In vitro determination of contact areas in the normal elbow joint of dogs

OBJECTIVE: To evaluate areas of articular contact of the proximal portions of the radius and ulna in normal elbow joints of dogs and the effects of axial load on size and location of these areas. SAMPLE POPULATION: Forelimbs obtained from cadavers of 5 adult mixed-breed dogs. PROCEDURE: After forelimbs were removed, liquid-phase polymethyl methacrylate was applied to articular surfaces of the elbow joint, and limbs were axially loaded. Articular regions void of casting material were stained with water-soluble paint. Relative articular contact areas were determined by computer-assisted image analyses of stained specimens. Repeatability of the technique was evaluated by analyses of casts from bilateral forelimbs of 1 cadaver. Incremental axial loads were applied to left forelimbs from 4 cadavers to determine effects of load on articular contact. RESULTS: Specific areas of articular contact were identified on the radius, the craniolateral aspect of the anconeus, and the medial coronoid process. The medial coronoid and radial contact areas were continuous across the radioulnar articulation. There was no articular contact of the medial aspect of the anconeus with the central trochlear notch. Coefficients of variation of contact areas between repeated tests and between contralateral limbs was < 20%. Significant overall effects of axial load on contact area or location were not identified. CONCLUSIONS: Three distinct contact areas were evident in the elbow joint of dogs. Two ulnar contact areas were detected, suggesting there may be physiologic incongruity of the humeroulnar joint. There was no evidence of surface incongruity between the medial edge of the radial head and the lateral edge of the medial coronoid process.     

In vitro evaluation of biomechanical effects of multiple hemilaminectomies on the canine lumbar vertebral column

OBJECTIVE: To conduct an in vitro investigation of the biomechanical characteristics of the canine lumbar spinal column in flexion and extension and measure the destabilizing effects of multiple consecutive unilateral and bilateral hemilaminectomies. SAMPLE POPULATION: 30 isolated multisegmental spinal units (L1-L4) from nonhypochondroplastic dogs weighing 15 to 30 kg. PROCEDURES: Physically normal and surgically altered spinal specimens were subjected to 4-point bending in flexion and extension to determine effects of multiple consecutive hemilaminectomies on the basis of analysis of test system load-displacement data. Six groups with 5 spinal columns in each were defined on the basis of the following procedures: hemilaminectomy at L2-L3, 2 adjacent hemilaminectomies at L1-L3, 3 adjacent hemilaminectomies at L1-L4, bilateral hemilaminectomies at L2-L3, 2 bilateral hemilaminectomies at L1-L3, and no hemilaminectomy (intact). Spinal stability before and after surgery was determined in all groups. Each group served as its own control for nondestructive testing. Spinal strength was evaluated through destructive testing to determine deformation at failure, strength to failure, and mode of catastrophic failure. The intact group served as the control for destructive testing. RESULTS: Stability in extreme flexion and extreme extension did not change significantly following any hemilaminectomy procedure. Postoperative stability within the neutral zone was significantly decreased in all groups. Range of motion within the neutral zone was not significantly different from the intact condition in any group. CONCLUSIONS AND CLINICAL RELEVANCE: Multiple hemilaminectomies did not decrease stiffness of the lumbar spinal column during flexion and extension. These results support clinical recommendations regarding multiple consecutive hemilaminectomies in dogs.     

Some aspects of the radiographical examination of the canine elbow joint

A radiological method of examining the elbow joint of the dog is described with particular reference to conditions which result in osteoarthrosis. The importance of taking oblique projections for the diagnosis of osteochondritis dissecans of the distal humerus and ununited medial coronoid process of the ulna is discussed.     

Post natal development of the canine elbow joint: a light and electron microscopical study.

The elbows of 13 puppy cadavers were dissected, samples were taken for light and electron microscopy, and the thickness of the articular cartilage of the distal humerus and proximal ulna was measured. Throughout post natal development differences were found in the arrangement of the growth plate and articular chondrocytes. At birth, the articular surface had remnants of a fibrous limiting membrane that was continuous with the perichondrium, a finding not previously recorded in dogs. Orientation of the collagen fibrils within the matrix of the articular cartilage was initially lacking but became established by three weeks. In the humerus cartilage canals were present up to 12 weeks old. The articular cartilage of the humeral condyle varied in thickness across the joint surface, being thicker on the medial than on the lateral side; it was also thicker at the apex of the medial coronoid process. These regions of thick cartilage correspond with the sites where cartilage defects arise in elbow osteochondrosis. No histological evidence was found that the medial cornoid process of the ulna is a separate centre of ossification.     

