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Results of operative treatment of double Morton’s neuroma in the same foot
J Orthop Sci (2009) 14:574–578 DOI 10.1007/s00776-009-1375-2
Original article Results of operative treatment of double Morton’s neuroma in the same foot KYUNG TAI LEE1, YOUNG KOO LEE2, KI WON YOUNG1, HAK JUN KIM3, and SHIN YI PARK1 1 2 3
Foot and Ankle Service, Department of Orthopedic Surgery, Eulji Hospital, Eulji University, College of Medicine, Seoul, Republic of Korea Department of Orthopedic Surgery, Soonchunhyang University, Bucheon Hospital, Gyeonggi-Do, Republic of Korea Department of Orthopedic Surgery, Korea University, Guro Hospital, Seoul, Republic of Korea
Abstract Background. Double Morton’s neuroma in one foot has rarely been reported in the literature. Methods. In the current study, the authors treated 11 patients with a total of 14 cases of double Morton’s neuroma in one foot. During the research period, 157 cases of Morton’s neuroma were treated with surgery. The neuromas were excised through a single skin incision, and all operations occurred within a 17-month period from April 2005 to October 2006. Results. The mean preoperative AOFAS score was 54 points, and the mean postoperative AOFAS score was 78 points. Seven patients underwent additional foot procedures, and the other half did not. There was no significant difference in improvement in the postoperative AOFAS score between patients treated with a combined procedure and patients treated without a combined procedure. Protective sensation was present postoperatively in most patients, except for the four patients who had hypoesthesia or hyperesthesia. No patients were administered anesthesia. Conclusions. We report success in surgical excision of double Morton’s neuroma in one foot through a single skin incision, and recommend that in cases of compound diseases, excision of a double Morton’s neuroma must be performed as a combination procedure.
Introduction Interdigital neuromas comprise a common disorder that produces pain in the forefoot. They normally occur in the web space between the third and fourth toes; but though occurrence in the first, second, or fourth interdigital space is unusual, it is not rare.1–3 Multiple inter-
Offprint requests to: Y.K. Lee, Department of Orthopedic Surgery, Soonchunhyang University 4 Jung-Dong, WonmiGu, Bucheon-Si, Gyeonggi-Do 420-767, Republic of Korea Received: January 27, 2009 / Accepted: June 3, 2009
digital neuromas have been described in the past, with an incidence usually reported at 1.5%–3.0%.4–7 Many surgeons have reported that the expected outcome of surgery for multiple interdigital neuromas is worse than that for a neuroma in one interspace. The most common postoperative complication following excision of interdigital neuroma is dysparesthesia in the territory of the dorsal cutaneous nerve area. Postoperative dysparesthesia in the territory of the dorsal cutaneous nerve is due to resection or irritation of dorsal cutaneous nerves. To address this situation, surgeons have reported many methods for avoiding anesthesia of the dorsal cutaneous nerve territory and improving clinical results. We report the use of single curved incision that produces good clinical results and requires no anesthesia of the dorsal cutaneous nerve territory. We also recommend the use of a combination procedure in cases of compound disease.
