The stifle joint is a common site of pain resulting in hind limb lameness among horses of many breeds and athletic disciplines.1,2 The equine stifle joint is complex and comprises 3 synovial joint compartments: the femoropatellar joint, medial compartment of the femorotibial joint, and lateral compartment of the femorotibial joint.1 Although pain resulting in lameness can originate from any of these 3 compartments of the stifle joint, it most commonly originates from the femoropatellar joint and medial compartment of the femorotibial joint.1,3
Intra-articular injection of the stifle joint is performed for both diagnostic analgesia and treatment, and these injections are commonly performed via separate approaches into each joint compartment because the prevalence of direct communication between compartments differs among stifle joints.1,3 Communication between the medial or lateral compartments of the femorotibial joint and the femoropatellar joint has been documented, most commonly between the medial compartment of the femorotibial joint and the femoropatellar joint.1,3 Additionally, communication has been documented between the medial and lateral compartments of the femorotibial joint.4 In a recent study,5 investigators found that lameness originating within a specific compartment of a stifle joint was most reliably resolved with direct injection of local anesthetic into that compartment. Therefore, it has been recommended to inject each compartment separately and to not rely on communication between joint compartments.5,6
Several techniques have been described for individual injection of each compartment of the stifle joint.1 However, compared with an approach for insertion of a single needle, approaches for multiple individual injections require a larger area of aseptic preparation and > 1 insertion of a needle, and multiple needle entry points through the skin may increase the risk of infection and risk to the person performing the injection because horses may react when a needle penetrates the skin. When multiple compartments of the stifle joint require injection, a technique of needle redirection at a single craniolateral site is preferred by many of the clinicians at our institution because all 3 of these synovial compartments can be accessed from 1 needle insertion site.1 Although use of this technique of needle redirection at a single craniolateral site has been reported,1 a description of specific landmarks, including the angle for needle entry and accuracy of the technique, has not been reported.
Objectives of the study reported here were to determine accuracy of the technique of needle redirection at a single craniolateral site for injection of each of 3 compartments of the equine stifle joint, describe the angle of needle advancement and depth of penetration, and identify the location of the tip of the needle within each joint compartment. The hypotheses were that the technique of needle redirection at a single craniolateral site would result in accurate (> 80% success) injection of each of these 3 compartments of the stifle joint for all persons who performed injections and that the angle of needle advancement and depth of penetration for successful injections would not differ among persons who performed the injections.
Materials and Methods
Sample
Stifle joints (from midfemur to midtibia) were collected from cadavers of horses that were euthanized for reasons unrelated to the stifle joint. Body weight of horses ranged from 450 to 600 kg. Specimens were stored frozen and then thawed in room temperature water (approx 20°C) for 36 to 48 hours prior to use or were stored in a cooler (approx 4°C) and used within 48 hours after collection.
Measurement of the angle of the stifle joint
The typical angle of the stifle joint during full weight bearing was measured on 17 live mixed-breed horses. The central disk of a handheld double-armed goniometera was placed at the lateral epicondyle of the femur, and the 2 arms were extended proximally and distally along the long axis of the femur and tibia, respectively. Three separate measurements were obtained for each stifle joint (left and right) of each horse, and a mean value was calculated for each stifle joint (left and right).
Preparation of cadaver stifle joints
Skin on the craniolateral aspect of each stifle joint was clipped of hair and cleaned with alcohol. Each stifle joint was placed in a customized limb stand at approximately 145° of flexion, which was based on angle measurements determined for the live horses. The skin and underlying muscle were placed under tension by use of baling twine inserted through stab incisions to maintain and replicate in vivo tautness of skin and patellar ligaments. One investigator (BBN) applied a small amount of acrylic paint (3 to 4 mm in diameter) to mark the skin on the cranioproximal aspect of the tibial tuberosity as well as the proximal aspect of the lateral tibial condyle. These markings were used for external measurements of needle positioning; all external needle measurements on all cadaver stifle joints were obtained by 1 investigator (VJM).
