Anatomic basis of dorsoradial approach for radioulnar synostosis

Nabil Ebraheim

Anatomic basis of dorsoradial approach for radioulnar synostosis

Nabil Ebraheim

1998, Surgical and Radiologic Anatomy

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The object of this study was to identify the best approach for exposing the radioulnar interosseous membrane while protecting the posterior interosseous n. (PIN). Twenty paired upper limbs were used to obtain measurements of the PIN and expose the distal two-thirds of the interosseous membrane in the forearm through a dorsoradial approach. The length of the PIN from the radial head to the arcade of Frohse (AF) was 26.5 ± 1.6 mm in males and 25.3 ± 1.1 mm in females. The length of the PIN between the radial head and the point where the PIN exits from the supinator was 66.7 ± 4.7 mm in males and 64.0 ± 2.5 mm in females. The length of the PIN covered by the supinator was 44.0 ± 0.5 mm in males and 37.0 ± 0.5 mm in females. The distance between the point where the PIN exits from the supinator and the lateral margin of the radius was 15.0 ± 0.9 mm in males and 14.5 ± 0.9 mm in females. The distance between the exit point of the PIN from the supinator and the lateral margin of the ulna was 18.2 ± 0.6 mm in males and 17.9 ± 0.7 mm in females. The distance from the point where the most lateral branch of the PIN entered the abductor pollicis longus (APL) to the lateral margin of the radius was 3.5 ± 0.5 mm. In 20 cadaveric upper limbe, the middle and distal portions of the interosseous membrane were exposed through the interval between the extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC) m., after the origine of the extensor pollicis brevis (EPB), and extensor pollicis longus (EPL) mm. had been elevated from the lateral margin of the radius. The present study suggests that usina dorsoradial approach facilitates exposure of the middle and distal portions of the interosseous membrane.

