Finite element study on post-screw removal stress in toy poodle radius with different plate designs and screw arrangements.

Background: The study employs finite element analysis to investigate stress distribution in the radius of toy poodles after screw removal. The examination focuses on the biomechanical implications of varied screw hole configurations using 1.5 and 2.0-mm locking compression plates (LCPs) with notched head T-Plates. Aim: To provide a noninvasive approach to analyzing the immediate consequences of screw removal from the radius bone in toy poodles. Specifically, it explores the impact of varied plate designs and screw arrangements on stress distribution within the forelimb bones. Methods: The study constructs a three-dimensional bone model of the toy poodle's forelimb based on computed tomography (CT) images. Simulations were designed to replicate jumping and landing from a 40 cm height, comparing stress distribution in the radius post-screw removal. Results: The analysis reveals significant variations in stress distribution patterns between the two LCPs. The radius implanted with the 2.0-mm LCP displays a uniform stress distribution, contrasting with the 1.5-mm plates. Localized stress concentration is observed around the screw holes, while trabecular bone regions near the screw holes exhibit lower stress levels. Conclusion: The study highlights the plate designs and screw configurations that affect bone stress in toy poodle forelimbs post-screw removal. The findings provide valuable insights for veterinarians, aiding informed decisions in veterinary orthopedic practices.

Successful centralisation technique for treatment of post-traumatic absence of the radial shaft in a dog.

This report describes a centralisation procedure for the treatment of a radial non-union, characterised by extensive bone loss and an intact ulna, in an 18-month-old toy poodle. A lateral approach to the radius/ulna shafts was realised and, after debridement of the non-union site, an ulnar osteotomy was performed proximal to the styloid process of the ulna. Transposition of the distal fragment of the radius to the distal end of the osteotomised proximal segment of the ulna was performed and the stabilisation was obtained using a locking plate with proximal screws in the ulnar shaft and distal screws in the radius epiphysis. The patient achieved bone union in 10 weeks and the last evaluation, performed 112 weeks postoperatively, showed a full return to pre-injury function. Based on the results of this report, the centralisation was effective in the treatment of post-traumatic absence of the radial shaft in a dog.

Influence of screw configuration on reduction and stabilization of simulated complete lateral condylar fracture in equine limbs.

OBJECTIVE: To determine the influence of screw configuration on the reduction and stabilization of simulated complete lateral condylar fracture. STUDY DESIGN: Randomized experimental crossover study. METHODS: A lateral condylar fracture was simulated in 18 cadaver limbs from nine horses. Each limb underwent repair with 4.5 mm diameter cortex screws, tightened to 4 Nm, in a linear and triangular configuration. Computed tomography (CT) of each repair was performed with the limbs in unloaded and loaded conditions. Fracture gaps were measured at the dorsal, palmar, and middle locations of the third metacarpal condyle. Fracture gap measurements were graded 0-4, based on voxels. Following descriptive analysis, a Bayesian network (BN) model was fitted to the data. RESULTS: The median fracture grade was 0 (range: 0-4) for unloaded linear repairs and 2 (0-4) for loaded linear repairs. The median fracture grade was 0 (0-3) for unloaded triangular repairs and 1 (0-3) for loaded triangular repairs. Bayesian network sensitivity analysis showed that the construct configuration reduced the uncertainty in the measured fracture outcome by 0.8%. CONCLUSION: Triangular screw configuration resulted in better fracture reduction and stability in comparison with linear screw configuration. However, the BN sensitivity analysis results showed that the effect of construct configuration on fracture outcome was weak. CLINICAL SIGNIFICANCE: These findings indicate a low probability that triangular repair of lateral condylar fracture will result in improved outcomes, when compared with linear repair.

Fluoroscopically-assisted closed reduction and percutaneous fixation of sacroiliac luxations in cats using 2.4 mm headless cannulated compression screws: Description, evaluation and clinical outcome.

