Clinical assessment following tibial tuberosity advancement in 28 stifles at 6 months and 1 year after surgery

Abstract

This prospective study evaluated the effect of tibial tuberosity advancement (TTA) on lameness, thigh circumference, range of motion (ROM), and radiographic osteoarthritis (OA) scores at 6 wk, 6 mo, and 1 y after surgery in 24 client-owned dogs with cranial cruciate ligament (CrCL) deficiency. Complications associated with TTA were also assessed. A significant improvement in lameness score and thigh circumference was observed in CrCL deficient limbs that received TTA, but no significant overall change in range of motion occurred in the affected limbs over the course of the study. Post-operative complications were identified in 33.3% of the dogs. This study demonstrates that TTA results in significant clinical improvement in patients up to 1 y after surgery. However, 21% of the dogs had post-operative recurrent lameness.

Introduction

The cranial cruciate ligament (CrCL) functions to prevent cranial translation of the tibia in relation to the femur, prevent internal rotation of the stifle, and to prevent hyperex-tension of the stifle (1). Rupture of the CrCL in dogs results in translational as well as rotational instability and secondary osteoarthritis (OA) (2–5). Tibial plateau leveling osteotomy (TPLO) and tibial tuberosity advancement (TTA) are techniques that change the geometry of the proximal aspect of the tibia in a way that restores dynamic stability of the stifle, thus preventing deterioration of the medial meniscus, and minimizing the development of secondary OA in the CrCL-deficient stifle (2–5). Tibial tuberosity advancement was developed by Montavon and Tepic as a “less invasive” alternative to the TPLO for treatment of CrCL deficiency in dogs (4,6). The technique was initially described in humans (Maquet procedure) as a means to alleviate patellofemoral pain by decreasing patellofemoral joint contact forces. Advancement of the tibial tuberosity results in a change in the angle of the patellar tendon and the quadriceps tendon, thus affecting the resultant force acting on the patellofemoral surface (2,7–9). The angle between the tibial plateau and the patellar ligament is responsible for the production of tibiofemoral shear forces that are directed cranially as the stifle is extended (2,4,9). Modifications to the stifle geometry that occur as a result of TTA also succeed in neutralizing the dynamic cranial tibial translation in the CrCL-deficient stifle. The end result is stabilization of the stifle during weight-bearing and compensation for the deficient CrCL (10,11).

A variety of conformational variables have been implicated in the etiology of canine CrCL rupture. Smaller tibial tuberosity width (rTTW) as well as increased tibial plateau slope angle have been suggested to predispose patients to CrCL rupture through increased strain on the CrCL (3,12). Tibial tuberosity advancement overcorrects for rTTW and counteracts cranial tibial thrust (12).

Tibial tuberosity advancement restores 3-dimensional alignment and normal femorotibial contact mechanics to values observed in non-CrCL-deficient stifles (2). However, clinical force plate analysis studies have reported that while limb function improves to 90% of full function after TTA, peak vertical forces (PVF) remain significantly lower than in dogs that have not suffered CrCL injury (13,14).

Thigh circumference correlates with thigh muscle atrophy in humans, and the quadriceps muscle accounted for the majority of the deficit (15,16). Muscle atrophy commonly occurs following CrCL rupture in dogs and may progress after surgical intervention (15,17,18). Sufficient joint stabilization should increase limb use after surgery, resulting in improved limb use and muscle mass, reflected as an increase in thigh circumference.

Goniometry is a simple and practical method to assess joint motion. In awake dogs, goniometric measurements are an indication of pain-free range of joint motion (19). Mean stifle flexion and exension previously described in healthy Labradors was 42° and 162°, respectively (19).

Progression of OA has been identified following both TPLO and TTA (5,14,20). Although OA does not resolve with these procedures, progression is decreased in dogs undergoing TPLO compared with those that undergo extracapsular stabilization (5). Radiographic evidence of OA is indicative of joint pathology; however, the severity of radiographic OA does not correlate well with clinical function (14,21).

Few in vivo clinical studies have been performed to evaluate the stifle joint or clinical function long-term after TTA (11,22,23). The authors have found no long-term studies that quantitatively evaluated the effects of TTA on muscle mass and range of motion (ROM) after surgery.

The purpose of this study was to determine the effect of tibial tuberosity transposition (TTA) on post-operative lameness, thigh circumference, ROM, and radiographic OA scores in canine patients with CrCL rupture. We hypothesized that, with the exception of OA scores, all of these parameters would improve post-operatively as a result of dynamic stabilization of the CrCL deficient stifle.

