Enhancement of the fixation of pyrolytic carbon implants by using atomic oxygen texturing

The purpose of this study was to examine the effect on the biocompatibility and biologic fixation of atomic oxygen-textured pyrolytic carbon. The implants consisted of unalloyed pyrolytic carbon rods, with half the length of the rod textured by atomic oxygen, and the other half retaining the as-deposited surface that normally occurs during the manufacturing process. The rods were implanted transcortically across the distal portion of the femurs of 6 adult male rabbits for 8 weeks. The implants were assessed mechanically by measuring the interface strength between the implant and the bone. The implant-bone interface was also examined by light microscopy. No adverse reaction to either the as-deposited or the textured pyrolytic carbon was seen. Percent bone apposition was greater for textured implants than for the as-deposited implants; however, it was not significant. The bone apposition efficiency factor, calculated by dividing the interface strength by the fraction of bone apposition, was greater for the textured implants than for the as-deposited implants. This indicates that the fixation obtained was more effective for the textured implants. The findings of this study suggest that biologic fixation of pyrolytic carbon implants can be enhanced by surface texturing by using direct exposure to atomic oxygen, without compromising its biocompatibility.

Minimum 10-year radiographic follow-up of a cementless acetabular component for primary total hip arthroplasty with a bulk autograft

We radiographically investigated 36 hips in 34 patients with osteoarthritis of the hip who had undergone total hip arthroplasty. Their mean age was 59.2 years (range 36-79 years), and the mean follow-up period was 11.2 years (range 10-14 years). The long-term outcome and the chronological changes in the bulk autograft were examined. The acetabular component of the prosthesis was a Lord-type threaded cup with a smooth surface. At follow-up, bone absorption was minor in 17 joints, moderate in 11, and major in 8. The hips with graft coverage of >==20% (group A) had a significantly higher loosening rate than hips with coverage of <<20% (group B) ( P << 0.05). The cup position changed markedly in group A. Our findings indicate that graft coverage should be less than 20% when a bulk graft is used together with a smooth-surfaced cementless cup.

Threaded cortical bone dowels in lumbosacral arthrodesis: a review

Lumbar fusion is a common spinal surgery, for which numerous devices have been developed to aid in segment stabilization. A threaded cortical bone dowel is a machined and processed bone allograft which is one such development. Threaded cortical bone dowels are attractive because of their osteoconductive nature and the opportunity to load them with osteogenic morselized bone autograft or osteoinductive growth factors, such as bone morphogenetic proteins. Although threaded cortical bone dowels have been in clinical use for more than 5 years, they have not been the subject of a comprehensive review. The current article covers the history, preparation, uses, safety, and efficacy of threaded cortical bone dowels in lumbosacral interbody fusion.

Transplantation of cultured bone cells using combinations of scaffolds and culture techniques

The transplantation of cultured bone cells is expected to become a candidate for bone regeneration therapy. For the clinical application of this therapy, there remain several problems to be overcome, for example, the improvements of scaffolds and culture techniques. In this review article, two kinds of porous ceramics, a novel sintered porous hydroxyapatite and a porous beta-tricalcium phosphate (TCP), as well as a collagen-phosphosphoryn sponge are introduced as new scaffolds for bone regeneration. The former two ceramic scaffolds proved to be applicable for bone regeneration therapy. The collagen-phosphophoryn sponge proved to have bone formation ability in vivo. Moreover, for the application of this therapy to the regeneration of large bone defects, we improved the culture method by applying a low-pressure system and a perfusion system. Both culture systems accelerated the formation of bone in vivo in this transplantation model. Combinations of the scaffolds and culture techniques might be considered when designing therapeutic strategies.