OBJECTIVE: To describe fluoroscopically-assisted closed reduction and percutaneous fixation of sacroiliac-luxation (SIL) in cats and report radiographic results and long-term functional outcomes. STUDY DESIGN: Retrospective clinical study. ANIMALS: Eleven cats. METHODS: Percutaneous fixation of 17 SILs in 11 cats was performed with 2.4 mm headless cannulated compression screws under fluoroscopic guidance. Luxation-reduction, screw placement and purchase within the sacral body, pelvic canal diameter ratio (PCDR) and hemipelvic canal width ratio (HCWR) were assessed on pre- and postoperative radiographs. Radiographic follow-up was performed to assess the same parameters when available. Long-term clinical outcome was evaluated with an owner questionnaire. Wilcoxon paired-test was performed for comparison. RESULTS: Mean age and bodyweight of the cats were 3.3 ± 2.6 years and 4.0 ± 0.82 kg, respectively. Nine cats presented with concurrent pelvic injuries. Median luxation-reduction was 94.1% (IQR = 13.9) and median screw-purchase within the sacral body was 73.3% (IQR = 17.0) immediately postoperatively. One screw exited the sacral body caudally. Upon 7-week radiographic follow-up, luxation-reduction (88.3%, IQR = 20.1) and screw-purchase (70.7%, IQR = 12.8) had decreased compared to immediately postoperatively (p = .008 and p = .013 respectively). Screw migration was not observed. PCDR and HCWR measured on postoperative radiographs indicated successful restoration of the pelvic canal width. Owners reported an excellent long-term functional outcome (mean postoperative time: 19 ± 5 months). CONCLUSION: Fluoroscopically-assisted closed reduction and fixation of feline SIL using 2.4 mm headless cannulated compression screws allowed good reduction and optimal screw purchase within the sacral body. An excellent functional outcome was reported. CLINICAL SIGNIFICANCE: Minimally invasive reduction and fixation with headless compression screws should be considered in cats with SIL.

Medial versus lateral transcondylar screw placement for canine humeral intracondylar fissures: A randomized clinical trial.

OBJECTIVE: To determine the influence of screw direction on complications following transcondylar screw placement for the treatment of canine humeral intracondylar fissures (HIFs). STUDY DESIGN: Equivalence, parallel group, randomized clinical trial. SAMPLE POPULATION: Fifty-two client owned dogs (73 elbows). METHODS: Transcondylar screw placement was randomized to either a medial or lateral approach. The primary outcome was the incidence of postoperative complications. RESULTS: There were 37 cases in the lateral approach group and 36 cases in the medial approach group. There was a significantly greater proportion of postoperative complications following placement of transcondylar screws from a lateral to medial direction (p = .001). There were seven cases with complications (19%) in the medial approach group versus 23 cases with complications (62%) in the lateral approach group. The majority of complications were seromas (n = 13) and surgical site infections (n = 16) with 4 complications requiring further surgery. Implant area moment of inertia (AMI), normalized to bodyweight, was lower in dogs with a major complication (p = .037). CONCLUSION: Transcondylar screws placed from lateral to medial for canine HIFs had a greater proportion of postoperative complications in this randomized clinical trial design. Implants with a lower AMI, relative to bodyweight, were more likely to lead to major complications. CLINICAL SIGNIFICANCE: We recommend placing transcondylar screws from medial to lateral for canine HIFs to reduce the risk of postoperative complications. Relatively small diameter implants had an increased risk of major complications.

Biomechanical Comparison of Double 2.3-mm Headless Cannulated Self-Compression Screws and Single 3.5-mm Cortical Screw in Lag Fashion in a Canine Sacroiliac Luxation Model: A Small Dog Cadaveric Study.

OBJECTIVE: The aim of this study was to evaluate the feasibility of safe positioning of double 2.3-mm headless cannulated self-compression screws (HCS) in a small dog cadaveric sacroiliac luxation model and to compare the static rotational biomechanical properties of fixation repaired using two different screw systems with a minimally invasive osteosynthesis technique: double 2.3-mm HCS and a single 3.5-mm standard cortical screw placed in a lag fashion. STUDY DESIGN: A unilateral small dog sacroiliac luxation model was stabilized using double 2.3-mm HCS (n = 11) or a single 3.5-mm cortical screw (n = 11). Radiographic and computed tomography (CT) imaging analyses and biomechanical testing of rotational force on the sacroiliac joint of both fixations were performed. The maximum load at failure and failure modes of each fixation were recorded and compared. RESULTS: Fluoroscopically guided percutaneous application of double HCS was safe in a unilateral sacroiliac luxation model in small dogs without violation of the vertebral and ventral sacral foramen. Furthermore, resistance to rotational force applied on fixation of the sacroiliac joint repaired with double 2.3-mm HCS estimated by maximum failure load was significantly higher than that of a single 3.5-mm cortical screw (p < 0.001). CONCLUSION: Although this was an experimental cadaveric study, based on our results, the use of smaller double HCS may be beneficial as an alternative to the conventional single lag screw for stabilization of sacroiliac luxation in small dogs.

