Effect of tibial plateau leveling on cranial and caudal tibial thrusts in canine cranial cruciate-deficient stifles: an in vitro experimental study

OBJECTIVES--To investigate the effect of tibial plateau leveling (TPL) on tibial subluxation and tibial axial rotation; to determine the minimal tibial plateau rotation (MinTPR) angle that provides stifle stability; and to evaluate caudal cruciate ligament (CaCL) strain following tibial plateau rotation in cranial cruciate ligament (CrCL)-deficient stifles. ANIMALS--Fifteen canine cadaver hind limbs. METHODS--Tibial subluxation was measured from lateral radiographs in intact, loaded stifles and after sequential CrCL transection, MinTPR, TPL, and CaCL transection. The MinTPR angle was determined using a custom-made hinge plate and compared with the TPL angle. Tibial axial rotation was evaluated in CrCL-deficient stifles before and after TPL. Finally, CaCL strain was recorded in intact, loaded stifles, and following MinTPR, TPL, and tibial plateau over-rotation (MaxTPR) using a force probe. RESULTS--Cranial tibial subluxation in CrCL-deficient stifles was eliminated with TPL. Tibial plateau rotation, however, induced caudal tibial subluxation, which significantly increased from MinTPR to TPL before and after CaCL transection. The MinTPR angle was 6.5 degrees +/- 0.9 degrees less than the TPL angle (P <.05). Tibial internal rotation decreased significantly after TPL in CrCL-deficient stifles. Finally, CaCL strain increased with increasing tibial plateau rotation. CONCLUSIONS--This study suggests that, during stance phase, TPL transforms cranial tibial thrust into caudal tibial thrust, thereby stabilizing the stifle in the cranio-caudal plane via the constraint of the CaCL. The increase in CaCL stress, which results from tibial plateau rotation, could predispose the CaCL to fatigue failure and therefore would caution against tibial plateau over-rotation.     

An in vitro study to determine the effectiveness of a patellar ligament/fascia lata graft and new tibial suture anchor points for extracapsular stabilization of the cranial cruciate ligament-deficient stifle in the dog

OBJECTIVE: (1) To determine whether an extracapsular patellar ligament/fascia lata graft would provide stability in the cranial cruciate ligament (CrCL)-deficient stifle comparable with that of the intact stifle. (2) To determine if different tibial anchor points would enhance stability of the CrCLdeficient stifle when compared with the standard fabellar-tibial suture (FTS) placement. STUDY DESIGN: Experimental. ANIMALS: Twenty-eight canine cadaver hind limbs. METHODS: Stifles were mounted in a jig and tested between loads of -65 and 80 N. After testing the intact CrCL, 4 stabilization techniques were tested after CrCL transection: lateral graft technique (LGT) and 3 FTS with different tibial anchor points. RESULTS: There were no significant differences in displacement between the LGT and standard FTS, between the LGT and the intact CrCL, or between the FTS and the intact CrCL, in either the Securos or the Screw-washer experiments. Stiffness of the intact CrCL was significantly greater than that of any stabilization technique and the cut CrCL. The standard FTS showed the least displacement of all suture stabilization techniques. Differences in stiffness were not significant between the suture stabilization techniques. CONCLUSIONS: Securely anchored, the LGT results in a reduction in drawer motion similar to that of the intact CrCL and the standard FTS. Altering the tibial anchor point for the FTS does not improve stiffness or enhance stabilization of the CrCL-deficient stifle. CLINICAL RELEVANCE: The LGT could be used for the treatment of CrCL ruptures in the dog. A clinical study is recommended.     