Materials and methods The present study was approved by our institutional research board, and all patients were informed about the study and gave informed consent prior to their enrollment. A retrospective review of 157 cases of Morton’s neuroma between April 2005 and October 2006 was conducted through medical records. It revealed 14 cases of adjacent interdigital neuroma in one foot, an 8.9% incidence, among 11 patients. Patients with adjacent simultaneous interdigital neuromas underwent adjacent nerve excision through a single incision by the same surgeon. The average age of the patients at surgery was 50 years (range 30–69 years). All patients were female. The presence of the adjacent irritation was determined by evaluating the patient’s medical history and by physical examination. All patients described forefoot pain that was exacerbated by walking, running, or
K.T. Lee et al.: Excising a double Morton’s neuroma
575
Fig. 2. A 3-cm oblique, curved, dorsal skin incision centered on the third metatarsal head and neck to reach the two distal digital nerve branches Fig. 1. Double Morton’s neuroma in the second intermetatarsal space and the third intermetatarsal space in a 63-year-old woman. A Sonogram of the second intermetatarsal space in the coronal plane shows a 3.5-mm ovoid, hypoechoic nodule (arrow) between the second and third metatarsal heads. B Sonogram of the third intermetatarsal space in the coronal plane shows a 5-mm round, hypoechoic nodule (arrow) between the third and fourth metatarsal heads
jogging; marked limitations of activity before the operation; and tenderness at both the second and third interspaces in response to palpation. Each of these patients had been previously treated nonoperatively for more than 6 months with medication and steroid injections and with a metatarsal pad inserted into the shoe — none showed any improvement. In all patients, positive findings were obtained with Mudlers’ click at both the second and third interspaces. All patients underwent ultrasonography and were found to have masses >3 mm (Fig. 1). Other causes of foot pain were ruled out by physical examination, simple radiography, and ultrasonography; and confirmation was obtained by the macroscopic appearance during operation. The time of postoperative follow-up varied, with a mean time of 25 months. During operation, seven patients underwent additional foot procedures, consisting of proximal chevron metatarsal osteotomy and Akin’s osteotomy due to hallux valgus. Surgical technique The foot was prepared and draped in the usual fashion, and the operation was performed under ankle nerve block anesthesia. An Esmarch bandage was applied to exsanguinate the foot, after which the bandage was unwrapped distally and was left around the ankle to serve as a tourniquet. A 3-cm oblique curved dorsal skin incision was made and centered at the third metatarsal head and neck to allow access to the two distal inter-
Fig. 3. Excised double Morton’s neuromas
metatarsal nerve branches (Fig. 2). The subcutaneous tissue was separated by sharp dissection to reach the second and third intermetatarsal spaces. The dorsal cutaneous nerve was identified and retracted by Surg-ILoop (Scanlan, St. Paul, MN, USA). A Senn retractor was placed between the metatarsal head to increase the intermetatarsal space. The intermetatarsal ligament was identified, and a curved elevator was passed underneath the ligament. The common interdigital nerve was identified, and its pathology was macroscopically evaluated, after which the nerve, including the neuroma, was freed and resected proximally to the transverse metatarsal ligament. The two distal branches were freed and excised 2 mm distally from the neuroma. The neuroma was then removed (Fig. 3). The wound was copiously irrigated with isotonic normal saline and then closed with absorbable 4-0 Vicryl sutures.
576
K.T. Lee et al.: Excising a double Morton’s neuroma
Table 1. Discrepancies between preoperative and postoperative AOFAS scores Parameter AOFAS score Median Range (25%–75%) Wilcoxon sign rank test % Change Median Range (25%–75%) Mann-Whitney test
Hallux valgus
None
Preoperative
Postoperative
Preoperative
Postoperative
49 39–69
82 69–86
49 42–73
72 68–84
P = 0.028 40.8 24.6–102.6
P = 0.902
P = 0.018 46.9 15.1–61.9
There were no discrepancies between the combined procedure and the not combined procedure
Postoperative regimen Compression dressings and postoperative shoes were applied for up to 1 week following the operation, and each operated foot was allowed to bear weight as tolerated from the postoperative first day, with full weight allowed by 1 week depending on any additional procedures that were performed. Statistical analysis Statistical analysis of the results was performed by the paired t-test using SPSS 13.0 (Windows Release 13.0; SPSS, Chicago IL, USA). P < 0.05 was considered statistically significant.
