Biomechanical comparison of lesser tuberosity osteotomy versus subscapularis tenotomy in total shoulder arthroplasty.

BACKGROUND: Total shoulder arthroplasty is traditionally performed through an anterior deltopectoral exposure with subscapularis tenotomy. Postoperative subscapularis dysfunction is common and adversely affects clinical outcomes. Consequently, surgeon interest in lesser tuberosity osteotomy has grown in an effort to improve subscapularis repair strength. This study investigated the biomechanical strength of subscapularis tenotomy vs lesser tuberosity osteotomy in the setting of total shoulder arthroplasty. MATERIALS AND METHODS: Uncemented humeral prostheses were placed in 20 paired upper extremities from 10 cadavers. For each respective cadaver, 1 limb underwent lesser tuberosity osteotomy and the contralateral limb underwent subscapularis tenotomy. The cadaveric specimens then underwent cyclic displacement and maximum load to failure testing. RESULTS: The subscapularis tenotomy specimens exhibited significantly less cyclic displacement (0.8 mm) than the osteotomy group (1.8 mm), with a 95% confidence interval (CI) for the difference of 0.5 to 1.5 mm (P = 0.002). The maximum load to failure was 439 ± 96 N for tenotomy and 447 ± 89 N for osteotomy (95% CI for the difference of -58 to 75), which was not significant (P = .78). CONCLUSION: Lesser tuberosity osteotomy was not significantly stronger than subscapularis tenotomy in maximum load to failure testing, with minimal clinical significance set at 100 N. Subscapularis tenotomy repair showed statistically significant less cyclic displacement than lesser tuberosity osteotomy. Further research is needed to clarify how the biomechanical results immediately after subscapularis tenotomy and lesser tuberosity osteotomy correlate with clinical outcomes.

Triceps tendon properties and its potential as an autograft.

BACKGROUND: Although the triceps tendon has been used as a graft for ligament reconstruction about the elbow, and has been postulated to be useful as a graft in the treatment of massive rotator cuff tears, no data exists on the tensile properties of the triceps tendon. The purpose of this study was to define the tensile properties of the medial, lateral, and central thirds of the triceps tendon, in order to examine its potential as an autograft for upper extremity pathology. MATERIALS AND METHODS: Ten fresh frozen upper extremity specimens were used. The triceps tendon was dissected from its musculotendinous junction and left attached to its insertion at the olecranon. The tendon was split into thirds and its tensile properties were recorded using a materials testing machine. RESULTS: The lateral portion was significantly thinner and less stiff than the medial and central portions (P < .05). It failed at significantly lower ultimate load than the central portion (P < .05). There were no significant differences between the medial, central, and lateral portions of the triceps tendons with regards to ultimate stress (P = .20) or modulus of elasticity (P = .64). CONCLUSION: Data from the current study were compared to available literature regarding tensile properties of the rotator cuff and elbow ligaments. Both the medial and central portions of the triceps tendon offer sufficient strength to be used in the reconstruction of the rotator cuff or ligament reconstruction in the elbow.

Gliding resistance and strength of composite sutures in human flexor digitorum profundus tendon repair: an in vitro biomechanical study.

PURPOSE: Although the strength of a tendon repair is clearly important, the friction of the repair is also a relevant consideration. The purpose of this study was to characterize the frictional coefficient, gliding resistance, and breaking strength of suture materials and a suture construct commonly used for flexor tendon repair. METHODS: We measured the friction coefficients of 3-0 braided nylon enclosed in a smooth nylon outer shell (Supramid, S. Jackson, Alexandria, VA), 3-0 braided polyester coated with polybutilate (Ethibond, Ethicon, Somerville, NJ), and 3-0 braided polyester/monofilament polyethylene composite (FiberWire, Arthrex, Naples, FL) sutures. We also measured the gliding resistance, linear breaking strength, and resistance to gapping of zone 2 modified Pennington tendon repairs with the 2 lowest-friction sutures in 20 human cadaveric flexor digitorum profundus tendons. RESULTS: The braided polyester/monofilament polyethylene composite had a significantly lower friction coefficient (0.054) than either the coated polyester (0.076) or nylon (0.130) sutures. The gliding resistances of the repaired tendons with braided/monofilament polyethylene composite suture and those of coated, braided polyester were similar. The strength of the 2 repairs (force to produce a 2 mm gap) and resistance to gap formation were also not significantly different. CONCLUSIONS: Braided polyester composite is a low-friction suture material. However, when this suture was used for tendon repair with a locking suture technique, it did not show a significant effect on the gliding resistance and repair strength compared with the same repair using a coated polyester suture.