Injection solution
Each joint compartment was injected with a volume of 30 mL, composed of 15 mL of iodinated contrast medium,b 13 mL of water, and approximately 2 mL of food-coloring dye. Red dye was used for the medial compartment of the femorotibial joint, blue dye was used for the lateral compartment of the femorotibial joint, and yellow dye was used for the femoropatellar joint. The volume of 30 mL was chosen because injection of a volume of 20 to 30 mL of local anesthetic has typically been recommended for anesthetizing a stifle joint compartment.6
Injection personnel
Four individuals performed stifle joint injections; one was an equine veterinarian who had previous experience with use of the technique, and the other 3 were third-year veterinary students who had not previously performed stifle joint injections. The veterinary students were provided general guidelines for performing the injection,1 and all 3 observed the experienced equine veterinarian perform the technique on a cadaver limb before they attempted injections. The veterinary students also were provided with guidance on means to identify that the needle was placed within a joint compartment (ie, felt the needle tip contact a cartilage surface and no resistance to injection).
Stifle joint injection technique
The technique of needle redirection at a single craniolateral site for injection of the stifle joint was performed as reported elsewhere.1 An 8.9-cm, 18-gauge spinal needle was inserted between the middle and lateral patellar ligaments at a location approximately 1 to 2 cm proximal to the palpable proximal aspect of the tibia and directed toward the axial aspect of the medial femoral condyle for injection of the medial compartment of the femorotibial joint. Each individual was allowed to retract the needle to a subcutaneous position and redirect the needle until satisfied with the needle placement. The number of redirections was recorded. Once the person was satisfied with the needle placement, the stylet was removed, and the contrast medium–dye solution was injected. The stylet was replaced, and radiographs were obtained to determine the location of the needle tip and distribution of the contrast medium. Each person performing the injections was allowed to examine the radiographs as they were obtained. Next, the needle was retracted but kept within the subcutaneous tissues and redirected caudally toward the cranial aspect of the lateral femoral condyle into the lateral compartment of the femorotibial joint. Again, each individual could redirect the needle until satisfied with the needle placement, and the number of redirections was recorded. The contrast medium–dye solution was injected, and radiographs were obtained. Again, each person performing the injections was allowed to examine the radiographs as they were obtained. Then, the spinal needle was retracted, but kept within the subcutaneous tissues, and redirected proximally into the femoropatellar joint. The number of redirections was recorded, contrast medium–dye solution was injected, and radiographs were obtained; each person performing the injections was allowed to examine the radiographs as they were obtained. Each person performed injections of each of the 3 compartments on 6 stifle joints.
External needle measurements
After the spinal needle was inserted into each joint compartment, the distance of the needle from the cranioproximal aspect of the tibia (marked with acrylic paint) to the site of insertion through the skin, angles of needle insertion, and depths of needle insertion were measured and recorded. All distances, angles of insertion, and needle depths were measured by the same investigator (VJM). The angles of needle insertion and advancement were measured by use of the handheld goniometer. The proximal-distal angle was measured relative to the long axis of the tibia (with increasing degrees as the needle hub was positioned more proximally), and the medial-lateral angle was measured relative to cranial (positive values indicated medial position of the needle tip, and negative values indicated lateral position of the needle tip). Depth of needle insertion was determined with a ruler by measuring the length of the needle shaft from the level of the skin to the hub of the needle; this value was then subtracted from the total needle length. These measurements were further categorized on the basis of the success of each attempt for injection of a joint compartment.
