Modular neck stems in total hip arthroplasty: current concepts

Abstract

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

Comparison of single taper and dual taper versions of the same stem design in total hip arthroplasty for primary osteoarthritis

“…However, the outcomes of the present report are quite reassuring about neck breakage. Once again, the heavier men demonstrated to be unsuitable candidates for modularity due to the higher risk of neck breakage, as unanimously reported in the literature [5,6,17,18]. While no differences were noted in large cohorts, modular implants may still provide some additional benefits even in cases with primary osteoarthritis.…”

“…However, the outcomes of the present report are quite reassuring about neck breakage. Once again, the heavier men demonstrated to be unsuitable candidates for modularity due to the higher risk of neck breakage, as unanimously reported in the literature [ 5 , 6 , 17 , 18 ].…”

“…As demonstrated in other papers, DT implants did not provide any consistent advantage in terms of dislocations and instability [ 15 , 16 ]. This is a very relevant issue, as modular implants were developed with the aim to improve soft tissue tension and hip biomechanics: theoretically, a lower rate of dislocations would have ensued [ 17 ]. However, some beneficial effects on socket fixation were hypothesized, as a consequence of improved component positioning [ 8 ].…”

“…The most striking drawback of titanium-on-titanium femoral modularity is neck breakage [ 1 , 6 , 14 , 17 , 18 ]. The report described three neck failures, all due to neck breakage, occurring in heavy men weighting more than 90 kg.…”

Dual-Modular Versus Single-Modular Stems for Primary Total Hip Arthroplasty: A Long-Term Survival Analysis

“…This may be due to the relatively small number of Co-Cr necks (42.7%) used in the present series. It has been previously reported that Co-Cr modular necks in combination with Ti6Al4Ti femoral stems fracture earlier than Ti6Al4Ti modular necks and can lead to release of metal ions and debris resulting in local soft-tissue destruction [ 23 , 24 , 25 , 26 , 27 ]. Even though no formal data of ALTRs were found in the patients’ records, the higher revision rates of DM stem THA system because of aseptic loosening may be the consequence of additional modularity at the stem-neck junction.…”