Wrist Arthrotomy Saline Load Test

Abstract

Background:

Failure to recognize a potential wrist arthrotomy may lead to missed septic arthritis and devastating sequelae. The saline load test is routinely used to recognize traumatic arthrotomies of other joints; however, there are limited data optimizing this test for the wrist. The purpose of this study was to investigate and perform saline load testing to identify traumatic arthrotomies of the wrist.

Methods:

This was a cadaveric study of 15 wrists. Traumatic arthrotomies were created using a blunt trocar through the 3-4 portal. A 3-mL syringe with 0.1 mL markings was used to inject methylene blue dyed saline into the wrist through the 1-2 portal. Once extravasation was visible from the atherectomized site, the volume was recorded.

Results:

The mean (range) volume injected to identify the arthrotomy of all wrists was 1.22 mL (range, 0.1-3.1 mL). Multivariate regression demonstrated that cadaver age, laterality, and extension range of motion were not significantly associated with the injected saline volume at extravasation (P > .05, each). Greater joint range of motion was independently associated with higher saline volume load for extravasation (odds ratio: 1.049; 95% confidence interval: 1.024-1.075; P = .003).

Conclusions:

We found that 2.68 and 3.02 mL of methylene blue dyed saline offered 95% and 99% sensitivity, respectively, for diagnosing traumatic wrist arthrotomy. The maximum volume of saline needed to recognize an arthrotomy was 3.1 mL. We recommend this be the minimum volume used to evaluate a traumatic wrist arthrotomy.

Introduction

Traumatic arthrotomies of the wrist are severe, difficult to recognize injuries. They must be efficiently identified as they may result in septic wrist arthritis, leading to potentially devastating patient outcomes.^1-5 They are difficult to recognize because a small laceration may extend deeper than is obvious by inspection alone. Prior studies have demonstrated that following septic wrist arthritis, patients can lose 50% of wrist range of motion and 70% of grip strength compared with their contralateral wrists. ⁴ Lack of appropriate early care has been shown to require multiple debridements and salvage procedures to obtain source control, including carpectomies, wide soft tissue debridement, and forearm amputations. ⁴ Furthermore, time to surgical intervention is directly proportional to numbers of surgical procedures needed and inversely proportional to patient outcomes. ⁵ Notably, surgical debridement occurring fewer than 10 hours after diagnosis reliably leads to good outcomes, whereas delaying intervention by 16 hours portends poor outcomes. ⁵ As such, establishing efficacy of an easily administered test is crucial.

The saline load test is a well-described reliable tool to assess traumatic arthrotomies. ¹ Arthrotomy-sensitivity guidelines have been previous published on the saline load test in other major joints, including the knee, ankle, shoulder, and elbow, but information is limited on its application in the wrist.^1,3,6-10 Previous studies have proposed computer tomographic scans as a reliable option for arthrotomy identification^11,12; however, these are expensive and not always readily available. ¹ The saline load test for the wrist joint potentially offers providers an inexpensive, reliable, point-of-care tool for diagnosis of an arthrotomy.

Therefore, the purpose of this study was to identify the saline volume resulting in extravasation following wrist arthrotomy with 95% and 99% sensitivity. Wrist arthrotomies were created in cadaveric models, and saline load tests were subsequently performed.

Materials and Methods

This was a cadaveric study of 15 wrists. Only wrists without evidence of prior surgery or obvious trauma were included. The cohort consisted of 12 cadavers; the mean age of the 15 wrists was 78.2 years (range, 65-87 years). In all, 86.7% (13 of 15) of the wrists were from male cadavers, and 60% of the 15 included specimens were right wrists.

Prior to arthrotomy creation, the absolute passive range-of-motion value of each included wrist was recorded using a goniometer (Table 1).

Table 1.

Baseline Characteristics of the Included Cohort.

