Isolated MPFL reconstruction resulted in a low post-operative redislocation rate of 5.6% and significant clinical improvement of the knees’ function and patient’s perception. MPFL reconstruction restores the primary stabilization of the patella [
11,
12] and is the standard of care for the treatment of lateral patella instability [
21]. Osseous fixation techniques of the graft at the patella have been described with suture anchors, interference screws, and different drilling methods. These osseous fixation techniques are associated with the risk of implant failure and patella fracture [
13,
17]. Although only sparsely discussed in the literature, Hopper et al. reported a patella fracture rate of 5.6% with an interference screw technique [
18]. In contrast to these techniques, the investigated soft tissue fixation does not compromise the bone stock of the patella. Instead, the graft is weaved in a u shape through the capsule and the periosteum of the patella and fixed with resorbable sutures. For this quick and easy technique, the current study could demonstrate a low redislocation rate comparable to the one reported for osseous fixation techniques in the literature by Song et al. [
21]. While for their review focusing on MPFL reconstruction, knees with TD or patella alta were excluded, in the current study, these knees were included and treated merely with isolated MPFL reconstruction. Recent treatment recommendations increasingly advise combining MPFL reconstruction with bony correction in case of abnormal osseous anatomy [
3]. Rhee et al. specifically emphasized to correct patella alta by transfer of the tuberosity [
10]. However, Hopper et al. showed that MPFL reconstruction in combination with tuberosity transfer does not guarantee stable patellae [
18]. In the current study, we have not observed redislocations with patella alta, if TD was only mild or not present. By methods, patients with TT-TG larger than 20 mm were excluded from the study. Increased TT-TG displays a significant pathology for lateral patellar instability, which we believe should be treated with additional tuberosity transfer. All redislocations in the current study occurred in knees with severe TD, concurrent patella alta, and a TT-TG < 20 mm. For this subgroup, the post-operative redislocation rate was 13.8%. Balcarek et al. compared two treatment modalities in knees with severe TD but without patella alta: the knees treated with trochleoplasty and MPFL reconstruction had a redislocation rate of 2.1% whereas the rate for the knees treated with MPFL reconstruction only was 7.0%. But this difference was not significant [
14]. Still, the authors recommend to consider trochleoplasty as primary treatment option in knees with severe TD [
3]. This study comprises three cases with type D TD. No redislocation was seen in this subgroup, but two of the three patients reported positive apprehension sign in clinical examination. Thus, in knees with severe TD and patella alta, additional bony correction with trochleoplasty should be strongly considered.
There are several limitations to this study. Correctly completed questionnaires were obtained from only 67.6% (
n = 48). The missing questionnaires were caused by two problems. First is inability to complete the questionnaires and to send them to the study institution, if an appointment for clinical examination was not possible. Second is not matching answer possibilities leading to no, multiple, or incorrect answers. However, statistics resulted in highly significant results and the mean values compare closely to those reported in the literature [
14,
22]. Further, a recall bias for the questionnaires retrieving the preoperative condition might be relevant. However, the retrospective assessment of the scores certainly implements the patients’ satisfaction with the procedure.
Although not particularly investigated in the current study, soft tissue fixation does not require intra-operative fluoroscopy for placement control and might even decrease operation time. The soft tissue fixation technique does not produce a bony defect at the patella, which is an advantage of the described soft tissue patellar fixation technique, and thus, implant- or drilling-associated complications are avoided. As shown in the current study, more than half the knees with patella instability have cartilage lesions and thus, future patellar cartilage reconstructive or replacing therapies impede. Under these considerations, MPFL reconstruction with soft tissue patella fixation is a highly reasonable option that after a follow-up of 5.8 years now has proven very low post-operative redislocation rates and significant improvement in knee function scores.