Quasi-static mechanical evaluation of canine cementless total hip replacement broaches: effect of tooth design on broach and stem insertion.

BACKGROUND: Biomedtrix BFX® cementless total hip replacement (THR) requires the use of femoral broaches to prepare a press-fit envelope within the femur for subsequent stem insertion. Current broaches contain teeth that crush and remove cancellous bone; however, they are not particularly well-suited for broaching sclerotic (corticalized) cancellous bone. In this study, three tooth designs [Control, TG1 (additional V-grooves), TG2 (diamond tooth pattern)] were evaluated with a quasi-static testing protocol and polyurethane test blocks simulating normal and sclerotic bone. To mimic clinical broaching, a series of five sequential broach insertions were used to determine cumulative broaching energy (J) and peak loads during broach insertion. To determine the effect of broach tooth design on THR stem insertion, a BFX® stem was inserted into prepared test blocks and insertion and subsidence energy and peak loads were determined. RESULTS: Broach tooth design led to significant differences in broaching energy and peak broaching loads in test blocks of both densities. In low density test blocks, TG1 required the lowest cumulative broaching energy (10.76 ±0.29 J), followed by Control (12.18 ±1.20 J) and TG2 (16.66 ±0.78 J) broaches. In high density test blocks, TG1 required the lowest cumulative broaching energy (32.60 ±2.54 J) as compared to Control (33.25 ±2.16 J) and TG2 (59.97 ±3.07 J).  During stem insertion and subsidence testing, stem insertion energy for high density test blocks prepared with Control broaches was 14.53 ± 0.81 J, which was significantly lower than blocks prepared with TG1 (22.53 ± 1.04 J) or TG2 (19.38 ± 3.00 J) broaches. For stem subsidence testing in high density blocks, TG1 prepared blocks required the highest amount of energy to undergo subsidence (14.49 ± 0.49 J), which was significantly greater than test blocks prepared with Control (11.09 ±0.09 J) or TG2 (12.57 ± 0.81 J) broaches. CONCLUSIONS: The additional V-grooves in TG1 broaches demonstrated improved broaching performance while also generating press-fit envelopes that were more resistant to stem insertion and subsidence. TG1 broaches may prove useful in the clinical setting; however additional studies that more closely simulate clinical broach impaction are necessary prior to making widespread changes to THR broaches.

Radiographic and CT features of metallosis in a lame dog after total hip replacement: the cloud sign.

A 2-year-old female American Akita was referred for CT of the pelvis and hindlimbs due to a left hindlimb lameness after a left total hip replacement. Referral radiographs and CT images demonstrated amorphous soft-tissue and mineral opacities surrounding the proximal femur and the prosthetic stem, consistent with the "cloud sign" reported as a characteristic of metallosis in humans. Dorsomedial displacement of the prosthetic head, multiple foci of geographic osteolysis alongside the "cloud sign", presumed pseudotumor lesions, and medial iliac lymphadenopathy were also identified with CT. Metallosis was confirmed based on ultrasound-guided cytology, revision surgery, and histopathology.

Poor success rates with double pelvic osteotomy for craniodorsal luxation of total hip prosthesis in 11 dogs.

OBJECTIVE: To report the outcome of double pelvic osteotomy (DPO) for craniodorsal luxation of total hip replacement (THR). STUDY DESIGN: Retrospective case series. ANIMALS: Eleven client-owned animals. METHODS: Dogs with craniodorsal luxation of THR and high angle of lateral opening (ALO) were considered candidates for DPO. The ALO and the version angle (VA) were measured on pre- and post-DPO radiographs. Pre- and post-DPO ALO and VA were compared using a Wilcoxon signed-rank test. Clinical and radiographic outcomes were assessed at 2 and 6 months post-DPO. RESULTS: Eleven DPOs were performed on 11 dogs after THR luxation. The ALO was reduced from a median of 66.2° (range 37.3-73.1°) to 55.9° (range 13.2-60.0°) (p ≤ .001), and VA increased from a median of 25.6° (range 6.8-51.9°) to 35.3° (range 15.1-51.7°) (p ≤ .03). Craniodorsal luxation recurred in five dogs and was managed with closed reduction (one dog), capsulorrhaphy (one dog), or repositioning of the acetabular cup (three dogs). The median clinical follow-up duration was 19.7 months (range 3.4-73.0). In the long term, seven dogs required explantation (five aseptic loosenings, two infections) (median 8.2 months, range 2.6-50.6). CONCLUSION: Reluxation was frequent after DPO, 5/11 dogs requiring additional procedures, including three cup revisions. The long-term outcome was considered to be poor due to frequent explantation. CLINICAL SIGNIFICANCE: Double pelvic osteotomy may be considered to avoid cup replacement when managing craniodorsal THR luxations in dogs but is not recommended due to high complication rates.

