Abstract
Background:
The bipartite patella is a developmental variant in which incomplete ossification leads to a fibrocartilaginous synchondrosis between ossification centers; repetitive traction on the synchondrosis in young athletes may lead to pain. Few series of surgical cases exist to guide treatment approaches to refractory pain.
Hypothesis/Purpose:
To investigate the presenting features, clinical course, surgical techniques, and outcomes associated with operative treatment of symptomatic bipartite patella in pediatric and adolescent athletes, with comparison to a control group of symptomatic, non-operative patients.
Methods:
A retrospective medical record review of patients ≤20 years-old diagnosed with symptomatic, radiographically-confirmed bipartite patellae between 2003 and 2018 at a single tertiary-care pediatric hospital was conducted. Patients for whom knee pain could not be attributed to bipartite patella were excluded. Additional clinical and operative variables were collected for the subset that underwent surgical treatment. Outcomes analyzed included time to return to sport (RTS) and re-operation.
Results:
278 patients (37.8% females; mean age: 12.7 years, range 7-20 years) were included, 27 (mean age: 15.3 years, range 10-20 years) of whom were treated operatively (9.7%). Compared to the 251 patients who underwent non-operative treatment (consisting of physical therapy, activity modification, non-steroidal anti-inflammatory medicines, and cryotherapy), the operatively treated patients were more likely to be older (mean age 12.4 years vs. 15.3 years, p<0.001), female (35.5% vs. 59.3%, p=0.02) and competitive athletes (83.6% vs. 100%, p=0.10). Of the operative patients, 16 (59%) had Saupe III (superolateral) ossicles, 8 (30%) had Saupe II (lateral) ossicles, and 3 (11%) had Saupe I (inferior) ossicles. Most operative patients (79%) reported insidious onset of pain, with minor trauma precipitating symptom onset in the remainder (21%). Symptom duration prior to surgery was 2.2 years (range 1.7 mo-10.1yrs). Procedures were categorized as isolated fragment excision (n=10), fragment excision with lateral release (n=9), isolated lateral release (n=4), ORIF (n=3), and arthroscopic drilling (n=1). Operative outcomes are found in Table 1.
Conclusions:
Bipartite patella may be an underappreciated cause of knee pain in adolescent athletes. Patients who underwent surgery displayed symptoms lasting >2 years, representing ˜10% of cases, and were most likely to have superolateral bipartite fragments with a mean size of ˜1cm2. Surgery was more common amongst females, competitive athletes, and older adolescents. There was an overall 11% risk of persistent or recurrent symptoms warranting re-operation. Prospective multi-center investigations may be warranted to identify optimal candidates for earlier interventions, as well as optimal non-operative and operative treatment techniques.
Summary of operative outcomes for patients who underwent isolated fragment excision (FE), FE and lateral release (FE + LR), isolated LR, open reduction internal fixation (ORIF), or arthroscopic drilling for symptomatic bipartite patella.
| Surgical Technique | n (%) | Fragment area (mm2) | Fragment %* | Ave time to radiographic healing | Avg time to Return to Sport | Re-operation | Re-operation Technique |
|---|---|---|---|---|---|---|---|
| Isolated FE |
10 (37%) | 128.8 | 10.5% | --- | 2.0 mo | 1/10 (10%) | ALR (4 yrs postop) |
| FE + LR | 9 (33%) | 71.4 | 7.4% | --- | 2.7 mo | 1/9 (11%) | 2nd ALR (4 yrs postop) |
| Isolated LR |
4 (15%) | 75.8 | 9.5% | --- | 1.8 mo | 0 | --- |
| ORIF | 3 (11%) | 93.13 | 9.2% | 4.8 mo | 3.0 mo | 1/3 (33%) | ROH (2 yrs postop) |
| Arthroscopic Drilling | 1 (4%) | 64.03 | 6.7% | 3.2 mo | 3 mo | 0 | --- |
| All operations | 27 | 96.6 | 8.8% | --- | 2.2 mo | 3/27 (11%) | --- |
*Fragment % was calculated as the area of the bipartite fragment divided by the overall area of the patella.