Instruments

10.1055/b-0034-87597

Instruments

Theerachai Apivatthakakul, Reto Babst, Suthorn Bavonratanavech, Dankward Höntzsch

1 Introduction 51
2 Instruments to aid fracture reduction 51
2.1 Reduction handles 51
2.2 External fixators 53
2.3 Large distractor 53
2.4 Collinear reduction clamps 53
2.5 Periarticular reduction forceps 54
2.6 Percutaneous cerclage passer 54
3 Instruments to aid tunnel preparation for plate insertion and fixation 55
3.1 Tunneler 55
3.2 Plate holder 55
3.3 Temporary fixation device 57
3.4 Sleeves to aid percutaneous screw fixation 57
3.5 Minimally invasive screw-holding forceps 59
3.6 Soft-tissue spreader 59
3.7 Tension device 59
3.8 Hohmann holder 59
4 Instruments for plate and screw removal 61
5 Further reading 62

Introduction

Minimally invasive plate osteosynthesis (MIPO), in contrast to conventional open reduction and internal fixation using plates, is performed without exposure of the fracture site—the aim being to preserve biology with minimal disruption of soft-tissue attachments and vascular supply. To accomplish this, the fractures are usually reduced by indirect means and the implants introduced from a site remote from the fractures.

To facilitate this minimally invasive method of fracture reduction and fixation, special instruments are required. Instrument systems are still evolving but those introduced so far can be grouped according to the functions that they perform:

Instruments to aid fracture reduction
Instruments to create the tunnel for plate insertion and fixation
Instruments for plate and screw removal

Some of these instruments are commercially available; others are being developed to match the needs of the surgeon. As MIPO evolves, instruments will be refined to make the procedure easier and more reproducible in the hands of most surgeons.

To have a better understanding of the functions and applications of the various instruments, it is necessary to be familiar with the basic steps of a MIPO procedure, which is usually performed in the following sequence:

Indirect fracture reduction
Temporary fixation to hold the reduction if necessary
Skin incisions remote from the fracture site, corresponding to the ends of the plate, one on each side of the fracture
Creation of a submuscular, epiperiosteal tunnel for the plate
Introduction of the plate
Temporary fixation of the two ends of the plate through the original incisions
Checking the quality of reduction, length, axial alignment, and rotation
Fine-tuning reduction at the fracture site by direct reduction using instruments which cause minimal additional trauma
Definitive fixation with screws introduced through stab incisions making adjustments to the fracture reduction if necessary
Final check on fracture reduction and implant position
Wound closure

Instruments to aid fracture reduction

Reduction handles

Reduction handles can be used for minimally invasive fracture reduction. Available in two different sizes for use with large and small fragment implants, they come with toothed or rounded tips ( Fig 3-1 ).

They are used with self-drilling threaded pins or guide wires and application is easy. A self-drilling pin or guide wire is inserted through both cortices of the bone in a position that will not interfere with subsequent plate placement. The reduction handle is placed over the pin or wire onto the bone and secured with a wing nut. The toothed tip provides rotational stability and considerable force can be applied to the bone during fracture manipulation and reduction. The rounded tip is used with the threaded guide wire when a lower force is required during fracture reduction or when a push-pull maneuver is required. Reduction handles can be connected with clamps and rods to function as external fixators for temporary intraoperative fracture stabilization.

The same joystick principle for fracture reduction can also be achieved using a T-handle with a Schanz screw; however, it does not provide the rotational stability obtained by the toothed-tip reduction handles.

a The self-tapping threaded pin is drilled through the drill sleeve at the proximal segment. b The reduction handle is attached to the threaded pin and pushed close to the bone. Then the wing nut is tightened. The second self-tapping threaded pin and reduction handle is applied in the same way distally. c Combination clamps and rod are applied but without tightening the nuts. The fracture is reduced under image intensifier guidance. d After completing reduction, the nuts of the combination clamps are tightened to hold the fracture reduction temporarily.

a–b Modular external fixator used for indirect fracture reduction. a Two pins are inserted in each main fragment outside the zone of injury. They are fixed to a tube by universal clamps, and function as two handles for indirect reduction. b After reduction the two tubes are united by a third tube and two tube-to-tube clamps.

External fixators

The tubular external fixator system, together with Schanz screws, can be used in the same manner as reduction handles for indirect fracture reduction and temporary fracture fixation ( Fig 3-2 ). To reduce radiation exposure of the surgeon‘s hands during the maneuvers to achieve fracture reduction, two long tubes can be connected to the Schanz screws by clamps and used by the surgeon as handles. Once satisfactory fracture reduction is obtained, the tubes are locked in position using a third tube and two tube-to-tube clamps that have been preassembled.

Large distractor

The function of the large distractor is essentially the same as that of the external fixator, except that the distractor can be used to distract or compress the fracture zone by means of tightening a nut ( Fig 3-3 ).

Collinear reduction clamps

These clamps allow minimally invasive fracture reduction through a collinear closing mechanism. Different types of arms are available for the reduction of long-bone, pelvic, and articular fractures. Different positions of the arms are possible and they permit a continuous application of force. There are three types of modular arm: pelvic arm, periarticular arm, and Hohmann-style arm. These arms are cannulated to allow insertion of K-wires ( Fig 3-4 ).

The advantage of this instrument is that it allows a minimal access and footprint to reduce the fracture and to maintain the reduction for clinical assessment of length, axis, and rotation. In addition, it allows the surgeon to stay clear of radiation exposure.