Design and Verification of a Metaphyseal Filling Stem for Total Hip Arthroplasty Based on Novel Measurements of Proximal Femoral Anatomy

Background

Cementless metaphyseal filling stems rely on fixation in the medial-to-lateral and anterior-to-posterior (AP) planes. The purpose of this preclinical study was to develop Insignia, a new metaphyseal filling system to match the anatomy of the proximal femur, and then compare it to clinically successful stems in multiple simulations.

Methods

In this preclinical study, the geometry of the proximal femur in the AP plane among 1321 healthy subjects was evaluated using computed tomography. This data was then used to design insignia. Preclinical studies were performed to compare the broaching effort required to prepare a canal using this system, assess the reliability of seating heights for the stem, and compare in vitro micromotion testing of the stem under simulated stair climb activity.

Results

The proximal femur decreased approximately 50% in the AP plane spanning 20 mm above the lesser trochanter to 30 mm below the lesser trochanter. Additional bench top testing was performed, and the new stem system was found to demonstrate significantly reduced broaching effort (average 6 vs 29 hits, P-value = .000), reliable seating heights on stem placement, and 70% less proximal micromotion on 10,000-cyclic testing (P < .05) compared to another clinically successful metaphyseal filling stem.

Conclusions

The AP dimension of the proximal femur decreases nearly 50% throughout its length. Metaphyseal filling stems that match the AP anatomy of the proximal femur may require fewer hits during broaching, yield reproducible seating heights, and reduce micromotion on cyclic testing.

Ten-year comparison of two different techniques for femoral bone cavity preparation-broaching versus compaction in patients with cementless total hip arthroplasty : a randomized radiostereometric study of 30 total hip arthroplasties in 15 patients operated bilaterally

Aims

Femoral bone preparation using compaction technique has been shown to preserve bone and improve implant fixation in animal models. No long-term clinical outcomes are available. There are no significant long-term differences between compaction and broaching techniques for primary total hip arthroplasty (THA) in terms of migration, clinical, and radiological outcomes.

Methods

A total of 28 patients received one-stage bilateral primary THA with cementless femoral stems (56 hips). They were randomized to compaction on one femur and broaching on the contralateral femur. Overall, 13 patients were lost to the ten-year follow-up leaving 30 hips to be evaluated in terms of stem migration (using radiostereometry), radiological changes, Harris Hip Score, Oxford Hip Score, and complications.

Results

Over a mean follow-up period of 10.6 years, the mean stem subsidence was similar between groups, with a mean of -1.20 mm (95% confidence interval (CI) -2.28 to -0.12) in the broaching group and a mean of -0.73 mm (95% CI -1.65 to 0.20) in the compaction group (p = 0.07). The long-term migration patterns of all stems were similar. The clinical and radiological outcomes were similar between groups. There were two intraoperative fractures in the compaction group that were fixed with cable wire and healed without complications. No stems were revised.

Conclusion

Similar stem subsidence and radiological and clinical outcomes were identified after the use of compaction and broaching techniques of the femur at long-term follow-up. Only the compaction group had intraoperative periprosthetic femur fractures, but there were no long-term consequences of these.

Cite this article: Bone Jt Open 2021;2(12):1035–1042.

Broaching partially-shared identities: Critically interrogating power and intragroup dynamics in counseling practice with trans people of Color

Background: Much of the literature on transgender and nonbinary (TGNB) experiences in counseling focuses on White experiences with few recommendations for trans people of Color (TPOC). Research suggests mental health care providers lack intersectional sensitivity with TPOC, lack knowledge of TGNB issues and engage in microaggressive behaviors, notably with Queer-identified clinicians. Aim: To explore issues of power and privilege in the counseling relationship with Queer-identified clinicians and apply the multidimensional model of broaching behavior with TGNB clients of Color. Method: A critical review of conceptual and empirical literature focusing on the interaction and impact of client and clinician race, gender, and sexual/affectional identities in the counseling relationship is presented. Informed by the authors' counseling experiences and respective positionalities as a Black Queer ciswoman and a White Queer transman, the multidimensional model of broaching behavior is applied to a composite case vignette. Results: The model provides a practical tool to facilitate critical conversations of power, privilege and identity in the counseling relationship. Conclusion: With a dearth of scholarship addressing the role of cisgender or White privilege in the counseling relationship, this article outlines strategies to broach issues partially-shared identities with TGNB clients of Color. Recommendations for culturally informed counseling practice, supervision and research are also provided.

