Comparing the Interobserver Reliability of 4 Methods Used to Measure Knee Laxity on Coronal Plane Stress Radiograph

Background

Varus and valgus knee stress radiographs provide valuable information in the pre- and postoperative evaluation of joint laxity in patients with multiligament knee injuries (MLKIs).

Purpose

To review the literature for described techniques of quantifying laxity on coronal stress radiographs of the knee and identify the most reliable method.

Study Design

Cohort study (diagnosis); Level of evidence, 3.

Methods

A thorough literature search using the MEDLINE and Embase databases identified 4 studies with distinct methods for objectively measuring laxity on varus and valgus stress radiographs: Heesterbeek et al (2008), Jacobsen (1976), LaPrade et al (2004), and Sawant et al (2004). To compare these methods, 200 coronal plane stress radiographs from 50 patients with MLKIs were retrospectively reviewed from an MLKI database at a single institution. The amount of varus and valgus laxity on each radiograph was measured independently by 4 reviewers using each method. Intraclass correlation coefficients (ICCs) with 95% CIs were calculated to assess the interobserver reliability of each method overall and the varus and valgus measurements individually.

Results

For all 4 methods, the overall interobserver reliability was considered at least moderate. The method by Heesterbeek et al proved to have the highest interrater reliability in all domains-overall (ICC, 0.87 [95% CI, 0.85-0.90]), valgus (ICC, 0.83 [95% CI, 0.78-0.88]), and varus (ICC, 0.87 [95% CI, 0.83-0.90])-demonstrating good to excellent reliability both overall and in varus measurements and showing good reliability in valgus measurements. The method by Sawant et al demonstrated good reliability in valgus measurements. All other measures demonstrated moderate reliability.

Conclusion

Available methods for measuring knee joint laxity on varus and valgus knee stress radiographs in patients with MLKIs demonstrated moderate to good interobserver reliability. The method described by Heesterbeek et al proved to have the highest reliability overall as well as in measurements on varus and valgus views individually.

Usefulness of Force-Controlled Pelvic Stress Radiograph in the Evaluation and Treatment of Fragility Fractures of the Pelvis in Geriatric Patients: A Pilot Study

This study aimed to investigate the usefulness of force-controlled pelvic stress radiographs in the evaluation and treatment of fragility fractures of the pelvis (FFP) using a functional treatment strategy. We conducted a retrospective study of 55 geriatric patients with FFP who underwent pelvic stress radiographs on admission. The differences in the sacral width, pelvic ring width, and medial femoral head width between the radiographs with and without the Sam Sling II M size were defined as Δ sacral width, Δ pelvic ring width, and Δ medial femoral head width, respectively. We used Pearson's correlation test to assess the relationship between the degree of radiographic instability and the Johns Hopkins highest level of mobility scale (JH-HLM) at 10-days postadmission. Conventional receiver-operating-characteristic curve analysis was used to identify cases requiring surgery using the best cutoff value for radiographic instability. The JH-HLM was significantly correlated with Δ sacral width (r=-0.401, p=0.017), but not with Δ pelvic ring width (r=-0.298, p=0.080) nor with Δ medial femoral head width (r= -0.261, p=0.128). The best cutoff value of Δ sacral width in identifying surgical cases was 10.7 mm (sensitivity 75.0%, specificity 98.0%). Force-controlled pelvic stress radiographs could be helpful in assessing the need for surgery on admission.

What is the Optimal Posterior Cruciate Ligament Tension to Achieve Patient Satisfaction in Cruciate-Retaining Total Knee Arthroplasty?

INTRODUCTION

Achieving adequate posterior cruciate ligament (PCL) tension is important during PCL-retaining total knee arthroplasty (CR-TKA), but the effect of PCL release on this tension is unpredictable. This study assessed the relationship between postoperative PCL laxity and patient satisfaction at a 2-year follow-up.

METHODS

There were 44 varus osteoarthritis knees undergoing CR-TKA included. The PCL tension was adjusted by resizing the femoral component and modifying the posterior tibial slope, without PCL release. Postoperative PCL laxity at 90° of knee flexion was defined as the difference in radiographic anterior-posterior tibial translation with or without an 80-Newton posterior load at the tibial tubercle measured using a load device. Four subgroups were defined according to the PCL laxity: laxity ≤0 mm (n = 5); 0 mm < laxity ≤2 mm (n = 19); 2 mm < laxity ≤4 mm (n = 10); and laxity >4 mm (n = 10). The effect of PCL laxity on the 2-year postoperative 2011 Knee Society Score was determined.

