Abstract
Recurrent patellar dislocation has recently been treated with anatomic medial patellofemoral ligament (MPFL) reconstruction using a semitendinosus muscle tendon. Although it is necessary to add tension to fix the tendon graft without loading excess stress on the patellofemoral joint, adjustment of the tension can be difficult. To resolve this problem, we developed an MPFL reconstruction procedure using the ToggleLoc Fixation Device (Biomet, Warsaw, IN), in which the semitendinosus muscle tendon is folded and used as a double-bundle tendon graft and 2 bone tunnels and 1 bone tunnel are made on the patellar and femoral sides, respectively. The patellar side of the tendon graft is fixed with an EndoButton (Smith & Nephew, London, England), and the femoral side is fixed with the ToggleLoc. Stepless adjustment of tension of the tendon graft is possible by reducing the size of the loop of the ToggleLoc hung onto the tendon graft. It may be useful to position the patella in the center of the femoral sulcus by confirming the patellofemoral joint fitting. Stability can be confirmed by loading lateral stress on the patella in the extended knee joint. This procedure is less invasive because opening of the lateral side of the femur is not necessary, and it may be useful for MPFL reconstruction.
The medial patellofemoral ligament (MPFL) plays an important role in maintaining the stability of the patellofemoral joint, and patellar dislocation markedly reduces the function of the MPFL. Recurrent patellar dislocation has recently been treated using several techniques.1,2 Many studies have reported favorable outcomes with MPFL reconstruction.3-6 The anatomic characteristics of the MPFL have been clarified, and a procedure for MPFL reconstruction has been established using the semitendinosus muscle tendon as a tendon graft.7 We have analyzed the MPFL length change pattern and clarified that the MPFL experiences the most strain at 60° of flexion of the knee joint.8 In our previous surgical procedure for MPFL reconstruction, 2 bone tunnels and 1 bone tunnel were made in the patella and femur, respectively. First, the semitendinosus muscle tendon was passed through the patellar bone tunnels, the patellar side was fixed, the tendon was folded and passed through the femoral bone tunnel, and the femoral side was fixed at 60° of flexion of the knee joint. The tension was manually adjusted to obtain a favorable fitting of the patella and femur, but fine adjustment was difficult. In this study we developed a method by which this fixation procedure can be applied more simply and accurately.
The ToggleLoc Fixation Device (Biomet, Warsaw, IN) has recently been used for reconstruction of the anterior cruciate ligament and repair of the biceps femoris muscle tendon.9 The ToggleLoc Fixation Device with ZipLoop technology (loop length of about 178 mm) (catalog No. 904754; Biomet) has been designed to capture the cortical bone of the femur while providing significant fixation strength with virtually no slippage. The device also allows for changes in the length of its loop to make it fit virtually any length of tunnel. By use of the ToggleLoc, it is possible to adjust the tension of the tendon graft incrementally while fastening. We report a surgical MPFL reconstruction procedure in which the patella can be accurately placed in the center of the femoral sulcus while avoiding excess tension by loading tension on the tendon graft incrementally with the ToggleLoc (Tables 1 and 2).
Table 1.
Pearls of Surgical Technique for MPFL Reconstruction
| 1. When the tendon graft is longer than the bone tunnel, it is adjusted by lengthening the femoral bone tunnel to avoid patellar fracture. |
| 2. Attention should be paid to prevent slippage out of the iliotibial tract when the ToggleLoc device is hung on the lateral femoral cortex. |
| 3. A levator is inserted between the tendon graft and the lateral femur to avoid loading excessive tension on the tendon graft when pulling on the zip suture. |
Table 2.
Benefits and Limitations of Procedure
| Benefits |
| Small skin incision on lateral side of femur and in iliotibial tract |
| Stepless adjustment of tension of tendon graft |
| Limitations |
| Contraindication for patients before epiphyseal closure |
| Contraindications for patella alta or trochlear hypoplasia |
Technique
Bone Tunnel Preparation
The patient is placed in a supine position under general anesthesia. The affected leg is disinfected and affixed to an air tourniquet, and pressure is applied at 300 mm Hg. The semitendinosus muscle tendon is harvested according to the method reported by Hara et al.10
An approximately 5-cm transverse incision is made on the medial side of the knee joint along the distribution of the MPFL, and the subcutaneous tissue is dissected. The longitudinal length of the patella is measured in an image intensifier, and positions at one-third and at the center of the distance from the upper pole are marked. A 1.5-mm-diameter Kirschner wire is inserted from the medial to lateral side at the center of the patella. By use of this K-wire as a reference on the coronal view, a 2.4-mm-diameter K-wire is inserted from the proximal one-third site toward the lateral side of the patella while the axial image is observed. Similarly, another 2.4-mm-diameter K-wire is inserted from the center of the patella. By use of the image intensifier, it is confirmed that these 2 K-wires do not perforate the articular cartilage or anterior cortex of the patella. After confirming the appropriate insertion of the 2.4-mm-diameter K-wires, we remove the initially inserted 1.5-mm-diameter K-wire.