Radiography
Radiographs were obtained by use of a portable x-ray generatorc and digital radiograph systemd immediately after injection into each joint compartment. Craniocaudal and craniomedial-caudolateral oblique projections were obtained after injection of the medial compartment of the femorotibial joint injection, craniocaudal and craniolateral-caudomedial oblique projections were obtained after injection of the lateral compartment of the femorotibial joint, and a lateromedial projection was obtained after injection of the femoropatellar joint. Radiographs were examined to determine the location of the needle tip within each compartment, and the presence (or lack) of contrast medium in each joint compartment was recorded (Figure 1). For the medial compartment of the femorotibial joint, intra-articular location of the needle tip was categorized as axial (lateral aspect of the medial femoral condyle), midline (central aspect of the medial femoral condyle), abaxial (medial aspect of the medial femoral condyle), or other (Figure 2). For the lateral compartment of the femorotibial joint, intra-articular location of the needle tip was categorized as axial (medial aspect of the lateral femoral condyle), midline (central aspect of the lateral femoral condyle), or abaxial (lateral aspect of the lateral femoral condyle). For the femoropatellar joint, intra-articular location of the needle tip was categorized as subpatellar (proximal third of the femoral trochlea), middle third of the trochlea, or distal third of the trochlea.
A representative lateromedial radiographic view of the right stifle joint of an equine cadaver after injection of contrast medium–dye solution into each of 3 joint compartments by use of a technique of needle redirection at a single craniolateral site. The radiograph is slightly oblique (craniolateral-caudomedial) to demonstrate location of the contrast medium after successful injection into each joint compartment. The contrast medium outlines the articular margin of the medial femoral condyle (black arrow; medial compartment of the femorotibial joint) and lateral femoral condyle (black arrowhead; lateral compartment of the femorotibial joint) and the femoral trochlea (white arrow; femoropatellar joint).
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
A representative lateromedial radiographic view of the right stifle joint of an equine cadaver after injection of contrast medium–dye solution into each of 3 joint compartments by use of a technique of needle redirection at a single craniolateral site. The radiograph is slightly oblique (craniolateral-caudomedial) to demonstrate location of the contrast medium after successful injection into each joint compartment. The contrast medium outlines the articular margin of the medial femoral condyle (black arrow; medial compartment of the femorotibial joint) and lateral femoral condyle (black arrowhead; lateral compartment of the femorotibial joint) and the femoral trochlea (white arrow; femoropatellar joint).
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
A representative lateromedial radiographic view of the right stifle joint of an equine cadaver after injection of contrast medium–dye solution into each of 3 joint compartments by use of a technique of needle redirection at a single craniolateral site. The radiograph is slightly oblique (craniolateral-caudomedial) to demonstrate location of the contrast medium after successful injection into each joint compartment. The contrast medium outlines the articular margin of the medial femoral condyle (black arrow; medial compartment of the femorotibial joint) and lateral femoral condyle (black arrowhead; lateral compartment of the femorotibial joint) and the femoral trochlea (white arrow; femoropatellar joint).
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Craniocaudal radiographic view of the right stifle joint (A) and lateral radiographic view of the left stifle joint (B) of an equine cadaver for assessment of the intra-articular location of the needle tip into the joint compartments. Panel A reveals the medial and lateral compartments of the femorotibial joint; the radiographic marker (H) is located on the lateral side. The lines divide the femoral condyles into axial (a), middle (b), and abaxial (c) regions. Panel B reveals the femoropatellar joint; the lines divide the femoral trochlea into subpatellar (proximal third; a), middle third (b), and distal third (c) regions.
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Craniocaudal radiographic view of the right stifle joint (A) and lateral radiographic view of the left stifle joint (B) of an equine cadaver for assessment of the intra-articular location of the needle tip into the joint compartments. Panel A reveals the medial and lateral compartments of the femorotibial joint; the radiographic marker (H) is located on the lateral side. The lines divide the femoral condyles into axial (a), middle (b), and abaxial (c) regions. Panel B reveals the femoropatellar joint; the lines divide the femoral trochlea into subpatellar (proximal third; a), middle third (b), and distal third (c) regions.
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Craniocaudal radiographic view of the right stifle joint (A) and lateral radiographic view of the left stifle joint (B) of an equine cadaver for assessment of the intra-articular location of the needle tip into the joint compartments. Panel A reveals the medial and lateral compartments of the femorotibial joint; the radiographic marker (H) is located on the lateral side. The lines divide the femoral condyles into axial (a), middle (b), and abaxial (c) regions. Panel B reveals the femoropatellar joint; the lines divide the femoral trochlea into subpatellar (proximal third; a), middle third (b), and distal third (c) regions.