In vitro experimental study of the effect of radial shortening and ulnar ostectomy on contact patterns in the elbow joint of dogs

OBJECTIVE: To determine effects of incremental radial shortening and subsequent ulnar ostectomies on joint surface contact patterns in a canine elbow joint model. SAMPLE POPULATION: Paired forelimbs from 9 adult dogs. PROCEDURE: Joint casting was performed by placement of colored polymethylmethacrylate in the elbow joint cavity and loading in a materials testing system at physiologic angle and load. Joint casting was performed in unaltered specimens, after radial shortening, and after subsequent distal ulnar ostectomy, proximal ulnar ostectomy, and proximal ulnar ostectomy with intramedullary pinning. Computer-aided analysis of photographs of proximal radial and ulnar articular surfaces without joint casts was performed before and after each casting procedure. RESULTS: All increments of radial shortening changed the size and location of radial and ulnar contact areas. The radial contact area became smaller, the anconeal contact area disappeared, the medial coronoid contact area migrated craniolaterally, and the lateral projection of the coronoid process became a contact area. A proximal ulnar ostectomy stabilized with an intramedullary pin restored normal contact area size and location and restored continuity of the radial and coronoid contact areas across the radioulnar articulation in 6 of 10 specimens. A midshaft ulnar ostectomy, distal to the level of the radioulnar ligament, had no effect on contact patterns. A proximal ulnar ostectomy without stabilization resulted in varus deformity during loading. CONCLUSIONS AND CLINICAL RELEVANCE: Proximal radial shortening, which creates articular step incongruity, changes the location and size of the radioulnar contact areas. Dynamically stabilized ulnar ostectomies proximal to the radioulnar ligament restore contact patterns in vitro.     

Effect of humeral osteotomy on joint surface contact in canine elbow joints

OBJECTIVE: To determine the effect of sliding and wedge osteotomies of the humerus on the joint surface contact areas in anatomically normal elbow joints of dogs. SAMPLE POPULATION: Left thoracic limbs from 5 skeletally mature mixed-breed canine cadavers. PROCEDURE: Joint casting was performed by placement of colored polymethylmethacrylate in the elbow joint cavity followed by loading in a materials testing system at physiologic angle and load. Joint casting was performed in unaltered specimens, after 10 degrees medial opening wedge osteotomy, and after lateral sliding osteotomy of the proximal portion of the humerus. Computer-aided analysis of photographs of proximal radial and ulnar articular surfaces after each casting procedure was performed. RESULTS: The lateral sliding humeral osteotomy and 10 degrees medial opening wedge osteotomy significantly altered joint surface contact regions of the canine elbow joint. Osteotomies resulted in a reduction in the size of the radial, ulnar, and combined radioulnar contact areas. Both osteotomies also resulted in craniolateral migration of the radial contact area and craniomedial recession of the ulnar contact area. Although the reduction in ulnar contact area with these treatments is consistent with our hypotheses, the reduction in radial contact area was not anticipated. CONCLUSIONS AND CLINICAL RELEVANCE: Humeral osteotomies alter joint surface contact areas of the canine elbow joint in vitro. Humeral osteotomies may decrease contact areas on the diseased region of the joint in dogs with elbow dysplasia; however, the overall decrease in joint surface contact area suggests that these procedures may induce focal increases in pressure that may cause iatrogenic cartilage damage when applied in vivo.     

