Ex vivo contact mechanics and three-dimensional alignment of normal dog elbows after proximal ulnar rotational osteotomy

Effect of Medial Opening Wedge and External Rotational Humeral Osteotomies on Medial Elbow Compartment Pressure: An Ex Vivo Study

OBJECTIVE

 The aim of this study was to assess if the level of osteotomy (50 or 75% the length of the humerus), osteotomy angle (5, 10, or 20 degrees), direction of bone alteration (external rotational or medial opening wedge osteotomies), or orientation of osteotomy (perpendicular to the humeral long axis or perpendicular to the weight-bearing axis of the limb) affect pressure through the medial compartment of the elbow.

STUDY DESIGN

 Humeral osteotomies were performed at 50 and 75% the length of the humerus on 12 canine cadaver thoracic limbs and patient-specific three-dimensional (3D) printed plates applied to induce the desired alteration. Sensors were placed into the medial and lateral aspects of the elbow joint and the limb compressed to 90 N in a universal testing system.

RESULTS

 Increasing the angle of the induced change had a significant effect on the decreased load through the medial compartment. Performing the osteotomy at 75% of humeral length from proximal was significantly more effective at reducing the medial elbow load than performing it at 50%. Opening wedge osteotomies were more effective than external rotational osteotomies, but both were effective. Changing the direction of the osteotomy (comparing transverse to oblique) did not significantly affect the load reduction through the medial compartment.

CONCLUSION

 Performing an osteotomy at a more distal location along the humerus and increasing the angle of the induced change increased the effectiveness of load-shifting humeral osteotomies.

Performing a Three-Dimensional Finite Element Analysis (FEA) to Simulate and Quantify the Contact Pressure in the Canine Elbow Joint: A Pilot Study

OBJECTIVE

 The aim of this study was to measure surface pressures and force distribution on radius and ulna in healthy and dysplastic elbow joints in different positions using the finite element analysis (FEA).

STUDY DESIGN

 FEA was performed on computed tomographic data of healthy and fragmented coronoid process diseased elbow joints of Labrador Retrievers. It considered the articular cartilage, collateral ligaments, triceps and biceps muscle. The analysis of each joint was performed in four positions (standing position: 145 degrees and three positions of the stance phase of gait: beginning: 115 degrees, middle: 110 degrees, end: 145 degrees joint angle) in consideration of different ground reaction forces (standing: 88.3 N; stance phase of gait: 182.5 N).

RESULTS

 Mean values of total force of 317.5 N (standing), 590.7 N (beginning), 330.9 N (middle) and 730.9 N (end) were measured. The percentual force distribution resulted in a total of 49.56 ± 26.58% on the ulna with a very inhomogeneous distribution. A significant difference was detected between the positions 'standing' and 'end' (p = 0.0497) regardless of the joint condition. In some FEA results, visual assessment of the surface pressures indicated an increase in pressure in the region of the medial compartment without a uniform pattern. An increase in pressure resulted in an area increase in the pressure marks on the joint surface and measurable pressure was increased at a larger joint angle.

CLINICAL SIGNIFICANCE

 FEA can provide information about the transmission of force in the joint. Prior to the use of FEA in scientific clinical research for the simulation of force, further model improvements are necessary.

Effect of proximal abducting ulnar osteotomy (PAUL) on frontal plane thoracic limb alignment: An ex vivo canine study

OBJECTIVE

To determine the effect of proximal abducting ulnar osteotomy (PAUL) on frontal plane thoracic limb alignment in standing and recumbent positions.

STUDY DESIGN

Ex vivo cadaveric study.

SAMPLE POPULATION

Canine thoracic limbs (n = 15 limb pairs).

METHODS

Limbs were acquired from healthy Labrador retrievers that had been euthanized for reasons unrelated to this study. A limb press was used to obtain standing and recumbent caudocranial radiographs before and after PAUL. Foot lateralization and rotation were directly measured in standing position. Mechanical joint angles were determined using full limb radiographic montages and the center of rotation of angulation (CORA) method for pre-PAUL (Pre), 2-mm PAUL (PAUL2), and 3-mm PAUL (PAUL3). Data are reported as mean ± SD and 95% CI. Mixed linear modeling was used to identify differences in limb alignment values and foot position, with significance established at P ≤ .004.

