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Original Article

Radiographic subsidence in Excia hip prosthesesfollowing elective un-cemented total hiparthroplasty

Iain Ross MacPherson Bohler a,*, Vimal Kumar Velu a, Yahya Husami b,Alexander Craig Campbell a

a Trauma and Orthopaedics Department, Monklands Hospital, Airdrie, North Lanarkshire, ML6 OJS, United Kingdomb Radiology Department, Monklands Hospital, Airdrie, North Lanarkshire, ML6 OJS, United Kingdom

a r t i c l e i n f o

Article history:

Received 22 May 2014

Accepted 24 August 2014

Available online xxx

Keywords:

Subsidence

Excia

Hip

Arthroplasty

Radiographic

* Corresponding author.E-mail address: iain.bohler@doctors.net.u

Please cite this article in press as: Bohlecemented total hip arthroplasty, Journal

http://dx.doi.org/10.1016/j.jor.2014.08.0090972-978X/Copyright © 2014, Professor P K SLtd. All rights reserved.

a b s t r a c t

Aims: To quantify subsidence in uncemented Excia straight stem hip arthroplasty patients.

Methods: 51 patients (m:f; 25:26) received transplantation, 9 were incompletely followed up.

Patients were assessed for radiological subsidence on consecutive follow-up radiographs,

corrected for magnification error.

Results: Subsidence of >3 mm was noted in 62% of patients and subsidence of >10 mm

noted in 17%. One patient dislocated. Average 13 wks subsidence was 4.2 mm increasing

continually to 6.5 mm at 92wks.

Conclusion: Whilst we note the limitations of our study, data was thought too clinically

significant to account for human error alone. We suggest further review and use of alter-

native proven prostheses.

Copyright © 2014, Professor P K Surendran Memorial Education Foundation. Publishing

Services by Reed Elsevier India Pvt. Ltd. All rights reserved.

1. Introduction

The collarless, narrow trunnioned, narrow stemmed, Aescu-

lap Excia straight stem implant has been designed to preserve

bone and implant longevity whilst allowing a large range of

motion.1 To our knowledge and literature search, no study has

been done to analyze the rate of subsidence using the implant.

Cementless stems are a reliable option in total hip

arthroplasty,2e4 however subsidence of femoral stems is a

k (I.R.M. Bohler).

r IRM, et al., Radiographof Orthopaedics (2014),

urendran Memorial Educ

commonly reported complication.5e10 Multiple factors have

been reported to increase subsidence rates including osteo-

porosis, male sex,5,7 hip bone morphology11 and implant

design.7 Whilst subsidence has been shown to occur up to two

years post operatively, subsidence after 6 weeks post opera-

tively and of more than 3 mm is considered clinically signifi-

cant and abnormal.9,10

Aesculap offer two variations of Excia design (Fig. 1). The

cemented implant has a smoothwingless surface and flanges,

ic subsidence in Excia hip prostheses following elective un-http://dx.doi.org/10.1016/j.jor.2014.08.009

ation Foundation. Publishing Services by Reed Elsevier India Pvt.

Fig. 1 e Excia straight stem implants. Cemented (left),

cementless (right).

j o u r n a l o f o r t h o p a e d i c s x x x ( 2 0 1 4 ) 1e52

designed to preserve bone near the greater trochanter,

allowing for proximal fit within the cemented medulla.1

Cementless stems have a lateral wing and proximally,

have a rough porous coating with an additional 20 mm

resorbable m-CaP calcium phosphate surface to aid mechani-

cal stability.

We decided to undertake a retrospective audit of all pa-

tients receiving cementless Excia implants following the pre-

sentation of a patient with an Excia implant, with significant

subsidence, presenting as a dislocation of prosthetic hip Fig. 2.

The purpose of this study was to determine average subsi-

dence in the initial 3 months post-operative period and sub-

sequently until latest follow-up.

All radiological measurements and techniques were

assessed and aided by a radiology consultant.

