No abstract

Objective The purpose of this study was (1) to determine which risk factors for patellar instability were associated with the presence of patellofemoral cartilage lesions and (2) to determine how cartilage lesion presence, size, and grade affect postoperative disease-specific quality of life. Design Preoperative, intraoperative, and postoperative demographic, anthropometric (body mass index, Beighton score, hip rotation), radiographic (crossover sign, trochlear bump), cartilage lesion morphology (presence, size, location, grade), and outcomes data (Banff Patella Instability Instrument 2.0 [BPII 2.0]) were prospectively collected from patients undergoing isolated medial patellofemoral ligament reconstruction. For all knees ( n = 264), single and multivariable logistic regression was used to determine if any patellar instability risk factors affected the odds of having a cartilage lesion. In patients with unilateral symptoms ( n = 121), single variable linear regression was used to determine if the presence, size, or ICRS (International Cartilage Regeneration & Joint Preservation Society) grade of cartilage lesions could predict the 12 or 24+ month postoperative BPII 2.0 score. Results A total of 84.5% of knees had patellofemoral cartilage lesions (88.3% involved the distal-medial patella). Trochlear dysplasia (high grade: odds ratio = 15.7, P < 0.001; low grade: odds ratio = 2.9, P = 0.015) was associated with the presence of a cartilage lesion. The presence, size, and grade of cartilage lesions were not associated with 12 or 24+ month postoperative BPII 2.0 scores. Conclusions Trochlear dysplasia was a risk factor for the development of patellofemoral cartilage lesions in this patient population. Cartilage lesions most commonly involve the distal-medial patella. There was no significant relationship between patellofemoral cartilage lesion presence, size, or grade and postoperative BPII 2.0 scores in short-term follow-up.

Background: Kneeling posterior cruciate ligament (PCL) stress radiographs are commonly used to evaluate PCL laxity. Patients, however, report significant pain, and the method’s reproducibility may be challenged due to its dependence on patient body weight distribution to produce posterior tibial displacement. Weighted gravity stress radiography may offer better reproducibility and comfort than the kneeling technique, but its efficacy has not been studied. Hypothesis: Weighted gravity PCL stress radiographs will be more comfortable and produce similar measurements of side-to-side difference in posterior tibial displacement when compared with the kneeling technique. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: A total of 40 patients with nonoperatively or >6 months postoperatively treated PCL injuries (isolated or multiligamentous) underwent bilateral stress radiographs. Weighted gravity and kneeling stress radiographs were acquired, in random order, for each patient, as well as side-to-side difference in posterior tibial displacement between each knee, patient-reported visual analog scale knee pain (100 mm), time to acquire the images, and patient preference for technique. Paired t tests were used to compare the side-to-side difference, pain score, and time to complete the radiographs. Results: There was no difference between the 2 radiographic methods in the mean side-to-side difference (gravity: 6.45 ± 4.61 mm, kneeling: 6.82 ± 4.60 mm; P = .72), time required to acquire radiographs (kneeling: 307.3 ± 140.5 seconds, gravity: 318.7 ± 151.1 seconds; P = .073), or number of radiographs taken to obtain acceptable images (kneeling: 3.6 ± 1.6, gravity: 3.7 ± 1.7; P = .73). Patients reported significantly less knee pain during the weighted gravity views (kneeling: 31.8 ± 26.6, gravity: 4.0 ± 12.0; P < .0001). Of the patients, 88% preferred the weighted gravity method. Conclusion: Weighted gravity stress radiographs produce similar side-to-side differences in posterior tibial translation compared with the kneeling stress technique, but do not rely on patient weightbearing and provide significantly better patient comfort. Clinicians should therefore consider the use of weighted gravity stress radiographs in clinical practice to minimize the pain associated with stress radiography while allowing for accurate decision making.

