Intra-articular traumatic knee injuries
Davidson, Eleanor K.
Introduction: Tibial plateau and patellar fractures are common intra-articular fractures. An estimated 44% of patients develop post-traumatic arthritis (PTOA). PTOA is a disabling condition and the precise aetiology is unknown. Research to reduce the burden of PTOA has focussed primarily on operative reduction and rehabilitation protocols. Despite successful treatment of the fractures, clinical outcomes are frequently compromised. Initial chondrocyte death occurring at the time of injury may be the principal prognostic feature of PTOA. Chondrocyte death is irreversible and is followed by irreversible matrix degeneration and therefore cartilage degeneration. Aim: To investigate the clinical impact of traumatic injury to the knee, specifically tibial plateau and patellar fractures, and study chondrocyte death secondary to traumatic injury. Studies: Six complementary studies were performed. 1) An epidemiological analysis was carried out to determine the numbers, patient factors and mechanisms of injury of tibial plateau fractures in a large catchment area over 25 years. 2) A clinical study was performed looking at the patient reported outcomes of tibial plateau fractures in the defined population. This included the requirement for total knee replacement following tibial plateau fractures to look at the end stage of post-traumatic osteoarthritis in these patients. 3) An epidemiological analysis was carried out to determine the numbers, patient factors and mechanisms of injury of patellar fractures treated operatively in a large catchment area over 15 years. 4) A clinical study was then performed looking at the patient reported outcomes of these injuries in the defined population. This included the requirement for total knee replacement following patellar fractures to look at the end stage of post-traumatic osteoarthritis in these patients. 5) An in vitro animal model of two blunt trauma mechanisms was developed to investigate the effect on the chondrocytes in various controlled conditions. 6) A human fresh cadaveric whole joint model of blunt trauma was developed to link the animal models findings to the clinical work. Results: Tibial plateau fractures have an incidence of 11/100,000 per year and are common in elderly women following falls and young men following road traffic accidents. A third of patients suffered complications with 15% requiring further surgery. Symptomatic PTOA was seen in 5% of the population with arthroplasty required in 3%. Outcomes revealed mild to moderate knee problems and a significant decrease in general health following tibial plateau fractures. Patellar fractures that required operative management had an incidence of 3.4/100,000/year and were also common in elderly women and young men with the same mechanisms of injury as tibial plateau fractures. There were complications in 62% of the cases with nearly 50% requiring further surgery. More symptomatic PTOA was seen at 9% but only 1% of patients had arthroplasty surgery. Outcomes despite the higher rates of complications and further surgery were better than for tibial plateau fractures with only mild knee problems and no change in general health compared to the non-fracture population. Blunt trauma in the form of unintentional iatrogenic trauma during arthroscopy produced cell death with moderate pressure movement of the arthroscopic probe, equivalent to clinical practice. This damage was significantly decreased by the use of hyperosmolar saline in bovine tissue and a reduction trend in human tissue. Increased blunt trauma in the form of an impact injury was also shown to cause chondrocyte death in an energy dependant manner but hyperosmolar solution did not show decreased death in this study. Conclusion: Chondrocyte death was not limited to sharp trauma; seemingly benign blunt trauma caused measurable cell death in bovine tissue. This cell death was reduced to some extent by increasing the osmolarity of the irrigation fluid. The results in the human cadaveric studies correlated with the bovine model. Further work is required to develop the model to include fracture damage to articular cartilage. Intra-articular injuries including fractures cause chondrocyte death, which can lead to post-traumatic osteoarthritis. The factors influencing the amount of cell death and the progression to arthritis are numerous and some can be modified after injury. The cause of injury, pattern of injury and who it occurs to cannot be modified after the event but prevention of infection, the operative technique and chondroprotection could all be used to reduce the burden of intra-articular injuries leading to post-traumatic osteoarthritis.