Harish Hosalkar, MD., Orthopaedic Fellow, The Children’s Hospital of Philadelphia, John Dormans, MD., Chief of Orthopaedic Surgery, The Children’s Hospital of Philadelphia, Professor of Orthopaedic Surgery,
University of Pennsylvania School of Medicine
MHE usually manifests during early childhood more commonly with several knobby, hard, subcutaneous protuberances near the joints.
The likelihood of involvement of various anatomical sites as observed in a large series is as follows:
Anatomical location Percentage involvement
Distal femur 70
Proximal tibia 70
Proximal fibula 30
Proximal Humerus 50
Scapula 40
Ribs 40
Distal radius and ulna 30
Proximal femur 30
Phalanges 30
Distal fibula 25
Distal tibia 20
Bones of the foot 10-25
The Skull
Lesions in the skull, although reported are extremely rare. Mandibular osteochondromas, typically of the condyle, skull wall lesions and even intracranial lesions have been reported.
Affects of MHE on Skull
Exostoses can cause problems if they compress or entrap cranial nerves or cause extrinsic compression on the brain. Effects can range from bumpy external lesions that cause cosmetic problems, compression of adjacent structures, cranial nerve involvement and even focal neurological deficits due to compression. Even seizures are likely due to intracranial lesions.
Diagnostic Procedures
The orthopedist will manually feel for exostoses along the outer table of the skull, check movements of the mandible and also of the upper cervical spine. The orthopedist will also check cranial nerve function and perform a thorough neurological evaluation. X-rays or other imaging tests including CT and MRI may be ordered.
Possible Treatment Options
* Minor lesions on the outer table of the skull that are flat can sometimes be closely observed.
* Bigger lesions on the skull, mandibular lesions causing TM joint instability, and intracranial lesions causing pressure signs may need to be removed by neurosurgical intervention.
* Upper cervical spinal tumors, especially of the atlanto-occipital region may be dealt with by orthopedists. Decompression and or stabilization may be performed as required.
What Parents Should Watch Out For
* Pain. Is your child experiencing pain from exostoses?
* Visible lumps on the face or skull.
* Any symptoms of tingling, numbness, weakness in the hands or legs suggestive of focal deficits.
* Episodes of seizures or findings of cranial nerve involvement like altered smell, taste, ringing in ears etc.
* Problems in chewing, restricted motion of the jawbone or instability of the mandible.
* Parents can ask dentists and orthodontists to be on the lookout for signs suggestive of jawbone instability or joint involvement during their office visits especially in symptomatic cases.
Spine
The spine extends from the base of the skull to the tailbone. Spinal exostoses are rare (Figure 1). Spinal cord impingement is also a rare, but documented, complication of MHE. Cervical, thoracic or lumbar region can be affected. Scoliosis secondary to spinal osteochondromas and instability has been reported.
This section of the body is not commonly involved with MHE. Involvement of isolated vertebrae has been noted. Affects can range from instability to neural root or cord compression that can manifest as tingling, numbness or weakness in the involved roots or even major neurological deficits like paraparesis or quadriparesis in untreated cases. Rarely compression effects in the form of dysphagia, intestinal obstruction or urinary symptoms may occur.
Diagnostic Procedures:
With any of the red flags mentioned earlier, the orthopedist will perform a thorough spinal and neurological evaluation. Plain x-rays of the spine and if required, advanced imaging may be performed. The presences and extent of the lesion are best delineated with CT, while MRI of the spinal cord demonstrates the area of spinal cord impingement. In rare cases of peripheral nerve compression electromyography may be performed to check status of the nerve.
Possible Treatment Options:
* Minor lesions not causing compressive symptoms or neurologic manifestations may be kept under close observation.
* Progressive scoliosis and spinal instability may need to be treated with surgical stabilization involving spinal fusion.
What Parents Should Watch Out For:
* Any red flags in terms of tingling, numbness, weakness, night pain or bladder and bowel changes and get them evaluated.
