The effect of overlapping on the primary stability of osteochondral grafts in mosaicplasty

Our goal was to determine the primary stability of overlapping osteochondral grafts used in mosaicplasty by studying the effect of overlapping in an ex vivo model. Osteochondral grafts, 10 mm in diameter, were transplanted from the trochlea of cow femurs to the weight-bearing area of the lateral femoral condyle with 0, 15, or 30% overlap. The grafts were pushed in with a probe at a rate of 2 mm/min, and load (N)-displacement (mm) curves were recorded. In Group I (control, 0% overlap), insertion 1 and 2 mm below the cartilage level could be reached at 572.3 +/- 273.6 and 999.3 +/- 427.6 N, respectively. In Group II (15% overlap), insertion 1 and 2 mm below the cartilage level could be reached at 263.6 +/- 91.7 and 746.6 +/- 88.0 N, respectively. In Group III (30% overlap), insertion 1 and 2 mm below the cartilage level could be reached at 179.4 +/- 31.2 and 657.0 +/- 106.5 N, respectively. The loads that were necessary to produce a 1-mm dent in the grafts were significantly different between Groups I and II and Groups I and III (p < 0.05). These results suggest that stability may be reduced by graft overlapping in mosaicplasty surgery. The results of this ex vivo animal study contribute to a more complete understanding of the primary stability of osteochondral grafts in an overlapping position as well as postoperative protocols.     

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 allografts in the treatment of articular cartilage injuries of the knee

Osteochondral allografts have demonstrated encouraging clinical and scientific success in the treatment of full-thickness articular cartilage defects in multiple anatomic locations including the knee. The use of fresh grafts has shown the greatest potential for clinical success. There has been growing interest in cryopreservation techniques and the use of cryopreserved grafts owing to the delay in obtaining grafts secondary to regulatory testing, encouraging laboratory data surrounding their use, and the potential for more effective tissue banking. This article reviews the indications, operative technique, and clinical outcomes using osteochondral allografts for full-thickness articular cartilage defects in the knee.     

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.     

Primary stability of press-fit-implanted osteochondral grafts. Influence of graft size, repeated insertion, and harvesting technique

The aim of this study was to evaluate the fixation strength of press-fit-implanted osteochondral grafts with respect to graft size (length and diameter), the effect of repeated insertion after pullout, and harvesting technique. Experiments were performed using the Osteochondral Autograft Transfer System on porcine femoral condyles. Failure loads of 10-mm-long grafts (mean, 47 N) were significantly lower than failure loads of 15-mm-long grafts (mean, 93 N) and 20-mm-long grafts (mean, 110 N) (all grafts, 11 mm in diameter). Reinsertion of the 15-mm-long grafts after initial pullout resulted in a significant reduction of failure loads (mean, 93 N versus 44 N). Failure loads of 8-mm-diameter grafts (mean, 41 N) were significantly lower than those of 11-mm-diameter grafts (mean, 92 N) (all 15 mm long). Levering of the tubular chisel during graft harvest significantly decreased press-fit stability as compared with simple turning of the chisel (mean, 32 N versus 52 N) (8-mm diameter and 15-mm length). These results suggest that primary fixation strength of press-fit-inserted osteochondral grafts depends on the size of the grafts and that repeated pullout and reinsertion of grafts as well as a nonoptimal harvesting technique (levering) will reduce primary stability.     

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.     

自体镶嵌式骨软骨移植修复膝关节软骨缺损

目的 探讨膝关节软骨缺损的修复方法。方法 6例膝关节软骨缺损患者，关节镜下在其非负重区的软骨面上，用专用器械凿取圆柱状的骨软骨，并移植至软骨缺损部位，用于修复缺损。结果 随访2～24个月，患者的临床症状消失，关节活动度正常，MRI显示原软骨缺损区软骨表面平整，移植的骨软骨柱位置良好。结论 自体镶嵌式骨软骨移植术创伤小、操作简单、能保持关节面的曲度，是较为实用的手术。     

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.     

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.     

Clinical, histologic, and radiographic outcomes of distal femoral resurfacing with hypothermically stored osteoarticular allografts

