The effects of extra-articular suture tension on contact mechanics of the lateral compartment of cadaveric stifles treated with the TightRope CCL or lateral suture technique.

OBJECTIVE: To determine the effect of suture tension on contact pressures in the lateral compartment of the stifle for the TightRope CCL((R)) (TR) and circumfabellar-tibial suture (LS) techniques. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: Pelvic limbs (n=12) from dogs weighing 21-24 kg. METHODS: A pressure sensor was used to record peak contact pressure (PCP) and mean contact pressure (MCP) and contact area (CA) in limbs mounted in a materials testing machine. Stifles were stabilized using either a TR or LS technique and the prosthesis was tensioned increasingly from 25 to 70 N. PCP, MCP, and CA were collected at each applied tension before and after applying an axial load of 150 N. RESULTS: In the unloaded condition, LS stabilization resulted in a significant increase (P=.034) in PCP at >or=40 N tensions, whereas TR stabilization resulted in a significant increase (P=.047) in PCP at 70 N tension. There was a significant increase in CA at tensions >or=60 N in the LS group. No effect on MCP was noted. No significant differences in contact pressures were observed in the loaded condition. There were no significant differences in normalized PCP and CA between stabilization groups at any of the tension increment. CONCLUSIONS: The application of high tension to the extra-articular prosthesis alters lateral compartment contact pressures in the unloaded stifle in this ex vivo model. CLINICAL RELEVANCE: Over tightening of an extra-articular prosthesis may increase lateral compartment pressure at the time of surgery. The clinical implications of this finding are unknown, as weight bearing may negate any detrimental effect of high prosthesis tension.

Femorotibial contact mechanics and meniscal strain after serial meniscectomy.

OBJECTIVE: To evaluate changes in femorotibial contact areas (CA) and pressures and meniscal strain after serial meniscectomies of the caudal pole of the medial meniscus. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: Unpaired pelvic limbs from 8 adult dogs weighing 28-35 kg. METHODS: All specimens underwent sequentially, a 30% radial width partial meniscectomy, a 75% radial width partial meniscectomy, and a segmental caudal pole hemi-meniscectomy. Digital pressure sensors were used to measure lateral and medial peak and mean contact pressures and areas before and after serial meniscectomies. Meniscal strain was measured under load in the intact meniscus and after 30% and 75% radial width meniscectomy. Repeated measures analysis of variance with a post hoc Bonferroni's test (P<.05) was used for statistical analysis. RESULTS: A 30% radial width meniscectomy had no significant effect on contact mechanics. A 75% radial width caused a 60.9% increase and hemi-meniscectomy an 87.4% increase in peak contact pressures compared with control. Medial CA decreased by 34.7% after 75% radial width meniscectomy and 47.2% after hemi-meniscectomy. A 30% radial width meniscectomy resulted in 38.5%, and a 75% radial width meniscectomy a 69.2%, decrease in medial meniscal strain compared with control, but these differences were not statistically significant. CONCLUSIONS: In this cadaveric model, smaller (30%) partial meniscectomies had minimal effect on the biomechanics of meniscal function, whereas larger partial (75%) and segmental meniscectomies resulted in significant changes in meniscal and femorotibial contact mechanics. CLINICAL RELEVANCE: This ex vivo data should be considered in clinical decision making for treatment of meniscal problems in dogs.

Comparison of contact mechanics of three meniscal repair techniques and partial meniscectomy in cadaveric dog stifles.

