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Presenter: Limb length should be determined during preoperative planning for THA
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WAIKOLOA, Hawaii — In preparation of total hip arthroplasty, surgeons should determine limb length from physical examination and discussion with the patient, according to a presenter at Orthopedics Today Hawaii.
In his presentation, Thomas P. Schmalzried, MD, said that to help determine limb length, surgeons should know the patient’s spine and know that patients with a stiff spine are at an increased risk of dislocation. Schmalzried also said to check for pelvic obliquity and hip contracture and ask patients how their limb length feels to them.
“You need to manage their expectations of what you can do, what you can correct [and] what you cannot,” Schmalzried said.
Relative hip length can be determined radiographically and correlate with clinical assessment, according to Schmalzried, which is information that should be taken into the OR. Schmalzried noted he performs a low anterior-posterior pelvic X-ray centered on the pubis, a modified frog lateral X-ray and the Johnson shoot-through lateral X-ray.
“I get [the Johnson shoot-through] preop and postop, and you develop a library in your head of what the anatomy looks like and what your cup position looks like,” Schmalzried said.
He added templating should be broken down into the outside and inside of the bone to provide biomechanics, limb length and offset ,as well as fixation and stress transfer.
“The reason why the hip went bad in the first place, it was a poor mechanical environment,” Schmalzried said. “You want to make the mechanical environment better by virtue of how you put your parts in.”
To determine the center of rotation of the hip, Schmalzried noted the cup should be placed first.
“You want to get coverage in size,” he said. “That is what you are going to look for on your templating when you are picking your acetabular template. That is going to determine the center of rotation, then you put in the stem.”
Schmalzried noted the stem should provide the appropriate fit and fill, which is where surgeons will get the neck cut and offset. He added it is important to understand where the neck cut is supposed to be and for surgeons to reproduce it because the neck cut will determine limb length.
“You want to recreate the offset as best you can and most of the systems available today with the combination of variable offset stems and neck lengths, you can pretty much nail the offset every time,” Schmalzried said. – by Casey Tingle
Reference:
Schmalzried TP. Fundamentals of preop planning for primary THA. Presented at: Orthopedics Today Hawaii; Jan. 13-17, 2019; Waikoloa, Hawaii.
Disclosure: Schmalzried reports he receives royalties from DePuy Synthes.