Standing left recurrent laryngeal neurectomy for prospective evaluation of laryngeal hemiplegia evaluated by a high-speed treadmill test.

OBJECTIVE: To describe left recurrent laryngeal neurectomy (LRLn) performed under standing sedation and evaluate the effect of LRLn on upper respiratory tract function using a high-speed treadmill test (HST). We hypothesized that (1) unilateral LRLn could be performed in standing horses, resulting in ipsilateral arytenoid cartilage collapse (ACC); and (2) HST after LRLn would be associated with alterations in upper respiratory function consistent with dynamic ACC. ANIMALS: 6 Thoroughbred horses. METHODS: The horses were trained and underwent a baseline HST up to 14 m/s at 5% incline until fatigue. Evaluation included; airflow, pharyngeal and tracheal pressures, and dynamic upper respiratory tract endoscopy. Trans-laryngeal impedance (TLI) and left-to-right quotient angle ratio (LRQ) were calculated after testing. The following day, standing LRLn was performed in the mid-cervical region. A HST was repeated within 4 days after surgery. RESULTS: Standing LRLn was performed without complication resulting in Havemayer grade 4 ACC at rest (complete paralysis) and Rakestraw grade C or D ACC (collapse up to or beyond rima glottis midline) during exercise. Increasing treadmill speed from 11 to 14 m/s increased TLI (P < .001) and reduced LRQ (P < .001). Neurectomy resulted in an increase in TLI (P = .021) and a reduction in LRQ (P < .001). CLINICAL RELEVANCE: Standing LRLn induces laryngeal hemiplegia that can be evaluated using a HST closely after neurectomy. Standing LRLn may be useful for future prospective evaluations of surgical interventions for laryngeal hemiplegia.

Suspensory ligament size does not change after plantar fasciotomy and neurectomy of the deep branch of the lateral plantar nerve by ultrasonographic assessment.

OBJECTIVE: To determine the short-term effect of plantar fasciotomy and neurectomy (PFN) of the deep branch of the lateral plantar nerve on the proximal suspensory ligament (PSL) cross-sectional area (CSA) in horses with hindlimb proximal suspensory desmopathy (PSD). STUDY DESIGN: Analytical, observational, cohort study. SAMPLE POPULATION: Twenty-one horses. METHODS: Records of horses with chronic PSD treated by PFN were included if a preoperative ultrasonographic examination was available and at least one postoperative ultrasonographic examination. One masked observer measured the ultrasonographic cross-sectional area (CSA) of the PSL. Intraobserver reliability was determined by repeatedly measuring a subset of ultrasonographic images (n = 127). Two masked observers measured the cross-sectional area of the proximal suspensory ligament (PSL-CSA) on preoperative proton density (PD)-weighted transverse high field magnetic resonance images (n = 19 horses) . Agreements for PSL-CSA between preoperative ultrasonographic and MRI measures and between the two magnetic resonance imaging (MRI) observers were assessed. Follow up considered the horses' ability to return to exercise and their owners' satisfaction. RESULTS: The reliability of the ultrasonographic measurement of the PSL-CSA was excellent. Agreement between ultrasonographic assessment and MRI assessment of PSL-CSA was good. No difference was detected between preoperative (median, interquartile range; oblique-incidence, 2.07, 1.72-2.55; on-incidence, 2.23, 1.98-2.65) and postoperative (oblique-incidence, 2.08, 1.80-2.74; on-incidence, 2.28, 2.01-2.74) PSL-CSAs. At a median of 12 months (4-33 months), 16/20 (80%) owners reported the horse was "better" and 15/20 (75%) functioned at or above preoperative levels. CONCLUSION: Ultrasonographic measurement of the PSL-CSA was reproducible and in good agreement with MRI measurement. The PSL-CSA was not influenced by PFN. CLINICAL SIGNIFICANCE: The PSL-CSA cannot be used to guide return to function.

Outcome following neurectomy of the deep branch lateral plantar nerve and plantar fasciotomy for hindlimb proximal suspensory desmopathy in western performance horses: 21 cases.

