Tibia and fibula, distal—introduction

10.1055/b-0034-87661

Tibia and fibula, distal—introduction

Christoph Sommer, Rodrigo Pesantez

Introduction

Fractures of the distal tibia and fibula include extraarticular fractures (43-A) and fractures which involve the tibial plafond (43-B and 43-C). Minimally invasive techniques are excellent for fixation of extraarticular fractures of the distal tibia. Sometimes minimally invasive plate osteosynthesis (MIPO) techniques for the metaphyseal component of the injury may be combined with formal (limited) open reduction and internal fixation of the articular surface in order to achieve anatomical reconstruction. The best results for displaced articular fractures of the distal tibia have been achieved by reconstruction of the articular surface of the tibia, stable fixation, and early rehabilitation. However, conventional operative treatment of such injuries results in extensive soft-tissue dissection and periosteal stripping which is associated with high rates of wound dehiscence and infection, delayed union, and nonunion. For this reason staged management of these injuries has become the standard of care, especially in complex 43-B/43-C fractures. This staged management takes care of the soft tissues by using external fixation as a bridge to align and stabilize both bone and soft tissues, allowing the soft tissues to settle down. Once the soft tissues are in good enough condition to perform definitive fixation of the fracture, surgical techniques that minimize damage to the soft tissues are used, such as operating through the fracture lines to preserve the periosteum and the soft-tissue attachments.

Incidence

Compared to other fracture types the incidence of tibial pilon fractures is very low. They occur in 3–10% of all tibial fractures and in less than 1% of all fractures of the lower extremity. These fractures are most commonly caused by falls from a height or are due to rapid deceleration motor vehicle accidents. They are usually high-energy injuries, although they can also occur with low-energy trauma (rotational pattern as in skiing injuries or in osteoporotic bone).

Current methods of treatment

Regardless of the type of fracture, the soft tissues play a key role when considering operative treatment. Significant soft-tissue compromise calls for a staged procedure using a bridging external fixator as a first step to allow the swelling of the soft tissue to subside.

In 43-A fractures (extraarticular injuries) it is still debated whether intramedullary nailing (with new nail designs) or plating is the preferred method of fixation. Several clinical trials have showed that good results can be obtained by using either technique [ 1– 3]. In this kind of injury plating techniques using indirect reduction and percutaneous plating have resulted in a more soft-tissue-friendly approach and improved on the results of open techniques.

In 43-B fractures, (partial articular injuries) open reduction and internal fixation using AO principles, respecting soft-tissue injuries, and restoring the anatomy of the joint with conventional plating techniques are the gold standard of care.

In 43-C fractures (complete articular injuries) the gold standard of care is open reduction and internal fixation, since it is a combination of an articular and metaphyseal injury. There are two different goals of treatment. In the articular surface the surgeon must aim for an anatomical reduction and absolute stability. In the metaphysis only length, axial alignment, and rotation must be restored and absolute or relative stability may be used. In these injuries the most important factor determining outcome is the condition of the soft tissues. Open reduction and internal fixation is planned only when the soft-tissue swelling has reduced as shown by wrinkling of the skin. This is best achieved by following a staged protocol [ 4, 5].

Controversy remains over using external fixation as the definitive form of treatment for these severe injuries instead of a staged protocol. This can be achieved by applying bridging external fixation to the talus or by using hybrid external fixation (using rings and minimal internal fixation with screws for the articular surface). Problems with maintaining axial alignment and difficulties with residual articular incongruity occur with these techniques and have to be considered. Prolonged immobilization across the joint may result in joint stiffness.

Indications and contraindications for MIPO

Indications for MIPO in fractures of the distal tibia are extraarticular (43-A) fractures, and simple intraarticular injuries (43-B1, 43-C1, 43-C2) with or without proximal extension of the fracture into the distal diaphysis which are considered unsuitable for intramedullary nailing. Table 21.1-1 presents recommended techniques (approach, reduction, and fixation) for the definitive reconstruction of pilon fractures in relation to the zone and pattern of the fracture.

Pure MIPO is contraindicated in complex intraarticular injuries with depressed fragments that require anatomical reduction, which usually cannot be achieved by simple ligamentotaxis; these fractures are 43-B2, 43-B3, and 43-C3. In these situations articular reconstruction needs one or more open approaches to obtain an anatomical reduction of the joint block. The latter can then be bridged to the diaphysis using a MIPO technique with a medially and/or laterally slipped plate. This technique can be applied to both the tibia and the fibula.

This technique might become more difficult when following a staged procedure, due to the extent of soft-tissue adhesions at this late stage.

Recommended techniques (approach, reduction, and fixation) for the definitive reconstruction of pilon fractures in relation to the zone and pattern of the fracture.
Fracture		Approach		Reduction		Fixation
Zone	Pattern	Open	Percutaneous	Direct	Indirect	Internal	External
Articular	Simple	+	++	+	++	+++	–
	Complex	+++	–	++	+	+++	–
Meta-/Diaphyseal	Simple	+	++	+	++	++	+
	Complex	–	+++	–	+++	++	+
Fibular	Simple	+++	–	+++	–	+++	–
	Complex	+	++	–	+++	+++	–
+ alternatively indicated
++ mostly indicated
+++ strongly indicated
– not indicated

Surgical anatomy

Since the anteromedial surface of the distal tibia is only covered by skin and subcutaneous tissues, it is not protected by soft tissue. As a result of injury massive swelling may lead to the formation of fracture blisters, and skin necrosis may ensue.

The ankle joint is formed by the distal ends of the tibia and fibula as well as the talus, including the joint capsule and ligaments. Any incongruity of the articular surface or an unduly broad ankle mortise will lead to local overload, frequently resulting in cartilage degeneration and posttraumatic osteoarthritis.

