Clinical perioperative outcomes in 39 cats after single session bilateral femoral head and neck excision

Abstract

Objectives

The aim of the study was to evaluate the perioperative outcomes and complications of single session bilateral femoral head and neck excision (FHNE) in cats for treatment of bilateral coxofemoral joint disease.

Methods

The medical records of cats undergoing a single session bilateral FHNE were identified and the history, signalment, diagnosis, surgery reports, anesthetic records, postoperative radiographs, postoperative examinations, complications and outcomes were recorded.

Results

A total of 39 cats undergoing a single session bilateral FHNE were included. Bilateral slipped capital femoral epiphysis was the most commonly diagnosed etiology. All cats were discharged within 48 h of the procedure. One major complication and five minor complications were reported. All but one cat returned to normal activity and no owners reported concerns after the 2-week postoperative recheck.

Conclusions and relevance

Single session bilateral FHNE is a viable surgical option for the treatment of bilateral coxofemoral disease in cats that results in a quick return to function, especially when other options are not indicated, available or affordable.

Introduction

Femoral head and neck excision (FHNE), also referred to as femoral head and neck ostectomy, is a surgical option for cats with diseased or injured coxofemoral joints. Historically, FHNE has been used in dogs to alleviate pain associated with bony contact between the femur and acetabulum that may be associated with degenerative joint disease or trauma. ¹ In cats, FHNE has been utilized as a surgical option in cases of a slipped capital femoral epiphysis (SCFE) secondary to physeal dysplasia, femoral neck fracture, acetabular fracture, coxofemoral luxation and degenerative joint disease.^2,3 FHNE is a salvage procedure, with the goal of improving quality of life by allowing for pain-free mobility during activity.

Although most of the scientific literature is focused on the outcome of FHNE in dogs, several studies in cats have reported good-to-excellent mid-term and long-term functional outcomes after an adequately performed FHNE.^2–4 In these studies, cases of unilateral or staged bilateral FHNE have made up the majority of patients studied. In situations where patients may need bilateral FHNE, such as for the treatment of bilateral SCFE or hip dysplasia, the option of performing the procedure in a single session vs staged may be an option. A single anesthetic event, single recovery period and reduced cost to the owner are advantages of performing a single session bilateral FHNE. ⁵ A study evaluating single session bilateral FHNE in dogs found their recoveries to be uneventful and all owners were satisfied with their dogs’ outcome. ⁵ To date, an evaluation of cats undergoing single session bilateral FHNE has not been carried out.

The purpose of this study was to retrospectively evaluate the perioperative clinical outcome in cats undergoing single session bilateral FHNE for the treatment of bilateral coxofemoral disease.

Materials and methods

Medical record review

The electronic medical records of cats that had a single session bilateral FHNE at 12 Ethos Veterinary Health hospitals between June 2008 and May 2024 were identified and reviewed retrospectively. Search terms included ‘femoral head ostectomy’ and ‘femoral head and neck excision’. Search results were refined by species and for single session bilateral procedures.

Inclusion criteria

Feline cases were included in this study if they had a single session bilateral FHNE and complete medical records, including postoperative follow-up examinations recorded at approximately 2–6 weeks postoperatively. Cases were excluded if their records did not include the following information: breed; weight; sex; neuter status; diagnosis; anesthetic record; adequately performed FHNE on postoperative radiographs; hospitalization record; or record of recovery status at first recheck. Cases were also excluded if the procedures were not completed by a board-certified surgeon, board-eligible surgeon or by a surgical resident under direct supervision of a board-certified/eligible surgeon. All postoperative radiographs were evaluated for adequacy of the FHNE by the board-certified/eligible surgeon who performed the surgery or the board-certified/eligible surgeon overseeing the surgical resident who was the primary surgeon.

Data collection

For each record reviewed, the patient signalment, weight, diagnosis, perioperative antibiotic use, anesthetic agents, epidural administration, procedure time, anesthetic time, operative technique, surgeon, perioperative surgical complications, time to discharge and postoperative rechecks were recorded.

