DEFINITION

Articular cartilage lesions are focal, usually isolated, cartilage defects that may be either symptomatic or incidentally found.

Osteochondritis dissecans is an osteochondral lesion that occurs in adolescents and, therefore, may have different management ramifications from lesions in adults.

Lesions can be partial- or full-thickness, down to subchondral bone, or through subchondral bone. Lesions can be secondary to trauma or atraumatic, as is the case for osteochondritis dissecans.

Cases with a traumatic etiology may have associated ligamentous or meniscal injury.

Small full-thickness chondral defects may heal adequately with mechanically inferior fibrocartilage (primarily type I collagen), but larger defects often require cartilage transplant surgery to replace the damaged chondral surface.

 

 

ANATOMY

 

Articular cartilage is composed primarily of type II collagen.

 

 

Chondrocytes that produce the extracellular matrix are of mesenchymal stem cell origin. Osteochondral lesions may occur in all three compartments of the knee.

 

 

Chondral defects after a patellar dislocation typically are found on the medial patellar facet or lateral trochlea. Classically, osteochondritis dissecans occurs at the lateral aspect of the medial femoral condyle.

PATHOGENESIS

 

Osteochondral lesions may be traumatic or may have no known history of trauma (osteonecrosis).

 

Traumatic lesions may be caused by compaction, as with an anterior cruciate ligament tear and lateral-based osteochondral injury, or by a shearing mechanism, as seen with patellar dislocations.

 

Atraumatic lesions may be found in young persons, as is the case with osteochondritis dissecans, or in elderly persons, as seen with degenerative lesions.

 

The etiology of osteochondritis dissecans is uncertain. Traumatic, inflammatory, developmental, and ischemic causes have all been proposed but not proven.

 

NATURAL HISTORY

 

Few controlled, prospective outcome studies have been published.

 

The natural history for juveniles with nondisplaced osteochondritis dissecans is very favorable.

 

 

Those diagnosed as adults have a less favorable prognosis. In a study by Linden and Malmo,9 81% of patients had tricompartmental gonarthrosis at an average of 33 years follow-up.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patients with focal osteochondral lesions typically are active and young, ranging in age from adolescence to middle age.

 

 

Often, the history does not include a specific traumatic episode. History and physical findings can be subtle. Presentation is variable; it may mimic meniscal pathology, with intermittent pain and swelling.

 

Condylar defects may present with high-impact loading complaints, whereas patellofemoral defects may produce anterior knee pain-type complaints, with stairs and prolonged sitting causing symptoms.

 

Patients with large cartilage lesions who are candidates for osteochondral allograft transplant surgery may have a history of previous knee surgery and previous attempts at cartilage regeneration by other methods (eg, microfracture, autologous chondrocyte implantation, osteochondral autograft transplant). Many have underlying bony changes or deficient subchondral bone.

 

 

Physical findings can be nonspecific and may include joint effusion and painful range of motion. Tenderness at the defect, on either the condyle, patellar facets, or trochlea, may be elicited.

 

 

In the case of patellofemoral defects, patellar mobility and apprehension must be assessed. Ligament integrity must be determined.

 

Mechanical alignment must be assessed, and appropriate imaging studies obtained.

 

Failure to identify and address ligamentous deficiency or mechanical malalignment will lead to compromise of restorative cartilage procedures.

 

Physical examination of the knee should note the following:

 

 

Chronic or recurrent effusion associated with, although not predictive of, a chondral lesion

 

Pain at extremes of range of motion (ie, forced flexion or forced extension) may indicate meniscal pathology. An extension block may indicate a displaced meniscus tear or loose body. Osteochondral defects may cause decreased flexion via effusion or may have normal range of motion.

 

An isolated lesion may have point tenderness, although it often is difficult to palpate.

 

Increased patellar mobility may indicate generalized ligamentous laxity, increasing suspicion for patellar instability.

 

Mechanical axis views should be obtained if there is any malalignment noted on gait and stance analysis.

 

 

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FIG 1 • T2-weighted coronal (A), T1-weighted sagittal (B), and T2-weighted sagittal (C) MRI scans of a right knee with a medial femoral condyle osteochondral defect. D. Arthroscopic view of a large osteochondral defect. Full assessment of the lesion was not completed until the defect was débrided to stable rim.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Anteroposterior, lateral, and sunrise views are mandatory to determine overall knee condition, rule out diffuse degenerative arthritis, and assess patellar position within the trochlea.