Arthroscopically guided lag screw fixation of subchondral bone cysts in the medial femoral condyle in Thoroughbred racehorses: description of technique and comparative results.

OBJECTIVE: To describe an arthroscopically guided technique for lag screw placement across subchondral bone cyst (SBC) in the medial femoral condyle (MFC) and to compare postoperative racing performance with corticosteroid injection and cyst debridement. STUDY DESIGN: Retrospective cohort study. ANIMALS: One hundred twenty-three horses with 134 MFC SBCs undergoing treatment at a single referral hospital in the UK between January, 2009, and December, 2020. METHODS: Sex, age, limb affected, radiographic cyst dimensions, preoperative and postoperative lameness, surgical technique (lag screw placement, cyst debridement, intralesional corticosteroid injection), and, where applicable, screw positioning were recorded retrospectively. A ratio was calculated using measurements from preoperative and postoperative radiographs. Outcome was assessed by resolution or improvement in lameness, reduction in cyst size, and starting one race after treatment. Outcome data was compared between treatment groups. RESULTS: Twenty-six of 45 (57.8%) horses that underwent transcondylar screw placement raced postoperatively, at a median of 403 days between surgery and first postoperative race. There was no difference between treatment groups with regard to racing or preoperative and postoperative lameness. Cysts treated with transcondylar screw placement had a greater reduction in cyst size and a reduced period of convalescence in comparison with those that underwent debridement; the results were similar to those treated by intralesional corticosteroid injection. CONCLUSION: Postoperative racing rates were similar for all techniques. Convalescence was reduced for lag screw placement and corticosteroid injection compared to debridement. CLINICAL SIGNIFICANCE: The arthroscopically guided technique results in radiographically consistent screw placement and cyst engagement and offers a viable alternative to other treatments.

Biomechanical comparison of titanium alloy additively manufactured and conventionally manufactured plate-screw constructs.

AIM: To biomechanically compare the bending stiffness, strength, and cyclic fatigue of titanium additively manufactured (AM) and conventionally manufactured (CM) limited contact plates (LCP) of equivalent dimensions using plate-screw constructs. METHODS: Twenty-four 1.5/2.0-mm plate constructs (CM: n = 12; AM: n = 12) were placed under 4-point bending conditions. Data were collected during quasi-static single cycle to failure and cyclic fatigue testing until implants plastically deformed or failed. Bending stiffness, bending structural stiffness, and bending strength were determined from load-displacement curves. Fatigue life was determined as number of cycles to failure. Median test variables for each method were compared using the Wilcoxon rank sum test within each group. Fatigue data was also analysed by the Kaplan-Meier estimator of survival function. RESULTS: There was no evidence for a difference in bending stiffness and bending structural stiffness between AM and CM constructs. However, AM constructs exhibited greater bending strength (median 3.07 (min 3.0, max 3.4) Nm) under quasi-static 4-point bending than the CM constructs (median 2.57 (min 2.5, max 2.6) Nm, p = 0.006). Number of cycles to failure under dynamic 4-point bending was higher for the CM constructs (median 164,272 (min 73,557, max 250,000) cycles) than the AM constructs (median 18,704 (min 14,427, max 33,228) cycles; p = 0.02). Survival analysis showed that 50% of AM plates failed by 18,842 cycles, while 50% CM plates failed by 78,543 cycles. CONCLUSION AND CLINICAL RELEVANCE: Additively manufactured titanium implants, printed to replicate a conventional titanium orthopaedic plate, were more prone to failure in a shorter fatigue period despite being stronger in single cycle to failure. Patient-specific implants made using this process may be brittle and therefore not comparable to CM orthopaedic implants. Careful selection of their use on a case/patient-specific basis is recommended.

Outcomes for 15 cats with bilateral sacroiliac luxation treated with transiliosacral toggle suture repair.

