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Anatomic considerations for the anterior exposure of the proximal portion of the radius
Anatomic Considerations for the Anterior Exposure of the Proximal Portion of the Radius Anis O. Mekhail, MD, NabU A. Ebraheim, MD, William T. Jackson, MD, Richard A. Yeasting, PhD, Toledo, OH The rate of posterior interosseous nerve injury is still of major concern during surgical exposure of the proximal portion of the radius. The objective of this study was to find the best way to protect the important neurovascular structures during anterior exposure of the proximal radius and to define the safest anatomic orientation for plate and screw placement during open reduction and internal fixation of the proximal radius. In 30 cadaveric upper limbs, the proximal portion of the radius was exposed through a modified anterior Henry approach. The important anatomic structures were localized and demonstrated on radiographs. Plates and screws were applied anterolaterally (in five specimens) and laterally (in another five specimens), and the locations of the safe and danger zones were noted. Lateral placement of the plate is preferred over the more commonly used anterolateral plating, because it carries less risk of injuring the posterior interosseous nerve during screw application and it does not impinge on the biceps tendon and block pronation. (J Hand Surg 1996;21A:794-801 .)
The proximal portion of the radius may be approached surgically either anteriorly or posteriorly; both methods have advantages and disadvantages. With either approach, iatrogenic posterior interosseous nerve (PIN) injury has always been a concern. Since the anterior approach to the proximal radius was first described,1 there have been no subsequent studies relating the anatomic structures surrounding the proximal radius to the anterior approach. To our knowledge, there is no documentation as to whether the anterior or the posterior approach is the one more associated with iatrogenic PIN injury. Also, no protective measures against this
have been described. Surgery in the region of the proximal radius is risky because it is uncommon, and its indications usually involve alteration of the normal anatomy as in fractures, tumors, or inflammation. The purpose of this study is to describe the relationship between surgically important neurovascular and musculoskeletal structures around the proximal radius and define the risk and safe zones for open reduction and internal fixation of the proximal radius through a modified Henry anterior surgical exposure of the proximal radius. A better understanding of the pitfalls responsible for neurovascular injury may decrease or eliminate some of the unwanted complications of surgical procedures in the region of the proximal portion of the radius.
From the Deparmaents of Orthopaedic Surgery and Anatomy, the Medical College of Ohio, Toledo, OH. Received for publication June 9, 1995; accepted in revised form Dec. 7, 1995. 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: Nabil A. Ebraheim, MD, Professor and Chief of Orthopaedic Trauma, Department of Orthopaedic Surgery, Medical College of Ohio, 3000 Arlington Avenue, Toledo, OH 43699-0008.
Materials and Methods
794
The Journal of Hand Surgery
Thirty upper limbs from 15 skeletally mature embalmed cadavers (10 men and 5 women) were studied. Fifteen of the upper limbs were radiographed in anteroposterior and lateral views, after the brachial artery was injected high in the arm with lead oxide to demonstrate the vascular anatomy
The Journal of Hand Surgery/ Vol. 21A No. 5 September 1996 795;
around the elbow. The arteries could then be identified easily during dissection and their relation to the screws demonstrated on anteroposterior and lateral projection radiographs. The elbow flexion crease was also marked to identify the relation of the crease to the joint line on the radiographs. In each upper limb, the proximal portion of the radius was exposed anteriorly through an incision starting proximally at the elbow crease and extending distally in a line from just lateral to the biceps tendon to the styloid process of the radius. Care was taken to ligate and transect (1) the transversely running superficial median cubital vein (joining the cephalic vein just distal to the cubital fossa to the basilic vein above the medial epicondyle), (2) the antebrachial vein (of variable location), and (3) the perforating vein (which was consistently found). The lateral cutaneous nerve of the forearm, which is the cutaneous termination of the musculocutaneous nerve, was seen in all cases in conjunction with the forearm portion of the cephalic vein and was retracted laterally. Then dissection was carried out through deep fascia with blunt scissors on the lateral aspect of the biceps tendon, until there was a place for a finger to be passed distally along the guiding outer face of the biceps tendon. When the recurrent radial artery (RRA) and vein and their branches were felt (invisible in fat) as a resistance, they were lifted by the finger and then ligated and transected medially at their origins. This enabled the "mobile wad of three" (brachioradialis, extensor carpi radialis longus [ECRL], and extensor carpi radialis brevis [ECRB] muscles) to be mobilized laterally. The space between the brachioradialis and flexor carpi radialis (FCR), where the superficial radial nerve (SRN) could be detected, was thus exposed. The SRN was completely covered by the medial border of the brachioradialis, partly covered by the ECRL, and proceeded distally along the medial border of the ECRB underneath a deep fascial covering. Next, the elbow was flexed 90 ~. The mobile wad of three was retracted laterally, and both the pronator teres (PT) (with the radial artery along its lateral border) and the FCR were retracted medially to expose the supinator. Supination of the forearm at this point made it easier to incise the bicipital bursa flush with the lateral aspect of the bicipital tendon. The bicipital tuberosity could then be clearly seen embraced by the medial edge of the supinator insertion. The insertion of the supinator to the oblique line of the radius was continuous as far distal as the insertion of the PT muscle. The supinator insertion was then elevated subperiosteally from the radius and retracted laterally
(Fig. 1). The PIN, being sandwiched between the superficial and deep parts of the supinator, was safely protected. Gradual pronation of the forearm with continuous elevation of the supinator exposed the lateral aspect of the radius. A six-hole, small dynamic compression plate was applied in each of 10 specimens (on the anterolateral surface of the radius in 5, and on the lateral surface in the other 5). Observations and Measurements
Distances between the humeroradial joint (HRJ) and the level of each of the following were measured: division of the radial nerve, the musculotendinous junction on the outer surface of brachioradialis, the PIN entry and exit through the supinator canal, the origin of RRA, the penetration of the posterior interosseous artery (PIA) through the interosseous membrane, and the upper border of PT insertion on the lateral aspect of the radius. Danger zones of screw insertion (regarding level and direction) were also noted. Additionally, the relationships between the plate and the biceps tendon, PIN, and PT, were recorded. Cross-sections
Two additional frozen specimens (one embalmed and the other fresh) were cross-sectioned to demonstrate the relation between the PIN and the radius. Each section, measuring about 0.5 cm in thickness, was left to thaw. After that, sections were cleaned and stored in a fixative solution. These sections were used to verify the relationship between the previously mentioned structures and between these structures and the surgical approach and proposed sites of plate and screw placement. Radial Nerve Injection
In 10 specimens, the radial nerve was injected with Ethiodol (an oil-based contrast medium) before its division distally in the arm. This helped to image the course of the PIN on a radiograph.
