Osteochondral Grafting of Articular Cartilage Injuries Technique

Updated: Sep 26, 2017
  • Author: Andrew Turtel, MD; Chief Editor: Thomas M DeBerardino, MD  more...
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Technique

Approach Considerations

The use of large autogenous osteochondral fragments and patellar grafts has been reported, but results have been mixed, and concern exists regarding donor-site morbidity from such large grafts.

There is growing interest in the concept of smaller and more uniform cylindrical grafts, obtained locally, that can be implanted into prepared recipient sites in the lesion. Although there are some technical differences between the various commercially marketed techniques in which cylindrical osteochondral plugs are transferred, the overall concepts are similar. The technique can be used in specific situations of deficit size and location in properly selected patients. [36]

The biology of these grafts is well documented in animal and clinical studies. Strong data support the ability of cancellous bone plugs to heal, whether the recipient holes have been drilled, trephined, or cored (see the first image below). Biopsy studies also have shown the ability of transplanted cartilage to survive if placed in a mechanically advantageous position (see the second image below). 

Strong data support the ability of cancellous bone Strong data support the ability of cancellous bone plugs to heal, whether the recipient holes have been drilled, trephined, or cored.
Biopsy studies have shown the ability of transplan Biopsy studies have shown the ability of transplanted cartilage to survive if placed in a mechanically advantageous position.

The advantage of small grafts is obvious. If the hyaline cartilage could survive, there would be a great expectation of resurfacing damaged areas with more congruence than when larger autografts are used.

Questions that persist revolve around the following:

  • The fate of the interstices between the cylindrical grafts
  • The importance of their size in what material forms in this area
  • The relative inability to resurface the entire defect area (see the image below)
  • The concept of "robbing Peter to pay Paul" by taking cartilage from a healthy part of the knee and placing it into a damaged site
The relative inability to resurface the entire def The relative inability to resurface the entire defect area is a persisting concern.

This is an exciting time for biologic resurfacing of weightbearing joints. Osteochondral transplants, in comparison with some of the other technical procedures available, have many advantages and few reported drawbacks. The goal is to resurface defects with hyaline cartilage in a one-step procedure. This procedure offers this opportunity without the need for support labs or additional costs.

True double-blind comparisons with a sufficient number of patients and lengthy follow-up time may never be possible. In this age of quickly adopting new and better procedures, zeal to repair these defects must be tempered by the lack of true understanding of whether patients are improving. With the available reports, it appears that osteochondral grafting is an efficacious procedure to restore these surfaces. However, controversy persists as to its place in the temporal scope of care of these patients. [2, 3, 4, 33, 34]

Numerous tissue-engineering studies for articular cartilage injuries are ongoing worldwide. Some of these studies have demonstrated that bioengineered cartilage tissue can regenerate when implanted in patients with cartilage injuries. [37, 38, 39, 40, 41]

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Open Approach

After arthroscopy, an arthrotomy is made over the involved area. A medial or lateral anterior sagittal arthrotomy can be used, as well as a transvastus or subvastus approach for lesions on the medial femoral condyle.

For defects of the femoral condyles, the incision should be long enough distally to allow viewing of the lesion with the knee flexed, and it should extend proximally to allow viewing of the superior aspect of the trochlea (where donor grafts can be obtained) with the knee in extension. For the patellofemoral joint, the incision should be long enough to rotate the patella 90° on a longitudinal axis.

Cartilage lesions are debrided sharply back to a circumferentially stable articular cartilage. Abrasion arthroplasty of the exposed subchondral bone is then carried out (see the image below). This is performed even though the surface will be resurfaced to encourage the interstices between the grafts to form a fibrocartilage grout or seal between the native cartilage and the grafts.

After identification of the lesion, all cartilage After identification of the lesion, all cartilage is removed down to the subchondral bone. The edges of the lesion are taken back to areas of well-attached hyaline cartilage. Abrasion of exposed subchondral bone.

Hangody showed that at 8 weeks postoperatively, the areas between the cartilage interfaces seal with fibrocartilage that is generated from the abraded subchondral area (see the first image below).

Hangody has shown that at 8 weeks postoperatively, Hangody has shown that at 8 weeks postoperatively, the areas between the cartilage interfaces seal with fibrocartilage that is generated from the abraded subchondral area.

