1 General considerations topenlarge
The key concept of MIPO fixation is to preserve the soft-tissues and blood supply in the metaphyseal fracture area by not exposing them surgically. An entry site is developed over the distal tibia. The plate is then inserted from distal to proximal, through a tunnel between periosteum and intact overlying tissue.
By definition, type A fractures have no involvement of the articular surface, so accurate reduction of the joint is not required. The soft-tissue conditions usually dictate the choice of procedure: early single-stage or multiple-stage surgery. The decision is based on the individual situation and not necessarily on general principles. This type of fracture lends itself to MIPO type stabilization because of the minimum insult to the soft-tissue envelope.
(Image taken from Orozco R, et al. (1998) Atlas of Internal Fixation. Used with kind permission.)
Displaced fractures with minimal, closed soft-tissue injury
(Tscherne classification, closed fracture grade 0, rarely grade 1)
These injuries may be reduced and fixed primarily, as a single stage procedure, if the soft tissues are in truly excellent condition.
A distractor or external fixator may help reduction. Fibular reduction and fixation is the usual next step, but this reduction must be accurate, so that it does not prevent tibial reduction. Finally, the tibial plate is introduced with MIPO technique and final reduction of length, alignment and rotation is achieved.
Grossly displaced fractures and/or fractures with severe, closed soft-tissue injury
(Tscherne classification, closed fracture grade 2 or 3)
It is generally advisable to proceed in two or more stages:
- Closed reduction and joint bridging external fixation
- Definitive MIPO reconstruction after 5-10 days (wait for the apppearance of skin wrinkles)
Open distal tibial fractures
These are very severe injuries which may require plastic surgery for soft-tissue reconstruction. The management includes several stages:
- Emergency management: Wound debridement and lavage. Joint-bridging external fixation and stabilization of the fibula (if needed and soft tissues allow). Where possible, closure or coverage of any opening into the joint should be achieved.
- After 48 hours: Soft-tissue coverage (local or free flap). Plan for definitive stabilization at this time.
- Definitive stabilization: Bridging of the metaphyseal comminution, with or without bone graft.
Bone grafting at the time of soft-tissue coverage is possible if the envelope is obviously viable but in marginal soft-tissue situations or in the multi-traumatized catabolic patient bone grafting as a secondary procedure may be advisable.
2 Planning for reduction and fixation top
Fibula or tibia first? Sequence of bone stabilization
In most type 43-A3 fractures, the fibula is fractured as well and needs to be stabilized.
For simple fibular fractures, this is usually done first with ORIF and stable plate fixation. Alternatively, for transverse fractures, consider a small diameter, flexible intramedullary nail. Fibular reduction helps realign the tibia fracture. The operation is completed by stable plate fixation of the tibia. Finally, bone grafting is performed if required.
Some fibular fractures are complex and reduction may be difficult. Their fixation will impede reconstruction of the tibia. In this situation, fibular ORIF is better after the tibia has been fixed. The syndesmotic ligaments are usually intact, so gross realignment of the fibula occurs with reduction and fixation of the tibia. An option, which is attractive for comminuted fibular fractures, is to use a MIPO technique with a long bridging plate, or intramedullary fixation of the fibula with a small diameter, flexible nail. Fibular nailing is particularly applicable if the soft-tissue injury or complexity of the fracture makes extensive exposure for internal fixation hazardous.
Planning for reduction and fixation
Preoperative planning is an essential part of treatment of all distal tibial fractures. It consists of:
- Obtain good AP and lateral x-rays of both injured and uninjured side; CT if needed
- Careful study of the x-rays (and CT scan)
- Drawing of both the fracture fragments and the desired end result (often indicated by a reversed tracing of the intact opposite tibia)
- Consideration of intraoperative reduction techniques, including switching to to open procedure if indirect reduction is unsuccessful
- Choice of implants
Type A (extraarticular) fractures can often be reduced by ligamentotaxis alone with indirect manipulation. Direct exposure is therefore not often necessary. The shape of the implant serves as a reduction tool. A properly contoured plate applied according to a good preoperative plan improves your chances of a good reduction.