Mechanical strength of bone allografts subjected to chemical sterilization and other terminal processing methods.

Infectious disease transmission through the use of human donor allografts can be a catastrophic complication in an otherwise straightforward surgical procedure. The use of bone allograft in reconstructive orthopedic surgeries is increasing, yet severe complications, including death, can result if the transplanted tissues transmit a communicable disease to the tissue recipient. The BioCleanse tissue sterilization process is a fully automated, low-temperature chemical sterilization process that renders allograft tissue sterile. The purpose of this study was to evaluate the effect of a chemical tissue sterilization process on the mechanical strength of cortical bone allografts prior to implantation. Cylindrical cortical bone specimens were harvested from seven human cadaver donors and treated either by: chemical sterilization alone; chemical sterilization and terminal sterilization by gamma irradiation; chemical sterilization, lyophilization, terminal sterilization by STERRAD and rehydration; or untreated. The specimens were tested to failure in axial compression, diametral compression, shear, or bending. There were no significant differences in ultimate stress, strain, or fracture energy between the chemically sterilized and control groups in any of the testing modes.

The mechanical properties of the rabbit carpal tunnel subsynovial connective tissue.

The rabbit model is commonly used to study carpal tunnel syndrome (CTS). It has been proposed that the subsynovial connective tissue (SSCT) in the carpal tunnel may play a role in the etiology of CTS, but the material properties of the rabbit SSCT are unknown. The purpose of this study was to develop a method to measure the shear properties of the rabbit SSCT. In six rabbit cadaver forepaws, the excursion of the third digit flexor digitorum superficialis (FDS) and load to failure of the SSCT were measured in a custom device. The mean excursion to full flexion in this model was 7.08mm (S.D. 0.77). The mean shearing force at full flexion was 317 mN (S.D. 166). At full flexion percentage of maximum shear force in the SSCT was 54.5% (S.D. 19.4). The mean energy absorbed at full flexion was 0.29mJ (S.D. 0.31). The mean excursion needed to reach 5% of the maximum shear force was 3.04mm (S.D. 0.99). The testing model presented in this study demonstrates structural parameters to evaluate the shear properties of the SSCT in a rabbit model. The data presented could be used for estimating sample sizes in a more comprehensive study of the effect of CTS on the SSCT properties.

Substrate adhesion affects contraction and mechanical properties of fibroblast populated collagen lattices.

Fibroblasts can condense a hydrated collagen lattice to a tissue-like structure. The purpose of this study was to evaluate the effect of substrate adhesion on the contraction and mechanical properties of fibroblast populated collagen lattices. Bacteriological grade polystyrene (BGPS) plates and tissue culture polystyrene (TCPS) plates were used as substrates for incubation of fibroblast populated collagen lattices. Hydrophobicity of the polystyrene surfaces was measured by the static sessile contact angle method. Collagen lattice contraction was recorded for 2 weeks, after which the lattices were mechanically tested. The BGPS culture plate had a significantly larger contact angle and was more hydrophobic than the TCPS culture plate. Both hydrophobicity and peripheral detachment of the collagen gel significantly decreased the time lag before initiation of gel contraction and increased the strength of the fibroblast populated collagen lattices. Substrate adhesion affects the contractility and strength of cell seeded collagen gels. This information may be useful in developing tissue engineered tendons and ligaments.

