Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-014-2887-7
KNEE
Developmental anomaly of ossification type patella partita Yoshikazu Oohashi
Received: 5 October 2012 / Accepted: 30 January 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose Bipartite patella has been recognized as an incidental radiographic finding. However, symptomatic bipartite patella is occasionally diagnosed in adolescents and young athletes. The incidence of bipartite patella has been reported at 0.2–1.7, and 1–2 % of these cases are symptomatic. The purpose of this review article was to discuss current concepts relevant to developmental anomaly of ossification type patella partita. Methods A PubMed database search using the key words ‘‘bipartite patella’’ was performed. Clinical papers reporting the bipartite patella were included. Four German-language studies were also included, three for incidence of bipartite patella and one for classification. Results A new classification of developmental anomaly of ossification type patella partita based on location and number of fragment was recently proposed. It is simple and useful and applicable to all types of bipartite or tripartite patella. Several imaging studies have reportedly been used to evaluate symptomatic bipartite patella. MRI is currently the most appropriate method used to assess patients with bipartite patella. Although surgical procedures have been developed that reduce excessive traction force by the vastus lateralis muscle on the bipartite fragment, there is not sufficient evidence to support their use for routine treatment of painful bipartite patella. Conclusion In most symptomatic cases, movement at the interface between the bipartite fragment and the body of the patella presumably causes the pain. Therefore, the existence of apparent motion at the interface should be Y. Oohashi (&) Oohashi Orthopaedic Clinic, 38-20, Ninomiya-3-choume, Fukui City, Fukui-Ken 910-0015, Japan e-mail: [email protected]
confirmed by specific imaging studies before surgery. Magnetic resonance imaging findings may provide such evidence by demonstrating a fluid bright signal across the segmentation, typical of pseudoarthrosis. Level of evidence V. Keywords Patella partita Bipartite patella Developmental anomaly of ossification type Current concepts Review
Introduction The patella initially ossifies at 3–5 years of age. As the patellar ossification centre enlarges, expanding margins may be irregular and associated with accessory ossification centres, which are most commonly found superolaterally [24]. Approximately half of them coalesce during childhood and adolescence [28]. In the remaining individuals, this superolateral accessory ossification centre may fail to unite with the main portion of the patella, leading to patella partita—known as developmental anomaly of ossification type patella partita [3, 10, 24, 25, 28]. In 1975, Green reported three boys with painful bipartite patellae whose pain had been relieved by excision of the accessory ossification centres [12]. In 1977, Weaver reported a series of 21 patients with bipartite patellae and described two characteristic modes of symptom onset: (1) gradual onset during activity in athletes and (2) sudden onset after an injury in non-athletes, such as a direct blow to the knee [39]. Since these two reports were published, bipartite patella has been noticed as a cause of anterior knee pain in adolescents and young athletes. During these nearly three decades, many reports of patella partita have been published [1, 3–9, 11, 14–28, 31, 36–38, 40, 41], and
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its clinical significance has become more important than was previously recognized. A new classification of developmental anomaly of ossification type patella partita was recently proposed [27], and several imaging studies have reportedly been used to evaluate symptomatic bipartite patella [17, 18, 21, 26]. The most widely performed treatment is excision of a painful fragment [3, 4, 12, 14, 17, 22, 23, 30, 39, 40]. Recently, arthroscopic excision has also been reported [5, 9]. Although surgical procedures have been developed that reduce excessive traction force by the vastus lateralis muscle on the bipartite fragment [1, 20, 22], the use of these procedures for routine treatment of painful bipartite patella is controversial. The purpose of this article was to review current concepts related to developmental anomaly of ossification type patella partita. A PubMed database search using the key words ‘‘bipartite patella’’ was performed. Clinical papers reporting the bipartite patella were included. Four Germanlanguage studies were also included, three for incidence of bipartite patella and one for classification.
Epidemiology The reported incidences of ‘‘usual’’ bipartite patella in studies that included more than 1,000 patients were 0.2 % (3/1,500 patients) [29], 1.5 % (17/1,100 patients) [34], and 1.7 % (23/1,378 patients) [2]. Bipartite patella is more common in males than females. The reported male/female ratios were 3.0 (12:4) [3], 3.1 (40:13) [18], 3.3 (10:3) [22], 3.4 (86:25) [27], and 4.3 (17:4) [39]. The reported incidences of bilateral involvement were 25 % (28/111 patients) [27], 43 % (9/21 patients) [39], and 43 % (3/7 patients) [14].
