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.

Evaluation of closed reduction and screw fixation in lag fashion of sacroiliac fracture-luxations.

OBJECTIVE: To evaluate outcome by radiographic assessment after closed reduction and percutaneous screw fixation in lag fashion of sacroiliac fracture-luxations in dogs. STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n=24) with sacroiliac fracture-luxations. METHODS: Medical records (1999-2006) and radiographs of 24 dogs (29 fracture-luxations) that had stabilization of sacroiliac fracture-luxation by fluoroscopic-guided closed reduction and percutaneous screw fixation in lag fashion were reviewed. Signalment, body weight, number, and location of all concurrent injuries and implants used for repair were recorded. Radiographs were used to evaluate the accuracy of screw placement in the sacral body, screw depth/sacral width ratio, reduction of the sacroiliac joint, pelvic canal diameter, and hemipelvic canal width. Radiographic re-examination (range, 4 to >8 weeks postoperatively) was available for evaluation. RESULTS: Mean screw depth/sacral width ratio on immediate postoperative and re-examination radiographs was 64% and 61%, respectively. Mean percentage reduction of the sacroiliac joint on immediate postoperative and re-examination radiographs were 91% and 87%, respectively. Pelvic canal diameter ratio demonstrated successful restoration of the pelvic canal. Hemipelvic canal width ratio documented successful closed reduction repair independent of concurrent pelvic injuries. CONCLUSION: Successful repair of sacroiliac fracture-luxations, determined by radiographic assessment, can be achieved by fluoroscopic-guided closed reduction and percutaneous screw fixation in lag fashion. CLINICAL RELEVANCE: Fluoroscopic-guided closed reduction and percutaneous screw fixation in lag fashion of sacroiliac fracture-luxations is a minimally invasive technique that restores and maintains pelvic canal dimensions and should be considered as an alternative to open reduction or nonsurgical management of sacroiliac fracture-luxations.