Abstract
Cranial cruciate ligament rupture (CCLR) is a common cause of stifle joint pain in dogs. This study assessed the short-term outcomes in the management of CCLR, with or without concurrent medial patellar luxation (MPL), in small-breed dogs, comparing surgical intervention using tibial plateau leveling osteotomy (TPLO) with non-surgical approaches. Dogs weighing less than 10 kg and suffering from CCLR were divided into two groups: surgical and non-surgical (nine stifles per group). Both groups followed the same rehabilitation protocol. Measurements were taken on days 0, 14, 28, 42, 56, 70, and 84. These measurements included the mean difference in orthopedic assessment score (diffOAS) and thigh muscle circumference (TMC) assessed by veterinarians, as well as the Canine Brief Pain Inventory score (CBPI) evaluated by the owners. Six stifles had concurrent MPL in the surgical group and five in the non-surgical group. No significant differences were observed in diffOAS (P=0.685), TMC (P=0.557), CBPI pain severity score (P=0.062), and CBPI pain interference score (P=0.29) between the two groups. However, both groups showed a significant decrease (P<0.05) in diffOAS and CBPI. The TMC remained relatively stable in the non-surgical group (P>0.05), but it significantly increased in the surgical group (P<0.05). Both groups demonstrated improved clinical outcomes in the short term, with no significant differences. However, cautious consideration should be given to a conservative treatment in small-breed dogs, particularly when considering the exclusive improvement observed in TMC within the TPLO group.
Keywords: conservative treatment, cranial cruciate ligament rupture, rehabilitation, small-breed dog, tibial plateau leveling osteotomy
Cranial cruciate ligament rupture (CCLR) is a condition that can lead to instability and discomfort in the stifle joint. In small-breed dogs, CCLR frequently arises as a result of chronic medial patellar luxation (MPL). Cranial cruciate ligament rupture is the most common cause of canine stifle joint diseases, causing lameness [11, 33]. This condition primarily results from ligament degeneration rather than trauma injury [9]. Predisposing factors for CCLR include large-breed dogs, overweight conditions, neutered males, spayed females, a steep tibial plateau angle (TPA), and patellar luxation [4, 26]. In small-breed dogs, CCLR often results from excessive stress due to stifle instability and internal rotation of the proximal tibia, which is associated with MPL, especially grade 4 luxation [5, 6]. The management of CCLR can involve both non-surgical and surgical treatments.
Non-surgical treatments aim to alleviate pain and restore limb functions. They include medication, rehabilitation, nutritional management, and weight control. Rehabilitation plays a crucial role in the management of dogs with CCLR, both conservatively and postoperatively. One modality used in rehabilitation is low-level laser therapy (LLLT), which effectively reduces pain and inflammation by enhancing microcirculation and influencing the synthesis and degradation of inflammatory mediators [14, 22, 27]. An alternative approach to alleviate pain and reduce inflammation and swelling is cryotherapy. This method can be employed both during the tissue damage phase and the post-operative period. The low temperature is beneficial in decreasing cellular metabolism, inducing vasoconstriction, and diminishing enzyme-mediated tissue damage. This ultimately leads to reduced pain and swelling [13, 32]. Besides cryotherapy, therapeutic exercises, such as passive range of motion (PROM), standing exercises, leash walking, and the use of an underwater treadmill are valuable components of early rehabilitation. These exercises help improve the range of motion (ROM) and functionality of the affected joint, preserve muscle mass, and enhance proprioception [19].
Surgical approaches for managing CCLR involve extracapsular suture stabilization to provide joint stability and tibial osteotomy procedures aimed at enhancing the joint’s biomechanical stability. Tibial plateau leveling osteotomy (TPLO) provides stifle stability by neutralizing the tibiofemoral shear force and modifying the tibial plateau slope through proximal tibial osteotomy, ultimately restoring normal limb function [7, 21]. For dogs with concurrent MPL, a modified TPLO (mTPLO) has been introduced. This procedure combines a standard TPLO (sTPLO) with the medial translation of the proximal tibial segment to realign the quadriceps mechanism [10, 15]. The combination of TPLO and a structured rehabilitation program offers advantages in treatment outcomes, reducing the recovery duration when compared to non-surgical approaches, particularly in large-breed dogs [33].