Results Overall satisfaction was rated as excellent by two patients, good by seven, fair by four, and poor by one. Of the 14 feet, 13 were pain-free at the time of final follow-up; the other foot had a poor result and was still moderately painful. At the final follow-up, the average postoperative American Orthopaedic Foot & Ankle Society (AOFAS) score for the 14 double Morton’s neuroma patients was 78 points compared to their average preoperative AOFAS score of 54 points. For reference, the average AOFAS scores for single Morton’s neuroma patients were 83 points postoperatively and 59 points preoperatively. The seven double Morton’s neuroma patients who underwent combined procedures had scores of 82 points postoperatively and 49 points preoperatively. For single Morton’s neuroma patients, the average postoperative AOFAS score was 83 points compared to their average preoperative AOFAS score of 59 points. The seven patients without combined procedures had scores of 72 postoperatively and 49 preoperatively. There was no significant difference in the results between double Morton’s neuroma and single Morton’s
neuroma patients. However, there was a clear difference between preoperative and postoperative AOFAS scores within each group (P = 0.028 for combined procedures, p = 0.018 for not combined procedures). There was also no significant difference found between results with or without combined procedures (P = 0.902) (Table 1). Patients’ interdigital nerves were inspected at the time of surgery; in all cases they appeared bulbous with focal enlargement. Pathology reports were reviewed for all specimens and were consistent with interdigital neuroma with chronic inflammation and perineural fibrosis. No patients had a wound problem following surgery; all wounds healed uneventfully, with no infections and no indication of vascular damage in any toes. No patient experienced pain with compression of the interspace of the excised nerves. No anesthesia in the interspace was found in any patient, although hyperesthesia in the interspace was found in one case and hypoesthesia in three cases.
Discussion The most common theory of interdigital neuroma origin is the tunnel compression theory in which the tunnel — composed of two metatarsals, the tendons, the deep transverse metatarsal ligament (DTML), and the ground surface — compresses the neurovascular bundle and generates the Morton’s neuroma.8–11 Still, the precise cause of neuroma formation currently remains unclear. Owing to the uncertain cause of Morton’s neuroma, various treatments are in current use. The initial treatment of Morton’s neuromas generally consists of conservative methods, which include shoe modification and steroid injections. Saygi et al.12 reported that 82% of those treated with steroid injections had complete or partial relief of pain at a 12-month follow-up. When symptoms persisted, operative treatment was consid-
K.T. Lee et al.: Excising a double Morton’s neuroma
ered. Bradley et al.13 reported 70% good, 22% satisfactory, and 8% unsatisfactory results after surgical excision; and Lee et al. reported 21% good, 52% satisfactory, 17% tolerable, and 8% unsatisfactory results after surgical excision (unpublished data). Today, single Morton’s neuroma is well documented, and its excision is regarded as a reasonable treatment that produces comparatively good results. Multiple interdigital neuromas, however, are rarely reported. Nevertheless, with increasing recognition of the fact that foot pain can be caused by distal nerve compression, patients can be identified with multiple adjacent interdigital nerve compression.14 Both Mann and Reynolds4 and Bradley et al.13 found an incidence of multiple neuromas of 1.5% to 3.0%, and Beskin and Baxter reported an incidence of multiple neuromas of 16.6%.15 In our study, 8.9% of patients were diagnosed with double neuromas. An accurate incidence for double Morton’s neuroma and the best treatment to minimize complications have not yet been established. In the current study, we found that the improvement seen after treating double Morton’s neuroma was the same as for single Morton’s neuroma (P = 1.00). Benedetti et al. reported that excision of double Morton’s neuroma gives results similar to excision of single Morton’s neuroma.5 Bradley et al. reported the same result.13 The above data seem to indicate that postoperative pain relief obtained from excision of double Morton’s neuroma is comparable to that from excision of a single Morton’s neuroma. We think that residual pain and sensory loss after excision of Morton’s neuroma are the result of not knowing its etiology. If the approach and excision are carefully performed, excising a double Morton’s neuroma should have results similar to those after excising a single Morton’s neuroma. Our results demonstrate that excision of a double Morton’s neuroma is a viable, reasonable treatment; and they indicate that, for maximum benefit to the