Four common anatomic variants that predispose to unfavorable rhinoplasty results: a study based on 150 consecutive secondary rhinoplasties

A retrospective study was conducted of 150 consecutive secondary rhinoplasty patients operated on by the author before February of 1999, to test the hypothesis that four anatomic variants (low radix/low dorsum, narrow middle vault, inadequate tip projection, and alar cartilage malposition) strongly predispose to unfavorable rhinoplasty results. The incidences of each variant were compared with those in 50 consecutive primary rhinoplasty patients. Photographs before any surgery were available in 61 percent of the secondary patients; diagnosis in the remaining individuals was made from operative reports, physical diagnosis, or patient history. Low radix/low dorsum was present in 93 percent of the secondary patients and 32 percent of the primary patients; narrow middle vault was present in 87 percent of the secondary patients and 38 percent of the primary patients; inadequate tip projection was present in 80 percent of the secondary patients and 31 percent of the primary patients; and alar cartilage malposition was present in 42 percent of the secondary patients and 18 percent of the primary patients. In the 150-patient secondary group, the most common combination was the triad of low radix, narrow middle vault, and inadequate tip projection (40 percent of patients). The second largest group (27 percent) had shared all four anatomic points before their primary rhinoplasties. Seventy-eight percent of the secondary patients had three or all four anatomic variants in some combination; each secondary patient had at least one of the four traits; 99 percent had two or more. Seventy-eight percent of the primary patients had at least two variants, and 58 percent had three or more. Twenty-two percent of the primary patients had none of the variants and therefore would presumably not be predisposed to unfavorable results following traditional reduction rhinoplasty. This study supports the contention that four common anatomic variants, if unrecognized, are strongly associated with unfavorable results following primary rhinoplasty. It is important for all surgeons performing rhinoplasty to recognize these anatomic variants to avoid the unsatisfactory functional and aesthetic sequelae that they may produce by making their correction a deliberate part of each preoperative surgical plan.     

Nasal augmentation with Surgicel-wrapped diced cartilage: a review of 67 consecutive cases

Cartilage grafting has been used extensively to correct both the functional and aesthetic aspects of the nasal framework. The technique described by Erol ( 105: 2229, 2000) uses Surgicel-wrapped diced cartilage grafts in rhinoplasties. The advantages include its ease of preparation, the large volume of graft substrate available for use, and the avoidance of contour irregularities in the areas of placement. A retrospective case review of 67 consecutive patients who were treated with a Surgicel-wrapped diced cartilage graft as part of an aesthetic and/or functional rhinoplasty, in a 5-year period between 1995 and 2000, was performed in this study. All cases of congenital nasal deformities or deformities caused by trauma or tumors in which the technique was used were excluded. The charts were reviewed to determine demographic variables, the surgical procedures performed, prior operations, the rhinoplasty approach used, and the graft donor and recipient sites. Preoperative and postoperative photographs were examined, and the results were assessed. Data on the donor and recipient sites, complications, and the necessity for revisionary procedures were tabulated. There were two complications, namely, an infection, which resolved with aspiration and oral antibiotic therapy, and a recurrence of a dorsal depression, which necessitated repeated augmentation within 6 months. The technique of using Surgicel-wrapped diced cartilage proved to be effective for the augmentation of various areas of the nose. The complication and revision rates were acceptable and comparable to those of other techniques. Patient satisfaction with the aesthetic results was rated highly, with no reports of graft extrusion or contour irregularities. This technique is recommended for nasal augmentation and contouring for selected rhinoplasty patients.     

