The sacroiliac joints: evaluation using nuclear scintigraphy. Part 2: Lame horses

REASONS FOR PERFORMING STUDY: Sacroiliac (SI) joint disease is difficult to diagnose definitively on clinical grounds. HYPOTHESES: Lameness not attributable to SI joint pain may result in asymmetrical uptake of radiopharmaceutical in the tubera sacrale and SI joints; and that horses with clinical signs suggestive of sacroiliac joint disease would have differences in the ratios of radiopharmaceutical uptake between the fifth lumbar vertebra (L5) and either the tubera sacrale or SI joints compared with normal horses. OBJECTIVES: To determine whether differences in radiopharmaceutical activity could identify individuals with presumed SI joint region pain. METHODS: The scintigraphic appearance of the pelvic region of 234 horses (Group I) with lameness unrelated to the SI joints was compared with that for 40 normal horses (Group N) in full work and that for 41 horses with suspected SI joint disease (Group II). The effect of age, sex, lame limb and discipline were assessed in Group I. Motion-corrected scintigraphic images were assessed grossly, using profile analysis and by comparing ratios of uptake of mean count per pixel between L5 and each of the left (L) tuber sacrale (TS), right (R) TS, LSI and RSI joints. Left-right symmetry was compared. RESULTS: Lame horses (Group I) had greater asymmetry of radiopharmaceutical uptake in the tubera sacrale compared with normal horses. Horses with right hindlimb lameness had a larger RSI/LSI ratio compared to normal horses. In Group I L5/LTS, L5/RTS and L5/RSI increased with age, and there was a trend for L5/LSI to increase with age. In horses with presumed sacroiliac joint disease (Group II), L5/LTS, L5/RTS and L5/RSI were all greater compared with normal horses. Detection of marked left-right asymmetry by quantitative analysis or profile analysis was helpful in discriminating between those horses with clinical signs compatible with SI joint disease and either normal horses or those lame due to another cause. CONCLUSIONS AND POTENTIAL RELEVANCE: Scintigraphic evaluation of the SI region is useful to identify SI joint disease in combination with other clinical signs supportive of the diagnosis. However, diagnosis should not be based on this alone because of some degree of overlap in the range of radiopharmaceutical uptake between horses with SI joint disease and both normal horses and those with other causes of lameness.     

Clinical features and diagnosis of sacroiliac joint region pain in 296 horses: 2004–2014

There has been no large‐scale study of the clinical signs of sacroiliac (SI) joint region pain and its association with lameness and/or thoracolumbar pain. Horses with a positive response to infiltration of local anaesthetic solution around the SI joint regions (SI block) and/or abnormal radiopharmaceutical uptake (RU) in the region of the SI joints were included. History, clinical signs, diagnostic imaging findings, response to SI block, and concurrent lameness and/or thoracolumbar pain were recorded. Horses (n = 296) were divided into 2 groups: SI joint region pain only (Group 1, n = 43) and SI joint region pain and concurrent source(s) of pain (Group 2, n = 253). Clinical signs in Group 1 included increased tension in the longissimus dorsi muscles (40%), restricted flexibility of the thoracolumbar region (44%), trunk stiffness during exercise (61%) and poor hindlimb impulsion (56%). When ridden 65% had a poor contact with the bit, in 81% canter quality was worse than trot, and 35% bucked or kicked out with a hindlimb during canter. In both Groups 1 and 2 clinical signs were seen in a significantly greater proportion of horses during ridden work than lungeing (P<0.0001). Following SI block, 98% of horses showed dramatic improvement in clinical signs, including greater overall movement through the trunk, increased hindlimb impulsion and better quality canter. Abnormal RU in the SI joint regions was seen in 85/180 (47%) horses. Of horses with a positive response to SI block that underwent scintigraphy, only 43% had abnormal RU. Per rectum ultrasonographic examination of the SI joint region revealed abnormalities in 41/129 (32%) horses. Clinical signs of SI joint region pain are worse when horses are ridden. Sacroiliac joint region diagnostic analgesia is a useful, safe but nonspecific block. Ultrasonography and scintigraphy can provide additional information in some horses, but negative results do not preclude SI joint region pain.     

