Effects of various load magnitudes on ACL: an in vitro study using adolescent porcine stifle joints.

INTRODUCTION: The escalating incidence of anterior cruciate ligament (ACL) injuries, particularly among adolescents, is a pressing concern. The study of ACL biomechanics in this demographic presents challenges due to the scarcity of cadaveric specimens. This research endeavors to validate the adolescent porcine stifle joint as a fitting model for ACL studies. METHODS: We conducted experiments on 30 fresh porcine stifle knee joints. (Breed: Yorkshire, Weight: avg 90 lbs, Age Range: 2-4 months). They were stored at - 22 °C and a subsequent 24-h thaw at room temperature before being prepared for the experiment. These joints were randomly assigned to three groups. The first group served as a control and underwent only the load-to-failure test. The remaining two groups were subjected to 100 cycles, with forces of 300N and 520N, respectively. The load values of 300N and 520N correspond to three and five times the body weight (BW) of our juvenile porcine, respectively. RESULT: The 520N force demonstrated a higher strain than the 300N, indicating a direct correlation between ACL strain and augmented loads. A significant difference in load-to-failure (p = 0.014) was observed between non-cyclically loaded ACLs and those subjected to 100 cycles at 520N. Three of the ten samples in the 520N group failed before completing 100 cycles. The ruptured ACLs from these tests closely resembled adolescent ACL injuries in detachment patterns. ACL stiffness was also measured post-cyclical loading by applying force and pulling the ACL at a rate of 1 mm per sec. Moreover, ACL stiffness measurements decreased from 152.46 N/mm in the control group to 129.42 N/mm after 100 cycles at 300N and a more significant drop to 86.90 N/mm after 100 cycles at 520N. A one-way analysis of variance (ANOVA) and t-test were chosen for statistical analysis. CONCLUSIONS: The porcine stifle joint is an appropriate model for understanding ACL biomechanics in the skeletally immature demographic. The results emphasize the ligament's susceptibility to injury under high-impact loads pertinent to sports activities. The study advocates for further research into different loading scenarios and the protective role of muscle co-activation in ACL injury prevention.

Three-dimensional kinematic evaluation of lateral suture stabilization in an in vitro canine cranial cruciate deficient stifle model.

The impact of surgical correction of cranial cruciate ligament rupture (CCLR) on 3D kinematics has not been thoroughly evaluated in dogs. The success of current techniques remains limited, as illustrated by suboptimal weightbearing and progression of osteoarthritis. The inability to restore the stifle's 3D kinematics might be a key element in understanding these suboptimal outcomes. The objective of this study was to evaluate the impact of lateral suture stabilization (LSS) on the 3D kinematics of the canine stifle joint. We hypothesized that LSS would not restore 3D kinematics in our model. Ten cadaveric pelvic limbs collected from large dogs (25-40 kg) were tested using a previously validated apparatus that simulates gait. Three experimental conditions were compared: (a) intact stifle; (b) unstable stifle following cranial cruciate ligament transection (CCLt) and (c) CCLt stabilized by LSS. Three-dimensional kinematics were collected through 5 loading cycles simulating the stance phase of gait and curves were analyzed using a Wilcoxon signed-rank test. LSS restored baseline kinematics for the entire stance phase for cranial and lateromedial translation, flexion, and abduction. It restored distraction over 90% of the stance phase. Internal rotation was limited, but not restored. This in vitro study had limitations, as it used a simplified model of stifle motion and weight-bearing. The results of this study report that LSS can restore physiologic 3D kinematics largely comparable to those of healthy stifles. Suboptimal outcome in patients following CCLR stabilization by LSS may therefore result from causes other than immediate postoperative abnormal 3D kinematics.

Pathology-pain relationships in different osteoarthritis animal model phenotypes: it matters what you measure, when you measure, and how you got there.