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Stifle joint dissection
After all 3 injections were completed, the limb stand and stifle joint were placed horizontally on the ground. A transverse incision was used to transect the patellar ligaments and incise the femoropatellar joint. The stifle joint was flexed farther during disarticulation to expose the medial and lateral compartments of the femorotibial joint. The presence of colored dye in each joint compartment was recorded; active leakage of dye from the medial or lateral compartments of the femorotibial joint into the femoropatellar joint during flexion and additional locations of dye outside the appropriate compartment (extra-articular dye or mixing of dyes within a compartment) were also recorded. Photographs were obtained and used to determine the location of dye. Evidence of iatrogenic damage to intra-articular structures attributable to needle redirection was also evaluated.
Statistical analysis
Statistical analysis was performed with commercial software.e Normality of data was assessed by use of a Shapiro-Wilk test. All data were normally distributed; thus, mean, SD, and 95% CI were calculated. A Student t test was used to compare injections of left and right stifle joints. Accuracy of injection was defined as the presence of contrast medium evident during examination of radiographs and the correct color of dye detected within the appropriate joint compartment detected during gross dissection. Differences in external needle locations were compared among persons who performed injections using a 1-way ANOVA. Data met all the assumptions for an ANOVA. Post hoc comparisons were performed with a Tukey honestly significant difference test. Significance was set at P ≤ 0.05.
Results
Accuracy of injection
Accuracy of injection into each joint compartment was evaluated by the presence of contrast medium determined during examination of radiographs and dye detected during gross dissection (Figure 3). In total, all 3 joint compartments were successfully injected in 19 of 24 (79%) stifle joints, and there was a median of 0 or 1 unsuccessful attempt of compartment injection (ie, needle redirections)/stifle joint. For the medial compartment of the femorotibial joint, 21 of 24 (87.5%) stifle joints were successfully injected (median, 0 needle redirections/stifle joint; range, 0 to 8 needle redirections/stifle joint). For the lateral compartment of the femorotibial joint, 22 of 24 (91.7%) stifle joints were successfully injected (median, 1 needle redirection/stifle joint; range, 0 to 16 needle redirections/stifle joint). All 24 femoropatellar joints were successfully injected (median, 0 needle redirections/stifle joint; range, 0 to 3 needle redirections/stifle joint). No intra-articular iatrogenic damage as a result of needle placement was noted during gross examination of the stifle joints.
Photograph of the dissected right stifle joint of an equine cadaver after successful injection of contrast medium–dye solution into each of 3 joint compartments by use of a technique of needle redirection at a single craniolateral site. Notice that red dye stains the medial femoral condyle, blue dye stains the lateral femoral condyle, and yellow dye covers the femoral trochlea.
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Photograph of the dissected right stifle joint of an equine cadaver after successful injection of contrast medium–dye solution into each of 3 joint compartments by use of a technique of needle redirection at a single craniolateral site. Notice that red dye stains the medial femoral condyle, blue dye stains the lateral femoral condyle, and yellow dye covers the femoral trochlea.
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Photograph of the dissected right stifle joint of an equine cadaver after successful injection of contrast medium–dye solution into each of 3 joint compartments by use of a technique of needle redirection at a single craniolateral site. Notice that red dye stains the medial femoral condyle, blue dye stains the lateral femoral condyle, and yellow dye covers the femoral trochlea.