Classification In 1921, Saupe reported a 38-year-old man with Little’s disease (spastic diplegia) in whom both patellae were Fig. 1 Classification of the developmental anomaly of ossification type patella partita. Here, patella partita is classified by the location (superolateral or lateral) and the number of fragments (bipartite, tripartite, multipartite). L lateral, M medial
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divided by a transverse split line 1.5 cm above the lower end of the patella, forming an upper large bone fragment and a lower small one [33]. He also analysed several cases of bipartite patella reported up to then in the German-language literature and developed a classification of bipartite patella based on three groups [33]. In the first group, the patella is divided by a transverse split line into an upper large bone fragment and a lower small bone fragment. In the second, the patella is divided by a longitudinal split line into an outer one-fourth bone fragment and an inner three-fourths bone segment. In the third group, the patella is divided into a relatively large inner lower bone fragment and small upper outer bone fragment. This has been the most frequently used classification to date. However, this classification is based only on the location of the fragment. Therefore, diseases such as Sinding-Larsen–Johansson lesion [35], fragmentation of the distal part of the patella associated with spastic cerebral palsy (as reported by Saupe himself) [32, 33], and transverse fracture or stress fracture of the distal part of the patella are all included in the first group. There is also controversy over whether developmental anomaly of ossification type bipartite patella can occur at the lower part of the patella [24, 27]. Moreover, tripartite or multipartite patella and the rare medial bipartite patella [13] cannot be classified using Saupe’s classification. Therefore, Oohashi et al. [27] recently proposed a new classification for developmental anomaly of ossification type patella partita. They classified it by evaluating the location (superolateral or lateral) and number of fragments (bipartite, tripartite, and multipartite) (Fig. 1) [27]. The incidence of superolateral bipartite patella in their study was 83 % (n = 115), lateral bipartite patella 12 % (n = 16), superolateral and lateral tripartite patella 4 % (n = 6), and superolateral tripartite patella 1 % (n = 2) [27]. Among these patella partite in their study, bipartite patellae accounted for 94 % (131/139 knees) and tripartite patellae for 6 % (8/139 knees) [27].
Knee Surg Sports Traumatol Arthrosc
Histology Tissues interposed between the bipartite fragment and the body of the patella are reportedly fibrous tissue and fibrocartilage [10, 25], fibrocartilage only [17, 23, 30], or fibrocartilage and hyaline cartilage [4, 12]. Oohashi et al. [25] noted that a striking histopathological feature of interposed tissue of the painful bipartite patella was fibrous tissue (Fig. 2c) or necrotic fibrocartilage. The bone marrow adjacent to interposed tissue showed numerous small vessels. Additionally, the trabecular bone surfaces and fibrocartilage surfaces adjacent to the bone marrow were scalloped and lined with numerous osteoclasts [25]. Similar observations of areas of increased vascularity [12, 23] and osteoclastic activity [12] have been described. Such findings are consistent with a reparative reaction in the interposed tissue [25].
fragment has occurred after trauma, radiographs reveal that the bipartite fragment is displaced proximally [16]. Ishikawa et al. [17] found that in the symptomatic bipartite patella patient, weight-bearing skyline views obtained with the patient in a squatting position showed wider separation of the accessory fragment from the main patella than did non-weight-bearing skyline views. These authors noted that this finding may be a useful diagnostic feature of painful bipartite patella. Although it may reveal fragment movement, the ‘‘squatting position test’’ is somewhat difficult to perform [5]. Magnetic resonance imaging
A standard anteroposterior radiograph of the knee usually shows the accessory fragment (Fig. 2a). If separation of the
In 2007, Kavanagh et al. [18] reported that among 53 patients with bipartite patella and knee pain, 35 (66 %) had oedema within the bipartite fragment. Among these 35 patients, 20 (57 %) had a cartilage signal across the segmentation, 10 (29 %) had a fibrous signal, and 5 (14 %) had a fluid bright signal typical of pseudarthrosis [18]. In contrast, O’Brien et al. [21] reported a study of 25 patients with asymptomatic bipartite patella who showed no evidence of high signals or bone marrow oedema in either the patella or the fragment. Overall, MRI findings associated with a symptomatic bipartite patella include oedema in the
Fig. 2 A 12-year-old boy with a symptomatic superolateral bipartite patella of the left knee. a Anteroposterior radiograph. Arrow indicates the radiolucent demarcation. b Intraoperative photograph at the superolateral aspect of the left patella (right side, proximal; left side,
distal). The bipartite fragment shows gross mobility. c Photomicrograph of fibrous tissue interposed between the bipartite fragment (upper right side) and the body of the patella (lower left side) (H&E 920)
Diagnosis Radiography
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bipartite fragment and an abnormal fibrous or fluid signal across the segmentation [18]. Thus, MRI is currently the most appropriate method used to assess patients with bipartite patella [18].
deposited in the interspaces of a bipartite patella [8, 31, 36]. Its presence causes bone erosions of the bipartite fragment and the adjacent portion of the body of the patella [8, 19, 31, 36]. Acute arthritis with tophaceous gout in the bipartite patella has also been reported [19].
Bone scintigraphy Several authors have reported scintigraphic findings in bipartite or multipartite patellae [4, 7, 14, 15, 23, 26]. Some authors reported that bone scintigraphy was helpful for diagnosing symptomatic bipartite patella because there was increased uptake of technetium-99 m in the bipartite patellar region in those cases [4, 7, 14, 15]. However, each of these reports was a single-patient study evaluating only symptomatic patients. There have been no comparisons using bone scintigraphy that included asymptomatic patients. Oohashi et al. reported that abnormally high scintigraphic uptake occurs frequently in both symptomatic and asymptomatic bipartite patellae [26]. They also noted that bone scintigraphy does not differentiate between the two [26]. Thus, the use of bone scintigraphy is limited by its low specificity.