OBJECTIVE: To evaluate the biomechanical effect of horizontal, vertical, and cruciate suture repairs and partial meniscectomy on contact mechanics of dog stifles. STUDY DESIGN: Ex vivo experimental study. SAMPLE POPULATION: Cadaveric canine stifles (n=24). METHODS: Simulated bucket handle medial meniscal tears were created in cadaveric dog stifles. Tears were treated with 1 of 3 suture repair techniques or partial meniscectomy. Instantaneous contact area (CA), mean contact pressure (MCP), and peak contact pressure (PCP) measurements were recorded with a pressure sensing system. CA, MCP, and PCP for intact stifles (control), stifles with simulated tears, and stifles after treatment were recorded and compared using 1-way repeated measures ANOVA. RESULTS: Stifles with bucket handle tears had significantly decreased CA, increased MCP and increased PCP when compared with control. All meniscal repair techniques reestablished normal contact mechanics. When comparing meniscal repair and partial meniscectomy, stifles with partial meniscectomy had approximately 35% lower CA, 57% higher MCP, and 55% higher PCP than stifles undergoing repair. CONCLUSIONS: Contact mechanics obtained from each repair technique were mechanically superior to partial meniscectomy. Performing meniscal repair instead of partial meniscectomy in dogs with select meniscal tears may mitigate the development of degenerative joint disease. Criteria for selection of candidates for meniscal repair should be confirmed with future studies. CLINICAL RELEVANCE: Based on this ex-vivo model, meniscal repair will restore normal contact mechanics. Consideration should be given to meniscal repair as treatment for peripheral meniscal tears located in the vascular zone if the meniscal parenchyma is normal.

3D polarization-sensitive optical coherence tomography of canine meniscus based on a 2D high-fill-factor microelectromechanical Mirror.

A miniature optical imaging probe based on a high-fill-factor MEMS mirror has been developed for nondestructive diagnosis of articular joint diseases and injuries. The MEMS mirror scans +/-30 degrees at less than 6 V in both x- and y-axis. The outer diameter of the probe is 5.8 mm. Three-dimensional polarization-sensitive optical coherence tomography of canine meniscus has been successfully demonstrated.

Contact mechanics of simulated meniscal tears in cadaveric canine stifles.

OBJECTIVE: To evaluate the biomechanical effects of 5 types of meniscal lesions on contact mechanics in the canine stifle. STUDY DESIGN: Experimental study. ANIMALS: Cadaveric canine stifles (n=12 pair). METHODS: Medial meniscal lesions (radial, vertical longitudinal, nonreducible bucket handle, flap, and complex tears) were simulated in cadaveric stifles. A contact map was recorded from each tear type and contact area (CA) and peak contact pressure (PCP) from each tear type were compared. RESULTS: A significant difference in PCP was detected between control and nonreducible bucket handle, flap, and complex tears. PCP increased by >45% in nonreducible bucket handle, flap, and complex meniscal tears when compared with control. No significant difference was found in PCP between control and radial and vertical longitudinal tears. No significant difference was found in CA between any of the meniscal conditions. CONCLUSIONS: Nonreducible bucket handle, flap, and complex tears cause a significant increase in PCP. Radial and vertical longitudinal tears had a minimal impact on the contact pressures of the medial compartment of the stifle. CLINICAL RELEVANCE: Based on this ex vivo model, we support the clinical recommendation of debriding nonreducible bucket handle, flap, and complex tears because the injured portion of the meniscus no longer contributes significantly to the function of the meniscus. Radial and vertical longitudinal tears do not cause a change in contact mechanics allowing consideration of nonsurgical treatment and meniscal repair, respectively. Future experimental and clinical studies should aim to refine the treatment of specific meniscal injuries.

Extraction of mechanical properties of foot plantar tissues using ultrasound indentation associated with genetic algorithm.

This paper demonstrates the use of ultrasound indentation technique for estimating the mechanical properties of foot plantar tissues in virtue of the reconstruction of the force response using genetic algorithm (GA) from an indentation test based on a quasi-linear viscoelastic (QLV) model. The indentation test on the plantar tissues covering the right first metatarsal head of a normal subject was carried out to verify the feasibility of the GA for the extraction of the tissue properties. The QLV properties of the plantar tissues were determined by the GA with a fixed Poisson's ratio. Such results were then compared with those obtained using a classical optimization method. Moreover, the GA was further employed to simultaneously determine the QLV properties as well as the Poisson's ratio of the plantar tissues. The correlations between the QLV properties and the Poisson's ratio are discussed.