Commentary & Perspective

Commentary & Perspective on
"Effect of Fibular Plate Fixation on Rotational Stability of Simulated Distal Tibial Fractures Treated with Intramedullary Nailing"
by Anant Kumar, MD, et al.

Commentary & Perspective by
James Kellam, MD*,
Department of Orthopaedic Surgery, Carolinas Medical Center, Charlotte, NC

With the introduction of locked reamed intramedullary nailing for the treatment of tibial fractures, achieving and maintaining reduction of distal-third fractures has become problematic. This cadaveric study highlights the problems of achieving and maintaining reduction of distal tibial fractures that are associated with a fibular fracture at the same level. However, it is important to define the "distal tibia" to understand when the use of conventional locked nailing will not provide successful treatment of fractures of the tibial shaft.

Intramedullary fixation entails a three-point fixation within the diaphysis. Toward the ends of long bones, the medullary canal widens as the diaphysis continues into the metaphysis. Thus, in the metaphysis, the intramedullary nail will not be able to maintain three-point fixation so that adjunctive fixation, such as the use of transverse locking screws, is necessary to maintain stabilization of the fracture construct. Consequently a distal-third fracture can be defined as one that begins at the point of origin of the mismatch between the nail and the medullary canal so that there can be no contact between the nail and the cortex of the fragment. It will be difficult to reduce any fracture occurring in this region of the distal tibia and to maintain the reduction despite the use of locking screws. Reduction is even more difficult if there is a fibular fracture at the same level as the tibial fracture. This fracture pattern usually reflects a high-energy bending mechanism of injury that causes increased rotational instability and disruption of the soft tissue.

The first challenge is to achieve an acceptable closed reduction, which is defined as restoring the anatomical alignment of the mechanical axis of the tibia with neither loss of length nor malrotation. The difficulty of holding the small distal fragment makes reduction of these distal fractures problematical. A thin guide-wire cannot provide sufficient stability to maintain the reduction during intramedullary reaming and nailing. This is even more difficult when a distal-third fracture occurs in osteoporotic bone, because there is insufficient cancellous bone in the metaphysis to support the guide-wire. Therefore, great care must be taken to maintain the reduction during reaming and nail insertion.

The next challenge is maintenance of the reduction. In conventional locked nailing, the reduction is maintained by the contact between the nail and the endosteal cortex with supplemental fixation provided by locking screws. This bone-nail construct will support the reduction, limit varus-valgus motion of the fragment, and prevent loosening of the locking screws. The mechanical advantage of this construct is nonexistent in the distal tibial fracture because the contact between the nail and the cortex is lost; the distal fragment can then move in an anterior-posterior and/or a medial-lateral directions, with potential loosening of the screws and loss of reduction. This loss may be accelerated in osteoporotic bone, which may not be strong enough to hold the nail-and-screw construct whereas the strong cancellous bone of the distal metaphysis in a young individual will support the nail.

Finally, reduction may be lost as the screw-hole is being drilled prior to screw insertion. Excessive force applied to the drill as it perforates the bone will push the distal fragment into malposition. This technical error occurs more often in osteoporotic bone of the elderly or in the osteopenic bone of a nonunion or a delayed union. The use of sharp drill bits, repeated fluoroscopic imaging, and particularly careful technique will prevent this complication.

There are several solutions for these possible problems in achieving and maintaining reduction of these distal tibial fractures. One solution, described in this paper, is stabilization of the fibular fracture if it is at the same level as the tibial fracture. Initial plate fixation of the fibular fracture will allow the appropriate length and rotation of the tibia to be obtained, and then additional small adjustments can be used to obtain the proper varus-valgus alignment. Krettek et al. have described another technique that involves the use of blocking or Poller screws ¹. After guide-wire placement, these screws are inserted on either side of the guide-wire to guide the nail into the distal fragment and maintain the reduction. These screws also act as a false endosteal cortex to provide "jamming" between the screws and the nail and thus maintain the fracture alignment.

In this study, Kumar et al. have shown that there is an initial increase in rotational stability and control of the reduction of a distal tibial fracture with plate fixation of a fibular fracture that occurs at the same level as the distal-third tibial fracture, but they did not address possible increases in stability specifically in varus-valgus or flexion-extension.