Clinical features Symptomatic bipartite patella is occasionally observed in adolescents and young athletes, especially those who regularly participate in strenuous sports activities [1, 3, 5, 12, 13, 17, 20, 22, 23, 27, 39, 40]. Only 1–2 % of persons with bipartite patella have symptoms sufficient to cause them to seek medical attention [39]. The onset of pain in 58 % of patients with symptomatic bipartite patella is at 12–14 years of age [27]. The most common symptom is pain at the separated fragments during or after strenuous activity [1, 3, 5, 12, 13, 17, 20, 22, 23, 27, 39, 40]. Patients sometimes complain of pain during knee bending or when climbing stairs [27]. Localized tenderness over the separated fragments is the most common physical finding [1, 3, 5, 9, 12, 14, 17, 20, 22, 27, 30, 39]. An unusual bony prominence at the separated fragments [27, 39] and quadriceps muscle atrophy [5, 9, 27, 39] are sometimes present. In adults, bipartite patella becomes symptomatic following a minor injury, such as a blow to the knee [4, 14, 27] or a major injury such as acutely displaced separation of the bipartite fragment [16, 30]. Rarely, in middle-aged or elderly patients, a severe injury such as a fall causes both separation of the bipartite fragment and rupture of the quadriceps tendon [6, 11, 37, 38, 41]. Among adults, bipartite patella rarely becomes symptomatic in those with gout tophus in the space between the bipartite fragment and body of the patella [8, 19, 31, 36]. When that occurs, a chalky white-yellow material is
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Causes of pain Movement at the interface Several authors reported mobility at the interface between the bipartite fragment and the body of the patella in patients who had undergone surgery [3, 5, 12, 14, 22, 23, 39]. This movement presumably causes pain in most symptomatic patients (Fig. 2b) [3, 5, 12, 14, 22, 23, 39]. Articular cartilage of the bipartite fragment Although many authors have reported that the articular cartilage of the bipartite fragment of the superolateral bipartite patella was intact [1, 3, 10, 12, 20, 23], there have been a few cases of abnormal findings relevant to the articular cartilage of the bipartite fragment [22, 25]. Ogata found that the articular surface of the separated fragment had been replaced with fibrocartilage in one type II patella [22]. Oohashi et al. [25] also reported a patient with lateral bipartite patella in which the proximal one-fourth and distal one-half of the articular surface of the bipartite fragment were replaced by fibrous tissue (Fig. 3). Such occurrence of fibrous tissue on the articular cartilage surface of the
Fig. 3 A 15-year-old girl with symptomatic right lateral bipartite patella. Intraoperative photograph. Patella is reflected laterally, revealing the articular surface (right side, distal; left side, proximal). Proximal one-fourth (arrows) and distal one-half (arrowheads) of the articular surface of the separated fragment are replaced by fibrous tissue. The bipartite fragment does not show mobility
Knee Surg Sports Traumatol Arthrosc
separated fragment may be associated with lateral bipartite patella [25] and may rarely cause pain during articulation. Traction apophysitis Several authors have hypothesized that a major cause of pain in patients with a bipartite patella was excessive traction force by the vastus lateralis muscle on the bipartite fragment [1, 20, 22, 23]. This situation is analogous to Sinding-Larsen–Johansson disease at the inferior patellar pole or Osgood–Schlatter disease in the tibial tuberosity.
Treatment Conservative measures In most patients with symptomatic patella partita, the pain resolves with conservative management that includes rest, restriction of sports activities, physical therapy with isometric stretching exercises of the quadriceps muscle, and non-steroidal anti-inflammatory medications [1, 5, 9, 17, 22, 40]. Surgery Many authors have recommended at least 3 months of conservative treatment before considering surgery [1, 17, 22]. Operative treatment should be considered only for patients who cannot participate in activities of daily living or sports activity because of their pain [22]. Weckstro¨m et al. [40] reported that the incidence of painful, surgically treated bipartite patella was 9.2/100,000 military recruits. Excision of the bipartite fragment Open excision of the painful fragment has been most widely performed, with good results [3, 4, 12, 14, 17, 22, 23, 30, 39, 40]. The author prefers to reattach the vastus lateralis tendon directly to the body of the patella through drill holes after excising the bipartite fragment. Arthroscopic excision of a painful bipartite fragment has been reported [5, 9]. These authors suggest that the procedure is less invasive than an open procedure and allows early postoperative rehabilitation [5, 9]. Excision of a painful fragment is indicated if the fragment is grossly mobile [22]. Sometimes surgery reveals that the fragment is not mobile [9, 12, 22], however, and the surgeon may be reluctant to remove it [22]. Therefore, the existence of apparent motion at the interface should be confirmed by specific imaging studies before surgery. MRI findings may provide such evidence by demonstrating a fluid bright signal across the segmentation typical of pseudarthrosis.
