Factors Affecting the Candidacy for Total Hip Replacement Assessed in 953 Dogs

Abstract

To define reasons for delay to canine total hip replacement (THR). Retrospective clinical study of 953 dogs evaluated for THR between 2013 and 2020. Three hundred and fifty-three dogs (37%) proceeded to immediate THR. Reasons for the initial delay in 600 dogs (63%) included: medical management (42%), other orthopaedic conditions (25%), pyoderma (12%), neurologic disease (7%), concurrent medical condition (7%), immature age (3%), prohibitive behaviour (3%), and for lack of advanced imaging requirement (1%). Of the 92% of dogs with hip dysplasia/osteoarthritis (HD/OA), 32% proceeded to THR without delay. One-hundred and thirteen (19%) dogs that were rejected initially, subsequently had THR. The highest percentage returning for THR were those initially rejected for pyoderma (74%), advanced imaging (67%), and skeletal immaturity (35%). The lowest percentage for THR return included concurrent orthopaedic conditions (3%), neurologic disease (1%), and prohibitive behaviour (0%). The most common reason for referral for evaluation for a THR was OA. The majority of dogs were rejected because of incomplete medical management. Immediate THR following primary evaluation is uncommon and common reasons for delay are incomplete medical management, incorrect initial diagnosis, and prohibitive comorbidities.

Keywords

total hip arthroplasty - total hip replacement - hip dysplasia - canine

Introduction

Total hip replacement (THR) restores function in dogs with hip dysplasia and osteoarthritis (HD/OA) with discomfort refractory to medical management.[1] [2] THR is concurrently a treatment for avascular necrosis of the femoral head, traumatic coxofemoral luxation, femoral capital physeal fractures, unsatisfactory outcomes following femoral head ostectomy (FHO), and other coxofemoral pathologies.[3] [4] [5] [6] The optimal profile of a canine THR candidate has an ideal body condition score (BCS), permissive femoral morphology, absence of comorbidities, and localized hip pain refractory to comprehensive medical management.[5] [6] Comorbidities can constitute contraindications for THR resulting in complications such as luxation and implant-associated infection (IAI).[6] [7] [8] Infections, systemic diseases, neoplasia, and neurologic dysfunction are other contraindications for THR.[5] [7] [9] There remains a paucity of information on factors influencing canine THR candidacy or recommendations for alternative management.

Materials and Methods

Case Selection and Data Collection

A retrospective medical record review was performed for dogs referred for THR evaluation between January 2013 and March 2020. Signalment, BCS, diagnosis, comorbidities, THR delay, and alternative surgeries were recorded. Dogs were evaluated, had diagnostics performed, and progressed to THR the next business day based on clinician evaluation and owner decision-making. All THR procedures were performed by a single board-certified surgeon. Procedures were considered delayed if surgery was not performed at the earliest opportunity. Delayed cases were classified as: medical management (mildly dysplastic dogs without clinical signs, dogs clinically affected by HD/OA without comprehensive medical management, or dogs with HD/OA that received successful management resulting in minimal clinical lameness that did not warrant THR), other orthopaedic disease, pyoderma, neurologic disease, concurrent medical condition, immaturity, prohibitive behaviour, and cases requiring advanced imaging. Delayed dogs were based on clinical evaluation and not on financial decision-making. Dogs receiving bilateral THR were included once and dogs with incomplete medical records, THR performed by another surgeon, or at another institution and referred for revision were excluded.

Statistical Analysis

Multivariable logistic regression model compared odds of THR delay for dogs with HD/OA of different breeds, ages, weights, and sex. The multivariable Cox proportional hazards model compared probabilities that dogs with different reasons for delay would have a THR during the study period. The proportional hazards assumption was assessed visually with a log-minus-log survival plot and analyzed using Schoenfeld residuals. Kaplan Meier survival curves depicted time to THR for the eight delay categories. Data analyses were completed using StataCorp software (StataCorp LLC, College Station, TX).

Results

Study Population

The study population included 953 dogs evaluated for THR from 2013 to 2020. The signalment of dogs presenting for THR evaluation is shown in [Table 1]. Age at presentation followed bimodal distribution with a major peak at 1 year (n = 140) followed by a lesser peak at 3 years (n = 80). Breed did not influence the delay to THR.

Table 1 Signalment of dogs presenting for THR evaluation (n = 953)

Sex
Neutered male	445 (47%)
Spayed female	385 (40%)
Entire male	87 (9%)
Entire female	36 (4%)
Breed
Mixed breed	281 (29%)
German Shepherd	156 (16%)
Golden Retriever	106 (11%)
Labrador Retriever	102 (11%)
Rottweiler	34 (4%)
Newfoundland	31 (3%)
Saint Bernard	31 (3%)
Bernese Mountain dog	20 (2%)
Border Collie	18 (2%)
Australian Shepherd	12 (1%)
Other purebred (≤10 dogs)	162 (18%)
Age
Median age (y)	2 (0.3–13)
Weight
Median weight (kg)	33.5 kg (2–101.7)

Abbreviation: THR, total hip replacement.

