Leg Length Inequality: A Challenge
J. S. Makhani
Research Article from Archives
This article has been reproduced from the April 1980 issue of “The Clinician”.
The author Dr. J. S. Makhani could not be contacted for permission to reprint.
Leg length inequality may result in variable extent from causes such as congenital, inflammatory, traumatic, vascular, neoplastic and neurogenic. The commonest cause in India is motor paralysis from polio.
Leg length inequality of 1 cm rarely produces awareness and requires no treatment, whereas inequality up to 2 cm can be corrected by bone stimulation (periosteal stimulation or epiphyseal stimulation) in growing children, and discrepancy up to 3 cm can be corrected by combined periosteal and epiphyseal stimulation. In adults this group (2-3 cm discrepancy) may prefer to wear elevated shoe on shorter leg. Surgical treatment is definitely indicated in discrepancy over 3 cm. Bone lengthening is done in the tibia and even in the femur of the short leg whereas bone shortening is performed on the longer leg mostly in the femur though it can be done in tibia. Bone shortenings are safer to perform and are devoid of neurovascular complications which are liable to occur in lengthening operations.
Length inequality is a signal of a disease and to provide complete patient care the etiology should also be treated and corrected.
Both lower limbs are supposed to grow equally with the pelvis horizontal over them and the spinal column projecting perpendicular, keeping shoulders square on pelvis and the head midline. However, a slight variation in length of lower limbs (up to one centimeter) may be present without any obvious cause in otherwise normal individuals. Routine examination of leg length in backache and scoliosis patients reveals that this is not an uncommon finding.
There is always a cause for leg length inequality. History should be traced back to birth, infancy and growth period until a satisfactory explanation is found.
Hip dysplasia of varying magnitude produces shortening of varying degrees. Associated shortness in the femur aggravates the discrepancy. Congenital dislocations of the hip and congenital coxa vara are common examples.
Congenital short femur may or may not be associated with hip dysplasia. Proximal femoral focal deficiencies (PFFD) when present produce moderate to severe shortening. It may even be associated with hip dysplasia. Femur may even be absent in toto. Congenital short tibia is also an entity but occurs less frequently. Bowing of tibia is more common and is associated with retarded growth. Congenital pseudoarthrosis of tibia produces severe shortening.
Congenital amputations and absent longitudinal segments e.g. absence of tibia in part or in toto produce severe discrepancy in unilateral cases. They are a challenge to surgical treatment and rehabilitation processes. Prosthetists and orthotists have to be consulted to prepare Extention-Orthesis to equalize the limb length. Club foot, when unilateral, may produce a shortening of about 2 cm.
Multiple congenital lesions will add up the discrepancies. Congenital scoliosis with pelvis tilt, with or without hip or other associated lesions, is frequently seen with limb discrepancy.
Diseases like neurofibromatosis, angiomatosis, lymphangiomatosis, lipomatosis and similar conditions are known to cause increased length of the affected limb. Arteriovenous fistulas are known to produce increased length in the affected limb.
Some diseases like malerohostosis and other sclerosing diseases also produce length discrepancy. Hemiatrophy and hemihypertrophy account for occasional cases with similar length problems. In the growing child, coxa plana, slipped upper femoral epiphysis and the development of idiopathic scoliosis produce slight shortening (up to 1.5 cm)
Suppurative arthritis of the hip especially if drainage has been delayed results in partial or complete absorption of the femoral head and neck, and is associated with partial or complete dislocation of the hip with resultant shortening. This is a preventable lesion only if early surgical decompression is performed and aggressive antibiotic therapy is instituted.
Osteomyelitis may either increase the length or arrest the growth due to epiphyseal plate damage. Angulatory deformities may even be present.
Abduction contractures of the hip secondary to infection fibrosis of gluteal muscles, and transient synovitis or infective synovitis and even tuberculosis result in pelvic tilt and cause leg length discrepancy.
Ankylosis or stiff hip in abduction or adduction position also result in similar problems.
A fracture with angulation or overriding may cause shortening of the limb. Absorption of fracture ends in itself contributes to shortening. Communited fractures heal with shortening. Serious shortening results from bone loss in diaphyseal fractures. Ipsilateral fractures involving two major long bones (femur and tibia) often results in some degree of shortening.
Fracture of shaft and neck of femur may produce severe shortening.
