**5.2.1 Surgical technique**

Standard diagnostic arthroscopy is performed prior to assessment of a lesion amenable to microfracture. The use of a tourniquet is not recommended as this precludes assessment of depth of penetration of arthroscopic awl with egress of marrow fat or blood. The defect is prepared by creation of vertical walls with stable rims with a full radius resector or curette and removal of the calcified cartilage zone with a curette. Thus, poorly-shouldered lesions are not well-suited for this treatment. A stable subchondral plate is desired, so caution is warranted when debriding the calcified cartilage zone so that the plate is not compromised. Arthroscopic awls of variable angles (0°, 30°, 45°, 60°, and 90°) may be used to create multiple holes, the microfractures, perpendicular to the surface penetrated. The sequence of hole creation should be centripetal, from the periphery inward, approximately 3-4 mm apart and 3-4 mm deep (Figure 9). Do not place holes so close as to converge upon one another. Once complete, reduce arthroscopic pump pressure to visualize marrow contents from each of the holes. Do not use an intra-articular drain post-operatively, as this will remove the desired clot formation within the defect. Steadman has stressed the importance of postoperative rehabilitation following microfracture. Immediate continuous passive motion (CPM) is indicated for at least 8 hours per day for at least 8 weeks. Return to competitive sports is not allowed prior to 6 to 9 months.

#### **5.2.2 Outcomes**

In horse and human studies, microfracture has been consistently shown to produce a greater quantity of repair tissue versus no treatment of an isolated chondral defect(Frisbie, Trotter et al. 1999; Mithoefer, McAdams et al. 2009). Better outcomes have been demonstrated with the

Cartilage repair techniques intend to stimulate the subchondral bone marrow (marrowstimulation techniques, MST) to induce mesenchymal stem cell infiltration into a chondral defect with formation of a clot that may differentiate into repair tissue. This tissue is generally fibrocartilage, with a ratio of Type II to I collagen that is less than that of normal hyaline articular cartilage. The biomechanical properties and durability of fibrocartilage are inferior to that of hyaline cartilage. Microfracture, subchondral bone drilling, and abrasion

Standard diagnostic arthroscopy is performed prior to assessment of a lesion amenable to microfracture. The use of a tourniquet is not recommended as this precludes assessment of depth of penetration of arthroscopic awl with egress of marrow fat or blood. The defect is prepared by creation of vertical walls with stable rims with a full radius resector or curette and removal of the calcified cartilage zone with a curette. Thus, poorly-shouldered lesions are not well-suited for this treatment. A stable subchondral plate is desired, so caution is warranted when debriding the calcified cartilage zone so that the plate is not compromised. Arthroscopic awls of variable angles (0°, 30°, 45°, 60°, and 90°) may be used to create multiple holes, the microfractures, perpendicular to the surface penetrated. The sequence of hole creation should be centripetal, from the periphery inward, approximately 3-4 mm apart and 3-4 mm deep (Figure 9). Do not place holes so close as to converge upon one another. Once complete, reduce arthroscopic pump pressure to visualize marrow contents from each of the holes. Do not use an intra-articular drain post-operatively, as this will remove the desired clot formation within the defect. Steadman has stressed the importance of postoperative rehabilitation following microfracture. Immediate continuous passive motion (CPM) is indicated for at least 8 hours per day for at least 8 weeks. Return to competitive

Fig. 9. Arthroscopic photograph of microfracture of medial femoral condyle defect.

In horse and human studies, microfracture has been consistently shown to produce a greater quantity of repair tissue versus no treatment of an isolated chondral defect(Frisbie, Trotter et al. 1999; Mithoefer, McAdams et al. 2009). Better outcomes have been demonstrated with the

**5.2 Cartilage repair techniques** 

arthroplasty are MSTs.

**5.2.1 Surgical technique** 

sports is not allowed prior to 6 to 9 months.

**5.2.2 Outcomes** 

creation of smooth, vertical walls of the defect and removal of the calcified cartilage layer directly beneath the tidemark(Frisbie, Morisset et al. 2006).

Microfracture is generally indicated for a full-thickness, chondral defect (after debridement of the defect to stable rims with exposed bone) of the femoral condyles, trochlea, patella, or tibial plateau. The pioneer of microfracture (Steadman) has successfully utilized microfracture in degenerative arthritis(Miller, Steadman et al. 2004). Although microfracture has been used in high-performance athletes (NFL) with excellent outcomes and return-toplay(Steadman, Miller et al. 2003), other studies have shown less success in highperformance professional athletes, with low rates of return-to-sport and decreased performance if able to return(Cerynik, Lewullis et al. 2009; Namdari, Baldwin et al. 2009).

