Joseph P. Weigel

Biomechanics of the normal and abnormal hip joint

Static analysis of the canine hip has given some insight to the nature and trend of the force and subsequent stress that is normally applied to the joint. Using the static model, the magnitude and direction of force and stress worsens in the hip with the anatomic and stability changes associated with CHD. More sophisticated dynamic models that take into account unbalanced forces and moments with the resultant motion are needed to better understand the mechanics of the hip joint.

Use of an inverse dynamics method to compare the three-dimensional motion of the pelvic limb among clinically normal dogs and dogs with cranial cruciate ligament-deficient stifle joints following tibial plateau leveling osteotomy or lateral fabellar-tibial suture stabilization.

OBJECTIVE To compare the 3-D motion of the pelvic limb among clinically normal dogs and dogs with cranial cruciate ligament (CCL)-deficient stifle joints following tibial plateau leveling osteotomy (TPLO) or lateral fabellar-tibial suture (LFS) stabilization by use of an inverse dynamics method. ANIMALS 6 clinically normal dogs and 19 dogs with CCL-deficient stifle joints that had undergone TPLO (n = 13) or LFS (6) stabilization at a mean of 4 and 8 years, respectively, prior to evaluation. PROCEDURES For all dogs, an inverse dynamics method was used to describe the motion of the pelvic limbs in the sagittal, frontal, and transverse planes. Motion and energy patterns for the hip, stifle, and tibiotarsal (hock) joints in all 3 planes were compared among the 3 groups. RESULTS Compared with corresponding variables for clinically normal dogs, the hip joint was more extended at the beginning of the stance phase in the sagittal plane for dogs that had a TPLO performed and the maximum power across the stifle joint in the frontal plane was greater for dogs that had an LFS procedure performed. Otherwise, variables in all planes were similar among the 3 groups. CONCLUSIONS AND CLINICAL RELEVANCE Gait characteristics of the pelvic limb did not differ between dogs that underwent TPLO and dogs that underwent an LFS procedure for CCL repair and were similar to those of clinically normal dogs. Both TPLO and LFS successfully provided long-term stabilization of CCL-deficient stifle joints of dogs with minimal alterations in gait.

Use of an inverse dynamics method to describe the motion of the canine pelvic limb in three dimensions

OBJECTIVE To use an inverse dynamics method to describe the motion of the canine pelvic limb in 3 dimensions. ANIMALS 6 healthy adult dogs. PROCEDURES For each dog, 16 anatomic and tracking markers were used to define the center of rotation for the pelvic limb joints and a kinematic model was created to describe the motion of the pelvic limb. Kinetic, kinematic, and morphometric data were combined so that an inverse dynamics method could be used to define angular displacement, joint moment, and power of the hip, stifle, and tibiotarsal (hock) joints in the sagittal, frontal, and transverse planes. RESULTS Movement and energy patterns were described for the hip, stifle, and hock joints in the sagittal, frontal, and transverse planes. CONCLUSIONS AND CLINICAL RELEVANCE Knowledge of the 3-D movement of the pelvic limb can be used to better understand its motion, moment, and energy patterns in healthy dogs and provide a referent with which gaits of dogs with pelvic limb injuries before and after surgical repair or rehabilitation can be compared and characterized. This information can then be used to guide decisions regarding treatment options for dogs with pelvic limb injuries.

Variables Affecting Thigh Girth Measurement and Observer Reliability in Dogs

Objective: The purpose of the study reported here was to describe variables affecting thigh girth measurements preoperatively and 2 weeks after surgical stabilization of the stifle and to examine inter- and intra-observer reliability. Animals: Ten hound-type dogs with experimental, unilateral, cranial cruciate ligament transection, and surgical stabilization. Procedures: Dogs were placed in lateral recumbency for measurements of thigh circumference after the stifle was placed in flexed (F), estimated standing (S), and extended (E) positions. Measurements were made at 50 and 70% of thigh length (TL), with hair unclipped and then clipped prior to surgery, before and 2 weeks after cruciate ligament transection and stifle stabilization, and with and without sedation. A spring tension measuring tape was used to determine thigh girth that allowed a consistent amount of end-tension to be applied to the tape. All measurements were made by two blinded individuals in triplicate, data were recorded for each set of measurements and the mean of the three measurements for each condition was used for analysis. Results: Thigh girth was significantly greater at the more proximal site of 50% TL (36.7 ± 2.6 cm) when compared to the 70% TL (31.7 ± 2.7 cm) (P = 0.001). Sedation did not significantly affect thigh girth at any stifle position at the 70% and 50% TL. Although there were no differences in thigh circumference between the flexion and standing positions at 50% TL (F 38.2 ± 2.8 cm, S 38.1 ± 2.9 cm) and 70% TL (F 33.6 ± 1.6 cm; S 33.6 ± 1.8 cm), full extension of the stifle resulted in significantly less thigh girth (50% TL 36.6 ± 2.6 cm, P = 0.006; 70% TL 31.7 ± 2.6 cm, P = 0.006). Significant decreases in thigh girth were seen after surgery in all limb positions at both measurement sites. The highest correlations between Observer 1 (OB1) and Observer 2 (OB2) with least differences in measurements were with the stifle in the extended position. Agreement between two observers using standard measuring technique was significant at both the 50% (OB1: 34.10 ± 2.93 cm, OB2: 34.08 ± 2.65 cm, P = 0.007, ICC = 0.984) and 70% (OB1: 29.89 ± 2.43 cm, OB2: 30.04 ± 2.30 cm, P = 0.004, ICC = 0.981) TL positions with the stifle placed in extended position. Conclusion and Clinical Importance: Thigh girth measurement may be useful as an outcome measure when appropriate measuring technique is used. It is recommended that thigh girth be obtained at a distance of 70% thigh length, with the leg in an extended position while in lateral recumbency, and the dog relaxed or under sedation. Further studies should be performed in a variety of clinical situations.

