Comparison of basilar and axial sesamoidean approaches for digital flexor tendon sheath synoviocentesis and injection in horses

Richard A. Rocconi Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762.

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Sarah N. Sampson Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762.

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Abstract

Objective—To define a method for the basilar sesamoidean approach (BSA) to the digital flexor tendon sheath (DFTS) in horses and compare it with the axial sesamoidean approach (ASA) for DFTS synoviocentesis and injection.

Design—Evaluation study.

Animals—12 healthy adult mares without evidence of abnormalities related to the lower limbs.

Procedures—Each horse had 1 forelimb and 1 hind limb assigned to each DFTS approach (basilar vs axial, relative to the proximal sesamoid bones) in a Latin square design. The order of horses and of limb injection for each horse was randomly selected. All procedures were performed in standing sedated horses. The number of attempts to place a needle in the DFTS, presence of synovial fluid in the needle hub, time for DFTS injection, and number of accurate injections of sterile contrast material into the DFTS (evaluated by means of radiography) were compared between methods.

Results—Median time for injection was significantly shorter for the BSA, compared with the ASA. The median number of times the needle was redirected was also significantly less for the BSA. Odds of obtaining synovial fluid via the BSA were 5.7 times as great as for the ASA (95% confidence interval, 1.2 to 278). Successful injection of contrast material into the DFTS did not differ significantly between the BSA (24/24 limbs) and ASA (23/24).

Conclusions and Clinical Relevance—The BSA was a useful method for DFTS synoviocentesis in the forelimbs and hind limbs of standing sedated horses and was superior to the ASA in most aspects. This approach to the DFTS should be considered when DFTS injection or synovial fluid retrieval is desired, particularly in horses with minimal DFTS effusion.

Abstract

Objective—To define a method for the basilar sesamoidean approach (BSA) to the digital flexor tendon sheath (DFTS) in horses and compare it with the axial sesamoidean approach (ASA) for DFTS synoviocentesis and injection.

Design—Evaluation study.

Animals—12 healthy adult mares without evidence of abnormalities related to the lower limbs.

Procedures—Each horse had 1 forelimb and 1 hind limb assigned to each DFTS approach (basilar vs axial, relative to the proximal sesamoid bones) in a Latin square design. The order of horses and of limb injection for each horse was randomly selected. All procedures were performed in standing sedated horses. The number of attempts to place a needle in the DFTS, presence of synovial fluid in the needle hub, time for DFTS injection, and number of accurate injections of sterile contrast material into the DFTS (evaluated by means of radiography) were compared between methods.

Results—Median time for injection was significantly shorter for the BSA, compared with the ASA. The median number of times the needle was redirected was also significantly less for the BSA. Odds of obtaining synovial fluid via the BSA were 5.7 times as great as for the ASA (95% confidence interval, 1.2 to 278). Successful injection of contrast material into the DFTS did not differ significantly between the BSA (24/24 limbs) and ASA (23/24).

Conclusions and Clinical Relevance—The BSA was a useful method for DFTS synoviocentesis in the forelimbs and hind limbs of standing sedated horses and was superior to the ASA in most aspects. This approach to the DFTS should be considered when DFTS injection or synovial fluid retrieval is desired, particularly in horses with minimal DFTS effusion.

Accurate synoviocentesis and injection of the DFTS (vaginae synoviales tendinum digitorum manus) are important procedures for diagnosis and treatment of injury associated with this structure in horses. Access to the DFTS is needed for synovial fluid sample collection, administration of local anesthetics or other medication, tendon sheath lavage, and creation of portals for tenoscopy. Because of intimate associations between the DFTS and various tendons and ligaments in the distal aspect of the limb, the DFTS is commonly involved in orthopedic problems in horses.1–5 Diagnosis of pathological changes involving structures related to the DFTS is becoming even more common, in part owing to the increasing use of MRI to investigate lameness in horses.1–3 Diagnosis of lameness can be facilitated by administration of local anesthetic solution within the DFTS, which can be necessary in horses that have little or no DFTS effusion. The distal sesamoidean ligaments, distal digital annular ligament, DDFT, SDFT, palmar annular ligament, and intersesamoidean ligament are intimately associated with the DFTS, and these structures can be desensitized by deposition of local anesthetic solution within the sheath.2–4 Historically, collection of synovial fluid from the DFTS or injection into the structure has been difficult if little or no effusion is present.4,6 An efficient approach to the DFTS that simplifies performance of these procedures is needed.

