Introduction and Background

This chapter details the surgical technique for the implantation of TRUFIT CB plugs. This process involves creating perpendicular access to the articular surface via an arthroscopic or open approach, thereby creating a flush surface with one or two plugs. The technique can be expanded to allow implantation of multiple plugs.

The TRUFIT plug (Smith & Nephew, Andover, Massachusetts, United States) has been designed as a multiphase implant with tailored degradation (Fig. 4D-1). The implant is composed of a polylactic acid (PLA), polylactic glycolide (PLG), and polyglycolic acid (PGA) copolymer, with calcium sulphate, PGA fibers, and surfactant.^1,2,3 The bilayer design provides cartilage and bone phases, and initially the cartilage phase is softer and malleable enough to be physically contoured to joint curvature. The plug acts as a porous scaffold that provides structural support while allowing the growth of new healing tissue. The calcium sulphate resorbs in the first several months, and the remaining polymer dissolves over a 12- to 36-month period, allowing for complete filling of the defect by repair tissue.³

FIGURE 4D-1 The TRUFIT CB (cartilage/bone graft substitute) plug.

Indications/Contraindications

TRUFIT plugs are indicated for the repair of full-thickness articular cartilage or osteochondral lesions.⁵ The optimal lesion size is less than 2 cm² to ensure that the plugs are well shouldered by normal surrounding articular cartilage. However, the indication is extended for longitudinal patterns of defects in the articular surface when plugs can be inserted in a line. TRUFIT plugs are not indicated for larger areas where they would be positioned in a circle or group unless a 2 mm or more bone bridge is maintained between plugs.

Surgical Positioning

Surgery is performed under general or local anesthesia, and the patient is positioned supine on the operating table with a side post applied.

For femoral condyle lesions, the knee is positioned over the edge of the table against the side post and the angle of knee flexion is controlled by pushing the leg against the side of the table (Fig. 4D-2). This makes repositioning of the leg easier than the alternative of positioning the knee at 90 degrees on the table against a foot piece, which holds the knee more rigidly.

FIGURE 4D-2 Patient positioned with leg supported against a side post.

For lesions on the trochlea, the leg is positioned nearly straight on the operating table and is supported over a removable sterile bolster (Fig. 4D-3), such as a sandbag or a 3L irrigation fluid bag in a sterile Mayo cover, for example.

FIGURE 4D-3 Patient positioned with the knee flexed over a bolster.

Surgical Approach

Regarding the surgical approach, a decision has to be made as to where the lesion is and whether the surgeon is choosing an arthroscopic or a mini-open approach. When considering arthroscopic or a mini-open approach, there are various scenarios that make it more difficult for an arthroscopic technique. It may be quicker to make a small open arthrotomy rather than persevere arthroscopically, and it is certainly easier to visualize the surface to obtain a perpendicular approach.

Arthroscopic surgery, however, allows much better postoperative comfort for the patient and will produce a more cosmetic scar. A mini-open approach should be considered when there have been multiple previous operations, as this will create a more rigid envelope around the knee, restricting movement of the instruments. Space to approach the lateral femoral condyle with the knee in flexion is much tighter than on the medial side, and this makes it much more difficult when inserting two or more plugs.

The central trochlea is also more difficult to approach arthroscopically and again takes a fair amount of levering on the patella. In addition, some knees are simply tight and do not allow easy access. Arthroscopic portals are established to optimize the approach for arthroscopic repair, remembering that the overriding principle is to obtain perpendicular access for the TRUKOR instruments:

Surgical Technique

The technique for implanting the TRUFIT plugs is illustrated and detailed in Figures 4D-5 through 4D-14. The instrumentation comes in three parts. The reusable drill bits and sizing instruments are presented in a sterile box (Fig. 4D-4, A). All that is needed beyond these items and the standard arthroscopic instruments is a mallet. The sizers are used to determine the defect size and are matched to the size of the disposable TRUKOR drill sleeve (Fig. 4D-4, B) and TRUFIT CB plug kit (Fig. 4D-4,C).

FIGURE 4D-5 Sizing lesion on the medial femoral condyle of a right knee.

FIGURE 4D-6 Round-ended obturator is inserted into the chosen TRUKOR drill sleeve to facilitate insertion of the sharp sleeve into the knee.

FIGURE 4D-7 Once against the defect, the obturator is backed out and the drill sleeve is seated on to the articular surface, with care taken to keep it perpendicular.

FIGURE 4D-8 To check the alignment of the drill sleeve, it must be checked from at least two angles: A, initial view cartilage damage, B, mapping defect with 9-mm sizer, and, C, checking that the 9-mm sizer covers most of the area. D, The sleeve is gently impacted to the 2-mm line, and this line is then viewed from two or three directions to confirm perpendicular entry. E, Final depth at 12 mm maximum.