1376 THE BONE & JOINT JOURNAL FOOT AND ANKLE Outcomes following excision of Morton’s interdigital neuroma A PROSPECTIVE STUDY V. Bucknall, D. Rutherford, D. MacDonald, H. Shalaby, J. McKinley, S. J. Breusch From Royal Infirmary of Edinburgh, Edinburgh, United Kingdom V. Bucknall, MBChB, BMSc(Hons), MRCS, Trauma and Orthopaedic Registrar Department of Trauma and Orthopaedic Surgery D. Rutherford, MBChB, Foundation Year Doctor D. MacDonald, BA (Hons), Clinical Researcher H. Shalaby, MD, FRCS (Orth), Consultant Trauma and Orthopaedic Surgeon J. McKinley, MBChB, BMSc (Hons), FRCS (Orth), Consultant Trauma and Orthopaedic Surgeon S. J. Breusch, MD, PhD, FRCS (Orth), Consultant Trauma and Orthopaedic Surgeon Royal Infirmary of Edinburgh, Little France Crescent, Old Dalkeith Road, Edinburgh EH16 4SA, UK. Correspondence should be sent to Miss V. Bucknall; e-mail: [email protected]. uk ©2016 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.98B10. 37610 $2.00 Bone Joint J 2016;98-B:1376–81. Received 31 December 2015; Accepted after revision 4 May 2016 Aims This is the first prospective study to report the pre- and post-operative patient reported outcomes and satisfaction scores following excision of interdigital Morton’s neuroma. Patients and Methods Between May 2006 and April 2013, we prospectively studied 99 consecutive patients (111 feet) who were to undergo excision of a Morton’s neuroma. There were 78 women and 21 men with a mean age at the time of surgery of 56 years (22 to 78). Patients completed the Manchester-Oxford Foot Questionnaire (MOXFQ), Short Form-12 (SF-12) and a supplementary patient satisfaction survey three months pre-operatively and six months post-operatively. Results Statistically significant differences were found between the mean pre- and post-operative MOXFQ and the physical component of the SF-12 scores (p = 0.00081 and p = 0.00092 respectively). Most patients reported their overall satisfaction as excellent (n = 49, 49.5%) or good (n = 29, 29.3%), but ten patients were dissatisfied, reporting poor (n = 8, 8.1%) or very poor (n = 2, 2.0%) results. Only 63 patients (63%) were pain-free at follow-up: in eight patients (8.1%), the MOXFQ score worsened. There was no statistically significant difference in outcome between surgery on single or multiple sites. However, the MOXFQ scores were significantly worse after revision surgery (p = 0.004). Conclusions The patient-reported outcomes after resection of a symptomatic Morton’s neuroma are acceptable but may not be as good as earlier studies suggest. Surgery at several sites can be undertaken safely but caution should be exercised when considering revision surgery. Cite this article: Bone Joint J 2016;98-B:1376–81. Morton’s neuroma is a benign fibrous enlarge- ment of the tissue surrounding a common plantar digital nerve, most frequently in the second and third intermetatarsal spaces. 1-3 The condition is characterised by pain and burning in the interdigital webspace, which is exacerbated by periods of walking, standing and wearing constrictive footwear. 2,4-7 Ten- derness, even on light touch, can adversely affect activities of daily living. A palpable mass can often be felt in the intermetatarsal space. Axial compression may be accompa- nied by a demonstrable painful click known as Mulder’s sign. 2,8 The aetiology of this condition is still uncer- tain. It is thought that a traumatic entrapment neuropathy causes an inflammatory process which results in local symptoms. It has been suggested that the digital nerve is subjected to repetitive compression between the deep trans- verse ligament, the intermetatarsal bursa and plantar soft tissues. 9-11 Histologically, the digi- tal nerve adopts the characteristic features of fibrosis of the soft tissues, endoneurial fibrosis of the nerve and demyelination. 12 Ultrasound and MRI can be used to aid diagnosis and exclude other causes of metatar- salgia. However, the incidence of asympto- matic Morton’s neuroma on imaging is relatively high with some studies quoting rates of up to 54%. 13,14 Consequently, the clinical history and examination remain the most sen- sitive and specific methods of correctly diag- nosing a neuroma. 13,14 Morton’s neuroma can be managed conserv- atively with modification of footwear, orthoses or injections of local anaesthetic and steroid. However, due to the low response rate to these methods of treatment, excision of the interdig- ital nerve is often recommended. 2,15,16
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37610_layout.fm FOOT AND ANKLE
Outcomes following excision of Morton’s interdigital neuroma A PROSPECTIVE STUDY
V. Bucknall, D. Rutherford, D. MacDonald, H. Shalaby, J. McKinley, S. J. Breusch
From Royal Infirmary of Edinburgh, Edinburgh, United Kingdom
V. Bucknall, MBChB, BMSc(Hons), MRCS, Trauma and Orthopaedic Registrar Department of Trauma and Orthopaedic Surgery D. Rutherford, MBChB, Foundation Year Doctor D. MacDonald, BA (Hons), Clinical Researcher H. Shalaby, MD, FRCS (Orth), Consultant Trauma and Orthopaedic Surgeon J. McKinley, MBChB, BMSc (Hons), FRCS (Orth), Consultant Trauma and Orthopaedic Surgeon S. J. Breusch, MD, PhD, FRCS (Orth), Consultant Trauma and Orthopaedic Surgeon Royal Infirmary of Edinburgh, Little France Crescent, Old Dalkeith Road, Edinburgh EH16 4SA, UK.
