Role of MRI in detecting early physeal changes due to acute osteoarticular infection around the knee joint: a pilot study

MRI Findings in a Young Boxer with Septic Physitis of the Humerus

The MRI appearance of appendicular septic physitis has not been reported in small animals. MRI appearance of septic arthritis and osteomyelitis has been described in horses, and the use of MRI has been proposed as a diagnostic alternative to radiographs to allow for earlier diagnosis and treatment. MRI is also routinely used in human medicine for the diagnosis of osteomyelitis owing to increased accuracy of evaluation of the soft tissue involvement. In the case of a 5 mo old male boxer dog described here, radiographs were suggestive of the diagnosis of septic physitis, although an MRI was obtained to rule out neurologic etiologies of lameness based on history and physical exam findings. MRI identified a fluid pocket communicating with the physis. The diagnosis of septic physitis was then confirmed via ultrasound-guided fine-needle aspirate of the fluid pocket communicating with the physis that was seen on the MRI.

Ankylosis of the knee after septic arthritis following anterior cruciate ligament reconstruction in a 13-year-old male

We present the case of an adolescent male developing an ankylosis of the knee after septic arthritis following anterior cruciate ligament reconstruction (ACLR). The patient was shifted to our institution with postoperative septic arthritis associated with a systemic septic condition. Before, repeated arthroscopic surgery had been conducted without any improvement. MRI showed a concomitant osteomyelitis. The infection (Gächter IV, Staphylococcus aureus) was controlled by an open surgical approach and graft removal. An increasing joint stiffness was documented. X-rays showed an ankylosis at 30° of flexion and early closure of growth plates. Functional knee scores showed significantly worse results. Early diagnosis and a stage-adapted treatment in septic arthritis following ACLR are mandatory. In advanced stages or concomitant osteomyelitis an open approach and graft removal may be appropriate. The antibiotic treatment should be adapted consistently.

Water-content calculation in growth plate and cartilage using MR T1-mapping design and validation of a new method in a porcine model

OBJECTIVE

There is a close relation between cartilage health and its hydration state. Current magnetic resonance methods allow visualizing this tissue. However, a quantitative analysis is more useful when studying disease. The purpose of this study was to quantify water content in cartilage using magnetic resonance without contrast agents.

MATERIALS AND METHODS

Water-content estimations using T1 magnetic resonance mapping were done first in eight gelatin samples where the water content was previously known. The same method was used in the physeal areas of eight skeletally immature 30-kg pigs. To calculate accuracy, T1 calculations were compared to dry-freeze, which is considered the gold standard because it can remove the total water content form a tissue. Four fresh cartilage and seven gelatin samples were dry-frozen. Water content obtained from dry-freeze was compared to the one calculated from T1 map values. A mathematical model and statistical analysis were used to calculate the predictive value of the method and its significance.

RESULTS

T1-map-based magnetic resonance method can calculate water content in cartilage with an accuracy of 97.3 %. We calculated a coefficient of variance for this method against dry-frozen sample of 3.68 (SD = 1.2) in gelatin samples, and 2.73 (SD = 1.3) in in vivo samples. Between two independent observers, the coefficient of variance was 0.053, which suggests it can be easily reproduced.

CONCLUSIONS

Magnetic resonance was able to calculate, with high accuracy, the cartilage water content using T1 mapping sequences.