10 Fractures of the Patella, Clavicle, and Scapula
Fractures of the Patella (Segment 34)
Anatomic Features
The patella is the largest sesamoid bone in the human body and is an important component of the knee joint. It serves to increase the leverage of the quadriceps femoris as a fulcrum, protects the front of the joint, and maintains joint stability. It is a flat, triangular bone; its superior border is thick, while the medial and lateral borders are thinner, and it gives attachment to the tendon of the quadriceps femoris and the medial and lateral patellar retinacula. The lateral borders converge below to the apex, which gives attachment to the ligamentum patellae; the anterior surface is convex and rough, and covered by the expansion from the tendon of the quadriceps femoris; the posterior surface is a smooth, oval, articular area, and for the most part is covered with smooth, slippery cartilage; it is divided into two facets, medial and lateral, by a vertical ridge. Each facet is further subdivided into three facets: superior, middle, and inferior. Lateral to the inner facet is another longitudinal facet. These seven facets in total make contacts with the femur at various angles during the extension–flexion of the knee joint (▶ Fig. 10.1).
OTA Classification and Coding System for Patellar Fractures
Based on Orthopaedic Trauma Association (OTA) classification, the patella is coded as number “34” for its anatomic location. Patellar fractures are classified into three types according to the fracture pattern: type A, extra-articular; type B, partial articular, vertical; and type C, complete articular, nonvertical (▶ Fig. 10.2; ▶ Fig. 10.3).
Epidemiologic Features of Patellar Fractures in the China National Fracture Study
A total of 69 patients with 69 patellar fractures were investigated in the China National Fracture Study (CNFS). The fractures accounted for 3.91% of all patients with fractures and 3.76% of all types of fractures. The population-weighted incidence rate of patellar fractures was 13 per 100,000 population in 2014.
The epidemiologic features of patellar fractures in the CNFS are as follows:
• More males than females
• More right-side injuries than left-side injuries
• The highest-risk age group is 15–64 years
• Injuries occurred most commonly via slips, trips, or falls
Fig. 10.1 The patella.
Fig. 10.2 (a–c) Patellar fractures.
Patellar Fracture by Sex
See â–¶ Table 10.1 and â–¶ Fig. 10.4.
Table 10.1 Sex distribution of 69 patients with patellar fractures in CNFS
Sex | Number of patients | Percentage |
Male | 35 | 50.72 |
Female | 34 | 49.28 |
Total | 69 | 100.00 |
Fig. 10.4 Sex distribution of 69 patients with patellar fractures in China National Fracture Study (CNFS).
Patellar Fractures by Injury Side in CNFS
See â–¶ Table 10.2 and â–¶ Fig. 10.5.
Table 10.2 Injury side distribution of 69 patients with patellar fractures in CNFS
Injured side | Number of patients | Percentage |
Left | 32 | 46.38 |
Right | 37 | 53.62 |
Total | 69 | 100.00 |
Fig. 10.5 Injury side distribution of 69 patients with patellar fractures in China National Fracture Study (CNFS).
Patellar Fractures by Age Group and Sex in CNFS
See â–¶ Table 10.3 and â–¶ Fig. 10.6.
Fig. 10.6 (a) Age distribution of 69 patients with patellar fractures in China National Fracture Study (CNFS). (b) Age and sex distribution of 69 patients with patellar fractures in CNFS.
Patellar Fractures by Causal Mechanisms in CNFS
See â–¶ Table 10.4 and â–¶ Fig. 10.7.
Fig. 10.7 Causal mechanisms distribution of 69 patients with patellar fractures in China National Fracture Study (CNFS).
Clinical Epidemiologic Features of Patellar Fractures (Segment 34)
A total of 11,332 patients with 11,378 patellar fractures were treated in 83 hospitals of China over a 2-year period from 2010 to 2011. All cases were reviewed and statistically studied, accounting for 2.73% of all patients with fractures, and 2.63% of all kinds of fractures, respectively; of a total 11,332 patients, there were 279 pediatric patients (290 patellar fractures) and 11,053 adult patients with 11,088 fractures.