The sacroiliac joints: evaluation using nuclear scintigraphy. Part 1: The normal horse

REASONS FOR PERFORMING STUDY: Sacroiliac (SI) disease is recognised as a cause of poor hindlimb action but differential diagnosis is often difficult. HYPOTHESES: That in clinically normal horses there would be a significant difference in the ratio of radiopharmaceutical uptake (RU) between the fifth lumbar vertebra (L5) and each tuber sacrale (TS) and between L5 and each SI joint; and that these ratios would alter with age, but ratios would be bilaterally symmetrical. METHODS: Dorsal scintigraphic images of the SI region of 15 horses, selected randomly from the clinic database, were analysed by 2 of the authors, comparing noncorrected and motion-corrected images. To determine scintigraphic anatomy, the scintigraphic images of 10 Thoroughbred horses were superimposed over a ventrodorsal radiographic image of an isolated pelvis. Dorsal scintigraphic images of 40 clinically normal horses age 3-16 years were evaluated using subjective examination, profile analysis and quantification using regions of interest. RESULTS: The tubera sacrale were seen as 2 well-defined oval regions immediately to the left and right of the midline, abaxial to which were larger, approximately oval areas with less RU, representing uptake in the SI joints. The definition between the SI region and the TS was more obvious in younger horses. Nonmotion-corrected images were often not of diagnostic quality or could be misinterpreted as abnormal. There were significant differences in RU between the TS and SI joints compared to L5, and decreased RU in the tubera sacrale with increasing age, but no change of uptake in the SI joint region and no effect of gender on RU. There was a high degree of left-right symmetry of the TS and SI joint regions. CONCLUSIONS AND POTENTIAL RELEVANCE: The scintigraphic images of horses with suspected sacroiliac joint disease should be compared with images of normal horses of comparable age. In normal horses, there was a high degree of symmetry; therefore, marked left-right asymmetry is likely to be abnormal.     

Crooked tail carriage in horses: Increased prevalence in lame horses and those with thoracolumbar epaxial muscle tension or sacroiliac joint region pain

The relationship between lameness and crooked tail carriage (CTC) in horses is unclear. The objectives of this study were (i) to determine the association between CTC and lameness; (ii) among lame horses, to determine associations between CTC and lameness diagnosis, saddle slip, thoracolumbar range of motion (ROM), epaxial muscle tension and pain, and sacroiliac joint region (SIJR) pain, and (iii) to determine whether abolition of lameness and SIJR pain by diagnostic anaesthesia modified CTC. In this study, 520 lame and 170 nonlame sports horses were examined for CTC and other characteristics by one clinician (S.J.D.). All horses were evaluated when ridden. Lame horses were also assessed in hand and on the lunge. Crooked tail carriage, its direction, lameness, musculoskeletal and tack-related parameters were recorded as binary variables and analysed using 2 × 2 contingency tables. Sacroiliac joint region pain was diagnosed using local anaesthesia. Standard errors are shown in square brackets. 32.5% of lame horses had CTC, compared with 5.3% of nonlame horses (odds ratio = 8.6 [confidence intervals 4.4, 16.7]; P = 2×10⁻¹²). Of 169 lame horses with CTC, 103 (60.9% [3.8%]) held their tail to the left. There was no association between the side of the predominant lame limb and CTC direction. However, CTC was more common (P = 0.005) in horses with hindlimb lameness (35.7% [2.4%], N = 401) compared with forelimb lameness (21.0% [4.1%], N = 100). Crooked tail carriage was associated with SIJR pain (P = 0.0007) and thoracolumbar epaxial muscle tension (P = 0.0007), but not with saddle slip, reduced thoracolumbar ROM or thoracolumbar epaxial muscle pain. Limitations of the study included the facts that nonlame horses were a convenience sample and lameness assessment, other clinical observations and determination of the presence of CTC were subjective, with potential for bias. Video recordings and photographs are available for verification of tail position. It was concluded that CTC is more prevalent in lame horses than nonlame horses. There is a positive association between CTC and hindlimb lameness, SIJR pain and thoracolumbar epaxial muscle tension.     

SCINTIGRAPHIC AND RADIOGRAPHIC APPEARANCE OF THE SACROILIAC REGION IN HORSES WITH GAIT ABNORMALITIES OR POOR PERFORMANCE

Nuclear bone scintigraphy is commonly used in the diagnosis of sacroiliac disease in horses. The aim of the present retrospective study was to determine if there was an association between radiopharmaceutical uptake pattern and radiographic appearance of the sacroiliac region in horses. Seventy-nine horses undergoing bone scintigraphy with Tc-99 m-HDP and radiography of the pelvis because of lameness or poor performance were studied. Subjective and semiquantitative methods were used to characterize and compare radiopharmaceutical uptake between horses. Ventrodorsal radiographs of the region were obtained and were evaluated. Subjectively, 70 horses (88.6%) had an abnormal uptake pattern. In nine horses, the sacroiliac region was normal (11.4%). There was no association between subjective evaluation of the scintigraphic images and semiquantitative methods. There was a significant association between radiopharmaceutical uptake and conformation (T- or Y-like form) and shape (butterfly-, wing-, leaf-, or horn-like) of the sacrum. The radiopharmaceutical uptake of the tubera sacralia was significantly higher in males (left side P =0.002, right side P =0.003). In conclusion, the conformation of the sacrum may play an important role in the scintigraphic appearance and may be the cause of increased radiopharmaceutical uptake.     

