Dr. Grant Shaw November 28, 2017

By Dr Grant Shaw, Orthopaedic Surgeon, Portsmouth, UK

There are around 70,000 fractured neck of femur (#NOF or broken hip) cases admitted to hospital annually in the UK, about 1.6 million worldwide. It is a serious and potentially life threatening injury in older people and an increasing financial burden on the Health Service. Subcapital fracture is a common type (where the fracture line extends through the junction of the head and neck of femur) and is generally treated with hemiarthroplasty. Getting the surgery right first time is a critical part of the solution, as treating a subcapital neck of femur fracture well can significantly reduce mortality and morbidity as well as reduce associated costs for the hospital.

Uncemented Hemiarthroplasty with a correctly sized component and appropriate offset.

Uncemented Hemiarthroplasty with a correctly sized component and appropriate offset.

Over the last 10 years, the treatment of #NOF in elderly patients has changed from a subject of minor interest to a high profile area in the context of the UK national ranking of hospitals. Success rates for this procedure have been linked (in the UK) to significant financial incentives for the best performing hospitals, with the introduction of the BPT (Best Practice Tariff). During this time, the range and quality of available implants has also grown significantly, from a choice of two to a full range of THR implants with hemiarthroplasty heads, which allows more precise matching of the implant to patient anatomy and bone morphology.

 

Why templating matters

Preoperative planning informs prosthesis choice and size when treating #NOF, as with other orthopaedic procedures. In a number of ways, preoperative planning can be more important and influential in the outcome of #NOF than for an elective total hip replacement. However, the principle motivation for templating is the same for both i.e. identifying when one prosthesis may be unsuitable for a particular patient and a different prosthesis choice fits much better. A clear example of the importance of preoperative templating is in cases where the morphology of very porotic femoral bone in elderly patients means they require an implant that falls outside the range of many THR stems.

As fractured neck of femur operations are often performed by surgeons undergoing training, preoperative templating can also be helpful in guiding them logically through the operation, anticipating problems which might arise. Templating a Hemiarthroplasty is very similar to templating a THR and therefore also provide good training in this area for junior surgeons.

 

The importance of scaled X-rays

A vital prerequisite for choosing the right size of prosthesis when templating any orthopaedic procedure is to have scaled pre op images to assist appropriate sizing. This may require training and sustained encouragement of radiographers and radiography technicians in the emergency x-ray department but I have found the inclusion of a calibration marker on the image to be highly beneficial for achieving more precise measurements.

Additionally, it is usually most helpful to template the contralateral side, rather than the damaged side. The image of the fractured side can be quite distorted due to rotation and foreshortening, giving few clues as to the correct femoral size, offset or leg length.

 

Offset versus canal size

When choosing a stem to treat #NOF, one of the problems is that to get a stem to fill the canal may require a large component but sometimes the offset of a large component is too large for the patient. Using short heads can partially compensate but is often not enough to avoid increasing the offset. Most of these operations are done through an anterolateral approach and any increase in offset results in an overstrain and rupture of the abductor repair leading to poor muscle function and a Tendelenburg gait, increased pain and increased risk of dislocation.

More than half of available femoral components present some degree of correlation between femoral stem size and offset i.e. as the stem size increases so does the offset. Unfortunately, there is not such a clear correlation in reality. Some tall active men, for example, have very large offsets and a tight canal size whereas some small elderly, porotic patients have small offsets but a wide stove pipe (Dore C) femoral canal.

Example of a patient with a Dore C porotic canal. The large stem with a large offset shown does not fit this patient.

Example of a patient with a Dore C porotic canal. The large stem with a large offset shown does not fit this patient.

Cemented versus Uncemented

Choosing whether to use a cemented or uncemented hip stem is also important when choosing a suitable prosthesis in advance of surgery. Avoiding cement can be desirable for particularly frail patients when a quick operation with minimal cardiovascular insult is required. However, such patients often have the widest, most porotic, stove pipe femurs. These are the femurs which the uncemented femoral components do not fit well because the offset for the large-canal-filling prosthesis is too big

The same patient with a more suitable implant demonstrating the correct offset (in this case a Stryker Exeter cemented stem)

The same patient with a more suitable implant demonstrating the correct offset (in this case a Stryker Exeter cemented stem)

Preoperative templating provides a way of comparing implants to choose one that suits the specific patient’s anatomy. Materialise OrthoView makes it easy to compare the effect of alternative options on screen and you don’t have to reposition the template each time.

 

Conclusion

Settling on a plan prior to surgery helps everyone involved. The anaesthetist knows whether to expect cement; the theatre staff know which instruments to get and can collect the likely prosthesis sizes from the store; the surgeon, having anticipated most of the likely issues, has a plan A but can allow for a plan B or C, having also explored other options.

Most importantly, getting the treatment right first time helps the patient to have a swift, smooth and drama-free operation and a well-fitting, comfortable and functional prosthesis. This results in a good recovery and a short length of stay in hospital, which benefits everyone concerned.

 

If you would like to find out more about techniques for preoperative planning with Materialise OrthoView check out an inspiring webinar by Dr. Ross Barker or
watch our tutorial videos

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