Results Correlation of the general and specific observations of this study to those of the relevant literature yielded the following results. Through the modified anterior Henry incision, it was possible to visualize the radius clearly up to the HRJ (Fig. 1). The average distances between the HRJ
796
Mekhai[ et al. / Anterior Exposure of the Proximal Radius Biceps tendon
Elbow crease HRJ Lateralcutaneous nerve of forearm s Posterior interosseousnerve
Lateral wad
artery Peel~,~ ~
.....
v .......
Radius
Figure 1. A dissected right forearm showing the relationships of different anatomic structures. The dashed line denotes where the supinator insertion should be peeled off the radius. P, proximal; D, distal; L, lateral; M, medial; HRJ, humeroradial joint; SRN, superficial radial nerve; PT, pronator teres.
and some important anatomic structures were noted (Fig. 2). The level of the elbow crease was noted to be approximately 1.0 cm _+ 0.3 cm proximal to the HRJ or at about the distal edge of the olecranon fossa on the anteroposterior projection radiograph (Figs. 1, 2, 3). The average distances between the HRJ and the following structures measured as follows: division of
the radial nerve, -1.1 cm _+ 1.0 cm; the musculotendinous junction on the outer surface of the brachioradialis muscle, 14.0 cm + 1.3 cm; the PIN entry and exit through the supinator canal, 2.5 cm _+ 0.3 cm and 6.0 cm _+ 0.9 cm, respectively; the origin of the RRA from the radial artery, 2.4 cm _+ 0.5 cm; the penetration of the PIA through the interosseous membrane,
Radial n. division ..... -1.1 Level of e l b o w crease ..... -0.9 cr Humeroradial joir S u p i n a t o r m. Post, interosseous n. entry into supinator canal ..... 2.5 crr sm. ;t.
Origin of flexor digitorum superficialis n
... 6.2 cm Superior edge of insertion of pronator teres m ...... 9.3 c
Brachioradialis musculotendinc junction ..... 14
r teres 3n
interosseous a.
Posterior interosseous a.
Abductor policis Iongus m.
Figure 2. Illustration of the anterior aspect of a right forearm showing the relationships of the different anatomic structures to the humeroradial joint. Inset illustrates the lateral aspect of the forearm showing the course of the posterior interosseous nerve.
The Journal of Hand Surgery/ Vol. 21A No. 5 September 1996 797
Figure 3. Radiograph of the right forearm after injection of the brachial artery with lead oxide; the elbow flexion crease is marked with a lead wire.
6.2 cm + 0.7 cm; the upper border of PT insertion on the lateral aspect of the radius, 9.3 cm + 0.7 cm. A branch of the RRA accompanied the PIN in every specimen (Figs. 2, 3), and the nerve to the ECRB came off the SRN in four specimens (two cadavers). Anterolateral Plating
It was noted that a plate placed on the proximal radius cannot be applied anteriorly because of the bicipital tuberosity. Application of a six-hole, small dynamic compression plate (approximately 7.5 cm long) anterolaterally required slight supination of the forearm and the placement of a lateral subperiosteal Hohmann retractor. Anterolateral plates subsequently impinged on the biceps tendon during pronation. Also, the PIN, at its posterior location (especially at the point of exit from the supinator canal), was at risk of being injured during screw application at about the level of the fourth screw, provided the plate was placed as proximally as possible on the radial shaft (approximately 1.5 cm from the joint line) (Figs. 4, 5). Other distal screws might injure any of the branches o f the PIN. The six-hole plate, applied anterolaterally in each of the five specimens, ended at or just distal to the PT insertion (Fig. 4). Lateral Plating
Lateral application of the plate had to be done with the forearm fully pronated with retractors
Figure 4. The lateral left forearm showing a six-hole, small plate applied anterolaterally with screws inserted to show their relationship to the posterior interosseous nerve. A, anterior; 2, pronator teres tendon; P, posterior; 3, posterior interosseous nerve exit from supinator; 1, supinator muscle; 4, lateral epicondyle.
mainly placed medially. The structure found to be most at risk during screw application was the PIA during its penetration of the interosseous membrane (Figs. 2, 5). This was at or slightly distal to the level of exit of the PIN from the supinator (approximately 6 cm from the joint). Also, with lateral plating, the anterior interosseous nerve would be subjected to more traction by the medial retraction. The six-hole plate, applied laterally in each of the five specimens, ended distally either proximal to or just flush with the proximal edge of the insertion of the PT. Cross-sections and Radiographs Sections taken confirmed the relation of the neurovascular structures to the radius and verified the proximity of the PIN to the radius (Fig. 6). Also, radiographic findings, demonstrating the course of the PIN before dissection, correlated with dissection results (Fig. 7).