Materials and methods

Dogs (n = 24) diagnosed with CrCL rupture between July 2009 and September 2010 were voluntarily enrolled in a prospective study by their owners. Rupture of the CrCL was clinically diagnosed by a history of hind limb lameness, positive cranial drawer and/or positive cranial tibial thrust, pain on stifle extension on orthopedic examination, and radiographic evidence of stifle effusion or osteoarthritis. All dogs were skeletally mature and weighed more than 17 kg. Dogs developing CrCL disease in the contralateral limb during the study period were not excluded.

Patient age, weight, lameness score, thigh circumference (TC), stifle range of motion (ROM) of the affected limb and radiographic evidence of osteoarthritis (OA) were assessed. Lameness, thigh circumference, and stifle ROM in the affected and unaffected pelvic limbs were measured pre-operatively, 6 wk, 6 mo, and 1 y after surgery. CrCL deficient stifle radiographs were assessed pre-operatively, 6 m and 12 mo after surgery for evidence of OA.

Lameness was graded on a 5-point scale described by Stein and Schmoekel (22), with a score of 0 signifying no appreciable lameness and 4 signifying non-weight bearing lameness. Thigh circumference was measured with the patient in a standing position (24). Comfortable stifle ROM was determined as the maximum degree of pain-free flexion and extension measured using a goniometer positioned over the stifle (19,24).

Measurements were performed bilaterally in all patients. Follow-up complications were also described.

Mediolateral and craniocaudal radiographs of the affected stifle were taken pre-operatively and at follow-up examinations 6 wk, 6 mo, and 1 y after surgery. Mediolateral radiographs were taken with a femorotibial flexion angle of approximately 135°, the weight-bearing angle of the stifle joint (25). The radiographs were reviewed by a board-certified (ACVR) radiologist, who was blinded to the patient identification, surgery date, and outcome. Radiographic signs of OA were graded using a 5-point scale (26), in which 0 represents evidence of degenerative change, 1 indicates mild osteophyte formation, 2 represents mild to moderate osteophyte formation, 3 represents moderate osteophyte formation, and 4 indicates severe osteophyte formation.

Surgery

Premedication with midazolam hydrochloride (Baxter Healthcare Corporation, Deerfield, Illinois, USA), 0.2 to 0.4 mg/kg body weight (BW), IV and morphine sulfate (Baxter Healthcare Corporation), 0.4 mg/kg BW, IM was administered to each patient. Induction was achieved with propofol (PropoFlo; Abbott Laboratories, North Chicago, Illinois, USA), 0.4 to 0.6 mg/kg BW, IV and general anesthesia was maintained using isoflurane inhalant (Isothesia Butler Schein Animal Health, Dublin, Ohio, USA). A caudal epidural using preservative-free morphine sulfate (Hospira, Lake Forest, Illinois, USA), 0.1 mg/kg BW was administered to all patients pre-operatively under general anesthesia.

The hind limb was aseptically prepared and arthrotomy or arthroscopy of the stifle was performed. All dogs underwent arthrotomy or arthroscopic stifle examination immediately prior to TTA. The retropatellar fat pad was partially removed in some patients to facilitate visualization of the stifle. The intra-articular structures were explored for partial or complete CrCL tears, meniscal damage, and femoropatellar joint cartilage lesions. A partial meniscectomy was performed in cases in which a meniscal tear was identified. Damaged ligamentous tissue was not excised. No releasing procedure was performed for intact menisci. Intra-articular bupivicaine HCl 0.05% (0.2 mL/kg BW) (Hospira) was administered immediately following arthroscopy. A TTA procedure was performed using commercially available equipment (Securos USA, Fiskdale, Massachusetts, USA) following the recommended surgical procedure (10,20). A 6-, 9-, or 12-mm wide stainless steel cage of a length measured from the cut proximal tibial crest surface was implanted in the proximal osteotomy gap. The width of the cage was determined preoperatively using a template with a lateral stile radiograph with a femorotibial joint angle of approximately 135°. The cage was placed parallel to the joint surface 1 to 2 mm distal to the joint surface, and secured to the tuberosity and the remaining tibial shaft with 2 (2.4-mm) self-tapping bone screws. An appropriately sized Securos XGEN TTA plate (Securos USA) was secured to the medial aspect of the tibia with 2.4-mm, 2.7-mm, or 3.5-mm bone screws, as indicated by the plate selection. The osteotomy site was lavaged with sterile saline. An autologous cancellous bone graft was harvested from the caudal aspect of the tibial osteotomy site and placed into the osteotomy space in and around the cage. The surgical site was closed routinely. The surgery was performed by a single Diplomate of the American College of Veterinary Surgeons (ACVS) (JL) or by a surgical resident under the direct supervision of that surgeon.