OBJECTIVE: To determine whether osteoarthritis (OA) pain characteristics and mechanistic pathways in pre-clinical models are phenotype-specific. DESIGN: Male 11-week-old C57BL6 mice had unilateral medial-meniscal-destabilization (DMM) or antigen-induced-arthritis (AIA), vs sham-surgery/immunised-controls (Sham/Im-CT). Pain behaviour (allodynia, mechanical- and thermal-hyperalgesia, hindlimb static weight-bearing, stride-length) and lumbar dorsal root ganglia (DRG) gene-expression were measured at baseline, day-3, week-1/-2/-4/-8/-16, and pain-behaviour:gene-expression:joint-pathology associations investigated. RESULTS: DMM and AIA induced structural OA defined by progressively increasing cartilage erosion, subchondral bone sclerosis and osteophyte size and maturation. All pain-behaviours were modified, with model-specific differences in severity and temporal pattern. Tactile allodynia developed acutely in both models and persisted to week-16. During early-OA (wk4-8) there was; reduced right hindlimb weight-bearing in AIA; thermal-hyperalgesia and reduced stride-length in DMM. During chronic-OA (wk12-16); mechanical-hyperalgesia and reduced right hindlimb weight-bearing were observed in DMM only. There were no associations in either model between different pain-behaviour outcomes. A coordinated DRG-expression profile was observed in sham and Im-CT for all 11 genes tested, but not in AIA and DMM. At wk-16 despite equivalent joint pathology, changes in DRG-expression (Calca, Trpa1, Trpv1, Trpv4) were observed only in DMM. In AIA mechanical-hyperalgesia was associated with Trpv1 (r = -0.79) and Il1b (r = 0.53). In DMM stride-length was associated with Calca, Tac1, Trpv1, Trpv2, Trpv4 and Adamts5 (r = 0.4-0.57). DRG gene-expression change was correlated with subchondral-bone sclerosis in DMM, and cartilage damage in AIA. Positive pain-behaviour:joint-pathology associations were only present in AIA - for synovitis, subchondral-bone resorption, chondrocyte-hypertrophy and cartilage damage. CONCLUSION: Pain and peripheral sensory neuronal responses are OA-phenotype-specific with distinct pathology:pain-outcome:molecular-mechanism relationships.

Validation of an optical, computer-assisted technique for intraoperative tracking of 3-dimensional canine stifle joint motion.

Background: Cranial cruciate ligament (CCL) rupture is the most common orthopedic pathology in dog and in men. In human, optical computer-assisted technique is considered as a repeatable and reliable method for the biomechanical assessment of joint kinematics and laxity in case of CCL surgery. Aim: To evaluate the repeatability and reliability afforded by clinical tests in terms of laxity measured by means of a computer-assisted tracking system in two canine CCL conditions: CCL-Intact, CCL-Deficient. Methods: Fourteen fresh frozen canine stifles were passively subjected to Internal/External (IE) rotation at 120° of flexion and Cranial drawer test (CC). To quantify the repeatability and the reliability, intra-class correlation coefficient (ICC) and the mean percent error were evaluated (Δ r %). Results: The study showed a very good intra-class correlation, before and after CCL resection for kinematics tests. It was found a minimum ICC = 0.73 during the IE rotation in CCL-Intact and a maximum value of ICC = 0.97 for the CC displacement in CC-Deficient. IE rotation with CCL-Intact is the condition with the greatest Δ r % = 14%, while the lowest Δ r % = 6% was obtained for CC displacement in CCL-Deficient. Conclusion: The presented work underlined the possibility of using a computer-assisted method also for biomechanical studies concerning stifle kinematics and laxity.

Joint laxity varies in response to partial and complete anterior cruciate ligament injuries throughout skeletal growth.

Anterior cruciate ligament (ACL) injuries are increasingly common in the skeletally immature population. As such there is a need to increase our understanding of the biomechanical function of the joint following partial and complete ACL injury during skeletal growth. In this work, we aimed to assess changes in knee kinematics and loading of the remaining soft tissues following both partial and complete ACL injury in a porcine model. To do so, we applied anterior-posterior tibial loads and varus-valgus moments to stifle joints of female pigs ranging from early juvenile to late adolescent ages and assessed both kinematics and in-situ loads carried in the bundles of the ACL and other soft tissues including the collateral ligaments and the menisci. Partial ACL injury led to increased anterior tibial translation only in late adolescence and small increases in varus-valgus rotation at all ages. Complete ACL injury led to substantial increases in translation and rotation at all ages. At all ages, the medial collateral ligament and the medial meniscus combined to resist the majority of applied anterior tibial load following complete ACL transection. Across all ages and flexion angles, the contribution of the MCL ranged from 45 to 90% of the anterior load and the contribution of the medial meniscus ranged from 14 to 35% of the anterior load. These findings add to our current understanding of age-specific functional properties of both healthy and injured knees during skeletal growth.

Pressuring of Acupoints as a Complement to the Diagnosis of Stifle Diseases in Horses.

