Focal intratendinous radiolucency: A new radiographic method for diagnosing patellar tendon ruptures

The "Empty Merchant Sign" in acute patellar tendon ruptures

INTRODUCTION

We introduce a new sign on a Merchant view present in acute patellar tendon ruptures (APTR). We aim to determine the accuracy, sensitivity, and specificity of this new radiographic sign and measure the effect of a tutorial on these measures between trainees and non-trainees.

METHODS

Lateral and Merchant radiographs (22 images) of knees with four conditions (patellar instability, APTR, quadriceps tendon rupture, and controls) were randomly shown to 50 trainees and non-trainees who were asked to make a diagnosis based on radiographs. A brief tutorial was administered describing the "Empty Merchant Sign" and the same 22 images were randomly shown after the tutorial. Accuracy, sensitivity, specificity, and positive predictive value were calculated between the two image types and the effect of tutorial on these measures was assessed.

RESULTS

After the tutorial: 1. the "Empty Merchant Sign" had a higher specificity (100%) and positive predictive value (99%) compared to the lateral radiograph (81% and 64% respectively, P < 0.001), 2. There was significant improvement (from 56% to 95.3%; P < 0.001) in the accuracy of the Merchant view, making it as accurate as the lateral view (95.3% vs. 90.7%, respectively; P = 0.113). There was no difference in the accuracy of the Merchant view between trainees (97.2%) and non-trainees (90.5%) (P = 0.079).

CONCLUSION

The "Empty Merchant Sign" is a highly sensitive and specific diagnostic sign in cases of APTR. With very little training, physicians can identify this sign to diagnose APTRs on a Merchant view.

Evaluation of the age and gender related changes in the Blumensaat line

PURPOSE

The position of the patella according to the femur is very important in the evaluation of patella-femoral joint disorders. In 1938, Blumensaat (BS) described the BS line to evaluate the patella femoral congruence. This method is still valuable in clinical use. There is a limited number of studies demonstrating the accuracy of BS method as well as the affected variables. The aim of this study was to evaluate o the age and gender-related changes in the BS line.

METHODS

Standard lateral knee radiography was performed to all patients at 30° flexion. The relationship between the BS line and the patella inferior pole was examined and the variability of the measurements according to gender and age groups was investigated by statistical methods.

RESULTS

Ninety-five patients (43 men and 52 women) were enrolled in the study. Mean age of the patients were 43.7 ± 14.1 years (48.2 ± 11.7, 37.9 ± 14.8 in women and men, respectively). The BS line was passed through the inferior pole of the patella in only 2 (2.1%) of 95 patients. There was a statistically significant difference (p = 0.041) between BS measurement and gender which was found to be higher in females than males. There was no statistically significant correlation with this distance between the age groups (r = - 0.216, p = 0.427).

CONCLUSION

In our study, it was concluded that BS measurement differs according to gender but did not have any difference between different age groups.

Acute traumatic rupture of the patellar tendon in pediatric population: Case series and review of the literature

BACKGROUND

Intact knee extensor mechanism is required for the normal function of the lower extremity. Patellar tendon rupture is a relatively rare injury with peak age incidence around 40 years and usually occurs midsubstance. The occurrence of pure patellar tendon rupture without bony avulsion is an extremely rare injury in the pediatric population with few cases reported in the literature with limited information regarding frequency, complications, and outcomes in children. However, due to increased participation in sports and high-energy recreational activities during childhood, the frequency of such injuries has progressively increased.

OBJECTIVE

To evaluate the frequency of pediatric patellar tendon rupture injuries and describe the radiological findings, treatment modalities, and outcome of such injuries.

METHODS

Demographic and clinical data on a series of patients who sustained patellar tendon rupture were reviewed. These data included age at time of injury, sex, laterality, mechanism of injury, associated injuries, complications, presence or absence of Osgood-Schlatter disease, diagnostic imaging such as plain radiographs and magnetic resonance images (MRI), surgical technique, method of fixation, period of postoperative immobilization, total duration of physiotherapy, time to return to sports activities and follow-up duration. Insall-Salvati ratio was calculated on the preoperative lateral x-ray. The functional outcome was evaluated with regard to final knee active range of motion (AROM), manual quadriceps muscle testing, and presence or the absence of terminal extension lag. Clinical outcome rating using knee society score (KSS) was performed and functional outcome was further classified according to the calculated score.

RESULTS

Five male patients with patellar tendon rupture (7%) were identified among 71 pediatric patients who sustained acute traumatic injury of the knee extensor mechanism. The mean age at the time of injury was 13.6 years (range: 12-15 years). The injury occurred in relation to sports activities in 4 patients. Osteogenesis imperfecta and Osgood-Schlatter disease were identified in 2 patients. High riding patella is the hallmark diagnostic sign detected in plain x-ray with preoperative Insall-Salvati ratio ranged from 1.7 to 2.5. Three patients had pure soft tissue avulsion distally from the proximal tibia, 1 patient had pure soft tissue avulsion proximally from the inferior patellar pole, and 1 patient with midsubstance tendinous disruption. No associated intra-articular lesions were identified. Suture bridge double row technique, transpatellar suturing, and transosseous suturing through the proximal tibia were used for patellar tendon reinsertion. After a mean follow-up period of 18. 4 weeks (range: 10-30 weeks), patients achieved AROM ranging from 0 to 120° to 0-137° without terminal extension lag. The mean time to return to sports activity was 22 weeks (range: 13-30 weeks). Quadriceps muscle strength was 5/5 at the final follow-up visit in all patients; however, relative muscle atrophy was noted in comparison to the other side in one patient. The mean KSS was 91.8 points (range: 79-100 points) with excellent outcome in 4 patients and good outcome in 1 patient.

CONCLUSION

Patellar tendon rupture is rare in the pediatric population and represents 7% of pediatric patients who sustained acute traumatic injury of the knee extensor mechanism. Ruptures may occur midsubstance, or from proximal or distal insertions. High riding patella is the hallmark diagnostic sign for such injury. Although rare, it is considered a serious injury that necessitates early diagnosis and surgical intervention. Functional range of motion was obtained in all patients with different modalities of treatment.