Centerline canine cementless total hip arthroplasty as an alternative implant system; results in 17 dogs (2015-2020).

OBJECTIVE: To evaluate the clinical outcomes associated with the Biomedtrix Centerline canine cementless total hip arthroplasty implant (C-THA). ANIMALS: 17 dogs (20 hips) surgically implanted with C-THA to treat coxofemoral pathology. CLINICAL PRESENTATION AND PROCEDURES: Dogs with C-THA (2015 through 2020) with follow-up of ≥ 6 months were evaluated. Data included signalment, complications, management of complications, radiographs (bone implant interface), and clinical outcomes. Outcomes were assessed radiographically and subjectively via surgeon orthopedic examinations. RESULTS: 15 of 20 (75%) with long term radiographic follow-up had an excellent outcome. 5 hips (25%) had postoperative complications: femoral neck fracture (n = 1; 5%), aseptic loosening (2; 10%), and septic loosening (2; 10%). CLINICAL RELEVANCE: C-THA can restore function in dogs with coxofemoral pathology. This novel procedure showed outcomes comparable to initial reports of other traditional THA implants (cemented, cementless, and hybrid) but complications occurred at a higher rate than recent outcomes of other long-standing THA procedures. Increased case numbers and surgeon experience with this novel implant system may eventually yield results comparable to other accepted THA systems.

Outcomes and complications reported from a multiuser canine hip replacement registry over a 10-year period.

OBJECTIVE: To report outcomes and complications associated with total hip replacements (THR) using a multiuser canine hip registry (CHR) and owner-administered questionnaire. STUDY DESIGN: Prospective longitudinal clinical study. ANIMALS: Dogs (n = 1852). METHODS: Total hip replacement cases submitted to a CHR were reviewed. An online questionnaire including an adapted "Liverpool Osteoarthritis in Dogs" (LOAD) score was e-mailed to owners. Data were analyzed to determine associations between clinical variables and the agreement by veterinary surgeons and owners for complications. RESULTS: A group of 1329 (72%) dogs had unilateral THRs and another group of 523 (28%) dogs had bilateral THRs, resulting in 2375 THRs. Indications included hip dysplasia and osteoarthritis (n = 2028/2375, 85%). Implants were manufactured by Kyon (n = 1087, 46%), BioMedtrix CFX (n = 514, 22%), BioMedtrix hybrid (n = 264, 11%), BioMedtrix BFX (n = 221, 9%), and Helica (n = 107, 4.5%). Median veterinary surgeon and owner follow up were 1328 and 900 days respectively. Postoperative LOAD scores (21 ± 9) reported by 461 owners improved compared to preoperative scores (11 ± 9) (P < .001). Veterinary surgeons reported complications in 201/2375 (8.5%) THRs and owners in 107/461 (23%) THRs, with moderate agreement (weighted kappa = 0.44). No associations were identified between complications and weight, age, sex, or breed. BioMedtrix BFX and Helica implants were associated with increased complications (P = .031) when used for revisions of femoral head and neck excisions. CONCLUSION: Excellent outcomes, including improved canine mobility, were reported after THRs. Complications were underreported by veterinary surgeons compared to owners in this first multiuser CHR. CLINICAL SIGNIFICANCE: Canine THRs are safe, effective procedures but THR implants should be carefully selected when revising femoral head and neck excisions.

Clinical outcomes of canine total hip replacement utilizing a BFX lateral bolt femoral stem: 195 consecutive cases (2013-2019).

