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RCT
ACE Report #8459

Less periprosthetic bone loss with ultra-short stem vs conventional stem in THA at 2 years


Study Type:Therapy
OE Level Evidence:2
Journal Level of Evidence:N/A

Lower periprosthetic bone loss and good fixation of an ultra-short stem compared to a conventional stem in uncemented total hip arthroplasty

Acta Orthop. 2015 Dec;86(6):659-66

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Synopsis

51 patients with osteoarthritis undergoing total hip arthroplasty were randomized to receive either an uncemented conventional tapered stem or an uncemented ultra-short stem. The purpose of this randomized controlled trial was to compare the different stems in terms of periprosthetic bone loss in the proximal femur, safety, and migration, at 2 years postoperatively. The results suggested that the decrease in periprosthetic bone mineral density (Gruen zone 1 and 1-7) was significantly lower in the ultra-short stem patients. During the first 6 postoperative weeks, the ultra-short stem group displayed greater implant migration, which remained significant at 2 years. Between groups, clinical outcomes were similarly improved at 2 years and adverse events were comparable.

Publication Funding Details +
Funding:
Industry funded
Sponsor:
Ulla and Gustaf Ugglas Stiftelse, Ake Wibergs Stiftelse, Loo and Hans Ostermans Stiftelse, the Sven Noren Foundation, the regional agreement on medical training and clinical research (ALF) between Stockholm County Council and Karolinska Institutet, and DePuy Johnsson and Johnsson Foundation for Clinical Research
Conflicts:
Royalties

Risk of Bias

6/10

Reporting Criteria

18/20

Fragility Index

N/A

Was the allocation sequence adequately generated?

Was allocation adequately concealed?

Blinding Treatment Providers: Was knowledge of the allocated interventions adequately prevented?

Blinding Outcome Assessors: Was knowledge of the allocated interventions adequately prevented?

Blinding Patients: Was knowledge of the allocated interventions adequately prevented?

Was loss to follow-up (missing outcome data) infrequent?

Are reports of the study free of suggestion of selective outcome reporting?

Were outcomes objective, patient-important and assessed in a manner to limit bias (ie. duplicate assessors, Independent assessors)?

Was the sample size sufficiently large to assure a balance of prognosis and sufficiently large number of outcome events?

Was investigator expertise/experience with both treatment and control techniques likely the same (ie.were criteria for surgeon participation/expertise provided)?

Yes = 1

Uncertain = 0.5

Not Relevant = 0

No = 0

The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.

4/4

Randomization

2/4

Outcome Measurements

4/4

Inclusion / Exclusion

4/4

Therapy Description

4/4

Statistics

Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65

The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.

Why was this study needed now?

Total hip arthroplasty (THA) is a common procedure in patients with hip osteoarthritis, and there are various prosthetic designs and techniques utilized to minimize the risk of complications and revisions while maintaining excellent patient outcomes. Periprosthetic bone loss in uncemented femoral stems raises concerns of fracture, and shorter femoral stems have gained popularity as they aim to provide a more physiological load pattern in the femur and reduce stress shielding. The absence of a stem that engages the diaphysis of the femur prevents off-loading of the proximal femur, but may also affect the stability necessary for bone integration of the implant. The present study sought to analyze the effects of an ultra-short uncemented stem in patients with osteoarthritis undergoing THA.

What was the principal research question?

In patients undergoing total hip arthroplasty for the treatment of osteoarthritis, how did an ultra-short uncemented stem compare to a conventional tapered uncemented stem in terms of periprosthetic bone loss in the proximal femur, safety, and achievement of fixation at 2 years postoperatively?