Discussion In order to achieve maximum and safe exposure of the proximal portion of the radius, we have modified and thoroughly defined the known anterior exposure. This approach is indicated mainly in fractures of the radius, dislocation of the head of the radius, rupture of the biceps tendon, inflammations, and tumors. This study shows that the radius can be exposed up to the joint without the need for crossing the elbow flexion crease, because the elbow flexion
798
Mekhail et al. / Anterior Exposure of the Proximal Radius
Figure 5. Right forearm with a six-hole, small plate applied anterolaterally. Lead oxide was injected into the brachial artery to demonstrate the relationship of the vasculature to the proximal radius. A clip marks the point of exit of the posterior interosseous nerve from the supinator canal. (A) Anteroposterior view. (B) Lateral view.
crease is approximately 1 cm proximal to the joint space. This avoids a potentially unsightly scar. There are important superficial structures that could be injured, especially with a swollen limb. Since the radial artery passes from medial to lateral along the lateral border of PT muscle, one is unlikely
to injure the artery by starting the incision lateral to the biceps tendon. However, the RRA and a perforating vein could be easily injured. To avoid this, we recommend, as Henry I described, passing a finger distally along the outer face of the biceps tendon, feeling the leash of vessels (which lies invisible in
Figure 6. Cross-section of a right forearm 3.5 cm distal to the humeroradial joint to show the relation of the posterior interosseous nerve to the radius. The photograph was taken of the distal surface of the section to simulate a computed tomography scan. A, anterior; P, posterior; L, lateral; M, medial.
The Journal of Hand Surgery/Vol. 21A No. 5 September 1996
799
Figure 7. Right forearm showing the course of posterior interosseous nerve after injection of the radial nerve with contrast dye. (A) Anteroposterior view. (B) Lateral view.
fat), and lifting it up. As the RRA gives several branches (Henry suggested that only the most proximal branch deserves the n a m e RRA2), it is best to ligate and transsect the main trunk. This allows mobilization of the mobile lateral wad of muscles without vascular avulsi0n. However, care should be taken not to overstretch the nerve to the ECRB by over-retraction of the wad of muscles. Although the superficial branch of radial nerve provided nerve supply to the ECRB in 4 of 30 specimens (13%), this observation was different from that of Salsbury, 3 who reported that the ECRB receives nerve supply from the SRN in 56% of cases. Other reports merely mention that it sometimes obtains its nerve supply from the SRN.4,5 The finding of a branch of the RRA accompanying the PIN in all the specimens is comparable to what Papadopoulos and co-workers report. 6 Its importance is yet to be studied. The lateral cutaneous nerve of the forearm, the proximal part of which appears at the junction of biceps belly with biceps tendon, has to be protected. Some authors have recommended retraction of the nerve medially.7 We found no tension of the nerve when it is retracted laterally with its accompanying vein in using the modified Henry incision. Also, with lateral retraction, the pull on the nerve would be less if the approach is extended distally, since the nerve winds laterally at the distal part of the forearm. Transversely running superficial veins and the perfo-
rating vein are to be ligated and transected, after incising the skin and superficial fascia. Measurements of the levels of the radial nerve reported in the literature are comparable to our findings.6,8-10 Mayer and Mayfieldu and Sunderland5 state that the radial nerve divides just distal to the elbow in the majority of cases. Low et al. report that the radial nerve divides at an average of 1.8 cm below the lateral epicondyle. 12 Our findings confirm that the best way to identify the radial nerve is to locate its superficial branch underneath the brachioradialis muscle and along the medial border of the ECRB, then follow it up to the radial nerve division, which is usually at or just above the elbow crease. In order to avoid injuring the PIN, however, it should not be exposed. It is safer to fully supinate the forearm, cut tbaough the bicipital bursa, then detach the medial edge of supinator while gradually pronating the forearm. Prasartritha et el., 9 however, recommend that the PIN should be isolated to avoid possible iatrogenic complications. A Hohmann retractor placed subperiosteally on the lateral aspect of the radius would protect the nerve, but there would be the risk of stretching the nerve, as it winds around the radius. It was reported that the two heads of the supinator are not always continuous at their insertion, so that an area of the radius is left bare13,14; the PIN, being in direct contact with bone at this site, would be at greater risk of injury.