Diseases of the stifle joint remain a challenge for veterinarians. The objective of this study was to achieve a valuable acupuncture suggestive diagnosis to be considered for stifle joint diseases in horses. Thirty-nine nonlame horses involved in different activities were assessed. Acupuncture was independently performed by two evaluators. Reactions of the animal when pressurizing the point suggestive of stifle disease (PSSD), Bladder-20 and/or Bladder-21, were considered as the inclusion criteria for inclusion in the stifle group (SG, n = 31), and the animals with no reactions were assigned to the control group (n = 8). Radiographic and ultrasonographic examinations were performed and evaluated by two independent professionals blinded to the group allocation. Thermographic examination of the PSSD and stifles was also performed, after acclimatization. The ultrasound scores and radiographic findings were higher in the SG than in the control group. Thermography evidenced increased temperature in the PSSD and stifles in the SG. The minimum acupuncture diagnostic criteria for stifle joint disease had a sensitivity of 87.5% and a specificity of 57.0%, and the addition of the acupoints Gallbladder-dorsal tuber coxae, Gallbladder-27, and Spleen-13 to the minimum diagnostic criteria improved sensitivity and specificity. In conclusion, assessing the reaction at the demonstrated acupoints can facilitate a diagnosis of a potential stifle lesion.

Effect of Vertical or Beveled Chondral Defect Creation on Rim Deformation and Contact.

OBJECTIVE: To determine biomechanical effects of knee cartilage defect perimeter morphology based on cartilage strain and opposing subchondral bone contact. DESIGN: Articular cartilage defects were created in 5 bovine femoral condyles: group 1, 45° inner bevel with 8-mm rim; group 2, vertical with 8-mm rim; and group 3, 45° outer bevel with 8-mm base. Samples were placed into a custom-machined micro-computed tomography tube and subjected to 800 N of axial loading. DICOM data were used to calculate cartilage thickness 4 and 6 mm from the center, distance between tibial cartilage surface and femoral subchondral bone, and contact width between tibial cartilage and subchondral bone. Strain 4 mm from the center and both absolute and change in distance (mm) to subchondral bone were compared between groups 1 and 2 using paired t tests. Strain at 6 mm and distance changed, loaded distance, and contact width (mm) were compared between groups using the Friedman test with post hoc analysis using Wilcoxon signed rank test. RESULTS: No significant differences in rim strain were noted between groups 1 and 2 at 4 mm ( P = 0.10) and between groups 1, 2, and 3 at 6 mm ( P = 0.247) from the defect center. The loaded distance was significantly different between groups 1 and 3 ( P = 0.013). No significant change in distance to the subchondral bone was found between groups ( P = 0.156). The difference in subchondral bone contact area approached but did not reach significance ( P = 0.074). CONCLUSION: When debriding focal articular cartilage defects, establishment of an inner bevel decreases tissue deformation and contact with opposing subchondral bone.

Near Infrared Spectroscopic Evaluation of Ligament and Tendon Biomechanical Properties.

Knee ligaments and tendons are collagen-rich viscoelastic connective tissues that provide vital mechanical stabilization and support to the knee joint. Deterioration of ligaments has an adverse effect on the health of the knee and can eventually lead to ligament rupture and osteoarthritis. In this study, the feasibility of near infrared spectroscopy (NIRS) was, for the first time, tested for evaluation of ligament and tendon mechanical properties by performing measurements on bovine stifle joint ligament (N = 40) and patellar tendon (N = 10) samples. The mechanical properties of the samples were determined using a uniaxial tensile testing protocol. Partial least squares regression models were then developed to determine if morphological, viscoelastic, and quasi-static properties of the samples could be predicted from the NIR spectra. Best performance of NIRS in predicting mechanical properties was observed for toughness at yield point (median [Formula: see text], median normalized [Formula: see text]), toughness at failure point (median [Formula: see text], median normalized [Formula: see text]), and the ultimate strength of the ligament/tendon (median [Formula: see text], median normalized [Formula: see text]). Thus, we show that NIRS is capable of estimating ligament and tendon biomechanical properties, especially in parameters related to tissue failure. We believe this method could substantially enhance the currently limited arthroscopic evaluation of ligaments and tendons.

Using allogeneic cortical graft preserved in glycerin as spacer in the advancement of tibial tuberosity in 34 dogs / Uso de enxerto cortical alogênico preservado em glicerina como espaçador no avanço da tuberosidade tibial em 34 cães