In vitro study of the ilial anatomic landmarks for safe implant insertion in the first sacral vertebra of the intact canine sacroiliac joint

OBJECTIVE: To define landmarks on the canine ilial wing for accurate, consistent insertion of implants into the 1st sacral (S1) vertebral body when the sacroiliac joint is intact. STUDY DESIGN: Anatomic study. ANIMALS: Intact, cadaveric canine pelves and sacra (n=25). METHODS: Median sections (5 specimens) were drilled from the center of S1 in a lateral direction, exiting on the ilial wing. Landmarks on the ilial wing and shaft used to define this exit point were then used to locate this point on both wings of 20 articulated specimens, positioned and rigidly held so that the dorsal plane of the pelvis was aligned with a plumb line and the median plane of the pelvis was horizontal. A 2 mm hole was drilled from the marked point, parallel to the plumb line, until it exited the contralateral ilial wing. Distance of drill hole position from the geometric center (GC) of S1 was located on median and paramedian plane images derived from plane, computed tomographic (CT) scans. RESULTS: The entire drill hole was located within S1 in 18 specimens. Mean deviation of the hole from GC (ratio of the distance of GC from the closest S1 body border) in median section was 0.40 +/- 0.29 (craniocaudal direction) and 0.29 +/- 0.23 (dorsoventral). CONCLUSIONS: Use of ilial wing landmarks and drilling perpendicular to the median plane will improve accuracy for insertion of implants into S1 when the sacroiliac joint is intact. CLINICAL RELEVANCE: Ilial wing landmarks should be used to improve accuracy of implant insertion into S1.     

Use of reconstructed computed tomography for the assessment of joint spaces in the canine elbow

OBJECTIVES: To assess the accuracy of reconstructed computed tomography for imaging canine elbow joint spaces. METHODS: Computed tomography scans of eight cadaveric elbows were obtained and reconstructed computed tomography images were formatted in the dorsal and sagittal planes. Humeroradial and humeroulnar joint space measurements were obtained from these images. Intra-observer and inter-observer variations in joint space measurements were assessed, as was the effect of specimen positioning (inter-image variation). After freezing, four elbows were sectioned in the dorsal plane and four in the sagittal plane. In addition to visual comparison of the frozen sections with reconstructed computed tomography images, joint space measurements were obtained from frozen sections and compared with those from reconstructed computed tomography images. Variation was assessed using statistical calculations and graphical techniques. RESULTS: Both inter-image and intra-observer analyses revealed good agreement and low variation between data sets. Inter-observer correlation was only moderate, though variation was low. Visually, the reconstructed computed tomography images accurately reflected the frozen section anatomy. Agreement between frozen section and reconstructed computed tomography joint space measurements was good, with minimal variation. CLINICAL SIGNIFICANCE: These results indicate that reconstructed computed tomography is capable of accurately imaging elbow joint spaces and precise joint space measurements can be obtained. Reconstructed computed tomography may be useful for determining joint space measurements and detecting elbow incongruencies in dogs with elbow dysplasia.     

Viscosity determination of synovial fluids from the canine hip and elbow joint as well as the human knee joint

The development of pathological changes in both human and canine hip joints is mainly caused by a lack of synovial fluid lubrication. This results in an increased joint abrasion. Even after implantation of joint prosthesis, inadequate lubrication can lead to abrasion in the tribological pair. This can finally result in aseptic loosening of the prosthesis. In spite of the enormous number of studies that have been performed on human, only little knowledge about the tribological properties of the joints in dogs is available in the literature. For this reason the viscosities of synovial fluid, derived from physiological and pathologically changed canine elbow joints were measured. The viscosities were determined by the use of a cone-plate viscometer at different temperatures and shear rates. The obtained values were compared with the viscosity values of pathologically changed synovial fluids from human knee joints as well as with pathological samples from the canine hip joint. The results show that the viscosity values vary within a series of measurements and are inversely proportional to the temperature of the sample and the shear rate. The differences between the average viscosities of canine and human synovial fluids taken from pathologically changed joints are below 4% (22.5 s(-1) at theta1 = 25 degrees C). The findings of this study are being implemented in a FE-Model for the computation of actual forces in the hip joint during different movements. This would represent a contribution to an improved prosthetic treatment of canine and human hips.     

