The use of a single osteochondral autograft plug in the treatment of a large osteochondral lesion in the femoral condyle: an experimental study in sheep

BACKGROUND: The use of osteochondral autograft plugs can be restricted because of limited amount of donor material. HYPOTHESIS: A small osteochondral autograft plug placed in the center of a large defect in a sheep femoral condyle will yield results superior to either an untreated or a bone-grafted defect. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve adult sheep underwent bilateral hindlimb surgery. On 1 limb, a 6-mm circular osteochondral autograft plug was placed in the center of a 10-mm circular defect in the medial femoral condyle. The gap between the plug and the condyle was filled with bone graft. On the contralateral side, the defect was either left untreated or filled with bone graft (control specimens). Animals were studied at 6 and 12 months under gross examination, high-resolution radiography, and histologic evaluation. RESULTS: At 6 months, 4 of 6 plugs healed and showed good maintenance of the joint surface and cartilage viability in the plugs. One plug fractured and resorbed, and 1 plug settled but healed. At 1 year, all 5 plugs healed, 1 having settled slightly (1 animal died earlier). The plug specimens showed better maintenance of the condyle contour at both times, and the central plug had hyaline-appearing cartilage. The control specimens were more irregular, had a fibrocartilage fill, and appeared flatter, although no gross cavitation or collapse was indicated. Composite cartilage scores on histologic evaluation were significantly higher for the plug specimens after 6 months (P = .02) and 1 year (P = .036) compared with controls. CONCLUSION: At 6 months and 1 year, a 6-mm osteochondral plug placed in a 10-mm defect better preserved the articular surface and contour of the condyle compared to untreated or bone-grafted defects. CLINICAL RELEVANCE: Osteochondral autograft plugs may be able to treat larger articular lesions without complete fill of the defect.     

Mechanical effects of autogenous osteochondral surgical grafting procedures and instrumentation on grafts of articular cartilage

PURPOSE: To analyze the mechanical effects of autogenous osteochondral grafting procedures on articular cartilage. METHODS: The intensity, duration, and interval (indexes of stiffness, surface irregularity, and thickness) of the cartilage were assessed in a porcine model using an ultrasonic measurement system. In 7 of 12 knees, 6-mm-diameter plugs were harvested from the donor knees and grafted into 5-mm recipient holes at 3 different points per knee (21 plugs). In the remaining 5 knees, 5-mm plugs were harvested and returned to their original position (28 plugs). RESULTS: No significant differences in the intensity, duration, and interval of the cartilage were observed with the plugs before harvesting and after grafting by the paired t test. The 3 indexes of the 6- and 5-mm plugs that were grafted correlated significantly with those before they were. CONCLUSIONS: These results suggest that osteochondral graft surgery does not affect the stiffness, surface irregularity, and thickness of the cartilage of the plugs at time zero.     

The effect of graft height mismatch on contact pressure following osteochondral grafting: a biomechanical study

HYPOTHESIS: Incongruity of the articular cartilage following osteochondral transplantation affects surface contact pressure. STUDY DESIGN: An 80 N load was applied for 120 seconds to the femoral condyles of 10 swine knees. Contact pressures were measured using Fuji prescale film. Seven conditions were tested: (1) intact articular surface; (2) 4.5-mm diameter defect; (3) grafted with 4.5-mm diameter plug elevated 1 mm above adjacent cartilage; (4) plug elevated 0.5 mm; (5) plug flush; (6) plug sunk 0.5 mm below surface; and (7) sunk 1.0 mm. CONCLUSIONS: Peak contact pressures were significantly (P <.001) elevated by approximately 20% after defect creation and were reduced to normal when plugs were flush. There were large and significant (P<.001) increases in pressure with plugs elevated 1 and 0.5 mm. Contact pressures with plugs sunk 0.5 and 1 mm were significantly (P <.01) higher than intact cartilage but were significantly (P <.01) lower than an empty defect. Clinical Relevance: Normal contact pressures and patterns can be duplicated with flush articular surface grafts. However, small incongruities, particularly when the plug is elevated, can lead to significantly increased pressure. This reinforces the importance of articular surface congruity in the initial biomechanical state following osteochondral implantation.     

