Texture analysis of trabecular bone around RM-Pressfit cementless acetabulum in a series of 46 patients during a 5 year period

Mid-term clinical outcomes of the uncemented Robert Mathys pressfit cup

BACKGROUND

The use of uncemented cups during total hip arthroplasty (THA) has gained popularity in recent years. The Robert Mathys (RM) pressfit cup, an uncemented monoblock implant is expected to preserve bone density due to its composition and external surface, while reducing backside wear with its monoblock construction. These factors should lead to a high survival rate of the implant.

AIM

To evaluate the mid-term survival and functional outcome of the RM Pressfit cup in a large study population.

METHODS

Between 2011 and 2020, we included 1324 patients receiving a primary THA using the RM pressfit cup. Final clinical follow-up was performed at 2 years postoperatively with the Dutch arthroplasty register used to assess implant status thereafter. Revision for acetabular failure and reason for revision were reported to evaluate implant survival, while the hip disability and osteoarthritis outcome score (HOOS) scores were used to assess functional outcome.

RESULTS

The mean age at surgery was 64.9 years. The mean follow-up was 4.6 years. Of the 1324 THAs performed, 13 needed cup revisions within 5 years after index THA: 5 due to aseptic loosening, 6 due to infection, 2 due to dislocation and 2 due to other causes. This resulted in a 5-year cup survival of 98.8% (95%CI: 98.1-99.5). Nine of the cup revisions occurred within the first year after index THA. HOOS scores increased significantly in all domains during the first year and levelled out during the second year.

CONCLUSION

In the present study, the RM pressfit cup demonstrated excellent clinical outcomes at mid-term follow-up; however, future studies are needed to assess the long-term outcomes of this acetabular implant.

Liner type has no impact on bone mineral density changes around a 3D printed trabecular titanium acetabular component

BACKGROUND

Three-dimensional printing of implants allows the ability to produce implants and interfaces which theoretically better mimic "normal" bone behaviour, leading to a possible reduction in stress shielding thus maintaining bone mineral density (BMD). This issue was not investigated in vivo using bone scan and different bearings; therefore, we did a prospective study aiming to answer: 1) is there a loss of BMD around the 3D printed trabecular titanium cup, when compared to the native hip?; 2) does liner type influence the BMD changes around the acetabulum when a 3D printed trabecular titanium cup is used?

HYPOTHESIS

BMD changes around the acetabulum are not influenced by the liner type, and the cup will be associated with a reduction in BMD when compared to the native hip.

MATERIAL AND METHODS

This is a prospective observational study of patients receiving a primary total hip arthroplasty. A 3D printed trabecular titanium uncemented acetabular component was used in all cases. All patients received a ceramic femoral head, with either a ceramic or polyethylene acetabular liner. BMD measurements using DXA were performed at 6 weeks, 6, 12 and 24 months after surgery to evaluate remodeling changes. The 3 acetabular regions of interest (ROI) of DeLee and Charnley were used for serial comparisons of peri-acetabular BMD. The study was powered as a non-inferiority study with the principle variables compared using a two-step repeated analysis of variance.

RESULTS

A total of 48 consecutive patients were included in the study, with all patients completing their 2 year follow-up. There were no failures, revisions or complications within this cohort. We found no statistically significant difference in the BMD change scores between the operated and the native hip in any of the 3 ROI zones. We found no differences in BMD scores when comparing ceramic to polyethylene acetabular liners, head sizes and BMI.

DISCUSSION

This study shows a similar pattern of BMD behaviour around a 3D printed cup when compared to the contralateral native hip. We were unable to show a clinical or radiological difference between the bearing material, head size, or BMI when used with this type of acetabular component.

LEVEL OF EVIDENCE

III; prospective comparative study.

PERIACETABULAR BONE CHANGES AFTER TOTAL HIP ARTHROPLASTY WITH HIGHLY POROUS TITANIUM CUPS IN PATIENTS WITH LOW BONE MASS

OBJECTIVE

The aim: To assess the bone remodeling around highly porous titanium cups TTM in patients with low bone mass one year after total hip arthroplasty (THA).