Cranial cruciate ligament is the main responsible for knee stability by preventing cranial tibial displacement regarding the femur. Deficiency in this ligament (CCLD) may cause subluxation of the tibia and dysfunction of the pelvic member due to overloading. Tibial osteotomies are among the more current surgical techniques for treating CCLD in dogs and they proportionate the dynamic stability by means of modifying bone geometry and the distribution of forces acting on the articulation. The objective of this work is to describe the use of the allogeneic cortical bone graft conserved in glycerin as a spacer on the tibial tuberosity advancement (TTA) for treating the CCLD. In order to do that, 34 dogs submitted to TTA surgery correction were evaluated, being 23 males (67.35%) and 11 females (32.35%). Surgical procedures happened from May 2011 to October 2015. Regarding the surgical procedure after osteotomy of the tibial tuberosity, a disk of allogeneic cortical disk, sawn wedge-hapsed, conserved in glycerin, proportions of 2x1mm was applied as spacer, enabling TTA. Advancements from 3 to 12 mm were executed, depending on the need of the patient. For animals with patella dislocation, trochleoplasty and TTA were executed in order to correct the deviation. The mean ± SD age of animals was 6.67±3.58 and weight was 15.16±12.97 kg. Mongrel dogs, Poodles and Yorkshire terriers were the most affected ones. From the 36 evaluated knees, 11 (30.56%) were associated with some traumatic process and in 25 (69.44%) there was no relation with previous trauma. From those wounds, 20 (55.56%) happened in the right limb and 16 (44.44%) in the left limb and two animals had CCLD bilaterally. Animals had continuous support, discreet drawer movement and negative tibial compression 15 days after surgery. At 30 days, 26 cases (72.22%) had firm support (FS); at 45 days, 24 cases (66 test at 7 and 67%) had FS and eight cases (22.22%) without claudication (WC). During subsequent radiographic evaluations the progressive incorporation of the graft and osteotomy union were observed. In this study, most of the diagnosed CCLD occurred in males diverging from results obtained by other authors that found greater frequency in females. Support without claudication it was observed in most of the cases of implants at 60 days. We concluded that the conserved allogeneic cortical bone graft was able to promote bone union in TTA of dogs with CCLD. None of the animals had signs of contamination, infection of the surgical wound or rejection related with the presence of the graft, demonstrated by the complete graft-bone incorporation observed early at 45 days in some animals. The glycerin was a good conservation medium for those fragments intended for grafting because, besides being of low cost, it kept bone fragments free of contamination, reducing antigenicity and preserving the functions of osteoinduction and osteoconduction. The possibility of molding the graft to the animal need is a characteristic favorable to executing the modified technique that could be molded according to the size of the animal, allowing perfect adaptation to the osteotomized local in different breeds. Intercurrences commonly observed in TTA with patellar dislocation, meniscal lesions, tibial crest fracture and displacement were not found in the animals of this study, probably due to the better distribution of forces between the pass screw in TT and the TTA plate confirming that it has good adaptation to the technique conferring to the modified TTA advantages regarding the conventional TTA.(AU)

O ligamento cruzado cranial é o principal responsável pela estabilidade do joelho, impedindo o deslocamento da tíbia cranial em relação ao fêmur. A deficiência neste ligamento (CCLD) pode causar subluxação da tíbia e disfunção do membro pélvico devido à sobrecarga. As osteotomias tibiais estão entre as técnicas cirúrgicas mais atuais para o tratamento de CCLD em cães e proporcionam a estabilidade dinâmica por meio da modificação da geometria óssea da distribuição das forças que atuam sobre a articulação. O objetivo desse estudo é descrever o uso do enxerto ósseo cortical alogênico conservado em glicerina como espaçador no avanço da tuberosidade tibial (TTA) para o tratamento do CCLD. Para isso, 34 cães submetidos à cirurgia de TTA foram avaliados, sendo 23 machos (67,35%) e 11 fêmeas (32,35%). Os procedimentos curúrgicos aconteceram entre maio de 2011 e outubro de 2015. Com relação ao procedimento cirúrgico após a osteotomia da tuberosidade tibial, um disco alogênico cortical, em forma de cunha serrada, conservado em glicerina com proporções de 2 x 1mm foi aplicado como espaçador possibilitando a TTA. Avanços de 3 a 12mm foram executados, dependendo da necessidade do paciente. Para animais com luxação da patela, realizou-se a trocleoplastia e a TTA para a correção do desvio. A idade média dos animais foi de 6,67±3,58 anos e pesos médios de 15,16±12,97kg. Cães sem raça definida, Poodles e Yorkshire Terriers foram os mais afetados. Dos 36 joelhos avaliados, 11 (30,56%) foram associados a algum processo traumático e em 25 (69,44%) não havia nenhuma relação com um trauma prévio. Dos ferimentos, 20 (55,56%) aconteceram no membro direito e 16 (44,44%) no esquerdo, sendo que dois animais apresentavam CCLD bilateralmente. Os animais tiveram suporte contínuo, discreto movimento de gaveta e compressão tibial negativa 15 dias após a cirurgia. Aos 30 dias, 26 casos tinham suporte firme (FS); aos 45 dias, 24 casos tinham FS e oito casos sem claudicação (WC). Durante avaliações radiográficas subsequentes, observou-se a incorporação progressiva da união do enxerto e da osteotomia. Neste estudo, a maior parte do CCLD diagnosticado ocorreu em machos, divergindo dos resultados obtidos por outros autores que encontraram maior frequência em fêmeas. Suporte sem claudicação foi observado na maioria dos casos de implantes aos 60 dias. Foi concluído que o enxerto ósseo cortical alogênico conservado foi capaz de promover a união óssea na TTA de cães com CCLD. Nenhum dos animais apresentou sinais de contaminação, infecção da ferida cirúrgica ou rejeição relacionada à presença do enxerto, demonstrada pela incorporação completa do enxerto ósseo observada precocemente aos 45 dias em alguns animais. A glicerina foi um bom meio de conservação para os fragmentos destinados à enxertia porque, além do menor custo, manteve os fragmentos ósseos livres de contaminação, reduzindo a antigenicidade e preservando as funções de osteoindução e osteocondução. A possibilidade de moldagem do enxerto à necessidade do animal é uma característica favorável à execução da técnica modificada que pode ser moldada de acordo com o tamanho do animal, possibilitando perfeita adaptação ao local osteotomizado em diferentes raças. Intercorrências comumente observadas na TTA com luxação patelar, lesões meniscais, fratura da crista tibial e deslocamento não foram encontradas nos animais deste estudo, provavelmente devido à melhor distribuição de forças entre a passagem do parafuso no TT e a placa do TTA, confirmando que tem boa adaptação à técnica conferindo às vantagens da TTA modificada em relação à TTA convencional.(AU)