Mechanical behavior of articular cartilage after osteochondral autograft transfer in an ovine model

BACKGROUND: Grafting of autologous hyaline cartilage and bone for articular cartilage repair is a well-accepted technique. Although encouraging midterm clinical results have been reported, no information on the mechanical competence of the transplanted joint surface is available. HYPOTHESIS: The mechanical competence of osteochondral autografts is maintained after transplantation. STUDY DESIGN: Controlled laboratory study. METHODS: Osteochondral defects were filled with autografts (7.45 mm in diameter) in one femoral condyle in 12 mature sheep. The ipsilateral femoral condyle served as the donor site, and the resulting defect (8.3 mm in diameter) was left empty. The repair response was examined after 3 and 6 months with mechanical and histologic assessment and histomorphometric techniques. RESULTS: Good surface congruity and plug placement was achieved. The Young modulus of the grafted cartilage significantly dropped to 57.5% of healthy tissue after 3 months (P < .05) but then recovered to 82.2% after 6 months. The aggregate and dynamic moduli behaved similarly. The graft edges showed fibrillation and, in some cases (4 of 6), hypercellularity and chondrocyte clustering. Subchondral bone sclerosis was observed in 8 of 12 cases, and the amount of mineralized bone in the graft area increased from 40% to 61%. CONCLUSIONS: The mechanical quality of transplanted cartilage varies considerably over a short period of time, potentially reflecting both degenerative and regenerative processes, while histologically signs of both cartilage and bone degeneration occur. CLINICAL RELEVANCE: Both the mechanically degenerative and restorative processes illustrate the complex progression of regeneration after osteochondral transplantation. The histologic evidence raises doubts as to the long-term durability of the osteochondral repair.     

Osteochondral autograft transplantation in the porcine knee

BACKGROUND: Knee articular cartilage defects are not an uncommon problem. Because articular cartilage is limited in its ability to heal, these defects are difficult to manage. HYPOTHESIS: Osteochondral autografts will provide less of a cavitary defect and more viable hyaline articular cartilage than will control knees. STUDY DESIGN: Controlled laboratory study. METHODS: Osteochondral autografts were grossly and microscopically evaluated in the porcine knee and compared with a control at 6 weeks, 3 months, and 6 months. In 18 porcine specimens, a 1-stage surgical procedure was performed to harvest an osteochondral graft from a nonweightbearing articular cartilage surface, and the graft was transplanted into a defect created in the weight-bearing region of the medial femoral condyle. In the opposite control knee, a similar defect was created in the medial femoral condyle; an osteochondral transplant was not performed. Six pigs each were sacrificed at 6 weeks, 3 months, and 6 months. RESULTS: Gross inspection of the control knees showed a cavitary defect. The defect grossly decreased in size with fibrous ingrowth seen on microscopic analysis. An increasing amount of fibrous tissue and fibrocartilage was present at the 3 time periods. Gross inspection of the graft knee showed a healed osteochondral plug with no obvious displacement, cavitary defects, or surrounding necrotic tissue at each time interval. Microscopic analysis revealed the graft knee contained viable hyaline cartilage and healed viable subchondral bone. At all time intervals, 75% to 100% of the hyaline cartilage was viable in all specimens. In 6-month specimens, bridging cartilage at the autograft-host junction was incomplete in 50%, partial in 33%, and complete in 17%. CONCLUSION: Osteochondral autografts in the porcine knee resulted in viable hyaline cartilage for up to 6 months; there was inconsistent bridging hyaline cartilage at the periphery. Grafts appeared to heal into existing subchondral bone without displacement or evidence of necrosis. CLINICAL RELEVANCE: This type of osteochondral transplant can be used as a reliable reconstructive alternative for osteochondral defects.     

The effect of angled osteochondral grafting on contact pressure: a biomechanical study

