Photomicrograph shows the top 2 layers of grafted auricular cartilage and the bottom layer as the host cartilage bed. Viable chondrocytes are seen in all cartilage layers. Minimal osteogenesis, chondrogenesis, and inflammation is seen between the grafted auricular cartilage and host cartilage bed (hematoxylin-eosin, original magnification ×200).
Photomicrograph shows the top 2 layers of grafted auricular cartilage and the bottom layer as the host cartilage bed. A focal area of chondrogenesis and fibrous tissue formation is seen between a layer of the grafted cartilage and the host cartilage (arrow) (hematoxylin-eosin, original magnification ×200).
Photomicrograph shows 2 layers of grafted auricular cartilage. Vigorous fibrous tissue formation is seen at the surgically resected margins of the grafts (hematoxylin-eosin, original magnification ×200).
Photomicograph shows the top layers of grafted auricular cartilage and the bottom layer as the host cartilage bed. Chondrogenesis may been seen at the surgically resected margins of the grafts (arrow) (hematoxylin-eosin, original magnification ×200).
Photomicrograph shows the top 2 layers of grafted auricular cartilage and the bottom layer as the host cartilage bed. A foreign-body reaction may been seen at a suture site (arrow) (hematoxylin-eosin, original magnification ×100).
Wiseman JB, Holt GR, Keefe MA, Holck DE, Canaan RL, Clark WD. The Fate of Fresh, Layered, Nonsutured and Sutured, Autogenous Cartilage in the Rabbit Model. Arch Facial Plast Surg. 2000;2(4):256-259. doi:
From the Departments of Otolaryngology–Head and Neck Surgery (Drs Wiseman and Clark), Ophthamology (Dr Holck), and Pathology (Dr Canaan), Wilford Hall Medical Center, Lackland AFB, Lackland, Tex; the Departments of Otolaryngology–Head and Neck Surgery, John Hopkins Hospital, Baltimore, Md (Dr Holt); and Naval Medical Center, San Diego, Calif (Dr Keefe).
Objective To compare the thickness, area, and volume of sutured and nonsutured multilayered cartilage grafts in a rabbit population.
Design Autogenous rabbit cartilage grafts were harvested, layered, and placed in the contralateral auricle. Half the grafts were sutured; the other half were nonsutured. Graft thickness, area, and volume were measured before implantation, after 90 days in vivo, and after explantation.
Results The area and volume of the cartilage grafts increased during the 90-day period. Histologically, this was caused by increased fibrous tissue around the cartilage grafts. Minimal cartilage resorption was observed. No differences were noted between sutured and nonsutured grafts.
Conclusions Autogenous, fresh, uncrushed, layered nonsutured or sutured cartilage grafts are well tolerated. Statistically significant increases in the area and volume of autogenous, fresh, uncrushed, layered cartilage grafts occurred primarily because of fibrous tissue formation at the margins of the layered grafts. Suturing had no effect on the postoperative volume retention of these layered grafts. This information will be helpful to the facial plastic surgeon when using fresh-layered autogenous cartilage grafts during cosmetic or reconstructive procedures.
THE USE of autogenous cartilage grafts has been documented since the early 1900s and has been more frequently used in recent times by the facial plastic surgeon because of its availability near the operative site and because of good tolerance by the host tissues.1-4 When used in rhinoplastic surgery, this cartilage is used in a variety of forms, including fresh or fresh crushed, depending on whether the graft is needed for soft contour or support. It may be placed as a nonsutured, layered free graft or sutured into position depending on the facial plastic surgeon's preference. Final tissue volume is the ultimate goal of the graft when not strictly placed for support.
With the interest in cartilage as an autogenous graft material for reconstructive and cosmetic surgery, the survival of the cartilage grafts, as well as the degree of cartilage resorption have been examined.4-9 Most of these studies focused on single-layer grafts and only qualitatively assessed cartilage resorption. They did not quantify the final graft tissue thickness, area, and volume. Additionally, previous reports did not splint or cast onlay grafts, as one might in a reconstructive rhinoplastic procedure.
We evaluated postoperative cartilage thickness, area, and volumetric changes of sutured and nonsutured, fresh, noncrushed, multilayered cartilage grafts surgically embedded in a population of New Zealand white rabbits.
The rabbit model is a well-established subject for cartilage research.4-6,9 Ninety days was selected as our study end point to approximate a 1-year equivalent period in human life.6 Eight New Zealand white rabbits (Oryctolagus cuniculus) approximately 1 year old, weighing 2.25 to 2.70 kg, and of either sex were used in this study. All animals were cared for in accord with the ethical research standard set forth by our hospitals' institutional review boards.
