Working Diagnosis:
Implant failure/loss of fixation of the bioabsorbable screw

Treatment:
Postoperatively the patient was restricted from any cutting or sprinting. She was placed on a home exercise program with emphasis on core and quad strethening. Because the pain persisted and appeared to be getting worse, physical therapy was discontinued and the patient was restricted from all activity. Orthopedic surgery was consulted and the decision was made to take her back to the operating room.

Outcome:
The patient underwent a second Case Photo #3 , Case Photo #4 , Case Photo #5 arthroscopy of her right knee, which demonstrated a grade 4 osteochondral fragment on the weight bearing surface of her medial femoral condyle. Removal of loose osteochondral body and microfracture of the lesion was performed.

Return to activity and follow-up:
She remained non-weight bearing for 6 weeks postoperatively, then progressed to weight bearing as tolerated for 6 weeks, eventually returning to impact activities. She obtained excellent range of motion in her right knee, had no effusion, and was pain free.

Author's Comments:
Osteochondritis dissecans (OCD) is a common disorder of the knee that has been treated with a multitude of approaches.3 Biodegradable implants for internal fixation were developed to eliminate the need for a second surgical intervention for removal of the devices. In addition, the possible risks of retained metallic implants, such as device corrosion and stress-protection weakening of bone, can be avoided.1 Results of biodegradable pin fixation of osteochondritis dissecans fragments of the knee generally have been satisfactory and safe.4 However, complications such as reactive synovitis with effusion5 or backing out and breakage of the screw head leading to articular cartilage damage2. This case demonstrates a possible complication resulting from the treatment of an OCD flap lesion with a bioabsorbable screw. In a patient treated with bioabsorbable screws, effusion with increased pain warrants further investigation including MRI or arthroscopy.5

Editor's Comments:
This case highlights the need to have a high suspicion of an OCD lesion in a young athlete with pain and effusion. With an incidence of approximately 29 cases per 100,000 males and 18 cases per 100,000 females, it is not overly common. Also, the etiology of OCD remains unknown; family history, repetitive micro-trauma, growth disorders, and ischemia have been proposed as possible etiologies.6 Treatment of OCD lesions is nicely outlined above and the AAOS has recently released a pediactic guideline on OCD lesions of the knee in August 2013. See reference 6 below.

References:
1. Bostman, O. & Pilhaljamaki, H. (2000). Clinical biocompatibility of biodegradable orthopaedic implants for internal fixation: a review. Biomaterials, 21, 2615-2621.

2. Camathias, C., Festring, J. D., & Gaston, M. S. (2011). Bioabsorbable lag screw fixation of knee osteochondtitis dissecans in the skeletally immature. Journal of pediatric orthopedics B, 20, 74-80.

3. Friederichs, M. G., Greis, P. E., & Burks, R. T. (2001). Pitfalls associated with fixation of osteochondritis dissecans fragments using bioabsorable screws. Arthroscopy: the journal of arthroscopic and related surgery, 17 (5), 542-545.

4. Nakagawa, T., Kurosawa, H., Ikeda, H., Nozawa, M., & Kawakami, A. (2005). Internal fixation for osteochondritis dissecans of the knee. Knee surg sports traumatol arthroscopy, 13, 317-322.

5. Scioscia, T. N., Giffin, J. R., Allen, C. R., & Harner, C. D. (2001). Potential complication of bioabsorbable screw fixation for osteochondritis dissecans of the knee. Arthroscopy: the journal of arthroscopic and related surgery, 17 (2), E7.
6. Shea, Kevin G., et al. New pediactic guidelines on OCD Knee. AAOS Now. August 2013. 7(8).

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