Tumors affect longitudinal bone growth usually by destruction of growth potential. Resection of tumor can produce severe shortening depending on the nature of surgery, replacement provided, bone grafting performed and above all union obtained at grafted sites.
Infantile paralysis (Polio) is the commonest cause of leg length discrepancy in India.
Why the growth of an extremity is retarded after partial or complete paralysis is not clearly understood. Lack of normal muscular contractions acting as a stimulus to bone growth, both transverse and longitudinal, and blood circulation within the muscle and bone, associated with a possible compression effect of tight and contracted fascias, bands or muscle across the growing epiphyses are responsible for the “lag” in growth of the limb.
In polio shortening is almost always seen. It is proportionate to the severity and extent of paralysis, and progresses with age. However, the shortening may be unnoticeable or may become a severe disability. It may be compensated by pelvic tilt and raised heel or maybe beyond the limit of compensation. It may or may not be cosmetically acceptable to the patient. It is often associated with other deformities.
Actual shortening may be associated with deformities of the hip, pelvic tilt, scoliosis, knee contractures and angulatory deformities like Genu Valgum, thereby aggravating the length discrepancy. True shortening must be differentiated from apparent shortening. Limp due to shortening and weak gluteal muscles must also be differentiated.
What is True Shortening?
True shortening is actual discrepancy in the length of the affected limb. Apparent shortening on the other hand refers to a discrepancy not of actual limb length but instead caused by scoliosis, pelvic tilt and hip contracture. Angulatory deformities like Genu Valgum and Valgus deformity of ankle, if associated with growth disturbance will have both components of true and apparent shortening.
How to Measure leg length:
Clinical examination with a measuring tape or comparison of position of identical land marks with limbs in identical positions, though most commonly used is not of absolute reliability. Patients with pelvic deformities or hip and knee contractures pose a problem for measurement. Mobility of skin over bony land marks, abundance of subcutaneous fat and changes in position of two limbs make this method unreliable. There is only one accurate method to measure leg length and it is the radiological method.
Clinical examination is however essential. It gives an “idea” of leg length discrepancy. Tape measurement is taken from the anterior superior iliac spine (ASIS) to the medial malleolus along the medial side of patella but it can be measured to the plane of heel. Further measurement in leg and thigh will locate the zone of shortening or lengthening. Bryan triangle will locate the discrepancy in the hip region. Comparison of land marks can be conveniently done by standing on the foot side of the patient, and holding both feet to apply traction so that the hips, pelvis & spine assume neutral anatomical position. Now compare the level of both medial malleoli, now move over to the side of the patient and flex both hips so that the knees rest on chest. The chin should be between the knees. Now compare the level of knees and malleoli. Put both knees at level and check the malleoli and repeat the same observation by putting malleoli at level. Any discrepancy can be quickly identified.
Foot plane can be check by positioning the patient in supine and anatomical position. Plane of the heels is checked from the side of the short leg and their length difference is recorded. Make sure the pelvis is not tilted.
Block method is also a convenient method. Make the patient stand. Place the blocks of known height under the foot of short side till the patient feels corrected and check with the horizontal plane of ASIS.
Radiological Method (Ortho-roentgenogram)
This can be done in two ways (1) Full length scanogram. X-rays of the full length of the limb is taken by a moving tube from a fixed distance. Measurements are then made on the film from fixed identical points. (2) In this method certain portions of equal length are eliminated from the length of the limb and the x-ray is taken in 3 parts (hips, knees and ankles) on the same film without moving the patient. Measurements are then made from the top of the femoral head to the intercondylar notch in lower femur, from tibial spine to lower tibial articular surface and differences in length indicate the “inequality”. Shortening in the height of the foot can be measured separately in lateral radiographs of feet from the top of the talus to the soft tissue shadow of the heel.
Functional Effect of Unequal Leg Length:
It is generally believed that inequality up to 1 inch (2.5cm) causes little or no asymmetry of the body or limp, and rarely any discomfort. I beg to differ on this issue. No generalisation should be made. Compensatory equinous become painful over the years and in our Indian communities with our social customs and non-shoe habits where no compensatory heels or lifts can be used in shoes or sandals, it is our concern to revise our thoughts on this issue. What may be acceptable elsewhere is not necessarily acceptable in our culture.
Up to 1 inch (2.5cm) shortening is certainly of advantage with stiff knees, arthrosed knees, abducted hip, and when a long-leg caliper is used, and with weak hip abductors.
