Abstract
This study aimed to assess the volume of cancellous bone harvested by the medial approach from proximal tibia and compare the maximal compressive strength of decancellated tibias with intact tibias. Twelve cadavers were studied (11 male; 1 female). Cadavers with a history of bone disease and female cadavers over 60 years of age were excluded. Cancellous bone was taken from the right proximal tibia by the medial approach. Non-compressed and compressed cancellous bone volume was measured. Maximal compressive strength of decancellated tibias and intact tibias was measured and compared. The mean volume of bone harvested was 14.58 ± 3.30 ml with the non-compress technique (range 10.5–19.5 ml) and 6.62 ± 1.60 ml (range 4.0–9.2 ml) with the compress technique. There was no significant difference between the maximal compressive strength of the decancellated tibias and the intact tibias ( P = 0.085). Sufficient volume of cancellous bone for bone grafting in the oral maxillofacial surgery region can be harvested from the proximal tibia by the medial approach. The strength of decancellated tibias and intact tibias after harvesting cancellous bone graft were not different.
Autogenous bone grafting has been a gold standard for procuring bone-grafting material in maxillary and mandibular reconstruction because it has osteoconduction, osteoinduction and osteogenesis properties. Autogenous bone graft can be harvested from the iliac bone, calvarium, tibial bone, rib and intraoral bone. Each site has different advantages and disadvantages. The ilium is the most common source of autogenous bone used in oral and maxillofacial reconstructive surgery. Advantages of iliac bone are large bone volume, and harvesting both cancellous and cortical bone as bone blocks, as well as being a site that has been used by oral and maxillofacial surgeons. Iliac bone harvesting is associated with a postoperative complication rate as high as 9% especially when corticocancellous block grafts were harvested.
The proximal tibia is a source of autogenous bone graft which can be used in any bony defects. O’K eeffe et al. reported 230 cases using proximal tibial cancellous procurement with excellent results in the treatment of lower extremity fractures or nonunions. For oral and maxillofacial surgery, the proximal tibia has been used since 1992. C atone et al. reported the use of the proximal tibial metaphysis as cancellous bone graft in orthognathic surgery, the alveolar cleft, preprosthetic surgery and major jaw reconstruction. Several studies reported a complication rate of 1–4% from harvesting proximal tibia, which is less than the iliac bone harvesting rate. Proximal tibia harvesting also requires less operating time, is easy to perform and has less gait disturbance when compared to iliac bone harvesting . Most of the bone content harvested from the proximal tibia is cancellous bone which has an abundance of osteoblast and pleuripotential cells . The volume of cancellous bone taken from the proximal tibia has been mainly via the lateral approach. H erford et al. studied the amount of cancellous bone and related anatomy via the lateral and medial approach and concluded that an equal amount of bone graft was available from the medial and lateral approach, but that the medial approach offered an easier technique and possibly safer dissection.
Although proximal tibia bone harvesting has shown significantly fewer postoperative complications compared with iliac crest harvesting, rare major complications such as proximal tibia fracture can occur. A lt et al. studied nine cadavers to determine the risk of postoperative tibia plateau fracture after harvesting cancellous bone from the proximal tibia using the lateral approach. They found no significant difference in the risk of tibia plateau fractures between decancellated and intact tibia. No other studies reported fractures associated with the medial approach of proximal tibia harvesting. This study aimed to evaluate the volume of cancellous bone harvested by the medial approach and compare the compressive strength of decancellated tibias with intact tibias.
Materials and methods
Twelve cadavers from the Department of Anatomy, Faculty of Science, Prince of Songkla University, Songkhla were studied. Cadavers with any bone disease or female cadavers over 60 years of age were excluded from the study. The medial approach for harvesting cancellous bone from proximal tibia followed the procedure described by H erford et al. The cadavers were placed in a supine position. The tibial tuberosity was located and a line perpendicular and parallel to the long axis of the tibia was drawn, intersecting at the centre of the tuberosity. A point 15 mm medial to the vertical line and 15 mm superior to the horizontal line was marked.
This point represented the desired location of the centre of the osteotomy. A 1–1.5 cm oblique incision was made over this point down to the underlying bone ( Fig. 1 ). The periosteum was retracted and a 1 cm circular osteotomy was prepared. The thin cortex was removed to create a window and then cancellous bone was harvested with a curette. The upper boundary of curettage was not further than 1 cm above the bony window to avoid injury to the articular surface of the tibial plateau. The harvesting of medial and lateral boundaries was done until the cortical bone was reached. Lower harvesting was performed until a curette could no longer pass through the window ( Fig. 2 ).
A glass tube with 0.1 ml calibration and filled with 5 ml of distilled water was used for water displacement volumetry. The cancellous bone graft was placed into the tube. The increased level of water from 5 ml was recorded as non-compressed volume ( Fig. 3 a ). After that, the cancellous bone graft was placed into a 10 ml syringe and compressed with double thumb pressure . The volume of this measurement was recorded as compressed volume ( Fig. 3 b).
The decancellated and intact tibias in each cadaver were dissected out by cutting a tibia metaphysis below the articular surface of the knee joint for 15 cm ( Fig. 4 ). The anteroposterior and mediolateral diameters of the articular surface of decancellated tibia were measured for calculating the area of tibia plateau ( Fig. 5 ).
The decancellated tibias and matching contralateral intact tibias were put into a testing machine (Shimadzu-AG-100KNG) with a 150 mm metal circular plate to create the compression force distributed throughout the irregularities of the tibia plateau ( Fig. 6 ). The maximal force inducing an initiation of tibia plateau fracture was recorded as the maximal compressive strength, which determined the postoperative risk of tibia plateau fracture.
The mean value of non-compressive and compressive volume, maximal compressive strength, and area of tibia plateau were calculated. The difference in the maximal compressive strength inducing fracture of the decancellated tibia and the matching intact tibia was compared using Student’s paired t -test. Correlation between all variables was analysed by Pearson’s coefficient of correlation. Statistical significance was set at P < 0.05.
Results
Twelve cadavers (11 males; 1 female) were studied. The mean age of the cadavers was 61.67 years (46–78 years). The average non-compressive volume of cancellous bone from the proximal tibia was 14.58 ± 3.30 ml (range 10.5–19.5 ml). The average compressive volume was 6.62 ± 1.60 ml with a range of 4.0–9.2 ml. The maximal compressive strength of decancellated and intact tibias for the area of the tibia plateau is shown in Table 1 .
