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Cemented polished, tapered modular hip stem yielded excellent clinical results
At 6.5 years mean follow-up, there was 100% implant survivorship and no evident risk of revision or signs loosening.
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A new design of polished, tapered total hip replacement stem led to excellent clinical results and implant survival at a mean of 6.5-years follow-up, based on recently published results.
Investigators studied outcomes with the cemented ProfemurXm hip prosthesis (MicroPort Orthopedics Inc.), which has a cobalt chrome stem and modular titanium neck.
“Excellent results are obtained with a hybrid [total hip reconstruction] THR using a stem with taper slip design and modular neck, with almost complete restoration of normal anatomy, such as accurate leg length restoration, plus zero dislocation rate plus extremely low complication rate,” orthopedic surgeon Jan F.A. Somers, MD, head of the department of surgery at Jan Yperman Hospital in Ypres, Belgium, told Orthopedics Today. “We describe the lowest rate of leg length discrepancy reported in the literature with this technique.”
Excellent clinical results
Somers and his colleagues performed 115 consecutive hybrid THRs using the ProfemurXm prosthesis in 105 patients between October 2008 and December 2010. They collected patients’ University of California Los Angeles (UCLA) activity score, the Oxford hip score (OHS), the Harris hip score (HHS) and WOMAC score.
With the endpoint in the study of revision for any reason, results showed 100% implant survivorship at a mean of 6.5-years follow-up, at which time none of the implants were at risk for revision or showed signs of loosening. At a mean follow-up of 6.5 years, researchers noted improvements in patients’ mean clinical scores from 31 to 90 for the HHS, from 30 to 91 for the WOMAC score and from 3 to 6 for the mean UCLA activity score. In addition, the mean OHS was 44 at latest follow-up.
Somers and his colleagues also found none of the patients reported pain, squeaking or dislocation, and there was no osteolysis or calcar resorption in the hip area. Furthermore, none of the implants developed radiolucent lines at the stem-cement or at the cement-bone interface, according to the results.
The mean femoral subsidence of the stem within the cement mantle after 6.5 years was 0.31 mm. In addition, there was no measurable leg length difference after THR in 93% of hips and leg-length restoration was within the 5-mm limit possible in 99% of hips.
THR modularity
Somers said he hopes results of this study foster discussions about modularity in THR, which has recently fallen out of favor.
“Over the past 3 decades, we have seen several examples of unfortunate products,” Somers said. “I mention butylmethacrylate cement (nobody questions the value of “bone cement”), resurfacing hip replacement (registries are showing it is a useful option in the hands of the experienced surgeon) and ceramic-on-ceramic hips (not all are squeaking and/or breaking). So, care should be taken to evaluate each hip system,” he said. – by Casey Tingle
- Reference:
- Vanbiervliet J, et al. Hip Int. 2017;doi:10.5301/hipint.5000486.
- For more information:
- Jan F.A. Somers, MD, can be reached at Rijselstraat 86, 8900 Ypres, Belgium; email: orthosomers@telenet.be.
Disclosure: Somers reports he was a paid consultant for Microport Orthopedics, but has no relevant financial disclosures related to the ProfemurXm.
Perspective
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Michael A. Mont, MD
This is a follow-up study (mean 6.5 years, range 5 years to 8 years) of a cemented stem, which has some similarities to the Exeter stem (Stryker). It uses a different alloy (cobalt chrome vs. stainless steel), but has the advantage of neck modularity. With excellent cementing technique, the authors achieved 100% survivorship. Nevertheless, one must be wary because a number of modular stems have led to the development of adverse local tissue reaction. Some of the limitations of this study are that it represents a single center cohort with small numbers, the cases were performed by the surgeon designer and there was no matching group. Nevertheless, they have achieved excellent results. I look forward to seeing if these results hold up at 10-year or greater follow-up.
Perspective
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Thomas P. Schmalzried, MD
Cemented, polished, tapered stems have generally performed well. The authors are commended for these excellent middle-term results. The concern, of course, is the addition of a modular neck to this well-established stem type. The ability to adjust length, offset and femoral version are desirable attributes. However, these adjustments are all possible, to some degree, without a modular neck in a cemented stem. Given the same level of attention to surgical detail, I suspect these authors could have achieved similarly excellent results without neck modularity.
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