The DFTS is a complex synovial structure, approximately 14 to 20 cm in length, that surrounds the deep and superficial flexor tendons in the distal aspect of a limb.7 This sheath begins at the junction of the proximal two-thirds and the distal third of the metacarpus or metatarsus and extends distally past the metacarpophalangeal or metatarsophalangeal (fetlock) joint and pastern region (ie, the part of the digit between the fetlock joint and coronary band), terminating just proximal to the collateral sesamoidean ligament within the hoof.8 The DFTS houses the associated plicae, mesotenons, vinculae, and manica flexoria that function to maintain the flexor tendons in proper alignment within the sheath.7 The DDFT is completely enveloped by the DFTS in the fetlock joint and pastern regions; however, the branches of the SDFT exit the DFTS at midpastern level to insert on the proximopalmar or proximoplantar aspect of the middle phalanx.

Two sites typically accessed for DFTS synoviocentesis and injection in horses with effusion of this structure are the proximolateral pouch and the distal palmar or plantar pouch.9 Fluid accumulation in relatively large amounts results in distension in these locations. The proximolateral pouch is located abaxially at the proximal extent of the sheath between the suspensory ligament branches and the DDFT. The distal palmar or plantar pouch is located at midline on the palmar or plantar surface at the distal aspect of the pastern between the proximal and distal digital annular ligaments. A third site used for DFTS synoviocentesis and injection, accessed via a palmar or plantar ASA, has also been described. The ASA can be used in horses without DFTS effusion because proper technique is dependent on identification of anatomic landmarks and not the presence of synovial fluid.6 The ASA, in which a needle is inserted into the DFTS from a location axial to the midbody of either proximal sesamoid bone, has been shown to be superior to the proximolateral approach (with a needle inserted from the lateral aspect of the limb into the proximolateral pouch) in regard to speed at which the DFTS is entered and decreased number of attempts to penetrate the DFTS in a study6 of equine cadaver limbs. These approaches can result in successful DFTS penetration, but the time it takes to enter the sheath and the ability to obtain fluid can be quite variable.6

The proximal and distal collateral pouches of the DFTS are less commonly discussed in the literature. The proximal collateral pouch is found at the base of the proximal sesamoid bones between the distal aspect of the palmar or plantar annular ligament and the proximal aspect of the proximal digital annular ligament on either side of the palmar or plantar midline. The distal collateral pouch is found abaxially between the proximal and distal attachments of the proximal digital annular ligament.8 Neither of these pouches is easily detected, even with DFTS effusion, but the proximal collateral pouch can be accessed easily when the base of a proximal sesamoid bone and the edge of the SDFT are used as landmarks.

The proximal collateral pouch has been used clinically for many years as an alternative approach for DFTS access,1,2,9 but the approach has not been fully described in the literature, and the advantages and disadvantages of this approach have not been evaluated in a controlled study. Clinically, this approach has been used in standing and recumbent horses for administration of local anesthetic or medication and as a site for gaining access for lavage and tenoscopy.3,9,10

The purposes of the study reported here were to define a method for the BSA to the proximal collateral pouch of the DFTS and to compare it to the ASA6 for DFTS synoviocentesis and injection in standing horses.

Materials and Methods

Twelve healthy adult mares from a university-owned breeding herd were included in the study. The horses had no evidence of lameness at a walk, no palpable effusion of the DFTS, and no obvious conformational abnormalities related to the distal aspects of the limbs. There were 8 Quarter Horses, 3 Thoroughbreds, and 1 mixed-breed horse; median age was 12 years (range, 3 to 19 years) and body weight was 480 kg (1,056 lb; range, 400 to 600 kg [880 to 1,320 lb]). The study procedures were approved by the Institutional Animal Care and Use Committee at Mississippi State University.