Cancellous and cortical morselized allograft in revision total hip replacement: A biomechanical study of implant stability

To restore femoral intramedullary bone stock loss in revision surgery of failed total hip arthroplasties, impacted morselized cancellous allograft is recommended. This study investigated the mechanical properties of both impacted cortical (group A) and cancellous (group B) morselized bone graft for reconstruction of femoral bones. Ten matched pairs of fresh frozen human femora were prepared by over-reaming to create a smooth-walled cortical shell. Each pair had one cortical and one cancellous impacted morselized allograft and cement. Stem subsidence was evaluated by a cyclic axial load, which was applied by a servohydraulic test. The stem subsidence was measured for initial subsidence (subsidence at the first 1000 cycles), the total axial subsidence (subsidence at the end of cycles under load) and the final axial subsidence (subsidence after the unloading phase). Torque test was measured by torsional loads through the prosthetic femoral heads. Total axial subsidence was significantly higher in group B (mean: 1.32+/-0.32 mm) compared to group A (mean: 0.94+/-0.26 mm) (P<0.01). There was no significant difference between the two groups in terms of initial subsidence (P=0.09) and final axial subsidence. The mean maximum torque before failure was 39.5+/-22.2 N-m for the cortical morselized allograft and 32.5+/-18.1N-m for cancellous. We concluded that impacted morselized cortical bone graft used for reconstruction of contained femoral bone loss in revision hip arthroplasty, may reduce the stem subsidence. Further animal experimentation for mechanical and histological evaluation of in vivo application is warranted.

Cortical allografts in spinal tuberculosis

One-hundred-twenty-three patients with neurological deficit due to spinal tuberculosis underwent anterior spinal decompression and anterior column reconstruction with fresh-frozen femoral allograft. Fifty-two patients with a follow-up of more than 5 years were evaluated to assess the incorporation and the efficacy of allograft in maintaining correction. The allograft was incorporated in 49 patients at a mean follow-up of 6.5 (5.3-8.2) years. Complete neurological recovery occurred in 39 patients. The mean pre-operative kyphosis of 37 degrees (15 degrees -67 degrees ) was corrected to 18 degrees (5 degrees -45 degrees ). Fresh-frozen allografts are a suitable alternative to autologous rib and iliac crest grafts in the treatment of spinal tuberculosis.

[Value of autologous chondrocyte transplantation in the reconstruction of experimental cartilage defects. Part I. Extent of defect, macroscopic appearance of reconstructed articular surface and microscopic analysis of predominant tissue]

Articular cartilage defect is one of the main reasons of osteoarthritis. Currently, tissue engineering techniques are the methods concerning better cartilage reconstruction. The aim of this part of the study was macroscopic evaluation of degree of defect feeling, macroscopic appearance of repair tissue and microscopic analysis of predominant tissue after autologous chondrocytes transplantation. Repair of partial thickness cartilage defect on distal part of femur was evaluated (25 adolescent rabbits). Procedures were performed in II groups: I--autologous chondrocytes transplantation under periosteal flap, II--periosteal graft. Chondrocytes were isolated from the cartilage specimens by enzymatic digestion and cultured in vitro. The regenerates were inspected 4, 8 and 12 weeks after the operation. Macroscopic analysis in group I, in most cases revealed filling of the defect with tissue resembling surrounding cartilage. In group II the defect was partially filled, and there was many fissures and cracks in all regenerates. In microscopic analysis in group I, after 4 and 8 weeks following the transplantation the tissue similar to juvenile hyaline cartilage predominated. After 12 weeks it resembled mature hyaline cartilage. In group II, in all cases fibrous cartilage was observed after 4, 8, 12 weeks. Obtained results indicate, that macroscopic and microscopic characteristics of repair tissue after autologous chondrocytes transplantation more closely resembled hyaline cartilage, than in periosteal graft group. 12 weeks after autologous chondrocytes transplantation the repair tissue reached maturity, and demonstrated microscopic characteristics of hyaline-like cartilage. The method of autologous chondrocytes transplantation provides potential for clinical application.

[Value of autologous transplantation of osteo-chondral paste in reconstruction of experimental cartilage defects. Part II. Microscopic analysis of integration with surrounding cartilage, structural integrity and subchondral bone reconstruction in repair tissue]

INTRODUCTION

A limited ability of the cartilage to heal after trauma was the reason to start research on new methods concerning better cartilage reconstruction. The aim of the study was evaluation of repair tissue integration with surrounding cartilage, its structural integrity and subchondral bone reconstruction after osteo-chondral paste transplantation.

