Suture holes in anterior cruciate ligament bone-patellar tendon-bone grafts

Anterior cruciate ligament reconstruction with a bone-patellar tendon-bone graft is a common and technically demanding surgery. Traditional preparation of the femoral bone plug includes 2 transcortical holes with leading sutures to pull the graft into the knee. The pull of the sutures and patellar tendon are not colinear with the bone plug and femoral socket. The bone plug tilts, thus impairing passage into the femoral socket. A new preparation technique was devised that, by changing the location of the suture holes, decreases graft tilting and improves passage. In our study, traditional and new techniques of femoral bone plug preparation were investigated by force diagramming and then graft modeling. Bone plug tilting was caused by the trailing pull of the patellar tendon eccentric to the plug and socket. By preparing the femoral bone plug with a diametric, transverse trailing suture hole, the plug became colinear with the femoral socket for easier passage. The new technique was then surgically implemented with straighter and faster graft passage.

Incidence and risk factors for graft rupture and contralateral rupture after anterior cruciate ligament reconstruction

PURPOSE

The aim of this study was to determine the rates of contralateral anterior cruciate ligament (ACL) rupture and of ACL graft rupture after ACL reconstruction using either patellar tendon or hamstring tendon autograft, and to identify any patient characteristics that may increase this risk.

TYPE OF STUDY

Case series.

METHODS

Over a 2-year period, 760 endoscopic ACL reconstructions were performed in 743 patients. Bone-patellar tendon-bone autograft was used in 316 patients and 4-strand hamstring tendon in 427 patients. Those patients with a previous contralateral ACL rupture or those who underwent a simultaneous bilateral ACL reconstruction were excluded, leaving 675 knees (675 patients) for review. Persons not involved in the index operation or the care of the patient conducted follow-up assessment by telephone interview conducted 5 years after surgery. Patients were questioned about the incidence of ACL graft rupture, contralateral ACL rupture, symptoms of instability or significant injury, family history of ACL injury, and activity level according to the International Knee Documentation Committee scale. From our prospective database we obtained further information on graft source, meniscal or articular surface injury, and gender. Binary logistic regression was used to measure the relative association between the measured variables and the risk of graft rupture and contralateral ACL rupture.

RESULTS

Five years after primary ACL reconstruction, 612 of the 675 patients (90.7%) were assessed. ACL graft rupture occurred in 39 patients (6%) and contralateral ACL rupture occurred in 35 patients (6%). Three patients suffered both a graft rupture and a contralateral ACL injury. The odds of ACL graft rupture were increased 3-fold by a contact mechanism of initial injury. Return to level 1 or 2 sports increased the risk of contralateral ACL injury by a factor of 10. The risk of sustaining an ACL graft rupture was greatest in the first 12 months after reconstruction. No other studied variable increased the risk of repeat ACL injury.

CONCLUSIONS

After reconstruction, repeat ACL injury occurred in 12% of patients over 5 years. Twelve months after reconstruction, the ACL graft is at no greater risk than the contralateral ACL, suggesting that adequate graft and muscular function for most activities is achieved by this time. Risk factors for repeat ACL injury identified included a return to competitive side-stepping, pivoting, or jumping sports, and the contact mechanism of the index injury. Female patients were at no greater risk of repeat ACL injury than male patients and graft choice did not affect the rate of repeat ACL injury.

LEVEL OF EVIDENCE

Level IV, case series.

Cortical allograft as a vehicle for antibiotic delivery

BACKGROUND

Infection can be a devastating complication after implantation of a cortical bone allograft. The allograft could act as a vehicle for local antibiotic prophylaxis.