Experimental design—All limbs of each horse were used for 1 of 2 approaches for DFTS synoviocentesis and injection. Each horse had 1 forelimb and 1 hind limb assigned for the BSA and 1 forelimb and 1 hind limb assigned for the ASA in a Latin square design. This resulted in 24 limbs (12 forelimbs and 12 hind limbs) in each approach group. Horse order and the order of limb injection for each horse were randomly selected via a random-number generator,a which yielded 4 injection sequences. Each sequence was performed on 3 of the horses.

For each approach, hair was clipped from the entire lateral and palmar or plantar aspect of the fetlock joint region with a No. 40 blade, resulting in a clipped area of 10 × 10 cm centered over the lateral proximal sesamoid bone. The clipped area was aseptically prepared with povidone-iodine scrub for 10 minutes and rinsed with a 70% alcohol solution. Horses were then sedated with detomidine hydrochloride (4 to 12 μg/kg [1.8 to 5.5 μg/lb], IV) for DFTS synoviocentesis and injection. If needed, additional restraint was attained by application of a nose twitch. The limb to be injected was held in a flexed position by 1 assistant (SNS) for all experiments. Sterile technique was maintained for each injection, with sterile gloves replaced between injections.

BSA—The metacarpophalangeal or metatarsophalangeal joint was held in a mildly flexed position at an angle of approximately 200° to 220° from the dorsal surface of the third metacarpal or metatarsal bone (Figure 1). The injection site was identified in the non–weight-bearing limb by palpating the depression created by the base of the lateral proximal sesamoid bone proximally and the lateral border of the SDFT axially. An 18-gauge, 3.8-cm needle was directed into the palpable depression at an angle of approximately 45° to the transverse plane (in a lateromedial direction) and 45° to the dorsal plane (in a distoproximal direction), to a depth of ≤ 1 cm.

Figure 1—
Figure 1—

Schematic diagram of the flexed palmarolateral oblique view of the distal aspect of the limb of a horse showing needle placement and anatomic landmarks for the BSA and ASA to the DFTS for synoviocentesis and injection. DDAL = Distal digital annular ligament. PDAL = Proximal digital annular ligament.

Citation: Journal of the American Veterinary Medical Association 243, 6; 10.2460/javma.243.6.869

ASA—The ASA to the DFTS was performed as described in a previous report.6 Briefly, the metacarpophalangeal or metatarsophalangeal joint was held in a moderately flexed position at approximately 225° from the dorsal surface of the third metacarpal or metatarsal bone. An 18-gauge, 3.8-cm needle was inserted approximately 3 mm axial to the palpable axial border of the lateral proximal sesamoid bone, midway between the proximal and distal aspects of the bone, and advanced at an angle of 45° to the sagittal plane toward the intersesamoidean ligament, to a depth of 1.5 to 2.0 cm.6

Synoviocentesis and injection—All synoviocentesis and injection procedures were performed by 1 investigator (RAR) who had no prior clinical experience with either technique being evaluated but had practiced each technique on an equal number of cadaver limbs (n = 16) prior to beginning the study. For both approaches, 8 mL of sterile contrast materialb (iohexol [300 mg of iodine/mL]) was injected, with confirmation of positioning based on the spontaneous appearance of synovial fluid in the needle hub or by lack of resistance to injection if no synovial fluid was obtained. Lack of resistance to injection was subjective and determined on the basis of the investigator's experience performing injections into other synovial structures of horses prior to this study. Immediately following injection of each limb, a lateromedial radiograph was obtained under conditions of weight bearing to determine whether the contrast material was delivered accurately. At the end of the procedure, each horse received a dose of phenylbutazone (4.4 mg/kg [2.0 mg/lb], IV) to ameliorate any inflammation caused by the injections. All procedures were recorded with a digital video camera to ensure accurate documentation of time required for the procedure, number of attempts to enter the DFTS, and presence of synovial fluid in the needle hub. Video recordings were evaluated in random order (with randomization as previously described) by both investigators, and consensus findings were recorded. All horses were routinely monitored twice daily by the barn manager and were additionally evaluated on days 1 and 3 after the procedure by one of the investigators (RAR).

