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ORIGINAL ARTICLE

Isolated Chondral Fragment of the Lateral Femoral Trochlea in an Adolescent: Surgical Technique and Case Report

Rachel M. Frank, Joseph B. Wilson, Mark A. Slabaugh,  Maj USAF, Travis Smith,  Charles A. Bush-Joseph

Division of Sports Medicine, Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, USA.

Address for Correspondence:

Rachel M. Frank
Division of Sports Medicine
Department of Orthopaedic Surgery
Rush University Medical Center
1725 West Harrison Street Suite 1063
Chicago, IL 60612

Phone:
  
312-432-2460
Fax    :  312-563-0579
E-mail:  
rmfrank3@gmail.com

Abstract:

Isolated trochlear chondral fractures of the knee are extremely uncommon, especially in the adolescent population.  Little is known about the specific mechanisms of injury, and symptoms can often mimic other knee pathologies, making diagnosis difficult. Because these injuries cannot be diagnosed radiographically and patient symptoms typically mimic meniscal tears or other knee pathology, it is possible that these lesions are more prevalent than previously thought. The purpose of this report is to describe a case of chondral fracture of the lateral trochlea of the femur in an adolescent male, to elaborate on the surgical technique employed, and to provide an analysis for the mechanism responsible for this injury. 

J.Orthopaedics 2009;6(4)e2

Keywords:

Chondral fracture; adolescent; lateral trochlea; knee

 

Introduction:

Chondral fractures of the trochlea of the knee are uncommon and rarely reported in the literature.  Little is known about the specific mechanisms that cause these injuries, and symptoms can often mimic those of other knee pathologies, making diagnosis difficult.  In contrast, both osteochondral fractures as well as isolated chondral fractures of the weight-bearing portion of the femoral condyle are more frequently reported in the literature, and the associated mechanism of injury has been well described.1-9  Only two previous studies10, 11  in the literature report on isolated chondral injury to the lateral trochlea, and to our knowledge, there are no reports describing osteochondral fractures of the trochlea. The report by Oohashi et al.11 suggested that chondral fractures of the trochlea may occur as a result of shear force of the patella during rapid extension of the weight-bearing knee from a flexed position; however, this mechanism has not been verified.

The purpose of this report is to describe a case of chondral fracture of the lateral trochlea of the femur in an adolescent male, as well as to analyze the mechanism responsible for this injury. Prior to writing this manuscript, the authors obtained the written informed consent from the patient’s guardian (patient is a minor) for print and electronic publication of the case report.

Case Report:

A healthy-appearing 13-year-old male reported to the clinic with a one-month history of carrying some boxes and subsequently tripping, falling, and landing bluntly on the anterior aspect of his left knee.  The patient stated that he fully recovered from the injury uneventfully and returned to soccer-related activities.  The patient noted that four days prior to the initial clinic visit (approximately 3.5 weeks after resuming soccer activities), he attempted a sharp cutting maneuver and felt a pop in his knee with immediate pain, swelling, and inability to bear weight.  The patient had no history of previous surgery on the left knee.  The patient obtained an MRI and reported to the clinic for evaluation.

On physical examination, the patient had a moderate effusion of his left knee and was exquisitely tender to palpation in the anterior aspect of his knee.  The patient also had focal tenderness both medially and laterally surrounding the patella, and had significant patellar apprehension with lateral mobilization.  The patient had active flexion to 90 degrees but lacked ten degrees of full extension.  Passive range-of-motion testing was limited due to extreme guarding from discomfort.  Testing of the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial cruciate ligament (MCL), and lateral cruciate ligament (LCL) were normal, and the patient had no medial or lateral joint line tenderness.  The patient had a grade I-A Lachman.  Pivot shift testing was inconclusive due pain.  Gait examination was also not possible as the patient could only toe-touch with crutches.  The MR images, taken prior to the clinic visit, revealed what appeared to be a 20 mm (diameter) cartilaginous loose body originating from the lateral femoral condyle. The ACL, PCL, MCL, LCL, and both menisci appeared intact.