MATERIAL AND METHODS

Full thickness defect (IV degree--ICRS scale) on distal rabbit femur joint surface was made. Three groups were specified: A--defect with paste graft (cartilage and contiguous bone collected from joint surface, crushed into homogenous paste; B--defect with the paste graft covered with periosteum; C--defect left unfilled. The follow-up periods were established at 4, 8, 12 weeks. Repair tissue was evaluated microscopically according to modified O'Driscoll scale.

RESULTS

Newly formed tissue was well integrated with surrounding cartilage in group A (paste graft). That trade of repair tissue in group A was much better than in other groups, especially in late observations. Structural integrity of tissue filling the defect was similar to integrity of normal cartilage in groups A and C, but tissue formed in group C didn't represent a hyaline-like cartilage character. In all the examined groups reconstruction of subchondral bone exhibited similar rate. 12 weeks from the procedure, around 80% of subchondral bone was rebuilt. The obtained results indicate, that osteo-chondral paste autologous transplantation in cartilage defects treatment effects with forming well integrated (structurally and with surrounding cartilage) cartilage tissue, of almost complete subchondral bone rebuilding.

The effect of the small and unstable autologous osteochondral graft on repairing the full-thickness large articular cartilage defect in a rabbit model

We have investigated the effect of the insufficient autologous osteochondral graft on healing of the large articular cartilage defect using a rabbit model. An osteochondral defect, 7 mm in diameter, was made on the patellar groove of the femoral condyle and repaired with two surgical procedures: Group I, the osteochondral fragment as half as the defect was grafted. The graft was unstable and the size of the graft was smaller than the defect. This is a model of the insufficient autologous osteochondral graft to the large articular cartilage defect; Group II, the defect was left empty. At 2, 4, 12, and 24 weeks after the surgery, the specimens were analyzed macroscopically and histologically. To evaluate the microscopic morphology, a histologic grading scale composed of 5 categories was used. In Group I, although the graft sank a little, a grafted cartilage survived and the reparative fibrous tissue filled the defect covering implanted cartilage. In contrast, in Group II, the defect was only partially covered by fibrocartilaginous tissue with a faintly staining matrix. Throughout the entire observed periods, the scores of the repaired cartilage in Group I are significantly higher than those in Group II. Even the half size of osteochondral graft has an effect to reduce the size of the cartilage defect such as the spacer and leads to better healing compared to the cartilage defect untreated. In case that it is hard to transplant an optimal osteochondral graft because of large cartilage lesion, even the small and unstable osteochondral plug should be transplanted.

The use of proximal femoral allografts in revision total hip arthroplasty

The implant of a proximal femoral structural allograft is one of the possibilities to restore circumferential defects of multiply revised total hip arthroplasties. A review of 7 patients who underwent proximal femoral reconstruction with an allograft-prosthesis composite to restore bone loss in revision hip replacements is presented. The average follow-up period was 50.2 months. Two patients developed an infection and in one case an instability of the prosthesis appeared. Incorporation in the remaining 5 cases was/achieved in an average period of 8.2 months. Neither fractures nor high rate of resorption appeared in our series. The majority of patients have improved in the functional assessment. Despite the rate of complications, structural femoral allografts can be used with success in this difficult challenge of reconstructing major segmental bone loss of the proximal femur in revision hip surgery.

Growth and remodelling of the autologous bone transplant used in a pediatric femoral reconstruction

The aim of the present work was to assess how growth and remodelling changed the morphology of the transplanted fibula used to reconstruct the proximal femur of a 5 year old child affected by a Ewing's sarcoma during the first 3 years of follow-up. The morphological evolution of the transplant was quantitatively assessed on diagnostic images. Special software was developed to perform three-dimensional measurements on computed tomography (CT) datasets, while state-of-the-art image processing software was used for conventional radiography. The measurements were then correlated with the loads expected to act on the hip during the various stages of the rehabilitation protocol. A simple cantilever beam model was used for a gross estimate of the risk of fracture of the transplant. The results of the analysis showed that there is no clear correlation between the morphological changes of the autograft and the hip loading conditions experienced. Apart from a drastic increase in the periosteal radius in the frontal plane, occurring in the first 10 months after the operation, the growth of the transplanted fibula seems well within the ranges of the normal fibular growth. The cantilever beam model suggested that, although the autograft is currently subjected to subcritical stresses. morphological evolution could increase the risk of fracture in the next few years if a normal level of loading were allowed.

