Arthroscopy : The Journal of Arthroscopic and Related Surgery 10(6):693--695 Published by Raven Press, Ltd. © 1994 Arthroscopy Association of North America

Case Report

Lateral Femoral Condyle Fracture After Endoscopic Anterior Cruciate Ligament Reconstruction

E u g e n e E. Berg, M.D.

Summary: A case is described in which a coronal plane fracture of the lateral femoral condyle propagated through the femoral tunnel 2 months after endo- scopic anterior cruciate ligament reconstruction. Key Words: Anterior cruciate ligament--Endoscopic reconstruction--Lateral femoral condyle fracture-- Surgical complication--Stress riser.

Fracture through a drill hole stress riser is a rec- ognized hazard of fracture surgery (1-3) and im- plant removal (4). Many cruciate ligament recon- structive techniques use large-diameter osseous tunnels to accommodate various ligament substi- tutes (5-9). Although fractures of the patella (10,11) are a well-described complication of autogenous bone--patellar tendon-bone autograft anterior cruci- ate ligament (ACL) reconstruction, there are no known cases of femoral condyle or tihial fracture after ACL reconstruction.

CASE REPORT

M.C., a 38-year-old female firefighter, twisted her right knee, which caused her to fall. She devel- oped a hemarthrosis and had a positive Lachman maneuver. An magnetic resonance scan depicted an interstitial midsubstance ACL tear. Despite bracing and rehabilitation, she experienced recurrent giving way.

Two months after injury, a middle third autoge- nous bone-patellar tendon-bone ACL reconstruc- tion was performed using an endoscopic technique for femoral graft placement. The endoscopic drill cut through the posterior cortex of the lateral fem-

From the Department of Orthopaedics, University of South Carolina School of Medicine, Columbia, South Carolina, U.S.A.

Address correspondence and reprint requests to Dr. Eugene E. Berg, Department of Orthopaedics, 2 Richland Med. Pk. #404, University of South Carolina School of Medicine, Colum- bia, SC 29203, U.S.A.

oral condyle, which precluded interference fixation. Therefore, the ligament graft was secured both proximally and distally with traction sutures tied over screw posts. Early osteoarthritic joint surface changes were described that involved the lateral femoral condyle and tibial plateau. Both menisci were intact to arthroscopic visualization and probing.

Continuous passive motion was used postopera- tively, and the patient was discharged after an un- eventful hospital stay on the third postoperative day. Protected in a rehabilitation brace, the knee was allowed full extension and 90 ° of flexion. The patient was non-weight bearing on crutches for 2 weeks, after which progressive weight bearing was allowed. Two months after reconstruction, the pa- tient stated that her knee "gave way" and caused her to fall. This event was followed by intense knee pain and swelling. A radiograph showed a displaced coronal fracture of the posterior half of the lateral femoral condyle (Fig. A and B).

The fracture was treated (on 10/25/91) by an open reduction and multiple lag screw fixation. The screws used to fix the articular segment were placed extraarticularly to avoid transgression of the artic- ular cartilage. The patient was allowed to move her knee but was kept non-weight bearing. A radio- graph taken 3 weeks postoperatively showed that the fracture had displaced (Fig. 2). The fracture was grafted with lilac crest and refixed (on 11/16/91) (Fig. 3). A pulsed electromagnetic field, capacitance- coupled bone stimulator was applied to the knee.

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694 E. E. BERG

1A,B

FIG. 1. A: Anterior-posterior radiograph de- picting the autogenous patellar bone-tendon- bone graft secured with traction sutures over screw and washer posts. The femoral bone plug resides in a lucent region. There is an articular step off in the lateral femoral condyle. B: The lateral radiograph depicts the coronal fracture plane and displacement of the posterior lateral femoral condyle.

Tomograms taken 5 months later showed a per- sistent nonunion. The fracture was refixed with both interfragmentary screws and an L-plate, dense intraarticular adhesions were resected, and the frac-

ture was regrafted with cancellous iliac crest (on 6/25/92). Intraoperatively an anterolateral full- thickness femoral condyle cartilage defect was noted at the fracture site. The knee was casted in full extension for 8 weeks. Four months later (on 10/14/92), the radiographs demonstrated evidence of fracture union, knee range of motion was 0°--40 °,

FIG. 2. Lateral radiograph of initial fixation shows loss of frac- ture reduction.

FIG. 3. Lateral radiograph taken after the refixation and bone grafting.

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LATERAL FEMORAL CONDYLE FRACTURE 695

and the patient was allowed to bear weight. Six months after the final procedure the patient was allowed to be full weight bearing with knee motion of 00-70 °. The knee was stable to Lachman maneu- ver.

