**2. Preparation of allogenic "decal-bone" graft**

spinal fusion for gross deformities or severe instabilities especially in children, and repeat surgeries after total joint replacements. These procedures demand an abundant quantity of bone which the recipient's body cannot supply without significant morbidity and risks. At present popularly allogenic bone is preserved by deep-freezing or freeze-drying or by radiation for long-term preservation. These techniques have been shown to maintain sterility, reduce immunogenicity, and provide adequate structural integrity; however, such procedures also reduce the bone-forming biological activity and are expensive (**Table 1**). Autoclaving and

One of the most exciting works during the latter half of the twentieth century (1965–1994) has

After extensive experimental work [3, 4], we have been using partially demineralized allogenic bone (decal-bone) as grafts in clinical cases. For preparation and preservation of allogenic bone graft, we used the techniques described by Urist (1965–1987). We aimed at removal of approximately 50% of mineral from the graft, thus retaining adequate structural integrity (**Table 2**). We used this material since 1978, and we closely observed the clinical results on long-term bases in 67 benign cystic lesions, 32 wide-gap graftings, and 11 posterior

> **Frozen freeze-dried allogenic**

+++ +++ ++ ++ ++

**Partially decalcified** **Deproteinated allogenic**

been the clinical translation of the basic research performed by marshal Urist [1, 2].

**Fresh/unprocessed allogenic**

Osteoinduction ++++ +++ +++ ++++ 0 Osteoconduction +++ ++ ++ +++ ++ Osteogenic ++ 0 0 0 0 Immunogenicity 0 +++ ++ ?+ 0

Cost ?+ + +++ + +++

Frozen grafts require thawing, freeze-dried grafts require hydration before implantation, and the unused graft cannot

radiation completely destroy bone inductive principles.

44 Bone Grafting - Recent Advances with Special References to Cranio-Maxillofacial Surgery

**Fresh autogenous**

**A.** Treatment with 0.6 MHcl:

Mechanical strength

be re-preserved.

**B.** Treatment with ethanol:

• Leaches out fat ex vivo

chemosterilizes, and is virucidal

**Table 2.** Processing of allogenic decal-bone.

• Removes mineral and exposes BMP and other growth factors on matrix

• Reduces antigenicity, chemosterilizes, and is virucidal

**Table 1.** Commonly used bone grafts in clinical orthopedics.

• Opens and cleanses vascular, Haversian, Volkmann channels, and lacunar spaces of cells and debris

• These processes as a rule are done by the host scavenger cells in vivo in un-demineralized bone grafts

• Preserves without denaturing the bone morphogenetic protein (BMP) and other osteoinductive principles (OIP),

Human bones were obtained from freshly (posttraumatic) amputated extremities, under strict aseptic operation theater conditions. Soft tissues and periosteum were removed from the bones using sharp instruments. After a minimum of three washings with normal saline, the bones were placed and immersed in 0.6 M HCI solution for 3–5 days in a domestic refrigerator. The solution was changed every 24 hours. The partially decalcified bone was washed with normal saline to remove any traces of acid, sealed in 80–90% ethanol, and kept in a domestic refrigerator at about 4–6°C (**Figures 1** and **2**). The stored bone was used between 1 and 12 months of preservation. Osteoporotic bone from old persons would be ready by the third day; however, fully mineralized bone from athletic or healthy persons may take 5 days for achieving 50–40% decalcification. Bone obtained from total knee replacements in the operating rooms was another material processed for use as decal-bone.

When required for implantation, the preserved bone was washed thoroughly with normal saline. The superficial surface of graft was pared using a sharp scalpel, and it was cut to the required size to give a snug fit in the host bed for structural grafting, generally fixing to the host bone using an intramedullary nail. For filling large cystic cavities of bone, the decal-bone was cut like matchstick silvers with thickness and width of 4–6 mm and washed with normal saline. The cavities after thorough curettage were compactly packed with the matchstick graft.

For spinal fusions the recipient bed was decorticated, and abundant graft was placed oriented along the long axis of the spine. In cases with gross mechanical instability, a suitable implant with multi-segmental fixation was employed as an adjunct. Standard operative principles for such extensive procedures were followed with modifications to suit individual requirements.

For giant cell tumors of bone (GCT) prior to 1986, en bloc resection and structural reconstruction was performed as a standard procedure. We had an opportunity to observe the behavior of large allogenic segmental graft used for such patients. Global observation however advised less aggressive joint-sparing intralesional procedures since approximately 1987.

Currently for all containable cystic lesions including GTC, we use and recommend the following steps for grafting:


**VI.** Do compact filling of the cavity with decal-bone grafts.

**VII.** After wound closure protect the limb with suitable cast, and follow the standard postoperative care.

(ii) by periodic core biopsy of the graft after tetracycline administration, and (iii) by histologi-

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**Cavitary cystic lesions:** the observations regarding cystic lesions are listed in **Table 3**. The success after curettage and bone grafting was uneventful in 60% of cases of giant cell tumor (GCT), in 75% of cases of aneurysmal bone cyst (ABC), and in 85% of cases of unicameral bone cyst (UBC) **Figure 3**. Further success by supplementary curettage and bone grafting was obtained in 10% of cases of GCT, 25% of ABC, and 15% of UBC. Supplementary bone grafting was required because of unexplained resorption of the graft or low-grade infection leading to sequestration and resorption of the graft. Six cases of GCT failed because of uncontrolled

**Pathology Success Sup. success Failure** Typ. giant cell tumor 18 60% 10% 30%

Aneurysmal bone cyst 21 75% 25% Unicameral bone cyst 11 85% 15%

∙ Poly-OFD 4 3 1 ∙ Multiple enchondromas 2 1 1

**Table 3.** "Cystic lesions" of bone (67) treated by curettage and allogenic decal-bone grafting.

∙ Fibrous defect 6 6 ∙ Solitary chondroma 3 3 ∙ Chod. myxoid fibroma 2 2

cal studies of the retrieved graft in cases of reoperation.