Contribution of antirotational pins and an intact fibula to the ex vivo compressive strength of four tibial plateau leveling osteotomy constructs

OBJECTIVE To assess the contribution of antirotational pins (ARPs) and an intact fibula to the compressive strength of 4 tibial plateau leveling osteotomy (TPLO) constructs (bone and implants). SAMPLE 20 hind limbs from 10 canine cadavers. PROCEDURES Each hind limb was assigned to 1 of 4 TPLO constructs (construct in which the ARP was removed, constructs in which 1 or 2 ARPs were left in place, and construct in which the ARP was removed and the fibula was cut). Following TPLO completion, all limbs underwent mechanical testing that included 10,000 cycles of cyclic axial compression followed by testing to failure at a displacement rate of 1 mm/s. Displacement during cyclic testing; load generated at 0.5, 1.0, and 3.0 mm of displacement; ultimate load; and failure type were recorded for each limb. Mean values were compared among the groups. RESULTS None of the specimens failed during cyclic testing. None of the variables assessed during mechanical testing differed significantly among the 4 groups. During testing to failure, the majority (17/20) of specimens failed as the result of a long oblique fracture through the first screw hole in the distal segment. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the axial compressive strength and stiffness of a TPLO construct were not significantly affected by the addition of 1 or 2 ARPs or the presence of an intact fibula. These findings appear to support removal of ARPs during uncomplicated TPLOs, but further research is warranted to assess the effect of ARP removal on bone healing and complication rates.

Ex vivo biomechanical evaluation of pigeon (Columba livia) cadaver intact humeri and ostectomized humeri stabilized with caudally applied titanium locking plate or stainless steel nonlocking plate constructs

OBJECTIVE To evaluate mechanical properties of pigeon (Columba livia) cadaver intact humeri versus ostectomized humeri stabilized with a locking or nonlocking plate. SAMPLE 30 humeri from pigeon cadavers. PROCEDURES Specimens were allocated into 3 groups and tested in bending and torsion. Results for intact pigeon humeri were compared with results for ostectomized humeri repaired with a titanium 1.6-mm screw locking plate or a stainless steel 1.5-mm dynamic compression plate; the ostectomized humeri mimicked a fracture in a thin cortical bone. Locking plates were secured with locking screws (2 bicortical and 4 monocortical), and nonlocking plates were secured with bicortical nonlocking screws. Constructs were cyclically tested nondestructively in 4-point bending and then tested to failure in bending. A second set of constructs were cyclically tested non-destructively and then to failure in torsion. Stiffness, strength, and strain energy of each construct were compared. RESULTS Intact specimens were stiffer and stronger than the repair groups for all testing methods, except for nonlocking constructs, which were significantly stiffer than intact specimens under cyclic bending. Intact bones had significantly higher strain energies than locking plates in both bending and torsion. Locking and nonlocking plates were of equal strength and strain energy, but not stiffness, in bending and were of equal strength, stiffness, and strain energy in torsion. CONCLUSIONS AND CLINICAL RELEVANCE Results for this study suggested that increased torsional strength may be needed before bone plate repair can be considered as the sole fixation method for avian species.

Patellar groove replacement in patellar luxation with severe femoro-patellar osteoarthritis

OBJECTIVE To report a novel method of treating femoro-patellar instability in association with severe femoro-patellar osteoarthritis, by substituting the femoral trochlear with a patellar groove replacement prosthesis. STUDY DESIGN Retrospective case series. METHODS Preoperative lameness was scored from 0-4, and radiographic studies including standard positions for patellar luxation were obtained for evidence of malalignment and femoro-patellar osteoarthritis. Cases with or without previous surgeries were included. The size of trochlear implant was determined by transparent templates and confirmed intra-operatively with trials. Radiographic images, together with clinical examinations, were reviewed immediately and at three months postoperatively and at longer term when available. RESULTS Thirty-five cases of patellar luxation ranging from grades II to IV were included. Eleven of these cases had prior surgical interventions which failed to stabilize the patella. Fourteen dogs required additional surgical procedures in conjunction with patellar groove replacement. Complications occurred in six patients, of which three required revision. Complete resolution of subjectively-assessed lameness was evident in 24/35 cases by the third month and in another seven of 35 patients on the longer term re-evaluations. CLINICAL SIGNIFICANCE Use of a patellar groove replacement prosthesis has the potential to decrease the lameness associated with severe femoro-patellar arthritis, to improve patellar stability, and to correct the alignment of the extensor mechanism.

The use of cyclosporine-A in dogs with chronic osteoarthritis: a pilot study.

OBJECTIVE To evaluate the efficacy of cyclosporine-A in dogs with radiographic and physical evidence of chronic stifle osteoarthritis. MATERIALS AND METHODS Ten hound-type dogs with osteoarthritis induced by surgical transection of a cranial cruciate ligament followed by immediate stabilization of the stifle four years prior to study start were randomized to two groups. Cyclosporine-A was administered orally once daily at 5 mg/kg to one group for one month while the other group served as control. After a two week wash-out period during which the animals were not treated, and the degree of lameness was allowed to return to baseline, the treatments were switched so that the second group received treatment with cyclosporine-A and the first group served as control. Ground reaction forces were measured using a force platform in all animals at day zero and then every two weeks until the end of the study. RESULTS Cyclosporine-A did not alter the degree of lameness based on assessment of ground reaction forces. CONCLUSIONS At a dose of 5 mg/kg/day for 28 days, cyclosporine-A was not effective in decreasing lameness of dogs with chronic osteoarthritis induced by surgical transection of the cranial cruciate ligament.