Assessment of approaches—For each injection, the number of attempts needed to insert the needle into the DFTS was recorded. Any redirection of the needle constituted a new attempt to enter the DFTS. The presence of synovial fluid in the needle hub (yes or no) was recorded. All lateromedial radiographs were evaluated for the presence of contrast material within the DFTS, and inaccurate placement of contrast material was recorded and described. Evaluations were performed by both investigators together in a blinded manner. Successful injection of contrast material was defined as obvious contrast material filling the DFTS throughout the sheath from its proximal to distal extents. Elapsed time for DFTS injection was measured from needle insertion through the skin to the beginning of contrast injection into the sheath. The association between time to successful injection and horse and limb order for each approach was also assessed to determine whether the investigator gained proficiency with 1 or both of the techniques during the course of the study.

Statistical analysis—Statistical softwarec was used for analysis. Visual assessment of the results for injection time and number of times the needle was redirected (ie, number of attempts after the first needle placement) indicated the data were not normally distributed. Consequently, nonparametric methods of analysis that accounted for the hierarchic structure of the data were used. For each outcome, the data were ranked and ANOVA was performed. An estimation of the covariance parameters with a repeated statement specifying horse identity as the subject, limb as the group, and an unstructured covariance structure was obtained. Approach order, approach used on the previous limb, limb, method, and limb × approach interaction were initially included in the models as fixed effects. Subsequently, more refined models were considered by removing fixed effects that did not have significant impacts. Values of P ≤ 0.05 were considered significant. Recovery of fluid was treated as a dichotomous outcome and analyzed via logistic regression. A mixed model with horse identity as a random effect was analyzed. Approach order, approach used on the previous limb, limb, and approach were initially included in the model. The most refined model was developed via manual backward selection with sequential removal of the fixed effect with the highest P value until only variables with a value of P ≤ 0.05 remained. Odds ratios and their 95% confidence intervals were reported for each of the variables in the final models to express their strength of association with the recovery of fluid. Values of P < 0.05 were considered significant. Linear regression was used to assess the association between horse order and injection time for each method. Because of the nonnormal distribution of injection times, the outcome variable was transformed by taking its base 10 logarithm. Horse order, as an indication of the investigator's experience with each method over time, was included in the model as a predictor variable.

Results

Approach was the only variable retained in the models assessing injection time and number of attempts to redirect the needle into the DFTS. The median elapsed time for needle placement and injection of contrast material via the BSA to the DFTS (11.5 seconds; range, 4.2 to 114.9 seconds) was significantly (P = 0.037) less than that when the ASA was used (27.2 seconds; range, 4.9 to 192.5 seconds). The median number of times the needle was redirected for DFTS injection with the BSA (0.5; range, 0 to 7) was significantly (P < 0.001) less than that for the ASA (2.0; range, 0 to 17).

Synovial fluid was obtained more frequently with the BSA (21/24 [87.5%] limbs) than with the ASA (14/24 [58.3%]; P = 0.031). There was no gross evidence of blood in synovial fluid obtained via either approach. The BSA was 5.7 times as likely to yield synovial fluid (95% confidence interval, 1.2 to 27.8; P = 0.031), compared with the ASA. Injection of contrast material into the DFTS was successful in 24 of 24 limbs when the BSA was used and in 23 of 24 limbs when the ASA was used. Radiographic images revealed intra-articular injection of the left metacarpophalangeal joint in 1 horse following needle placement via the ASA. Comparisons of results over time for the BSA revealed that the time from initial needle insertion to injection decreased with increasing horse order (r2 = 0.30; P = 0.006). Comparisons for the ASA revealed no association between time and horse order (r2 = 0.03; P = 0.434).

Discussion

In healthy horses without evidence of lameness or other abnormalities related to the distal aspects of the limbs (including DFTS effusion), the BSA to the DFTS was performed more quickly and with fewer attempts at needle placement, compared with the ASA. The BSA was also significantly more likely to yield a synovial fluid sample than was the ASA. Injection of contrast material into the DFTS was unsuccessful in only 1 of 48 limbs, when use of the ASA resulted in delivery of the agent into the metacarpophalangeal joint.