patient, excision of double Morton’s neuroma should be performed simultaneously. It is important to exclude other causes of multiple web space pain before a diagnosis of multiple neuromas is made. Other causes include peripheral neuropathy, double crush syndrome, tarsal tunnel syndrome, and metatarsophalangeal joint pathology, such as arthritis, synovitis, dislocation, and Freiberg’s infraction.5 The effects of a complicating disease in Morton’s neuroma have not been well described in the literature. In our study, no difference in outcome was found between cases requiring combined procedures and cases of Morton’s neuroma alone (P = 0.902). There was, however, a difference observed between preoperative and postoperative AOFAS scores (P = 0.028 for combined procedures, P = 0.018 for no combined procedures), similar to the difference in preoperative and
577
postoperative scores also observed by all other groups. We observed more dramatic AOFAS scores in our study than have been reported in some previous studies. One explanation is that the medial dorsal cutaneous nerve can be considerably injured with the Akin procedure, but anesthesia is not given as it was in our procedure. We believe that another factor in our higher AOFAS scores may be the diminished accompanying disease symptoms rather than simply alleviation of the double Morton’s neuroma’s symptoms. We urge that in cases of combined diseases double Morton’s neuroma excision must be performed as a combined procedure. Complications after neuroma excision surgery have been reported by many surgeons. The most common cause of persistent symptoms has been inadequate initial resection of the nerve, as reported by Johnson et al.,16 and additional sources of pain such as primary neuromas in adjacent interspaces, may contribute symptoms to those from the involved interspaces as supported by Beskin and Baxter.15 Consequently, many surgeons report that the expected outcome is worse after exploration of a second interspace than after exploration of just one interspace.17 Stamatis and Myerson,18 however reported no significant difference between patients with surgery on an isolated interspace and patients who had two interspaces explored at the same time. To the best of our knowledge, Benedetti et al. were the first to report that most (84%) cases with simultaneous adjacent interdigital neurectomy had acceptable results. Unfortunately, all patients had dense sensory loss in the third toe from the metatarsal head to the tip, and resecting adjacent neuromas eliminates all sensory contribution to the plantar third toe and to the plantar pad distal to the third metatarsal head.5 To reduce sensory loss, Hort et al. reported that adjacent intermetatarsal nerve irritation occurring in some patients can be treated effectively with double nerve decompression and single nerve excision through one longitudinal dorsal incision over the third metatarsal.19 Rosson et al.14 reported a surgical approach of multiple dorsal interspace incision, as a novel Y incision, for adjacent simultaneous interdigital neuroma; and 93% of cases had acceptable results. In past practice, when the size of a Morton’s neuroma has been <3 mm, we have used decompression methods, and we have employed excision methods when the size has been in >3 mm. In the present study, any double Morton’s neuroma that was >3 mm was treated with excision. No signs of anesthesia have been observed, although three cases of hypoesthesia were observed and one case of hyperesthesia, in which it was evident that preservation of the dorsal cutaneous nerve was quite important. Gedge et al. emphasized that not more than one excision should be done in cases of adjacent interdigital nerve irritation, and they concurred that excision
578
of all multiple interdigital neuromas was a good method. Our results demonstrate that simultaneous adjacent interdigital neurectomy for double Morton’s neuroma is a viable, effective method and indicate that in cases of compound diseases double Morton’s neuroma excision should be performed in a combined procedure.
References 1. Weinfeld SB, Myerson MS. Interdigital neuritis: diagnosis and treatment. J Am Acad Orthop Surg 1996;4:328–35. 2. Kay D, Bennett GL. Morton’s neuroma. Foot Ankle Clin 2003;8: 49–59. 3. Stamatis ED, Karabalis C. Interdigital neuromas: current state of the art — surgical. Foot Ankle Clin 2004;9:287–96. 4. Mann RA, Reynolds JC. Interdigital neuroma — a critical clinical analysis. Foot Ankle 1983;3:238–43. 5. Benedetti RS, Baxter DE, Davis PF. Clinical results of simultaneous adjacent interdigital neurectomy in the foot. Foot Ankle Int 1996;17:264–8. 6. Wu KK. Morton’s interdigital neuroma: a clinical review of its etiology, treatment, and results. J Foot Ankle Surg 1996;35:112–9; discussion 87–8. 7. Colgrove RC, Huang EY, Barth AH, Greene MA. Interdigital neuroma: intermuscular neuroma transposition compared with resection. Foot Ankle Int 2000;21:206–11.
