Risk of Patellar Tendon Rupture After BPTB ACL Reconstruction
Patellar tendon rupture following BPTB ACL reconstruction is an extremely rare complication that can occur both in the early postoperative period and many years after surgery, though the absolute risk remains very low. 1, 2
Incidence and Timing
Patellar tendon ruptures after BPTB ACL reconstruction are rarely reported in the literature, with most cases occurring during the early postoperative period when rehabilitation loads are being advanced. 2
Late ruptures can occur even a decade after reconstruction, as documented in a case report of a healthy 36-year-old man who sustained a patellar tendon rupture 10 years after an uneventful BPTB ACL reconstruction during a skiing accident. 2
The rarity of this complication is notable given that BPTB autograft is one of the most commonly used techniques for ACL reconstruction, suggesting the absolute risk is extremely low despite theoretical concerns about donor site morbidity. 2
Risk Factors and Clinical Context
BPTB autografts are associated with higher donor site morbidity and anterior knee pain compared to hamstring grafts, which represents the primary trade-off for their lower graft failure rates (4.3% vs 12.7% for allografts). 3
The American Academy of Orthopaedic Surgeons recognizes that BPTB autografts reduce graft failure and infection risk but increase anterior or kneeling pain compared to hamstring alternatives. 4
Early mobilization protocols should be implemented with caution, monitoring specifically for signs of donor site pain or weakness that could indicate compromised patellar tendon integrity. 4
Rehabilitation Considerations to Minimize Risk
Open kinetic chain exercises for BPTB grafts can be started from 4 weeks postoperative in a restricted ROM of 90-45° with extra resistance allowed (unlike hamstring grafts which should avoid extra weight for 12 weeks), but this must be balanced against donor site protection. 5
Closed kinetic chain exercises should be prioritized from week 2 postoperative to mitigate patellofemoral stress while protecting the patellar tendon donor site. 5
Immediate knee mobilization within the first week is critical to prevent extension deficits and arthrofibrosis, but must be performed without excessive loading of the extensor mechanism. 5
Clinical Decision-Making
For patients at higher risk of complications or those with concerns about donor site morbidity, non-surgical management of ACL tears may be appropriate, or alternative graft sources should be considered. 4
When BPTB grafts are used, rehabilitation protocols should include specific protection strategies for the donor site, though the guidelines do not specify exact parameters beyond standard progression criteria. 4
The choice between BPTB and hamstring autografts should weigh the 3-fold lower rerupture rate of BPTB (4.3% vs 12.7%) against the increased risk of anterior knee pain and theoretical donor site complications. 3
Common Pitfalls
Aggressive early loading of the extensor mechanism during rehabilitation could theoretically increase stress on the healing patellar tendon donor site, though specific thresholds are not established in the literature.
Failure to monitor for donor site pain or weakness during rehabilitation progression may miss early signs of patellar tendon compromise.
Returning to high-risk activities (particularly those involving eccentric loading or jumping) without adequate strength restoration could place excessive stress on the weakened patellar tendon, though the exact timeline for safe return remains unclear given the rarity of late ruptures.