Following last weeks post on patellofemoral pain one of the Elves asked – “What about the bipartite patella?” The patella develops from an expanding mass of cartilage at the front of the knee that ossifies during childhood to form one bone. In 77% of the population this ossification occurs from one central site but 23% can involve 2 or 3 ossification sites. If these sites fail to fuse together they remain connected by a fibrocartilage union (synchondrosis). The result is a bipartite or tripartite patella and this affects around 1-2% of the population. Although usually an incidental finding on x-ray, around 2% can become painful, usually after trauma or participation in sports and more commonly in young adults. Pain is thought to be caused by fracture or separation at the synchondrosis. We found this study whose aim was to identify the most effective method for the treatment of the symptomatic bipartite patella.
Here’s what they did
After a preliminary search established a paucity of RCTs the authors included any studies investigating bipartite patella. The methodological quality of included studies was assessed using the Centre for Evidence-Based Management (CEBMa) critical appraisal tool for case studies and series. The primary outcome measure was pain, secondary measures were: function, radiographic evidence of bone healing and satisfaction.
Here’s what they found
Following a search of published and unpublished literature 22 studies investigating 127 cases of bipartite patella were included in the review. Most were case reports and small case series.
Quality of included studies was deemed ‘good’ with scores ranging from 8 to 9 out of ten. Meta-analysis was not possible due to heterogeneity therefore the authors produced a narrative review.
- Five studies (n= 7 cases) described conservative management including: immobilisation, rest, corticosteroid injection and ultrasound. All participants were symptom free at follow up (range >1.5 – 24 months)
- Six studies (n= 12 cases) described arthroscopic excision with 9 participants reporting resolution at follow up (1.5- 36 months), and 3 reporting occasional knee ache.
- Two studies (n= 2 cases) described combined arthroscopic and surgical excision with significant reduction in pain and return to sport.
- Five studies (n= 52 cases) described open surgical excision, reporting “excellent” improvement in pain and function at follow up. One study following 25 participants over a mean of 15 years (range 10 – 22 years) reported full range of movement, a mean score of 95 (75-100) on Kujala functional score, and a mean score of 1 (range 0-6) on a visual analogue score for pain.
- Three studies described tension band wiring in teenaged participants (n=3). Two participants required removal of hardware due to knee tenderness with one reporting some ongoing pain after extended exercise at 29 months.
- One single case report described open reduction internal fixation (ORIF) after failed conservative treatment. Resolution of pain was achieved by 6 weeks with bone healing at 12 weeks.
- Three studies described soft tissue release (n= 32 cases). One study reported complete bone healing at 6 months in 11 cases, and incomplete in the remaining 6. Outcomes for all three studies were described as ‘excellent’ or ‘good’ at follow up (range 4-36 months).
The authors concluded
This is a poorly answered treatment question. No firm guidance can be given as to the most appropriate method of treating the symptomatic bipartite patella.
The Musculoskeletal Elf’s view
In systematic reviews narrative synthesis uses words to describe findings when statistical meta-analysis methods cannot be applied to data. Narrative synthesis differs from a traditional narrative review in that a transparent and systematic approach is taken to literature searching and quality appraisal. Although the authors of this review used a systematic approach they did not state which databases were accessed, making it difficult to determine whether the literature search was exhaustive. The relatively small number of participants in each study may be explained by the low incidence of symptomatic bipartite patella in the general population. Unfortunately our question remains unanswered!
What do you think?
- Is this a condition you have encountered?
- How have you managed this?
- McMahon S.E., LeRoux J.A., Smith T.O., Hing C.B.2015, “The management of the painful bipartite patella: a systematic review”, Surg Sports Traumatol Arthrosc. [Abstract]