RESULTS

The femoral component was downsized in 27 of 44 knees, while the posterior tibia slope was increased in 6 of 44 knees, but no PCL was released intraoperatively. The 2011 Knee Society Score subscores improved significantly from preoperatively to postoperatively, and patients reported "neutral satisfaction" or better after 96% of operations. The mean PCL laxity was 2.3 mm on postoperative stress radiographs, and postoperative satisfaction scores were significantly highest in the subgroup with 2-4 mm laxity.

CONCLUSION

CR-TKA was successfully performed without PCL release. Moderate PCL laxity (2-4 mm) achieved excellent postoperative satisfaction.

Coronal Laxity at Flexion is Larger After Posterior-Stabilized Total Knee Arthroplasty Than With Cruciate-Retaining Procedures

BACKGROUND

It is unclear whether coronal stability differs between cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA). The purpose of this study was to compare coronal laxity, radiological, and clinical outcomes between CR-TKA and PS-TKA.

METHODS

Seventy five CR-TKAs and 72 PS-TKAs with a minimum 2-year follow-up were retrospectively evaluated. Coronal laxity was assessed at knee extension and 80° of flexion on varus and valgus stress radiographs. Radiological evaluation included femoral-tibial angle, hip-knee-ankle angle, and positions of femoral and tibial components. Clinical evaluation included the modified Hospital for Special Surgery score, the Western Ontario and McMaster Universities Osteoarthritis index, and range of motion.

RESULTS

PS-TKA resulted in significantly larger varus, valgus, and total laxities at 80° flexion (P = .034, .031, and 0.001, respectively) compared with CR-TKA, while no significant difference was found at extension (P = .513, .964, and .658, respectively). No statistical difference was found in radiological and clinical outcomes between CR-TKA and PS-TKA, but the functional scores were slightly better in CR-TKA. There were adverse correlations between varus laxity at flexion and the Western Ontario and McMaster Universities Osteoarthritis index, the modified Hospital for Special Surgery score, and range of motion (r = 0.933, -0.229, -0.472, respectively).

CONCLUSION

Coronal laxity at 80° of flexion was larger after PS-TKA than CR-TKA. In addition, clinical outcomes were adversely affected by the larger varus laxity at flexion. Care should be taken to maintain the coronal stability, especially at flexion, during surgery to obtain better patient-reported outcomes.

LEVEL OF EVIDENCE

Level III.

Effect of Lateral Gutter Osteophyte Resection on Correction of Varus Deformity in Arthroscopic Ankle Arthrodesis

BACKGROUND

Recently, arthroscopic ankle arthrodesis has been performed for moderate-to-severe varus-deformed ankle osteoarthritis. However, the effect of osteophyte resection in the lateral gutter in arthroscopic ankle arthrodesis has not been clarified. We hypothesized that a varus-deviated ankle with lateral gutter osteophytes can be corrected by osteophyte resection.

METHODS

Thirty-nine ankles of 38 patients were included. The mean age of patients was 70.0 (45-83) years. The patients were divided into the following groups: group with an osteophyte in the lateral gutter (osteophyte) and group with no osteophytes (nonosteophyte). Preoperative and postoperative tibiotalar angle, tibial plafond angle, and tibiotalar angle under valgus stress, as well as the Japanese Society for Surgery of the Foot (JSSF) ankle/hindfoot scale, were recorded. Twelve ankles underwent lateral gutter osteophyte resection, whereas the other 27 ankles did not require osteophyte resection.

RESULTS

Preoperative tibiotalar angle was higher in the osteophyte group than in the nonosteophyte group (21.8 vs 11.2 degrees, P = .01). The tibiotalar angle in the preoperative valgus stress imaging was higher in the osteophyte group (12.9 vs 5.7, P < .01). However, the postoperative tibiotalar angle was similar between the 2 groups (7.1 vs 5.4, P = .183). JSSF ankle/hindfoot scale improved in both groups.