Influence of aeration, storage, and rinsing conditions on residual ethylene oxide in freeze-dried bone allograft

Bone allografts sterilized with ethylene oxide gas (EO) are used in the field of orthopedic surgery, and the reduction of the EO residual concentration is an urgent clinical matter. We therefore investigated the efficacy of aeration and the effects of varied preservation periods and rinsing conditions on the reduction of EO residuals in freeze-dried bone allografts in the present study. Before aeration, the EO residual level was 12.6 ppm, and, after the repeating of aeration at 60 degrees C once, two times, and three times, the level decreased to 10.9 ppm, 3.1 ppm, and 0.47 ppm, respectively. Regarding the duration of preservation at room temperature, the mean EO residual level was 10.5 ppm, 4.9 ppm, and 4.6 ppm, 1, 2, and 3 weeks after EO sterilization, respectively. By rinsing with physiological salt solution, the level was decreased to 6.9 ppm by 5-min rinsing with 100 ml. Rinsing with 500 ml of this solution decreased the levels to 3.9 ppm, 2.8 ppm, and 2.0 ppm when done for 1, 5, and 10 min, respectively. Rinsing with 2000 ml of this solution decreased the levels to 3.6 ppm, 2.6 ppm, and 1.7 ppm when done for 1, 5, and 10 min, respectively. These experimental results with chip bone allografts lead us to recommend repeated preoperative aeration and more than 2 weeks' preservation before use for reducing the residual EO concentration. It was also evident that intraoperative rinsing with 500 ml of physiological saline for 10 min reduced the EO residual level.

The outcome of allografts and anterior instrumentation in spinal tuberculosis

Spinal tuberculosis is the most common form of osteoarticular tuberculosis. Fractures, slippage, and increasing deformity have been reported with the use of autologous rib grafts after anterior spinal decompression. Forty-one patients with neurologic deficits caused by spinal tuberculosis had radical anterior decompression, and the anterior column was reconstructed with fresh-frozen femoral allografts and stabilized with a single-rod screw construct. Antituberculous therapy was administered for 12 months and complete neurologic recovery occurred in 32 patients. The incorporation of allografts commenced between 12 and 18 months. Fusion and remodeling was observed in 33 patients and partial remodeling with fusion was observed in eight patients at a mean followup of 6.4 years. Forty-two percent correction of the kyphosis was achieved and there were no cases of fracture or late sepsis. Fresh-frozen allografts and anterior instrumentation are superior to rib grafts in supporting the anterior spinal column, and although fusion occurred late, the grafts remained stable.

Homograft microlathed femur prosthesis in stapedectomy

The use of homografts in ossiculoplasty has been well documented in the literature. In the early 1980s, nonossicular homograft otic capsule bone was used as a prosthetic material in stapedectomy. We began using homograft femur as a prosthetic material in the early 1990s. In this article, we report the results of a retrospective study of the use of homograft femur prostheses. A series of 300 stapedectomies was performed between Aug. 24, 1992, and Jan. 20, 2000. Total footplate removal with preservation of the posterior crus was our procedure of choice. However, in 116 of these cases, the posterior crus could not be used, and a homograft femur prosthesis was substituted. For these prostheses, all homograft femurs were obtained from the American Red Cross. All prostheses were prepared in the bone laboratory and stored in the bone bank until needed. After an adequate period of follow-up, we tabulated our results. We found that in 89 of 113 cases (78.8%) available for follow-up, the air-bone gap was completely closed. In addition, the air-bone gap was closed to within 5 dB in 11 patients (9.7%) and closed to within 10 dB in five patients (4.4%). In all, 105 of the 113 homograft femur prosthetic procedures (92.9%) resulted in a successful outcome.