Modification of regional bone mineral density due to femoral rasping in cementless proximally fixed total hip arthroplasty

BACKGROUND

Three-dimensional planning (3DP) in total hip arthroplasty using computed tomography (CT) to analyze bone mineral density (BMD) at the stem-femur interface has a high reported accuracy and excellent mid-term results in the literature. However, 3DP does not take into account the effect of femoral rasping on BMD distribution within the rasped cavity. Characterizing the impact of femoral rasping on BMD may help avoid mechanical failures, but this data is not accurately investigated. Therefore, we set out a cadaveric study to identify if: (1) Femoral rasping modified regional BMD in areas considered critical for bone anchorage of cementless metaphyseally fixed anatomic stems. (2) In areas of bone-implant contact with an initial high BMD, does femoral rasping increase BMD?

HYPOTHESIS

Femoral rasping increases BMD in some zones considered critical for bone anchorage of cementless metaphyseally fixed anatomic stems within the rasped femoral cavity.

METHODS

Four cadaveric femurs were selected to undergo a rasping procedure similar to surgical techniques used for metaphyseally fixed anatomic stems. Images of femurs before and after rasping were obtained with a micro-CT scanner (pixel size 35μm). BMD values before and after rasping were compared in a trabecular bone ring of 3mm thickness around the cavity created by the rasps, in a region extending 3cm above and 2cm below the middle of the lesser trochanter.

RESULTS

Average BMD increased significantly after rasping in 3 of the 4 femurs (13% (0.27 to 0.30) (p=0.004)), 12% (0.32 to 0.36 (p=0.034)) and 15% (0.4 to 0.46 (p=0.001)), while there was no significant variation in the last femur (0.32 to 0.32 (p>0.05)). Increases in regional BMD were significantly higher in the lateral and medial areas, as well as in the most distal femoral regions. There were significantly lower variations of BMD in regions with initially higher BMD.

DISCUSSION

Current opinion considers trabecular bone debris from femoral rasping to have an impact on final stem position and outcome. Our study has demonstrated an overall positive effect of femoral rasping on BMD in the rasped cavity. Understanding this in the context of 3DP may help avoid mechanical failures such as, suboptimal implant fit, fill, and stability as well as femoral fractures during stem implantation.

LEVEL OF EVIDENCE

IV, Prospective in vitro study.

The influence of broach design on bone friction and osseodensification in total hip arthroplasty

BACKGROUND

The process of cavity preparation by broaching has an impact on the primary stability of uncemented hip stems and on the periprosthetic fracture risk. Osseodensifying broaches may increase primary stability, but have the potential to raise cortex strains and facilitate fracture. The aim of this study was to determine the influence of broach design on the forces acting during broaching, on the microstructure of the broached bone bed and the amount and depth of osseodensification.

METHODS

Broach models representing compaction, blunt extraction and sharp extraction broaches, were used for quasi-static simulation of femoral cavity preparation on bovine trabecular bone cuboids. Broaching forces were measured and micro-computed tomography scans performed prior and after testing. Friction coefficients during broaching, bone densification parameters and size of the debris particles pushed into the bone were determined.

FINDINGS

Friction coefficients during sharp extraction exceeded those during compaction and blunt extraction broaching (by 38% and 37%, P < .001). Total bone densification was enhanced for compaction and blunt extraction compared to sharp extraction broaching (increase of 121% and 117%, P = .005), resulting from higher densification depths for compaction (P = .001) and higher maximum densification for blunt extraction broaching (P = .008), with the latter producing fewer large particles than compaction broaching (P = .005).

INTERPRETATION

Higher friction coefficients indicate a decreased periprosthetic fracture risk with sharp extraction broaches for equal implantation forces. The blunt extraction and compaction designs investigated densified the bone to a similar extent. Blunt extraction broaching may support better osseointegration due to smaller bone debris particles.

A complication during femoral broaching in total hip arthroplasty: a case report

Press-fit component fixation is one of the primary goals in uncemented total hip arthroplasty. When aiming at proximal load transfer, the stem size has to be selected with regard to the shape of the proximal femoral canal. This can be challenging in patients with 'champagne flute' femurs with a relatively narrow diaphysis, especially when a long stem femoral component is used. The present case report describes a complication during femoral broaching for a primary uncemented femoral component. Because of the narrow diaphysis, the distal portion of the broach got caught in the narrow canal and it became impossible to remove the broach with conventional techniques. Via a second distal incision, the femur was split from the distal tip of the broach to approximately 5 cm distal of the femoral neck cut along the posterior aspects of the femur. This loosened the broach enough to allow for an uncomplicated removal. The longitudinal split was secured with cables before a similar size primary implant was press fitted into the femoral canal.