Three hundred and fifty-three dogs (37%) progressed to THR without delay. Six hundred (63%) dogs did not progress to immediate THR. Hip pathology diagnoses for these dogs are shown in [Table 2]. A breakdown of reasons for delay to THR is depicted in [Fig. 1]. Two-hundred and seventy-nine dogs with HD/OA (32% [279/875]) proceeded to THR without delay and 596 dogs with HD/OA (68% [596/875]) did not proceed immediately to THR. One hundred and thirteen dogs with HD/OA (19% [113/596]) received a THR later in their management. All dogs with avascular necrosis of the femoral head, traumatic coxofemoral luxation, and chronic femoral capital physeal fracture proceeded to THR surgery without delay.

Table 2 Diagnoses of hip pathology for dogs presenting for total hip replacement

Hip pathology diagnosis
Hip dysplasia/osteoarthritis (HD/OA)	875 (92%)
Traumatic coxofemoral luxation (TCL)	37 (4%)
Chronic femoral capital physeal fracture (FCPF)	30 (3%)
Avascular necrosis of the femoral head (ANFH)	7 (1%)
No hip abnormalities	4 (<1%)
Cranial cruciate ligament deficiency	3 (75%)
Intervertebral disc disease	1 (25%)

Fig. 1 Canine hip diagnoses with and without delay to total hip replacement (n = 953).

Six hundred dogs were initially rejected for THR. Univariable Cox proportional hazards analyses found that breed (p = 0.89), sex (p = 0.69), and weight (p = 0.32), had no effect on the probability of THR. Multivariable logistic adjusting for age and weight demonstrated odds of delay for female dogs were 1.35 times greater than for males (p = 0.04).

Medical Management

Two-hundred and fifty-one dogs (42% [251/600]) did not receive immediate THR but a recommendation for comprehensive medical management. Three subsets of dogs received a recommendation for medical management. The first included mildly dysplastic dogs without clinical sign severity indicating joint replacement. The second was clinically affected by HD/OA without comprehensive management strategies. The third subset with HD/OA received successful medical management resulting in minimal clinical lameness that did not warrant THR. Recommended interventions for HD/OA included weight loss, non steroidal anti-inflammatory drugs (NSAIDs), joint supplementation (omega-3 fatty acids, glycosaminoglycans), exercise modification, and rehabilitation therapy. Sixty-four dogs (25% [64/251]) had a BCS ≥ 7/9 and weight loss was the most critical intervention. The remaining 187(75% [187/251]) had a BCS of ≤ 6/9 but had not received adequate medical management or had successful medical management with mild lameness. The success of medical management was evaluated by a clinical gait exam, tape measurement of increasing thigh circumference, and activity levels reported by the owner. If the dog had monthly decreasing thigh circumference, decreased activity levels, and increasing lameness, they were re-evaluated for candidacy for THR.

Other Orthopaedic Conditions or Alternative Management

Other orthopaedic conditions included dogs with lameness other than originating in the hip joint. One-hundred and fifty-three dogs (25% [153/600]) were rejected for concurrent orthopaedic conditions. Case descriptions for dogs evaluated for THR with concurrent orthopaedic conditions are shown in [Table 3]. Orthopaedic surgery for concurrent orthopaedic conditions occurred in 64% of dogs (98/153) and is shown in [Table 3]. Orthopaedic surgical intervention was neither recommended nor pursued in 36% of dogs (55/153). FHO was recommended for treatment due to prohibitive THR templating or financial limitations in seven dogs.

Table 3 Dogs evaluated for THR with concurrent orthopaedic conditions and prohibitive femoral and acetabular remodelling and orthopaedic surgeries performed for these dogs

Concurrent orthopaedic conditions and prohibitive remodelling (n = 153)
CCLR	95 (62%)
Patellar luxation	25 (16%)
Tarsal pathology	7 (4%)
Tarsal OCD	4/7
Tarsal torsional deformity	2/7
Talocrural instability	1/7
Femoral and acetabular pathology	7 (4%)
Femoral remodelling: luxoid conformation	2/7
Chronic expansive femoral remodelling—unknown etiology	2/7
Femoral OCD	1/7
Severe distal femoral varus	1/7
Pseudoacetabulum	1/7
Panosteitis	5 (3%)
Femoral panosteitis	4/5
Tibial panosteitis	1/5
Myopathy	3 (2%)
Gracilis muscle contracture	2/3
Iliopsoas strain	1/3
Elbow dysplasia	6 (4%)
Forelimb angular limb deformity (short radius syndrome)	1 (1%)
Humeral pathology	2 (2%)
Humeral OCD	1/2
Proximal humeroulnar subluxation	1/2
Bicipital tendon tear	1 (1%)
Osteochondrodysplasia	1 (1%)
Orthopaedic surgeries performed (n = 98)
Cranial cruciate ligament rupture	72 (73%)
TPLO	65/72
CCWO	7/72
Patellar luxation correction	16 (17%)
Tarsal OCD arthrotomy for OCD debridement	4 (4%)
Arthrotomy for OCD debridement	¾
OATS	¼
Bilateral debridement of fragmented medial coronoid processes	5 (5%)
Circular ring fixator for treatment of short radius syndrome	1(1%)
Femoral head ostectomy recommended (n = 7)
ANFH	3/7
Chronic FCPF	3/7
TCL	1/7

Abbreviations: AFNH, avascular necrosis of the femoral head; CCLR, cranial cruciate ligament rupture; CCWO, cranial closing wedge osteotomy; FCPF, femoral capital physeal fracture; OATS, osteochondral autograft transfer; OCD, osteochondrosis dissecans; TCL, traumatic coxofemoral luxation; THR, total hip replacement; TPLO, tibial plateau levelling osteotomy.