Reported complications were categorized into minor, major or catastrophic as defined by Cook et al. ⁶ Minor complications were defined as those that did not require additional surgical or medical treatment to resolve. Major complications were defined as those that were associated with morbidity requiring either further surgical or medical treatment to resolve. Catastrophic complications were defined as those associated with morbidity that caused permanent or unacceptable function or were directly related to death or cause for humane euthanasia.

Anesthesia

Patients were premedicated with an opioid ± dexmedetomidine (Dexdomitor; Zoetis) at 2 µg/kg IV or 3 µg/kg IM ± ketamine (Ketamine Hydrochloride; Dechra Vet Products) at 1 mg/kg IV. Opioids chosen included methadone (Methadone Hydrochloride; Mylan Institutional LLC) at 0.3 mg/kg IV or IM, hydromorphone at 0.1 mg/kg IV or IM (HYDROmorphone HCl Injection; Hikma Pharmaceuticals), fentanyl (Fentanyl Citrate Injection; Fresenius Kabi) at 2–4 µg/kg IV or butorphanol (Torbugesic; Zoetis) at 0.3 mg/kg IV or IM. General anesthesia was induced with propofol (Propofol; Sagent Pharmaceuticals) at 2–4 mg/kg IV or alfaxalone (Alfaxan Multidose; Zoetis) at 1–3 mg/kg IV ± midazolam (Midazolam Injection; Athenex) at 0.2 mg/kg IV titrated to effect and maintained with a gaseous mixture of isoflurane (Isoflurane; Covetrus North America) and oxygen through an endotracheal tube. In patients that received local anesthesia, an epidural using preservative-free bupivacaine (Bupivacaine; Hospira) at 2 mg/kg was administered. Cefazolin (Cefazolin; Qilu Pharmaceutical Co) at 22 mg/kg IV was administered every 90 mins intraoperatively.

Surgery

The FHNE procedures were performed from a craniolateral approach ⁷ or ventral approach ⁸ to the coxofemoral joint based on the surgeon’s preference. Each FHNE was performed as previously described.^9,10

Postoperative care

Postoperative analgesics included an opioid and a non-steroidal anti-inflammatory drug (NSAID), if not contraindicated. Choice of an opioid was made at the discretion of the surgeon: methadone at 0.15–0.2 mg/kg IV q6h; buprenorphine (Buprenorphine Hydrochloride; Par Pharmaceutical) at 0.015–0.02 mg/kg IV q8h; or fentanyl constant rate infusion at 2–3 µg/kg/h IV. In patients that were able to receive NSAIDs, either robenacoxib (Onsior; Elanco) at 2 mg/kg SC q24h or meloxicam (Metacam; Boehringer Ingelheim Animal Health) at 0.1 mg/kg SC q24h was used. An Elizabethan collar was placed on all cats after surgery and owners were instructed to keep the collar on until first recheck. Cats were discharged when they were comfortable and able to ambulate without requiring injectable analgesics, with a combination of the following medications at the discretion of the surgeon: gabapentin (Gabapentin Oral Solution; Amneal Pharmaceuticals) at 10 mg/kg PO q8–12h; buprenorphine at 0.01–0.02 mg/kg SL q8–12h; or tramadol (traMADOL Hydrochloride Tablets; Amneal Pharmaceuticals) at 1 mg/kg PO q12h ± oral NSAID (robenacoxib at 6 mg PO per cat or meloxicam at 0.1 mg/kg PO q24h). Follow-up examinations were recommended at 2 weeks and 4–6 weeks postoperatively based on the surgeon’s preference.

Statistical analysis

Data were analyzed using statistical software (GraphPad Prism 10.1.2). Normality for each continuous variable was assessed using Shapiro–Wilk tests. None of the continuous variables were normally distributed; therefore, descriptive statistics were reported using medians and ranges.