Epidemiologic features of patellar fractures are the following:
• More males than females
• More left-side than right-side fractures
• The high-risk age group is 41–50 years, the same age group for males, while for females the high-risk age group is 51–60 years
• The most common fracture type is type 34-C, the same fracture type for both males and females
• The most common fracture group is group 34-C1, the same fracture group for both males and females
Patellar Fractures by Sex
See â–¶ Table 10.5 and â–¶ Fig. 10.8.
Table 10.5 Sex distribution of 11,332 patients with patellar fractures
Sex | Number of patients | Percentage |
Male | 6,791 | 59.93 |
Female | 4,541 | 40.07 |
Total | 11,332 | 100.00 |
Fig. 10.8 Sex distribution of 11,332 patients with patellar fractures.
Patellar Fractures by Fracture Side
See â–¶ Table 10.6 and â–¶ Fig. 10.9.
Table 10.6 Fracture side distribution of 11,332 patients with patellar fractures
Fracture side | Number of patients | Percentage |
Left | 5,972 | 52.70 |
Right | 5,314 | 46.89 |
Bilateral | 46 | 0.41 |
Total | 11,332 | 100.00 |
Fig. 10.9 Fracture side distribution of 11,332 patients with patellar fractures.
Patellar Fractures by Age Group
See â–¶ Table 10.7 and â–¶ Fig. 10.10.
Fig. 10.10 (a) Age distribution of 11,332 patients with patellar fractures. (b) Age and sex distribution of 11,332 patients with patellar fractures.
Adult Patellar Fractures by Fracture Type
See â–¶ Table 10.8 and â–¶ Fig. 10.11.
Fig. 10.11 (a) Fracture type distribution of 11,088 adult patellar fractures by Orthopaedic Trauma Association (OTA) classification. (b) Sex and fracture type distribution of 11,088 adult patellar fractures by OTA classification.
Adult Patellar Fractures by Fracture Group
See â–¶ Table 10.9 and â–¶ Fig. 10.12.
Fig. 10.12 (a) Fracture group distribution of 11,088 adult patellar fractures by Orthopaedic Trauma Association (OTA) classification. (b) Sex and fracture group distribution of 11,088 adult patellar fractures by OTA classification.
34-A1 Avulsion 1,462 fractures M: 852 (58.28%) F: 610 (41.72%) 0. 39% of total adult fractures 13.19% of adult patellar fractures 81.18% of adult type 34-A fractures | 34-A1 Avulsion
|
34-A2 Isolated patellar body 339 fractures M: 182 (53.69%) F: 157 (46.31%) 0. 09% of total adult fractures 3.06% of adult patellar fractures 18.82% of adult type 34-A fractures | 34-A2 Body fractures simple: axial view of patella
|
34-B1 Lateral 754 fractures M: 461 (61.14%) F: 293 (38.86%) 0.20% of total adult fractures 6.80% of adult patellar fractures 63.79% of adult type 34-B fractures | 34-B1.1 Simple: axial view of patella
|
34-B1.2 Comminuted
| |
428 fractures M: 240 (56.07%) F: 188 (43.93%) 0.11% of total adult fractures 3.86% of adult patellar fractures 36.21% of adult type 34-B fractures | 34-B2.1 Simple: axial view of patella
|
34-B2.2 Comminuted
| |
34-C1 Transverse, simple 4,516 fractures M: 2,443 (54.10%) F: 2,073 (45.90%) 1.21% of total adult fractures 40.73% of adult patellar fractures 55.72% of adult type 34-C fractures | 34-C1.1 Middle
|
34-C1.2 Proximal
| |
34-C1.3 Distal
| |
34-C2 Transverse, fragmented (with three fragments) 1,420 fractures M: 930 (65.49%) F: 490 (34.51%) 0.38% of total adult fractures 12.81% of adult patellar fractures 17.52% of adult type 34-C fractures | 34-C2.1 Middle
|
34-C2.2 Proximal
| |
34-C2.3 Distal
| |
34-C3 Comminuted (with > 3 fragments) 2,169 fractures M: 1,499 (69.11%) F: 670 (30.89%) 0.58% of total adult fractures 19.56% of adult patellar fractures 26.76% of adult type 34-C fractures | 34-C3.1 With 4 fragments
|
34-C3.2 With > 4 fragments
| |
Injury Mechanism
Transverse fractures of the patella and avulsion fractures of the superior and inferior poles are often caused by indirect mechanisms, seen in hyperflexion of the knee due to sudden tensile force of the quadriceps. Comminuted, vertical, and oblique fractures are more clearly associated with direct mechanisms, such as from direct blows and crush injuries. The energy of the impacting force, which results in comminuted fractures of the patella, may also cause damage to the articular cartilage of both the patella and the femoral condyles.