Internal fixation of the bipartite fragment Internal fixation may be indicated for a fragment if it involves a large articular surface. Because this procedure usually requires a bone graft and immobilization of the knee for 3–4 weeks, it is considered more invasive than fragment excision [22]. Subperiosteal detachment of the vastus lateralis insertion, lateral retinacular release, and vastus lateralis release Subperiosteal detachment of the vastus lateralis insertion, lateral retinacular release, and vastus lateralis release was devised based on the idea that a major cause of symptomatic bipartite patella is excessive traction force exerted by the vastus lateralis muscle and is aimed at reducing this traction force on the bipartite fragment [1, 20, 22]. In 1994, Ogata performed subperiosteal detachment of the vastus lateralis insertion to the painful patellar fragment in 13 patients (15 knees) [22]. A grossly mobile patellar fragment was removed from five patellae after detachment. For the other ten patellae (seven type III and three type II) in which the fragment was not mobile, the fragment was left in situ after detachment [22]. All patients had prompt relieve from pain and returned to full sports activity within 2 months of the operation [22]. Among the ten whose fragment was left in situ, six of the seven type III patellae showed osseous union, whereas none of the three type II patellae showed union [22]. In 1995, Mori et al. [20] treated painful bipartite patella with a modified lateral retinacular release technique without excising the fragments in 15 patients (16 knees). Bony union of the bipartite fragment was obtained in 15 of the 16 knees within 8 months of the surgery. The authors noted that this surgical technique proved effective not only for relieving the pain but also for achieving bony union [20]. In 2002, Adachi et al. [1] performed a vastus lateralis release without excising fragments in 15 symptomatic patients with an average age of 13.8 years. The results, which were good, indicated that 64.7 % had bone union. Although both Mori et al. and Adachi et al. reported such good surgical results, it is unclear whether they provide sufficient evidence to support use of these procedures for routine treatment of painful bipartite patellae. At their preoperative arthroscopic examinations, apparent motion or significant change in the articular cartilage of the bipartite fragment was not observed in any of their patients [1, 20]. Therefore, pain in their patients might in fact have been caused by excessive traction force exerted by the vastus lateralis muscle. However, in many of these patients, symptoms might have resolved with conservative treatment, as usually occurs in patients with Osgood–Schlatter disease or Sinding-Larsen–Johansson disease.
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Conclusion In most symptomatic patients, the pain may be caused by movement at the interface between the bipartite fragment and the body of the patella. Therefore, the existence of apparent motion at the interface should be confirmed by specific imaging studies before surgery. MRI findings may provide such evidence by demonstrating a fluid bright signal across the segmentation.
References 1. Adachi N, Ochi M, Yamaguchi H, Uchio Y, Kuriwaka M (2002) Vastus lateralis release for painful bipartite patella. Arthroscopy 18:404–411 2. Blumensaat C (1932) Patella partita-Traumatische SpaltpatellaPatellarfraktur. Arch Orthop Chir 32:263–282 3. Bourne MH, Bianco AJ (1990) Bipartite patella in the adolescent: results of surgical excision. J Pediatr Orthop 10:69–73 4. Canizares GH, Selesnick FH (2003) Bipartite patella fracture. Arthroscopy 19:215–217 5. Carney J, Thompson D, O’Daniel J, Cassidy J (2010) Arthroscopic excision of a painful bipartite patella fragment. Am J Orthop 39:40–43 6. Carter SR (1989) Traumatic separation of a bipartite patella. Injury 20:244 7. Collings CL (1994) Scintigraphic findings on examination of the multipartite patella. Clin Nucl Med 19:865–866 8. Enomoto H, Nagosi N, Okada E, Ota N, Iwabu S, Kamiishi S (2006) Hemilaterally symptomatic bipartite patella associated with bone erosions arising from a gouty tophus: a case report. Knee 13:474–477 9. Felli L, Fiore M, Biglieni L (2011) Arthroscopic treatment of symptomatic bipartite patella. Knee Surg Sports Traumatol Arthrosc 19:398–399 10. George R (1935) Bilateral bipartite patellae. Br J Surg 22: 555–560 11. Gorva AD, Siddique I, Mohan R (2006) An unusual case of bipartite patella fracture with quadriceps rupture. Eur J Trauma 4:411–413 12. Green WT (1975) Painful bipartite patellae. Clin Orthop Relat Res 110:197–200 13. Halpern AA, Hewitt O (1978) Painful medial bipartite patellae. A case report. Clin Orthop Relat Res 134:180–181 14. Iossifidis A, Brueton RN (1995) Painful bipartite patella following injury. Injury 26:175–176 15. Iossifidis A, Brueton RN, Nunan TO (1995) Bone-scintigraphy in painful bipartite patella. Eur J Nucl Med 22:1212–1213 16. Ireland ML, Chang JL (1995) Acute fracture bipartite patella: case report and literature review. Med Sci Sports Exerc 27: 299–302 17. Ishikawa H, Sakurai A, Hirata S, Ohno O, Kita K, Sato T, Kashiwagi D (1994) Painful bipartite patella in young athletes. Clin Orthop Relat Res 305:223–228 18. Kavanagh EC, Zoga A, Omar I, Ford S, Schweitzer M, Eustace S (2007) MRI findings in bipartite patellae. Skelet Radiol 36: 209–214