MATERIAL AND METHODS

We studied the release of antibiotics in vitro from cortical bone allografts impregnated with antibiotics for different periods of time. We also studied whether cortical allografts impregnated with antibiotics could eradicate Staphylococcus aureus from an experimentally infected graft in vivo. In the in vitro study, pieces of cortical bone were impregnated with netilmicin, vancomycin, ciprofloxacin and rifampicin for 1 h, 10 h and 100 h. The antibiotics were eluted into phosphate-buffered saline (PBS) for 7 days, with daily transfer of the bone into fresh PBS. In the in vivo study, cortical allografts impregnated with antibiotics were placed in rats intramuscularly. 10 microL of an S. aureus suspension (0.6 x 10(5) CFU) was placed in the intramedullary cavity. After 15 days, the allografts were removed and examined for bacterial growth.

RESULTS

The amount of antibiotics released in vitro was influenced by the time used for antibiotic impregnation of the bone. Allografts impregnated with netilmicin, vancomycin and rifampicin effectively eradicated perioperative contamination with S. aureus in vivo.

INTERPRETATION

This study shows that a cortical bone allograft would be an effective vehicle for local antibiotic delivery.

Prolonged-fresh preservation of intact whole canine femoral condyles for the potential use as osteochondral allografts

Defects in articular cartilage are often repaired with fresh osteochondral grafts. While fresh allografts provide viable chondrocytes, logistic limitations require surgical implantation within seven days of graft harvest. Here, we provide information on cold preservation of whole intact osteochondral materials that retains cartilage cell viability and function, and histologic and biochemical integrity for 28 days. Canine femoral condyles were obtained and stored at 4 degrees C for 14, 21 or 28 days. At the end of the storage period, cartilage was assessed for cell viability, 35S uptake, proteoglycan content and histologic parameters. The most noticeable histologic change was reduced Safranin-O near the cartilage surface with 14 days of cold preservation, but had recovered with 21 and 28 days. Cartilage thicknesses did not vary significantly. Cell viability was >95% at 14 days, 75-98% at 21 days and reduced to 65-90% at 28 days. Cell function measures showed that the level of 35SO4 incorporation was suppressed in samples stored at 4 degrees C. However, no significant differences were seen among groups at 14, 21 or 28 days of cold preservation. This data has implications for tissue banking protocols for osteochondral allograft material obtained for transplantation suggesting that cold preserved allograft material be implanted within 28 days.

Promises and pitfalls of stem cell therapy for promotion of bone healing

There is promise in combining stem cells with allogeneic bone matrix to promote bone healing. Murine bone marrow, peripheral blood, and compact bone cells were transplanted ectopically under the kidney capsule in mice, alone or in combination with allogeneic matrix products: powder and putty to determine their bone forming potential in comparison to transplanted femoral bone fragments and long-term cultured bone marrow cells. The end point was the amount of bone formed as determined by quantitative histology. Mononuclear cells from marrow, peripheral blood, or bone alone transplanted under the kidney capsule did not form bone. Mononuclear cell populations did not combine readily with matrix products and there was in vivo migration of the transplanted combinations. Kidney subcapsular transplanted cultured bone marrow cells formed bone in proportion to the culture period, but after 9 weeks, the extent was only 20% by area of that of similarly transplanted femoral bone fragments. An inductive stimulus for bone formation seemed necessary. Osteoprogenitor cells were not detected in significant numbers in blood unless high doses of cytokines were administered. A better definition of the optimal cell populations and manipulations required for promotion of bone healing is needed along with new (transplant) models that allow for cell tracking. Much work remains to overcome current pitfalls in the use of stem cells to promote allograft integration and bone healing.

LEVEL OF EVIDENCE

Therapeutic study, Level V (expert opinion). See the Guidelines for Authors for a complete description of levels of evidence.

Allograft bone decreases in strength in vivo over time

Allograft bone is the primary source of graft material for structural oncological limb salvage procedures. Failure rates after massive allograft reconstructions have been reported as high as 60% at 10 years, which are associated with a multitude of biologic processes influencing the graft incorporation and functional capacity. It is unknown if mechanical failure is associated with a gradual loss of bulk material properties of the bone (strength and modulus), loss of bone mineral density, osteoclastic resorption of the allograft, unrepaired allograft microfractures or microcracks, and/or local stress concentration within the tissue. Allograft material properties, bone mineral density, microcrack prevalence, and cortical porosity were quantified in 13 failed human allograft retrievals ranging in longevity from 1 to 13 years in vivo. Nonimplanted allograft tissue (n = 27) served as the baseline for comparison. A 50% loss in strength of allograft tissue was noted after 10 years in vivo. Loss of strength was correlated with an increase in microfracture prevalence and decrease in bone mineral density within the retrieved allograft cortex. This study suggests functional failure of allograft limb salvage procedures may, in part, be attributed to degradation of the tissue's material properties, bone mineral density and prevalence of microcracks.