BACKGROUND: Flush osteochondral plugs can reduce contact pressure compared with an empty defect in the articular cartilage. However, incongruities such as graft angulation have an unknown effect. HYPOTHESIS: Incongruity of the articular cartilage after osteochondral transplantation affects articular surface contact pressure. STUDY DESIGN: Controlled laboratory study. METHODS: An 80-N load was applied with a material testing system for 120 seconds to the femoral condyles of 50 fresh swine knees. Contact pressures were measured using Prescale super low film. Five conditions were tested: (1) intact articular surface; (2) surface with 4.5-mm-diameter circular defect; (3) defect grafted with a flush 4.5-mm-diameter plug from the contralateral condyle; (4) defect grafted with a 30 degrees angled 4.5-mm-diameter plug, with lower edge flush (tip elevated with respect to the adjacent surface); and (5) defect grafted with a 30 degrees plug, with tip flush to the adjacent surface (lower edge sunk). Angled grafts were obtained using a rotational bearing vise aligned with a 30 degrees fixed-angle track. The film was digitally scanned and analyzed, and standard statistical tests were performed. RESULTS: Mean peak pressures of intact cartilage (8.57 kg/cm2), flush graft (9.81 kg/cm2), and sunk and angled graft (9.15 kg/cm2) were not significantly different (P < .5). The mean pressures for defects (12.01 kg/cm2) and the elevated angled graft (14.50 kg/cm2) were significantly (P < .05) higher than that of intact cartilage. CLINICAL RELEVANCE: Slightly sunk grafts were still able to reduce elevated contact pressures to normal levels. However, elevated angled grafts increased contact pressure. These results suggest that it is preferable to leave an edge slightly sunk rather than elevated.     

An analysis of surface profile for cylindrical osteochondral grafts of the knee quantitative evaluation using a three-dimensional laser scanner

Purpose

To investigate the congruency of the articular cartilage surface of the knee between the recipient and donor site during autogenous osteochondral grafting using a three-dimensional (3D) laser scanning.

Methods

Six cadaveric knees were included in this study. The 3D profiles of the articular surface were obtained by a 3D laser scanner (FastSCAN^®, Polhemus). We divided each of the donor and recipient sites into 6 areas in each. The 2 central areas of the donor site were excluded from evaluation because of the trochlear groove. In the donor site, the peripheral and the middle one-third of the femoral articular surface in the medial and lateral patellofemoral joint were extracted. In the recipient site, the peripheral and the middle one-third of the articular surface in the medial and lateral femoral condyle were assessed. In each recipient area, vertical intervals (VIs) of grafts of 6, 8, and 10 mm diameter, showing the distance between highest and lowest point of articular surface were calculated from the data obtained and to the donor sites for matching.

Results

?6- and ?8-mm grafts The VI of the middle area of the donor site did not differ significantly from that of either the peripheral or the middle area of the recipient site. The VI of the peripheral area of the donor site was significantly higher than that of the peripheral area of the recipient site (p < 0.01). ?10-mm grafts The VI of the middle area of the donor site was significantly lower than that of the peripheral area of the recipient site. The VI of the peripheral area of the donor site was significantly higher than that of the middle area of the recipient site (p < 0.01).

Conclusions

An osteochondral graft harvested from the peripheral area of the patellofemoral joint might protrude into the middle area in the recipient site, whereas a ?10-mm osteochondral graft harvested from the middle area might be depressed from the peripheral area into the recipient site.     

Effects of small incongruities in a sheep model of osteochondral autografting

BACKGROUND: Exact reconstruction of an osteochondral defect by autogenous transplantation (mosaicplasty) is difficult given the variation in joint surface contour. Clinical and experimental studies do not show the extent to which incongruity can be tolerated in autografting. HYPOTHESIS: Grafted articular cartilage will hypertrophy to correct the incongruity created by recession of the transplanted surface. STUDY DESIGN: Controlled laboratory study. METHODS: To test the response of grafts to incongruities, osteochondral autografts were transplanted from the trochlea to the femoral condyle in adult male sheep stifle joints. In groups of 6 animals, graft surfaces were placed flush, countersunk 1 mm or countersunk 2 mm, then histologically analyzed 6 weeks after surgery. Cartilage thickness, condition of the articular surfaces, and preservation of hyaline characteristics were the primary features compared. RESULTS: Bony union, vascularization, and new bone formation were present in all grafts. Cartilage-to-cartilage healing did not occur. In flush specimens, cartilage changed minimally in thickness and histologic architecture. The specimens countersunk 1 mm demonstrated significant cartilage thickening (54.7% increase, P <.05). Chondrocyte hyperplasia, tidemark advancement, and vascular invasion occurred at the chondroosseous junction, and the surface remained smooth. Cartilage necrosis and fibrous overgrowth were observed in all grafts countersunk 2 mm. CONCLUSIONS: Minimally countersunk autografts possess a capacity for remodeling that can correct initial incongruities while preserving hyaline characteristics. Grafts placed deeper do not restore the contour or composition of the original articular surface. CLINICAL RELEVANCE: If preservation of normal hyaline cartilage is the objective, thin grafted articular cartilage can remodel, but the tolerance for incongruity is limited and probably less than that reported for an intra-articular fracture.     

