Abstract
Background
Intra-articular injections are a standard therapy and diagnostic tool for a variety of wrist conditions. Accurate needle placement is crucial for proper therapeutic benefit and prevention of complications. While some studies claim accurate needle placement requires imaging, others conclude that anatomical guidance is sufficient. This study aimed to evaluate the accuracy of intra-articular wrist needle placement with the ulnocarpal approach across differing levels of training using clinical anatomy alone.
Methods
Fourteen fresh-frozen, above-elbow cadaveric specimens were used. Intra-articular needle placement into the wrist via an ulnocarpal approach was attempted by nine study participants: two interns, two junior-level residents, two senior-level residents, two hand fellows, and one attending hand surgeon. Each injection was performed based on clinical examination and landmarks alone. The number of attempts and total time taken for each injection was recorded.
Results
Overall success rate was 71%, (89 of 126 attempts) and did not vary significantly across levels of training. Average time for needle placement among all participants was 10.9 ± 6.5 seconds. Timing of successful intra-articular needle placement (10.4 ± 5.2 seconds) significantly differed between levels. However, timing did not trend in any direction with more or less training. No significant difference was noted in total attempts or attempts with successful outcomes when comparing level of training.
Conclusion
The ulnocarpal approach is a viable option for injection or aspiration of the wrist without image guidance. We were unable to show any relevant trends with timing or number of attempts in comparison to level of training.
Level of Evidence: V
Keywords: ulnocarpal, intra-articular needle placement, wrist, level of training
Introduction
Therapeutic intra-articular injections are routinely performed in painful joints of the hand and wrist.1 The wrist is a complex synovial joint consisting of the articulation between the distal radius, ulna, and proximal carpal row. Dislocations, chronic instability, and osteoarthritis may all cause functional and often painful limitations. In patients who fail early conservative management, injections may be considered.2 Additionally, arthrocentesis is an important diagnostic tool for various arthritic conditions.
Accurate placement of the needle is of paramount importance in achieving desired therapeutic benefit and reducing the incidence of complications.1 Although recent studies suggest the use of imaging guidance for injections, many support the use of anatomic landmark palpation to inject without the aid of fluoroscopy or ultra-sound.1,3,4 The dorsal approach is commonly advocated for wrist injections and arthrocentesis.5 The approach is just distal and ulnar to Lister’s tubercle, between the distal radius and lunate. It utilizes the palpable sulcus between the extensor pollicis longus (EPL) and the index finger extensor digitorum communis (EDC) tendon.6 We hypothesized that an ulnocarpal approach similar to the 6U arthroscopy portal would be more accurate than the traditional dorsal approach when performing anatomically based intra-articular injections.
Methods
Fourteen fresh-frozen, above-elbow cadaveric specimens were obtained for completion of this study (75.7 ± 11.6; 8 F, 6 M; 7 left, 7 right). Prior to the start of the study, each specimen was deidentified and numbered 1-14. Specimens were allowed sufficient time for thawing prior to any attempt at injection to allow for adequate palpation of landmarks. Two specimens were noted to have healed surgical scars on the volar wrist, and after completion of the injections, they were confirmed fluoroscopically to have distal radius plates in place. We did not exclude these cadavers, as these variations are likely encountered in a clinical setting in which intra-articular wrist access would be necessary.
Nine participants from various levels of orthopedic surgery training were recruited to complete the injections: two interns (PGY-1), two junior-level residents (PGY-2 and 3), two senior-level residents (PGY-5), two Hand/Upper Extremity fellows, and one practicing orthopedic hand surgeon (10 years in practice). As a group, the participants were instructed on how to complete intra-articular needle placement in the wrist via an ulnar approach. The instruction consisted of a single demonstration and explanation by the participating attending physician just prior to the start of the study. Participants were instructed to palpate the ulnar head and ulnar styloid and locate the extensor carpi ulnaris (ECU) tendon running over the distal ulna on the dorsal-ulnar aspect of the wrist. Palpating just ulnar to the ECU tendon will identify a “soft-spot” that correlates with the ulnar fovea and the intra-articular space that the needle should be directed towards. The triquetrum also forms the distal border of this portal and its slope runs slightly retrograde going ulnarly to radially, thus the needle should also be angled in a slightly retrograde fashion as well. Of note, this injection approach is comparable to the intra-articular wrist access gained using the 6U wrist arthroscopy portal.
