Influence of Age on Healing Capacity of Acute Tears of the Anterior Cruciate Ligament Based on Magnetic Resonance Imaging Assessment.

OBJECTIVE: The purpose of this study was to evaluate the influence of patient age on the effects of conservative treatment of the anterior cruciate ligament (ACL). METHODS: A total of 102 consecutive patients with acute ACL injury were allowed to heal without surgery. Final magnetic resonance imaging images of the ACL were classified from grade I, indicating good morphological recovery, to grade IV, indicating poor recovery. Chi-square analysis was used to determine significant differences in the incidence of grades I and II among those less than 20 versus those 20 years or more of age. RESULTS: The mean follow-up to final magnetic resonance imaging was 9 months. A significant difference in the frequency of grades I and II was observed between age groups (<20 years, 13.0%; ≥20 years, 69.6%; P < 0.0001). CONCLUSION: ACL injury was more severe, and morphological recovery with conservative treatment was poorer among younger patients than among adults.

Effect of Changing the Joint Kinematics of Knees With a Ruptured Anterior Cruciate Ligament on the Molecular Biological Responses and Spontaneous Healing in a Rat Model.

BACKGROUND: The poor healing capacity of a completely ruptured anterior cruciate ligament (ACL) has been attributed to an insufficient vascular supply, cellular metabolism, and deficient premature scaffold formation because of the unique intra-articular environment. However, previous studies have focused on intra-articular factors without considering extra-articular factors, including the biomechanical aspects of ACL-deficient knees. HYPOTHESIS: Changing the joint kinematics of an ACL-ruptured knee will improve cellular biological responses and lead to spontaneous healing through the mechanotransduction mechanism. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 66 skeletally mature Wistar rats were randomly assigned to a sham-operated group (SO), ACL-transection group (ACL-T), controlled abnormal movement group (CAM), and an intact group (IN). The ACL was completely transected at the midportion in the ACL-T and CAM groups, and the CAM group underwent extra-articular braking to control for abnormal tibial translation. The SO group underwent skin and joint capsule incisions and tibial drilling, without ACL transection and extra-articular braking. The animals were allowed full cage activity until sacrifice at 1, 2, 4, 6, and 8 weeks postoperatively for histological, molecular biological, and biomechanical assessment. RESULTS: All injured ACLs in the ACL-T group were not healed, but those in the CAM group healed spontaneously, showing a typical ligament healing response. Regarding the molecular biological response, there was an upregulation of anabolic factors (ie, transforming growth factor-ß) and downregulation of catabolic factors (ie, matrix metalloproteinase). Examination of the mechanical properties at 8 weeks after injury showed that >50% of the strength of the intact ACL had returned. CONCLUSION: Our results suggest that changing the joint kinematics of knees with a ruptured ACL alters the molecular biological responses and leads to spontaneous healing. These data support our hypothesis that the mechanotransduction mechanism mediates molecular responses and determines whether the ACL will heal. CLINICAL RELEVANCE: Elucidating the relationship between the mechanotransduction mechanism and healing responses in knees with completely ruptured ACLs may result in the development of novel nonsurgical treatment that enables the ACL to spontaneously heal in patients who are not suitable for reconstruction.

Subchondral insufficiency fracture of the femoral head may be associated with hip dysplasia: a pilot study.

BACKGROUND: Subchondral insufficiency fracture of the femoral head occurs mainly in elderly patients with osteoporosis. Spontaneous resolution is observed after nonoperative treatment in some patients whereas other show progressive joint destruction requiring THA. Several studies report the occurrence of subchondral insufficiency fracture of the femoral head in dysplastic hips. QUESTIONS/PURPOSES: We asked whether the extent of hip dysplasia or osteoporosis was greater in patients with subchondral insufficiency fracture of the femoral head than in normal control subjects. PATIENTS AND METHODS: We compared the clinical and imaging findings of 13 patients with subchondral insufficiency fractures of the femoral head and 12 patients scheduled for TKA with asymptomatic hips. Age, gender, and body mass index were comparable in the two groups. RESULTS: Higher mean Sharp angles, lower acetabular head indices, lower center-edge angles, and higher acetabular roof angles in patients with subchondral insufficiency fracture of the femoral head than in those with asymptomatic hips suggested a greater degree of hip dysplasia. Bone mineral density and serum levels of Type I collagen cross-linked N-telopeptide and bone alkaline phosphatase were similar in the two groups. CONCLUSIONS: We speculate an excessive amount of stress on the acetabular edge from dysplasia may be associated with the occurrence of subchondral insufficiency fracture of the femoral head.