Greater trochanteric transfer for the treatment of coxa brevis

We reviewed the outcomes of 28 patients for whom we did greater trochanteric transfer. Twenty-two (79%) patients treated for coxa brevis by greater trochanteric transfer had good relief of pain and limp. Four (1%) outcomes were fair and two (0.7%) were poor. Our outcomes compared favorably with those already reported in the literature. Patients who had avascular necrosis caused by Perthes disease tended to have a better outcome than those caused as a complication of treatment for hip dysplasia. A computer model based on radiographic measurements was useful in planning the placement of the transfer for biomechanical efficiency. The surgical technique and osteotomy planning is described. Our goal is to review (1) the effectiveness of our surgical procedure, (2) whether deformity etiology influences outcome, (3) the best way to achieve optimal biomechanical efficiency, and (4) how software assisted planning can assist in surgical planning.

The use of structural distal femoral allografts for acetabular reconstruction. Average ten-year follow-up

BACKGROUND

Acetabular fixation during revision total hip arthroplasty in patients who have a nonsupportive superior dome and proximal migration of the acetabular component (a Paprosky Type-IIIa defect) cannot be achieved reliably with use of a hemispherical porous-coated component alone. The purposes of the present study were to determine the long-term results associated with the use of a porous-coated hemispherical acetabular component, supported with a distal femoral structural allograft, for revision at the site of a Type-IIIa defect and to determine if graft resorption leads to late failure.

METHODS

Thirty-one patients who had an acetabular reconstruction with use of a distal femoral allograft for the treatment of a Type-IIIa defect between January 1985 and December 1990 were followed annually with clinical and radiographic evaluations. At the time of the latest follow-up, eight patients had died and one patient had been lost to follow-up. One of the patients who died had had a clinical failure at 4.5 years postoperatively and was included in the analysis. Therefore, twenty-three patients, who had had an average age of sixty-one years at the time of the index procedure, were evaluated at an average of 10.3 years postoperatively.

RESULTS

Five acetabular components were re-revised because of aseptic loosening at an average of 5.3 years after the index procedure. Radiographically, all but one of the remaining components were stable and showed evidence of bone ingrowth. The average Merle D'Aubigné and Postel hip score improved from 5 points preoperatively to 10 points at the time of the latest follow-up. Allograft bone resorption, although difficult to quantitate, was observed around six of the seventeen stable components and around two of the five components that failed clinically.

CONCLUSIONS

Acetabular revision with use of a porous-coated acetabular component along with a structural distal femoral allograft for the treatment of a Type-IIIa defect demonstrated a high rate of clinical and radiographic success after an average of ten years of follow-up.

Total hip replacement with the CLS expansion shell and a structural femoral head autograft for patients with congenital hip disease

BACKGROUND

Reconstruction of a dysplastic acetabulum in a patient with osteoarthritis of the hip may be accomplished with a variety of surgical techniques. The aim of our study was to assess the outcomes of total hip replacement with the uncemented CLS expansion shell and a structural femoral head autograft to augment the deficient acetabulum in patients with osteoarthritis secondary to congenital hip disease.