800
Mekhail et al. / Anterior Exposure of the Proximal Radius
In experimental studies, it was concluded that the PIN moves 1 cm or more medially relative to the radius on passive pronation of the forearm.ha 4 For this reason, it is suggested that the forearm should be positioned in full pronation during radial head resection.~5,16 Supinating the forearm before elevation of the supinator insertion gives better visualization and access to the anteromedial aspect of the radius and also aids in protection of the PIN by mobilizing it laterally. Placing a plate on the lateral surface of the proximal portion of the radius--as opposed to anterolateral plating--is relatively safe and avoids the potential risk of fraying the biceps tendon. A laterally placed six-hole, small dynamic compression plate barely reaches to the proximal border of the PT; by contrast, anterior plating may require distal retraction or even partial elevation of the insertion of the PT because of the obliquity of the PT tendon insertion. However, there is a risk of injuring the PIA, passing to the posterior aspect of the interosseous membrane approximately 6 cm from the joint, during placement of the screws. Irritation of the interosseous membrane with the possibility of subsequent radioulnar synostosis has to be assessed clinically. Theoretically, the interosseous membrane can be irritated by long screws applied with lateral plating. On the other hand, bone grafting in the region of a plated fracture seems easier and safer with lateral plating, in which the bone graft can be applied anteriorly. The anterior interosseous nerve is at risk of injury from hardware applied on the medial side of the radius, especially at the distal end of the plate. After plating the radius in 12 cadaveric upper limbs, Hope reported that the bone-holding forceps had trapped the main trunk of the anterior interosseous nerve in two instances and the nerve to the flexor pollicis longus in two instances of the 6 anteriorly approached specimens) 7 In all instances, the nerve had been trapped at the distal end of a six-hole plate, approximately 10 cm from the head of the radius. He concluded that sharp subperiosteal dissection should be used to provide tracks for the tips of the forceps. However, he did not mention on which surface of the radius he had applied the plates. A more distal exposure will usually require detachment of the insertion of the PT, the radial part of the origin of flexor digitomm superficialis, and the underlying origin of flexor pollicis longus. It seems safer to subsequently remove a plate through an anterior approach, because the PIN does
not have to be exposed. By contrast, the scarring caused by the posterior approach may make visualization of the nerve more difficult. Anderson and Meyer, 18 who believe that there is less hazard to the PIN through the posterior approach, also agree on the greater hazard to the nerve if the plate has to be removed. In a retrospective study that analyzed the results of 80 shaft fractures of the radius treated by open reduction and plating by a volar approach,~9 it was noted that an advantage was the possibility of an easy extension of the approach to the distal or proximal part of the forearm and an optimal covering of the plate by soft tissue. Also, exposure of the SRN was obligate, and the PIN should also be exposed in proximal fractures. In that study, only two incomplete lesions of the SRN were seen, both of which recovered spontaneously. No other neural or vascular complications were noticed. From this study, we conclude that the anterior approach to the proximal portion of the radius is relatively safe, provided that care is taken to protect neurovascular structures by following the steps of the approach. It appears that lateral plating is better than anterolateral plating, especially if the plate must be placed proximally to avoid impingement on the biceps tendon. Lateral plating would facilitate bone grafting when required. Also, anterolateral plating carries more risk of injury to the PIN during screw application. However, lateral plating carries more risk of injury to the PIA during screw application. Further investigation is needed to determine whether a plate placed laterally would cause postoperative irritation to the PIN as it winds laterally around the plate with pronation and supination. Whichever approach is used, it seems that the PIN would always be at risk of injury, especially by traction, and the best way to lessen the chances of its injury in all instances is to be familiar with the anatomy of this region.
References 1. Henry AK. Complete exposure of the radius. In: Exposures of long bones and other surgical methods. Bristol: John Wright & Sons Ltd, 1927:9-12. 2. Henry AK. Extensile exposure. 2nd ed. New York: Churchill Livingstone, 1973:94-105. 3. Salsbury CR. The nerve to extensor carpi radialis brevis. Br J Surg 1938;26:95-97. 4. Kaplan EB. Surgical approach to the proximal end of the radius and its use in fractures of the head and neck of the radius. J Bone Joint Surg 1941;23B:86-92.
The Journal of Hand Surgery/Vol. 21A No. 5 September 1996 5. Sunderland S. Nerves and nerve injuries. 2nd ed. Baltimore: Williams & Wilkins, 1978:802-804. 6. Papadopoulos N, Pm'aschos A, Pelekis E Anatomical observations on the arcade of Fr6hse and other structures related to the deep radial entrapment neuropathy. Folia Morphol 1989;3:319-329. 7. Bauer R, Kerschbaumer F, Poisel S. Operative approaches in orthopedic surgery and traumatology. New York: Thieme, 1987:275-277. 8. Fuss FK, Wurzl GH. Radial nerve entrapment at the elbow: surgical anatomy. J Hand Surg 1991; 16A:742-747. 9. Prasartritha T, Liupolvanish R Rojanakit A. A study of the posterior interosseous nerve (PIN) and the radial tunnel in 30 cadavers. J Hand Surg 1993;18A: 107-112. 10. Rath AM, Perez M, Mainguene C, Masquelet AC, Chevrel JR Anatomic basis of the physiopathology of the epicondyloplegias: a study of the branch of the radial nerve. Surg Radiol Anat 1993;15:15-19. 11. Mayer JH Jr, Mayfield FH. Surgery of posterior interosseous branch of radial nerve: analysis of 58 cases. Surg Gynec Obstet 1947;84:979-982. 12. Low CK, Chew JT, Mitra AK. The surgical approach to the posterior interosseous branch of the radial nerve through
13. 14.
15.
16. 17.
18.
19.
