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Review Article: J. S. Mulford, C. J. Wakeley, and J. D. J. Eldridge Assessment and management of chronic patellofemoral instability J Bone Joint Surg Br 2007; 89-B: 709-716 [Abstract] [Full text] [PDF]

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Jonathan D J Eldridge, Jonathan Mulford, Charles Wakeley   (17 August 2007)

Assessment and management of chronic patellofemoral instability

Benedict A Rogers   (1 August 2007)

Authors' reply: 17 August 2007
Jonathan D J Eldridge, Consultant Orthopaedic Surgeon Bristol Royal Infirmary, Jonathan Mulford, Charles Wakeley Send letter to journal: Re: Authors' reply: jonathan.eldridge{at}btinternet.com Jonathan D J Eldridge, et al.	Sir, The authors thank Mr Rogers for his observations. Our review was not intended as an exhaustive list but as a guide. The Caton Deschamps ratio is certainly well accepted. It is, however, our opinion that none of the described ratios give a complete picture of the true functional patellar height. This is the subject of a future paper. A further review article would be required to answer the question regarding patellofemoral complications following total knee arthroplasty. J.D.J. Eldridge, Consultant Orthopaedic Surgeon, J. Mulford, C. Wakeley, Bristol Royal Infirmary, Bristol, UK.
Assessment and management of chronic patellofemoral instability 1 August 2007
Benedict A Rogers, Specialist Registrar The Princess Royal Hospital, Haywards Heath Send letter to journal: Re: Assessment and management of chronic patellofemoral instability benedictrogers{at}hotmail.com Benedict A Rogers	Sir, I read this paper with interest and would like to make the following points: 1. As stated, the measurement of patellar height is critical in the assessment of patellofemoral instability, however, only two methods of patellar height measurement, the Insall–Salvati and the Blackburne-Peel methods, are mentioned. The Caton-Deschamp method,1 measuring from the anterior border of tibial plateau to the inferior aspect of patellar articular surface with respect to the length of patellar articular surface, is an accurate and reproducible alternative that is not affected by differences in skeletal maturity.2 There are several other methods of assessing patellar height including the Labelle-Laurin method,3 and in children the Koshino method.4 Are the Insall-Salvati and Blackburne-Peel methods more suitable in the assessment of patellar height in patellofemoral instability per se? 2. It is important to highlight that the accurate measurement of patellar height from a lateral radiograph necessitates the knee being in at least 30° of flexion. This enables not only the patella to engage the distal femoral trochlea but affords some tension within the patellar and quadriceps tendons. 3. The article alluded to difficulties in the measurement of the Q-angle with rotational deformities; similarly, an accurate assessment of patellar height can only be achieved in the absence of any rotational deformity or error. 4. Patellofemoral instability and pain is a known complication following total knee arthroplasty5 and a common cause of revision surgery.6,7 The assessment of patellar height following arthroplasty surgery, although technically easier to measure,8 is more complex to interpret.9 Do the authors suggest a similar protocol for the assessment and management of patellofemoral instability following joint replacement surgery? BA Rogers, MA, MSc, MRCGP, MRCS, Specialist Registrar, South West Thames, The Princess Royal Hospital, Haywards Heath, Sussex, UK. 1. Caton J, Deschamps G, Chambat P, Lerat JL, Dejour H. [Patella infera. Apropos of 128 cases]. Rev Chir Orthop Reparatrice Appar Mot 1982;68:317-25. 2. Aparicio G, Abril JC, Albiñana J, Rodriguez-Salvanés F. Patellar height ratios in children: an interobserver study of three methods. J Pediatr Orthop B 1999;8:29-32. 3. Labelle H, Peides JP, Levesque HP, Fauteux P, Laurin CA. [Evaluation of patellar position by tangential x-ray visualization]. Union Med Can 1976;105:870-3. 45. Koshino T, Sugimoto K. New measurement of patellar height in the knees of children using the epiphyseal line midpoint. J Pediatr Orthop 1989;9:216-8. 5. Scuderi GR, Insall JN, Scott NW. Patellofemoral Pain After Total Knee Arthroplasty. J Am Acad Orthop Surg 1994;2:239-46. 6. Cameron HU, Hunter GA. Failure in total knee arthroplasty: mechanisms, revisions, and results. Clin Orthop Relat Res 1982;141-6. 7. Mochizuki RM, Schurman DJ. Patellar complications following total knee arthroplasty. J Bone Joint Surg [Am] 1979;61-A:879-83. 8. Rogers BA, Thornton-Bott P, Cannon SR, Briggs TW. Interobserver variation in the measurement of patellar height after total knee arthroplasty. J Bone Joint Surg [Br] 2006;88-B:484-8. 9. Grelsamer RP. Patella baja after total knee arthroplasty: is it really patella baja? J Arthroplasty 2002;17:66-9.