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CASE DESCRIPTION A 9-month-old 4.6-kg (10.1-lb) spayed female Shih Tzu was examined for a 4-week history of left forelimb lameness. CLINICAL FINDINGS Moderate left forelimb lameness was present when weight bearing, accompanied by buckling of the left carpal joint and moderate signs of pain with hyperextension of the elbow joint. A 32° angular deformity of the left radius in a 45° craniomedial oblique plane (equivalent to 23° valgus and 23° procurvatum) and a 55° external torsional deformity were measured on 3-D reconstructed CT images. Humeroulnar incongruity of the left elbow joint was also evident. Single oblique osteotomy (SOO) and dynamic proximal ulnar osteotomy were recommended. TREATMENT AND OUTCOME Creation of a 3-D printed bone model from reconstructed CT images aided surgical planning. The SOO was located 45° medial to the sagittal plane of the left radius at the level of the center of rotation of angulation. The SOO was oriented 32° distolaterally from the transverse plane of the radius and traversed the left ulna. The bones were rotated along the osteotomy into grossly proper alignment and stabilized with a plate and bone screws. Dynamic proximal ulnar osteotomy was then performed. Six months after surgery, radiographs showed remodeling at the SOO site and the lameness had resolved. The owners expressed satisfaction with the outcome. CLINICAL RELEVANCE In dogs with angular and torsional long bone deformities, SOO may be a viable alternative to wedge osteotomies. The SOO simultaneously addressed angular and torsional deformities without bone loss and provided rigid internal fixation.

Objective: To compare accuracy and consistency of sacral screw placement in canine pelves treated for sacroiliac luxation with open reduction and internal fixation (ORIF) or minimally invasive osteosynthesis (MIO) techniques., Methods: Unilateral sacroiliac luxations created experimentally in canine cadavers were stabilized with an iliosacral lag screw applied via ORIF or MIO techniques (n = 10/group). Dorsoventral and craniocaudal screw angles were measured using computed tomography multiplanar reconstructions in transverse and dorsal planes, respectively. Ratios between pilot hole length and sacral width (PL/SW-R) were obtained. Data between groups were compared statistically (p <0.05)., Results: Mean screw angles (±SD) were greater in ORIF specimens in both transverse (p <0.001) and dorsal planes (p <0.004). Mean PL/SW-R was smaller (p <0.001) in the ORIF group, yet was greater than 60%. While pilot holes exited the first sacral end-plate in three of 10 ORIF specimens, the spinal canal was not violated in either group., Conclusions: This study demonstrates that MIO fixation of canine sacroiliac luxations provides more accurate and consistent sacral screw placement than ORIF. With proper techniques, iatrogenic neurological damage can be avoided with both techniques. The PL /SW-R, which relates to safe screw fixation, also demonstrates that screw penetration of at least 60% of the sacral width is achievable regardless of surgical approach. These findings, along with the limited dissection needed for accurate sacral screw placement, suggest that MIO of sacroiliac luxations is a valid alternative to ORIF.

This article reviews the development of long bones, the microanatomy and physiology of the growth plate, the closure times and contribution of different growth plates to overall growth, and the effect of, and prognosis for, traumatic injuries to the growth plate. Details on surgical treatment of growth plate fractures are beyond the scope of this article.

