Long-Term Outcomes of Arthroscopic Lateral Retinacular Release Combined with Medial Reefing for Proximal Realignment of the Patella in Patients with Acute or Subacute First-Time Patellar Dislocation

1. Introduction

Patellar dislocation accounts for 2-3% of total cases of knee joint injuries [1,2]. It commonly occurs on the lateral side, which subsequently causes a rupture of the medial patellofemoral ligament (MPFL) in about 90% of total cases [1,3]. Moreover, it is frequently seen in young, active individuals aged between 10 and 20 years old, showing no male or female predilection [2,4,5]. Most cases of the first-time patellar dislocation occur during sport activities at a reported incidence of 55-72% [2,4]. The multifactorial pathophysiology of patellar dislocation has been documented; patients with patella alta, trochlear dysplasia, increased tibial tuberosity-trochlear groove [TT-TG] distance, femoral torsion or genu varum deformity are vulnerable to it [6,7,8].

To date, diverse surgical procedures have been performed for patients with patellar dislocation; these include medial MPFL reconstruction and medial soft tissue realignment surgery [9,10]. According to a systematic review, medial soft tissue realignment surgery produces less favorable outcomes as compared with MPFL reconstruction [11]. Considering that considerable efforts have been made to surgically treat patients with patellar dislocation, however, medial soft tissue realignment surgery deserves special attention.

It has been shown that patients undergoing isolated lateral release are at increased risks of recurrent patellar dislocation and poor clinical outcomes [12,13]. When combined with medial soft tissue reefing, however, lateral release was reported to be effective in lowering the rate of recurrent instability and raising the degree of patients’ satisfaction with surgical outcomes [14]. Moreover, full-arthroscopic or arthroscopically-assisted stabilization of the patella has been reported to show good treatment outcomes according to short-to-mid-term follow-up studies [15,16].

To date, an arthroscopically-assisted proximal extensor mechanism realignment procedure, involving both the lateral retinacular release and reefing of the vastus medialis, has been mainly performed for patients with recurrent patellar dislocation of subluxation. Of note, however, the acute patellar dislocation is commonly accompanied by medial retinacular tears and MPFL tears [17]. We have therefore devised a surgical technique for patients with acute patellar dislocation as we have done for those with recurrent patellar dislocation.

Given the above background, we have efficiently combined lateral retinacular release with medial reefing for proximal realignment of the patella in patients with patellar dislocation. We therefore conducted this study to assess long-term outcomes of our technique in a retrospective, single-institution setting.

2. Materials and Methods

2.1. Study Patients and Setting

The current single-center, retrospective, observational study was conducted in a total of 67 patients (n = 67) who were surgically treated at our medical institution between February 2012 and March 2024.

Inclusion criteria for the current study are as follows:

(1)

Chief complaint of symptoms in the patellofemoral joint

(2)

Diagnosis of acute or subacute first-time patellar dislocation

(3)

Failed conservative treatments

(4)

Osteochondral injury or loose body

(5)

Treatment with arthroscopic lateral retinacular release combined with medial reefing

(6)

The patients who had been followed up during a mean period of ≥ 24 months.

Exclusion criteria for the current study are as follows:

(1)

Chronic patellar dislocation (n = 1)

(2)

Trochlear dysplasia with crossing sign (n = 3)

(3)

Dislocation after total knee arthroplasty (n = 1)

(4)

Treatment with lateral retinacular release without medial reefing (n = 3)

(5)

Patellofemoral osteoarthritis of ≥ Grade 3 based on the Kellgren-Lawrence classification system (n = 10)

(6)

Fulkerson’s operation (n = 1)

(7)

The need for distal realignment of the extensor mechanism (e.g., Q-angle ≥ 20°, deformity of the lateral femoral condyle or rotational malalignment of the lower extremity) (n = 1).

We therefore included a total of 47 patients (n = 47) in the current study; it was conducted in compliance with the relevant ethics guidelines following the approval by the Institutional Review Board of our medical institution (DMC-2024-05-013). All procedures described herein were performed in accordance with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. But informed consent was waived due to its retrospective nature.

1.1. Treatment Protocol

On physical examination, the patients were evaluated for patellar gliding test and patellar tilt. Then, they received a plain radiography and a magnetic resonance imaging (MRI), based on which they were diagnosed with acute or subacute patellar dislocation. Moreover, they were also examined for whether they had concurrent injuries. Preoperatively, they received conservative therapies such as long leg splint and brace. The patients presenting with instability and pain at the patellofemoral joint despite the above therapies underwent surgery. Thus, they underwent arthroscopic lateral retinacular release and medial joint capsule plication.