Pyoderma

Seventy-three dogs (12% [73/600]) were rejected for THR due to pyoderma and no correlation was found between sex or breed. Treatments included dietary modification, systemic antibiotic therapy, and medicated shampoo. Treatments included systemic broad-spectrum antibiotics (cephalexin or amoxicillin clavulanic acid) and medicated shampoo (Douxo chlorhexidine: Ceva Animal Health, Lenexa KS; TrizChlor 4: Dechra Veterinary products, KS; Malaseb: Bayer Health Care LLC, KS) in the majority of dogs 59/73 (81%). The remainder of dogs received medicated shampoo alone 4/73 (6%), systemic antibiotics alone 3/73 (4%), systemic antibiotics + diet trial + shampoo 2/73 (3%), diet trial + medicated shampoo 1/73 (1%), diet trial alone 1/73 (1%), and a single dog was refractory and required referral to a veterinary dermatologist 1/73 (1%).

Neurologic Disease

Forty-three dogs (7% [43/600]) were rejected for concurrent neurologic disease. The majority (47% [20/43]) were diagnosed with thoracolumbar myelopathy (TM) and full case descriptions are shown in [Table 4].

Table 4 Case description for concurrent neurologic diseases diagnosed when evaluated for THR

Concurrent neurologic disease (n = 43)
TM	20 (47%)
Intervertebral disc disease—MRI diagnosed	6/20
Degenerative myelopathy—genetic testing	4/20
Clinical signs of TM but no further diagnostics	10/20
LS	17 (40%)
Lumbosacral myelopathy—MRI diagnosed	7/17
Lumbosacral myelopathy—radiographs	1/17
Clinical signs of LS but no further diagnostics	9/17
Neuromuscular disease	3 (7%)
Epaxial and scapular myositis (muscle biopsy)	1/3
Neuropathy/denervation (nerve + muscle biopsy)	1/3
Hindlimb polyneuropathy (hypothyroidism)	1/3
CCM	2 (5%)
Multifocal neurologic disease (cerebellum, cervical spine)	1 (2%)

Abbreviations: CCM, caudal cervical myelopathy LS, lumbosacral myelopathy/radiculopathy; MRI, magnetic resonance imaging; THR, total hip replacement; TM, thoracolumbar myelopathy.

Concurrent Medical Condition

Forty-one dogs (7% [41/600]) were rejected for concurrent medical conditions. Categories included neoplasia, infectious, inflammatory, and immune-mediated disease, preoperative illness, and other medical conditions and are shown in [Table 5].

Table 5 Case description for concurrent medical conditions diagnosed when evaluated for THR

Concurrent medical conditions (n = 41)
Neoplasia	15 (37%)
Proximal femoral neoplasia—no biopsy diagnosis	3/15
Histiocytic sarcoma	2/15
Mast cell tumour	2/15
Osteosarcoma	1/15
Apocrine gland anal sac adenocarcinoma	1/15
Intermuscular lipoma	1/15
Follicular thyroid carcinoma	1/15
Peripheral nerve sheath tumour	1/15
Soft tissue sarcoma	1/15
CNS thalamic neoplasia—MRI diagnosis	1/15
Pulmonary metastasis on radiographs—unknown primary	1/15
Infectious, inflammatory, immune-mediated	11 (27%)
Septic arthritis	4/11
Urinary tract infection	2/11
Pneumonia	1/11
Immune-mediated poly arthropathy	2/11
Non-specific inflammatory leukogram	2/11
Preoperative illness resulting in THR delay	9 (22%)
Profuse diarrhoea	2/9
Preoperative vomiting	2/9
Regurgitation	1/9
Idiosyncratic ketamine reaction	1/9
Severe cutaneous chlorhexidine scrub reaction	1/9
Haematuria	1/9
Hypertension	1/9
Other concurrent medical conditions	6 (15%)
Atypical hypoadrenocorticism	1/6
Protein-losing nephropathy	1/6
Dilated cardiomyopathy	1/6
Primary hypercholesterolemia	1/6
Mixed hepatocellular/cholestatic hepatopathy	1/6
Airway compromise from brachycephalic airway syndrome	1/6

Abbreviations: MRI, magnetic resonance imaging; THR, total hip replacement.

Age (Skeletally Immature) and Requirement for Advanced Imaging

Seventeen dogs (3% [17/600]) were initially rejected for THR for skeletal immaturity with open greater trochanteric physes at initial evaluation. Median age at presentation was 8 months (min: 3 months, max: 1 year). Six dogs (1% [6/600]) required a delay to print a CT-based 3D model for surgical rehearsal based on significant femoral or acetabular anatomic remodelling. These dogs required advanced imaging for chronic traumatic pelvic and acetabular malunion 2/6 (33%), asymmetrical transitional lumbosacral vertebrae one-sixth (17%), luxoid conformation one-sixth (17%), chronic craniodorsal hip luxation one-sixth (17%), and osteochondrodysplasia of the femoral head one-sixth (17%). Prohibitive femoral anatomic remodelling consisted of severe luxoid conformation with lateral drift of the medial cortex of the femur. This resulted in a very narrow isthmus at the level of the lesser trochanter. Prohibitive acetabular remodelling included chronic traumatic pelvic and acetabular malunion resulting in a prohibitive fitting of an appropriately sized acetabular cup.