K.T. Lee et al.: Excising a double Morton’s neuroma 8. Alexander IJ, Johnson KA, Parr JW. Morton’s neuroma: a review of recent concepts. Orthopedics 1987;10:103–6. 9. Bossley CJ, Cairney PC. The intermetatarsophalangeal bursa — its significance in Morton’s metatarsalgia. J Bone Joint Surg Br 1980;62:184–7. 10. Gauthier G. Thomas Morton’s disease: a nerve entrapment syndrome: a new surgical technique. Clin Orthop 1979:90–2. 11. Shapiro SL. Endoscopic decompression of the intermetatarsal nerve for Morton’s neuroma. Foot Ankle Clin 2004;9:297–304. 12. Saygi B, Yildirim Y, Saygi EK, Kara H, Esemenli T. Morton neuroma: comparative results of two conservative methods. Foot Ankle Int 2005;26:556–9. 13. Bradley N, Miller WA, Evans JP. Plantar neuroma: analysis of results following surgical excision in 145 patients. South Med J 1976;69:853–4. 14. Rosson GD, Dellon AL. Surgical approach to multiple interdigital nerve compressions. J Foot Ankle Surg 2005;44:70–3. 15. Beskin JL, Baxter DE. Recurrent pain following interdigital neurectomy: a plantar approach. Foot Ankle 1988;9:34–9. 16. Johnson JE, Johnson KA, Unni KK. Persistent pain after excision of an interdigital neuroma: results of reoperation. J Bone Joint Surg Am 1988;70:651–7. 17. Coughlin MJ, Pinsonneault T. Operative treatment of interdigital neuroma: a long-term follow-up study. J Bone Joint Surg Am 2001;83:1321–8. 18. Stamatis ED, Myerson MS. Treatment of recurrence of symptoms after excision of an interdigital neuroma. A retrospective review. J Bone Joint Surg Br 2004;86:48–53. 19. Hort KR, DeOrio JK. Adjacent interdigital nerve irritation: single incision surgical treatment. Foot Ankle Int 2002;23:1026–30.
Original article Results of operative treatment of double Morton’s neuroma in the same foot KYUNG TAI LEE1, YOUNG KOO LEE2, KI WON YOUNG1, HAK JUN KIM3, and SHIN YI PARK1 1 2 3
Foot and Ankle Service, Department of Orthopedic Surgery, Eulji Hospital, Eulji University, College of Medicine, Seoul, Republic of Korea Department of Orthopedic Surgery, Soonchunhyang University, Bucheon Hospital, Gyeonggi-Do, Republic of Korea Department of Orthopedic Surgery, Korea University, Guro Hospital, Seoul, Republic of Korea
Abstract Background. Double Morton’s neuroma in one foot has rarely been reported in the literature. Methods. In the current study, the authors treated 11 patients with a total of 14 cases of double Morton’s neuroma in one foot. During the research period, 157 cases of Morton’s neuroma were treated with surgery. The neuromas were excised through a single skin incision, and all operations occurred within a 17-month period from April 2005 to October 2006. Results. The mean preoperative AOFAS score was 54 points, and the mean postoperative AOFAS score was 78 points. Seven patients underwent additional foot procedures, and the other half did not. There was no significant difference in improvement in the postoperative AOFAS score between patients treated with a combined procedure and patients treated without a combined procedure. Protective sensation was present postoperatively in most patients, except for the four patients who had hypoesthesia or hyperesthesia. No patients were administered anesthesia. Conclusions. We report success in surgical excision of double Morton’s neuroma in one foot through a single skin incision, and recommend that in cases of compound diseases, excision of a double Morton’s neuroma must be performed as a combination procedure.
Introduction Interdigital neuromas comprise a common disorder that produces pain in the forefoot. They normally occur in the web space between the third and fourth toes; but though occurrence in the first, second, or fourth interdigital space is unusual, it is not rare.1–3 Multiple inter-
Offprint requests to: Y.K. Lee, Department of Orthopedic Surgery, Soonchunhyang University 4 Jung-Dong, WonmiGu, Bucheon-Si, Gyeonggi-Do 420-767, Republic of Korea Received: January 27, 2009 / Accepted: June 3, 2009
digital neuromas have been described in the past, with an incidence usually reported at 1.5%–3.0%.4–7 Many surgeons have reported that the expected outcome of surgery for multiple interdigital neuromas is worse than that for a neuroma in one interspace. The most common postoperative complication following excision of interdigital neuroma is dysparesthesia in the territory of the dorsal cutaneous nerve area. Postoperative dysparesthesia in the territory of the dorsal cutaneous nerve is due to resection or irritation of dorsal cutaneous nerves. To address this situation, surgeons have reported many methods for avoiding anesthesia of the dorsal cutaneous nerve territory and improving clinical results. We report the use of single curved incision that produces good clinical results and requires no anesthesia of the dorsal cutaneous nerve territory. We also recommend the use of a combination procedure in cases of compound disease.