CONCLUSION

Lateral gutter osteophyte resection enabled correction of the varus malalignment in arthroscopic ankle arthrodesis.

LEVEL OF EVIDENCE

Level III, retrospective comparative series.

Initial Fibular Displacement as a Predictor of Medial Clear Space Widening in Weber B Ankle Fractures

BACKGROUND

The diagnosis of medial ankle instability in Weber B ankle fractures remains controversial. Manual stress and gravity stress radiographs as well as magnetic resonance imaging (MRI) are used, but there is no consensus gold standard. The purpose of this study was to determine the relationship between initial fibular displacement and medial clear space widening on a gravity stress radiograph as a predictor of instability.

METHODS

A retrospective review was conducted of all patients with isolated Weber B ankle fractures with both initial injury radiographs and gravity stress view from August 1, 2014, through April 1, 2016. A total of 17 patients were identified. On the mortise view of initial injury radiographs, medial clear space (MCS), superior clear space, lateral fibular displacement (LFDP), and fibular shortening (FS) were measured, and on the lateral view, anterior to posterior fibular gap (A to P FG) was measured. MCS was again measured on the gravity stress view (MCS-W). Statistical analyses identified the correlations of each displacement variable relative to MCS-W as well as the sensitivity and specificity of each parameter.

RESULTS

A cutoff point for MCS-W was set as less than 5.0 mm (n = 8) and 5.0 mm or more (n = 9). Strong significant correlations with MCS-W were found for A to P FG (0.84, P < .001), with a trend for LFDP (0.62, P = .008), but no significance with FS (0.38, P = .84). Linear regression analysis revealed significant ability to predict MCS-W for both LFDP ( P = .002) and A to P FG ( P = .001) but not FS. Receiver operating characteristic analysis for A to P FG using a threshold value of 1.0 mm yielded sensitivity and specificity of 100% in predicting an MCS-W of 5.0 mm or more.

CONCLUSION

The initial fibular displacement was a strong predictor of MCS-W in Weber B ankle fractures. On lateral radiographs, an A to P FG greater than 1.0 mm showed a sensitivity and specificity of 100% in predicting an MCS-W of 5.0 mm or more on gravity stress view.

LEVEL OF EVIDENCE

Level III case series, prognostic.

Does Foot Position and Location of Measurement Influence Ankle Medial Clear Space?

PURPOSE

There is still controversy regarding normal and abnormal values of the medial clear space (MCS) of the ankle. The aim of this study was to assess how much different degrees of plantar flexion, with and without stress, influenced the MCS.

METHODS

We submitted 30 volunteers to 6 different anteroposterior ankle radiographs in the following positions: neutral, neutral with external rotation stress, physiologic plantar flexion (FPF), physiologic plantar flexion with external rotation stress, maximum plantar flexion (MPF), and maximum plantar flexion with external rotation stress. The MCS oblique (MCSo) and perpendicular (MCSp) were measured in all images by an experienced foot and ankle surgeon.

RESULTS

The data showed that the position of the foot does influence the value of MCSp and MCSo ( P < .05), except for 3 comparisons. MCSo did not change between FPF with stress and MPF with stress. MCSp did not change in 2 situations: between FPF and neutral with stress and between MPF and FPF with stress.

CONCLUSIONS

This study is unique in showing that different ways of positioning the foot and performing stress radiographs results in different MCS values and that these values differ depending on the anatomical site where they are measured.

LEVELS OF EVIDENCE

Diagnostic, Level IV.

Magnetic Resonance Imaging and Stress Radiography in Chronic Lateral Ankle Instability

BACKGROUND

Studies regarding magnetic resonance imaging (MRI) findings of the lateral ankle ligaments in chronic lateral ankle instability and their clinical relevance for surgery are lacking. This study classified the lateral ankle ligament MRI findings of the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) in chronic lateral ankle instability (CLAI) and correlated these findings with ankle stress radiographs.

METHODS

We included 132 ankles with CLAI that underwent ligament reconstructions from 2006 to 2013. The distributions of the ATFL and CFL morphologies were evaluated using the following categories: (1) the amount of thickness: normal/thickened/attenuated/non-visualized, (2) the presence of discontinuity, (3) wavy or irregular contour, and (4) increased signal intensity on T2-weighted images. The relationships between the ligament morphologies and stress radiographs were analyzed.