Inequality of 1 to 2 inches (2.5 cm to 5cm) causes a noticeable limb and asymmetry of the body alignment. It can be compensated by pelvis tilt, heel elevation and shoe lift.
An inequality of 2 inches (5cm) or more prevents the patients from standing with the legs together unless the hip and the knee are flexed on the long side; this consequently interferes with the patients walking and other locomotion activities. Compensation is possible with a cork-soled shoe.
Pelvic tilt and even lumbar scoliosis have the ability to adjust length discrepancy to a certain extent. When a patient stands with legs straight, without a lift, shortening of the body is only half the shortening of the leg as the pelvic tilt is corrected while the opposite leg remains the same. On the other hand, when a patient stands on short leg with the knee and the hip of the long leg flexed, body height is not lowered after the shortening operation as the long flexed leg has been made straight. If the patient is already using a raised shoe and is habituated to a “height”, shortening operation with return to regular shoes will reduce his/her height by the amount of the lift. Associated scoliosis, deformities of the hip with or without pelvic tilt, ankylosed hip or knee, and weakness of trunk, hip and leg muscles may further complicate the leg length discrepancy.
Leg length inequality may cause pain in the lumbar spine, hip, knee or even ankle and foot.
Skeletal age is more important than chronologic age in determining maturity and timing of epiphyseal arrest. To assess skeletal maturity, roentgenogram of hand and foot are taken and by reference to Todd’s atlas or that of Greulich and Pyle, skeletal age may be determined. Average skeletal age at which the distal femoral and proximal tibial epiphyses close, according to Green and Anderson, is 15 ¼ years in girls and 17 ¼ years in boys. Average annual growth at distal femoral epiphysis is 3/8 inch (0.9 cm) and at the proximal tibial and fibular epiphyses ¼ inch (0.6 cm) according to White. There are numerous factors influencing bone growth. No method with mathematical accuracy can be described or devised.
Is exact equalisation desirable?
No, it is not always desirable. Each patient has different requirements. Evaluate individually. Consider severity, sex, effectiveness of shoe lift, joint stability and function (1 to 2 cm shortening is essentially required for caliper use or for a fused knee). Functional evaluation of the whole limb should be considered. Social status and distorted body image are important factors for consideration and final decisions, while considering severity of shortening and its management remember that up to 1 cm causes no concern at all. Acceptability may vary from individual to individual.
Methods of Corrections:
There are several methods of reducing or correcting leg length discrepancy depending on whether the epiphyseal plates are open or fused.
Open Epiphyseal Plates:
Stimulation of growth of the short leg can be planned in children with open epiphyseal plates with growth potential. It can be achieved by drilling operations, periosteal stripping and using some irritants in the metaphysis like homogenous bone pegs, and screws made of various materials.
A) Periosteal Stripping:
Periosteal stripping operation is indicated in young growing children for minor discrepancies. It is commonly performed in the tibia and 1 to 1.5 cm of length can be gained.
B) Screw Stimulation:
Metallic screws are placed in the metaphyses of lower femur and upper and lower tibia parallel to the epiphyseal plate within 1 inch distance from it. This may be performed even in combination with periosteal stimulation. Screw stimulation is also performed for minor discrepancy. Whereas periosteal stripping is effective only for a year or so, screw stimulation effect is seen throughout the potential growth period. It is therefore indicated in a child with a 2 to 3 cm discrepancy. Bone screws get gradually absorbed and incorporated. So their “stimulation” effect is not lasting as compared to metallic screws. Over the years the screws seem to move away from the ends of the bones. There is a danger of delayed fractures occurring at the screw level especially in femur.
C) Combined periosteal stripping and screw stimulation:
Sustained stimulation of bone growth can be achieved through this combination. After periosteal stripping, screws are inserted at the appropriate level. This is mostly done in the tibia. Beneficial effects of both procedures are seen. Width of the tibia increases. New bone formation is seen around the screws and the limb length shows sustained increase during the potential growth period.
In cases of epiphyseal arrest of the affected side, retardation of growth on the longer side can also be planned. Commonly used methods are “Stapling” or “Epiphysiodesis”. Though simple in technique, they require proper “timing” for arresting the growth and the “choice” for arresting various epiphyseal plates requires a lot of experience. A number of studies of leg growth in children and their relation to the height of other members of the family have been carried out and are available for reference but their exactness is doubtful as they are average figures and have to be carefully applied to a given individual. Growth pattern in the individual over a few years of observation, and observation on height of other members of the same family are more relevant and should be considered while planning epiphyseal arrest.
