Treatment of Equine Hindlimb Proximal Suspensory Desmopathy

Comparison of Two Surgical Techniques for the Treatment of Equine Hindlimb Proximal Suspensory Desmopathy

by Kendra D. Freeman,M. Norris Adams,Allison E. Salinger,Nathaniel A. White IIORCID andJennifer G. Barrett *ORCID
Marion duPont Scott Equine Medical Center, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, 17690 Old Waterford Rd., Leesburg, VA 20177, USA

Animals 2025, 15(17), 2598; https://doi.org/10.3390/ani15172598

Simple Summary
This study compared two different surgical treatments of a common problem causing lameness in horses: hind limb suspensory ligament injury in 141 horses. One surgical technique is minimally invasive, and splits the ligament and the overlying tissue that constricts the ligament desmoplasty with fasciotomy (DF). The other surgery cuts the overlying constrictive tissue, but also cuts the nerve that specifically goes into the suspensory ligament deep branch of the lateral plantar neurectomy with fasciotomy (NF). Both techniques resulted in soundness at similar levels, and in return to work at similar levels. One technique (DF) was used more often in horses with evidence of tearing of the suspensory ligament, which may indicate surgeon preference. Neither surgery was associated with serious operative complications; however, three horses had their suspensory ligaments loosen too much resulting in dropped fetlocks.

4. Discussion
Suspensory DF and NF have been previously described with resolution of lameness and return to the previous level of performance in 82% and 75% of horses, respectively [15,21]. Performing neurectomy of the deep branch of the lateral plantar nerve has been suggested to ameliorate pain due to nerve compression [22]. Alternatively, atrophy of muscle fibers within the proximal suspensory after neurectomy could help relieve compartment pressure [24]. The common feature of both surgical procedures is the fasciotomy, which hypothetically can relieve pressure within the compartment made up by the 2nd, 3rd, and 4th metatarsal bones and fascia on the proximal plantar surface of the ligament. Interestingly, the use of fasciotomy alone or neurectomy alone have not been reported in the literature for treatment of proximal hindlimb suspensory desmopathy, but both are currently used in our hospital, along with neurectomy with fasciotomy. We are no longer performing desmoplasty. This retrospective was performed (and data were collected) prior to switching surgical approaches in our hospital.
The results of this study showed similar return to soundness (DF 79%, NF 88%) and intended level of performance for NF (75%), but a lower return to the intended level of performance after DF (67%). Dyson and Murray reported 77.8% of horses treated with NF returned to full athletic function for at least one year [15]. Seventy percent of these horses started work two months after surgery. In our study, 75% of horses returned to full work following NF using their criteria. Thus, results for NF seem to be consistent between studies. Hewes and White reported 87% of horses with hindlimb suspensory core lesions treated with DF were able to return to full work [21]. These horses also returned to work after a mean of 7.5 months following the procedure. The lower numbers in the Hewes and White study may account for this difference. Surgery failed to resolve lameness in 20 horses overall, with 17 failures due to continued suspensory desmopathy. Adhesions of the suspensory ligament to surrounding soft tissue structures may represent a surgical complication contributing to persistent lameness [25].
Horses in the present study treated with DF returned to work approximately 10 months after surgery, which in univariate analysis was significantly longer than horses treated with NF, 7 months (p = 0.0023). The post-op protocol for DF recommended a minimum of 4 months of gradually increasing exercise before initiating a return to full work, based on evidence of healing of the core lesion on ultrasound, whereas the NF rehabilitation protocol was to gradually increase work after 2 months, similar to the recommendations by Dyson and Murray [15]. The longer rest period recommended after DF may partly explain the extended rehabilitation time, though it remains unclear whether this delay conferred any clinical benefit. Although not recorded, season of the year or owner decisions may also have affected when horses were placed back in full work.
Limitations of this retrospective study include incompleteness of medical records, recall bias, and lack of randomization of treatment. As a consequence, there were significant treatment biases noted, in particular the horses with worse ultrasonography scores were treated with DF, and horses treated with DF had longer rehabilitation periods. It would also have been preferable to have MRI as the diagnostic imaging method of choice; however, only one horse had this technique performed in this population. Inclusion of adjunct treatments such as platelet rich plasma injection may also have affected results.
Dyson and Murray [15] identified excessively straight hock conformation and/or hyperextension of the metatarsophalangeal joints as a risk for lack of resolution of hindlimb proximal suspensory desmopathy after surgery. Horses with this conformation, as well as hindlimb proximal suspensory desmopathy, were not able to return to work compared to 77.8% of horses without this conformation [15]. Concurrent sources of lameness also had a negative effect on the outcome. Horses in our study had no concurrent lameness reported at the time of surgery, and hindlimb conformation was not always noted in the medical records. It is possible that some horses with straight tarsi and/or hyperextended metatarsophalangeal joints were treated surgically, thereby contributing to fewer horses returning to full use.
Two important differences existed between the two surgical groups. Firstly, horses treated with DF had significantly higher ultrasound severity scores compared to those treated with NF, indicating that DF was preferentially selected for more severe cases (Table 2) (p = 0.001). This aligns with the original description of DF by Hewes and White, who proposed the technique for horses with core lesions as a method to decompress acute lesions and enhance blood supply to chronic injuries [21]. In contrast, NF has been described to decompress the suspensory ligament [22] and cause neurogenic atrophy of intraligamentous muscle fibers [24]. Despite the bias toward using DF in horses with more severe ultrasonographic abnormalities, treatment type was not associated with differences in postoperative soundness or return-to-work outcomes. Ultrasound severity itself was also not significantly predictive of outcome, reinforcing that once severity is accounted for, surgical technique does not appear to influence prognosis.
Horses treated with DF were more likely to receive adjunctive non-surgical treatments such as platelet-rich plasma, stem cells, or extracorporeal shockwave therapy. While these were presumably targeted toward the more severely affected individuals, their use did not translate into improved outcomes in the present cohort. The only factor significantly associated with outcome was age, with older horses more likely to fail to return to work due to suspensory disease.