Structural and biomechanical aspects of equine sacroiliac joint function and their relationship to clinical disease

Review of the clinical diagnosis of sacroiliac dysfunction in horses - Challenges and limitations

Sacroiliac dysfunction (SID) is a condition seen in horses associated with poor performance that affects hind limb gait and impulsion. The condition comprises pain and dysfunction but there lacks clarity around the aetiopathogenesis and whether SID encompasses abnormal joint pathology, abnormal joint movement, abnormal regional biomechanical function, joint laxity and pain, or various combinations of these that may vary over time. Clinical assessment remains challenging for equine clinicians due to the deep location of the sacroiliac joint (SIJ) and surrounding structures which limits access for palpation, diagnostic imaging and joint-specific injection. There is no recognised single reference standard diagnostic test for SID. Clinical diagnosis has been based on ruling out other causes of hind limb lameness, along with combinations of ultrasonography, scintigraphy and periarticular anaesthesia of the SIJ. Recent studies have highlighted the lack of specificity of injections targeting the SIJ, with significant dispersal of injectate into surrounding structures including around the lumbosacral joint (LSJ). Advanced imaging modalities such as computed tomography offers promise for assessment of the structure and pathology of the SIJ and surrounding bony structures. However, there is a need to improve the understanding of the significance of anatomic variation of the sacroiliac region structures, with recent studies reporting detailed anatomic variation in groups of horses with and without SID. There are also limitations around functional assessment of the joint which is still largely reliant on a thorough clinical examination. This review aims to present an update on clinical approaches to the diagnosis of horses with SID, and to consider the challenges and limitations.

Gross post-mortem and histological features in 27 horses with confirmed lumbosacral region pain and five control horses: A descriptive cadaveric study

BACKGROUND

There is a lack of understanding of the pathological and/or physiological nature of lumbosacral region pain.

OBJECTIVES

To describe the gross variations of the osseous and soft tissues of the lumbosacral region and report the histological findings of sections of nerve tissue in affected and control horses.

STUDY DESIGN

Descriptive post-mortem case series.

METHODS

All horses had undergone full clinical and gait assessment, including ridden exercise. Horses with a substantial response to infiltration of local anaesthetic solution around the sacroiliac joint regions were included in the affected group (n = 27). Horses for which the source(s) of pain was confirmed by diagnostic anaesthesia to be distant to the lumbosacral region were included in the control group (n = 5). The pelvic regions were isolated and the soft tissues were assessed grossly. Sections of the lumbosacral plexus and cranial gluteal, sciatic and obturator nerves were examined histologically. The osseous specimens were evaluated for anatomical variants and abnormalities. Data were analysed using descriptive statistics.

RESULTS

Gross discolouration of the sciatic or obturator nerves was observed in 7 (26%) affected and no control horses. Grade 3/3 histological abnormality scores were assigned in 22% of nerve sections from affected horses compared with 3% from control horses. Several osseous variants (bifid sacral spinous processes, straight-shaped sacroiliac joint surface, short arrow-shaped sacral alae, left-right asymmetry of sacral alae, sacral curvature, absence of the fourth to fifth and ankylosis of the fifth to sixth lumbar articular process joints, left-right asymmetry of caudocranial position of the fourth to fifth and lumbar-sacral articular process joints) and abnormalities (sacroiliac enthesopathy, extra ventral sacroiliac joint surface, lumbosacral symphyseal periarticular modelling, lumbosacral intertransverse joint pitting lesions) were more frequently observed in affected horses.

MAIN LIMITATIONS

Both control and affected horses may have had preclinical abnormalities.

CONCLUSIONS

Lumbosacral region pain may reflect the presence of a number of pathological changes. Neural pain may play an important role in some horses.

Retrospective analysis of horses with ultrasound evaluation of the sacroiliac region and response to local corticosteroid injection: 42 cases

Local injection of corticosteroids is commonly performed in horses with sacroiliac (SI) region pain and/or dysfunction, ,and ultrasound findings of normal horses and those with SI pain have also been well described. However, no studies have been performed that have evaluated if ultrasound findings, injection technique, or medications injected affect prognosis for return to function. The objectives of the current study are to determine if findings on ultrasound, injection technique, or medications injected are predictive of return to function in horses with SI region pain and/or dysfunction. Medical records were evaluated for horses that had ultrasound exam of the SI region as well as local injection with corticosteroids. A client survey was sent to determine the horse's return to performance. Logistic regression was performed to determine which variables were predictive of horses with SI pain and/or dysfunction returning to performance. A return to the same or higher level of work was found in 26 of 42 (62%) of horses after SI injections, 4 of 42 (10%) of horses returned to a lower level of work, and 12 of 42 (28%) did not return to work at any level. Horses that were injected with methylprednisolone were 4.2 times more likely to return to performance than horses injected with triamcinolone. Factors evaluated on ultrasound of the SI region did not predict whether a horse would return to performance following SI region injection.

