The effect of lysophosphatidic acid using a hydrogel or collagen sponge carrier on bone healing in dogs.

OBJECTIVES: The purposes of this study were to determine: 1) the efficacy of polycaprolactone-g-polyethylene glycol (PCL-g-PEG) and polylactic-co-glycolic acid (PLGA-g-PEG) hydrogels and an absorbable collagen sponge (ACS) as carriers for lysophosphatidic acid (LPA), 2) the effect of LPA on bone healing in dogs, and 3) the ideal dose of LPA to maximally stimulate bone healing. METHODS: Bilateral ulnar ostectomies were performed on purpose bred dogs. Control defects were filled with a PCL-g-PEG or PLGA-g-PEG hydrogel, or a saline soaked ACS. Contralateral defects were filled with a PCL-g-PEG or PLGA-g-PEG hydrogel, or an ACS with each carrying differing concentrations of an LPA solution. Dual-energy X-ray absorptiometry (DXA) was performed. Total bone area (TBA), mineral density (BMD), and mineral content (BMC) were determined at each time point. Relationships between the effect of treatment over time on TBA, BMC and BMD were determined. RESULTS: Phase 1 - There was no significant difference in DXA-based TBA (p = 0.09), BMC (p = 0.33), or BMD (p = 0.74) over time between LPA treatments, or between the LPA treated and control groups TBA (p = 0.95), BMC (p = 0.99), or BMD (p = 0.46). Phase 2 - There was no significant difference over time between LPA treatments in DXA-based TBA (p = 0.33), BMC (p = 0.45), or BMD (p = 0.43), or between the LPA treated and control groups TBA (p = 0.94), BMC (p = 0.38), or BMD (p = 0.17). Phase 3 - There was no significant difference over time between LPA treatments in DXA-based TBA (p = 0.78), BMC (p = 0.88), or BMD (p = 0.35), or between the LPA treated and control groups TBA (p = 0.07), BMC (p = 0.85), or BMD (p = 0.06). There was a significant increase in TBA (p <0.0001) and BMC (p = 0.0014), but a significant decrease in BMD (p <0.0001) was noted over time when all groups were combined. CLINICAL SIGNIFICANCE: Although LPA has shown promise as an osteoinductive agent in research, its performance as a bone graft substitute, as utilized in this study, is unsupported. Further studies are necessary to determine the incorporation and elution kinetics of LPA from the PLGA-g-PEG hydrogel and from an ACS. Hydrogels may have clinical applications for delaying or preventing bone formation.

Evaluation of the drawer test and the tibial compression test for differentiating between cranial and caudal stifle subluxation associated with cruciate ligament instability.

OBJECTIVE: To determine the sensitivity and specificity of the drawer test (DT) alone and in combination with the tibial compression test (TCT) to detect stifle subluxation after transection of the cranial cruciate (CrCL), caudal cruciate (CdCL) or both cruciate ligaments (total cruciate ligament or TCL). STUDY DESIGN: Experimental study. SAMPLE POPULATION: Cadaveric, skeletally mature canine pelvic limb pairs (n = 8). METHODS: Pelvic limbs disarticulated at the coxofemoral joint were randomly assigned to the following 1 of 4 groups: (1) limbs had complete transection of the CrCL; (2) limbs had complete transection of the CdCL; (3) limbs had complete transection of both ligaments; and (4) both ligaments were left intact. Participants performed the DT and the TCT and a diagnosis was given based on the DT and on the combination of these tests. RESULTS: DT had a poor sensitivity for correctly identifying CrCL (69%), CdCL (45%), and TCL (26%) rupture, but had a high sensitivity when identifying intact limbs (97%). Specificity for DT was greatest when identifying limbs with CdCL (97%) and TCL (92%) rupture, and the lowest when palpating limbs with CrCL rupture (75%). Combining DT and TCT did not increase sensitivity or specificity values, nor did an increased level of evaluator training. CONCLUSIONS: Independent of evaluator training, the DT alone or combined with the TCT poorly differentiates the cause of stifle instability associated with CrCL, CdCL, and TCL rupture.

In vitro comparison of proximal ulnar osteotomy and distal ulnar osteotomy with release of the interosseous ligament in a canine model.

OBJECTIVE: To determine the effect of proximal ulnar osteotomy (PUO), distal ulnar osteotomy (DUO), and DUO with release of the interosseous ligament (DOLR) on displacement of the proximal ulna at the radioulnar joint. STUDY DESIGN: Experimental mechanical study. SAMPLE POPULATION: Cadaveric, skeletally mature canine thoracic limb pairs (n=11). METHODS: Thoracic limbs disarticulated at the elbow were randomly assigned to 1 of 2 groups: (A) limbs were tested with no treatment (NOTX), then with PUO; (B) limbs were tested with DUO followed by DOLR. A distraction force was applied to the proximal ulna with the distal limb secured in a frame, and displacement of the proximal ulnar segment at the radioulnar joint was recorded. RESULTS: Mean displacement was 0.36 mm (95% confidence interval [CI]: 0-1.12 mm) in the NOTX group, 4.68 mm (95% CI: 3.82-5.55 mm) for PUO limbs, 0.95 mm (95% CI: 0.52-1.39 mm) for the DUO group, and 4.36 mm (95% CI: 3.71-5.02 mm) for the DOLR group. Mean ulnar displacement of the DOLR group was significantly different compared with the DUO group, but there was no significant difference between the PUO and DOLR groups. CONCLUSIONS: No significant difference was observed in displacement of the proximal ulnar segment after DOLR compared with PUO.