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the brachioradialis: a cadaveric study. Singapore Med J 1994;35:394-396. Davies F, Laird M. The supinator muscle and the deep radial nerve. Anat Rec 1948;101:243-250. Spinner M. Injuries to the major branches of peripheral nerves of the forearm. Philadelphia: WB Saunders, 1972: 28-32. Strachan JCH, Ellis BW. Vulnerability of the posterior interosseous nerve during radial head resection. J Bone Joint Surg 1971;53B:320-323. Wadsworth T. The elbow. Edinburgh: Churchill Livingstone, 1982:24-27. Hope PG. Anterior interosseous nerve palsy following internal fixation of the proximal radius. J Bone Joint Surg 1988;70B:280-282. Anderson LD, Meyer FN. Fractures of the shafts of the radius and ulna. In: Rockwood C, Green D, eds. Fractures. 3rd ed. New York: JB Lippincott, 1991:701. Kwasny O, Fuchs M, Schabus R. Results of a volar approach to plate osteosynthesis of radius shaft fractures: theoretical basis--clinical results. Unfallchirurgie 1992; 18:24-30.
The proximal portion of the radius may be approached surgically either anteriorly or posteriorly; both methods have advantages and disadvantages. With either approach, iatrogenic posterior interosseous nerve (PIN) injury has always been a concern. Since the anterior approach to the proximal radius was first described,1 there have been no subsequent studies relating the anatomic structures surrounding the proximal radius to the anterior approach. To our knowledge, there is no documentation as to whether the anterior or the posterior approach is the one more associated with iatrogenic PIN injury. Also, no protective measures against this
have been described. Surgery in the region of the proximal radius is risky because it is uncommon, and its indications usually involve alteration of the normal anatomy as in fractures, tumors, or inflammation. The purpose of this study is to describe the relationship between surgically important neurovascular and musculoskeletal structures around the proximal radius and define the risk and safe zones for open reduction and internal fixation of the proximal radius through a modified Henry anterior surgical exposure of the proximal radius. A better understanding of the pitfalls responsible for neurovascular injury may decrease or eliminate some of the unwanted complications of surgical procedures in the region of the proximal portion of the radius.
From the Deparmaents of Orthopaedic Surgery and Anatomy, the Medical College of Ohio, Toledo, OH. Received for publication June 9, 1995; accepted in revised form Dec. 7, 1995. 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: Nabil A. Ebraheim, MD, Professor and Chief of Orthopaedic Trauma, Department of Orthopaedic Surgery, Medical College of Ohio, 3000 Arlington Avenue, Toledo, OH 43699-0008.
Materials and Methods
794
The Journal of Hand Surgery
Thirty upper limbs from 15 skeletally mature embalmed cadavers (10 men and 5 women) were studied. Fifteen of the upper limbs were radiographed in anteroposterior and lateral views, after the brachial artery was injected high in the arm with lead oxide to demonstrate the vascular anatomy
The Journal of Hand Surgery/ Vol. 21A No. 5 September 1996 795;
around the elbow. The arteries could then be identified easily during dissection and their relation to the screws demonstrated on anteroposterior and lateral projection radiographs. The elbow flexion crease was also marked to identify the relation of the crease to the joint line on the radiographs. In each upper limb, the proximal portion of the radius was exposed anteriorly through an incision starting proximally at the elbow crease and extending distally in a line from just lateral to the biceps tendon to the styloid process of the radius. Care was taken to ligate and transect (1) the transversely running superficial median cubital vein (joining the cephalic vein just distal to the cubital fossa to the basilic vein above the medial epicondyle), (2) the antebrachial vein (of variable location), and (3) the perforating vein (which was consistently found). The lateral cutaneous nerve of the forearm, which is the cutaneous termination of the musculocutaneous nerve, was seen in all cases in conjunction with the forearm portion of the cephalic vein and was retracted laterally. Then dissection was carried out through deep fascia with blunt scissors on the lateral aspect of the biceps tendon, until there was a place for a finger to be passed distally along the guiding outer face of the biceps tendon. When the recurrent radial artery (RRA) and vein and their branches were felt (invisible in fat) as a resistance, they were lifted by the finger and then ligated and transected medially at their origins. This enabled the "mobile wad of three" (brachioradialis, extensor carpi radialis longus [ECRL], and extensor carpi radialis brevis [ECRB] muscles) to be mobilized laterally. The space between the brachioradialis and flexor carpi radialis (FCR), where the superficial radial nerve (SRN) could be detected, was thus exposed. The SRN was completely covered by the medial border of the brachioradialis, partly covered by the ECRL, and proceeded distally along the medial border of the ECRB underneath a deep fascial covering. Next, the elbow was flexed 90 ~. The mobile wad of three was retracted laterally, and both the pronator teres (PT) (with the radial artery along its lateral border) and the FCR were retracted medially to expose the supinator. Supination of the forearm at this point made it easier to incise the bicipital bursa flush with the lateral aspect of the bicipital tendon. The bicipital tuberosity could then be clearly seen embraced by the medial edge of the supinator insertion. The insertion of the supinator to the oblique line of the radius was continuous as far distal as the insertion of the PT muscle. The supinator insertion was then elevated subperiosteally from the radius and retracted laterally
(Fig. 1). The PIN, being sandwiched between the superficial and deep parts of the supinator, was safely protected. Gradual pronation of the forearm with continuous elevation of the supinator exposed the lateral aspect of the radius. A six-hole, small dynamic compression plate was applied in each of 10 specimens (on the anterolateral surface of the radius in 5, and on the lateral surface in the other 5). Observations and Measurements
Distances between the humeroradial joint (HRJ) and the level of each of the following were measured: division of the radial nerve, the musculotendinous junction on the outer surface of brachioradialis, the PIN entry and exit through the supinator canal, the origin of RRA, the penetration of the posterior interosseous artery (PIA) through the interosseous membrane, and the upper border of PT insertion on the lateral aspect of the radius. Danger zones of screw insertion (regarding level and direction) were also noted. Additionally, the relationships between the plate and the biceps tendon, PIN, and PT, were recorded. Cross-sections
Two additional frozen specimens (one embalmed and the other fresh) were cross-sectioned to demonstrate the relation between the PIN and the radius. Each section, measuring about 0.5 cm in thickness, was left to thaw. After that, sections were cleaned and stored in a fixative solution. These sections were used to verify the relationship between the previously mentioned structures and between these structures and the surgical approach and proposed sites of plate and screw placement. Radial Nerve Injection
In 10 specimens, the radial nerve was injected with Ethiodol (an oil-based contrast medium) before its division distally in the arm. This helped to image the course of the PIN on a radiograph.
