Acceleration of surgical angiogenesis in necrotic bone with a single injection of fibroblast growth factor-2 (FGF-2).

The aim of this study was to accelerate angiogenesis in necrotic bone by combining vascular bundle implantation and fibroblast growth factor-2 (FGF-2) administration. Twenty-four Japanese white rabbits were evaluated in this study. A portion of a rabbit iliac crest bone was removed as a free bone graft and frozen in liquid nitrogen to ensure complete cellular necrosis. A narrow hole was created in the bone and the graft was placed in the proximal thigh. In group 1, FGF-2 was injected into the hole at a single dose of 100 microg, and the saphenous artery and its venae comitantes were passed through the hole of the bone. In group 2, injection of saline into the hole and the vascular bundle implantation was used as a control. Neovascularization around the vessel was evaluated at weeks 1 and 2 after surgery. Neovascularization was observed along the implanted vascular bundle in both groups. At both 1 and 2 weeks after surgery, the vessel density of group 1 was significantly higher than that of group 2. The average length of newly formed vessels of group 1 was also significantly longer than that of group 2 at both 1 and 2 weeks after surgery. Both the vessel density and length were greater in week 2 animals than week 1. A local single injection of FGF-2 improved surgical angiogenesis in necrotic bone in this study. As FGF-2 is recognized as a potent mitogen for a variety of mesenchymal cells, the combination of vascular bundle implantation and FGF-2 administration may contribute to the treatment of ischemic osteonecrosis.     

VEGF-promoted surgical angiogenesis in necrotic bone

The ability of vascular endothelial growth factor (VEGF) to accelerate neoangiogenesis from implanted arterovenous (AV) bundles in necrotic bone was evaluated. A saphenous AV bundle was placed in a necrotic segment of rabbit ilium. In group II, VEGF (100 ng/h x 3 days) was administered by continuous infusion. Bone blood flow was measured with radioactive-labeled microspheres, and capillary density was determined by microangiography combined with Sp?lteholtz bone clearing at 1, 2, and 4 weeks. Neovascularization was observed along the implanted vascular bundle in both groups. One week after surgery, bone blood flow and vessel area were significantly higher in VEGF-treated animals (P < 0.05). No significant difference was observed at later times. Direct VEGF administration increased surgical angiogenesis and improved blood flow and neovascularization in necrotic bone 1 week after AV bundle implantation. Thereafter, a robust angiogenic response from the AV bundle was seen in both groups.     

Systemic zoledronate precoating of a bone graft reduces bone resorption during remodeling

Background Cartilage degeneration often occurs after osteosynthesis of a devascularized intermediary fragment in a joint fracture, in mosaicplasty or in whole-joint toe-to-finger transplantation. Hypothetically, the degeneration is secondary to a collapse of the transferred subchondral bone as it remodels during high mechanical load. Bisphosphonates are used to reduce resorption of necrotic bone. We tested a systemic pretreatment before harvesting the graft in order to protect the bone and cartilage against collapse and secondary arthrosis.

Methods Rats were given one zoledronate injection and bone grafts were harvested. The grafts were frozen, thawed and placed into bone chambers, and implanted into another batch of rats. Graft resorption and new bone formation was measured by histomorphometric analysis and compared with untreated grafts.

Results In the remodeled area of the controls, the graft was almost totally resorbed and replaced by bone marrow. In the zoledronate-treated specimens, the graft remained and the graft trabeculas were lined with new bone. By histomorphometry, the total amount of bone (graft plus new bone) within the remodeled area was 16% in the zoledronate-treated grafts and 5% in the controls (p = 0.003).

Interpretation A bone graft can be pretreated with bisphosphonate and remain protected against resorption once implanted again. ▪     

No positive effects of OP-1 device on the incorporation of impacted graft materials after 8 weeks: a bone chamber study in goats

Background Bone morphogenetic proteins (BMPs) have the potential to improve clinical outcome after hip revision surgery by improving graft incorporation and implant fixation. However, impaction of cancellous bone grafts and TCP/HA bone substitute mixed with OP-1 device in a bone chamber in goats in a previous study led to reduced fibrous tissue ingrowth after 4 weeks. New bone formation was not promoted by OP-1. In the current study we examined whether this reduction represented a final loss of ingrowth or was just a delay, and whether the reduction can be overcome and ultimately results in a better late ingrowth.