Diagnosis
Patellar fractures usually present with a history of trauma. Physical examination reveals ecchymosis over the anterior aspect of the knee, hemarthrosis, swelling, tenderness, and partial to complete limitation of knee joint mobility. If fracture displacement is present, then a gap between fragments and retropatellar crepitus can be noted. Radiographs of anteroposterior (AP) and lateral views of the knee joint usually confirm the diagnosis. If vertical or border fractures are clinically suspected, an axial view or computed tomography (CT) scan of the knee joint may be indicated. Magnetic resonance imaging (MRI) is necessary for comminuted patellar fractures due to damage of the articular cartilage of both the patella and the femoral condyles. The diagnosis of a vertical fracture of the patella should be differentiated from that of a patellar variation. Vertical fractures present with a clear trauma history, positive physical examination findings, fracture lines, and a jagged surface of the broken ends: this is in contrast to variations of the patella (binary or trinary patella), which are known to have wide gaps, smooth broken ends, or mild to absent physical signs/syndrome. In addition, the thin layer of cortex may be exposed.
Treatment
If the fracture is displaced by less than 3 mm, or the intra-articular step-off is less than 2 mm, then the fracture may be treated with a nonoperative modality. However, for elderly patients, operative management with rigid internal fixation should be considered to allow early postoperative mobilization and to minimize knee fibro-adhesive scar formation. In young healthy patients, patellar fractures can be treated with immobilization followed by casting, external fixation devices, and tuck loop fixation, etc. Surgical treatment is advised for displaced fractures, which are defined as fractures that have an intra-articular step-off of more than 2 mm or a separation of more than 3 mm. Additional caution should be taken for pediatric patients with patellar fractures when considering an operative approach because operative procedures have the potential to damage growth cartilage, and subsequently impact the growth and development of the patella. Because children have a greater potential for tissue bone repair and molding, fractures with marked displacement, or even with a comminuted pattern, should initially be treated with nonoperative management. Partial surgical removal of the patella should be considered for severe comminuted fractures that are not able to be anatomically reduced. Severe comminuted patellar fractures in elderly patients should be treated with primary total surgical removal of the patella.
Further Classifications of Patellar Fractures: The Regazzoni Classification
Based on the fracture location, pattern, and presence of displacement, Regazzoni classified patellar fractures into three types, with three subgroups for each fracture type:
• Type A: Vertical fracture: A1, with no displacement; A2, with displacement; A3, comminuted.
• Type B: Transverse fracture: B1, avulsion fracture of the superior and inferior poles of the patella (< 5 mm in diameter of the superior pole, < 15 mm in diameter of the inferior pole); B2, simple; B3, comminuted.
• Type C: Comminuted fractures: C1, with no displacement; C2, with displacement of less than 2 mm; C3, burst fractures with displacement of more than 2 mm.
