Closed-wedge Patelloplasty for the Treatment of Distal Patellofemoral Maltracking and Instability due to Severe Patellar Dysplasia: Case Report and Surgical Technique

Abstract

Background: Patellofemoral maltracking is caused by different anatomical factors. Most of them are associated with a proximal maltracking, which alters the patella's engagement into the trochlear groove and predisposes the patellofemoral joint for instability. Different surgical techniques have been described to realign patellar tracking, however, most of which address proximal patellar maltracking.

Aim: The aim of this article is to demonstrate the influence of patella-related deformities on patellar tracking and to present a novel surgical technique for the treatment of distal patellar maltracking, caused by a severe patellar dyplasia.

Case description: We report the case of a 23-year-old patient with a severe patellar dysplasia, presenting a distal patellar maltracking with recurring dislocations in deep flexion. Due to her instability, the patient was immobilised and dependent on the constant use of walking aids. Radiological images showed a concavely shaped patellar, which articulated exclusively with the lateral epicondyle and caused the patella to dislocate laterally, starting at a flexion angle of 60°. An anterior closing-wedge osteotomy was used to reshape and recenter the patella, which was complemented by a medial patellofemoral ligament reconstruction. At the 18-month follow-up, the patient presented pain free and fully remobilised, without the use of walking aids. Patellar tracking was reestablished, with a possible knee flexion until 140°. No redislocation of the patella had occurred.

Conclusion: Distal patellofemoral maltracking, caused by a severe patellar dysplasia, can successfully be treated with an anterior closed-wedge osteotomy of the patella. In combination with a medial patellofemoral ligament reconstruction, patellofemoral stability can be reestablished, to prevent further dislocations.

Clinical significance: There are multiple factors, which may cause patellar maltracking. A thorough clinical and radiological preoperative analysis is mandatory, in order to clearly identify the underlying pathologies, as these may affect patellar tracking proximally or distally.

How to cite this article: Frings J, Freudenthaler F, Krause M, et al. Closed-wedge Patelloplasty for the Treatment of Distal Patellofemoral Maltracking and Instability due to Severe Patellar Dysplasia: Case Report and Surgical Technique. Strategies Trauma Limb Reconstr 2020;15(3):184-192.

Keywords: Distal maltracking; Instability; Maltracking; Osteotomy; Patella; Patelloplasty.

Figs 1A to G

A lateral radiograph of the left knee showed a patella infera, with a CDI of 0.74 (A), while the leg axis in the frontal plane was found to be straight in the standing long-leg radiograph (E). On tangential radiographs of the patella in 30, 60 and 90° of knee flexion, the patella was found to lateralise increasingly (B–D), which was caused by a concavely shaped patella accompanied by a type B trochlear dysplasia (F, G)

Figs. 2 A to D

A three-dimensional CT reconstruction of the left knee impressively revealed an articulation between the lateral epicondyle and the patella, while the trochlear groove (yellow star) did not participate in the articulation

Figs. 3 A to F

The diagnostic arthroscopy revealed a lateralised patella (+), riding on top of the lateral condyle (*), while the trochlea groove remains empty (A,B). Due to the concave shape of the dysplastic patella, its reduction into the trochlear groove was impossible at this point of surgery. The pre-operatively measured and planned wedge was marked with two K-wires and controlled with the image intensifier (C, D). After the bony wedge was removed (green arrow) (E), the osteotomy was closed and osteosynthesis was performed with cannulated screws (F). Subsequently, the patella could be centralised into the trochlear groove. In addition, a medialisation and proximalisation of the tibial tubercle was performed

Fig. 4

Arthroscopically, patellar tracking was found to remain slightly lateralized (a), while the patella (+) could easily be reduced into the trochlear groove (T), by applying gentle lateromedial pressure (b). After medializing and proximalizing the tibial tubercle, restoring physiological conditions, it was fixed with three bicortical 3.5 mm screws (blue arrow) (c, d). The lateral condyle (*), which previously functioned as the primary counterpart of patellofemoral articulation, was now located lateral to the patellofemoral joint (d)

Figs. 5 A to C

The postoperative radiograph of the left knee in two planes showed an improved patellar height (A) and the correct position of all osteosynthesis materials (B). An additional postoperative CT scan showed the correct position of the femoral drill channel (#) and demonstrated an improved patellofemoral articulation that was enabled by the newly created conformity of the retropatellar joint surface (C, D)

Figs. 6 A to D

A three-dimensional reconstruction of a postoperative CT scan presented a notable improvement of patellofemoral articulation

Figs. 7 A to F

Before the surgery was started, the left knee was re-examined regarding its full range of motion, showing an obvious lateralization of the patella with progressive knee flexion (A). At the 12-month follow-up examination, the wound had healed completely (B) and physiological patellar tracking was restored up to a passive flexion angle of 130° (C, D). Examination of the contralateral right knee demonstrated similar findings of a distal patellar maltracking (E, F)

Figs. 8 A to E

After 18 months, the patient presented for implant removal of the screws. Preoperative patellar tracking during passive range of motion was physiological throughout a range of motion between full extension and 145° of knee flexion (from left to right)

Figs. 9 A to D

The arthroscopic re-evaluation of the patellar tracking at the beginning of the implant removal surgery documented a centralised position of the patella in full extension (A, B), as well as a physiological engagement of the patella into the trochlear groove (C, D)