Post-operative pain medication consisted of morphine (0.2 mg/kg BW, IM, q4 to 6h PRN) or hydromorphone (Baxter Healthcare Corporation), 0.05 to 0.1 mg/kg BW, IV, q4 to 6h PRN for the first 24 h. A fentanyl patch (2 to 4 μg/kg BW) was placed immediately after surgery. A non-steroidal anti- inflammatory drug (Carprofen; 2.2 mg/kg BW, PO, q12h; Meloxicam; 0.1 mg/kg BW, PO, q24h; or Deracoxib; 1 to 2 mg/kg BW, PO, q24h) was administered beginning the morning following surgery and continued for 7 to 14 d.

Activity restriction with short walks only on leash for the first 6 wk after surgery was recommended. Upon radiographic confirmation of adequate osseous healing at 6 wk after surgery, patients were permitted to begin a rehabilitation program including an increase in controlled exercise over the following 4 to 8 wk.

Statistical analysis

Changes in the measured variables were tested for significance at 6 wk, 6 mo, and 1 y for unaffected, unilaterally affected, and bilaterally affected limbs using a Wilcoxon sign rank test. A Kruskal-Wallis test was used at each time point to compare the amount of change between groups. A Wilcoxon sign rank test was used to determine if affected and unaffected limbs had significant differences on presentation for all variables. Analysis of variance (ANOVA) for repeated measures with time group and their interaction as factors was used to compare OA scores across groups and over time. A Shapiro-Wilk test and examination of the residuals was used to assess the data for normality. Significance was set at P ≤ 0.05. A post hoc Dunnett’s test was applied to compare changes in time back to baseline.

Results

Patient data reported included age, gender, weight, limb(s) affected, complete versus partial CrCL rupture, and other concurrent stifle disease. These values were reported as mean +/− standard deviation unless otherwise stated.

A total of 24 dogs (17 males and 7 females) were included in the study, and TTA was performed on 28 stifles. Mean age of patients was 5.5 y ± 2.7 y. Mean body weight ranged from 17.3 kg to 56.8 kg, with a mean of 35.7 kg ± 9.9 kg.

Sixteen dogs had unilateral disease and TTA was performed on the affected limb. Eight dogs suffered bilateral CrCL rupture, with 4 of those dogs undergoing bilateral TTA in succession, at least 6 wk apart. The 4 dogs with bilateral disease that did not undergo bilateral TTA were suspected of having a partial CrCL rupture in the non-operated limb and surgical stabilization was not performed at the request of each owner. Three dogs had concurrent hind limb orthopedic disease in addition to CrCL rupture. Of these 3 dogs, 2 dogs had concurrent medial patellar luxation (MPL) (1 dog in the limb undergoing TTA and the other dog in the contralateral limb), and 1 dog had suffered a previous tibial tuberosity fracture in the affected limb. The MPL was corrected at the time of TTA if it occurred in the CrCL-deficient stifle. In total, TTA was performed in 14 right stifles and 14 left stifles.

Stifles were explored using arthroscopy in 23/28 stifles, and arthrotomy in 5/28 patients. Complete CrCL rupture was confirmed in 22/28 (79%) stifles, and partial CrCL rupture was indentified in 6/28 (21%) stifles. Meniscal tear was confirmed in 2/28 stifles and partial meniscectomy was performed in those cases. In no case was a TTA performed on a stifle that had undergone previous surgery for CrCL disease.

Post-operative complications were identified in 8 (33.3%) dogs. Complications included superficial surgical incision infection in 2 dogs that resolved with 7 to 14 d of oral antibiotic therapy. Fracture of the distal tibial tuberosity was identified radiographically in 1 dog 6 wk after surgery. Evidence of active osseous remodeling and healing was present at that time. There was no evidence of surgical implant failure or instability in this dog and there was no appreciable lameness at that time or during subsequent follow-up. This patient showed adequate osseous healing at 6 mo and 1 y. Recurrent lameness in the operated limb occurred in 6 dogs. Lameness resolved in each affected patient with activity restriction and treatment with a non-steroidal anti-inflammatory drug.

