or a exible metallised
plastic pad which is connected to the generator. The surgeon
uses a pointed electrode to make contact with the tissue. The
electric current ows from the electrical tip through the body
to the return electrode and then back to the electrosurgical
generator.
Electrosurgery
Coagulation
Blend
Fulguration
Desiccation
10.8 Safety Measures
• Insulation
The patient must lie fully insulated on the operating table
(dry drapes, plastic mats, etc.). He/she must also be insulated from all metal items and any tubes capable of conducting electricity. Dry cellulose pads are necessary in
skinfolds, breastfolds and between extremities. For highpower surgical uses under anaesthesia, the monopolar
modality relies on good electrical contact between return
electrode and the body. If contact with the return electrode is insufcient, severe burns (third-degree) can occur
in areas of poor contact with the return electrode or where
contact is made with grounded metal objects serving as an
unintended return path.
• Position and type of neutral electrode
The neutral electrode should be placed as close to the
operating area as possible and should have good contact
with the patient tissue. So-called split return electrodes
should always be used. These monitor the contact quality of the return electrode to the patient. The so-called
return electrode monitoring (CQM) system (safety system) was developed to avoid burns under the return electrodes. This system measures the contact quality of the
surface between the return electrode and the patient all
the time, also while the generator is activated, and monitors every change during the entire surgical procedure.
• Anaesthesia equipment
For preoperative monitoring, only ECG cables with high
resistance inputs or HF choke may be used. Before the operation, it is important to ensure that the current from the active
electrode to the return electrode is not conducted through the
heart area or that any such conduction is minimised.
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Table 10.1 Differences between the monopolar and bipolar congurations in electrosurgery
Monopolar Bipolar
Poles Electrodes with small surface area in operating region, return via
large area neutral electrode
Action Strong local heating of the tissue at the electrode tissue junction
(coagulation) and sparking and fulguration at high voltages
Uses Coagulation; desiccation; fulguration; tissue cutting, sometimes
with sloughing/scab formation; blood vessel closure
Advantages Many different applications possible with change of electrodes;
rapid haemostasis
Disadvantages Neutral electrode needs to be xed, risk of burns if neutral
electrode comes unstuck, current ow through the body cannot
be precisely controlled, short circuiting possible via contact with
earthed metal items
Both poles are held directly over the tissue with forceps
whose tines are insulated against each other. Current
ows between the two poles only
Local heating of the tissue only between the electrodes;
coagulation as a result
Coagulation, good closure of blood vessels
Small currents required (only about 20–30% of that
needed for monopolar HF), route followed by current
can be calculated, risk of burns
Tissue cutting, fulguration
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10.9 Tips andTricks
• Correct positioning (dry and insulated)
• No contact with grounded objects
• No skin-to-skin contact (between individual parts of the
patient’s body)
• Short cables, no contact to grounded metal parts
• No looping of cables and no xation with metal brackets
• Cautious handling of disinfectants (the alcohol contained
can be ignited by electric sparks)
• Return electrode monitoring (CQM) system (safety
system)
10.10 Current Trends
Further developments in electrosurgery involve the use of
helium gas (cold plasma coagulation) or ionised argon
gas (argon plasma coagulation) which allows current
flow without contact between electrode and the tissue.
Both plasma coagulation techniques require no return
electrode and do not involve current flow through the
body or areas of vaporisation within the tissue. It therefore permits rapid and controlled haemostasis without
major tissue damage.
References
1. Hainer BL.Fundamentals of electrosurgery. J Am Board Fam Pract.
1991;4:419–26.
2. Arnold P, Advincula WK.The evolutionary state of electrosurgery:
where are we now? Curr Opin Obstet Gynecol. 2008;20:353–8.
3. Boughton RS, Spencer SK. Electrosurgical fundamentals. J Am
Acad Dermatol. 1987;16:862–7.
4. Elliott-Lewis EW, Mason AM, Barrow DL. Evaluation of a new
bipolar coagulation forceps in a new bipolar coagulation forceps in
a thermal damage assessment. Neurosurgery. 2009;65(6):1182–7.