A) Epiphysiodesis Operations:
In the Phemister technique, a rectangular section of bone (3cm long and 1 cm or 1.5 cm wide) crossing the epiphyseal plate is taken. The Epiphyseal plate is chiseled out for a distance of 3 to 5 cm in each direction and to a depth of about 1 cm. A cortical graft is reinserted in its bed with reversed ends.
In the White Technique, using a hollow chisel, a plug of bone is taken across the epiphyseal plate to a depth of 1 inch and rotated through 90 degrees. Complications of epiphysiodesis include overcorrection, under correction, asymmetrical fusion and low fusion, because of these it is necessary to plan this operation and perform it skillfully. However, it remains a safe and reliable procedure when done properly.
B) Stapling Operations:
In principle, epiphyseal stapling should arrest growth and on removal of staples growth should resume. However as this does not happen always, this method has lost importance and has not stood the test of time. Complications like angulatory deformities in antero-posterior and lateral planes are not infrequent. It is almost never done now for growth arrest, though it is a good procedure for control of angulatory deformities in growing children.
Lengthening of the Short leg:
Short leg may be lengthened in tibia or femur. Lengthening procedure consists of osteotomy of the bone, followed by very gradual traction in a special apparatus and continues immobilization until bone healing takes place. This has the advantage of restoring the affected bone to normal or near normal length and the patient to a height corresponding to the longer segment; it also eliminates the risk of damage to the good or unaffected leg. It is less suitable if the abnormal leg is longer and it is less suitable if the abnormal leg is considerably short. Technically it has its own share of complications and a long convalescent period. Delayed or non-union and breakdown of skin are serious complications.
(i) Tibial Lengthening:
Tibia is usually selected for lengthening operation. It is never lengthened more than 10% of its length. Both femur and tibia should never be lengthened in the same individual for fear of neurovascular complications.
(ii) Femoral Lengthening:
It is a rather dangerous operation because if not successful, the results are disastrous. Main part of the operation consists of release of the soft tissues extraperiosteally over about 5 inches of femur to form a periosteal sleeve. Lateral inter muscular septum is also released. This sleeve is longitudinally incised, and transversely divided in its lower limit. In its proximal end, the femur is osteotomised and an intramedullary nail which is rather loose in the canal is fixed to preserve alignment. I have inserted split rib graft in the periosteal tube to promote bony union. Steinmann pins are used to anchor upper and lower ends of femur and even upper tibia which are then fixed on the distraction frame. Postoperatively one or two turns of the ‘distraction’ apparatus are made daily till desired lengthening is obtained. No more than 2 inches should be aimed at.
Why shorten the long leg? By and large it is the normal or good leg. Whereas lengthening is considered over ambitious, shortening operations are considered wiser procedures, however lowering of height has been argued as a point against the shortening procedures.
(i) Tibial Shortening:
The tibia is chosen when the shortening is below the knee so that knees can be levelled. Two inches is the maximum permissible shortening in tibia. Complications are few as compared to those in tibial lengthening operations.
(ii) Femoral Shortening:
Femoral shortening is a recognized operative procedure. Accidentally if the femur is fractured, adequate over riding may be permitted to equalize to the shorter leg without altered muscle and joint function. In principle, it involves shortening by osteotomy of femur in the subtrochanteric region, shaft or supracondylar portion of the femur. Shortening is achieved by over riding of fragments or excision of a segment of bone of desired length or by planned step out osteotomy. After reducing the length of femur the fragments are internally fixed by screws, or transfixed by Steinmann pins passed through skin, or by intramedullary nail or with a Blount or Thorton plate. With rigid nail plate fixation, distraction of fragments is prevented and there is no need of plaster spica immobilization. Healing occurs promptly.
Excessive bulk of muscles due to lengthening may present a serious problem in wound closure. In resections up to 5 cm usually no problem is encountered in wound closure whereas with increasing segmental resections, muscle bulk causes a problem in wound closure. It is more so in individuals with thick layer of subcutaneous tissue and bulky muscles in the normal limb. It does take a long time for the bulk to reduce. Though unsightly to start with, it resumes shape in due course of time ranging from 6 months to 1 year and occasionally it may take a longer time.
Recovery of quadriceps function is a slow process. It is directly proportionate to the length of segmental resection. It may also take 6 month to 1 year or even longer. Original quadriceps power should recover.
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