S38 Oral and Poster Presentations / Journal of Biomechanics 43S1 (2010) S23–S74

[4] Buchler P, Farron A. Benefits of an anatomical reconstruction of the

humeral head during shoulder arthroplasty: a finite element analysis.

Clin Biomech. (Bristol, Avon). 2004 Jan;19(1):16–23.

[5] Jonsson E, Egund N, Kelly I, Rydholm U, Lidgren L. Cup arthroplasty of

the rheumatoid shoulder. Acta Orthop Scand. 1986 Dec;57(6):542–6.

[6] Levy O, Copeland SA. Cementless surface replacement arthroplasty of

the shoulder. 5- to 10-year results with the Copeland mark-2 prosthesis.

J Bone Joint Surg Br. 2001 Mar;83(2):213–21.

[7] Walch G, Boileau P. Prosthetic adaptability: a new concept for shoulder

arthroplasty. J Shoulder Elbow Surg. 1999 Sep-Oct;8(5):443–51.

[8] Boileau P, Walch G. The three-dimensional geometry of the proximal

humerus. Implications for surgical technique and prosthetic design.

J Bone Joint Surg Br. 1997 Sep;79(5):857–65.

[9] Edwards TB, Kadakia NR, Boulahia A, Kempf JF, Boileau P, Nemoz C,

Walch G. A comparison of hemiarthroplasty and total shoulder

arthroplasty in the treatment of primary glenohumeral osteoarthritis:

results of a multicenter study. J Shoulder Elbow Surg. 2003 May-

Jun;12(3):207–13.

[10] Thomas SR, Sforza G, Levy O, Copeland SA. Geometrical analysis of

Copeland surface replacement shoulder arthroplasty in relation to

normal anatomy. J Shoulder Elbow Surg. 2005 Mar-Apr;14(2):186–92.

[11] McMahon PJ, Dee DT, Yang BY, Lee TQ. Mal-aligning humeral offset may

not effect shoulder hemiarthroplasty: a biomechanical study. Med Sci

Monit. 2003 Aug;9(8): CR346–52.

[12] Nyffeler RW, Werner CM, Sukthankar A, Schmid MR, Gerber C.

Association of a large lateral extension of the acromion with rotator

cuff tears. J Bone Joint Surg Am. 2006 Apr;88(4):800–5.

[13] Nyffeler RW, Sheikh R, Atkinson TS, Jacob HA, Favre P, Gerber C. Effects

of glenoid component version on humeral head displacement and joint

reaction forces: an experimental study. J Shoulder Elbow Surg. 2006

Sep-Oct;15(5):625–9.

[14] Kircher J, Morhard M, Gavriilidis I, Magosch P, Lichtenberg S,

Habermeyer P. Is there an association between a low acromion index

and osteoarthritis of the shoulder? Int Orthop. 2009 Nov 6.

S-21

Cementless Surface Replacement Arthroplasty of the Shoulder:

15 to 25 Year Results with the Copeland Prosthesis

A. Patel, A. Narvani, T. Even, O. Levy, S. Copeland. Reading Shoulder

Unit, Royal Berkshire Hospital, UK

Introduction: Cementless surface replacement arthroplasty of the

shoulder is designed to replace the damaged joint surfaces and

restore normal anatomy with minimal resection of bone (Levy &

Copeland, 2001). We have used the Copeland shoulder arthroplasty

for 25 years. Between 1986 and 1995, 90 surface replacement

arthroplasties were implanted in our unit. The prosthesis has

evolved during this time, but the principle of minimal bone

resection has remained the same (Levy & Copeland, 2004). The

operations were carried out for the treatment of osteoarthritis,

rheumatoid arthritis, avascular necrosis, instability arthropathy,

post-traumatic arthropathy and cuff arthropathy.

Methods: Out of the 90, 43 patients with mean a follow-

up of 18.2 years (15 to 25) were available for follow up

where functional outcome assessment using Constant score and

radiological assessments were performed. 25 patients had died

and 22 were lost to follow up. The operations were carried out

for the treatment of osteoarthritis (43.3%), rheumatoid arthritis

(33.6%) avascular necrosis (3.3%), instability arthropathy (5.6%),

post-traumatic arthropathy (4.4%), cuff arthropathy (4.4%) and post

infection arthropathy (2.2%). Mean age at the time of surgery was

62.3 (range; 25–87).

