Comparison of Different Lateral Tibia Locking Plates in Schatzker V tibial plateau fractures

A Biomechanical Comparison of Three Different Lateral Tibia Locking Plates

By Bennie Lindeque, MD, PhD; Todd Baldini, MS
ORTHOPEDICS 2010; 33:18

Purpose:  -how well laterally placed modern tibia locking plates used in the treatment of Schatzker V tibial plateau fractures would uphold the medial plateau during axial loading.

- Fifteen third generation Sawbone tibias were obtained and an osteotomy was cut beneath the medial plateau to recreate Schatzker V type plateau fractures. Three groups were created (n=5 per group). Each group was plated with either a Synthes 4.5-mm LCP proximal tibial plate, a Zimmer NCB proximal tibia plate, or a DePuy Polyax tibial plate.
- A vertical load was applied over the medial plateau using an Instron servohydraulic test machine. Load measurements were analyzed at 2 and 3 mm of subsidence as well as load to failure.
- Failure was defined as closure of the wedge osteotomy or the medial condyle collapsing.
- The Synthes and DePuy plates both held up better than the Zimmer plate at 2 and 3 mm of subsidence. Despite this fact, all plates tested held up well above physiological forces of full and partial weight bearing and therefore would be appropriate for the treatment of Schatzker V type tibial plateau fractures

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The knee is one of the major weight bearing joints of the lower extremity, therefore proper fracture fixation following injury is of the utmost importance.
- These fractures can be divided into 4 groups: distal femur versus proximal tibia and intra-articular versus extra-articular.
-This article focuses on fixation of Schatzker V tibial plateau fractures with large medial defects.¹
- Overall, tibial plateau fractures account for 1.2% of all fractures.²
- In the past, this type of plateau fracture has been treated with medial and lateral fixation^3-5 or even a combination of internal and external fixation.^6-8 But with the advent of locking plates, it has been shown to be as effective in maintaining reduction and stability during healing with unilateral plating as with the traditional methods.⁹ It has also proven to be an effective technique to offer more fixation strength, which can be of benefit to patients with osteoporotic bone.¹⁰

The purpose of this study was to determine whether modern locking plates would be able to uphold a medial plateau fracture above physiological forces.

Lateral Locking Plates
Each company’s plates used different screw configurations, screw sizes, materials, and were of different lengths (Table 1)

Figure 1: Synthes (A), Zimmer (B), and DePuy (C) lateral tibia locking plates.

The shortest plate available was used from each company and every hole was filled. If there was a variable angle to the proximal subchondral locking screws, the screws were placed as far apart as possible.

Results

The load data is shown in Table 2. The DePuy Polyax plate had a significantly larger failure load than the Synthes locking compression plates or Zimmer noncontact bridging plates with further analysis. The Synthes locking compression plate and DePuy Polyax plates proved to carry significantly larger loads than the Zimmer noncontact binding plate when looked at with the Tukey-Kramer HSD test.

The stainless steel Synthes locking compression plates all failed by condyle collapse when the Sawbone fractured at the distal screw. The titanium Zimmer noncontact bridging and titanium DePuy Polyax plates all failed by osteotomy closing without plate breakage.

Discussion

The aim of this study was to ascertain whether 3 different modern locking plates would be strong enough to uphold a Schatzker V fracture under physiological loading conditions and secondarily to directly compare 3 different proximal, lateral tibia plates with locking and nonlocking options in the treatment of Schatzker V type tibial plateau fractures. The use of fully locked and hybrid locking/nonlocking plating systems have been recognized as appropriate treatment of proximal tibial fractures, even with significant bone loss medially.^10,12,13

Conclusion

Based on our data, the Synthes and DePuy plates both held up better than the Zimmer plate at 2 and 3 mm of subsidence. Despite this fact, all plates tested held up well above physiological forces of full and partial weight bearing and therefore would be appropriate for the treatment of Schatzker V type tibial plateau fractures.

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