Results Correlation of the general and specific observations of this study to those of the relevant literature yielded the following results. Through the modified anterior Henry incision, it was possible to visualize the radius clearly up to the HRJ (Fig. 1). The average distances between the HRJ
796
Mekhai[ et al. / Anterior Exposure of the Proximal Radius Biceps tendon
Elbow crease HRJ Lateralcutaneous nerve of forearm s Posterior interosseousnerve
Lateral wad
artery Peel~,~ ~
.....
v .......
Radius
Figure 1. A dissected right forearm showing the relationships of different anatomic structures. The dashed line denotes where the supinator insertion should be peeled off the radius. P, proximal; D, distal; L, lateral; M, medial; HRJ, humeroradial joint; SRN, superficial radial nerve; PT, pronator teres.
and some important anatomic structures were noted (Fig. 2). The level of the elbow crease was noted to be approximately 1.0 cm _+ 0.3 cm proximal to the HRJ or at about the distal edge of the olecranon fossa on the anteroposterior projection radiograph (Figs. 1, 2, 3). The average distances between the HRJ and the following structures measured as follows: division of
the radial nerve, -1.1 cm _+ 1.0 cm; the musculotendinous junction on the outer surface of the brachioradialis muscle, 14.0 cm + 1.3 cm; the PIN entry and exit through the supinator canal, 2.5 cm _+ 0.3 cm and 6.0 cm _+ 0.9 cm, respectively; the origin of the RRA from the radial artery, 2.4 cm _+ 0.5 cm; the penetration of the PIA through the interosseous membrane,
Radial n. division ..... -1.1 Level of e l b o w crease ..... -0.9 cr Humeroradial joir S u p i n a t o r m. Post, interosseous n. entry into supinator canal ..... 2.5 crr sm. ;t.
Origin of flexor digitorum superficialis n
... 6.2 cm Superior edge of insertion of pronator teres m ...... 9.3 c
Brachioradialis musculotendinc junction ..... 14
r teres 3n
interosseous a.
Posterior interosseous a.
Abductor policis Iongus m.
Figure 2. Illustration of the anterior aspect of a right forearm showing the relationships of the different anatomic structures to the humeroradial joint. Inset illustrates the lateral aspect of the forearm showing the course of the posterior interosseous nerve.
The Journal of Hand Surgery/ Vol. 21A No. 5 September 1996 797
Figure 3. Radiograph of the right forearm after injection of the brachial artery with lead oxide; the elbow flexion crease is marked with a lead wire.
6.2 cm + 0.7 cm; the upper border of PT insertion on the lateral aspect of the radius, 9.3 cm + 0.7 cm. A branch of the RRA accompanied the PIN in every specimen (Figs. 2, 3), and the nerve to the ECRB came off the SRN in four specimens (two cadavers). Anterolateral Plating
It was noted that a plate placed on the proximal radius cannot be applied anteriorly because of the bicipital tuberosity. Application of a six-hole, small dynamic compression plate (approximately 7.5 cm long) anterolaterally required slight supination of the forearm and the placement of a lateral subperiosteal Hohmann retractor. Anterolateral plates subsequently impinged on the biceps tendon during pronation. Also, the PIN, at its posterior location (especially at the point of exit from the supinator canal), was at risk of being injured during screw application at about the level of the fourth screw, provided the plate was placed as proximally as possible on the radial shaft (approximately 1.5 cm from the joint line) (Figs. 4, 5). Other distal screws might injure any of the branches o f the PIN. The six-hole plate, applied anterolaterally in each of the five specimens, ended at or just distal to the PT insertion (Fig. 4). Lateral Plating
Lateral application of the plate had to be done with the forearm fully pronated with retractors
Figure 4. The lateral left forearm showing a six-hole, small plate applied anterolaterally with screws inserted to show their relationship to the posterior interosseous nerve. A, anterior; 2, pronator teres tendon; P, posterior; 3, posterior interosseous nerve exit from supinator; 1, supinator muscle; 4, lateral epicondyle.
mainly placed medially. The structure found to be most at risk during screw application was the PIA during its penetration of the interosseous membrane (Figs. 2, 5). This was at or slightly distal to the level of exit of the PIN from the supinator (approximately 6 cm from the joint). Also, with lateral plating, the anterior interosseous nerve would be subjected to more traction by the medial retraction. The six-hole plate, applied laterally in each of the five specimens, ended distally either proximal to or just flush with the proximal edge of the insertion of the PT. Cross-sections and Radiographs Sections taken confirmed the relation of the neurovascular structures to the radius and verified the proximity of the PIN to the radius (Fig. 6). Also, radiographic findings, demonstrating the course of the PIN before dissection, correlated with dissection results (Fig. 7).