The lesion is measured in an attempt to estimate the number and sizes of grafts that will appropriately fill the lesion. An instrument with a known size (generally supplied in the instrumentation) allows accurate measurement of the lesion (see the second image below). Controversy exists regarding whether larger or smaller grafts should be used. In either case, perpendicular access is critical.

The lesion is measured in an attempt to estimate t The lesion is measured in an attempt to estimate the number and sizes of grafts that will appropriately fill the lesion. An instrument with a known size (generally supplied in the instrumentation) allows for accurate measurement of the lesion.

The appropriate graft size for a given lesion is a matter of debate. Some believe that multiple smaller diameter (2.7 mm, 3.5 mm, and 4.5 mm) grafts should be used. Others believe that larger (>5 mm diameter) but fewer grafts should be used. No data conclusively favor one opinion over another; thus, the choice appears to be personal.

In either case, after the defect is sized, the sizes and number of grafts needed are estimated. The estimate is based on a combination of measurement and experience. Regardless of whether larger or smaller grafts are used, the first grafts obtained and placed are the larger of those chosen. After these are placed, the smaller grafts can be used to fine-tune any smaller gaps remaining.

Once the size of the grafts and the number of each size graft are determined, harvesting begins (see the image below). Typically, harvest sites include the superior trochlear ridge and the intercondylar notch area. Considerable debate exists regarding where the best hyaline cartilage for grafting can be harvested. The periphery of the supracondylar ridge is the most commonly used area, in that it has relatively thick hyaline cartilage, is relatively nonweightbearing, and is easily accessible in both  open and arthroscopic techniques.

Once the size of the grafts and the number of each Once the size of the grafts and the number of each size graft are determined, harvesting begins. Typically, harvest sites include the superior trochlear ridge and the intercondylar notch area.

Some reports have suggested use of the medial, rather than the lateral, side out of concern regarding earlier and greater patella contact on the lateral side during early flexion. The intercondylar area is useful as well, in that it can be approached arthroscopically, though fewer grafts are available because of the decreased surface area. (Previous reference has been made to questions regarding the quality and shape of the cartilage in this area.) With perpendicularity again being of utmost importance, appropriately sized grafts are harvested.

The various commercially available instrumentations have subtle differences, but the end result is that cylinders of osteochondral grafts are obtained. The devices used are specially designed tubular chisels, which allow harvesting of a core of hyaline cartilage, subchondral bone, and cancellous bone.

Care must be taken to obtain appropriate-length grafts for the defects being addressed. For chondral lesions, grafts generally are 15 mm in length, whereas for osteochondral defects, slightly longer (20 mm) grafts are needed. Grafts that are too short compromise the surface area of the press fit and are not stable enough. Longer (>20 mm) grafts generally are unnecessary. For the patella, slightly shorter grafts are used owing to its thickness, depending on the facet being resurfaced.

Commercial devices each have a particular way to break or cut the medullary bone base so that the core can be removed. Each has its own recommendations and admonitions for its use, which should be studied in detail.

While inside the harvesting device, the base of the graft is either cut or broken in a controlled manner. The extractor should not be spun to remove the harvester before the base is broken, because the graft may become loose in the device, making removal difficult. The grafts are removed from the device by tamping on the cancellous side to avoid damaging the hyaline cartilage.

After the graft is removed, it is inspected for damage. The hyaline cartilage thickness and its appropriate adherence to its subchondral bone are noted. In addition, the angle that the articular cartilage makes with the long axis of the cylinder is examined. Ideally, it should be perpendicular to this axis. The graft is placed in isotonic sodium chloride solution–soaked gauze.

The recipient site now is prepared. The periphery is the best place to start, and attention is directed to the surrounding surfaces, the radius of curvature, and the donor graft that has been obtained. With these factors in mind, an appropriate recipient hole is created, so that when filled with the donor graft, it will recreate the surface intended. These holes can be drilled, trephined, or cored, depending on the technique being used. The depth of holes varies. For chondral lesions, about 15 mm is needed, and for osteochondral lesions, 20 mm is necessary. The hole is inspected.