Correspondence should be sent to Miss V. Bucknall; e-mail: [email protected]. uk
©2016 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.98B10. 37610 $2.00
Bone Joint J 2016;98-B:1376–81. Received 31 December 2015; Accepted after revision 4 May 2016
Aims This is the first prospective study to report the pre- and post-operative patient reported outcomes and satisfaction scores following excision of interdigital Morton’s neuroma.
Patients and Methods Between May 2006 and April 2013, we prospectively studied 99 consecutive patients (111 feet) who were to undergo excision of a Morton’s neuroma. There were 78 women and 21 men with a mean age at the time of surgery of 56 years (22 to 78). Patients completed the Manchester-Oxford Foot Questionnaire (MOXFQ), Short Form-12 (SF-12) and a supplementary patient satisfaction survey three months pre-operatively and six months post-operatively.
Results Statistically significant differences were found between the mean pre- and post-operative MOXFQ and the physical component of the SF-12 scores (p = 0.00081 and p = 0.00092 respectively). Most patients reported their overall satisfaction as excellent (n = 49, 49.5%) or good (n = 29, 29.3%), but ten patients were dissatisfied, reporting poor (n = 8, 8.1%) or very poor (n = 2, 2.0%) results. Only 63 patients (63%) were pain-free at follow-up: in eight patients (8.1%), the MOXFQ score worsened. There was no statistically significant difference in outcome between surgery on single or multiple sites. However, the MOXFQ scores were significantly worse after revision surgery (p = 0.004).
Conclusions The patient-reported outcomes after resection of a symptomatic Morton’s neuroma are acceptable but may not be as good as earlier studies suggest. Surgery at several sites can be undertaken safely but caution should be exercised when considering revision surgery.
Cite this article: Bone Joint J 2016;98-B:1376–81.
Morton’s neuroma is a benign fibrous enlarge- ment of the tissue surrounding a common plantar digital nerve, most frequently in the second and third intermetatarsal spaces.1-3
The condition is characterised by pain and burning in the interdigital webspace, which is exacerbated by periods of walking, standing and wearing constrictive footwear.2,4-7 Ten- derness, even on light touch, can adversely affect activities of daily living. A palpable mass can often be felt in the intermetatarsal space. Axial compression may be accompa- nied by a demonstrable painful click known as Mulder’s sign.2,8
The aetiology of this condition is still uncer- tain. It is thought that a traumatic entrapment neuropathy causes an inflammatory process which results in local symptoms. It has been suggested that the digital nerve is subjected to repetitive compression between the deep trans-
verse ligament, the intermetatarsal bursa and plantar soft tissues.9-11 Histologically, the digi- tal nerve adopts the characteristic features of fibrosis of the soft tissues, endoneurial fibrosis of the nerve and demyelination.12
Ultrasound and MRI can be used to aid diagnosis and exclude other causes of metatar- salgia. However, the incidence of asympto- matic Morton’s neuroma on imaging is relatively high with some studies quoting rates of up to 54%.13,14 Consequently, the clinical history and examination remain the most sen- sitive and specific methods of correctly diag- nosing a neuroma.13,14
Morton’s neuroma can be managed conserv- atively with modification of footwear, orthoses or injections of local anaesthetic and steroid. However, due to the low response rate to these methods of treatment, excision of the interdig- ital nerve is often recommended.2,15,16
OUTCOMES FOLLOWING EXCISION OF MORTON’S INTERDIGITAL NEUROMA 1377
VOL. 98-B, No. 10, OCTOBER 2016
Despite the frequency with which this surgery is under- taken, there is little information regarding surgical out- comes. Furthermore, where validated patient-reported outcomes and satisfaction scores have been described, many of the patient cohorts are small and the data collected retrospectively.1,17
This is the first prospective study to report the pre- and post-operative patient-reported outcomes and satisfaction scores after excision of a Morton’s neuroma in a large cohort of patients.