Use of allograft femoral rings for spinal deformity in adults

Anterior structural support plays an important role in spinal deformity surgery. Femoral ring allografts have been widely used for this purpose despite numerous alternative implants such as cages. The literature and the authors' experience support the use of femoral ring allograft as a structural and biologic compatible implant to reconstruct anterior column defects. Pseudarthrosis rates and the rate of subsidence and loss of correction are low. No long-term studies exist that show that cages are superior in correction of deformity. Femoral ring allograft remains a viable, cost-effective, and biologic sound alternative.

A novel surgical procedure for osteochondritis dissecans of the lateral femoral condyle: Exchanging osteochondral plugs taken from donor and recipient sites

We treated a 16-year-old boy who had a large symptomatic osteochondritis dissecans (OCD) lesion of the lateral femoral condyle by exchanging osteochondral plugs taken from the donor site with plugs taken from the recipient site. At final inspection 36 months after surgery, he had full range of motion and no symptoms in his knees. Our methods can be used to treat grade 2 or 3 OCD lesions, as classified by Clanton and DeLee.

Long-term followup of fresh femoral osteochondral allografts for posttraumatic knee defects

Fresh osteochondral allografts were used to repair articular defects in the distal femur in 72 patients. Sixty patients were available for long-term followup (mean, 10 years) to determine graft survivorship and patient outcomes using a modified Hospital for Special Surgery score. Twelve of 60 grafts have failed with three having graft removal alone and nine being converted to total knee replacement. Kaplan-Meier survivorship analysis showed 85% graft survival at 10 years and 74% survival at 15 years. Patients with surviving grafts had good function, with a mean Hospital for Special Surgery score of 83 points at 10 years followup. Ten patients (17%) required meniscal transplantation whereas 41 (68%) required realignment osteotomy done simultaneously with the osteochondral allograft. Patients requiring meniscal transplantation, limb realignment, or both, had equally good outcomes at 10 years as those who underwent osteochondral transplantation alone. Likewise, transplantation to the medial or the lateral condyle had no bearing on long-term outcomes. Radiographs were available for 38 patients. These radiographs showed that 18 (48%) patients had no or mild arthritis, 10 (26%) had moderate, and 10 (26%) had severe arthritis. Late osteoarthritic degeneration as seen on radiographs was associated with outcomes, with patients with more severe arthritis having lower Hospital for Special Surgery scores. The authors think that osteochondral allograft transplantation is a valuable treatment option in patients with large osteochondral defects in the distal femoral articular surface.

Time-sequential changes in biomechanical and morphological properties of articular cartilage in cryopreserved osteochondral allografting

This study examined time-sequential changes in the biomechanical and morphological properties of articular cartilage that had received cryopreserved osteochondral allografting. Osteochondral blocks obtained from the femurs of 18 rabbits were cryopreserved with dimethylsulfoxide (DMSO), using a two-step freezing method, and allografted to the femurs of another 18 rabbits. Specimens for biomechanical and morphological examinations were prepared at the second, fourth, and twelfth weeks after allografting (n = 18). In 12 allografted rabbits, biomechanical features were examined with an indentation test apparatus, and histological changes were studied with a light microscope (second week, n = 4; fourth week, n = 4; twelfth week, n = 4). In the other 6 allografted rabbits, cartilage surfaces were studied with a scanning electron microscope (second week, n = 2; fourth week, n = 2; twelfth week, n = 2). For controls, fresh, DMSO-treated, or DMSO-treated + cryopreserved specimens were examined biomechanically and morphologically. In the time-sequential examination of biomechanical features, both the parameter for elasticity (i.e., ratio of instant elastic strain to maximum strain) and the parameter for viscosity (i.e., average retardation time) significantly changed. Light microscopy showed chronological decreases in safranin-O staining intensity in the matrix, and progression of degeneration. On scanning electron microscopy, disruption of the cartilage surface was also recognized. Therefore, changes in biomechanical properties due to cryopreservation could cause irreversible changes in the cartilage in cryopreserved osteochondral allografting.