PATIENTS AND METHODS

Materials and methods: In this prospective study were included 18 patients (18 hips), whom was performed primary THA with the use of TTM cups. According to T-score of Lumbar Spine, patients were divided into 2 groups: normal bone mineral density (BMD) (n=9) if T-score ≥ -1, and low BMD (n=9) if T-score < -1. According to DeLee and Charnley's model BMD in 3 periacetabular regions were evaluated 1 week and 1 year after THA.

RESULTS

Results: One year after primary THA, BMD of all 3 periacetabular regions did not differ in patients of both groups comparing with initial data. One week after THA, it was found that BMD R1 and BMD R3 in low BMD group were lower by 1.4 times (p=0.035) and 1.5 times (р=0.001) respectively, BMD R2 did not differ from the normal BMD group. One year after THA it was found that in low BMD group BMD R1 and BMD R2 were lower by 1.5 times (р=0.005) and 1.3 times (р=0.050) respectively, BMD R3 did not differ from the group with normal BMD.

CONCLUSION

Conclusions: The use of highly porous titanium cups TTM in patients with low bone mass did not lead to a bone loss in DeLee and Charnley periacetabular zones one year after THA. Consequently, the use of these cups in patients with low bone mass undergoing THA is a valuable treatment option.

Bone Preservation in Total Hip Arthroplasty

BACKGROUND

Preserving bone stock in younger and more active patients after total hip arthroplasty (THA) is important for future revision. Newer prosthesis designs, including short femoral stems and isoelastic acetabular cups, are likely to preserve more bone stock. However, long-term follow-up studies on bone remodeling after short-stem THA with an isoelastic monoblock acetabular cup are few. Therefore, we evaluated bone preservation after THA using these prostheses at a 5-year follow-up.

METHODS

This prospective observational study is a 5-year follow-up of our previously reported 2-year observational study on the same cohort of patients. We included 45 patients with primary osteoarthritis treated with a calcar-guided femoral short-stem prosthesis and a monoblock press-fit acetabular cup. We evaluated bone mineral density (BMD) around the prostheses using dual-energy X-ray absorptiometry and reported functional outcomes preoperatively and at 3, 12, 24, and 60 months postoperatively. All complications were recorded.

RESULTS

At the final follow-up, the BMD was comparable with that at 24 months in Gruen zones 3, 4, 5, 6, and 7, whereas it significantly differed in Gruen zones 1 (P < .0001) and 2 (P < .004). On the acetabular side, the BMD leveled off similarly in all DeLee and Charnley zones between 24 and 60 months (P > .05). Moreover, all measured clinical outcomes significantly improved (P < .001). One perioperative dislocation was reported.

CONCLUSION

Patients undergoing THA with a calcar-guided femoral short-stem prosthesis and a monoblock acetabular cup can expect preservation of bone stock over a longer follow-up with excellent clinical outcomes and few complications.

Peri-acetabular bone remodelling after uncemented total hip arthroplasty with monoblock press-fit cups: an observational study

Background

Bone stock preservation in total hip replacement is essential to allow for later revisions in an increasingly younger and fitter index patient population. While contemporary modular press-fit acetabular cups lead to rigid fixation with equatorial stress and central osteolysis, more elastic fixation may cause different peri-acetabular bone remodelling. The purpose of this study was to investigate changes in peri-acetabular bone mineral density (BMD) in uncemented elastic fixation with monoblock press-fit cups.

Methods

This prospective observational study included 45 patients with monoblock cups. We evaluated peri-acetabular BMD using dual-energy X-ray absorptiometry and reported functional outcomes and complications.

Results

At a mean follow-up of 24.2 ± 2.2 months, we found that BMD stabilised in DeLee and Charnley zones I and III and recovered to baseline value in zone II. The mean Harris Hip Scores improved significantly from 56.9 ± 20.0 to 97.2 ± 4.0 (p <  0001). Other than one peri-operative dislocation, we saw no post-operative complications.

Conclusions

We found favourable adaptive bone changes with BMD stabilisation in the equatorial zones and recovery to pre-operative values in the central zone. Additionally, excellent clinical outcomes and few prosthesis-related complications strengthened the favourable results of monoblock acetabular cups.

Trial registration

Registration number DRKS00017076.