The effect of stifle angle on cranial tibial translation following tibial plateau leveling osteotomy: an in vitro experimental analysis

This study was designed to determine the ability of tibial plateau leveling osteotomy (TPLO) to eliminate cranial tibial translation (CTT) through a loaded range of motion. Twenty-four large-breed canine cadaver limbs were compared. Each limb was placed in a custom designed jig at 120° of stifle extension under an axial load of 20% body weight. A force of approximately 10 N/s mimiced the action of the quadriceps muscle and allowed the limb to move from 120° to maximal extension. Positional data were acquired using electromagnetic motion-tracking sensors. Each limb was tested under normal, cranial cruciate ligament (CrCL)-deficient, and TPLO-treated conditions. Cranial tibial translation significantly increased after transection of the CrCL. The TPLO failed to normalize CTT within the CrCL deficient stifle; however, values trended towards intact values throughout the range of motion. The TPLO was more effective at higher angles of flexion. These altered biomechanics may help explain the continued progression of osteoarthritis in TPLO repaired stifles. This loaded model may serve as a method for future evaluation of other surgical techniques.     

Synovitis in dogs with stable stifle joints and incipient cranial cruciate ligament rupture: a cross-sectional study

Objective: To evaluate stifle joints of dogs for synovitis, before development of joint instability and cranial cruciate ligament rupture (CrCLR). Study Design: Cross‐sectional study. Animals: Dogs (n=16) with CrCLR and stable contralateral stifles; 10 control dogs with intact CrCL. Methods: Arthritis and tibial translation were graded radiographically. Synovitis severity and cruciate pathology were assessed arthroscopically. Presence of inflammatory cells in synovial membrane biopsies was scored histologically. CrCLR stifle pairs and control stifles were compared. Results: Radiographic evidence of arthritis, cranial tibial translation, and arthroscopic synovitis were increased in unstable stifles, when compared with stable contralateral stifles in CrCLR dogs (P<.05). Arthroscopic synovitis in both joints of CrCLR dogs was increased compared with controls, was correlated with radiographic arthritis (S_R=0.71, P<.05), and was present in all stable contralateral stifles. Arthroscopically, 75% of stable stifle joints had CrCL fiber disruption, which correlated with severity of synovitis (S_R=0.56, P<.05). Histologic evidence of synovitis was identified in all CrCLR dogs, but was only significantly correlated with arthroscopic observations in stable stifles (r²=0.57, P<.005). Conclusion: Synovitis is an early feature of the CrCLR arthropathy in dogs before development of joint instability clinically. Severity of synovitis is correlated with radiographic arthritis in joints with minimal to no clinically detectable CrCL damage.     

Effect of tibial tuberosity advancement on cranial tibial subluxation in canine cranial cruciate-deficient stifle joints: an in vitro experimental study

OBJECTIVE: To evaluate the effect of tibial tuberosity advancement (TTA) on tibiofemoral shear force as reflected by measurement of cranial tibial subluxation (CTS) and patella tendon angle (PTA) in the canine cranial cruciate ligament (CrCL) deficient stifle joint. STUDY DESIGN: In vitro cadaver study. ANIMALS: Canine cadaveric hind limbs (n=10). METHODS: CTS and PTA were evaluated from lateral radiographic projections in axially loaded intact CrCL stifle joints, after transection of the CrCL, at a maximally advanced tibial tuberosity position, and at a critical point position. A custom-designed hinge plate allowed alteration of the tibia to tibial tuberosity distance (Ti-TT) under axial load. Digitized radiographic images were used to quantify CTS, PTA, and Ti-TT. Comparisons within groups were made using 1-way repeated measures ANOVA. A post hoc Tukey's HSD test was used to determine post-ANOVA pair-wise comparison within these groups. Significance was set at a value of P<.05. RESULTS: CTS occurred after CrCL transection, which was significantly different from the intact position (P<.01). Subsequent stability of the stifle joint was obtained by advancing the tibial tuberosity. In the maximally advanced tibial tuberosity position, caudal tibial thrust was generated resulting in caudal tibial subluxation that was significantly different from the transected CrCL position (P<.01) and from the intact CrCL position (P<.01). Despite a stable joint, there was slight CTS at the critical point position, which was significantly different from the intact CrCL position (P<.05). The PTA at the maximally advanced position was significantly different from the intact, critical point and reference 90 degrees PTAs (P<.01). The PTA at the critical point position was significantly different from the intact and maximally advanced tibial tuberosity PTAs (P<.01), but not different (P>.05) from the reference 90 degrees PTA. CONCLUSION: We demonstrated that advancement of the tibial tuberosity neutralized cranial tibial thrust, and converted cranial tibial thrust into caudal tibial thrust. Neutralization of tibiofemoral shear forces occurred at a PTA of 90.3+/-9.0 degrees. CLINICAL RELEVANCE: TTA can effectively change the magnitude and direction of the tibiofemoral shear force, and thus may be used to prevent craniotibial translation in a CrCL deficient stifle joint.     

