Imagine this scenario: a four-year-old Border Collie who participates in agility is presented for poor performance and consistently missing weave poles. You find pain with manipulation of the shoulder joint and suspect medial shoulder instability (MSI). What is the best way to treat this patient?
Ten studies were critically appraised; none were clinical prospective studies and most had single or low numbers of subjects. No meta-analyses or systematic reviews were identified and there are no randomised studies evaluating multiple treatments, so it is challenging to make any direct comparisons and assess outcomes between treatment methods. Franklin et al. (2013) reported that surgical intervention may be superior to medical management. Of 101 dogs with MSI, 48 percent were treated through medical management, 9 percent with radiofrequency induced thermal capsulorrhaphy (RITC) and 44 percent with reconstruction. In the 62 dogs available for follow-up, reconstruction was three times more likely to have a successful outcome than medical management and 1.6 times more likely than RITC. RITC was 1.8 times more likely to be successful than medical management. Medical treatment was still successful in 69 percent of dogs.
In a retrospective study by Cook et al. (2005), 43 dogs were treated arthroscopically with RITC. At one year or greater follow-up, 93 percent of dogs were considered improved and 79 percent were considered to have an excellent outcome (no timescale given). This study provides some of the more robust evidence, as an objective evaluation of shoulder abduction angles was performed. RITC appears to have a high rate of success for treating MSI; however, the reported return to improved function took 12 to 16 weeks with full function only occurring around five to six months post-operatively.
In a study by O’Donnell et al. (2017), 39 dogs received arthroscopic assisted extracapsular stabilisation with a prosthetic ligament. All dogs were deemed to have a successful outcome, with 77 percent regaining full function and the remaining 23 percent having an acceptable outcome. This provided a more rapid time frame for return to function compared to RITC treatment in the study by Cook et al. (2005), with full sport activity occurring on average 16 to 20 weeks post-operatively. A case report of full arthroscopic assisted treatment of MSI with a prosthetic ligament (Penelas et al., 2018) was the first published using this technique. The owner reported no lameness at a six-month follow up, but no objective outcome measures were reported.
A case report of a three-year-old Springer Spaniel that was treated with RITC (O’Neil and Innes, 2004) showed that the dog’s gait was improved five months post-treatment, though no further follow-ups were recorded.
Medial tendon transposition provided a good to excellent functional outcome in 82 percent of cases reported by Puchea and Duhautois (2008). However, this retrospective case series included cases of lateral shoulder instability as well as traumatic cases of medial instability, which are different aetiologies than chronic use leading to MSI.
A case series reported by Pettit et al. (2007) demonstrated that imbricating the subscapularis tendon for treatment of shoulder instability was successful, with lameness fully resolved in three cases and greatly improved in two cases. Fitch et al. (2001) also reported that placing a prosthetic capsule with suture anchors and/or bone tunnels resulted in a good to excellent outcome for seven out of eight dogs with MSI following surgery. No objective evaluation of outcomes was reported in either study.
Becker et al. (2015) discussed four cases of MSI treated medically with shockwave therapy. Only three patients were available for long-term follow up and all were still lame, suggesting that shockwave alone may not be a good medical treatment option for MSI.
In a study by Vasseur et al. (1983), the tendon of the subscapularis tendon, medial joint capsule and medial glenohumeral ligament were transected. This was not true medial shoulder instability, but rather a manufactured instability that was treated immediately, so does not truly mimic disease.
Overall, the evidence shows that surgical and medical treatment of medial shoulder instability can be successful, with no strong evidence to support one surgical treatment over another.
MSI can encompass damage to the medial glenohumeral ligament or the subscapularis muscle/tendon, or a combination of both, as well as the joint capsule. This poses a challenge when evaluating the best treatment options, as medical management may be more appropriate for one instability, while another may require surgical intervention.
There is a lack of prospective randomised studies comparing the effectiveness of medical management and the various surgical techniques available. Future studies that are comparative and prospective are required to make a definitive assessment of the optimal treatment practice for dogs with MSI.