Introduction

Full-thickness defects of weight-bearing articular surfaces have poor healing capacity and cause pain, effusion, and impaired joint function. Fibrocartilage-type repair promoted by different marrow stimulation techniques has limited value because of moderate biomechanical features of the regenerative tissue. Cell therapies—such as autologous chondrocyte implantation—and osteochondral transfer techniques aim to create more durable hyaline cartilage surface in the defected area. Transplantation of autologous osteochondral blocks has been used for several decades and results in long-lasting survival of the transplanted hyaline cartilage. However, this technique had only limited practical value because of missing proper donor areas and congruency problems. Mosaicplasty is a recent modification of osteochondral transplantation using several small osteochondral cylinders instead of one big block of bone and cartilage tissue. By linear graft harvest from the less weight-bearing periphery of the trochlea donor site, availability can be managed and a mosaic-like implantation technique can provide proper contouring in the defected area. After preclinical experimental work, mosaicplasty was introduced into the clinical practice on February 6, 1992.

Surgical Principles and Objective

Surgical Technique)

The following explanations relate to the figures identified.

Step 1

An arthroscopy is performed to examine the intraarticular conditions. The type, site, and size of the defect is determined, and the quality of other chondral surfaces as well as donor site availability are checked (Fig. 5-1).

FIGURE 5-1 Determination of perpendicular approach to the defect.

Choosing a procedure (arthroscopic or miniarthrotomy) depends on the type, size, and exact location of the defect determined during arthroscopy.

As placing the grafts perpendicular to the surface is paramount to the success of the operation, the first task is to determine whether an arthroscopic or open procedure is required.

Patellotrochlear and tibial lesions always require an open procedure.

Most of the femoral condylar defects can be managed arthroscopically. Take care in making the viewing and working portals.

Use a 1.2-mm K-wire or 18-gauge spinal needle initially to locate the portal sites.

Step 2

Use a full-radius resector or curette and a knife blade to bring the edges of the defect back to good hyaline cartilage at a right angle (Fig. 5-2).

FIGURE 5-2 Abrasion arthroplasty of the subchondral bone.

Clean the base of the lesion with an arthroscopic burr or half-round rasp to viable subchondral bone. Abrasion arthroplasty of the defect site promotes fibrocartilage grouting from the bony base.

Step 3

Because tapping the cutting edge of the guide into the bony base and removing it can mark the defect site, use the drill guide to determine the number and size (2.7, 3.5, 4.5, 6.5, and 8.5 mm in diameter) of grafts needed (Fig. 5-3).

FIGURE 5-3 Planning the optimal filling.

Step 4

Filling of the defect by same-sized contacting rings allows a filling rate of about 70% to 80%, but use of additional sizes to cover the dead spaces and cutting the grafts into each other can improve the coverage up to 90% to 100% (Fig. 5-4).

FIGURE 5-4 Maximal filling by overlapping grafts.

This way of filling is technically more demanding and requires more graft harvest. Finally, measure the depth of the defect with the laser marks of the dilator.

Step 5

The medial femoral condyle periphery of the patellofemoral joint above the line of the notch is the most preferred harvest site (Fig. 5-5).

FIGURE 5-5 Graft harvest by tubular chisel from the medial periphery of the patellofemoral joint.

The lateral femoral condyle above the sulcus terminalis and, in exceptional cases, the notch area can serve as additional donor areas.

Grafts harvested from the notch area have less favorable features because they have concave cartilage caps and less elastic underlying bone.

In case of arthroscopic mosaicplasty, the medial patellofemoral periphery has easier access than the lateral one as fluid distension can promote lateral positioning of the patella and may provide easier perpendicular positioning for the harvesting chisel.

The best view for harvesting grafts is obtained by introducing the scope through the standard contralateral portal. Extend the knee and use the standard ipsilateral portal to check the perpendicular access to the donor site. Extended position should provide perpendicular access to the most superior donor hole. Gradual flexion allows the harvest of additional grafts from the lower portions of the patellofemoral periphery. If the standard portals do not allow a perpendicular approach, use a spinal needle or a K-wire to determine the location of additional harvesting portals.

Once the necessary portal has been determined, introduce the proper-sized tube chisel filled with the appropriate harvesting tamp.

Once the site has been clearly identified, the chisel is located perpendicular to the articular surface and driven by a hammer to the appropriate depth.

The minimal length of the graft should be at least two times its diameter, but, as a rule, take 15-mm-long grafts to resurface chondral lesions and 25-mm-long plugs for osteochondral defects.