The anatomy of the proximal collateral pouch of the DFTS, the targeted entry point for the BSA, provides a superficial recess with an absence of overlying structures that makes this a practical alternative to conventional approaches and results in shallow needle penetration into the limb. In contrast, the ASA requires needle placement into a region of the DFTS that has a narrow point of entry and a deep synovial fluid reservoir.6 The DFTS passes through an inelastic canal created by the palmar or plantar annular ligament, the palmar or plantar surface of the proximal sesamoid bones, and the intersesamoidean ligament, located between the proximal sesamoid bones.6 Needle insertion for the ASA must be precise to ensure that the flexor tendons are not inadvertently penetrated. It is likely that the ease of entry into the DFTS via the BSA in the present study was in part because of the easily identifiable landmarks (specifically, the lateral border of the SDFT and the base of the lateral proximal sesamoid bone). A depression at the site of needle entry is formed when the fetlock joint is flexed at approximately 200° to 220° from the dorsal surface of the third metacarpal or metatarsal bone, making a palpable target for needle insertion.

Clinically, an important aspect of this study was the ability to obtain a synovial fluid sample, which occurred significantly (P = 0.031) more frequently when the BSA was used (21/24), compared with results for the ASA (14/24). Needle size could have influenced these results, but the authors believe that use of an 18-gauge, 3.8-cm needle was necessary to have the best chance of retrieving synovial fluid, and a needle of this size is commonly used for synoviocentesis. The needle used in the present study was slightly larger than the 20-gauge, 3.8-cm needle used in a previous study6 evaluating use of the ASA for DFTS access; however, the larger-diameter needle would be expected to make the retrieval of synovial fluid easier, regardless of the approach, because there is less resistance to fluid with a larger-diameter bore. An 18-gauge needle requires slightly more space during insertion, and this could have been an issue with the ASA because the anatomic space for this approach is narrow. It is possible that a smaller diameter and shorter (eg, 2.5-cm) needle could be used for either of these approaches, but other needle sizes were not evaluated in this study. One of the authors (SNS) has used 18-gauge needles in equine patients for years, and these have been well tolerated in nonsedated and sedated horses for both synoviocentesis and injection. On the basis of the depth of penetration needed for each approach in this study, a 2.5-cm needle was considered to be of sufficient length to enter the DFTS with either the ASA or BSA.

In the present study, synovial fluid retrieval was determined solely on the basis of visual detection of synovial fluid in the needle hub. This decision was made prior to beginning the study because the authors considered that the use of suction with a syringe to obtain fluid could cause tissue to plug the end of the needle and that this could hinder subsequent interpretation of needle entry into the DFTS. On the basis of our clinical experience with equine patients, synovial fluid aspiration from a nondistended DFTS is not usually successful, and the risk of potential complications, compared with the possible advantages, was considered too high. When synovial fluid was not obtained in the hub of the needle, needle placement within the DFTS was determined by lack of resistance to injection. With the 18-gauge needle, injection of contrast was accomplished with very little pressure exerted on the syringe plunger, indicating there was minimal resistance to flow of contrast into the DFTS.

Another potential advantage of the BSA over the ASA was the ability of a veterinarian unfamiliar with either approach to gain proficiency more quickly with the BSA, although this was evaluated for only 1 investigator. Results of linear regression modeling indicated a significant association between horse order and time for DFTS injection. Given the number of other factors that could contribute to this outcome, the effect of horse order was shown to have a substantial effect by explaining 30% of the variation in time. Gaining efficiency quickly is particularly important to veterinarians who are attempting to learn a new procedure. In the present study, the ASA required more time, and even with more experience, it was subjectively more difficult to enter the DFTS at the exact angle and depth necessary to avoid penetration of the surrounding structures. Because the ASA requires precise needle placement, the lack of improvement in time for injection may have been attributable to subtle anatomic variations among individual horses included in this study.