Results of arthroscopic fixation of osteochondritis dissecans lesion of the knee with cylindrical autogenous osteochondral plugs

BACKGROUND: In situ fixation of unstable lesions of osteochondral dissecans of the knees with cylindrical osteochondral autograft transplantation has been reported to provide excellent results with healing of the osteochondral dissecans fragment. PURPOSE: To evaluate the clinical results and magnetic resonance imaging findings of the osteochondral dissecans of knees treated with in situ fixation of the osteochondral fragments with osteochondral autograft transplantation. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Twelve knees (12 patients; mean age, 16.0 years) with osteochondral dissecans lesions were treated with in situ fixation with autogenous osteochondral plugs. The mean lesion size was 2.4 cm(2) (range, 1.0-4.9 cm(2)). The osteochondral dissecans lesions were located on the medial femoral condyle in 10 patients and on the lateral femoral condyle in 2 patients. Seven lesions were located in the weightbearing area. The International Cartilage Repair Society classification in arthroscopic findings was grade II in 1 patient, grade III in 8 patients, and grade IV in 3 patients. All patients were evaluated with the Hughston Rating Scale form with the mean follow-up at 4.5 years (range, 2.8-5.9 years). The interface between the osteochondral fragment and subchondral bone and changes in donor site of the osteochondral graft were evaluated with T2-weighted magnetic resonance image up to 12 months postoperatively. RESULTS: The Hughston Rating Scale scored 8 knees as excellent, 3 as good, and 1 as fair. The interface between the osteochondral fragment and subchondral bone had disappeared on magnetic resonance image by 3 months postoperatively in all cases. No complications arising from the donor site area were observed. Signal intensity of donor site changed from high signal preoperatively to homogeneous surrounding cancellous bone by 1 year postoperatively. CONCLUSION: Biological fixation of the osteochondral dissecans lesion with cylindrical osteochondral autograft provided healing of the osteochondral fragments.     

A cadaveric analysis of contact stress restoration after osteochondral transplantation of a cylindrical cartilage defect

Osteochondral transplantation is a successful treatment for full-thickness cartilage defects, which without treatment would lead to early osteoarthritis. Restoration of surface congruency and stability of the reconstruction may be jeopardized by early mobilization. To investigate the biomechanical effectiveness of osteochondral transplantation, we performed a standardized osteochondral transplantation in eight intact human cadaver knees, using three cylindrical plugs on a full-thickness cartilage defect, bottomed on one condyle, unbottomed on the contralateral condyle. Surface pressure measurements with Tekscan pressure transducers were performed after five conditions. In the presence of a defect the border contact pressure of the articular cartilage defect significantly increased to 192% as compared to the initially intact joint surface. This was partially restored with osteochondral transplantation (mosaicplasty), as the rim stress subsequently decreased to 135% of the preoperative value. Following weight bearing motion two out of eight unbottomed mosaicplasties showed subsidence of the plugs according to Tekscan measurements. This study demonstrates that a three-plug mosaicplasty is effective in restoring the increased border contact pressure of a cartilage defect, which may postpone the development of early osteoarthritis. Unbottomed mosaicplasties may be more susceptible for subsidence below flush level after (unintended) weight bearing motion.     

Ex vivo magnetic resonance microscopy of an osteochondral transfer

A 49-year-old woman with right knee pain and a chondral defect on the medial femoral condyle underwent an osteochondral transfer. The patient initially had pain relief, but then sustained a twisting injury and had progressive chondromalacia and pain on the affected side. She subsequently underwent a total knee replacement, and the tissue from the osteochondral transfer (OATS) site was harvested for analysis. In vitro MR microimaging of the excised joint segment revealed undamaged, full-thickness cartilage on the OATS plug, intact cartilage on the posterior condyle, and severely thinned and damaged cartilage on the anterior condyle. Alcian blue-stained sections revealed that proteoglycans were present throughout the OATS core but were nearly absent in the native cartilage. Quantitative T(1) data acquired after equilibration with Gd-DTPA indicated a distribution of matrix fixed charge in the OATS plug and anterior tissue that agreed well with histology and literature observations, while the posterior native cartilage appeared to have fixed charge similar to that of the OATS tissue. Histology revealed poor graft integration between OATS and native cartilage, with a distinct layer of fibrous tissue at the posterior interface. MRI images, by comparison, showed a hypointense feature at the posterior interface but uniform intensity across the anterior interface. Quantitative T(2), magnetization transfer and T(1) data acquired with and without gadolinium contrast showed dependences on depth, location, and pathology that were consistent with measurements reported in the literature for articular cartilage.     

