Vol. 8, No.4 July 1983

These factors may cause tissue swelling, pressure rise, and ischemia of the nerve. 2 The supinator can be dem­onstrated to compress the nerve in passive pronation or active supination. 3 It seems likely that the location of greatest stress may vary depending on other concomi­tant motions of the forearm.

Spinner" has reported posterior interosseous nerve compression at the distal edge of the supinator by a 1.5 em fibrous band. Derkash and Niebauer10 have reported intermittent compression of the posterior interosseous nerve that caused weakness precipitated by pronation and immediately relieved by supination. In this patient a thick band in the distal supinator had eroded a groove in the radius and its division resulted in symptomatic relief. A slightly different lesion in this continuum, a symptomatic fibrous band in the midportion of the supinator, was described by Comtet and Chambaud. 12

Thus, in addition to the four sites of potential com­pression described by Lister et al., 1 we would like to call attention to that portion of the radial tunnel distal to the arcade of Frohse (Fig. 4). This fifth area of potential compression of the posterior interosseous nerve might be overlooked at standard surgical exploration. The possibility of a double-level entrapment lesion should also be considered if a patient has two distinct locations of pain and tenderness along the course of the posterior interosseous nerve. Of the four patients in Roles and Maudsley's series and the one in Lister's series who did not obtain "good" relief from their operation, some may have had this lesion. Increased awareness of this possibility may help achieve more uniform relief with surgical decompression.

ERRATUM

Double-entrapment radial tunnel syndrome 423

REFERENCES 1. Lister GD, Belsole RB, Kleinert HE: The radial tunnel

syndrome. J HAND SURG 4:52-9, 1979 2. Roles NC, Maudsley RH: Radial tunnel syndrome. J

Bone Joint Surg [Br] 54:499-508, 1972 3. Capener N: The vulnerability of the posterior interosse­

ous nerve of the forearm. J Bone Joint Surg [Br] 48:770, 1966

4. Engel J, Farin Y, Horozovsky H, Shilo R: Thermog­raphy of the elbow joint. J Bone Joint Surg [Br] 58:382, 1976

5. Bowen TL, Stone K: Posterior interosseous nerve paral­ysis caused by a ganglion at the elbow. J Bone Joint Surg [Br] 48:774, 1966

6. Millender LH, Nalebuff EA, Holdsworth DE: Posterior interosseous-nerve syndrome secondary to rheumatoid synovitis. J Bone Joint Surg [Am] 55:753-7, 1973

7. Moon N, Marmor L: Parosteal lipoma of the proximal part of the radius. J Bone Joint Surg [Am] 46:608,1964

8. Spinner M: The arcade of Frohse and its relationship to posterior interosseous nerve paralysis. J Bone Joint Surg [Br] 50:809-12, 1968

9. Upton ARM, McComas AJ: The double crush in nerve entrapment syndromes. Lancet 2:359-62, 1973

10. Derkash RS, Niebauer 11: Entrapment of the posterior interosseous nerve by a fibrous band in the dorsal edge of the supinator muscle and erosion of a groove in the prox­imal radius. J HAND SURG 6:524-6, 1981

11. Spinner M: Injuries to the major branches of peripheral nerves of the forearm. Philadelphia, 1978, WB Saunders Co, pp 109-11

12. Comtet 11, Chambaud D: Paralysie "Spontanee" du nerf inter-osseux posterieur par lesion inhabituelle. Rev. Chir. Orthop. 61:533-41, 1975

In the letter by David M. Lichtman, "Management of Chronic Rotary Subluxation of the Scaphoid by Scapho-trapezio-trapezoid Arthrodesis," published in the March 1983 issue of THE JOURNAL OF HAND SURGERY, p. 223, the triquetrohamate joint was inadvertently called the "trapeziohamate" joint on two occasions (see paragraph three).