Outcomes of microfracture are mixed. Long-term outcomes have been successful (mean 11 years, range 7 to 17 years) in patients less than 45 years age, without malalignment or meniscal or ligamentous pathology, graded by both subjective and objective outcome measures(Steadman, Briggs et al. 2003). Recent systematic reviews have shown excellent short-term clinical outcomes following microfracture(Mithoefer, McAdams et al. 2009; Harris, Siston et al. 2010). However, after 18 to 24 months, outcomes tend to deteriorate, especially in patients with defects larger than 2 to 4 cm2, longer pre-operative duration of symptoms, prior surgeries to the knee, and older age (Mithoefer, McAdams et al. 2009; Harris, Brophy et al. 2010; Harris, Siston et al. 2010). Further, microfracture may compromise future outcomes following ACI. A three times greater risk of failure after ACI has been shown in those patients with previous microfracture versus those without(Minas, Gomoll et al. 2009). In general, it appears that microfracture is best suited for younger patients with small defects who have normal alignment and a short pre-operative duration of symptoms and are willing to comply with post-operative rehabilitation.

#### **5.3 Cartilage restoration techniques**

Cartilage restoration techniques either transfer (mosaicplasty, osteochondral autograft and allograft) or attempt to produce (cell-based treatments such as ACI) normal hyaline articular cartilage.

#### **5.3.1 Osteochondral autograft / mosaicplasty**

Osteochondral autograft (OAT) and mosaicplasty are two similar techniques that harvest an osteochondral plug(s) from a "less weight-bearing" part of the knee and transplant them to a defect on a more weight-bearing, articulating location. Given the three-dimensional complexity of the articular surfaces of the knee, one can anticipate that stable congruity of the transplanted plug is paramount to the procedure's technical success. This procedure (Figure 10) can place one or many plugs of variable sizes to fill a defect. If one plug is used and is flush with surrounding cartilage, no fibrocartilaginous tissue from the underlying subchondral bone will be formed. If more than one plug is used, however, the intervening areas fill with fibrocartilage. Since this is an osteochondral transplant, chondral *and* osteochondral defects may be treated without the need for bone grafting (as opposed to other cartilage surgery). This technique, however, is limited by donor-site supply. This has prompted most authors to limit the size transplanted to no greater than 4 or 5 cm2. Despite concerns for donor-site morbidity following harvest, long-term donor-site complaints (measured by Bandi score) are minor and present in small numbers of patients, including high-level athletes (3% - 5%)(Hangody, Vasarhelyi et al. 2008; Hangody, Dobos et al. 2010).

Management of Knee Articular Cartilage Injuries 117

follow-up, good or excellent clinical outcomes were observed in 91% of femoral condyle OAT, 86% tibial, and 74% patellofemoral(Hangody, Dobos et al. 2010). The timing of return to sport after OAT is faster than that after microfracture or ACI(Harris, Brophy et al. 2010). Also, the rate of return to sport and overall clinical outcomes after OAT are better than that after microfracture(Harris, Brophy et al. 2010). Except for more rapid clinical improvement, no significant difference has been demonstrated between OAT and ACI with regard to

Principles of osteochondral allograft are similar to those of autograft, with the difference being the source of the osteochondral plug. Although concern for disease transmission, cell viability, and host-graft immunogenicity exist, this technique is a very useful treatment for larger chondral and osteochondral defects (usually greater than 2 to 4 cm2). There is no limitation to the size of graft used, as entire condyles may be transplanted. Given the size constraints imposed by the transplanted graft, most allografts are implanted via an arthrotomy, although some cases may allow all-arthroscopic placement,

Just as with OAT, the defect is prepared to stable smooth rims with vertical walls using a sharp curette or full-radius resector and then sized. The cylindrical dowel graft is then prepared to match the size of the defect. The dowel graft is then press-fit into its recipient socket via instrumented manual impaction. Supplemental fixation is generally not required. A shell graft technique is another viable option when the dowel technique is not possible because of defect location or size. The shell is prepared freehand and usually requires

Outcomes after osteochondral allograft demonstrate good to excellent outcomes in 72% to 94% of patients at long-term follow-up with 5 year Kaplan-Meier survivorship around 95%, 10 year survival around 80% - 85%, and 15 year survival around 65%(Garrett 1994; Shasha, Krywulak et al. 2003; Gross, Shasha et al. 2005; Emmerson, Gortz et al. 2007). Although technically demanding, osteochondral allograft has long-term proven success in patients

ACI is a two-stage cartilage restoration technique indicated for lesions greater than 2 cm2 on the femoral condyles, trochlea, or patella. Stage 1 involves arthroscopic assessment of the defect and a full-thickness cartilage biopsy. Stage 2 involves cell implantation via arthrotomy under a periosteal or collagen membrane patch or, more recently, outside the U.S., cell placement onto a three-dimensional scaffold that can potentially be placed allarthroscopically. The premise behind ACI is that a biopsy and growth in culture of your own cells should theoretically produce normal hyaline articular cartilage upon implantation. However, dedifferentiation of chondrocytes when grown in monolayer culture and subsequent re-differentiation upon implantation has produced "hyaline-like" cartilage. This tissue has a Type II collagen and proteoglycan composition that is close, but not identical to

clinical outcomes(Harris, Brophy et al. 2010; Harris, Siston et al. 2010).

fixation. This technique is technically more demanding than the dowel.

with larger defects and bone loss that may have failed a prior cartilage surgery.