RESULTS

The ATFL was normal in 5 (4%) ankles, thickened in 35 (27%), attenuated in 76 (58%), and non-visualized in 16 (12%), while the CFL was normal in 39 (30%) ankles, thickened in 42 (32%), attenuated in 44 (33%), and non-visualized in 7 (5%). Discontinuity of the ATFL or CFL was observed in 46 (35%) ankles. Wavy or irregular contours were observed in 55 (42%) ATFLs and 37 (28%) CFLs, and signal intensity of both ligaments was increased in 19 (14%) ankles. ATFL ( P < .001) and CFL thickness ( P = .007) correlated with the talar tilt angle.

CONCLUSIONS

The MRI findings of CLAI showed several morphologies and specific incidences for each morphology. Attenuated, wavy appearance was the most frequent MRI pattern. Thickness was related to the degree of instability.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

The Valgus Stress Radiograph Does Not Determine the Full Extent of Correction of Deformity Prior to Medial Unicompartmental Knee Arthroplasty

Routine preoperative stress radiographs have been advocated, in part, to determine "full correctability" of deformities before proceeding with unicompartmental knee arthroplasty (UKA) despite limited data supporting their utility. Fifty consecutive patients undergoing medial UKA with robotic navigation were studied. In 20° of flexion, significantly greater correctability was achieved after removal of osteophytes by an additional 1.8°, with a mean corrected alignment of 2.5° varus. Seventy-four percent of knees were not correctable to neutral alignment or more. In conclusion, preoperative stress radiographs have overstated value in patients undergoing medial UKA since the full extent of correctability of varus deformity cannot be determined until after removal of osteophytes and since most deformities are not fully correctable to neutral in UKA.

Surgical treatment of subacute and chronic valgus instability in multiligament-injured knees with superficial medial collateral ligament reconstruction using Achilles allografts: a quantitative analysis with a minimum 2-year follow-up

BACKGROUND

Symptomatic medial collateral ligament (MCL) instability is rare, and it is frequently associated with multiligament injuries. Most clinical investigations have failed to clearly define the specific objective outcome measures assessing the stability of the MCL quantitatively before and after the reconstruction procedure.

PURPOSE

To quantitatively evaluate the early clinical outcomes of patients with valgus instability of knee joints who had undergone superficial MCL reconstruction using Achilles tendon allografts.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

From August 2005 to December 2010, 19 consecutive patients with MCL injuries were included in this study. The inclusion criteria were (1) a subacute or chronic MCL injury, with a time from initial injury to surgery of longer than 3 weeks, and (2) valgus laxity graded C or D according to the International Knee Documentation Committee (IKDC). All patients underwent superficial MCL reconstruction using Achilles tendon allografts. To evaluate the laxity of the MCL preoperatively and postoperatively, valgus stress radiographs using a Telos device were used. Other assessments included the IKDC subjective functional evaluation and Lysholm score estimation.

RESULTS

Sixteen of the 19 patients (12 men and 4 women) were available for final follow-up. The median age of the patients was 37 years (range, 19-53 years); mean body mass index (BMI) was 26.4 (range, 21.7-29.4). The mean time from injury to surgery was 15.9 months (range, 24 days to 84 months), and median follow-up period was 34 months (range, 24-67 months). The mean medial knee laxity (side-to-side difference) was 8.9 ± 3.2 mm (range, 6-15.9 mm) preoperatively and 1.1 ± 0.9 mm (range, -1.1 to 3.2 mm) postoperatively (P < .001). The preoperative mean IKDC subjective knee functional score was 49.8 ± 6.9 (range, 31-57.5), while the postoperative functional score was 84.3 ± 6.0 (range, 71.3-93.1) (P < .001). The mean Lysholm score was 69.3 ± 5.9 (range, 55-78) preoperatively and 88.6 ± 5.0 (range, 75-95) postoperatively (P < .001). There was no significant correlation between patients' BMI and the final clinical outcome scores (P = .311).

CONCLUSION

In a small set of patients with multiligament-injured knees, valgus laxity can be effectively restored through surgical management with superficial MCL reconstruction, when the other associated ligament injuries are reconstructed as well. The subjective functional results were significantly improved postoperatively at short-term follow-up.