Development and validation of a periarticular injection technique of the sacroiliac joint in horses

REASONS FOR PERFORMING STUDY: Sacroiliac joint osteoarthritis has been recognised as a significant cause of poor performance in competition and racehorses. Reliable diagnostic tools are currently lacking. The diagnosis has been based typically on exclusion of other possible causes of poor performance, back pain and hindlimb lameness. OBJECTIVES: To develop a safe, reliable and minimally invasive periarticular or intra-articular injection technique of potential use for diagnosis and therapy of sacroiliac joint disease in horses. METHODS: Twenty-six horses were used to develop and assess a medial approach to the sacroiliac joint with a 15 gauge, 25 cm long spinal needle. In Part I, the cadaveric study, the spinal needle was introduced cranial to the contralateral tuber sacrale and advanced along the medial aspect of the ipsilateral iliac wing until the dorsal surface of the sacrum was encountered. One ml methylene blue (MB) was injected in both sacroiliac joint regions of the sacropelvic specimens. The location of MB-stained tissues relative to the sacroiliac joints was recorded after dissection and disarticulation of the sacroiliac joint. In Part II, the in vivo study, 18 horses were used to validate the in vivo application of the sacroiliac joint injection technique. Horses were restrained in stocks and sedated in preparation for needle placement. One ml MB was injected bilaterally prior to euthanasia. Stained tissues were identified and recorded at necropsy. Successful joint injections were characterised as having MB located intra-articularly or < or = 2 cm periarticularly from the sacroiliac joint margin and localised to the middle or caudal third of the sacroiliac joint. RESULTS: Intra-articular MB was not observed in any specimen. However, MB-stained tissue was identified periarticularly in all injection sites (n = 48). Based on the predetermined success criteria, 96% of the methylene blue depots were located at the middle or caudal third of the sacroiliac joint. Dye-stained tissue was located < or = 2 cm from the sacroiliac joint margins in 88% of the specimens. Median distance of the MB from the sacroiliac joint margins was 1.0 cm (range 0.2-3.8 cm). The overall success rate considering both location and distance of the MB-stained tissue relative to sacroiliac joint margins was 83% (40 of 48 joints). CONCLUSIONS: The injection technique provides a reliable, easy to perform and consistent access to the medial periarticular aspect of the sacroiliac joint. POTENTIAL RELEVANCE: The described injection technique has the potential for both diagnostic and therapeutic applications in the medical management of equine sacroiliac joint disease. Further investigation is necessary to evaluate clinical efficacy and potential adverse effects.     

The effects of local anaesthetic solution in the navicular bursa of horses with lameness caused by distal interphalangeal joint pain

REASONS FOR PERFORMING STUDY: Analgesia of the palmar digital (PD) nerves has been demonstrated to cause analgesia of the distal interphalangeal (DIP) joint as well as the sole. Because the PD nerves lie in close proximity to the navicular bursa, we suspected that that analgesia of the navicular bursa would anaesthetise the PD nerves, which would result in analgesia of the DIP joint. OBJECTIVES: To determine the response of horses with pain in the DIP joint to instillation of local anaesthetic solution into the navicular bursa. METHODS: Lameness was induced in 6 horses by creating painful synovitis in the DIP joint of one forefoot by administering endotoxin into the joint. Horses were videorecorded while trotting, before and after induction of lameness, at three 10 min intervals after instilling 3.5 ml local anaesthetic solution into the navicular bursa and, finally, after instilling 6 ml solution into the DIP joint. Lameness scores were assigned by grading the videorecorded gaits subjectively. RESULTS: At the 10 and -20 min observations, median lameness scores were not significantly different from those before administration of local anaesthetic solution into the navicular bursa (P > or = 0.05), although lameness scores of 3 of 6 horses improved during this period, and the 20 min observation scores tended toward significance (P = 0.07). At the 30 min observation, and after analgesia of the DIP joint, median lameness scores were significantly improved (P < or = 0.05). CONCLUSIONS: These results indicate that pain arising from the DIP joint can probably be excluded as a cause of lameness, when lameness is attenuated within 10 mins by analgesia of the navicular bursa. POTENTIAL RELEVANCE: Pain arising from the DIP joint cannot be excluded as a cause of lameness when lameness is attenuated after 20 mins after analgesia of the navicular bursa.     

