The primary treatment for an increased Tibial Tubercle-Trochlear Groove (TT-TG) distance, a key factor in patellofemoral instability, is often a surgical procedure known as the anteromedialization osteotomy.
Understanding the TT-TG Distance
The TT-TG distance is a crucial measurement used in orthopedics to assess patellofemoral alignment. It quantifies the lateral offset of the tibial tubercle (the bony prominence on the shinbone where the patellar tendon attaches) relative to the trochlear groove (the V-shaped groove on the thigh bone where the kneecap tracks). An increased TT-TG distance indicates that the kneecap (patella) is pulled too far to the outside, leading to improper tracking and potential instability.
Surgical Treatment: Anteromedialization Osteotomy
One of the most prominent surgical techniques for addressing an increased TT-TG distance and associated patellofemoral instability is the anteromedialization osteotomy, famously described by Fulkerson et al. This procedure aims to realign the patellar tracking mechanism by repositioning the tibial tubercle.
The Fulkerson Procedure Explained
The anteromedialization osteotomy involves making an incision in the tibial tubercle, creating a bone block that includes the attachment point of the patellar tendon. This bone block is then moved both anteriorly (forward) and medially (towards the midline of the body). Once repositioned, the bone block is secured with screws.
This two-pronged movement achieves specific biomechanical goals:
- Medialization: Shifts the patellar tendon attachment inward, reducing the lateral pull on the patella and promoting better alignment within the trochlear groove.
- Anteriorization: Elevates the patellar tendon attachment, which helps to offload pressure from the patellofemoral joint, particularly in cases where there is cartilage damage.
Key Indications for Anteromedialization Osteotomy
The anteromedialization osteotomy is a targeted surgical solution indicated for patients experiencing patellofemoral issues, especially when an increased TT-TG distance is a contributing factor. According to Fulkerson et al., this procedure is specifically indicated for:
- Instability due to maltracking: Patients whose kneecap consistently shifts out of place or dislocates because it's not moving correctly within the groove.
- Increased TT-TG distance: This is a direct anatomical indicator for the procedure, as it signifies a lateralized pull on the patella.
- Patella alta: A condition where the kneecap sits too high in the trochlear groove, contributing to instability.
- Patellofemoral osteochondral lesions: Damage to the cartilage and underlying bone surfaces of the kneecap or the thigh bone groove, which can be exacerbated by maltracking.
The table below summarizes the primary indications for this surgical intervention:
| Indication for Anteromedialization Osteotomy | Description |
|---|---|
| Patellofemoral Instability (Maltracking) | Recurrent episodes of the kneecap feeling unstable, dislocating, or subluxing. |
| Increased TT-TG Distance | An anatomical measurement signifying excessive lateral positioning of the tibial tubercle relative to the trochlear groove. |
| Patella Alta | A high-riding kneecap, which can predispose to instability and poor tracking. |
| Patellofemoral Osteochondral Lesions | Damage to the articular cartilage and/or subchondral bone of the patella or femoral trochlea. |
By addressing the underlying anatomical misalignment, the anteromedialization osteotomy aims to stabilize the patella, improve its tracking, and alleviate symptoms associated with patellofemoral pain and instability.