Study Characteristics -
Population:
51 patients (aged 40-70) with primary osteoarthritis scheduled to undergo total hip arthroplasty. Additional inclusion criteria were bone stock suitable for uncemented hip arthroplasty and a femoral anatomy allowing for implantation of either stem type, including no hip dysplasia or previous surgery. Surgery was performed using a posterolateral approach with repair of the posterior capsule and the external rotator muscles. A modular 32mm cobalt-chrome head was used with an uncemented press-fit cup and highly cross-linked ultra-high-molecular weight polyethylene liner. Immediate full weight bearing was allowed.
Intervention:
Ultra-short stem group: Patients received an ultra-short wedge-shaped porous and hydroxyapatite coated titanium stem (Proxima, Depuy). The stem was fully porous-coated with sintered beads, with a mean pore size of 250 um, covered with 30 um highly amorphous hydroxyapatite, and stem length of 71-83mm (n=26, 26 completed; Mean age: 62 +/- 5; 11M/15F).
Comparison:
Conventional stem group: Patients received a proximally porous and hydroxyapatite coated, conventional tapered titanium stem (Bi-metric, Biomet). The stem was proximal 30% porous-coated, with a pore sizes of 100-200 um, covered with plasma-sprayed hydroxyapatite, and stem length of 130-155mm (n=25, 25 completed; Mean age: 62 +/- 6; 11M/14F).
Outcomes:
Primary outcome was the change in femoral periprosthetic bone mineral density (BMD) in Gruen zones 1 and 7 (assessed with dual-energy X-ray absorptiometry [DXA]). Zones 1-2 and 6-7 in the ultra-short stem group were compared to zones 1 and 7, respectively, in the conventional stem group, to account for differences in size of the stems. Secondary outcomes included the change in periprosthetic BMD in the entire periprosthetic region (zones 1-7), stem migration (assessed using radiostereometric analysis [RSA]), and functional clinical results. Clinical outcomes included mid-thigh pain, the Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the EuroQol 5-dimensions (EQ-5D).
Methods:
RCT: prospective.
Time:
Assessments were made preoperatively, and at 2 days, 6 weeks, 3, 6, 12, and 24 months postoperatively.

What were the important findings?

  • At 2 years, the decrease in BMD in zone 1 was significantly smaller in the ultra-short stem group compared to the conventional group (MD: 18.2% [95% CI 9.5, 26.8]; p<0.001). In zone 7, the decrease in BMD did not significantly differ between groups (MD: 4.5% [95% CI 2.8, 11.8]; p=0.4).
  • At 2 years, the decrease in BMD in the entire periprosthetic region (Zone 1-7), was significantly less in the ultra-short stem group (MD: 5.3% [95% CI 1.5, 9.1]; p=0.02).
  • After 6 weeks postoperative, the ultra-short stems demonstrated significantly median maximum total point motion (1.51mm [0.33-5.44]) compared to the conventional stem group (0.74mm [0.13-5.29]), and significance was maintained up to 2 year follow-up (1.71mm [0.39-6.00] vs. 0.87 [0.87-7.47], respectively; p=0.01). Migration had stopped after 3 months for the majority of components in both groups, and all components were stable at 2 years.
  • Both groups displayed significant improvements from baseline to 2 years postoperatively in the median HHS and WOMAC scores. However, no significant differences were noted in these outcomes between groups (p=0.2 and p=0.5, respectively)
  • The improvement in health-related quality of life (EQ-5D) was similar between groups at 2 years. The number of patients suffering from mid-thigh pain was greater in the conventional group during the first 6 months, without reaching statistical significance at any point.
  • Adverse events were similar between groups (Ultra-short: 45 vs. Conventional: 51). Periprosthetic fracture occurred in one patient in the Ultra-short stem group and periprosthetic infection occurred in one patient in the conventional stem group

What should I remember most?

At 2 years, the decrease in periprosthetic bone mineral density in the proximal femur at Gruen zone 1 was significantly lower in the total hip arthroplasty patients who received an uncemented ultra-short stem when compared to a conventional tapered uncemented stem. During the first 6 postoperative weeks, the ultra-short stem group displayed significantly more migration when compared to conventional stems, this difference lasted to the 2 year follow-up. Between groups, all clinical outcomes (HHS, WOMAC, EQ-5D, mid-thigh pain) were similarly improved at 2 years, and adverse events were comparable.

How will this affect the care of my patients?

The results of this randomized controlled trial suggest that at 2 years, the use of an uncemented ultra-short stem may reduce periprosthetic bone loss in the greater trochanteric region and along the entire preriprosthetic region, though was associated with greater migration early in the follow-up period compared to a conventional stem. Nevertheless, clinical outcome and adverse events did not appear to be affected within this time frame. Further study is warranted given the small evidence base of high-quality literature on the topic, and limited results regarding long-term stability and survivorship between the two designs.

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