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19. Kobayashi K, Deie M, Okuhara A, Adachi N, Yasumoto M, Ochi M (2005) Tophaceous gout in the bipartite patella with intraosseous and intra-articular lesions: a case report. J Orthop Surg (Hong Kong) 13:199–202 20. Mori Y, Okumo H, Iketani H, Kuroki Y (1995) Efficacy of lateral retinacular release for painful bipartite patella. Am J Sports Med 23:13–18 21. O’Brien J, Murphy C, Halpenny D, McNeill G, Torreggiani WC (2011) Magnetic resonance imaging features of asymptomatic bipartite patella. Eur J Radiol 78:425–429 22. Ogata K (1994) Painful bipartite patella. A new approach to operative treatment. J Bone Joint Surg Am 76:573–578 23. Ogden JA, McCarthy SM, Jokl P (1982) The painful bipartite patella. J Pediatr Orthop 2:263–269 24. Ogden JA (1984) Radiology of postnatal skeletal development. X. Patella and tibial tuberosity. Skelet Radiol 11:246–257 25. Oohashi Y, Noriki S, Koshino T, Fukuda M (2006) Histopathological abnormalities in painful bipartite patellae in adolescents. Knee 13:189–193 26. Oohashi Y, Koshino T (2007) Bone scintigraphy in patients with bipartite patella. Knee Surg Traumatol Arthrosc 15:1395–1399 27. Oohashi Y, Koshino T, Oohashi Y (2010) Clinical features and classification of bipartite or tripartite patella. Knee Surg Traumatol Arthrosc 18:1465–1469 28. Oohashi Y, Koshino T, Oohashi Y (2010) Natural history of the supero-lateral bipartite fragment of the patella in children. J Orthop 7(4):e5 29. Paas HR (1931) Zur Frage der Patella partita und ihrer Entstehung unter besonderer Beru¨cksichtigung der Schra¨gteilung. Dtsch Z Chir 230:261–277 30. Puddu G, Mariani PP, Alzani R (1978) Detachment of the accessory fragment in ‘‘patella partita’’. Ital J Orthop Traumatol 4:197–203 31. Reber P, Crevoisier X, Noesberger B (1996) Unusual localisation of tophaceous gout. A report of four cases and review of the literature. Arch Orthop Trauma Surg 115:297–299 32. Rosenthal RK, Levine DB (1977) Fragmentation of the distal pole of the patella in spastic cerebral palsy. J Bone Joint Surg Am 59:934–939 33. Saupe E (1921) Beitrag zur Patella bipartita. Fortschr Ro¨ntgenstr 28:37–41 34. Siemens W (1931) Patella partita. Dtsch Z Chir 233:727–755 35. Sinding-Larsen MF (1921) A hitherto unknown affection of the patella in children. Acta Radiol 1:171–173 36. Tashiro S, Sugita T, Nakamura S, Kurata Y (2002) Gout tophus in the bipartite patella. Orthopedics 25:1295–1296 37. Thomas AL, Wilson RH, Thompson TL (2007) Quadriceps avulsion through a bipartite patella. Orthopedics 30:491–492 38. Tonotsuka H, Yamamoto Y (2008) Separation of a bipartite patella combined with quadriceps tendon rupture: a case report. Knee 15:64–67 39. Weaver JK (1977) Bipartite patellae as a cause of disability in the athlete. Am J Sports Med 5:137–143 40. Weckstro¨m M, Parviainen M, Pihlajama¨ki HK (2008) Excision of painful bipartite patella. Good long-term outcome in young adults. Clin Orthop Relat Res 466:2848–2855 41. Woods GW, O’Connor DP, Elkousy HA (2007) Quadriceps tendon rupture through a superolateral bipartite patella. J Knee Surg 20:293–295
KNEE
Developmental anomaly of ossification type patella partita Yoshikazu Oohashi
Received: 5 October 2012 / Accepted: 30 January 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose Bipartite patella has been recognized as an incidental radiographic finding. However, symptomatic bipartite patella is occasionally diagnosed in adolescents and young athletes. The incidence of bipartite patella has been reported at 0.2–1.7, and 1–2 % of these cases are symptomatic. The purpose of this review article was to discuss current concepts relevant to developmental anomaly of ossification type patella partita. Methods A PubMed database search using the key words ‘‘bipartite patella’’ was performed. Clinical papers reporting the bipartite patella were included. Four German-language studies were also included, three for incidence of bipartite patella and one for classification. Results A new classification of developmental anomaly of ossification type patella partita based on location and number of fragment was recently proposed. It is simple and useful and applicable to all types of bipartite or tripartite patella. Several imaging studies have reportedly been used to evaluate symptomatic bipartite patella. MRI is currently the most appropriate method used to assess patients with bipartite patella. Although surgical procedures have been developed that reduce excessive traction force by the vastus lateralis muscle on the bipartite fragment, there is not sufficient evidence to support their use for routine treatment of painful bipartite patella. Conclusion In most symptomatic cases, movement at the interface between the bipartite fragment and the body of the patella presumably causes the pain. Therefore, the existence of apparent motion at the interface should be Y. Oohashi (&) Oohashi Orthopaedic Clinic, 38-20, Ninomiya-3-choume, Fukui City, Fukui-Ken 910-0015, Japan e-mail: [email protected]
confirmed by specific imaging studies before surgery. Magnetic resonance imaging findings may provide such evidence by demonstrating a fluid bright signal across the segmentation, typical of pseudoarthrosis. Level of evidence V. Keywords Patella partita Bipartite patella Developmental anomaly of ossification type Current concepts Review