Each study participant then attempted to insert a 25-gauge injection needle into the wrist joint via the described ulnar approach. This process was completed in each of the 14 cadaveric specimens. The total number of attempts per cadaver was recorded, and the collective attempts on each cadaver were timed until the participating surgeon was satisfied with the location of the needle. After insertion of the needles, they were left in place for fluoroscopic examination. Two blinded orthopedic residents who did not participate in the injections performed anteroposterior (AP) and lateral fluoroscopic images of each wrist to confirm the location of the needles as intra-or extra-articular (Figures 1-2). When definitive confirmation was difficult to obtain with the two orthogonal images, an air arthrogram under live fluoroscopy was performed.
Figure 1.
Intra-articular needle placement. Anteroposterior (a) and lateral (b) view of successfully-placed intra-articular needle.
Figure 2.
Extra-articular needle placement. Anteroposterior (a) and lateral (b) view of unsuccessful needle placement attempt.
The primary outcome measure included determining the accuracy of intra-articular wrist injection via an ulnar approach and comparing accuracy across different levels of training. Secondarily, the number of attempts and total time taken to perform each injection was recorded to evaluate efficiency across the various levels of training. Study participants were blinded to their performance during the study. Additionally, surgeons performing fluoroscopic evaluation and those performing statistical analysis remained blinded. A Pearson Chi-square test was used to compare accuracy among the different levels of training. One-way ANOVA was used to compare timing and number of attempts between different levels. A two-sample t-test was used to compare outcome parameters between successful attempts and non-successful attempts.
Results
Fourteen cadavers were included in the study; seven were left elbows and seven were right elbows. The mean age was 75.7 ± 11.6 years with eight female and six male elbows. Among all participants, the accuracy rate was 71% with 89 of the 126 injections being confirmed as intra-articular with the majority of misses being either midcarpal or dorsal. Accuracy did not vary significantly across different training levels (p = 0.466) (Table 1).
Table 1.
Comparison of Successful Intra-Articular Needle Placement and Mean Time to Needle Placement by Training Level
| Training Level | Successful N (%) | Total (N) | p-value |
|---|---|---|---|
| Attending | 10 (71.4) | 14 | |
| Fellow | 20 (71.4) | 28 | |
| Senior | 21 (75) | 28 | 0.466 |
| Junior | 22 (78.6) | 28 | |
| Intern | 16 (57.1) | 28 | |
| Total | 89 (70.6) | 126 | |
| Training Level | Mean time to needle placement, seconds (±S.D.¥) | Attempts (N) | p-value |
| Attending | 12.0 (±8.9) | 14 | |
| Fellow | 8.1 (±3.6) | 28 | |
| Senior | 8.7 (±3.6) | 28 | <0.001 |
| Junior | 15.3 (±8.7) | 28 | |
| Intern | 11.1 (±4.7) | 28 | |
| Total | 10.9 (±6.5) | 126 |
¥Standard deviation
The average time for needle placement, whether successful or unsuccessful, among all participants was 10.9 ± 6.5 seconds. There was a significant difference in timing between levels of training (p<0.001) (Table 1). The average time for successful placement of the needle among all participants was 10.4 ± 5.2 seconds; for unsuccessful placement, it was 12.3 ± 8.8 seconds (p = 0.139) (Table 2). When evaluating the timing of only successful intra-articular needle placement, a significant difference (p<0.001) was present when comparing the junior-level residents’ time to each other level of training (Table 3).
Table 2.
Comparison of Time Taken For Placement of Needle Between Successful and Unsuccessful Attempts
| Outcome | Attempts (N) | Mean time to needle placement, seconds (±S.D.¥) | p-value |
|---|---|---|---|
| Successful | 89 | 10.4 (±5.2) | 0.139 |
| Unsuccessful | 37 | 12.3 (±8.8) |
¥Standard deviation
Table 3.
Comparison of Average Number of Number of Attempts and Average Time For Successful Intra-Articular Needle Placement by Training Level
| Training Level | Mean number of attempts (±S.D.¥) | Number of successfully placed attempts (N) | p-value |
|---|---|---|---|
| Attending | 1.3 (±0.5) | 10 | |
| Fellow | 1.4 (±0.5) | 10 | |
| Senior | 1.6 (±0.7) | 11 | 0.408 |
| Junior | 1.7 (±0.6) | 11 | |
| Intern | 1.4 (±0.2) | 6 | |
| Total | 1.5 (±0.6) | 48 | |
| Training Level | Mean time to needle placement, seconds (±S.D.¥) | Number of successfully placed attempts (N) | p-value |
| Attending | 10.6 (±4.1) | 10 | |
| Fellow | 8.5 (±3.2) | 10 | |
| Senior | 8.5 (±2.2) | 11 | <0.001 |
| Junior | 14.5 (±2.8) | 11 | |
| Intern | 8.6 (±1.1) | 6 |
¥Standard deviation
The average number of total attempts among all participants was 1.6 ± 1.07, and there was no significant difference noted between different levels of training (p = 0.291). Similarly, no difference was noted when comparing total number successful versus unsuccessful attempt (1.53 ± 0.89; 1.76 ± 1.4; p = 0.275) outcomes. When evaluating number of attempts to achieve only successful intra-articular needle placement, the average number of attempts among all participants was 1.5 ± 0.6, and this value was not statistically significant when comparing levels of training (p = 0.408) (Table 3).