The "iatrogenic-hanging columella": preserving columellar contour after tip retroprojection

This article discusses a method for treating the ultraprojecting tip by the resection of columellar skin in open rhinoplasty. Lack of postoperative contraction of columellar skin and soft tissue may result in an "iatrogenic-hanging columella." Columellar skin resection frequently produces its own deformities because of a discrepancy in the width of the columellar base side and the infralobular flap side. The ultraprojecting tip was present in 56 of 660 consecutive rhinoplasty patients (8 percent) over 8 years (1991 to 1998). Of these 56 patients, 48 underwent partial resection of the infralobular skin flap. Of these 48 patients, eight (17 percent) required secondary skin revision of the columellar resection area. The technique was then modified since 1998. Over 2 years, 13 of 129 consecutive rhinoplasty patients (10 percent) were judged to have an ultraprojecting tip. Of these, eight patients were treated with a modification in the technique by resecting skin on the posterior columellar base. No resection areas were revised in the second series. Of the 789 patients in both series, 647 (82 percent) underwent primary rhinoplasties, 126 (16 percent) had secondary rhinoplasties, and 16 (2 percent) had tertiary rhinoplasties. The treatment of excess columella skin adds a subtle aesthetic improvement to the postoperative nasal contour. By resecting skin on the posterior columellar base or the posterior columellar base and, rarely, the anterior flap, an iatrogenic-hanging columella can be avoided.     

Augmentation rhinoplasty: observations on 1200 cases

Over the past 14 years, from January of 1975 to December of 1988, we have done 1263 aesthetic rhinoplasties using ear cartilage. In the field of augmentation rhinoplasty, many kinds of materials, such as bone, septal cartilage, ear cartilage, and prostheses, were used. In this paper, we limit discussion to our experience with the technique for the augmentation of the nasal dorsum using the ear cartilage and compare this with other materials. Patient ages ranged from 15 to 72 years, with an average of 24 years. Some 95 percent of patients (1199) were female, and only 5 percent (64) were male. Patients were followed for a minimum of 6 months and a maximum of 20 months, with average follow-up only 8 months. Of course, we know that this is a very short follow-up period, but we could not follow patients longer because if they had no complaint about the results at the 6-month visit, they never returned, despite our efforts. Five-hundred and ten of the 1263 patients (40 percent) had been augmented elsewhere, and the silicone prosthesis was already in place. However, 753 patients (60 percent) had no previous operation. For the 510 patients (secondary rhinoplasty patients), too-high or too-large a prosthesis was the largest complaint in number, totaling 378 cases (74 percent), and psychological dissatisfaction, such as pain or an uncomfortable sensation, was the second largest in number, totaling 104 cases (20 percent). For the 753 patients (primary rhinoplasty patients), the main complaint was too-short or too-flat a nose (100 percent).(ABSTRACT TRUNCATED AT 250 WORDS)     

A problem-oriented and segmental open approach to alar cartilage losses and alar length discrepancies

Alar cartilage losses and alar length discrepancies present problems in nasal tip support, contour, and symmetry. The true extent of the cartilage defect is often not apparent until the time of surgery. This article examines a problem-oriented and segmental open approach to such deformities. It is based on the size of the defect, its location within the dome and lateral crus, and the presence or absence of alar collapse. The defects are classified as major when there is a total or near total loss of the lateral crus, moderate when more than 5 mm is involved, and minor when less than 5 mm is affected. In major defects, a segmental reconstruction of the nasal tip cartilages is undertaken. It consists of a septal graft for columellar support and a conchal shield graft and umbrella graft for nasal tip contour. The whole length of the lateral crus is not reconstructed unless alar collapse is present. In moderate cartilage defects, usually seen laterally in secondary rhinoplasties, the remaining central dome segments are remodeled with shaping sutures. Moderate cartilage length discrepancies, as seen in unilateral cleft lip noses, are equalized through reversed alar rotations. The short crus is rotated laterally, taking length from the medial crus, and the long crus is rotated medially, with the excess advanced into the medial crural footplate. Additional shortening of the long crus can be achieved through cartilage division and advancement. The balanced alar units are then raised with tip projection-vector sutures, and onlay grafts are added if required. In minor cartilage losses, symmetry is usually obtained by shortening the opposite uninjured crus. A total of 33 patients are examined in this review. The average follow-up is 14 months. An improvement in nasal tip shape and support was achieved in all patients.     