The prevalence of CCLR, including cases involving concurrent MPL, is increasing among small-breed dogs. In small-breed dogs, TPLO has shown favorable results in terms of subjective lameness assessment and force plate gait analysis within 4 to 6 weeks [1, 2, 8]. However, the decision regarding surgical or non-surgical interventions may be influenced by various factors, including age, health status, and financial considerations. Notably, small dogs can exhibit acceptable responses to conservative treatment without rehabilitation over a period of 4 months [30]. As of our knowledge, there are no data supporting the clinical outcomes of conservative treatment with a specific rehabilitation protocol to manage CCLR in small-breed dogs. Consequently, establishing a definitive conclusion regarding the treatment outcomes of surgical and non-surgical approaches remains challenging. This study aims to ascertain the short-term outcomes of surgical and non-surgical interventions for CCLR in small-breed dogs. Our assessment incorporated both objective and subjective measurements. We tested the hypothesis that dogs undergoing surgical treatment demonstrate better outcomes and quicker recovery compared to those receiving non-surgical treatment.
MATERIALS AND METHODS
Study design
This prospective study was approved by the Institutional Animal Care and Use Committee (No 2031032). Seventeen small-breed dogs (18 stifles) with clinical signs (i.e., lameness, stifle joint swelling, and positive of cranial drawer test) and radiographic evidence (i.e., stifle joint effusion and cranial translation of the proximal tibia) related to CCLR were included in this study between 2019 and 2021. Before enrolment in the study, written informed consent was obtained from the owners. The dogs were non-randomly assigned to either the surgical or non-surgical group (nine stifles per group). The dogs remained under the care of their owners throughout the study. Outcome measures were assessed at predetermined intervals on days 0, 14, 28, 42, 56, 70, and 84.
Animals
The study included small-breed dogs weighing less than 10 kg and diagnosed with CCLR. All dogs underwent complete physical examination and had their hematological profiles assessed to confirm their normal health status. Dogs with neurological deficits or other orthopedic diseases, except for MPL, were excluded from the study. Dogs prescribed non-steroidal anti-inflammatory drugs (NSAIDs) were given a 1-week washout period. During the study, if the lameness score and/or articular pain score worsened by at least 1 score compared to the previous visit, a dosage of 10 mg/kg gabapentin (Gabutin; Siam Bheasach Co., Ltd., Bangkok, Thailand) was administered twice daily. All dogs in both groups followed the same rehabilitation protocol and received a joint supplement.
Non-surgical treatment group
Dogs were given oral carprofen (Rimadyl; Zoetis Ltd., Parsippany, NJ, USA) 2.2 mg/kg twice daily for 14 days. Additionally, they received PCSO-524 (Antinol; Pharmalink International Limited, Central Hong Kong, Hong Kong), a joint supplement, one capsule/10 kg twice daily for the initial 14 days, followed by administration once daily until the end of the study period. Data collected on the pre-treatment day, before starting the rehabilitation program, were established as baseline values (day 0).