Prohibitive Behaviour

Sixteen dogs (3% [16/600]) were rejected for behavioural concerns. The majority of dogs demonstrated fear-based aggression 9/16 (56%). The remainder demonstrated moderate to severe generalized anxiety 6/16 (38%), and severe separation anxiety 1/16 (6%).

THR in Dogs with Delayed Surgical Intervention

One-hundred and thirteen (19% [113/600]) dogs were initially rejected and ultimately received THR. The majority of dogs advancing to THR had surgery within 1 year from initial presentation, with a median postponement duration of 9 weeks (min: 1 week, max: 210 weeks; [Fig. 2]). Dogs initially rejected for pyoderma, advanced imaging, and immaturity had the highest percentage return for THR shown in [Table 6]. The relationship between categories and time to THR is illustrated with Kaplan–Meier survival curves ([Fig. 3]).

Fig. 2 Time to total hip replacement surgery in dogs that were initially delayed.

Table 6 Case description for time to return for THR after initial rejection for pyoderma, advanced imaging, immaturity, concurrent medical conditions, medical management, and concurrent orthopaedic and neurologic disease

Pyoderma (n = 73)
Percentage returning for THR	54/73 (74%)
Median time to surgery	7 wks (min 2, max 99)
Advanced Imaging (n = 6)
Percentage returning for THR	4/6 (67%)
Median time to surgery	14 wks (min 9, max 18)
Immaturity (n = 17)
Percentage returning for THR	6/17 (35%)
Median time to surgery	13 wks (min 10, max 20)
Concurrent medical condition (n = 41)
Percentage returning for THR	13/41 (32)
Median time to surgery	8 wks (min 1, max 44)
Medical management (n = 251)
Percentage returning for THR	30/251 (12%)
Median time to surgery	21 wks (min 1, max 210)
Concurrent orthopaedic conditions (n = 153)
Percentage returning for THR	5/153 (3%)
Median time to surgery	19 wks (min 6, max 120)
Concurrent neurologic disease (n = 43)
Percentage returning for THR	1/43 (1%)
Median time to surgery	106 wks
Prohibitive behavior (n = 16)
Percentage returning for THR	0/16 (0%)
Median time to surgery	N/A

Abbreviation: THR, total hip replacement.

Fig. 3 The relationship between categories for delay and time to total hip replacement (THR) illustrated with Kaplan–Meier survival curves for 600 dogs presenting for THR.

Dogs with concurrent medical conditions returning for THR are shown in [Table 6]. Dogs returned following the resolution of diarrhoea, haematuria, hypertension, regurgitation, vomiting, UTI, inflammatory leukogram, and resection of low-grade mast cell tumours. The dog with reaction to ketamine was induced with alternative anaesthetic agents. One case received betadine for surgical preparation having demonstrated a previous cutaneous chlorhexidine scrub reaction.

Dogs representing for THR with discomfort refractory to comprehensive medical management are shown in [Table 6]. The mean BCS was 6/9 for dogs advancing to THR. Younger dogs were more likely to fail medical management with (53% [16/30]) being 2 years of age or less.

Concurrent orthopaedic conditions, neurologic disease, and prohibitive behaviour were least likely to advance to THR and are shown in [Table 6]. Only 2% (2/95) of dogs diagnosed with CCLR received THR later on. Only one dog with concurrent neurologic disease, mild lumbosacral stenosis, moved forward to THR. No dog with behavioural concerns moved forward to THR.

Cox Proportional Hazards Analysis (All Categories)

The hazard ratio compared the probability of THR surgery during the study period between delay categories with medical management as a reference ([Table 7]). Dogs delayed for pyoderma (12×), or advanced imaging (8×) had the greatest probability of advancement to THR. Dogs with delay for behaviour had the smallest probability of return to THR with none moving forward to surgery.

Table 7 Results of the Cox proportional hazards analysis

Reason for delay	Hazard ratio	p-Value	Confidence interval
Medical management (ref)	1.00
Advanced imaging	7.86	<0.001	3.25–18.98
Skeletal immaturity	3.27	0.006	1.40–7.64
Pyoderma	11.94	<0.001	7.60–18.77
Concurrent medical condition	3.27	<0.001	1.66–6.47
Neurologic diagnosis	0.18	0.089	0.03–1.30
Other orthopedic diagnosis	0.26	0.005	0.10–0.67

Note: The hazard ratio compares the probability of total hip replacement during the study period between the delay categories.

Discussion

This study is the first to evaluate delay to canine THR. The majority of dogs referred for evaluation for a THR received recommendations for medical management. This study supports that certain diagnoses delay but do not preclude THR candidacy; with pyoderma, advanced imaging, and young age having the highest return for THR.

Multivariable logistic regression demonstrated female dogs having 1.35 times greater odds of THR delay. The human literature reports gender differences for joint replacement however, these predominantly include socioeconomic factors not applicable to veterinary populations.[10] The increased likelihood of delay to surgery in female dogs was unexpected, may signify statistical aberration, and may warrant further investigation.