METHODS

Between 1990 and 1994, we used a CLS expansion shell with a structural femoral head autograft in forty-three consecutive patients (forty-three hips) with osteoarthritis secondary to congenital hip disease. The ratio of male to female patients was 5:38, and the mean age of the patients was forty-eight years. According to the preoperative radiographic assessment, the dysplasia was categorized as Crowe type I in six patients, Crowe type II in thirty-one patients, and Crowe type III and type IV in three patients each. No patient was lost to follow-up. The mean duration of follow-up was 120 months. Plain radiographs were made immediately after surgery and at the latest follow-up evaluation. Clinical outcomes were determined with use of the Harris hip score and the Merle d'Aubigné and Postel score, and a radiographic analysis was performed.

RESULTS

Postoperatively, the mean Harris hip score had improved 58 points for patients with Crowe type-I and II dysplasia, 47 points for patients with Crowe type-III dysplasia, and 46 points for patients with Crowe type-IV dysplasia (p < 0.05 for all). At the latest follow-up examination, the mean Harris hip score for all patients was 92.6 points. The mean Merle d'Aubigne and Postel score was 8.3 points preoperatively and 15.8 points at the time of the latest follow-up. The mean coverage of the shell by the graft immediately after surgery was 32.2%. Osteointegration of the CLS expansion shell was evident radiographically in all forty-three hips at the latest follow-up evaluation. There were no failures of the bone grafts. Clinical survival of the CLS expansion shell with a structural femoral head autograft was 100% at a mean of ten years after surgery. The rate of survival of the shell, with radiographic signs of loosening as the end point, was 88.2% at ten years.

CONCLUSIONS

The CLS uncemented expansion shell, when used with a structural femoral head autograft, provides a reliable reconstruction, augments deficient acetabular bone stock, and allows placement of the socket at or close to the anatomic center of hip rotation in patients undergoing total hip arthroplasty to treat the sequelae of congenital hip disease.

Chondrocyte death associated with human femoral osteochondral harvest as performed for mosaicplasty

BACKGROUND

Autologous osteochondral transfer is an option for the treatment of articular defects. However, there are concerns about graft integration and the nature of the tissue forming the cartilage-cartilage bridge. Chondrocyte viability at graft and recipient edges is thought to be an important determinant of the quality of repair. The purpose of the present study was to evaluate early cell viability at the edges of osteochondral grafts from ex vivo human femoral condyles.

METHODS

Fresh human tissue was obtained from eleven knees at the time of total knee arthroplasty for the treatment of osteoarthritis. Osteochondral cylinders were harvested with use of a 4.5-mm-diameter mosaicplasty osteotome from regions of the anterolateral aspect of the femoral condyle that were macroscopically nondegenerate and histologically nonfibrillated. Plugs were assessed for marginal cell viability by means of confocal laser scanning microscopy.

RESULTS

The diameter of the cartilaginous portion of the osteochondral plugs was a mean (and standard error of the mean) of 4.84 +/- 0.12 mm (as determined on the basis of three plugs). This value was approximately 300 microm greater than the measured internal diameter of the osteotome. There was a substantial margin of superficial zone cell death (mean thickness, 382 +/- 68.2 microm), with >99% cell viability seen more centrally (as determined on the basis of five plugs). Demiplugs were created by splitting the mosaicplasty explants with a fresh number-11 scalpel blade. The margin of superficial zone cell death at the curved edge was significantly greater than that at the site of the scalpel cut (390.3 +/- 18.8 microm compared with 34.8 +/- 3.2 microm; p = 0.0286). Similar findings were observed when the cartilage alone was breached and the bone was left intact, with the margin of superficial zone cell death being significantly greater than that obtained in association with the straight scalpel incision (268 +/- 38.9 microm compared with 41.3 +/- 13.4 microm; p = 0.0286). The margin of superficial zone cell death showed no increase during the time-period between fifteen minutes and two hours after plug harvest. A mathematical approximation of the mosaicplasty region suggested that early cell death of this magnitude affects about one third of the superficial graft area.

CONCLUSIONS

The results of the present study suggest that mosaicplasty, while capable of transposing viable hyaline cartilage, is associated with an extensive margin of cell death that is likely to compromise lateral integration and articular reconstruction.

