Ganglions of the foot and ankle. A retrospective analysis of 63 procedures.

A retrospective study was conducted to evaluate treatment of foot and ankle ganglion cysts seen at the Foot and Ankle Institute at the Pennsylvania College of Podiatric Medicine (now Temple University School of Podiatric Medicine). From 1990 to 1997, 63 patients (63 ganglion cysts) were treated by conservative or surgical means. Statistical analysis of data collected showed a significant relationship between type of treatment received and recurrence of the cyst. Surgical intervention resulted in significantly less recurrence (11%) than conservative treatment (63%). Regardless of whether treatment was conservative or surgical, there was no significant relationship between location of the cyst and recurrence. The type of conservative treatment was not significantly related to recurrence of the cyst. The surgical recurrence rate reported here is comparable to that reported in other studies of foot and ankle ganglion cysts. The number of foot and ankle ganglion cysts evaluated in this study is the largest in the literature.

Bone cell behavior on Matrigel-coated Ca/P coatings of varying crystallinities.

Rat calvarial cell mitogenic behavior was investigated on various biomaterials coated with Matrigel, a basement membrane matrix containing growth factors. Low (20-40%) and high (70-90%) crystallinity hydroxyapatite (rHA and cHA), rough titanium (Ti), and tissue culture polystyrene (TP) surfaces were compared. Surface chemistry and calcium resorption of HA coatings, alkaline phosphatase activity (APA), and growth of cells were measured for Matrigel-coated and uncoated surfaces at 2, 7, and 14 days. Gene expression for four noncollagenous bone-related proteins (osteonectin, osteopontin, alkaline phosphatase, and osteocalcin) was also investigated by reverse transcription and polymerase chain reaction up to 28 days. Ca concentration in incubating solutions increased with time for the two types of HA coatings and was always greater for rHA than cHA. Surface chemistry and coating dissolution rates were not affected by the presence of Matrigel or cells throughout the study. APA of cells on the two HA-coated surfaces was comparably enhanced in the presence of Matrigel and was greater than on Ti surfaces. Only HA surfaces showed an increased APA of cells with time in the presence of Matrigel. Cell growth peaked at 7 days and was greatest for cells on the two HA surfaces and without Matrigel. At 14 days, cell growth was comparable on the four surfaces. The presence of HA and Matrigel enhanced cell-specific APA at 14 days. Gene expression for all four proteins investigated showed no differences between surfaces after 7 days. At 2 and 7 days, gene expression was indicative of proliferation for Ti, and of proliferation, differentiation, and mineralization for HA and TP more so without Matrigel. The addition of this matrix significantly enhanced mitogenicity of calvarial cells on HA only after 14 days. Matrigel eliminated differences seen between the two HA coatings. Gene expression was not enhanced or inhibited by the presence of Matrigel.

Effect of Ca/P coating resorption and surgical fit on the bone/implant interface.

The effect of coating resorption on bone apposition and attachment strength to resorbable hydroxyapatite (HA), nonresorbable HA-coated, and uncoated rough titanium implants was evaluated in interference- and noninterference-fit (gap of 2-3 mm) surgical models 2, 4, and 12 weeks postoperatively. Interference and noninterference fits showed differences in bone bridging. Bone apposition was circumferential around the implants in noninterference fit. Significantly greater bone apposition was seen to nonresorbable HA-coated implants than uncoated and resorbable HA-coated implants at 4 and 12 weeks. Only resorbable HA coatings showed significantly lower bone apposition for noninterference versus interference fit and from 4-12 weeks. At 2 weeks, strengths of bone attachment to resorbable HA-coated implants were greater than the other implants, and decreased to lower values (not significant) than the nonresorbable HA-coated implants at 4 and 12 weeks. Differences in push-out shear strengths between interference- and noninterference-fit surgical models were significant for uncoated implants at 4 weeks, but not for HA-coated implants at any time period. Significant differences were seen between the three implant types only for the noninterference-fit model, where the HA-coated implants showed greater strengths than the uncoated implants (significant at 2 and 4 weeks). This study showed that presence of resorbable or nonresorbable HA coatings is beneficial when a gap of 2-3 mm is present between the implant and the bone. The resorbable HA-coated implants showed greatest strengths at the early time period. At later time periods, resorbable HA-coated implants showed lower bone apposition and attachment strengths than nonresorbable HA coatings.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraosseous incorporation of composite collagen prostheses designed for ligament reconstruction.