Methods Bone chambers with impacted allografts and impacted TCP/HA granules mixed with 2 doses of OP-1 device were implanted in proximal medial goat tibias. Impacted allografts and TCP/HA not treated with OP-1 served as controls. After 8 weeks, the incorporation was evaluated using histology and histomorphometry.

Results Histology revealed evidence of bone graft incorporation, which proceeded in a similar way in both allografts and TCP/HA, with and without the addition of OP-1. After 8 weeks, no difference in bone ingrowth was found between the OP-1 groups and their controls. It was only in the allografts that the addition of OP-1 resulted in more fibrous tissue ingrowth.

Interpretation We conclude that the previously observed delay in fibrous tissue ingrowth can be only partially overcome.     

Tartrate-resistant acid phosphatase 5b (TRAP 5b) as a marker of osteoclast activity in the early phase after cementless total hip replacement

Background After total hip replacement, increased bone metabolism is seen. A local periprosthetic osteopenia can be measured by dual-energy X-ray absorptiometry (DXA), but it is still unkown whether biochemical markers can be used to monitor the local remodeling at an earlier stage.

Patients and methods In this prospective study we compared the biochemical markers tartrate-resistant acid phosphatase 5b (TRAP 5b), bone ALP, osteocalcin and CrossLaps with periprosthetic DXA in 17 consecutive patients after uncemented total hip replacement.

Results We found a highly significant early increase in TRAP 5b after 2 weeks and 6 weeks, which was followed by a densitometrically detectable decrease in bone mineral density after 26 weeks, especially in periprosthetic section Gruen zone 7. Bone ALP and osteocalcin levels as markers of osteoblast activity, and also Cross-Laps as a further marker of osteoclast activity, did not appear to allow any significant prediction of local bone remodeling.

Discussion Our findings show that TRAP 5b is a sensitive parameter for monitoring of osteoclast activity after cementless total hip replacement, and may predict local osteopenia.     

Surface-bound bisphosphonates enhance screw fixation in rats--increasing effect up to 8 weeks after insertion

Background A bisphosphonate coating improves screw fixation 2 weeks after implantation in cancellous bone. This study on rats examined further development of fixation over time for screws inserted in cancellous and cortical bone.

Methods SS screws were coated with a multiple layer of fibrinogen. Half of the screws were coated further with bisphosphonates, which were linked to the fibrinogen. The screws were inserted in cancellous and cortical bone in rats. The rats were killed after 5 h, 4 days, 1, 2, 4, 8, and 24 weeks, and fixation was evaluated by pullout test.

Results There was a gradual increase in pull-out force over time in both cancellous and cortical bone. The bisphosphonate coating improved fixation. Moreover, the difference between the bisphosphonate and control groups increased with time. The pull-out force was almost twice that of the controls for screws inserted in cancellous bone at 8 weeks. Energy uptake was increased more than 3-fold.

Discussion The energy uptake and pull-out force of a screw depends on the bone engaged with the threads. Thus, the presence of bisphosphonates increased the amount or quality of this bone by affecting the resorp-tion/formation in a positive way. The increased effect of the bisphosphonates with time thus suggests that bisphosphonate is retained within the remodeling bone, with a positive effect on its gradual adaptation to the implant.     

Long-standing increased bone turnover at the fixation points after anterior cruciate ligament reconstruction: a positron emission tomography (PET) study of 8 patients

Background A secure incorporation of the graft in a bone tunnel is a prerequisite for successful anterior cruciate ligament reconstruction. In this cross-sectional pilot study, we studied the healing process with positron emission tomography (PET) scanning.

Patients and methods 8 young patients underwent an anterior cruciate ligament reconstruction with a bonepatellar tendon-bone graft (BTB, n = 4) or a quadruple semitendinosus and gracilis graft (ST/G, n = 4). Regional bone turnover was quantified with an 18F-fluoride PET scan in each patient 1 day, 3 weeks, 7 months, or 22 months after surgery.

Results The highest activity level was found 3 weeks after surgery, but the activity at the femoral fixation points was markedly increased even after 7 months. The bone turnover was almost normalized 22 months after the operation.

Interpretation It would take at least 7 months until an anterior cruciate ligament graft, fixed with an interference screw, is completely incorporated. This finding is important for postoperative rehabilitation. Furthermore, PET is a feasible tool when studying new ways of fixing soft tissue to bone.     