Quantitative findings are listed in Table 1. Patients were presented with a mean pre-operative lameness score of 2.9 +/− 0.5. All dogs were partially weight-bearing within 24 h after surgery. There was no significant difference in pre-operative lameness between stifles with partial CrCL rupture (3.1 +/− 0.38) versus those with complete CrCL rupture (3 +/− 0.52). There was a significant improvement in lameness (P < 0.05) in affected limbs of dogs with unilateral and bilateral disease at 6 mo and 1 y after surgery. Dogs with unilateral disease showed significant improvement in lameness of the affected limb that was greater than those with bilateral disease 6 wk after surgery, but this difference was not significant at 6 mo and 1 y after surgery.

Table 1.

Lameness, thigh circumference, range of motion, and radiographic osteoarthritis data (mean ± standard deviation) for unilaterally, bilaterally and unaffected limbs in 24 dogs that had tibial tuberosity advancement surgery

	Time
Parameter	Pre-operative	6 weeks	6 months	1 year
Lameness (scale 0–4)	2.9 ± 0.5	0.84 ± 0.9	0.28 ± 0.6a	0 ± 0.3a
Thigh circumference (cm)
Unilateral affected	31.1 ± 4.6b	30.3 ± 4.2	30.7 ± 4.6	31.3 ± 4.4a
Bilateral affected	30.2 ± 3.1	30.4 ± 2.9	31.2 ± 2.2	31.8 ± 3.1
Unaffected	32.4 ± 5.7	32.1 ± 4.6	31.1 ± 4.5	31.4 ± 4.5
Stifle flexion (degrees)
Unilateral affected	52 ± 8.2	58.1 ± 27.5	58.2 ± 9.5a	59.0 ± 7.4a
Bilateral affected	50 ± 11.9	48.8 ± 13.6	49.3 ± 11.3	60.6 ± 5.0a
Unaffected	51.8 ± 13.1	53.4 ± 11.2	56.4 ± 7.7a	59.0 ± 4.7a
Stifle extension (degrees)
Unilateral affected	148 ± 11.5b	151.1 ± 10.2	146.8 ± 7.2	151.0 ± 7.8
Bilateral affected	151 ± 6.4	146.3 ± 5.8	149.3 ± 5.3	145.0 ± 11.7
Unaffected	156 ± 8.3	156.3 ± 8.3	151.4 ± 8.0	154.0 ± 8.1
Stifle range of motion (degrees)
Unilateral affected	96 ± 13.8	98.3 ± 17.6	88.6 ± 13.9	92.0 ± 10.0
Bilateral affected	101.5 ± 9.2	97.5 ± 9.6	100.0 ± 16.1	84.4 ± 9.8
Unaffected	104.5 ± 15.8	104.7 ± 13.1	95.0 ± 8.6a	95.0 ± 10.5a
OA scores (scale 0–4)
Unilaterally affected	2.1 ± 1.0	2.6 ± 1.0a	3.1 ± 1.1a	3.4 ± 0.9a
Bilaterally affected	2.1 ± 0.6	2.3 ± 0.8a	3.3 ± 0.8a	3.5 ± 0.5a

^aIndicates significant post-operative change (P < 0.05).

^bIndicates significant difference compared with unaffected limb before surgery (P < 0.05).

Mean thigh circumference of the affected limb was significantly less than that of the unaffected limb in dogs with unilateral disease on presentation (Table 1). Significant increase in thigh circumference was only noted in the affected limb of dogs with unilateral disease 1 y after surgery. Comparing unilaterally and bilaterally affected dogs, post-operative changes in TC between the groups was not significantly different.

Pre-operative and post-operative findings for stifle flexion, extension, and total range of motion are listed in Table 1. Range of motion of the affected limbs was significantly less than that of the unaffected limb in dogs with unilateral disease on presentation. A significant decrease (P < 0.05) in flexion was detected in the affected limb of dogs with unilateral disease at 6 mo and 1 y after surgery, as well as in dogs with bilateral disease at 1 y after surgery. There was also a significant (P < 0.05) decrease in flexion in unaffected limbs at 6 mo and 1 y after surgery. There was no statistically significant change in overall range of motion after surgery in stifles receiving a TTA in dogs with unilateral or bilateral disease. However, a significant decrease in range of motion was observed in the unaffected limb at 6 mo and 1 y after surgery. When comparing dogs with unilateral disease and bilateral disease, changes in range of motion after surgery were not significantly different between the 2 groups.