OBJECTIVE: To report a surgical technique and outcomes of transiliosacral toggle suture repair to treat feline bilateral sacroiliac luxation/fracture (SILF). STUDY DESIGN: Retrospective study. ANIMALS: Fifteen client-owned cats. METHODS: The medical records of cats with bilateral SILF treated using a transiliosacral toggle suture repair were reviewed. Short- and medium-term outcomes were assessed through standard postoperative clinical evaluation and radiographs, including measurements of angle of deviation (AoD), percentage of reduction (PoR), and pelvic canal width ratio (PCWR). Long-term functional follow up was obtained from a questionnaire derived from the Feline Musculoskeletal Pain Index (FMPI). RESULTS: Fifteen cats were enrolled retrospectively, among which 13 survived to discharge. One minor wound complication, treated by secondary intention healing, was encountered. No major complication was reported. Immediately postoperatively, the mean absolute PoR values were 88.1 ± 11.2% and 91 ± 11.6% on the right and left side, respectively. The mean absolute AoD was 3.1 ± 2.8°, and the mean PCWR was 1.24 ± 0.08. The medium-term radiographic follow up at a median of 205 (71-682) days postsurgery revealed the good stability of the repair. Excellent functional outcomes were identified upon the analysis of 12 long-term questionnaires at a median of 365 (119-798) days postsurgery. CONCLUSION: Anatomic reduction was satisfactory and comparable with previously described techniques with good implant placement documented. Functional outcomes based on FMPI-derived questionnaires were good to excellent in our population. CLINICAL SIGNIFICANCE: Transiliosacral toggle suture stabilization of bilateral SILF was associated with good outcomes in cats. Further studies are required to compare biomechanical properties and outcomes between this technique and previously described transiliosacral stabilization.

Evaluation of a 3-D printed drill guide to facilitate fluoroscopic-assisted Kirschner wire placement for minimally invasive iliosacral screw placement in dog cadavers.

OBJECTIVE: To evaluate the ease and accuracy of using a 3-D printed (3-DP) drill guide to insert Kirschner wires through the ilium and into the sacral body in preparation for minimally invasive iliosacral screw placement in dog cadavers. ANIMALS: 10 dog cadavers weighing 20 to 30 kg (mean ± SD, 24.5 ± 5 kg). METHODS: Kirschner wires were placed using a limited approach to the lateral ilium. Fluoroscopy was used in freehand and 3-DP drill guide application groups to facilitate the placement of a 1.0-mm Kirschner wire that was over-drilled using a 2.5-mm cannulated drill bit. Kirschner wires were placed using a 3-DP drill guide on 1 hemipelvis and freehand wire placement was done on the contralateral hemipelvis. Postprocedural CTs were obtained, and 2-D and 3-D analyses were performed. The Student t-test and Wilcoxon rank sum test were used to compare groups. A Pearson correlation coefficient was performed to evaluate the in-group correlation. RESULTS: Likert scores that assessed the ease of the procedure were significantly greater (P = .04) and the incision length was significantly shorter (P = .016) in the 3-DP drill guide group compared with the freehand group. The time of the procedure, the number of attempts to obtain accurate Kirschner wire placement, and fluoroscopy images did not differ (P > .05) between application groups. Drill tracks were primarily confined to the sacral body, with minor projected screw thread cortical breeches occurred in 1 cadaver in the freehand group and 2 cadavers in the 3-DP drill guide group. CLINICAL RELEVANCE: The 3-DP drill guide simplified appropriate iliosacral Kirschner wire placement through a smaller incision compared with freehand drilling and would appear to be an efficient, practical instrument to facilitate accurate fluoroscopic-assisted screw placement when stabilizing sacroiliac luxations in dogs.

Biomechanical comparison of compact versus standard flute drill bits, and interlocking versus buttress thread self-tapping cortical bone screws in cadaveric equine third metacarpal condyle.