Introduction The patella initially ossifies at 3–5 years of age. As the patellar ossification centre enlarges, expanding margins may be irregular and associated with accessory ossification centres, which are most commonly found superolaterally [24]. Approximately half of them coalesce during childhood and adolescence [28]. In the remaining individuals, this superolateral accessory ossification centre may fail to unite with the main portion of the patella, leading to patella partita—known as developmental anomaly of ossification type patella partita [3, 10, 24, 25, 28]. In 1975, Green reported three boys with painful bipartite patellae whose pain had been relieved by excision of the accessory ossification centres [12]. In 1977, Weaver reported a series of 21 patients with bipartite patellae and described two characteristic modes of symptom onset: (1) gradual onset during activity in athletes and (2) sudden onset after an injury in non-athletes, such as a direct blow to the knee [39]. Since these two reports were published, bipartite patella has been noticed as a cause of anterior knee pain in adolescents and young athletes. During these nearly three decades, many reports of patella partita have been published [1, 3–9, 11, 14–28, 31, 36–38, 40, 41], and
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its clinical significance has become more important than was previously recognized. A new classification of developmental anomaly of ossification type patella partita was recently proposed [27], and several imaging studies have reportedly been used to evaluate symptomatic bipartite patella [17, 18, 21, 26]. The most widely performed treatment is excision of a painful fragment [3, 4, 12, 14, 17, 22, 23, 30, 39, 40]. Recently, arthroscopic excision has also been reported [5, 9]. Although surgical procedures have been developed that reduce excessive traction force by the vastus lateralis muscle on the bipartite fragment [1, 20, 22], the use of these procedures for routine treatment of painful bipartite patella is controversial. The purpose of this article was to review current concepts related to developmental anomaly of ossification type patella partita. A PubMed database search using the key words ‘‘bipartite patella’’ was performed. Clinical papers reporting the bipartite patella were included. Four Germanlanguage studies were also included, three for incidence of bipartite patella and one for classification.
Epidemiology The reported incidences of ‘‘usual’’ bipartite patella in studies that included more than 1,000 patients were 0.2 % (3/1,500 patients) [29], 1.5 % (17/1,100 patients) [34], and 1.7 % (23/1,378 patients) [2]. Bipartite patella is more common in males than females. The reported male/female ratios were 3.0 (12:4) [3], 3.1 (40:13) [18], 3.3 (10:3) [22], 3.4 (86:25) [27], and 4.3 (17:4) [39]. The reported incidences of bilateral involvement were 25 % (28/111 patients) [27], 43 % (9/21 patients) [39], and 43 % (3/7 patients) [14].
Classification In 1921, Saupe reported a 38-year-old man with Little’s disease (spastic diplegia) in whom both patellae were Fig. 1 Classification of the developmental anomaly of ossification type patella partita. Here, patella partita is classified by the location (superolateral or lateral) and the number of fragments (bipartite, tripartite, multipartite). L lateral, M medial
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divided by a transverse split line 1.5 cm above the lower end of the patella, forming an upper large bone fragment and a lower small one [33]. He also analysed several cases of bipartite patella reported up to then in the German-language literature and developed a classification of bipartite patella based on three groups [33]. In the first group, the patella is divided by a transverse split line into an upper large bone fragment and a lower small bone fragment. In the second, the patella is divided by a longitudinal split line into an outer one-fourth bone fragment and an inner three-fourths bone segment. In the third group, the patella is divided into a relatively large inner lower bone fragment and small upper outer bone fragment. This has been the most frequently used classification to date. However, this classification is based only on the location of the fragment. Therefore, diseases such as Sinding-Larsen–Johansson lesion [35], fragmentation of the distal part of the patella associated with spastic cerebral palsy (as reported by Saupe himself) [32, 33], and transverse fracture or stress fracture of the distal part of the patella are all included in the first group. There is also controversy over whether developmental anomaly of ossification type bipartite patella can occur at the lower part of the patella [24, 27]. Moreover, tripartite or multipartite patella and the rare medial bipartite patella [13] cannot be classified using Saupe’s classification. Therefore, Oohashi et al. [27] recently proposed a new classification for developmental anomaly of ossification type patella partita. They classified it by evaluating the location (superolateral or lateral) and number of fragments (bipartite, tripartite, and multipartite) (Fig. 1) [27]. The incidence of superolateral bipartite patella in their study was 83 % (n = 115), lateral bipartite patella 12 % (n = 16), superolateral and lateral tripartite patella 4 % (n = 6), and superolateral tripartite patella 1 % (n = 2) [27]. Among these patella partite in their study, bipartite patellae accounted for 94 % (131/139 knees) and tripartite patellae for 6 % (8/139 knees) [27].