Irradiation has no effect on the incorporation of impacted morselized bone: a bone chamber study in goats

Background Gamma irradiation has been widely used for sterilization of bone allografts. However, gamma irradiation alters proteins. This is favorable when it reduces immunogenicity, but is undesirable when osteoinductive proteins are damaged. Although the effect of gamma irradiation on BMPs has been studied, the effect of irradiation on the process of incorporation of morselized bone chips remains unclear. We studied the effects of sterilization by gamma irradiation on the incorporation of impacted morselized allografts.

Methods Bone chambers with impacted allografts, rinsed impacted allografts, allografts that were rinsed and subsequently irradiated, and an empty control were implanted in proximal medial tibiae of goats. Incorporation was evaluated using histology and histomorphometry.

Results Histology revealed evidence of bone graft incorporation, which proceeded in a similar way in unprocessed, rinsed, and both rinsed and irradiated bone grafts. After 12 weeks, no difference in bone and tissue ingrowth was found between the unprocessed, the rinsed, and the rinsed and subsequently irradiated allografts. The amount of unresorbed graft remnant was highest in the unprocessed bone grafts.

Interpretation We conclude that sterilization with gamma irradiation does not influence the incorporation of impacted rinsed bone allografts.     

Structural allografts for bone stock reconstruction in two-stage revision for infected total hip arthroplasty: good outcome in 16 of 18 patients followed for 5-14 years

Background The use of massive bone allografts in cases of revision of failed total hip arthroplasties (THAs) due to infection is controversial.

Patients and methods 18 patients presented with infection at the site of a THA and were treated with a two-stage protocol. In the first stage, the prosthesis was removed together with all necrotic tissues and cement material if present. A custom-made mold of Palacos R cement containing 1 g of gentamicin was then inserted in 17 of the 18 patients. Systemic antibiotics were used during the interval period. In the second stage, the patients had either acetabular or femoral reconstruction using bulk allograft bone.

Results Mean follow-up was 9 (5-14) years. 1 patient presented with recurrent infection and underwent a Girdlestone resection arthroplasty as definitive treatment. Another patient had a mechanical failure of the acetabular component, which was revised 10 years after the second stage of the reconstruction. The mean Harris Hip Score improved from 34 points preoperatively to 71 points at the last review. By our definition, 16/18 of the patients had a successful outcome.

Interpretation Our results support the use of massive allografts in staged reconstructions of infected THAs complicated by considerable bone loss. ▪     

Postoperative analgesia in total hip arthroplasty: a randomized double-blinded, placebo-controlled study on peroperative and postoperative ropivacaine, ketorolac, and adrenaline wound infiltration

Background Comfort and lack of pain are important for optimal mobilization after hip replacement. We investigated the efficacy of double wound infiltration.

Patients and methods 40 consecutive patients undergoing total hip replacement were randomized into two groups in this double-blinded study. They received wound infiltration at the end of surgery and through an intraarticular catheter 24 h postoperatively. The catheter was placed at the end of surgery. One group received solutions of ropivacaine, ketorolac, and adrenaline. Patients in the control group were injected with saline instead. The observation period was 6 weeks.

Results The patients who received the analgesic solution had less pain up to 2 weeks postoperatively. They reached an earlier and lower pain minimum during the first days postoperatively, had lower use of analgesia up to day 4 postoperatively, and were more satisfied. Use of analgesic solution resulted in less joint stiffness and better function 1 week postoperatively.

Interpretation Operative and postoperative wound infiltration with multimodal drugs reduces pain and the requirement for analgesics after hip replacement, leading to faster postoperative mobilization.     

Safe fixation with two acetabular screws after Ganz periacetabular osteotomy

Background and purpose With Ganz periacetabular osteotomy, the osteotomized acetabular fragment is reoriented in an adducted, extended, and rotated position. The acetabular fragment is fixated with 2 screws and the patients are allowed 30 kg of weight bearing immediately after surgery. We were interested in examining the stability of the reoriented acetabulum after Ganz osteotomy; thus, the migration of the acetabular fragment was assessed by radiostereometry.

Patients and methods 32 dysplastic patients (27 females; 32 hips) were included in the study. Median age was 39 (20-57) years. Radiostereometric examinations were done at 1 week, 4 weeks, 8 weeks and 6 months. Data are presented as mean (SD).

Results 6 months postoperatively, the acetabular fragment had migrated 0.7 (0.8) mm medially, and 0.7 (0.5) mm proximally. Mean rotation in adduction was 0.5° (1.3). In other directions, mean migration was below 0.5 mm/°. There were no statistically significant differences in migration at 8 weeks and 24 weeks postoperatively regarding translation and rotation.