Clinical Epidemiologic Features of Patellar Fractures by the Regazzoni Classification
A total of 11,088 adult patellar fractures were treated in 83 hospitals of China over a 2-year period from 2010 to 2011; all cases were reviewed and statistically studied. Their epidemiologic features are as follows:
• More males than females
• The most common fracture type was Type B (Transverse)
See â–¶ Table 10.10 and â–¶ Fig. 10.13.
Fig. 10.13 (a) Fracture type distribution of 11,088 adult patellar fractures by Regazzoni classification. (b) Sex and fracture type distribution of 11,088 adult patellar fractures by Regazzoni classification.
Type A Vertical 1,182 fractures M: 701 (59.31%) F: 481 (40.69%) 0.32% of total adult fractures 10.66% of adult patellar fractures | Regazzoni A1 Without displacement
|
Regazzoni A2 With displacement
| |
Regazzoni A3 Comminuted
| |
7,737 fractures M: 4,407 (56.96%) F: 3,330 (43.04%) 2.07% of total adult fractures 69.78% of adult patellar fractures | Regazzoni B1 Avulsion fracture of superior and inferior poles (< 5 mm in diameter of superior pole) (< 15 mm in diameter of inferior pole)
|
Regazzoni B2 Simple
| |
Regazzoni B3 Comminuted
| |
2,169 fractures M: 1,499 (69.11%) F: 670 (30.89%) 0.58% of total adult fractures 19.56% of adult patellar fractures | |
Regazzoni C1 Without marked displacement
| |
Regazzoni C2 With displacement of < 2 mm
| |
Regazzoni C3 Combined with burst fractures with displacement of > 2 mm
| |
Clavicle Fractures (Segment 15)
Anatomic Features
The clavicle forms the anterior portion of the shoulder girdle, and is placed nearly horizontally at the upper and anterior part of the thorax. It serves as the only direct bony attachment of the arm to the trunk. The clavicle is connected strongly to a number of muscles and accordingly to facets, most of which are essential for the stability of the shoulder girdle. It is a long bone, curved somewhat like the letter “S” in the superior view, but appears straight in the anterior view. The lateral third of the clavicle is flattened from above and downward, to accommodate the attachment and traction of muscles; furthermore, its middle third is tubular, and its medial third has a prismatic form to withstand the axial compression load and traction (▶ Fig. 10.14).
The lateral third of the clavicle provides attachment for the trapezius and deltoid muscles. On the posterior–superior border of the medial third is a rough area for attachment of the sternocleidomastoid muscle. The clavicular portion of the pectoralis major originates from the anterior surface of medial border of the medial third. The subclavius muscle originates from the inferior border of the middle third of the clavicle and inserts on the first rib, just dorsal to the subclavian surface (▶ Fig. 10.15).
Fig. 10.14 The clavicle.
Fig. 10.15 Muscle attachments of the clavicle.
Anatomic Features and Muscular Attachment of the Clavicle
From an anatomic point of view, four factors that result in the displacement of clavicle fractures can be summarized as follows:
1. The proximal fragment is typically displaced upward because of the pull of the sternocleidomastoid muscle.
2. Although there may be some upward movement of the clavicle due to the pull of the trapezius muscle, the major displacement is caused by the downward pull of the upper extremity, since most patients would not be able to withstand the weight of the upper arm due to the pain.
3. However, if the upward pull of the trapezius muscle surpasses the weight of the upper arm, or patients are using a sling to support the arm, then the distal fragment may also be displaced upward.
4. The pull of the pectoralis major, pectoralis minor, and latissimus dorsi draw the distal fragment medially (â–¶ Fig. 10.16).
The clavicle articulates medially with the clavicular notch of the manubrium sterni, forming the sternoclavicular joint, which is supported by the anterior and posterior sternoclavicular and interclavicular ligaments. The lateral end of the clavicle articulates with the acromion of the scapula, forming the acromioclavicular joint, which is stabilized by the acromioclavicular, coracoacromial, and coracoclavicular ligaments; these three ligaments form the coracoacromial arch. The coracoclavicular ligament consists of two fasciculi, the trapezoid and conoid ligaments, which are attached between the coracoid process of the scapula and the underside of the clavicle; they primarily provide stabilization to the acromioclavicular joint and prevent superior dislocation of the shoulder joint (â–¶ Fig. 10.17).