Discussion
The overall success rate of intra-articular needle placement was 71%, and this was comparable to previously cited accuracy rates of 50-97% when using the traditional dorsal approach to the wrist.3,4,7–9 Luz et al., Cunnington et al., and To et al. compared the accuracy of anatomically-based injections with image-guided injections for a dorsal wrist approach, and found no increase in accuracy using image guidance. There are currently no studies reporting the accuracy of injections via the ulno-carpal approach using clinical assessment alone.
Our study found no significant difference between the accuracy rates or number of attempts between the different levels of training. There was a significant difference in timing between levels of training, specifically when comparing the junior-level residents’ time for successful intra-articular placement to the other levels of training.
However, this difference does not seem to be relevant as there are no other pertinent trends in timing, accuracy rates, or number of attempts in comparison to level of training. Similarly, other studies have also reported confounding results in regard to different levels of training. One clinical study found that their junior-level trainees had significantly higher accuracy rates for joint injections when using ultrasound guidance compared to their senior trainees and consultants using clinical examination.7 Another study looking at accuracy of common hand injections reported that a participant with fewer years of experience had better overall accuracy rates without using image guidance compared to another participant with more years of experience.3 Due to the contradictory nature of these findings, the results of this study support the previous literature.
Prior to attempting access to the wrist, study participants were briefly educated on the ulnocarpal approach. Participants were instructed to palpate and locate the extensor carpi ulnaris (ECU) tendon and place the needle just ulnar to the ECU tendon in the “soft-spot” that correlates with the intra-articular space. Our study did not evaluate for nearby structures at risk, but this is similar to the 6U wrist arthroscopy portal, which is not routinely used because of its proximity of the dorsal sensory branch of the ulnar nerve.10 Additionally, the triangular fibrocartilage complex is also close in proximity and is at theoretical risk for injury when using the ulnocarpal approach.
Our study does have the same limitations commonly associated with cadaveric studies in that it is difficult to extrapolate clinical outcomes in a patient undergoing injection via this approach. Although there was variety in the levels of orthopedic surgery training, this study only had a total number of nine participants. It is possible that a larger number of participants would discern further statistical differences in regard to levels of training. The presence of an additional attending physician may have also uncovered more statistically significant trends. Another limitation was the need for use of radiographic confirmation of needle placement whereas normally there is the expected tactile feedback associated with an injection. For equivocal cases, needle location was determined by air arthrograms performed by two independent observers. Air arthrograms have been reported in literature as an acceptable alternative to dye arthrograms.11 Air arthrograms were chosen for this study over dye arthrograms as dye could have played a factor in obscuring anatomical landmarks on radiographic imaging and would have limited the repeated use of cadavers in the study.
The strengths of this study include a large number of total attempts across a variety of training levels. Also, anatomic variability was not a confounding factor in this study since all participants used the same cohort of wrists. The use of a small-caliber (25G) needle was purposefully chosen to help limit the creation of visible skin punctures, keeping the participants blinded to previous entry sites made by other study participants. Also, each participant was not aware of their performance during the study, which helped to prevent technique adjustments. Future studies should include an image-guided ulnocarpal approach for direct comparison of accuracy rates and an in vivo study to evaluate clinical outcomes.
Knowledge of multiple approaches for joint injection and aspirations is a helpful tool for providers in a variety of clinical situations including limited joint access due to skin integrity or anatomy variation. This study proposes a viable, alternative approach for wrist injections and aspirations that is not dependent on image guidance or user experience level. The 71% success rate is comparable to cited rates of successful intra-articular needle placement of the wrist with and without the use of supplemental imaging which can add procedural time, resources, and cost.
The level of participant training did not have an effect on the number of attempts or outcomes for successful intra-articular placement of the needle. It is plausible to consider the use of image guidance to achieve greater confidence of intra-articular needle placement of the wrist and to assist with navigation of difficult anatomic variations and avoidance of known structures at risk including the dorsal sensory branch of ulnar nerve and the triangular fibrocartilage complex.
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