Based on the clinical findings and imaging studies, it appeared that the patient had a patellar dislocation with a cartilage loose body.  Given the patient’s age and desire to return to athletics, it was recommended that the patient undergo surgical repair with arthroscopy, mini-arthrotomy, and loose body fixation using screws.

The patient was brought to surgery 3 days later.  General anesthesia and antibiotics were administered, and a tourniquet was placed.  Examination under anesthesia revealed a stable knee with a moderate effusion and full range-of-motion.  A diagnostic arthroscopy was then performed utilizing standard superloateral, inferolateral, and inferomedial portals.  Upon entering the joint, the effusion was evacuated and an intact 35 by 35 mm osteochondral fragment in the superior pouch of the knee was revealed (Figure 1). The patella, lateral and medial femoral condyles, lateral and medial menisci, lateral and medial tibial plateaus, ACL, and PCL were all normal.  Because of the size, depth, and location of the chondral lesion, we decided to make a mini-arthrotomy as opposed to attempt an all-arthroscopic repair.

Figure 1a: Arthroscopic image portraying the isolated chondral fragment
Figure 1b:
Arthroscopic image portraying the defect on the lateral trochlea

A 5 cm mini-arthrotomy incision was made over the anterolateral patella and a lateral retinacular release was performed to allow for adequate visualization and to prevent further episodes of patellar dislocation.  The capsule was opened and approximately 2 cm of the distal vastus lateralis was excised.  The chondral fragment was isolated, removed, and placed in moist saline on the back table. The bed of the lesion, located in both the convex and concave surface of the lateral trochlea, was curetted down to the bleeding bone.  As the chondral fragment was intact, orientation and alignment of the fragment back into the defect was readily achieved.  After placement into the defect, the fragment was secured using three Arthrex chondral darts, two Arthrex 2.8 mm bioabsorbable screws, and one Arthrex 3.5 mm cannulated metal screw.  Excellent alignment and fixation were achieved, and the tourniquet was released for a total tourniquet time of just over 1 hour (Figure 2).

Figure 2a: Intra-operative photograph showing the size of the removed, intact chondral fragment as well as the fracture site on the lateral trochlea.

Figure 2b: Intra-operative photograph showing the bed of the lesion after being curetted down to the bleeding bone surface.

Figure 2c: Intra-operative photograph showing one of the Arthrex chondral darts that was used to fix the fragment into place.

Figure 2d: Intra-operative photograph showing excellent alignment and fixation of the fragment back into the defect.

The patient was allowed to have full weight-bearing following surgery, with the utilization of a brace and limited range-of-motion. Ten days post-operatively, the patient returned to the clinic and had significantly reduced pain, was not taking narcotics, and was able to stand and bear weight.  Radiographs demonstrated a single metallic screw in the appropriate location and not contacting the growth plate (Figure 3).  We opened his brace to 45 degrees to permit increased range of motion.  Approximately 5 weeks post-operatively, the patient had returned to school, was off of all medication, was walking with only a mild limp, and was performing light activities without pain.  Physical examination revealed moderate quadriceps atrophy, consistent with being 5 weeks out of knee surgery.  The patient’s range of motion was 0 to 95 degrees, with a 10 degree extensor lag and active extension.

Figure 3: Post-operative radiographs showing a single metallic screw in the appropriate location and not contacting the growth plate (a: anterior-posterior view; b: lateral view)

Ten weeks following surgery, the patient returned for follow-up evaluation and arthroscopic hardware removal of the metallic screw.  The patient was brought to surgery and general anesthesia was administered.  Examination under anesthesia revealed a completely stable knee with full range of motion.  Arthroscopic incisions were made and a superomedical outflow was used.  The patella appeared completely normal and the large trochlear defect was united throughout.  After identification of the central metallic screw, it was removed through a transpatellar tendon technique. The peripheral margins of the lesion were probed and were completely intact (Figure 4).  No debridement was necessary, and following surgery the patient was taken to recovery in stable condition.

