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Hip Replacement Surgery

Total hip replacement has been referred

to as ‘the operation of the 20th Century’

due to the dramatic change in quality of

life patients often experience following

this procedure. Last year, approximately

70,000 total hip replacements were

performed in the UK, with 90% of patients

expressing satisfaction thanks to the

resulting cure to their chronic pain, and

an associated improvement in their

mobility and overall level of activity.

Despite undeniably impressive results,

there are potential risks with such surgery,

and a range in the functional level patients

experience as their final outcome. This

could be from a complication resulting

in a hip that dislocates, a patient that

finds his leg lengths are not equal (either

shorter or longer), or a patient that finds,

after walking for a distance, they develop

a limp or the hip feels tired.

So why is it that some hip replacements

have a better functional result than

others? To answer this, we need to

understand what has to be achieved by

a hip replacement to provide the patient

with the feeling of a normal hip and

resultant high level of function. This level

of outcome can only be accomplished

when the patient’s normal anatomy has

been accurately restored by the hip

replacement. This involves more than

just ensuring the leg lengths have been

equalised, it also depends on accurately

restoring the abductor arm (the

transverse distance from the centre

of the femoral head to the greater

trochanter, into which the hip abductor

muscles insert). If the length and

lateralisation of the hip abductor muscles

are not accurately restored, then the

most important muscle group for normal

walking cannot function optimally. The

extent to which this factor impacts on

the patient depends on how far it is

from the patient’s normal anatomy.

In order to accurately restore the

patient’s specific hip anatomy, it first has

to be clearly defined. Surprisingly, the

current standard practice for assessing

hip anatomy pre-operatively is still a basic

X-ray, which is notoriously inaccurate.

Ironically, with the development of digital

imaging, fewer surgeons currently perform

any pre-operative surgical templating.

Morphological studies have demonstrated

a considerable range in defining what is

‘normal’, and demonstrated how misleading

a ‘normal’ hip X-ray can be.

The most reliable technique to define

these anatomical parameters is a CT

scan, and with the application of specific

software, an exact surgical plan can be

undertaken. This allows precise surgical

templating to be done, defining which

combination of components will result in

an accurate restoration of all anatomical

parameters, and anticipation of any surgical

challenges that may be encountered. This

also identifies any anatomical outliers for

which a custom-made prosthesis would

be beneficial.

Does the surgical approach matter?

The ideal surgical approach provides

excellent visualisation and access to the

joint, whilst causing the least amount of soft

tissue damage possible. Such an approach

facilitates the surgeon in aiming to implant

the prosthesis in the optimal orientation

(which we know to be critical to the

implants long-term function and survival).

Given the importance of the hip abductor

muscle function, the optimal surgical

approach preserves them. This also leads to

a faster post-operative recovery, and return

to normal gait. The two approaches that

do not violate the hip abductors are the

posterior approach, and the direct anterior

approach. Both approaches can provide

an excellent exposure. The great appeal

of the direct anterior approach is that in

addition to preserving hip abductors, it also

preserves the short external rotators. It is,

therefore, the most conservative approach

used for hip replacement surgery, resulting

in a rapid post-operative

recovery. It is also associated

with a lower dislocation rate, and

therefore lessens the requirement

for hip restrictions after surgery.

The final element is in implanting a

prosthesis which will recreate all of

the anatomical parameters that have

been quantified by the planning CT

scan. As previously mentioned, the

‘normal’ hip anatomy has a considerable

range over several parameters, and

therefore, the limited range of size and

shape options offered in many hip

systems results in some compromise.

This great variability in anatomy can be

addressed using a versatile modular

system, with a pre-defined combination

of components that will reliably and

accurately reconstruct the patient’s

anatomy. In approximately 10% of

cases, even this system does not offer

an accurate reconstruction due to

outlying anatomy – in which case a

custom-made component is manufactured

and no compromise is required.

This contemporary approach to hip

replacement is focused on preserving

and restoring the patient’s anatomy,

which leads to a predictably high

functional outcome, and rapid

post-operative recovery.

Total Hip

Replacement

Raising the bar

Advances in hip replacement surgery for a rapid recovery

and return to optimal function.

Pre-operative CT planning

Hip Replacement Surgery

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