 

Large chondral defects may not be visible on plain radiographs or may have a small radiodense bone fragment attached.

 

“Notch views” may better define more central lesions.

 

Long-leg mechanical axis views are mandatory in patients with malalignment on physical examination and should be considered in all candidates for osteochondral autograft transfer.

 

MRI is the best modality to determine the presence, size, and location of cartilage lesions, as well as to determine the integrity of menisci and ligaments. It will also offer information about the supporting bone surrounding the lesion (FIG 1A-C).

 

Arthroscopy remains the gold standard for evaluation of articular cartilage lesions (FIG 1D).

 

DIFFERENTIAL DIAGNOSIS

 

 

 

 

 

Meniscal tear Degenerative arthritis Patellar instability Bone contusion Avascular necrosis

 

Undiagnosed ligamentous injury

 

NONOPERATIVE MANAGEMENT

 

Patients with asymptomatic osteochondral lesions (often found incidentally on standard knee arthroscopy) may be candidates for nonoperative treatment.

 

Long-term studies may indicate an increased risk for degenerative arthritis with conservative management,9 but no randomized controlled studies exist.

 

 

Nonoperative treatment should consist of physical therapy to obtain or maintain painless, full range of motion. Aggravating impact activities should be avoided.

 

Patients may participate in sports as tolerated.

 

Unloader braces or shoe wedges may help alleviate mild symptoms.

 

SURGICAL MANAGEMENT

 

Osteochondral allograft transplantation often is a two-stage procedure.

 

The magnitude of the lesion and, occasionally, the diagnosis itself often are not appreciated until first-look arthroscopy (FIG 2).

 

Size and location of the cartilage lesion is determined.

 

 

Lesions 1 cm (>2 cm2) in diameter or larger are considered for allograft transplant. Smaller lesions may be amenable to microfracture or autograft cartilage transplant with single or

 

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multiple plugs. (Lesions with deficient subchondral bone are also considered for allograft transplant.)

 

 

 

 

FIG 2 • Patient positioning, with tourniquet, using a lateral post and footrest.

 

The remainder of the knee is inspected to ensure this is not a diffuse cartilage process and to examine the integrity of the cruciate ligaments and menisci.

 

Preoperative Planning

 

Mechanical alignment must be assessed and, if necessary, osteotomy planned for.

 

Templated radiographs are obtained for appropriate allograft sizing based on the medial-lateral dimension of the lesion.

 

The patient must be informed that there is no way to predict when an appropriate-sized donor will become available and that a moderate waiting period (weeks to months) may be required before surgery can be done.

 

Fresh osteochondral allografts are used. Frozen chondral grafts are associated with poor chondrocyte viability and are unacceptable.

 

Allografts are harvested within 24 hours of donor death.

 

Because of concerns of disease transmission, tissue is now stored at 4° C for a minimum of 14 days and

maximum of 28 days to allow for bacterial cultures and viral testing to be analyzed13 preserved for up to 4 days at 4° C.

 

Chondrocyte viability likely declines after 14 days6 and allografts generally should be implanted by 28 days.11,15,14

 

After 28 days, chondrocyte viability significantly declines.6

 

Tissue matching and immunologic suppression are unnecessary with osteochondral grafts.

 

Donors are screened with a multifactorial process promoted by the American Association of Tissue Banks to minimize the risk of disease transmission. The allograft is tested for hepatitis B virus (HBV), hepatitis C virus (HCV), HIV, and syphilis.

 

Positioning

 

We prefer to have the patient supine, keeping the foot of the table up.

 

 

A lateral post and sliding footrest or taped sandbag allow for 90-degree flexion positioning of the knee. The surgeon should be able to flex the knee to 120 degrees if needed.

 

A tourniquet is placed but is inflated only if visualization is compromised by intra-articular bleeding.

 

Approach

 

The approach depends on the location of the defect.

 

The defect typically is on the medial or lateral femoral condyle, requiring a longitudinal parapatellar tendon arthrotomy.

 

Large trochlear or patellar defects amenable to osteochondral allograft transplantation (rare) may require a larger parapatellar incision and eversion of the patella.

 

TECHNIQUES

• Femoral Condyle Osteochondral Allograft Transplant

Diagnostic Arthroscopy

 

 

A brief diagnostic arthroscopy is performed to fully assess or reassess the condylar defect (TECH FIG 1A) as well as to examine for additional knee pathology and any changes from the original arthroscopy.