Mechanical characteristics of the bone-graft-cement interface after impaction allografting

Impaction allografting is an attractive procedure for the treatment of failed total hip replacements. The graft-cement-host bone interface after impaction allografting has not been characterized, although it is a potential site of subsidence for this type of revision total hip reconstruction. In six human cadaveric femurs, the cancellous bone was removed proximally and local diaphyseal lytic defects were simulated. After the impaction grafting procedure, the specimens were sectioned in 6 mm transverse sections and push-out tests were performed. From the adjacent sections the percentage cement contact of the PMMA cement with the endosteal bone surface was determined. The host bone interface mechanical properties varied significantly along the femur largely due to different interface morphologies. The apparent host bone interface shear strength was highest around the lesser trochanter and lowest around the tip of the stem. A significant positive correlation was found between the percentage cement contact and the apparent host bone interface shear strength (r2 = 0.52). The sections failed in 69% of the cases through a pure host bone interface failure without cement or allograft failure, 19% failed with local cement failure, and 12% with a local allograft failure. The apparent host bone interface strength was on average 89% lower than values reported for primary total hip replacements and were similar to cemented revisions proximally and lower distally. This study showed that cement penetration to the endosteal surface enhanced the host bone-graft interface.

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 novel murine segmental femoral graft model

To further understand the cellular and molecular mechanisms underlying cortical bone graft healing, we have developed a novel mouse femur model that permits quantitative and molecular analysis of structural bone graft healing. A 4 mm mid-diaphyseal femoral segment was removed and replaced by either immediate implantation of a fresh autograft, a frozen, genetically identical isograft or a frozen allograft from a different strain of mouse, which was secured with a 22-gauge metal intramedullary pin. Healing was evaluated by radiology, histomorphometry, and in situ hybridization. Autograft repair occurred by endochondral bone formation at the host-graft junction and by intramembranous bone formation along the length of the graft bed at 2 weeks, with maturation and remodeling apparent by 4 weeks. Bone repair in allografts and isografts completely relied on endochondral bone formation at the host-graft cortical junction, with absence of periosteal bone formation along the length of the graft, suggesting that live periosteal cells from the donor tissue are necessary for this response. This small animal model of structural bone grafting can be used to evaluate tissue-engineered allografts and novel bone graft substitutes using quantitative and molecularly defined outcome measures.

Proximal femoral allografts for bone deficiencies in revision hip arthroplasty: a medium-term follow-up study

Fifteen patients who had undergone hip reconstruction using a proximal femoral allograft-prosthesis composite because of failed total hip arthroplasty were reviewed retrospectively. The average length of allograft was 11 cm. The average follow-up period was 7.6 years. Ten patients retained the allograft-prosthesis construct, yielding a success rate of 67% for the procedure. The average preoperative Harris Hip Score of all patients was 21.7 points. At the latest follow-up, the average hip score for 10 patients with retained allograft-prosthesis composite was 81 points. Complications included junction nonunion (13%), allograft fracture (6.7%), loosening of acetabular component (6.7%), trochanteric escape (26.7%), allograft infection (20%), and allograft resorption (20%). Although proximal femoral allograft-prosthesis composite achieved good clinical results in most of the patients at medium-term follow-up, the late development of infection and resorption of the allograft warranted continued observation of patients who had undergone such procedures.

Donor-site morbidity after osteochondral autograft transfer procedures

We report on 2 patients who had donor-site morbidity after an autogenous osteochondral grafting was performed. Both patients had fibrocartilage hypertrophy at the donor sites that contributed to knee pain and occasional locking; the second patient also had a lack of fibrocartilaginous regrowth with symptomatic residual osteocartilaginous defects. Additional arthroscopic surgery was required in both cases to trim the fibrocartilage. In addition, for the second case, a fresh osteoarticular allograft was used to transfer osteocartilaginous plugs back into the original knee donor sites due to continued knee pain. When performing an osteochondral autograft transfer, the benefits provided at the recipient site must be weighed against the possible donor-site morbidity that may result.