Diced cartilage grafts in rhinoplasty surgery

The use of diced cartilage grafts in rhinoplasty surgery was recently revived by Erol with the publication of his technique for "Turkish delight" grafts (i.e., diced cartilage grafts wrapped in Surgicel). The present study details the authors' experience with 50 consecutive diced cartilage grafts used in three configurations during a prospective study of 50 primary and secondary aesthetic rhinoplasty procedures performed by the senior author (Daniel). Part I consists of 22 diced cartilage grafts wrapped in Surgicel and placed in the radix (n = 14), radix/upper dorsum (n = 4), and full-length dorsum (n = 4). All grafts were performed adhering meticulously to Erol's technique without modification. This portion of the study was halted abruptly at 4 months because of the unexpected absorption and clinical failure of all diced cartilage grafts wrapped in Surgicel. Subsequently, five patients had revision surgery, and biopsy specimens were taken at the prior grafting site and analyzed histologically. After this clinical failure, part II of the study began, consisting of 20 patients who had diced cartilage grafts wrapped in fascia. The range of applications was comparable: radix (n = 12), radix/dorsum (n = 3), and full-length dorsum (n = 5). Because of our prior practice of overcorrecting by 20 percent with diced cartilage grafts wrapped in Surgicel, we had excessive amounts of material in six of our initial diced cartilage wrapped in fascia radix grafts, but no subsequent grafts. The overcorrections were easily reduced at 6 weeks to 11 months postoperatively using a pituitary rongeur under local anesthesia, and the material was sent for histologic analysis. Minimum 1-year follow-up of all 20 cases has shown maintenance of the grafts without evidence of absorption. Part III of this study comprised eight patients who had diced cartilage grafts without a fascial covering placed throughout the nose, including on the sides of osseocartilaginous rib grafts to the dorsum. At 14 months, there was no evidence that any of these grafts had been absorbed. Histologic analysis of the biopsy specimens from the diced cartilage grafts wrapped in Surgicel showed evidence of fibrosis and lymphocytic infiltrates with small amounts of Surgicel visible on birefringent microscopy. Remnants of cartilage were present but were metabolically inactive on the basis of negative glial fibrillary acidic protein staining. Control specimens of fresh septal cartilage and banked septal cartilage were remarkably similar to each other and demonstrated normal cartilage architecture and cellular activity. The diced cartilage grafts wrapped in fascia showed coalescence of the diced cartilage into a single cartilage mass, with viable cartilage cells and normal metabolic activity on the basis of glial fibrillary acidic protein staining. All of the diced cartilage grafts wrapped in Surgicel absorbed and failed to correct the clinical problem for which they were performed. All of the diced cartilage grafts wrapped in fascia and pure diced cartilage grafts did correct the clinical deformities and appear to have survived completely. The diced cartilage grafts wrapped in fascia placed along the dorsum were distinctly palpable throughout the postoperative period, as was one prior case with a 6-year follow-up. The authors' clinical experience confirms the experimental studies of Yilmaz et al. that question the use of Surgicel for wrapping diced cartilage grafts in clinical rhinoplasty surgery.     

Reconstruction with irradiated homograft costal cartilage

The authors present their experience with 51 patients who underwent 55 reconstructive and cosmetic operative procedures with irradiated homograft costal cartilage, who were studied between August of 1988 and June of 2001. The procedures included 52 rhinoplasties and three penile implantations among a total of 130 grafts. Follow-up ranged from 7 months to 12 years. There were two immediate graft exposure complications. Late complications included displacement of the graft in two patients, fracture of the graft in one patient, and partial resorption in one patient at 6 months postoperatively. The experience is described and the literature is reviewed.     

A new technique in nasal-tip reduction surgery.

This article presents a technique for the reduction of the overprojected nasal tip with a proportional reduction of the nostril-margin circumference. To achieve these reductions, a modified open rhinoplasty technique is used, which is unique in that it involves the total transection of the columella through the medial crura of the alar cartilage. The alar cartilage is raised with the flap.The technique was first developed and introduced by the senior author (R.A.S.) 25 years ago and has since been refined through the execution of several thousand rhinoplasties. The results continue to be consistent and pleasing from both the patients' and the surgeon's points of view.     