Force plate gait analysis to assess limb function after tibial tuberosity advancement in dogs with cranial cruciate ligament disease

OBJECTIVE: To assess functional outcome in dogs with cranial cruciate ligament (CrCL) disease after tibial tuberosity advancement (TTA) using force plate gait analysis, and to evaluate parameters potentially influencing outcome. STUDY DESIGN: Prospective clinical study. ANIMALS: Consecutive clinical patients (n = 37) with CrCL-deficient stifles (n = 40). METHODS: The stifle joints were examined arthroscopically prior to TTA. Meniscal release was not performed if the medial meniscus was intact. Open medial arthrotomy and partial meniscectomy were performed in the presence of meniscal tears. Vertical ground reaction forces were measured preoperatively and at follow-up examinations four to 16 months postoperatively (mean: 5.9 months). The ground reaction forces of a group of 65 healthy dogs were used for the comparison. The potential effects of clinical parameters on functional outcome were evaluated statistically. RESULTS: Complete CrCL rupture was identified in 28 joints, and partial CrCL rupture in 12 joints. The medial meniscus was damaged in 21 stifles. Vertical ground reaction forces were significantly higher at follow-up (P < 0.01), but remained significantly lower than those of control dogs (P < 0.01). Complications were identified in 25% of joints, and the dogs with complications had significantly lower peak vertical forces at follow-up than the dogs without complications (P = 0.04). Other clinical parameters did not influence outcome. CONCLUSIONS: Tibial tuberosity advancement significantly improved limb function in dogs with CrCL disease, but did not result in complete return to function. Complications adversely affected functional outcome. CLINICAL SIGNIFICANCE: A return to a function of approximately 90% of normal can be expected in dogs with CrCL disease undergoing TTA.     

In vivo evaluation of intra-articular protection in a novel model of canine cranial cruciate ligament mid-substance elongation injury

OBJECTIVES: To evaluate the effects of intra-articular protection (IAP) on the canine cranial cruciate ligament (CrCL) and stifle in a CrCL midsubstance elongation injury model. STUDY DESIGN: Experimental longitudinal cohort study. ANIMALS: Skeletally mature female mixed breed hounds (n=12; mean+/-SEM weight, 25.6+/-0.7 kg). METHODS: After CrCL elongation in 1 stifle of each dog, IAP was applied in 6 joints. In vivo assessment included radiographs, cranial-caudal joint translation, gait analysis, and synovial fluid levels of 3B3(-) (proteoglycan epitope) and C2C (collagen II neoepitope) up to 12 weeks after surgery. Joint translation and rotation were quantified at necropsy. CrCL midsubstance length was determined before and after elongation and at necropsy. CrCLs were subjectively assessed with light microscopy. Comparisons were made between stifles containing elongated CrCLs with and without IAP and unoperated controls. RESULTS: Four weeks after surgery, ground reaction forces were significantly decreased in operated limbs. Absolute C2C levels were significantly elevated in operated stifles 4 weeks post-surgery. C2C and 3B3(-) levels normalized to total protein were significantly elevated in IAP+ stifles 8 weeks after surgery. Protected CrCLs appeared to have decreased granulation tissue and better collagen fiber alignment. CONCLUSIONS: IAP has negligible effects on the canine stifle based on the response variables evaluated in this 12-week study. Protection of elongated CrCLs may promote reduced, organized scar formation. CLINICAL RELEVANCE: These results support the healing capacity of the canine CrCL midsubstance following elongation injury and IAP application to potentially reduce cicatrix formation in elongated CrCLs.     