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Needle position
External needle measurements, including angle of needle insertion for successful injection into each of the stifle joint compartments, were determined (Figure 4; Table 1). Mean distance from the cranioproximal aspect of the tibia to the site of needle insertion through the skin was 2.00 cm (95% CI, 1.72 to 2.28 cm), and there was no significant difference in this distance between right versus left stifle joints (P = 0.968) or among people who performed injections (P = 0.052). For the medial compartment of the femorotibial joint, the proximal-distal angle was significantly different (P = 0.023) between left and right stifle joints. Mean proximal-distal angle was 77.2° (95% CI, 71.4° to 83.0°) for left stifle joints and 85.8° (95% CI, 80.4° to 91.1°) for right stifle joints. The medial-lateral angle and needle depth were not significantly different between right and left stifle joints (P = 0.438 and P = 0.380, respectively). For the medial compartment of the femorotibial joint, there was not a significant difference in proximal-distal angle (P = 0.301), medial-lateral angle (P = 0.592), and needle depth (P = 0.310) among the 4 people who performed injections. For the lateral compartment of the femorotibial joint, there was a significant (P = 0.036) difference in needle depth between the right and left stifle joints. Mean needle depth was 5.50 cm (95% CI, 5.04 to 5.95 cm) for the left stifle joints and 6.09 cm (95% CI, 5.72 to 6.46 cm) for the right stifle joints. The proximal-distal and medial-lateral angles were not significantly different between the right and left stifle joints (P = 0.717 and P = 0.864, respectively). For the lateral compartment of the femorotibial joint, needle depth differed significantly (P = 0.050) among the 4 people who performed injections; there were differences between a student and the veterinarian and between that same student and another student. There was not a significant difference in the proximal-distal angle (P = 0.326) and medial-lateral angle (P = 0.100) among the 4 people who performed injections. For the femoropatellar joint, there were no significant differences among the 4 people who performed injections when the right and left stifle joints were compared for needle depth, proximal-distal angle, or medial-lateral angle.
Frontal (A), sagittal (B), and transverse (C) plane CT renditions for the mean needle angle of insertion into each joint compartment of the left stifle joint by use of a technique of needle redirection at a single craniolateral site. The lateral side is indicated (L). The solid line indicates the mean entry angle of the needle into the medial compartment of the femorotibial joint (directed 82.1° proximally and 28° medially), the dotted line indicates the mean entry angle of the needle into the lateral compartment of the femorotibial joint (directed 80.3° proximally and 7.3° laterally), and the dashed line indicates the mean entry angle of the needle into the femoropatellar joint (directed 18.5° proximally and 1.3° laterally). The proximal-distal angle of the needle was in reference to the long axis of the tibia, and the medial-lateral angle was measured relative to cranial.
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Frontal (A), sagittal (B), and transverse (C) plane CT renditions for the mean needle angle of insertion into each joint compartment of the left stifle joint by use of a technique of needle redirection at a single craniolateral site. The lateral side is indicated (L). The solid line indicates the mean entry angle of the needle into the medial compartment of the femorotibial joint (directed 82.1° proximally and 28° medially), the dotted line indicates the mean entry angle of the needle into the lateral compartment of the femorotibial joint (directed 80.3° proximally and 7.3° laterally), and the dashed line indicates the mean entry angle of the needle into the femoropatellar joint (directed 18.5° proximally and 1.3° laterally). The proximal-distal angle of the needle was in reference to the long axis of the tibia, and the medial-lateral angle was measured relative to cranial.
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Frontal (A), sagittal (B), and transverse (C) plane CT renditions for the mean needle angle of insertion into each joint compartment of the left stifle joint by use of a technique of needle redirection at a single craniolateral site. The lateral side is indicated (L). The solid line indicates the mean entry angle of the needle into the medial compartment of the femorotibial joint (directed 82.1° proximally and 28° medially), the dotted line indicates the mean entry angle of the needle into the lateral compartment of the femorotibial joint (directed 80.3° proximally and 7.3° laterally), and the dashed line indicates the mean entry angle of the needle into the femoropatellar joint (directed 18.5° proximally and 1.3° laterally). The proximal-distal angle of the needle was in reference to the long axis of the tibia, and the medial-lateral angle was measured relative to cranial.