5. Vellimana AK, Sciubba DM, Noggle JC, etal. Current technological advantages of bipolar coagulation. Neurosurgery. 2009;64:11–9.
6. Hausmann V.High-frequency surgery. In: Krettek C, Aschemann D,
editors. Positioning techniques in surgical applications. Heidelberg:
Springer; 2006. p.41–54.
7. Reidenbach HD.Fundamentals of bipolar high-frequency surgery.
Endosc Surg Allied Technol. 1993;1:85–90.
Surgical Motor Systems inSpinal
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Surgery
FrankGrochulla andUweVieweg
11
11.1 Introduction and Core Messages
Surgical motor systems are important power tools in
microsurgical procedures at the cervical, thoracic and
lumbar spine, whenever preparation and removal of
the bone become necessary.
Motor systems are surgical instruments, which are
divided in high- and low-speed systems. The motor
systems are operating with electrical, pneumatic or
Akku power source controlled by foot pedal or hand
tip. Common power tools in spinal surgery are drill
systems, bone saws and burrs. Especially high-speed
drill systems are important tools for opening procedures of the spinal canal.
11.2 History
Important milestones were the invention of the rst electric
surgical motor in 1935 by Aesculap, the introduction of
pneumatic power systems in the 1960s, the pioneering work
with exible cable motors in the 1970s, the battery-powered
motor systems in the 1980s and the incorporation of pneumatic and electric high-speed systems in the 1990s. Power
tools have undergone many improvisations and modications in the past two decades and have improved tremendously in their functionality and versatility [1–4].
F. Grochulla (*)
Metropol Medical Center, Clinic for Orthopedics, Trauma Surgery
and Spinal Surgery, Nuremberg, Germany
e-mail: frank.grochulla@mmc-nuernberg.de
U. Vieweg
Department of Conservative and Surgical Spine Therapy with
Interdisciplinary Spinal Deformities Centre and Rummelsberg
Sectional Center, Hospital Rummelsberg,
Schwarzenbruck, Germany
e-mail: uwe.vieweg@sana.de
11.3 Components andTechnical Details
There are a number of surgical motor systems on the market.
Differences exist in the source of power, the revolutions per
minute (rpm) ranging from 10,000rpm up to 90,000rpm and
more and the activation of the motor system (by hand or by
foot).
11.3.1 Power Systems
• Pneumatic high-speed power system (HiLAN® XS,
ComPact Air Drive II, Air Pen Drive, Synthes)
The sterilisable coaxial exible hose connects the pneumatic motor with a foot pedal.
• Electric power system (microspeed® uni Aesculap;
Servotronic EC I/II 100, Medicon Instruments; Linotec
E9000, Stryker; Zimmer surgical motor systems, Electric
Pen Drive, Synthes) (Fig.11.1)
The differences between electric and pneumatic power
systems are in respect to personal preference and electric
instead of pressured air.
Personal
preference Electric instead of pressured air
Noise level
Handling Electric systems is easier to set up (no need for
Versatility Electric system can usually cover more indication
Individuality Individual settings and acceleration/stopping
Price Electric systems tend to be more expensive than
Pneumatic systems generate a higher noise level
than electric motor systems
pressured air)
Cable is more exible and lighter than air
hoses
elds (low speed, high speed, pistol, shave in one
system)
characteristics
Oscillation angle, etc., can be adjusted via the
control unit to individual preferences
pneumatic ones
© Springer-Verlag GmbH Germany 2023
U. Vieweg, F. Grochulla (eds.), Manual of Spine Surgery, https://doi.org/10.1007/978-3-662-64062-3_11
71
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Fig. 11.1 Components of surgical motor systems (motor unit, handpiece, control unit, connecting cable, foot control) (with permission of
Aesculap AG, Tuttlingen, Germany)
F. Grochulla and U. Vieweg
Fig. 11.2 Cutting and diamond burrs, Rosen burr and diamond burr
11.3.2 Accessories
The motor systems consist of various attachments (burrs,
drills, saws). Burrs and drills are available in different sizes
and shapes (Fig. 11.2). The more aggressive cutting burrs
(cylindrical burr, Rosen burr) are applicable to remove the
hard cortical and cancellous bone. These cutting burrs should
not be used in the spinal canal because of the risk of tearing
the soft tissue (dura, neural structures). Less aggressive burrs
such as diamond burrs are more applicable for preparing in
the near of important soft tissue structures such as vessels,
nerves and dura.