Augmentation rhinoplasty: dorsal onlay grafting using shaped autogenous septal cartilage

We describe our experience with autogenous septal cartilage onlay grafts for augmentation of the nasal dorsum in primary and secondary rhinoplasty cases. After careful nasofacial analysis, the grafts are custom-shaped into inverted-V-frame, A-frame, or inverted-U-frame grafts, depending on the type and degree of augmentation desired. The dorsal elevation is thus tailored to fit the imperfection at hand, resulting in a smooth, natural-looking nasal contour. The indications for each type of graft are reviewed, and the surgical technique of graft harvesting and carving is detailed and illustrated.     

Grafting the nasal dorsum with tandem ear cartilage

A technique for autogenous grafting of the nasal dorsum with ear cartilage is suggested based on the results of 25 consecutive cases. The technique involves (1) harvesting the entire cymba conchae and cavum conchae of the ear; (2) separating them and suturing them to each other in tandem fashion; (3) filling the underside concavity of the cymba conchae part of the graft with scraps of cartilage; (4) avoiding any bruising or crushing of the graft; and (5) filling any minor residual irregularities of the dorsum with soft tissue or cartilage from the cephalic trim of the lateral crus. The results suggest a consistent augmentation of the nasal dorsum for deficiencies from 3 to 6 mm in size. Four of the 25 cases did require secondary correction for dorsal convexity, inadequate augmentation, and surface irregularities. The technique, however, has been helpful in that ear cartilage is invariably available, allowing septum to be used for more important grafts. The procedure is easily performed under local anesthesia with no significant distortion to the donor site.     

First evidence of dinosaurian secondary cartilage in the post-hatching skull of Hypacrosaurus stebingeri (Dinosauria, Ornithischia)

Bone and calcified cartilage can be fossilized and preserved for hundreds of millions of years. While primary cartilage is fairly well studied in extant and fossilized organisms, nothing is known about secondary cartilage in fossils. In extant birds, secondary cartilage arises after bone formation during embryonic life at articulations, sutures and muscular attachments in order to accommodate mechanical stress. Considering the phylogenetic inclusion of birds within the Dinosauria, we hypothesized a dinosaurian origin for this "avian" tissue. Therefore, histological thin sectioning was used to investigate secondary chondrogenesis in disarticulated craniofacial elements of several post-hatching specimens of the non-avian dinosaur Hypacrosaurus stebingeri (Ornithischia, Lambeosaurinae). Secondary cartilage was found on three membrane bones directly involved with masticatory function: (1) as nodules on the dorso-caudal face of a surangular; and (2) on the bucco-caudal face of a maxilla; and (3) between teeth as islets in the alveolar processes of a dentary. Secondary chondrogenesis at these sites is consistent with the locations of secondary cartilage in extant birds and with the induction of the cartilage by different mechanical factors - stress generated by the articulation of the quadrate, stress of a ligamentous or muscular insertion, and stress of tooth formation. Thus, our study reveals the first evidence of "avian" secondary cartilage in a non-avian dinosaur. It pushes the origin of this "avian" tissue deep into dinosaurian ancestry, suggesting the creation of the more appropriate term "dinosaurian" secondary cartilage.     

Anatomic reconstruction of the nasal tip cartilages in secondary and reconstructive rhinoplasty

