Clinical and Radiological Outcomes of Rectangular Tapered Cementless Stem According to Proximal Femoral Geometry in Elderly Asian Patients

Novel radiologic indices for stem type decision in total hip arthroplasty in patients with metaphyseo-diaphyseal mismatched Dorr A proximal femur

BACKGROUND

In metaphyseo-diaphyseal (M-D) mismatched Dorr A femurs, it is difficult to achieve proper fixation with a type 1 stem. Proper interpretation of the geometry of the femur is integral at the preoperative stage in an M-D mismatched femur, but there has been a scarcity of studies on the radiologic indices. Therefore, we analyze the previous radiologic indices and suggest the novel ones for M-D mismatched femurs.

METHODS

Our study was a retrospective review of preoperative radiographs of patients who underwent total hip arthroplasty with the smallest type 1 stem or with type 3 C stem at a single institution from July 2014 to March 2022. A Type 3 C stem was used when the smallest type 1 stem failed to achieve metaphyseal fixation. One hundred twenty-six patients were categorized into two main groups. Canal-flare index, canal-calcar ratio, modified morphological cortical index, and two novel indices (lesser trochanter-to-distal ratio-α and -β [LDR-α and -β]) were assessed on preoperative pelvic radiographs.

RESULTS

Multivariate and ROC analysis demonstrated that high LDR-β (Exp[B]: 485.51, CI: 36.67-6427.97, p < 0.001) was associated with a more mismatched tendency group and had clinically acceptable discriminatory power (AUC: 0.765, CI: 0.675-0.855, p < 0.001) between the two cohorts.

CONCLUSION

Correct assessment of preoperative femoral morphology would be fundamental in the selection of a suitable stem. The ratio based on 3 cm below the lesser trochanter of the femur seemed crucial. We recommend evaluating the newly described radiological index preoperatively in M-D mismatched Dorr A femur for planning precisely and selecting a proper stem.

Results of Hip Arthroplasty Using a COREN Stem at a Minimum of Ten Years

Purpose

We report on the 10-year clinical hip function and radiologic outcomes of patients who underwent hip arthroplasty using a COREN stem.

Materials and Methods

A consecutive series of 224 primary cementless hip arthroplasty implantations were performed using a COREN stem between 2009 and 2011; among these, evaluation of 128 hips was performed during a minimum follow-up period of 10 years. The mean age of patients was 65.4 years (range, 40-82 years) and the mean duration of follow-up was 10.8 years (range, 10-12 years). Evaluation of clinical hip function and radiologic implant outcomes was performed according to clinical score, thigh pain, and radiologic analysis.

Results

Dramatic improvement of the mean Harris hip score (HHS) from 59.4 preoperatively to 93.5 was observed at the final follow-up (P≤0.01). Stable fixation was demonstrated for all implants with no change in position except for one case of Vancouver type B2 periprosthetic femur fracture. A radiolucent line (RLL) was observed in 16 hips (12.5%). Thigh pain was observed in only two hips (1.6%) at the final follow-up. There were no cases of osteolysis around the stem. The survival rate for the COREN stem was 97.7%.

Conclusion

Good long-term survival with excellent clinical and radiological outcomes can be achieved using the COREN femoral stem regardless of Dorr type.

Cementless femoral stem fixation and leg-length discrepancy after total hip arthroplasty in different proximal femoral morphological types

PURPOSE

Leg-length changes at total hip arthroplasty (THA) may result from too proximal position of the femoral component, i.e. not being sunk deep enough into the femoral canal due to the size and shape of both medullary canal and implant. Some femoral implants are designed to achieve such fixation in the mediolateral dimension, while others also engage the bone anteroposteriorly. Our aim was to examine the relationship between proximal femoral morphology, osseointegration and leg-length equalization at THA. We asked whether the Dorr classification, femoral cortical index and canal flare index on preoperative radiographs had significant impact on THA aseptic loosening rates and post-operative leg-length discrepancy (LLD).

METHODS

Literature review included original articles on proximal femoral morphology with post-operative LLD and other clinical outcomes of THA, published in the last decade. Case reports and biomechanical studies without clinical data were excluded.

RESULTS

Higher femoral cortical index and/or canal flare index (corresponding to the Dorr type A) increases the risk of leg lengthening at THA. This is particularly notable in femoral stems with metaphyseal fixation, where high canal flare index has also been linked to osseointegration failure and implant loosening. On the other hand, lower canal flare index (corresponding to the Dorr type C) is more prevalent in the elderly population and increases late periprosthetic fracture rates and stress shielding. Even the most commonly used cementless femoral stems cannot offer optimal fit to intra-/extramedullary geometry or offset restoration in up to 30% of clinical cases.

CONCLUSIONS

Femoral morphology can have significant impact on post-operative LLD and osseointegration of cementless THA. Quantitative measurements of the proximal femoral canal may improve the choice of a particular implant and fixation method.