All dogs presenting with avascular necrosis of the femoral head, femoral capital physeal fractures, and traumatic coxofemoral luxation advanced to THR or FHO immediately. The chronic nature of these injuries (FCPF), disease process (ANFH), or degree of HD and OA (TCL) precluded primary repair.[3] [11] [12] [13] Difficulty diagnosing these dogs could be due to a lack of observed trauma and insidious onset of lameness.[3] [14] Unfortunately, difficulty in diagnosis or lack of a contemporary primary repair option resulted in the surgical recommendation for THR, which may not have been indicated earlier in these disease processes.[3] [12] [15] For traumatic coxofemoral luxation and femoral capital physeal fractures, THR could have possibly been avoided with an earlier referral. However, earlier diagnosis would not have changed the treatment for cases of avascular necrosis of the femoral head.

The majority of dogs were diagnosed with HD/OA and only 1 in 3 dogs moved forward to immediate THR. These dogs had comprehensive medical management with refractory discomfort, a BCS compatible with THR, clinical lameness with coxofemoral joint localization and consistent HD/OA radiological changes. Similar inclusion criteria for THR candidacy are described in people with OA, pain uncontrollable with medical management, decreased function, and concurrent radiological changes commonly reported.[16]

The recommendation for comprehensive medical management was the most common reason for initial THR rejection. In seventy five percent of dogs a recommendation for comprehensive medical management for HD/OA was prescribed and followed by owners. Following the implementation of this recommendation, a proportion of dogs had subjective clinical lameness evaluated through gait analysis but not force plate analysis, which did not necessitate THR. Although representing the majority of initial rejections, only 12% of dogs returned for THR after appropriate medical management and lack of clinical improvement. This emphasizes the importance of exhausting medical options to ensure appropriate candidate selection.

Twenty-five percent of these cases consisted of obese dogs with BCS ≥ 7/9. An association was established for increased BCS and higher severity of HD/OA in age, sex, and breed-matched populations.[17] Furthermore, exacerbation of lameness in dogs with OA has been demonstrated with increases in BCS through force platform gait analysis.[18] Obesity is not a directly reported THR risk factor, however, selection toward ideal BCS is suggestive in the current study and a large retrospective canine THR study with a mean BCS of 6/9.[19] [20] We acknowledge there is no validated BCS threshold for THR delay. However, clinically, the authors have experienced that obese dogs can be harder to manage postoperatively and have a more difficult surgical approach.

A quarter of dogs evaluated for THR had orthopaedic comorbidity. These dogs presented for evaluation of HD/OA; however, other orthopaedic conditions caused the primary lameness. CCLR was most prevalent and is reported as a common cause of lameness previously attributed to HD/OA, accounting for 32% in one study.[9] One in ten dogs evaluated was diagnosed with CCLR as the primary cause of lameness and subsequent advancement to THR was uncommon (2%) despite a high prevalence of HD/OA on radiographic examination (96%). These findings support recommendations for meticulous palpation, sedated orthopaedic exam, and high-quality lateral stifle radiograph prior to referral for THR. Radiographic findings must be interpreted within a clinical context to differentiate the primary cause of lameness between CCLR and HD/OA.[5] [9] [21] Patellar luxation, predominantly medial, occurred in 16% of dogs. Historically, the effects of THR on patellar luxation have been hard to predict due to potential femoral lateralization and the requirement for concurrent or future patellar correction.[6] In this study, 64% received surgical intervention for patellar luxation and no dogs returned for THR despite the prevalence of HD/OA on radiographic examination (100%).

Diagnosis of pyoderma was common and generally identified under anaesthesia during surgical preparation. Active pyoderma is a contraindication to joint replacement.[14] [22] [23] Previous skin infection is a risk factor for surgical site infection (SSI) in people with affected individuals three times more likely for development and IAI associated with dermatitis distant to the surgical site.[24] [25] In people, colonization of methicillin-resistant Staphylococcus aureus (MRSA) accounts for the majority of SSIs, and screening and decolonization with mupirocin and chlorhexidine-baths have decreased the percentage of MRSA-related SSIs.[26] [27] Similarly, treatment of pyoderma in dogs is essential to decrease the risk of IAI.[5] [22] The reported incidence of canine THR infection currently ranges from 1 to 5%.[22] [28] The efficacy of topical antimicrobial treatment has been reported for THR candidates presenting with superficial pyoderma.[29] Average time to THR was 17 weeks and only 2.5% were diagnosed with IAI requiring explanation; suggesting no overt increase in IAI following resolution of pyoderma.[29] IAI was not evaluated in the current study and time to THR was a median of 8 weeks. The decreased time to THR might be geographical differences or higher prevalence of administration of systemic antibiotics in conjunction with topical therapy and warrants further exploration. Currently, the increased risk for IAI following THR in a dog with pyoderma is unknown. The authors suggest screening for pyoderma by evaluating the inguinal, perivulvar, hip, axilla, and abdominal regions for signs of infection. Presurgical clipping is not recommended as clipping ≥ 4 hours prior to surgery has been associated with an increased risk of SSI.[30] Presurgical clipping of the surgical site under premedication could be considered for diagnosis prior to general anaesthesia. No study has reported the efficacy of bathing prior to elective orthopaedic procedures in dogs; clinically, authors appreciated the resolution of pyoderma following serial baths with chlorhexidine-based shampoo. However, pyoderma in dogs has been effectively treated without antibiotic therapy.[24] Bathing was commonly performed in conjunction with a 4-week course of broad-spectrum antibiotics. Resolution of superficial pyoderma to move forward to THR occurred in 75% of treated cases. The authors suggest a 4-week re-evaluation and moving forward with THR after resolution of pyoderma.

