Clinical experience in femoral revision with the modular Profemur R stem

Clinical, functional and radiographic outcomes after revision total hip arthroplasty with tapered fluted modular or non-modular stems: a systematic review

PURPOSE

The aim of the study was to systematically evaluate clinical outcomes of tapered fluted stems, either monoblock or modular, in revision total hip arthroplasty.

METHODS

PubMed, EMBASE and Web of Science and Cochrane databases were systematically searched by 2 researchers. Clinical studies reporting primarily on survival and re-revision rates, and secondarily on subsidence, dislocation, intraoperative fractures, periprosthetic fractures and infection were included. 2 investigators assessed the quality of the studies.

RESULTS

46 studies were included in this review, reporting on 4601 stem revisions. The pooled re-revision rate was 5.1% and long-term survival ranged from 75% to 98.5%. No differences were observed between monoblock and modular stems regarding re-revision rate, dislocation rate, periprosthetic fracture rate or infection rates. Monoblock stems exhibited more subsidence and modular stems displayed more intraoperative fractures.

CONCLUSIONS

Satisfactory results can be obtained with the use of tapered fluted end-bearing stems. Monoblock stems offer the same clinical results as modular stems.

Technical Note for Transfemoral Implantation of Tapered Revision Stems. The Advantage to Stay Short

Background

The aim was to test the hypothesis that during transfemoral implantation of a conical revision stem, the fixation of the stem at the distal tip leads to a low rate of periprosthetic fractures.

Material and Methods

Two hundred eighty-two stem revisions by a transfemoral approach in cases of Paprosky Type II and IIIA-defects (with a sufficient isthmus) were carried out and analyzed during and radiographically after the surgery for unintentional periprosthetic fractures below the osteotomy.

Results

In all cases, fixation was always achieved at the tip of the distal component in the isthmus of the femur. No periprosthetic fractures were observed.

Conclusions

When the isthmus of the femur is intact, a transfemoral implantation of a tapered revision stem at the distal end reduces the risk of periprosthetic fractures by preventing bypassing the isthmus with the stem. Knowing the difference between the nominal diameter and the diameter at the distal start of the conical zone can help to create this fixation technique resulting in short revision stems.

Fixation of a modular curved revision stem with a taper of 2° in the femur

INTRODUCTION

Modular revision stems with a short distal component can prevent the bypassing of the femoral isthmus and hereby theoretically have advantages concerning risk of periprosthetic fractures, breakage of the junction and a technically easier revision procedure.

MATERIALS AND METHODS

Radiological evaluation of 202 stem revision operations with the modular curved revision stem "Revitan Curved" with a 2° taper was carried out after a mean follow-up period of 7.44 ± 2.09 years (3-13 years) to investigate whether short-stem combinations are effective in Paprosky 2 and 3A defects with respect to rate of subsidence and loosening.

RESULTS

Sixty of 62 endofemoral (96.8%) and 137 of 140 transfemoral implantations (97.9%) involved the short, 140 mm distal component. Significant subsidence was seen in 3.3% of cases following endofemoral implantation and in 2.1% of cases following transfemoral implantation. Neither aseptic loosening nor periprosthetic fracture were observed.

CONCLUSION

The use of combinations of short modular components leads to reproducibly good outcomes in femoral revision with respect to subsidence and loosening.

A biomechanical testing system to determine micromotion between hip implant and femur accounting for deformation of the hip implant: Assessment of the influence of rigid body assumptions on micromotions measurements

BACKGROUND

Accurate pre-clinical evaluation of the initial stability of new cementless hip stems using in vitro micromotion measurements is an important step in the design process to assess the new stem's potential. Several measuring systems, linear variable displacement transducer-based and other, require assuming bone or implant to be rigid to obtain micromotion values or to calculate derived quantities such as relative implant tilting.

METHODS

An alternative linear variable displacement transducer-based measuring system not requiring a rigid body assumption was developed in this study. The system combined advantages of local unidirectional and frame-and-bracket micromotion measuring concepts. The influence and possible errors that would be made by adopting a rigid body assumption were quantified. Furthermore, as the system allowed emulating local unidirectional and frame-and-bracket systems, the influence of adopting rigid body assumptions were also analyzed for both concepts. Synthetic and embalmed bone models were tested in combination with primary and revision implants. Single-legged stance phase loading was applied to the implant - bone constructs.

FINDINGS

Adopting a rigid body assumption resulted in an overestimation of mediolateral micromotion of up to 49.7μm at more distal measuring locations. Maximal average relative rotational motion was overestimated by 0.12° around the anteroposterior axis. Frontal and sagittal tilting calculations based on a unidirectional measuring concept underestimated the true tilting by an order of magnitude.

INTERPRETATION

Non-rigid behavior is a factor that should not be dismissed in micromotion stability evaluations of primary and revision femoral implants.

Mid term results with the curved modular tapered, fluted titanium Revitan stem in revision hip replacement

We report our experience of revision total hip replacement (THR) using the Revitan curved modular titanium fluted revision stem in patients with a full spectrum of proximal femoral defects. A total of 112 patients (116 revisions) with a mean age of 73.4 years (39 to 90) were included in the study. The mean follow-up was 7.5 years (5.3 to 9.1). A total of 12 patients (12 hips) died but their data were included in the survival analysis, and four patients (4 hips) were lost to follow-up. The clinical outcome, proximal bone regeneration and subsidence were assessed for 101 hips. The mean Harris Hip Score was 88.2 (45.8 to 100) after five years and there was an increase of the mean Barnett and Nordin-Score, a measure of the proximal bone regeneration, of 20.8 (-3.1 to 52.7). Five stems had to be revised (4.3%), three (2.9%) showed subsidence, five (4.3%) a dislocation and two of 85 aseptic revisions (2.3%) a periprosthetic infection. At the latest follow-up, the survival with revision of the stem as the endpoint was 95.7% (95% confidence interval 91.9% to 99.4%) and with aseptic loosening as the endpoint, was 100%. Peri-prosthetic fractures were not observed. We report excellent results with respect to subsidence, the risk of fracture, and loosening after femoral revision using a modular curved revision stem with distal cone-in-cone fixation. A successful outcome depends on careful pre-operative planning and the use of a transfemoral approach when the anatomy is distorted or a fracture is imminent, or residual cement or a partially-secured existing stem cannot be removed. The shortest appropriate stem should, in our opinion, be used and secured with > 3 cm fixation at the femoral isthmus, and distal interlocking screws should be used for additional stability when this goal cannot be realised.

Modular neck femoral stems

Following the recall of modular neck hip stems in July 2012, research into femoral modularity will intensify over the next few years. This review aims to provide surgeons with an up-to-date summary of the clinically relevant evidence. The development of femoral modularity, and a classification system, is described. The theoretical rationale for modularity is summarised and the clinical outcomes are explored. The review also examines the clinically relevant problems reported following the use of femoral stems with a modular neck. Joint replacement registries in the United Kingdom and Australia have provided data on the failure rates of modular devices but cannot identify the mechanism of failure. This information is needed to determine whether modular neck femoral stems will be used in the future, and how we should monitor patients who already have them implanted.

Dissociation of modular total hip arthroplasty at the neck-stem interface without dislocation

Modular femoral and acetabular components are now widely used, but only a few complications related to the modularity itself have been reported. We describe a case of dissociation of the modular total hip arthroplasty (THA) at the femoral neck–stem interface during walking. The possible causes of this dissociation are discussed. Successful treatment was provided with surgical revision and replacement of the modular neck components. Surgeons who use modular components in hip arthroplasties should be aware of possible early complications in which the modularity of the prostheses is the major factor of failure.