Abstract
Objectives:
Patellar instability is a common condition in adolescents and young adults that often requires surgical stabilization. Trochlear dysplasia is the most common anatomic risk factor associated with patellar instability and is characterized by a shallow, flat or convex proximal trochlea. Trochleoplasty is gaining acceptance as a procedure to treat patellar instability. While the volume of research studying trochleoplasty continues to expand, more work is needed to better understand the indications and outcomes of this procedure. The objective of this study was to describe the short to medium term outcomes as well re-operation rates for a patient population indicated for a trochleoplasty, medial patellofemoral ligament reconstruction (MPFLR), and lateral retinacular lengthening (LRL) to treat recurrent patellar instability due to high grade trochlear dysplasia.
Methods:
A total of 170 patients who underwent combined trochleoplasty, MPFLR, and LRL (2017-2021) were contacted to complete the Banff Patellar Instability Index (BPII), either International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC) or Pediatric IKDC (Pedi-IKDC), and a series of questions to describe pain, function, and satisfaction following surgery. Of these, 71 patients (87 knees) responded and completed the questionnaires. Initial evaluation and intra-operative data included age, sex, BMI, prior surgery, and time to surgery from onset of symptoms. Pre-operative MRI studies were reviewed to determine the degree of trochlear dysplasia via the lateral trochlear inclination (LTI) and sulcus angle, and to measure pre-operative tibial tubercle to trochlear groove (TT-TG) distances. From the cohort of 87 knees, pre-operative BPII and IKDC/Pedi-IKDC scores were also collected from 31 and 39 knees, respectively.
Results:
The responding sample was 16.6±4.0 years at time of surgery, 70.4% females, and had a BMI of 25.4±6.03. Prior failed patellar stabilization surgery occurred in 20% (17 knees). The average time from onset of symptoms to surgery was 3.3±3.6 years. Pre-operative LTI was -5.35±7.53° and sulcus angle was 159.6±6.8°. TT-TG was 17.4±4.4 mm. Average follow up reporting was 4.3±1.1 years (range 2.6-6.4) after surgery. The average post operative BPII score was 79.2±18.0 and IKDC/Pedi-IKDC score was 69.2±16.9. Any additional surgeries are listed in Table 1. Subjective reported improvements were noted for pain (lower 90.0%, same 3.3%, higher 6.7%) activity level after surgery (higher 48.3%, same 35.0%, lower 16.7%), happiness with surgery (yes 98.3%, no 1.7%), and positive experience to have surgery again (yes 85.0%, no 15.0%). Patients with an index surgery (N=74) demonstrated higher BPI (82.6±16.9; 66.1±18.1, p=0.006) but no difference in IKDC/Pedi-IKDC (70.0.6±17.7; 74.1±16.1, p=0.310) compared to revision surgeries. The cohort of patients completing pre-operative and follow up surveys demonstrated improvements in BPII (pre: 39.6±23.1, follow up: 76.7±19.5, p=0.0275) and IKDC/Pedi-IDKC (pre: 54.1±19.5, follow up: 61.5±12.6, p<0.001). Female patients reported lower BPIi scores at follow up compared to males (77.1±19.6, 84.6±12.8, p=0.035). There were no repeat dislocations. The re-operation rate on the ipsilateral knee for any reason was 5.7%. (Table 2) The patients without pre-operative PRO’s were compared to the patients with pre-operative PRO’s and there were no difference in post operative PRO’s or any demographics (all p >0.05).
Conclusions:
Trochleoplasty with combined MPFLR and LRL is effective at treating patellar instability due to high grade trochlear dysplasia. The re-operation rate was very low and no repeat instability episodes occurred. Patient satisfaction was almost 100% and approximately 67% maintained or increased their activity level. As one would expect, patients with prior failed surgery did not do as well as those in which it was an index procedure.