Femorotibial kinematics in dogs with cranial cruciate ligament insufficiency: a three-dimensional in-vivo fluoroscopic analysis during walking.

BACKGROUND: Cranial cruciate ligament (CrCL) insufficiency is a degenerative condition that is a common cause of pelvic limb lameness and osteoarthritis in dogs. Surgical therapies developed to treat dogs with naturally occurring CrCL insufficiency aim to address the resultant instability, but the in-vivo alterations in stifle kinematics associated with CrCL insufficiency have not been accurately defined. The objective of this study was to quantify the 3-dimensional femorotibial joint kinematics of dogs with naturally occurring cranial cruciate ligament (CrCL) insufficiency during ambulation. Eighteen client-owned dogs (20-40 kg) with natural unilateral complete CrCL rupture were included. Computed tomographic scans were used to create digital 3-dimensional models of the femur and tibia bilaterally for each dog. Lateral fluoroscopic images were obtained during treadmill walking and 3 complete gait cycles were analyzed. Stifle flexion/extension angle, craniocaudal translation, and internal/external rotation were calculated throughout the gait cycle using a previously described 3D-to-2D image registration process. Results were compared between the pre-operative CrCL-deficient and 6-month post-operative contralateral stifles (control). RESULTS: CrCL-deficient stifles were maintained in greater flexion throughout the gait cycle. Cranial tibial subluxation was evident in CrCL-deficient stifles at all time points throughout the gait cycle [9.7 mm at mid-stance (P < 0.0001); 2.1 mm at mid-swing (P < 0.0017)], and the magnitude of cranial tibial subluxation was greater at mid-stance phase than at mid-swing phase (P < 0.0001). Greater internal tibial rotation was present in CrCL-deficient stifles during stance phase (P < 0.0022) but no difference in axial rotation was evident during swing phase. CONCLUSIONS: Naturally occurring CrCL rupture causes profound craniocaudal translational and axial rotational instability, which is most pronounced during the stance phase of gait. Surgical stabilization techniques should aim to resolve both craniocaudal subluxation and axial rotational instability.

Patellofemoral kinematics in dogs with cranial cruciate ligament insufficiency: an in-vivo fluoroscopic analysis during walking.