OBJECTIVE: To evaluate the clinical outcomes of total hip replacements (THR) utilizing a BFX lateral bolt stem in dogs with coxofemoral joint disease. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: A total of 149 dogs representing 195 THR. METHODS: Consecutive THRs utilizing a BFX lateral bolt stem were studied. Preoperative, immediate postoperative, 1-, 2-, 3-, 4-, and 12-month postoperative radiographs were performed. All major and minor complications, revisions, outcomes, subsidence, canal flare index (CFI) were recorded. RESULTS: An intraoperative complication rate of 11.8% was observed. The postoperative complication rate was 13.6%, with 9.2% major and 4.4% minor complications. Complications included: postoperative femur fractures (3.6%), coxofemoral luxation (3.6%), stem failure (0.5%), septic loosening (0.5%), aseptic loosening (0.5%), and acetabular fracture (0.5%). Three dogs underwent prophylactic plating after subjective assessment of cortical thickness. Five of 195 (2.6%) cases underwent explant of their prostheses (median = 3 months). Mean stem subsidence at 1 month postoperatively was 1.22 ± 0.16 mm. An increased CFI was associated with postoperative femur fractures (p < .05). A total of 190 of 195 (97.4%) cases returned to normal function in the long-term follow-up period. CONCLUSION: Use of the BFX lateral bolt stem resulted in minimal postoperative subsidence, a low femoral stem complication rate, and a high rate of achieving normal limb function. CLINICAL SIGNIFICANCE: The BFX lateral bolt stem should be considered in canine THR as the femoral failure rate is low and the long-term success rate is high.

Ex vivo postimplantation biomechanical properties of a press-fit cementless femoral stem with transfixation pin for canine total hip replacement.

OBJECTIVE: To compare ex vivo postimplantation biomechanical characteristics of 3 implants for canine total hip replacement: a cementless press-fit femoral stem with a pin in the femoral neck (p-pfFS), a press-fit cementless femoral stem without this pin (pfFS), and a cemented femoral stem (cFS). SAMPLE: 18 cadaveric femurs from 9 dogs. PROCEDURES: Femurs were assigned randomly to 3 groups, and biomechanical testing was performed by measuring vertical displacement during cyclic loading and resistance to failure with compression parallel to the longitudinal axis of the femur. Force-displacement curves were assessed for failure tests, and work necessary for failure was calculated. RESULTS: No significant differences were observed in vertical displacement during cyclic loading (P = .263) or work necessary for failure (P = .079). Loads to failure for cFS and p-pfFS implants were significantly greater than that for the pfFS, but no significant difference in load to failure was observed between cFS and p-pfFS implants (P = .48). CLINICAL RELEVANCE: Cementless femoral stems with a transfixation pin offer significantly greater immediate resistance to failure to compressive loads parallel to the longitudinal axis of the femur than standard cementless stems, and a level of stability comparable to that of cemented stems. p-pfFS implants may be valuable in total hip replacement, potentially reducing the risk of fracture during the early postoperative period prior to osteointegration.

Long-term follow up of 44 cats undergoing total hip replacement: Cases from a feline hip registry (2010-2020).

OBJECTIVE: To report indications, complications, and long-term outcomes following feline total hip replacement (THR) using a client-based clinical metrology questionnaire, the Feline Musculoskeletal Pain Index (FMPI), and owner satisfaction. STUDY DESIGN: Multi-institutional retrospective cohort study. ANIMALS: Cats (n = 44) that underwent THR (n = 56). METHODS: Feline THRs submitted to a registry over a 10-year period were reviewed. The FMPI and owner satisfaction surveys were used to assess outcome. RESULTS: Forty-four cats met the inclusion criteria. Median age was 2 years (range: 0.9-11), and median bodyweight 5 kg (range: 3.3-7.6). British Shorthair and Domestic Shorthair were the most frequent breeds. Most cats were neutered males (33/44) and slipped capital femoral epiphysis (SCFE) was the most common surgical indication (34/56). All implants were cemented micro and nano hip implants. Overall complications (11/56) included 9 major complications. The median duration of follow up was 752 days (range: 102-3089). No association was found between clinical variables and complications. The FMPI score improved from 0.111 (range: 0-1.222) to 2.111 (range: 0.888-3.666) postoperatively (P < .001). Owner satisfaction was reported as "very good" in 30/33 cases (90.9%). CONCLUSION: A validated client metrology questionnaire showed clinical improvement in cats following THR. The most common indication for THR in cats was SCFE occurring in young male neutered cats. Complication rates were comparable to previous reports. CLINICAL SIGNIFICANCE: Total hip replacement appears to be a successful surgical treatment for feline hip disease with very good owner satisfaction and acceptable complication rates.

