Bone union and structural changes in the articular cartilage of the knee joint after immediate and delayed antegrade locked intramedullary nailing of femoral shaft fractures. Experimental findings

Background Antegrade locked intramedually nailing (IMN) is considered to be a method of choice for repair of femoral shaft fractures. We studied the articular cartilage of the canine femoral condyles in the conditions of immediate and delayed antegrade IMN to reveal whether timing of operation results in any structural changes in the cartilage tissue. Material and methods Femoral shaft fractures were modelled in 12 adult mongrel dogs and fixed using antegrade IMN immediately after the injury in group 1 (n = 6) and four days after the injury in group 2 (n = 6). Five dogs were intact. Results In group 1, fractures united after 42 days but in group 2 the union was seen in the radiographs only by day 70. Unified bone marrow cavity and cortex were formed by day 70 in group 1 while in group 2 it was seen only by day 100. The histological study showed that the structure of the articular cartilage of the femoral condyles was not damaged in group 1 at all time points. The changes were the decrease in the cartilage thickness and in the volumetric density of condrocytes. In group 2, the cartilage of the femoral condyles featured defibration of the articular surface that was accompanied by breakage of the basophilic line integrity and penetration of vessels into the cartilage. Conclusion Delayed antegrade locked IMN provoked destructive changes in the articular cartilage of the femoral condyles and decreased chondrocyte proliferation. We suppose that delayed IMN of a femoral shaft fracture might cause initiation or deteriorate the existing knee osteoarthritis. Level of evidence: IV.