Fractures of the tibia (shin bone) are frequently treated with a metal nail that is passed down the inside of the bone (an intra-medullary nail). This nail is inserted through the top of the tibia at the level of the knee joint. There are two ways for the nail to be inserted - either through an incision below the patella (kneecap) or above the patella.

The benefit of the incision above the patella is that it can make it technically easier to insert the nail into the correct position. However, the perceived risk of damage to the knee cartilage has prevented this technique from being widely adopted.

The investigators will use MRI scanning to assess the cartilage for damage using both techniques. The results will enable the investigators to determine if the theoretical risk of cartilage damage is found in real-world scenarios and to generate data for further, larger studies.

Intra-medullary nailing is a common form of treatment for a variety of tibial shaft fractures. Traditionally this has been done via an infra-patella approach. More recently the use of a supra-patella approach has become more popular. However, there are concerns that the supra-patella approach may cause unacceptable damage to the cartilage of the patello-femoral joint (PFJ).

This study will use a novel MRI technique developed at the University of Cambridge to compare the amount of damage caused to the knee joint by both infra- and supra-patella nailing techniques. Specific cartilage assessment sequences will enable a fuller assessment of cartilage damage than can be achieved with normal structural sequences. Participants will also be asked to complete Patient Reported Outcome Measures (PROMs) regarding their injury to assess their clinical outcome.

Infra-patella and supra-patella nailing techniques are now both routine methods of carrying out intra-medullary nailing of the tibia. Further evidence is required, however, in order to fully assess whether one method is superior to the other.

Inclusion Criteria:

• Closed tibial shaft fracture suitable for intramedullary nailing
• Able to consent
• Able to undergo MRI scanning
• Able to attend follow up for 6 months post operatively
• Suitable for surgery

Exclusion Criteria:

• Polytrauma
• Ipsilateral acute ligamentous knee injury
• A contra-indication to MRI scanning

It is not possible to mask participants or investigators as the surgical interventions in each arm will have different scars, making blinding impossible.