Concurrent neurologic disease was uncommon. A single case progressed to THR following an MRI diagnosis of mild lumbosacral stenosis. Neurologic disease has historically been considered a contraindication for THR due to the increased risk of postoperative luxation in dogs and people.[5] [25] [31] The differentiation between orthopaedic and neurologic diseases can be challenging. The authors recommend a thorough neurologic examination including gait analysis at the walk and trot, circling the dog in both directions and walking them in a serpentine up and down a curb to identify subtle ataxia and caudal paresis. For dogs presenting with neurologic signs, further, work up and delay to THR is recommended to gain information about pathology and disease progression. If neurological disease does not progress, re-evaluation is recommended in 4 to 6 months.

Concurrent medical conditions comprised a small case number rejected for THR. The majority of dogs with neoplasia did not move forward to THR, with the exception of two dogs following complete resection of low-grade mast cell tumours. Furthermore, a retrospective review evaluating longevity following THR in dogs demonstrated neoplasia as the most common cause of death.[19] These findings support systemic and musculoskeletal neoplasia as contraindications to THR.

Dogs with prohibitive behaviour comprised the minority and none advanced to THR. Dogs were disqualified if the behaviour was considered to carry an excessive risk of recovery and postoperative complications. Identification of dogs with significant aggressive behaviour is not challenging, but a meaningful modification of behaviour proved prohibitively difficult. Currently, there remains a paucity of information surrounding elective orthopaedics in dogs with behavioural diagnoses. Oral administration of trazodone has been shown to facilitate confinement and calming postoperatively but further research is warranted to fully evaluate efficacy for dogs undergoing THR.[32]

Skeletal immaturity and advanced imaging frequently required delay to THR due to case complexity. Skeletal maturity allowed advancement to THR in 35% of dogs initially delayed. Advanced imaging allowed advancement to THR in 67% of dogs. Clinically, a small percentage of this population demonstrates luxoid coxofemoral conformation and prospective evaluation for THR is required, as age and degree of luxation may increase the potential for complications. Luxoid conformation is used to describe chronic luxation of the dysplastic juvenile hip.[5] Remodelling changes of the luxoid femur can be prohibitive and include lateral migration of the proximal medial femoral cortex and narrowing of the proximal femur. The narrow isthmus resulted in a very small implant size with a high risk of fatigue failure. Furthermore, depleting the cortex in these dogs may have been needed for implant placement, which can result in a higher risk of femoral fracture and catastrophic complications. These changes may place dogs at a higher risk of major complications such as intraoperative fissure/fracture or postoperative dorsal luxation.[33] Authors recognize that in a luxoid population, femoral conformation can change rapidly and that a luxoid dog might easily accommodate an appropriately sized stem at 6 months of age but due to ongoing femoral morphologic changes this dog would require downsizing after lateral drift of the proximal medial femoral cortex within 2 to 3 months. Prohibitive templating may occur due to weight recommendations or prohibitive femoral morphologic changes.[34] This issue is complex as there are conflicting factors to operate early or late.[33] THR in this study was preferentially performed following the closure of the greater trochanteric physis to mitigate the risk of trochanteric avulsion during or after surgery. In the author's experience, a difficult reduction in a dog with luxoid morphology could increase the risk of trochanteric avulsion associated with the use of the greater trochanter as a rake anchor point. However, recent studies have shown that THR performed in skeletally immature dogs can be successful and may have minimal impact on femoral diaphyseal growth.[5] [35] [36] Prohibitive acetabular remodelling included chronic traumatic pelvic and acetabular malunion resulting in a prohibitive fitting of an appropriately sized acetabular cup.

Prescreening for THR at our institution includes CBC, serum chemistry, and evaluation for pyoderma. Preoperative CBC and chemistry demonstrated changes consistent with systemic health concerns delaying THR in less than 1%. The reporting clinician does not routinely perform urinalysis or urine culture unless clinical history or physical exam warrants further evaluation. Dogs older than ten receive thoracic radiographs to screen for neoplasia. Abdominal ultrasound or CT are not routinely recommended and spaying or neutering is not a prerequisite.

Limitations of the current study include the retrospective nature of case selection inconsistencies and decision-making by a single surgeon. The results of this study solely reflect the caseload and subjective inclusion criteria for a single academic institution. The authors acknowledge other surgeons may have employed different approaches to surgical care and implicit bias is present in this case selection process. In this study, overweight dogs were delayed to THR for medical management and weight loss. The authors acknowledge that obesity is a relative contraindication for THR and that this case selection may have been performed differently by other surgeons and that an earlier THR surgery may have helped certain dogs with quicker weight loss and return to comfort. THR in this study was preferentially performed following the closure of the greater trochanter physis to decrease impacts on femoral diaphyseal growth. However, recent studies have shown that THR performed in skeletally immature dogs can be successful and may have minimal impact on femoral diaphyseal growth suggesting these dogs may have benefited from earlier intervention with THR.[35] [36] Another limitation of this study is the lack of longitudinal infection data and follow-up on postoperative infection rates for dogs treated for pyoderma. Furthermore, the evaluation of bilateral HD was limited to clinical evaluation, not objective force plate gait analysis, which could have decreased subjective bias in case selection for THR. Preoperative staging with thoracic radiographs was recommended for dogs older than 10. However, offering this screening to younger animals may have increased the sensitivity of cancer screening prior to THR and is a limitation of this study.