BACKGROUND: Complete rupture of the cranial cruciate ligament (CrCL) in dogs causes profound disturbance to stifle joint biomechanics. The objective of this study was to characterize the effects of cranial cruciate ligament (CrCL) insufficiency on patellofemoral (PF) kinematics in dogs during walking. Ten client-owned dogs (20-40 kg) with natural unilateral complete CrCL rupture were included. Dogs underwent computed tomographic scans to create digital bone-models of the patella and femur. Lateral projection fluoroscopy of the stifles was performed during treadmill walking. Sagittal plane PF kinematics were calculated throughout the gait cycle by overlaying digital bone models on fluoroscopic images using a previously described 2D-3D registration technique. For acquisition of kinematics in the contralateral (control) stifle, fluoroscopy was repeated 6-months after stabilizing surgery of the affected side. Results were compared between the pre-operative CrCL-deficient and 6-month post-operative control stifles. RESULTS: Craniocaudal PF translation was similar between CrCL-deficient and control stifles throughout the gait cycle. The patella was more distal and positioned in greater flexion throughout the gait cycle in CrCL-deficient stifles when compared to the control stifle at equivalent time points. There was no significant difference in PF poses between CrCL-deficient and control stifles at equivalent femorotibial flexion angles; however, common femorotibial flexion angles were only found over a small range during the swing phase of gait. CONCLUSIONS: CrCL insufficiency altered PF kinematics during walking, where the changes were predominately attributable to the femorotibial joint being held in more flexion. Abnormal PF kinematics may play a role in the development of osteoarthritis that is commonly observed in the PF joint CrCL-deficient stifles.

Combined tibial plateau levelling osteotomy and lateral fabellotibial suture for cranial cruciate ligament rupture with severe rotational instability in dogs.

OBJECTIVE: To report the use of tibial plateau levelling osteotomy and lateral fabellotibial suture in combination for treatment of severe internal tibial rotational stifle instability in cranial cruciate-deficient stifles. METHODS: Twenty-three stifles in 19 dogs were diagnosed with cranial cruciate ligament rupture with severe stifle instability, characterised by marked cranial tibial translation and internal tibial rotation that was evident during orthopaedic examination. A combined tibial plateau levelling osteotomy and lateral fabellotibial suture procedure were performed to stabilise the stifle joint. The surgical complications, short-term lameness scores and owner satisfaction were evaluated. RESULTS: The postoperative complication rate was 21 · 7% with one minor (4 · 3%) and four major (17 · 4%) complications. At short-term follow-up one dog had an intermittent low-grade lameness and two dogs had mild tibial internal rotational instability present on palpation without lameness. Owner's overall satisfaction with the operation and recovery was good (21 · 4%) to excellent (78 · 6%). CLINICAL SIGNIFICANCE: The use of lateral fabellotibial suture in combination with tibial plateau levelling osteotomy was an effective technique for managing cranial cruciate ligament rupture with severe internal tibial rotational stifle instability.

Diagnosis and surgical correction of congenital bilateral patellar luxation in two dwarf zebu calves.

This case study presents two female dwarf zebu calves with permanent bilateral flexion of the stifle joint secondary to bilateral congenital lateral patellar luxation. The patella could be manually repositioned bilaterally in the first calf (14 days old), but re-luxated immediately with release of manual pressure (luxation grade III). In the second calf (28 days old) both patellae were permanently luxated laterally (grade IV). The right and left stifles of each calf were operated in a staged procedure with approximately 14 days between surgery of the two sides. While a lateral release and a medial imbrication were sufficient for correction in the left stifle of the younger calf, a trochlear wedge resection was required in the other three stifle joints with hypo- to aplastic trochleas in order to stabilize the patella. Postoperatively each stifle was immobilized for 10 days with a cast. The younger calf regained full function of the hind limbs during the complete gait cycle in walk and in trot one month after the procedure. The older calf regained full function in the hind limbs in walk but in trot there was some degree of lameness due to a reduced extension of approximately 20°.

Biomechanics of an orthosis-managed cranial cruciate ligament-deficient canine stifle joint predicted by use of a computer model.

OBJECTIVE To evaluate effects of an orthosis on biomechanics of a cranial cruciate ligament (CrCL)-deficient canine stifle joint by use of a 3-D quasistatic rigid-body pelvic limb computer model simulating the stance phase of gait and to investigate influences of orthosis hinge stiffness (durometer). SAMPLE A previously developed computer simulation model for a healthy 33-kg 5-year-old neutered Golden Retriever. PROCEDURES A custom stifle joint orthosis was implemented in the CrCL-deficient pelvic limb computer simulation model. Ligament loads, relative tibial translation, and relative tibial rotation in the orthosis-stabilized stifle joint (baseline scenario; high-durometer hinge]) were determined and compared with values for CrCL-intact and CrCL-deficient stifle joints. Sensitivity analysis was conducted to evaluate the influence of orthosis hinge stiffness on model outcome measures. RESULTS The orthosis decreased loads placed on the caudal cruciate and lateral collateral ligaments and increased load placed on the medial collateral ligament, compared with loads for the CrCL-intact stifle joint. Ligament loads were decreased in the orthosis-managed CrCL-deficient stifle joint, compared with loads for the CrCL-deficient stifle joint. Relative tibial translation and rotation decreased but were not eliminated after orthosis management. Increased orthosis hinge stiffness reduced tibial translation and rotation, whereas decreased hinge stiffness increased internal tibial rotation, compared with values for the baseline scenario. CONCLUSIONS AND CLINICAL RELEVANCE Stifle joint biomechanics were improved following orthosis implementation, compared with biomechanics of the CrCL-deficient stifle joint. Orthosis hinge stiffness influenced stifle joint biomechanics. An orthosis may be a viable option to stabilize a CrCL-deficient canine stifle joint.