Surgical treatment group
Anesthesia protocols were decided for each patient based on their individual requirements and assessed using the American Society of Anesthesiologists (ASA) patient scale. The TPLO procedure was performed by a board-certified veterinary surgeon, following the method described previously [25] without the use of a jig. The sizes of the TPLO saw blades, ranging from 8 to 10 mm, were determined following pre-operative radiographic planning. The remaining tibial tuberosity width (D1) was calculated by using a range of 25–30% of the craniocaudal tibial width. If patients had concurrent MPL and realignment of the quadriceps mechanism was deemed necessary, a mTPLO was performed. This procedure involves the medial translation of the proximal segment, as described previously [10]. Adjunctive surgical techniques to address MPL, such as block recession trochleoplasty, medial release, and lateral fascial imbrication, were performed at the surgeon’s discretion. Three different TPLO plate systems, including a 1.7-mm T plate and a clover plate (Fixin; Intrauma S.p.A., Turin, Italy), and a 1.5-mm TPLO plate (Arix; Jeil Medical Corp., Seoul, Republic of Korea), were used in this study, selected based on the surgeon’s preference and the proximal tibial morphology. For stifles with and without MPL, standard arthrotomy and mini-arthrotomy procedures were performed, respectively, followed by the removal of the cranial cruciate ligament (CCL) remnant. In cases indicating meniscal damage, partial or complete meniscectomy was performed. A prophylactic antibiotic (cefazolin 25 mg/kg; L.B.S. Laboratory Ltd., Bangkok, Thailand) was administered and continued orally twice daily for 7 days. Postoperative analgesia consisted of 4.4 mg/kg of carprofen administered subcutaneously, followed by oral administration of carprofen at a dosage of 2.2 mg/kg twice daily for 14 days. The PCSO-524 was administered following the same protocol as that used in the non-surgical group. Data collected on the surgical day, prior to surgery, were established as baseline values (day 0). Post-operative radiographs of the operated limb were performed in both lateral and craniolateral views to assess implant placement, TPA, D1, and bone healing immediately after surgery, at 1 month, and at 3 months post-operatively.
Rehabilitation protocol
All dogs adhered to a standardized rehabilitation protocol overseen by a certified canine rehabilitation veterinarian. During the initial two months of the study period, the dogs attended rehabilitation sessions at the hospital every 7 days, which were then extended to every 14 days in the last month of the study. Laser therapy (MLS; ASA S.r.l., Milan, Italy) with a dosage ranging from 4–8 J/cm2 began on day 7 and was repeated at each rehabilitation visit. Underwater treadmill sessions commenced on day 14 and were continued during each visit, with the speed and duration tailored individually for each dog. Owners were instructed to perform home rehabilitation, including 10 min hot compressions followed by 15 repetitions of PROM exercise on the affected joint, twice daily from day 7 until the end of the study period. Leash walking was initiated on day 14, initially at 5 min per day and gradually increasing up to 20 min, depending on the clinical signs. This exercise was maintained daily throughout the entire study period. In the surgical treatment group, cold compressions were administered for 15 min every 6 hr for 5 days post-operatively before following the rehabilitation protocol as in the non-surgical group, starting from day 7 post-operatively. After the 3-month study period, the ongoing rehabilitation protocol and frequency were individually adjusted based on the clinical signs exhibited by the patients.
Measurement outcomes
The same veterinarian conducted a physical examination, including general and orthopedic assessments, during each visit. The orthopedic assessment score (OAS), with a total score of 11, adapted from a previous study [20], was employed in this study (Table 1). The mean difference of OAS (diffOAS) between the baseline (day 0) and subsequent follow-up days (days 14, 28, 42, 56, 70, and 84) was calculated. Articular mobility was assessed using a goniometer, with the normal ROM for the stifle joint set at 121 degrees [12]. The TMC was measured using a Gulick tape at 70% of the femur length from the greater trochanter [18]. The average values of three measurements for both TMC and ROM were recorded. Additionally, the Canine Brief Pain Inventory Score (CBPI) was determined by the same owner during each visit. The CBPI consists of a pain severity score (PSS) and a pain interference score (PIS), with total scores of 40 and 60, respectively.
Table 1. Scoring system for the orthopedic assessment score (OAS).