**5.3.3 Autologous chondrocyte implantation (ACI)** 

that of normal hyaline articular cartilage.

**5.3.2 Osteochondral allograft** 

just as with OAT.

**5.3.2.2 Outcomes** 

**5.3.2.1 Surgical technique** 

Fig. 10. 10a) Sagittal MRI demonstrating osteochondral defect of medial femoral condyle; 10b) Coronal MRI demonstrating same defect; 10c) Arthroscopic photograph of defect; 10d) Mini-arthrotomy image after recipient site preparation; 10e) Flush plug placed.

#### **5.3.1.1 Surgical technique**

Osteochondral autograft may be performed all-arthroscopically or via mini-arthrotomy. Either is acceptable, although arthroscopically may be technically more demanding. Standard diagnostic arthroscopy is performed initially. The defect is prepared by obtaining stable smooth edges with vertical walls. Once this is complete, the defect is then precisely measured and templated. There are several unique proprietary designs available to harvest and place plugs. However, the general principles of each are the same: A sharp cutting harvester, perpendicular to the surface, is impacted to a pre-determined depth and donor plug is harvested. The size of the harvester can be range from 2.5 to 10 mm in diameter. Donor sites include the intercondylar notch, and superomedial and superolateral borders of the femoral condyles. These donor sites should properly be described as "less weightbearing" regions, rather than non-weight-bearing regions(Simonian, Sussmann et al. 1998; Ahmad, Cohen et al. 2001). The recipient site is prepared to accept the graft to the correct depth. The plug is then placed press-fit via instrumented manual impaction. Plugs should be placed flush circumferentially, as plugs placed proud demonstrate significantly greater contact pressure around the plug's rim and the opposing surface(Harris, Solak et al. 2011). Even plugs countersunk beneath the surrounding normal cartilage create significant pressure increases around the rim of the normal cartilage(Koh, Wirsing et al. 2004). It cannot be overemphasize that critical for this procedure's success is flush plug placement achieved via perpendicular plug harvest and transplantation.

#### **5.3.1.2 Outcomes**

Outcomes following osteochondral autograft / mosaicplasty have been largely good or excellent. In an exclusively athletic population of nearly 400 patients at nearly 10 year mean

Fig. 10. 10a) Sagittal MRI demonstrating osteochondral defect of medial femoral condyle; 10b) Coronal MRI demonstrating same defect; 10c) Arthroscopic photograph of defect; 10d)

Osteochondral autograft may be performed all-arthroscopically or via mini-arthrotomy. Either is acceptable, although arthroscopically may be technically more demanding. Standard diagnostic arthroscopy is performed initially. The defect is prepared by obtaining stable smooth edges with vertical walls. Once this is complete, the defect is then precisely measured and templated. There are several unique proprietary designs available to harvest and place plugs. However, the general principles of each are the same: A sharp cutting harvester, perpendicular to the surface, is impacted to a pre-determined depth and donor plug is harvested. The size of the harvester can be range from 2.5 to 10 mm in diameter. Donor sites include the intercondylar notch, and superomedial and superolateral borders of the femoral condyles. These donor sites should properly be described as "less weightbearing" regions, rather than non-weight-bearing regions(Simonian, Sussmann et al. 1998; Ahmad, Cohen et al. 2001). The recipient site is prepared to accept the graft to the correct depth. The plug is then placed press-fit via instrumented manual impaction. Plugs should be placed flush circumferentially, as plugs placed proud demonstrate significantly greater contact pressure around the plug's rim and the opposing surface(Harris, Solak et al. 2011). Even plugs countersunk beneath the surrounding normal cartilage create significant pressure increases around the rim of the normal cartilage(Koh, Wirsing et al. 2004). It cannot be overemphasize that critical for this procedure's success is flush plug placement achieved

Outcomes following osteochondral autograft / mosaicplasty have been largely good or excellent. In an exclusively athletic population of nearly 400 patients at nearly 10 year mean

Mini-arthrotomy image after recipient site preparation; 10e) Flush plug placed.

**5.3.1.1 Surgical technique** 

**5.3.1.2 Outcomes** 

via perpendicular plug harvest and transplantation.

follow-up, good or excellent clinical outcomes were observed in 91% of femoral condyle OAT, 86% tibial, and 74% patellofemoral(Hangody, Dobos et al. 2010). The timing of return to sport after OAT is faster than that after microfracture or ACI(Harris, Brophy et al. 2010). Also, the rate of return to sport and overall clinical outcomes after OAT are better than that after microfracture(Harris, Brophy et al. 2010). Except for more rapid clinical improvement, no significant difference has been demonstrated between OAT and ACI with regard to clinical outcomes(Harris, Brophy et al. 2010; Harris, Siston et al. 2010).