DISCUSSION

Fractures through drill holes are a well recog- nized complication of fracture surgery (1-3,10). Af- ter screw removal the residual screw hole defect can act as a stress riser and places the bone at risk for refracture, especially in cortical diaphyseal bone. Refracture rates as high as 33% have been reported after removal of forearm screws and plates (10). The transcondylar interosseous tunnel used in many techniques of cruciate ligament reconstruc- tion is usually 1 cm in diameter (6). Ternes et al. recently reported an extraarticular supracondylar femur fracture after a GOR-TEX prosthetic (WL Gore & Assoc., Inc., Flagstaff, AZ, U.S.A.) ACL reconstruction (7). This case is the first known case of an intraarticular fracture of the femoral condyle.

Femoral tunnel placement, predicated by tibial tunnel position, is technically more difficult with the endoscopic method of ACL reconstruction. If the femoral tunnel is insufficiently surrounded by bone, either the endoscopic drill will cut through the posterior aspect of the femoral condyle, or the interference screw may fracture a thin tunnel wail. When the tunnel is fashioned high in the intercondy- lar notch, the graft can be placed in the intramed- uUary canal. In this case, the fracture not only oc- curred through the lateral femoral condyle but also comminuted the metaphyseal cortex of the poste- rior femur, which suggests that a portion of the fem- oral tunnel was intramedullary.

Several factors contributed to this devastating complication. As an older white woman, her under- lying osteopenic bone may have had a predilection for fracture. Preexisting osteoarthritis transmitted the friction stresses of knee motion to the condylar bone defect, which both helped propagate the frac- ture and interfere with its healing. The vascularity and healing potential of this fracture were also sub- optimal because the posterior femoral condyle was covered extensively by hyaline cartilage and had a

meager soft-tissue envelope. Furthermore, fibrino- genie healing mechanisms were impeded by expo- sure of the interarticular fracture to a host of syno- vial fibrinolytic enzymes.

Interfragmentary compression screw fixation does not effectively resist torsional stresses. If early motion is to be safely instituted, plate fixation should be considered to counter the rotatory forces placed on the lateral femoral condyle during normal knee motion.

ACL reconstructions that use condylar bone tun- nels are clinically effective (5,6,8,9). The resulting bone defects can act as a stress riser and may frac- ture. The magnitude of transosseous tunnel stress concentration is biomechanically unknown. The postoperative duration of increased risk for fracture is also unknown. This case suggests the need to study these issues.

REFERENCES

1. Bechtol CO, Lepper H Jr. Fundamental studies in the design of metal screws for internal fixation of bone, J Bone Joint Surg [Aml 1956;38:1385.

2. Brooks DB, Burstein AH, Frankel VH. The biomechanics of torsional fracturesmthe stress concentration effect of a drill hole. J Bone Joint Surg [Am] 1970;52:507-14.

3. Burstein AH, Currey J, Frankel VH, Heiple KG, Lunseth P, Vessely JC. Bone strength: the effect of screw holes, JBone Joint Surg [Am] 1972;54:1143-56.

4. Hidaka S, Gustilo RB. Refracture of bones of the forearm after plate removal. J Bone Joint Surg [Am] 1978;60:9411-7.

5. Cbo KO. Reconstruction of the anterior cruciate ligament by semi-tendinous tenodesis, J Bone Joint Surg [Am] 1975;57: 608-12.

6. Clarity WG, Nelson DA, Reider B. Anterior cruciate liga- ment reconstruction using one-third of the patellar ligament, augmented by extra-fibular tendon transfers, J Bone Joint Surg [Aml 1982;64:352-9.

7. Ternes JP, Blasier RB, Alexander AH. Fracture of the femur after anterior crnciate ligament reconstruction with a GOR- TEX prosthetic graft. Am J Sport Med 1993;21:147-9.

8~ Thompson SK, Calver R, Monk CJE. Anterior cruciate lig- ament repair for rotatory instability: the Lindeman dynamic muscle-transfer procedure. J Bone Joint Surg [Am] 1978;60: 917-20.

9. Zarins B, Rowe CR. Combined anterior crnciatc ligament reconstruction using semitendinous and fliotibial band. J Bone Joint Surg [Am] 1986;68:160-77.

10. Christen B, Jakob RP. Fractures associated with patellar ligament grafts in cruciate ligament surgery, J Bone Joint Surg [Br] 1992;74:6t7-9.

11. McCarroll JR. Fractures of the patella during a golf swing following reconstruction of the anterior cruciate ligament: a case report. Am J Sports Med 1983;11:26-7.

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