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Histology Tissues interposed between the bipartite fragment and the body of the patella are reportedly fibrous tissue and fibrocartilage [10, 25], fibrocartilage only [17, 23, 30], or fibrocartilage and hyaline cartilage [4, 12]. Oohashi et al. [25] noted that a striking histopathological feature of interposed tissue of the painful bipartite patella was fibrous tissue (Fig. 2c) or necrotic fibrocartilage. The bone marrow adjacent to interposed tissue showed numerous small vessels. Additionally, the trabecular bone surfaces and fibrocartilage surfaces adjacent to the bone marrow were scalloped and lined with numerous osteoclasts [25]. Similar observations of areas of increased vascularity [12, 23] and osteoclastic activity [12] have been described. Such findings are consistent with a reparative reaction in the interposed tissue [25].
fragment has occurred after trauma, radiographs reveal that the bipartite fragment is displaced proximally [16]. Ishikawa et al. [17] found that in the symptomatic bipartite patella patient, weight-bearing skyline views obtained with the patient in a squatting position showed wider separation of the accessory fragment from the main patella than did non-weight-bearing skyline views. These authors noted that this finding may be a useful diagnostic feature of painful bipartite patella. Although it may reveal fragment movement, the ‘‘squatting position test’’ is somewhat difficult to perform [5]. Magnetic resonance imaging
A standard anteroposterior radiograph of the knee usually shows the accessory fragment (Fig. 2a). If separation of the
In 2007, Kavanagh et al. [18] reported that among 53 patients with bipartite patella and knee pain, 35 (66 %) had oedema within the bipartite fragment. Among these 35 patients, 20 (57 %) had a cartilage signal across the segmentation, 10 (29 %) had a fibrous signal, and 5 (14 %) had a fluid bright signal typical of pseudarthrosis [18]. In contrast, O’Brien et al. [21] reported a study of 25 patients with asymptomatic bipartite patella who showed no evidence of high signals or bone marrow oedema in either the patella or the fragment. Overall, MRI findings associated with a symptomatic bipartite patella include oedema in the
Fig. 2 A 12-year-old boy with a symptomatic superolateral bipartite patella of the left knee. a Anteroposterior radiograph. Arrow indicates the radiolucent demarcation. b Intraoperative photograph at the superolateral aspect of the left patella (right side, proximal; left side,
distal). The bipartite fragment shows gross mobility. c Photomicrograph of fibrous tissue interposed between the bipartite fragment (upper right side) and the body of the patella (lower left side) (H&E 920)
Diagnosis Radiography
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bipartite fragment and an abnormal fibrous or fluid signal across the segmentation [18]. Thus, MRI is currently the most appropriate method used to assess patients with bipartite patella [18].
deposited in the interspaces of a bipartite patella [8, 31, 36]. Its presence causes bone erosions of the bipartite fragment and the adjacent portion of the body of the patella [8, 19, 31, 36]. Acute arthritis with tophaceous gout in the bipartite patella has also been reported [19].
Bone scintigraphy Several authors have reported scintigraphic findings in bipartite or multipartite patellae [4, 7, 14, 15, 23, 26]. Some authors reported that bone scintigraphy was helpful for diagnosing symptomatic bipartite patella because there was increased uptake of technetium-99 m in the bipartite patellar region in those cases [4, 7, 14, 15]. However, each of these reports was a single-patient study evaluating only symptomatic patients. There have been no comparisons using bone scintigraphy that included asymptomatic patients. Oohashi et al. reported that abnormally high scintigraphic uptake occurs frequently in both symptomatic and asymptomatic bipartite patellae [26]. They also noted that bone scintigraphy does not differentiate between the two [26]. Thus, the use of bone scintigraphy is limited by its low specificity.
Clinical features Symptomatic bipartite patella is occasionally observed in adolescents and young athletes, especially those who regularly participate in strenuous sports activities [1, 3, 5, 12, 13, 17, 20, 22, 23, 27, 39, 40]. Only 1–2 % of persons with bipartite patella have symptoms sufficient to cause them to seek medical attention [39]. The onset of pain in 58 % of patients with symptomatic bipartite patella is at 12–14 years of age [27]. The most common symptom is pain at the separated fragments during or after strenuous activity [1, 3, 5, 12, 13, 17, 20, 22, 23, 27, 39, 40]. Patients sometimes complain of pain during knee bending or when climbing stairs [27]. Localized tenderness over the separated fragments is the most common physical finding [1, 3, 5, 9, 12, 14, 17, 20, 22, 27, 30, 39]. An unusual bony prominence at the separated fragments [27, 39] and quadriceps muscle atrophy [5, 9, 27, 39] are sometimes present. In adults, bipartite patella becomes symptomatic following a minor injury, such as a blow to the knee [4, 14, 27] or a major injury such as acutely displaced separation of the bipartite fragment [16, 30]. Rarely, in middle-aged or elderly patients, a severe injury such as a fall causes both separation of the bipartite fragment and rupture of the quadriceps tendon [6, 11, 37, 38, 41]. Among adults, bipartite patella rarely becomes symptomatic in those with gout tophus in the space between the bipartite fragment and body of the patella [8, 19, 31, 36]. When that occurs, a chalky white-yellow material is
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Causes of pain Movement at the interface Several authors reported mobility at the interface between the bipartite fragment and the body of the patella in patients who had undergone surgery [3, 5, 12, 14, 22, 23, 39]. This movement presumably causes pain in most symptomatic patients (Fig. 2b) [3, 5, 12, 14, 22, 23, 39]. Articular cartilage of the bipartite fragment Although many authors have reported that the articular cartilage of the bipartite fragment of the superolateral bipartite patella was intact [1, 3, 10, 12, 20, 23], there have been a few cases of abnormal findings relevant to the articular cartilage of the bipartite fragment [22, 25]. Ogata found that the articular surface of the separated fragment had been replaced with fibrocartilage in one type II patella [22]. Oohashi et al. [25] also reported a patient with lateral bipartite patella in which the proximal one-fourth and distal one-half of the articular surface of the bipartite fragment were replaced by fibrous tissue (Fig. 3). Such occurrence of fibrous tissue on the articular cartilage surface of the
Fig. 3 A 15-year-old girl with symptomatic right lateral bipartite patella. Intraoperative photograph. Patella is reflected laterally, revealing the articular surface (right side, distal; left side, proximal). Proximal one-fourth (arrows) and distal one-half (arrowheads) of the articular surface of the separated fragment are replaced by fibrous tissue. The bipartite fragment does not show mobility
Knee Surg Sports Traumatol Arthrosc
separated fragment may be associated with lateral bipartite patella [25] and may rarely cause pain during articulation. Traction apophysitis Several authors have hypothesized that a major cause of pain in patients with a bipartite patella was excessive traction force by the vastus lateralis muscle on the bipartite fragment [1, 20, 22, 23]. This situation is analogous to Sinding-Larsen–Johansson disease at the inferior patellar pole or Osgood–Schlatter disease in the tibial tuberosity.