Clostridium infections associated with musculoskeletal-tissue allografts

BACKGROUND

Allografts are commonly used in orthopedic reconstructive surgery. In 2001, approximately 875,000 musculoskeletal allografts were distributed by U.S. tissue banks. After the death from Clostridium sordellii sepsis of a 23-year-old man who had received a contaminated allograft from a tissue bank (Tissue Bank A), the Centers for Disease Control and Prevention initiated an investigation, including enhanced case finding, of the methods used for the recovery, processing, and testing of tissue.

METHODS

A case of allograft-associated clostridium infection was defined as a culture-proven infection of a surgical site within one year after allograft implantation, from January 1998 to March 2002. We traced tissues to tissue banks that recovered and processed these tissues. We also estimated the rates of and risk ratios for clostridium infections for tissues processed by the implicated tissue bank and reviewed processing and testing methods used by various tissue banks.

RESULTS

Fourteen patients were identified, all of whom had received allografts processed by Tissue Bank A. The rates of clostridium infection were 0.12 percent among patients who received sports-medicine tissues (i.e., tendons, femoral condyles, menisci) from Tissue Bank A and 0.36 percent among those who received femoral condyles in particular. The risk-ratio estimates for clostridium infections from tissues processed by Tissue Bank A, as compared with those from other tissue banks, were infinite (P<0.001) for musculoskeletal allografts, sports-medicine tissues, or tendons. Because Tissue Bank A cultured tissues only after treating them with a nonsporicidal antimicrobial solution, some test results were probably false negatives. Tissues from implicated donors were released despite the isolation of clostridium or bowel flora from other anatomical sites or reports of infections in other recipients.

CONCLUSIONS

Clostridium infections were traced to allograft implantation. We provide interim recommendations to enhance tissue-transplantation safety. Tissue banks should validate processes and culture methods. Sterilization methods that do not adversely affect the functioning of transplanted tissue are needed to prevent allograft-related infections.

The use of structural proximal femoral allografts in complex revision hip arthroplasty

Between April 1992 and November 1998 we used 34 massive proximal femoral allografts for femoral reconstruction at revision hip arthroplasty. Seven patients have died and two have been lost to follow-up. There were thus 25 grafts in 24 patients for review. The mean follow-up was 53 months (16 to 101). By the time of the review two patients had undergone a further revision for failure of the allograft. Another had required secondary plating and grafting at the graft-host junction for symptomatic nonunion. One had recurrence of deep sepsis and was being managed conservatively. Trochanteric union was considered to have occurred radiologically in 16 of the 25 grafts and union at the host-graft junction in 20. Resorption of the allograft was significant in only two hips. We recommend this technique in cases in which femoral bone loss has been catastrophic.

Osteochondritis dissecans of the talus treated with the mosaicplasty technique: a case report

The authors present the use of osteochondral autografting with mosaicplasty technique performed on a 20-year-old man for a large osteochondral talar dome lesion. The patient had sustained a right ankle sprain many times while playing rugby football. The lesion measured 15 mm in diameter and encompassed more than one-third of the articular surface. After exposing the talus to a medial malleolar osteotomy, 3 osteochondral grafts taken from the medial femoral condyle of the ipsilateral knee were press-fit into the lesion. One year postoperatively, the patient has returned to playing rugby football. Radiographically, there was incorporation of the grafts. The authors believe that the mosaicplasty technique presents a promising new option in the treatment of osteochondritis dissecans of the talus.

Demineralized Bone Matrix-Induced Ectopic Bone Formation in Rats: In Vivo Study with Follow-up by Magnetic Resonance Imaging, Magnetic Resonance Angiography, and Dual-Energy X-Ray Absorptiometry