Clinical significance of osseous spurs on the dorsoproximal aspect of the third metatarsal bone

Reasons for performing study: Osseous spurs on the dorsoproximal aspect of the third metatarsal bone (MtIII) are common, but their clinical significance is unknown. Objectives: To verify the sites of insertion of the dorsal metatarsal ligament and the tendons of tibialis cranialis and fibularis tertius in order to determine if periarticular osteophytes and entheseophytes could be differentiated radiologically; and to determine the frequency of occurrence of osseous spurs on the dorsoproximal aspect of MtIII. Hypotheses: The frequency of osseous spurs on the dorsoproximal aspect of MtIII would be higher in lame than in clinically normal horses and higher in horses with distal hock joint pain or proximal suspensory desmitis than in horses with other causes of hindlimb lameness. Methods: A retrospective study of data from the clinical work up and tarsal radiographs of 455 horses was performed. Horses were divided into: Group 1, clinically normal horses; Groups 2–5, according to the diagnosis of hindlimb lameness. Radiographs were examined for the presence of an osseous spur on the dorsoproximal aspect of MtIII; pathology of the distal tarsal joints was graded. The associations between the presence of a spur and lameness, diagnosis group and the grade of distal tarsal joint abnormalities were analysed statistically using Chi‐squared tests. Results: An osseous spur was present in 25% of horses; 13% of horses with bilateral radiographs had bilateral spurs. There was no significant difference in frequency of the presence of a spur between lame and nonlame horses, or between horses with other causes of hindlimb lameness and horses with proximal suspensory desmitis and/or distal tarsal joint pain. The presence of an osseous spur was significantly associated with the grade of radiological abnormality in the distal tarsal joints (tarsometatarsal joint P = 0.018: centrodistal joint P = 0.027). In many horses it was not possible to differentiate accurately between osteophytes and entheseophytes. Conclusions and potential relevance: The presence of an osseous spur on the dorsoproximal aspect of MtIII in the absence of other radiological abnormalities may be an incidental finding. Osseous spurs occur more frequently in hocks with radiological abnormalities in the distal tarsal joints and may be an indicator of distal tarsal joint osteoarthritis. The clinical significance must be established by intra‐articular analgesia.     

Subjective and quantitative scintigraphic assessment of the equine foot and its relationship with foot pain

It was hypothesised that in solar bone images of the front feet of clinically normal horses, or horses with lameness unrelated to the front feet, there would be less than a 10% difference in the ratio of uptake of radiopharmaceutical in either the region of the navicular bone, or the region of insertion of the deep digital flexor tendon (DDFT), compared to the peripheral regions of the distal phalanx. Nuclear scintigraphic examination of the front feet of 15 Grand Prix show jumping horses, all of which were free from detectable lameness, was performed using dorsal, lateral and solar images. The results were compared with the examinations of 53 horses with primary foot pain, 21 with foot pain accompanying another more severe cause of lameness and 49 with lameness or poor performance unrelated to foot pain. None of the horses with foot pain had radiological changes compatible with navicular disease. All the images were evaluated subjectively. The solar views were assessed quantitatively using regions of interest around the navicular bone, the region of insertion of the deep digital flexor tendon and the toe, medial and lateral aspects of the distal phalanx. In 97% of the feet of normal showjumpers, there was <10% variance of uptake of the radiopharmaceutical in the navicular bone, the region of insertion of the DDFT and the peripheral regions of the distal phalanx. There was a significant difference in uptake of radiopharmaceutical in the region of the navicular bone in horses with foot pain compared to normal horses. There was a large incidence of false positive results related to the region of insertion of the DDFT. Lateral pool phase images appeared more sensitive in identifying potentially important DDFT lesions. There was a good correlation between a positive response to intra-articular analgesia of the distal interphalangeal joint and intrathecal analgesia of the navicular bursa and increased uptake of radiopharmaceutical in the region of the navicular bone in the horses with primary foot pain. It is concluded that quantitative scintigraphic assessment of bone phase images of the foot, in combination with local analgesic techniques, can be helpful in the identification of the potential source of pain causing lameness related to the foot, but false positive results can occur, especially in horses with low heel conformation.     