In vitro validation of a technique for assessment of canine and feline elbow joint collateral ligament integrity and description of a new method for collateral ligament prosthetic replacement

Objective— To assess the ability of an operator to differentiate intact from transected canine and feline elbow joint collateral ligaments (CL) using a reported manipulative test (Campbell's test) and to determine the potential for elbow joint luxation in canine and feline elbows with intact, transected, and surgically stabilized CL. Study Design— In vitro biomechanical study. Sample Population— Canine (n=6) and feline cadavers (n=3). Methods— Thoracic limb specimens were mounted on a custom‐built jig with the elbows and carpi fixed in 90° of flexion. Angles of pronation and supination were recorded after applying rotational forces to the manus. Attempts were made to manually luxate each elbow with intact CL. Constructs were re‐evaluated after sequential sectioning of the medial (MCL) and lateral (LCL) collateral ligaments and after insertion of a new CL prosthesis. Results— Mean (±SD) angles of rotation in dogs increased from 27.3±8° (range, 16.7–41.3°) in pronation to 58.9±9.2° (range, 38–88.3°) after sectioning the MCL and from 45.5±10.8° (range, 30.7–67.3°) in supination to 68.9±17.2° (range, 45–94°) after sectioning the LCL. Angles of pronation and supination were subject to significant interanimal variability, with a strong correlation between increasing animal weight and smaller angles of rotation. Elbow luxation in dogs was not possible unless at least the LCL was transected. In cats, mean angles of rotation increased from 49.8±14.9° (range, 30.7–70°) in pronation to 99.1±17.6° (range, 79–111.7°) after sectioning the MCL and from 128.7±18.8° (range, 108.3–151.7°) in supination to 166.7±13.1° (range, 157.3–181.7°) after sectioning the LCL. Luxation in cats was not possible unless both CL were cut. Use of the ligament prosthesis without primary CL repair reliably prevented reluxation in all canine and feline elbows. Conclusions— Campbell's test allowed reliable differentiation of intact, transected and surgically stabilized canine and feline elbow joint CL in a cadaveric model. Luxation could not be performed by application of rotational forces to specimens with intact CL. Clinical Relevance— Clinical examination findings, specifically Campbell's test, can be used to determine elbow CL integrity in dogs and cats. The contralateral elbow should be used as a control, because of interanimal variability in angles of rotation.     

The surgical treatment of osteochondritis dissecans and ununited coronoid process in the canine elbow joint

The case details of ten dogs with osteochondritis dissecans of the medial condyle of the humerus and seven dogs with ununited coronoid process are presented. Seventeen dogs were treated surgically and the medial approach to the elbow is described.     

Measurement of humeroradial and humeroulnar transarticular joint forces in the canine elbow joint after humeral wedge and humeral slide osteotomies

Objective— To determine the effect of humeral wedge and humeral slide osteotomies on force distribution between the articular surfaces of the humerus and the radius and ulna in normal canine thoracic limbs.
Study Design— In vitro mechanical testing.
Sample population— Cadaveric canine right thoracic limbs (n=12).
Methods— Transarticular elbow force maps were measured using a tactile array pressure sensor in elbow joints of axially aligned limbs under 200 N axial load before and after humeral wedge and humeral slide osteotomies.
Results— Loading induced 2 distinct areas of high forces that corresponded with the proximal articular surfaces of the radius and ulna. Mean force on the proximal articular surface of the ulna was reduced by 25% and 28% after 4 and 8 mm sliding osteotomies, respectively. Statistically significant differences were not observed for the wedge osteotomies.
Conclusion— Humeral slide osteotomy significantly decreases force on the proximal articular surface of the ulna.
Clinical Relevance— The proximal articular surface of the ulna contributes significantly to load transfer through the canine elbow joint. Abnormalities that significantly increase this force might contribute to canine elbow dysplasia, specifically fragmentation of the medial coronoid process and osteochondritis dissecans of the medial aspect of the humeral condyle. Under the conditions studied, the overall reduction in mean joint surface force across the proximal articular surface of the ulna after humeral slide osteotomy indicates that this technique merits further investigation for potential use in medial compartmental osteoarthritis of the canine elbow joint.     

In vitro biomechanical comparison of a plate-rod combination-construct and an interlocking nail-construct for experimentally induced gap fractures in canine tibiae

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.     