We first performed an arthroscopy for concurrent injuries in the knee joint, particularly including osteochondral fracture, injuries to the loose body or the meniscus. Then, we performed arthroscopic repair of these lesions. On arthroscopic diagnosis, there were 15 cases of osteochondral fracture and loose body, for which we performed both loose body removal and chondroplasty. We also examined whether the patients had a tear of the medial retinaculum and confirmed the patellar tilt and the degree of lateral dislocation during full extension of the knee joint. Finally, we measured the patellar tracking during the movement of the knee joint. Following this, an arthroscope was placed in the anterolateral portal and an electrocauter was placed in the anteromedial portal. Approximately 1 cm vertical to the lateral border of the patella, the fatty layer and the surface of lateral quadriceps femoris could be exposed from the proximal pole of the patella to the lower fibers of the vastus lateralis, lateral patellar retinacula and joint capsule were released. Thereafter, the location and tracking of patella were evaluated again. A spinal needle with a non-cutting edge was inserted in the medical capsular membrane from both directions. The suture was performed using arthroscopic all-inside suture technique. In the same manner, 4-5 sutures were made using PDS #1-0 (Figure 1).

There are no established criteria for assessing the degree of plication. At a gap distance of approximately 2-2.5 cm, however, the articular membrane was overlapped using approximately three threads. Then, the patellar tilt, the degree of lateral dislocation and patellar tracking were assessed. If insufficient, the plication was strengthened by 1-2 overlaps. Finally, we confirmed that there were improvements in the patellar tilt and dislocation (Figure 2).

Postoperatively, the patients were recommended to wear long leg brace for three weeks and to perform active movement of the knee joint. Only the patients with satisfactory results of quadriceps setting test were recommended to wear patellar supporting knee brace.

1.1. Outcome Measures

(1)

Patellar tilt angle: The patellar tilt angle is a measure of the medial/lateral tilt of the patellar plane relative to the femur. The normal patellofemoral joint is characterized by the lateral opening of the angle between the lateral facet of the patella and any horizontal line. In the abnormal patellofemoral joint, however, the lines forming the patellar tilt angle are parallel or open medially. The patellar tilt angle measuring as 0°-5°, 5°-10° and > 10° is rated as normal, borderline and abnormal, respectively [18].

(2)

Congruence angle: The congruence angle is an indicator of medial/lateral subluxuation of the patella within the trochlear groove, which is similar to physical examination of the patellar glide. Its mean values are measured as -6° ± 11° in individuals with no patellar dislocation [18].

(3)

Insall-Salvati index: The Insall-Salvati index is the ratio of length of distal part of tendon of quadriceps femoris extending from distal pole of patella to tibial tuberosity to diagonal length of the patella on lateral radiographic view of knee joint taken at 30°-angle of flexion [19].

(4)

TT-TG distance: TT-TG distance is a measure of lateralization of the tibial tuberosity relative to the femoral trochlea. It is considered a key factor that is used to assess patellofemoral disorders, which is based on published studies showing that lateralization of the tibial tuberosity is closely associated with patellofemoral instability [20].

(5)

Lysholm knee score: The Lysholm score is a 100-point scoring system for examining a patient’s knee-specific symptoms; it is composed of eight items, such as limp, support, locking, pain, instability, swelling, stair climbing and squatting, whose total scores are rated as “Excellent” (95-100 points), “Good” (84-94 points), “Fair” (65-83 points) or “Poor” (< 65 points) [21].

(6)

Kujala scores: The Kujala scoring system is composed of a 13-item screening instrument, comprising 13 multiple choice Questions (the presence of a limp, the need for support, an ability to walk, to climb stairs, to squat, to run and to jump, prolonged sitting with knees in the flexed position, the presence of knee pain, knee swelling and presence of abnormal painful patellar movement, atrophy of the thigh muscles and deficiency of knee flexion). It was originally designed to assess patellofemoral pain in adolescents and young adults, with a variable ordinal response format [22].

1.1. Patient Evaluation and Criteria

The patients underwent plain radiography and MRI both preoperatively and postoperatively. Preoperatively, they were evaluated for the measurement of the Q-angle and sulcus angle, as indices of malalignment of the extensor mechanism of the knee [23,24]. Then, they were evaluated for the measurement of the patellar tilt angle, congruence angle, TT-TG distance, Insall-Salvati index, Lysholm knee scores and Kujala score both preoperatively and postoperatively. We analyzed whether there were significant differences in these measurements between preoperatively and postoperatively.

Through a retrospective analysis of the patients’ medical records, we analyzed their age, sex, height, weight, body mass index (BMI), the side of the affected knee, the mode of anesthesia and length of follow-up period. Postoperative outcomes were assessed as proposed by Crosby and Insair [25].

1.1. Statistical Analysis

All data was expressed as mean ± standard deviation or the number of the subjects with percentage, where appropriate. Statistical analysis was done using the SPSS ver. 18.0 for windows (SPSS Inc., Chicago, IL). The patients’ characteristics were analyzed using the χ²-test. Moreover, clinical and radiological outcomes were compared between preoperatively and postoperatively using a paired t-test. A p-value of < 0.05 was considered statistically significant.

5. Conclusions

Based on our results, it can be concluded that arthroscopic lateral retinacular release combined with medial reefing for proximal realignment of the patella is an effective, safe modality in patients with acute or subacute first-time patellar dislocation. But further large-scale, multi-center studies with long periods of follow-up are warranted to corroborate our results.