Clinical, radiographic, and survivorship analysis of a modular fluted tapered stem in revision hip arthroplasty

Implant breakage and revision factors for modular fluted tapered stems in revision total hip arthroplasty

PURPOSE

Modular stems in revision total hip arthroplasties allow diaphyseal fixation and optimal restoration of the architecture of the proximal femur. Several studies report metaphyseal implant breakage having a negative impact on survivorship. The aim of the study was to evaluate the outcome of an uncemented modular fluted tapered stem (MFT) in revision surgery.

METHODS

In a retrospective study, 316 patients who had revision surgery using the same design of MFT implant (Modular Revision Stem [MRS], Lima Corporate, Italy) between 2012 and 2017 were identified. Patients were male in 51% of cases and mean age was 74 years. Indications were 110 periprosthetic fractures, 98 periprosthetic joint infection, 97 aseptic loosening, 10 instability and 1 other cause. Survivorship, complications, clinical and radiographic outcomes, were assessed. Mean follow-up was 5 years.

RESULTS

There was no implant breakage. At 5-year follow-up, the survivorship, free from revision for aseptic loosening and free of revision for any reason were 96% and 87%, respectively. At last follow-up (8 years), these figures were 92% and 71%, respectively. 31 implants were revised. The risk of revision for any cause was higher for extreme length metaphyseal implants, hazard ratio was 3.7 (95% CI, 1.82-7.52). A mean stem subsidence of 9 mm was noted in 37 cases; 4 were revised for aseptic loosening. The Harris Hip Score at final follow-up was 82.

CONCLUSIONS

At 5-year follow-up, the MFT implant showed a good survivorship and outcomes with no specific complications. Unlike literature reports, no specific complications occurred with this design. Stem junction positioning and therefore metaphyseal length may be key to optimise long-term survivorship. However, a longer follow-up is needed as implant breakage is more often seen after long implantation times.

Micromotion and stress shielding between taper fluted and cylindrical femoral stems for Paprosky bone deficiency type IIIB

PURPOSE

Taper fluted and cylindrical femoral stems have been commonly used for revision surgery with femoral bone loss. Shape and material differences between taper fluted and cylindrical confused surgeons whether superiority and inferiority in comparisons especially for type IIIB Paprosky bone deficiency. This study aims to investigate the micromotion between implant and bone interface and stress distribution around the implant in human cadaveric experiments.

METHODS

Paired comparisons of 7 cadavers between taper fluted stem and cylindrical stem were tested under dynamic cyclic loading.

RESULTS

The results showed appropriate bone-implant micromotions for bone osteointegration could be observed between both taper fluted and cylindrical stems (85 ± 10 μm and 113 ± 80 μm respectively, p = 0.59). Taper fluted stem attained the load distribution from the proximal to distal surrounding bone (from 4.92 ± 2.87 MPa to 2.14 ± 1.43 MPa, p = 0.43), while the cylindrical stem type showed the proximal bone stress shielding (from 2.56 ± 0.76 MPa to 5.23 ± 0.77 MPa, p = 0.03).

CONCLUSION

Both taper fluted and cylindrical femoral stems provided an adequate initial stability with a proper micromotions for bone-implant osteointegration for type IIIB Paprosky femoral bone loss. The taper fluted femoral stem had better biomechanical advantage in terms of greater stress transfer to periprosthetic bone.

Revision total hip arthroplasty using a fluted, tapered, modular stem follow-up method for a mean of three years: A preliminary study