Objectives: Kneeling stress radiographs are commonly used to evaluate posterior cruciate ligament (PCL) laxity. Patients, however, report significant pain, and reproducibility is challenged due to its dependence on patient body weight distribution to produce posterior tibial displacement (PTD). Weighted gravity stress radiographs may offer better reproducibility and comfort than the kneeling technique, but its efficacy has not been studied. Hypothesis: weighted gravity radiographs will be more comfortable and produce similar PTD measurements when compared to the kneeling technique. Methods: Patients 18-70 years old with non-operatively or >6 months post-operatively treated PCL injuries (isolated or multi-ligamentous) were recruited from two academic level one trauma centers to undergo bilateral PCL stress radiographs. Exclusions: open/bilateral injuries, fractures. Patients underwent PCL stress radiographs by two randomly ordered methods. Kneeling stress views: patients knelt on padded scales (separate for each knee) with the padding distal to the tibial tubercle. Patients were verbally encouraged to place equal weight on both knees (scale outputs not visible to the patient). A digital radiography plate was placed between the legs to acquire bilateral lateral radiographs. Weighted gravity stress views: Patients lay supine with their hip and knee at 90°with the heel supported. A 20 lb weight was placed on the anterior tibia just distal to the tibial tubercle. A lateral radiograph was taken and then repeated on the contralateral leg. Images were anonymized and uploaded to PACS for measurement. Outcomes: side to side difference (SSD) in translation of the posterior tibial condyles relative to the posterior femoral condyles (primary outcome); patient-reported VAS knee pain (100 mm) during the radiographs; time required to acquire the images; patient preference for technique. Statistics: sample size = 31 patients to detect a 2 mm difference (α=0.05, power 80%, SD = 2.8 mm [Jung, 2006]). Paired t-tests were used to compare the SSD between the kneeling and weighted gravity methods, VAS pain, and time to complete the radiographs. Results: 40 patients (77.5% male, 34.5 ± 12.8yrs old, 65% left knee) were recruited. 42.5% had undergone PCL reconstruction. There was no difference between the two radiographic methods in the mean SSD (kneeling = 6.29 ± 4.58 mm, gravity = 6.82 ± 4.60 mm, p= 0.61). There was no difference in the total time required to perform the radiographs (kneeling = 307.3 s ± 140.5 s, gravity = 318.7 s ± 151.1 s, p= 0.73) or the number of radiographs taken to obtain acceptable images (kneeling = 3.6 ± 1.6, gravity = 3.7 ± 1.7, p= 0.73). The amount of weight placed on each knee during the kneeling views differed slightly but was not significant (affected = 21.5 ± 11.3 kg, unaffected = 26.1 ± 12.1 kg, p= 0.09). There was significantly less knee pain reported for the gravity views (kneeling = 31.8 ± 26.6, gravity = 4.0 ± 12.0, p < 0.0001). 94.6% of patients preferred the gravity method. Conclusion: Weighted gravity PCL stress radiographs should be considered for use in clinical practice as they produce similar posterior tibial translation values to the kneeling technique, do not rely on patient weightbearing, and provide significantly better patient comfort.

with interest the article comparing the efficacy of kneeling stress radiographs and weighted stress radiographs to assess posterior cruciate ligament (PCL) deficiency by Holliday et al. 1 The authors set out well the benefits of a simple and inexpensive technique that is comfortable for the patient.Unfortunately, they did not discuss that, as with all stress radiograph techniques, the measurement of sideto-side differences of relative position of the tibia and the femur is problematic. This relates to the simple fact that a radiograph is a 2-dimensional (2D) reflection of a 3D reality. Axial malrotation of the leg will have a very adverse effect on the validity of measurements by moving in space bony landmarks referenced in measurements. In describing the technique of obtaining ''weighted gravity stress radiographs,'' the authors did not mention the importance of axial alignment of the leg (the tibia and the fibula). Presumably, one technique is to always maintain the foot with the ankle at 90°vertical. Furthermore, the authors themselves have fallen afoul of the problem of axial malalignment and difficulty in making accurate measurements. In the article, Figure 3 is used by the authors as an illustration of how to measure side-to-side difference in the position of the tibia relative to the femur. Unfortunately, it demonstrates 3 sources of error. First, the lines shown are not perpendicular to the tibial plateaux as the authors state they should be, nor is the tibial line on the right radiograph of a knee with PCL deficiency, midway between the posterior limits of the medial and the lateral tibial plateaux, as the text states. However, most importantly, the 2 knees cannot even be compared as their axial alignments are grossly different, as shown by the relative position of the fibulae and the shape of the posterior proximal tibia. The abnormal knee is internally rotated, which causes the medial tibial plateau to move posteriorly and exaggerate any ''posterior sag'' of the tibia.Stress radiographs to measure ligament laxity is good in concept but are very hard to measure reliably. Errors in obtaining the images and making measurements are easily made, and frequently.