Anatomic bases of medical, radiological and surgical techniques Anatomic basis of dorsoradial approach for radioulnar synostosis F. Jin, M. Skie, N.A. Ebraheim and J. Lu Department of Orthopaedic Surgery, Medical College of Ohio, P.O. Box 10008, Toledo, Ohio 43614, USA Received November 7, 1997 / Accepted in final form May 4, 1998 Key words: Interosseous membrane --Radioulnar synostosis -- Posterior interosseous nerve -Surgical approach --Anatomy Correspondence to: N.A. Ebraheim Abstract The object of this study was to identify the best approach for exposing the radioulnar interosseous membrane while protecting the posterior interosseous n. (PIN). Twenty paired upper limbs were used to obtain measurements of the PIN and expose the distal two-thirds of the interosseous membrane in the forearm through a dorsoradial approach. The length of the PIN from the radial head to the arcade of Frohse (AF) was 26.5 ± 1.6 mm in males and 25.3 ± 1.1 mm in females. The length of the PIN between the radial head and the point where the PIN exits from the supinator was 66.7 ± 4.7 mm in males and 64.0 ± 2.5 mm in females. The length of the PIN covered by the supinator was 44.0 ± 0.5 mm in males and 37.0 ± 0.5 mm in females. The distance between the point where the PIN exits from the supinator and the lateral margin of the radius was 15.0 ± 0.9 mm in males and 14.5 ± 0.9 mm in females. The distance between the exit point of the PIN from the supinator and the lateral margin of the ulna was 18.2 ± 0.6 mm in males and 17.9 ± 0.7 mm in females. The distance from the point where the most lateral branch of the PIN entered the abductor pollicis longus (APL) to the lateral margin of the radius was 3.5 ± 0.5 mm. In 20 cadaveric upper limbe, the middle and distal portions of the interosseous membrane were exposed through the interval between the extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC) m., after the origine of the extensor pollicis brevis (EPB), and extensor pollicis longus (EPL) mm. had been elevated from the lateral margin of the radius. The present study suggests that usina dorsoradial approach facilitates exposure of the middle and distal portions of the interosseous membrane. Radioulnar synostosis is a rare deformity of the upper extremity which can be divided into two types: congenital and posttraumatic [1, 4, 8]. Surgical intervention may improve pronation and supination, and thus the function of the forearm, when patients have loss of forearm axial rotation or when the position of the forearm is fixed. Sachar [13] reported that nearly all patients presented with a fixed pronation deformity, and that surgical complications are common, especially injury to the posterior interosseous n. (PIN). Surgical approaches to proximal radioulnar synostoses have been addressed by several authors [4, 5]. To our knowledge there is little material describing exposure of synostoses in the middle and distal forearm. There is current interest in the anatomy of the interosseous membrane as it relates to longitudinal stability of the forearm. As reconstructive alternatives for the interosseous ligament evolve, approaches to the middle third of the interosseous membrane may gain in clinical importance. Our study focussed primarily on posttraumatic radioulnar synostosis involving the distal two-thirds of the forearm, the regional anatomy of the PIN, and recommandations for a safe approach to the middle and distal thirds of the radioulnar interosseous membrane. Material and methods Twenty paired cadaver upper limbs were obtained from the Department of Anatomy, Medical College of Ohio. The age ranged from 53 to 94 years with an average of 78.9 years. Six were males and four females. The following parameters were measured with a calmer accurate to 0.1 mm: a) the length of the PIN from the radial head to the arcade of Frohse; b) the length of the PIN from the radial head to the PIN exit point from the supinator m.; c) the distance between the PIN exit point from the supinator m. to the lateral margin of the radius; d) the distance between the PIN exit point from the supinator m. to the lateral margin of the ulna; and e) the distance from the point where the most lateral branch of the PIN enfers the abductor pollicis longus m. (APL) to the lateral margin of the radius (Fig. 1). Fig. 1 Illustrations of measurements on a right forearm, a, length of the PIN from radial head to the arcade of Frohse; b, length of the PIN from radial head to the PIN exit point from supinator m.; c, distance between the PIN exit point from supinator m. and the lateral margin of the radius; d, distance between the PIN exit point from the supinator m. and the ulnar margin of the ulna; e, distance from the point of the far lateral branch entering the APL m. The middle and distal portions of the interosseous membrane were exposed through the interval between the extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC) m., after the origin of the abductor pollicis longus (ABPL), extensor pollicis brevis (EPB) and extensor pollicis longus (EPL) m. had been elevated from the lateral margin of the radius. The statistical significance of the data obtained on the PIN and its branches was analyzed using the Students t-test. Results Through a dorsoradial approach, it was possible to visualize the interosseous membrane of the middle and distal portions of the forearm (Fig. 2a, b). The anatomic locations of the PIN and associated structures were noted (Fig. 3). The length of the PIN from the radial head to the AF averaged 26.5 ± 1.6 mm in males and 25.3 ± 1.1 mm in females. The length of the PIN from the radial head to the PIN exit point from the supinator m. was 66.7 ± 4.7 mm in males and 64.0 ± 2.5 mm in females. The length of the PIN which was covered by the supinator m. was 44.0 ± 0.5 mm in males and 14.5 ± 0.5 mm in females. The distance between the PIN exit point from the supinator m. to the lateral margin of the radius was 15.0 ± 0.9 mm in males and 14.5 ± 0.9 mm in females. The distance between the PIN exit point from the supinator m. to the lateral margin of the ulna was 18.2 ± 0.6 mm in males and 17.9 ± 0.7 mm in females. The distance from the point where the most lateral branch enters the APL m. to