Effect of Tibial Plateau Leveling Osteotomy on Femorotibial Contact Mechanics and Stifle Kinematics

Objective— To evaluate the effects of tibial plateau leveling osteotomy (TPLO) on femorotibial contact mechanics and 3-dimensional (3D) kinematics in cranial cruciate ligament (CrCL)-deficient stifles of dogs.
Study Design— In vitro biomechanical study.
Animals— Unpaired pelvic limbs from 8 dogs, weighing 28–35 kg.
Methods— Digital pressure sensors placed subjacent to the menisci were used to measure femorotibial contact force, contact area, peak and mean contact pressure, and peak pressure location with the limb under an axial load of 30% body weight and a stifle angle of 135°. Three-dimensional static poses of the stifle were obtained using a Microscribe digitizing arm. Each specimen was tested under normal, CrCL-deficient, and TPLO-treated conditions. Repeated measures analysis of variance with a Tukey post hoc test ( P <.05) was used for statistical comparison.
Results— Significant disturbances to all measured contact mechanical variables were evident after CrCL transection, which corresponded to marked cranial tibial subluxation and increased internal tibial rotation in the CrCL-deficient stifle. No significant differences in 3D femorotibial alignment were observed between normal and TPLO-treated stifles; however, femorotibial contact area remained significantly smaller and peak contact pressures in both medial and lateral stifle compartments were positioned more caudally on the tibial plateau, when compared with normal.
Conclusion— Whereas TPLO eliminates craniocaudal stifle instability during simulated weight bearing, the procedure fails to concurrently restore femorotibial contact mechanics to normal.
Clinical Relevance— Progression of stifle osteoarthritis in dogs treated with TPLO may be partly the result of abnormal stifle contact mechanics induced by altering the orientation of the proximal tibial articulating surface.     

In vitro 3-dimensional kinematic evaluation of 2 corrective operations for cranial cruciate ligament-deficient stifle

The objective of this study was to determine the immediate postoperative effect of 2 corrective operations for cranial cruciate ligament (CCL)-deficient stifle by evaluating 3-dimensional (3-D) stifle kinematics. Ten hindlimbs from large-breed canine cadavers were used. Range of motion was induced by applying 100 N of traction on the quadriceps tendon and recorded with electromagnetic movement sensors for each situation: intact stifle (control), CCL-sectioned stifle, and surgical correction of the sectioned ligament with the modified retinacular imbrication technique (MRIT) and then with a tibial plateau leveling osteotomy--Montavon (TPLO-M). The results for the experimental situations were compared with the results for the control situation by 1-way repeated-measures analysis of variance and with each other by post-hoc analysis with the least-significant-difference method. Range of motion was significantly decreased by MRIT as compared with the other situations. Normal cranial tibial translation was restored after MRIT, whereas TPLO-M resulted in significant caudal translation. A significant increase in external rotation was observed after both MRIT and TPLO-M. A significant increase in tibial adduction throughout the range of motion was observed with TPLO-M, whereas a significant increase in tibial abduction was observed after MRIT. This study allowed us to better understand objectively the effects on 3-D canine stifle kinematics of MRIT and TPLO-M. We suggest that this type of in vitro study would be useful to evaluate established and upcoming surgical techniques and potentially improve corrective surgery.     