* Any deformity in the spine or evidence of shoulder or pelvic imbalance.
* Gait or posture disturbances. Remember that gait and posture disturbances can be caused by hip or leg exostoses as well (due to either limb-length discrepancy or deformity) and do not necessarily mean tumors in the spine. In any case evaluation by a clinician is important.
Ribs and Sternum
Affects of MHE on the ribs and sternum
The typically flat bones of the ribs are prone to effects of MHE, with approximately 40% of MHE patients having rib involvement. Prominent chest wall lesions are common although intrathoracic lesions including rare presentations like spontaneous hemothorax (build-up of blood and fluid in the chest cavity) as a result of rib exostoses have been described. Typically, these lesions create issues of cosmesis due to their obvious visibility. Other symptoms may include shortness of breath and other breathing difficulties, pain when taking a deep breath, when walking or exercising, or pain from exostoses “catching”.
Diagnostic Procedures
The orthopedist will probably manually feel for exostoses along the chest wall and the ribcage. Size and extent of the lesions are noted. A thorough pulmonary evaluation is warranted in all cases when specific symptoms of cough, chest pain or breathing problems are encountered. X-rays or other imaging tests may be ordered.
Possible Treatment Options:
* Minor bumps can sometimes be kept under observation.
* Cosmetic problems, rapid increase in size, large size, and signs of compression are some indications for early removal.
* Consult may be required with specialists:
Pulmonary: when there are severe breathing difficulties with increasing chest pain.
Thoracic surgeons: when intrathoracic (within the chest wall) exostoses may need to be excised.
What Parents Should Watch Out For:
* Breathing difficulties, shortness of breath
* Pain when taking deep breath.
Shoulder girdle
The scapula is a fairly common site (40%) of involvement in MHE. The lesions may be located on the anterior or posterior aspect of the scapula. Anterior scapular lesions may lead to discomfort during scapulothoracic motion. Winging of the scapula due to exostoses has been described. Clavicle (collar bone) involvement has also been described (5% cases).
What is winging?
The scapula (also known as shoulder blade) is a triangular flat bone that is located in the upper back and takes part in forming the shoulder joint. The scapula usually lies flat on the chest wall without any prominence. Winging of the scapula is a phenomenon when a part of the scapula including the inferior angle becomes prominent either at rest or during movements. The two most common causes for this are
1. Exostosis on the inner (chest wall) aspect of the scapula.
2. Damage to the nerve (long thoracic) causing weakness or paralysis of muscles (serratus anterior) attached to the scapula.
Diagnostic Procedures
The orthopedist will probably manually feel for exostoses along the outer aspect of the shoulder blade. Some limited areas of the inner aspect are amenable to clinical examination. Range and feel of the scapulothoracic motion is helpful in clinical assessment. It is important to check individual groups of scapular muscles to rule out nerve compression leading to winging of scapula. X-rays (including special tangential views of the scapula) or other imaging tests may be ordered.
Possible Treatment Options
* Both outer aspect lesions and inner ones may need excision in symptomatic cases. Smaller lesions on outer aspect amenable to clinical palpation may be observed with regular clinical follow-up.
What Parents Should Watch Out For:
* Crunching or crackling sound when moving that area
* Pain
* Tingling, numbness
Note from The MHE Coalition:
Exostoses in the shoulder girdle (collarbone (clavicle) and shoulder blade can impact a child’s ability to raise his/her arm in class, write on a blackboard, participate in certain sports, or wear a backpack. In addition, adolescent girls (and women) may be unable to wear a bra because of pressure not only on shoulder girdle exostoses but also on rib exostoses.
Arms
* Upper Arm (Humerus)
* Elbow
* Forearm (Radius and Ulna)
* Wrists
The arm bone is called the humerus while the forearm bones are the radius (curved bone) and the ulna (straighter bone of the two).