| Clinical parameter | Scoring system | Score |
|---|---|---|
| Lameness | Normal | 0 |
| Slight, intermittent lameness | 1 | |
| Obvious weight-bearing lameness | 2 | |
| Severe weight-bearing lameness | 3 | |
| Intermittent non-weight-bearing lameness | 4 | |
| Continuous non-weight-bearing lameness | 5 | |
| Articular mobility | No limitation of movement | 0 |
| 10–20% decrease in range of motion | 1 | |
| 20–50% decrease in range of motion | 2 | |
| More than 50% decrease in range of motion | 3 | |
| Articular pain | No sign of pain | 0 |
| Mild pain (dog turns head in recognition) | 1 | |
| Moderate pain (dog pulls limb away or wants to move away) | 2 | |
| Severe pain (dog vocalizes and becomes aggressive) | 3 | |
Statistical analysis
Group homogeneity was assessed using the Chi-Square test for the breed, sex, affected limb side, concurrent MPL, MPL grading, and body condition score (BCS). A generalized linear model was used to compare variables such as age, body weight, duration of injury, diffOAS, TMC, PSS, and PIS between the groups at each visit. Repeated measures analysis was performed to evaluate treatment effects between the groups, using SAS OnDemand for Academics (SAS Institute, Cary, NC, USA). Tukey’s Studentized Range test was employed to assess differences between visits within each treatment group. Statistical significance was defined as a P-value less than 0.05.
RESULTS
The 17 small-breed dogs, comprising nine females and eight males, included Chihuahua (n=7), Pomeranian (n=3), Yorkshire Terrier (n=3), Toy Poodle (n=3), and Maltese (n=1), with a total of 18 stifles for evaluation (9 stifles per group). One dog underwent staged bilateral surgery with a 17-month interval between surgeries. The median (interquartile range) body weights of dogs in the non-surgical and surgical groups were 3.9 kg (3–6 kg) and 3.5 kg (3–4.7 kg), respectively. The median (interquartile range) ages of dogs in the non-surgical and surgical groups were 99 months (82–126 months) and 60 months (48–100 months). Eleven stifles (61%) had concomitant MPL, with grades 1 (n=1), 2 (n=5), 3 (n=4), and 4 (n=1) observed in both the non-surgical (n=5) and surgical (n=6) groups. No significant differences were observed in age (P=0.104), body weight (P=0.464), BCS (P=0.781), breed (P=0.312), sex (P=0.819), affected limb side (P=0.343), concurrent MPL (P=0.317), MPL grading (P=0.502), disease duration (P=0.11), OAS (P=0.055), TMC (P=0.419), PSS (P=0.373), and PIS (P=0.654) between the two groups during the pre-treatment evaluation (day 0) (Table 2).
Table 2. Demographic variables, patellar status and mean ± SD of the duration of disease, orthopedic assessment score (OAS), thigh muscle circumference (TMC), CBPI: pain severity score, and CBPI: pain interference score at pre-treatment values (day 0) of both groups.
| Variable | Non-surgical | Surgical | P-value |
|---|---|---|---|
| Number of dogs | 9 | 8 | |
| Number of studied stifles | 9 | 9 | |
| Median BW (kg) (range) | 3.9 (3−6) | 3.5 (3−4.7) | 0.464 |
| Median age (months) (range) | 99 (82−126) | 60 (48−100) | 0.104 |
| Body condition score | 0.781 | ||
| 1/5 | 0 | 0 | |
| 2/5 | 0 | 0 | |
| 3/5 | 4 | 3 | |
| 4/5 | 4 | 4 | |
| 5/5 | 1 | 2 | |
| Breed | 0.312 | ||
| Chihuahua | 3 | 4 | |
| Pomeranian | 1 | 2 | |
| Yorkshire Terrier | 2 | 1 | |
| Toy Poodle | 3 | 0 | |
| Maltese | 0 | 1 | |
| Sex | 0.819 | ||
| Male | 5 | 4 | |
| Female | 4 | 4 | |
| Concomitant MPL (stifles) | 0.317 | ||
| Yes | 5 | 6 | |
| No | 4 | 3 | |
| Patellar status | 0.502 | ||
| Normal | 4 | 3 | |
| Grade 1 MPL | 0 | 1 | |
| Grade 2 MPL | 2 | 3 | |
| Grade 3 MPL | 3 | 1 | |
| Grade 4 MPL | 0 | 1 | |
| Side of affected limb | 0.343 | ||
| Left | 5 | 3 | |
| Right | 4 | 6 | |
| Duration of disease (days) | 21 ± 8 | 59 ± 66 | 0.11 |
| Orthopedic assessment score (OAS) | 7 ± 1.5 | 5.7 ± 1.2 | 0.055 |
| Thigh muscle circumference (cm) | 14.3 ± 3.7 | 13.2 ± 1.2 | 0.419 |
| CBPI: pain severity score (PSS) | 23.1 ± 6.8 | 19.8 ± 8.5 | 0.373 |
| CBPI: pain interference score (PIS) | 29.1 ± 12.1 | 32.3 ± 17.4 | 0.654 |
BW: body weight, MPL: medial patella luxation, CBPI: canine brief pain inventory score. *P-value <0.05.