Fracture resistance of gamma radiation sterilized cortical bone allografts

Gamma radiation is widely used for sterilization of human cortical bone allografts. Previous studies have reported that cortical bone becomes brittle due to gamma radiation sterilization. This embrittlement raises concern about the performance of a radiation sterilized allograft in the presence of a stress concentration that might be surgically introduced or biologically induced. The purpose of this study was to investigate the effect of gamma radiation sterilization on the fracture resistance of human femoral cortical bone in the presence of a stress concentration. Fracture toughness tests of specimens sterilized at a dose of 27.5 kGy and control specimens were conducted transverse and longitudinal to the osteonal orientation of the bone tissue. The formation of damage was monitored with acoustic emission (AE) during testing and was histologically observed following testing. There was a significant decrease in fracture toughness due to irradiation in both crack growth directions. The work-to-fracture was also significantly reduced. It was observed that the ability of bone tissue to undergo damage in the form of microcracks and diffuse damage was significantly impaired due to radiation sterilization as evidenced by decreased AE activity and histological observations. The results of this study suggest that, for cortical bone irradiated at 27.5 kGy, it is easier to initiate and propagate a macrocrack from a stress concentration due to the inhibition of damage formation at and near the crack tip.

[Shape optimization of the femoral component of hip prosthesis using the finite element method]

Aseptic loosening of implants in bone is the main reason of prosthesis failure. Stress distribution around the implant surface plays a major role in this process, which can be minimized by implant shape optimization. Numerical methods, particularly the finite element method, are an important tool in the analysis of stress distribution and design optimization. The paper presents the problem formulation for this method, illustrated by computational examples.

Supportive strut grafts for diaphyseal bone defects in revision hip arthroplasty

Large femoral cortical strut allografts were used to provide structural support of the femur in 20 patients in whom uncemented, extensively porous-coated, press-fit revision femoral stems were applied. The mean followup was 4.7 years. Radiographic analysis of the patients who had revision surgery revealed that in all 20 patients, the cortical femoral strut allografts showed incorporation. Small areas of graft resorption were observed in only two patients. Seventeen of the uncemented femoral revision stems radiographically showed bone ingrowth. Three of the revision femoral stems were interpreted as being fixed only by fibrous ingrowth after early subsidence after surgery. There were no reoperations. Before surgery, all patients were unable to walk and had severe pain. At followup, all patients were ambulatory and had considerable improvement in pain relief and in their ability to walk. The mean Harris hip score after surgery was 75 (range, 57.5-92). Complications consisted of one peroneal nerve palsy, which resolved; one deep venous thrombosis; one gastrointestinal ulcer; and one case of pneumonia. Supportive cortical strut allografts represent an alternative to the use of circumferential bulk allografts and total femoral replacements in patients with large combined proximal and diaphyseal bone defects.

Arthroscopic mosaic arthroplasty in the equine third carpal bone

OBJECTIVE

To investigate survival and function of autogenous heterotopic osteochondral grafts in a site where injuries are common.

STUDY DESIGN

Three osteochondral grafts were harvested arthroscopically from the femoropatellar joint and transplanted to the third carpal bone (C(3)). Nine months later, histologic, histomorphometric, and biochemical comparisons were made between the transplanted grafts in C(3) and tissue adjacent to the recipient site, the opposing radial carpal bone (C(r)), the donor site in the femoropatellar joint, and the sham-operated contralateral C(3).

ANIMALS

One mixed-breed pony and 5 Standardbred horses aged 3 to 8 years old.

METHODS

Using instruments modified for equine use, four 4.5-mm-diameter osteochondral grafts were harvested arthroscopically from the distal aspect of the lateral trochlea of the right femur and inserted into the radial facet of the right third carpal bone. The fourth graft was kept as a donor-site control sample. Three months later, regular exercise was started and at 6 months, repeat arthroscopy was conducted to evaluate healing. The horses were euthanatized 9 months after transplantation, and comparisons were made between the grafts, opposing radial carpal bone, and contralateral third carpal bone. The assessment criteria included paravital staining, a modified Mankin scoring system, and biochemical analyses for collagen type, total collagen content, and sulfated glycosaminoglycan concentration.