Relationship between increased in vivo meniscal loads and abnormal tibiofemoral surface alignment in ACL deficient sheep is varied.

The aim of this study was to quantify how abnormal dynamic tibiofemoral surface alignment affects the load bearing function of menisci in vivo. Using a sheep model of ACL deficiency, we tested the hypothesis that increased in vivo meniscal loads correlate with greater tibiofemoral surface alignment abnormality. Stifle kinematics were recorded using a bone-mounted instrumented spatial linkage in four sheep before, and at four and twenty weeks (w) after ACL transection. A parallel robotic manipulator was used to quantify stifle kinetics by reproducing each animal׳s in vivo kinematics and measuring tissue loads during gait. Meniscal resultant loads were estimated from the change in joint reaction force after sequentially removing load-bearing tissues. Tibiofemoral subchondral surfaces were then traced and modeled using thin plate splines. Proximity disturbance is a surface interaction measure used to quantify dynamic tibiofemoral surface alignment abnormality. ACL transection increased meniscal loads by 30-145% at 20w post-ACL transection, whereas the degree of dynamic tibiofemoral subchondral surface alignment varied between sheep. Positive and significant correlations between increased meniscal loads and proximity disturbance values >10mm were observed (R2=0.04-0.57; p≤0.05). Our results suggest that the proximity disturbance measure reflects abnormal meniscal loads following ACL injury; however given the range of R2 values, perturbations in dynamic tibiofemoral subchondral surface alignment do not explain abnormal joint kinetics entirely, and point to the presence of other dynamic compensatory mechanisms that may have a significant bearing on in vivo joint function and long-term joint health.

Improved functional assessment of osteoarthritic knee joint after chondrogenically induced cell treatment.

OBJECTIVES: Our previous studies on osteoarthritis (OA) revealed positive outcome after chondrogenically induced cells treatment. Presently, the functional improvements of these treated OA knee joints were quantified followed by evaluation of the mechanical properties of the engineered cartilages. METHODS: Baseline electromyogram (EMGs) were conducted at week 0 (pre-OA), on the locomotory muscles of nine un-castrated male sheep (Siamese long tail cross) divided into controls, adipose-derived stem cells (ADSCs) and bone marrow stem cells (BMSCs), before OA inductions. Subsequent recordings were performed at week 7 and week 31 which were post-OA and post-treatments. Afterwards, the compression tests of the regenerated cartilage were performed. RESULTS: Post-treatment EMG analysis revealed that the control sheep retained significant reductions in amplitudes at the right medial gluteus, vastus lateralis and bicep femoris, whereas BMSCs and ADSCs samples had no further significant reductions (P < 0.05). Grossly and histologically, the treated knee joints demonstrated the presence of regenerated neo cartilages evidenced by the fluorescence of PKH26 tracker. Based on the International Cartilage Repair Society scores (ICRS), they had significantly lower grades than the controls (P < 0.05). The compression moduli of the native cartilages and the engineered cartilages differed significantly at the tibia plateau, patella femoral groove and the patella; whereas at the medial femoral condyle, they had similar moduli of 0.69 MPa and 0.40-0.64 MPa respectively. Their compression strengths at all four regions were within ±10 MPa. CONCLUSION: The tissue engineered cartilages provided evidence of functional recoveries associated to the structural regenerations, and their mechanical properties were comparable with the native cartilage.

The effect of medial meniscal horn injury on knee stability.

