Evaluation of the Tibial Tubercle to Posterior Cruciate Ligament Distance in a Pediatric Patient Population.

BACKGROUND: Evaluation of distal extensor mechanism alignment continues to evolve in children with patella instability. Prior studies support the use of the tibial tubercle to trochlear groove (TT-TG) distance but limitations exist for this measurement including: changes in the TT-TG distance with knee flexion, difficulty with finding the deepest part of a dysplastic trochlea, and limitations regarding identification of the site of the anatomic abnormality. The tibial tubercle-posterior cruciate ligament (TT-PCL) distance has been introduced as an alternative measure to address the shortcomings in the TT-TG distance by quantifying the position of the TT independent of the trochlea and with respect to the tibia only. The objectives of this study were to (1) confirm that TT-PCL measurements in the pediatric population are reliable and reproducible; (2) determine whether normal TT-PCL distance changes with age; and (3) compare TT-PCL distances in patients with and without patellar instability to assess its utility in the workup of pediatric patellar instability. METHODS: All knee magnetic resonance imaging performed for patients from birth to 15.9 years of age at our institution between December 2004 and February 2012 were retrospectively collected (total 566). Eighty-two patients had patellar instability and 484 patients did not have patellar instability. Two magnetic resonance imaging reviewers measured TT-PCL distance on T2-weighted axial images in a blinded manner. Intraobserver and interobserver agreement was measured. Correlation between TT-PCL distance and age as well as group differences between mean TT-PCL distances was evaluated. RESULTS: Intraobserver and interobserver agreement was excellent (0.93) and very good (0.80), respectively. The mean TT-PCL distance was 20.1 mm with a range of 5.8 to 32.1 mm. The mean age was 12.6 years with a range of 0.8 to 15.9 years. The average TT-PCL distance was 21 mm for the instability group and 19.9 mm for the control group. TT-PCL distance increased significantly as subject age increased; however, there was no significant measurement difference shown between the patellar instability group and the control group. CONCLUSIONS: TT-PCL distance increased with age in the pediatric population but did not correlate with recurrent patella instability in this pediatric cohort. LEVEL OF EVIDENCE: Level III-diagnostic.

Geographic mapping of meniscus and cartilage lesions associated with anterior cruciate ligament injuries.

BACKGROUND: Detailed descriptions of meniscus and articular cartilage lesions associated with anterior cruciate ligament injury have not been presented in the literature. Our goal was to determine the associations between patient sex, age, and surgical delay and the frequency and location of meniscus and articular cartilage lesions seen at the time of the anterior cruciate ligament reconstruction. METHODS: Data were obtained retrospectively from a database of 1209 consecutive patients undergoing anterior cruciate ligament reconstruction between 1988 and 2002. All knee cartilage, meniscus, and ligament injuries were documented on anatomic maps at the time of surgery, and the data were analyzed. RESULTS: Meniscus injuries were identified in 722 (65%) of the 1104 patients who met the criteria for inclusion in the study. Female patients were less likely to have a meniscus injury than male patients were (56% compared with 71%), and male patients were more likely to have combined medial and lateral meniscus injuries than female patients were (20% compared with 11%). Patients with a surgical delay of less than three months were less likely to have a medial meniscus injury (8% compared with 19%). Femoral articular cartilage injuries were identified in 472 patients (43%). Patients who were twenty-five years of age or older were more likely to have multiple cartilage lesions throughout the knee (7.7% compared with 1.3%) and to have more isolated medial femoral condyle lesions (24.2% compared with 13.3%). Patients with a surgical delay of more than one year were more likely to have a lesion (60% compared with 47% for all others), and a surgical delay of more than one year resulted in a greater proportion of large and grade-3 lesions of the lateral femoral condyle. Female patients had a greater proportion of grade-1 lesions of the medial femoral condyle (29% compared with 16%), whereas male patients had a greater proportion of grade-3 and 4 lesions of the medial femoral condyle (49% compared with 35%). In patients who were thirty-five years of age or older, meniscus injuries were more frequent and were located more frequently on the medial side; femoral articular cartilage lesions were also located more frequently on the medial side. CONCLUSIONS: Increased age, male sex, and increased surgical delay all increase the frequency and severity of injuries of the meniscus and/or articular cartilage after an anterior cruciate ligament tear.