Fig. 2 e Dislocation of an Excia impl

Please cite this article in press as: Bohler IRM, et al., Radiographcemented total hip arthroplasty, Journal of Orthopaedics (2014),

2. Patient's and methods

We undertook a retrospective data analysis of all consecutive

Excia uncemented Total hip arthoplasties undertaken within

the department between July 2010 and November 2013. In

total there were 51 patients who received a joint replacement

using the Excia stem. There were 25 male and 26 female with

an average age of 61 years. At the point of writing, 7 (5 male, 2

female) of the most recent patients were awaiting first follow

up appointments, and two patients (both male) were lost to

follow up, and thus were excluded from the study.

Patients receiving Excia implants presented to our hospital

as elective patients requiring total hip arthroplasty for

degenerative joint disease. All procedures were undertaken by

one of four orthopaedic consultants or by senior registrars

under their assistance using either standard antero-lateral or

posterior approaches. Three surgeons allowed immediate full

weight bearing (25 patients) whilst the fourth permitted only

partial weight bearing in the initial 6e8weeks post operatively

(17 patients). Patients were X-rayed either on the day of

operation, or post operative day 1. Radiographic measure-

ments were taken for distance from the tip of the greater

trochanter to the most lateral proximal aspect of the shoulder

of the prosthesis, and taken as the set implant depth. Patients

were re X-rayed on consecutive appointments throughout

their active period of follow up. Subsidence was then

measured as the difference in depth measured between the

greater trochanter and shoulder of prosthesis in successive

radiographs. Subsidence was measured between each radio-

graph and its predecessor, with the total subsidence values

presented in this paper a reflection of cumulative subsidence

values (Figs. 2 and 3). To overcome error in magnification on

radiographic images, subsidence measurements were

adjusted in accordance to measurements of the prosthetic

femoral head component.

The need for informed consent was waived by the ethical

committee since the rights and interests of patients would not

ant with significant subsidence.

ic subsidence in Excia hip prostheses following elective un-http://dx.doi.org/10.1016/j.jor.2014.08.009

Fig. 3 e Significant subsidence in a left Excia THR.

j o u r n a l o f o r t h o p a e d i c s x x x ( 2 0 1 4 ) 1e5 3

be violated and their privacy and anonymity would be assured

by this study design. This study was seen to conform to the

declaration of Helsinki.

3. Results

The mean average age of patients in the study was 61 years

with little differentiation between male (average 62.1) and

female (average 60.7) patients. Female patients however rep-

resented a larger age range (39e80 yrs) compared to male

(53e81 yrs).

Fig. 4 e Subsidence values in all 42 patients (

Please cite this article in press as: Bohler IRM, et al., Radiographcemented total hip arthroplasty, Journal of Orthopaedics (2014),

The average (mean) overall subsidence (of 42 patients) was

5.4 mm, ranging from 0.0 to 22.3 mm (Fig. 4). Sub grouping the

follow ups as first, second, third and fourth, there were 42

patients at first follow up, mean 13 weeks, with average sub-

sidence 4.2 mm (range 0.4 mm�19 mm). At mean 35 weeks

follow-up, the subsidence increased to 5.1 mm (26 pts, range

4.6 mm to �1.3 mm), whilst at mean 67 weeks follow-up, 18

patients still actively receiving follow up demonstrated an

average subsidence of 6.1 mm (range 3.6 mm to �0.2 mm). By

the fourth and final follow up, mean 92 weeks, 7 patients still

actively receiving follow up demonstrated an average subsi-

dence of 6.5 mm (range 1 mm�0.7 mm). Average subsidence

date of operation in chronological order).

ic subsidence in Excia hip prostheses following elective un-http://dx.doi.org/10.1016/j.jor.2014.08.009

j o u r n a l o f o r t h o p a e d i c s x x x ( 2 0 1 4 ) 1e54

was seen to be progressive throughout the follow-up periods

with a trend towards plateauing of subsidence at our last

follow-up mean of 92 weeks. Minimal variation was demon-

strated between weight bearing and non weight bearing

patients.

