Background

Patellar tendon rupture is an uncommon but disastrous complication in patients with total knee arthoplasty (TKA) and revision TKA. Several techniques have been described for treatment of this complication with variable results.

Objectives
The modified Achilles allograft technique (MAAT) is an option for chronic ruptures. This technique can be use in resurfaced and non resurfaced patella.

Study Design & Methods
We retrospectively reviewed 12 patients who were treated with the modified Achilles tendon allograft technique due to chronic patellar tendon ruptures following TKA and revision TKA. The average age was 80 years (range between 71 to 92 years), mean BMI was 30 kg/m2. Three patients had previous surgery for TKA, 8 had two or more previous interventions and 1 was treated for an acute proximal avulsion of the patellar tendon and re- rupture treated with TKA and our allograft technique. The mean follow up was 14.08 months (range of 2 to 37 months). Evaluation of the pre op and last follow up x-rays were evaluated for consolidation of the allograft and then statistically analyzed with three patellar height ratios Insall- Salvati, Blackburn-Peel and Caton Deschamps, range of motion (ROM) of the last follow up was also measured . The endpoint was last follow up, infection with need of debridement or traumatic rupture.

Results

Three patients had a traumatic failure. Three previously treated patients due to prosthetic joint infection (PJI) presented a reactivation of infection with MAAT. The remaining six had a mean follow up of 20 months (range between 6 to 37 months) four patients had complete extension, two cases with extension lag no greater than 15º and flexion was greater than 90º in all cases . The Insall- Salvati improves significantly along with Blackburn-Peel ratio (p < 0.001 and p < 0.013 respectively); however Caton Deschamps did not (p= 0.17).

Conclusions

Consolidation of the allograft was observed in 100% of the sample with 50% of successful results with adequate ROM regained. Patellar height improvement was statistically significant in which allograft measure did not affect de ratio. Failure of the allograft was seen in 25% of patients due to infection related to previous septic revision TKA and 25% in traumatic ruptures.
This technique remains a good option for patellar tendon rupture in primary TKA even in resurface patella. A large sample needs to be studied to statistically analyze the relation between previous infection and failure.