Trochlear bump, patella alta may predict recurrent instability after MPFL reconstruction
Key takeaways:
- Dysplasia with a trochlear bump and patella alta are risk factors for instability after MPFL reconstruction.
- Patient age, sex and tibial tubercle to trochlear groove distance were not linked with failed surgery.
According to published results, patients with dysplasia with a trochlear bump and patella alta may be at increased risk for recurrent instability after medial patellofemoral ligament reconstruction.
“As our understanding of patellofemoral instability expands, so does the number of risk factors we can identify, presenting increasing challenges to surgeons: Which ones do we focus on?” Adam B. Yanke, MD, PhD, associate professor in the department of orthopedics and assistant director of the Cartilage Restoration Center at Rush University Medical Center, told Healio. “It is easy to get lost in the alphabet soup of [Caton-Dechamps index] CDI, [patellotrochlear index] PTI, [tibial tubercle-trochlear groove] TT-TG, TT-PCL, TG-PCL, [patellar-tendon beyond lateral trochlear ridge] PT-LTR and Dejour A,B,C [and] D, and we still do not have an evidence-based gold-standard answer to what surgeon-modifiable risk factors we should address when any combination of tibial tubercle lateralization, trochlear groove medialization, supratrochlear bump, patella alta, femoral or knee malrotation, or valgus alignment are present. In this study, we sought to definitively answer at least one component of the algorithm, identifying the supratrochlear bump and patella alta as significant risk factors for recurrent patellar instability despite isolated MPFL reconstruction.”
Yanke and colleagues performed a systematic review and meta-analysis of nine studies that reported risk factors associated with recurrent instability after isolated MPFL reconstruction in 807 patients (mean age, 20.2 years).
In six studies that reported CDI, Yanke and colleagues found patients with patella alta, defined by a CDI of 1.3 or more, had a significantly increased risk for failed MPFL reconstruction compared with patients with a CDI of less than 1.3 (OR = 2.72; 95% CI, 1.17-6.34).
In six studies that reported trochlear dysplasia, Yanke and colleagues found patients who had dysplasia with a trochlear bump, defined by Dejour types B and D, had a significantly increased risk for failed MPFL reconstruction compared with patients with Dejour types A and C (OR = 3.28; 95% CI, 1.66-6.46).
Yanke and colleagues found no data supported age, sex or tibial tubercle to trochlear groove distance as risk factors for failed surgery.
“An isolated MPFL reconstruction is a powerful tool for the treatment of patellar instability and can likely overcome a large percentage of patellar instability patients with a variety of nonmodifiable and modifiable risk factors,” Yanke said. “However, when there are structural bony abnormalities, such as patella alta and a large supratrochlear bump, causing that patella to jump over the lateral trochlear ridge with significant force as the knee ranges from flexion to extension, an isolated soft-tissue procedure is more likely to fail, which is supported by the findings of this meta-analysis.”
Perspective
Back to TopThe recent systematic review and meta-analysis titled “The presence of a trochlear bump and patella alta may predict the risk of recurrent instability after isolated medial patellofemoral ligament reconstruction” by Navya Dandu, MD, and colleagues effectively highlights key risk factors for recurrent instability following isolated MPFL reconstruction. The findings emphasize the strong predictive value of trochlear dysplasia with a trochlear bump (Dejour type B or D) and patella alta (CDI greater than 1.3), with odds ratios of 3.28 and 2.72, respectively. These results reinforce the importance of considering bony morphology when planning surgical intervention, as these anatomical features significantly impact patellar stability and the risk of failure.
A particularly important consideration from this study is the need for precise femoral tunnel placement during MPFL reconstruction. Errors in tunnel positioning, particularly deviations from Schӧttle’s point, have been associated with altered graft tension, excessive medial patellar pressures and suboptimal outcomes. Even minor inaccuracies in tunnel placement can lead to overconstraint or laxity, contributing to recurrent instability or patellofemoral joint overload. This underscores the critical role of meticulous surgical techniques in optimizing MPFL graft function and preventing postoperative complications.
In addition, while the study found no direct correlation between TT-TG distance and recurrent instability, this does not eliminate the necessity of tibial tubercle osteotomy in cases of patellar maltracking. In the presence of chondral damage and an elevated TT-TG, addressing maltracking via tibial tubercle osteotomy may be essential for improving patellofemoral engagement and reducing long-term degenerative changes.
Overall, this review provides valuable insights into risk stratification for MPFL reconstruction, reinforcing the need for an individualized approach that carefully considers trochlear dysplasia, patellar height and precise surgical execution, particularly in femoral tunnel placement.
References:
Dandu N, et al. Am J Sports Med. 2025;doi:10.1177/03635465241266594.
Dejour H, et al. Knee Surg Sports Traumatol Arthrosc. 1994;doi:10.1007/BF01552649.
Hopper GP, et al. Am J Sports Med. 2014;doi:10.1177/0363546513518413.
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