Interpretation Due to the limited amount of migration, we find our postoperative partial weight-bearing regime safe.     

Exogenous collagen-enhanced recruitment of mesenchymal stem cells during rabbit articular cartilage repair

Background Despite the well-known effect of type-I collagen in promoting cartilage repair, the mechanism still remains unknown. In this study we investigated this mechanism using a rabbit model of cartilage defects.

Animals and methods 5-mm-diameter full-thickness defects were created on both patellar grooves of 53 Japanese white rabbits (approximately 13 weeks old). The left defect was filled with collagen gel and the right defect was left empty. The rabbits were killed and examined morphometrically until the twenty-fourth postoperative week, by (1) evaluation of matrix production, (2) enumeration of the total number of cells engaged in cartilage repair, (3) enumeration of the proliferating cells, (4) localization of mesenchymal stem cells, and (v) localization of apoptotic cells.

Results We found that type-I collagen enhances cell recruitment, and thereby increases the number of proliferating cells. A considerable proportion of the proliferating cells were identified as bone marrow-derived mesenchymal stem cells. However, type-I collagen does not prevent the chondrocyte precursors from undergoing apoptotic disengagement from the chondrogenic lineage.

Interpretation Type-I collagen promotes cartilage repair by enhancing recruitment of bone marrowderived mesenchymal stem cells. Additional use of agent(s) that sustain mesenchymal stem cells along the chondrogenic path of differentiation may constitute an appropriate environment for cartilage repair.     

Effect of bone marrow grafting on the titanium porous-coated implant in bilateral total knee arthroplasty

Background and purpose Poor bone ingrowth into the porous coating of tibial components has been reported. We hypothesized that iliac marrow grafting might be useful to enhance bone ingrowth into a porous-coated implant. The first part of this study was to examine the presence of fibroblast colony-forming units (CFUF) containing osteogenic precursor cells in tibial bone marrow and iliac bone marrow. The second aim was to compare the clinical and radiographic results after bilateral total knee arthroplasty (TKA) with and without autologous bone marrow transplantation to the bone-implant interface.

Methods Simultaneous bilateral TKA was performed in 21 patients with osteoarthritis. Aspirated iliac bone marrow was transplanted to the interface of one randomly selected porous-coated tibial component in each patient, and contralateral knees served as controls. All of the 21 patients were followed for 5 years.

Results The average number of CFU-F was significantly lower in tibial marrow than in iliac marrow (p = 0.008). The final fluoroscopically-guided radiographs revealed a decrease in the number of knees with radiolucent lines after marrow grafting compared to those without grafting (p = 0.004).

Interpretation Iliac bone marrow is useful as a bone grafting material to enhance the biological fixation in porous-coated implants.     

Continuous bone loss around a tapered uncemented femoral stem: a long-term evaluation with DEXA

Background Periprosthetic bone loss is a well-docu-mented phenomenon after uncemented total hip arthroplasty (THA); however, little is known about how bone mineral density (BMD) changes after 2 years.

Patients and methods 14 patients with hip arthrosis (group A) were operated with a proximally porous- and hydroxyapatite-coated stem and followed for 10 years with DEXA, radiographs and Harris hip score (HHS). Another group of 14 patients (group B) was evaluated at 6 and 14 years using the same prosthesis and protocol.

Results No stem was revised and all stems were well-Fixed. At final follow-up, HHS was 97 points in group A after 10 years and 94 points in group B after 14 years. Bone mineral changes in group A were greatest in Gruen zones 1 and 7, where the losses were 31% and 26%, respectively, after 2 years on the operated side. The decrease in BMD continued after 2 years and in Gruen zone 7 it was faster than the rate of bone loss on the control side. In group B, the annual change in BMD on the operated side was not significantly different from the bone loss in group A.

Interpretation Up to 14 years after implantation of a tapered uncemented stem, the BMD in the calcar region continues to decrease faster than would be expected from normal ageing.     

Injection of the subacromial-subdeltoid bursa: blind or ultrasound-guided?

Background Blind injection of the subacromial-sub-deltoid bursa (SSB) for diagnostic purposes (Neer test) or therapeutic purposes (corticosteroid therapy) is frequently used. Poor response to previous blind injection or side effects may be due to a misplaced injection. It is assumed that ultrasound (US)-guided injections are more accurate than blind injections. In a randomized study, we compared the accuracy of blind injection to that of US-guided injection into the SSB.

