Modular neck femoral stems

Abstract

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.

How Have Alternative Bearings and Modularity Affected Revision Rates in Total Hip Arthroplasty?

“…According to all registry reports, THA modular necks had lower survivorship as did the clinical series that we reviewed for this aspect of modularity [1,4,6,8,12,17,19,20,24,35,40,44,48,68,71,73,75,[78][79][80][81]. Similar survivorships and revision rates were found for modular stem/body and body/neck femoral components, whereas registry data revealed similar results except when these types of stems were paired with a MoM articulating bearing, which was reported to increase revision rates even further [1].…”

“…No study involving retrieval analysis or metal ion levels was included. Twenty reports on dual modular femoral components in the literature met inclusion criteria [4,6,8,12,17,19,20,24,35,40,44,48,68,71,73,75,[78][79][80][81]. The levels of evidence for these articles that met inclusion criteria were: Level I (zero), Level II (four), Level III (four), and Level IV (twelve).…”

“…This increased frequency of revision with exchangeable neck prostheses occurred with all bearing surfaces in the Australian Registry (Table 3). Twelve studies reported on various types of modular femoral neck and stem components with a range of survivorship from 91% to 100% with a range of followup of 8.6 and 5 years, respectively [4,8,17,19,20,35,44,68,73,[79][80][81]. Eight reports dealing specifically with the S-ROM modular stem/body (DePuy Orthopaedics Inc, Warsaw, IN, USA) reported a range of survivorships for aseptic loosening of 93.3% to 100% with a range of followup of 19 years and 10 years, respectively [6,12,24,40,48,71,75,78].…”

“…These marketed advantages have, however, come with increased risks and complications [4,15,27,44,70]. Unfortunately, adding another metal taper junction may increase the burden of corrosion debris and the risk of local tissue reactions as well as serve as a possible weak link that can increase the risk of a catastrophic failure [4,15,27,44,70]. As with any additional technological advancement in implant designs, both alternative bearings and increased modularity add cost to the implants in most cases.…”

Are titanium-on-titanium TiAl6V4 modular necks safe in total hip arthroplasty for non-overweight patients? Results of a prospective series at a minimum follow-up of 7 years

“…Modular femoral necks in THA have been developed as an option to optimize the restoration of hip biomechanics [2] with the possibility to manage independently leg lengths, offset and anteversion intraoperatively [3][4][5][6]. Modularity, however, also renders several postulated disadvantages that must be taken into consideration, [7][8][9][10][11][12] due to the number of fatigues fractures observed with the first titanium-on-titanium alloy modular stem THA, CoCr head and neck segments have been developed [6,7,12,13]. Some authors initially reported no increment of corrosion or metal ion release under simulated in vivo conditions with these alloys, [13] when others have described increased amount of debris products and accelerated osteolysis [14,15].…”