A recent narrative review assessing treatment options for small dogs (< 15 kg) concludes that “There is a lack of evidence regarding the optimal management of CrCL rupture in small dogs”. “The limited evidence available shows that conservative management is likely to result in prolonged recovery time (average time to recovery approximately 4 months).”
“Given the lack of evidence in the literature, it is difficult to draw evidence-based conclusions regarding when conservative management may be indicated and what is the most appropriate protocol for conservative management. Furthermore, the success rate of conservative management is also unclear and the time to recovery is likely to be prolonged (the average recovery time as reported by Vasseur (1984) is approximately 4 months)”
All these conclusions are based on two historical reports from 1972 and 1984 (Pond & Campbell and Vasseur). In those studies the dogs were treated with cage rest for 3 to 8 weeks and painkillers. 90% of small breed dogs had a good outcome (no detectable lameness reported by owner) vs. 78% of large breed dogs. Recovery time unclear. The newer 1984 study found 85% of small breed dogs had a good outcome (as assessed by veterinarian) and only 19% of large breed dogs.
A RCT for overweight dogs > 20 kg shows that there are only slight differences in outcomes at 1 year with conservative treatment (physiotherapy, weight loss, painkiller) vs TPLO (1). According to an arbitrary definition of “success”, 64% of conservatively treated and 75% of operatively treated dogs had a “successful outcome”. Study poorly done, very high risk of bias, not reported patient-important/owner-relevant outcomes. Very small differences in some of the owner-rated outcomes (see below, dashed line = surgery, solid line = conservative). There was no difference between the groups for investigator-assessed lameness and pain scores. Also no significant differences in drawer motion. The trial was open label.
Vet surgeon opinions on conservative treatment: Duerr et al. survey (2): only 6% would consider conservative treatment as first option. If forced to use conservative treatment, 90% would use NSAIDs, 80% rest, 70% glucosamine/chondroitin supplementation. Treatments “very unlikely to recommend” were stemcell therapy, shockwave therapy, and orthoses (50%). Similar results in UK survey (3).
Most common reasons for owners to seek stifle orthosis instead of surgery for CrCL disease according to 2017 survey were “dislike the idea of surgery/too invasive”, “age of dog”, and “cost of surgery” (see table below). The median dog weight was 33 kg in the survey. Almost all owners would “likely” or “maybe” pursue rehabilitation in concert with the orthosis.
Vasseur 1984 study: 86% of dogs ≤ 15 kg were clinically normal after 3 years. Larger dogs in the same study didn’t fare well; 19% improved and 81% did not improve or deteriorated leading to surgery. These dogs had either severe comorbidities or their owner couldn’t afford surgery.
Pond & Campbell 1972: 91% of small breed and 78% of large breed dogs had “no detectable lameness” after conservative treatment. Conservative treatment produced even better outcomes than surgery in small breed dogs (<20 kg) (91% vs 85%). 90% of large dogs treated surgically had “no detectable lameness”.
Evidence from cats
Retrospective study of 18 cats treated with mainly painkillers and exercise restriction for 4-8 weeks shows that 72% became weight bearing within a week (4). After 3 months, 83% of cats had no lameness observable by owner. At long term follow-up (several years, probably?), 94% of owners reported their cat had good to excellent outcome.
Another study (5) reports on 50 cats treated with either conservative treatment or LFS surgery (retrospective cohort study). 27% of surgically treated cats had complications. Not reported if cons treated cats had any complications. Conservatively treated cats had a median FMPI score of 0.5 (VERY LOW = VERY GOOD!). Surgically treated cats had 5, meaning significantly higher pain and lower activity scores. This difference can be largely or partly due to selection bias, but anyhow it shows that conservative treatment works well in many cases of CrCL disease in cats.
Evidence from humans
Of young, highly active adults, 60% are totally fine with rehabilitation and do not need surgery (6). Patients with rehabilitation only have identical outcome scores at two years compared to those that had either early surgery or rehab + later surgery if needed. Another RCT with older and slightly less active patients had similar results: 50% did not need surgery and outcomes were similar between the groups at 1 year (7). Thus, it seems that at least half of human patients (and probably even more among sedentary humans) are totally fine with rehabilitation after ACL injury.
CrCL surgery complication rate
The complication rate for CrCL surgery was 28% according to a 2003 retrospective study of 400 cases (8). Re-surgery was needed in 5% of cases. Infection rate about 3%. Another study of 50 dogs found 13% complication rate for TightRope lateral suture technique and 17% for TPLO (9).
