4.1 What does planning include?

The surgeon should consider:

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  Position of the patient, surgeon, surgical assistant, and operating room personnel

  
  
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  Specific instruments and implants

  
  
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  C-arm location and draping, type of operating table (eg, radiolucent)

  
  
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  Draping of patient

  
  
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  Biomechanical fixation concept

  
  
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  Surgical approach

  
  
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  Surgical sequence

  
  
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  Tactic(s) for reduction

  
  
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  Fixation steps

  
  
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  Closure and aftercare

Several questions should be answered before starting a MIPO procedure:

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  Where are the danger zones or safe corridors in respect to the planned implant access?

  
  
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  Should the fixation provide relative stability by using a bridge plate or is the fracture best treated with absolute stability with interfragmentary compression?

  
  
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  How can reduction be achieved and maintained?

  
  
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  How best to check for length, alignment, and rotation with the C-arm before fixation?

  
  
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  Are the surgical assistants and instruments for direct and indirect reduction available?

  
  
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  Is the C-arm available with a competent technician?

  
  
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  Is there need for additional instruments to facilitate percutaneous reduction?

  
  
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  Is there need to precontour the plate?

  
  
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  How and when does the surgeon proceed when the original goal of MIPO cannot be achieved (back-up plan)?

4.2 Danger zones

A thorough knowledge of surgical anatomy is necessary to avoid damaging vital structures, such as nerves and blood vessels. Several danger zones must be considered when inserting and manipulating instruments and implants through small incisions without visual control of the endangered structures.

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  Proximal humerus:

  
  
  
  
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    – Axillary nerve passes 5–7 cm below the acromion tip, around the proximal humerus, coming from posterior to anterior.

  
  
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  Humeral shaft:

  
  
  
  
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    – Radial nerve passes from proximal posterior to distal anterolateral and then between the brachialis and brachioradialis muscle.

    
    
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    – Musculocutaneous nerve passes beneath the biceps muscle along the anterior and medial brachialis muscle.

  
  
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  Femoral shaft:

  
  
  
  
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    – Superficial femoral artery runs from proximal anterior to distal posterior through the adductor canal at the junction of the middle and distal third of the femur and comes close to the medial and posterior femur shaft before emerging in the popliteal fossa.

  
  
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  Distal tibial shaft:

  
  
  
  
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    – Neurovascular bundle of the anterior tibial artery and the deep peroneal nerve are closely adjacent to the distal third of the tibia running from posterior to the anterior surface of the tibia.

  
  
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  Medial malleolus:

  
  
  
  
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    – Saphenous nerve and vein are at the level of the medial malleolus.

4.3 Reduction

Closed reduction

Closed reduction using indirect reduction is a main tenet in MIPO. This technique can be demanding when the fracture has to be reduced without touching the fracture site. The soft-tissue envelope together with traction forces alongside the limb axes are needed to counteract the deforming forces and to create a stable operative field for MIPO. Complete muscle relaxation by an anesthetist may also be needed. This should result in restoration of length, alignment, and rotation. Several instruments, like the traction table, one or two large femoral distractors [5] or an external fixator can create a stable operative field. The insertion of the plate, which is temporarily or definitively fixed to the distal or the proximal fragment, can also be used to align the fracture. Additional tools like bumps or radiolucent triangles can also help reduce the fracture. Schanz screws, percutaneous ball spike pushers, manipulators, collinear forceps ( Fig 3.1.3-1 ) or intramedullary rods help to fine tune the reduction of the fracture and to maintain it for x-ray control before MIPO fixation.

Limited open reduction

Displaced intraarticular fractures and simple metaphyseal or diaphyseal fractures require anatomical reduction with lag screw fixation. This can be achieved by percutaneous manipulation using pushers, tamps and balloons for articular fractures under arthroscopic and C-arm control. For simple metaphyseal fractures, percutaneous applied clamps may provide anatomical reduction followed by insertion of a lag screw. A protection plate is then inserted through small incisions. In these situations, a limited open approach to achieve an anatomical reduction and stable fixation is recommended ( Fig 3.1.3-2 ).

4.4 Absolute or relative stability?

For most MIPO techniques, relative stability is the recommended biomechanical principle. The indirect reduction technique using long plates to bridge a multifragmentary metaphyseal or diaphyseal fracture is a classic example. This corrects length and alignment and allows undisturbed indirect fracture healing by callus formation.

However, the surgeon must be aware of rotational malalignment, as the literature shows a surprisingly high rate of this specific deformity (as high as 25% of cases) [7].