Effects of carpal tunnel release on the relative motion of tendon, nerve, and subsynovial connective tissue in a human cadaver model.

BACKGROUND: The purpose of this study was to evaluate the effect of flexor retinaculum division (simulated carpal tunnel release) on the relative motion of flexor tendon, subsynovial connective tissue, and median nerve in human cadaver specimens. METHODS: Using fluoroscopy, we measured the relative motion of middle finger flexor digitorum superficialis tendon, subsynovial connective tissue, and median nerve in twelve human cadavers with simulated fist motion. Measurements were obtained for three wrist positions: neutral; 60 degrees flexion; and 60 degrees extension. The shear index was defined as the difference in motion between two tissues (tendon, subsynovial connective tissue, or nerve) relative to tendon excursion, expressed as a percentage. After testing with an intact carpal tunnel, the flexor retinaculum was cut and the testing procedure was repeated. FINDINGS: With an intact flexor retinaculum, the wrist flexion position showed significantly less displacement for the subsynovial connective tissue and median nerve relative to tendon displacement, and thus the highest potential shear strain between subsynovial connective tissue-tendon, and tendon-nerve. The wrist extension position also had a significantly higher potential shear strain for tendon-nerve compared to the neutral position. After division of the flexor retinaculum, the differences in shear index among wrist positions were reduced. For the wrist flexion position, the subsynovial connective tissue and median nerve displacements significantly increased, indicating lower shear index values. INTERPRETATION: These findings suggest that division of flexor retinaculum reduces the potential shear strain and thus possibly the risk of shear injury to tissues with the carpal tunnel.

Mechanical properties of intrasynovial and extrasynovial tendon fascicles.

BACKGROUND: Tendon grafting in tendon reconstruction often involves the interchange of intrasynovial and extrasynovial tendons. Although many studies have examined the cellular and biological differences between tendons of various sources, few have studied the mechanical properties of these two different types of tendons. The purpose of this study was to investigate the mechanical properties of intrasynovial and extrasynovial tendons. METHODS: Canine peroneus longus (extrasynovial) and flexor digitorum profundus (intrasynovial) tendons, further subdivided into intrasynovial tendinous and intrasynovial fibrocartilaginous segments, were used in the study. An indentation test was used to measure the compressive modulus. Tensile testing was performed on 400mum longitudinal sections. FINDINGS: The compressive modulus of the intrasynovial fibrocartilaginous segment was significantly higher than that of the intrasynovial tendinous segment, which was in turn significantly higher than that of the extrasynovial tendon (P<0.0001). The tensile modulus of extrasynovial tendon was significantly higher than that of intrasynovial fibrocartilaginous and intrasynovial tendinous segments (P<0.005). The tensile modulus of the intrasynovial fibrocartilaginous and tendinous segments was not significantly different (P=0.14). INTERPRETATION: The results suggest that extrasynovial tendons exhibit superior tensile properties but inferior compressive properties when compared to intrasynovial tendons, which is consistent with their biological role in situ, but which could lead to complications when these tendons are repositioned during tendon graft surgery.

WOUND-HEALING PROPERTIES OF TRANSFORMING GROWTH FACTOR ß (TGF-ß) INDUCIBLE EARLY GENE 1 (TIEG1) KNOCKOUT MICE.

Transforming growth factor beta (TGF-ß) has a broad effect on wound healing, but many questions remain about the regulation of TGF-ß during the healing process. TGF-ß inducible early gene 1 (TIEG1) is a primary response gene for TGF-ß that controls the activities of the TGF-ß/Smad pathway, the primary TGF-ß signaling pathway. The purpose of this study was to investigate the role of TIEG1 in cutaneous wound healing using TIEG1 knockout mice. The wound healing in TIEG1 knockout mice and wild-type controls was evaluated by wound breaking strength, Western blot, and histology at postoperative days 3, 7, and 14. Although re-epithelialization of both groups was similarly complete at day 7, the TIEG1 knockout mice had a significantly lower wound breaking strength than the controls at postoperative day 14. These results suggest that TIEG1 expression may be an important factor involved in the initiation and support of normal cutaneous wound healing.