Variable	Mean (range) or count (%)
N	15
Age, y	78.18 (86-65)
Sex (male)	13 (86.7)
Laterality (right)	9 (60)
Flexion range of motion, deg	69.33 (40-84)
Extension range of motion, deg	58.20 (40-70)
Total joint range of motion, deg	127.53 (100-154)
Saline load to extravasation, mL	1.22 (0.1-3.1)

An arthrotomy was performed from the dorsal aspect of the wrist through the standard 3-4 compartment portal; this location was chosen for arthrotomy creation, due to easily palpable and reproducible anatomical landmarks. A superficial 1-cm incision was made using an 11 blade just distal to Lister’s tubercle (Figure 1). Following blunt spreading to the joint capsule, an arthrotomy was created using a blunt trocar (Figure 2). The standard 1-2 compartment portal was identified, and a 3-mL syringe with 0.1 mL markings was inserted with the wrist in neutral position, followed by injection of methylene blue dyed saline (Figure 3). Saline was injected at a standardized rate of 0.1 mL per second. Once extravasation was visualized from the arthrotomy site, the injected volume was recorded. After performing the arthrotomy and injection, the wrist joint was opened to confirm the intra-articular location of methylene blue. All experiments on each specimen were performed by 2 of the authors (M.C. and J.P.S.); while 1 author created the arthrotomy and injected, the other monitored and recorded volume.

Figure 1.

Superficial incision using an 11 blade just distal to Lister’s tubercle without arthrotomy.

Figure 2.

Breach of the joint capsule with a blunt trocar.

Figure 3.

Methylene blue dyed saline joint loading using the 1-2 compartment portal via a 3-mL syringe with 0.1 mL markings.

Descriptive statistics were performed for results. Data were reported as means and ranges for continuous variables, and frequencies and proportions for categorical variables. Multivariate regression analysis was used to evaluate whether associations of age, laterality, or joint range of motion and injection volumes existed. The test sensitivity at 95% and 99% was calculated. Multivariable regression analyses were performed to determine whether age, laterality, or joint range of motion had any effect on volume.

Results

Fifteen wrists were included in the experiment. The mean (range) flexion and extension were 69.3° (40°-80°) and 58.2° (40°-70°), respectively. The mean total range of motion was 127.5° (100°-154°). The mean (range) volume injected to identify arthrotomies was 1.2 mL (range, 0.1-3.1 mL). There were no significant associations of laterality (P = .290), or cadaveric age (P = .111) and injection volume (Table 2). Greater joint range of motion was independently associated with a higher saline volume load at extravasation (odds ratio: 1.049; 95% confidence interval: 1.024-1.075; P = .003).

Table 2.

Multivariate Regression Outlining the Association Between Baseline Determinants and the Volume of Saline Required for Extravasation.

Predictor	Odds ratio	95% confidence interval	P value
Age	1.059	0.994-1.126	.111
Laterality (reference: right)	0.611	0.259-1.443	.290
Joint range of motion	1.049	1.024-1.075	.003

Injection volumes of 2.68 and 3.02 mL were required to detect wrist arthrotomies at sensitivities of 95% and 99%, respectively. None of the included wrists required an injected volume >3.1 mL to detect arthrotomy.

Discussion

Traumatic arthrotomies of the wrist can present a challenge to the treating physician and require early diagnosis and surgical intervention. Failure to properly recognize and treat a wrist arthrotomy to prevent a fulminant septic arthritis has been shown to have devastating outcomes.^4,5 Developing an efficient, easily administered, and dependable diagnostic test is therefore crucial for appropriate patient care. The saline load test has been proven reliable in other joints, but few studies have described its applicability to the wrist.^1,3,6,9-11 We created traumatic wrist arthrotomies in 15 cadaver specimens and performed the saline load test to determine with 95% and 99% specificity the volume required to cause extravasation. We found that the range of volume to diagnose a traumatic arthrotomy of the wrist was 0.1 to 3.1 mL, with a mean of 1.23 mL, and volumes needed for 95% and 99% specificity were 2.68 and 3.02 mL, respectively.