Biomechanical and topographic considerations for autologous osteochondral grafting in the knee

This study characterizes the donor and recipient sites involved in osteochondral autograft surgery of the knee with respect to articular cartilage contact pressure, articular surface curvature, and cartilage thickness. Five cadaveric knees were tested in an open chain activity simulation and kinematic data were obtained at incremental knee flexion angles from 0 degrees to 110 degrees. Surface curvature, cartilage thickness, and contact pressure were determined using a stereophotogrammetry method. In all knees, the medial trochlea, intercondylar notch, and lateral trochlea demonstrated nonloadbearing regions. Donor sites from the distal-medial trochlea were totally nonloadbeadng. For the intercondylar notch, lateral trochlea, and proximal-medial trochlea, however, the nonloadbearing areas were small, and typical donor sites in these areas partially encroached into adjacent loadbearing areas. The lateral trochlea (77.1 m(-1)) was more highly curved than the typical recipient sites of the central trochlea (23.3 m(-1)), medial femoral condyle (46.8 m(-1)), and lateral femoral condyles (42.9 m(-1)) (P < 0.05). Overall, the donor sites had similar cartilage thickness (average, 2.1 mm) when compared with the typical recipient sites (average, 2.5 mm). The lateral trochlea and medial trochlea curvatures were found to better match the recipient sites on the femoral condyles, while the intercondylar notch better matched the recipient sites of the central trochlea. The distal-medial trochlea was found to have the advantage of being nonloadbearing. Preoperative planning using the data presented will assist in more conforming, congruent grafts, thereby maximizing biomechanical function.     

Weightbearing ovine osteochondral defects heal with inadequate subchondral bone plate restoration: implications regarding osteochondral autograft harvesting

Purpose

It is unknown what causes donor site morbidity following the osteochondral autograft transfer procedure or how donor sites heal. Contact pressure and edge loading at donor sites may play a role in the healing process. It was hypothesized that an artificially created osteochondral defect in a weightbearing area of an ovine femoral condyle will cause osseous bridging of the defect from the upper edges, resulting in incomplete and irregular repair of the subchondral bone plate.

Methods

To simulate edge loading, large osteochondral defects were created in the most unfavourable weightbearing area of 24 ovine femoral condyles. After killing at 3 and 6?months, osteochondral defects were histologically and histomorphometrically evaluated with specific attention to subchondral bone healing and subchondral bone plate restoration.

Results

Osteochondral defect healing showed progressive osseous defect bridging by sclerotic circumferential bone apposition. Unfilled area decreased significantly from 3 to 6 months (P?=?0.004), whereas bone content increased (n.s.). Complete but irregular subchondral bone plate restoration occurred in ten animals. In fourteen animals, an incomplete subchondral bone plate was found. Further common findings included cavitary lesion formation, degenerative cartilage changes and cartilage and subchondral bone collapse.

Conclusions

Osteochondral defect healing starts with subchondral bone plate restoration. However, after 6 months, incomplete or irregular subchondral bone plate restoration and subsequent failure of osteochondral defect closure is common. Graft harvesting in the osteochondral autograft transfer procedure must be viewed critically, as similar changes are also present in humans.

Level of evidence

Prognostic study, Level III.     

Fresh osteochondral allografting

The treatment of articular cartilage defects in the knee is a difficult challenge. Fresh, small-fragment osteochondralallografting is a technique involving the transplantation of articular (hyaline) cartilage into the defective joint surface. The graft, a composite of living cartilage and a thin layer of underlying subchondral bone, provides a mature matrix with viable chondrocytes along with an osseous component that provides a surface for fixation and integration with the host. Fresh allografting is particularly useful in larger lesions (greater than 2 cms) or when associated osseous defects are present. Clinical experience with fresh osteochondral allografts now extends over 2 decades. Up to 90% of individuals treated for femoral condyle lesions are improved. The allograft tissue appears well tolerated by the host, with documented long-termsurvival of chondrocytes and intact matrix. Successful clinical outcomes have established fresh osteochondrall allografting as an appropriate alternative in the treatment of chondral and osteochondral lesions of the knee.     