Greater trochanter morphology and association with patient demographics, surgical factors, and post-operative stem position: a retrospective assessment of 150 cementless THRs in 135 dogs.

BACKGROUND: Total hip replacement (THR) in the gold standard surgical treatment for the canine hip. While it has been shown that greater trochanter morphology affects post-operative cementless stem position in humans, trochanter morphology and the effect on cementless stem position has not been extensively evaluated in dogs. The objective of this study was to classify greater trochanter morphology and identify potential associations between trochanter morphology and patient demographics, femoral canal geometry, surgical time, technique modifications, and post-operative stem position in client-owned dogs undergoing cementless THR. RESULTS: In this retrospective study, medical records and radiographs of 135 dogs undergoing 150 cementless total hip replacements from 2013 to 2020 were included. Trochanters were classified in the frontal plane using an ordinal grading system adapted from human THR. A Grade I trochanter denoted a trochanter positioned lateral to the periosteal surface of the lateral femoral cortex, whereas a Grade IV trochanter denoted a trochanter positioned medial to the anatomic axis of the femur. Associations between trochanter grade and other variables were examined using ANOVA, Kruskall-Wallis, or chi-squared tests. Significance was assumed at P ≤ .05. Trochanters were classified as follows: Grade I (44/150, 29.3%), Grade II (56/150, 37.4%), Grade III (44/150, 29.3%), Grade IV (6/150, 4.0%). Grade IV trochanters had lower anatomic lateral distal femoral angle (aLDFA; 91.0 ± 6.2°), angle of inclination (117.7 ± 10.5°), and canal flare index (1.53 ± 0.27). When compared to all groups, Grade IV trochanters were associated with longer surgical times (Grade IV: 227.0 ± 34.2 min; all grades: 183.2 ± 32.9 min) and technique modifications (Grade IV: 83.3%; all grades: 18%). Grade I trochanters had stems placed in valgus (- 1.8 ± 2.33°), whereas Grade II (0.52 ± 2.36°), III (0.77 ± 2.58°), and IV (0.67 ± 2.73°) trochanters exhibited varus stems. Depth of stem insertion was greater (11.2 ± 4.2 mm) for Grade IV trochanters. CONCLUSIONS: Trochanter grade was associated with post-operative stem alignment and translation in the frontal plane. Grade IV trochanters were associated with altered femoral geometry, increased surgical time, technique modifications, and stem insertion depth. Pre-operative greater trochanter classification may prove useful in identifying cases requiring prolonged surgical times or technique modifications.

Case factors for selection of femoral component type in canine hip arthroplasty using a modular system.

OBJECTIVE: To describe a femoral stem selection process based on case features in dogs treated with total hip replacement (THR) by an expert surgeon, compare complications between implant types, and develop an algorithm for stem type selection. STUDY DESIGN: Retrospective study. ANIMALS: 128 dogs, 135 THR. METHODS: Data collected included breed, age, weight, canal flare index (CFI), and implant type: cementless (BFX), cementless with a collared stem (BFX-C), hybrid (cementless acetabular component with cemented stem), and cemented (CFX). RESULTS: Of the 135 THRs, 69 BFX, 47 hybrid, and 18 BFX-C were performed. Dogs receiving hybrid (mean 5.5 years) were older than those receiving BFX (2.5 years, p < .0001) and BFX-C implants (2.5 years, p = .0014). The mean weights of dogs with hybrid, BFX, and BFX-C implants were 40.0, 31.0, and 35.3 kg, respectively, with dogs receiving hybrid heavier than those receiving BFX (p < .0001). Mean CFI for hybrid (1.52) was lower than for BFX (1.79, p < .0001) and BFX-C (1.76, p = .0021). Total complication rate was 14.0% with catastrophic complications in 1.5% and no association between implant type and risk of complications (p = .36). Femur fractures occurred in 2.9% of all cases and 1.1% of cementless THR cases. CONCLUSIONS: Dogs receiving hybrid THR were older with lower CFI than dogs receiving BFX and BFX-C and heavier than dogs receiving BFX. There was no difference in complications between groups. Catastrophic complications and femur fractures occurred less frequently compared to recent studies of BFX THR. CLINICAL SIGNIFICANCE: Careful preoperative assessment and implant selection can reduce complications of canine THR.