3 Implant choice and plate preparation top
A variety of precontoured distal tibial plates are available. If such an implant is not available, it is important to precontour the plate prior to insertion. A 3.5 or occasionally 4.5 mm standard or locked plate (LC-DCP or LCP) can often be used, but distal purchase may be compromised without a specially designed plate. For distal fractures and osteoporosis, angular stable screws (locking head screws) may be more stable distally. With MIPO plate constructs it is preferable to choose as long an implant as possible for the widest distribution of load at the fracture site.
A non-contoured plate can be shaped prior to sterilisation, using a sawbone model as a template. First, determine the length of the plate from preoperative x-rays. Remember that the plate must be twisted to fit the distal tibia. As illustrated, the medial tibia distally lies closer to the sagittal plane while the shaft rotates externally above the metaphysis.
4 Preliminary reduction topenlarge
Reduction with a distractor
An appropriately positioned distractor or external fixator is a very helpful tool for reduction, especially for length and rotation.
Where possible this should be positioned on the medial side of the leg. Distraction can be used for the open reduction and plate fixation of the fibula as first step (if not already fixed) and for the reduction of the tibia as a second stage after previous fibular stabilization.
Schanz screws are positioned in safe zones of the tibial shaft and talar neck (or the calcaneal tuberosity). In case of previously applied joint-bridging fixator, the already existing Schanz screws can be used.
The final reduction occurs during plate application and depends upon bringing the proximal and distal tibial segments into proper position against a correctly contoured plate. Conventional screws or a push-pull reduction devices can be used to approximate the bone to the plate.
5 Final reduction top
Tibial length and rotation are restored indirectly with distractor or external fixation. Angulation may be approximated in the same way, but is definitively corrected by plate application.
Insert the plate after proximal tunneling with a blunt instrument. Depending on the fracture situation, the plate is usually positioned on the anteromedial aspect of the tibia.
Proximally, above the fracture zone, make a small incision (2-3 cm). This incision will aid plate positioning. It is important that the plate and proximal screw be centered on the tibia, particularly if locking screws will be used. The distal end of the plate should be at the level of the tibial plafond. The proximal end should extend at least three screw holes proximal to the fracture zone.
Temporary plate fixation can be performed with K-wires through the screw holes (or inserted drill sleeves) to approximate the final plate position before screw insertion. Make sure the plate is positioned to fit the properly reduced distal segment.
Preliminary plate stabilization
If the plate position is satisfactory, provisionally fix the plate to the proximal segment with a single conventional “positioning” screw through the plate. This screw brings the plate and bone together.
Assuming the plate is properly contoured and positioned, fitting the distal tibial segment to the plate will complete fracture reduction. A second conventional screw can be used to draw plate and bone together to achieve the final reduction distally ("reduction" screw). Check reduction with image intensification (see assessment of reduction).
Subsequently, locking head screws (LHS) may be inserted into the reduced distal fragment.
6 Finish fixation topenlarge
Finish plate fixation of the tibia
Once the preliminary fixation and reduction are satisfactory, additional screws are added for stability. Some may be placed through stab wounds, particularly closer to the fracture site.
The number and position of the screws inserted depends on the specific fracture pattern. The goal is “balanced fixation”. This means roughly equivalent fixation strength in both proximal and distal segments. Usually, the metaphysis requires more screws (3-5) than the diaphysis (2-3). Cortical bone provides better screw purchase than cancellous. In osteoporotic bone, the number of screws should be increased, particularly in the cancellous distal segment.
Bone grafting is almost never required, except in open type A fractures with bone loss. In such cases, it should be delayed until the soft-tissue envelope is stable.
Fixation of the fibula
In most A3-type fractures, the fibula is fractured as well and needs to be stabilized. Complex fractures of the fibula are better addressed after stabilization of the tibia (see also considerations in step 2).
Atraumatic skin sutures are used for closure of screw insertion wounds. Occasionally, additional deeper sutures are needed for distal and proximal incisions.
The x-ray imaging and physical exam should confirm the anatomical restoration of length, alignment and rotation (see assessment of reduction).