Composite collagen prostheses are potentially useful for reconstruction of the anterior cruciate ligament (ACL). We evaluated the intraosseous response to composite collagen prostheses to determine if "biological fixation" could be used to secure the prostheses within surgical bone tunnels. The rate of degradation of the prosthesis and the response of the tissue were evaluated, as a function of collagen crosslinking agent and time, in nonloaded bone tunnels in rabbits. Prostheses were fabricated by the alignment of 200 reconstituted type-I collagen fibers (60 microns in diameter) and the embedding of the fibers within a collagen matrix. The prostheses degraded rapidly within the bone tunnels in comparison with soft-tissue implantation sites. Dehydrothermal-cyanamide crosslinked collagen fibers were completely degraded by 8 weeks. Only 10% of glutaraldehyde cross-linked collagen fibers remained intact at 12 weeks. Fibrous tissue and inflammatory cells rapidly infiltrated the prostheses, and new bone surrounded the circumference of the prostheses, advancing toward the center at longer times. At the lateral cortex, where fibrous tissue emerged, the bone/soft-tissue interface was delineated by a tidemark, similar to that observed in a normal ligament insertion site. Preliminary pull-out testing of the soft tissue from the bone was discontinued because failure consistently occurred in the soft tissue; this suggests rapid incorporation of the prostheses within the bone tunnels. Composite collagen prostheses designed for ACL reconstruction degrade rapidly in bone and induce rapid ingrowth of fibrous tissue and bone. These results suggest that tissue ingrowth in the bone tunnels might provide biological fixation for collagen prostheses used for ACL reconstruction.

Mechanical and histological evaluation of amorphous calcium phosphate and poorly crystallized hydroxyapatite coatings on titanium implants.

The effect of amorphous calcium phosphate (Ca/P) and poorly crystallized (60% crystalline) hydroxyapatite (HA) coatings on bone fixation to "smooth" and "rough" (Ti-6A1-4V powder sprayed) titanium-6Al-4V (Ti) implants was investigated. Implants were evaluated histologically, mechanically, and by scanning electron microscopy (SEM) after 4 and 12 weeks of implantation in a rabbit transcortical femoral model. Histological evaluation of amorphous vs. poorly crystallized HA coatings showed significant differences in bone apposition (for rough-coated implants only) and coating resorption (for smooth- and rough-coated implants) that were increased within cortical compared to cancellous bone. The poorly crystallized HA coatings showed most degradation and least bone apposition. Mechanical evaluation, however, showed no significant differences in push-out shear strengths between the two types of coatings evaluated. Differences between 4 and 12 weeks were significant for coating resorption and push-out shear strength but not for bone apposition. Significant enhancement in interfacial shear strengths for bioceramic coated as compared to uncoated implants were seen for smooth-surfaced implants (3.5-5 times greater) but not for rough-surfaced implants at 4 and 12 weeks. Rough implants showed greater mean interfacial strengths than uncoated smooth implants at 4 and 12 weeks (seven times greater) and to coated smooth implants at 12 weeks only (two times greater). Mechanical failure of the bone/coating/implant interface consistently occurred within the bone, even in the case of the poorly crystallized HA coatings, which had almost completely resorbed on rough implants. These results suggest that once early osteointegration is achieved biodegradation of a bioactive coating should not be detrimental to the bone/coating/implant fixation.

In vitro evaluation of amorphous calcium phosphate and poorly crystallized hydroxyapatite coatings on titanium implants.

Studies of various apatite coatings on metal orthopaedic prostheses suggest that coating dissolution may promote enhanced bone bonding. Little is known concerning the effects of crystallinity and the underlying roughness on calcium phosphate (Ca/P) coating dissolution rate. To address these issues, the surface chemistry of amorphous Ca/P and poorly crystallized hydroxyapatite (HA) coatings on "smooth" and "rough" titanium (Ti) alloy (Ti-6A1-4V) implants was studied following immersion in Hank's physiologic solution at pH 7.2 and 5.2 for 0-, 4-, and 12-week periods. Changes in Calcium (Ca) ion concentrations in the solutions, coating chemistry, and surface morphology were studied by ion selective electrode, x-ray diffraction (XRD), and scanning electron microscopy (SEM) respectively. The amount of Ca dissolved from Ca/P-coated implants was strongly dependent on the chemistry of the coating and less dependent on pH or time of incubation. The effect of the underlying surface (smooth vs. rough) was not significant. The poorly crystallized HA coating underwent the most degradation, greatest crystallographic alteration, and greatest surface film formation. The amorphous coating was more stable in the saline environment, and may be more suitable in vivo if coating longevity is desired. These results suggest that this in vitro method is an effective way of determining differences in HA coating integrity.

Hydroxyapatite-coated orthopedic implants.

Hydroxyapatite (HA)-coated metal implants were developed in order to capitalize on the excellent biological properties of HA, and minimize the potential for mechanical failure of the HA in vivo. Results of implantation studies suggest that synthetic HA is osteoconductive (enhances local bone healing) and becomes osteointegrated (forms an intimate bond with bone). HA-coated prostheses are currently being evaluated for use in cementless total joint arthroplasty. The purpose of this article is to review the experimental studies leading to the development of HA-coated orthopedic devices, and to summarize the current status of clinical studies. Finally, the concerns and future directions for HA-coated implants are addressed.