It is important to hold the chisel firmly to avoid its shifting at the cartilage–bone interface, producing a crooked graft. By flexing the knee, lower sites can be obtained. The lower limit is the level of the top of the intercondylar notch (sulcus terminalis). Insert the appropriate harvesting tamp into the cross-hole in the tubular chisel and use it as a lever. The chisel should be toggled, not rotated, causing the graft to break free at the chisel tip. Eject the grafts from the chisel by sliding the appropriately sized chisel guard over the cutting end. Use the tamp to push out the graft onto gauze in a saline-wetted basin.

Step 6

Flex the knee again and establish good distension. Reintroduce the drill guide using the dilator as an obturator. Place these tools perpendicularly to the defected surface (Fig. 5-6).

FIGURE 5-6 Recipient tunnels are created by drilling.

By rotating the arthroscope, the drill guide and the perpendicularity of the laser mark can be seen from different angles, ensuring proper orientation. Tap the cutting edge of the guide into the subchondral bone. Insert the appropriately sized drill bit and drill to the desired depth. Generally, a recipient hole a few millimeters deeper than the length of the graft is desirable to minimize high intraosseal pressure.

Step 7

Insert the conical-shaped dilator into the drill guide again. Tap it to the desired depth, depending on the actual features of the recipient bone. Stiff bone needs more dilation than normal or soft bone. Hold the drill guide firmly, and remove the dilator from the hole (Fig. 5-7).

FIGURE 5-7 Dilation of the recipient tunnels by conical dilator.

Step 8

Adjust the delivery tamp by turning the handle to initially allow the graft to sit slightly higher than the depth of the defect. This will minimize the likelihood of overpenetrating the graft (Fig. 5-8).

FIGURE 5-8 Insertion of the graft through drill guide.

Stop the inflow to eliminate the graft being forced out of the tube by fluid flow.

Deliver the graft under direct visualization into the recipient hole through the drill guide with the delivery tamp.

Insert the graft deeper by turning the delivery tamp handle counterclockwise.

The graft should be matched to the original articular surface.

Remove the drill guide to inspect the graft. If the graft is protruded, reinsert the drill guide and tap the graft down gently with a tamp of the appropriate size. Insert subsequent grafts in a similar manner by placing the drill guide immediately adjacent to the previously placed grafts.

Step 9

Such step-by-step graft implantation has several advantages. Dilation of the actual recipient hole allows an easy graft insertion (low insertion force on the hyaline cap), but dilation of the next hole affects surrounding bone to the previously implanted grafts, which can result in a safe press fit fixation (Fig. 5-9).

FIGURE 5-9 Dilation of the neighboring recipient tunnel can finalize the press fit fixation of the previously implanted graft.

Step 10

Finally, when the grafts have filled all of the holes, move the knee throughout its range of motion, provoking varus or valgus stress also, depending on the site of the resurfaced area (Fig. 5-10).

FIGURE 5-10 Filling of the defect by seven grafts harvested from the medial and lateral femoral periphery of the patellofemoral joint.

Close the portals and introduce suction drainage into the joint through a superior portal. Use an elastic bandage to fix the appropriate dressing.

Open Mosaicplasty

An open procedure may be chosen in the learning curve or when an arthroscopic approach is not practical because of the size or location of the lesion. Arthroscopic or open mosaicplasties have the same steps and technique. If an arthroscopic approach is impractical, it may be necessary to create a medial or lateral anterior sagittal incision or an oblique incision to perform a miniarthrotomy mosaicplasty.

Special Considerations

Mosaicplasty is often combined with concomitant procedures such as ACL reconstruction and high-tibial osteotomy. In such cases, mosaicplasty should be done first, as this procedure often requires 120-degree (or more) flexion and different stressed positions. After finishing the mosaicplasty, the fixation of the grafts is safe enough to tolerate special stresses during the concomitant procedure.

Postoperative Management

Postoperatively, the drain should be removed at 24 hours.

Appropriate pain and cool therapy as well as nonsteroidal antiinflammatory drugs can reduce the complaints of the patient.

Postoperative thrombosis prophylaxis is recommended.

Routine use of a continuous passive motion machine (CPM) is not necessary, but can be useful to lessen swelling and to provide optimal contouring if the initial clot is between the grafts and at the donor tunnel surfaces.

Immediate ROM exercises are encouraged, a non-weight-bearing and partial loading period of a few weeks is necessary. Usually 2 weeks non–weight bearing followed by 2 weeks partial loading (30 to 40 kg) are ordered before full weight bearing. Detailed rehabilitation recommendations are presented in Tables 5-1 and 5-2.