Ultrasonographic examination of the equine sacroiliac region

REASONS FOR PERFORMING STUDY: Little information exists about the normal ultrasonographic appearance of the equine sacroiliac region, but knowledge of the ultrasonographic anatomy is necessary to understand the possible pathological changes in sacroiliac diseases. OBJECTIVES: The normal ultrasonographic appearance of soft tissues and bony structures of the sacroiliac region in horses was studied in order to establish clinically relevant reference parameters. METHODS: Thirteen cadaver specimens were examined using a transcutaneous approach above the tubera sacrale to image the dorsal sacroiliac ligament and the tendon of the longissimus dorsi muscle. A rectal approach was used to outline the sacroiliac joint and its adjacent structures. Thirteen sound horses with no history of back pain were examined following the same protocol as for the post mortem examinations. RESULTS: The tendon of the longissimus dorsi muscle can clearly be distinguished from the dorsal sacroiliac ligament, especially in longitudinal images. Transrectal examination of the sacroiliac joint consists of evaluation of the bony surfaces of the sacrum and ilium in comparison with the contralateral side. CONCLUSIONS: Ultrasonographic examination of the sacroiliac region provided clear images of the caudomedial border of the sacroiliac joint and its adjacent structures and is a useful aid in the diagnosis of sacroiliac joint diseases and adjacent lesions. The study has shown ultrasonography to be a useful method for examining and differentiating the longissimus dorsi muscle and the dorsal sacroiliac ligament at the level of the tubera sacrale. POTENTIAL RELEVANCE: Diagnostic ultrasound is available to most practitioners. These reference ultrasound parameters may help to improve the diagnosis of sacroiliac diseases.     

Effects of analgesia of the distal interphalangeal joint and navicular bursa on experimental lameness caused by solar pain in horses

It has been hypothesized that pain originating from the dorsal margin of the sole of the hoof in horses can be attenuated by analgesia of either the distal interphalangeal (DIP) joint, or of the navicular bursa (NB). To test this hypothesis, an experimental lameness was induced in the toe region of the left forelimb in six adult horses. After this, both synovial structures were blocked and the effects on the lameness were semi-quantitatively scored. Lameness was induced by creating pressure on the dorsal margin of the sole with the help of set-screws that were screwed into a nut, welded to the inside of each branch of the shoe. Gaits were recorded on a videotape before and after application of the screws, and after application of either a local anaesthetic or saline into the DIP joint or NB. The gaits were independently evaluated by two blinded clinicians and scored. Lameness scores were high after application of the screws and remained high after the administration of saline, but decreased significantly (P < 0.05) after administration of the local anaesthetic. Analgesia of the DIP joint as well as the NB appeared to be able to desensitize a portion of the sole. It was concluded that pain arising from the toe region of the sole should not be excluded as a cause of lameness when lameness is attenuated by analgesia of the DIP joint, or of the NB.     

Ultrasonographic abnormalities detected in the sacroiliac area in twenty cases of upper hindlimb lameness

REASONS FOR PERFORMING STUDY: The pelvis is covered with extensive musculature and often presents a challenge in diagnostic imaging. Ultrasonography provides diagnostic information about soft tissue, articular cartilage and bone surfaces, although little information exists about the normal ultrasonographic appearance of the equine sacroiliac region. OBJECTIVES: To determine the clinical applicability of ultrasonographic examination in horses with sacroiliac pain. METHODS: Horses presented to the University of Minnesota Veterinary Teaching Hospital for hindlimb lameness were evaluated and lower limb lameness was ruled out with examination and local anaesthesia. Twenty cases were diagnosed with sacroiliac pain, characterised by response to palpation over the tuber sacrale. Seven of the 20 had visible asymmetry of the tuber sacrale. Ultrasonography was performed percutaneously and per rectum. Structures imaged were measured and compared to normal reference measurements. Other methods used to confirm diagnoses included thermography, scintigraphy and radiology. RESULTS: All 20 cases with sacroiliac pain showed ultrasonographic abnormalities of the sacroiliac area. Abnormalities were detected in the dorsal sacroiliac ligaments. Ligament size was significantly different from the normal ranges (P < 0.01). Malalignment of the sacroiliac area and sacral fractures were also imaged. CONCLUSIONS: Ultrasonography of the sacroiliac region aided diagnosis of ligament damage and displacement of bone surfaces; and may aid in monitoring the progression of healing. Potential relevance: Diagnostic ultrasound is readily available to most practitioners. Therefore the findings of this study show that diagnosis of sacroiliac injuries is possible in the field.     

Review of injection techniques targeting the sacroiliac region in horses

Local anaesthetic techniques and diagnostic imaging tools are currently used in conjunction with thorough physical and lameness examinations to diagnose sacroiliac disease (SID) in the horse. The deep and inaccessible location of the sacroiliac joint (SIJ), however, often renders diagnostic imaging modalities, such as radiography, nuclear scintigraphy and ultrasonography, unreliable in identifying sacroiliac problems. The equine clinician therefore often has to rely on positive results of local anaesthetic techniques to confirm a diagnosis of SID. Regional infiltration techniques have been described but result in a diffuse distribution of large volumes of local anaesthetic solution throughout the entire lumbosacroiliac region, which is nonspecific to the SIJ and has the potential to produce false positive results. Several periarticular injection approaches to the SIJ have recently been described. A combination of periarticular SIJ injections with the use of modest amounts of local anaesthetic solution provides increased SIJ specificity, but may lead to false negative results in cases where the pain originates from surrounding soft tissues. This article clarifies terminology related to sacroiliac injections, reviews current injection techniques, highlights the advantages and disadvantages of each approach, and investigates injectate volume considerations.     

