There have been a small number of early complications and to date these have numbered 24 (6%). This include wound inflammation, wound haematoma, wound dehiscence, haemarthrosis, post-operative stiffness requiring manipulation and one case of septic arthritis, which occurred two months after operation and resolved satisfactory. This total accounts for 6% to date.

There have been to date only 14 cases of recurrent subluxation, 2 of which required a distal realignment procedure, 2 have had a proximal Insall realignment and 6 have had a mid lateral release. This amounts to 2% showing a dramatic improvement on previous designs of arthroplasty. There have been 18 subsequent operations including the 4 realignments. These are 1 manipulation under anaesthetic at three weeks for stiffness, 1 resuture at wound for wound dehiscence and 12 arthroscopies for haematoma, septic arthritis, disease progression and clicking possibly caused by subluxation.

To date their has been one case of patella loosening, and two cases of trochlea loosening but no cases of patella fracture. There has been one possible case of patella wear and there have been two cases of deep infection.

The main long-term problem is that of disease progression in the tibio femoral part of the joint. This has been recorded in 48 cases so far which have required revision to a total knee replacement (9%) (ref. 1)

A concern has been the fact that in deep flexion the polythene patella bears against the anterior parts of the medial and lateral femoral condyles. This has led to the development and introduction in 2001 of the odd facet on the patella button. In deep flexion when the patella internally rotates into the inter-condylar notch a flat odd facet on the most medial part of the patella is presented against the condyle. Investigation of several cases with disease progression by arthroscopy has in all cases shown that the area of progression is well away from any point of contact with the patella button.

The number of cases with disease progression remains small and this may be due to natural progression of the arthritic process. There is no evidence to date to suggest that the arthroplasty itself has influenced this in any way. It is probable that some of the earlier cases in the series were performed for a more advanced arthritic process. Survivorship at 5 years is 99.7% for revision due to failure of the prothesis and 95.8% for revision due to disease progression (ref. 2).

Preoperative views of significant Patellofemoral arthritis.

Disease progression in the medial compartment 8 years later.
Pain score is 87% suggesting little serious pain but the function score has dropped to 56%.

References

1. Ackroyd CE, Newman JH, Evans R, Eldridge JDJ, Joslin CC.  The Avon patellofemoral arthroplasty five year survivorship and functional results.  J Bone Jt Surg. 2007; 89-B: 310-15.
2. Porteous AJ, Mulford JS, Newman JH, Ackroyd CE.  A review of revision patellofemoral arthroplasty patients. J Bone Jt Surg. 2008; 90-B; (Suppl 3) 575.