Outcome of canine cementless collared stem total hip replacement with proximal femoral periprosthetic cerclage application: 184 consecutive cases.

OBJECTIVE: To report outcomes of cementless collared stem total hip replacement (THR) with proximal femoral periprosthetic cerclage application in dogs. STUDY DESIGN: Retrospective case series. ANIMALS: Client-owned dogs (n = 150) with THR (n = 184). METHODS: Serial postoperative radiographs and medical records of dogs that underwent consecutive index cementless THR, with a single full cerclage wire placed distal to the femoral neck osteotomy line and proximal to the lesser trochanter, were reviewed for intraoperative and postoperative complications. RESULTS: No proximal femoral fractures occurred. No complications associated with the use of the cerclage wire were encountered. A fissure (n = 1) or fractures (n = 2) occurred near the tip of the femoral stem in three cases postoperatively. All three cases required plate and screw fixation. All dogs returned to subjectively normal function at home and all owners were satisfied with the outcome. CONCLUSION: A single full cerclage wire may minimize the risk of a proximal femur fracture following cementless collared stem total hip replacement in dogs. No complications were encountered with the cerclage wire. CLINICAL SIGNIFICANCE: Application of a cerclage wire is a simple and economically feasible procedure that requires minimal additional instrumentation, takes little time, and may decrease the risk of proximal femur fractures after cementless press-fit THR.

Short-Term Clinical Assessment of Hip Hemi-Arthroplasty in 11 Dogs.

OBJECTIVE: The aim of this study was to assess the short-term clinical outcome in dogs following a hip hemi-arthroplasty for the treatment of primary pathological disorders of the hip and as a salvage procedure following failure of the cup component of a total hip replacement. STUDY DESIGN: Medical records of dogs that had a unilateral hip hemi-arthroplasty performed between 2015 and 2020 were reviewed. Data collected included follow-up orthopaedic examinations performed at 0, 2, 8 and 52 weeks postoperatively, pelvic radiography at 0, 8 and 52 weeks postoperatively and an owner questionnaire (Helsinki chronic pain index [HCPI]). RESULTS: Eleven unilateral hip hemi-arthroplasty procedures were identified. The median age at time of surgery was 3.6 years (8 months-10 years) and the median follow-up time was 13 months (range: 2 months-3 years). The HCPI for all dogs at follow-up was median 8 ± 7.30 (range: 5-25). Total HCPI was < 12 for 7/10 dogs and ≥ 12 for 3 dogs. Pelvic radiographs at 1 year confirmed osteointergration of the femoral stem implant and no evidence of implant subsidence or progression of osteoarthritis. However, there was some evidence of mild lucency of the acetabular bed around the prosthetic femoral head and mild peri-acetabular sclerosis in four cases. CONCLUSION: Hip hemi-arthroplasty provides a clinically acceptable treatment for disabling disease of the coxofemoral joint with 10/11 patients achieving acceptable short-term clinical function. Long-term assessment of the hip hemi-arthroplasty and comparison with total hip replacement is indicated.

Effect of Stem Positioning on Biomechanical Performance of a Novel Cementless Short-Stem Canine Total Hip Implant.