Indicators of Horse Welfare: State-of-the-Art

Animal welfare is defined as a chronic state reflecting an individual's subjective perception of its situation. Because it is possible to be in a good welfare state and nevertheless experience acute fear or pain, and conversely, short-term positive emotions can be experienced during impaired welfare states, welfare as a chronic state has to be clearly distinguished from temporary states related to emotions, pain or stress. The evaluation of non-verbal individuals' welfare state, particularly in interspecific situations, is a real challenge that necessarily implies animal-based measures and requires multidisciplinary scientifically validated measures. In the last decade, studies investigating horses' welfare flourished together with new measures that were not always scientifically tested before being used. At a time were legal decisions are made on animal welfare, it is crucial to rely on reliable welfare indicators in order to prevent false evaluation. The aim of this review is to identify the scientifically tested and reliable indicators of horses' welfare (e.g., body lesions, apathy, aggressiveness, stereotypic behaviours) from signals of temporary states related to acute pain emotions or stress and from popular beliefs, in order to give the scientific community and the horse industry accurate evaluation tools.

Long-term prognosis for return to athletic function after interspinous ligament desmotomy for treatment of impinging and overriding dorsal spinous processes in horses: 71 cases (2012-2017)

OBJECTIVE

To determine the long-term return to performance of horses with impinging and/or overriding dorsal spinous processes (ORDSP) treated with interspinous ligament desmotomy (ISLD) and to determine the prognostic value of radiographic and scintigraphic grades.

STUDY DESIGN

Retrospective study.

ANIMALS

Seventy-one horses with ORDSP treated with ISLD.

METHODS

Medical records were reviewed for signalment, physical examination, gait evaluation, and number of interspinous spaces treated. Preoperative radiographic and scintigraphic images were evaluated with grading scales. Follow-up was obtained with a telephone questionnaire. Prognostic value of the number of affected interspinous spaces, radiographic grading, and scintigraphic grading was tested by using a χ² test.

RESULTS

A median follow-up of 35 months (range, 8-64) was available for 56 horses. Fifty-one of 56 (91.1%) horses returned to some level of performance, with 27 of 51 (52.9%) horses achieving equivalent or higher level of performance. Achieving a lower level of performance was attributed to recurrent back pain in nine of 24 (37.5%) horses and to unassociated lameness in nine of 24 (37.5%) horses. Owners of 44 of 56 (78.6%) horses were satisfied with the postoperative performance level, and owners of 46 of 56 (82.1%) horses would recommend the procedure. None of the variables tested influenced the return to performance.

CONCLUSION

Interspinous ligament desmotomy allowed horses with ORDSP to return to some level of performance, although fewer returned to an equivalent or higher level of performance than had previously been reported.

CLINICAL SIGNIFICANCE

Interspinous ligament desmotomy allows affected horses to return to some level of performance, regardless of the severity of radiographic and scintigraphic findings.

Comparison of two ultrasound-guided injection techniques targeting the sacroiliac joint region in equine cadavers

Objectives: To compare the accuracy and distribution of injectate for cranial (CR) and caudomedial (CM) ultrasound-guided injections of equine sacroiliac joints.

Methods: Both sacroiliac joints from 10 lumbo sacropelvic specimens were injected using cranial parasagittal (CR; curved 18 gauge, 25 cm spinal needles) and caudomedial (CM; straight 18 gauge, 15 cm spinal needles) ultrasound-guided approaches. Injectate consisted of 4 ml iodinated contrast and 2 ml methylene blue. Computed tomo-graphical (CT) scans were performed before and after injections. Time for needle guidance and repositioning attempts were recorded. The CT sequences were analysed for accuracy and distribution of contrast.