Under general anesthesia each rabbit auricle was depilated, sterilely prepared, and draped. The left auricle of each rabbit was used to harvest the cartilage grafts. Four square blocks of cartilage, 1 cm in length and width, and of similar thickness were harvested. Perichondrium was preserved on both sides of the cartilage grafts. The incision site was closed using a 4-0 polypropylene suture and compression dressing was placed over the wound. Two of the 4 square blocks of cartilage were layered and sutured together with a 5-0 absorbable polydioxanone suture. The thickness of the graft was measured at several compass points (ie, 0°, 90°, 180°, and 270°) with a caliper. The remaining 2 square blocks of cartilage were layered without suturing, and the thickness measured at corresponding locations with a caliper at the graft site center and 1 mm from the edges at the 4 compass points of 0°, 90°, 180°, and 270° prior to implantation by 2 independent observers (J.B.W. and a laboratory technician). These measurements formed the layered cartilage graft (LCG) baseline values.
Two pockets were created at the base of each rabbit's right auricle. In one pocket, the nonsutured, layered blocks of cartilage were placed. In the second pocket, the sutured, layered blocks were placed and sutured to the underlying ear cartilage using a 5-0 absorbable polydioxanone suture. The cartilage grafts were placed supraperichondrially. The total thickness of grafts and right auricular host site were measured. These measurements formed the skin–cartilage graft complex (SCGC) baseline values. The wounds were closed with a 5-0 polypropylene suture and a compression dressing and splint applied. The compression dressings remained in place for 7 days and were then removed. The sutures were removed at 14 days postoperatively.
At 90 days postoperatively, under general anesthesia, the total thickness of the right auricle and cartilage grafts were remeasured in a similar fashion as during the initial procedure. The length, width, and thickness of the in vivo nonsutured and sutured cartilage grafts were measured to obtain their respective thickness, area, and volume. After the initial measurements were completed, the overlying skin–transplanted cartilage grafts and underlying host cartilage were harvested. The SCGC specimens were paraffin-embedded, hematoxylin-eosin stained, and sectioned into 1-mm slices. The specimens were microscopically examined to assess the graft-host site interface. Each SCGC was evaluated for the presence of viable chondrocytes, vascular endothelial growth, adipose tissue, fibrous tissue, inflammatory response, osteogenesis, and chondrogenesis. Both nonsutured and sutured grafts were evaluated. Additionally, each SCGC and LCG specimen had their respective length, width, and thickness measured with an optical micrometer. The skin was closed with a 4-0 polypropylene suture over the cartilage harvest sites after adequate undermining to fill the harvest defect. Compression dressings were applied for 3 days. No rabbits were killed for this study.
Measurements for the study (thickness, area, and volume of the LCG and SCGC, nonsutured and sutured, at days 0 and 90) were compared and analyzed using a repeated measures analysis of variance. The analysis evaluated whether the day 0 to day 90 graft changes were significantly different between the nonsutured and sutured groups (ie, treatment × time interaction), as well as whether there was a significant change in the grafts from days 0 to 90.
No rabbit had complications from the surgery. Table 1 summarizes the mean thickness, area, and volume of the SCGC and LCG, nonsutured and sutured, at day 0 and day 90. The change in the mean thickness of the SCGC, nonsutured and sutured, increased 14% from day 0 to day 90 (P = .001). The change in the mean area of the SCGC, nonsutured and sutured, increased 116% from day 0 to day 90 (P = .001). The change in the mean volume of the SCGC, nonsutured and sutured, increased 164% from day 0 to day 90 (P = .002). The mean thickness of the nonsutured SCGC compared with the sutured SCGC from day 0 to day 90 demonstrated no statistically significant difference (P = .001). The mean area of the nonsutured SCGC compared with the sutured SCGC from day 0 to day 90 demonstrated no statistically significant difference (P = .001). The mean volume of the nonsutured SCGC compared with the sutured SCGC from day 0 to day 90 demonstrated no statistically significant difference (P = .002).
The change in the mean thickness of the LCG, nonsutured and sutured, decreased 31% from day 0 to day 90 (P = .002). The change in the mean area of the LCG which included fibrous tissue, nonsutured and sutured, increased 116% from day 0 to day 90 (P = .001). The change in the mean volume of the LCG, nonsutured and sutured, increased 57% from day 0 to day 90 (P = .005). The mean thickness of the nonsutured LCG compared with the sutured LCG from day 0 to day 90 demonstrated no statistically significant difference (P = .001). The mean area of the nonsutured LCG compared with the sutured LCG from day 0 to day 90 demonstrated no statistically significant difference (P = .001). The mean volume of the nonsutured LCG compared with the sutured LCG from day 0 to day 90 demonstrated no statistically significant difference (P = .001).
