We retrospectively reviewed 34 patients (43 knees) who underwent osteochondral allografting for osteonecrosis of the knee between 1984 and 2006. These patients declined prosthetic arthroplasty and were referred for consideration of allografting as an alternative to arthroplasty owing to their young age (younger than 50 years) and symptoms that did not respond to other treatment modalities and were enrolled in an Institutional Review Board-approved study to evaluate the effectiveness of osteochondral allografting for various knee diseases. All 34 patients were at least 2 years postoperative at the time they were identified from the database. Of these, 23 patients (29 knees) had received osteochondral allografts for osteoarticular lesions sustained secondary to steroid-associated osteonecrosis of the femoral condyles. One patient (one knee) was deceased attributable to his underlying condition and the status of his knee was not ascertained. The remaining 22 patients (28 knees) comprise the current study population, including 16 females and six males with an average age of 24.3 years (range, 16–44 years) and a mean body mass index of 21.5 (range, 17.1–28.1). All patients were referred for consideration of osteochondral allografting as an alternative to arthroplasty and presented with radiographic evidence of advanced, Stages III–IV (modified Ficat/Arlet stage) [12
] lesions at the time of surgery. All had a history of a medical diagnosis requiring prednisone use exceeding doses of 20 mg per day, but only two of 22 were actively receiving corticosteroid therapy at the time of surgery (Table ). All patients were evaluated preoperatively for limb malalignment with 54-inch standing radiographs and realignment osteotomy was ruled out as a treatment option before consideration of osteochondral allografting. No patients were lost to followup. All data were entered prospectively in an Institutional Review Board-approved clinical database.
Twelve of the surgeries involved only the left knee, four involved only the right, and six involved bilateral surgeries, for a total of 28 knees treated. Twenty-one knees had unicondylar lesions (12 lateral, nine medial), whereas seven knees had bicondylar involvement (medial and lateral femoral condyles in the same knee) and received allografts to both condyles. The mean total allograft surface area was 10.8 cm2 (range, 5.0–19.0 cm2). Thirteen of 28 (46%) knees had multiple grafts; these included grafts to both condyles in the case of bicondylar involvement, two grafts on the same condyle in the case of large lesions undergoing the plug technique, and additional nonstructural particulate bone grafting of necrotic areas beneath the osteochondral allografts in 18 of the 28 patients. Fourteen of 28 (50%) knees had an average of 1.5 previous surgeries (range, 1–5 surgeries), including arthroscopic debridement (seven), drilling (four), loose body removal (four), bone grafting (three), and distal femoral osteotomy (one). The remaining 14 had no prior surgery. The minimum followup in the 25 surviving grafts was 25 months (mean, 67 months; range, 25–235 months).
Preoperatively, donor and recipient were matched based on mediolateral dimension of the tibial plateau using a standard AP radiograph of the recipient corrected for magnification and direct measurement of the tibial width of the donor. No blood or tissue typing was performed and no immunosuppressive therapy was used. Fresh anatomically appropriate tissue was obtained from healthy donors aged 15 to 40 years who met the criteria of the American Association of Tissue Banks. Donor tissue was recovered within 24 hours of donor death and then processed and stored fresh at 4°C in tissue culture media (Modified Eagle’s Medium with 10% fetal bovine serum [Mediatech Inc, Herndon, VA]). Grafts were implanted between 5 and 21 days of donor death.