OBJECTIVES: To compare (1) performance of compact versus standard flute drill bits, (2) screw insertion properties and (3) pullout variables between interlocking thread (ITS) and buttress thread (BTS) self-tapping screws in third metacarpi. STUDY DESIGN: In vitro experimental study. SAMPLE POPULATION: Paired third metacarpi from 11 Thoroughbreds aged 2-4 years. METHODS: Screws were inserted into the lateral condylar fossae following bone preparation using the respective drill bit for each screw type. Screw pullout was achieved using a mechanical testing system. Density and porosity of bone surrounding screw holes was measured with microcomputed tomography following each pullout test. Drilling, screw insertion and pullout variables were compared between drill bit and screw types using repeated measures ANOVA. Linear regression analyses were used to characterize relationships between bone tissue properties and drill bit and screw outcomes. RESULTS: Maximum torque power spectral density (PSD) was lower for compact flute drill bits. Insertion torque was 50% higher for ITS. BTS had 33% greater preyield stiffness and 7% greater mean yield force. Bone tissue properties affected measured variables similarly for both screw and drill bit types. CONCLUSIONS: Lower torque PSD may increase durability of the compact flute drill bit. ITS had greater insertional torque, which may reflect greater bone engagement. BTS had greater resistance to axial pullout forces. CLINICAL SIGNIFICANCE: Metacarpal bone provides a simple model for comparison of drill bit and screw designs. Use of ITS to repair equine fractures subject to predominantly tensile forces is not justified based on the results of this study.

Ex-vivo biomechanical analysis of an original repair of canine calcaneal tendon rupture using a synthetic implant as mechanical support fixed by sutures in the proximal tendinous part and by an interference screw in the bone distal part.

Background: Rupture of the common calcaneal tendon is the second most frequent tendon rupture in dogs and may lead to severe lameness and pain. Surgical repair consists of re-apposition of the damaged tendon ends using sutures, but this type of repair is not always possible especially if the tendon has retracted. Tendon augmentation with an ultra-high molecular weight polyethylene (UHMWPE) implant is a recent solution to support the sutures and allow the repair of the canine calcaneal tendon. However, its biomechanical fixation strength remains untested for this pathology. Aim: To evaluate the biomechanical fixation strength of a UHMWPE implant for the repair of the canine calcaneal tendon. Methods: Ex-vivo biomechanical study was carried out on eight cadaveric hindlimbs from four adult dogs. Hindlimbs were tested under two independent modalities: proximal tendinous fixation (PTF) and distal calcaneus fixation (DCF), using a testing machine. PTF was achieved by eight simple interrupted polypropylene sutures performed through the UHMWPE implant. The latter was sandwiched inside the gastrocnemius tendon, which had previously been incised over about 5 cm longitudinally, and through the tendon of the superficial digital flexor. DCF was performed using an interference screw, which locked the UHMWPE implant into a calcaneus tunnel drilled perpendicularly. Results: Yield, failure load, and linear stiffness (mean ± SD) for the DCF modality were 920 ± 139 N, 1,007 ± 146 N, and 92 ± 15.21, respectively, which were greater than for the PTF modality (663 ± 92 N, 685 ± 84 N and 25.71 ± 5.74, respectively, p < 0.05). Failure modes were different between fixation modalities: for PTF it was suture breakage (n = 7/8), while for DCF it was implant damage and slippage (n = 8/8). Conclusion: The biomechanical fixation strength of the UHMWPE implant was greater for DCF than that of PTF, and should be suitable for calcaneal tendon repair in dogs. The clinical prediction of rupture of this calcaneal tendon repair will occur at the level of the PTF.

Biomechanical Comparison of Cortical Lag Screws and Cortical Position Screws for Their Generation of Interfragmentary Compression and Area of Compression in Simulated Lateral Humeral Condylar Fractures.

OBJECTIVE: The aim of this study was to compare the interfragmentary compressive force and area of compression generated by cortical screws inserted as either a lag screw or position screw in simulated lateral humeral condylar fractures. STUDY DESIGN: Ex vivo biomechanical study. MATERIALS AND METHODS: Thirteen pairs of cadaveric humeri from skeletally mature Merinos with simulated lateral humeral condylar fractures were used. Pressure sensitive film was inserted into the interfragmentary interface prior to fracture reduction with fragment forceps. A cortical screw was inserted as a lag screw or a position screw and tightened to 1.8Nm. Interfragmentary compression and area of compression were quantified and compared between the two treatments groups at three time points. RESULTS: After fracture reduction using fragment forceps (Time point 1: T1), there was no significant difference in interfragmentary compression and area of compression between the two treatments. A combination of fragment forceps and a cortical screw inserted as a lag screw (Time point 2: T2) produced significantly greater interfragmentary compression and area of compression compared with the same screw inserted as a positional screw. After removal of the fragment forceps, leaving only the cortical screw (Time point 3: T3), both the interfragmentary compression and area of compression remain significantly greater in the lag screw group. CONCLUSION: Lag screws generate a greater force of compression and area of compression compared with position screws in this mature ovine humeral condylar fracture model.