In the surgical group, six stifles had concurrent MPL, with four of them undergoing mTPLO and two undergoing sTPLO. Adjunctive MPL correction was employed in five stifles with concurrent MPL (four in mTPLO and one in sTPLO). Three stifles without concomitant MPL received sTPLO. The mean ± SD of the pre-operative TPA was 30.0 ± 3.3°, whereas the post-operative TPA was 5.0 ± 1.1°. The mean ± SD of D1, measured from post-operative mediolateral radiographs, was 3.9 ± 0.7 mm. Micro-TPLO plates, including a 1.7 Fixin T plate (three stifles), a 1.7 Fixin clover plate (five stifles), and a 1.5 Arix TPLO plate (one stifle) were used. Partial meniscectomy was performed in two stifles (22%) with medial meniscal injury at the caudal horn (Table 3). No complications related to TPLO implants, infection, or wound problems were observed in this study. However, one stifle (11%) had recurrent grade 4 MPL at 10 days post-operatively, having had pre-operative grade 4 MPL.
Table 3. The information of each dog in the surgical treatment group.
| Dog | Breed | Side | BW (kg) | Concomitant MPL (grade) | Surgical procedures | Plate system | Pre-operative TPA (°) | Post-operative TPA (°) | Meniscal tear | Saw blade |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Maltese | Left | 3 | 3 | mTPLO, TBR, Imbrication, lateral suture | Fixin 1.7 mm T plate | 33.5 | 4.4 | Yes | 8 |
| 2 | Chihuahua | Right | 4.7 | 1 | sTPLO | Fixin 1.7 mm T plate | 30 | 6.2 | No | 8 |
| 3 | Chihuahua | Right | 4.5 | None | sTPLO | Fixin 1.7 mm clover plate | 26.6 | 5.9 | No | 10 |
| 4 | Chihuahua | Right | 3.5 | 4 | mTPLO, TBR, Imbrication | Fixin 1.7 mm clover plate | 34 | 6.9 | No | 8 |
| 5 | Chihuahua | Left | 3.4 | None | sTPLO | Fixin 1.7 mm T plate | 33.8 | 4.5 | Yes | 8 |
| 6 | Pomeranian | Right | 5.7 | None | sTPLO | Fixin 1.7 mm clover plate | 26 | 2.6 | No | 8 |
| 7 | Pomeranian | Right | 4.7 | 2 | sTPLO, TBR, patelloplasty, Imbrication | Fixin 1.7 mm clover plate | 27 | 5.3 | No | 10 |
| 8 | Yorkshire Terrier | Right | 2.9 | 2 | mTPLO, TBR, Imbrication | Arix 1.5 TPLO plate | 28 | 5.6 | No | 8 |
| Left | 3 | 2 | mTPLO, TBR, Imbrication | Fixin 1.7 mm clover plate | 27.5 | 5.1 | No | 8 |
mTPLO: modified tibial plateau leveling osteotomy, sTPLO: standard modified tibial plateau leveling osteotomy, TBR: trochlear block recession, MPL: medial patellar luxation, TPA: tibial plateau angle.
There was no significant difference in diffOAS between the surgical and non-surgical groups (P=0.685). However, both groups exhibited a significant decrease in diffOAS from day 28 onward when compared to the baseline value (P<0.05) (Table 4). Similarly, there was no significant difference in TMC between the two groups (P=0.557). When assessing changes within each group, no significant alteration was observed in the non-surgical group (P>0.05). However, a significant increase in TMC was observed in the surgical group on day 70 compared to the baseline value (P<0.05) (Table 5).
