Limb axis assessment
The correctness of the limb axis is determined visually or graphically by drawing imaginary lines through the centers of the joints. Normally, the limb axis is a straight line.
Pathological curvatures are divided into three main types:
- Varus deformity (varus). The distal (lower) segment of the limb deviates medially. An angle is formed that opens inward. Visually, this appears as O-shaped bowing of the legs.
- Valgus deformity (valgus). The distal segment deviates laterally, and the formed angle opens outward. This is the so-called X-shaped deformity.
- Recurvatum (recurvatum). A specific deformity in the sagittal plane. It represents excessive hyperextension in a joint (e.g., in the knee), where the axis curves with a posterior convexity.
Assessment of trunk and limb symmetry
To objectively assess symmetry, the method of constructing a geometric figure—a pentagon—is used. This is done by connecting specific anatomical landmarks. A key landmark on the lower leg is point III—the tips of the medial (inner) malleoli on the left (sinister) and right (dexter).
Criteria for ideal symmetry:
- The segments between the key points of the right and left sides are absolutely equal.
- Lines connecting symmetrical points are strictly parallel to each other.
- These parallel lines are perpendicular to the central longitudinal axis of the patient's body.
If the length of at least one forming line changes, it is referred to as simple asymmetry. If the total distance from the upper point to the medial malleolus on the right does not match the corresponding distance on the left, uncompensated asymmetry is diagnosed.
Physical examination: palpation and crepitus
Palpation is performed with the fingertips or the whole hand. It is an informative stage that allows for the assessment of local temperature (hyperthermia in inflammation, hypothermia in poor blood flow), tissue condition (edema, infiltrate), skin mobility, and vascular pulsation.
In trauma, palpation allows the physician to feel bone fragments under the skin, identify pathological mobility, and check how effectively reduction has been performed. When examining joints, hydrarthrosis (fluid accumulation) and altered contours can be detected.
Crepitus (crunching) is a crucial symptom with various causes:
- Friction of bone fragments in fractures.
- Inflammation of bursae and tendons (bursitis, tenosynovitis).
- Presence of foreign bodies or osteoarthritis.
- Subcutaneous emphysema (air accumulation due to lung trauma or gas gangrene).
Auscultation and percussion
Although fractures are diagnosed using X-rays today, acoustic methods have not lost their significance.
During percussion (tapping) over a bone, its sound conductivity is assessed. If the sound is not transmitted or is strongly muffled when listened to with a stethoscope, it indicates a fracture (or the presence of a pseudoarthrosis or tumor). Auscultation also helps hear joint crepitus in osteoarthritis.
Furthermore, these methods are exceptionally important for detecting trauma complications—pneumonia, hemopneumothorax, or free fluid in the abdominal cavity.
Length measurement and types of shortening
The main task of measurement is to detect changes in length. Shortening is the most common finding in practice. The simplest method is visual comparison "by eye" of symmetrical segments:
- For the legs: the patient lies on their back, bends the legs at the knee joints, and the physician compares the length of the lower legs by the level of the knees.
- For the arms: the elbow joints are flexed, and the physician assesses the length of the shoulders from behind.
Three types of lower limb shortening are distinguished:
- Absolute (true) shortening. The anatomical length of the bone tissue itself is disrupted. A classic example is a femoral shaft fracture with displacement of fragments along the length.
- Relative shortening. Anatomically, the bone is undamaged and has preserved its length, but the leg has become shorter due to the displacement of articular ends. Example: dislocation of the femoral head.
- Functional shortening. Both bones and joints are fine, but the limb is shorter due to a forced posture. For example, in a knee flexion contracture, a person cannot fully straighten the leg and bear weight on the foot.
Briefly: answers to topical questions
What anatomical landmarks are used to measure the absolute length of the lower limb with a tape measure?
The following bony landmarks are used to measure the absolute length of the lower limb and its segments:
- Entire limb: from the tip of the greater trochanter of the femur to the tip of the medial (less commonly, lateral) malleolus.
- Thigh: from the tip ofუნქ of the greater trochanter of the femur to the lateral epicondyle of the femur (or the lateral joint space of the knee).
- Lower leg: from the medial joint space of the knee to the tip of the medial malleolus.
Under what conditions is functional limb shortening diagnosed?
Functional (apparent) limb shortening is diagnosed in conditions accompanied by a forced posture or fixed pathological positioning in the joints while the anatomical length of the bones is preserved. These conditions include:
- Contracture—for example, a knee flexion contracture that prevents full weight-bearing on the foot.
- Ankylosis—complete immobility of a joint.
- Rigidity—marked limitation of mobility.
Through which anatomical structures does Nélaton's line (Roser-Nélaton line) pass?
Nélaton's line passes through the anterior superior iliac spine and the ischial tuberosity. Normally, when the hip is flexed at an angle of 135°, the tip of the greater trochanter of the femur also lies on this projection line.
What anatomical landmarks are used to measure upper limb length?
The following bony landmarks are used to measure the upper limb length and its segments:
- Entire limb, relative length: from the acromion process of the scapula to the tip of the third digit of the hand.
- Entire limb, absolute length: from the tip of the greater tubercle of the humerus to the styloid process of the radius or the tip of the third digit.
- Arm (shoulder): from the tip of the greater tubercle of the humerus to the lateral epicondyle of the humerus.
- Forearm: from the tip of the olecranon to the styloid process of the radius.
Absolute means the bone is broken; relative means the joint has "slipped" (dislocation); functional means the joint cannot straighten (contracture).
Class and exam questions
How to quickly compare leg length without a tape measure?
You need to place the patient on their back and ask them to bend their legs at the knee joints. Different knee levels will immediately indicate the presence of lower leg shortening.
What is the difference between varus and valgus deformity?
In varus deformity, the distal segment deviates medially, forming an O-shaped curve. In valgus deformity, it deviates laterally, resulting in an X-shaped limb shape.
Why does bone sound conduction disappear in a fracture?
A normal bone conducts sound excellently. In a fracture, the integrity of the dense bone tissue is disrupted, and the transmission of percussion sound is interrupted.
In which cases does crepitus occur in the absence of a fracture?
Crepitus may be caused by subcutaneous air (emphysema), tendonitis, bursitis, or friction in osteoarthritis.
What else to study on this topic
- Method for constructing the pentagon: identifying points I and II on the trunk.
- Features of palpation in intra-articular effusion (hydrarthrosis).
- Differential diagnosis of types of crepitus: fractures versus emphysema.
- Assessment of tenderness on palpation: localization and relationship with body position.
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