The distal fibula is held in the notch of the tibia by the interosseous membrane and the anterior and posterior tibiofibular ligaments. In pilon fractures involving both bones the syndesmotic ligaments are usually intact, but they may sometimes be avulsed from the tibia together with bone fragments. The talofibular ligaments may be torn, especially in the type of valgus injury where the fibula remains intact. Most often the deltoid ligaments are intact, permitting indirect reduction of the medial malleolar fragment by ligamentotaxis in selected cases. Due to these ligament attachments, the type C injury pattern demonstrates three main fracture fragments: the anterolateral or Chaput fragment (attached to the anterior tibiofibular ligament), the posterior or Volkmann fragment (attached to the posterior tibiofibular ligament), and the medial malleolar fragment (attached to the deltoid ligament).

The thick-walled, triangular-shaped diaphysis of the tibia flares distally at the transition from the diaphysis to the metaphysis. The distal tibial metaphysis cortex is thin and the metaphysis is filled with relatively dense cancellous bone. The medial aspect of the distal tibia has approximately 25° of medial angulation and 20° of internal torsion.

The type C injuries of the pilon fractures are characterized by two major fracture planes either in the coronal or sagittal orientation. Coronal plane fractures tend to show a valgus deformity with a more distal metaphyseal disruption and predominantly occur in elderly patients. Sagittal plane fractures tend to have a varus deformity and show a more proximal metaphyseal disruption. They are usually encountered as a result of high-energy injuries in young adults [ 6].

The blood supply of the tibia has been studied by Borelli et al [ 7], showing that the distal metaphyseal areas of the tibia have a rich extraosseous blood supply provided by the anterior tibial artery and posterior tibial artery (see also chapter 20.1 Tibia and fibula, shaft, Fig 20.1-2 ). He demonstrated that open plating of the distal tibia caused a greater disruption of this blood supply than a percutaneous technique. Furthermore, open plating increases the risk of delayed union and nonunion. These studies and results show why minimally invasive plating techniques are preferred.

Preoperative assessment

Soft tissues

The soft-tissue condition should be evaluated circumferentially for degree of swelling, the severity of contusions, the presence of abrasions, blisters, open wounds, and compartment syndrome. Displaced fracture fragments may cause skin tension and should therefore be reduced as soon as possible. Once the tibia is realigned it should be immobilized in a well-padded splint before radiological examination.

Imaging

X-ray evaluation includes AP, mortise, and lateral views of the ankle and full-length x-rays of the lower leg. The analysis of the images should focus on presence and location of the fibular fracture, the degree of articular damage, the direction of displacement of the talus, and the associated fracture fragments. This information is usually sufficient for planning temporary fixation using a joint bridging fixator. A CT scan is performed once the distal tibia has been aligned using ligamentotaxis. Thin-slice CT cuts in an axial, sagittal, and coronal orientation as well as 3-D reconstruction help to analyze the major fracture planes, the amount of articular impaction, and the degree of metaphyseal comminution. In simple and minimally displaced fractures a CT scan may be ordered immediately. In these cases if the soft tissues are not compromised, immediate definitive fixation may be performed.

Preoperative planning

Based on the imaging a preoperative plan is developed, which takes into account the position of the main fracture fragments as well as the articular surface injury. The sequential steps for reduction, as well as fixation of the different fragments while respecting the soft-tissue envelope, should be drawn and written. The planned implant should be placed at the best position indicated to secure and neutralize the major displacing forces both at the joint level and in the metadiaphyseal region.

Operative procedure

This chapter describes in detail the operative stabilization of the distal tibial metaphysis for extraarticular or simple intraarticular 43- and distal 42- fractures with possible distal articular extension. The complex intraarticular pilon fracture (43-B3 and 43-C3) cannot be treated purely by MIPO technique. With these fractures one or two approaches optimally positioned (anteromedial, anterolateral, posteromedial, posterolateral) are required. The location of the surgical approach depends on the individual soft-tissue situation and the fracture pattern as well as what is required for adequate reconstruction of the articular surface of the distal tibia. These details are described elsewhere [ 8].

General principles

Fibula

Most distal tibial fractures are accompanied by fibular fractures. The fibula, if fractured below the level of the midshaft, is stabilized in all intraarticular distal tibial fractures (43-B and 43-C). In higher distal metadiaphyseal tibial fractures (42-), fixation of the fibula is recommended under the following three conditions:

In case of a very distal tibial fracture with a short articular fragment (43-A), resulting in a critical fixation to the distal tibial metaphysis.
Combination type injury: distal tibial shaft fracture (42-) in combination with an ankle fracture (44-), which is often visible by the presence of a posterolateral fracture extension on the tibia (Volkmann triangle).
Poor patient compliance with suspected full loading occurring soon after the operation. This can lead to bending of the tibial plate with secondary valgus malalignment in those cases where the plate was applied to the medial side.

Fibular fractures may be simple two-part fractures, or have multiple fragments. The simple two-part fracture is anatomically reduced and fixed using a traditional open reduction and internal fixation technique as the first step of the procedure ( Fig 21.1-1 ). Fractures with comminution are difficult to reduce anatomically using the open technique. Efforts to reduce and fix such fractures as an initial stage in the treatment of distal tibial fractures may fail due to fibular malreduction. In fact, it may be easier to reduce the fibula indirectly, using the correctly positioned talus as a guide after operative stabilization of the tibia. These complex fractures of the fibula can be plated using a MIPO technique similar to that used for the tibia ( Fig 21.1-2 ) [ 9]. In these situations, the assessment of correct fibular alignment (length, axis, rotation) is difficult and therefore intraoperative image intensifier control is mandatory. Preoperative x-rays of the intact opposite ankle joint are helpful to assess the reduction of the injured side (see 5.1 Assessment of reduction).