Radial Nerve Palsy: Nerve Transfer Versus Tendon Transfer to Restore Function

Abstract

Background:

Radial nerve injuries cause profound disability, and a variety of reconstruction options exist. This study aimed to compare outcomes of tendon transfers versus nerve transfers for the management of isolated radial nerve injuries.

Methods:

A retrospective chart review of 30 patients with isolated radial nerve injuries treated with tendon transfers and 16 patients managed with nerve transfers was performed. Fifteen of the 16 patients treated with nerve transfer had concomitant pronator teres to extensor carpi radialis brevis tendon transfer for wrist extension. Preoperative and postoperative strength data, Disabilities of the Arm, Shoulder, and Hand (DASH) scores, and quality-of-life (QOL) scores were compared before and after surgery and compared between groups.

Results:

For the nerve transfer group, patients were significantly younger, time from injury to surgery was significantly shorter, and follow-up time was significantly longer. Both groups demonstrated significant improvements in grip and pinch strength after surgery. Postoperative grip strength was significantly higher in the nerve transfer group. Postoperative pinch strength did not differ between groups. Similarly, both groups showed an improvement in DASH and QOL scores after surgery with no significant differences between the 2 groups.

Conclusions:

The nerve transfer group demonstrated greater grip strength, but both groups had improved pain, function, and satisfaction postoperatively. Patients who present early and can tolerate longer time to functional recovery would be optimal candidates for nerve transfers. Both tendon transfers and nerve transfers are good options for patients with radial nerve palsy.

Introduction

The radial nerve is commonly injured, and loss of radial nerve function leads to significant disability.^1,2 Primary repair of radial nerve injuries in close proximity to the motor endplates in the proximal forearm is often successful. ³ Although good recovery may also be achieved with nerve grafting, primary repair has been noted to have better and more consistent outcomes.^2-5 Alternative reconstructive options are preferable for injuries affecting the radial nerve that are very proximal, have extensive zones of injury, or present in a delayed fashion.

Tendon transfers have been used for over a century to restore function after radial nerve injury or paralysis ¹ with good results.^6-8 The donor muscle/tendon unit must be expendable, must have appropriate strength and excursion, must be synergistic, must have a straight line of pull, and should reconstruct only 1 function. ⁹ The patient should have supple passive range of motion. Disadvantages of tendon transfers include altered biomechanics, extensive dissection that could result in scar and adhesion formation, and prolonged immobilization. ²

Nerve transfers are an alternative method of restoring radial nerve function.^2,10-13 Typically, expendable branches of the median nerve are used, and a variety of donor and recipient nerve combinations have been described.^11-15 Ideal donor nerves have redundant/expendable function that is synergistic with the recipient, no sensory fibers (ie, pure motor nerve), favorable axon counts, and proximity close to the recipient nerve and recipient motor endplates to facilitate direct coaptation without tension and minimize time to reinnervation.^16,17 The anatomy of the median nerve in the proximal forearm has been extensively studied,^10,18-21 and its branching pattern allows for predictable nerve branches located close to the radial nerve and its motor endplates without requiring internal neurolysis. Disadvantages of nerve transfers include the longer time to functional recovery while reinnervation occurs and the time-sensitive nature of the procedure due to the need to restore innervation prior to motor endplate demise. ²

Many studies have evaluated patient outcomes after radial nerve tendon transfers, and fewer studies have assessed nerve transfers to restore function after radial nerve injury. However, only 1 study has directly compared the 2 techniques for patients with radial nerve or posterior cord injuries. ¹³ The purpose of this study was to augment the available literature assessing outcomes of tendon transfers versus nerve transfers for restoration of radial nerve function. We hypothesized that both techniques would improve function and patient satisfaction, but there would be differing advantages associated with each technique.