The length of forearm bones inversely correlates with the size of the exostoses. Thus, the larger the exostoses and the greater the number of exostoses, the shorter the involved bone. Moreover, lesions with sessile rather than pedunculated morphology have been associated with more significant shortening and deformity. Thus, the skeletal growth disturbance observed in MHE is a local effect of benign growth. Exostoses in the forearm are known to involve both the radius and the ulna. Since movements of the forearm (pronation and supination) are dependant on the radius moving in an arc of motion around the ulna, mobility may be restricted depending upon the severity of presentation. Also the lower end radius exostoses can lead to compression of the median nerve (in a closed space at the level of the wrist called the carpal tunnel) and present with weakness, tingling and numbness in the hand. Exostoses in the carpal bones can seriously hamper the wrist motion and cause pain.
Complete dislocation of the radial head is a serious progression of forearm deformity and can result in pain, instability, and decreased motion at the elbow. Surgical intervention should be considered to prevent this from occurring. When symptomatic, this can be treated in older patients with resection of the radial head.
Diagnostic Procedures:
The orthopedist will clinically feel for exostoses along the arm, elbow and forearm, and check range of motion (“ROM”) by moving the arm in different directions. The orthopedist will also check measurements on each arm and forearm to see if there is a difference. X-rays or other imaging tests may be ordered.
Possible Treatment Options:
Indications for surgical treatment include painful lesions, an increasing radial articular angle, progressive ulnar shortening, excessive carpal slip, loss of pronation, and increased radial bowing with subluxation or dislocation of the radial head
* Minor lesions can sometimes be observed with careful follow up.
* Bowing and some length discrepancies and be treated with a surgical procedure called “stapling,” where surgical staples are inserted into the growth plate of the bone growing faster than the other. This will hopefully give the slower growing bone the chance to “catch up” and the forearm will straighten over time.
* Limb Lengthening with a fixator. (See Section on Fixators)
* Resection of the radial head
* Excision of exostoses
* Osteotomy
* Epiphysiodesis
* Non-surgical measures for treatment of soft-tissue compression, irritation or inflammation (anti-inflammatories, heat, rest, etc.)
* Adaptive devices to aid those with shortened forearms, such as grippers, long-handled sock aides, etc.
What Parents Should Watch Out For:
* Any red flags in terms of sudden increase in size of swelling, pain, nerve compression, tingling, numbness, or weakness.
* Possibility of exostoses irritating or catching on overlying tissue, such as muscles, tendons, ligaments, or compressing nerves.
* Loss of range of motion
* Pain
* Difficulty and/or pain when raising arm(s), lifting, carrying
Hands and Fingers
Hand involvement in MHE is common. Fogel et al. observed metacarpal involvement and phalangeal involvement in 69% and 68%, respectively, in their series of 51 patients. In their series of 63 patients, Cates and Burgess found that patients with MHE fall into two groups: those with no hand involvement and those with substantial hand involvement averaging 11.6 lesions per hand. They documented involvement of the ulnar metacarpals and proximal phalanges most commonly with the thumb and distal phalanges being affected less frequently. While exostoses of the hand resulted in shortening of the metacarpals and phalanges, brachydactyly was also observed in the absence of exostoses.
Diagnostic Procedures:
The orthopedist will manually feel for exostoses in the hands and check range of motion (“ROM”) in different directions. X-rays or other imaging tests may be ordered.
Possible Treatment Options:
* Isolated lesions growing rapidly, or interfering with the smooth motion of tendons or joint motion may need to be excised. Multiple surgeries for small, insignificant lesions is usually not advocated.
* Occupational therapy, physical therapy
* Use of pencil grips, laptop computers, and other adaptive devices
What Parents Should Watch Out For:
* Complaints of pain when writing
* Some children will not complain of pain, but will have poor penmanship, write slowly, avoid writing, etc. Parents should also observe how the child holds writing and eating utensils.
