34th Annual Scientific Meeting proceedings

Desmitis of the proximal suspensory ligament (PSL) is a common cause of lameness in equine athletes (Müller et al. 2023). Conventional surgical management of the condition includes neurectomy of the deep branch of the lateral palmar/plantar nerve that is usually combined with a fasciotomy of the deep metatarsal fascia in the hindlimb (Dyson and Murray 2012, Guasco et al. 2013). A fasciotomy approach in the equine forelimb is not described in detail and the fasciotomy in the hindlimb is associated with a high risk of iatrogenic damage to the PSL as the procedure is commonly performed blindly (Sidhu et al. 2019). The aim of this study was therefore to develop and validate a minimally invasive endoscopic approach for palmar/plantar deep metacarpal/metatarsal fasciotomy under visual control that additionally facilitates direct visual assessment of the equine PSL region.

Endoscopically guided fasciotomy was initially performed in equine fore- (n = 18) and hindlimb (n = 18) specimens by three surgeons with varying level of experience (equine surgeon in training, Diplomate ECVS with less than 10 years of experience; Diplomate ECVS with more than 10 year of experience). Surgery time, local anatomical variations, collateral damage and completeness of the fasciotomy were recorded. The surgery was subsequently performed in clinical cases (n=18) that presented with PSL desmitis.

Surgery was completed via two portals located 8-10 cm distal to the head of MTII/IV. A medial portal was created for a standard arthroscope (4 mm; 30° forward-angled; Karl Storz) to be inserted in the space between the deep metacarpal/metatarsal fascia and the deep digital flexor tendon outside the digital flexor tendon sheath. The lateral instrument portal was created under arthroscopic guidance. Loose connective tissue was bluntly dissected under CO2 insufflation using an arthroscopic probe until the transverse fibres of the deep metacarpal/metatarsal fascia and the most proximal aspect of the fascia were identified. A hook-knife was then inserted and positioned at the proximal border of the fascia. Fasciotomy was completed as the hook-knife was retracted towards the lateral portal. Following fasciotomy, the PSL under the fascia was evaluated and the varying amount of fat between fascia and PSL was documented.

Surgery time was 20.5 (range 8-43) minutes, and the fasciotomy had a median length of 4.3cm (1.5-7cm) in the specimens. The risk of iatrogenic damage to neurovascular structures was significantly higher in forelimbs when compared to hindlimbs (p=0.001) and there was a wide variation in the amount of adipose tissue present between the deep metacarpal/metatarsal fascia and the PSL. Minimally invasive fasciotomy was successfully performed in all clinical cases. Based on the results of the initial study, portals were created under ultrasonographic guidance in all clinical cases to avoid neurovascular injury. Adhesions between the fascia and the PSL were removed using the arthroscopic probe or the hook-knife in affected cases. Mild to moderate subcutaneous emphysema at the surgical site had ceased after the first bandage change 48 hours post-surgery in all horses. Telephone follow- up confirmed return to ridden work in 77% of cases.

Minimally invasive transection of the deep metacarpal/metatarsal fascia can be performed safely under endoscopic guidance. Endoscopic evaluation of the PSL region allows visual control of the fascia transection. Additionally, adhesions between fascia and PSL can be identified and removed to facilitate direct inspection of the PSL.

References:

1. Dyson, S. & R. Murray (2012) Management of hindlimb proximal suspensory desmopathy by neurectomy of the deep branch of the lateral plantar nerve and plantar fasciotomy: 155 horses (2003-2008). Equine Vet J, 44, 361-7.
2. Guasco, P. G., G. Kelly, J. Schumacher & R. W. Henry (2013) Excision of the deep branch of the lateral palmar nerve of horses to resolve lameness caused by proximal suspensory desmitis. Vet Surg, 42, 296-301.
3. Müller, E. M. T., K. Vanderperren, R. Merle, S. Rheinfeld, P. Leelamankong, C. J. Lischer & A. Ehrle (2023) Findings consistent with equine proximal suspensory desmitis can be reliably detected using computed tomography and differ between affected horses and controls. Vet Radiol Ultrasound, 64, 1005-1014.
4. Sidhu, A. B. S., S. M. Rosanowski, A. M. Davis, J. F. Griffith & P. Robinson (2019) Comparison of Metzenbaum scissors and Y-shaped fasciotome for deep metatarsal fasciotomy for the treatment of proximal suspensory ligament desmopathy in horses. Vet Surg, 48, 57-63.