RESULTS

There were differences in five of 12 limb alignment values pre-PAUL and post-PAUL in standing and recumbent positions. In the standing position, there was an increase in mechanical medial proximal radioulnar angle (Pre, 80.6° ± 2.5°; PAUL2, 82.6° ± 2.4°; PAUL3, 84° ± 2.4°) and a decrease in elbow compression angle (Pre, 1.4° ± 1.3°; PAUL2, 1° ± 0.9°; PAUL3, 0.8° ± 1°). There was a movement of mechanical humeral radioulnar angle (Pre, -8.9° ± 2.8°; PAUL2, -6.1° ± 2.7°; PAUL3, -5.2 ± 2.7°), mechanical thoracic humeral angle (Pre, 3.9° ± 1.7°; PAUL2, 2.4° ± 1.4°; PAUL3, 2.6° ± 1.5°), and elbow mechanical axis deviation (Pre, 1.9% ± 1.1%; PAUL2, 0.9% ± 1.1%; PAUL3, 0.4% ± 1.4%) toward a value of "0" representing coaxial alignment of the limb. The foot underwent lateralization (Pre, 1.4 ± 0.6 cm; PAUL2, 1.8 ± 0.7 cm; PAUL3, 2.3 ± 0.7 cm) and external rotation (Pre, 10.5° ± 4.7°; PAUL2, 13.7° ± 5.1°; PAUL3, 16° ± 6.6°).

CONCLUSION

In the ex vivo setting, PAUL resulted in translation of the mechanical axis of the thoracic limb from a medial to lateral direction through alterations in limb alignment values associated with the elbow, humerus, and proximal radius/ulna.

CLINICAL SIGNIFICANCE

Additional studies are required to determine whether PAUL alters thoracic limb alignment in client-owned dogs.

Effects of realistic sheep elbow kinematics in inverse dynamic simulation

Looking for new opportunities in mechanical design, we are interested in studying the kinematic behaviour of biological joints. The real kinematic behaviour of the elbow of quadruped animals (which is submitted to high mechanical stresses in comparison with bipeds) remains unexplored. The sheep elbow joint was chosen because of its similarity with a revolute joint. The main objective of this study is to estimate the effects of elbow simplifications on the prediction of joint reaction forces in inverse dynamic simulations. Rigid motions between humerus and radius-ulna were registered during full flexion-extension gestures on five cadaveric specimens. The experiments were initially conducted with fresh specimens with ligaments and repeated after removal of all soft tissue, including cartilage. A digital image correlation system was used for tracking optical markers fixed on the bones. The geometry of the specimens was digitized using a 3D optical scanner. Then, the instantaneous helical axis of the joint was computed for each acquisition time. Finally, an OpenSim musculoskeletal model of the sheep forelimb was used to quantify effects of elbow joint approximations on the prediction of joint reaction forces. The motion analysis showed that only the medial-lateral translation is sufficiently large regarding the measuring uncertainty of the experiments. This translation assimilates the sheep elbow to a screw joint instead of a revolute joint. In comparison with fresh specimens, the experiments conducted with dry bone specimens (bones without soft tissue) provided different kinematic behaviour. From the results of our inverse dynamic simulations, it was noticed that the inclusion of the medial-lateral translation to the model made up with the mean flexion axis does not affect the predicted joint reaction forces. A geometrical difference between the axis of the best fitting cylinder and the mean flexion axis (derived from the motion analysis) of fresh specimens was highlighted. This geometrical difference impacts slightly the prediction of joint reactions.

Erosion of the medial compartment of the canine elbow: occurrence, diagnosis and currently available treatment options

Erosion of the medial compartment of the elbow joint refers to full thickness cartilage loss with exposure of the subchondral bone (modified Outerbridge grades 4–5) of the medial part of the humeral condyle (MHC) and the corresponding ulnar contact area. This finding may appear in the absence of an osteochondral fragment or a cartilage flap, or in combination with fragmentation of the medial coronoid process (MCP) or osteochondritis dissecans (OCD) of the MHC. With regard to the prognosis, it is important to diagnose these severe erosions. Imaging of cartilage lesions by means of radiography, ultrasonography, computed tomography or magnetic resonance imaging is challenging in dogs. In contrast, direct arthroscopic inspection provides detailed information about the cartilage.