 

A standard parapatellar arthrotomy is carried out to expose the defect on the affected side of the knee. It is lateral for a lateral femoral condylar defect and medial for a medial femoral condylar defect (TECH FIG 1B).

Sizing

 

The size of the defect is determined using a cannulated cylindrical sizing device.

 

 

 

TECH FIG 1 • A. Arthroscopic view of a large osteochondral defect. B. Open view of a large osteochondral defect.

 

 

A circumferential mark is placed around the sizer to outline the margins of the defect to be grafted (TECH FIG 2A).

 

Occasionally, a chondral defect is large or irregularly shaped, and requires more than one allograft. The resultant graft may be in the form of a “snowman,” with two or even three differently sized circular grafts stacked on top of one another.

 

A central guide pin is placed through the sizer into bone to a depth of 2 to 3 cm. The sizer is then removed (TECH FIG 2B).

 

A reference mark is placed at the superior (12 o'clock) position of the recipient site.

Recipient Site Preparation

 

The recipient site is prepared by first scoring the periphery of the lesion (TECH FIG 3A).

 

Next, a counterbore or reamer is used to drill the defect to a depth of 8 to 10 mm circumferentially, to bleeding subchondral bone (TECH FIG 3B).

 

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TECH FIG 2 • A. Sizing of osteochondral defect. B. Placement of a central pin through the center of the sizer into the center of the defect after circumferential marking of the sizer on the condyle.

 

 

Following that, the recipient bed should be drilled with a small (1.6 to 2.0 mm) drill bit to stimulate additional vascular response (TECH FIG 3C).

 

The recipient site depth is then measured in four positions, as on the face of a clock: 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock. This may be done using a standard paper ruler or by a measuring device supplied by the equipment company (TECH FIG 3D).

 

 

 

TECH FIG 3 • A. Scoring of peripheral cartilage. Note placement of the 12 o'clock reference mark. B. Counterbore reaming of a defect, over the central pin, to a depth of 8 to 10 mm. C. Recipient site reamed to subchondral bone and drilled with 2.0-mm drill bit to enhance subchondral bleeding. D. Measuring of defect depth.

 

 

The depth of the recipient site may not be precisely consistent throughout its circumference. Donor modification will allow for fine-tuning.

Donor Preparation

 

The same sizer used for defect sizing is used to template the allograft hemicondyle on the back table. Careful comparison of defect location (eg, relative to femoral notch) and donor position is imperative to ensure optimal donor-recipient fit (TECH FIG 4A,B).

 

We use the Arthrex Osteochondral Allograft Transfer System (OATS) Workstation (Naples, FL) to help secure the donor graft. This instrument allows for multiple degrees of freedom while positioning and contouring the graft (TECH FIG 4C).

 

The angle of harvest of the donor tissue must match the angle at which the recipient site was reamed (TECH FIG 4D).

 

Next, the donor osteochondral plug(s) is harvested. The Arthrex system makes it possible to completely

drill through the donor condyle, which is held in place with the OATS Workstation. The relevant donor graft tissue is then carefully removed from the harvester drill (TECH FIG 4E,F).

Graft Harvest

 

The graft depth is now measured and marked to the precise degree that the recipient bed was measured in the same four quadrants.

 

The graft is held using allograft holding forceps, similar to the manner in which the patella is prepared during total knee arthroplasty. The graft cut is made using a power saw, with care taken to match the cut to the previously made depth measurements. The osteochondral portion of the graft should be held within the forceps, so as not to drop the relevant portion of the graft once the cut is completed (TECH FIG 5A-C).

 

P.437

 

 

 

TECH FIG 4 • A. Comparing donor hemicondyle to recipient condyle, to specifically localize donor site. B. Schematic of intraoperative donor-recipient matching. C,D. Donor graft workstation. E. Perpendicular drilling of donor condyle. F. Precontoured donor plug.

 

 

 

TECH FIG 5 • A. Donor plug. B. Sawing of excess subchondral bone to exact depth of four quadrants of recipient site. C. Diagram of sawing excess bone at precise quadrant levels. (continued)

 

 

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TECH FIG 5 • (continued) D. Contouring of osteochondral plug. E. Fully contoured and bulletized osteochondral plug.

 

 

The bony end of the graft's edges should be slightly rounded, or “bulletized,” to ease insertion of the graft into the recipient socket (TECH FIG 5D,E).

