Hypoplasia of the humeral trochlea

Radiographic studies of three cases of hypoplasia of the humeral trochlea were done. Several other anomalies were also detected, including a hypoplastic capitellum in case 2, a hyperplastic radial head in cases 2 and 3, and bulging of the loose joint capsule in case 3. Operations in cases

1 and 3, disclosed that ganglions and fibrous septa compressed the ulnar nerve. The cause of ulnar nerve palsy in patients with hypoplasia of the humeraf trochlea is thought to be associated with the high incidence of ganglions in hypoplastic elbow joints. The ganglion may play a role.

(J HAND SURG 1990;15A:1004-7.)

Keiji Sato, MD, and Takayuki Miura, MD, Nagoya, Japan

H ypoplasia of the humeral trochlea is a

rare congenital anomaly of the elbow joint. Only four cases have been reported in the English-language lit- erature and all were Japanese patients. ‘. ’ However, 44

cases have been reported in Japan; the first was reported in 1927 by Saito.3 This rare malformation has been found exclusively in Japanese subjects. Three cases of hypoplasia of the humeral trochlea are reported and the pathogenesis of ulnar nerve palsy and the high incidence of associated ganglion is discussed.

Case reports

Case 1. The patient, a 31-year-old, left-handed man con- sulted our hospital complaining of pain on the medial side of his left elbow and numbness of the ulnar side of the left hand.

He first recognized a deformity of both his elbow joints in junior high school. At the age of 21 a small subcutaneous

tumor was found on the medial side of his left elbow joint. Tapping the tumor caused pain to radiate to the tip of the ring

and small fingers. Puncture of the nodule was twice done at another hospital, and the subjective symptoms were relieved

for a while. X-ray films of the left elbow joint in the anteroposterior

view (Fig. 1) clearly demonstrated hypoplasia of the humeral trochlea on both sides and the olecranon was slightly shifted towards the medial side. In the lateral view (Fig. 2), there

From the Department of Orthopaedic Surgery, Nagoya University, School of Medicine, Nagoya, Japan.

Received for publication Feb. 23, 1989; accepted in revised form Dec. 4, 1989.

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

Reprint requests: Keiji Sato, MD, Department of Orthopaedic Sur- gery, Nagoya University, School of Medicine, 65 Tsurma-cho, Showa-ku, Nagoya 466, Japan.

3/l/18919

Fig. 1. Anterorposterior x-ray view shows the hypoplasia of the humeral trochlea and slight medial shift of the olecranon. In the lateral view, the humeroradial joint also seems to be hypoplastic .

seemed to be hypoplasia of the humeroradial joint in both sides.

On examination the left elbow joint was normal in shape and the carrying angle was 0 degrees. Joint instability was not demonstrated even in the flexed position. The range of motion of his elbow joint showed mild restriction in every direction, extension - 30 degrees on the right and - 20 de- grees on the left, flexion 135 degrees on the right and 130 degrees on the left, supination 90 degrees on both sides, pronation 50 degrees on the right and 60 degrees on the left. A small subcutaneous lump was palpable on the medial side of the right elbow, but Tinel’s sign was negative. Two small nodules were discovered on the medial side of the left elbow and one showed a positive Tinel’s sign. The patient com- plained of hypesthesia over the ulnar side of the left forearm, but claw-finger deformity was not present. Muscle atrophy was detected in the hypothenar and the first interosseous mus- cle of the left hand. Muscle strength in abduction was rated good in the manual muscle test. Froment’s sign was not dem- onstrated clearly, and grasping power was slightly decreased on the left side at 46 kg, compared with 50 kg on the right

1004 THE JOURNAL OF HAND SURGERY

Vol. 15A, No. 6 November 1990 Hypoplasia of humeral trochlea 1005

Fig. 2. Anterorposterior x-ray view of case 2. Only the left side was affected and clearly demonstrated the hypoplasia of the humeral trochlea.

side. Nerve conduction velocity was delayed on the left side at 36 m/set, compared with 50 m/set on the right in the

ulnar nerves. An operation on October 2 1, 1983 showed under the sub-

cutaneous tissue, a small ganglion (0.5 X 1.0 cm), which was resected. A fibrous bundle over the flexor carpi ulnaris compressed the ulnar nerve, and a pseudoneuroma was pres- ent. Resection of this fibrous bundle and release of the ulnar

nerve revealed another ganglion (1.5 X 1 .O cm) under the ulnar nerve, and this was also resected.

The postoperative course was satisfactory. The pain sub- sided just after the operation and muscle strength recovered, but slight numbness on the palmar side of the left small and ring finger persisted.

Case 2. The patient, a 34-year-old woman, visited our hospital with a complaint of pain, present even at rest, in the left elbow region. She had recognized a deformity of her left elbow at the age of 6. Vague pain had continued from the age of 15 years, and the pain gradually became worse.

On examination several nevi were detected in her left arm and forearm. The left elbow joint showed a varus deformity, and the carrying angle was - 10 degrees. There was a lim- itation of motion, with a loss of 13 degrees in extension but supination and pronation were 90 degrees. Grasping power was 29 kg on the right and 21 kg on the left. Touch and pin prick sensibility was normal, but subjective numbness existed over the ulnar side of the left palm. Lateral instability was demonstrated. Neither muscle atrophy nor claw finger defor- mity was detected.