Table 4. The mean (± SD) difference of orthopedic assessment score (diffOAS) between pre-treatment (day 0) and other follow-ups in both groups.
| Non-surgical group | Surgical group | P-value* | ||
|---|---|---|---|---|
| diffOAS | Day 0 | 0.0 ± 0.0a | 0.0 ± 0.0a | 0.685 |
| Day 14 | −0.4 ± 1.6ab | −0.4 ± 1.9a | ||
| Day 28 | −3.3 ± 2.7bc | −2.6 ± 2.1b | ||
| Day 42 | −3.0 ± 2.6c | −3.3 ± 1.9b | ||
| Day 56 | −4.0 ± 2.0c | −3.4 ± 2.2b | ||
| Day 70 | −3.9 ± 2.4c | −3.4 ± 2.0b | ||
| Day 84 | −4.0 ± 2.1c | −3.7 ± 2.1b |
a–cP-value <0.05 from Turkey’s studentized range within each group. *P-value from repeated measurement analysis of both groups.
Table 5. Thigh muscle circumference (TMC) (mean ± SD) of each visit in both groups.
| Non-surgical group | Surgical group | P-value* | ||
|---|---|---|---|---|
| TMC (cm) | Day 0 | 14.3 ± 3.7 | 13.2 ± 1.6a | 0.557 |
| Day 14 | 14.4 ± 3.6 | 13.2 ± 1.5a | ||
| Day 28 | 14.6 ± 3.6 | 13.5 ± 1.7ab | ||
| Day 42 | 14.4 ± 3.5 | 13.5 ± 1.6ab | ||
| Day 56 | 14.0 ± 3.6 | 13.7 ± 1.7ab | ||
| Day 70 | 14.2 ± 3.8 | 14.0 ± 1.5b | ||
| Day 84 | 13.9 ± 3.2 | 13.6 ± 1.6ab |
a,bP-value <0.05 from Turkey’s studentized range within each group. *P-value from repeated measurement analysis of both groups.
No significant treatment effect was observed in the CBPI for PSS (P=0.062) and PIS (P=0.29) between the two groups. Nevertheless, both PSS and PIS showed a significant decrease within both groups (P<0.05) (Table 6). In the non-surgical treatment group, a significant decrease in PSS was noted from day 14 onward and in PIS from day 42 onward, compared to the baseline values. In the surgical group, significant decreases in both PSS and PIS were observed from day 28 onward compared to the baseline values.
Table 6. CBPI: Pain severity score (PSS) and CBPI: pain interference score (PIS) (mean ± SD) of each visit in both groups.
| Non-surgical group | Surgical group | P-value* | ||
|---|---|---|---|---|
| PSS (point) | Day 0 | 23.1 ± 6.8a | 19.8 ± 8.5a | 0.062 |
| Day 14 | 13.1 ± 7.2b | 12.0 ± 6.6ac | ||
| Day 28 | 10.3 ± 6.7bd | 6.6 ± 4.6bc | ||
| Day 42 | 9.1 ± 7.0b | 3.4 ± 2.4bc | ||
| Day 56 | 6.6 ± 5.2cd | 2.3 ± 2.9bc | ||
| Day 70 | 6.8 ± 6.8b | 1.1 ± 1.7bd | ||
| Day 84 | 6.3 ± 6.8cd | 0.6 ± 1.3bd | ||
| PIS (point) | Day 0 | 29.1 ± 12.1a | 32.3 ± 17.4a | 0.29 |
| Day 14 | 22.1 ± 13.5ac | 22.3 ± 13.6ac | ||
| Day 28 | 19.5 ± 16.9ab | 10.4 ± 8.1bc | ||
| Day 42 | 10.9 ± 9.7bc | 5.3 ± 4.5b | ||
| Day 56 | 9.3 ± 10.0b | 3.9 ± 3.4bc | ||
| Day 70 | 9.9 ± 13.1bc | 3.8 ± 4.5b | ||
| Day 84 | 9.4 ± 13.0bc | 0.7 ± 1.7b |
CBPI: canine brief pain inventory score. a–dP-value <0.05 from Turkey’s studentized range within each treatment group. *P-value from repeated measurement analysis for both treatment groups.