Effect of host response (incorporation, encapsulation, mixed incorporation and encapsulation, or resorption) on the tensile strength of graft-reinforced repair in the rat ventral hernia model.

OBJECTIVE: The objective of the study was to determine whether the elicited histologic response to synthetic and xenograft materials affected the tensile strength of mesh-reinforced repairs in the rat ventral hernia model. STUDY DESIGN: Hernias were repaired with Gynemesh, Pelvicol, Pelvisoft, or Surgisis (representing incorporation, encapsulation, mixed incorporation and encapsulation, or resorption responses) and were compared with a suture-plicated control. Six animals per group were killed at 1 and 3 months after graft implantation. Preimplantation tensile strength was also measured for each graft material and native rat abdominal wall. RESULTS: Before implantation, Pelvicol had significantly higher adjusted tensile strength when compared with the rat abdominal wall (P < .001) or the other graft materials (P

Direct tendon attachment and healing to porous tantalum: an experimental animal study.

BACKGROUND: The ability to directly attach soft-tissue to metal would have broad clinical application. Previous attempts to obtain normal tendon-to-bone attachment strength have been unsuccessful. In the present study, we hypothesized that when the initial interface mechanical environment is carefully controlled, a highly porous form of tantalum metal would allow the ingrowth of tendon tissue with clinically relevant tendon-to-implant fixation strength approaching that of an intact tendon-to-bone insertion. METHODS: Supraspinatus tendons from forty skeletally mature dogs were reattached to the greater tuberosity between two custom-designed porous tantalum washers. Clinical function as judged on the basis of gait analysis, reattachment fixation strength and stiffness, and tendon function as seen through muscle volume were evaluated preoperatively, immediately postoperatively, and at three, six, and twelve weeks after surgery. Qualitative and quantitative histomorphologic evaluation was performed at three, six, and twelve weeks after surgery. RESULTS: Gait analysis with use of force-plate measurements demonstrated return to a normal gait pattern by three weeks after surgery. Tendon-implant strength as a percentage of normal, contralateral controls increased significantly, from 39% at the time of surgery to 67% at three weeks, 99% at six weeks, and 140% at twelve weeks (p < 0.0014). The stiffness of the construct also increased and approached that of normal tendon, measuring 47% at the time of surgery, 62% at three weeks, 94% at six weeks, and 130% at twelve weeks (p < 0.0299). Supraspinatus muscle volume initially decreased by 33% but recovered to 92% of normal by twelve weeks (p < 0.01). Histomorphologic evaluation showed Sharpey-like fibers inserting onto the surface of the porous tantalum. Quantitative histomorphometric analysis revealed a time-dependent increase in the density of the collagen tissue filling the metal voids below the implant surface of first the bottom washer and then the top washer. CONCLUSIONS: Robust biologic ingrowth of tendon into a porous tantalum implant surface can be achieved under conditions of secure initial mechanical fixation. The strength and stiffness of the tendon-implant construct reached normal levels by six to twelve weeks in this animal model.

Factors related to contraction and mechanical strength of collagen gels seeded with canine endotenon cells.

