What is a tubercle

Tubercle is a small rounded projection or process of a bone, for example greater tubercle of humerus, tibial tubercle, conoid tubercle of clavicle and adductor tubercle of the distal femur.

Tubercle also refers to a nodule attached to bone, mucous membrane (moist layer lining parts of the body), or skin.

The term tubercle is less commonly used to refer to skin irritation resulting from a tuberculosis (TB) infection.

Darwin’s tubercle is a blunt point projecting from the upper part of the helix of the ear.

Lister’s tubercle

Lister’s tubercle is an old term for prominent bony tubercle over the dorsal aspect of the distal radius ¹, which functions as a pulley for the extensor pollicis longus tendon before the tendon pivots and turns obliquely to insert onto the distal phalanx of the thumb ². As a palpable structure, Lister’s tubercle has been used as an anatomical landmark for localizing the first dorsal extensor compartment ³, posterior interosseous nerve ⁴, superficial branch of the radial nerve ⁵ and dorsal radiotriquetral ligament ⁶. Lister’s tubercle is also used as a surgical landmark in wrist arthrography injections, wrist arthroscopy and wrist joint injectionsy ⁷, dorsal wrist capsulotomy ⁸, hand microsurgery ⁹, radioscapholunate arthrodesis ¹⁰, Kirschner wire placement, and internal fixation of Colles fractures ¹¹.

Besides being an anatomic landmark during surgery, there is also some clinical importance to the anatomical localization of Lister’s tubercle. For instance during volar plate fixation for distal radius fractures, when the screws are applied in unsuitable orientation and length, they may irritate the extensor pollicis longus tendon which lies in the groove medial to the dorsal tubercle. Over a long period this may cause extensor pollicis longus tendon ruptures ⁶.

Because of its proximity to carpal structures and overlapping bony densities, conventional radiology does not provide a detailed outline of Lister’s tubercle or its relationship to the adjacent tendon structures.

Despite the importance of Lister’s tubercle in modern surgical procedures and its close spatial relationship with the extensor pollicis longus tendon, few reports have described the variations of Lister’s tubercle and its relationship with the extensor pollicis longus tendon. Pichler et al. ¹² reported the height variations of Lister’s tubercle on computed tomography (CT) and Ağır et al. ¹³ described its variable location along the dorsal radius using cadaveric radii. To our best knowledge, currently, there is no literature describing variations in anatomical morphology of Lister’s tubercle and its relationship with the course of the extensor pollicis longus tendon in the third dorsal extensor compartment.

Figure 1. Lister’s tubercle

Conoid tubercle

Conoid tubercle is located near the posterior border on the junction of the lateral one-fourth along with medial three-fourth of the clavicle on the inferior surface. The trapezoid ridge spreads forwards as well as laterally through conoid tubercle.

The conoid tubercle gives the attachment for the conoid ligament and is situated on the posterior inferior surface of the lateral curvature of the clavicle.

• The attachment of the trapezoid ligament is indicated by the trapezoid line that spreads out laterally from the conoid tubercle.
• A groove that extends over the central one-third of the inferior surface of the clavicle is medial to the conoid tubercle.
• The acromial end has a rough inferior surface that bears a ridge, the trapezoid line, and a slight rounded projection, the conoid tubercle above the coracoid process.

Figure 2. Conoid tubercle

Tibial tubercle

Tibial tubercle is the bony bump where the patellar tendon attaches to the tibia (shinbone).

Figure 3. Tibial tubercle

Tibial tubercle pain

Osgood-Schlatter disease also known as osteochondrosis or traction apophysitis of the tibial tubercle. Osgood-Schlatter disease is an inflammation of the area just below the knee where the tendon from the kneecap (patellar tendon) attaches to the shinbone (tibia). Osgood-Schlatter disease causes tibial tubercle pain. Osgood-Schlatter disease is a common cause of knee pain in growing adolescents ¹⁴. Osgood Schlatter’s disease is one of the most common causes of knee pain in the skeletally immature, adolescent athlete. Onset coincides with adolescent growth spurts between ages 10 to 15 years for males and 8 to 13 years for females. The condition is more common in males and occurs more frequently in athletes that participate in sports that involve running and jumping. In adolescents, age 12 to 15, the prevalence of Osgood Schlatter disease is 9.8% (11.4% in males, 8.3% in females). Symptoms present bilaterally in 20% to 30% of patients ¹⁵.

