Habitual patellar dislocation is prevalent among children and adolescents. In a group of 35 children with patellar dislocation, Gao [4] reported that 23 of them had habitual patellar dislocation. As the pathological basis of this condition is complex, including the anatomical features, various surgical techniques have been designed. In 1964, Gunn[5] proposed that a contracture of quadriceps femoris can cause patellar dislocation; hence, Joo [6] suggested the use of quadriceps femoris tenolysis for the treatment of patellar dislocation.
The surgical techniques for early habitual patellar dislocation in children can be classified into 3 types: simple bone surgery; muscle and tendon surgery; and joint capsule and ligament surgery. However, the simple application of these techniques to any of the operation types can lead to different complications. In recent years, many scholars have advocated the combined application of multiple surgical methods. While the main goal of surgical treatment of habitual patellar dislocation is to correct the aetiology and anatomical abnormality of patellar dislocation and restore a normal range of motion, the combination approach adopted in this study was based on the release of the lateral soft tissue of knee joint and contraction of the medial joint capsule integrated with vastus medialis anterior placement, medial patellofemoral ligament reconstruction, and rectus femoris insertion reconstruction. This combination of five reconstructive surgeries covers three aspects of muscle, bone, and ligament, with satisfactory clinical effects.
The medial patellofemoral ligament is vital for maintaining the static stability of the patella. Matsushita T et al. [7] believed that the main problem of habitual patellar dislocation was disorder of the medial patellofemoral ligament, and reconstruction can solve >50% of its static stability problems.
For the reconstruction of the medial patellofemoral ligament, the semitendinosus tendon, gracilis tendon or patellar ligament, hamstring tendon, allogeneic ligament, and an artificial ligament are required. Satisfactory effects in restoring a normal range of motion can be achieved with all those anatomical structures. For performing surgery in adolescents with habitual patellar dislocation, more attention is necessary to prevent injury and instability of the tissues around the knee joint, which could occur because of the application of autologous tendons. In this study, the double-row fixation with a suture anchor was applied without lapse and no other damage to tissues of the knee joint occurred. It was also cheaper than the artificial ligament. When considering the fixed position of the reconstructed ligament, the best fit position of the patellar graft is the proximal end of the patellar footprint because its isotonic property has been reported to be favourable [8,9]. From previous studies, the insertion of the medial patellofemoral ligament is known to cover the proximal two-thirds of the patella in 56.9% of cases, the insertion is located in the proximal half of the patella and in the distal end in 41.2% and 1.3% of the cases, respectively, whereas it remains attached to the entire medial edge of the patella in another 1.3% of cases [10]. Therefore, the upper-middle quarter of the patella and the med-patellar region is selected to establish the patellar tunnel. We used a 2.0 mm Kirschner wire to establish a patella double channel and a suture anchor was used to reconstruct the medial patella ligament. Applying both these instruments not only ensures better stress distribution but also restores the anatomical and physiological structure of the medial patellofemoral ligament to the maximum extent.
Patellofemoral joint stability is determined by both, the bone structure and soft tissue. Specifically, the static structure consists of an articular cartilage on the patellofemoral joint surface and the surrounding supportive tissue, while the dynamic stability structure includes the quadriceps muscle. The vastus medialis muscle, however, is the only dynamic structure that can pull the patella inward and backward [11]. In this study, the most important step for the vastus medialis insertion reconstruction surgery is the physical examination of the patient before surgery. If the vastus medialis muscle is severely atrophied, it should not be operated upon.
Since the epiphysis of adolescent patients with habitual patellar dislocation has not been completely closed, soft tissue surgery is important, with the ultimate goal of improving the Q-angle. If the abnormal Q-angle can be improved by surgery (meaning that the angle is corrected to <15°), the proximal force line of the patella can be improved, thereby achieving the purpose of treating patella dislocation. We were further able to achieve the maintenance of patellar range of motion in the femoral trochlea when the knee was flexed >20° by pulling the rectus femoris tendon inward using the pedicled fascia flap, which has not been reported so far.