The first article in this miniseries reviewed the various treatment options for dogs with hip dysplasia and the typical cases of surgical total hip replacement (THR). The second part of this miniseries reviews the surgical procedure and post-operative care.
General anaesthesia and analgesia
A premedication of methadone (0.2mg/kg) and medetomidine (0.005mg/kg) was administered intravenously with good effect. Anaesthesia was then induced intravenously with propofol, 200mg total to effect. A size 12mm endotracheal tube was placed and attached to a circle breathing circuit to supply oxygen and inhalation agents. Anaesthesia was maintained on isoflurane.
The patient received a spinal epidural with bupivacaine (1mg/kg) and preservative-free morphine (0.1mg/kg). This allowed a lower percentage of inhalational agent to be used, thus reducing any cardiorespiratory depressive effects (Duke-Novakovski, 2016). An epidural also provides post-operative analgesia (Pettitt, 2018).
Surgical preparation of the patient
A purse-string suture was placed in the patient’s rectum by the theatre nurse under Schedule 3 of the Veterinary Surgeon’s Act 1966. This prevents faecal matter from contaminating the surgical field (Scott and Hotston Moore, 2007). A sign was placed on the patient’s head as a visual reminder together with a tick box on the paperwork to ensure removal before recovery from anaesthesia.
The right hindlimb was prepared by clipping fur from the entire leg to include a quadrant draping field over the pelvis. The skin was vacuumed to remove loose fur and then scrubbed with chlorhexidine gluconate (4 percent) at a 50:50 dilution rate with lint-free swabs (Pettitt, 2018). A bandage was applied to the foot to aid a hanging leg final preparation in theatre (Bexfield and Lee, 2014).
The patient was placed in left lateral recumbency with the pelvis carefully aligned to be perpendicular to the table. This was achieved by palpating the ischial tuberosities and using a vacuum-aided bean bag to steady the patient. A final aseptic surgical site preparation was carried out by the circulating theatre nurse who wore surgical gloves and used a disposable sponge with 2 percent chlorhexidine gluconate/70 percent isopropyl alcohol.
There is a significant amount of equipment required for a total hip replacement, including Biomedtrix Universal Total Hip Replacement System, Collibri II battery powered tool, standard orthopaedic surgical kit and ancillary equipment (Figure 1).
A modified craniolateral approach to the hip joint (Johnson and Piermattei, 2014) was made, and femoral head and neck excision was performed with a cutting guide. The femoral canal was opened through the trochanteric fossa with an intramedullary pin. Then a 5mm drill bit followed by increasing sizes of tapered reamers were used to widen this opening, all the while using guides to give correct orientation. Femoral broaches were then used to create the correct shape for the implant. Femoral stem trials were used to ensure the implant was correctly angled and had adequate space for a cement mantle.
Next the acetabulum was prepared to receive an implant. The powered rounded cutting reamer removes cartilage and bone to provide the correct space for the acetabular implant. This is used with a guide for correct orientation until cancellous bone is seen. Once a suitable depth was achieved, the finishing reamer was used to smooth the bone. A trial acetabulum cup (the same size as the final implant) was placed to ensure a good fit. The final acetabular implant was inserted using an impactor and mallet.
Cementing the femoral implant takes care and precision when using any technique; in this case, a second-generation procedure was followed (Gemmill et al., 2011), which includes injecting the cement (polymethyl methacrylate) in its liquid form under pressure to improve the fill. The acetabular cup is protected at this stage by packing with swabs.
Cementing the femoral implant takes care and precision when using any technique; in this case, a second-generation procedure was followed
It is important for the cement to tightly interface with the inside of the bone. The femur was prepared by pulsatile flushing of cold saline and suctioning of any debris. A cement restrictor was placed in the distal medullary cavity to stop the cement escaping beyond the location of the implant and to create a smaller more pressurised space for the cement to set. The cement was carefully mixed and syringed into the medullary canal, smoothly to prevent air bubbles. A stem centraliser was attached to the bottom of the implant to prevent metal implant from directly touching bone and then inserted and allowed to set in the cement for approximately 12 minutes.
Once the cement was set, a trial reduction of the new hip joint with a trial plastic femoral head on the cemented stem was carried out. The length of neck was decided based on the subsequent range of motion of the joint; if it were loose, then a longer neck could be achieved by using a different head.
The final metal femoral head was placed and hip reduction was achieved with a good range of motion and stability. Standard layered soft tissue closure was performed after generous saline lavage of the surgical site. Radiographs were then taken post-operatively to assess the implant placement, which was correct, and a good cement mantle could also be seen (Figure 2A and 2B).
Recovery and rehabilitation
The patient recovered from general anaesthesia in the recovery suite and later returned to the orthopaedic ward for the remainder of her stay. She spent a total of five days in hospital. Using the short form Glasgow composite pain scale for dogs, a score was recorded every four hours and methadone was prescribed for analgesia in a range of 0.1 to 0.2mg/kg (Self, 2019). The patient was weaned onto buprenorphine on day four when the pain score was less than four.
