Proper THA implant selection necessary to suit shorter-stature female patients

Issue: February 2011

ORLANDO, Fla. — Compared with men, women tend to have proportionally smaller femoral metaphyses, head heights and offsets. While these differences are important to account for when selecting total hip arthroplasty implants, there are other more important differences to consider among the female population, according to an orthopedic surgeon at Rush University Medical Center in Chicago.

During a presentation here, at the Current Concepts in Joint Replacement 2010 Winter Meeting, Wayne G. Paprosky, MD, FACS, explained that these gender differences are directly related to stature, and that the stature of some women is essentially like that of most men and they can therefore be treated similarly to male total hip arthroplasty (THA) patients. Other women of shorter stature will have shorter neck lengths and less offset and will require the correct implant for their specific body type.

“So it’s the differences in the statures [among women],” Paprosky told Orthopedics Today. “And if you add osteoporosis, that also changes things because the anatomy of the female femur changes as osteoporosis sets in and it is much more difficult to match that in the smaller statures.” Simply using a smaller-sized implant will not achieve the perfection that patients today demand, he added.

Leg-length discrepancy

Even within the shorter female population, offset can vary significantly enough so that the implant must be more specific to achieve optimal results. A slight leg-length discrepancy in a 5-ft 3-in woman, or an increase in the width of their hips can really make them quite miserable, Paprosky said.

“It [leg-length discrepancy] is probably the most common reason for litigation in the orthopedic community, and hell hath no fury as a woman with a long leg,” he said, noting that tissue tensioning via leg-lengthening is therefore not an effective means of reducing dislocation rates in female THA patients.

One reason Paprosky provided as an explanation for the higher prevalence of leg-length discrepancy among female THA patients, in addition to his belief that women are more likely to report the discrepancy than men, is that women wear high heels. “And that really changes things tremendously, an eighth- or a quarter-inch leg-length difference really makes it difficult to wear high heels. And the woman younger than 65 years old, if they are short, wants those 3-inch heels, and unless you can make them as close [anatomically] as you possibly can, they are not going to be happy with you.”

Proper implant selection

Paprosky offered suggestions as to how to potentially improve outcomes among shorter-stature female THA patients. To avoid leg-lengthening in those patients with osteoporosis who require larger implants, “stems must be designed with shorter base neck lengths and smaller metaphyses,” he said.

The majority of shorter-stature female THA patients can be effectively managed with implants that are currently available, but Paprosky urged physicians to be aware that, if they use “brand X,” and that manufacturer produces small, intermediate and large implants, they will most likely be unable to match about 20% of the population.

“Having said that, I still think there are probably a small percentage of people where we are still not able to perfectly re-establish the offset and leg length, and I think that we probably need to pay more attention to developing some more of the nonmodular, monoblock stems that give a little bit more flexibility,” he said.

Paprosky stressed the importance of creating awareness of the stature issue among his colleagues, many of whom have disagreed with him over the years. “I’ve even been told, ‘I’ve been doing hips for 20 years and I’ve never had a problem with this,’” he said. “We have to really look at our results and our X-rays, preoperatively and postoperatively, critically to see, ‘Yeah, well, you know, this offset is pretty good.’ Well if you had used a different kind of prosthesis, it might be even better.” – by Thomas M. Springer

Reference:

Paprosky WG. Gender-specific stem design: When the shoe fits! Paper #13. Presented at the Current Concepts in Joint Replacement 2010 Winter Meeting. December 8-11, 2010. Orlando, Fla.

Wayne G. Paprosky, MD, FACS, can be reached at Rush University Medical Center, 1653 W. Congress Parkway, Chicago, IL 60612; 630-682-5653; e-mail: parp1210@gmail.com.
Disclosure: Paprosky receives monetary compensation/consulting fees for design consulting from Zimmer, Inc.

As surgeons, we are all trying to more accurately re-establish leg length and offset in total hip replacement; however, this is problematic in some patients, particularly the short stature patient. Short stature patient have femoral necks with less length and offset then the average femoral component that fits into their femoral canal. This is particularly true as the short stature patient ages; the proximal femur remodels with age and osteoporosis, requiring a larger stem, but the native femoral neck’s lesser length and offset remain small. As surgeons, we either have to use a different stem design or significantly change our technique. Awareness of this problem is the first step to solving it.

– Richard A. Berger
Assistant professor of orthopedic surgery
Rush Presbyterian Medical Center
Chicago, Ill.
Disclosure: He receives royalties from Zimmer and is a paid consultant to Salient Surgical and Smith & Nephew.