DISCUSSION
This study represents the first investigation and comparative analysis of outcomes between non-surgical and surgical treatment for CCLR in small-breed dogs. All dogs followed a specific rehabilitation protocol. The TPLO was employed in all dogs in the surgical group because it has shown superior outcomes compared to other methods such as extracapsular and intracapsular suturing techniques [3, 28]. The TPLO stabilizes the affected stifle by neutralizing tibiofemoral shear forces and controlling cranial tibial thrust during the gait cycle. In contrast, intra- or extra-articular procedures may eliminate the cranial drawer sign but could potentially sacrifice the ROM of the stifle [25].
A previous study suggested that TPLO provides greater benefits than conservative treatment for dogs weighing over 15 kg [33]. However, other studies have reported improvements in unilateral CCLR-affected dogs weighing under 15 kg within 4 months when treated conservatively and without rehabilitation [23, 30]. In the current study, short-term assessments did not reveal significant differences in diffOAS, CBPI scores, or TMC between TPLO and conservative treatments in small-breed dogs weighing less than 10 kg. The diffOAS significantly improved by day 28 in both groups when compared to the baseline value. Furthermore, a significant improvement in CBPI scores was observed between day 14 and day 42 in both groups, in comparison to the baseline value. These results align with prior studies, indicating that TPLO in small-breed dogs led to significant improvements in force plate gait analysis and lameness scores, particularly at 4 and 6 weeks post-operatively [1, 2, 8]. However, the conservative group demonstrated substantial improvements in both veterinary assessments and owner’s questionnaires within 42 days in this study, a significant departure from a previous study that indicated observable improvements after 4 months [30]. This finding deviated from our initial hypothesis. The previous studies recommended confining dogs for 4–8 weeks to allow natural restabilization through periarticular fibrosis of the stifle joint [23, 30], while this study chose to initiate rehabilitation just seven days after the injury. Therefore, the earlier positive outcomes may be attributed to the rehabilitation program and pain control. The PCSO-524, a nutraceutical, offers anti-inflammatory properties by reducing the synthesis of proinflammatory mediators such as leukotrienes, prostaglandins, and thromboxane [31, 34]. The combination of carprofen, LLLT, and PCSO-524 contributed to anti-inflammation and early pain control in the affected joint, facilitating earlier limb usage [14, 22, 27]. The underwater treadmill introduced low-impact exercise, enhancing muscle strength and endurance, and correcting proprioception with minimal joint load [16]. Additionally, PROM contributed to restoring the normal range of motion (ROM) in the affected joint [19].
While no significant difference in short-term results was found between both groups, the TPLO group showed a significant increase in TMC at day 70, whereas the conservative group exhibited no significant change. Additionally, a consistent decline in PSS and PIS was observed in the surgical group, reaching nearly zero at day 84. In contrast, the non-surgical group displayed stable PSS and PIS scores from day 56 at levels 6 and 9, respectively. This consistent pattern suggests the presence of persistent stifle instability and chronic pain in the conservative group. Whilst our short-term findings do not definitively establish TPLO as the superior approach for addressing CCLR in small-breed dogs, TPLO, with its ability to provide functional stifle stability, may contribute to an expedited recovery process and enhanced limb function compared to conservative treatment.
The TPLO procedure can effectively address dogs with concurrent MPL, employing the mTPLO technique. The MPL is a recognized predisposing factor for CCLR [15]. When patellar luxation leads to malalignment of the quadriceps mechanism, it increases stress on the CCL, potentially causing degeneration and rupture [10]. Consequently, CCLR in small-breed dogs typically manifests in middle-aged (5–10 years) animals [4], which is consistent with the findings of this study. Our study revealed a concomitant occurrence of CCLR and MPL in 61% of the cases, which is higher than the 45.5% reported in a previous study [1]. Previous research has documented favorable outcomes when surgically correcting CCLR that co-occurs with MPL in both small- (<15 kg) and large-breed dogs (>30 kg) using the mTPLO approach, with a low complication rate [10, 15]. In the present study, we used the mTPLO technique in 67% of cases where MPL co-occurred, intending to realign the quadriceps mechanism.
