Working Diagnosis:
Ultrasound study, injury mechanism, and clinical exam were concerning for patellar sleeve fracture. MRI suggested tibial tubercle cortical avulsion fracture and patellar tendinosis.

Treatment:
The patellar tendon was surgically released from the tibial tubercle and later re-tensioned, restoring normal patellar height. Patient was locked in extension for 4 weeks at which time he was placed in a hinged knee brace and started with physical therapy. The knee was progressively flexed and at 9 weeks post-op patient could actively flex knee to 110 degrees and was walking without assist.

Outcome:
At 7 months post-op, patient was cleared for light jogging. Functional rehabilitation was offered but declined, patient instead opting for guided workouts with athletic trainer.

He was to resume spring conditioning with football; unfortunately, all sports were suspended due to coronavirus pandemic.

Author's Comments:
This case was complicated by patient's time frame of presentation and his physical abilities despite age. Appearance of the knee did not change per the patient, suggesting an initial traumatic acute patella alta. Both potential diagnoses suggested by imaging are rare (Photo 1,Photo 2). We suspect the patient did suffer a patellar sleeve fracture. With delayed recognition and persistent attempt to return, he developed tendinosis as the tendon was functioning in an abnormal mechanism. We propose a concurrent initial avulsion injury that lengthened over time. Urgent diagnosis of a patellar sleeve injury is important to limit potential for ectopic bone formation, with treatment options dependent on the degree of displacement

Editor's Comments:
This case provides a good example of some of the complexities that arise due to the unique anatomy of the skeletally immature athlete. The delayed presentation unfortunately creates an unclear view of the initial injury - patellar sleeve fracture vs avulsion of the tibial tuberosity apophysis. Both of these injuries share a common mechanism: sudden, forceful contraction of the quadriceps mechanism. In general, avulsion fractures in the lower extremity are seen with kicking, sprinting or jumping and occur at one of the apophyses or secondary ossification centers. Most of these sites close by age 17 with the exceptions of the ischial apophysis and the ASIS which close by age 25. Avulsion fractures of the tibial tuberosity are rare accounting for only 0.4-2.7% of all pediatric fractures (1). Most avulsion fractures can be treated conservatively with relative rest, altered weight bearing and gradual return to play based on radiographic evidence of healing over the course of 6-8 weeks. However, tibial tubercle avulsions typically require early surgical fixation to avoid downstream complications. Indications for surgical intervention include displacement of one or more fragments of the tuberosity or extension of the fracture through the proximal tibial ossification center into the joint disrupting the articular surface (1). While patellar fractures are rare in the pediatric population, patellar sleeve fractures are the most common type representing 57% of all patellar fractures in this age group (2). It is the most common type of patellar fracture in patients under the age of 16 with a peak incidence or 12.7 years (2). A patellar sleeve fracture differs from a typical avulsion fracture by the fact that a “sleeve” of periosteum is avulsed off the patella and thus maintains the potential to form bone. If unrecognized, this can lead to the complication of ectopic bone formation either enlarging the patella or even leading to duplication of the patella. Additionally, prompt recognition and treatment of sleeve fractures can lead to potential permanent disability with patella alta, instability, extensor lag, and quadriceps wasting and weakness. Treatment of sleeve fractures invariably requires surgery but in cases where a bony fragment is visible on xray and displacement is less than 2mm, a trial of conservative therapy with casting or bracing in extension is reasonable but has a high risk of failure (2).


References

Schiller J, DeFroda S, Blood T. Lower Extremity Avulsion Fractures in the Pediatric and Adolescent Athlete. J Am Acad Orthop Surg 2017; 25:251-259.

Hunt D, Somashekar N. A review of sleeve fractures of the patella in children. The Knee 2005; 12: 3-7.

References:
Schiller J, DeFroda S, Blood T. Lower Extremity Avulsion Fractures in the Pediatric and Adolescent Athlete. J Am Acad Orthop Surg 2017; 25:251-259.
Hunt D, Somashekar N. A review of sleeve fractures of the patella in children. The Knee 2005; 12: 3-7.

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