33rd Annual Scientific Meeting proceedings

There is a number of shoulder pathologies that can cause lameness in small animals, ranging from articular conditions and bone diseases to soft tissue injuries. When conservative management is unsuccessful, when some specific conditions affect the shoulder, or when degeneration of the shoulder and subsequent clinical signs are severe, then surgical treatment would be indicated. In this lecture we will review the surgical treatment options available for various shoulder conditions, their evidence and the challenges they may pose.

Shoulder instability/ luxation

• • Closed reduction can be attempted if the luxation is acute, it is secondary to a traumatic event, the joint anatomy is normal and there are no fractures associated. Open reduction and surgical stabilization is indicated in chronic luxations, when there are fractures or when the joint reluxates after closed reduction.
  • Cases of MSI can be classified as mild, moderate or severe, and treatment varies depending on the severity of the findings. Moderate and severe cases would require surgical intervention. Surgical techniques that can be used can be classified as:
    •  Transposition of the bicipital tendon This technique involves releasing and displacing the tendon medially or laterally.  Attachment may be done by means of a bone flap and kwires, a screw and washer or a staple/tunnel technique. This procedure has been reported to provide good outcomes but it should be reserved to mild/moderate cases of MSI.  Good to excellent results have been reported in 84,5% of dogs undergoing this technique (Pucheu et al. 2008). Unfortunately this procedure is associated with alteration of joint biomechanics, incongruency of the articular surfaces and OA.
    • Imbrication of the subscapularis tendon : This has been shown to be a moderately effective procedure for management of MSI that is unresponsive to medical management (Pettit et al. 2007).
    • Radiofrequency-induced thermal capsulorraphy (RITC): This causes  denaturalization of the collagen fibers in the joint capsule, causing shrinkage and stability. However collagen fibers tend to stretch to their original length with time and use. Success rate has been reported in 80% and 93% of cases in 2 studies with a complication rate of 7%. This technique  was 1,8 times more likely to have a successful outcome over non-surgical management.

• Prosthetic reconstruction. Suture anchors and bone tunnels have been reported to anchor large monofilament suture at the origins and insertions of the medial glenohumeral ligament (MGHL). This technique prevents medial subluxation and preserves normal shoulder motion in comparison to biceps transposition. Prosthetics reconstruction can be done as a modified Campbell´s technique or in a V-shaped manner. Surgical reconstruction  was 3 times more likely to have a successful outcome over non-surgical management, and 1,6 more likely than RITC (but this was not significant) . The prosthetics can also be placed arthroscopically (Tightrope) showing a success rate of 100% of animals (77% with full function) and 23% with acceptable limb function as described by O´Donell in 2017. Postoperative physiotherapy and rehabilitation are essential part of recovery.
• Excisional arthroplasty: The osteotomy is performed just proximal to the glenoid cavity, in a laterodistal to proximomedial direction and another osteotomy is made through the humeral head, removing the main articular surface. Montasell et al (2018) reported long-term improvement in lameness and pain, but this technique also decreased ROM in the operated joint and was associated with persistent mild lameness after this procedure in small breed dogs.
• Arthrodesis:  Unfortunately studies are also lacking but those published reported good outcomes after this procedure. Removal of the articular cartilage can be done by burring or by performing osteotomies in the scapula and humeral head (specially in very deformed joints) to obtain a physiological shoulder angle. Outcome is generally acceptable and predictable, with a clear circumduction of the limb. Fitzpatrick et al in 2012 reported a high complication rate (50%), being catastrophic/major in almost half of these. Applying 2 LCP plates has been reported in a variety of dog sizes (6-29Kg) with very good outcome  (full function in 91% of dogs) and low complication rate (16% minor complications) (Phipps and Solano 2022). Only 2/12 dogs showed  limb circumduction of the operated limb.

Osteochondritis dissecans (OCD)
Surgical treatment is the recommended treatment by means of removal of the cartilage flap and curettage of the subchondral bone. This can be done by arthroscopy or arthrotomy. Other advanced techniques (i.e OATS, SynACART) are also available.

• • Arthroscopy: This allows not only the diagnosis and inspection of the joint but also removal of the cartilage flap and debridement of the subchondral bone until bleeding is observed. Forage, micro picking or burring can be done to stimulate bleeding from the exposed subchondral bone and its coverage with fibrocartilage. However, although most dogs improve clinically, DJD continues progressing. It has previously been reported a complete recovery 6 weeks after surgery (Oliveiri 2007).  Larger defects and those located in a more central position have been reported to have worse prognosis.
  • Osteochondral Autograft Transfer System (OATS) and Osteochondral Allograft Transplantation: OATS involves transplantation of osteochondral cores from a region of limited load bearing to an articular cartilage defect in a load-bearing area. Benefits of OATS include reconstruction of subchondral and articular surface, resurfacing with hyaline cartilage, and creation of a barrier between synovial fluid and subchondral bone. Fitzpatrick et al (2009) reported excellent outcomes longterm. Second look arthroscopy confirmed satisfactory articular contour and resilience of the chores. Unfortunately donor joint morbidity is a concern but it is generally minor, and it has been reported to disappear in 98% of the cases within 1 year. Osteochondral allograft transplantation involves the transfer of viable, “fresh,” osteochondral tissue from a deceased donor to a recipient patient. A modified lateral shoulder approach or Cheli approach can be performed. Franklin et al (2021) reported 35 joints with osteochondral allograft (16 were complex), 16/35 had complications (5/35 were major) and 30 cases had successful outcomes. After 12 months from implantation, no differences were found between  osteochondral autografts and allografts in an experimental study in dogs stifles. (McCarty et al 2016)
  • Synthetic Osteochondral Implants (SynACART): This involves implantation of a synthetic “plug” which consists of a surface layer of polycarbonate urethane and a bone ingrowth lattice-type titanium material. Favourable results have been reported after experimental and clinical studies in stifle OCD. These  implants have been considered effective in regards to bone integration, lack of damage to adjacent articular cartilage, and maintenance of implant integrity and architecture. Murphy et al (2019) reported an excellent outcome in dogs with large caudocentral OCD lesions in the shoulder managed with SynACART, with no lameness present after 10-12 weeks postoperatively in any of the dogs.

Bicipital Tenosynovitis/Tendinopathy
Surgical treatment is usually recommended if conservative management has been unsuccessful or tendon partial rupture is suspected. Tenotomy of the tendon can be performed by arthrotomy, arthroscopy, percutaneously with a scalpel blade or guided by US with a needle. Tenodesis to the proximal humerus is not necessary, although some debate exists about performing this procedure in sporting and working dogs or in patients with a bilateral condition. Tenodesis has been reported to return patients to full function 12-18 weeks after bicipital tenodesis. Studies performed in human medicine failed to find any significant functional differences between bicipital tenotomy and tenodesis. The only difference was tenodesis prevented Popeyes deformity.

Mineralized and non-mineralized supraspinatus tendinopathy
Surgical treatment is recommended if conservative management has been unsuccessful. A craniomedial  approach to the shoulder allows making longitudinal incisions along the insertion of the tendon on the greater tubercle in order to remove the mineralization foci and increase vascularisation of the area. Debulking the ST tendon medially is useful to take a sample for histopathology and relief its pressure over the bicipital tendon. Previous studies reported a good to excellent outcome in 66% of patients, and a longterm full recovery in 80% of patients managed surgically for ST. Complication rate of this procedure was low, with no intra-operative complications, an 8% minor complication rate and a 4% major complication rate.

References
Available upon request