This study adds to the current literature on traumatic wrist arthrotomies. Of the published reports evaluating the saline load test for wrist arthrotomy detection, there is wide variance in recommendations.^3,10 One previous study on 7 cadaveric wrists determined that loading with 7 and 9 mL of saline offered 95% and 99% sensitivity for a wrist arthrotomy. ¹⁰ Notably, this study created arthrotomies using an 11-blade puncture wound rather than a blunt instrument and did not use dyed saline for injection, which could make visualization more difficult. ¹⁰ Another prospective study by Goyal et al ³ on 20 patients undergoing wrist arthroscopy determined that following a 0.5-mm arthrotomy, 2.3 and 2.5 mL were required to detect extravasation with 95% and 99% sensitivity. This study had the benefit of being performed in vivo on a younger patient population (mean, 41.2 years). However, 20% of the patients included had prior wrist surgeries, which may affect the joint capsule. Moreover, performing this test with the wrist in traction may alter the capsular anatomy and may not represent a realistic diagnostic scenario. Given these variances in results and recommendations, it becomes important to study this further. Table 3 summarizes results of prior articles and this study

Table 3.

Summary of Wrist Arthrotomy Studies.

Study	Study type	Population	Number of wrists	Mean (range) of SLT volumes	95% sensitivity	99% sensitivity
Goyal et al 3	Prospective	In vivo	20	0.8 mL (0.2-2.5 mL)	2.3 mL	2.5 mL
Gittings et al 10	Cadaveric	Ex vivo	7	4 mL (2-7 mL)	7 mL	9 mL
Scollan et al	Cadaveric	Ex vivo	15	1.22 mL (0.1-3.1 mL)	2.68 mL	3.02 mL

Note. SLT = saline load test.

There are several limitations to this study. Experiments were performed on cadavers, and all arthrotomies were made at the 3-4 portal through a 1-cm superficial skin incision and blunt trocar introduction through the joint capsule. These controlled, replicated arthrotomies cannot characterize the broad range of possible traumatic wrist arthrotomies in terms of methodology, location, and extent of capsular disruption. Nevertheless, the blunt trocar created a small simulated arthrotomy with a minimal footprint; this likely allows for more instillation of saline before extravasation, theoretically optimizing the results. This more closely imitates a trauma than simply using an 11-blade stab incision as had been done in a previous study. ¹⁰ In a traumatic setting, there may be confounding effects of hematomas, hemarthroses, and synovial fluid present, for which this study could not account. Of the cadaver specimens available, only 2 were women; as men are typically larger, this may also confound our results. By determining volume by witnessing extravasation through the skin defect created, this study could not control for possible subcutaneous extravasation of saline. However, as this possibility is also unable to be accounted for in clinical practice, wherein subcutaneous extravasation is also possible and perhaps even more likely due to potentially extensive subcutaneous traumatic degloving injuries, we did not attempt to control for this confounding effect.

Although our 95% and 99% sensitivity volumes may overestimate the actual volume needed, this does decrease the likelihood of a provider preforming the test appropriately and failing to identify a small arthrotomy, resulting in a false-negative test result. An additional limitation is the cadaver population that was included. The specimens were on average older individuals and predominantly men. Considering we found a significant association between joint range of motion and capsular volume, an older study population with more arthritic wrists and smaller joint spaces is likely to require a smaller extravasation volume than a young person. Although this may lead to an underestimation of saline volume needed to extravasate, we expect that the small arthrotomies performed would mitigate this possible specimen bias. Notably, the reported in vivo study by Goyal et al was performed on a younger study population than our cadavers and recommended similar, and in fact, lower SLT volumes for 95% and 99% sensitivity. ³ Therefore, while range of motion may have a statistically significant impact on SLT volume, it is unclear whether it makes a clinically significant impact. Despite these limitations, this study represents the largest cadaveric study group to date on the saline load test in wrist arthrotomies and helps to establish diagnostic recommendations for providers. This study also offers a platform for future studies to build and improve on.

Traumatic wrist arthrotomies may be challenging to diagnose and require urgent surgical debridement to prevent reported devastating consequences.^4,5 To provide physicians an accurate tool for diagnosis, we performed the saline load test on wrist joints in a cadaveric model. We found that performing this test with 2.68 and 3.02 mL of methylene blue dyed saline offers a 95% and 99% sensitivity for diagnosing traumatic arthrotomy. The maximum volume of a saline load test to recognize a traumatic arthrotomy to the wrist was 3.1 mL. This volume closely resembles a similar investigation performed in vivo. ³ We recommend that 3.1 mL be the minimum volume used to evaluate a traumatic wrist arthrotomy.