Citation: American Journal of Veterinary Research 78, 9; 10.2460/ajvr.78.9.1077
Mean and 95% CI values for external needle angle of insertion and depth of needle insertion after successful injections into each equine cadaver stifle joint compartment by use of a technique of needle redirection at a single craniolateral site.
| Joint compartment | Variable | Mean | 95% CI |
|---|---|---|---|
| Medial compartment of the femorotibial joint (n = 21) | Proximal-distal angle (°) | 82.1 | 78.0 to 86.2 |
| Medial-lateral angle (°) | 28.0 | 24.2 to 31.8 | |
| Needle depth (cm) | 5.75 | 5.43 to 6.08 | |
| Lateral compartment of the femorotibial joint (n = 22) | Proximal-distal angle (°) | 80.3 | 76.5 to 84.1 |
| Medial-lateral angle (°) | −7.3 | −12.1 to −2.5 | |
| Needle depth (cm) | 5.79 | 5.50 to 6.09 | |
| Femoropatellar joint (n = 24) | Proximal-distal angle (°) | 18.5 | 13.4 to 23.5 |
| Medial-lateral angle (°) | −1.3 | −5.2 to 2.5 | |
| Needle depth (cm) | 5.58 | 5.10 to 6.07 |
The n is the number of successful joint compartment injections; injections were considered successful when there was presence of contrast medium detected during examination of radiographs as well as detection of the appropriate food-coloring dye during gross dissection in each joint compartment. The proximal-distal angle of the needle was in reference to the long axis of the tibia, and the medial-lateral angle was measured relative to cranial (positive values indicate that the needle was directed medially, and negative values indicate that the needle was directed laterally).
Intra-articular location of the needle tip, as determined by use of radiography, for successful injections into each joint compartment were summarized (Table 2). For the medial compartment of the femorotibial joint, the most common needle tip location for successful injections was axially (lateral aspect of the medial femoral condyle). For unsuccessful injections, the needle tip was located at the cranial aspect of the intercondylar eminence (2 stifle joints) and in the intercondylar region (1 stifle joint). For the lateral compartment of the femorotibial joint, the needle tip for most of the successful injections was located axial (medial aspect of the lateral femoral condyle) or at the central aspect of the lateral femoral condyle. For unsuccessful injections, the needle tip was located axial and proximal to the lateral femoral condyle (2 stifle joints). All femoropatellar joint injections were successfully performed, and the needle tip for most of these injections was located in the middle third of the trochlea.
Distribution of the location of the needle tip within each equine cadaver stifle joint compartment, as determined radiographically, after successful injection by use of a technique of needle redirection at a single craniolateral site.
| Joint compartment | Location of needle tip* | Proportion† |
|---|---|---|
| Medial compartment of the femorotibial joint | Axial | 14/21 |
| Midline | 5/21 | |
| Abaxial | 1/21 | |
| Other | 1/21 | |
| Lateral compartment of the femorotibial joint | Axial | 11/22 |
| Midline | 9/22 | |
| Abaxial | 2/22 | |
| Femoropatellar joint | Subpatellar | 6/24 |
| Middle third of trochlea | 16/24 | |
| Distal third of trochlea | 2/24 |
For the medial compartment of the femorotibial joint, axial was the lateral aspect of the medial femoral condyle, midline was the central aspect of the medial femoral condyle, abaxial was the medial aspect of the medial femoral condyle, and other was the medial aspect of the intercondylar eminence. For the lateral compartment of the femorotibial joint, axial was the medial aspect of the lateral femoral condyle, midline was the central aspect of the lateral femoral condyle, and abaxial was the lateral aspect of the lateral femoral condyle. For the femoropatellar joint, subpatellar was the proximal third of the trochlea.
Proportions represent the number of needle tip locations/the number of successful injections of the joint compartment.
See Table 1 for remainder of key.