SCINTIGRAPHY OF THE SACROILIAC JOINT REGION IN ASYMPTOMATIC RIDING HORSES: SCINTIGRAPHIC APPEARANCE AND EVALUATION OF METHOD

The sacroiliac region in 33 clinically normal riding horses was examined with scintigraphy to determine the normal scintigraphic appearance, to evaluate a semiquantitative method used to calculate a sacroiliac joint (SI joint) ratio, and to identify factors that affect the scintigraphic appearance of the pelvis. The scintigraphic examination included dorsal views of each SI joint region and one lateral view of the urinary bladder. Two predefined areas (the SI joint and the area between the tuber sacrale and the SI joint) were evaluated subjectively by comparing the intensity in each area to the intensity in the tuber sacrale, and a semiquantitative method was applied on the images to calculate an SI joint ratio. The thickness of the muscle mass overlying each SI joint was measured by using ultrasound. A corrected ratio was calculated based on a corrected pixel count for each SI joint. Of 29 evaluated horses, 28 had normal radiotracer uptake in the SI joints and 10 horses had symmetric normal radiotracer uptake in the area between the tuber sacrale and the SI joint. The mean SI joint ratio was 0.53 on both the left and right sides, and the mean corrected SI joint ratio was 2.15 on the left side and 2.13 on the right side. Factors that affect the scintigraphic appearance of the pelvis were identified and included attenuation, radioactive urine, and muscle symmetry. The muscle thickness ranged from 8-11 cm, causing 71-82% attenuation. Radioactive urine in the urinary bladder was located ventral to the SI joint region in 16 horses, and four of these were excluded from further evaluation because of risk of misinterpretation. A visual assessment of symmetry of the horses' gluteal muscle mass was compared with the ultrasound measurements. Fourteen horses (14/33) were regarded symmetric by both techniques. Soft tissue attenuation was found to severely compromise the result and indicated that only lesions in the SI joint with severely increased radiotracer uptake can be detected with scintigraphy. Knowledge about presence of radioactive urine ventral to the SI joint region and assessment of muscle symmetry is essential for a correct subjective evaluation. Any situation with difference in muscle mass between the left and right side of the pelvis will give a false impression of increased radiotracer uptake on the side with lesser muscle mass.     

ULTRASONOGRAPHIC TECHNIQUE AND NORMAL ANATOMIC FEATURES OF THE SACROILIAC REGION IN HORSES

The purpose of this study was to establish the normal percutaneous ultrasonographic appearance of anatomic structures within the equine sacroiliac region. Percutaneous ultrasonography was performed in a cranial-to-caudal direction in 10 normal adult live horses. The following structures were examined in detail: supraspinous ligament, lumbar and sacral spinous processes, thoracolumbar fascia and its caudal extension, tubera sacralia, ilial wings, dorsal and lateral portions of the dorsal sacroiliac ligaments, lateral part of the sacrum, and the lateral sacral crest. After ultrasonography, all animals were euthanized and detailed dissection of the lumbosacropelvic region was performed in six horses. Four lumbosacropelvic specimens were frozen and sectioned transversely for evaluation of cross-sectional anatomy. Gross anatomic findings were correlated with ante-mortem ultrasonographic images. On percutaneous ultrasonography, all horses had tubera sacralia with a mild-to-moderate roughened surface with occasional irregular hyperechoic mineralizations located within the apophyseal cartilage of younger horses. At the level of the tuber sacrale the caudal extension of the thoracolumbar fascia joined the dorsal portion of the dorsal sacroiliac ligament and assumed two different configurations relative to the dorsal portion of the dorsal sacroiliac ligament, with the predominant configuration of the thoracolumbar fascia located medial to the dorsal portion of the dorsal sacroiliac ligament. The less frequently encountered configuration had the thoracolumbar fascia positioned dorsal to the dorsal portion of the dorsal sacroiliac ligament. Caudal to the tuber sacrale the dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia consolidated to form a single, fused structure with a common insertion on the sacral spinous processes. A large variability in linear fiber pattern, echogenicity (small focal hypoechoic areas), ligament height, and cross-sectional measurements was identified in the fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia of normal horses. Diagnosing mild-to-moderate desmitis of the fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia based solely on ultrasonography may therefore be difficult. To correlate ultrasonography with histology, samples of a fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia with bilateral hypoechoic lesions were submitted for histology and revealed diffuse mild-to-moderate loss of fiber density, multifocal fibrocyte degeneration, and cartilagenous metaplasia with multifocal, mild myofiber mineralization, which was compatible with age-related changes. As controls, sections of ultrasonographically normal fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia from three horses demonstrated similar but milder histologic findings, which were considered normal.     