Fibroblasts can construct a hydrated collagen lattice to a tissue-like structure that is greatly influenced by initial culture conditions. The purpose of this study was to investigate the effects of cell concentration and collagen concentration on the contraction kinetics and mechanical properties of resultant endotenon-derived fibroblast-seeded collagen lattice. The experiment was designed to evaluate the effect of cell concentration (0, 0.25, 0.5, and 1.0 x10(6) cells/mL) and collagen concentration (0.5, 1.0, 1.5, and 2.0 mg/mL). Collagen lattice contraction was recorded for 42 days, after which time the lattices were mechanically tested. The collagen lattices seeded with higher initial cell concentration had a shorter contraction lag phase (p < 0.01), and exhibited a higher ultimate stress (p < 0.01) and instantaneous and equilibrium modulus (p < 0.01) than those seeded with a lower initial cell concentration. The collagen lattices cultured with a lower initial collagen concentration also had a shorter contraction lag phase, and exhibited greater instantaneous and equilibrium modulus (p < 0.01) than those cultured with higher initial collagen concentration. The collagen lattices of initial 0.5 mg/mL collagen concentration had the highest value of ultimate stress (p < 0.03).

Mechanical properties of patellar tendon allografts subjected to chemical sterilization.

PURPOSE: We tested the hypothesis that the preimplantation mechanical properties of BioCleanse-treated bone-patellar tendon-bone (BPTB) allografts are not significantly different from those of untreated specimens. METHODS: For this controlled laboratory study, specimens were harvested as central third or hemi-BPTB units from both knees of 17 cadaveric tissue donors (11 men and 6 women) aged 19 to 88 years. Donor-matched specimens (20 per group) were randomly assigned to either BioCleanse-treated or untreated control groups. Specimens were subjected to 25 minutes of pretensioning at 89 N and then cyclically loaded under longitudinal tension between 50 N and 250 N for 1,000 cycles at 1 Hz, followed by ramp to failure at 50 mm/min. RESULTS: No statistically significant difference was found between untreated and BioCleanse-treated specimens in stiffness (235.3 +/- 37.6 N/mm v 222.3 +/- 53.4 N/mm, P = .37), cyclic creep (0.38 +/- 0.42 mm v 0.40 +/- 0.26 mm, P = .81), maximum force (1,685.7 +/- 471.6 N v 1,807.0 +/- 657.8 N, P = .47), or ultimate stress (29.0 +/- 9.8 MPa v 29.0 +/- 12.8 MPa, P = .98). CONCLUSIONS: The preimplantation mechanical properties of BPTB allografts treated with BioCleanse are not significantly different from those of untreated controls. CLINICAL RELEVANCE: This laboratory study compares the biomechanical properties of chemically treated allografts, which are currently being used in anterior cruciate ligament reconstruction, with those of nontreated fresh-frozen allografts.

The number of screws, bone quality, and friction coefficient affect acetabular cup stability.

One of the major causes of loosening of cementless acetabular cup implants is insufficient initial stability. This study used three-dimensional finite element models of the pelvis and acetabular components to investigate the effects of the number of screws, bone quality, and friction coefficient of the acetabular cup on the initial stability under normal walking. A commercially available hemispherical acetabular cup with five screw holes was used as the default model. The stiffness of the pelvis and the friction coefficient of the cup were systematically varied, within a realistic range, to assess the initial stability of the acetabular cup. The simulations showed that the inserted screws provide only a localized reduction in the relative micromotion between the cup and pelvis therefore inserting several screw closed together might not be useful. Changes in the pelvic stiffness have a non-linear effect on the initial stability of acetabular cup and the subchondral bone provides good support for fixation of the cementless cup. The friction coefficient of the acetabular cup plays a limited role, comparing with the factor of bone quality, in resisting relative micromotion in the cup-pelvis interface.

Permeability of the subsynovial connective tissue in the human carpal tunnel: a cadaver study.