Other considerations
Extracapsular techniques are gaining popularity and have roughly similar outcomes compared to TPLO. The theory behind extracapsular techniques (such as TightRope, lateral fabello-tibial suture, etc) is that the suture provides temporary stabilization of the joint, while periarticular fibrosis develops. Apparently, no suture is intact for very long, and the “reason why” extracapsular techniques work is because this newly developed periarticular fibrosis stabilizes the joint. In my opinion, if this theory really is true, the same effect should be possible to achieve with an orthosis (hinge orthosis). On the other hand, I really doubt that the periarticular fibrosis really develops and that it somehow stabilizes the joint in any meaningful way. I think that some kind of natural adaptation occurs (as in humans) and the dog simply stops limping after a while (regardless of whether there is a suture or not). Why would the periarticular fibrosis develop only after CrCL rupture and not before??
References
1. Wucherer KL, Conzemius MG, Evans R, Wilke VL. Short-term and long-term outcomes for overweight dogs with cranial cruciate ligament rupture treated surgically or nonsurgically. JAVMA. 2013;242(10):1364–72.
2. Duerr FM, Martin KW, Rishniw M, Palmer RH, Selmic LE. Treatment of canine cranial cruciate ligament disease: A survey of ACVS Diplomates and primary care veterinarians. Veterinary and Comparative Orthopaedics and Traumatology. 2014;27(6):478–83.
3. Comerford E, Forster K, Gorton K, Maddox T. Management of cranial cruciate ligament rupture in small dogs: A questionnaire study. Veterinary and Comparative Orthopaedics and Traumatology. 2013;26(6):493–7.
4. Stoneburner RM, Howard J, Gurian EM, Jones SC, Karlin WM, Kieves NR. Conservative nonsurgical treatment for cranial cruciate ligament disease can be an effective management strategy in cats based on validated owner-based subjective assessment in some cases. J Am Vet Med Assoc. 2022 Jun 9;1–4.
5. Boge GS, Engdahl K, Moldal ER, Bergström A. Cranial cruciate ligament disease in cats: an epidemiological retrospective study of 50 cats (2011–2016). J Feline Med Surg. 2020 Apr 1;22(4):277–84.
6. Frobell RB, Roos EM, Roos HP, Ranstam J, Lohmander LS. A Randomized Trial of Treatment for Acute Anterior Cruciate Ligament Tears. New England Journal of Medicine. 2010 Jul 22;363(4):331–42.
7. Reijman M, Eggerding V, van Es E, van Arkel E, van den Brand I, van Linge J, et al. Early surgical reconstruction versus rehabilitation with elective delayed reconstruction for patients with anterior cruciate ligament rupture: COMPARE randomised controlled trial. The BMJ. 2021 Mar 9;372.
8. Pacchiana P, Morris E, Gillings S, Jenssen C, Lipowitz A. Surgical and postoperative complications associated with tibial plateau leveling osteotomy in dogs with cranial cruciate ligament rupture: 397 cases (1998–2001). JAVMA. 2003;222(2):184–93.
9. Cook JL, Luther JK, Beetem J, Karnes J, Cook CR. Clinical comparison of a novel extracapsular stabilization procedure and tibial plateau leveling osteotomy for treatment of cranial cruciate ligament deficiency in dogs. Veterinary Surgery. 2010 Apr;39(3):315–23.
10. Stauffer KD, Abvp D, Tuttle TA, Elkins BAD, Wehrenberg AP, Character BJ. Complications Associated With 696 Tibial Plateau Leveling Osteotomies (2001-2003) [Internet]. Vol. 42, J Am Anim Hosp Assoc. 2006. Available from: http://meridian.allenpress.com/jaaha/article-pdf/42/1/44/1331912/0420044.pdf
11. Stein S, Schmoekel H. Short-term and eight to 12 months results of a tibial tuberosity advancement as treatment of canine cranial cruciate ligament damage. Journal of Small Animal Practice. 2008 Aug;49(8):398–404.
12. Priddy N, Tomlinson J, Dodam J, Hornbostel J. Complications with and owner assessment of the outcome of tibial plateau leveling osteotomyfor treatment of cranial cruciate ligament rupturein dogs: 193 cases (1997–2001). JAVMA. 2003;222(12):1726–32.
13. Corr SA, Brown C. A comparison of outcomes following tibial plateau levelling osteotomy and cranial tibial wedge osteotomy procedures. Vol. 20, Veterinary and Comparative Orthopaedics and Traumatology. 2007. p. 312–9.
14. Lafaver S, Miller NA, Stubbs WP, Taylor RA, Boudrieau RJ. Tibial tuberosity advancement for stabilization of the canine cranial cruciate ligament-deficient stifle joint: Surgical technique, early results, and complications in 101 dogs. Veterinary Surgery. 2007 Aug;36(6):573–86.
15. Casale S, McCarthy R. Complications associated with lateral fabellotibial suture surgery for cranial cruciate ligament injury in dogs: 363 cases (1997–2005). JAVMA. 2009;234(2):229–35.