TABLE 5-1 Mosaicplasty Rehabilitation Protocol_a—General Viewpoints

^bThe main point of the rehabilitation is to ensure the early motion of treated joint to promote appropriate nutrition of transplanted cartilage. Cool therapy can be used during the first week to avoid postoperative bleeding and decrease postoperative pain. In a case of a concomitant procedure requiring external fixation of the affected joint (e.g., meniscus reinsertion), limitation of ROM for a short period by bracing can be allowed.

a Uzsoki Hospital and Sanitas Private Clinic, Budapest, Hungary.

c Extent, type (chondral or osteochondral), and location of the defect may modify weight bearing (see next page).

d Partial loading promotes to transform connecting tissue (between transplanted plugs) into fibrocartilage, so these exercises are mainly important in the half-weight-bearing period. On the other hand, with some closed chain exercises (e.g., cycling), it is possible to ensure cyclic loading that makes the fluid and nutrition transport much more efficient between synovial-fluid and hyaline cartilage.

e Approximately 4 to 5 months are needed to form a composite hyaline-like surface on transplanted area, which tolerates shear forces.

f Depending on depth and extent of the defect. If strength, power, endurance, balance, and flexibility are not satisfying, sport activity is allowed only later.

TABLE 5-2 Mosaicplasty Rehabilitation Protocol—Special Viewpoints

Errors, Hazards, and Complications

One of the most common problems is neglecting the main instructions of the protocol. Perpendicular harvest and implantation of the grafts are crucial for successful transplantation.

Oblique harvest and insertion may result in steps on the surface. Careful control from different angles by the arthroscope can eliminate such problems.

Another frequent mistake is to implant a graft deeper than the desired level. First of all, appropriate use of the delivery tamp can help avoid too deep insertion. If the graft has been inserted too deep, the following steps are recommended:

FIGURE 5-11 Elevation of the graft by arthroscopic probe.

As soon as the expected graft level has been achieved, continue the recommended protocol for the rest of the insertions. Dilation of the adjacent tunnel will provide perfect press fit fixation of the previously implanted graft.

Septic or thromboembolic complications may result in a negative influence on the clinical outcome. Correct aseptic conditions, one-shot antibiotics, and thrombosis prophylaxis can decrease the chance of these complications.

According to 17 years of follow-up, long-term donor site morbidity does not occur frequently. Patellofemoral complaints, such as pain or swelling after strenuous physical activity, follow the mosaicplasty procedure in fewer than 3% of cases. However, excessive postoperative bleeding occurs in 8% of cases. Precise postoperative drainage, cool therapy, and elastic bandages can diminish the chance of this complication.

Results

Between February 6, 1992, and December 31, 2008, 1179 mosaicplasties were performed at the authors’ institution: 849 implantations on femoral condyles, 171 in the patellofemoral joint, 36 on the tibia condyles, 101 on talar domes, 8 on the capitulum humeri, 3 on humeral heads, and 11 femoral heads. Two thirds of the cases were operated on because of a localized Grade 3 or Grade 4 cartilage lesion, whereas the rest of the patients underwent surgery because of osteochondral defects. In 81% of the patients, concomitant surgical interventions were also carried out, which influenced the clinical results of the mosaicplasty procedures. The majority of these concomitant procedures were ACL reconstructions, realignment osteotomies, meniscus surgeries, and patellofemoral realignment procedures.

Femoral, tibial, and patellar implantations were evaluated by the modified Hospital for Special Surgery (HSS), modified Cincinnati, Lysholm, and International Cartilage Repair Society (ICRS) scoring systems, whereas possible donor-site disturbances and morbidity were evaluated by the Bandi scoring system. Patients with talar lesions were subjected to Hannover ankle evaluations. Analysis of clinical scores has shown good to excellent results in 92% of patients with femoral condylar implantations, 87% of tibial resurfacings, 74% of patellar or trochlear mosaicplasties, and 93% of talar procedures. Moderate and severe donor-site disturbances were present in 3% of patients according to the Bandi score¹ (evaluations were done in a 1- to 10-year interval). Postoperative complications were four deep infections and 56 painful hemarthroses. Arthroscopic or open debridement resolved all deep infections, and 12 cases of hemorrhage also required arthroscopic or open debridement. The remaining patients with hemarthroses were treated by aspiration and cryotherapy. Four patients had minor thromboembolic complications.^1–8

Several independent centers have published retrospective or comparative studies about the clinical outcome of autologous osteochondral mosaicplasty technique. Marcacci et al. (2005) (in a 2-year follow-up publication), Chow et al. (2004), Gudas et al. (2005), and Solheim et al. (1999) reported the same clinical efficacy.^9,10,11 Horas et al. (2003) reported outstanding clinical results of mosaicplasty in a comparative, prospective study of mosaicplasty versus autologous chondrocyte transplantation.¹² Nakagawa et al. (2004) published trochlear results, and Matsusue et al. (2001) reported successful tibial outcomes.^13,14 Duchow et al. (2000) and Kordás et al. (2005) discuss important details of press-fit implantation.^15,16