Most techniques for secondary rhinoplasty assume that useful residual remnants of the tip cartilages remain, but frequently the alar cartilages are missing--unilaterally, bilaterally, completely, or incompletely--with loss of the lateral crura, middle crura, and parts of the medial crura. In such severe cases, excision of scar tissue and the residual alar remnants and their replacement with nonanatomic tip grafts have been recommended. Multiple solid, bruised, or crushed cartilage fragments are positioned in a closed pocket or solid shield-shaped grafts are fixed with sutures during an open rhinoplasty. These onlay filler grafts only increase tip projection and definition. Associated tip abnormalities (alar rim notching, columellar retraction, nostril distortion) are not addressed. Problems with graft visibility, an unnatural appearance, or malposition have been noted. Fortunately, techniques useful in reconstructive rhinoplasty can be applied to severe cosmetic secondary deformities. Anatomic cartilage replacements similar in shape, bulk, and position to normal alar cartilages can be fashioned from septal, ear, and rib cartilage, fixed to the residual medial crura and/or a columellar strut, and bent backward to restore the normal skeletal framework of the tip. During an open rhinoplasty, a fabricated and rigid framework is designed to replace the missing medial, middle, or lateral crus of one or both alar cartilages. The entire alar tripod is recreated. These anatomic alar cartilage reconstructive grafts create tip definition and projection, fill the lobule and restore the expected lateral convexity, position the columella and establish columellar length, secure and position the alar rim, and brace the external valve against collapse, support the vestibular lining, and restore a nostril shape. The anatomic form and function of the nasal tip is restored. This technique is recommended when alar cartilages are significantly destroyed or absent in secondary or reconstructive rhinoplasty and the alar remnants are insufficient for repair. Anatomically designed alar cartilage replacements allow an aesthetically structured skeleton to contour the overlying skin envelope. Problems with displacement are minimized by graft fixation. Graft visibility is used to the surgeon's advantage. A rigidly supported framework with a nasal shape can mold a covering forehead flap or the scarred tip skin of a secondary rhinoplasty and create a result that may approach normal. Anatomic alar cartilage reconstructions were used in eight reconstructive and eight secondary rhinoplasties in the last 5 years. Their use in the repair of postrhinoplasty deformities is emphasized.     

The universal tip: a systematic approach to aesthetic problems of the lower lateral cartilages

A systematic approach to the various common aesthetic problems of the lower lateral cartilages is presented. Since this approach and technique may be applied to a wide variety of problems, we have taken the liberty of calling this the universal tip. These concepts have emerged from study of the literature and have evolved over the past thousand rhinoplasties. A classification of lower lateral cartilage problems includes five basic variations: (1) the wide, amphorous, ill-defined tip, (2) insufficient projection of the tip, (3) overprojection of the tip, (4) dependent tip with lack of definition, and (5) asymmetrical tip. It is important to realize that any of these five categories may be found in various combinations with each other. The details and fundamental steps of this universal tip technique are presented along with illustrative case examples in each of the five basic variations. In approximately 4 percent of patients there is a postoperative asymmetry in the position of cartilaginous flaps in the region of the dome of the lower lateral cartilage. These abnormalities plus abnormal ridges or bossa can usually be corrected at the time of secondary surgery under local anesthesia.     

Mesenchymal and mechanical mechanisms of secondary cartilage induction

Secondary cartilage occurs at articulations, sutures, and muscle attachments, and facilitates proper kinetic movement of the skeleton. Secondary cartilage requires mechanical stimulation for its induction and maintenance, and accordingly, its evolutionary presence or absence reflects species-specific variation in functional anatomy. Avians illustrate this point well. In conjunction with their distinct adult mode of feeding via levered straining, duck develop a pronounced secondary cartilage at the insertion (i.e., enthesis) of the mandibular adductor muscles on the lower jaw skeleton. An equivalent cartilage is absent in quail, which peck at their food. We hypothesized that species-specific pattern and a concomitant dissimilarity in the local mechanical environment promote secondary chondrogenesis in the mandibular adductor enthesis of duck versus quail. To test our hypothesis we employed two experimental approaches. First, we transplanted neural crest mesenchyme (NCM) from quail into duck, which produced chimeric “quck” with a jaw complex resembling that of quail, including an absence of enthesis secondary cartilage. Second, we modified the mechanical environment in embryonic duck by paralyzing skeletal muscles, and by blocking the ability of NCM to support mechanotransduction through stretch-activated ion channels. Paralysis inhibited secondary cartilage, as evidenced by changes in histology and expression of genes that affect chondrogenesis, including members of the FGF and BMP pathways. Ion channel inhibition did not alter enthesis secondary cartilage but caused bone to form in place of secondary cartilage at articulations. Thus, our study reveals that enthesis secondary cartilage forms through mechanisms that are distinct from those regulating other secondary cartilage. We conclude that by directing the musculoskeletal patterning and integration of the jaw complex, NCM modulates the mechanical forces and molecular signals necessary to control secondary cartilage formation during development and evolution.     

