Bone Bruise Patterns in Skeletally Immature Patients with Anterior Cruciate Ligament Injury: The Airbag Effect
Author(s):
Novaretti J. (United States of America)
,
Novaretti J. (United States of America)
Affiliations:
Shin J.
,
Shin J.
Affiliations:
Albers M.
,
Albers M.
Affiliations:
Chambers M.
,
Chambers M.
Affiliations:
Cohen M.
,
Cohen M.
Affiliations:
Musahl V.
,
Musahl V.
Affiliations:
Fu F.
Fu F.
Affiliations:
ESSKA Academy. Novaretti J. 05/09/18; 209372; P04-1677
João Novaretti
João Novaretti
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Abstract
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Objectives: Bone bruises are frequently found on magnetic resonance imaging (MRI) after anterior cruciate ligament (ACL) injury and have been related to the amount of energy at the time of injury. Yet, little is known about bone bruise distribution pattern in skeletally immature patients and its relation to the physis. In these patients, the presence of an open physis may play a role in the energy dissipation pattern due to its unique cartilaginous and corticocancellous structure. The purpose of this study was to describe and compare the location and distribution of the tibial and femoral bone bruise between two groups of ACL injured patients: first group with open physis and the second with closed physis. It was hypothesized that bone bruise patterns in skeletally immature patients would not extend into the metaphysis and instead be more concentrated along the epiphysis compared to adult patients.

Methods: A retrospective search was conducted from January 2012 to December 2016 to identify all cases of primary ACL tears in patients younger than 16 years old, with MRI imaging within 6 weeks of injury. Overall, 106 patients were identified, 53 cases with open physis to the Skeletally-Immature (SI) group and, for the control group, 53 young adult patients with closed physis were identified to the Skeletally-Mature (SM) group. MRI scans were reviewed regarding presence and location of bone bruises. Longitudinal bone bruise distribution pattern was described as epiphyseal and metaphyseal, in both femur and tibia. Tibial epiphysis was further divided in 9 zones: 1-anterolateral, 2-anterocentral, 3-anteromedial, 4-centrolateral, 5-centrocentral, 6-centromedial, 7-posterolateral, 8-posterocentral and 9-posteromedial. Descriptive statistics were calculated for all variables. Student T test was used to analyze continuous variables. Differences in bone bruise pattern distribution in MRI imaging were compared by use of chi-square tests between SI and SM groups. Statistical significance was set at P < .05.

Results: The Skeletally-Immature (SI) group had significantly less bone bruise crossing the physis and extending into the metaphysis than the Skeletally-Mature (SM) group in the tibia (25% vs. 85%; P < .05) and in the femur (4% vs. 42%; P < .05). In tibial epiphysis, bone bruise in the SI group was observed more frequently in Zones 1, 2, 4 and 5 (each P < .05) compared to SM group.

Conclusions: Patients with open physis have unique bone bruise patterns compared to those with closed physis in acute ACL rupture. In the skeletally immature patients, bone bruise pattern is significantly less observed in the metaphysis and is found significantly more frequently in the anterior and central zones of the tibial epiphysis. The physis, therefore, may present an "airbag effect", dissipating and distributing energy, leading to less trabecular microfracture in the metaphysis compared to adults. Bone bruises crossing the physis may have implications in the development of post-traumatic leg deformity in patients.

Keywords:
bone bruise; anterior cruciate ligament; skeletally immature
Objectives: Bone bruises are frequently found on magnetic resonance imaging (MRI) after anterior cruciate ligament (ACL) injury and have been related to the amount of energy at the time of injury. Yet, little is known about bone bruise distribution pattern in skeletally immature patients and its relation to the physis. In these patients, the presence of an open physis may play a role in the energy dissipation pattern due to its unique cartilaginous and corticocancellous structure. The purpose of this study was to describe and compare the location and distribution of the tibial and femoral bone bruise between two groups of ACL injured patients: first group with open physis and the second with closed physis. It was hypothesized that bone bruise patterns in skeletally immature patients would not extend into the metaphysis and instead be more concentrated along the epiphysis compared to adult patients.

Methods: A retrospective search was conducted from January 2012 to December 2016 to identify all cases of primary ACL tears in patients younger than 16 years old, with MRI imaging within 6 weeks of injury. Overall, 106 patients were identified, 53 cases with open physis to the Skeletally-Immature (SI) group and, for the control group, 53 young adult patients with closed physis were identified to the Skeletally-Mature (SM) group. MRI scans were reviewed regarding presence and location of bone bruises. Longitudinal bone bruise distribution pattern was described as epiphyseal and metaphyseal, in both femur and tibia. Tibial epiphysis was further divided in 9 zones: 1-anterolateral, 2-anterocentral, 3-anteromedial, 4-centrolateral, 5-centrocentral, 6-centromedial, 7-posterolateral, 8-posterocentral and 9-posteromedial. Descriptive statistics were calculated for all variables. Student T test was used to analyze continuous variables. Differences in bone bruise pattern distribution in MRI imaging were compared by use of chi-square tests between SI and SM groups. Statistical significance was set at P < .05.

Results: The Skeletally-Immature (SI) group had significantly less bone bruise crossing the physis and extending into the metaphysis than the Skeletally-Mature (SM) group in the tibia (25% vs. 85%; P < .05) and in the femur (4% vs. 42%; P < .05). In tibial epiphysis, bone bruise in the SI group was observed more frequently in Zones 1, 2, 4 and 5 (each P < .05) compared to SM group.

Conclusions: Patients with open physis have unique bone bruise patterns compared to those with closed physis in acute ACL rupture. In the skeletally immature patients, bone bruise pattern is significantly less observed in the metaphysis and is found significantly more frequently in the anterior and central zones of the tibial epiphysis. The physis, therefore, may present an "airbag effect", dissipating and distributing energy, leading to less trabecular microfracture in the metaphysis compared to adults. Bone bruises crossing the physis may have implications in the development of post-traumatic leg deformity in patients.

Keywords:
bone bruise; anterior cruciate ligament; skeletally immature
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