Significant subsidence, correlated as those values over

3 mm as per literature review,7 was seen in 62% of patients

(26/42 patients), of which subsidence over 10 mm was seen in

17% of patients (5 male and 2 female). One patient dislocated

requiring MUA.

4. Discussion

The above results stimulated us to publish findings before

further analysis of risk factors associated with increased

subsidence in the Excia stem have been researched.

Female patients demonstrated a greater age range, likely

attributable to a combination of factors including femoral

anatomy and a greater propensity for age related bone

demineralisation (the onset of the menopause and longer life

expectancies).12,13 Male patients were seen to have a greater

degree of subsidence in keeping with previous papers.

The accurate measurement of subsidence is key to the

publication of sound clinical rhetoric of an implant's migra-

tion. Several modalities are widely described in literature.

The measuring technique described above, calculating subsi-

dence manually from AP radiographs is a basic however well

documented, and widely replicated method.7,14,15 Femoral

Component Analysis (FCA)- involves the use of computer

software to reproduce manual calculations using series of a

minimum of 4 AP radiographs to determine subsidence and

version of the prosthetic stem.

The gold standard of investigating subsidence is Radio-

stereometric analysis (RSA). The technique involves insertion

of radio-opaque tantalum beads in the prosthesis and medial

and lateral walls of cancellous bone in the proximal femur.

Opposing X rays beamsþ computer software are then capable

of calculating various measurements to give a highly detailed

information on stem positioning. This technique is however

only of use in prospective studies.16

Previous literature on femoral prosthesis subsidence has

shown 1 or 2 mm of subsidence in the first 6 weeks post-

operatively to be common ground. These studies showed

implants that subsided 3 mm or more, or continually after the

first 6 weeks were unstable, however this occurrence was

unusual.8e10 The above results show subsidence over 3 mm in

amajority of patients receiving the Excia stem. Implants were

also shown to commonly subside progressively until average

18 months follow-up in our study.

Whilst this audit presents significant data, we are aware of

the limitations of our study. The small data set needs

increased to improve its statistical reliability. We now intend

on gathering and correlating results with others hospitals in

the health board using the Excia stem. Whilst multiple sur-

geons were involved in the above data set, an increased pool

of data from different surgeons will allow us to assess the

degree of surgical error in the above data. Human error in

alignment and implant sizing would adversely affect the im-

plant's integration. We are also aware of the limitations of our

Please cite this article in press as: Bohler IRM, et al., Radiographcemented total hip arthroplasty, Journal of Orthopaedics (2014),

measuring technique. Whilst all measurements were calcu-

lated in the same way and cross checked with other authors,

the technique is somewhat primitive in comparison to more

advanced FCA/RSA techniques. Improvements would also

need to be made in radiograph positioning. Whilst exact

specifications for hip radiographs exist in our hospital, de-

grees of rotation on A-P radiographs, could contribute to a

measuring error.

Research value could also be improved by assessing other

clinically significant criteria such as radiographic deteriora-

tion of bone quality, and pre and post surgery Harris Hip

Scores for pain.

5. Summary

Based on this analysis, it is our opinion that the Aesculap

Excia implant subsides considerably with slow osteo-

integration. Whilst we note the limitations of our own study,

data results were thought to be too clinically significant to

account for human error alone. We suggest the use of alter-

native proven prosthesis whilst further review of this pros-

thesis is undertaken.

Conflicts of interest

All authors have none to declare.

Acknowledgements

This paper would like to acknowledge and thank M.Agarwal

and M. Mathew for their contribution to this study.

r e f e r e n c e s

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12. Kaptoge S, Dalzell N, Loveridge N, Beck T, Khaw K-T, Reeve J.Effects of gender, anthropometric variables, and aging on the

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evolution of hip strength in men and women aged over 65.Bone. 2003;32:561e570.

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ic subsidence in Excia hip prostheses following elective un-http://dx.doi.org/10.1016/j.jor.2014.08.009