Some techniques call for impacting the internal cancellous bone of the created tunnel in order to remove any impediment to placement of the graft. The graft then is tamped gently into the recipient hole (see the image below). It need not bottom out, in that it is a circumferential press that creates stability. Once this is done, successive grafts are harvested and placed.

Graft insertion. Graft insertion.

Grafting is started at the periphery of the lesion, closest to the major part of the weightbearing area. The sequence of progression is to fill this major weightbearing periphery and work toward the center. As noted above, regardless of the commercial system being used, the larger of the grafts are used initially, followed by smaller grafts that fill in any gaps left by the larger grafts.

Depending on the number of grafts needed, spacing of the grafts must be planned. The grafts should not lie directly side by side, because stability will be compromised. Approximately 0.5-1 mm of bone is left between each graft. This ensures a solid wall for the press fit.

In addition, care must be taken so that convergence does not cause the grafts to hit each other, which will damage the cancellous bone of its base and affect its stability and ability to be fully seated. Occasionally, this cannot be avoided, because the radius of curvature changes too rapidly. If convergence happens at depth, this should not pose a problem.

In short, grafts should be inserted more for their tangency to the articular surface than to avoid deep convergence. Recipient holes generally are drilled 2-3 mm past the length of the individual donor grafts. The sequence of recipient hole creation and recipient hole filling is important because as recipient hole filling affects subsequent holes. Avoid the urge to save time by creating all of the holes first with the thought of filling them later.

It is acceptable to obtain multiple donor grafts if the size and numbers needed are adequate. As the defect is filled from the periphery, grafts progress from larger to smaller, enabling fine-tuning of the amount of coverage achieved.

Finally, the surface is examined to ensure that the grafts are at the proper depth. At first, it may be prudent to leave the grafts too proud (~1 mm) rather than too deep; extraction, though possible, can be difficult and risks damaging the grafts. The knee is taken through a final range of motion. Routine closure is done in layers. Use of a drain is optional.

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Arthroscopic Approach

The arthroscopic approach is technically challenging. Both location and lesion size determine whether the experienced surgeon chooses this route. Again, perpendicular access and portal placement are critical. Generally, portals are slightly more central than usual because the approach to the main weightbearing areas points more centrally than expected. After debridement and subchondral abrasion, the lesion is measured for size.

If the working portal being used does not appear to be perpendicular, knee flexion can be altered or a spinal needle can be used to reassess proper portal placement and perpendicular position. Multiple viewing angles are used to be sure that the measuring device is flush on the lesion from edge to edge to accurately gauge its size, to determine the number and size(s) of grafts needed, and to assess the direction that is perpendicular to the surface. This is more difficult arthroscopically, and experience with the open technique is beneficial here.

Donor grafts are obtained from either the supracondylar ridge or the intercondylar notch. The medial trochlea is easier to approach when the scope is used. As the knee inflates with fluid, the patella naturally moves laterally away from the medial ridge. The lateral side is used for the intercondylar notch. This site is useful when only a few grafts are needed. The supracondylar ridge can be approached with the arthroscopic donor instrumentation via a portal or small open incision. As in the open procedure, care must be taken to ensure that the harvesting device is perpendicular to the articular surface.

Generally, the ipsilateral inferior portal can be used to visualize the harvest sites. In taking multiple transplants arthroscopically, it is important to remember that the previous donor site must be visualized while subsequent grafts are taken. If the previous donor site cannot be seen, there is a risk of breaking into that site. Therefore, taking grafts in succession is suggested, going away from the visualization portal. In this way, the edge of the donor site can be seen and protected from being broken through.

Either a cylindrical chisel or a drill creates recipient holes. Care must be taken because significant changes of curvature radius necessitate marked changes in the approach angle of the device creating the recipient hole. Perform multiple visual checks before committing to coring or drilling. With some instrumentation devices, a dilator is used to smooth and compact the recipient canal of cancellous bone. This is helpful in arthroscopic procedures, in that irrigation fluid can cause narrowing of the canal secondary to cancellous bone swelling. In addition, debris can find its way into the canal and inhibit graft insertion.

The grafts are impacted into place with specialized tamps, and the next recipient hole is created if necessary, as in the image below. Wounds are closed in routine fashion, and a compression dressing is placed on the knee.