Surgery was performed with the patient in the supine position under tourniquet control using a full or mini-arthrotomy through a midline incision, as previously described [6
]. The necrotic lesion(s) was debrided to identify the location, size, and shape. These characteristics determined whether a shell (Fig. ) or plug type graft(s) was used. After initial debridement, graft beds were prepared down to healthy bleeding bone to a maximum depth of 12 mm (Fig. ). Lesions extending deeper than 12 mm were curetted out manually and particulate bone graft was placed before seating the osteochondral allograft. Allograft thickness did not exceed 12 mm and we considered a 50% viable, bleeding bone in the prepared host bed acceptable for graft placement. The grafts were prepared to match the prepared lesion in size, shape, and depth (Fig. ). Trial fittings were performed after the grafts were copiously pulse lavaged with saline to remove debris and marrow elements to decrease the immunogenicity of the graft. After grafts had been positioned and an acceptable fit and condylar reconstruction were established, fixation was supplemented using absorbable internal fixation devices or compression screws, if necessary, for graft stability (Fig. ). The use of supplemental screw fixation was determined on a case-by-case basis and typically used when grafts extended to the medial, lateral, or posterior edge of the condyle and therefore were uncontained and did not have a stable press fit. The decision to use a shell or plug graft depended on the size and location of the lesion. For example, lesions of the posterior femoral condyles were inaccessible to the instruments used for plug grafts and thus a shell technique was used. The shell technique involves fashioning the graft and recipient site into complementary geometric shapes (trapezoidal) using burrs and hand tools. More anterior lesions less than 30 mm in diameter (the maximum dimension of the available instruments) were treated with a round plug graft. The plug technique involves preparation of the lesion site with a reaming tool placed over a guide wire and preparing a cylindrical graft using a coring device (Fig. ). This requires placement of a guide wire and instruments perpendicular to the articular surface. Large, extensive lesions or long and narrow lesions were treated either with one trapezoidal shell graft or multiple overlapping round plugs, depending on which technique would result in the least amount of removal of healthy bone and cartilage. Seven of nine knees treated with the plug technique had multiple grafts. Regardless of the type of technique, no graft exceeded 12 mm in maximum thickness.
An intraoperative photograph shows the donor condyle with ink markings outlining dimensions of the planned shell allograft.
A lateral view of the prepared shell allograft shows the thickness of the compound graft aimed at restoring subchondral bone loss secondary to osteonecrosis.
A photograph shows a comparison view of the shell allograft (left) and removed pathologic recipient osteoarticular segment (right).
An intraoperative photograph of the osteochondral allograft in situ in anatomic position after fixation with five bioabsorbable chondral darts shows restoration of the weightbearing portion of the lateral femoral condyle.
An intraoperative photograph shows a reconstruction of the medial femoral condyle using two plug-type allografts.
Postoperative physical therapy included supervised ROM exercises and quadriceps strengthening. Closed chain exercises such as cycling were begun by 1 month after surgery. Weightbearing was limited to touch down for the first 6 weeks followed by gradual increases (single-crutch gait) until 3 months. Full weightbearing was allowed at 3 months if radiographs showed evidence of osseous integration of the graft (Fig. ). Unrestricted activities were allowed at 6 months with counseling regarding potential risks of high-impact loading activities.
A Rosenberg view radiograph taken 3 months postoperatively, of the same patient as in Fig. , shows ongoing osseointegration of the osseous graft portion and restoration of the left lateral femoral condyle articular surface.
Clinical evaluation was performed preoperatively and at 6 weeks, 3 months, 6 months, and annually thereafter, using a modified D’Aubigné and Postel (18-point) scale [3
], IKDC pain and function scores [8
], and Knee Society function scores [7
]. Patients unable to return for followup in person were contacted by telephone by one of us (SG), interviewed using a standardized questionnaire (Appendix 1
), and asked to provide radiographs and clinical examination from their local physician. Sixteen patients (19 knees) were examined by the authors and six patients (nine knees) were interviewed by telephone only. We used a modified D’Aubigné and Postel scale [3
] for assessing patients at each followup. Modification was made to the ROM component, with values relevant to the knee rather than the hip. This scale allots a maximum of six points each for absence of pain, knee ROM, and knee function, for a maximum total of 18 points. Any additional surgeries occurring on the operative joint were documented. Failure was defined as any subsequent operation on the allografted knee.
Radiographic evaluation for determination of allograft healing was performed by one unblinded observer (WDB) at 6 weeks, 3 months, 6 months, and 1 year. Three criteria were used to define healing: presence of bony trabeculae across the interface, disappearance of the initial radiolucent line between graft and host bone, and no change in position or fracture of the graft on serial radiographs. All patients completed the 1-year radiographic followup analysis. Fourteen knees (11 patients) had subsequent radiographic evaluation at a mean of 4.5 years (range, 2–7 years) to determine graft status. Failure was defined as resorption, collapse or fragmentation of the osseous portion of the graft, or loss of 50% of the initial joint space (representing the chondral portion of the allograft) in the involved compartment.
Preoperative and postoperative IKDC pain and function scores, Knee Society function scores, and the modified D’Aubigné and Postel scores were compared using nonparametric Wilcoxon signed-rank tests. Data were analyzed using SPSS® Version 13.0 (SPSS Inc, Chicago, IL).