Mean pre-operative OA score of affected limbs was 2.14 +/− 0.89. Osteoarthritis scores are listed in Table 1. There was a statistically significant increase in OA scores at all time points after surgery in stifles receiving a TTA. Osteoarthritis scores did not differ between patients with unilateral versus patients with bilateral disease at any time point.

Discussion

Partial CrCL rupture was identified in 21% of stifles and complete CrCL rupture in 79% of stifles in this study. This is comparable to previous studies that reported frequencies of 20.6% to 31% partial CrCL rupture and 69% to 79.3% complete CrCL rupture in CrCL deficient stifles (20,27).

Optimal management of a partial CrCL rupture remains controversial. It has been theorized that some function of the remaining CrCL fibers may be preserved, thus leaving remaining CrCL fibers undisturbed, which may provide some protection against secondary meniscal damage (22). In this study, remaining fibers in partial CrCL ruptures were not surgically debrided.

The primary goal of TTA is to return the stifle to normal dynamic stability and function. Significant improvement in lameness in all patients at 6 mo and 1 y after surgery in this study suggests that this goal was achieved. Patients undergoing unilateral TTA showed significantly decreased lameness at 6 wk after surgery compared with those undergoing bilateral TTA, suggesting an earlier return to function in patients with unilateral disease. Our findings are consistent with those of a previous study that reported lameness resolution in 68% of patients at 4 mo after surgery following TTA (22).

Studies in humans have demonstrated that there is a direct correlation between TC and cross-sectional thigh muscle area as measured by computed tomography (CT) (15). Even small changes in muscle mass correlate with significant changes in muscle strength (15). Studies assessing anterior cruciate ligament rupture in human patients show that the unaffected limb is 2.59% to 3.46% larger perioperatively (15). A recent study assessing TC in CrCL deficient canine stifles undergoing TPLO reported a 1.5% decrease in TC of the affected limb compared with the contralateral unaffected limb (28). Results of our study are consistent with these findings with a 4% decrease in TC of affected limbs pre-operatively.

In dogs undergoing iatrogenic CrCL transection and immediate stifle stabilization, muscle atrophy was evident by 2 wk and progressed until 5 wk after surgery. A slight recovery in muscle mass was evident at 10 wk after surgery (18). This is similar to studies in humans reporting that disuse atrophy occurs, mainly during the initial days of immobilization (15,29). It is expected that dogs undergoing adequate stabilization of CrCL deficient stifles would experience an increase in TC at a similar rate to the aforementioned. Significant increase in thigh circumference of CrCL deficient limbs was noted only at 1 y after surgery in our study. Although the increase was observed in both unilaterally and bilaterally affected dogs, the increase was not significant in dogs undergoing bilateral TTA. Due to the low number of patients undergoing bilateral TTA, it is difficult to draw conclusions from this group.

Thigh muscle atrophy in patients with CrCL rupture has been associated with delayed return to function and more severe radiographic osteoarthritic changes (30). Post-operative pain and activity restriction may exacerbate these changes by inhibiting muscle mass recovery after surgery. Appropriate post-operative analgesia as well as early physical rehabilitation therapy may accelerate return to function. Some authors have recommended that physical rehabilitation be instituted soon after stifle stabilization surgery in canine patients, and continued for at least 5 wk after surgery to minimize muscle mass atrophy (18). Variability in physical rehabilitation between patients, as well as variability in time between CrCL injury, patient presentation, and subsequent stifle stabilization may have contributed to the delayed recovery of TC in our patients.

Mean pre-operative stifle flexion and extension in unaffected limbs in the present study (Table 1) were comparable to values previously described in healthy Labradors (19). Previous studies assessing ROM in cruciate deficient canine stifles reported a decrease following TPLO and extracapsular techniques 1 to 6 y after surgery (28,31). In the present study, decreases were appreciated in stifle extension pre-operatively, and in flexion at 6 mo and 1 y after surgery in CrCL deficient stifles. A significant decrease in overall range of motion occurred in unaffected limbs at 6 mo and 1 y after surgery.