Materials and methods The present study was approved by our institutional research board, and all patients were informed about the study and gave informed consent prior to their enrollment. A retrospective review of 157 cases of Morton’s neuroma between April 2005 and October 2006 was conducted through medical records. It revealed 14 cases of adjacent interdigital neuroma in one foot, an 8.9% incidence, among 11 patients. Patients with adjacent simultaneous interdigital neuromas underwent adjacent nerve excision through a single incision by the same surgeon. The average age of the patients at surgery was 50 years (range 30–69 years). All patients were female. The presence of the adjacent irritation was determined by evaluating the patient’s medical history and by physical examination. All patients described forefoot pain that was exacerbated by walking, running, or
K.T. Lee et al.: Excising a double Morton’s neuroma
575
Fig. 2. A 3-cm oblique, curved, dorsal skin incision centered on the third metatarsal head and neck to reach the two distal digital nerve branches Fig. 1. Double Morton’s neuroma in the second intermetatarsal space and the third intermetatarsal space in a 63-year-old woman. A Sonogram of the second intermetatarsal space in the coronal plane shows a 3.5-mm ovoid, hypoechoic nodule (arrow) between the second and third metatarsal heads. B Sonogram of the third intermetatarsal space in the coronal plane shows a 5-mm round, hypoechoic nodule (arrow) between the third and fourth metatarsal heads
jogging; marked limitations of activity before the operation; and tenderness at both the second and third interspaces in response to palpation. Each of these patients had been previously treated nonoperatively for more than 6 months with medication and steroid injections and with a metatarsal pad inserted into the shoe — none showed any improvement. In all patients, positive findings were obtained with Mudlers’ click at both the second and third interspaces. All patients underwent ultrasonography and were found to have masses >3 mm (Fig. 1). Other causes of foot pain were ruled out by physical examination, simple radiography, and ultrasonography; and confirmation was obtained by the macroscopic appearance during operation. The time of postoperative follow-up varied, with a mean time of 25 months. During operation, seven patients underwent additional foot procedures, consisting of proximal chevron metatarsal osteotomy and Akin’s osteotomy due to hallux valgus. Surgical technique The foot was prepared and draped in the usual fashion, and the operation was performed under ankle nerve block anesthesia. An Esmarch bandage was applied to exsanguinate the foot, after which the bandage was unwrapped distally and was left around the ankle to serve as a tourniquet. A 3-cm oblique curved dorsal skin incision was made and centered at the third metatarsal head and neck to allow access to the two distal inter-
Fig. 3. Excised double Morton’s neuromas
metatarsal nerve branches (Fig. 2). The subcutaneous tissue was separated by sharp dissection to reach the second and third intermetatarsal spaces. The dorsal cutaneous nerve was identified and retracted by Surg-ILoop (Scanlan, St. Paul, MN, USA). A Senn retractor was placed between the metatarsal head to increase the intermetatarsal space. The intermetatarsal ligament was identified, and a curved elevator was passed underneath the ligament. The common interdigital nerve was identified, and its pathology was macroscopically evaluated, after which the nerve, including the neuroma, was freed and resected proximally to the transverse metatarsal ligament. The two distal branches were freed and excised 2 mm distally from the neuroma. The neuroma was then removed (Fig. 3). The wound was copiously irrigated with isotonic normal saline and then closed with absorbable 4-0 Vicryl sutures.