Effect of medial meniscal release on tibial translation after tibial plateau leveling osteotomy

OBJECTIVE: To evaluate the biomechanical effects of medial meniscal release (MMR) and medial, caudal pole hemimeniscectomy (MCH) on joint stability in the cranial cruciate ligament (CCL)-deficient canine stifle before and after tibial plateau leveling osteotomy (TPLO). STUDY DESIGN: Experimental study. ANIMALS: Thirty-one dogs. METHODS: In experiment 1, 16 pairs of normal hindlimbs randomly assigned to an intact or transected CCL group were studied to determine the magnitude of tibial translation after MMR and MCH under 20% body weight load using radiographic imaging of radio-opaque markers. In experiment 2, 15 pairs of CCL-deficient hindlimbs were randomly assigned to a TPLO or sham TPLO group. The remainder of the experiment was performed as described for experiment 1. The effect of CCL transection, MMR, MCH and TPLO were analyzed using 2-way repeated measures ANOVA; P<.05 was considered significant. RESULTS: We found a greater effect of MMR on tibial translation in transected CCL stifles than in intact stifles (P=.0016). We found no further effect of MCH after MMR (P>.05). We found a greater effect of MMR in sham TPLO than TPLO stifles (P=.0013) but no further effect of MCH after MMR (P>.05). CONCLUSIONS: By resisting tibial translation the medial meniscus might be at greater risk of tearing in CCL-deficient stifles. TPLO may spare the medial meniscus by neutralizing the tibial thrust and eliminating the wedge effect of the medial meniscus. CLINICAL RELEVANCE: MMR may not be indicated in the CCL-deficient stifle stabilized by TPLO.     

Effect of Tibial Tuberosity Advancement on Femorotibial Contact Mechanics and Stifle Kinematics

Objective— To evaluate the effects of tibial tuberosity advancement (TTA) on femorotibial contact mechanics and 3-dimensional kinematics in cranial cruciate ligament (CrCL)-deficient stifles of dogs.
Study Design— In vitro biomechanical study.
Animals— Unpaired pelvic limbs from 8 dogs, weighing 28–35 kg.
Methods— Digital pressure sensors placed subjacent to the menisci were used to measure femorotibial contact force, contact area, peak and mean contact pressure, and peak pressure location with the limb under an axial load of 30% body weight and a stifle angle of 135°. Three-dimensional static poses of the stifle were obtained using a Microscribe digitizing arm. Each specimen was tested under normal, CrCL-deficient, and TTA-treated conditions. Repeated measures analysis of variance with a Tukey post hoc test ( P <.05) was used for statistical comparison.
Results— Significant disturbances to all measured contact mechanic parameters were evident after CrCL transection, which corresponded to marked cranial tibial subluxation and internal tibial rotation in the CrCL-deficient stifle. No significant differences in any contact mechanic and kinematic parameters were detected between normal and TTA-treated stifles.
Conclusion— TTA eliminates craniocaudal stifle instability during simulated weight-bearing and concurrently restores femorotibial contact mechanics to normal.
Clinical Relevance— TTA may mitigate the progression of stifle osteoarthritis in dogs afflicted with CrCL insufficiency by eliminating cranial tibial thrust while preserving the normal orientation of the proximal tibial articulating surface.     

Effect of 9 mm tibial tuberosity advancement on cranial tibial translation in the canine cranial cruciate ligament-deficient stifle

Objective— To assess the effect of 9 mm tibial tuberosity advancement (TTA) on cranial tibial translation (CTT) in a cranial cruciate ligament (CCL)-deficient canine stifle model.
Study Design— In vitro cadaveric study.
Animals— Canine pelvic limbs (n=12).
Methods— Each stifle was placed in a jig at 135° with a simulated quadriceps force and tibial axial force. CTT distance was measured with the CCL intact (iCCL), transected (tCCL), and after performing TTA using a 9 mm cage.
Results— Mean CTT for iCCL was 0.42 mm, 1.58 mm after severing the CCL, and 1.06 mm post-TTA. The tCCL CTT measured without any quadriceps force was 2.59 mm. Differences between the intact and tCCL ( P <.0001) and tCCL and TTA ( P =.0003) were significant. The difference between the tCCL with and without the quadriceps force was not significant ( P =.0597).
Conclusions— These data confirm that TTA does reduce CTT in tCCL stifles in this model. The CTT noted was less than that noted clinically. The addition of a simulated quadriceps force to a CCL-deficient stifle before a TTA, by itself, may not significantly lessen CTT.
Clinical Relevance— Whereas this in vitro model demonstrated that TTA reduced CTT in canine stifles with CCL transected, the model limitations preclude extrapolation to the effect of TTA in a live dog.     