Graft insertion. Graft insertion.
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Postoperative Care

Controversy exists regarding postoperative protocols for these procedures. Some use fewer and larger grafts and recommend shorter (2- to 3-day) nonweightbearing periods. For most techniques and surgeons who have performed them, especially for larger lesions, when smaller grafts were used, a more cautious attitude toward weightbearing was initially adopted (6-8 weeks), but the approach has since become more aggressive (2-3 weeks).

Patients in Hangody's early series were encouraged to remain nonweightbearing for approximately 6-8 weeks to allow for cancellous bone healing. This period is not arbitrary; excessive compressive pressure may tend to force the transplants into a more recessed position prior to cancellous healing.

In his original animal studies with dogs in 1991, Hangody showed early 4-week healing of cancellous bone cylinders. However, when the animals were allowed to bear weight immediately after surgery, approximately one third of the grafts in weightbearing areas showed subsidence. None of the grafts in nonweightbearing areas showed any sign of subsidence. This prompted the suggestion of nonweightbearing for 6-8 weeks in early clinical practice.

Since 1994, in the largest series to date, Hangody has revised this suggestion to 2-3 weeks of nonweightbearing, with a slow progression through partial weightbearing on to full weightbearing over the following 2-3 weeks. Larger lesions probably necessitate a more conservative approach postoperatively because more grafts generally are used to resurface a larger area. At present, not enough follow-up information is available to determine what is needed for each size and depth of lesion. Smaller lesions may need less respite from weightbearing, but this area of discussion is still open to debate.

When surgery is performed on the trochlear groove, the retropatellar area, or both, weightbearing is allowed while a knee immobilizer is worn. This decreases the contact pressures at the patellofemoral joint. The immobilizer can be removed for sedentary activity and range-of-motion exercises during the initial 3-week postoperative period, followed by progressive unsupported weightbearing.

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Complications

Donor-site morbidity remains a concern for osteochondral transplantation. Hangody recognized a 3% complication rate, which included excessive postoperative bleeding (with the larger of his grafts) and donor-site pain. In the long term, he has not noted any deleterious effects of graft harvest.

Arthroscopic follow-up of the graft sites shows filling of the defects with connective tissue at depth and a fibrocartilage cap at the surface. In these situations, no evidence of degeneration is present at the site of or the opposite side of the joint. Work is under way on developing plugs to fill these defects so as to reduce the incidence of immediate postoperative bleeding and further promote filling of the defect.

Another concern is that the various techniques call for harvesting of osteochondral grafts from nonarticular areas. However, it has been demonstrated that these areas are indeed contact- and stress-bearing.

In a study specifically targeting donor sites, significant contact stresses were recorded from 0º to 110º of knee motion. This was done by creating donor site defects by obtaining round osteochondral plugs (8 mm in diameter) from some of the recommended sites. The lateral superior trochlear area above the femoral condyles and medial and lateral intercondylar notch areas were used as areas of harvest. Unfortunately, no data were reported from one of the more favored locations of harvest, the medial femoral condyle periphery of the patellofemoral joint.

No long-term studies demonstrate whether articular contact contributes to degenerative changes at these donor sites. However, data exist confirming increased stress concentration at the rim of weightbearing osteochondral defects in smaller lesions than these. The long-term clinical significance of these findings is unknown. Certainly, the utmost care must be taken to ensure that the areas of harvest are remote from major weightbearing areas.

Work currently is under way to assess bone cores and articular surfaces via magnetic resonance imaging (MRI). This will be helpful, in that the techniques learned should help improve the diagnosis of cartilage injuries and assess transplants.

During this assessment, an interesting observation has been made. Significant metallic debris has been noted at the sites of implantation of osteochondral plugs. The cause has not been definitively established; however, some of the devices that use disposable instruments for implantation are thought to be at potential risk for shedding metallic debris. The decreased tough material of disposable instruments comes into question; reported cases of outright device failure and collapse of coring devices may represent a more catastrophic failure, with more subtle failure and debris generation going unnoticed at the time of surgery.

The significance or long-term problems related to this debris is unknown, but its occurrence must be considered in the performance of postoperative MRI.

Computed tomography (CT) arthrography has been suggested as a potentially useful alternative to radiography or MRI for postoperative evaluation of osteochondral allograft transplants of the distal femur; however, it does not appear to predict functional outcome. [42]

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