The anatomy of the proximal tibia in pediatric and adolescent patients: implications for ACL reconstruction and prevention of physeal arrest.

Although the treatment of anterior cruciate ligament (ACL) tears in skeletally immature patients is still controversial, several studies have advocated ACL reconstruction in selected patients to prevent secondary injury. The proximal tibial physis is a structure at risk during ACL reconstruction in young patients, and physeal growth complications have been reported after surgery in this area. The relationship between the ACL and the proximal tibial physeal/apophyseal regions is poorly understood. This study examined the MRI anatomy of the ACL and the proximal tibia apophysis and epiphysis. MRIs of 59 skeletally immature knees were reviewed (Average age = 12.75 years, range 6-15) to define the anatomy of the epiphyseal and apophyseal regions. Measurements were recorded in three parasagittal planes: (1) at the lateral border of the patellar tendon, (2) the lateral edge of the ACL insertion, and (3) the medial edge of the ACL insertion. A single three-dimensional (3D) computed tomography (CT) scan was used to evaluate the position of standard drill holes used in ACL reconstruction to assess for potential degree of injury to the epiphyseal and apophyseal growth plates. In the parasagittal planes, the average height of the epiphysis was 19.6, 20.7, and 21.5 mm at the lateral border of the patellar tendon, the lateral border of the ACL, and the medial border of the ACL, respectively. At the level of the same landmarks, the apophysis extended below the physis at an average of 20.2, 16.8, and 7.0 mm, respectively. Expressed as a percentage of epiphysis height this was an average of 104, 82, and 33%, respectively. Examination of 3D CT images revealed that variations in drill hole placement had effects on the volume of injury to the proximal tibial physis and apophysis. Drill holes that started more medial, distal, and with a steeper angle of inclination reduced the amount of physis and apophysis violated when compared with holes placed more lateral, proximal, and with a shallow angle of inclination. The proximal tibial physis and apophysis is vulnerable to injury by drill hole placement during ACL reconstruction in skeletally immature patients. This paper defines the anatomic relationship of the apophyseal and epiphyseal regions of the physis in the proximal tibia. The volume of injury to the physis can be reduced by avoiding tunnel placement that is too lateral or too proximal on the tibia. A better understanding of these relationships may guide the placement of tibial drill holes, which have a lower risk of producing significant physeal damage.

Comparison of radiographs and CT scans in the prospective evaluation of the fusion of hindfoot arthrodesis.

BACKGROUND: This prospective study compared radiographs and CT scans for the quantitative evaluation of healing of hindfoot arthrodeses. METHODS: Patients undergoing subtalar or triple arthrodesis were prospectively evaluated. Serial radiographs and CT scans were obtained after surgery. The percent of fusion of the joints was sequentially measured on all radiographs and CT scans. At 6 and 12 months after surgery, the patients completed American Orthopaedic Foot and Ankle Society (AOFAS) and Short Form-12 (SF-12) instruments and a visual analog scale (VAS). RESULTS: The mean observed fusion of the posterior facet of the subtalar joint ranged from 41% at 6 weeks to 61% at 12 weeks and to 86% at 6 months on the radiographs; the mean fusion of the posterior facet on the CT scans ranged from 23% to 48% to 64% at the same time intervals. The agreement between the two methods was poor. The clinical results based on the AOFAS, VAS and SF-12 scores were compared to the percent of joints fused on the CT scans. Clinical results appeared to be independent of radiographic results. CONCLUSIONS: We believe the progress of the fusion cannot be determined accurately from standard radiographs. CT scanning appears to be significantly more reliable. The concept of what constitutes an adequate fusion deserves more extensive study.

The tibial attachment of the anterior cruciate ligament in children and adolescents: analysis of magnetic resonance imaging.

Recent studies have demonstrated that skeletally immature athletes with an ACL injury may require surgical reconstruction if they return to high-demand sports. This study used MRI to compare the anatomy of the ACL in skeletally immature and adult subjects. Measurements were recorded in the sagittal plane for the anterior-posterior dimension of the proximal tibia, and the anterior, center, and posterior limits of the ACL, and the roof inclination angle of the femur. These values were compared to established reference values for adult knee anatomy. In skeletally immature women ( n=7) the ACL anterior limit, center and posterior limit, and roof inclination angle were 28%, 46%, 63%, and 38 degrees, respectively, compared to 28%, 44%, 60%, and 35 degrees in adult women. In skeletally immature men ( n=15) the ACL anterior limit, center, posterior limit, and roof inclination angle were 27%, 43%, 59%, and 40 degrees, respectively, compared to 28%, 44%, 59%, and 37 degrees in adult men. In the younger subjects the overall dimensions of the proximal tibia were smaller than that in adults, but the anatomical landmarks for the ACL were proportional. If ACL reconstruction is performed in skeletally immature subjects, the smaller dimensions of the tibia need to be considered, and the use of anatomical landmarks is an important factor in graft placement