A prospective study of the results of the Avon patellofemoral arthroplasty has been undertaken since its initial implantation in September 1996. To date 496 primary arthroplasties have been performed in the Bristol Knee Unit for isolated patellofemoral arthritis and significant chondral damage, which has failed to respond to conservative surgical treatment. Detailed information has been recorded about the patients including the diagnosis, previous surgical treatment and specific pathological and radiographic findings. Pre and post-operative assessments have been carried out using a variety of outcome tools. Firstly the Bristol Knee Score (ref. 1), which records separately pain, overall patient function and knee specific function. In addition Melbourne Patella Score (ref. 2) has been used, which specifically records information about patellofemoral function. Patients have also been scored on the Oxford Knee Score (ref. 3), which is a disease specific fully validated patient administered scoring system. More recently the Womac 12 score (ref. 4) has been used.

Patients have been reviewed at 8 months, 2 years, 5 years and 8 years, and will then be followed at 10, 12 and 15 years.  The median scores are recorded for all patients in the follow-up, excluding those who have dropped out through death or through revision. The graphs of these follow-ups are shown below.  The median outcome scores improve by 50% at 2 years and 5 years.  113 knees have now been reviewed at 5 to 8 years and the median scores have remained satisfactory with a slight improvement.  It is interesting to note that the median scores for all outcome measures have remained remarkably consistent throughout the follow-up period of 8 years.  There has been no change in the median outcomes with increasing numbers of patients entered into the study.  This would seem to suggest a constant performance of the arthroplasty.  Initially most cases were performed by the senior authors but the trial has now been widened considerably to include more than 20 different surgeons some of whom are in residency training. (ref. 5 - 9).

Pre-op case example: female aged 62, Pain 40%, Oxford 66%

Post-op case at 10 years with full function and no pain

COMPARISON of Avon v TKR Kmx  (International)
WOMAC Pain: 100

COMPARISON of Avon v TKR
WOMAC Function: 100

Oxford Knee Score:
Rebased to 100

Disease progression, 5 Year Survivorship --- 95.8%

References

1. Bach ChM, Steingruber I, Nogler M, Orgon M, Wimmer C, Gobel G, Kristmer M. Scoring systems in total knee arthroplasty. Clin Orthop 2002; 399: 184-196.
2. Feller JA, Bartlett RJ, Lang DM. Patellar resurfacing versus retention in total knee arthroplasty. J Bone Joint Surg (Br) 1996; 78-B:  226-228.
3. Dawson J, Fitzpatrick R, Murray D, Carr A. Questionnaire on the perceptions of patients about total knee replacement.  J Bone Joint Surg (Br) 1998; 80-B: 63-69.
4. Whitehouse S, Lingard EA, Katz JN, Learmonth ID. Development and testing of a reduced  WOMAC function scale. J Bone Joint Surg (Br) 2003; 85-B: 706-711.
5. Ackroyd CE, Development and early results of a new patellofemoral arthroplasty. Clin Orthop Relat Res 2005;436; 7-13.
6. Ackroyd CE, Newman JH. The Avon patellofemoral arthroplasty. Two to five year results. J Bone Joint Surg (Br) 2003; 85-B: Suppl II, 162-3.
7. Ackroyd CE, Newman JH. Patellofemoral Arthroplasty. Sixteen years experience with 436 cases. Proceedings of combined orthopaedic Associations Meeting, Sydney 2004. J. Bone Joint Surg (Br) 2005; 87-B: Supp III 338.
8. Ackroyd CE, Newman JH, Eldridge J. Patellofemoral Arthroplasty eight years experience with the Avon Design. EFORT, 2005
9. Ackroyd CE: Newman JH, Evens R, Eldridge JDJ, Joslin CC. The Avon patellofemoral arthroplasty: five-year survivorship and functional results. J Bone Jt Surg 2007;89B:310-5.