Materials and Methods

A retrospective review of all patients with isolated radial nerve injuries who underwent either tendon or nerve transfer procedures between 2009 and 2017 at the senior author’s institution was performed in accordance with the institutional review board. Patient charts were reviewed for demographic data, electrodiagnostic studies, and surgical details. Preoperative and postoperative pinch and grip strength data, Medical Research Council (MRC) grade strength data, Disabilities of the Arm, Shoulder, and Hand (DASH) scores, and quality-of-life (QOL) scores were obtained. Patients scored their overall QOL on a visual analogue scale at each visit. Data from the preoperative visit and final follow-up visits were recorded.

Seventy patients were identified, and 24 were excluded due to having sustained additional nerve injuries. All patients underwent electromyography and nerve conduction studies at least 3 months after the initial injury, and no patient had evidence of reinnervation. Evidence of receptive motor endplates with fibrillations and positive sharp waves was required for consideration of nerve transfer. Sixteen patients were treated with nerve transfers, and 30 were treated with tendon transfers (Table 1). The most common combination of tendon transfers (15 of 30 patients) was pronator teres to extensor carpi radialis brevis, flexor carpi radialis to extensor digitorum communis, and palmaris longus to extensor pollicis longus. The most common combination of nerve transfers (13 of 16 patients) was flexor digitorum superficialis branch to extensor carpi radialis brevis branch and flexor carpi radialis branch to posterior interosseous nerve. Fifteen of the 16 patients in the nerve transfer group had concomitant pronator teres to extensor carpi radialis brevis tendon transfer for wrist extension.

Table 1.

Surgical Details for Each Patient.

	Patient	Age	Time to surgery	Procedure
Nerve transfer	1	49	17	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT, SBRN-median ETS
	2	53	25	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT, SBRN-median ETS
	3	12	3	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT, SBRN-median ETS
	4	53	70	FDS-PIN and ECRB ETE
	5	23	37	FCR-PIN ETE, PT-ECRB TT, LABC-SBRN with allograft, BR release
	6	16	10	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT, radial-median with allograft
	7	22	6	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT
	8	14	82	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT
	9	57	51	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT, LABC-radial ETS
	10	34	2	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT, SBRN-median ETS
	11	28	70	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT, SBRN-median ETS
	12	27	14	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT
	13	40	15	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT
	14	36	16	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT, LABC-radial ETE
	15	13	4	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT
	16	41	26	FCR-PIN ETE, FDS-ECRB ETE, PT-ECRB TT
Tendon transfer	1	64	118	PT-ECRB, BR-ECRL, FCR-EDC, FDS III-EPL
	2	66	321	PT-ECRB, FCR-EDC, PL-EPL
	3	80	37	PT-ECRB, FCR-EDC, FDS IV-EPL
	4	21	18	PT-ECRB, FCR-EDC, FDS IV-EPL
	5	60	129	BR-ECRB, FCR-EDC, EDQ-EIP, PL-EPL
	6	60	50	PT-ECRB
	7	76	67	PT-ECRB, FCR-EDC, PL-EPL
	8	53	49	PT-ECRB, FCR-EDC, PL-EPL
	9	60	143	FCR-EDC, FDS IV-EPL
	10	62	40	PT-ECRB, FCR-EDC, PL-EPL
	11	26	44	PT-ECRB, FCR-EDC, PL-EPL
	12	33	817	PT-ECRB, FCR-EDC, PL-EPL
	13	80	39	PT-ECRB, FCR-EDC, PL-EPL
	14	39	77	FCR-EDC, PL-EPL
	15	28	97	PT-ECRB, FCR-EDC, PL-EPL
	16	46	20	PT-ECRB, FCR-EDC, PL-EPL
	17	41	38	PT-ECRB, FCR-EDC, PL-EPL, ECRB-ECRL
	18	48	429	PT-ECRB, FCR-ECRB, FDS III-EPL
	19	23	187	PL-EPL, FCR-EDC
	20	31	30	PL-EPL, FCR-EDC
	21	21	78	PT-ECRB, FCR-EDC, PL-EPL, ECRL-ECRB side to side
	22	11	1560	FCR-EDC, PL-EPL
	23	51	77	FCR-EDC, PL-EPL
	24	64	169	PT-ECRB, FCR-ECRB, FDS III-EPL
	25	81	81	FCR-EDC, PL-EPL
	26	87	108	PT-ECRB, FCR-EDC, PL-EPL
	27	32	34	PT-ECRB, FCR-EDC, PL-EPL, LABC-radial
	28	37	259	PT-ECRB, FCR-EDC, PL-EPL
	29	51	31	FDS III-ECRB, FCR-EDC, PL-EPL
	30	22	51	PT-ECRB, FCR-EDC, PL-EPL