Discussion In order to achieve maximum and safe exposure of the proximal portion of the radius, we have modified and thoroughly defined the known anterior exposure. This approach is indicated mainly in fractures of the radius, dislocation of the head of the radius, rupture of the biceps tendon, inflammations, and tumors. This study shows that the radius can be exposed up to the joint without the need for crossing the elbow flexion crease, because the elbow flexion
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Figure 5. Right forearm with a six-hole, small plate applied anterolaterally. Lead oxide was injected into the brachial artery to demonstrate the relationship of the vasculature to the proximal radius. A clip marks the point of exit of the posterior interosseous nerve from the supinator canal. (A) Anteroposterior view. (B) Lateral view.
crease is approximately 1 cm proximal to the joint space. This avoids a potentially unsightly scar. There are important superficial structures that could be injured, especially with a swollen limb. Since the radial artery passes from medial to lateral along the lateral border of PT muscle, one is unlikely
to injure the artery by starting the incision lateral to the biceps tendon. However, the RRA and a perforating vein could be easily injured. To avoid this, we recommend, as Henry I described, passing a finger distally along the outer face of the biceps tendon, feeling the leash of vessels (which lies invisible in
Figure 6. Cross-section of a right forearm 3.5 cm distal to the humeroradial joint to show the relation of the posterior interosseous nerve to the radius. The photograph was taken of the distal surface of the section to simulate a computed tomography scan. A, anterior; P, posterior; L, lateral; M, medial.
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Figure 7. Right forearm showing the course of posterior interosseous nerve after injection of the radial nerve with contrast dye. (A) Anteroposterior view. (B) Lateral view.
fat), and lifting it up. As the RRA gives several branches (Henry suggested that only the most proximal branch deserves the n a m e RRA2), it is best to ligate and transsect the main trunk. This allows mobilization of the mobile lateral wad of muscles without vascular avulsi0n. However, care should be taken not to overstretch the nerve to the ECRB by over-retraction of the wad of muscles. Although the superficial branch of radial nerve provided nerve supply to the ECRB in 4 of 30 specimens (13%), this observation was different from that of Salsbury, 3 who reported that the ECRB receives nerve supply from the SRN in 56% of cases. Other reports merely mention that it sometimes obtains its nerve supply from the SRN.4,5 The finding of a branch of the RRA accompanying the PIN in all the specimens is comparable to what Papadopoulos and co-workers report. 6 Its importance is yet to be studied. The lateral cutaneous nerve of the forearm, the proximal part of which appears at the junction of biceps belly with biceps tendon, has to be protected. Some authors have recommended retraction of the nerve medially.7 We found no tension of the nerve when it is retracted laterally with its accompanying vein in using the modified Henry incision. Also, with lateral retraction, the pull on the nerve would be less if the approach is extended distally, since the nerve winds laterally at the distal part of the forearm. Transversely running superficial veins and the perfo-
rating vein are to be ligated and transected, after incising the skin and superficial fascia. Measurements of the levels of the radial nerve reported in the literature are comparable to our findings.6,8-10 Mayer and Mayfieldu and Sunderland5 state that the radial nerve divides just distal to the elbow in the majority of cases. Low et al. report that the radial nerve divides at an average of 1.8 cm below the lateral epicondyle. 12 Our findings confirm that the best way to identify the radial nerve is to locate its superficial branch underneath the brachioradialis muscle and along the medial border of the ECRB, then follow it up to the radial nerve division, which is usually at or just above the elbow crease. In order to avoid injuring the PIN, however, it should not be exposed. It is safer to fully supinate the forearm, cut tbaough the bicipital bursa, then detach the medial edge of supinator while gradually pronating the forearm. Prasartritha et el., 9 however, recommend that the PIN should be isolated to avoid possible iatrogenic complications. A Hohmann retractor placed subperiosteally on the lateral aspect of the radius would protect the nerve, but there would be the risk of stretching the nerve, as it winds around the radius. It was reported that the two heads of the supinator are not always continuous at their insertion, so that an area of the radius is left bare13,14; the PIN, being in direct contact with bone at this site, would be at greater risk of injury.