Results

Signalment

In total, 54 cats were found to have a single session bilateral FHNE, with 39 cats meeting eligibility for inclusion. Nine cats were excluded because of lack of follow-up, three cats as a result of concurrent hindlimb injuries, two cats for having incomplete anesthetic records and one cat because the operating veterinarian did not have advanced surgical training.

Of the 39 cats, there were 33 (84.6%) castrated males, five (12.8%) spayed females and one (2.6%) intact female. Represented breeds included 27 (69.2%) domestic shorthair cats, eight (20.5%) Maine Coon cats, two (5.1%) Siamese cats and one (2.6%) each of domestic mediumhair and Balinese cats. The median age at the time of surgery was 1.9 years (range 0.4–8.7), with over 90% of cats aged ⩽2 years, and median body weight was 5.7 kg (range 2.1–9.9).

Injury type

Of the 39 cats, 35 (89.7%) were diagnosed with bilateral SCFE, with one cat having a concurrent bilateral sacroiliac luxation and another having an acute SCFE and a previously performed inadequate FHNE on the right side for treatment of a right-sided SCFE. Two cats (5.1%) were diagnosed with bilateral hip dysplasia. One cat (2.6%) had a right-sided acetabular fracture and left-sided femoral neck fracture and one (2.6%) cat was diagnosed with a right-sided femoral head fracture and left-sided hip dysplasia.

Procedure

Of the 39 cats, 32 (82.1%) had documented anesthesia start and end times. The median duration of anesthesia was 192 mins (range 100–345). Of these 32 cats, 20 (52.3%) were documented to have received a preoperative epidural.

Of the 39 cats, 28 (71.8%) had duration of surgery documented and a completed surgery report. Of these 28 cats, 21 (75%) underwent craniolateral approaches with a median duration of surgery of 92 mins (range 35–190), which included the time required to reposition and prep the contralateral side. Seven cats (25%) underwent ventral approaches, with a median duration of surgery of 100 mins (range 65–191).

Of the 39 cats, one (2.6%) was discharged the same day of surgery; 25 (64.1%) were discharged the next day, but within 24 h; and 13 (33.3%) were discharged within 48 h. A total of 15 cats (15/39, 38.5%) were discharged with an opioid and an NSAID. Nine cats (9/39, 23.1%) were discharged with gabapentin and an NSAID. Seven cats (7/39, 17.9%) were discharged with an opioid, gabapentin and an NSAID. Five cats (5/39, 12.8%) were discharged with an opioid only. Three cats (3/39, 7.7%) were discharged with an opioid and gabapentin. All cats survived to discharge.

Postoperative outcomes

Of the 39 cats, 36 (92.3%) presented for scheduled incision rechecks at a median of 13 days (range 9–16). All incisions (72/72, 100%) were reportedly healed. Based on the surgeon’s subjective assessment, 7/39 (19.4%) cats were reported to have a lameness in one or both hindlimbs, 5/39 (13.9%) cats were reported to have muscle atrophy, 4/39 (11.1%) cats were reported to have resistance to hip extension and 1/39 (2.6%) cats was reported to have discomfort. Of the 39 cats, three (7.6%) had both muscle atrophy and lameness, one (2.6%) had resistance to hip extension and lameness, and one (2.6%) was reported to have atrophy and resistance to hip extension. There was no mention of lameness, discomfort, muscle atrophy or resistance to hip extension in the physical examination findings of the other 24 cats (24/36, 66.7%). In total, 35/36 (97.2%) cats were allowed to return to normal activity after the 2-week recheck. One cat (1/36, 2.6%) was advised to remain in confinement while healing from repair of its left greater trochanter.

A total of 14/39 (35.9%) cats presented for scheduled rechecks at 4–6 weeks postoperatively with a median of 41 days (range 25–60). Of these 14 cats, 11 (78.6%) had also presented for an incision recheck. On examination, two (14.3%) cats had lameness noted, two (14.3%) had muscle atrophy and one (7.1%) had mild hip discomfort. No owner concerns were reported for any patient.