BACKGROUND: Fresh osteoarticular allograft transplantation has a long history of clinical success. These grafts have typically been implanted less than 1 week from donor asystole. HYPOTHESIS: Osteoarticular allografts stored 4 to 6 weeks represent a viable alternative to treat full-thickness cartilage and osteochondral defects of the distal femur as measured by clinical, histologic, and magnetic resonance imaging (MRI) criteria. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Osteoarticular allografts were implanted after a mean graft storage time (at 4 degrees C) of 36 days (range, 28-43). Sixty-seven patients received massive hypothermically stored osteoarticular allografts. Ten knees in 8 of these patients underwent second-look arthroscopic evaluation and biopsy at a mean of 40 months (range, 23-60) after implantation. Clinical assessment was performed using multiple outcome measures and sequential MRI evaluations. Biopsy specimens were obtained from the graft as well as from native articular cartilage at the time of second-look arthroscopy for histologic analysis. RESULTS: The mean International Knee Documentation Committee scores were as follows: preoperative, 27 (range, 9-55); postoperative, 79 (range, 56-99); P = .002. The mean Lysholm scores were as follows: preoperative, 37 (range, 12-47); postoperative, 78 (range, 55-90); P = .002. The mean Short Form-36 physical scores were as follows: preoperative, 38 (range, 24-55); postoperative, 51 (range, 39-61); P = .002. The mean Tegner scores were as follows: preoperative, 4.3 (range, 1-9); postoperative, 5.3 (range, 4-7); P = .16. The mean International Cartilage Repair Society score at follow-up was 10 (nearly normal) (range, 7-11). The mean modified Outerbridge scores were as follows: preoperative, 4.3 (range, 3-5); postoperative, 0.6 (range, 0-1); P = .002. The mean graft and native cartilage cellular density and viability were not statistically different. CONCLUSIONS: Fresh-stored osteoarticular grafts for full-thickness articular surface defects of the distal femur appear to offer a viable biological method to restore knee function. Our study suggests that osteoarticular grafts stored in cell culture medium at 4 degrees C for 4 to 6 weeks provide successful short-term clinical outcomes.     

Anterior cruciate reconstruction combined with autologous osteochondral transplantation

The purpose of this prospective study was to evaluate the results of simultaneous anterior cruciate ligament (ACL) reconstruction and osteochondral autograft transplantation performed in patients suffering an anterior instability associated with symptomatic full-thickness cartilage defects. Our clinical report includes the first 21 patients (six women, 15 men) who have been followed up for 32 months or longer. The average patient age was 29 years (range 22–44 years), and mean time from injury to the combined reconstructive surgery was 10 months (range 4–27 months). The cartilage defects had a mean area of 3.5 cm² (range 2.0–5.0 cm²). All patients were evaluated according to the IKDC, Lysholm and Tegner scoring scales by an independent observer. A visual analogue scale (VAS) reflecting patient pain was evaluated. Assessment using the IKDC knee scoring scale revealed 81% of the patients with a normal or nearly normal knee joint. There was a significant improvement in subjective discomfort, and the KT-1000 arthrometric evaluation showed a reduction of the ventral tibial translation (5.9 to 1.9 mm). All but two patients had returned to full activities without restriction and were asymptomatic. The results of this study suggest that symptomatic full-thickness articular cartilage defects associated with ACL instability can be effectively treated by performing ACL reconstruction and osteochondral autologous grafts in one procedure. However, only the years which follow will show the long-term outcome of the patients.     

Braided hamstring tendons for reconstruction of the anterior cruciate ligament. A biomechanical analysis

BACKGROUND: In an effort to improve the strength and stiffness of anterior cruciate ligament grafts, several authors have advocated alterations of graft structure and orientation, including braiding the tendons in hamstring tendon grafts. HYPOTHESIS: Braiding hamstring tendons does not increase graft strength and stiffness. STUDY DESIGN: Controlled laboratory study. METHODS: Sixteen hamstring tendon and 21 bone-patellar tendon-bone grafts were harvested from 12 cadavers and divided into three groups: 1) braided four-strand hamstring tendon, 2) unbraided four-strand hamstring tendon, and 3) bone-patellar tendon-bone. All grafts were placed under a 50-N preload on a servohydraulic testing device and were tensioned to failure. RESULTS: The strength and stiffness of the tested specimens averaged 427 +/- 36 N and 76 +/- 10 N/mm, respectively, for braided specimens, 532 +/- 44 N and 139 +/- 18 N/mm for unbraided specimens, and 574 +/- 46 N and 158 +/- 15 N/mm for patellar tendon specimens. There was a 20% decrement in hamstring tendon graft tensile strength and a 45% decrease in stiffness after braiding because of the suboptimal multidirectional orientation of individual tendons within the braided grafts. CONCLUSIONS: In vitro braided hamstring tendon grafts demonstrated mechanically inferior strength and stiffness characteristics compared with unbraided hamstring tendon grafts and patellar tendon grafts. CLINICAL RELEVANCE: Braiding of hamstring tendon grafts provides no mechanical advantage in anterior cruciate ligament reconstruction.     

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.     

Initial fixation strength of two bioabsorbable pins for the fixation of hamstring grafts compared to interference screw fixation: single cycle and cyclic loading

BACKGROUND: During the early postoperative period, the fixation of a hamstring graft to the bone tunnel is the primary factor in limiting rehabilitation. HYPOTHESIS: The initial fixation strength of a double cross pin fixation technique is comparable with the biodegradable interference screw fixation technique. STUDY DESIGN: Experimental laboratory study. METHODS: The authors examined the initial fixation strength of two 3.3-mm bioabsorbable pins compared to interference screws for hamstring grafts in bovine knees. RESULTS: Analysis of yield load, maximum load, and stiffness in the single-cycle loading test showed no statistically significant differences for cross pin and interference fixation (P <.05). For cross pins and interference screws, the mean displacement under 1000 cycles to 250 N was 5.07 ( +/- 1.9) mm and 4.81 ( +/- 2.5) mm, stiffness 252 ( +/- 78) N/mm and 289 ( +/- 148) N/mm. Only grafts fixed with cross pins survived 1000 cycles to 450 N. CONCLUSION: The initial fixation strength of the double cross pin technique is comparable to that of interference screw fixation with a stiffness comparable to that of the native ACL. Clinical Relevance: Hamstring graft fixation using two cross pins provides an alternative to bioabsorbable interference screw fixation.     