OBJECTIVE: To report the outcome of horses used in western performance disciplines after deep branch lateral plantar neurectomy/fasciotomy surgery for hind limb proximal suspensory desmopathy (PSD). STUDY DESIGN: Retrospective analysis. SAMPLE POPULATION: Twenty-one client-owned horses. METHODS: Medical records were reviewed (2009-2019) for horses involved in western performance disciplines that had been treated with deep branch lateral plantar neurectomy and plantar fasciotomy for lameness due to hind limb PSD. Follow-up was obtained by reexamination and/or verbal interviews with owners >2 years postoperatively. RESULTS: Sixteen quarter horses and five paints were used for western pleasure (14/21), barrel racing (2/21), cutting (1/21), steer wrestling (1/21), working cow horse (1/21), team roping (1/21) and reining (1/21). A median duration of 8 months was required before horses were able to resume training or athletic work. Nine horses were able to return to a similar or higher level of athletic use, nine horses returned to a lower level of athletic performance, and three horses could not return to intended function. Owner satisfaction with outcome after the procedure was high (16/21), average (3/21), and low (2/21). CONCLUSION: Deep branch lateral plantar neurectomy and plantar fasciotomy allowed most horses to resume some athletic function as western performance horses. CLINICAL SIGNIFICANCE: These results provide evidence of potential outcomes when considering surgical treatment of hind limb PSD in western performance horses.

Neurofibroma of the ulnar nerve in the carpal canal in a dog: treatment by marginal neurectomy.

Peripheral nerve sheath tumours arising in the plexus or peripheral nerves can be treated by limb amputation. There are few reports of these tumours affecting peripheral nerves in the distal regions of the limbs. Here we describe a case of neurofibroma affecting the palmar branch of the ulnar nerve in an Irish setter. Surgical treatment in the region of the carpus by ulnar neurectomy resulted in resolution of chronic thoracic limb lameness. At 11 months following the surgery, clinical examination and MRI did not detect any evidence of recurrence. Neurectomy may be a feasible option for management of selected cases of distally located peripheral nerve sheath tumours.

Extrinsic nerves are not involved in branchial 5-HT dynamics or pulsatile urea excretion in Gulf toadfish, Opsanus beta.

Gulf toadfish (Opsanus beta) can switch from continuously excreting ammonia as their primary nitrogenous waste to excreting predominantly urea in distinct pulses. Previous studies have shown that the neurotransmitter serotonin (5-HT) is involved in controlling this process, but it is unknown if 5-HT availability is under central nervous control or if the 5-HT signal originates from a peripheral source. Following up on a previous study, cranial nerves IX (glossopharyngeal) and X (vagus) were sectioned to further characterize their role in controlling pulsatile urea excretion and 5-HT release within the gill. In contrast to an earlier study, nerve sectioning did not result in a change in urea pulse frequency. Total urea excretion, average pulse size, total nitrogen excretion, and percent ureotely were reduced the first day post-surgery in nerve-sectioned fish but recovered by 72h post-surgery. Nerve sectioning also had no effect on toadfish urea transporter (tUT), 5-HT transporter (SERT), or 5-HT2A receptor mRNA expression or 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) abundance in the gill, all of which were found consistently across the three gill arches except 5-HIAA, which was undetectable in the first gill arch. Our findings indicate that the central nervous system does not directly control pulsatile urea excretion or local changes in gill 5-HT and 5-HIAA abundance.

Effects of denervation of the hip joint on results of clinical observations and instrumented gait analysis in dogs with sodium urate crystal-induced synovitis.

OBJECTIVE To evaluate the effects of selective hip joint denervation on gait abnormalities and signs of hip joint pain in dogs. ANIMALS 6 healthy adult hound-type dogs. PROCEDURES Minimally invasive denervation was performed on the right hip joint of each dog. Two weeks later, sodium urate was injected into the right hip joint to induce synovitis. Dogs were evaluated clinically and by use of instrumented gait analysis before and 2 weeks after minimally invasive denervation and 4, 8, and 24 hours after induction of synovitis. Dogs were euthanized, and necropsy and histologic examination were performed. RESULTS No kinetic or kinematic gait modifications were detected 2 weeks after minimally invasive denervation. Denervation did not eliminate signs of pain and lameness associated with sodium urate-induced synovitis. Results of histologic examination confirmed that denervation was an effective method for transecting the innervation of the craniolateral and caudolateral aspects of the hip joint capsule. CONCLUSIONS AND CLINICAL RELEVANCE In this study, minimally invasive denervation did not result in gait modifications in dogs. Denervation did not abolish the signs of pain and lameness associated with generalized induced synovitis of the hip joint. Further studies are required before conclusions can be drawn regarding the clinical usefulness of hip joint denervation for dogs with hip dysplasia.