Objective: This study aimed to evaluate the results and complications related to revision total hip arthroplasty within a short-to-medium follow up period. Methods: From January 2016 to January 2020, we reviewed 31 prosthetic hip arthroplasty stem revisions using a fluted, tapered modular stem with distal fixation. The median age of the patients was 74.55-79 years. The survival rate was 100%, and there were no re-revisions. The Harris hip score improved from an average of 36.5 ± 7.8 before surgery to 81.8 ± 6.2 at the final follow-up. Results: The average final follow-up was 36 (24-60) months. During this time, there was no periprosthetic infection, no prosthesis loosening or breakage, and no sciatic nerve injury. Complications included four (12.9%) intraoperative fractures and eight (25.8%) dislocations that had no stem fractures. The postoperative limb was lengthened by 17.8 ± 9.8 mm. In most cases, bone regeneration was an early and important finding. Three cases underwent extended trochanteric osteotomy, and bone healing was achieved by the final follow-up. Conclusion: The modular tapered stem reviewed in this study was very versatile, could be used in most femoral revision cases, and allowed for rapid bone reconstruction. However, a long-term follow-up study is needed to confirm these results.

Cementless, modular, titanium stem in Vancouver B2 and B3 periprosthetic femoral fractures

INTRODUCTION

The periprosthetic femoral fracture (PFF) is a serious complication after primary total hip arthroplasty. We conducted a retrospective study to determine whether the PRIUS^® system presented similar survival to other existing implants for the treatment of Vancouver B2 or B3 PFFs. Bone consolidation rate, functional results and complications were analysed.

METHOD

This is a bi-centric retrospective study between 2012 and 2017 including 39 patients with (B2/B3) PFFs treated by senior surgeons using a PRIUS^® femoral implant. Implant survival, radiological outcome (fracture healing) and clinical scores (Oxford-OHS, Harris Hip Score-HHS, Postel Merle d'Aubigné-PMA, Devane and Charnley) were analysed. 10 patients had died before data collection and 5 patients were lost to follow-up. A total of 21 patients were able to undergo a clinical and radiological evaluation. The mean follow-up period was 3 years.

RESULTS

The 3-year PRIUS^® stem survival rate was 88.6% [95% CI, 77.2-100]. The consolidation rate was 81% (17/21). The rate of satisfied or very satisfied patients was 85.6% (18/21). Regarding the Devane score, activity level was maintained in 70.6% of cases (12/17) and decreased in 29.4% of cases (5/17), the Charnley score was stable in 94% of cases (16/17) and decreased in 6% of cases (1/17). The mean Oxford score was 28.8/48 (9.3; 16-48), the mean HHS was 67/100 (16.4; 46-91) and the mean PMA score was 12.6/18 (4.5; 2-18).

CONCLUSION

The results in terms of survival rate and bone consolidation are comparable to other literature series. The PRIUS® System can be added to the surgical arsenal in the treatment of (B2/B3) PFF, subject to confirmation of these results in the longer term.

Primary stability of a cementless modular revision hip stem in relation with the femoral defect size: A biomechanical study

PURPOSE

Cementless modular fluted hip stems are commonly used in revision arthroplasty. Nevertheless, there is a wide spectrum of recommendations concerning the minimum bone stock required to enable osseous ingrowth and implant-bone micromotions <100 µm. This experimental study investigated the primary stability of a tapered cementless fluted revision stem depending on different types of bone defects.

METHODS

Implant-bone interface movements with a bimodular stem were examined under cyclic axial and torsional loading using composite femora. In four degrees of freedom, the implant subsidence and micromotions were captured with linear variable differential transformers for the intact femora and seven different defects ranging from Paprosky type I to type IIIB.

RESULTS

With a 7-cm length of intact diaphysis proximal to the isthmus (Paprosky IIIA), mean implant-bone micromotions of 66 µm occurred. An implant-bone contact zone of only 5 cm (Paprosky IIIA) resulted in micromotions notably over 100 µm and significantly increased subsidence (p < 0.05). With a Paprosky IIIB defect (3 cm of intact diaphysis) rotational instability occurred in all specimens.

CONCLUSIONS

Aside from critically increased interfacial micromotions (>100 µm), rotational instability emerged as a mechanism of fixation failure when the implant-bone contact zone was only 5 cm or less. Hence, future studies investigating the implant fixation in the case of femoral bone defects should consider both axial and torsional loading. With regard to the clinical application, our data suggest maintaining 7 cm of diaphyseal implant-bone contact for a safe anchorage of cementless fluted hip revision stems.