Fig. 10.16 (a) Fracture displacement of the clavicle. (b) Joint and ligaments of the clavicle.
OTA Classification and Coding System for Clavicle Fractures
Based on OTA classification, the clavicle is coded as number “15” for its anatomic location, and is divided into three segments according to the Heim Square method: proximal, shaft, and distal. The OTA classification of clavicle fractures is as shown in ▶ Fig. 10.18.
Epidemiologic Features of Clavicle Fractures in the China National Fracture Study
A total of 89 patients with 89 clavicle fractures were investigated in the CNFS. The fractures accounted for 5.05% of all patients with fractures and 4.86% of all types of fractures. The population-weighted incidence rate of clavicle fractures was 16 per 100,000 population in 2014.
The epidemiologic features of clavicle fractures in the CNFS are as follows:
• More males than females
• More left-side injuries than right-side injuries
• The highest-risk age group is 15–64 years
• Injuries occurred most commonly via slips, trips, or falls and traffic accident
Fig. 10.17 Radiograph of the clavicle.
Fig. 10.18 Algorithm.
Clavicle Fracture by Sex
See â–¶ Table 10.11 and â–¶ Fig. 10.19.
Table 10.11 Sex distribution of 89 patients with clavicle fractures in CNFS
Sex | Number of patients | Percentage |
Male | 57 | 64.04 |
Female | 32 | 35.96 |
Total | 89 | 100.00 |
Fig. 10.19 Sex distribution of 89 patients with clavicle fractures in China National Fracture Study (CNFS).
Clavicle Fracture by Injury Side in CNFS
See â–¶ Table 10.12 and â–¶ Fig. 10.20.
Table 10.12 Injury side distribution of 89 patients with clavicle fractures in CNFS
Injured side | Number of patients | Percentage |
Left | 45 | 50.56 |
Right | 44 | 49.44 |
Total | 89 | 100.00 |
Fig. 10.20 Injury side distribution of 89 patients with clavicle fractures in China National Fracture Study (CNFS).
Clavicle Fracture by Age Group and Sex in CNFS
See â–¶ Table 10.13 and â–¶ Fig. 10.21.
Fig. 10.21 (a) Age distribution of 89 patients with clavicle fractures in China National Fracture Study (CNFS). (b) Age and sex distribution of 89 patients with clavicle fractures in CNFS.
Clavicle Fracture by Causal Mechanisms in CNFS
See â–¶ Table 10.14 and â–¶ Fig. 10.22.
Fig. 10.22 Causal mechanisms distribution of 89 patients with clavicle fractures in China National Fracture Study (CNFS).
Clinical Epidemiologic Features of Clavicle Fractures (Segment 15)
A total of 18,502 patients with 18,587 clavicle fractures were treated in 83 hospitals of China over a 2-year period from 2010 to 2011. All cases were reviewed and statistically studied, accounting for 4.46% of all patients with fractures and 4.30% of all kinds of fractures, respectively. Among 18,502 patients, there were 4,424 pediatric patients (4,430 clavicle fractures) and 14,078 adult patients with 14,157 clavicle fractures.
Epidemiologic features of clavicle fractures are as follows:
• More males than females
• More left side than right side fractures
• The high-risk age group is 0–5 years, the same age group for females, while for males the high-risk age group is 41–50 years
• The most common fracture type is Type B
Clavicle Fractures by Sex
See â–¶ Table 10.15 and â–¶ Fig. 10.23.
Table 10.15 Sex distribution of 18,502 patients with clavicle fractures
Sex | Number of patients | Percentage |
Male | 12,827 | 69.33 |
Female | 5,675 | 30.67 |
Total | 18,502 | 100.00 |