Patients and Methods Between May 2006 and April 2013, 108 consecutive patients who were to undergo excision of a suspected Mor- ton’s neuroma were invited to take part in the study. One patient died four months following surgery and eight were lost to follow-up. The remaining 99 patients (111 feet) were included in the study. There were 78 women and 21 men with a mean age at the time of surgery of 56 years (22 to 78).
Conservative treatment was undertaken pre- operatively in 75 patients (75.8%): five (7%) of these received steroid injections, 14 (19%) tried orthotics alone and 56 (75%) used both steroids and orthotics. The mean interval between presentation and surgery was 25 months (3 to 91).
All operations were undertaken by one of four specialist foot and ankle consultant surgeons (SB, JM, HS and G. Keenan) at two centres in the United Kingdom; The Royal Infirmary of Edinburgh and St John’s Hospital Livingston. With the patient under general anaesthetic and a tourniquet
applied, a dorsal approach to the neuroma was used in each case.
In total, 137 neuromas were excised from 111 feet belonging to 99 patients: 39 patients underwent excision of a neuroma from the second webspace in isolation, 46 from the third web space and 26 patients underwent simultane- ous excision from both the second and third web spaces on the ipsilateral side during the same surgical sitting. A total of 12 patients had operations on both feet. The left foot was involved in 45 patients and the right foot in 66. Of the 99 patients, 24 were for surgery of a single webspace due to recurrence.
Of the 99 patients undergoing excision of a Morton’s neu- roma, 12 underwent concurrent surgery to the foot. These procedures included cheilectomy (n = 1), first ray osteotomy (n = 3), Weil’s osteotomy (n = 3), proximal interphalangeal joint fusion (n = 3), Lapidus fusion (n = 1) and BioPro hemi- arthroplasty (Port Huron, Michigan) (n = 1).
All patients were examined and outcome measures including the Manchester-Oxford Foot Questionnaire (MOXFQ),18 the Short-Form 12 (SF-12)19 were recorded three months pre- and six months post-operatively. The MOXFQ is a validated scoring system with three main domains which grade pain, walking/standing and social interaction during the previous four weeks. There are 16 items with five responses scored from 0 to 4, where 0 is the best score attainable. The total raw scores out of 64 can be subsequently converted to a metric scale 0 to 100, where 0 is the best score possible and represents an excellent outcome.
To what extent do you agree with the following statement? Tick one box for each question where:
1 = Strongly agree, 2 = Agree, 3 = No opinion, 4 = Disagree, 5 = Strongly disagree
Question 1 2 3 4 5
(2) I no longer have pain in the area operated
(3) My ability to undertake daily tasks is now improved
(4) I am able to participate in sports/ heavy work
(5) The surgery has met my expectations
(7) I would recommend this surgery to a friend
(1) I am satisfied with the outcome of my foot surgery
(6) I would have the surgery again if needed
Fig. 1
Supplementary patient satisfaction survey.
1378 V. BUCKNALL, D. RUTHERFORD, D. MACDONALD, H. SHALABY, J. MCKINLEY, S. J. BREUSCH
THE BONE & JOINT JOURNAL
The SF-12 is a generic age-dependent measure of health which incorporates both physical (PCS) and mental (MCS) components. There are 12 questions. The scores derived from the responses are converted into a metric scale and compared with a national norm with a mean score of 50.0 and a standard deviation of 10.0. Scores in the region of 24.0 for PCS and 19.1 for MCS represent poor health, whereas a PCS of 56.6 and an MCS of 60.8 represent good health.