* Difficulty in rotating hand(s),
Pelvic Girdle (Hips and Pelvis)
Osteochondromas of the proximal femur (Figure 3) may lead to progressive hip dysplasia. There have been reported cases of acetabular dysplasia with subluxation of the hip in patients with MHE. This results from exostoses located within or about the acetabulum that may interfere with normal articulation.
Diagnostic Procedures
Manual palpation is sometimes very difficult in these deep lesions. The orthopedist will check range of motion (“ROM”) by manipulating (moving) the leg in different directions. The orthopedist will also check measurements on each leg to see if there is a difference in limb lengths. X-rays or other imaging tests may be ordered.
Possible Treatment Options
* Minor length discrepancies can sometimes be effectively treated with the use of orthotics (specially made shoes or lifts that will equalize leg length).
* Bowing and some limb length discrepancies can be treated with a surgical procedure called “stapling,” where surgical staples are inserted into the growth plate of the leg bone growing faster than the other. This will hopefully give the slower growing bone the chance to “catch up” and the limb will straighten over time.
* Limb Lengthening with a Fixator. (See Section on Fixators)
* Pelvic lesions of concern may need to be surgically excised.
* Osteotomies.
* Hip replacement.
What Parents Should Watch Out For
* Limping
* Pain in hips, back, legs
* Pain, discomfort, difficulty in sitting
* Inability to sit “tailor” style
* Stiffness in hips and/or legs after sitting
* Pain and fatigue from walking
Legs and Knees
* Femur
* Knees
* Lower Leg (Tibia and Fibula)
Genu Valgum or Knock-knee deformities are found in 8-33% of patients with MHE. Genu valgum is defined as a mechanical malalignment of the lower limb when the knees knock against each other and the legs are pointed away from the body. Although distal femoral involvement is common, the majority of cases of angular limb deformities are due mostly to lesions of the tibia and fibula (Figures 8,9 & 10), which occur in 70-98% and 30-97% of cases, respectively. The fibula has been found by Nawata et al. to be shortened disproportionately as compared to the tibia, and this is likely responsible for the consistent valgus direction of the deformity. Genu varum or Bowlegs may also occur in some cases. This is defined as a mechanical malalignment of the lower limb when the knees drift away from the body and the legs are bowed and close together.
The orthopedist will probably manually feel for exostoses along the leg, and check range of motion (“ROM”) by manipulating (moving) the leg in different directions. The orthopedist will also check measurements on each leg to see if there is a difference. X-rays or other imaging tests may be ordered.
Possible Treatment Options
* Minor length discrepancies can sometimes be effectively treated with the use of orthotics (specially made shoes or lifts that will equalize leg length).
* Bowing and some limb length discrepancies and be treated with a surgical procedure called “stapling,” where surgical staples are inserted into the growth plate of the leg bone growing faster than the other. This will hopefully give the slower growing bone the chance to “catch up” and the limb will straighten over time.
* Limb Lengthening with a Fixator. (See Section on Fixators)
* Excision of exostoses
* Osteotomy
What Parents Should Watch Out For
* Any red flags in terms of sudden increase in size of swelling, pain, nerve compression, tingling, numbness, or weakness.
* Possibility of exostoses irritating or catching on overlying tissue, such as muscles, tendons, ligaments, or compressing nerves.
* Leg cramps, bluish color, difference in skin temperature may indicate compression of an artery (most often the popliteal artery, located behind the knee).
* Compression of the peroneal nerve, which runs along the outside of the leg, can cause a condition known as “drop foot”, in which the foot cannot voluntarily be flexed up. Compression can be caused by exostoses growth, or as a complication of surgery.
* Limping, pain when walking
* Bowing of leg(s)
* Exostoses on inside of legs bumping into each other
* Exostoses interfering with normal movements, either by blocking movement or by causing pain (bending, sitting, walking up or down stairs)
* Pain and fatigue when walking
* Gait problems (awkwardness, limping, slow movements, etc.)
