Excellent mid-term results of a new polished tapered modular cemented stem: a study of 113 hip replacements with minimum 5-year follow-up

Modular neck stems in total hip arthroplasty: current concepts

Modular neck (MN) implants can restore the anatomy, especially in deformed hips such as sequelae of development dysplasia.

Early designs for MN implants had problems with neck fractures and adverse local tissue, so their use was restricted to limited indications.

Results of the latest generation of MN prostheses seem to demonstrate that these problems have been at least mitigated.

Given the results of the studies presented in this review, surgeons might consider MN total hip arthroplasty (THA) for a narrower patient selection when a complex reconstruction is required.

Long MN THA should be avoided in case of body mass index > 30, and should be used with extreme caution in association with high offset femoral necks with long or extra-long heads. Cr-Co necks should be abandoned, in favour of a titanium alloy connection.

Restoring the correct anatomic femoral offset remains a challenge in THA surgeries.

MN implants have been introduced to try to solve this problem. The MN design allows surgeons to choose the appropriate degree and length of the neck for desired stability and range of motion.

Cite this article: EFORT Open Rev 2021;6:751-758. DOI: 10.1302/2058-5241.6.200064

Bilateral neck fracture in bimodular femoral stem after primary total hip arthroplasty: a case report

Background

Bi-modular stems were introduced in primary total hip arthroplasty (THA) to enable better control of the femoral offset, leg length, and hip stability. Despite numerous reports on modular femoral neck fractures, some designs are still marketed worldwide. While the risk factors for the sudden failure are multifactorial and mostly known, the timing of this new THA complication is not predictable by any means.

Case presentation

In this report, the literature regarding one of the most popular bi-modular stems with specific neck-stem coupling (oval Morse taper) is reviewed and illustrated with a case of bilateral modular neck fracture in a patient with idiopathic aseptic necrosis of femoral heads treated with primary bi-modular THA. Because of bilateral modular femoral neck fracture, which occurred 3 years on the left side and 20 years after implantation on the right side, the patient required a total of 6 revisions and 208 days of hospitalized care.

Conclusion

To our knowledge, this is the first report of bilateral modular neck fracture in a single patient. Even though the same surgeon performed both operations and used the same neck length and orientation, fractures occurred with a 17-year time difference after implantation. This shows that we cannot predict with certainty when a fracture might occur. Orthopaedic surgeons should use bi-modular stem designs for primary THA very cautiously.

Interchangeable neck failures of bi-modular femoral stems in primary total hip arthroplasty cannot be predicted from serum trace element analysis

INTRODUCTION

Revision of a well-fixed stem due to unexpected modular neck fracture is a catastrophe for the patient and a challenge for the surgeon. This study aimed to test the possibility of predicting interchangeable neck fracture from serum levels of the stem/neck alloy-consisting metals.

MATERIALS AND METHODS

Nineteen patients at high risk for interchangeable neck fracture were randomly selected out of a cohort of 680 bimodular stems made from Ti6Al4V alloy. Serum levels of titanium, aluminium and vanadium were determined. Nine age- and gender-matched patients were used as controls.

RESULTS

Mean serum levels of Ti were 6.04 ± 2.52 μg/L, of Al 3.89 ± 1.68 μg/L and of V 0.07 ± 0.04 μg/L in the high-risk group, and 8.22 ± 4.74 μg/L, 4.99 ± 3.98 μg/L and 0.27 ± 0.44 μg/L in the low-risk group, respectively. No statistically significant differences were found between the groups.

DISCUSSION

Interchangeable neck fracture of bimodular femoral stems cannot be predicted from serum trace element analysis.

Outcomes of neck modularity in total hip arthroplasty: an Italian perspective

BACKGROUND

The aim of this study is to conduct a systematic review of clinical outcomes and complications of modular neck THA among Italian cohorts.

METHODS

Only reviewed publications focused on Italian cohort patients in English language were considered for inclusion. Studies were included if they involved patients who underwent total hip replacement surgery with modular necks, and reported aetiology or survival rate or bone stability or clinical scores or complications.

RESULTS

The studies included in our search reported data on 3714 patients and 3856 hips. Most of the studies were from high-volume surgery centres. The most frequent diagnosis was osteoarthritis that occurred in 2910 cases (75.9%). The average survival rate and average bone stability were 97.20% and 99.37%, respectively. The average HHS improved from 42.1 prior to surgery to 89.52 after surgery. Studies included in our search reported 40 complications. The most frequently reported complication was dislocation (40%).

CONCLUSION

This review showed excellent survival rate and bone stability and good clinical outcomes in Italian cohort patients treated with modular neck THA, and these clinical results are comparable with international cohort rates. This review suggests that modular implants represent a very satisfying choice when practised by expert orthopaedic joint surgeons.

Midterm outcomes of titanium modular femoral necks in total hip arthroplasty

Background

Modular femoral necks present surgical and biomechanical advantages in total hip arthroplasty (THA), but their benefits remain controversial due to risks of corrosion and fracture at the additional junction. This study aimed to report 10-year survival and clinical outcomes of a titanium femoral stem with a titanium modular neck in consecutive series.

Methods

The authors reviewed the records of 97 patients (99 THAs) using uncemented modular stem and ceramic-on-ceramic acetabular components. Patients were evaluated at minimum follow-up of 5 years using the Harris Hip Score (HHS) and Postel Merle-D'Aubigné score (PMA). Survival was calculated using the Kaplan-Meier (KM) method with any reoperation or revision as endpoint.

Results

From the original cohort, 14 patients died, 6 were lost to follow-up, and 5 had revision operations with exchange of the femoral stem. The KM survival at 10 years was 94.2% (CI, 86.5-97.5). Clinical assessment was performed on 67 of the 72 patients (69 of the 74 hips) presently living with their original THA components. At mean follow-up of 9.4±1.0 years (median, 10; range, 5-11), the HHS was 93.6±8.2 and the PMA score 17.0±1.6. The X-rays revealed no signs of adverse reactions or bone loss.

Conclusions

The uncemented titanium hip stem with modular titanium neck provided a satisfactory 10-year survival and clinical outcomes. Neck modularity enabled restoration of patient-specific femoral offset and limb length thanks to five possible neck configurations, though greater follow up is required to confirm the long-term benefits and safety of this design concept.