Seven supplementary questions involving a five-point Likert scale where ‘1’ represents an excellent outcome and ‘5’ a poor outcome were also used to assess satisfaction (Fig. 1). Statistical analysis. This was undertaken using Microsoft Excel (Microsoft, Redmond, Washington) and IBM SPSS statistical software (SPSS, IBM Inc., Armonk, New York). Non-parametric tests were used where data were not nor- mally distributed. Changes in scores before and after
surgery were analysed using the paired t-test and factors affecting outcome were analysed using Pearson’s chi- squared. A p-value < 0.05 was used to define statistical sig- nificance.
Results Histological results for eight of the 137 neuromas excised were not available. Of the remaining 129 specimens, 100 (78%) had the characteristic histological changes of Mor- ton’s neuroma. However, there was no statistically signifi- cant correlation between outcome and the confirmatory histological findings (p = 0.24, 0.097 and 0.152 for MOXFQ, PCS and MCS, respectively).
Statistically significant differences were found between the mean pre- and post-operative MOXFQ and physical component of the SF-12 scores (p < 0.001) (Table I). The MOXFQ score worsened post-operatively in eight patients (8%) by a mean 11.75 points (2 to 34). Of these patients, five (5%) also had worse SF-12 scores with a mean reduc- tion of 10.30 in the PCS (9.18 to 12.53) and 15.62 points in the MCS (4.55 to 24.24).
Using Pearson’s chi-squared test, no statistically signifi- cant differences in outcome scores were found when com- paring multiple site with single site surgery (Table II), Similarly, no statistically significant differences were found when comparing excision of neuroma from the second webspace compared with the third or in the subgroup of 12 patients who underwent additional simultaneous ipsilateral surgery to the foot. However, revision surgery after previ- ous excision of a Morton’s neuroma gave a poorer mean MOXFQ score (p = 0.003) (Table II).
Satisfaction was reported by most patients as excellent (n = 49) or good (n = 29): 11 patients were indifferent and ten patients were dissatisfied with poor (n = 8) or very poor (n = 2) results (Fig. 2, Table III). Of those patients who reported dissatisfaction, nine (90%) had histological con- firmation of a Morton’s neuroma.
Table I. Changes in pre- and post-operative MOXFQ and SF-12 scores
Pre-operative MOXFQ
Post-operative MOXFQ
Pre-operative PCS SF-12
Post-operative PCS SF-12
Pre-operative MCS SF-12
Post-operative MCS SF-12
Mean 59.71 39.53 35.84 42.12 47.14 48.55 Range 13.00 to 64.00 0.00 to 63.00 19.20 to 55.59 21.34 to 56.4 20.61 to 64.49 23.79 to 64.77 Mean difference -20.19 6.28 1.41 SD 18.28 10.66 10.85 p-value 0.00081* 0.00092* 0.200
* Statistically significant MOXFQ, Manchester-Oxford Foot Questionnaire; PCS, physical component summary; MCS, mental component summary; SF-12, short form-12; SD, standard deviation
Table II. The effect of surgical parameters on the outcome following excision of an interdigital neuroma
p-value MOXFQ p-value PCS SF-12 p-value MCS SF-12
Multiple site surgery 0.142 0.094 1.000 Second vs third webspace 0.510 0.278 0.116 Revision surgery 0.003* 0.625 0.614
MOXFQ, Manchester-Oxford Foot Questionnaire; PCS, physical component summary; SF-12, short form-12
0
5
10
15
20
25
30
35
40
45
50
%
Fig. 2
Bar chart showing percentage patient satisfaction following excision of Morton’s neuroma.
OUTCOMES FOLLOWING EXCISION OF MORTON’S INTERDIGITAL NEUROMA 1379
VOL. 98-B, No. 10, OCTOBER 2016
Only 63 patients were pain-free at six months follow-up (Fig. 3, Table III). Of the 21 patients who reported ongoing dis- comfort, five (24%) avoided long-distance walking and pro- longed periods of standing, four (19.0%) described shooting pains and three (14%) had night pain using the MOXFQ tool.
Overall, 25 patients (25.3%) reported no improvement in their ability to undertake activities of daily living and 26 patients (26.3%) were unable to participate in heavy work. However, 83 patients (83.8%) said they would undergo the surgery again and 82 (82.8%) would recommend the sur- gery to a friend (Table III).