Note. FCR = flexor carpi radialis; PIN = posterior interosseous nerve; ETE = end-to-end; FDS = flexor digitorum superficialis; ECRB = extensor carpi radialis brevis; PT = pronator teres; TT = tendon transfer; SBRN = superficial branch of radial nerve; ETS = end-to-side; LABC = lateral antebrachial cutaneous nerve; BR = brachioradialis; ECRL = extensor carpi radialis longus; EDC = extensor digitorum communis; EPL = extensor pollicis longus; PL = palmaris longus; EDQ = extensor digiti quinti; EIP = extensor indicis proprius.

The surgical techniques for both tendon and nerve transfers have previously been described (Figures 1 and 2). Patients in the tendon transfer group were splinted with the elbow at 90° of flexion, the forearm in pronation, the wrist at 30° of extension, the metacarpophalangeal joints in extension, and a thumb spica for 2 weeks. Patients were then transitioned into a removable wrist extension splint for an additional 2 weeks. Motor reeducation and range of motion exercises were begun 4 weeks after surgery with gradual progression to strengthening approximately 2 months postoperatively. Patients who underwent nerve transfers with concomitant pronator teres to extensor carpi radialis brevis tendon transfer initially followed the tendon transfer rehabilitation protocol (above). Patients with no tendon transfer were transitioned into a removable wrist splint on postoperative day 2 or 3. In the nerve transfer group, hand therapy was initiated after 2 weeks and focused on passive range of motion (except wrist flexion for patient with concomitant tendon transfer for wrist extension) and edema management. Motor reeducation was taught in the first month after surgery. Therapy progressed to include active-assisted wrist and finger extension when initial evidence of reinnervation (MRC grade 1 strength) was identified, typically 3 to 4 months postoperatively. Donor activation focused rehabilitation approach was used. ²³ Patients in both groups were weaned from the wrist splint when the wrist extension strength reached MRC grade 3.

Figure 1.

(a) Setup and (b) completion of the pronator teres to extensor carpi radialis brevis tendon transfer. The divided flexor carpi radialis (FCR) is also visualized. (c) Setup and (d) completion of the FCR to extensor digitorum communis tendon transfer. (e) Setup and (f) completion of the palmaris longus to extensor pollicis longus tendon transfer. ²²

Figure 2.

(a) Pronator teres (PT) tendon was elevated off the radius with periosteum for tendon transfer augmentation. (b) Median to radial nerve transfers just prior to coaptation demonstrating flexor carpi radialis branch to posterior interosseous nerve, flexor digitorum superficialis branch to extensor carpi radialis brevis (ECRB) branch, and radial sensory nerve end-to-side coaptation to sensory aspect of median nerve. (c) Completed PT to ECRB tendon transfer.

Demographic data (age, time to surgery, and length of follow-up) were compared between surgical groups with unpaired t tests. The proportion of female and male patients was compared between groups with a χ² test. Pinch strength, grip strength, DASH scores, and QOL scores were compared between the preoperative and postoperative time points within each surgical group using paired t tests. The same measures were compared between groups with unpaired t tests both preoperatively and postoperatively. Patients marked the impact of their injury on QOL anywhere along a line from 0 (no impact) to 10 (worst impact). The score was then measured from this line and, therefore, was considered a continuous variable. The DASH scores range from 0 (no disability) to 100 (most severe disability). A 15-point difference has been reported as the minimum clinically important difference in DASH scores. ²⁴

Results

Demographic Data

The most frequent mechanisms of injury in this cohort were iatrogenic injury, fractures, and motor vehicle collisions. The average follow-up time for the cohort was 67 weeks. Patients in the nerve transfer group were significantly younger (P = .010), had less time from injury to surgery (P = .015), and had longer follow-up periods (P = .034) (Table 2).

