Physiologic effects of long-term immobilization of the equine distal limb.

OBJECTIVE: To describe the effects of distal limb immobilization and remobilization in the equine metacarpophalangeal joint. STUDY DESIGN: Randomized, prospective experimental study. ANIMALS: Eight healthy, skeletally mature horses. METHODS: One forelimb of each horse was immobilized in a fiberglass cast for 8 weeks; this was followed by 12 weeks of a treadmill-based training program after the cast had been removed. Clinical examinations, radiography, computed tomography (CT), nuclear scintigraphy, MRI, and histomorphometry were used to examine the third metacarpal (MC3), proximal phalanx, proximal sesamoid bones, and associated soft tissues in each horse. Serum and synovial fluid were collected for biomarker analyses. RESULTS: Distal limb immobilization resulted in persistent lameness (P < .001), effusion (P = .002), and a decreased range of motion (P = .012) as well as radiographically visible fragments (P = .036) in the cast forelimb. Bone density was decreased (P < .001) in MC3 according to CT, and trabecular bone fluid was increased (P < .001) according to MRI in the cast forelimb. The cast forelimbs had a change (P = .009) in the appearance of the deep digital flexor tendon according to MRI immediately after removal of the cast. Numerous clinical, radiographic, CT, and MR abnormalities were visible at the end of the study period. CONCLUSION: Eights weeks of cast immobilization induced changes in bone, cartilage, and periarticular soft tissues that were not reversed after 12 weeks of remobilization. CLINICAL SIGNIFICANCE: Cast application should be used judiciously in horses with musculoskeletal injuries, balancing appropriate stabilization with potential morbidity secondary to cast placement.

COMPARISON BETWEEN COMPUTED TOMOGRAPHIC ARTHROGRAPHY, RADIOGRAPHY, ULTRASONOGRAPHY, AND ARTHROSCOPY FOR THE DIAGNOSIS OF FEMOROTIBIAL JOINT DISEASE IN WESTERN PERFORMANCE HORSES.

The femorotibial joints are a common source of lameness in Western performance horses. The objective of this prospective study was to compare the radiography, ultrasonography, computed tomographic arthrography (CTA), and arthroscopy findings in horses with lameness localized to the femorotibial joints. Twenty-five stifles in 24 horses were included and were evaluated with all four of these diagnostic methods. Defects detected in femorotibial joint structures were compared between diagnostic methods using a McNemar's test to evaluate for disagreement. Cranial medial meniscotibial desmopathy was most detected on arthroscopy (in 14/25 cases) and was only detected on ultrasonography in three out of 11 (27.3%) arthroscopically observed cases, but was detected on CTA in nine out of 12 (75%) arthroscopically observed cases. Medial meniscal injury located on the craniolateral border was most detected on arthroscopy (n = 9) and was detected on CTA in five cases, but on ultrasonography in 0 cases. Detection of articular cartilage defects on the medial femoral condyle was most detected with arthroscopy (24/25, 96% cases) and was also detected on CTA in 12/20 (60%) cases with a significant disagreement identified between modalities (P = 0.02). Cranial and caudal cruciate ligament defects were detected on CTA in 6/22 (27.3%) and 7/19 (36.8%) cases, respectively, and with arthroscopy in 3/25 (12%) and 2/25 (8%) cases, respectively. The use of CTA detected more defects in the cruciate ligaments, proximal tibia, and ligament entheses than the other diagnostic methods, but was not reliable for detection of articular cartilage damage on the medial femoral condyle.

Addition of Mesenchymal Stem Cells to Autologous Platelet-Enhanced Fibrin Scaffolds in Chondral Defects: Does It Enhance Repair?

BACKGROUND: The chondrogenic potential of culture-expanded bone-marrow-derived mesenchymal stem cells (BMDMSCs) is well described. Numerous studies have also shown enhanced repair when BMDMSCs, scaffolds, and growth factors are placed into chondral defects. Platelets provide a rich milieu of growth factors and, along with fibrin, are readily available for clinical use. The objective of this study was to determine if the addition of BMDMSCs to an autologous platelet-enriched fibrin (APEF) scaffold enhances chondral repair compared with APEF alone. METHODS: A 15-mm-diameter full-thickness chondral defect was created on the lateral trochlear ridge of both stifle joints of twelve adult horses. In each animal, one defect was randomly assigned to receive APEF+BMDMSCs and the contralateral defect received APEF alone. Repair tissues were evaluated one year later with arthroscopy, histological examination, magnetic resonance imaging (MRI), micro-computed tomography (micro-CT), and biomechanical testing. RESULTS: The arthroscopic findings, MRI T2 map, histological scores, structural stiffness, and material stiffness were similar (p > 0.05) between the APEF and APEF+BMDMSC-treated repairs at one year. Ectopic bone was observed within the repair tissue in four of twelve APEF+BMDMSC-treated defects. Defects repaired with APEF alone had less trabecular bone edema (as seen on MRI) compared with defects repaired with APEF+BMDMSCs. Micro-CT analysis showed thinner repair tissue in defects repaired with APEF+BMDMSCs than in those treated with APEF alone (p < 0.05). CONCLUSIONS: APEF alone resulted in thicker repair tissue than was seen with APEF+BMDMSCs. The addition of BMDMSCs to APEF did not enhance cartilage repair and stimulated bone formation in some cartilage defects. CLINICAL RELEVANCE: APEF supported repair of critical-size full-thickness chondral defects in horses, which was not improved by the addition of BMDMSCs. This work supports further investigation to determine whether APEF enhances cartilage repair in humans.

