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KneeFurther Opinion

The patellar thinning osteotomy in patellofemoral arthritis

J Vaquero, JA Calvo, F Chana, R Perez-Mañanes

J Bone Joint Surg [Br] 2010;92-B:1385-91.

 

The management of patellofemoral (PF) osteoarthritis (OA) in the younger patient is difficult. Arthroscopic debridement and physiotherapy are at best holding measures, and if symptoms subsequently deteriorate the options are limited to realignment procedures such as the Elmslie-Trillat type medialisation alone or combined with anteriorisation of the tibial tubercule in a Fulkerson procedure or anteriorisation alone with a Maquet procedure. The former has reasonable results for isolated bone on bone lateral facet osteoarthritis with a lateral tracking patella achieving up to 87% good or excellent results1 but the outcome for central or medial wear is poor. The Maquet procedure works best to offload distal patella wear and increases the load on the proximal patella but results are generally poorer and it has a risk of significant wound problems due to the anteriorisation of the tibial tubercule.

There are reasonable results from PF joint replacement using modern designs.  Ackroyd et al2 found that 78% of their patients had a modified Oxford score of > 25, which they defined as indicating a satisfactory outcome, at five years using the Avon PFR. Odumenya et al3 had similar results using the same prosthesis with 64% having an Oxford score of > 25 at five years. The mean age, however, in the two series was 68 and 66 years, respectively. Most surgeons would be wary of performing PF joint replacement in the under 55 age group.

Ideally, a procedure that could prolong the life of a degenerative PF joint and postpone replacement surgery without making it harder to eventually perform, is required. This would be analogous to the high tibial osteotomy (HTO) for medial knee OA, and like HTO, would give good symptomatic relief in the 40 to 55 years age group but with isolated PF joint disease.

The patellofemoral thinning osteotomy may offer this opportunity. Biomechanical work was performed by Vaquero and Arriaza4 in 1992.   This cadaveric study showed a reduction in PF contact pressures at varying angles of up to 20% following a 7 mm coronal plane thinning osteotomy, raising the possibility of adapting this to clinical practice.

This paper reports the clinical application of this technique. The inclusion criteria were a 50% reduction in PF joint space on a 20 degree skyline view, a patella thickness of greater than 20 mm and a maximum TTTG distance of 20 mm (the upper limit of normal) plus varus/valgus alignment of < 5°. Thus patients with significant malalignment, the most common cause of isolated PF joint OA, were excluded from the study. This may account for the fact that this procedure was performed on only 31 patients and 35 knees in 17 years.

The technique is interesting and obviously care must be taken to prevent devascularisation of the articular fragment, as seen in one case. The knee is cycled before fixing the articular fragment with vicryl pins. The authors feel the improved pain after surgery is due to offloading the patellar articular surface, decompressing the patella, realigning the articular surface by cycling the knee before fixation and denervation due to the lateral release to approach the knee.  The long term results are good with an improved and maintained KSS score.  Only 4 of 31 patients required a subsequent total knee arthroplasty, and during this procedure no problems were encountered dealing with the patella.

It is not clear how well this procedure works in younger patients.  The mean age in this study was 61.5 years with a range of 44 to 77 years. Most surgeons would be happy to perform a PF joint replacement for patients over 55 so it is the 40 to 55 year age group that are of most interest.  Although this appears to be a promising new way to treat patients with isolated PF OA, a better idea of the longevity and success of the procedure in the younger patient does need to be identified before it can be truly recommended.

References

1. Farr J, Schepsis A, Cole B. Anteromedialisation: review and technique. J Knee Surg 2007;20:120-8.
2. Ackroyd CE, Newman JH, Evans R, Eldridge JDJ, Joslin CC. The Avon patellofemoral arthroplasty; five year survivorship and functional results. J Bone Joint Surg [Br] 2007;89-B:310-15.
3. Odumenya M, Costa ML, Parsons N,  Achten J, Dhillon M, Krikler SJ. The Avon patellofemoral joint replacement: five year results from an independent centre. J Bone Joint Surg [Br] 2010;92-B:56-60.
4. Vaquero J, Arriaza R. The patella thinning osteotomy: an experimental study of a new technique for reducing patellofemoral pressure. Int Orthop 1992;16:372-6.
 

Chissell H

Clare Park Hospital, Crondall, Franham, Surrey

E-mail: hchissell@doctors.org.uk