Correlation between the Insertion Side of a Transcondylar Screw for the Surgical Management of Humeral Intracondylar Fissures in Dogs and the Incidence of Postoperative Surgical Site Infection.

OBJECTIVE: An increased rate of surgical site infection (SSI) following treatment of canine humeral intracondylar fissure (HIF) with a lateromedially (LM) placed transcondylar screw (TCS) compared with a mediolateral (ML) TCS has been previously postulated. We hypothesized that the direction of insertion of the TCS would not affect the incidence of postoperative SSI. STUDY DESIGN: It was single-centre retrospective study. Dogs with HIF confirmed by computerized tomography, treated by TCS placement (between 2008 and 2019) and with a minimum follow-up of 12 weeks, were included. The following data were recorded: signalment, presenting clinical signs, direction of placement and size of the utilized TCS, surgical and anaesthetic times, concurrent surgical procedures, presence of concomitant elbow pathology, perioperative and postoperative antibiotic usage and postoperative complications. Recorded data were analysed with a multinomial logistic regression model with a p-value less than or equal to 0.05. RESULTS: Thirty-five dogs (46 elbows) met the inclusion criteria. Median clinical follow-up interval was 52 weeks. Seven of thirty-one elbows with a ML TCS, and 4/15 elbows with a LM TCS developed SSI. Four of nine dogs that underwent bilateral single-surgery TCS placement developed SSI unilaterally. CONCLUSION: No significant difference was shown in short-term SSI occurrence between the ML and the LM direction of placement of the TCS.

The Surgical Repair of a Salter-Harris Type-2 Physeal Fracture of the Proximal Phalanx in a Foal.

A 6-month-old thoroughbred colt foal was referred to a private equine referral hospital for evaluation of an acute onset, left hind limb lameness. On arrival the foal was 4/5 lame on the left hind at walk and there was diffuse swelling of the left hind pastern and fetlock region. The physical exam was otherwise unremarkable. Digital radiographs of the left hind pastern identified a Salter-Harris type-2 physeal fracture of the proximal phalanx. The fracture was initially treated conservatively using a cast, but the immobilization was not sufficient at achieving adequate reduction. As a result, the fracture was stabilized surgically using a construct consisting of a cortical lag screw, four locking head screws and a locking T-plate. The foal recovered uneventfully and was sound and in race training at a 2 year follow up. This case report highlights that surgical repair via internal fixation is preferable to conservative management of proximal physeal fractures of the first phalanx.

The effect of an aiming device on the accuracy of humeral transcondylar screw placement.

OBJECTIVES: (1) To evaluate the accuracy of an aiming device on placement of humeral transcondylar screws compared to fluoroscopic methods. (2) To compare experience level on outcome. STUDY DESIGN: Randomized, match pair, prospective ex-vivo study. SAMPLE POPULATION: A total of 68 dogs. METHODS: Canine cadaveric forelimbs were randomly assigned to either aiming device or fluoroscopic-guided groups, and to diplomate or resident. Digital radiography was used to evaluate screw trajectory deviation and eccentricity on the humeral condyle. Procedure time, outcome based on experience, and complications were recorded. RESULTS: The aiming device screw trajectory angle was decreased in the right limb (1.9 ± 1.1°) compared with the left (3.6 ± 1.1°, p = .0178), and compared to fluoroscopy (3.4 ± 1.1° p = .0128). There was no difference between leg laterality with fluoroscopy (p = .9979). Trajectory angle was increased with resident versus diplomate (3.4 ± 1.1° and 2.5 ± 1.1° respectively, p = .0366). Eccentricity deviation was decreased using fluoroscopy versus aiming device (3.1 ± 0.36 mm, 4.2 ± 0.36 mm, respectively, p = .0017). The risk of joint involvement was 8 times greater in aiming device groups, though not significant (p = .0575). Significant complications included increased drill attempts in fluoroscopic groups (p = .0237). CONCLUSION: The aiming device provided accurate placement of transcondylar screws, in terms of both position on the condyle and trajectory angle. Results were similar to fluoroscopic-guided method. CLINICAL SIGNIFICANCE: An aiming device is an acceptable means of placing humeral transcondylar screws. The use of the aiming device had an eight times increased risk of joint involvement compared to fluoroscopy.