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In experimental studies, it was concluded that the PIN moves 1 cm or more medially relative to the radius on passive pronation of the forearm.ha 4 For this reason, it is suggested that the forearm should be positioned in full pronation during radial head resection.~5,16 Supinating the forearm before elevation of the supinator insertion gives better visualization and access to the anteromedial aspect of the radius and also aids in protection of the PIN by mobilizing it laterally. Placing a plate on the lateral surface of the proximal portion of the radius--as opposed to anterolateral plating--is relatively safe and avoids the potential risk of fraying the biceps tendon. A laterally placed six-hole, small dynamic compression plate barely reaches to the proximal border of the PT; by contrast, anterior plating may require distal retraction or even partial elevation of the insertion of the PT because of the obliquity of the PT tendon insertion. However, there is a risk of injuring the PIA, passing to the posterior aspect of the interosseous membrane approximately 6 cm from the joint, during placement of the screws. Irritation of the interosseous membrane with the possibility of subsequent radioulnar synostosis has to be assessed clinically. Theoretically, the interosseous membrane can be irritated by long screws applied with lateral plating. On the other hand, bone grafting in the region of a plated fracture seems easier and safer with lateral plating, in which the bone graft can be applied anteriorly. The anterior interosseous nerve is at risk of injury from hardware applied on the medial side of the radius, especially at the distal end of the plate. After plating the radius in 12 cadaveric upper limbs, Hope reported that the bone-holding forceps had trapped the main trunk of the anterior interosseous nerve in two instances and the nerve to the flexor pollicis longus in two instances of the 6 anteriorly approached specimens) 7 In all instances, the nerve had been trapped at the distal end of a six-hole plate, approximately 10 cm from the head of the radius. He concluded that sharp subperiosteal dissection should be used to provide tracks for the tips of the forceps. However, he did not mention on which surface of the radius he had applied the plates. A more distal exposure will usually require detachment of the insertion of the PT, the radial part of the origin of flexor digitomm superficialis, and the underlying origin of flexor pollicis longus. It seems safer to subsequently remove a plate through an anterior approach, because the PIN does
not have to be exposed. By contrast, the scarring caused by the posterior approach may make visualization of the nerve more difficult. Anderson and Meyer, 18 who believe that there is less hazard to the PIN through the posterior approach, also agree on the greater hazard to the nerve if the plate has to be removed. In a retrospective study that analyzed the results of 80 shaft fractures of the radius treated by open reduction and plating by a volar approach,~9 it was noted that an advantage was the possibility of an easy extension of the approach to the distal or proximal part of the forearm and an optimal covering of the plate by soft tissue. Also, exposure of the SRN was obligate, and the PIN should also be exposed in proximal fractures. In that study, only two incomplete lesions of the SRN were seen, both of which recovered spontaneously. No other neural or vascular complications were noticed. From this study, we conclude that the anterior approach to the proximal portion of the radius is relatively safe, provided that care is taken to protect neurovascular structures by following the steps of the approach. It appears that lateral plating is better than anterolateral plating, especially if the plate must be placed proximally to avoid impingement on the biceps tendon. Lateral plating would facilitate bone grafting when required. Also, anterolateral plating carries more risk of injury to the PIN during screw application. However, lateral plating carries more risk of injury to the PIA during screw application. Further investigation is needed to determine whether a plate placed laterally would cause postoperative irritation to the PIN as it winds laterally around the plate with pronation and supination. Whichever approach is used, it seems that the PIN would always be at risk of injury, especially by traction, and the best way to lessen the chances of its injury in all instances is to be familiar with the anatomy of this region.
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The Journal of Hand Surgery/Vol. 21A No. 5 September 1996 5. Sunderland S. Nerves and nerve injuries. 2nd ed. Baltimore: Williams & Wilkins, 1978:802-804. 6. Papadopoulos N, Pm'aschos A, Pelekis E Anatomical observations on the arcade of Fr6hse and other structures related to the deep radial entrapment neuropathy. Folia Morphol 1989;3:319-329. 7. Bauer R, Kerschbaumer F, Poisel S. Operative approaches in orthopedic surgery and traumatology. New York: Thieme, 1987:275-277. 8. Fuss FK, Wurzl GH. Radial nerve entrapment at the elbow: surgical anatomy. J Hand Surg 1991; 16A:742-747. 9. Prasartritha T, Liupolvanish R Rojanakit A. A study of the posterior interosseous nerve (PIN) and the radial tunnel in 30 cadavers. J Hand Surg 1993;18A: 107-112. 10. Rath AM, Perez M, Mainguene C, Masquelet AC, Chevrel JR Anatomic basis of the physiopathology of the epicondyloplegias: a study of the branch of the radial nerve. Surg Radiol Anat 1993;15:15-19. 11. Mayer JH Jr, Mayfield FH. Surgery of posterior interosseous branch of radial nerve: analysis of 58 cases. Surg Gynec Obstet 1947;84:979-982. 12. Low CK, Chew JT, Mitra AK. The surgical approach to the posterior interosseous branch of the radial nerve through
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the brachioradialis: a cadaveric study. Singapore Med J 1994;35:394-396. Davies F, Laird M. The supinator muscle and the deep radial nerve. Anat Rec 1948;101:243-250. Spinner M. Injuries to the major branches of peripheral nerves of the forearm. Philadelphia: WB Saunders, 1972: 28-32. Strachan JCH, Ellis BW. Vulnerability of the posterior interosseous nerve during radial head resection. J Bone Joint Surg 1971;53B:320-323. Wadsworth T. The elbow. Edinburgh: Churchill Livingstone, 1982:24-27. Hope PG. Anterior interosseous nerve palsy following internal fixation of the proximal radius. J Bone Joint Surg 1988;70B:280-282. Anderson LD, Meyer FN. Fractures of the shafts of the radius and ulna. In: Rockwood C, Green D, eds. Fractures. 3rd ed. New York: JB Lippincott, 1991:701. Kwasny O, Fuchs M, Schabus R. Results of a volar approach to plate osteosynthesis of radius shaft fractures: theoretical basis--clinical results. Unfallchirurgie 1992; 18:24-30.