Operative Techniques in Orthopaedic Surgery (4 Volume Set) 1st Edition

39. Allograft Cartilage Transplantation

Eric C. McCarty, R. David Rabalais, and Kenneth G. Swan, Jr.

DEFINITION

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

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

images Lesions can be partialor full-thickness, down to subchondral bone.

images Lesions can be secondary to trauma or atraumatic, as is the case for osteochondritis dissecans.

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

images 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

images Articular cartilage is composed primarily of type II collagen.

images Chondrocytes that produce the extracellular matrix are of mesenchymal stem cell origin.

images Osteochondral lesions may occur in all three compartments of the knee.

images Chondral defects after a patellar dislocation may be found on the medial patellar facet or lateral trochlea.

images Classically, osteochondritis dissecans occurs at the lateral aspect of the medial femoral condyle.

PATHOGENESIS

images Osteochondral lesions may be traumatic or may have no known history of trauma.

images 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.

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

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

NATURAL HISTORY

images Few controlled, prospective outcome studies have been published.

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

images Those diagnosed as adults have a less favorable prognosis. In one study, 81% of patients had tricompartmental gonarthrosis at an average of 33 years follow-up.5

PATIENT HISTORY AND PHYSICAL FINDINGS

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

images Often, the history does not include a specific traumatic episode. History and physical findings can be subtle.

images Presentation is variable; it may mimic meniscal pathology, with intermittent pain and swelling.

images 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.

images 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).

images Physical findings can be nonspecific and may include joint effusion and painful range of motion.

images Tenderness at the defect, on either the condyle, patellar facets, or trochlea, may be elicited.

images In the case of patellofemoral defects, patellar mobility and apprehension must be assessed.

images Ligament integrity must be determined.

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

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

images Physical examination of the knee should note the following.

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

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

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

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

images Mechanical axis views are obtained if there is any hint of malalignment based on gait and stance analysis.

IMAGING AND OTHER DIAGNOSTIC STUDIES

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

images

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.

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

images “Notch views” may better define more central lesions.

images 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.

images 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 (FIG 1AC).

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

DIFFERENTIAL DIAGNOSIS

images Meniscal tear

images Degenerative arthritis

images Patellar instability

images Bone contusion

images Avascular necrosis

images Undiagnosed ligamentous injury

NONOPERATIVE MANAGEMENT

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

images Long-term studies may indicate an increased risk for degenerative arthritis with conservative management,5 but no randomized controlled studies exist.

images Nonoperative treatment should consist of physical therapy to obtain or maintain painless, full range of motion.

images Aggravating impact activities should be avoided.

images Patients may participate in sports as tolerated.

images Unloader braces or shoe wedges may help alleviate mild symptoms.

SURGICAL MANAGEMENT

images Osteochondral allograft transplantation often is a two-stage procedure.

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

images Size and location of the cartilage lesion is determined.

images Lesions 1 cm in diameter or larger are considered for allograft transplant. Smaller lesions may be amenable to microfracture or autograft cartilage transplant with single or mutliple plugs.

images

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

images 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 mensici.

Preoperative Planning

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

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

images 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.

images Fresh osteochondral allografts are used. Frozen chondral grafts are unacceptable.

images Allografts are harvested within 24 hours of donor death and can be preserved for up to 4 days at 4° C.

images Chondrocyte viability likely declines after 5 days, but prolonged storage—up to 21 days—currently is acceptable.6

images After 28 days, chondrocyte viability is unacceptably diminished.4

images Tissue matching and immunologic suppression are unnecessary with osteochondral grafts.

images Donors are screened with a multifactorial process promoted by the American Association of Tissue Banks to minimize the risk of disease transmission.

Positioning

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

images A lateral post and sliding footrest or taped sandbag allow for 90-degree flexion positioning of the knee.

images The surgeon should be able to flex the knee to 120 degrees if needed.

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

Approach

images The approach depends on the location of the defect.

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

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

TECHNIQUES

FEMORAL CONDYLE OSTEOCHONDRAL ALLOGRAFT TRANSPLANT

Diagnostic Arthroscopy

images A brief diagnostic arthroscopy is peformed 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.

images

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

images 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

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

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

images 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.

images 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).

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

Recipient Site Preparation

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

images 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).

images 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).

images 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).

images

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.

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

Donor Preparation

images 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).

images 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).

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

images 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

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

images 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 5AC).

images

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.

images

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.

images

images

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. D. Contouring of osteochondral plug. E.Fully contoured and “bulletized” osteochondral plug.

images 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

images 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.)

images The graft is then inserted manually, after lining up the 12 o'clock 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).

images Additional fixation usually is unnecessary (TECH FIG 6CE).

images

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.

images

POSTOPERATIVE CARE

images Patients typically are discharged home from same-day surgery.

images An ice cuff about the knee helps alleviate postoperative pain and swelling.

images Bracing is not indicated for isolated OATS.

images Continuous passive motion is begun on day 1 and progressed 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.

images Patients are given strict non–weight-bearing instructions.

images Our preference is strict non–weight bearing for 8 weeks, followed by partial weight bearing for another 4 weeks.

images Patients may be expected to return to full activities by 6 to 8 months.

OUTCOMES

images Gross et al2 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.

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

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

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

images Shasha et al7 reported the results of 60 fresh femoral allografts for varying etiologies (ie, posttraumatic, osteoarthritis, osteonecrosis, osteochondritis dissecans) with an average follow-up of 10 years.

images 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.

images 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.

images Jamali et al3 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.

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

COMPLICATIONS

images Infection

images Stiffness

images Thromboembolic events

images Reflex sympathetic dystrophy

images 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.     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.

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

4.     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.

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

6.     Shahgaldi BF, Amis A, Heatley FW. Repair of cartilage lesions using biological implants. A comparative histological and biomechanical study in goats. J Bone Joint Surg 1991;73B:57–65.

7.     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 and Tissue Banking 2002;3:175–182.



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