Patients and methods 20 consecutive patients with impingement syndrome of the shoulder were randomized for blind or US-guided injection in the SSB. Injection was performed either by an experienced orthopedic surgeon or by an experienced musculoskeletal radiologist. A mixture of 1 m'L methylprednisolone acetate, 4 mL prilocaine hydrochloride and 0.02 mL (0.01 mmol) Gadolinium DTPA was injected. Immediately after injection, a 3D-gradient T1-weighted magnetic resonance scan of the shoulder was performed. The location of the injected fluid was independently assessed by 2 radiologists who were blinded as to the injection technique used.

Results The accuracy of blind and US-guided injection was the same. The fluid was injected into the bursa in all cases.

Interpretation Blind injection into the SSB is as reliable as US-guided injection and could therefore be used in daily routine. US-guided injections may offer a useful alternative in difficult cases, such as with changed anatomy postoperatively or when there is no effective clinical outcome.     

Serum total acid phosphatase for monitoring the clinical course of giant cell tumors of bone--26 patients with 5 local recurrences

Background Giant cell tumor of bone (GCT) is a bone-destroying tumor that sometimes recurs locally after treatment. A recent study showed increased levels of serum total acid phosphatase (TACP).

Methods We assessed TACP in the serum of 26 patients with primary GCT, and in 5 of them who developed a local recurrence.

Results We found a correlation between TACP level in serum and tumor size. TACP levels that were elevated preoperatively in patients with GCT became normalized after surgery, but increased in 3 of the 5 patients with local recurrence.

Interpretation TACP could be used as a tumor marker for monitoring response to treatment of GCT.     

The effect of recombinant human bone morphogenetic protein-2 on the osteogenic potential of rat mesenchymal stem cells after several passages

Background Since the osteogenic potential of bone marrow derived mesenchymal stem cells (BMSCs) becomes reduced with passage, establishment of culture condition that permit the rapid expansion of BMSCs while retaining their potential for differentiation is needed for clinical application. Bone morphogenetic proteins stimulate osteogenic differentiation in mesenchymal progenitor cells as well as increase stem cell numbers. Thus, we analyzed the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on the osteogenic potential of rat BMSCs over several passages.

Material and methods Osteogenic differentiation in vitro was evaluated in terms of the alkaline phosphatase (ALP) activity and the osteocalcin (OC) concentration in the supernatants, and the expression of ALP and OC mRNA in the cultured cells. For in-vivo osteogenesis, BMSCs cultured with and without rhBMP-2 through all passages were implanted into athymic mice.

Results  The levels of osteogenic markers were significantly higher in the cells of the BMP(+) group than in the cells of the BMP(-) group, although they decreased with passage irrespective of whether or not rhBMP-2 was added. Similar to the in-vitro experiments, there was a greater degree of bone and cartilage tissue formation in the BMP(+) group over all passages.

Interpretation  From our results, osteogenic potential can be maintained even in BMSCs that have been passaged several times in the presence of rhBMP-2. These cells are capable of inducing and participating in bone formation and can be used for clinical applications.     

White blood cell scintigraphy for differentiation of infection and aseptic loosening: a retrospective study of 76 painful hip prostheses

Background Diagnosis of an infected arthroplasty is often difficult. Fever, abnormal physical findings, radiographic changes, findings at bone scintigraphy, an elevated erythrocyte sedimentation rate, CRP, and leucocytosis are not specific enough. We evaluated the diagnostic value of white blood cell scintigraphy.

Methods We retrospectively reviewed 76 cases (66 patients) admitted for white blood cell scintigraphy with a clinical suspicion of infection in a hip prosthesis during the period 1995-2003. The leukocytes were labeled with ^99mTc-HMPAO or with ¹¹¹In-oxin. Anterior and posterior views were taken of both hip joints at 3 different time points after injection: 1 h, 3 h, and 22 h. Infection was verified by means of bacteriological cultures, histopathological findings, intraoperative frozen sections, and follow-up (up to 3.5 years).

Results Of 76 scintigraphies, 51 were negative and 25 were positive. There were 81% true positive, 94% true negative, 6% false positive, and 19% false negative outcomes.

Interpretation White blood cell scintigraphy with additional late imaging is an effective tool for differentiation between loosening and infection in painful hip arthroplasty.