Physical rehabilitation was recommended in 3/39 (7.6%) cats and carried out in 2/39 (5.1%) cats. These two cats were noted to have lameness, decreased hip extension and muscle atrophy during the first session. Both cats made improvements in these parameters: one cat after three weekly sessions and the other cat after five weekly sessions.

Complications

There were six complications recorded in five cats within the perioperative period. Five complications (5/39, 12.8%) were considered minor and one (2.6%) was considered major. There were no catastrophic complications. Of the 39 cats, four (10.3%) had missing staples/sutures from the incision site within the postoperative period.

An intraoperative complication occurred in one cat. In this case, an inadvertent left-sided greater trochanter osteotomy was performed during the ventral approach procedure that required repair with a lag screw. During the 6-week postoperative examination, radiographs were performed to assess the healing of the repair and the screw was found to have migrated from its original position. Despite screw migration, the osteotomy site was healing as expected; as the patient was reportedly comfortable at home and the owners were satisfied with the outcome, the screw was left in place. For this reason, this complication was considered a minor one.

Discussion

To the authors’ knowledge, this is the largest retrospective study of single session bilateral FHNE in cats. The findings show that in this cohort of cats, single session bilateral FHNE was performed with a low rate of complications with discharge to owners within 24–48 h of surgery, ultimately leading to a low rate of lameness and issues reported by the owner during the perioperative recovery.

In this study, there was only one major complication that occurred intraoperatively when an inadvertent greater trochanteric osteotomy was performed during FHNE. Aside from this major complication, only minor incisional complications were noted, showing that single session bilateral FHNE is a low-risk procedure. Outcome assessment in this study was limited to 36 cats that presented for 2-week rechecks and 14 cats that presented for 4–6-week rechecks. Abnormal physical examination findings included lameness, muscle atrophy, reduced hip extension and/or discomfort that were found in 12 cats 2 weeks postoperatively and five cats 4–6 weeks postoperatively. There were no concerns reported by owners, which may be interpreted as these individuals being satisfied with their cat’s recovery; however, this should be interpreted with caution given that there may have been variability in history note-taking at the time of these examinations. In all patients that returned for a follow-up at 4–6 weeks, continued activity was encouraged.

Postoperative physical rehabilitation was recommended in three cats and utilized in two. Otherwise, there was no specific recommendation for this in other cases. Although it is generally accepted that cats would benefit from postoperative rehabilitation,^11,12 many clinicians and owners are reluctant to pursue this owing to the compliance issues that can be encountered in cats, which may have impacted decision-making. It should be noted that over 90% of cats included in this study were younger and had acute conditions that may limit difficulties in recovery or reduce the need for rehabilitation compared with patients with chronic conditions.

Although the results show that the cats were doing well perioperatively, with no perceptible pain and few with ongoing lameness, it has been postulated that cats are often less expressive when it comes to pain compared with dogs, ¹³ making subjective evaluations less reliable. A study evaluating ground reaction forces using force plate analysis in cats 1 year or more after unilateral FHNE found these parameters to be reduced when compared with normal limbs. ¹⁴ In addition, the measured reduction in weightbearing did not positively correlate with the results of owner questionnaires and visual gait analysis by surgeons. Nine cats in that study that were found to be sound on orthopedic examination were shown to have reduced ground reaction forces, illustrating that lameness and pain are difficult to assess in cats and a lack of these findings on examination may not be a reliable measure in some patients. ¹⁴

Previously reported postoperative changes seen in cats in other FHNE studies include caudodorsal malposition of the femur, shortening of the limb, muscle atrophy, reduced range of motion and pain on passive movement.^4,15 In a subset of the patients in the present study, muscle atrophy and reduced range of motion were noted, but neither caudodorsal malposition of the femur nor shortening of the limb was documented. Although this may be due to the lack of longer-term follow-up, the results show that the immediate recovery from this procedure leads to an acceptable perioperative outcome demonstrated by a quick return to function for this cohort of cats.

