The influence of the centre of rotation on implant survival using a modular stem hip prosthesis

Abstract

The restoration of the hip centre of rotation in an anatomical position is considered to be relevant for total hip prosthesis survival. When the cup is implanted with a high centre of rotation, the lever arm of the abductor muscles is decreased, causing higher joint-reaction forces. Modular stems with varying lengths and geometries can be used to balance soft tissues, and ceramic bearing surfaces can be used to reduce the wear rate. Forty-four hip replacements performed with a high hip centre of rotation were matched with 44 performed with an anatomical centre of rotation. In all cases the preoperative diagnosis was dysplasia of the hip (DDH) and cementless modular neck prostheses with ceramic bearing surfaces were used. At nine years follow-up the mean Harris hip and WOMAC scores were not statistically different. All stems and cups were stable; the femoral offset was no different between the two groups (p = 0.4) as leg-length discrepancy (p = 0.25).

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].…”

Biomechanical reconstruction of the hip: comparison between modular short-stem hip arthroplasty and conventional total hip arthroplasty

“…First, modular necks are supposed to improve the biomechanical reconstruction of the hip [25,26]. In this study, the modular SHA implant did not show better results as compared to the monoblock THA implant.…”

Long-term survivorship and complication rate comparison of a cementless modular stem and cementless fixed neck stems for primary total hip replacement

“…Blakey et al reported no modular neck fractures for over 350 THRs and a Kaplan-Meier survivorship estimate of 97.5 % at 5 years [20]. Similarly, Traina et al reported no modular neck fractures in 88 THRs with a mean follow-up of nine years [21]. Pattyn et al also reported no modular neck fractures for 68 revision THRs performed using a revision femoral stem from the same manufacturer with identical modular necks [22].…”