Figure 4a: Arthroscopic image portraying the healed chondral fragment 10 weeks following fixation

Figure 4b: Arthroscopic image portraying removal of the central metallic screw through a transpatellar tendon technique 10 weeks following initial fragment fixation

Figure 4c: Arthroscopic image portraying complete healing of the peripheral margins of the lesion 10 weeks after initial fragment fixation

Ten days following arthroscopic screw removal, the patient reported to the clinic with full weight-bearing (no crutches or assistance) with mild discomfort upon palpation and minor swelling.  Physical examination revealed a small effusion with moderate tenderness and guarding associated anterior knee palpation.  The patient’s range of motion was 0 to 65 degrees.  At this point, we felt the patient was progressing excellently and he was recommended to undergo formal physical therapy to improve range of motion and strengthening.  The patient was asked to avoid use of the leg-extension and leg-press machines and was asked to avoid all impact activities.

At most recent follow-up, 10 months after open reduction and internal fixation of the chondral fragment, the patient is asymptomatic with full active and passive range-of-motion.  Clinically he had no effusion and no patellar apprehension with lateral mobilization. He had returned back to activity without restrictions and was able to play soccer, run, squat, jump, and hop.

Discussion :

Isolated chondral fractures of the lateral trochlea of the knee are difficult to diagnose and thus are rarely reported in the literature. Because these injuries cannot be diagnosed radiographically and patient symptoms typically mimic meniscal tears or other knee pathology, it is possible that these lesions are more prevalent than previously thought. While several reports in the literature describe osteochondral and chondral fragments of the weight bearing portion of the knee, there are only 2 reports that describe chondral fragments of the trochlea and no reports on osteochondral fragments of the trochlea.10, 11    One additional report describes chondral injuries to the trochlea of the knee, but does not specifically report on chondral fractures.12

Because there are so few reports of chondral fracture of the trochlea, it is difficult to determine specific factors that put someone at risk for this type of injury.  It is equally difficult to determine a common mechanism of injury. While the study by Huegli et al. does not describe trochlear chondral fractures, the authors do state that trochlear chondral lesions typically occur following a sudden movement incorporating both flexion and rotational components.12 The 15 patients described in this study had an average age of 44 years, and all were older than 17 years old.  In a recent report described by Oohashi et al., an isolated case of chondral fracture of the lateral trochlea of the femur in a 13-year-old boy is described.11  In this case, the patient was playing basketball and experienced a snap in his knee while extending his knee from approximately 50-60 degrees of flexion.  The MRI and diagnostic arthroscopy revealed the chondral fragment, however no other significant knee pathology was noted.  The authors described the mechanism of injury to be a result of “shear force transmitted by the patella to the convex surface of the trochlea during rapid extension of a weight bearing knee from a flexed position.”  In a report by Dory et al., an isolated chondral fracture of the intercondylar area of the knee in a 15-year-old boy subsequent locking of his knee during a tennis match was described.10  Following arthrography, this patient was found to have osteochondritis dissecans (OCD) of the medial femoral condyle.  In this report, the author stated that the fracture had been caused by patellar impingement of the intercondylar groove; however, it is unknown if the underlying OCD predisposed this patient to a traumatic chondral fracture of the trochlea.

While the patient presented in this report is a young male, similar to the patients presented in both the Oohashi and Dory reports, we cannot conclude that adolescent males are more prone to isolated chondral fracture of the trochlea as the overall reported incidence of this injury is so low.  Similarly, while the patient in our report had no prior diagnosis of OCD, unlike the patient presented by Dory, it is possible that the initial traumatic injury sustained by the boy during his fall approximately 3.5 weeks prior to his soccer injury predisposed him to chondral fracture of the trochlea.  The mechanism of injury experienced by our patient is also different from those reported by Oohashi and Dory, further increasing the complexity of the understanding of this type of injury.  Our patient experienced chondral fracture of the trochlea during an athletic cutting maneuver while in full weight-bearing, but unlike the patient from the Oohashi report, this patient did not undergo rapid extension from a flexed position.