Common sports seen in association with traction apophysitis of the tibial tubercle or Osgood-Schlatter disease include:

• Basketball
• Volleyball
• Sprinters
• Gymnastics
• Football

Clinical presentation classically associates atraumatic, insidious onset of anterior knee pain, with tenderness at the patellar tendon insertion site at the tibial tuberosity. The condition is self-limited and occurs secondary to repetitive extensor mechanism stress activities such as jumping and sprinting. Pain level dictates overall treatment, and management includes symptomatic treatment with ice and NSAIDs, as well as activity modification and relative rest from inciting activities in association with lower extremities stretching regimen to correct underlying predisposing biomechanical factors.[1][2][3][4]

The bones of children and adolescents possess a special area where the bone is growing called the growth plate. Growth plates are areas of cartilage located near the ends of bones. When a child is fully grown, the growth plates harden into solid bone.

Some growth plates serve as attachment sites for tendons, the strong tissues that connect muscles to bones. A bony bump called the tibial tubercle covers the growth plate at the end of the tibia. The group of muscles in the front of the thigh (called the quadriceps) attaches to the tibial tubercle.

When a child is active, the quadriceps muscles pull on the patellar tendon which in turn, pulls on the tibial tubercle. In some children, this repetitive traction on the tubercle leads to inflammation of the growth plate. The prominence, or bump, of the tibial tubercle may become very pronounced.

Osgood-Schlatter disease most often occurs during growth spurts, when bones, muscles, tendons, and other structures are changing rapidly. Because physical activity puts additional stress on bones and muscles, children who participate in athletics — especially running and jumping sports – are at an increased risk for this condition. However, less active adolescents may also experience this problem.

In most cases of Osgood-Schlatter disease, simple measures like rest, over-the-counter medication, and stretching and strengthening exercises will relieve pain and allow a return to daily activities.

Osgood-Schlatter disease causes

Osgood Schlatter’s disease is an overuse injury that occurs in active adolescent patients. It occurs secondary to repetitive strain and microtrauma from the force applied by the strong patellar tendon at its insertion into the relatively soft apophysis of the tibial tubercle. This force results in irritation and severe cases partial avulsion of the tibial tubercle apophysis. Force is increased with higher levels of activity and especially after periods of rapid growth. Rarely trauma may lead to full avulsion fracture. Predisposing factors include poor flexibility of quadriceps and hamstrings or other evidence of extensor mechanism misalignment ¹⁶.

Osgood-Schlatter disease pathophysiology

The tibial tubercle develops as a secondary ossification center that provides attachment for the patellar tendon. Bone growth exceeds the ability of the muscle-tendon unit to stretch sufficiently to maintain previous flexibility leading to increased tension across the apophysis. The physis is the weakest point in the muscle-tendon-bone-attachment (as opposed to the tendon in an adult) and therefore, at risk of injury from repetitive stress. With repeated contraction of the quadriceps muscle mass, especially with repeated forced knee extension as seen in sports requiring running and jumping (basketball, football, gymnastics), softening and partial avulsion of the apophyseal ossification center may occur with a resulting osteochondritis ¹⁷.

The appearance and closure/fusion of the tibial tubercle occurs in the following sequence pattern:

• Tibial tubercle is entirely cartilagenous (age < 11 years)
• Apophysis forms (age 11 to 14 years)
• Apophysis fuses with the proximal tibial epiphysis (age 14 to 18 years)
• The proximal tibial epiphysis and tibial tubercle apophysis fuses with the rest of the proximal tibia (age > 18 years) ¹⁸

Osgood-Schlatter disease symptoms

Painful symptoms are often brought on by running, jumping, and other sports-related activities. In some cases, both knees have symptoms, although one knee may be worse than the other.