Communication between joint compartments
Communication between joint compartments was determined during gross dissection. The most commonly identified communication was between the medial compartment of the femorotibial joint and the femoropatellar joint (16/24 [66.7%] stifle joints). Communication between the femoropatellar joint and both the medial and lateral compartments of the femorotibial joint was observed in 2 of 24 (8.3%) stifle joints. Communication between only the lateral compartment of the femorotibial joint and the femoropatellar joint was observed in 1 of 24 (4.2%) stifle joints.
Discussion
In the present study, a technique of needle redirection after insertion at a single craniolateral site was highly accurate for injection of each of the 3 stifle joint compartments, which was an expected outcome. There was a slightly lower accuracy (79.1%) for successful injection of all 3 compartments within a single stifle joint. However, inaccurate injection of 1 compartment did not preclude successful injection of the other 2 compartments. By use of our definition of success (presence of contrast medium detected during examination of radiographs as well as detection of dye during gross dissection), successful injection of the medial compartment of the femorotibial joint was likely underestimated. If success had been defined by use of either method alone, the accuracy of injection into the individual compartments would have been slightly higher (22/24 [91.7%] stifle joints).
Other techniques have been described for injection of individual stifle joint compartments,1 but there is little information on the accuracy for these techniques. To our knowledge, there have been no reports on the rate of success for use of alternative techniques for injection of the medial compartment of the femorotibial joint. The lateral compartment of the femorotibial joint reportedly is the most difficult of the 3 compartments to inject because of its smaller size and deeper location, compared with the medial compartment of the femorotibial joint and femoropatellar joint.6 Investigators of 1 study7 reported the highest accuracy (100%) when placing a needle through the tendon of the long digital extensor muscle, which was similar to the success rate for injection for the lateral compartment of the femorotibial joint in the present study (91.7%). The other 3 approaches to the lateral compartment of the femorotibial joint investigated in that study7 were less accurate (range, 16.7% to 66.7%), compared with accuracy for the single-needle injection technique described in the study reported here.
Investigators of another study8 compared a cranial and a lateral approach for arthrocentesis of the femoropatellar joint and concluded that the lateral approach was more likely to yield synovial fluid than was the standard cranial approach. Similar to results for that study,8 there was a high rate of success (100%) for placing a needle within the femoropatellar joint in the present study.
A general description of the external landmarks and needle direction for this technique of needle redirection at a single craniolateral site for injection of the equine stifle joint has been reported but lack detail.1 In general, the needle depth in the joint for all 3 joints compartments was approximately two-thirds the length of the spinal needle. The needle tip was advanced in a slightly proximal direction for the medial and lateral compartments of the femorotibial joint, whereas the angle was much steeper for the femoropatellar joint. The medial-lateral angle was approximately 30° (directed medially) for the medial compartment of the femorotibial joint, a few degrees lateral for the lateral compartment of the femorotibial joint, and almost craniocaudal for the femoropatellar joint. The most common intra-articular location of the needle tip among the successful injections, as determined on the basis of examination of radiographs, was the axial (lateral) aspect of the medial femoral condyle for injection of the medial compartment of the femorotibial joint, the axial (medial) aspect of the lateral femoral condyle for injection of the lateral compartment of the femorotibial joint, and the middle third of the femoral trochlea for injection of the femoropatellar joint. There were a low number of unsuccessful injections during the present study for both the medial and lateral compartments of the femorotibial joint, and there were no unsuccessful injections for the femoropatellar joint. However, the needle tip was located toward the intercondylar eminence for unsuccessful injections into the medial compartment of the femorotibial joint. For unsuccessful injections of the lateral compartment of the femorotibial joint, the needle tip was located on the axial aspect of the lateral femoral condyle but was positioned too proximally. Because the radiographic position can alter the appearance of needle location, multiple radiographic projections can be helpful for determining the position of the needle tip. Radiographically determined location of the needle tip within each compartment can be used as general rather than specific guidelines for the direction of needle advancement.