Denervation of the Tensor Veli Palatini Muscle and Effusion in the Tympanic Cavity.

An English springer spaniel was presented for right-sided atrophy of the muscles of mastication, analgesia and paralysis of the face, and vestibular dysfunction. Neurological signs were consistent with a lesion involving the pons and rostral medulla resulting in deficits in the function of the trigeminal, facial, and vestibular nerves. MRI disclosed a right-sided extraparenchymal mass consistent with a trigeminal nerve sheath neoplasm that was compressing and invading the pons and medulla. Atrophy of the muscles of mastication, innervated by the trigeminal nerve, was also observed on MRI. Additionally, effusion was present in the ipsilateral tympanic cavity. Gross and microscopic evaluation of the right tensor veli palatini muscle (TVPM) was consistent with neurogenic atrophy. Effusion in the tympanic cavity was likely the result of an inability to open the auditory tube as a consequence of paralysis of the TVPM. Without the ability to open the auditory tube, gases present within the auditory tube and tympanic cavity may be absorbed, creating a negative pressure environment that leads to fluid transudation and effusion build up. To the authors' knowledge, this is the first report to document neurogenic atrophy of the TVPM with concurrent effusion in the ipsilateral tympanic cavity.

A time differential staining technique coupled with full bilateral gill denervation to study ionocytes in fish.

Branchial ionocytes (ICs) are the functional units for ionic regulation in fish. In adults, they are found on the filamental and lamellar epithelia of the gill where they transport ions such as Na+, Cl- and Ca2+ via a variety of ion channels, pumps and exchangers. The teleost gill is extrinsically innervated by the facial (VI), glossopharyngeal (IX) and vagus (X) nerves. The IX and X nerves are also the extrinsic source of branchial IC innervation. Here, two techniques used to study the innervation, proliferation and distribution of ICs are described: a time differential staining technique and a full bilateral gill denervation technique. Briefly, goldfish are exposed to a vital mitochondrion-specific dye (e.g., MitoTracker Red) which labels (red fluorescence) pre-existing ICs. Fish were either allowed to recover for 3-5 days or immediately underwent a full bilateral gill denervation. After 3-5 days of recovery, the gills are harvested and fixed for immunohistochemistry. The tissue is then stained with an α-5 primary antibody (targets Na+/K+ ATPase containing cells) in conjunction with a secondary antibody that labels all (both new and pre-existing) ICs green. Using confocal imaging, it was demonstrated that pre-existing ICs appear yellow (labelled with both a viable mitochondrion-specific dye and α-5) and new ICs appear green (labelled with α-5 only). Both techniques used in tandem can be applied to study the innervation, proliferation and distribution of ICs on the gill filament when fish are exposed to environmental challenges.

Neurectomy of the deep branch of the lateral plantar nerve can cause neurogenic atrophy of the muscle fibres in the proximal part of the suspensory ligament (M. interosseous III).

Neurectomy of the deep branch of the right lateral plantar nerve was performed on a single healthy mature horse. Six weeks after surgery, the horse was subjected to euthanasia and both hind suspensory ligaments harvested. The cross sectional area of the muscular part of the proximal part of the suspensory ligament was measured and assessed for morphological abnormalities in a blinded fashion. There was a clear difference in cross sectional area of the muscular part between treated and control ligament and there was profound neurogenic atrophy of the muscular fibres in the treated ligament.

Ground reaction force analysis of unilateral coxofemoral denervation for the treatment of canine hip dysplasia.

Coxofemoral denervation has success rates of 90-96% reported retrospectively for palliative treatment of hip dysplasia. The aim of this study was to objectively evaluate ground reaction forces (GRF) in dysplastic dogs after unilateral denervation. Unilateral coxofemoral denervation was performed by means of a previously reported technique on 10 dogs with asymmetric gait. GRF were measured at zero, one and three months. Statistical analysis was performed using repeated measures analysis of variance and paired t-tests, with p< or =0.05. There was a lack of significant difference in mean peak vertical force (PVF) or vertical impulse (VI) in the operated limb (TX) over time. For the unoperated limb (UnTX), mean PVF and VI significantly decreased over time. The dogs were significantly more lame in the TX limb initially and at one month, however, there was no significant difference between limbs by three months. In the UnTX limb, 40% of dogs decreased PVF by >5%, by three months. Over time, there was no significant difference in mean average rise or mean average fall for TX or UnTX limbs. Between limbs, mean rise in the TX limb was significantly less at zero months, but not at one or three months. Decreased compensatory load shifting to the UnTX limb due to procedural efficacy could explain decreases in the UnTX limb. Worsening disease could also explain decreases in the UnTX limb, and may indicate a protective effect denoted by a lack of change in the TX limb. Longer follow-up would be required in improved dogs in order to document continued efficacy.