Delivery

 

Before graft insertion, the recipient bed may be further prepared by using a dilator to widen the socket by

0.5 mm and to smooth the socket surfaces. (This step is optional.)

 

TECH FIG 6 • A. Manual graft insertion. B. Diagram of insertion using graft delivery tube. C. Final graft, open. D. Final graft, as seen through the arthroscope. E. Three-month follow-up with a secondlook arthroscopy.

The graft is then inserted manually after lining up the 12 o'clock position recipient and donor reference marks (TECH FIG 6A). If the press-fit method is inadequate, an appropriately sized tamp is used to gently tap the graft into position (TECH FIG 6B).

Additional fixation usually is unnecessary (TECH FIG 6C-E).

 

 

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PEARLS AND PITFALLS
	Full-length radiographs to check alignment should be ▪ Malalignment must be corrected considered in all patients. before or during the OATS procedure.   Guide pin insertion at the recipient site must be ▪ Mismatch positioning between perpendicular and in the center of the lesion. Donor graft recipient and donor will risk early must be harvested in same perpendicular plane. failure of the graft.   Excess donor condyle should be removed with a power ▪ A large condylar block will not fit in saw before it is placed in the workstation. the workstation.   Donor graft undergoes pulse lavage before final ▪ Removal of marrow elements from preparation. bone will minimize subtle immune response about the allograft plug.

 

 

 

	The recipient bed should be drilled with a small, 1.6-mm ▪ Minimal drilling should be done, drill bit to enhance vascular response. avoiding fracture of subchondral bone.     Bony edges of the donor plug should be rounded with a ▪ Sharp edges may make insertion of rongeur to aid insertion. graft more challenging.

 

POSTOPERATIVE CARE

 

Patients typically are discharged home the day of surgery.

 

 

An ice cuff about the knee helps alleviate postoperative pain and swelling. Bracing is not indicated for isolated OATS.

 

Continuous passive motion begins on day 1 and progresses to full as tolerated; typically 0 to 60 degrees on postoperative day 1, then increased by 5 degrees per day; however, there are no passive range-of-motion restrictions.

 

Patients are given strict non-weight-bearing instructions.

 

 

Our preference is strict non-weight bearing for 8 weeks followed by partial weight bearing for another 4 weeks. Patients may be expected to return to full activities by 6 to 8 months.

 

 

OUTCOMES

Gross et al4 reported on 60 fresh femoral osteochondral allografts at an average of 10 years and 65 fresh tibial plateau osteochondral allografts at 11.8 years (average) with 84% good/excellent results and 86% good/excellent results, respectively, for posttraumatic defects.

Kaplan-Meier survivorship analysis determined 95% survival at 5 years, 85% at 10 years, and 74% at 15 years for femoral grafts.

Tibial allografts were reported to have 95% survivorship at 5 years, 80% at 10 years, and 65% at 15 years.

We determined no negative outcome with meniscal transplant or limb realignment surgery.

 

Shasha et al12 reported the results of 60 fresh femoral allografts for varying etiologies (ie, posttraumatic, osteoarthritis, osteonecrosis, and osteochondritis dissecans) with an average follow-up of 10 years.

Survivorship data revealed 95% survivorship at 5 years, 85% at 10 years, and 74% at 15 years, with 84% good/excellent results and 12 graft failures.

Bakay et al1 reported 22 good/excellent results in 33 patients at 2 years follow-up with cryopreserved or cryoprotected osteochondral allografts in the femur, tibial plateau, and patella.

Jamali et al5 reported the results of 20 fresh osteochondral allografts in the patellofemoral joint at 94 months follow-up with 12 good/excellent results and 5 failures.

Kaplan-Meier survivorship data determined 67% survivorship at 10 years.

 

Davidson et al3 reported on 10 knees treated with hypothermically stored osteoarticular allograft with a

 

mean follow-up of 40 months. Mean time from donor death to implantation was 36 days. Significant improvements were seen with IKDC, Lysholm, SF-36 physical scores. ICRS was nearly normal at 10 out of 12. Mean thickness of the allograft specimen biopsy at second-look arthroscopy was 3.2 mm, compared to 3.3 mm in the native cartilage. Chondrocyte viability was 78%. Follow-up MRI showed incorporation of the bony component of the graft in all cases.

McCulloch et al10 reported on 2-year outcomes of 25 patients in a prospective study. Significant improvements were seen in multiple standardized outcome measures and 88% graft incorporation rate.

