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Short stem prosthesis did not lead to better joint offset during THA
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Investigators who studied femoral neck preservation and other factors affected by total hip arthroplasty performed with a short-stem prosthesis vs. a full-length uncemented prosthesis found the short-stem design offered no statistically significant differences in biomechanical reconstruction of the hip.
The study, which was selected as a top paper to be presented at the EFORT Congress in Prague in May, was conducted by orthopaedic surgeon Jakob Van Oldenrijk, MD, MSc, of Amsterdam, and colleagues. They sought to determine if short-stem femoral neck preserving total hip arthroplasty (THA) led to a more favorable biomechanical reconstruction.
However, none of their findings led the investigators to conclude short-stem implants were any better for patients.
“We could not confirm this type of stem could create better joint reconstruction. We did see an increase in femoral offset ratio in both the conventional group and the short-stem group,” Van Oldenrijk told Orthopaedics Today Europe.
Short-stems had same outcomes
The randomized controlled clinical trial, which is registered at the Dutch Trial Registry, included 142 patients and 142 hips that were randomly allocated to receive the short-stem Collum Femoris Preserving THA prosthesis (Waldemar LINK GmbH; Hamburg) or the conventional Zweymüller-type Alloclassic prosthesis (Zimmer Inc.; Warsaw, Ind., USA) straight THA stem. Patients were blinded to the stem they received throughout the 5 years of follow-up.
Researchers measured the femoral offset of the stems, which was the perpendicular distance between the longitudinal femoral axis and the hip joint center of rotation, as well as the offset of the patients’ contralateral hip. They then compared these measurements to confirm that each patient’s anatomy was reconstructed properly.
“We also measured the height of the center of rotation, varus, valgus and leg length discrepancy to see if there were differences between the two groups. We did not find any significant differences. It is always disappointing, but it is also a very relevant finding. If you make a claim, you expect it to be proved, so it is very relevant when it is not,” Van Oldenrijk said.
Functional outcomes of interest
“What we did find, the offset ratio was increasing using both of the stems and only decreased in a very small percentage. That is a very relevant finding. Both of the stems were able to recreate the leg length adequately,” Van Oldenrijk said.
The offset was increased in 62% of patients in the short-stem group and in 50% of patients in the conventional group. The offset was decreased in 11% of patients in the short-stem group and in 10% of the conventional group. Neither of these differences, however, were statistically significant, Van Oldenrijk said.
Van Oldenrijk and his colleagues are scheduled to separately present at the EFORT Congress in Prague in May the mid-term functional outcomes associated with each implant. – by Robert Linnehan
- Reference:
- Van Oldenrijk J, et al. Paper #2905. Scheduled to be presented 27 May at: EFORT Congress; May 27-29, 2015; Prague.
- For more information:
- Jakob Van Oldenrijk, MD, MSc, can be reached at Nuffield Orthopaedic Centre, Oxford University Hospitals, Oxford, United Kingdom; email: jakobvanoldenrijk@gmail.com.
Disclosure: Van Oldenrijk has no relevant financial disclosures. See the full study for a list of all other authors’ relevant financial disclosures.