Notes from The MHE Coalition:
A good way to track possible bowing in your child’s legs is to take a photo of your child dressed in shorts, standing straight with back to wall, legs together. Every few months take another photo of your child in the same position, and date and keep these photos to show your child’s doctor. You can even have your child hold a sign with the date you take the picture (written dark enough to be picked up by the camera!).
Ankles
Valgus deformity of the ankle is also common in patients with MHE and is observed in 45-54% of patients in most series. This valgus deformity can be attributed to multiple factors including shortening of the fibula relative to the tibia. A resulting obliquity of the distal tibial epiphysis and medial subluxation of the talus can also be associated with this deformity, while developmental obliquity of the superior talar articular surface may provide partial compensation.
Diagnostic Procedures:
The orthopaedist will probably manually feel for exostoses along the leg, and check range of motion (“ROM”) by manipulating (moving) the leg in different directions. The orthopaedist will also check measurements on each leg to see if there is a difference. X-rays or other imaging tests may be ordered.
Possible Treatment Options:
* Minor length discrepancies can sometimes be effectively treated with the use of orthotics (specially made shoes or lifts that will equalize leg length).
* Bowing and some limb length discrepancies and be treated with a surgical procedure called “stapling,” where surgical staples are inserted into the growth plate of the leg bone growing faster than the other. This will hopefully give the slower growing bone the chance to “catch up” and the limb will straighten over time.
* In more advanced cases, excision of exostoses with early medial hemiepiphyseal stapling of the tibia in conjuction with exostosis excision can correct a valgus deformity at the ankle of 15° or greater associated with limited shortening of the fibula.
* Fibular lengthening has been used effectively for severe valgus deformity with more significant fibular shortening, (i.e. when the distal fibular physis is located proximal to the distal tibial physis).
* Supramalleolar osteotomy of the tibia has also been used effectively to treat severe valgus ankle deformity.
* Growth of exostoses can also result in tibiofibular diastasis that can be treated with early excision of the lesions.
What Parents Should Watch Out For:
* Limping, pain when walking
* Recurrent falls and instability while walking on uneven surfaces.
Feet and Toes
Osteochondromas may occur in the tarsal and carpal bones, however they are often less apparent. Relative shortening of the metatarsals, metacarpals, and phalanges may be noted.
Diagnostic Procedures
Plain radiographs are probably more useful in defining the extent of involvement of the small bones of the feet in MHE. Other imaging studies may be ordered as and when required.
Possible Treatment Options
* Large bumps can be surgically excised when symptomatic
* Deformities of the foot (like hallux valgus) may be corrected by stapling of the growing epiphysis in younger children or by surgical osteotomy in older patients.
What Parents Should Watch Out For
* Compression of the peroneal nerve, which runs along the outside of the leg, can cause a condition known as “drop foot”, in which the foot cannot voluntarily be flexed up. Compression can be caused by exostoses growth, or as a complication of surgery.
Note from The MHE Coalition
Parents should know that finding shoes for children affected with ankle and/or foot exostoses can be challenging. Shoes must be found that do not cut into or press on exostoses. In some cases, they must be made specially for the child. In addition, some children will require lifts to help equalize a limb length discrepancy. Children who have exostoses on the bottom of their heel can sometimes benefit from gel cushions that are sold in drug/grocery stores. In addition, many children and teens will have difficulty tying shoes due to affected hands, shortened forearms, etc., and may need shoes with Velcro or shoes that slip on.
In general
What Parents Should Watch Out For
* If your child is limping, check to see if it is due to an injury, or is something that is occurring and continuing without obvious reason. Limping may signal a limb length discrepancy or other problem.
* Bowing of one or both legs
* Mobility problems. Is your child experiencing pain when walking or running?
* Pain. Is your child experiencing pain from exostoses that bump each other? Is your child experiencing pain during certain activities, or pain at night. If so, keep a pain diary.