Microscopic examination of the SCGC and LCG revealed viable chondrocytes (Figure 1) and minimal osteoid formation and ossification at the graft-host interface. No osteoid or ossification was noted on nongrafted auricular cartilage. Some specimens demonstrated chondrogenesis and fibrous tissue formation between the cartilage grafts and underlying host cartilage (Figure 2). Most specimens demonstrated some chondrogenesis and fibrous tissue formation beyond the surgical resected margin of the original LCG with most growth owing to fibrous tissue formation (Figure 3 and Figure 4). Minimal inflammation was seen between the cartilage grafts, graft-skin interface, or the graft-host interface. A mild foreign body reaction was observed at the suture site (Figure 5). Minimal cartilage graft resorption was detected.
Autologous cartilage grafting is commonly performed in facial plastic and reconstructive surgery. Researchers have reported the clinical, biological, and mechanical characteristics of cartilage grafts.1-9 Guyuron and Friedman7 showed both crushed and noncrushed fresh or preserved cartilage grafts had a success rate from 85.5% to 93.8% when used in rhinoplastic surgery. They believed that fresh and preserved grafts retain much of their volume after transplantation. Donald and Col,8 however, reported a 23.7% mean resorption rate of autogenous cartilage grafts. Rudderman et al6 used crushed and noncrushed single-layer cartilage grafts in a rabbit model. They demonstrated a volume retention after 90 days of 94.5% for the fresh noncrushed cartilage graft and 70% for the crushed cartilage graft. The act of crushing cartilage had the greatest effect on volume reduction in their study.
In our study, the change in the mean volume of the SCGC increased 164% while the change in the mean volume of the LCG increased by 57%. The increases in volume for the SCGC and LCG are largely attributable to the measured increase in the area of the grafts. The SCGC and LCG, nonsutured and sutured, increased in area over 116%. The increase in area under microscopic analysis is because of new cartilage growth and fibrosis adjacent and extending beyond the incised surgical margin of the layered cartilage grafts. Fibrous tissue formation was the dominant factor for the increase in the area and volume of these grafts. Brown et al,9 using the rabbit model, found results similar to our study that in most cases the junction between the graft and host auricular cartilage was fibrous and a fibrous capsule developed around the graft.
Most published studies of cartilage grafting used qualitative methods to assess the degree of cartilage graft resorption and did not discriminate between fibrous tissue replacing resorbed cartilage. Our study demonstrated an actual increase in volume of both SCGC and LCG that was shown histologically to be due primarily to an increase in fibrous tissue. Rudderman et al6 in their study demonstrated cartilage graft volume retention rates of 94.5% yet their rabbit model experiment did not describe if and how measurements of cartilage graft thickness were obtained. Volume and microscopic analysis of the cartilage grafts were the only data presented in their study. Our microscopic analysis of the cartilage grafts and host tissue demonstrated minimal inflammation and minimal cartilage graft resorption, which is similar to findings in most studies. However, we demonstrated with precise measurements and microscopy that cartilage graft resorption does occur along with fibrous deposition during a 90-day period.
In this study suturing layered grafts had no effect on the outcome of thickness, area, or volume in either the SCGC or LCG. These grafts were placed in a tight pocket with minimal load or shearing stress. Further studies are necessary on cartilage grafts in a high-load or high-shear environment to determine if suturing has an effect.
Fresh, layered autologous cartilage grafts are well tolerated, and clinically are associated with an increase in graft area and volume over a 90-day period. Significant increases in area and volume occurred in the SCGC, and significant increases in area appeared in the LCG. Increases in volume occurred in the LCG, but to a lesser degree when compared with the SCGC. A decrease in thickness of the LCG was observed caused by increases in area and volume of the SCGC and LCG and were histologically shown to be mainly because of fibrous tissue formation, and to a lesser extent because of new cartilage formation at the LCG incised surgical margin.
Suturing layered grafts had no effect on the final thickness, area, or volume when compared with nonsutured layered grafts. Minimal inflammation, osteogenesis, and adipose tissue were observed microscopically at the graft site. This information may be useful for the facial plastic surgeon in planning when using fresh, layered autologous cartilage grafts during reconstruction or cosmetic procedures.
Accepted for publication March 10, 2000.
The views expressed in this article are those of the authors and are not to be construed as official or as reflecting those of the Department of the Air Force, Department of the Navy, or the US government.
Corresponding author: Lt Col Joe B. Wiseman, USAF, MC, 125 Stone Crest Dr, San Antonio, TX 78209 (e-mail: firstname.lastname@example.org).