Wu and colleagues34 used tibial osteotomies in New Zealand white rabbits to investigate cartilage and bone changes of the knee after creation of varus or valgus tibial deformities. Thirty-four weeks after osteotomy, rabbits with up to 30° of deformity had severe cartilage changes with osteophytes, fibrillation, derangement of cell columns, and associated increased subchondral bone density of the knees. Cadaveric studies have also shown increased contact pressures within the knees and ankles with ever increasing amounts of tibial deformity.6,10 In each cadaveric study, malalignment in the distal third of the tibia caused the largest changes in the ankle, and changes in the alignment in the proximal third caused the largest changes in the knee.
Consistent with these animal and cadaveric studies are several retrospective clinical studies that have correlated tibial malalignment (particularly varus) with development of knee and ankle arthrosis.3,5,8 Kettelkamp and colleagues3 found a direct correlation between magnitude of deformity and length of time with development of knee arthrosis. These findings have led many to recommend that surgeons try to restore tibial alignment to as near normal as possible to reduce the likelihood of arthrosis after tibia fracture. We found significant improvement toward normative values for maximum hip adduction (increased) and tibial varus (decreased) after surgery. These improvements would shift the weight-bearing forces back to the central part of the knee and therefore more uniformly distribute weight-bearing forces.
Posttraumatic arthrosis that develops after fracture is thought to result from increased joint pressures and possibly factors related to the injury. Although surgical correction of tibial alignment is unlikely to reverse these cartilage changes, it may restore joint pressure symmetry and “offload” compromised compartments. Offloading of already degenerative compartments may explain our patients’ improved perceptions of function and overall health status.
There were several limitations to our study. First, plain radiographs of malaligned and uninjured tibia and fibula were used, and these do not allow complete assessment of the weight-bearing access of the limb. Our patients, however, had isolated tibia fractures, which involved a normal limb before injury, so any alterations in joint kinematics, gait, or function would likely be the result of the fracture. Another limitation of our study is its nonrandomized design. However, the patients reflect the typical heterogeneous trauma patient population, who typically develop tibial malunions and seek correction. Another limitation was the lack of a treatment protocol regarding exact surgical technique and implants used to stabilize the osteotomies. In general, the patients were treated similarly, and their preoperative and postoperative assessments were exactly the same, as was their state-of-the-art joint kinematics and gait analysis, combined with the use of previously validated outcome measures. In addition, the lack of improvement in gait could have resulted from postoperative physical therapy that focused on joint mobilization and muscle strengthening and not on correction of abnormal gait parameters noted on preoperative gait analysis. Despite the potential limitations of the study, surgical correction of these symptomatic tibial malunions resulted in significant improvement in functional outcome and improved joint kinematics on the operative side.
Conclusion
Significant effort should be made to restore and maintain near-anatomical tibial alignment until a tibia fracture is healed. In patients who develop a symptomatic tibial malunion, surgical correction should be undertaken with the intent to restore normal limb alignment and improve joint kinematics, function, and overall health status.