The femoral bone tunnels are prepared with reference to the osseous landmarks according to the method reported by Nomura et al.11 A 2.4-mm-diameter K-wire is inserted from distal to the adductor tubercle (proximally and posteriorly from the center of the medial femoral epicondyle) toward the lateral femoral bone cortex. By use of this K-wire as a guidewire, a bone tunnel with a 30-mm depth is prepared in the femur with a reamer with a diameter of 7 mm (bone tunnel 1). In the patella 2 bone tunnels with a depth of 15 mm are prepared with a reamer with a diameter of 4.5 mm (bone tunnels 2 and 3). After preparing the bone tunnels, we remove all 2.4-mm-diameter K-wires.
Tendon Graft Preparation
The length of the tendon graft is determined. At 60° of flexion of the knee joint, the patella is manually reduced onto the femoral sulcus. Distance X, representing the distance between the femoral (bone tunnel 1) and patellar (bone tunnel 2) bone tunnels, is measured (Fig 1). Distance X is usually between 50 and 60 mm but can vary depending on the physique. Distance Y, representing the distance of the ligament insertion into the femoral bone tunnel, is 20 mm, and distance Z, representing the distance of the ligament insertion into the patellar femoral bone tunnel, is 15 mm. The length of the tendon graft is determined according to the following equation: 2 × (X + Y + Z). It is about 180 mm. By use of the tendinous region of the excised semitendinosus muscle tendon, the tendon is sutured to both ends of No. 2 FiberWire (blue) (catalog No. AR-7201; Arthrex, Naples, FL) (Fig 2) and is used as a double-bundle tendon graft. The tendon graft is passed through the loop of the ToggleLoc Fixation Device, with adjustment of the lengths of the tendon graft at the 2 ends of the loop to be the same.
Fig 1.
Bone tunnel preparation and determination of tendon graft length. For MPFL reconstruction, the patient is positioned in the supine position. Two 2.4-mm-diameter K-wires are inserted from the proximal one-third and one-half site toward the lateral side of the patella. Another 2.4-mm-diameter K-wire is inserted from distal to the adductor tubercle toward the lateral femoral bone cortex. By use of this K-wire as a guidewire, a bone tunnel with a 30-mm depth is prepared in the femur with a reamer with a diameter of 6 mm (bone tunnel 1). In the patella 2 bone tunnels with a depth of 15 mm are prepared with a reamer with a diameter of 4.5 mm (bone tunnels 2 and 3). The tendon graft length is determined from distance X, representing the distance between bone tunnel 1 and bone tunnel 2 (usually 50 to 60 mm); distance Y, representing the distance of the tendon graft insertion into bone tunnel 1; and distance Z, representing the distance of tendon graft insertion into bone tunnel 2 or 3. The length of the tendon graft is determined according to the following equation: 2 × (X + Y + Z). It is about 180 mm.
Fig 2.
Explanation of ToggleLoc parts and tendon graft preparation. The semitendinosus tendon is harvested as tendon graft. The No. 2 FiberWire is baseball sutured to both ends of the tendon graft. The tendon graft is passed through the loop of the ToggleLoc to prepare a double bundle. The loop size is reduced by pulling the zip suture. A passing suture is used to pass through the femoral bone tunnel, and the ToggleLoc device is hung on the lateral femoral cortex.
Transplantation of Tendon Graft
Fixation of Patellar Side
The FiberWire at one end of the tendon graft is passed through bone tunnel 2 with a passing pin. The FiberWire is pulled to the lateral side of the patella to guide the tendon graft into bone tunnel 2. Similarly, the FiberWire at the other end is passed through bone tunnel 3 to guide the tendon graft into bone tunnel 3. By use of the EndoButton (4 mm × 12 mm) (catalog No. 013186; Smith & Nephew, London, England), the ends of the FiberWire that have passed through bone tunnels 2 and 3 are tied and fixed. This procedure fixes the patellar side of the tendon graft.
Fixation of Femoral Side
The passing suture of the ToggleLoc is passed through the femoral bone tunnel with a passing pin and is exposed on the skin on the lateral femoral side. The ToggleLoc device reaches the opening of bone tunnel 1 by pulling the passing suture and is pulled completely through the lateral side of the femur (Fig 3A). Consequently, the ToggleLoc device is hung on the lateral femoral cortex and fixed in place. The position of the ToggleLoc device is confirmed on the image, and attention is paid to prevent slippage out of the iliotibial tract.