Results: Intra-articular contrast was detected in sacroiliac joints following 15/40 injections. The CR and CM approaches deposited injectate ≤ 2 cm from sacroiliac joint margins following 17/20 and 20/20 injections, respectively. Median distance of closest contrast to the sacroiliac joint was 0.4 cm (interquartile range [IQR]: 1.5 cm) for CR approaches and 0.6 cm (IQR: 0.95 cm) for CM approaches. Cranial injections resulted in injectate contacting lumbosacral intertrans-verse joints 15/20 times. Caudomedial injections were perivascular 16/20 times.

Limitations: Safety and efficacy could not be established.

Clinical relevance: Cranial and CM ultra-sound-guided injections targeting sacroiliac joints were very accurate for periarticular injection, but accuracy was poor for intra- articular injection. Injectate was frequently found in contact with interosseous sacroiliac ligaments, as well as neurovascular and synovial structures in close vicinity of sacroiliac joints.

Muscular and neuromotor control and learning in the athletic horse

Athletic performance or the kinematics of locomotion is ultimately the result of the actions of muscles. Muscular actions differ depending on the muscle group involved with anatomical and functional properties depending on the primary roles of the muscle; from stabilisation to powering locomotion. The functional (contractile and metabolic) properties of a muscle are determined by its fibre type or relative fibre type proportions in the muscle. The actions of muscle require the coordination of the nervous system with muscle contraction to produce movement or resist movement to avoid unwanted motion and tissue damage. The coordination of muscular action with the nervous system is termed neuromotor control and it requires precise proprioceptive input from the periphery, processing and input from the central nervous system (including learned or trained movements) and involves timing of muscle recruitment as well as muscle contraction. Training of muscles involves training for strength (or force generation) and stamina with measureable physiological changes with training including increased fibre size, alterations in fibre type, alterations in glycogen concentrations and lactate transport and alterations in mitochondrial and capillary density. As well as standard athletic training, skills training can make the difference in athletic performance and injury prevention in the equine athlete. This involves training of neuromotor control; training motor skills by motor relearning and conditional learning. Practical specific training techniques can be used in injury prevention, rehabilitation post injury and maintenance of the athlete. In this review we will focus on the thoracolumbar and hindlimb areas of the horse and review the importance of muscular control of locomotion, neuromotor control, the physiological effects of training and practical ways to maximise performance potential by specific physiotherapy skills training.

Introduction to Equine Physical Therapy and Rehabilitation

Physical therapy (physiotherapy, or PT) can be broadly defined as the restoration of movement and function and includes assessment, treatment, and rehabilitation. This review outlines the history, definition, and regulation of PT, followed by the core scientific principles of PT. Because musculoskeletal physiotherapy is the predominant subdiscipline in equine PT, encompassing poor performance, back pain syndromes, other musculoskeletal disorders, and some neuromuscular disorders, the sciences of functional biomechanics, neuromotor control, and the sensorimotor system in the spine, pelvis, and peripheral joints are reviewed. Equine PT also may involve PT assessment and treatment of riders.

Hindlimb response to tactile stimulation of the pastern and coronet

REASONS FOR PERFORMING STUDY

Lightweight tactile stimulators attached to the hind pasterns increase the height of the hind hoof flight arc but details of the induced changes in swing phase kinematics and kinetics have not been investigated.

HYPOTHESES

Stimulators on the hind pasterns are associated with increased hindlimb joint flexions and increased positive work performed by the hip and tarsal musculature.

MATERIALS AND METHODS

Nine nonlame horses trotted 4 times with and without 55 g tactile stimulators loosely attached around the hind pasterns. Height of the flight arc and peak flexion angles of the hindlimb joints were measured and net positive and negative work performed across each joint during the swing phase were calculated using inverse dynamics analysis and compared across paired conditions.

RESULTS

Speed and stride duration did not change but stimulators were associated with a reduction in hind stance duration. The flight arc was higher with stimulators due to increased flexions of the stifle, tarsal, metatarsophalangeal and distal interphalangeal joints. Positive work increased in the tarsal musculature, but not in the hip musculature, and negative work increased across the stifle, metatarsophalangeal and distal interphalangeal joints.

POTENTIAL RELEVANCE

The effects of tactile stimulation of the hind pasterns on joint motion and muscle activation may be used in physiotherapy and rehabilitation to restore or increase flexion of the hindlimb joints with the exception of the hip joint. The ability to stimulate concentric activity of the tarsal musculature may have therapeutic applications in conditions such as toe dragging.