BACKGROUND: The purpose of this study was to determine the permeability of the normal carpal tunnel subsynovial connective tissue. METHODS: Subsynovial connective tissue samples (10mm(2)) were obtained from 10 fresh frozen human cadavers without a history of carpal tunnel syndrome. The thickness of the sample was measured using a charge-coupled device laser displacement system. Each specimen was tested for permeability in a closed pressure chamber at 13.8, 41.3, 68.9 and 96.5 kPa. FINDINGS: Since permeated flow was very low in all specimens, the permeability could be calculated only for eight specimens at 96.5 kPa pressure and for three specimens at 68.9 kPa. The mean permeability at 96.5 kPa was mean 0.89 (SD 0.93)x10(-14)m(4)/Ns and at 68.9 kPa was mean 1.04 (SD 1.54)x10(-14)m(4)/Ns. INTERPRETATION: The subsynovial connective tissue is the most characteristic tissue in the carpal tunnel; it is found in no other location in such abundance. It is well known that carpal tunnel syndrome is the result of increased pressure within the carpal tunnel. This lack of permeability in the subsynovial connective tissue may explain the predisposition of this region for pressure buildup and subsequent neuropathy.

Evaluation of the material properties of the subsynovial connective tissue in carpal tunnel syndrome.

BACKGROUND: The purpose of this study was to determine the material properties of the normal carpal tunnel subsynovial connective tissue in response to shear stress. METHODS: The shear modulus and maximum shear strength were measured with a custom-made micro-tester in 10 specimens of subsynovial connective tissue from 10 wrists in eight patients with idiopathic carpal tunnel syndrome and in 10 specimens from five fresh frozen cadavers without a history of carpal tunnel syndrome. FINDINGS: The mean shear modulus was 22.8 (SD 15.4)kPa for the patient group and 2.7 (SD 1.8)kPa for the control group. The mean maximum shear strength was 54.6 (SD 20.3)kPa for the patient group and 23.3 (SD 10.7)kPa for the control group. The values for the patient group were significantly higher than the control group (P<0.05). INTERPRETATION: The material properties of subsynovial connective tissue are altered in patients with idiopathic carpal tunnel syndrome. The impact, if any, of these altered properties on carpal tunnel syndrome remains to be elucidated.

Histological and biomechanical evaluation of implanted graft materials in a rabbit vaginal and abdominal model.

OBJECTIVE: The objective of the study was to describe the histologic and biomechanical changes of implanted dermal collagen graft materials. STUDY DESIGN: Twenty rabbits were randomized into 2 groups (6 and 12 weeks, respectively). Each rabbit had 4 graft segments (human dermis, porcine dermis, porcine collagen-coated polypropylene mesh, and autologous fascia) randomly implanted into the abdomen and the vagina. Biomechanical testing and histologic analysis was performed after recovery of graft segments. RESULTS: Dermal graft segments showed a marked decrease in ultimate strength (84% to 86%) and elastic modulus (73% to 82%) that was significantly different from the decrease seen in autologous fascia or coated synthetic mesh (P < .0008 and P < .0001, respectively). The decrease in ultimate strength was associated with vaginal implantation (P = .057). Dermal graft materials had moderate inflammation and minimal collagen infiltration. CONCLUSION: The mechanical properties of dermal graft materials decline after implantation. Vaginal implantation may cause a different tissue response to graft material than abdominal implantation. Dermal graft material caused moderate inflammation and minimal collagen ingrowth remote from implantation.

Effect of wrist and ulna head position on gliding resistance of the extensor digitorum minimi and extensor digitorum communis III tendons: a cadaver study.