OBJECTIVE: The aim of this study was to evaluate the effect of stem positioning on the biomechanical performance of a novel, collared, short-stem total hip implant under compression and torsion ex vivo. STUDY DESIGN: Six canine cadaveric femurs were implanted with a collared short-stem femoral implant. Canal flare index (CFI), stem angle, absolute and relative cut heights and relative size were measured radiographically and used as independent variables. Biomechanical performance of the construct was evaluated using physiologic loading (loading) and supraphysiologic loading (failure) protocols. RESULTS: During loading protocols, compressive stiffness was influenced by absolute cut height (p = 0.018). During failure protocols, peak torque was influenced by CFI (p = 0.004) and craniocaudal relative size (p = 0.005). Peak load and torsional stiffness were not impacted by any of the radiographic variables (p > 0.05). Three of six femurs developed longitudinal fractures originating at the medial calcar at the time of failure. CONCLUSION: The biomechanical performance of the collared short-stem implant was positively impacted by preserving more of the femoral neck, having a higher CFI and using a smaller implant size relative to the femoral neck isthmus.

Ventral acetabular augmentation for management of caudoventral luxation following total hip replacement in dogs.

OBJECTIVE: To report ventral acetabular augmentation with an internal fixator for management of caudoventral luxation following total hip replacement in dogs and to report clinical outcomes. MATERIALS AND METHODS: Clinical records from three UK-based referral hospitals were reviewed retrospectively between 2010 and 2020 to identify dogs with caudoventral hip luxation managed by ventral acetabular augmentation. Hip prosthesis component orientation was radiographically assessed to identify potential risk factors associated with the luxation. Clinical and radiographic assessments were performed at short-term (≤12 weeks) and long-term (>12 months) follow-up and all complications were recorded. A standardised owner telephone questionnaire was used to assess long-term outcomes when a clinical assessment was unavailable. RESULTS: Nine dogs were included. Risk factors contributing to the luxation could not be defined. Implants used included a string-of-pearls plate (6/9), a polyaxial locking plate combined with a polyethylene implant (1/9) or a polyethylene implant alone (2/9). Complications occurred in two of nine dogs, including recurrent luxation and femoral stem loosening; both dogs had received a polyethylene implant alone, of which one received explantation of the hip prosthesis. Median long-term follow-up was 39 months (range 13.5-62). Seven dogs who received a ventral acetabular plate achieved full function of the operated limb and the overall outcome was good for eight dogs. Follow-up radiographs revealed stable hip prostheses in dogs who received a ventral plate, with the longest assessment at 37 months postoperatively. Owner satisfaction was good for all cases. CLINICAL SIGNIFICANCE: Ventral acetabular augmentation can successfully manage caudoventral luxation following total hip replacement in dogs.

Evaluation of a novel method to calculate cementless femoral stem level on craniocaudal projection radiographs.

OBJECTIVE: To assess the accuracy of a proportion-corrected radiographic cementless femoral stem level calculation in a cadaver model. STUDY DESIGN: Cadaveric study. SAMPLE POPULATION: Twelve cadaveric canine femurs. METHODS: Cementless femoral stems were implanted in 12 cadaver femurs at three stem levels. Craniocaudal projection radiographs of the implanted femurs were obtained at 0°, 10°, 20°, 30°, and 45° angulations in the sagittal plane (relative to the radiographic plate) and at 0°, 15°, and 30° internal and external axial rotation. A proportional calculation including actual stem length, radiographically measured stem length, and radiographically measured stem level relative to the greater trochanter (uncorrected stem level) was solved to yield a corrected stem level. The errors of the stem level measurements were compared. RESULTS: With 0° or 15° of internal rotation, the true stem level differed by more than 0.5 mm from corrected stem level in 2 of 30 tested femoral positions. It differed from the uncorrected stem level in 10 of 30 positions. With 15° and 30° external rotation or 30° internal rotation, the corrected stem level was not more accurate than the uncorrected stem level for any femoral position. CONCLUSION: Use of a proportion correction minimized variability in the stem-level measurements due to sagittal angulation (up to 30°) of the femur at 0° or 15° of internal rotation. CLINICAL SIGNIFICANCE: A proportion correction can improve the accuracy of femoral stem-level assessment on craniocaudal projection radiographs, which may aid in the detection of subsidence after cementless total hip replacement.

Zurich Cementless Dual Mobility Cup for Canine Total Hip Prosthesis: Implant Characteristics and Surgical Outcome in 105 Cases.