**Figure 2.** Partially decalcified bone stored in ethanol.

∙ Number is too small to express as valid percentage.

Poly-OFD = polyostotic fibrous dysplasia.

*2.1.1. Observations*

This routine has appreciably reduced the incidence of infection and recurrence, and the success rate has markedly improved.

#### **2.1. Cytological and histological observations**

In addition to clinical and radiological assessment, postimplantation observations were made by (i) periodic fine-needle aspiration cytology (FNAC) from the graft and perigraft area,

**Figure 1.** After complete decalcification, the bone (radius in picture) becomes soft like leather.

(ii) by periodic core biopsy of the graft after tetracycline administration, and (iii) by histological studies of the retrieved graft in cases of reoperation.

#### *2.1.1. Observations*

**VI.** Do compact filling of the cavity with decal-bone grafts.

46 Bone Grafting - Recent Advances with Special References to Cranio-Maxillofacial Surgery

operative care.

cess rate has markedly improved.

**2.1. Cytological and histological observations**

**VII.** After wound closure protect the limb with suitable cast, and follow the standard post-

This routine has appreciably reduced the incidence of infection and recurrence, and the suc-

In addition to clinical and radiological assessment, postimplantation observations were made by (i) periodic fine-needle aspiration cytology (FNAC) from the graft and perigraft area,

**Figure 1.** After complete decalcification, the bone (radius in picture) becomes soft like leather.

**Cavitary cystic lesions:** the observations regarding cystic lesions are listed in **Table 3**. The success after curettage and bone grafting was uneventful in 60% of cases of giant cell tumor (GCT), in 75% of cases of aneurysmal bone cyst (ABC), and in 85% of cases of unicameral bone cyst (UBC) **Figure 3**. Further success by supplementary curettage and bone grafting was obtained in 10% of cases of GCT, 25% of ABC, and 15% of UBC. Supplementary bone grafting was required because of unexplained resorption of the graft or low-grade infection leading to sequestration and resorption of the graft. Six cases of GCT failed because of uncontrolled

**Figure 2.** Partially decalcified bone stored in ethanol.


Poly-OFD = polyostotic fibrous dysplasia.

**Table 3.** "Cystic lesions" of bone (67) treated by curettage and allogenic decal-bone grafting.

**Figure 3.** A recurred giant cell tumor of distal femur with pathological fracture. The healed status achieved by intralesional curettage and decal-bone grafting following 12 years.

further autologous bone grafts for areas of non-union at host graft junctions or for pseudarthrosis in the intermediate part of the graft 20%, for control of infection, or for a combination

**Pathology Success Supp. success Failure** Giant cell tumor 28 40% 38% 28% ∙ Aneurysmal bone graft 1 1 – – ∙ Unicameral bone graft 1 1 – – ∙ Central fibrosarcoma 1 – 1 ∙ Traumatic extrusion 1 1 – –

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Six patients were considered a failure because the reconstruction failed. Two had recurrence of tumor, one had uncontrolled infection, and these ended up in amputations. In three patients despite two attempts at supplementary grafting, the areas of pseudarthrosis did not heal; these patients accepted an orthosis till further decision. One case of malignant fibrous histiocytoma failed because of recurrence of tumor within 4 months of limb salvage attempt. Of the 11 patients of posterior or posterolateral spinal fusion, 10 were considered to have obtained satisfactory osseous fusion based upon clinical assessment and stress X-rays done 12–24 months after the operation (**Figure 6**). One young nurse who had posterior fusion along with Steffi's fixation at L3–L4 for spondylolisthesis was considered a failure because of the

Fine-needle aspiration cytology (FNAC) was done from the perigraft region (in 20 patients) between the 10th and 40th day after grafting. The FNAC showed high cellularity composed of

**Figure 5.** Intercalary reconstruction after en bloc resection of giant cell tumor of distal femur. Note gradual incorporation

of these factors (18%).

∙ Number is too small to express valid percentage.

**Table 4.** Large osteoperiosteal gaps (32) and structural grafts (1979–1999).

implant breakage observed 2 years after operations.

**3.1. Cytological and histological observation**

and remodeling as observed in the 12-year follow-up.

**Figure 4.** A case of polyostotic fibrous dysplasia. The cyst in the trochanteric area remained healed after curettage and decal-bone grafting. After about 14 years of gap, another cyst in the supra-acetabular region needed treatment.

infection (three cases) and massive recurrence of tumor (three cases). All patients of solitary osseous lesions healed successfully. Polyostotic fibrous dysplasia (4), multiple fibrous defects (6), enchondromas (3), chondromyxoid fibroma (2), and enchondromatosis (2) by their biological nature may need reoperation for an increase in the size of the lesions which were insignificant at the time of the first surgery. One patient of fibrous dysplasia had to undergo a second operation for a new lesion, and one patient of enchondromatosis is awaiting surgery for the additional area (**Figure 4**).
