Femoral subchondral insufficiency fracture - treated by subchondroplasty
Diagnosis certain
Presentation
~3 months of anteromedial knee pain and swelling. Exacerbated to weight bearing.
Patient Data
Age: 50 years
Gender: Male
Baseline x-ray
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- possible mild patellofemoral compartment osteoarthritis (early superior patellar osteophyte?)
- normal-appearing tibio-femoral compartments
- small knee effusion
Initial MRI (3 months later)
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-
medial compartment:
- 12 mm crescentic hypointensity of subchondral bone, consistent with insufficiency fracture with minimal collapse
- overlying hyaline cartilage appears flattened, but intact
- normal meniscus
-
lateral compartment:
- normal cartilage
- normal meniscus
-
patellofemoral compartment:
- full-thickness chondrosis of central trochlea (best seen on axial), with possible 9 mm loose body posterior to ACL within intercondylar notch (best seen on sagittal T2)
- normal patellar cartilage
-
other:
- small knee joint effusion and small Baker's cyst
- marked thickening of lateral patellofemoral ligament, suggestive of chronic sprain
- extensive superficial anterior edema/bursitis
- cruciate and collateral ligaments intact
Operative note
- Arthroscopic knee chondroplasty: trochlea, medial femoral condyle, lateral tibial plateau
- Removal of loose bodies
- Percutaneous subchondroplasty of the medial femoral condyle insufficiency fracture
Description of procedure (abridged)
-
medial compartment:
- shaver used to debride unstable flaps of cartilage off the medial femoral condyle
- grasper was used to remove the loose body
-
lateral compartment:
- shaver used to debride unstable fibrillations off lateral tibial plateau
-
suprapatellar pouch:
- graspers used to remove two additional loose bodies
-
trochlea:
- straight biter, left biter, and shaver used to debride [cartilage] back to a stable remaining shoulder
- result was a remaining diffuse high grade III lesion over a 3 cm area
-
subchondroplasty:
- fluoroscopic guidance was used to find appropriate starting point for percutaneous subchondroplasty of medial femoral condyle
- once appropriate starting point was determined, it was drilled into the femur to appropriate depth and location
- cement was mixed and a total of four vials were injected into the knee carefully under fluoroscopic evaluation. Cement was allowed to harden and the trocar was backed out of the knee. Final fluoroscopic shots were taken
- scope was reintroduced into the joint, showing no extravasation
1mth routine postOp evaluation
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- new ill-defined and area of speckled sclerosis centered at medial femoral condyle, consistent with interval subchondroplasty
- no other changes
~2 yr postOp persistent pain
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-
medial compartment:
- interval subchondroplasty - stellate hypointense signal centrally within the medial femoral condyle corresponding to bone cement on x-ray
- mild interval collapse along previously-identified insufficiency fracture (best visualized on coronal T2FS)
- new partial thickness defects of central cartilage overlying the lesion, which may represent changes of chrondroplasty or chondrosis
-
other:
- interval removal of loose body at posterior intercondylar notch
- mild improvement in small knee joint effusion and superficial edema/bursitis
Case Discussion
This case demonstrates a typical scenario for which subchondroplasty may be attempted, as well as expected imaging findings.
Initial presentation with focal knee pain out of proportion to x-ray findings, and so MRI was obtained. Because MR findings of insufficiency fracture correlated to patient's symptoms, and after trial of non-operative management (intra-articular steroid injection and offloader brace) did not mitigate symptoms, it was decided to pursue subchondroplasty for pain relief and to prevent articular collapse.
Post-operatively, patient continued with daily pain from 4/10 to 8/10.