Influence of basal support and early loading on bone cartilage healing in press-fitted osteochondral autografts

Purpose

The influence of basal graft support combined to early loading following an osteochondral autograft procedure is unclear. It was hypothesized that bottomed grafts may allow for early mobilization by preventing graft subsidence and leading to better healing.

Methods

Osteochondral autografts were press fitted in the femoral condyles of 24 sheep (one graft per animal). In the unbottomed group (n = 12), a gap of 2 mm was created between graft and recipient bone base. In the bottomed group (n = 12), the graft firmly rested on recipient bone. Animals were allowed immediate postoperative weightbearing. Healing times were 3 and 6 months per group (n = 6 per subgroup). After killing, histological and histomorphometric analyses were performed.

Results

Unbottomed grafts at 3 months showed significantly more graft subsidence (P = 0.024), significantly less mineralized bone (P = 0.028) and significantly worse cartilage and subchondral bone plate healing (P = 0.034) when compared to bottomed grafts. At 6 months, no differences were seen. Compared to the native situation, unbottomed grafts showed significantly more graft subsidence (P = 0.024), whereas bottomed grafts did not. Cystic lesions were seen in both groups. Osteoclasts were closely related to the degree of bone remodelling.

Conclusion

In the animal model, in the case of early loading, bottomed osteochondral autografts have less chance of graft subsidence. Evident subsidence negatively influences the histological healing process. In the osteochondral autograft procedure, full graft support should be aimed for. This may allow for early mobilization, diminish graft subsidence and improve long-term integration.     

Disease-specific clinical problems associated with the subchondral bone

The subchondral bone is involved in a variety of diseases affecting both the articular cartilage and bone. Osteochondral defects in distinct locations and of variable sizes are the final results of different etiologies. These include traumatic osteochondral defects, osteochondritis dissecans, osteonecrosis, and osteoarthritis. Traumatic osteochondral defects are caused by osteochondral fractures, separating an osteochondral fragment that includes articular cartilage and both subchondral and trabecular bone from the joint surface. In osteochondritis dissecans, the disease originates in the subchondral bone and secondarily affects the articular cartilage. Location, stage, size, and depth of osteochondral lesions play a role in the treatment of traumatic osteochondral defects and osteochondritis dissecans. Surgical options include fragment refixation, transplantation of osteochondral autografts, or bone restoration by impacted cancellous bone grafts combined with autologous chondrocyte transplantation. An insufficiency fracture of the subchondral bone may be the initiating factor of what was formerly believed to be a spontaneous osteonecrosis of the knee (SPONK). Recent histopathological studies suggest that each stage of SPONK reflects different types of bone repair reactions following a fracture of the subchondral bone plate. Osteoarthritis is a disease that does affect not only the articular cartilage, but also the subchondral bone. Reconstructive surgical techniques aim at preserving joint function, inducing fibrocartilaginous repair, and at correcting malalignment. This review summarizes the current status of the clinical treatment of traumatic osteochondral defects, osteochondritis dissecans, osteonecrosis, and osteoarthritis as they affect the subchondral bone region and its adjacent structures.     

A biomechanical comparison of initial soft tissue tibial fixation devices: the Intrafix versus a tapered 35-mm bioabsorbable interference screw

BACKGROUND: Biomechanical testing of the Intrafix device has not been performed using human tibiae. HYPOTHESIS: The Intrafix device would provide comparable or superior tibial fixation of a quadrupled hamstring tendon graft to a 35-mm-long bioabsorbable interference screw. STUDY DESIGN: In vitro, biomechanical study. METHODS: Eight paired human tibiae and 16 quadrupled hamstring tendon grafts were divided into 2 groups. Each quadrupled hamstring tendon graft was fixed in a tunnel sized to 0.5 mm graft diameter with either an Intrafix device or a screw. RESULTS: Displacement at failure was greater in the Intrafix group (17.3 +/- 4.6 mm versus 10.9 +/- 4.4 mm, P =.002). Load at failure (796 +/- 193 N versus 647 +/- 269 N), stiffness (49.2 +/- 21.9 N/mm versus 64.5 +/- 22 N/mm), and bone mineral density (0.74 +/- 0.15 gm/cm(3) versus 0.74 +/- 0.14 gm/cm(3)) did not display significant differences for the Intrafix device and the screw, respectively (P >.05). CONCLUSIONS: Displacement at failure was greater for the Intrafix device. CLINICAL RELEVANCE: Increased displacement at failure for the Intrafix group suggests slippage from sheath channel deployment. Concentric fixation may not occur when less than optimal tibial bone mineral density increases the difficulty of attaining precise sheath deployment and quadrupled hamstring tendon graft strand alignment.     

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.