Kinematic gait analysis of the hind limb after tibial plateau levelling osteotomy and cranial tibial wedge osteotomy in ten dogs

This study identifies and compares the kinematic gait changes occurring in tibial plateau levelling osteotomy (TPLO) and cranial tibial wedge osteotomy (CTWO) limbs after transection of the cranial cruciate ligament (CrCL). Ten, healthy, adult beagle dogs were assigned to TPLO (five dogs) and CTWO (five dogs) groups. Hind limb kinematics were assessed, while dogs were trotted at speeds ranging from 2.0 to 2.3 m/s. The animals were evaluated preoperatively (prior to TPLO and CTWO surgery) and at both 8 and 12 weeks after surgery. Two-dimensional evaluation was synchronized to obtain the three-dimensional coordinates using the APAS motion analysis software. Gait patterns were assessed by measuring stifle, tibiotarsal joint angles and stifle joints angular velocity. Stifle and tibiotarsal joint functions were not affected by TPLO surgery, but stifle and tibiotarsal joint angles were changed, following CTWO surgery, compared with their preoperative values. The angular velocity patterns of CTWO were characterized by increased stifle joint extension velocity from the middle to end swing phase and decrease in the peak velocities (flexion) during swing phase. None of these changes was observed in the stance phase after the CTWO surgery. These kinematic results showed that dogs that underwent a CTWO procedure were more likely to have significantly hyperextended gait patterns of the swing phase postoperatively than the dogs that had a TPLO procedure for repair of a ruptured CrCL.     

Hamstring graft technique for stabilization of canine cranial cruciate ligament deficient stifles

OBJECTIVE: To investigate the harvest and application of hamstring grafts for canine cranial cruciate ligament (CrCL) reconstruction. STUDY DESIGN: Experimental study. ANIMALS: Four adult female hounds, weighing 26.3 +/- 1.6 kg (mean +/- SEM). METHODS-One stifle in each dog was randomly chosen for hamstring graft CrCL reconstruction after native CrCL transection. Arthroscopy was performed to evaluate graft integrity at 12 weeks. Gait analysis and stifle radiographs were performed preoperatively and up to 52 weeks after graft placement. Dogs were killed 12 (n = 2) or 52 weeks (n = 2) after CrCL reconstruction. Tissues were evaluated grossly and with light and confocal laser microscopy. RESULTS: Hamstring grafts were intact in all stifles at 12 weeks (n = 4) and 52 weeks (n = 2). Grossly, there was no osteoarthritis in stifles at 12 weeks and only chondrophytes along the trochlear ridges at 52 weeks. Minimal radiographic evidence of osteoarthritis developed in stifles with grafts during the study. Lameness in limbs with grafts resolved by 52 weeks. Graft tissue was highly vascular, ligamentized, and undergoing active remodeling at 12 weeks. Fifty-two weeks after graft placement, intraarticular graft tissue was well vascularized, mature, and encapsulated by synovium, and graft-bone interfaces were characterized by Sharpey's fiber insertions. There was no evidence of graft necrosis using confocal laser microscopy at either time point. CONCLUSIONS: The hamstring graft technique may be a viable method of canine CrCL reconstruction. CLINICAL RELEVANCE: Hamstring grafts may be an alternative technique for canine CrCL reconstruction. Further study is needed before clinical application.     

