The indications for patellofemoral arthroplasty should be as strict as those for total knee replacement. There should be significant pain and disability. The use of functional scoring tools such as the reduced WOMAC score (Ref 1), the Oxford Knee Score (Ref 2) and the Melbourne patella score (Ref 3) can be helpful in assessing the severity of the condition. The use of functioning scoring tools can be very helpful in assessing the severity of the condition and producing a firm validated baseline for assessing the quality of the result.  Validated self-administered questionnaires can easily be introduced in the pre-operative assessments.  Knee status can be assessed using the pain and function sections of the WOMAC score (Western Ontario McMasters University) (Ref 4)  Physical health can be assessed using the physical component score of the SF12 and mental health can be assessed using the 5-time Mental Health Index from the SF36 (Ref 5, 6).  Quality of life in relation to the knee can be measured using the Knee Injury Osteoarthritis Outcome Score (KOOS) (Ref 7).

Strict Indications for Arthroplasty

• Severe symptoms and signs
• Age
• Radiographically proven severe osteoarthritis of the PFJ
• No significant deformity, especially axis mal-alignment and fixed flexion
• "Normal" tibiofemoral joint
• Extended indications
• Final decision made at arthrotomy

There is a large group of patients in their middle years who have got significant damage and dysfunction of the patello-femoral joint and would be much too young for a total knee replacement. Such patients should initially be treated with conservative surgical procedures including chondrectomy, articular cartilage grafting and realignment osteotomies. These treatments can often be successful for a number of years but progressive chondral damage is usually inevitable, leading on to early osteoarthritis. In such cases when there is severe pain and disability and all other surgical options have been exhausted an isolated patellofemoral arthroplasty may be considered as appropriate treatment. In patients over the age of 70 satisfactory results from arthroplasty of the knee can usually be obtained with a total knee replacement.  A compartmental patellofemoral arthroplasty should only be considered when the tibio femoral joint is normal with no significant degenerative change in any of the articular structures.  In some circumstances a patellofemoral arthroplasty may be appropriate in the older age group because of the reduced surgical trauma with lower risk of complications and easier recovery.

The age range can, therefore, vary from the early 30s to the mid 70s depending on the surgical pathology and the specific circumstances of the particular patient.

Extended indications

• Failed realignment - Fulkerson/Elmslie
• Younger patient with early disease
• Dislocation & trochlea dysplasia
• Failed patellectomy
• Post - trauma (fracture or chondral damage)

Sizing of the prosthesis

• Patients over   
• Patients
• Patients
• Patients under   
• Patients under   

5 ft 10"
5 ft 6" to 5 ft 10"   
5 ft 2" to 5 ft 6"   
5 ft 2"
4 ft8"

(1m78)
(1m68 - 1m78)   
(1m58 - 1m68)   
(1m58)
(1m48)

Large
Medium
Small
Extra Small
Custom made prothesis

This gives some guide to sizing. There will be overlaps between the different sizes.

References

1. 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.
2. 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.
3. Feller JA, Bartlett RJ, Lang DM. Patellar resurfacing versus retention in total knee arthroplasty. J Bone Joint Surg (Br) 1996; 78-B:  226-228.
4. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW.  Validation study of WOMAC:  A Health status instrument for measuring clinical important patient relevant outcomes to anti-rheumatic drug therapy with osteoarthritis of the hip or knee.  J Rheumatology 1988; 15: 1833-40.
5. Weare J Jnr, Kosins KM, Keller SD.  A 12-item short form health survey:  Construction of scales and preliminary tests of reliability and validity.  Med Care 1996; 34: 220-33.
6. Weare JE Jnr, Sherbourne CD.  The MOS 36-item short form health survey (SF36).  1: Conceptual framework and item selection. Med Care 1992; 30: 473-83.
7. Roos M, Roos HP, Lohmander LS, Ekdahl C, Beynnon BD.  Knee injury and osteoarthritis outcome score (KOOS): Development of a self-administered outcome measure.  J Orthop.Sports Phys.Ther. 1998; 20: 88-96.