Fig 3.
Guidance of tendon graft. First, the patellar side of the tendon graft is fixed. The FiberWire at 1 end of the tendon graft is passed through the patellar bone tunnel with a passing pin. Similarly, the FiberWire at the other end is passed through bone tunnel 3 to guide the tendon graft into another patellar bone tunnel. By use of the EndoButton, the ends of the FiberWire that have passed through the patellar bone tunnels are tied. (A) Fixation of femoral side. The passing suture of the ToggleLoc is passed through the femoral bone tunnel with a passing pin and is exposed on the skin on the lateral femoral side. The ToggleLoc device is passed through the femoral bone tunnel and hung on the lateral cortex of the femur. (B, C) The knee joint is positioned at 60° of flexion. The tendon graft is guided into the femoral bone tunnel by pulling the zip suture. (D) While one is observing the axial image of the patella, the zip suture is pulled until subluxation of the patella is reduced. The zip suture is carefully pulled because once it has been pulled, it cannot be returned to the previous position. It is better to insert a levator between the tendon graft and lateral femur to avoid loading excessive tension on the tendon graft.
Positioning of Tendon Graft in Femoral Bone Tunnel
The knee joint is positioned at 60° of flexion. The size of the loop of the ToggleLoc device is reduced by pulling the “zip” suture (Figs 3B and 3C), through which the tendon graft is guided into bone tunnel 1. While one is observing the axial image of the patella, the zip suture is pulled until subluxation of the patella is reduced (Fig 3D); attention should be paid to avoid excess shifting and tilting of the patella. The zip suture is carefully pulled because once it has been pulled, it cannot be returned to the previous position. It is better to insert a levator between the tendon graft and lateral femur to avoid loading excessive tension on the tendon graft. The knee joint is extended and bent to confirm that subluxation of the patella is reduced. The wound is irrigated and closed. Our technique is demonstrated in Video 1.
Discussion
Anatomic reconstruction of the MPFL has been attracting attention.12 The MPFL is not a simple funicular ligament, and it has a fan-like morphology, widening from the femoral attachment site toward the patella. We use an anatomic method in the MPFL reconstruction, in which 2 bone tunnels in the patella and 1 bone tunnel in the femur are prepared, and the patella is fixed with the semitendinosus muscle tendon. In the anatomic reconstruction, the length of the tendon graft is adjusted to an appropriate length, guided into the bone tunnels, and then tied outside the bone tunnels. When the tendon graft is longer than the bone tunnel, it is adjusted by lengthening the bone tunnel, not by shortening the tendon graft. Because preparation of a large or long bone tunnel can lead to fracture of the patella,13 we resolve the problem by adjusting the length of the femoral bone tunnel, which is first fixed on the patellar side during the MPFL reconstruction, followed by femoral-side fixation because the bone tunnel can easily be adjusted in the femur. Although excess tension on the tendon graft fixation increases the pressure of the patellofemoral joint and causes postoperative pain, patellar instability can remain when the tension is weak.14 Thus it may be useful to position the patella in the center of the femoral sulcus by confirming the patellofemoral joint fitting incrementally.
The size of the loop of the ToggleLoc is reduced only by pulling the zip suture, by which the length of the tendon graft pulled into the femoral bone tunnel can be adjusted; that is, stepless adjustment of tension of the tendon graft is possible while tracking the patella using an image intensifier. In addition, stability can be confirmed by loading lateral stress on the patella in the extended knee joint. It is also possible to reduce surgical stress using this procedure. Previously, we used an EndoButton for fixation of the femoral side, which made it necessary to make a skin incision on the lateral side of the femur and in the iliotibial tract. By use of the ToggleLoc, it is not necessary to open the lateral side of the femur, and surgery is possible by making only a small incision to guide the ligament.
A limitation of this study is the actual application of the surgical procedure. There has been one report of an association between the anatomic predisposition of the knee joint and instability of the patella.15 Thus this procedure alone may not be useful for patients with patella alta and trochlear hypoplasia. Another limitation is the need for preparation of a bone tunnel near the epiphyseal line. Thus application of the procedure should be carefully considered for patients before epiphyseal closure.16
By use of the described procedure, tension of the tendon graft may be simply and appropriately adjusted during MPFL reconstruction.
Footnotes
The authors report that they have no conflicts of interest in the authorship and publication of this article.
Supplementary Data
MPFL reconstruction procedure using suspensory femoral fixation system.
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Associated Data
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Supplementary Materials
MPFL reconstruction procedure using suspensory femoral fixation system.