LaPrade et al7 prospectively studied 25 knees treated with refrigerated osteochondral allograft implanted between 14 and 28 days from harvest with 3-year follow-up. Significant improvements were seen in outcomes. No failures were seen and 22/23 of grafts incorporated.

Levy et al8 reported the result of 129 knees that underwent femoral osteochondral allograft with median follow-up of 13.5 years. Sixty-one (47%) knees underwent reoperation. Survivorship was 82% at 10 years, 74% at 15 years, and 66% at 20 years. Age older than 30 years and having two or more prior procedures on the operative knee were predictive of failure.

Chahal et al2 performed a systematic review of level IV studies that evaluated clinical outcomes of patients that underwent osteochondral allograft of the knee. Nineteen studies with a total of 644 knees were reviewed. Mean follow-up was 54 months. Most common indications were posttraumatic (38%), osteochondritis dissecans (30%), osteonecrosis (12%), and idiopathic (12%). Sixty-five percent showed little or no arthritis at final follow-up. Short-term complication rate was 2.4% and failure rate was 18%.

 

 

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COMPLICATIONS

Infection Stiffness

Thromboembolic events Reflex sympathetic dystrophy Graft dislodgment/failure

 

 

REFERENCES

1. Bakay A, Csonge L, Papp G, et al. Osteochondral resurfacing of the knee joint with allograft: clinical analysis of 33 cases. Int Orthop 1998;22:277-281.

    

    

2. Chahal J, Gross AE, Gross C, et al. Outcomes of osteochondral allograft in the knee. Arthroscopy 2013;29(3):575-588.

    

    

3. Davidson PA, Rivenburgh DW, Dawson PE, et al. Clinical, histologic, and radiographic outcomes of distal femoral resurfacing with hypothermically stored osteoarticular allografts. Am J Sports Med 2007;35:1082-1090.

    

    

4. Gross AE, Shasha N, Aubin P. Long-term follow-up of the use of fresh osteochondral allografts for post-

   traumatic knee defect. Clin Orthop Rel Res 2005;435:79-87.

    

    

5. Jamali AA, Emmerson BC, Chung C, et al. Fresh osteochondral allografts. Clin Orthop Rel Res 2005;437:176-185.

    

    

6. Kwan MK, Wayne JS, Woo SL, et al. Histological and biomechanical assessment of articular cartilage from stored osteochondral shell allografts. J Orthop Res 1989;7:637-644.

    

    

7. Laprade RF, Botker J, Herzog M, et al. Refrigerated osteoarticular allografts to treat cartilage defects of the femoral condyles: a prospective outcomes study. J Bone Joint Surg Am 2009;91(4):805-811.

    

    

8. Levy Y, Gortz S, Pulido P, et al. Do fresh osteochondral allografts successfully treat femoral condyle lesions? Clin Orthop Relat Res 2013;471:231-237.

    

    

9. Linden B, Malmo S. Osteochondritis dissecans of the femoral condyles. J Bone Joint Surg Am 1977;59:769-776.

    

    

10. McCulloch PC, Kang RW, Sobhy M, et al. Prospective evaluation of prolonged fresh osteochondral allograft transplantation of the femoral condyle: minimum 2-year follow-up. Am J Sports Med 2007;35:433-420.

     

     

11. Pearsall AW IV, Tucker JA, Hester RB, et al. Chondrocyte viability in refrigerated osteochondral allografts used for transplantation within the knee. Am J Sports Med 2004;32:125-131.

     

     

12. Shasha N, Aubin PP, Cheah HK, et al. Long-term clinical experience with fresh osteochondral allografts for articular knee defects in high demand patients. Cell Tissue Bank 2002;3:175-182.

     

     

13. William JM, Virdi AS, Pylawka TK, et al. Prolonged-fresh preservation of intact whole canine femoral condyles for the potential use as osteochondral allografts. J Orthop Res 2005:23:831-837.

     

     

14. Williams RJ III, Dreese JC, Chen CT. Chondrocyte survival and material properties of hypothermically stored cartilage: an evaluation of tissue used for osteochondral allograft transplantation. Am J Sports Med 2004;32(1):132-139.

     

     

15. Williams SK, Amiel D, Ball ST, et al. Prolonged storage effects on the articular cartilage of fresh human osteochondral allografts. J Bone Joint Surg Am 2003;85:2111-2120.