The handpieces are available in angulated or straight
designed shape. Angulated handpieces are more useful in
microsurgical procedures. Irrigation is always necessary
when using a high-speed motor system in order to avoid
local hyperthermic reactions. Continuous irrigation should
11 Surgical Motor Systems inSpinal Surgery
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73
Fig. 11.3 Pre-drilling for osteosynthesis screws (with permission of
Aesculap AG, Tuttlingen, Germany)
Fig. 11.5 Preparation of implant bed for corpectomies or interbody
fusions (with permission of Aesculap AG, Tuttlingen, Germany)
be used with an integrated irrigation system which provides
an electronically controlled permanent irrigation. If not
available, a simple irrigation by using a syringe is possible.
11.4 Indications
All the different systems available for varied indications on
the spine are the following:
• Decortications/pre-drilling for distraction, pedicle or
osteosynthesis screws with a high-speed burr or highspeed drill (see Figs.11.2 and 11.3)
• Preparation of implant bed for corpectomies or interbody
fusions (see Fig.11.4)
• Harvesting and modelling of autologous bone graft with
saws/high-speed or low-speed burrs (see Figs.11.5 and 11.6)
• Decompression/access preparation (laminoplasty, laminotomy, laminectomy, facetectomy, foraminotomy)
with a high-speed or low-speed burr or laminectomy
drill/craniectomy (see Figs.11.7, 11.8, 11.9, 11.10 and
11.11)
Fig. 11.4 Decortications/pre-drilling for distraction, pedicle or osteo-
synthesis screws with a high-speed burr or high-speed drill (with permission of Aesculap AG, Tuttlingen, Germany)
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Figs. 11.6 and 11.7 Harvesting
and modelling of autologous
bone graft with saws/high-speed
or low-speed burrs (with
permission of Aesculap AG,
Tuttlingen, Germany)
F. Grochulla and U. Vieweg
Figs. 11.8 and 11.9 Access preparation (laminoplasty, laminotomy, laminectomy facetectomy, foraminotomy) with a high-speed or low-speed
burr or laminectomy craniectomy drill (with permission of Aesculap AG, Tuttlingen, Germany)
ab
11 Surgical Motor Systems inSpinal Surgery
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Fig. 11.10 Vertebral body resection with a
long handpiece over a mini- thoracotomy (with
permission of Aesculap AG, Tuttlingen.
Germany)
75
c
Fig. 11.11 (a) Pneumatic motor (HiLAN, Aesculap), (b) electric motor system (Midas Rex Legend, Medtronic) and (c) electric motor system
with different handpieces (HiLAN, Aesculap) (with permission of Aesculap AG, Tuttlingen, Germany)
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F. Grochulla and U. Vieweg
11.5 Tips andTricks
• Lubricating the power systems is a simple and safe affair.
The motor and handpieces are sprayed with special oil
spray before sterilisation cycle.
• Complete lubrication of the motor and handpieces is
ensured, making permanent intraoperative lubrication
unnecessary.
• Before use, the instrument should be completely checked
by the surgeon.
• A high-speed burr with foot pedal should be controlled by
the surgeon only.
• Always work with intact and sharp tools (drills) to avoid
damage or overheating of the motor system.
References
1. Albee FH. Some scientic aspects of orthopaedic surgery. J Bone
Joint Surg Am. 1929;XI:696.
2. Beer RR, et al. Biorobotic approaches to the study of motor systems. Curr Opin Neurobiol. 1998;8(6):777–82.
3. Dyas FG. The treatment of acute osteomyelitis of the long bones
by means of the dental engine and a large burr: preliminary report.
JAMA. 1914;LXII(1):216.
4. Kale S.Power tools in orthopaedic surgery– an update. Orthop Prod
News. 2008;48:56–62.
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