The present study had some limitations. First, cadaver stifle joints were used to simulate a live horse standing in a typical weight-bearing posture. The stifle joint angle and configuration with the limb stand were designed to approximate in vivo conditions. However, height of the stifle joint was similar to that of a pony or short horse, which would not perfectly mimic the manner in which the technique would be performed in taller horses. Additionally, cadaver stifle joints did not move during the procedure and did not mimic conditions that exist with a live horse. In live horses positioned for injection of the stifle joint with the limb extended and bearing weight, the patellar ligaments are more taut and easier to palpate. The cadaver stifle joints were manipulated so that the patellar ligaments were taut and could be palpated in a similar manner to that of a live horse. However, tissue characteristics differed between the cadaver stifle joints and stifle joints in live horse. Stifle joints were used as soon as possible after the horses were euthanized to minimized tissue autolysis or were frozen and thawed prior to use.
Another potential source of bias was the use of acrylic paint to mark the cranial and lateral aspects of the tibia. This marking allowed consistent measurements to be obtained after the needles were placed into each joint compartment. However, it is possible that the cranial mark influenced placement of the needle by the persons who performed the injections. Despite this potential influence, each individual was instructed to place the needle on the basis of palpation of the patellar ligaments and not on the basis of the location of the acrylic paint.
Finally, 3 of the 4 people who performed injections were inexperienced. However, use of cadaver joint stifles provided an excellent method for inexperienced veterinary students to learn the technique of needle redirection at a single craniolateral site for injection of all 3 of these stifle joint compartments.
For the present study, there was acceptable accuracy for the technique of needle redirection at a single craniolateral site for injection of 3 compartments of the equine stifle joint. This investigation also provided general information for needle placement into all 3 compartments on the basis of external needle angles and depth of insertion. These results can be used as guidelines for successfully performing the technique in clinical patients.
Acknowledgments
Supported by a 2015 Center for Companion Animal Studies Young Investigator Grant.
The authors declare that there were no conflicts of interest.
Presented as an abstract at the American Association of Equine Practitioners Convention, Orlando, Fla, December 2016.
The authors thank Dr. Melissa King and Callie Kuntz for technical assistance.
ABBREVIATIONS
| CI | Confidence interval |
Footnotes
Extendable goniometer, Lafayette Instruments Co Inc, Lafayette, Ind.
Omnipaque-350, GE Healthcare, Princeton, NJ.
MinX HF80, MinXray Inc, Northbrook, Ill.
Mark III, Sound Eklin, Carlsbad, Calif.
STATA, version 13.1, StataCorp, College Station, Tex.
References
1. Baxter GM, Stashak TS. Perineural and intrasynovial anesthesia. In: Baxter GM, ed. Adams and Stashak's lameness in horses. 6th ed. Chichester, West Sussex, England: Wiley-Blackwell, 2011; 173–202.
2. Ross MW, Dyson SJ, eds. Diagnosis and management of lameness in the horse. 2nd ed. St Louis: Elsevier Inc, 2011.
3. Reeves MJ, Trotter GW, Kainer RA. Anatomical and functional communications between the synovial sacs of the equine stifle joint. Equine Vet J 1991;23:215–218.
4. Vacek JR, Ford TS, Honnas CM. Communication between the femoropatellar and medial and lateral femorotibial joints in horses. Am J Vet Res 1992;53:1431–1434.
5. Tóth F, Schumacher J, Schramme MC, et al. Effect of anesthetizing individual compartments of the stifle joint in horses with experimentally induced stifle joint lameness. Am J Vet Res 2014;75:19–25.
6. Bassage LH, Ross MW. Diagnostic analgesia. In: Ross MW, Dyson SJ, eds. Diagnosis and management of lameness in the horse. 2nd ed. St Louis: Elsevier Inc, 2011; 100–135.
7. Schumacher J, Schumacher J, Wilhite R. Comparison of four techniques of arthrocentesis of the lateral compartment of the femorotibial joint of the horse. Equine Vet J 2012;44:664–667.
8. Hendrickson DA, Nixon AJ. Comparison of the cranial and a new lateral approach to the femoropatellar joint for aspiration and injection in horses. J Am Vet Med Assoc 1994;205:1177–1179.