The aim of this study was to further explore the use of magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and dual-energy X-ray absorptiometry (DEXA) to assess bone formation and blood circulation in a pedicled bone graft substitute. In 14 Wistar rats, initially 10 weeks old, heterogeneous demineralized femur bone matrix implants were wrapped in pedicled adductor thigh muscle flaps. One rat died after surgery. Subsequently, bone formation and maintenance of blood vessel functionality were evaluated in six rats 6 weeks postimplantation by means of in vivo MRI/MRA and postmortem histomorphometry. The other seven rats were left for 12 weeks, whereafter bone formation was evaluated by in vivo DEXA and postmortem histomorphometry. The results demonstrated that after 6 weeks bone formation was present in four of six animals, quantified as 42 (+/-35)% and 25 (+/-19)% by means of MRI and histomorphometry, respectively. MRA was able to show patency of the pedicles of these four rats only, which suggests that the lack of blood supply in the other two rats is the cause of the failure to form bone. In the 12-week group, histology showed increased bone formation without signs of osteolysis, which was quantified histomorphometrically to be as high as 48 (+/-15)%. DEXA failed to show bone formation. It is concluded that in vivo MRI proved to be a reliable method for monitoring ectopic bone formation in a rat model, whereas in vivo DEXA was unable to detect the implants. Furthermore, in vivo MRA proved to be a useful technique for studying the circulation of muscle flaps in this animal model.

Effect of platelet concentration in platelet-rich plasma on peri-implant bone regeneration

This study analyzed the effect of the platelet count in platelet-rich plasma (PRP) on bone regeneration in vivo. Twenty male New Zealand white rabbits were used. PRP was produced using the Platelet Concentrate Collection System (PCCS) (3i, Miami, FL, USA). After inducing ketamine-xylazine anaesthesia, a self-tapping titanium screw (Branemark MK III TiUnite, 3.75 x 7 mm) was inserted in each distal femur; the femurs were randomized so that one side was treated with PRP while the other (control) was not. Intravital fluorochrome staining was performed on days 1, 7 (1.5 ml of 2% doxycycline/kg bodyweight), 14 (6% xylenol orange, 1.5 ml/kg), and 21 (1% calcein green, 5 ml/kg). Animals were euthanized on day 28 (n = 20). Specimens were prepared for histomorphological evaluation according to Donath and Breuner [J. Oral Pathol. 11 (1982) 318]. Comparing the bone regeneration (fluorochrome staining) in the 4-week implants (n = 19), the only significant difference (sign test, P = 0.004) was seen with intermediate platelet concentrations (n = 9,503,000-1,729,000 platelets/microl PRP). There were no differences in the bone/implant contact rates between the test and the control side among the three groups. The platelet concentration required for a positive PRP effect on bone regeneration seems to span a very limited range. Advantageous biological effects seem to occur when PRP with a platelet concentration of approximately 1,000,000/microl is used. At lower concentrations, the effect is suboptimal, while higher concentrations might have a paradoxically inhibitory effect. On the other hand, the effect of this type of platelet concentrate was not beneficial to accelerate the osseointegration of enosseous dental implants.

Management of periprosthetic femoral fractures after total knee arthroplasty using a distal femoral allograft

This study is a review and discussion of 12 consecutive patients who were revised with a distal femoral allograft for periprosthetic supracondylar fractures of the femur associated with poor bone quality by the same surgeon between 1990 and 2001. Two were lost to follow-up. The average age was 65 years, and the mean follow up was 6 years. Charts were reviewed to identify complications and graft survivorship. Functional assessment consisted of the modified Hospital for Special Surgery (HSS) knee score and the MOS 36-ITEM Short Form Health Survey. Radiographs were evaluated by 3 independent observers to determine graft union, resorption, and component loosening. The average postoperative HSS score and SF-36 were 75 and 88, respectively. Mean flexion was 100 degrees. Nine patients achieved union and were able to fully bear weight. Three patients required more surgery as a result of postoperative complications. Radiographs showed no migration, no loosening, and good interface union in 9 of the 10 patients available for follow-up. We concluded that this is a viable salvage procedure for this type of injury.

Manual punch versus power harvesting of osteochondral grafts

PURPOSE

The purpose of the study was to analyze the effect on chondrocyte viability of 2 existing methods of harvesting osteochondral grafts used for articular cartilage resurfacing.

TYPE OF STUDY

Acute animal experiment.

