Sulcus-deepening trochleoplasty may address instability in skeletally immature patients
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Key takeaways:
- Sulcus-deepening trochleoplasty may address patellar instability for skeletally immature patients with open distal femoral physes.
- Most patients had postoperative satisfaction scores of 9 or 10.
According to published results, thick-shell sulcus-deepening trochleoplasty may yield clinical improvements and high satisfaction for skeletally immature patients with patellar instability and open distal femoral physes.
Neil P. Blanchard, MD, orthopedic surgeon from the department of orthopedic surgery at University of Virginia Health System, and colleagues analyzed 21 knees from 17 adolescents with less than 2 years of growth remaining who had trochlear dysplasia and open distal femoral physes. All patients underwent thick-shell sulcus-deepening trochleoplasty at a single institution. Mean postoperative follow-up was 64 months.
At the time of surgery, male patients (n = 5 patients; n = 5 knees) had a chronological age of 15.6 years and a bone age of 15.2 years, while female patients (n = 12 patients; n = 16 knees) had a chronological age of 15.2 years and a bone age of 14.3 years.
Blanchard and colleagues found mean change in anatomic lateral distal femoral angle was 0.73° and mean change in Blumensaat angle was 0.88°. They found median IKDC scores improved from 57.3 preoperatively to 90.9 postoperatively, while median Kujala scores improved from 55 preoperatively to 95 postoperatively.
Overall, one patient had recurrent patellar instability, which required revision. However, all other patients reported satisfaction scores of 9 or 10, with a mean satisfaction score of 9.26 out of 10. Blanchard and colleagues noted all distal femoral physes were closed at final follow-up and found no evidence of leg length discrepancies or rotational abnormalities on radiographs at final follow-up.
“The findings of the present study contribute to the limited, but growing, body of evidence surrounding the use of trochleoplasty to address recurrent patellar instability,” Blanchard and colleagues wrote in the study. “The outcomes of this study are also particularly notable, as current consensus recommendations caution against trochleoplasty in skeletally immature patients due to the concern of potential injury to the distal femoral physis.”
Perspective
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Skeletally immature patients with trochlear dysplasia constitute a difficult subset to treat, with a high rate of re-dislocation after surgical stabilization for patellofemoral instability. Trochleoplasty is generally not recommended for skeletally immature patients due to the potential for injury to the anterior aspect of the distal femoral physis, which can lead to growth disturbances. After the early adolescent growth spurt, which typically ends at around 12 years skeletal age in girls and 14 years in boys, there is a rapid decline in the skeletal growth rate until the end of growth.
In this group of patients with less than 2 years of remaining growth, the authors of the current study and a previous study have reported on the safety and outcomes of thick-shell and thin-flap trochleoplasty, respectively, with medial patellofemoral ligament reconstruction. One must be cautious as skeletal maturation is a continuum and estimation of skeletal age cannot be relied upon using a single criterion. Also, with the lack of a control group with isolated MPFL reconstruction, the contribution of trochleoplasty to the overall satisfactory outcome is unknown. The indications of trochleoplasty are still evolving in adults due to the concerns about cartilage degeneration in the future.
The authors must be congratulated for their first step toward establishing safety of trochleoplasty in skeletally immature patients with less than 2 years of remaining growth. Future comparative studies and long-term follow-up would be required to better understand the role of trochleoplasty in management of patellofemoral instability in skeletally immature patients.
Reference:
Nelitz M, et al. AM J Sports Med. 2018;doi:10.1177/0363546518794671.
Perspective
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The authors are known trochleoplasty experts, and this paper establishes reasonable expectations for their style of trochleoplasty. As Parikh has said, this group of young, patella instability patients can be very difficult to treat. Also, as Parikh has said, long-term arthritis is a real concern after any deepening trochleoplasty.
Most experienced patellofemoral surgeons use deepening trochleoplasty in less than 2% of their patella instability surgeries, as accurate medial patellofemoral complex reconstruction is often sufficient without trochlea deepening, using medialization of the extensor mechanism as needed.
Every surgeon should evaluate his or her own skills and weigh the known risks of eventual arthritis associated with deepening trochleoplasty, particularly when medial patellofemoral complex reconstruction with and without patella tendon medialization works well for most patellofemoral surgeons. The patients in this study presumably have unusually advanced trochlea dysplasia.
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