Proximal suspensory ligament desmitis (PSLD) is a common cause of bilateral lameness in hindlimbs or poor performance (Dyson, 1991; Dyson, 2007). Horses with chronic PSLD have a poor prognosis regardless of the treatment (Dyson and Genovese, 2011). Ultrasonography has been demonstrated to be an accurate predictor of the presence of SL pathology at post-mortem examination verified histologically (Dyson et al. 2017), although sometimes the diagnosis can be challenging (Meehan and Labens, 2016).
In hindlimbs the persistence of the symptoms can be caused by a compartment-like syndrome with pressure on the plantar metatarsal nerve (Dyson and Genovese, 2011) or to an excessive accumulation of proteoglycans within the SL (Degenerative SL desmitis) (Baxter and Stashak, 2011).
Surgery includes Neurectomy of the Deep Branch of the Lateral Plantar Nerve alone or in
combination with Plantar Fasciotomy but none of them is suggested, because of a poor prognosis, in patients with a straight hocks conformation and hyperextended fetlocks (Dyson and Murray, 2012).
During surgery the injection of bone marrow-derived cells, PRP or porcine urinary bladder matrix have been described leading to a 79-84% success rate, but follow up period has not been documented (Bathe, 2008). The lack of a follow-up > 1 year is the main limitation of the majority of studies. Other surgical options include Desmoplasty and fasciotomy, with a reported success rate of 85% (Hewes and White, 2006) or Tibial neurectomy (Dyson and Genovese, 2011), but literature is very poor.
Conservative management and rest (Dyson, 1994), Extracorporeal ShockWave Therapy (ESWT) (Lischer et al., 2006) and radial pressure wave therapy (Crowe et al., 2004) have disappointing results, because after a period of controlled exercise for 3 months there can be an initial improvement but then no further one is usually observed (Dyson and Genovese, 2011).
The use of PRP has been used in acute SL desmitis, in presence of core lesions (Romagnoli et al, 2015) and for midbody SL desmitis (Waselau and Genovese, 2008) reporting an excellent prognosis following a period of controlled exercise, but they both include a small number of horses with acute injury. PRP, Equine Serum and Acellular Bone Marrow (ABM) seem to have an in vitro ability to enhance healing of the SL (Smith et al., 2006) but further studies in vivo are needed, especially on chronic cases and not only on acute injuries. In a recent paper Giunta et al. (2019) considered both PRP and ESWT safe treatments for PSLD with a 79% success after 1 year following treatment; this high percentage is related to a low baseline lameness and low grade ultrasound abnormalities.
Seabaugh et al. (2017) showed in vitro how a PRP injection followed by ESWT may stimulate the release of growth factors from platelets. The combination of these two modalities needs in vivo studies but it can be in future a further possible treatment.
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