There were post-operative complications in ten patients (10%): these included tenderness along the scar (n = 4); neu- ropathic pain (n = 3); superficial wound infection (n = 2) and splaying of the toes (n = 1): none underwent further surgery. In all, seven patients underwent revision surgery for the re- excision of a neuroma after a mean 26 months (9 to 52): five of the seven were a re-revision.
Discussion This is the largest known study to assess the pre- and post- operative patient reported outcomes of Morton’s neuroma prospectively using validated scoring tools. Other studies have attempted to quantify outcome, but these have been retrospec- tive in design, involved few patients or have relied on the find- ings of clinical examination to quantify improvement.1,19
We found that statistically significant benefit can be expected from the excision of a Morton’s neuroma. The MOXFQ and the physical component of the SF-12 both showed significant improvements post-operatively. How- ever, this is the first study to highlight that mental improve- ment may trail physical recovery, as the mental component of the SF-12 did not achieve statistical significance.
In this study, there was a predilection for Morton’s neu- roma to affect the interdigital nerve of the third web space. This has previously been reported.1,19,20 It has been sug- gested that this is due to greater mobility between the third and fourth metatarsals, causing local injury to the third interdigital nerve which, being formed by the branches of the medial and lateral plantar nerves, is larger and therefore more susceptible to such injury.20 However, contrary to the findings of Womack et al,21 we found no statistically signif- icant difference when comparing the outcome of excision of neuroma from the second and third webspaces.10
We also found that the outcome of resecting Morton’s neuromas from adjacent web spaces can be expected to be as good as that of resecting a single neuroma. This is con- sistent with the findings of Benedetti, Baxter and Davis.22
However, it is contrary to the findings of others.23 Further- more, concomitant ipsilateral forefoot surgery undertaken at the time of excision of a neuroma does not statistically worsen the outcome. The presence of concurrent foot pathology in this study accords with the findings of Mor- ris,6 who suggests that the mechanics of the foot are rele- vant in the development of Morton’s neuroma. Diez and Mas24 have also suggested that Morton’s neuroma can be associated with other forefoot pathology in up to 80% of patients. In our study, 12 patients underwent ipsilateral forefoot procedures at the same time as excision of a Mor- ton’s neuroma – their outcome was not statistically worse. This is consistent with findings reported by Kasparek and Schneider.10
Table III. Number of patients responding to each supplementary satisfaction question using a 5-point Likert scale
Number of patients responses
Question 1 2 3 4 5 (1) I am satisfied with the outcome of my foot surgery 49 29 11 8 2 (2) I no longer have pain in the area operated 34 29 15 11 10 (3) My ability to undertake daily tasks is now improved 29 34 11 13 12 (4) I am able to participate in sports/ heavy work 26 29 18 11 15 (5) The surgery has met my expectations 42 22 6 19 10 (6) I would have the surgery again if needed 62 21 6 6 4 (7) I would recommend this surgery to a friend 59 23 7 4 6
1, strongly agree; 2, agree; 3, no opinion; 4, disagree; 5, strongly disagree
Disagree 11%
Pie chart showing patient agreement to relief of pain post-operatively.
1380 V. BUCKNALL, D. RUTHERFORD, D. MACDONALD, H. SHALABY, J. MCKINLEY, S. J. BREUSCH
THE BONE & JOINT JOURNAL
The rate of failure after revision surgery ranges from 14% to 21%. The most common causes of recurrent symp- toms are inadequate resection, friction, pressure or forma- tion of a terminal neuroma.23,25,26 We found statistically worse outcomes in those who underwent revision surgery: five of seven patients who had further surgery did so for re- revision. Some studies have recommended methods of reducing this incidence, including implanting the stump of the nerve into muscle.23
The satisfaction scores described in this study are in line with those reported by Friscia et al27 who found that in the long term (mean 5.9 years, 2.8 to 13), of the 313 patients studied, 45.2% of patients were completely satisfied and 33.8% were satisfied. Kasparek and Schneider10 also found similar results. However, Akermark, Saartok and Zuber28
reported much higher scores where 86% of the 55 patient cohort expressed excellent or good results following sur- gery with a mean follow-up of 29 months.
Excision of a Morton’s neuroma is not always success- ful. In this study, only 63 patients (64%) were pain-free at follow-up and eight (8%) were worse. Other studies have also reported persistent pain in the affected foot after exci- sion of a Morton’s neuroma.23 The presence of unrecog- nised pathology may, however, account for the persistent pain.