Comparison of fresh osteochondral autografts and allografts: a canine model

BACKGROUND: Osteochondral autografts and allografts have been widely used in the treatment of isolated grade IV articular cartilage lesions of the knee. However, the authors are not aware of any study that has prospectively compared fresh osteochondral autografts to fresh allografts with regard to imaging, biomechanical testing, and histology. HYPOTHESIS: The imaging, biomechanical properties, and histologic appearance of fresh osteochondral autograft and fresh allograft are similar with respect to bony incorporation into host bone, articular cartilage composition, and biomechanical properties. STUDY DESIGN: Controlled laboratory study. METHODS: Eighteen adult dogs underwent bilateral knee osteochondral graft implantation after creation of an Outerbridge grade IV cartilage defect. One knee received an autograft, and the contralateral knee received a fresh allograft. Nine dogs were sacrificed at 3 months, and 9 dogs were sacrificed at 6 months. Graft analysis included gross examination, radiographs, magnetic resonance imaging, biomechanical testing, and histology. RESULTS: Magnetic resonance imaging demonstrated excellent bony incorporation of both autografts and allografts. Biomechanical testing demonstrated no significant difference between autografts versus allografts versus control at 3 or 6 months (P = .36-.91). A post hoc calculation showed 80% power to detect a 30% difference between allograft and control. Histologic examination showed normal cartilage structure for both autografts and allografts. CONCLUSION: Fresh osteochondral autograft and fresh allograft tissues are not statistically different with respect to bony incorporation, articular cartilage composition, or biomechanical properties up to 6 months after implantation. CLINICAL RELEVANCE: The use of fresh allograft tissue to treat osteochondral defects eliminates morbidity associated with harvesting autograft tissue without compromising the results of the surgical procedure.     

Topographic matching of selected donor and recipient sites for osteochondral autografting of the articular surface of the femoral condyles

The purpose of this study was to define the topography of the articular surface of the femoral condyles and to develop a method for computerized topographic matching of donor and recipient sites for osteochondral transplantation. The condyles of seven fresh cadaveric femurs were mounted on the rotating stage of a laser-based coordinate measuring machine. An anatomic coordinate system defining the articular surface of the condyles was created. Customized software was developed to allow selection and topographic matching of osteochondral graft donor and recipient sites from any location on the surface of the condyles. For cartilage defects within the weightbearing portions of the medial or lateral femoral condyles, grafts taken from sites from the most medial or lateral portions of the patellar groove provided a significantly better topographic match than did grafts taken from the central intercondylar notch.     

Biomechanical and histological evaluation of osteochondral transplantation in a rabbit model

BACKGROUND: Biomechanical and histological properties of osteochondral transplantation have not been extensively examined. HYPOTHESIS: Osteochondral grafts have properties similar to native articular cartilage. STUDY DESIGN: Controlled laboratory study. METHODS: A 2.7 mm (diameter) x 4.0 mm (depth) osteochondral defect was created in 17 New Zealand white rabbit knees. An osteochondral graft, harvested from the contralateral knee, was transplanted into the defect. Eight rabbits were sacrificed each at 6 and 8 weeks. RESULTS: The 12-week grafts (1213.6 +/- 309.0 N/mm) had significantly higher stiffness than the 6-week grafts (483.1 +/- 229.1 N/mm; P <.001) and of normal cartilage (774.8 +/- 117.1 N/mm; P <.003). Stiffness of the 6-week grafts was significantly lower than normal cartilage (P <.036). At all time points, full-thickness defects had significantly lower stiffness than normal cartilage (P <.001). Histologically, transplanted grafts scored significantly higher than the full-thickness defects (P <.001). The defects showed inconsistent, fibrocartilage healing. The grafts demonstrated cartilage viability, yet with a persistent cleft between the graft and host. CONCLUSIONS: Osteochondral transplants undergo increased stiffness in the short term, with evidence of structurally intact grafts. Clinical Relevance: Osteochondral transplantation may be a viable treatment option; however, long-term investigation on graft function is necessary.     