• Knee pain and tenderness at the tibial tubercle
• Swelling at the tibial tubercle
• Tight muscles in the front or back of the thigh

Osgood-Schlatter disease diagnosis

During the appointment, your doctor will discuss your child’s symptoms and general health. He or she will conduct a thorough examination of the knee to determine the cause of the pain. This will include applying pressure to the tibial tubercle, which should be tender or painful for a child with Osgood-Schlatter disease. In addition, your doctor may also ask your child to walk, run, jump, or kneel to see if the movements bring on painful symptoms.

Your doctor may also order an x-ray image of your child’s knee to help confirm the diagnosis or rule out any other problems. Classic radiographic findings in Osgood-Schlatter disease include an elevated tibial tubercle with soft tissue swelling, fragmentation of the apophysis, or calcification in the distal patellar tendon. It is worth noting that these findings can also be seen as normal variants and do not always represent pathology, so clinical correlation is of utmost importance. If ordering radiographs consider comparing bilateral images to delineate normal versus abnormal in the individual patient ¹⁹.

Osgood-Schlatter disease treatment

Ultimately, Osgood-Schlatter disease is self-limiting but may persist for up to 2 years until the apophysis fuses. Treatment for Osgood-Schlatter disease focuses on reducing pain and swelling. This typically requires limiting exercise activity until your child can enjoy activity without discomfort or significant pain afterwards. In some cases, rest from activity is required for several months, followed by a strength conditioning program. However, if your child does not have a large amount of pain or a limp, participation in sports may be safe to continue. There is no evidence to suggest that rest speeds up recovery, but activity restriction is effective in reducing pain ¹⁴.

Your doctor may recommend additional treatment methods, including:

• Stretching exercises. Stretches for the front and back of the thigh (quadriceps and hamstring muscles) may help relieve pain and prevent the disease from returning.
• Non-steroidal anti-inflammatory medication. Drugs like ibuprofen and naproxen reduce pain and swelling.

In severe, prolonged cases a short period of knee immobilization may be considered. There is no evidence to recommend injection therapy or surgical intervention for Osgood-Schlatter disease. Symptoms typically are self-limiting with a resolution of pain upon closure of the apophysis. Long-term sequelae may include a thickened or prominent tibial tubercle, but this is asymptomatic in the vast majority of cases ²⁰.

In up to 10% of cases, symptoms may persist >1-2 years beyond skeletal maturity. In skeletally mature patients with persistent symptoms, tibial tubercle osteotomy may be performed.

Osgood-Schlatter disease prognosis

Most symptoms will completely disappear when a child completes the adolescent growth spurt, around age 14 for girls and age 16 for boys. For this reason, surgery is rarely recommended. However, the prominence of the tubercle will persist.

Tibial tubercle fracture

Isolated tibial tubercle fractures or patellar tendon ruptures are common injuries in adolescents through a mechanism involving eccentric contraction of the patellar tendon when the proximal tibial physis is closing ²¹.

Tibial tubercle fracture will need anatomical reduction to ensure restoration of knee function ²². Methods for treatment of tibial tuberosity fracture include use of tension band wire, independent cortical lag screws or screws placed through a plate, which serve to increase the surface area covered by the screws ²³. The choice of treatment should be guided by the morphology of tibial tuberosity fracture and the characteristics of the tibial plateau fracture. When the tibial tubercle fracture is a single large noncomminuted fragment, use of tension band wire or fixation of the tubercle to the posterior tibial cortex with one or more lag screw is the traditionally preferred surgical option ²⁴. In cases where comminution of the tibial tubercle fracture or posterior tibial cortex is present, the cortex of the posterior tibia does not always offer good purchase for screw fixation; plate and screws are preferred in such cases ²³. The plate in effect serves to resist the pull of the extensor mechanism on the tibial tubercle. This allows rigid fixation of the tubercle fragment. In this study, the treating surgeon selected screw to fix the fracture.

Maroto et al ²³ suggested the tibial tubercle should also be conformed and treated when a suspected or incomplete fracture exists, so as to avoid displacement or malunion in the postoperative period with early mobilization of the knee. As the tibial tubercle has relatively sparse overlying soft tissue, care must be taken to protect the soft tissue envelope during exposure and fixation. Further, it may be necessary to remove the fixation device after bony union has occurred.

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