Table 2.

Age in Years (Mean ± SD), Sex, Time Between Injury and Surgery in Weeks (Mean|Median), and Length of Follow-up in Weeks (Mean|Median) for the Nerve Transfer Group and Tendon Transfer Group.

	Nerve	Tendon	P value
Age	32.4 ± 15.3 a	48.5 ± 21.2 a	.010
Sex	6 F, 10 M	8 F, 22 M	.447
Time to surgery	28.1|17 a	173.2|77 a	.015
Length of follow-up	105.8|62 a	45.7|41 a	.034

Note. F = female, M = male.

^aStatistical significance.

Strength Outcomes

The nerve transfer group demonstrated significant improvements in both grip (P = .002) and pinch strength (P = .009) postoperatively (Table 3). Similarly, the tendon transfer group demonstrated significant improvements in both grip (P = .023) and pinch strength (P = .008) postoperatively (Table 3). Preoperative grip strength was significantly lower in the nerve transfer group (P = .049; Figure 3). Conversely, postoperative grip strength was significantly higher in the nerve transfer group (P = .007; Figure 3). The postoperative MRC grade for wrist extension was only recorded for 7 patients in the tendon transfer group. All of these 7 patients recovered grade 4 or greater wrist extension. The MRC grades for finger/thumb extension were only recorded in 2 patients and were MRC grade 4 or greater in both. In the nerve transfer group postoperatively, wrist extension MRC grades were recorded in 13 patients and were 4 or greater in 11 of 13 patients. Finger/thumb extension was recorded in 11 patients and was MRC grade 4 or greater in 7 of the 11 patients. The limited MRC grade data in the tendon transfer group precluded statistical analysis.

Table 3.

Pinch Strength (Pounds), Grip Strength (Pounds), DASH Scores, and QOL Scores Compared Before and After Surgery (Mean ± SD).

	Nerve transfer			Tendon transfer
Measure	Preoperative	Postoperative	P value	Preoperative	Postoperative	P value
Pinch	7.2 ± 5.6 a	15.7 ± 5.4 a	.009	10.1 ± 5.4 a	15.5 ± 8.3 a	.008
Grip	14.7 ± 18.3 a	56.1 ± 22.5 a	.002	25.5 ± 16.1 a	34.4 ± 21.5 a	.023
DASH	56.8 ± 16.7 a	29.4 ± 22.6 a	.001	47.5 ± 24.7 a	36.8 ± 23.5 a	.005
QOL	5.1 ± 3.9 a	2.0 ± 1.8 a	.039	5.0 ± 3.6 a	2.2 ± 2.7 a	.001

Note. DASH scores range from 0 (no disability) to 100 (most severe disability). QOL scores range from 0 (no impact) to 100 (most severe impact). DASH = Disabilities of Arm, Shoulder, and Hand; QOL = quality of life.

^aStatistical significance.

Figure 3.

Pinch strength (pounds), grip strength (pounds), DASH scores, and QOL scores compared between the nerve transfer and tendon transfer groups before and after surgery (mean ± SD).

Note. DASH scores range from 0 (no disability) to 100 (most severe disability). QOL scores range from 0 (no impact) to 10 (most severe impact). DASH = disabilities of arm, shoulder, and hand; QOL = quality of life.

*Statistical significance.

Functional Outcomes

The DASH scores significantly improved for both the nerve transfer (P = .001) and tendon transfer (P = .005) groups (Table 3). Similarly, QOL scores significantly improved for both the nerve transfer (P = .039) and tendon transfer (P = .001) groups (Table 3). Neither the DASH scores nor the QOL scores differed between groups before or after surgery (Figure 3).