Effects of the combination of microfracture and self-assembling Peptide filling on the repair of a clinically relevant trochlear defect in an equine model.

BACKGROUND: The goal of this study was to test the ability of an injectable self-assembling peptide (KLD) hydrogel, with or without microfracture, to augment articular cartilage defect repair in an equine cartilage defect model involving strenuous exercise. METHODS: Defects 15 mm in diameter were created on the medial trochlear ridge and debrided down to the subchondral bone. Four treatment groups (n = 8 each) were tested: no treatment (empty defect), only defect filling with KLD, only microfracture, and microfracture followed by filling with KLD. Horses were given strenuous exercise throughout the one-year study. Evaluations included lameness, arthroscopy, radiography, and gross, histologic, immunohistochemical, biochemical, and biomechanical analyses. RESULTS: Overall, KLD-only treatment of defects provided improvement in clinical symptoms and improved filling compared with no treatment, and KLD-only treatment protected against radiographic changes compared with microfracture treatment. Defect treatment with only microfracture also resulted in improved clinical symptoms compared with no treatment, and microfracture treatment resulted in repair tissue containing greater amounts of aggrecan and type-II collagen compared with KLD-only treatment. Microfracture treatment also protected against synovial fibrosis compared with no treatment and KLD-only treatment. Treatment with the self-assembling KLD peptide in combination with microfracture resulted in no additional improvements over microfracture-only treatment. In general, the nature of the predominant tissue in the defects was a mix of noncartilaginous and fibrocartilage tissue, with no significant differences among the treatments. CONCLUSIONS: Treatment of defects with only KLD or with only microfracture resulted in an improvement in clinical symptoms compared with no treatment; the improvement likely resulted from different causes depending on the treatment. Whereas microfracture improved the quality of repair tissue, KLD improved the amount of filling and protected against radiographic changes. CLINICAL RELEVANCE: Treatment of defects with only microfracture and with KLD only resulted in clinical improvements compared with untreated defects, despite differing with respect to the structural improvements that they induced.

A descriptive study of the equine proximal interphalangeal joint using magnetic resonance imaging, contrast arthrography, and arthroscopy.

OBJECTIVE: To describe regions of the thoracic and pelvic limb proximal interphalangeal (PIP) joints that are arthroscopically accessible and identify soft tissue structures that should be avoided during arthroscope and instrument placement. STUDY DESIGN: Experimental ex vivo descriptive study. ANIMALS: Horses (n = 15). METHODS: Cadaver limbs (n = 36) were used for anatomic modeling, magnetic resonance imaging (MRI) with MRI-compatible needles, computed tomography with contrast arthrography, and arthroscopy of the PIP joint. Two arthroscopic approaches to the dorsal joint pouch were compared. RESULTS: With arthroscopy, 62.4% of the joint perimeter could be observed from the dorsal and palmar/plantar joint pouches with no significant difference in the amount of joint observed when using the more proximal or distal approach to the dorsal joint pouch (P =.59). CONCLUSION: The dorsal and palmar/plantar joint pouches provide adequate arthroscopic visibility for the axial portions of the articular surface of the proximal and middle phalanx. The abaxial portions of the articular surface were difficult to view because of narrowing of the joint pouches abaxially. When comparing the proximal and distal approach to the dorsal joint pouch, arthroscope insertion 1.5 cm proximal to the joint allowed the easiest manipulation of the arthroscope. Palmar/plantar portals were placed dorsal to the neurovascular bundle, proximal to the epicondyle of the middle phalanx to prevent tendon and ligament injury.

Evaluation of intra-articular mesenchymal stem cells to augment healing of microfractured chondral defects.