A quantitative analysis of the nerve fibres of the acetabular periosteum of dogs.

There are many techniques for the treatment of hip dysplasia, and novel research is currently being undertaken in the hope of obtaining more efficient and less traumatic techniques. The denervation of the hip joint capsule is a simple and effective technique that allows recovery of the functional activity of the affected limbs in significantly less time than other techniques. This surgical procedure consists of removing the acetabular periosteum, thus eliminating the nerve fibres with consequent analgesia. The aim of this investigation was to quantify the number of nerve fibres present in different regions of the acetabular periosteum. The knowledge of regional differences is potentially valuable for the refining of the denervation technique of the hip joint capsule. Thirty canine acetabular fragments were used to compare the nerve fibre density of the periosteum. The results showed a significant difference between the mean density of nerve fibres at the cranial and dorsal-lateral portion (approximately 75 fibres/mm2) and caudal lateral portion (approximately 60 fibres/mm2) of the acetabulum. Those fibres at the periosteum are almost positioned in a sagittal plane, pointing towards the joint capsule, suggesting the same density in the latter region. These results indicate a new approach to the articular denervation technique, thus obtaining even better results for the treatment of hip dysplasia in dogs.

Denervação acetabular cranial e dorsal no tratamento da displasia coxofemoral em cães: 360 dias de evolução de 97 casos / Cranial and dorsal acetabular denervation technique in treatment of hip dysplasia in dogs: 360 days evaluation of 97 cases

Realizou-se a pesquisa com o intuito de avaliar os resultados clínicos da denervação acetabular cranial e dorsal por curetagem em cães com displasia coxofemoral. Foram estudados, para tanto, 97 cães, sem predileção racial ou sexual, de 1-7 anos de idade, com diagnóstico clínico e radiográfico de displasia coxofemoral. Para avaliação dos resultados da técnica cirúrgica, de curetagem das fibras nervosas do periósteo acetabular cranial e dorsal, exames clínicos foram realizados no momento pré-operatório (exame inicial), e pós-operatório, nos dias dois, sete, 14, 21, 30, 60, 180 e 360. Todos os animais foram avaliados quanto à claudicação, dor à movimentação e toque, grau de atrofia muscular, sensibilidade dolorosa ao teste de Ortolani, e qualidade de vida. A denervação reduziu a claudicação, e dor à movimentação e toque à partir de dois dias de pós-operatório, reduziu atrofia muscular aos 60 dias pós-operatórios, e melhorou a qualidade de vida dos pacientes tratados, sob a ótica dos proprietários e veterinários aos 360 dias de pós-operatório. A dener-vação acetabular dorsal é técnica factível no tratamento da dor conseqüente à displasia coxofemoral em cães, com decréscimo significativo desta após dois dias da intervenção cirúrgica, aumenta qualidade de vida e proporciona maior atividade aos pacientes com proprietários satisfeitos quanto aos resultados do procedimento. A técnica cirúrgica deve incluir a curetagem das fibras nervosas do periósteo acetabular tanto da região cranial quanto dorsal.

The aim was to evaluate the clinical results of cranial and dorsal acetabular denervation using curettage in dysplastic dogs. Ninty seven dogs without distinction of breed and sex, 1 to 7 years of age, were analyzed for diagnosis and treatment of hip dysplasia, based on physical examination, clinical signs and radiographic findings. For evaluation of results of the surgical denervation technique, clinical examinations were performed preoperatively (initial exam) and postoperatively at days 2, 7, 14, 21, 30, 60 180 and 360. All animals were evaluated for lameness, pain to movement and touch, muscular atrophy degree, pain sensivity to Ortolani's test and assessment of life quality. The surgical denervation procedure decreases lameness, pain to movement and touch after 2 days of procedure, decreases muscular atrophy after 60 days of procedure, and improves quality of life from the owner's and veterinarian's point of view even after 1 year of the treatment. Dorsal acetabular denervation is a feasible surgical technique in treatment of pain secondary to hip dysplasia in dogs, with significant decrease of pain after 2 days of treatment, improvement of quality of life, decrease of lameness, and consequently joyful animals and owners extremely satisfied with the results obtained by the proposed treatment. The surgical technique must include the curettage of nerve fibers from the cranial-dorsal and dorsal region of the acetabular periosteum.