* Any red flags in terms of sudden increase in size of swelling, pain, nerve compression, tingling, numbness, or weakness.
The MHE Coalition and its member organization, MHE and Me, offers the
Following Patient Support Information:
* “Tips for When Your Child Needs Surgery”
* The Bumpy Bone Tracker
* The Bumpy Bone Pain Tracker
* The Bumpy Bone Pain Tracker for Little Kids
* The Bumpy Bone Pain Diary
* The MHE and Me Handbook: A Guide for Families, Friends, Teachers and Classmates
* School Needs Checklist for Kids with MHE
* Common School Concerns for Kids with MHE
What Adults Should Be Aware Of:
* Sudden growth in an existing exostosis and pain can be symptomatic of a malignant transformation. It is smart to check out any changes with your orthopaedist. However, it is important to remember that chondrosarcoma is rare.
* Years of wear and tear on joints can result in chronic pain. There is also the possibility of exostoses irritating or catching on overlying tissue, such as muscles, tendons, ligaments, or compressing nerves. Possible Treatment Options for these common problems, include pain medications, physical therapy (including stretching, strengthening and modalities), heat, rest, bracing (supportive orthosis acting as load sharing devices) etc.
Glossary of terms and procedures:
Synonyms of multiple exostoses: A number of synonyms have been used for this disorder including osteochondromatosis, multiple hereditary osteochondromata, multiple congenital osteochondromata, diaphyseal aclasis, chondral osteogenic dysplasia of direction, chondral osteoma, deforming chondrodysplasia, dyschondroplasia, exostosing disease, exostotic dysplasia, hereditary deforming chondrodysplasia, multiple osteomatoses, and osteogenic disease.
Anterior: Situated in the front; forward part of an organ or limb
Ball and socket joints: Movable (synovial) joints, such as hips and shoulders, that allow a wide range of movement.
Bilateral: having two sides or pertaining to both sides.
Biopsy: Take a piece of the lesion to study the histological characteristics.
Cartilage: Form of connective tissue, more elastic than bone, which makes up parts of the skeleton and covers joint surfaces of bones.
Coxa-valga: When the thighbones are drawn farther apart from the midline due to an increase in the neck-shaft angle of the femur.
Coxa-vara: When the thighbones are drawn closer to the midline due to a decrease in the neck-shaft angle of the femur.
Dislocation: When the normal articulating joint surfaces have lost total contact.
Distal: Away from the midline or the beginning of a body structure (the distal end of the humerus forms part of the elbow).
Epiphysiodesis: To surgically stop the growth of the growing end of the bone either temporarily or permanently.
Excision: To surgically remove the lesion.
Genu-valgum: Knock-knees.
Genu-varum: Bowlegs.
Hinge joints: movable joints, such as knees and elbows, that allow movement in one direction.
Limb-lengthening: Process of increasing the length of bones using one of the various devices.
LLD: Limb-length discrepancy- difference in limb lengths.
Medial: Pertaining to the middle or toward the midline.
MHE: An autosomal-dominant disorder manifested by multiple osteochondromas and frequently associated with characteristic skeletal deformities.
Osteochondromas: Cartilage capped tumors found commonly at rapidly growing ends of bones.
Osteotomy: The surgical division or sectioning of a bone.
Pedunculated: Lesion with a stalk connecting it to the main bone.
Posterior: Situated in the back; back part of an organ or limb
Proximal: Near the midline or beginning of a body structure (the proximal end of the humerus forms part of the shoulder).
Sessile: Lesion without a stalk connecting it to the main bone.
Stapling: Process of insertion of a mechanical device (staple) following surgical intervention.
Subluxation: When the joint surfaces are still facing each other but not totally in contact.
ABC's of MHE - Table of Contents
ABC's of MHE - Diagnostic Tools
ABC's of MHE - Multiple Exostoses and the Lower Limb
ABC's of MHE - The Genetics of Multiple Hereditary Exostoses