In this study, 89.7% of cats were diagnosed with SCFE, which often occurs bilaterally.^3,16 In cats, this injury is often due to physeal dysplasia rather than trauma. ¹⁶ Prior studies have suggested that overweight, neutered male cats are at higher risk,^16,17 which is reflected in the weight and sex distribution of the present patient population. Although the results report body weight and not body condition scores (BCSs), the median body weight (5.7 kg) can be correlated to a BCS of 7/9, which is considered overweight. ¹⁸ Treatment options for this condition include primary stabilization, FHNE or total hip replacement (THR). For primary stabilization, there is a concern that appropriate healing will not take place owing to the underlying physeal dysplasia;^16,17 therefore, a procedure such as FHNE is often considered to alleviate pain and allow function.

THR has been reported with increasing frequency to be a good option for bilateral coxofemoral disease in cats.^13,19,20 Most patients that undergo THR are reported to have good-to-excellent outcomes with good owner satisfaction.^13,19–23 Despite this, there is up to a 20% risk of complications in surgery or thereafter, including fissure/fracture of the femur, recurrent lameness, luxation of the coxofemoral joint, patellar luxation, implant failure and sciatic neurapraxia.^19,20,24 For owners, consideration must be given to the fact that staged bilateral THR and the potential for complications may impose multiple procedure/anesthetic events and a larger financial burden when compared with FHNE. For owners whose cats have bilateral disease, the option of single session bilateral FHNE may be more appealing compared with staged bilateral THR for these reasons.

As demonstrated in this study, the FHNE procedure can be performed from a craniolateral or ventral approach. Utilization of the ventral approach for a single session bilateral FHNE may be beneficial to eliminate the time required to reposition and prepare the patient for the contralateral side. However, in this cohort of cats, the duration of surgery was similar in cases that underwent a craniolateral vs ventral approach. Although the ventral approach may hypothetically decrease the procedure and anesthetic time, our study indicated that most surgeons chose to perform the procedure using a craniolateral approach. This may be due to increased familiarity and relative ease of this approach for an FHNE when compared with a ventral approach. ¹⁰ In one study comparing the two approaches, the mean duration of the procedure of the craniolateral approach was shorter than the ventral approach. ¹⁰ The study also discussed that an FHNE through a ventral approach may have more perceived challenges including proximity of the medial circumflex artery and vein, obstruction of the lesser trochanter by the iliopsoas muscle, lack of visualization of the greater trochanter and difficulty of removal of additional bone after the initial ostectomy.

Although we cannot make a direct comparison between single session vs staged bilateral FHNE, the benefits of single session surgery include a single anesthetic and hospitalization event, single convalescence time and less monetary cost to the owners. In the most recent study of FHNE in cats, ³ the majority of which had unilateral FHNE, the authors used an owner-completed questionnaire assessment to show that medium- to long-term functional outcome was good to excellent, which is also consistent with the findings of previous studies. ² In the present study, all patients were discharged from the hospital within 24–48 h of surgery and the records of all patients that returned for perioperative follow-up did not report any owner concerns regarding ability to ambulate well enough to resume a normal routine. Although this assessment is subjective in nature, it provides some evidence that these patients were recovering well with few difficulties, which is consistent with the previous reports evaluating unilateral FHNE.^2,3

The limitations of this study include its retrospective nature, relatively small number of cases, variability of postoperative treatments and limited long-term follow-up in most patients. Information regarding preoperative and postoperative pain scores and force plate analysis were not included in this study and would have provided a more objective method of evaluating outcome.

Conclusions

This study confirmed that single session bilateral FHNE can be performed in cats with acceptable procedure/anesthesia times and few major or minor postoperative complications that did not result in prolonged hospitalization. Further prospective studies would be helpful to assess short-, mid- and long-term outcomes associated with this procedure, so that these initial findings can be supported with more objective data.