Surgical denervation of porcine ovaries during the middle luteal phase of the oestrous cycle changes their morphology and steroidogenic activity.

Changes in both the morphology and the steroidogenic activity of porcine ovaries denervated surgically on day 12 of the oestrous cycle were studied. Neurectomy of the plexus and the superior ovarian nerves caused a dramatic reduction in the number (or even a disappearance) of dopamine-beta-hydroxylase- and/or neuropeptide tyrosine-immunoreactive nerve terminals. On day 20 of the subsequent oestrous cycle, the number of small follicles increased (P < 0.01) and that of large follicles decreased (P < 0.05) in the denervated ovaries, as compared to the controls. Neurectomy led to a decrease in the level of progesterone (P4; P < 0.001) and androstenedione (A4; P < 0.01) in the fluid from small follicles, A4 (P < 0.001) and testosterone (T; P < 0.05) in the fluid from medium-sized follicles, as well as in the content of all these steroids in the fluid from large-sized follicles (P < 0.001 for P4 and P < 0.05 for A4 and T). Denervation also caused a decrease in the content of A4 (P < 0.01) and T (P < 0.001) in the wall of follicles. Neurectomy resulted in a significant increase in the immunoexpression of cholesterol side-chain cleavage cytochrome P450 in the follicles and a decrease of 33-hydroxysteroid dehydrogenase. After denervation, plasma levels of LH, P4, A4, T, oestrone and oestradiol-17beta were lower (P < 0.05-0.001) on the particular days of the study than in the control group. Our data revealed that the denervation of ovaries during the middle luteal phase of the oestrous cycle in gilts caused distinct changes in both the morphology and the steroidogenic activity of the organ, confirming an important role of the peripheral nervous system in the control of the gonad in this species.

Denervation of the porcine ovaries performed during the early luteal phase influenced morphology and function of the gonad.

We studied both morphology and steroidogenic activity of ovaries in gilts after bilateral surgical denervation performed on day 3 of the estrous cycle. Blood samples were collected from day 4 of the first estrous cycle to day 11 of the subsequent cycle. Denervation resulted in a dramatic reduction in the number or in the disappearance of tyrosine hydroxylase/dopamine-beta-hydroxylase- and/or neuropeptide Y-immunoreactive nerve fibres. On day 11 of the second cycle, the number of follicles (3-6 mm in diameter) was lower (p<0.001) in the denervated ovaries, while corpora lutea were not present. Neurectomy also led to a decrease in the concentrations of progesterone, androstendione and 17beta-estradiol in the follicular fluid originated from small (1-3 mm in diameter) as well as medium-sized follicles (3-6 mm in diameter). Similar to follicular fluid, concentration of androstendione in the follicular wall of medium-sized follicles decreased in experimental gilts in comparison to that of control animals. In addition, plasma concentrations of LH and steroid hormones were lower in the control than in the experimental group. Our results show that denervation of ovaries during the early luteal phase of the estrous cycle in gilts resulted in the changes in both morphology and steroidogenic activity. These results confirm the important role of the peripheral nerves in the function of ovaries.

[10 years experience with denervation of the hip joint capsule for treatment of canine hip joint dysplasia and arthrosis]. / 10 Jahre Erfahrung mit der Denervation der Hüftgelenkkapsel zur Therapie der Hüftgelenkdysplasie und -arthrose des Hundes.

Denervation of the canine hip joint capsule is described as a surgical therapy method in the treatment of canine hip joint dysplasia and arthrosis. The goal of this operation is a removal of the pain immediately and a reactivation of the dynamic active component of the hip joint in moving the body forward. Simple removal of the periosteum of the craniolateral acetabulum edge destroys the rami articulares of the cranial glutaeal nerve and the rami articulares dorsalis of the sciatic nerve. Within 10 years now we performed the denervation of the canine hip joint capsule. Evaluation of the post operative clinical course in 269 cases revealed an impressive improvement of lameness due to pain relief in almost 92% of the cases.