In contrast, simple metaphyseal or diaphyseal fractures (AO/OTA Classification type A fractures) require anatomical reduction and absolute stability obtained by interfragmentary compression using a lag screw and protection plate. This is the recommended principle to prevent high strain at the fracture gap and results in direct bone healing.

4.5 Implants

Minimally invasive plate osteosynthesis can be performed using many types of plates. Long straight plates are usually adequate for midshaft fractures. In recent years, anatomically preshaped locking compression plates (LCP) have become available.

Conventional plates (LC-DCP)

Conventional plates should be long (10–14 holes in the tibia and the humerus; 16–24 holes in the femur).

As a rule, the plate length should be three times longer than the fracture length.

The plate should reach from one metaphysis to the other [8]. Exact contouring of the plate is necessary to fit metaphyseal flares: conventional screws will bring the bone to the plate and if contouring is not precise, there will be a loss of reduction when the first screw is tightened ( Fig/Animation 3.1.3-3 ). Precontouring the plate with a plastic bone model is helpful. This plate is sent for sterilization before the operation.

4.6 Intraoperative imaging

Without intraoperative imaging, MIO and MIPO are not feasible. An approach through soft-tissue windows remote from the fracture site with no direct visualization of the fractured fragments needs repetitive imaging to check the reduction. It is important to create a stable operative field, which allows maintenance of the reduction achieved. Fracture reduction can be maintained by indirect reduction tools like the traction table, the large femoral distractor, or the external fixator. Additional tools like bumps, towels, percutaneous clamps and K-wires are also helpful. This provides an environment where C-arm pictures in AP and lateral projection can be taken without radiation exposure of the surgeon′s hands (see chapter 4.9).

4.7 Alternative plan

There should always be an alternative plan in case MIO/MIPO cannot be carried out as desired. This should include:

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  Limited opening at the fracture site to apply an instrument for direct reduction

  
  
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  Exposing the fracture as in conventional plating (ORIF)

  
  
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  Asking for help from a more experienced surgeon

A thorough knowledge of the pros and cons of MIPO will help to reduce pitfalls associated with this demanding technique including malunion, delayed union, and nonunion.

4.8 Postoperative management

Postoperative management after MIPO surgery is not different from other MIO or ORIF cases. Pain medication may be required for a shorter time due to limited skin incisions. Antibiotic and thromboembolic prophylaxis is also mandatory like in other implant surgery. The affected limb should be well positioned and elevated and wrapped to reduce swelling. Splints will help to prevent contractures, eg, application of a U-slab to the ankle and the foot to prevent equinus. Physical therapy should be started as soon as pos sible after MIPO procedures. Joints should be mobilized by active or active-assisted movements or by passive continuous motion, especially after articular fractures. Weight bearing should be limited according to the fitness of the patient, the bone quality, and the fixation stability.

Implant removal may be considered after 1–2 years depending on the bone segment if:

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  The patient is young

  
  
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  When the implant is in the lower extremity

  
  
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  When the implant limits limb function during work or sport or causes irritation

The patient should be informed about the possibility that broken screws may be left in situ because removal may cause soft-tissue and bone damage and increase the risk of refracture. When removing LHSs, special removal instruments should be available to remove jammed screw heads with conical extraction screws or special drill bits. To reduce the risk of refracture, patients should be advised to avoid contact sports or heavy labor for 2–4 months after implant removal [9].

5.1 Clavicle

Principle: Plate contouring and plate position is an important issue when deciding to perform MIPO of the clavicle. Superior plate position is easier to apply. The plate has to be bent in a horizontal S-shape fashion using a reconstruction plate 3.5 or an anatomical plate. Fixation of the plate is possible with conventional screws due to the flat surface of the clavicle. If anterior plate position is preferred, a vertical S-shape must be contoured or an anatomical plate is used. For anterior plate position, LCPs are preferred because they tolerate malcontour without compromising the achieved reduction. The fracture has to be reduced and stabilized either by a temporary plate or by a mini external fixator placed 90° to the definitive plate ( Fig 3.1.3-4 ). The patient can be positioned in a supine or beach chair position. C-arm views in AP [10–12] are taken during the operation. Superior plate position causes more skin irritation than anterior position and is cosmetically less appealing in slim patients.

Patient selection: Simple clavicular shaft fractures are a good indication for MIO surgery with titanium elastic nails (ESIN, see chapter 6.1-2), whereas the indication for MIPO in clavicle fractures is multifragmentary clavicle fractures. Compared with ORIF, MIPO of midshaft clavicle fractures seems to be an effective fixation method ( Fig 3.1.3-4 ) [19], but there may be a slightly increased risk of nonunion.