Minimally Invasive Arthrodesis of the Equine Proximal Interphalangeal Joint: A Biomechanical Comparison of Three 5.5-mm Cortical Screws Inserted in Lag Fashion and Two 7.0-mm Headless Cannulated Dual-Pitch Compression Screws.

OBJECTIVE: The aim of this study was to compare the biomechanical properties of two minimally invasive arthrodesis techniques of the equine proximal interphalangeal (PIP) joint (three transarticular 5.5-mm cortical screws [AO-3TLS] vs. two transarticular 7.0-mm headless cannulated multi-use compression screws [MUC-2TS]) in dynamic non-destructive testing and compression testing to failure. STUDY DESIGN: The experimental study included six pairs of cadaveric adult equine forelimbs; one limb from each horse was randomly assigned to one of the treatments, and the contralateral limb was submitted to the remaining treatment. The dynamic test was performed alternating non-destructive compression tests at a displacement rate of 5 mm/min up to 5,000 N and sinusoidal compressive cyclic tests at 6 Hz, using a 3,600-N amplitude for 8,550 cycles. Construct stiffness and maximum sagittal plane rotation about the PIP joint markers were determined during the dynamic test. After the dynamic test reached 136,800 cycles, the monotonic compressive test until failure was performed on each construct: load, displacement and sagittal plane rotation about the PIP joint marker at failure were analysed. RESULTS: The evaluated biomechanical properties showed no statistical difference between the AO-3TLS and MUC-2TS treatment groups in any of the ramps of the dynamic non-destructive test and in the compression loading until failure test. CONCLUSION: The MUC-2TS treatment produced biomechanical properties equivalent to the AO-3TLS treatment for PIP joint arthrodesis.

Proximal femoral deformity correction and total hip arthroplasty in a dog using 3D printed custom guides.

OBJECTIVE: To report the successful correction of a proximal femoral deformity (PFD) and total hip arthroplasty (THA) in a dog with the use of three-dimensionally (3D) printed custom surgical guides (CSGs). STUDY DESIGN: Case report. ANIMALS: One-year-old, male neutered, Goldendoodle. METHODS: Uniapical proximal varus and recurvatum femoral deformity (PFD) precluded femoral stem placement for THA, which was indicated for severe hip dysplasia. Using CT-derived bone and implant models, custom ostectomy and reduction guides for deformity correction were designed. A 13-hole 3.5 mm locking compression plate was contoured and applied to 3D printed models of the corrected femur and screw trajectory holes were incorporated into the CSGs. RESULTS: A caudolateral closing wedge ostectomy of the proximal femur was achieved with the aid of the CSGs and precontoured plate to within 2° of varus and 1° of recurvatum of the virtual surgical plan. Placement of a press-fit femoral stem was achieved with 7° of varus and 9° of caudal angulation. The plate was secured using six locking screws, two cortical screws, and two 18-gauge double-loop cerclage wires. No lameness and normal range of motion of the hip were observed on clinical examination 3 months after surgery. Radiographs at 3 and 6 months revealed static implant positioning, and complete bony union at the ostectomy site. CONCLUSION: Virtual surgical planning and CSGs led to successful concurrent THA and femoral deformity correction.

Humeral unicondylar fractures in immature dogs treated using a bone screw and Kirschner wire.

BACKGROUND: To investigate the incidence of implant-related complications when humeral unicondylar fractures in immature dogs are stabilised with a transcondylar bone screw and epicondylar Kirschner wire (K-wire)/pin. METHODS: Records of cases treated by the author in this clinic over a 10-year period were screened for those involving humeral condylar fractures. These were then reduced to include those patients who were less than 7 months of age with unicondylar fractures and follow-up radiographs. RESULTS: Thirty fractures in 29 dogs met the inclusion criteria. All of these had been stabilised with a transcondylar bone screw and epicondylar K-wire. Fracture healing was documented in all dogs. Surgical site infection was not recorded. Implant-related major complications were reported in four (13%) dogs and successfully treated by either implant removal or replacement. Short-term outcome was judged as excellent in 23 out of 30 and good in seven out of 30 of these fractures. CONCLUSION: The use of a transcondylar bone screw in combination with an epicondylar K-wire is an appropriate fixation method for humeral unicondylar fractures seen in puppies less than 7 months of age.