Cold packing of the surgical site three times a day was carried out by surgical ward nurses who also facilitated walk outs with slings and supports (Marcellin-Little et al., 2005). Bladder checks and expression were completed in the 12-hour post-operative phase when the epidural was still effective. Cefalexin at 20mg/kg was continued per os for seven days and the non-steroidal anti-inflammatory drug (NSAID) robenacoxib at 600mg once daily for a further 14 days.
A careful balance between patient stress and post-operative management was needed as a distressed patient can lead to a delay in wound healing. The owner did not visit the patient in hospital so as not to over-excite the patient. The patient was encouraged with positive interactions, such as grooming and physical affection, by the nursing staff (Andrade, 2021).
A careful balance between patient stress and post-operative management was needed as a distressed patient can lead to a delay in wound healing
Trazadone 100mg once daily for 14 days was prescribed to aid smooth recovery. Gabapentin 300mg three times daily was prescribed and advised would likely be needed for long-term management of the contralateral hip. The owner was given a post-operative care report (Table 1).
|Crate rest||Recommended while the patient isn’t supervised. Otherwise, the patient can sit calmly with owner under strict supervision. No running, jumping or vigorous play|
|Sling when walking for the first two weeks||Sling under abdomen to aid sit-to-stand and while on short walk outs. Risk of luxation is high in the post-operative period. Important to stress sling use regardless of patient’s ambulatory function|
|Lead-only walks on strict schedule||Lead-only to control walking speed.|
For one to two weeks post-operatively, 5 to 10 minutes two to three times daily. Increase by five minutes every two weeks until at eight weeks and complete post-operative recheck
|Monitor wound||Monitor for any signs of infection (redness, heat, swelling, exudate, pain) or patient interference. The patient should be wearing a preventative collar. Re-exam at local vets in 10 to 14 days|
|Monitor swelling and use||Important to assess the surgical site for any acute swelling, indicating infection, seromas, wound breakdown or even luxation. The patient should be using the leg the same if not slightly better each day and any acute change should be reported to the veterinary surgeon as soon as possible|
|Reduce food by 20 percent||The patient will be on strict rest for around eight weeks and weight gain is strongly contraindicated|
|Hydrotherapy/physiotherapy||Hydrotherapy on an underwater treadmill is preferred as is a more controlled movement.|
Physiotherapy, such as passive range of motion, is described and demonstrated to the owner on discharge and encouraged to continue. Veterinary physios are recommended
At eight weeks post-operatively the patient was sedated to allow radiographs to be taken. The patient was gaining muscle mass in her leg and was comfortable on hip extension and flexion and had discontinued NSAIDs. No complications were reported and the client was pleased with the outcome.
Luxation or failure of implants
Aseptic loosening of implants
A THR is considered a salvage operation and is not without surgical risk as numerous studies have demonstrated (Box 1) (Gemmill et al., 2011; Vezzoni et al., 2015).
Surgical learning curves are described with cementless procedures and we know that surgeon experience and technique are important for overall outcome (Hayes et al., 2010). The hybrid system allows both the cementless and cemented systems to work together to better meet the needs of each individual patient (Schiller, 2017) and allow the surgeon to use their preferred method.
In a study by Forster et al. (2012), data was collected from multiple sources across the UK and reported a 20 percent complication rate with owners having described a “very good” satisfaction level with successful outcomes, which was a significant improvement compared to preoperative results.
Surgical learning curves are described with cementless procedures and we know that surgeon experience and technique are important for overall outcome
In 2011, Gemmill et al. reviewed 78 THRs, of which only nine dogs had minor intraoperative complications. An owner questionnaire was carried out to assess their perception of success, asking them to grade their dog’s level of disability. Out of 71 owners, 57 classed their dogs as having “no disability” and 14 rated as their dogs as having only a “mild disability” with a “good” quality of life for 67/71 dogs.
In a study by Vezzoni et al. (2015) of 439 THRs, body condition score (BCS) increase was shown to be a common factor for post-operative complications, but still had a good complication rate of less than 20 percent. The author advises to reduce diet by 20 percent and to monitor BCS and weight gain. At the patient’s eight-week check there was some success with weight loss, thanks to the cooperation of the owner.
In 2010, Liverpool University with the British Veterinary Orthopaedic Association developed a system to record and collate surgical data (Forster et al., 2012). The data is anonymised and focuses on research into surgical complications and success rate and recognising variables (BVOA-CHR). Future developments of such complex techniques, such as arthroplasties, rely on the veterinary field recording and collating data (Schiller, 2017) and therefore could benefit from the resource. The profession must demand unbiased prospective research reporting patient outcomes and implant survivorship as the primary agent of change in arthroplasty (Peck et al., 2013).
Hip dysplasia is a common disease, and with the right candidate and clinical support, surgical intervention can restore function and relieve long-term pain. The specialised team worked well to coordinate a high standard of care for the patient. The patient had an uncomplicated surgical procedure and successful rehabilitation to restore normal activities, resulting in an improved quality of life with dedicated and compliant owners.
|The author wishes to thank the Royal Veterinary College and Biomedtrix for kind permission for use of material|