While attrition from sharp bony surfaces is the most common cause of extensor digiti minimi (EDM) tendon rupture, the etiology of other cases of spontaneous EDM tendon rupture is still unknown. Friction within the compartment may play a role, especially with ulna dislocation. The purpose of this study was to compare gliding resistance of the EDM tendon with that of a tendon which rarely ruptures spontaneously, the extensor digitorum communis of the middle finger (EDC III) tendon, under various wrist and ulna head positions. Eight fresh frozen cadavers were used. Gliding resistance between the tendon and its sheath in each compartment was measured in five different wrist positions and three different ulna head positions. Gliding resistance of the EDM tendon (0.13 +/- 0.03 N) was significantly greater than the EDC III tendon (0.09 +/- 0.03 N) (p < 0.05). For the EDM tendon, the gliding resistance in ulnar deviation or pronation was higher than the gliding resistance in neutral, radial deviation, or supination (p < 0.05), and the gliding resistance with ulnar lengthening (over 6 mm) or dorsal ulnar dislocation (over 9 mm) was higher than in neutral ulnar head positioning. For the EDC III tendon, the gliding resistance in ulnar deviation was significantly higher than the gliding resistance in neutral, radial deviation, or supination, or dorsal dislocation with ulnar lengthening (p < 0.05). Wrist ulnar deviation, ulnar dorsal dislocation (over 9 mm), and ulnar lengthening (over 6 mm) increased the gliding resistance of the EDM tendon. In patients at risk for EDM rupture, such as those with rheumatoid arthritis or distal radioulnar joint osteoarthritis, avoiding such positions may be advantageous.

Optimization of surface modifications of extrasynovial tendon to improve its gliding ability in a canine model in vitro.

Previous studies have shown that the carboxyl groups in hyaluronic acid (HA) could be activated by 1-ethy 1-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) to form intermediate O-acylisoureas, which can chemically bind to exposed amino groups on the tendon surface, leading to improved gliding ability. However, the optimal ratio and concentrations of the components in this chemical mixture were not investigated. The purpose of this study was to optimize the constituents of this tissue engineering approach to tendon surface modification, to reduce friction and improve durability. Peroneus longus (PL) tendons (n=40) were harvested from adult mongrel dogs along with the A2 pulley obtained from the ipsilateral hind paw. After the gliding resistance of the normal PL tendon was measured, the tendons were treated under varying concentrations of HA (0.5, 1, and 2%) and EDC/NHS (0.05, 0.25, and 1%) mixed with a 10% gelatin. Tendon friction was measured for 1000 cycles of simulated flexion/extension motion. Following testing, the residual HA on the tendon surface was evaluated by immunohistochemisty. The gliding resistance of the untreated PL tendons had a mean value of 0.087+/-0.021 N. After surface treatment, there was no significant difference in friction due to HA concentration alone, but the concentration of EDC/NHS and the interaction between HA concentration and EDC/NHS concentration had a significant effect on friction. Regardless of HA concentration, the friction after 1000 cycles was significantly decreased in preparations which included a 1% concentration of EDC/NHS. The tendons with lower gliding resistance presented a smoother surface on light microscopy and maintained more residual HA on the tendon surface. By varying the relative concentrations of HA, EDC, and NHS it is possible to optimize the effect of surface treatment on friction and durability in a canine extrasynovial tendon in vitro.

Effect of curing time and concentration for a chemical treatment that improves surface gliding for extrasynovial tendon grafts in vitro.

The purpose of this study was to evaluate whether treatment time and concentration of these reagents have an effect on the resulting gliding resistance. Forty peroneus longus (PL) tendons were used, from 20 adult mongrel dogs, along with the A2 pulley obtained from the ipsilateral hind paw. After the baseline gliding resistance was measured, the PL tendons were treated with one of three concentrations of hyaluronic acid (HA) and 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC) or N-hydroxysuccinimide (NHS) mixed with 10% gelatin for various times (5, 30, and 60 min). Tendon friction was measured over 1000 cycles of simulated flexion/extension motion. Gliding resistance of the untreated PL tendons had no significant difference among the groups. After surface treatment with low concentration of HA and EDC/NHS for 5-min cure, the gliding resistance was similar to that of the untreated PL tendon and significantly higher than its 30- and 60-min treatment. For the rest of high concentration of HA and EDC/NHS groups, the gliding resistance was lower than that of untreated PL tendon. However, there was no significant difference among the timing points. It is possible to optimize the effect of surface treatment on friction and durability by regulating cure time and concentration of reagents in a canine extrasynovial tendon in vitro.