X-ray films showed a congenital anomaly of the left elbow joint. The main deformity was thought to be hypoplasia of the humeral trochlea (Fig. 2). but several other anomalies were also detected. One was a hypoplastic humeral capitel- lum, and the other was a hyperplastic radial head with a

Fig. 3. Lateral view in case 2. The humeral capitellum is

also hypoplastic, but the radial head is reversely hyperplastic and is convex on its joint surface.

convex deformity of the joint surface (Fig. 3). These minor deformities were clearly demonstrated by comparison of the x-ray films of both sides. The pain was effectively alleviated

by oral intake of antiinflammatory analgesics, and surgery

was not indicated. Case 3. The patient was a right-handed, 46-year-old man,

who consulted our hospital complaining of numbness over the palmar side of his right small and ring fingers of 9 months’ duration. He first recognized a deformity of his left elbow at the age of 12. Examination of his left elbow showed a cubitus

varus deformity with a carrying angle of - 15 degrees. The right elbow was normal. Lateral instability was clearly dem- onstrated even in maximum extension. The range of motion of both his elbow joints was restricted in flexion and exten- sion. Flexion was 120 degrees on the right side and 125 degrees on the left. Extension was - 20 degrees on the right and - 15 degrees on the left. A small, elastic soft tumor was palpable under the skin on the medial side of the right elbow. Tinel’s sign was positive, and pain radiated over the distal ulnar nerve region. Muscle atrophy was present in the right thenar muscle and the right first interosseous muscle. The strength of finger abduction was good. Froment’s sign was clearly positive on the right. Mild claw-finger deformity was also observed on the right side. Grasping power was weak on the right i.e., 28 kg compared with 36 kg on the left side. Nerve conduction velocity of the right ulnar nerve was de- layed at the level of the cubital tunnel.

Anteroposterior x-ray films (Fig. 4) showed that the hu- meral trochlea was hypoplastic in both elbow joints, but the right radial head was conversely hyperplastic (Fig. 5). Ar- thrography of the right elbow showed that the joint capsule was loose and part of it bulged towards the medial side of the elbow joint like a ganglion (Fig. 6).

At operation, December 13, 1988, the base of the ganglion was found firmly attached to the joint capsule and also ad- herent to the ulnar nerve. Just distal to this lesion, the fibrous septum of the flexor carpi ulnaris constricted the ulnar nerve and a pseudoneuroma was found. Resection of the fibrous bundle of the flexor carpi ulnaris and the ganglion with neu-

1006 Sato and Miura The Journal of

HAND SURGERY

Fig. 4. Anteroposterior x-ray view of case 3 shows hypoplasia of the humeral trochlea on both sides.

Fig. 5. Lateral view of case 3 shows similiar changes as in case 2. The humeral capitellum is hypoplastic but, the radial head is reversely hyperplastic

rolysis and anterior transposition of the ulnar nerve yielded good results.

Discussion

Hypoplasia of the humeral trochlea seems to be a

rare condition, and, including our three cases, 46 cases have now been reported. We exclude a case reported by Mead3 of an extremely rare aplasia of the humeral trochlea. Thirty cases were male and the other 16 cases were female. Twenty-five cases were affected bilater- ally, and 21 cases were unilateral.

The shape of the elbow was noted in 57 cases. Among them, a majority, 41 (72%) hands, showed the cubitus varus deformity. The cubitus valgus deformity was found in only five cases, or 9%. The other 11 cases, or 18%, had a diagnosis of normal shape.

Fig. 6. Arthrography of the right elbow joint of case 3. White arrow demonstrates the ganglion in the sulcus ulnaris bal- looned out from the joint capsule.

The range of motion was reported for 54 limbs. Fifty (92%) hands showed restriction of motion, especially in extension. Instability was mentioned in 14 cases, and 8 of them were unstable in both lateral and medial directions.

Only two reports of a family history are published. One was a case of twins reported by Moriwaki,5 and the other was Osaka’@ article in which a brother of the case reported was affected.

Several other bone and soft tissue abnormalities have been recorded. Abnormalities of insertion of the flexor carpi ulnaris muscle were reported by Matsuzaki’ and Wada.’ Tsukada’ mentioned positional derangement of the flexor muscle group, pronator muscle group, and the ulnar nerve. Yamamoto” pointed out loosening and ballooning of the joint capsule as shown by arthrog- raphy. Tanabu” observed abnormalities of the epicon- dyle, olecranon and lengths of the humerus and radius. In our cases, the deformity was not restricted to the humeral trochlea; it extended to the medial epicondyle. These abnormalities might be a cause of the anomaly of the joint capsule and collateral ligament followed by joint instability. The humeral capitellum was slightly hypoplastic in our cases, and radial head deformity was

observed in cases 2 and 3. Forty-five (63.8%) limbs in 37 cases were operated

on for a diagnosis of ulnar nerve palsy, and a ganglion was found in 1.5 limbs in 15 (33.3%) cases. This figure is thought to be abnormally high compared with the incidence of ganglions in cases of ulnar nerve palsy without hypoplasia of the humeral trochlea; that is, 2.6% as reported by Ikuta.”

The explanation of this abnormally high rate of gan- glions and ulnar nerve palsy in the patients of hypo- plasia with humeral trochlea is thought to be as follows. Hypoplasia of the elbow joint, mainly in the humeral

Vol. 15A, No. 6 November 1990 Hypoplasia of humeral trochlea 1007

trochlea, partly of the medial collateral ligament, joint

capsule and humero-radial joint, will give rise to in- stability of the elbow joint, and a ganglion may be induced by ballooning or loosening of the joint capsule

and/or instability. lo. ” Hypoplasia, or dysplasia of the sulcus ulnaris, may push the ulnar nerve anteriorly, and

a fibrous bundle of the flexor carpi ulnaris and periph- eral soft tissue derangement may compress the ulnar nerve.9, I’. 13, I4 The ganglion may play a role in the

cause of ulnar nerve palsy.

1.

2.

3.

4.

5.

6.

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