Discussion

The substantial disability caused by radial nerve injury can be greatly improved with reconstructive surgery. Reconstructive options include nerve repair, nerve grafting, tendon transfers, and nerve transfers. Prior debates regarding ideal management of proximal radial nerve injuries focused on nerve grafting versus tendon transfers.^4,25 However, outcomes following grafting of proximal radial nerve injuries are unpredictable. Bertelli et al ⁴ reported results of nerve grafts for proximal radial nerve injuries in 13 patients with a minimum of 2 years of follow-up. Although all 7 patients who had preoperative elbow extension weakness regained MRC grade 4 elbow extension, the return of more distal function was not as favorable. A good outcome was defined as MRC grade 4 wrist extension and MRC grade 3 finger and thumb extension. Only 5 patients met these criteria. ⁴ Conversely, consistent outcomes have been demonstrated with tendon transfers for radial nerve palsy.^6-8 However, as the paradigm shift in the management of nerve injuries now includes nerve transfers, the new debate is between tendon transfers and nerve transfers for the management of proximal radial nerve injuries.^4,14,25

Nerve transfers to restore radial nerve function were first described in 1948. ²⁶ The musculocutaneous nerve was transferred to the radial nerve in 2 patients with proximal radial nerve injuries. Thirteen to 15 months postoperatively, the patients had recovery of some wrist extension, but neither patient saw any return of finger or thumb extension. ²⁶ This was likely due to both the long distance to the motor endplates and the lack of synergistic function. The first clinical results of median to radial distal nerve transfers were described by Lowe et al. ¹⁴ Two patients were treated with transfer of the median nerve branches to the palmaris longus and flexor digitorum superficialis to the posterior interosseous nerve and nerve branch to extensor carpi radialis brevis, respectively. Both patients regained MRC grade 4 wrist extension strength, and 1 of the 2 also demonstrated MRC grade 4 finger extension. ¹⁴ Ray and Mackinnon ¹² reported MRC grade 4 or higher wrist extension strength in 18 of 19 patients and MRC grade 4 or higher finger and thumb extension strength in 12 of 19 at a minimum of 12-month follow-up. While there was some variability, the most common nerve transfers performed were flexor digitorum superficialis branch to extensor carpi radialis brevis branch and flexor carpi radialis branch to posterior interosseous nerve. ¹² Garcia-Lopez et al ¹⁵ evaluated 6 patients treated with pronator teres branch to extensor carpi radialis longus branch and flexor carpi radialis branch to posterior interosseous nerve transfers and found that all patients had return of MRC grade 4 wrist extension, and 4 of 6 patients had return of MRC grade 4 finger and thumb extension. The MRC grades demonstrated in the nerve transfer group in the present cohort are comparable with these previously reported results.

The patients in the tendon transfer group in this cohort demonstrated improvements in both functional and patient-reported outcomes, which is consistent with the existing literature. Ropars et al ⁶ evaluated 15 patients treated with tendon transfers and followed an average of 9.5 years. They noted that 11 of the 15 patients reported excellent results, and 2 had good results. They recommend transfer of pronator teres to the radial wrist extensors, flexor carpi radialis to extensor digitorum communis, palmaris longus to extensor pollicis longus, and abductor pollicis longus tenodesis to best restore function and balance the hand and wrist. ⁶ The same set of transfers was recommended by Ishida and Ikuta ⁷ who assessed 21 patients with an average follow-up of 11.3 years. They reported an average grip strength of 63% of the contralateral side, average wrist extension of 54°, and average finger extension of 5° with the wrist in extension and reported that most patients were satisfied with their results. ⁷

One prior study has directly compared the outcomes of nerve and tendon transfers to restore radial nerve function. Bertelli ¹³ evaluated 14 patients who had transfer of the anterior interosseous nerve to extensor carpi radialis brevis branch and flexor carpi radialis branch to posterior interosseous nerve and 13 patients who had transfer of pronator teres tendon to extensor carpi radialis brevis, flexor carpi ulnaris tendon to extensor digitorum communis, and palmaris longus tendon to extensor pollicis longus. They noted better wrist range of motion, thumb carpometacarpal joint extension, and grip strength in the nerve transfer group. In addition, all patients in the nerve transfer group were able to extend their fingers with the wrist in neutral or extension. In the tendon transfer group, wrist flexion was required to fully extend the fingers in half of the patients. ¹³ This phenomenon was anecdotally noted in our cohort as well (Supplemental Videos 1 and 2).

