Bilateral Congenital Anterior Cruciate Ligament Deficiency. A case report and review of the literature Abstract Congenital absence of anterior cruciate ligaments is rare. A 16 year old male presented with bilateral knee pain without a particular trauma. Bilateral knee MRI’s revealed a congenital absence of an ACL. An ACL reconstruction of the left knee was performed. Introduction/Background Bilateral congitenal absence of the anterior cruciate ligament is rarely reported in the literature and is often associated with other congenital musculoskeletal abnormalities such as longitudinal deficiencies of the lower limb, congenital mensical abnormalities, and others. We report on a patient with bilateral absence of anterior cruciate ligaments without evidence of any other congenital abnormality. Case Report A 16 year old Caucasian male presented with complaints of bilateral knee pain on February 19, 2011. He stated the pain has been present for the last five years with the left knee being worse than the right. There was a remote history of trauma to the left knee after a dirt bike accident approximately 3 years ago but no history of trauma to the right knee. The patient had no medical history, was not currently on medications and had not surgical history. The birth history was unremarkable with the patient being a normal gestation age at birth without any complications or hospitalizations. The patient was 60 inches tall and weighed 155 pounds. The vital signs were all within normal limits. Generally the patient was alert and oriented to time and place. Examination of the head, neck and abdomen was unremarkable. The lower extremities were neurovascularly intact. The leg lengths were symmetric. No syndactly was noted. Examination of the knees showed no effusion with full extension and flexion to 130 degrees bilaterally. Lachmans Test was difficult to ascertain in both knees as the patient was guarding. McMurrays and Patellar Grind tests were negative bilaterally. Anterior and Posterior Drawer tests were negative bilaterally. The patient did not have laxity with varus or valgus stress testing at 30 degrees of flexion or at full extension in both knees. The Pivot Shift test was not tolerated by the patient on either knee. X-rays taken of the bilateral knees revealed no obvious hypoplasia or absence of the tibial spines. There was some decrease in the lateral femoral condyle size bilateral. A notch view of the left knee revealed a notch height of 29.4mm and a notch width of 27.4mm. No osteochondral lesions or discoid meniscus was noted. Magnetic resonance imaging was obtained from both knees with revealed absence of the anterior cruciate ligaments bilaterally without any other obvious abnormality. Risks and benefits of an arthoscopically assisted ACL reconstruction versus conservative treatment were discussed with the patient and patient’s family and the patient opted for and ACL reconstruction with hamstring autograph of the left knee. Discussion Congenital absence of the anterior cruciate ligament is rare in the literature with only a few reports. It is a rare condition with a prevalence of 0.017 per 1000 live births (11). The knee joint starts its formation from vascular mesenchyme between femur and tibia in the fourth week of gestation between the blastoma of femur and tibia. A distinct (amount) bundle (of fibers) of ACL fibers appear in approximately the 8th week after gestation (6). Ratajczak[8] has shown that the cruciate ligaments first appear in stage 19 (nearly 39th Jeff Cochran ! 5/31/11 4:43 PM Comment: Awkward, consider removing (amount postovulatory days). The primordial cells, lie in the middle part of the interzone which faces and of fibers and replace with bundle the intercondylar fossa of the femur where the cells are more loosely arranged in obliquely passing strands, are forming the cruciate ligaments. During stage 22, intercondylar tibial eminence formation occurs, and in stage 23 all intraarticular structures are formed and the shafts of the tibia and femur begin to ossify. Congenital absence of an ACL has been showed to be associated with discoid meniscus[2], hypoplasia of intercondylar notch, hypoplasia of intercondylar tibial eminence, shortness of femur, hypertrophy of the meniscofemoral ligament of Humphrey. Radiographic findings have been seen that indicate aplasia of the cruciate ligaments. Common findings include hypoplasia of the tibial eminence, a hypoplastic lateral femoral condyle (10) and a narrow intercondylar notch (1). The study by Manner et al. attempted to classify the type of dysplasia based on radiography and MRI. The classification system (Type I-III) is based on a tunnel view radiograph according to differences in the notch width index, notch height and changes in the lateral and/or medial tibial spine (1). In type I, partial closure of the femoral intercondylar notch and hypoplasia of the tibial eminence are observed and the anterior cruciate ligament is hypoplastic or aplastic. In type II, these findings are accentuated and there is additional hypoplasia of the posterior cruciate ligament. In type III, the femoral intercondylar notch and the tibial eminence are completely absent and there is aplasia of both cruciate ligaments (1). Using the Manner classification, our patient falls into the Type I Classification. Surgical reconstruction versus conservative treatment is an area of debate. The long term effect of having a congenital absence of an ACL is not known. In adults, numerous studies have shown the long term consequences such as meniscal damage and earlier osteoarthritis but this is not known if this is true with a congenital absence. Our patient requested a reconstruction using allograft hamstring tendons. Summary In summary the patient presented with bilateral knee pain without instability and a congenital absence of the anterior cruciate ligaments was identified. The patient underwent ACL reconstruction of the left knee. Conclusion This case report offers up questions such as the appropriate treatment. There is no clear answer in the literature in determining operative versus non-operative treatment of such a condition. Most of the information is based on case reports such as this one. This case could also raise the possibility of physician or surgeon missing the diagnosis. Presenting this case gives further exposure to the presence of this clinical entity. References 1. Manner HM, Radler C, Ganger R, Grill F. Dysplasia of the cruciate ligaments: radiographic assessment and classification. J Bone Joint Surg Am 2006; 88: 130-137. 2. Niebauer JJ, King DE. Congenital dislocation of the knee. J Bone Joint Surg Am 1960; 42: 207-225. 3. Tolo VT. Congenital absence of the Menisci and Cruciate Ligaments of the Knee. J Bone Joint Surg Am 1981; 63: 1022-1024 4. Noble J. Congenital absence of the anterior cruciate ligament associated with a ring meniscus. report of a case. J Bone Joint Surg Am 1975; 57: 1165-1166. 5. HU Jun. Bilateral congenital absence of anterior cruciate ligaments associated with the scoliosis and hip dysplasia: a case report and review of the literature. Chinese Medical Journal 2010; Vol 123 Num 8 1099-1102 6. Zantop T. Anatomy of the Anterior Cruciate Ligament. Oper Tech Orthop 2005 15:20-28 7. Ergun S. A case of multiple congenital anomalies including agenesis of the anterior Acta Orthop Traumatol Turc 2008;42(5):373-376 8. Ratajczak W. Early development of the cruciate ligaments in staged human embryos. Folia Morphol 2000;59:285-90 9. Katz MP, Grogono BJ, Soper KC: The etiology and treatment of congenital dislocation of the knee. J Bone Joint Surg Br 1967, 49:112-120. 10. Kaelin A, Hulin PH, Carlioz H: Congenital aplasia of the cruciate ligaments. A report of six cases. J Bone Joint Surg Br 1986, 68:827-828 11. Tachdjia, MO. Pediatric Orthopedics. 2nd Ed. Philadelphia. Saunders; 1990 .