Decreased flexion and ROM in the affected and unaffected limbs in this study may be associated with decreased activity during convalescence. Decreased ROM has been documented previously in the unaffected stifle in dogs receiving a TPLO on the contralateral CrCL deficient limb (31). Initiation of physical rehabilitation therapy early in the post-operative period may maintain or improve ROM in both affected and unaffected limbs during this period.

Although the tibial tuberosity is slightly proximally displaced during the TTA procedure, increased tension on the patellar tendon was not assessed in this study and could be a contributing factor in the decreased stifle flexion in affected limbs. However, if this were the case, one would expect an immediate post-operative decrease in stifle flexion rather than the delayed (6 mo and 1 y) effect observed in this study. Also, each of the 4 patients diagnosed with bilateral CrCL disease that did not undergo bilateral TTA was suspected of having a partial CrCL tear in the non-operated limb based on examination findings. These stifles were included in the unaffected group as they did not undergo surgery and they may have affected the ROM flexion results in this group.

Osteoarthritis scores increased significantly in all CrCL deficient limbs over the 1 y follow-up period in this study. This is consistent with previous studies reporting a significant increase in OA scores 8 wk after surgery in dogs undergoing TTA (14). Radiographic evidence of OA progression was more profound in the CrCL deficient stifle compared with the unaffected limb in side-to-side comparison (9). Extensive arthrotomy and removal of CrCL remnants may predispose patients to increased progression of OA (32). Osteoarthritis progressed in the patients in our study despite a lack of CrCL debridement and the use of arthroscopy in the majority of patients.

Excellent long-term outcome has been reported in 92% to 93% of patients following TTA (22). The complication rate of 33% in the present study is comparable to previously reported rates of 6.5% to 59% in dogs undergoing TTA (10,14,20,22,27). The most common complications include late meniscal damage and fracture of the tibial tuberosity (22). Recurrent lameness of the affected limb constituted the most common complication in this study (21% of stifles). These patients improved with activity restriction and NSAID therapy; second-look arthroscopy was not performed to rule out meniscal injury.

Meniscal injury was identified in 7% of stifles in this study, in association with complete CrCL rupture. This rate is lower than previously reported rates of 10% to 70% (33–35). Latent (hidden) meniscal injury could account for the decreased rate of meniscal injury in this study and may have contributed to the 21% rate of recurrent lameness. Meniscal release was not performed in the absence of meniscal injury. Previous studies indicated that medial meniscal release results in significant change in femorotibial contact mechanics and leads to OA and dysfunction postoperatively in the CrCL-intact canine stifle (36,37). Other studies report increased subsequent meniscal tears in CrCL deficient stifles undergoing TPLO and arthrotomy or arthroscopy when meniscal release was not performed (33,34). There was no significant difference in clinical outcome in dogs undergoing meniscal release versus no meniscal release in that study (34). Hoffman et al (20) reported subsequent medial meniscal tearing following TTA in 10% of stifles. Proposed mechanisms for subsequent meniscal injury include a change in direction of tibial thrust caudally, persistence of cranial drawer during various phases of limb motion, and failure to eliminate tibiofemoral shear forces due to inadequate advancement of the tuberosity (20). These findings provide an argument to consider medial meniscal release in patients undergoing TTA.

There are limitations in the present study. Although thigh circumference and range of motion are useful measures of limb use, PVF is the most accurate ground reaction force for kinetic lameness evaluation (38). Peak vertical force should be assessed in conjunction with TC and ROM in order to validate the findings of this study. Force plate analysis was not available in our facility and thus PVF was not measured. Also, second-look arthroscopy was not performed in patients suffering post-operative lameness. Further studies investigating follow-up arthroscopy of patients with recurrent lameness may be beneficial in providing a more accurate assessment of the rate of subsequent meniscal injury. Another factor is that postoperative rehabilitation therapy was performed by owners and represents an uncontrolled variable. A standardized controlled rehabilitation therapy program performed by a trained physical therapist would be useful in order to minimize the variable outcomes of thigh circumference and range of motion between patients.

In conclusion, our study demonstrates a significant improvement in clinical lameness and thigh circumference in CrCL-deficient limbs receiving TTA, but no significant overall change in range of motion over 1 y following surgery. Significant progression of radiographic OA occurred in all CrCL deficient stifles after surgery. Clinical improvement occurred long-term in all patients, but further studies measuring PVF to quantify long-term improvement in limb use are indicated. CVJ