Large osteochondral defects of the femoral condyle: press-fit transplantation of the posterior femoral condyle (MEGA-OATS)

BACKGROUND AND AIMS: Large osteochondral defects in the weight-bearing zone of the knee remain a challenging therapeutic problem. Surgical options include drilling, microfracturing, and transplantation of osteochondral plugs but are often insufficient for the treatment of large defects of the femoral condyle. PATIENTS AND METHODS: Large osteochondral defects of the femoral condyle (mean defect size 7.2 cm(2) range 3-20) were treated by transplantation of the autologous posterior femoral condyle. Between 1984 and 2000, 29 patients were operated on: in 22 the medial, in 6 the lateral femoral condyle, and in one the trochlear groove was grafted. Thirteen patients underwent simultaneous high tibial valgus osteotomy. In the first series (1984-1999) the graft was temporarily fixed with a screw ( n=12), but from 1999 we used a newly developed press-fit technique ( n=17) avoiding screw fixation of the graft. The operative technique comprising graft harvest, defect preparation, transplantation, and fixation is described. Patients were clinically evaluated using the Lysholm score, and magnetic resonance imaging with intravenous contrast was performed 6 and 12 weeks after surgery (mean follow-up 17.7 months (range 3-46). RESULTS: Pain and swelling were reduced in 26 patients. Three patients of the first series reported persistent problems and were subjectively not satisfied. The mean Lysholm score rose from preoperatively 52 to 77 points after 3 months, 74 after 6, 88 after 12, and 95 after 18. Magnetic resonance imaging showed good graft viability in all cases. We saw one arthrofibrosis after 6 months but noted no problems related to the loss of the missing posterior condyle. CONCLUSION: Large osteochondral defects of the femoral condyle can be treated by transplantation of the autologous posterior femoral condyle. The use of only one osteochondral piece renders better approximation of the femoral cartilage curvature and thus joint congruence than in mosaic plasty. However, whether loss of the posterior condyle has a long-term negative impact on the knee joint remains to be elucidated.     

Experimental autologous osteochondral plug transfer in the treatment of focal chondral defects: magnetic resonance imaging signs of technical success in sheep

PURPOSE: To describe the magnetic resonance imaging (MRI) signs of technically successful osteochondral plug transfer and to correlate the findings with histology using the Mankin score. MATERIAL AND METHODS: The study was done in a prospective animal experiment: 11 adult black-head sheep underwent surgical treatment with osteochondral plug transfer of a knee joint. The animals were killed 6 months later and MRI of the joints was done immediately. MRI was applied with a 1.5T MR scanner using a spin-echo (SE) T1-weighted, turbo spin-echo (TSE) T2-weighted with spectral fat suppression and a fat-suppressed 3D-spoiled gradient echo (GRE) sequence (manufacturer's acronym: FLASH) (TR 50.0 ms, TE 11.0 ms, flip 35 degrees). After MRI, all knee joints were dissected and a biopsy of the plug and the adjacent cartilage was taken. Classification of the cartilage biopsies was carried out in accordance with a modified Mankin score. RESULTS: Cartilage repairs with a hypointense cartilage signal in the FLASH 3D sequence were correlated with poor histological results (lower Mankin score). Histologically, the regions of cartilage with a hypointense signal showed a fibrocartilage-like repair tissue. Hyaline cartilage with well-defined layers had the same signal intensity in the FLASH sequence relative to adjacent hyaline cartilage. There were two plugs with a surface defect, graded as Outerbridge grade 1 in MRI and histology. Both had a poor outcome in the histologic Mankin score. Grade 2-4 lesions were not observed in the MRI study nor in the histologic study. CONCLUSION: MRI is a useful non-invasive tool for evaluating the morphologic status of osteochondral plug transfers. A good postoperative result of the cartilage repair was found histologically if an isointense cartilage signal of the graft was documented in the FLASH 3D sequence, and the graft had good congruity with the articular surface without defects.     

Ultrasonography of osteochondritis dissecans of the knee. A preliminary report

Twenty-five radiographically proven cases of osteochondritis dissecans of the femoral condyles were examined by real-time sonography using a 5 MHz linear transducer. The medial condyle was involved in 19 cases and the lateral in 6. The size of the lesions varied from a few mm to more than 30 mm in diameter. The fragmentation of the subchondral bone was demonstrated in all cases, and furthermore the osteochondral fragment and the condition of the overlying articular cartilage could be assessed. The exact indications for the technique have not yet been defined, but awaits further clinical studies.