Osteoarthritis of the talocalcaneal joint in 18 horses

REASONS FOR PERFORMING STUDY: Talocalcaneal osteoarthritis (TO) is an uncommon cause of moderate to severe hindlimb lameness, on which only isolated case reports have been published to date. OBJECTIVES: To review the clinical features of TO and determine optimal methods for diagnosis, management and prognosis. METHODS: The case records from 4 referral centres of 18 horses showing hindlimb lameness considered, as a result of clinical investigation, to be caused by TO, were reviewed. RESULTS: TO affected mature sports and pleasure horses (age 7-16 years) and caused moderate to severe lameness, usually of sudden onset with no obvious inciting cause. There were few localising signs, other than worsening of lameness by hock flexion. Tarsocrural joint analgesia produced improvement in lameness in 6/11 horses (55%) and perineural analgesia of the tibial and fibular nerves complete soundness in 6/14 horses (43%) in which it was performed; 7/14 horses (50%) showed a further substantial improvement. Radiological findings included subchondral bone lysis and sclerosis and irregular joint space width, seen most obviously in a lateromedial view. Nuclear scintigraphy revealed marked uptake of radiopharmaceutical predominantly plantaromedially in the region of the talus in the 7 horses in which it was performed. Fourteen horses were treated conservatively with box- or pasture-rest, with or without intra-articular corticosteroids, hyaluronic acid or polysulphated glycosaminoglycan, and all remained lame. Intra-articular corticosteroids appeared to have no effect in any horse. Of 10 horses receiving conservative management only, 6 were subjected to euthanasia, 3 were retired and 1 remained in light work, but was still lame. Two horses treated by either partial tibial and fibular neurectomy or subchondral forage failed to regain soundness and were retired. Six horses were treated by surgical arthrodesis of the talocalcaneal joint with 2 or three 5.5 mm AO screws introduced obliquely across the joint from the plantarolateral aspect of the calcaneus, which resulted in improvement in lameness in all cases. CONCLUSIONS: Osteoarthritis of the talocalcaneal joint causes acute onset severe lameness, but clinical findings and diagnostic analgesia often fail to identify precisely the site of pain. Consistent radiographic changes suggested TO was contributing to the lameness and this diagnosis was supported by nuclear scintigraphy. The poor success of conservative treatment (including intra-articular medication) suggests that surgical arthrodesis is the treatment of choice, although the prognosis is still poor for a return to full soundness. POTENTIAL RELEVANCE: The clinical features described should facilitate more accurate diagnosis and prognosis. A novel surgical treatment is described which appears to offer significant improvement in the lameness. Further work is necessary to determine the causes of this condition and more effective management.     

Kinematics of the hind limb in trotting horses after induced lameness of the distal intertarsal and tarsometatarsal joints and intra-articular administration of anesthetic

OBJECTIVE: To identify hind limb and pelvic kinematic variables that change in trotting horses after induced lameness of the distal intertarsal and tarsometatarsal joints and after subsequent intra-articular administration of anesthetic. ANIMALS: 8 clinically normal adult horses. PROCEDURE: Kinematic measurements were made before and after transient endotoxin-induced lameness of the distal intertarsal and tarsometatarsal joints and after intra-articular administration of anesthetic. Fourteen displacement and joint angle (metatarsophalangeal [fetlock] and tarsal joints) measurements were made on the right hind limb, sacrum, and the right and left tubera coxae. Kinematic measurements were compared by general linear models, using a repeated measures ANOVA. Post hoc multiple comparisons between treatments were evaluated with a Fisher least squared difference test at alpha = 0.05. RESULTS: After lameness induction, fetlock and tarsal joint extension during stance decreased, fetlock joint flexion and hoof height during swing increased, limb protraction decreased, and vertical excursion of the tubera coxae became more asymmetric. After intra-articular administration of anesthetic, limb protraction returned to the degree seen before lameness, and vertical excursion of the tubera coxae became more symmetric. CONCLUSIONS AND CLINICAL RELEVANCE: Increased length of hind limb protraction and symmetry of tubera coxae vertical excursion are sensitive indicators of improvement in tarsal joint lameness. When evaluating changes in tarsal joint lameness, evaluating the horse from the side (to assess limb protraction) is as important as evaluating from the rear (to assess pelvic symmetry).     