PURPOSE: This study investigated the effect of damage of the posterior and anterior horns of the medial meniscus on knee stability. METHODS: Twenty fresh-frozen porcine knees were divided into two groups (anterior horn and posterior horn injury). Each group was tested in three states: intact medial meniscus, posterior or anterior horn of medial meniscus resection and total medial meniscectomy. A robotic testing system was used to test anterior tibial translation (ATT) at 30° (full extension), 60° and 90° of knee flexion with an external anterior tibial load of 89 N, internal rotation (IR) and external rotation (ER) at 30° and 60° of knee flexion under a 4 N m tibial rotation torque. RESULTS: In response to an IR torque, there was a significant difference between the state of intact medial meniscus and anterior and posterior horn damage, except for anterior horn resection at 60° of knee flexion. In response to an ER torque, there were no significant differences between the state of intact meniscus and horn damage except for anterior horn resection at 30° of knee flexion. Meniscal damage had no significant effect on ATT. CONCLUSION: The results indicated that the posterior horn was more important in controlling the IR stability than the anterior horn with knee flexion, and the anterior horn was more important in controlling the ER stability than the posterior horn at full knee extension in the anterior cruciate ligament-intact knee. These findings further the understanding of the mechanisms, the prevention of injuries and rehabilitation of meniscal horn injury in clinical practice.

Interaction between gastrocnemius muscle weakness and moderate exercise deteriorates joint integrity in rat knee.

The aim of this study was to determine the effect on the knee joint of the interaction between ankle muscle weakness and moderate exercise. Gastrocnemius muscle weakness was induced by intramuscular injection of botulinum toxin type A (BTX) in rats. Low-speed treadmill running (12 m/min for 60 min) was applied for 6 weeks in rats with and without BTX. Untreated animals were used as controls. After BTX injection, the gastrocnemius muscle weakness was confirmed by 3-D motion analysis in kinematic features of the hindlimb during locomotion as an increased maximal dorsiflexion angle during the stance phase. Serum biomarker analysis by enzyme-linked immunosorbent assay revealed that low-speed running decreased the catabolic effect on type II collagen. However, the inhibition of catabolism induced by running exercise was significantly counteracted by BTX injection. In addition, thinning of the cartilage layer and a reduction in the chondrocyte density was also found in the tibial plateau of the knee in the BTX-injected rats after running for 6 weeks. These data suggest that moderate exercise have a positive effect on joint homeostasis. However, ankle muscle weakness may alter the mechanical environment of the knee and impair the integrity of joint cartilage with moderate exercise.

Effect of tibial subluxation on the measurements for tibial tuberosity advancement in dogs with cranial cruciate ligament deficiency. An ex vivo study.

OBJECTIVES: The main objectives were to evaluate the impact of femorotibial subluxation on the preoperative measurements for tibial tuberosity advancement (TTA) by defining radiographic landmarks and testing the repeatability for assessing cranial tibial subluxation (CTS). Also, we aimed at developing a formula to calculate the necessary adjustment in measurement of TTA in stifles with CTS. METHODS: Forty stifles were used to examine the influence of CTS on preoperative TTA measurements before and after transection of the cranial cruciate ligament. Mediolateral radiographs were obtained and measurements performed by three investigators. The observed variabilities were assessed by inter- and intra-observer differences. RESULTS: Measurements of CTS and preoperative TTA showed a good to excellent inter- and intra-observer correlation. We found a significant influence of CTS on TTA measurements and developed a formula to calculate the necessary adjustment in measurement of TTA in stifles with CTS. CONCLUSION: We found a correlation between the tibial subluxation and the measurements for TTA, with the latter decreasing with increasing subluxation. This has to be taken into account when measuring the advancement in stifles with complete rupture of the cranial cruciate ligament. We provided a formula to calculate the necessary addition to the measured advancement.

A new measure of tibiofemoral subchondral bone interactions that correlates with early cartilage damage in injured sheep.

We have demonstrated previously that chondral damage is associated with increased knee surface velocities following ligament and meniscus injuries in sheep. We tested the hypothesis that cartilage damage scores would correlate with a new bone surface interaction measure that captures complex changes in tibiofemoral alignment, "proximity disturbance" (PD). Six sheep underwent combined anterior cruciate and medial collateral ligament transection (ACL/MCLx), five complete lateral meniscectomy (Mx), and four sham arthrotomy (Sham). Tibiofemoral subchondral bone surfaces were modeled, and the post-operative changes in relative separation of the surfaces (i.e., "proximity") were derived from subject-specific in vivo 3D stifle kinematics. Surface areas of regions of near contact were determined, and PD was calculated as the range of change in tibiofemoral proximity, divided by normalized overlapping proximity surface areas between baseline and post-operative time points. Cartilage morphology was graded at dissection. ACL/MCLx PD was significantly elevated relative to Mx and Shams, and correlated with cartilage damage (r(2) = 0.88-0.98). Although not statistically significant, Mx PD values tended to be higher than those of Shams, and correlated with cartilage damage. Results from both injury models suggest that increasing change in tibiofemoral surface alignment may be increasingly deleterious to long-term cartilage health in sheep.