Prior studies reported overall complication rates of 4.4–10% for TPLO procedures in small-breed dogs, with no major complication, whereas large-breed dogs had a 22% complication rate [17, 24]. When mTPLO was used in small-breed dogs, the total complication rate was 18.4% with minor and major complication rates of 7.8% and 10.5%, respectively. Additionally, recurrent patellar luxation was observed in 6.6% of cases [10]. These complications were associated with various factors, including breed, age, pre-operative TPA, proximal screw-joint distance, and body weight [4, 24]. This study presents an overall complication rate of 11% associated with the recurrence of grade 4 MPL identified 10 days after surgery. The recurrence of MPL was attributed to the untreated 11° distal femoral varus and internal tibial rotation, which were not adequately addressed by mTPLO. It appears that mTPLO alone may not suffice to realign the tibial tuberosity in this case. However, it is important to note that the dog still showed a significant improvement in limb function and alignment when compared to the contralateral limb with grade 4 MPL. Furthermore, the owner expressed satisfaction with the outcomes and chose not to pursue additional surgery for recurrent patellar luxation. Major complications, such as implant failure or surgical site infection, were not observed in this study. This favorable outcome can be attributed to several factors, including the absence of open wounds and soft tissue trauma at the surgical site, the dog’s low body weight, and the cooperative efforts of the owners. These collaborative factors collectively contributed to the overall success of fracture fixation, encompassing biological, mechanical, and clinical aspects, as assessed by the Patient Fracture Assessment Score [29].
This study has, however, certain limitations. First, the relatively small sample size could result in type II errors, potentially impacting the study’s statistical power. Second, this study is non-randomized and the participating owners were not blinded to the treatment protocols. This lack of blinding introduces the possibility of bias, particularly in the assessment of results obtained through owner questionnaires. Nevertheless, the study aimed to reduce bias by including objective measurements such as TMC using a Gulick tape and ROM assessed with a goniometer. Third, both treatment groups received rehabilitation therapy and a joint supplement, which alleviated pain and improved joint mobility in the affected joints. As a result, the positive impact of these interventions on clinical outcomes may complicate direct comparisons between surgical and non-surgical treatments. However, both treatment groups received the same joint supplement dosages and followed an identical rehabilitation protocol to standardize the study and minimize the impact of confounding variables on the outcomes. Finally, the study’s timeframe is relatively short, which may not provide sufficient data to assess and compare the long-term outcomes of TPLO and conservative treatment. However, it should be emphasized that the main objective of this study was to investigate and compare the short-term outcomes of TPLO and conservative treatments for CCLR in small-breed dogs. Therefore, we closely monitored patients at biweekly intervals to evaluate which treatment yielded superior outcomes and facilitated rapid recovery over the short term.
In summary, this study observed short-term improvements in both the conservative and surgical treatment groups. Whilst no significant differences were identified in the parameters assessed between the two groups, it is worth emphasizing that the TPLO group exhibited improvements in the thigh muscle, along with a consistent decrease in pain scores based on the CBPI owner’s questionnaire. These results suggest the potential for a rapid recovery and enhanced limb functionality with TPLO treatment, contributing to improved stifle stability. Consequently, in terms of short-term clinical outcomes, both conservative and surgical treatments can effectively manage CCLR in small-breed dogs, with surgical treatment potentially resulting in a slightly superior outcome.
DECLARATION OF INTERESTS
The authors report no conflicts of interest.
Acknowledgments
The authors would like to thank Pharmalink International Ltd. for their support of PCSO-524 (Antinol) to all patients participating in this study. Pharmalink International Ltd. did not play any role in the study design, execution, analysis, and reporting of the study. This study was funded by the Routine to Research (R2R) grant, Faculty of Veterinary Sciences, Chulalongkorn University.
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