Thin flap sulcus-deepening trochleoplasty in patellar instability yields good functional outcomes without progressive cartilage deterioration in the short-term follow-up-A retrospective single-surgeon cohort study

Abstract

Purpose: Sulcus-deepening trochleoplasty (TP) effectively treats patellofemoral (PF) instability (PFI) caused by high-grade trochlear dysplasia (TD), but current evidence is based on small case series. We hypothesised, that TP would result in significant functional improvements and a low re-dislocation rate but would not accelerate the progression of PF cartilage deterioration.

Methods: We retrospectively reviewed all TP cases performed by a single surgeon between 2015 and 2021. Inclusion criteria were postoperative Magnetic resonance imaging (MRI) >6 and >12 months and a clinical follow-up >12 months. Patients with simultaneous cartilage repair, open physes or incomplete records were excluded. Clinical outcomes were assessed using pre- and postoperative scores, postoperative Banff Patellofemoral Instability Instrument (BPII) 2.0 and Knee Injury and Osteoarthritis Outcome Score (KOOS), re-dislocation rate and patient satisfaction. PF cartilage was evaluated via Area Measurement and Depth & Underlying Structures (AMADEUS) scores preoperatively, at 6 months and at the final follow-up.

Results: We included 113 patients (25.8 ± 8.3 years) with high-grade TD (Dejour B-D; mean lateral inclination angle: -2.9 ± 9.1°), 85% of whom had advanced cartilage lesions. All underwent TP, lateral retinacular lengthening (LRL) and medial patellofemoral ligament reconstruction (MPFL-R). After 34.8 ± 20.9 months, function, pain levels and Tegner scores improved significantly (p < 0.001). KOOS dimensions were: symptoms 79.9 ± 13.5, pain 86.4 ± 12.1, activity 91.9 ± 8.3, sports 71.7 ± 22.2 and quality-of-life 58.1 ± 23.8. BPII 2.0 was 64.3 ± 31.4. Preoperative AMADEUS scores (55.2 ± 17.4) remained stable at 6 months (p = 0.343) but improved to 58.4 ± 16.0 at 28.6 (12-89) months (p = 0.004). Complication and re-dislocation rates were 5.3% and 1.8%, with 93% patient satisfaction.

Conclusion: Sulcus-deepening TP with MPFL-R and LRL yields good to excellent short-term results without progressive chondral deterioration, enabling patients to return to their prior or higher activity levels despite advanced preoperative chondral lesions. TP can be considered a safe, joint-preserving technique for PF stabilisation.

Level of evidence: Level III, retrospective cohort study.

Keywords: cartilage deterioration; maltracking; patellofemoral instability; trochlear dysplasia; trochleoplasty.

Figure 1

Preoperative planning of trochleoplasty. The planned trochlear sulcus angle (pTSA) was designed according to the patellar facet angle (PFA) so that the pTSA corresponded to the PFA and was related to the dorsal femoral condylar line (dFCL) (a). The resection depth (RD) was determined according to the maximum femoral offset. In this case, a pTSA of 145° was targeted, resulting in a planned resection depth of 8 mm, measured from the most anterior part of the femoral offset (proximal to this slice) (b).

Figure 2

Thin‐flap sulcus‐deepening trochleoplasty. A periostal flap was developed (a), followed by a subchondral osteotomy (b). Dysplastic subchondral bone was removed according to the preoperative plan (c) to create a new groove (d). The reduced chondral flap was refixed with 3 mm Vicryl tape (e), followed by lateral retinacular lengthening.

Figure 3

Flowchart on the composition of the patient collective.

Figure 4

Preoperative versus postoperative functional outcome parameters, indicating significant improvements after the surgery.

Figure 5

Postoperative KOOS and BPII 2.0 after 34.8 ± 21 months, showing good to excellent results.

Figure 6

Patellofemoral cartilage evolution in a 14‐year‐old female patient. Initial magnetic resonance imaging (MRI) showed high‐grade dysplasia and signs of cartilage thinning at the lateral patellar facet (a). Eighteen months after trochleoplasty and MPFL‐R, patellofemoral congruence was improved (b). Follow‐up MRI at 35 months (c) and 112 months (d) showed an intact patellofemoral articular cartilage with no evidence of further degeneration. MPFL‐R, medial patellofemoral ligament reconstruction.

Figure 7

AMADEUS grading preoperatively and at final follow‐up. After 28.6 (12–89) months, no significant changes were observed. AMADEUS, Area Measurement and Depth & Underlying Structures.