[Sensory innervation of the hip joint capsule in dogs]. / Die sensible Innervation der Capsula articularis coxae beim Hund.

The innervation of the canine hip joint has become increasingly important in the treatment of hip dysplasia and hip arthrosis, since investigations proved that simple removal of periosteum around attachment of hip joint capsule, called denervation results in an instant analgesia and allows the dog to regain joyful freedom of movement. A macroscopic-anatomic examination of 16 canine hips furnished new findings and knowledge in the field of veterinary medicine on the sensitive innervation of the canine hip joint capsule. Accordingly, the craniolateral area of hip joint capsule is innervated by rami articulares of N. glutaeus cranialis, the caudolateral area by rami articulares of N. ischiadicus and the medial area by rami articulares of N. femoralis.

Acute effects of perineural administration of sodium hyaluronate on palmar digital neurectomy sites in horses.

Biaxial palmar digital neurectomy of all limbs was performed on 6 mixed-breed castrated adult male horses, using a standard guillotine method. Using a Teflon catheter, 20 mg (2 ml) of sodium hyaluronate (group 1), 2 ml of phosphate-buffered saline solution (group 2), or catheter placement with no infusion (group 3) was applied to 4 (group 1) or 2 (groups 2 and 3) of 8 incisions/horse. Treatments were administered after closure of the neurectomy incision, and the catheter was removed. Horses were evaluated daily for 1 week, then weekly over a 9-week period for evidence of lameness, swelling, and ultrasonographic changes. On week 9, horses were euthanatized and neurectomy sites were removed en bloc for histologic evaluation of axonal regrowth, inflammation, and fibrosis. Neither lameness nor sign of painful neuroma was observed clinically in any of the horses. Neurectomy eliminated cutaneous heel sensation in all limbs for the duration of the study. Swelling was evident at all neurectomy sites. There were no significant differences between treatment sites for measurement of pastern circumference or ultrasonographic evaluation of incisional swelling. Foci of ultrasonographic hyperechogenicity increased over time, but there was no significant difference in hyperechogenicity between treatment groups. Histologic evidence of neuroma formation was observed at all sites. Morphometric assessment of neuroma cross-sectional areas revealed no significant difference between the groups, as did subjective histologic assessment of neuroma density and fibrous tissue content.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of intraneural doxorubicin in association with palmar digital neurectomy in 28 horses.

Painful neuroma formation after palmar digital neurectomy in the horse is common. Experimentally, injection of doxorubicin (Adriamycin) into the proximal transected nerve stump has been shown to prevent axon sprouting and neuroma formation for up to 5 months. This procedure was used in 28 horses with navicular disease, preexisting painful neuroma, or wing fractures of the distal phalanx. At 1 month, 16 horses had incisional complications. At 1 year, 15 horses were sound. Eight horses were lame, although three were improved. Three horses required a second surgical procedure, two of which became sound. Follow-up was not available in two horses. The technique used in this study has an unacceptable rate of wound complications and no benefit over other palmar digital neurectomy techniques currently in use.

Clinicopathological studies on neurectomy in equids.

Clinical and pathological changes following neurectomy were studied experimentally in 46 male and female equids. Sixty-three operations were performed using either the traditional or the Fackelman and Clodius methods of neurectomy. The effect of arteriovenous ligation was studied in 12 animals and 20 angiograms were performed post mortem to study the arterial pattern of the extremities of the operated limb. Neuroma formation (31 cases) and sloughing of the hoof (five cases) were the two main untoward sequelae. Neurectomy by the technique of Fackelman and Clodius proved superior to the traditional method. No essential changes were observed after ligation of the blood vessels, except in one case where collateral circulation was established.

Effects of denervation of the digit of the horse.

A study was conducted in an effort to explain why digital necrosis sometimes follows neurectomy in the horse. Six horses were subjected to unilateral section of the medial and lateral palmar nerves. Arteriography was done on each digit prior to surgery. Terminally, arteriography was repeated. Sections of bone, nerve, artery, skin, coronary band, and deep flexor tendon were examined histologically. Changes in arterial pattern and bone quality were noted. During the study, 2 of the horses had clinical signs of digital necrosis. The composite findings suggested trauma or infection, or both, of the denervated digit as the main cause(s) of the digital necrosis. Osteolysis was believed to be the primary contributing factor in disruption and collapse of the supporting structures of the foot.