Write up by Laura Acevedo, DVM, WEMT-B December 17, 2023
An adult, male porcupine entered Think Wild Wildlife Hospital on August 25, 2023 as a transfer from the Sunriver Nature Center after bystanders noted that he was limping on his right pelvic limb. This was the second instance in which the public had noted an abnormality with this individual. This porcupine had been seen in the area prior and was noted to have a gait abnormality, at which point the nature center had attached an Apple Airtag onto this animal to monitor movements prior to it falling off. At that time, a collective decision was made not to bring the animal into captive care after it was noted to be climbing well and moving adequately. Prior to transfer to Think Wild, the porcupine was in the care of Sunriver Nature Center for holding purposes only and it was noted that there was a draining abscess on the R pelvic limb.
At time of intake, the porcupine was bright, alert, and responsive in his kennel and aggressively whipping/thumping his tail with human interaction. While ambulating, this porcupine had no obvious gait abnormalities but had a marked amount of purulent debris pouring from a puncture wound on the cranial aspect of the right femur. A decision was made to sedate this porcupine for further investigation of the wound, radiographs, and to determine prognosis.
The porcupine was sedated with a combination of ketamine, midazolam, and dexmedetomidine and after 10 minutes, was sedate enough for wound care. He was maintained on oxygen via face mask at 2L/min and was monitored with a pulse oximeter and with manual monitoring of ventilation. A physical examination found abnormalities of muscle atrophy of the quadriceps muscles bilaterally but with otherwise good body condition. Two, ~1cm diameter punctures approximately ~8cm apart were noted over the right femur with a marked amount of purulent debris, fibrin tissue, and missing quills. An additional ~1.5cm diameter puncture wound was identified over the L femur with minimal purulent debris. Otherwise, the physical examination had no other glaring abnormalities.
Both wounds on the near the right femur were flushed copiously with sterile saline until the material ran clear and no further discharge was appreciated. A cold sterile Carmalt was used to burrow through subcutaneous tissue to connect the two puncture wounds, and rolled brown gauze was threaded through the tunnel and tied onto itself loosely to create a drain. The site on the left side was also flushed out well and due to minimal debris noted, no drain was placed. The porcupine received analgesic injections of meloxicam and Simbadol (buprenorphine, 24 hour acting). Two view radiographs of the pelvic limbs and hips showed a concern for a very faint (radiolucent), but well defined opacity of the right femoral head. The porcupine was reversed with atipamezole and recovery was uneventful. The porcupine was prescribed trimethoprim sulfamethoxazole (TMS) and meloxicam PO with a plan to keep the drain in for seven days and monitor ambulation for 1 week with a game camera. A discussion was made with an emphasis on euthanasia if concerns were noted about the ability for this individual to survive post-release. A concern was noted about a disease process named avascular necrosis of the femoral head (AVN), well documented in cats, dogs, and rats but with no documentation in porcupines that the author is aware of.
Over the next few days, medicating this individual was met with great difficulty - a concern regarding twice daily catch-up to medicate orally was expressed and it was not guaranteed that this porcupine was consuming medication left on food items in his enclosure. Due to this, the decision was made to discontinue the TMS and instead begin once daily intramuscular injections of enrofloxacin on August 30, 2023. Veterinary consultation to notable rehabilitation facilities was sought.
On September 7, 2023, this porcupine was once again sedated with a combination of ketamine, midazolam, and dexmedetomidine to remove the drain and re-evaluate the wounds. He was monitored and maintained on the same protocol as previous. At this point, the porcupine had lost 0.65kg. The drain over the R femur was removed with minimal debris and adequate healing, though during the course of the week, the wound over the left femur had worsened, resulting in significant purulent debris. The area was flushed copiously with sterile saline and scrubbed in a surgical fashion with chlorhexidine scrub and solution, alternating. An indwelling infusion port using a 7Fr red rubber catheter with fenestrations was placed into the wound and tacked with two sutures onto the skin to allow for flushing of the wound without physical capture of the porcupine. Despite adequate climbing noted on the game camera, repeat radiographs indicated new concerns for a R femoral head fracture. The porcupine was reversed with atipamezole and it was decided to continue treatment until a response was heard back from other, large wildlife rehabilitation centers that were contacted previously since adequate climbing was seen on game camera. The porcupine was prescribed an additional week of meloxicam and enrofloxacin.
On September 15, 2023, this porcupine was sedated for a final time with the protocol used previously, despite not hearing back from local facilities. At this time, the indwelling infusion port was removed and a marked amount of purulent discharge was still noted in the left wounds with recrudescence in the previously healed right wounds. Updated radiographs confirmed a complete right femoral head fracture, now with lysis, and involvement of the pelvis. Perimortem sampling of blood was performed via the tail vein and culture swabs were obtained of the wounds. Pentobarbital sodium was administered IV via the tail vein and death was confirmed with auscultation.
A necropsy was performed immediately post-mortem and the entirety of the right coxofemoral joint, including the femur and the pelvis, was removed and placed in formalin. On necropsy, the medullary cavity of the entirety of the right side of the pelvis was soft and spongy, with purulent debris easily expressed when compressing. A fracture of the right femoral head was confirmed and the right femoral head was necrotic. Samples were submitted to OSU VDL, confirming a severe, necrotizing and suppurative osteomyelitis, likely from a penetrating wound. Comment is still being awaited by the OSU pathologist regarding AVN. Bloodwork found a significantly elevated creatinine kinase (an enzyme that indicates muscle damage) and a leukocytosis (elevated WBC count).
Avascular necrosis of the femoral head is a condition where the blood supply to a bone is disrupted, leading to the death of bone tissue (the femoral head). This condition occurs both in human and veterinary medicine and can be caused by a multitude of factors. In companion veterinary species, if the condition is severe enough, it can warrant a femoral head osteotomy (FHO) that largely cures the animal of future affliction but has been reported in cats to affect their climbing abilities. Unfortunately for our porcupine patient, that was not a viable option for release.
The patient was minimally compensating before it arrived at our facility and from the history, had been affected for some time. Infections of the joint are notoriously difficult to treat with systemic antibiotics alone and usually a joint flush and gavage, a procedure that has to be done under anesthesia with adequate analgesia.
In wildlife rehabilitation, it is rare to see pathological fractures - a fracture that occurs when the bone is weakened by some other abnormality rather than direct trauma (hit by car, window strike, etc). While suspicions were present at the time of the intake examination, we could not have predicted a joint infection so severe to develop with the imaging that we obtained. Similar to fractures near a joint, joint infections are likely a grave prognosis with medical management alone - the rehabilitation facility needs to weigh the benefits of continued treatment, surgery, or euthanasia for cases that present this way.