Dislocation after total hip arthroplasty (THA) remains a troublesome complication, and a source of frustration for the owner and the surgeon. The dislocation rate of hip prostheses in dogs is reported to range from 4 to 15%, representing the most common short-term complication. This is especially true in large and giant breed dogs, usually requiring revision surgery. With the increase in the number of THA being performed in veterinary surgery, reducing or preventing complications such as postoperative THA dislocation will be of paramount importance. The Zurich cementless dual mobility (DM) system allows impingement-free range of angulation of 80 to 132 degrees between the ceramic head and the polyether ether ketone (PEEK) cup when combined with the range of the PEEK cup in the outer metal cup. In this article, we review the use of the DM cup in THA in large and giant breed dogs, in terms of its history, biomechanics, outcomes and complications based on 105 cases.

Measurement of Acetabular Component Position in Total Hip Arthroplasty in Dogs: Comparison of a Radio-Opaque Cup Position Assessment Device Using Fluoroscopy with CT Assessment and Direct Measurement.

OBJECTIVES: The aim of this study was to compare measurements of angle of lateral opening (ALO) and version determined using a radioopaque cup position assessment device imaged with fluoroscopy to measurements obtained by CT and direct measurement in a cadaveric model. Our null hypothesis was that there would not be any difference in the angles measured by the techniques. METHODS: Six cadavers were implanted with BFX acetabular components. The CPAD was placed and images were obtained with fluoroscopy. Measurements were obtained from the radiopaque marker bars on the CPAD device, and version and ALO were calculated. The ALO and version were determined by CT and DM. Comparisons were made using a two-way analysis of variance and a generalized linear model procedure analysis. RESULTS: There were no significant differences between the measurements for ALO (p = 0.275) or version (p = 0.226). Correlation between methods was 0.948 and 0.951 for ALO and version, respectively. The mean difference (standard deviation [SD], and 95% confidence interval [CI]) for ALO were: CT versus CPAD 1.85 degrees (± 2.32 degrees [-2.99-3.31]), CT versus DM 1.96 degrees (± 1.99 degrees [-2.2-4.27]), CPAD versus DM1.74 degrees (±2.21 degrees [-1.13 and 5.24]). The mean difference (SD [CI]) for version was CT versus CPAD 2.86 degrees (±1.56 degrees [ -2.63-1.69]), CT versus DM 1.10 degrees (±1.42 degrees [-1.57-2.09]), CPAD versus DM 1.07 degrees (±0.76 degrees [0.13-2.09]). CLINICAL RELEVANCE: The results demonstrate that intraoperative imaging in cadaveric specimens with the CPAD is an accurate method to determine ALO and version of the acetabular component.

Treatment Outcomes for Periprosthetic Femoral Fractures in Cementless Press-Fit Total Hip Replacement.

OBJECTIVE: The aim of this study was to report outcomes in dogs with periprosthetic femoral fractures associated with a press-fit cementless femoral total hip replacement implant. MATERIALS AND METHODS: Electronic medical records and digital radiographs were used to identify dogs with periprosthetic femoral fractures associated with press-fit cementless total hip replacement. Data collected included signalment, weight, time of fracture, cause of fracture, presence of intra-operative fissure, fracture type, repair technique, and clinical and radiographic outcomes. Long-term patient outcome was assessed by communication with owners or referring veterinarians. RESULTS: Twenty-eight dogs with femoral fracture repair associated with cementless press-fit total hip replacement were identified. Eight of the fractures occurred intraoperatively and 20 occurred at a median of 2 days postoperatively. An oblique or spiral configuration was noted in 19 cases and 15 occurred at the distal end of the femoral stem (type B), with thirteen type B1, one type B2 and one type B3 fractures. Fractures were repaired with non-locking (18/28) or locking-plate fixation (10/28). Cerclage wire was applied around the plate and proximal bone segment in 17/28 dogs. Major complications occurred in 7/28 cases (five deep infection, two mechanical failures). Bone healing was noted in 21/23 cases, for which follow-up radiographic interpretation was available. Return to function was complete in 17 cases, acceptable in 8 cases and unacceptable in 3 cases. CONCLUSIONS: While cementless total hip replacement periprosthetic femoral fractures can be successfully repaired with lateral plate fixation, the risk of infection appears to be high.