The Effect of Intercondylar Notchplasty on the Normal Canine Stifle

This study evaluated the effect of notchplasty (enlargement of the intercondylar fossa) in stable and unstable canine stifles. Bilateral notchplasty and unilateral cranial cruciate ligament (CrCL) transection were performed in 6 dogs. Exercise, consisting of walking 1.5 miles three times a week, began 1 month after surgery and continued until euthanasia 6 months after surgery. Evaluation methods included orthopedic examination, serial radiographs, thin section radiography, histopathology, and gross pathology. Notchplasty in the stable stifle did not cause lameness beyond 3 weeks, joint instability, or degenerative joint disease. In the stable stifle, smooth resurfacing of the notchplasty site with fibrous and osseous tissue occurred. Stifles with notchplasty and CrCL transection exhibited persistent lameness, instability, and degenerative joint disease. In CrCL deficient stifles osteophytes formed within the notchplasty site, resulting in a rough surface. Our observations indicated significant refilling in notchplasties of both stable and unstable stifles ( P <.05). However, the intercondylar fossa (ICF) width 6 months after notchplasty was significantly smaller in unstable stifles compared with stable stifles ( P <.05) indicating that greater refilling of the notchplasties occurred in the unstable stifles. In clinical cases, notchplasty should be larger than the desired final result to accomodate the partial refilling that occurs even in stable stifles.     

Evaluation of a Transcondylar Toggle System for Stabilization of the Cranial Cruciate Deficient Stifle in Small Dogs and Cats

Objective— To evaluate use of a transcondylar toggle system (TCTS) for stabilization of the cranial cruciate ligament (CrCL) deficient stifle in small dogs and cats. Study Design— Prospective clinical study. Animals— Small dogs (<7 kg; n=14) and cats (2) with CrCL‐associated lameness of <3 months duration and a tibial plateau angle <32°. Methods— Affected animals had an extracapsular CrCL repair using the TCTS. Lameness score, muscle atrophy, osteoarthritis (OA) score, and range of motion (ROM) were evaluated preoperatively, and at 6 weeks and 7–10 months postoperatively. Results— Operative time was 75 ± 16 minutes. Fifty‐six percent required >1 bone tunnel attempts. One dog required revision at 2 weeks because of suture loosening. All stifles were stable at 6 weeks postoperatively. Fifteen animals were available for follow‐up (7–10 months). Lameness improved significantly at 6 weeks (P<.0001), whereas muscle atrophy was worse at 6 weeks (P=.008) but improved at 7–10 months (P<.0001). OA scores were unchanged at 6 weeks (P=.08) but were significantly worse at 7–10 months (P<.0001). ROM remained unchanged at 6 weeks (P=1) and 7–10 months (P=.6). Conclusions— The medially placed toggle provides a reliable short‐term proximal anchor for the extracapsular suture with outcomes similar to other extracapsular techniques. The aiming device and drill bit are not recommended in their current form. Clinical Relevance— The TCTS appears to be a well‐tolerated technique for proximal suture anchoring in extracapsular CrCL repair in small dogs and cats where instrumentation and anatomic constraints preclude other techniques.     

Pre- and postoperative force plate analysis of dogs with experimentally transected cranial cruciate ligaments treated using tibial plateau leveling osteotomy

Objective— Quantitative and objective assessment of hindlimb kinetics after cranial cruciate ligament (CrCL) transection and subsequent stifle stabilization using the tibial plateau leveling osteotomy (TPLO) in normal dogs.
Study Design— In vivo experimental biomechanical evaluation.
Animals— Six healthy adult foxhounds.
Methods— Dogs were screened by orthopedic and radiographic examination before study entry. Force plate analysis of gait was measured before extirpation of the right CrCL and TPLO and again at 8 and 18 weeks after surgery.
Results— There was a significant decrease in peak vertical forces (PVFs) and vertical impulse (VI) of the treated hindlimb at 8 weeks when compared with preoperative and 18-week measurements. When compared with preoperative values, there was no significant difference in 18 week PVF and VI in dogs that had TPLO.
Conclusion— TPLO can restore kinetic measures of limb function at 18-weeks after surgery when compared with preoperative values after experimental transection of the CrCL in dogs.
Clinical Relevance— TPLO induces lameness that returns to near normal at 18 weeks. The severity and duration of lameness was similar to that reported for other experimental models of stifle instability repaired by different techniques.     