Treatment Conservative measures In most patients with symptomatic patella partita, the pain resolves with conservative management that includes rest, restriction of sports activities, physical therapy with isometric stretching exercises of the quadriceps muscle, and non-steroidal anti-inflammatory medications [1, 5, 9, 17, 22, 40]. Surgery Many authors have recommended at least 3 months of conservative treatment before considering surgery [1, 17, 22]. Operative treatment should be considered only for patients who cannot participate in activities of daily living or sports activity because of their pain [22]. Weckstro¨m et al. [40] reported that the incidence of painful, surgically treated bipartite patella was 9.2/100,000 military recruits. Excision of the bipartite fragment Open excision of the painful fragment has been most widely performed, with good results [3, 4, 12, 14, 17, 22, 23, 30, 39, 40]. The author prefers to reattach the vastus lateralis tendon directly to the body of the patella through drill holes after excising the bipartite fragment. Arthroscopic excision of a painful bipartite fragment has been reported [5, 9]. These authors suggest that the procedure is less invasive than an open procedure and allows early postoperative rehabilitation [5, 9]. Excision of a painful fragment is indicated if the fragment is grossly mobile [22]. Sometimes surgery reveals that the fragment is not mobile [9, 12, 22], however, and the surgeon may be reluctant to remove it [22]. Therefore, the existence of apparent motion at the interface should be confirmed by specific imaging studies before surgery. MRI findings may provide such evidence by demonstrating a fluid bright signal across the segmentation typical of pseudarthrosis.
Internal fixation of the bipartite fragment Internal fixation may be indicated for a fragment if it involves a large articular surface. Because this procedure usually requires a bone graft and immobilization of the knee for 3–4 weeks, it is considered more invasive than fragment excision [22]. Subperiosteal detachment of the vastus lateralis insertion, lateral retinacular release, and vastus lateralis release Subperiosteal detachment of the vastus lateralis insertion, lateral retinacular release, and vastus lateralis release was devised based on the idea that a major cause of symptomatic bipartite patella is excessive traction force exerted by the vastus lateralis muscle and is aimed at reducing this traction force on the bipartite fragment [1, 20, 22]. In 1994, Ogata performed subperiosteal detachment of the vastus lateralis insertion to the painful patellar fragment in 13 patients (15 knees) [22]. A grossly mobile patellar fragment was removed from five patellae after detachment. For the other ten patellae (seven type III and three type II) in which the fragment was not mobile, the fragment was left in situ after detachment [22]. All patients had prompt relieve from pain and returned to full sports activity within 2 months of the operation [22]. Among the ten whose fragment was left in situ, six of the seven type III patellae showed osseous union, whereas none of the three type II patellae showed union [22]. In 1995, Mori et al. [20] treated painful bipartite patella with a modified lateral retinacular release technique without excising the fragments in 15 patients (16 knees). Bony union of the bipartite fragment was obtained in 15 of the 16 knees within 8 months of the surgery. The authors noted that this surgical technique proved effective not only for relieving the pain but also for achieving bony union [20]. In 2002, Adachi et al. [1] performed a vastus lateralis release without excising fragments in 15 symptomatic patients with an average age of 13.8 years. The results, which were good, indicated that 64.7 % had bone union. Although both Mori et al. and Adachi et al. reported such good surgical results, it is unclear whether they provide sufficient evidence to support use of these procedures for routine treatment of painful bipartite patellae. At their preoperative arthroscopic examinations, apparent motion or significant change in the articular cartilage of the bipartite fragment was not observed in any of their patients [1, 20]. Therefore, pain in their patients might in fact have been caused by excessive traction force exerted by the vastus lateralis muscle. However, in many of these patients, symptoms might have resolved with conservative treatment, as usually occurs in patients with Osgood–Schlatter disease or Sinding-Larsen–Johansson disease.
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Conclusion In most symptomatic patients, the pain may be caused by movement at the interface between the bipartite fragment and the body of the patella. Therefore, the existence of apparent motion at the interface should be confirmed by specific imaging studies before surgery. MRI findings may provide such evidence by demonstrating a fluid bright signal across the segmentation.
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