How 3D printing resolved a complex industrial forearm injury
Mr Murray recalls, “Sometimes for these injuries, rather than putting plates and screws on the break, an external fixator is put on. In this case the patient’s arm was not successfully reset and healed in the wrong position.”
The patient’s arm was considerably bent in multiple planes. The deformity affected both forearm bones; the radius and the ulna had rotated. The arm was also bent downwards and to the side at a 45-degree angle, in the middle of the forearm. “The patient couldn't turn his hand over, which resulted in great difficulty in performing everyday tasks. If he wanted to change his clothes, he had to bend his whole body around to bend his arm over. This gave him pain and decreased mobility,” says Mr Murray.
“The correction was quite straightforward. A bent bone needs straightening. But the risk is a few degrees out of alignment can affect the arm biomechanics. The patient had alignment problems in three planes – and initially lost most of the skin. Rather than having a skin graft, it healed naturally, forming very thin scar tissue, adding more complications.”
For the correction, a CT scan of both arms was required to create a 3D reconstruction of the injury. A mirror image model was developed by superimposing the ‘good’ image from the opposite arm onto the ‘bad’ image of the injured arm. “To repair this injury back to the correct anatomy, cuts are needed at specific angles in the bones to get the rotation right. The only way of doing that is to use the ‘good’ arm as a mirror template,” says Mr Murray.
“Going into surgery to try to estimate where to cut the bone is complex; there is no way to ever get it back to anatomical positioning – a lot of bone would be lost. One plane may be corrected, but it may be impossible to correct the rest,” says Mr Murray. For the complexity of the injury, Mr Murray knew a 3D jig, a printed surgical aid, would be the patient’s best chance for repair.
The printed jig fits exactly to the patient's bone because it's created based on the 3D rendering of the injury from the CT scan. The jig then fits over the bone and is held in place by wires while cutting block landmarks and barrels guide where to place the saw and drills. The 3D image also helps to determine the angle for any cuts, and can show what the bone will look like after the operation. It's all precalculated; the surgeon doesn't have to wait until after they've cut to visualise a patient's injury.
“It's a very simple, clever system,” says Mr Murray. “Predrilled holes and guides for the saw mean when the bone is turned around in its new place, it automatically falls into position.”
Mr Murray emphasises it's still not a straightforward procedure. “Making the cut, resetting the bone, and putting a plate over the bones to set them in place is simple. But, if you make a cut in a bone that's bent and then straighten it, an ‘opening’ wedge forms, which needs to fill with bone to heal. The bone cannot jump across a one- or two-millimetre gap.”
Complications remain. “It's still a long procedure because there's lots of soft tissue dissection. There is still a risk to skin tension and blood vessels, plus damage to the nerves. When a bone is bent for three years, as this patient’s bone was, the nerves and arteries shorten. If these are then stretched out during a repositioning, there's a chance that nerves can be damaged or blood supply to the hands stops.”
The complexity of this case meant Mr Murray discussed potential complications with a multidisciplinary team, sharing knowledge and learning from other procedures, giving the patient access to the wisdom, experience and feedback from the full team.
Mr Murray successfully performed the operation, and the patient now has a near full range of movement. The arm is straight, and he can twist his hand over. The patient is happy and doing very well.
Mr Murray states we wouldn't have been able to do this procedure 10 or 15 years ago. The 3D jig made such a difference to the surgery. “Technology is always improving and we’re seeing medical science combining with the technology. Previously, 3D jigs couldn't give the level of precision, or the cost was too high. Now 3D printers are being used to aid surgeons directly within the operating theatre. I’ll use it more; now we can cut the bone more accurately than ever before,” says Mr Murray.
Surgeons are quickly discovering the multiple benefits to having technology assist their surgical decision making. Mr Murray has adopted 3D technology to deliver personalised treatments for patients in his orthopaedic surgeries including bone realignment and reconstructive surgeries.