Comparison of age-dependent expression of aggrecan and ADAMTSs in mandibular condylar cartilage, tibial growth plate, and articular cartilage in rats

A disintegrin and metalloproteinase with thrombospondin motif (adamalysin–thrombospondins, ADAMTS) degrades aggrecan, one of the major extracellular matrix (ECM) components in cartilage. Mandibular condylar cartilage differs from primary cartilage, such as articular and growth plate cartilage, in its metabolism of ECM, proliferation, and differentiation. Mandibular condylar cartilage acts as both articular and growth plate cartilage in the growing period, while it remains as articular cartilage after growth. We hypothesized that functional and ECM differences between condylar and primary cartilages give rise to differences in gene expression patterns and levels of aggrecan and ADAMTS-1, -4, and -5 during growth and aging. We employed in situ hybridization and semiquantitative RT-PCR to identify mRNA expression for these molecules in condylar cartilage and primary cartilages during growth and aging. All of the ADAMTSs presented characteristic, age-dependent expression patterns and levels among the cartilages tested in this study. ADAMTS-5 mainly contributed to ECM metabolism in growth plate and condylar cartilage during growth. ADAMTS-1 and ADAMTS-4 may be involved in ECM turn over in articular cartilage. The results of the present study reveal that ECM metabolism and expression of related proteolytic enzymes in primary and secondary cartilages may be differentially regulated during growth and aging.     

An immunohistochemical study of localization of type I and type II collagens in mandibular condylar cartilage compared with tibial growth plate

Immunohistochemical localization of type I and type II collagens was examined in the rat mandibular condylar cartilage (as the secondary cartilage) and compared with that in the tibial growth plate (as the primary cartilage) using plastic embedded tissues. In the condylar cartilage, type I collagen was present not only in the extracellular matrix (ECM) of the fibrous, proliferative, and transitional cell layers, but also in the ECM of the maturative and hypertrophic cell layers. Type II collagen was present in the ECM of the maturative and hypertrophic cell layers. In the growth plate, type II collagen was present in the ECM of whole cartilaginous layers; type I collagen was not present in the cartilage but in the perichondrium and the bone matrices. These results indicate that differences exist in the components of the ECM between the primary and secondary cartilages. It is suggested that these two tissues differ in the developmental processes and/or in the reactions to their own local functional needs.     

The Turkish delight: a pliable graft for rhinoplasty

In nose surgery, carved or crushed cartilage used as a graft has some disadvantages, chiefly that it may be perceptible through the nasal skin after tissue resolution is complete. To overcome these problems and to obtain a smoother surface, the authors initiated the use of Surgicel-wrapped diced cartilage. This innovative technique has been used by the authors on 2365 patients over the past 10 years: in 165 patients with traumatic nasal deformity, in 350 patients with postrhinoplasty deformity, and in 1850 patients during primary rhinoplasty. The highlights of the surgical procedure include harvested cartilage (septal, alar, conchal, and sometimes costal) cut in pieces of 0.5 to 1 mm using a no. 11 blade. The fine-textured cartilage mass is then wrapped in one layer of Surgicel and moistened with an antibiotic (rifamycin). The graft is then molded into a cylindrical form and inserted under the dorsal nasal skin. In the lateral wall and tip of the nose, some overcorrection is performed depending on the type of deformity. When the mucosal stitching is complete, this graft can be externally molded, like plasticine, under the dorsal skin. In cases of mild-to-moderate nasal depression, septal and conchal cartilages are used in the same manner to augment the nasal dorsum with consistently effective and durable results. In cases with more severe defects of the nose, costal cartilage is necessary to correct both the length of the nose and the projection of the columella. In patients with recurrent deviation of the nasal bridge, this technique provided a simple solution to the problem. After overexcision of the dorsal part of deviated septal cartilage and insertion of Surgicel-wrapped diced cartilage, a straight nose was obtained in all patients with no recurrence (follow-up of 1 to 10 years). The technique also proved to be highly effective in primary rhinoplasties to camouflage bone irregularities after hump removal in patients with thin nasal skin and/or in cases when excessive hump removal was performed. As a complication, in six patients early postoperative swelling was more than usual. In 16 patients, overcorrection was persistent owing to fibrosis, and in 11 patients resorption was excessive beyond the expected amount. A histologic evaluation was possible in 16 patients, 3, 6, and 12 months postoperatively, by removing thin slices of excess cartilage from the dorsum of the nose during touch-up surgery. This graft showed a mosaic-type alignment of graft cartilage with fibrous tissue connection among the fragments. In conclusion, this type of graft is very easy to apply, because a plasticine-like material is obtained that can be molded with the fingers, giving a smooth surface with desirable form and long-lasting results in all cases. The favorable results obtained by this technique have led the authors to use Surgicel-wrapped diced cartilage routinely in all types of rhinoplasty.     