Identification of Equine Subclinical Lameness Induced by Pressure to the Sole of Fore- or Hindlimb

Lameness has been investigated in past studies with kinematic analyses, and the features of lameness have been qualitatively and quantitatively analyzed. The output was, however, limited to visible lameness that was scored by experienced clinicians. Subclinical supporting lameness that was induced by subtle pressure to the sole of limb, but that could not be detected by visual check, has yet to be extensively analyzed. To find specific kinematic parameters that were influenced by such subclinical lameness of the fore- or hindlimb, we produced subclinical, subtle and mild lameness in five sound horses by applying slight pressure to the sole. Trot on a treadmill was recorded by a high-speed camera. Symmetric properties of acceleration of the head and the tuber sacrale were disturbed in mild fore- and hindlimb lameness, respectively. In subclinical forelimb lameness, no obvious changes in the symmetric properties of the head, the withers, or the tuber sacrale were observed; however, the vertical lift-off acceleration of the treated forelimb was decreased. In the case of subclinical hindlimb lameness, the lift-off points of both the treated and sound hindlimb shifted posteriad. These findings may contribute to further investigations of subclinical lameness aiming to establish new procedures for early detection of subclinical musculoskeletal disease, which would enable more timely treatment.     

Evaluation of discriminant analysis based on dorsoventral symmetry indices to quantify hindlimb lameness during over ground locomotion in the horse

Reasons for performing study: Advances in gait analysis techniques have led to assessment tools that can aid in detecting and quantifying lameness; here, bilateral tuberà coxae and pelvic movement during over ground locomotion are compared in order to investigate a practical method to assess hindlimb lameness in the horse. Objectives: To evaluate which parameters from anatomical landmarks on trunk and proximal hindlimbs are the best indicators of degree and side of hindlimb lameness. Methods: Fifteen horses (age 11–23 years, 6 nonlame and 9 unilaterally hindlimb lame horses 1/10 to 2/10 lame) were fitted with 4 inertial sensors: tuber sacrale, left and right tubera coxae and withers; 889 strides were collected from 6 trot trials per horse. Horses were assessed for lameness by a qualified equine orthopaedic surgeon from videos. Vertical displacement data for each sensor were used to calculate symmetry indices as well as published Fourier analysis based parameters. Linear discriminant analysis was used to determine the most discriminative parameters for 2 scenarios: grading of severity of lameness and identification of the affected limb. Results: Pelvic energy ratio gave the best indication for the degree of lameness. Directional symmetry index of the tubera coxae sensors yielded the highest discriminative power for identification of the lame limb. Conclusions and potential relevance: A good indication of the degree of hindlimb lameness can be obtained from vertical displacement data of the pelvic midline, collected from inertial sensors during over ground locomotion. The trunk mounted inertial sensor system allows for a time efficient collection of a representative database from horses with differing grade and site of lameness in a clinical setting. This is crucial for future work on a robust definition of the best parameters for lameness classification under practical conditions.     

The effect of induced hindlimb lameness on thoracolumbar kinematics during treadmill locomotion

REASON FOR PERFORMING STUDY: There are no detailed studies describing a relationship between hindlimb lameness and altered motion of the back. OBJECTIVES: To quantify the effect of induced subtle hindlimb lameness on thoracolumbar kinematics in the horse. METHODS: Kinematics of 6 riding horses were measured during walk and trot on a treadmill before and during application of pressure on the sole of the left hindlimb using a well-established sole pressure model. Reflective markers were located at anatomical landmarks on the limbs, back, head and neck for kinematic recordings. Ground reaction forces (GRF) in individual limbs were calculated from kinematics to detect changes in loading of the limbs. RESULTS: When pressure on the sole of the hindlimb was present, horses were judged as lame (grade 2 on the AAEP scale 1-5) by an experienced clinician. No significant unloading of this limb was found in the group of horses (unloading was observed in 4 animals, but was not detectable in the other 2), but statistically significant effects on back kinematics were detected. The overall flexion-extension (FE) range of motion (ROM) of the vertebral column was increased at walk, especially in the thoracic segments. Axial rotation (AR) ROM of the pelvis was also increased. At trot, the FE ROM was decreased only in the segment L3-L5-S3. During the stance phase of the lame limb, the segment T6-T10-T13 was more flexed and the neck was lowered at both gaits; the thoracolumbar segments were more extended at walk and trot. There were no significant changes in the stride length or protraction-retraction angles in any of the limbs. CONCLUSIONS: Subtle hindlimb lameness provoked slight but detectable changes in thoracolumbar kinematics. The subtle lameness induced in this study resulted in hyperextension and increased ROM of the thoracolumbar back, but also in decreased ROM of the lumbosacral segment and rotational motion changes of the pelvis. POTENTIAL RELEVANCE: Even subtle lameness can result in changes in back kinematics, which emphasises the intricate link between limb function and thoracolumbar motion. It may be surmised that, when chronically present, subtle lameness induces back dysfunction.