Postural control capability of ACL-deficient knee after sudden tilting.

Loss of neurophysiological function in an anterior cruciate ligament (ACL)-deficient knee leads to irregularities in neuromuscular coordination, and any sudden change in circumstances is believed to contribute to deterioration in postural control. The aim of this study was to investigate differences between ACL-deficient patients and healthy subjects through examination of postural control in response to perturbation. Twelve patients awaiting ACL reconstruction were compared with 12 healthy athletes. Subjects were instructed to stand on an unstable board that was then tilted suddenly from behind. The stepping power and reaction time of subjects to this perturbation were measured through accelerometers attached to both the unstable board and the subjects' knees. In healthy athletes, stepping power was stronger on the tilted side than on the opposing side, while their step reaction, as part of anticipatory postural control, was faster on the opposing side than on the tilted side. In patients with ACL-deficient knees, the opposite was true; stepping power was no stronger on the tilted side, while their step reaction was no faster on the opposing side. In terms of postural control capability, both the affected and the healthy knee of ACL-deficient patients were impaired as a result of control patterns that differed from the usual model.

Distal femoral cut perpendicular to the mechanical axis may induce varus instability in flexion in medial osteoarthritic knees with varus deformity in total knee arthroplasty: a pitfall of the navigation system.

Two factors that influence the external rotation angle of the femoral rotational axis in total knee arthroplasty (TKA) were assessed in 40 medial osteoarthritic knees with varus deformity. First, the anatomic configuration of the femur was assessed using standardized radiographs of the patients' lower extremities before TKA. Second, the degree of medial soft tissue release was assessed during TKA. The radiographs showed that the characteristics of the femur were lateral bowing of the shaft and external rotation of the condyle in the coronal plane. Therefore, when the distal femur is cut perpendicular to the mechanical axis, the cut surface may be in too much of a valgus position. Furthermore, some degree of medial soft tissue release was necessary in all knees. Medial soft tissue release rotates the femur externally in extension in the coronal plane, and it rotates the femur externally around the femoral axis in flexion relative to the tibia. A distal femoral cut in too much of a valgus position and medial soft tissue release induces varus instability in flexion in knees with lateral bowing of the femoral shaft. Anatomic variation such as femoral bowing should be considered when a navigation system is used for TKA because the navigation system shows only the mechanical axis.

Distance of the femorotibial joint gap can be controlled in the modified ligament dependent cut procedure during total knee arthroplasty.

During total knee arthroplasty in fifty consecutive cases, the distal femur and proximal tibia were initially cut. After posterior cruciate ligament excision, the femorotibial joint was expanded by a Tensor/balancer device with 30 inch-pounds of torque (in.lbs) both in extension and flexion, and ligament balancing was obtained in full extension. Then the knee was flexed at 90 degrees, and the femoral rotational axis was decided so that the axis was parallel to the tibial cut surface and the joint gap was the same between extension and flexion. The relationship between the distance of the joint gap expanded by a Tensor/balancer device with 30 in.lbs and the size of the bearing insert was assessed. The results showed that a 24 or 25-mm joint gap expanded by a Tensor/balancer device in full extension was optimal for a 10-mm bearing insert. Therefore, if the resection level of the tibia is set 24 or 25 mm from the femoral cut surface, a 10-mm bearing insert can be used. In 49 cases, the size of the femoral component was one size (4 mm) larger than that predicted based on the bony structure shown in the radiographs of the knee. With this procedure, ligament balancing and optimal joint gap both in extension and flexion can be obtained based on the predicted bearing insert in the knee.