The treatment of these severe erosions is difficult because of the limited regenerative capacity of cartilage and presumed mechanical or physical triggering factors. Several conservative and surgical treatment methods have been proposed to treat elbows with severe cartilage defects. However, due to irreversible loss of cartilage, the prognosis in these cases remains guarded.

Theory and development of a unicompartmental resurfacing system for treatment of medial compartment disease of the canine elbow

Medial compartment disease (MCompD) of the canine elbow can be defined as clinical signs attributable to articular cartilage loss of the medial coronoid process (MCP) of the ulna and medial aspect of the humeral condyle without significant lateral compartment pathology. Whereas outcomes associated with treatment of defined cohorts of dogs with MCompD have not been published, the impressions of many surgeons are that non-surgical management or surgical treatment of the MCP alone does not result in long term highly functional outcomes. Thus, alternative surgical options for treatment of MCompD have been developed including various osteotomies and total elbow replacement (TER) with "successful" outcomes reported in case series. Results and data on safety have been reported for relatively few of these procedures and when reported, major complication rates have been >10% and catastrophic complications have been reported. Accordingly, we sought to develop a surgical technique with the objective of obtaining higher levels of safety and efficacy in the treatment of dogs with MCompD. This report describes the rationale for, and development of, a unicompartmental resurfacing system for treatment of MCompD in the canine elbow.

Thoracic limb alignment in healthy labrador retrievers: evaluation of standing versus recumbent frontal plane radiography

OBJECTIVE

To report thoracic limb alignment values in healthy dogs; to determine if limb alignment values are significantly different when obtained from standing versus recumbent radiographic projections.

STUDY DESIGN

Prospective cross-sectional study.

ANIMALS

Labrador Retrievers (n = 45) >15 months of age.

METHODS

Standing and recumbent radiographs were obtained and limb montages were randomized before analysis by a single investigator blinded to dog, limb, and limb position. Twelve limb alignment values were determined using the CORA methodology. Measurements were performed in triplicate and intra-observer variability was evaluated by intra-class correlation coefficient (ICC). Limb alignment values were reported as mean ± SD and 95% confidence intervals. Linear mixed models were used to determine if significant associations existed between limb alignment values and limb, limb position, gender, age, weight, and body condition score.

RESULTS

There were significant differences in standing and recumbent limb alignment values for all values except elbow mechanical axis deviation (eMAD). Limb, gender, age, body weight, and body condition score had no effect. ICC values ranged from 0.522 to 0.758, indicating moderate to substantial agreement for repeated measurements by a single investigator.

CONCLUSIONS

Limb alignment values are significantly different when determined from standing versus recumbent radiographs in healthy Labrador Retrievers.

In vitro biomechanical comparison of load to failure testing of a canine unconstrained medial compartment elbow arthroplasty system and normal canine thoracic limbs

Elbow dysplasia, primarily affecting the medial compartment, is the most common cause of lameness in the thoracic limb. Elbow arthroplasty is an option for end stage or severely affected patients. The purpose of this study was to compare ex vivo axial load to failure of an implanted novel elbow arthroplasty system to control limbs. The partial arthroplasty is a medial compartmental, unconstrained system, intended to allow conversion to total arthroplasty. We hypothesized that there would not be any significant difference between implanted and controlled limbs when loaded to failure. Six pairs of medium mixed breed canine cadaveric thoracic limbs were prepared for comparison of failure loading of control and implanted limbs. Axial compression was performed using a mechanical testing system. Failure loads were normalized to bodyweight. The mean normalized failure load (N/kg) for the implanted limbs and control limbs were 2.47 (range: 1.62-3.38) and 2.68 (range: 2.25-3.25), respectively. An implanted to control ratio of 0.93 ± 0.19 was calculated. The difference between paired control and implanted limbs in normalized failure loading was not significant (p = 0.38). There were not any differences noted in the yield load (p = 0.30), stiffness (p = 0.62), or energy (0.58). Failure modes were recorded. We concluded that the differences between implanted and control limbs in supra-physiologic axial load to failure were not significant.