Feasibility of utilizing the patellar ligament angle for assessing cranial cruciate ligament rupture in dogs

The patellar ligament angle (PLA) was assessed in 105 normal stifle joints of 79 dogs and 33 stifle joints of 26 dogs with a ruptured cranial cruciate ligament (CrCL). The PLA of stifles with complete CrCL rupture was significantly lower than that of normal stifles, particularly at a flexion angle of 60~80° in both plain and stress views. If the PLA was <90.55° on the stress view with a 60~80° flexion angle, the dog was diagnosed with a complete rupture of the CrCL with a sensitivity of 83.9% and specificity of 100%. In conclusion, measuring the PLA is a quantitative method for diagnosing complete CrCL rupture in canines.     

Tibial osteotomies for cranial cruciate ligament insufficiency in dogs

Objective— To review the biomechanical considerations, experimental investigations, and clinical data pertaining to tibial osteotomy procedures for treatment of cranial cruciate ligament (CrCL) insufficiency in dogs.
Study Design— Literature review.
Methods— Literature search through Pub Med, Veterinary Information Network, Commonwealth Agricultural Bureau Abstracts, and conference proceedings abstracts (November 1977 to March 2007).
Results— Reported tibial osteotomy procedures attempt to eliminate sagittal instability (cranial tibial thrust) in CrCL-deficient stifles by altering the conformation of the proximal tibia. Functional stability can be achieved by decreasing the tibial plateau slope (cranial tibial closing wedge osteotomy [CTWO], tibial plateau leveling osteotomy [TPLO], combined TPLO and CTWO, proximal intraarticular osteotomy, chevron wedge osteotomy), altering the alignment of the patellar tendon (tibial tuberosity advancement), or both (triple tibial osteotomy). Clinical reports assessing the efficacy of these procedures frequently use subjective outcome measures, and the periods of follow-up evaluation are highly variable. Satisfactory results have been reported in most (>75%) dogs irrespective of the type of tibial osteotomy procedure.
Conclusions— Currently available data does not allow accurate comparisons between different tibial osteotomy procedures, or with traditional methods of stabilizing the CrCL-deficient stifle. Carefully designed long-term clinical studies and further biomechanical analyses are required to determine the optimal osteotomy technique, and whether these procedures are superior to other stabilization methods.
Clinical Relevance— Limb function in dogs with CrCL insufficiency can be improved using the currently described tibial osteotomy techniques.     

Angle between the patellar ligament and tibial plateau in dogs with partial rupture of the cranial cruciate ligament

OBJECTIVE: To measure the angles between the patellar ligament and the tibial plateau and between the patellar ligament and the common tangent at the tibiofemoral contact point (TFCP) in stifle joints of dogs with partial rupture of the cranial cruciate ligament (CrCL) for comparison with data obtained for stifle joints in dogs with intact CrCLs. SAMPLE POPULATION: 60 stifle joints of 54 dogs with surgically confirmed partial CrCL rupture. PROCEDURES: Mediolateral radiographic views of the stifle joints were obtained, and the angles between the patellar ligament and the conventionally defined tibial plateau (angle gamma) and between the patellar ligament and the common tangent to the TFCP (angle alpha) were measured at incidental stifle joint flexion (angle beta) by 2 independent observers. Data underwent linear regression analysis and were compared with findings in joints of dogs without degenerative joint disease. RESULTS: In stifle joints of dogs with a partial rupture of the CrCL, angles gamma and alpha were 5 degrees and 2 degrees larger than each corresponding angle in healthy canine joints. At 100 degrees of flexion, the patellar ligament was perpendicular to the conventionally defined tibial plateau. At 110 degrees of flexion, the patellar ligament was perpendicular to the common tangent at the TFCP. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, stifle joints with partially ruptured CrCLs have marginally larger angles between the patellar ligament and the tibial plateau, compared with joints with intact CrCLs; at equivalent angles of flexion, comparatively greater shear force affects the CrCLs in stifle joints with partial CrCL ruptures.