METHODS

Power (P) trephine versus manual (M) punch harvesting was tested; 2.7-mm and 4.5-mm dowels were harvested from 8 femoral trochlea from 4 sheep using the Acufex MosaicPlasty system (Andover, MA). Grafts were harvested perpendicular to the articular surface to a depth of 10 mm under constant saline irrigation. Power trephine grafts (n = 46, 2.7 P; n = 45, 4.5 P) were harvested by coupling the serrated trephine to a standard orthopaedic nitrogen powered drill. Manual punch grafts (n = 41, 2.7 M; n=33, 4.5 M) were harvested by malleting the punch to the required depth, minimizing rocking, and only slightly turning the punch on removal. Five 40-microm-thick fresh cartilage sections oriented perpendicular to the articular surface were obtained from each graft and then stained with Syto 13 and ethidium bromide vital stains, and the proportion of live cells per field and physical damage were compared between groups. Masson's trichrome stain was used on paraffin-embedded histologic sections.

RESULTS

Power harvesting was technically more difficult and resulted in more gross and light microscopic damage to the osteochondral grafts. Chondrocyte viability was significantly greater for manual punch versus power harvesting of both graft sizes (P <.005). Chondrocyte viability was greater for 4.5 P versus 2.7 P grafts (P <.005), but no difference was found between the 2.7 M and 4.5 M groups (P =.357).

CONCLUSIONS

Chondrocyte viability is significantly greater using manual punch versus serrated power trephines when harvesting osteochondral grafts for cartilage resurfacing procedures. Power trephines should not be used for this procedure.

CLINICAL RELEVANCE

This study shows that the original method (power trephine) of harvesting osteochondral grafts results in great loss of chondrocyte viability versus manual punch harvesting and should no longer be used.

Composite vascularized skin/bone graft model: A viable source for vascularized bone marrow transplantation

In this study, we introduce a new model for vascularized skin and bone marrow transplantation. Twenty-five Lewis (RT1(1)) rats were studied. Anatomic dissection studies were performed in 5 animals. In the experimental group, 10 isograft transplantations were performed between Lewis rats. Combined groin skin and femoral bone flaps were transplanted based on the femoral artery and vein. Transplants were evaluated on a daily basis. All flaps survived without problems over 100 days posttransplant. The skin component remained pink and pliable, and grew new hair. Histological examination of the femoral bone (except the femoral head) revealed active hematopoiesis with a viable compact and cancellous bone components on day 100 posttransplant. This model can be applied to tolerance induction studies across the major Histocompatibility (MHC) barrier, where bone will serve as donor of stem and progenitor cells, and the skin flap will serve as a monitor of graft rejection.

Subchondral bone reaction associated with chondral defect and attempted cartilage repair in goats

Repair of cartilage damage with autologous chondrocyte transplantation (ACT) has become popular in clinical use during the past few years. Although clinical results have mostly been successful, several unanswered questions remain regarding the biological mechanism of the repair process. The aim of this study was to develop a goat model for ACT. The repair was not successful due to the graft delamination, but we characterize the subchondral changes seen after the procedure. A chondral lesion was created in 14 goat knees, operated on 1 month later with ACT, and covered with periosteum or a bioabsorbable poly-L/D-lactide scaffold. After 3 months, only two of the five lesions repaired with ACT showed partly hyaline-like repair tissue, and all lesions (n = 4) with the scaffold failed. Even though the lesions did not extend through the calcified cartilage, the bone volume and collagen organization of bone structure were decreased when assessed by quantitative polarized light microscopy. There was a significant loss of bone matrix and distortion of the trabecular structure of subchondral bone, which extended several millimeters into the bone. The subchondral bone demonstrated strong hyaluronan staining in the bone marrow and cartilaginous areas with signs of endochondral ossification, suggesting structural remodeling of the bone. The goat model used here proved not to be an optimal model for ACT. The changes in subchondral bone may alter the biomechanical properties of the subchondral plate and thus the long-term survival of the repair tissue after ACT.