RESULTS

All horses were sound 21 days' postoperatively. At 6 months, all 18 grafts were intact but somewhat soft and opaque compared with surrounding carpal cartilage. Nine months' postoperatively, the bony portions of the grafts were well integrated with the recipient sites, but 6 grafts had histologic evidence of cartilage degeneration. From biochemical analysis of grafts, there was little or no new repair tissue invading the experimental sites, but sulfated glycosaminoglycan (proteoglycan) loss from the transplanted cartilage was marked.

CONCLUSIONS

Heterotopic transfer of osteochondral grafts from the distal aspect of the lateral femoral trochlea to the third carpal bone is feasible with minor modifications of human mosaic arthroplasty instruments. The bony portion of the osteochondral grafts was quickly remodeled to provide subchondral support to the transplanted articular cartilage. The loss of proteoglycan from the transplanted cartilage indicates that the grafts might have been injured during harvesting or insertion, or, more likely, did not remodel to meet the demands of a new biomechanical environment.

CLINICAL RELEVANCE

These findings suggest that arthroscopic resurfacing of focal osteoarticular defects will not be successful in the long term unless donor and recipient sites can be matched with respect to cartilage thickness, biochemical constituents, and physical properties. Mosaic arthroplasty may be indicated in selected cases in which no other options exist to create a confluent cartilage-covered surface.

The effect of adjuvant chemotherapy on osteoarticular allografts

Two hundred lower extremity osteoarticular allografts (in 200 patients) performed for aggressive or malignant bone tumors between 1976 and 1997 included 124 grafts of the distal femur, 46 of the proximal tibia, and 30 of the proximal femur. Seventy-four patients did not receive chemotherapy, and 126 received either adjuvant or neoadjuvant therapy. The diagnoses, mean ages, and length of followup were different for the two groups because most of the patients in the chemotherapy group had osteosarcoma, whereas the largest number in the control group had chondrosarcoma or parosteal osteosarcoma. The extent of the surgery was essentially the same for both patient groups, as is reflected by a low recurrence rate (7% for the control and 6% for the chemotherapy group). A statistical comparison of the various parameters showed that the infection, fracture, and amputation rates were the same, but the nonunion rate was markedly increased in the patients who received chemotherapy (32% versus 12%). Cox regression and Kaplan-Meier studies showed that chemotherapy had a significant effect on outcome, with the success rates for the two groups being quite different (72% versus 56%). The results for the distal femur showed a greater effect than for either the proximal tibia or the proximal femur. Analysis of these data suggest the distal femur is perhaps the most prone to healing problems, possibly based in part on the extent of the surgery. A final study supports the concept that the results improved in later years, suggesting a modification or application of the drugs used, better selection of patients, and improvements in surgical technique.

Demineralized bone matrix as a biological scaffold for bone repair

Experimental models were created in rat fibula to represent impaired bone healing so that biological deficiencies that cause bone repair to fail or to be delayed may be investigated. These models consist of a 4-mm-long segmental defect, created in rat fibula by osteotomy, and fitted with a 7-mm-long tubular specimen of demineralized bone matrix (DBM) over the cut ends of the fibula. The experiments in this study involved various modifications of the DBM scaffold designed to reduce its osteoinductive activity: steam sterilization (sDBM), ethylene oxide sterilization (eoDBM), trypsin digestion (tDBM), and guanidine hydrochloride extraction (gDBM). Bone healing was evaluated by bending rigidity of the fibula and mineral content of the repair site at 7 weeks post-surgery. The sDBM scaffolds resorbed completely by 7 weeks and hence this model was a nonhealing negative control. Rigidities in the unmodified DBM and tDBM groups were comparable, whereas in the gDBM and eoDBM groups it was significantly reduced. Histologically, in the 4-mm defects repaired with unmodified DBM, direct and endochondral bone formation in the scaffold and the defect resulted in a neocortex consisting of woven and lamellar bone uniting the broken bone by 7 weeks post-surgery. We conclude that the eoDBM and gDBM groups represent failure or delay of the bone repair process when compared with the unmodified DBM group in which the process is analogous to normal bone healing.