An in vitro biomechanical study of bone plate and interlocking nail in a canine diaphyseal femoral fracture model

OBJECTIVE: To compare the structural properties and the interfragmentary motion in ostectomized canine femurs stabilized with either an 8-mm interlocking nail system (IN) or a 10-hole dynamic compression broad plate (DCP). ANIMAL OR SAMPLE POPULATION: Ten pairs of adult canine femurs with a 25-mm mid-diaphyseal gap. METHODS: Bone specimens were divided into 2 groups (10 femurs each). Left femurs were stabilized with a DCP and 8 bicortical screws; right femurs were stabilized with an IN and 3 screws. Mechanical tests were performed in eccentric axial loading and in craniocaudal bending. The testing was first conducted nondestructively and then until breakage. Structural properties, ie, stiffness, yield limits, and failure limits, were determined. Interfragmentary motion was measured during nondestructive tests with the use of an optoelectronic device. Axial, transverse, and rotational motions were calculated. Mean values of stiffness, yield and failure limits, and axial and shear motions for each fixation method were compared using a paired t test within each group (P <.05). RESULTS: Mean (+/-SD) values of stiffness and failure limit were significantly higher for IN constructs than for DCP constructs in compression, while there was little difference in the results between each tested group in bending. Mean yield load values were significantly higher for IN than for DCP specimens in compression as well as in bending. The axial-motion analysis revealed significant differences between IN and DCP groups during bending tests only. The highest score of transverse motion at the gap was recorded during bending tests, and was higher for DCP than for IN specimens. There were insignificant differences between the two groups with regard to rotation around the diaphyseal axis. CONCLUSIONS AND CLINICAL RELEVANCE: Structural properties and interfragmentary shear motion analysis demonstrated a much higher rigidity in the IN-bone than in the DCP-bone constructs.     

In vitro cyclic biomechanical properties of an interlocking equine tibial nail

OBJECTIVE: To determine cyclic biomechanical properties of gap osteotomized adult equine tibiae stabilized with an equine interlocking nail (EIN). STUDY DESIGN: In vitro experimental biomechanical investigation. SAMPLE POPULATION: Thirteen adult equine cadaveric tibiae. METHODS: Adult equine tibiae with transverse, midshaft, 1-cm gap osteotomies, stabilized with an equine interlocking nail, underwent cyclic biomechanical testing in vitro under axial compression, 4-point bending, and torsion. Different specimens were subjected to different load levels that represented estimated in vivo loads at 2 Hz for 740,000 cycles. Fatigue life and gap strain were calculated. RESULTS: Compression and bending, but not torsional, fatigue life were longer than time necessary for bone healing. Compressive, but not bending or torsional, gap strains were small enough to be compatible with fracture healing by primary bone formation. Gap strains for compressive, bending, and torsional loads were compatible with indirect, or secondary, bone formation. CONCLUSIONS: Further modification should be made to the equine interlocking nail to increase bending stiffness and torsional fatigue life. CLINICAL RELEVANCE: The stainless steel equine intramedullary interlocking nail is unlikely to provide appropriate long-term stability for fracture healing in adult equine tibiae without modifications in the nail design and material.     

Effect of tibial plateau leveling on stability of the canine cranial cruciate-deficient stifle joint: an in vitro study

OBJECTIVE: To evaluate the effect of tibial plateau leveling on joint motion in canine stifle joints in which the cranial cruciate ligament (CCL) had been severed. STUDY DESIGN: In vitro cadaver study. ANIMALS: Six canine cadaver hind legs. METHODS: Radiographs of the stifle joints were made to evaluate the tibial plateau angle with respect to the long axis of the tibia. The specimens were mounted in a custom-made testing device to measure cranio-caudal translation of the tibia with respect to the femur. An axial load was applied to the tibia, and its position was recorded in the normal stifle, after transection of the CCL, and after tibial plateau leveling. Further, the amount of caudal tibial thrust was measured in the tibial plateau leveled specimen while series of eight linearly increasing axial tibial loads were applied. RESULTS: Transection of the CCL resulted in cranial tibial translation when axial tibial load was applied. After tibial plateau leveling, axial loading resulted in caudal translation of the tibia. Increasing axial tibial load caused a linear increase in caudal tibial thrust in all tibial plateau-leveled specimens. CONCLUSIONS: After tibial plateau leveling, axial tibial load generates caudal tibial thrust, which increases if additional axial load is applied. CLINICAL RELEVANCE: Tibial plateau leveling osteotomy may prevent cranial translation during weight bearing in dogs with CCL rupture by converting axial load into caudal tibial thrust. The amount of caudal tibial thrust seems to be proportional to the amount of weight bearing.