One important limitation of the present study was the inability to grossly or microscopically evaluate the limbs internally for trauma from needle penetration because none of the horses in this study were euthanized. However, the authors speculate that the BSA may potentially be a less traumatic means of entering the DFTS because the needle does not need to enter into deep structures of the limb and there is minimal interference with needle placement by surrounding structures, compared with the ASA. There was no evidence of blood within the synovial fluid during the study with either approach, but resistance to needle placement from surrounding tissues was felt as the needle was inserted deeper into the limb with the ASA.

The only complication encountered during the study was inadvertent injection of contrast material into the metacarpophalangeal joint in 1 limb following needle placement via the ASA. This may have resulted from excessive advancement of the needle through the intersesamoidean ligament. Exact needle depth was not measured in each limb, and therefore, the needle penetration depth in this horse was not known. If this happened in a horse with DFTS sepsis, bacterial inoculation of the metacarpophalangeal or metatarsophalangeal joint could lead to joint sepsis, and this should be considered in situations where infection is suspected. Although we speculate that the BSA may be a safer technique because the required needle insertion depth is shallow (≤ 1 cm, compared with 1.5 to 2 cm for the ASA), this could not be evaluated in the present study.

In the study reported here, injections were performed in standing sedated horses, and there was some movement of the limb as there would be when performing the same techniques on standing nonsedated horses in a clinical setting. The BSA has been used by one of the authors (SNS) in many equine patients for lameness diagnosis, medication administration, diagnosis of sepsis, evaluation of wound penetration, and tendon sheath lavage in nonsedated, sedated, and anesthetized horses as well as for tenoscopic portals in anesthetized horses. In that author's experience, the BSA is no more difficult than a metacarpophalangeal or metatarsophalangeal joint injection and does not elicit more uncooperative behavior than the latter procedure; thus, it can be done with minimal restraint in many horses.

Results of the study reported here provided evidence that the BSA is a useful method for DFTS synoviocentesis and injection in forelimbs and hind limbs of clinically normal standing horses and is superior in most aspects when compared with the ASA. Given the high frequency of obtaining a synovial fluid sample with the BSA in clinically normal horses (21/24 limbs), use of the BSA should be considered when DFTS synovial fluid analysis is desired. Also, use of the BSA should be considered when DFTS synoviocentesis is to be performed on limbs with minimal or no DFTS effusion.

ABBREVIATION

ASA

Axial sesamoidean approach

BSA

Basilar sesamoidean approach

DDFT

Deep digital flexor tendon

DFTS

Digital flexor tendon sheath

SDFT

Superficial digital flexor tendon

a.

RAND, Microsoft Excel, Microsoft Corp, Redmond, Wash.

b.

Omnipaque 300, GE Healthcare Inc, Princeton, NJ.

c.

PROC UNIVARIATE, SAS, version 9.2 for Windows, SAS Institute Inc, Cary, NC.

References

  • 1. Sampson SN, Schneider RK, Gavin PR, et al. Magnetic resonance imaging observations in 72 horses with recent onset of clinical signs of navicular syndrome. Vet Radiol Ultrasound 2009; 50: 339346.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Cohen JM, Schneider RK, Zubrod CJ, et al. Desmitis of the distal digital annular ligament in 7 horses: MRI diagnosis and surgical treatment. Vet Surg 2008; 37: 336344.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3. Sampson SN, Schneider RK, Tucker RL, et al. Magnetic resonance imaging features of oblique and straight distal sesamoidean desmitis in 27 horses. Vet Radiol Ultrasound 2007; 48: 303311.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Schramme MC, Smith RKW. Disease of the digital synovial sheath, palmar annular ligament, and digital annular ligaments. In: Ross MW, Dyson SJ, eds. Diseases and management of lameness in the horse. Philadelphia: WB Saunders Co, 2003;674684.

