Treatment
High-volume arthroscopic lavage and debridement of the affected LFTJs (including SERs) was performed. A cranial approach was taken and a synovial resector was introduced between the lateral patellar and lateral collateral ligaments to clear the visual field. Examination of the menisci revealed grade III tears in all cases (Figures 2 d & 3 f). In Foal 1, tearing of the cranial MTL was also apparent. In all cases, the meniscus appeared prolapsed and displaced craniolaterally (Figure 2 c; Figures 3 e & f). Fibrinous deposits were present adjacent to the tears, with purulent material apparent within the torn fibers (Figure 3 e). The unhealthy tissue and torn fibers were removed using a synovial resector. In all 3 Foals, the caudal aspect of the LFTJs were also arthroscopically examined, and in Foal 2, evidence of meniscal tearing could also be seen in the caudal horn. Where multiple joint involvement was present, other joints were treated similarly, with high volume arthroscopic lavage and debridement.
Postoperative treatment included a combination of broad-spectrum antimicrobials (parenteral and IA), based on culture and sensitivity results, where available; analgesia (NSAIDs and opioids, as indicated), and gastroprotectants. Hyperimmune plasma was administered to Foals 1 & 2. Response to treatment was monitored based on comfort levels, US findings, and synovial fluid analysis.
Foal 2 and 3 required a second arthroscopic lavage and debridement of the L LFTJ 14 days, and 3 days respectively, after the initial surgery to remove further fibrin accumulations around the LM. In both cases, progression of the tearing and meniscal protrusion/displacement could be seen.
In Foals 2 & 3, following resolution of the septic arthritis and recovery, US and radiographic-guided bone marrow aspirates were taken from the sternebrae under general anesthesia, for production of autologous bone marrow-derived mesenchymal stem cells (BMSCs) (Figure 5 a). Briefly, the sternum was aseptically prepared, and the intersternebral spaces identified using US. A stab incision with a No. 11 scalpel was performed through the skin and a Jamshidi biopsy needle (11 gauge, 10 cm) introduced into the sternebra, using digital x-ray to guide depth of needle introduction (Figure 5 a). A 60 ml syringe, preloaded with 1000 IU of heparin was used to aspirate the bone marrow. BMSCs were isolated aseptically and expanded in high glucose Dulbecco’s modified eagle’s medium (DMEM) supplemented with 10% v/v fetal bovine serum and 100 U/mL penicillin –100 mg/mL streptomycin (all Gibco, Biosciences, USA) at 20% pO2(Smith et al. , 2013). Following colony formation, BMSCs were obtained with accutase (Gibco, Biosciences, USA), counted (Countess™ II FL Automated Cell Counter, Thermo Fisher, USA), seeded at density of 5000 cells/cm2 and expanded until Passage 3. A final cell suspension of 2-4 million cells per ml was obtained and suspended in saline for final injection in the patient.
Foal 2 received 3 US-guided IA injections of 10 million autologous BMSCs, in the L LFTJ, at 44 d, 65 d, and 97 d post-operatively (Figure 5 b). Foal 3 received 3 US-guided IA injections of autologous BMSCs, in the R LFTJ, at 19 d, 51 d and 86 d post-operatively.