the lateral margin of the radius was 3.5 ± 0.5 mm (Fig. 1). Fig. 2a, b Dissected left forearm showing the approach to the interosseous membrane. R, radius; U, ulna; ED, extensor digitorum communis m.; ECRB, extensor carpi radialis brevis m.; APL, abductor pollicis longus m.; EPB, extensor pollicis brevis m.;EPL, extensor pollicis longusm.; IM, interosseous membrane; B, Illustration of the posterior aspect of a right forearm showing approach to interosseous membrane Fig. 3 Dissected right forearm showing the PIN and its main branches The middle and distal thirds of the interosseous membrane were exposed through the interval between the ECRB and EDC m., after the origin of the ABPL, EPB, and EPL m. had been elevated from the lateral margin of the radius. No statistical differences were found between male and female specimens, nor between right and left forearms. Discussion Radioulnar synostosis may be congenital or acquired as a result of a fracture of one or both forearm bones [1, 4, 8]. Although Mital and Simmons [9, 14] found approximately 300 cases of congenital radioulnar synostosis reported in the literature, post-traumatic radioulnar synostosis is a much more frequent and often reported occurrence [2, 3, 4, 10, 11, 12, 15]. Options for treatment vary depending on classification, and postoperative complications are common. Simmons [14] reported that the incidence of complications following excision of radioulnar synostosis which resulted from forearm fractures was 36%. One of the serious neural complications was injury to the PIN. Therefore, an appropriate surgical approach to minimize the complications is critical. Our study showed that the safest and simplest exposure for proximal portion of the forearm was through a dorsoulnar approach, and that the distal two thirds of the interosseous membrane could be exposed through a dorsoradial approach. Cleary and Omer's [4] classified congenital radioulnar synostosis into four types depending on the shape and position of the radial head. When the region of the synostosis is located in the proximal portion of the forearm, a dorsal incision along the subcutaneous border of the ulna between the anconeus and ECU mm. was chosen [5, 6]. In our study, the length of the PIN from the radial head to the distal border of the supinator m. was 60 to 75 mm where the nerve descends from anterior to posterior and then continues along the lateral side of the radius. The distance between the PIN exit point from the supinator m. and the ulnar margin of the ulna was 17 to 19 mm. It should be kept in mind that these measurements apply to adult specimens. Exposure of the proximal interosseous membrane through the interval between the anconeus and ECU mm. is relatively safe. Vince and Miller [15] classified posttraumatic radioulnar synostoses into three types depending on location: type 1 occurs in the distal radioulnar joint, type 2 in the middle third or nonarticular portion of the forearm, and type 3 in the proximal radioulnar joint. Type 2 accounted for 50% of all posttraumatic radioulnar synostoses [15]. According to our study, the distance from where the PIN exits from the supinator m. to the lateral margin of the radius was 13 to 16 mm, with the branch to the APL m. being situated at the most radial side of the bundle. The smallest distance from the lateral margin of the radius to where the nerve branch enfers the APL m. was 3.5 ± 0.5 mm. Therefore, a dorsoradial approach from the lateral margin of the radius with subperiosteal elevation to the interosseous membrane of the mid- and distal forearm is safe. On the other hand, the dorsoulnar approach offers safe exposure, but requires greater muscular elevation to reach the interosseous membrane. The APL m. originates from both bones of the forearm obliquely from supero-ulnar to infero-radial, and the EPL and EDI m. arise primarily from the ulna. The dorsoradial approach, in our opinion, allows relatively safe exposure of the interosseous membrane with less muscle dissection and soft tissue stripping. This may be of benefit in reducing the recurrence of synostosis, or in preventing its occurrence when exposing the membrane for other indications. References 1. Abrams RA, Simmons BP (1993) Treatment of posttraumatic radioulnar synostosis with excision and long-dose radiation. J Hand Surg 18A: 703-707 2. Bauer G, Arand M, Mutschler W (1991) Post-traumatic radioulnar synostosis after forearm fracture osteosynthesis. Arch Orthop Trauma Surg 110: 142-145 3. Breir R (1983) Post-traumatic radioulnar synostosis. Clin Orthop Rel Res 174: 149-152 4. Cleary JE, Omer GE (1985) Congenital proximal radioulnar synostosis. Natural history and functional assessment. J Bone Joint Surg 67A: 539-545 5. Green WT, Mital MA (1979) Congenital radioulnar synostosis: Surgical treatment. J Bone Joint Surg 61A: 738-743 6. Hankin FM, Smith PA (1987) Ulnar nerve palsy following rotational osteotomy of congenital radioulnar synostosis. J Pediatr Orthop 7: 103-106 7. Last RJ (1978) The extensor compartment of the forearm. In: Anatomy regional and applied. Churchill Livingstone, Edinburgh London New York, pp 88-91 8. Maempel FZ (1984) Post-traumatic radioulnar synostosis. A report of two cases. Clin Orthop Rel Res: 182-185 9. Mital MA (1976) Congenital radioulnar synostosis and congenital dislocation of the radial head. Orthop Clin North Am 7: 375-383 10. Posman CL, Little RE (1986) Radioulnar synostosis following an isolated fracture of the ulnar shaft. A case report. Clin Orthop Rel Res 213: 207-210 11. Roth JH, Vandersluis R (1993) Pin-site radioulnar synostosis after external fixation of a distal radial fracture: Two case reports. J Canad Surg 36: 137-140 12. Roy DR (1986) Radiouloar synostosis following proximal radial fracture in child vol. XV, n° 2. Orthop Rev 13. Sachar K, Akelman E, Ehrlich MG (1994) Radioulnar synostosis. Hand Clinics 10: 399-404 14. Simmons BP, Southmayd WW (1983) Original communications congenital radioulnar synostosis. J Hand Surg 9A: 829-838 15. Vince KG, Miller J (1987) Cross union complicating fractures of the forearm. J Bone Joint Surg Vol. A: 640-653 Surg Radiol Anat 20: 239-242 © Springer-Verlag France 1998

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