576
K.T. Lee et al.: Excising a double Morton’s neuroma
Table 1. Discrepancies between preoperative and postoperative AOFAS scores Parameter AOFAS score Median Range (25%–75%) Wilcoxon sign rank test % Change Median Range (25%–75%) Mann-Whitney test
Hallux valgus
None
Preoperative
Postoperative
Preoperative
Postoperative
49 39–69
82 69–86
49 42–73
72 68–84
P = 0.028 40.8 24.6–102.6
P = 0.902
P = 0.018 46.9 15.1–61.9
There were no discrepancies between the combined procedure and the not combined procedure
Postoperative regimen Compression dressings and postoperative shoes were applied for up to 1 week following the operation, and each operated foot was allowed to bear weight as tolerated from the postoperative first day, with full weight allowed by 1 week depending on any additional procedures that were performed. Statistical analysis Statistical analysis of the results was performed by the paired t-test using SPSS 13.0 (Windows Release 13.0; SPSS, Chicago IL, USA). P < 0.05 was considered statistically significant.
Results Overall satisfaction was rated as excellent by two patients, good by seven, fair by four, and poor by one. Of the 14 feet, 13 were pain-free at the time of final follow-up; the other foot had a poor result and was still moderately painful. At the final follow-up, the average postoperative American Orthopaedic Foot & Ankle Society (AOFAS) score for the 14 double Morton’s neuroma patients was 78 points compared to their average preoperative AOFAS score of 54 points. For reference, the average AOFAS scores for single Morton’s neuroma patients were 83 points postoperatively and 59 points preoperatively. The seven double Morton’s neuroma patients who underwent combined procedures had scores of 82 points postoperatively and 49 points preoperatively. For single Morton’s neuroma patients, the average postoperative AOFAS score was 83 points compared to their average preoperative AOFAS score of 59 points. The seven patients without combined procedures had scores of 72 postoperatively and 49 preoperatively. There was no significant difference in the results between double Morton’s neuroma and single Morton’s
neuroma patients. However, there was a clear difference between preoperative and postoperative AOFAS scores within each group (P = 0.028 for combined procedures, p = 0.018 for not combined procedures). There was also no significant difference found between results with or without combined procedures (P = 0.902) (Table 1). Patients’ interdigital nerves were inspected at the time of surgery; in all cases they appeared bulbous with focal enlargement. Pathology reports were reviewed for all specimens and were consistent with interdigital neuroma with chronic inflammation and perineural fibrosis. No patients had a wound problem following surgery; all wounds healed uneventfully, with no infections and no indication of vascular damage in any toes. No patient experienced pain with compression of the interspace of the excised nerves. No anesthesia in the interspace was found in any patient, although hyperesthesia in the interspace was found in one case and hypoesthesia in three cases.
Discussion The most common theory of interdigital neuroma origin is the tunnel compression theory in which the tunnel — composed of two metatarsals, the tendons, the deep transverse metatarsal ligament (DTML), and the ground surface — compresses the neurovascular bundle and generates the Morton’s neuroma.8–11 Still, the precise cause of neuroma formation currently remains unclear. Owing to the uncertain cause of Morton’s neuroma, various treatments are in current use. The initial treatment of Morton’s neuromas generally consists of conservative methods, which include shoe modification and steroid injections. Saygi et al.12 reported that 82% of those treated with steroid injections had complete or partial relief of pain at a 12-month follow-up. When symptoms persisted, operative treatment was consid-
K.T. Lee et al.: Excising a double Morton’s neuroma
ered. Bradley et al.13 reported 70% good, 22% satisfactory, and 8% unsatisfactory results after surgical excision; and Lee et al. reported 21% good, 52% satisfactory, 17% tolerable, and 8% unsatisfactory results after surgical excision (unpublished data). Today, single Morton’s neuroma is well documented, and its excision is regarded as a reasonable treatment that produces comparatively good results. Multiple interdigital neuromas, however, are rarely reported. Nevertheless, with increasing recognition of the fact that foot pain can be caused by distal nerve compression, patients can be identified with multiple adjacent interdigital nerve compression.14 Both Mann and Reynolds4 and Bradley et al.13 found an incidence of multiple neuromas of 1.5% to 3.0%, and Beskin and Baxter reported an incidence of multiple neuromas of 16.6%.15 In our study, 8.9% of patients were diagnosed with double neuromas. An accurate incidence for double Morton’s neuroma and the best treatment to minimize complications have not yet been established. In the current study, we