Diastrophic dwarfism was first described as a separate entity by Lamy and Maroteaux in I960.1 They coined the term from the Greek word diastrophe, meaning twisted or distorted. Although this is a rare condition, and fewer than 200 cases have been reported in the world literature, it is still one of the more common kinds of dwarfism. Diastrophic dwarfs, in addition to a short stature, have characteristic facial features and severe joint deformities.1-3 The underlying disorder is presumably a primary cartilage defect, with a histologic appearance similar to that of degenerative arthritis.
Diastrophic dwarfism frequently is confused with the more common achondroplastic dwarfism. However, the major medical problems of the diastrophic dwarf are orthopedic in nature.1,6
M. J., a 36-year-old woman, was first seen at our institution in 1974 because of progressive hip, knee, and pelvic pain. This had been present over a 10-year time span. The pain was mechanical in nature, increased with activity, and decreased with rest. She had noted progressive stiffness in her hips and increasing pain with walking. She had undergone a cesarean section delivery in 1964, because her hips could not be abducted sufficiently to allow for vaginal delivery. She had a tubal ligation in 1977. Otherwise her health had been good. Family history revealed that her mother was normal size. Her father was 5' tall, with prominent ulnar styloids and short stubby fingers. Her older sister is 4' 3" and has physical features similar to those of the patient. One sister, who died at age 2 months, was described as having extremely short arms. The patient has a son, age 14, who is congenitally deaf but normal in stature.
Physical examination showed a short woman, 4' 3", weighing 135 pounds, with an arm span of 50". Bilateral deformities about the external ear made it resemble a prize-fighter's "cauliflower" ear. Her face was cherub-like, with a narrow nasal bridge, an elongated forehead, and a high-arched palate. There were upper and lower dentures. She had a pectus excava turn deformity. There was no scoliosis. There was decreased range of motion of the shoulders and upper arms. The forearms were shortened in relationship to the arms, with prominent ulnar styloids bilaterally. Her fingers were short and stubby and the tips of her thumbs were almost at right angles to the rest of her hand. (This has been called a "hitchhiker's" thumb by various authors,) The metacarpophalangeal joints would not flex beyond 20° although the proximal and distal interphalangeal joints were normal. There was no internal or external rotation of either hip, 10° of abduction bilaterally, and both hips were held in the adducted position with the knees together. Both hips flexed 30-60°. The right leg was 1" shorter than the left. There was a 15° genu valgum deformity bilaterally. The patient walked with a scissoring gait, using a walker, and had bilateral positive Trendelenburg signs.
Roentgenograms showed loss of both joint spaces and flattening of both femoral heads, characteristic of severe degenerative changes.
The patient was treated conservatively initially, with analgesics and an exercise program. This failed to improve her symptoms over a four-year period. In 1968 she quit her job as a cashier because of pain in her hips. In May 1978 a right total hip replacement was carried out usinga CAD system. The femoral canal required drilling before the small mini-stem component could be inserted. Two cement cages were used in the acetabulum to prevent intrapelvic extrusion of the cement.
The postoperative course was benign and the patient was discharged from the hospital on the 15th postoperative day with good relief of pain. In September 1978 a left total hip replacement was performed, using the same system. The femoral component could be fitted without drilling, but the greater trochanter required osteotomy for exposure. Postoperatively her course was benign. At the 18-month followup she was ambulating without pain, had 20° of abduction, 10° of internal rotation, and flexed the same as preopera lively.
Certain clinical characteristics help to differentiate the diastrophic dwarf from other patients with short stature, especially those of the achondroplastic dwarf (Table I). Both achondroplastic and diastrophic dwarfs are short, rarely is either over 4' 5". The achondroplastic dwarf has a characteristic broad nasal flare with a depressed nasal bridge, while the diastrophic dwarf has a narrow nasal bridge. None of the achondroplastic dwarfs has the pinna deformities seen in diastrophic dwarfs.7 (See Fig. 1, 2).
The mode of inheritance is autosomal dominant in the achondroplastic dwarf and autosomal recessive in the diastrophic dwarf.6 Achondroplasts have characteristic "trident" hands, while the diastrophics have a "hitchhiker's thumb," in which the thumb is slightly more proximal and is abducted in relationship to the hand. (See Fig. 3). The achondroplast may develop hydrocephalus secondary to a small foramen magnum; often there is increased lumbar lordosis with accompanying spinal stenosis. Diastrophics have no such problems with hydrocephalus or spinal stenosis, but they may develop severe scoliosis.8
Bowleg deformities are seen often in the achondroplast while there are no characteristic knee deformities seen in the diastrophic. Club feet are seen in more than half of the diastrophic dwarfs; these may be the earliest indications of proper diagnosis. Kite mentions these club foot deformities as being extremely resistant to cast treatment. Kite originally thought that these patients with resistant club feet were achondroplastic dwarfs, but in retrospect they are quite obviously diastrophic dwarfs.9
Most importantly to the orthopedic surgeon, achondroplasts have mild degenerative arthritis usually secondary to abnormal biomechanical stresses, while the diastrophics have early severe degenerative arthritis secondary to their defective cartilage metabolism. Importantly, it should be noted that these patients are of normal intelligence with a presumably normal life span. Not all of these characteristics are present in all patients, but there are usually enough, particularly the distinctive facial and hand deformities, to identify these patients as diastrophic dwarfs. We believe that these patients should be differentiated from achondroplastic dwarfs because their joint deformities are more severe and they are likely to develop disabling symptoms in weight-bearing joints at a far earlier age.
Fig. 1: Characteristic physical features of diastrophic dwarfism.
Fig. 2: Ear of diastrophic dwarf showing pinna deformities l'cauliflower ear").
Fig. 3: Characteristic appearance of the hand in a diasirophic dwarf C'hitchhiker's thumb").
Fig. 4: Preoperative AP roentgenogram.
Like achondroplastic dwarfs, diastrophic dwarfs are potentially employable and productive citizens. Joint deformities and disabilities that are amenable to reconstructive surgery can be managed aggressively. Careful preoperative planning is necessary and custom-made components may be required. The same criteria used for considering arthroplasty in a normalsize patient should be considered in a diastrophic dwarf, although more preoperative planning may be required.
Fig. 5: Postoperative A P roentgenogram.
Our patient had bilateral disabling hip symptoms that we felt indicated the need for total hip replacement. Her surgical and postoperative course was benign, with no anesthetic problems. She is young, and as with any young patient who requires a cement arthroplasty, certain long term sequelae must be considered and monitored.
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2. Walker BA, Scott CI et al. Diastrophic dwarfism. Medicine 1972; 51:41-59.
3. Amuso SJ. Diastrophic dwarfism. J Bone Joint Surg 1968; 50A:1 13-22.
4. Rimoin DL. Histopathology and ultrastructive of cartilage in the chondrodystrophies. Birth Defects 1974; 10(9):1-18.
5. Hollister DW. Diastrophic dwarfism. Clin Orthop 1976; 114:61-69.
6. Spranger JW, Langer LO, Wiedemann HR. Bone Dysplasias. Philadelphia, WB. Saunders, 1974; 102-07.
7. Hall JG. Diastrophic dwarfism with ossicle malformation. Birth Defects 1971; 7(4):125.
8. Kopits SE. Orthopedic complications of dwarfism. Clin Orthop 1976; 114:153-79.
9. Kite JH: Achondroplasia: The club foot problem in achondroplasia. South Med J 1961; 54:577-83.