An immunohistochemical study of localization of type I and type II collagens in mandibular condylar cartilage compared with tibial growth plate

Summary Immunohistochemical localization of type I and type II collagens was examined in the rat mandibular condylar cartilage (as the secondary cartilage) and compared with that in the tibial growth plate (as the primary cartilage) using plastic embedded tissues. In the condylar cartilage, type I collagen was present not only in the extracellular matrix (ECM) of the fibrous, proliferative, and transitional cell layers, but also in the ECM of the maturative and hypertrophic cell layers. Type II collagen was present in the ECM of the maturative and hypertrophic cell layers. In the growth plate, type II collagen was present in the ECM of whole cartilaginous layers; type I collagen was not present in the cartilage but in the perichondrium and the bone matrices. These results indicate that differences exist in the components of the ECM between the primary and secondary cartilages. It is suggested that these two tissues differ in the developmental processes and/or in the reactions to their own local functional needs.     

Development of a computational technique to measure cartilage contact area

Computational measurement of joint contact distributions offers the benefit of non-invasive measurements of joint contact without the use of interpositional sensors or casting materials. This paper describes a technique for indirectly measuring joint contact based on overlapping of articular cartilage computer models derived from CT images and positioned using in vitro motion capture data. The accuracy of this technique when using the physiological nonuniform cartilage thickness distribution, or simplified uniform cartilage thickness distributions, is quantified through comparison with direct measurements of contact area made using a casting technique. The efficacy of using indirect contact measurement techniques for measuring the changes in contact area resulting from hemiarthroplasty at the elbow is also quantified. Using the physiological nonuniform cartilage thickness distribution reliably measured contact area (ICC=0.727), but not better than the assumed bone specific uniform cartilage thicknesses (ICC=0.673). When a contact pattern agreement score (s_agree) was used to assess the accuracy of cartilage contact measurements made using physiological nonuniform or simplified uniform cartilage thickness distributions in terms of size, shape and location, their accuracies were not significantly different (p>0.05). The results of this study demonstrate that cartilage contact can be measured indirectly based on the overlapping of cartilage contact models. However, the results also suggest that in some situations, inter-bone distance measurement and an assumed cartilage thickness may suffice for predicting joint contact patterns.     

Nonuniform swelling-induced residual strains in articular cartilage

Swelling effects in cartilage originate from an interstitial osmotic pressure generated by the presence of negatively charged proteoglycans in the tissue. This swelling pressure gives rise to a non-zero residual strain in the cartilage solid matrix in the absence of externally applied loads. Previous studies have quantified swelling effects in cartilage as volumetric or dimensional change of excised samples in varying osmotically active solutions. This study presents a new optical technique for measuring two-dimensional swelling-induced residual strain fields in planar samples of articular cartilage attached to the bone (i.e., in situ). Osmotic loading was applied to canine cartilage bone samples by equilibration in external baths of varying NaCl concentration. Non-zero swelling-induced strains were measured in physiological saline, giving evidence of the existence of residual strains in articular cartilage. Only one component of planar strain (i.e., in thickness direction) was found to be non-zero. This strain was found to be highly non-uniform in the thickness direction, with evidence of compressive strain in the deep zone of cartilage and tensile strain in the middle and surface zones. The obtained results can be used to characterize the material properties of the articular cartilage solid matrix, with estimated values of 26 M Pa for the tensile modulus for middle zone cartilage. The method provides the basis to obtain material properties of the cartilage solid matrix from a simple, free-swelling test and may be useful for quantifying changes in cartilage properties with injury, degeneration and repair.