In conclusion, the most common reason dogs were referred for evaluation for a THR was HD/OA. The majority of dogs were rejected to allow medical management following clinical evaluation of lameness: monitoring of thigh muscle atrophy, and owner-assessed activity levels at home. Following the implementation of conservative treatment, only a small percentage of dogs demonstrated persistent clinical lameness and returned for THR. If THR is being considered for a dog with HD/OA, we recommend they prove refractory to medical management, that weight loss be implemented to approach an ideal BCS compatible with THR, and that consideration be given to diagnosis and treatment of comorbidities. To improve canine candidacy for THR, authors recommend a meticulous orthopaedic examination both awake and sedated, and a comprehensive neurologic exam. In cases of bilateral arthrosis of the hips, the classic signs of hind leg lameness may not be present, but hip pain can be assessed by careful observation of the dog's gait, weight shift to the front legs, limitation in range of motion and pain on hip extension. Diagnostic imaging is based on orthopaedic exam findings and includes calibrated orthogonal views of the pelvis and femur and consideration for a lateral stifle radiograph to confirm HD/OA and to exclude CCLR. Screening bloodwork (CBC, chemistry) and thorough examination for superficial pyoderma is also recommended.

Conflict of Interest

None declared.

Acknowledgement

The abstract was presented online at the Veterinary Orthopaedic Society Conference on March 19th, 2021.

Authors' Contributions

A.K.E.: substantial contribution to conception and study design, acquisition, analysis, interpretation of data, drafting and revision of work, and final approval of version to be published.

C.E.O: substantial contribution to data collection, drafting and revision of work, and final approval of version to be published.

E.M.P.: substantial contribution to data analysis, drafting and revision of work, and final approval of version to be published.

J.D.: substantial contribution to conception and study design, acquisition, analysis, interpretation of data, drafting and revision of work, and final approval of version to be published.