Objective: To compare structural properties of a plate-rod combination-bone construct (PRCbc) and interlocking nail-bone construct (ILNbc) by use of an experimentally induced gap fracture in canine tibiae., Sample Population: 12 paired canine tibiae., Procedure: Specimens were implanted with a plate-rod combination consisting of a 3.5-mm, limited-contact, dynamic-compression plate combined with an intramedullary rod or 6-mm interlocking nail. Ostectomy (removal of 10-mm segment) was performed. Paired constructs were loaded for bending, compression, or torsion measurements (4 constructs/group). Compliance was determined by fitting regression lines to the load-position curves at low (initial compliance) and high (terminal compliance) loads., Results: Bending compliances did not differ significantly between constructs. For the ILNbc, initial compliance was greater than terminal compliance in compression and torsion. Initial compliance and terminal compliance for the PRCbc were similar in compression and torsion. Initial compliance in compression and torsion was greater for the ILNbc, compared with initial compliance for the PRCbc. Maximum deformations in bending and compression were similar between constructs; however, maximum torsional angle was significantly greater for the ILNbc, compared with values for the PRCbc., Conclusions and Clinical Relevance: The study documented that for an experimentally induced gap fracture in canine tibiae, a plate-rod combination is a significantly less compliant fixation method in torsion and compression, compared with an interlocking nail. Considering the deleterious effects of torsional deformation on bone healing, a plate-rod combination may represent a biomechanically superior fixation method, compared with an interlocking nail, for the treatment of dogs with comminuted tibial diaphyseal fractures.

Objective: To compare the biomechanical properties of pantarsal arthrodesis achieved with a dorsal bone plate-alone (BPA) or pin-plate combination (PPC)., Sample Population: 8 pairs of cadaver canine tarsi., Procedure: Within a pair, 1 tarsus was arthrodesed by use of a 13-hole 3.5-mm broad dynamic compression bone plate applied to the dorsal aspect of the tarsus; the paired tarsus received an identical plate similarly applied, with the addition of an intramedullary pin filling approximately 40% of the tibial medullary canal, spanning the tibiotarsal joint. Plates were instrumented with strain gauges proximal and distal to the solid portion of the plate. Specimens were mounted on a servo-hydraulic testing machine and loaded at 20%, 40%, and 80% of body weight for 10 cycles at 1 Hz. Construct compliance, angular deformation, and plate strain were determined during the 10th cycle., Results: PPC specimens were less compliant than BPA specimens at all loads and had significantly less angular deformation than BPA specimens at loads of 40% and 80% of body weight. Tibiotarsal gauge microstrain was significantly less in PPC specimens, compared with BPA specimens, regardless of loads. Maximal strains were 33.5% to 40.5% less in PPC than BPA specimens., Conclusions and Clinical Relevance: For pantarsal arthrodesis in dogs, our results indicate that the PPC construct is biomechanically superior to the BPA construct. By improving construct stability, addition of an intramedullary pin to the traditional BPA technique may lessen implant-related complications and improve plate fatigue life. A subsequent decrease in postoperative morbidity may occur with little addition of time or complexity to the surgical procedure.

Objective: To define the vertical position of the patella in clinically normal large-breed dogs., Sample Population: Cadavers of 13 clinically normal large-breed dog., Procedure: Both hind limbs were harvested with intact stifle joints and mounted on a positioning device that allowed full range of motion of the stifle joint. Lateral radiographic views were obtained with the stifle joints positioned at each of 5 angles (148 degrees, 130 degrees, 113 degrees, 96 degrees, and 75 degrees). Vertical position of the patella through a range of motion was depicted on a graph of mean stifle angle versus corresponding mean proximal patellar position (PPP) and distal patellar position (DPP) relative to the femoral trochlea for each dog. Ratio of length of the patellar ligament to length of the patella (L:P) was determined for each dog. Overall mean, SD, and 95% confidence intervals for L:P were calculated for all dogs., Results: Evaluation of vertical position of the patella through a range of motion revealed a nearly linear relationship between joint angle and PPP and joint angle and DPPF Evaluation of L:P results did not reveal significant differences between limbs (left or right) or among joint angles. Overall mean +/- SD L:P for all dogs was 1.68 +/- 0.18 (95% confidence interval, 1.33 to 2.03)., Conclusions and Clinical Relevance: The L:P proved to be a repeatable measurement of vertical patellar position, which is independent of stifle angles from 75 degrees to 148 degrees. This measurement could be used as a quantitative method for diagnosing patella alta and patella baja in large-breed dogs.