In their study, the authors reported 6° of the so-called windshield wiper effect (involving the varus-valgus movement of the screw) between the locking bolt and the hole in the nail. This probably explains why specimens with fibular plate fixation had less displacement initially at the first torque point than did specimens without fibular plate fixation, but subsequently the differences did not increase as the torque was increased. The first measurement of local rotation without fibular plate fixation absorbed the windshield wiper effect, and after that, the screws were jammed into the hole, thus preventing rotation. Plating the fibular fracture completely eliminated this varus-valgus movement of the screw. The resultant increase in rotational control may be of great clinical value.

What would be of more clinical value would be to add further testing of the fixation to include a simulation study of normal physiological activities that involve the ankle for a number of cycles equivalent to three months of lower-leg function to determine whether fibular plate fixation would prevent the loosening of the locking screws. Such testing might provide the answers to questions raised in the authors' unpublished clinical series in which reduction was lost gradually when the fibular fracture at the same level as the tibial fracture was not treated with plate fixation.

Another concern about the clinical relevance of this study is that the interosseous membrane was intact. In high-energy fractures of the tibia with an associated fibular fracture at the same level, the interosseous membrane is highly unlikely to remain intact. Consequently, the distal fragment of the fracture will be able to move into either varus or valgus because it will not be stabilized by the interosseous membrane.

Kumar et al. tried to justify their study by presenting an unpublished clinical series of sixty distal tibial fractures in which those patients who did not have the fibular plate fixation of a fracture at the same level as the tibial fixation went on to develop a valgus malunion. They stated that this adverse outcome was apparently related to normal stresses to the ankle joint. Plate fixation of the fibular fracture at the same level as the tibial fracture was not associated with this gradual loss of reduction. This loss of reduction also was not seen by Robinson et al. in their report of sixty-three consecutive distal tibial metaphyseal fractures, twenty-two of which represented the fracture pattern of interest². Those authors found that the closed reduction and the placement of the guide-wire must be extremely accurate; in particular, the guide-wire must touch or penetrate the subchondral bone. At all times, at least two, and when possible, three cross-screws, two of these being medial-lateral and one being anteroposterior, were very helpful in maintaining this alignment. Care must be taken when inserting the screws in a medial-lateral direction because excessive force on the drill will also cause malpositioning of the distal fragment. Robinson et al. reported that all fractures in their series healed and only two had a varus deformity, which was related to an inadequate reduction at the time of surgery. Fibular plate fixation was not attempted nor was adjunctive fixation with Poller screws in these two patients. Mosheiff et al. ³and Tyllianakis et al. ⁴ also reported the successful adjunctive use of fibular plate fixation to obtain reduction with intramedullary nailing of distal-third tibial fractures.

These techniques are not without complications. The distal fibula at this level has a curve that must be matched with a contoured plate to avoid a rotational malunion. Also, plating of the fibula must be done accurately and one must take into account that fibular plate fixation amounts to a second surgical assault with resulting increased swelling and compromised wound-healing. This procedure requires a well-contoured 3.5-mm small-fragment reconstruction or dynamic compression plate. One-third tubular plates provide a little more leeway as they tend to conform to the anatomical position of the fibula. Also, it is necessary to avoid creating an apex-posterior angulation of the fibula, which will also compromise the tibial reduction.

In conclusion, this paper is important because the authors address the problem of malreduction of distal tibial fractures with a fibular fracture at the same level. This malreduction is first and foremost the surgeon's responsibility. Meticulous intramedullary techniques combined with the use of fibular plate fixation or blocking screws will achieve the best results in maintaining reduction of these distal tibial fractures to union.

*The author did not receive grants or outside funding in support of the research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

References

1. Krettek C, Miclau T, Schandelmaier P, Stephan C, Mohlmann U, Tscherne H. The mechanical effect of blocking screws ("Poller screws") in stabilizing tibia fractures with short proximal or distal fragments after insertion of small-diameter nails. J Orthop Trauma. 1999;13:550-3.
2. Robinson CM, McLauchlan GJ, McLean IP, Court-Brown CM. Distal metaphyseal fractures of the tibia with minimal involvement of the ankle. Classification and treatment by locked intramedullary nailing. J Bone Joint Surg Br. 1995;77:781-7.
3. Mosheiff R, Safran O, Segal D, Liebergall M. The unreamed tibial nail in the treatment of distal metaphyseal fractures. Injury. 1999;30:83-90.
4. Tyllianakis M, Megas P, Giannikas D, Lambiris E. Interlocking intramedullary nailing in distal tibial fractures. Orthopedics. 2000;23:805-8.