• References

• 1 Budsberg SC, Chambers JN, Lue SL, Foutz TL, Reece L. Prospective evaluation of ground reaction forces in dogs undergoing unilateral total hip replacement. Am J Vet Res 1996; 57 (12) 1781-1785
• 2 Marcellin-Little DJ, DeYoung BA, Doyens DH, DeYoung DJ. Canine uncemented porous-coated anatomic total hip arthroplasty: results of a long-term prospective evaluation of 50 consecutive cases. Vet Surg 1999; 28 (01) 10-20
• 3 Jankovits DA, Liska WD, Kalis RH. Treatment of avascular necrosis of the femoral head in small dogs with micro total hip replacement. Vet Surg 2012; 41 (01) 143-147
• 4 Heo SY, Seol JW, Lee HB. Total hip replacement in two dogs with unsuccessful femoral head ostectomy. J Vet Sci 2015; 16 (01) 131-134
• 5 Peck JN, Liska WD, DeYoung DJ, Marcellin-Little DJ. Clinical application of total hip replacement. In: Jeffrey NP, Denis JM-L. eds. Advances in Small Animal Total Joint Replacement. Wiley; Hoboken, NJ, USA: 2012: 69-107
• 6 Vezzoni A, Peck JN. Surgical management of hip dysplasia. In: Johnson SA, Tobias KM. eds. Veterinary Surgery Small Animal. 2nd ed.. Elsevier; Amsterdam: 1001-1017 https://cabidigitallibrary.org by 182.73.182.38
• 7 Dyce J, Olmstead ML. Removal of infected canine cemented total hip prostheses using a femoral window technique. Vet Surg 2002; 31 (06) 552-560
• 8 Slover JD, Rubash HE. Hip resurfacing arthroplasty: time to consider it again? No. Instr Course Lect 2008; 57: 267-271
• 9 Powers MY, Martinez SA, Lincoln JD, Temple CJ, Arnaiz A. Prevalence of cranial cruciate ligament rupture in a population of dogs with lameness previously attributed to hip dysplasia: 369 cases (1994-2003). J Am Vet Med Assoc 2005; 227 (07) 1109-1111
• 10 Hawker GA, Wright JG, Coyte PC. et al. Differences between men and women in the rate of use of hip and knee arthroplasty. N Engl J Med 2000; 342 (14) 1016-1022
• 11 Kalis RH, Liska WD, Jankovits DA. Total hip replacement as a treatment option for capital physeal fractures in dogs and cats. Vet Surg 2012; 41 (01) 148-155
• 12 Preston CA, Schulz KS, Vasseur PB. Total hip arthroplasty in nine canine hind limb amputees: a retrospective study. Vet Surg 1999; 28 (05) 341-347
• 13 Gemmill TJ, Pink J, Clarke SP, McKee WM. Total hip replacement for the treatment of atraumatic slipped femoral capital epiphysis in dogs. J Small Anim Pract 2012; 53 (08) 453-458
• 14 Faraday N, Rock P, Lin EE. et al. Past history of skin infection and risk of surgical site infection after elective surgery. Ann Surg 2013; 257 (01) 150-154
• 15 Moores AP, Owen MR, Fews D, Coe RJ, Brown PJ, Butterworth SJ. Slipped capital femoral epiphysis in dogs. J Small Anim Pract 2004; 45 (12) 602-608
• 16 Gademan MG, Hofstede SN, Vliet Vlieland TP, Nelissen RG, Marang-van de Mheen PJ. Indication criteria for total hip or knee arthroplasty in osteoarthritis: a state-of-the-science overview. BMC Musculoskelet Disord 2016; 17 (01) 463
• 17 Kealy RD, Lawler DF, Ballam JM. et al. Evaluation of the effect of limited food consumption on radiographic evidence of osteoarthritis in dogs. J Am Vet Med Assoc 2000; 217 (11) 1678-1680
• 18 Moreau M, Troncy E, Bichot S, Lussier B. Influence of changes in body weight on peak vertical force in osteoarthritic dogs: a possible bias in study outcome. Vet Surg 2010; 39 (01) 43-47
• 19 Israel SK, Liska WD. Outcome of canine cementless collared stem total hip replacement with proximal femoral periprosthetic cerclage application: 184 consecutive cases. Vet Surg 2022; 51 (02) 270-278
• 20 Andrews CM, Liska WD, Roberts DJ. Sciatic neurapraxia as a complication in 1000 consecutive canine total hip replacements. Vet Surg 2008; 37 (03) 254-262
• 21 Conzemius MG, Vandervoort J. Total joint replacement in the dog. Vet Clin North Am Small Anim Pract 2005; 35 (05) 1213-1231 , vii
• 22 Olmstead ML. The canine cemented modular total hip prosthesis. J Am Anim Hosp Assoc 1995; 31 (02) 109-124
• 23 Aggarwal VK, Tischler EH, Lautenbach C. et al. Mitigation and education. J Arthroplasty 2014; 29 (Suppl. 02) 19-25
• 24 Valentine B. Treating pyoderma without the use of systemic antibiotics. Can Vet J 2019; 60 (12) 1361-1363
• 25 Dargel J, Oppermann J, Brüggemann GP, Eysel P. Dislocation following total hip replacement. Dtsch Arztebl Int 2014; 111 (51–52): 884-890
• 26 Weiser MC, Moucha CS. The current state of screening and decolonization for the prevention of Staphylococcus aureus surgical site infection after total hip and knee arthroplasty. J Bone Joint Surg Am 2015; 97 (17) 1449-1458
• 27 Rao N, Cannella B, Crossett LS, Yates Jr AJ, McGough III R. A preoperative decolonization protocol for Staphylococcus aureus prevents orthopaedic infections. Clin Orthop Relat Res 2008; 466 (06) 1343-1348
• 28 Guerrero TG, Montavon PM. Zurich cementless total hip replacement: retrospective evaluation of 2nd generation implants in 60 dogs. Vet Surg 2009; 38 (01) 70-80
• 29 Silveira CJ, Saunders WB, McDaniel S. et al. Evaluation of dermatologic factors associated with implant associated infection in dogs following total hip replacement. Paper presented at: Veterinary Orthopedic Society Conference; March 18, 2021; Virtual Forum.
• 30 Mayhew PD, Freeman L, Kwan T, Brown DC. Comparison of surgical site infection rates in clean and clean-contaminated wounds in dogs and cats after minimally invasive versus open surgery: 179 cases (2007-2008). J Am Vet Med Assoc 2012; 240 (02) 193-198
• 31 Fessy MH, Putman S, Viste A. et al; SFHG. What are the risk factors for dislocation in primary total hip arthroplasty? A multicenter case-control study of 128 unstable and 438 stable hips. Orthop Traumatol Surg Res 2017; 103 (05) 663-668
• 32 Gruen ME, Roe SC, Griffith E, Hamilton A, Sherman BL. Use of trazodone to facilitate postsurgical confinement in dogs. J Am Vet Med Assoc 2014; 245 (03) 296-301
• 33 Horwood C, Carvajal JL, Pozzi A, Kim SE. Complications and outcomes of total hip arthroplasty in dogs with luxoid hip dysplasia: 18 cases (2010-2022). Vet Surg 2024; 53 (04) 620-629
• 34 Meltzer LM, Dyce J, Leasure CS, Canapp Jr SO. Case factors for selection of femoral component type in canine hip arthroplasty using a modular system. Vet Surg 2022; 51 (02) 286-295
• 35 Forzisi I, Vezzoni A, Vezzoni L, Drudi D, Bourbos A, Marcellin-Little DJ. Evaluation of the effects of cementless total hip replacement on femoral length in skeletally immature dogs. Vet Surg 2025; 54 (01) 199-207
• 36 Fitzpatrick N, Law AY, Bielecki M, Girling S. Cementless total hip replacement in 20 juveniles using BFX arthroplasty. Vet Surg 2014; 43 (06) 715-725

Publication History

Received: 11 October 2024

Accepted: 05 February 2025

Article published online:
26 March 2025