    • Search Google Scholar
    • Export Citation
  • 5. Wright IM, McMahon PJ. Tenosynovitis associated with longitudinal tears of the digital flexor tendons in horses: a report of 20 cases. Equine Vet J 1999; 31: 1218.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. Hassel DM, Stover SM, Yarbrough TM, et al. Palmar-plantar axial sesamoidean approach to the digital flexor tendon sheath in horses. J Am Vet Med Assoc 2000; 217: 13431347.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7. International Committee on Veterinary Gross Anatomical Nomenclature. Nomina anatomica veterinaria; with nomina histologica. 3rd ed. Ithaca, NY: International Committee on Veterinary Gross Anatomical Nomenclature, 1983;A45.

    • Search Google Scholar
    • Export Citation
  • 8. Dyce KM, Wensing CJG. The forelimb of the horse. In: Dyce KM, Sack WO, Wensing CJ, eds. Textbook of veterinary anatomy. 2nd ed. Philadelphia: WB Saunders Co, 1996;573610.

    • Search Google Scholar
    • Export Citation
  • 9. Bassage LH, Ross MW. Diagnostic analgesia. In: Ross MW, Dyson SJ, eds. Diseases and management of lameness in the horse. Philadelphia: WB Saunders Co, 2003;93124.

    • Search Google Scholar
    • Export Citation
  • 10. Davis CS, Smith RKW. Diagnosis and management of tendon and ligament disorders. In: Auer JA, Stick JA, eds. Equine surgery. 3rd ed. St Louis: WB Saunders Co, 2006;1104.

    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Schematic diagram of the flexed palmarolateral oblique view of the distal aspect of the limb of a horse showing needle placement and anatomic landmarks for the BSA and ASA to the DFTS for synoviocentesis and injection. DDAL = Distal digital annular ligament. PDAL = Proximal digital annular ligament.

  • 1. Sampson SN, Schneider RK, Gavin PR, et al. Magnetic resonance imaging observations in 72 horses with recent onset of clinical signs of navicular syndrome. Vet Radiol Ultrasound 2009; 50: 339346.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Cohen JM, Schneider RK, Zubrod CJ, et al. Desmitis of the distal digital annular ligament in 7 horses: MRI diagnosis and surgical treatment. Vet Surg 2008; 37: 336344.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3. Sampson SN, Schneider RK, Tucker RL, et al. Magnetic resonance imaging features of oblique and straight distal sesamoidean desmitis in 27 horses. Vet Radiol Ultrasound 2007; 48: 303311.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Schramme MC, Smith RKW. Disease of the digital synovial sheath, palmar annular ligament, and digital annular ligaments. In: Ross MW, Dyson SJ, eds. Diseases and management of lameness in the horse. Philadelphia: WB Saunders Co, 2003;674684.

    • Search Google Scholar
    • Export Citation
  • 5. Wright IM, McMahon PJ. Tenosynovitis associated with longitudinal tears of the digital flexor tendons in horses: a report of 20 cases. Equine Vet J 1999; 31: 1218.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. Hassel DM, Stover SM, Yarbrough TM, et al. Palmar-plantar axial sesamoidean approach to the digital flexor tendon sheath in horses. J Am Vet Med Assoc 2000; 217: 13431347.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7. International Committee on Veterinary Gross Anatomical Nomenclature. Nomina anatomica veterinaria; with nomina histologica. 3rd ed. Ithaca, NY: International Committee on Veterinary Gross Anatomical Nomenclature, 1983;A45.

    • Search Google Scholar
    • Export Citation
  • 8. Dyce KM, Wensing CJG. The forelimb of the horse. In: Dyce KM, Sack WO, Wensing CJ, eds. Textbook of veterinary anatomy. 2nd ed. Philadelphia: WB Saunders Co, 1996;573610.

    • Search Google Scholar
    • Export Citation
  • 9. Bassage LH, Ross MW. Diagnostic analgesia. In: Ross MW, Dyson SJ, eds. Diseases and management of lameness in the horse. Philadelphia: WB Saunders Co, 2003;93124.

    • Search Google Scholar
    • Export Citation
  • 10. Davis CS, Smith RKW. Diagnosis and management of tendon and ligament disorders. In: Auer JA, Stick JA, eds. Equine surgery. 3rd ed. St Louis: WB Saunders Co, 2006;1104.

    • Search Google Scholar
    • Export Citation

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