found that the improvement seen after treating double Morton’s neuroma was the same as for single Morton’s neuroma (P = 1.00). Benedetti et al. reported that excision of double Morton’s neuroma gives results similar to excision of single Morton’s neuroma.5 Bradley et al. reported the same result.13 The above data seem to indicate that postoperative pain relief obtained from excision of double Morton’s neuroma is comparable to that from excision of a single Morton’s neuroma. We think that residual pain and sensory loss after excision of Morton’s neuroma are the result of not knowing its etiology. If the approach and excision are carefully performed, excising a double Morton’s neuroma should have results similar to those after excising a single Morton’s neuroma. Our results demonstrate that excision of a double Morton’s neuroma is a viable, reasonable treatment; and they indicate that, for maximum benefit to the patient, excision of double Morton’s neuroma should be performed simultaneously. It is important to exclude other causes of multiple web space pain before a diagnosis of multiple neuromas is made. Other causes include peripheral neuropathy, double crush syndrome, tarsal tunnel syndrome, and metatarsophalangeal joint pathology, such as arthritis, synovitis, dislocation, and Freiberg’s infraction.5 The effects of a complicating disease in Morton’s neuroma have not been well described in the literature. In our study, no difference in outcome was found between cases requiring combined procedures and cases of Morton’s neuroma alone (P = 0.902). There was, however, a difference observed between preoperative and postoperative AOFAS scores (P = 0.028 for combined procedures, P = 0.018 for no combined procedures), similar to the difference in preoperative and
577
postoperative scores also observed by all other groups. We observed more dramatic AOFAS scores in our study than have been reported in some previous studies. One explanation is that the medial dorsal cutaneous nerve can be considerably injured with the Akin procedure, but anesthesia is not given as it was in our procedure. We believe that another factor in our higher AOFAS scores may be the diminished accompanying disease symptoms rather than simply alleviation of the double Morton’s neuroma’s symptoms. We urge that in cases of combined diseases double Morton’s neuroma excision must be performed as a combined procedure. Complications after neuroma excision surgery have been reported by many surgeons. The most common cause of persistent symptoms has been inadequate initial resection of the nerve, as reported by Johnson et al.,16 and additional sources of pain such as primary neuromas in adjacent interspaces, may contribute symptoms to those from the involved interspaces as supported by Beskin and Baxter.15 Consequently, many surgeons report that the expected outcome is worse after exploration of a second interspace than after exploration of just one interspace.17 Stamatis and Myerson,18 however reported no significant difference between patients with surgery on an isolated interspace and patients who had two interspaces explored at the same time. To the best of our knowledge, Benedetti et al. were the first to report that most (84%) cases with simultaneous adjacent interdigital neurectomy had acceptable results. Unfortunately, all patients had dense sensory loss in the third toe from the metatarsal head to the tip, and resecting adjacent neuromas eliminates all sensory contribution to the plantar third toe and to the plantar pad distal to the third metatarsal head.5 To reduce sensory loss, Hort et al. reported that adjacent intermetatarsal nerve irritation occurring in some patients can be treated effectively with double nerve decompression and single nerve excision through one longitudinal dorsal incision over the third metatarsal.19 Rosson et al.14 reported a surgical approach of multiple dorsal interspace incision, as a novel Y incision, for adjacent simultaneous interdigital neuroma; and 93% of cases had acceptable results. In past practice, when the size of a Morton’s neuroma has been <3 mm, we have used decompression methods, and we have employed excision methods when the size has been in >3 mm. In the present study, any double Morton’s neuroma that was >3 mm was treated with excision. No signs of anesthesia have been observed, although three cases of hypoesthesia were observed and one case of hyperesthesia, in which it was evident that preservation of the dorsal cutaneous nerve was quite important. Gedge et al. emphasized that not more than one excision should be done in cases of adjacent interdigital nerve irritation, and they concurred that excision
578
of all multiple interdigital neuromas was a good method. Our results demonstrate that simultaneous adjacent interdigital neurectomy for double Morton’s neuroma is a viable, effective method and indicate that in cases of compound diseases double Morton’s neuroma excision should be performed in a combined procedure.
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