Significantly greater grip strength was found postoperatively in the nerve transfer group in this study, although the nerve transfer group also had longer follow-up time. Fifteen of the 16 patients treated with nerve transfer underwent a concomitant pronator teres to extensor carpi radialis brevis tendon transfer to serve as an internal splint. This tendon transfer, in conjunction with the subsequent strength recovery of extensor carpi radialis brevis and/or extensor carpi ulnaris from the nerve transfer, likely resulted in improved wrist extension strength and/or range of motion and, subsequently, improved grip strength. In this study, patients treated with both tendon transfers and nerve transfers had improved DASH and QOL scores with no significant differences between the 2 groups.

The time between injury and surgery was significantly shorter for patients treated with nerve transfers compared with tendon transfers. Nerve transfers must be performed before permanent degeneration of the motor endplates occurs and in general are not indicated in patients who present more than 12 months from injury. ² Thus, patients who presented early were offered nerve transfer, whereas those who presented late underwent tendon transfer. Length of follow-up was significantly longer in the patients treated with nerve transfers. This longer follow-up was in part because of the time to reinnervation (MRC grade 1: 3-4 months, MRC grade 3: 8 months) and our own interest in following this unique patient population. Patients treated with tendon transfer see faster return of function and predictable, well-understood results; thus, shorter follow-up periods were appropriate.

Limitations of this study include the retrospective design. Medical Research Council strength grades were not available for most of the tendon transfer patients. In addition, specific tasks of interest could not be assessed, such as typing, texting, and heavy grasp. Anecdotally, our experience is that nerve transfers allow independent finger extension and dexterity, as well as composite finger and wrist extension (Supplemental Videos 3 and 4; Figure 4). This is difficult to measure and quantify with existing outcome measures. In future studies, specific measurement of independent finger flexion and extension would facilitate better understanding of a patient’s functional recovery with nerve versus tendon transfers. Selection bias could affect the findings as patients with labor-intensive jobs usually elected to undergo tendon transfers rather than nerve transfers, and patients often report satisfaction with their chosen treatment course. Minimizing selection bias would require randomization in a prospective study. Finally, a comparison of nerve transfer alone versus nerve transfer with concomitant tendon transfer for wrist extension was not possible as 15 of the 16 patients in the nerve transfer group had concomitant pronator teres to extensor carpi radialis brevis tendon transfer.

Figure 4.

Composite wrist and finger extension demonstrated following median to radial nerve transfer.

Both tendon transfers and nerve transfers improve function in patients with radial nerve injuries with similar improvements seen in patient-reported outcomes (DASH and QOL scores). Grip strength was significantly greater postoperatively in the nerve transfer group compared with the tendon transfer group. Nerve transfers should be considered in patients who present early after their injury and can tolerate the longer recovery period. We recommend nerve transfers in younger patients with activity expectations of finger dexterity such as typing and playing musical instruments (Supplemental Video 5). The authors recommend concomitant pronator teres to extensor carpi radialis brevis tendon transfer to provide early wrist strength and stability prior to motor recovery from the nerve transfers and facilitate optimal function. As outcomes with nerve transfers improve, outcome measurements need to evolve to facilitate proper functional assessment. Tendon transfers are more appropriate for patients who present a year or more after injury or require a shorter time for return of function. Knowledge of the advantages and disadvantages of both techniques is important in guiding preoperative discussions, encouraging shared decision making, and establishing appropriate expectations regarding anticipated outcomes.