Results: Ninety percent of patients considered their shoulder to be

much better or better than before the operation. 85% were pain

free. 80% felt that their shoulder did not limit their daily living.

90% felt that their recreational activities were not limited by their

shoulder. 85% felt that their shoulder did not disturb their night

sleep. 19% of the patients have had revision.

Conclusions: These results indicate that vast majority of patients

are pain free and have good functional outcome 15–25years post

Copeland cementless surface replacement.

Reference(s)

[1] Levy, O., Copeland, S. A. (2001) Cementless surface replacement

arthroplasty of the shoulder. 5- to 10-year results with the Copeland

Mark-2 Prosthesis. JBJS. 83-B (2). 213–221.

[2] Levy, O., Copeland, S. A. (2004) Cementless surface replacement

arthroplasty (Copeland CSRA) for osteoarthritis of the shoulder. JBJS.

13 (3). 266–271.

S-22

Complications Following Hip Hemiarthroplasty; Are We Within

Acceptable Standards?

A. Hamza, N. Aslam-Pervez. Leeds General Infirmary, UK

In the UK, it is estimated that 70,000 hip fractures occur a year

and this is projected to rise by 2% per annum. The mortality

rate following a fractured neck of femur is between 20% and 35%

within one year in patients aged 82±7 years [1]. This has huge

clinical and financial impact on health and social care services. As

clinicians it is important to recognise and reduce this burden by

improving clinical practice. The six standards of hip fracture care

in the National Hip Fracture Database (NHFD) are based on best

available evidence [2]. They aim to improve clinical practice and

reduce morbidity and mortality rates. We conducted a retrospective

clinical audit to compare the complication rates following hip

hemiarthroplasties at our tertiary centre to NHFD standards. Over a

6 month period, we gathered data from 60 patients who underwent

a hip hemiarthroplasty. 5 patients (8.3%) suffered from wound

infection when compared to the standard of <5%. It was found

that 10 patients (16.6%) did not receive antibiotic prophylaxis at

induction. Three of these had wound infection. 3 patients (5%)

suffered from a post operative pulmonary embolism compared

to a standard of <1%. It was found that three patients (5%) did

not receive any form of thrombo-prophylaxis two of these had a

pulmonary embolism. Our dislocation and peri-prosthetic fracture

rates was within acceptable standards, 2% and 1.6% respectively.

Furthermore, ten (17%) medically fit patients did not have their

operation within the 48 hour standard. This study highlights the

importance of prompt administration of antibiotics and thrombo-

prophylaxis to patients undergoing hip hemiarthroplasties. As well

as educating health care staff, a new prescription chart was designed

to improve the thromboprophylaxis and antibiotics prescription. In

addition to meet the 48 hour standard in hip fracture patients a

designated trauma list was introduced.

Reference(s)

[1] Goldacre MJ, Roberts SE, Yeates D; Mortality after admission to

hospital with fractured neck of femur; Database study; BMJ. 2002 Oct

19;325(7369), pp. 868–9.

[2] British Orthopaedic Association; The care of patients with fragility frac-

ture. September 2007. Available from http://www.ccad.org.uk/nhfd.nsf/

Blue_Book.pdf.

S-23

Influence of Femoral Component Material Properties on Stress

Shielding in Total Hip Replacement

A. Lakzadeh1, T. Khazaei2, A. Ataei1. 1Iran University of Science and

Technology, Iran; 2Iran Azad University, Iran

One of the most frequent complications of total hip replacement

(THR) is aseptic loosening of femoral component which is primarily

due to changes of post-operative stress distribution pattern with

respect to intact femur. The objective of the current study

was to evaluate the influence of femoral prosthesis material

properties on stress shielding through the surrounding bone

which could cause aseptic loosening of the femoral prosthesis

in long-term periods. Three different three-dimensional (3D)

finite element (FE) models i.e. an intact human proximal femur

model and two post-operative models were developed based on

computed tomography (CT) images. In the post-operative models,

a commercially used cementless femoral prosthesis with two