PURPOSE: This study evaluated intra-articular injection of bone marrow-derived mesenchymal stem cells (BMSCs) to augment healing with microfracture compared with microfracture alone. METHODS: Ten horses (aged 2.5 to 5 years) had 1-cm2 defects arthroscopically created on both medial femoral condyles of the stifle joint (analogous to the human knee). Defects were debrided to subchondral bone followed by microfracture. One month later, 1 randomly selected medial femorotibial joint in each horse received an intra-articular injection of either 20 × 10(6) BMSCs with 22 mg of hyaluronan or 22 mg of hyaluronan alone. Horses were confined for 4 months, with hand walking commencing at 2 weeks and then increasing in duration and intensity. At 4 months, horses were subjected to strenuous treadmill exercise simulating race training until completion of the study at 12 months. Horses underwent musculoskeletal and radiographic examinations bimonthly and second-look arthroscopy at 6 months. Horses were euthanized 12 months after the defects were made, and the affected joints underwent magnetic resonance imaging and gross, histologic, histomorphometric, immunohistochemical, and biochemical examinations. RESULTS: Although there was no evidence of any clinically significant improvement in the joints injected with BMSCs, arthroscopic and gross evaluation confirmed a significant increase in repair tissue firmness and a trend for better overall repair tissue quality (cumulative score of all arthroscopic and gross grading criteria) in BMSC-treated joints. Immunohistochemical analysis showed significantly greater levels of aggrecan in repair tissue treated with BMSC injection. There were no other significant treatment effects. CONCLUSIONS: Although there was no significant difference clinically or histologically in the 2 groups, this study confirms that intra-articular BMSCs enhance cartilage repair quality with increased aggrecan content and tissue firmness. CLINICAL RELEVANCE: Clinical use of BMSCs in conjunction with microfracture of cartilage defects may be potentially beneficial.

Evaluation of adipose-derived stromal vascular fraction or bone marrow-derived mesenchymal stem cells for treatment of osteoarthritis.

The purpose of this study was the assessment of clinical, biochemical, and histologic effects of intraarticular administered adipose-derived stromal vascular fraction or bone marrow-derived mesenchymal stem cells for treatment of osteoarthritis. Osteoarthritis was induced arthroscopically in the middle carpal joint of all horses, the contralateral joint being sham-operated. All horses received treatment on Day 14. Eight horses received placebo treatment and eight horses received adipose-derived stromal vascular fraction in their osteoarthritis-affected joint. The final eight horses were treated the in osteoarthritis-affected joint with bone marrow-derived mesenchymal stem cells. Evaluations included clinical, radiographic, synovial fluid analysis, gross, histologic, histochemical, and biochemical evaluations. No adverse treatment-related events were observed. The model induced a significant change in all but two parameters, no significant treatment effects were demonstrated, with the exception of improvement in synovial fluid effusion PGE2 levels with bone marrow-derived mesenchymal stem cells when compared to placebo. A greater improvement was seen with bone marrow-derived mesenchymal stem cells when compared to adipose-derived stromal vascular fraction and placebo treatment. Overall, the findings of this study were not significant enough to recommend the use of stem cells for the treatment of osteoarthritis represented in this model.

Clinical, biochemical, and histologic effects of intra-articular administration of autologous conditioned serum in horses with experimentally induced osteoarthritis.

OBJECTIVE: To assess the clinical, biochemical, and histologic effects of intra-articular administration of autologous conditioned serum (ACS) in the treatment of experimentally induced osteoarthritis in horses. ANIMALS: 16 horses. PROCEDURES: Osteoarthritis was induced arthroscopically in 1 middle carpal joint of all horses. In 8 placebo- and 8 ACS-treated horses, 6 mL of PBS solution or 6 mL of ACS was injected into the osteoarthritis-affected joint on days 14, 21, 28, and 35, respectively; PBS solution was administered in the other sham-operated joints. Evaluations included clinical assessment of lameness and synovial fluid analysis (performed biweekly); gross pathologic and histologic examinations of cartilage and synovial membrane samples were performed at necropsy. RESULTS: No adverse treatment-related events were detected. Horses that were treated with ACS had significant clinical improvement in lameness, unlike the placebo-treated horses. Among the osteoarthritis-affected joints, ACS treatment significantly decreased synovial membrane hyperplasia, compared with placebo-treated joints; although not significant, the ACS-treated joints also appeared to have less gross cartilage fibrillation and synovial membrane hemorrhage. The synovial fluid concentration of interleukin-1 receptor antagonist (assessed by use of mouse anti-interleukin-1 receptor antagonist antibody) was increased following treatment with ACS. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this controlled study indicated that there was significant clinical and histologic improvement in osteoarthritis-affected joints of horses following treatment with ACS, compared with placebo treatment. On the basis of these findings, further controlled clinical trials to assess this treatment are warranted, and investigation of the mechanisms of action of ACS should be pursued concurrently.