The lateral trochlea in general may be more prone to chondral fracture due to traumatic contact from the patella as it is larger and more prominent than the medial trochlea.  In addition, while the association between OCD and trochlear chondral fracture is unknown, several authors have shown that OCD of the trochlea is more often lateral.13-15

In conclusion, the patient presented in this report is similar in age and gender to the patients previously reported to have isolated chondral fractures of the lateral trochlea of the knee.  Different from the previous reports of causation of this injury, the mechanism of injury in this case was due to patellar dislocation during a cutting movement while in full weight-bearing.

Reference :

  1. Gilley JS, Gelman MI, Edson DM, Metcalf RW. Chondral fractures of the knee. Arthrographic, arthroscopic, and clinical manifestations. Radiology. Jan 1981;138(1):51-54.

  2. Hopkinson WJ, Mitchell WA, Curl WW. Chondral fractures of the knee. Cause for confusion. Am J Sports Med. Sep-Oct 1985;13(5):309-312.

  3. Kennedy JC, Grainger RW, McGraw RW. Osteochondral fractures of the femoral condyles. J Bone Joint Surg Br. Aug 1966;48(3):436-440.

  4. Milgram JW, Rogers LF, Miller JW. Osteochondral fractures: mechanisms of injury and fate of fragments. AJR Am J Roentgenol. Apr 1978;130(4):651-658.

  5. Terry GC, Flandry F, Van Manen JW, Norwood LA. Isolated chondral fractures of the knee. Clin Orthop Relat Res. Sep 1988(234):170-177.

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  7. Mashoof AA, Scholl MD, Lahav A, Greis PE, Burks RT. Osteochondral injury to the mid-lateral weight-bearing portion of the lateral femoral condyle associated with patella dislocation. Arthroscopy. Feb 2005;21(2):228-232.

  8. Luthje P, Nurmi-Luthje I. Osteochondral fracture of the knee treated with bioabsorbable implants in two adolescents. Acta Orthop Belg. Apr 2008;74(2):249-254.

  9. Dines JS, Fealy S, Potter HG, Warren RF. Outcomes of osteochondral lesions of the knee repaired with a bioabsorbable device. Arthroscopy. Jan 2008;24(1):62-68.

  10. Dory MA. Chondral fracture of the anterior intercondylar groove of the femur. Clin Rheumatol. Jun 1983;2(2):175-177.

  11. Oohashi Y. Chondral fracture of the lateral trochlea of the femur occurring in an adolescent: mechanism of injury. Arch Orthop Trauma Surg. Nov 2007;127(9):791-794.

  12. Huegli RW, Moelleken SM, Stork A, et al. MR imaging of post-traumatic articular cartilage injuries confined to the femoral trochlea. Arthroscopic correlation and clinical significance. Eur J Radiol. Jan 2005;53(1):90-95.

  13. Peters TA, McLean ID. Osteochondritis dissecans of the patellofemoral joint. Am J Sports Med. Jan-Feb 2000;28(1):63-67.

  14. Marshall KW, Marshall DL, Busch MT, Williams JP. Osteochondral lesions of the humeral trochlea in the young athlete. Skeletal Radiol. May 2009;38(5):479-491.

  15. Takahashi Y, Nawata K, Hashiguchi H, Kawaguchi K, Yamasaki D, Tanaka H. Bilateral osteochondritis dissecans of the lateral trochlea of the femur: a case report. Arch Orthop Trauma Surg. May 2008;128(5):469-472.

This is a peer reviewed paper 

Please cite as: Rachel M. Frank: Isolated Chondral Fragment of the Lateral Femoral Trochlea in an Adolescent: Surgical Technique and Case Report..

J.Orthopaedics 2009;6(4)e2

URL: http://www.jortho.org/2009/6/4/e2

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