In this study, 100 out of 129 specimens (78%) had histo- logical evidence of neuroma. These findings are similar to those of Pace, Scammell and Dhar2 and Vachon, Lemay and Bouchard,29 who reported that up to a third of operation specimens were histologically normal. Histological confir- mation of the diagnosis has little bearing on patient- reported outcome measures as nine patients (90%) in this study who were reported to be dissatisfied post-operatively had a Morton’s neuroma confirmed on histological exami- nation. This would suggest that outcomes are not solely dependent on complete excision.
The patients in this study were reviewed at six months post-operatively. This is a limitation of the study as a longer period of follow-up may have revealed changing results with time. However, many of the outcomes shown in this study are comparable to those reported in current literature where longer periods of follow-up have been used. Further- more, this is the largest study to record and compare pre- and post-operative outcomes using standardised validation tools, thus making this study highly important in our mod- ern understanding of surgical resection of Morton’s neuroma.
In conclusion, patient-reported outcomes after resection of a symptomatic Morton’s neuroma are acceptable, but may not be as favourable as earlier studies have suggested. Excision of neuromas from several sites give comparable results, but caution should be exercised when considering revision surgery, which has been shown to be a poor prog- nostic indicator.
Surgical excision of a Morton’s neuroma does not improve the mental component of SF-12.
Take home message: Revision surgery for Morton’s neuroma should be undertaken
with caution as less favourable outcomes in this cohort are
demonstrated.
Author contributions: V. Bucknall: Data collection, Drafting, writing and editing the paper. D. Rutherford: Data collection, Data analysis, Editing the paper. D. MacDonald: Editing the paper, Data collection. H. Shalaby: Performed surgery, Editing the paper. J. McKinley: Performed surgery, Editing the paper. S. J. Breusch: Study concept, Performed surgery, Editing the paper.
The authors would like to acknowledge G. Keenan who carried out some of the surgery included in the study.
No benefits in any form have been received or will be received from a commer- cial party related directly or indirectly to the subject of this article.
This article was primary edited by A. C. Ross and first proof edited by J. Scott.
References 1. Pastides P, El-Sallakh S, Charalambides C. Morton’s neuroma: A clinical versus
radiological diagnosis. Foot Ankle Surg 2012;18:22–24. 2. Pace A, Scammell B,…
Outcomes following excision of Morton’s interdigital neuroma A PROSPECTIVE STUDY
V. Bucknall, D. Rutherford, D. MacDonald, H. Shalaby, J. McKinley, S. J. Breusch
From Royal Infirmary of Edinburgh, Edinburgh, United Kingdom
V. Bucknall, MBChB, BMSc(Hons), MRCS, Trauma and Orthopaedic Registrar Department of Trauma and Orthopaedic Surgery D. Rutherford, MBChB, Foundation Year Doctor D. MacDonald, BA (Hons), Clinical Researcher H. Shalaby, MD, FRCS (Orth), Consultant Trauma and Orthopaedic Surgeon J. McKinley, MBChB, BMSc (Hons), FRCS (Orth), Consultant Trauma and Orthopaedic Surgeon S. J. Breusch, MD, PhD, FRCS (Orth), Consultant Trauma and Orthopaedic Surgeon Royal Infirmary of Edinburgh, Little France Crescent, Old Dalkeith Road, Edinburgh EH16 4SA, UK.
Correspondence should be sent to Miss V. Bucknall; e-mail: [email protected]. uk
©2016 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.98B10. 37610 $2.00
Bone Joint J 2016;98-B:1376–81. Received 31 December 2015; Accepted after revision 4 May 2016
Aims This is the first prospective study to report the pre- and post-operative patient reported outcomes and satisfaction scores following excision of interdigital Morton’s neuroma.
Patients and Methods Between May 2006 and April 2013, we prospectively studied 99 consecutive patients (111 feet) who were to undergo excision of a Morton’s neuroma. There were 78 women and 21 men with a mean age at the time of surgery of 56 years (22 to 78). Patients completed the Manchester-Oxford Foot Questionnaire (MOXFQ), Short Form-12 (SF-12) and a supplementary patient satisfaction survey three months pre-operatively and six months post-operatively.
Results Statistically significant differences were found between the mean pre- and post-operative MOXFQ and the physical component of the SF-12 scores (p = 0.00081 and p = 0.00092 respectively). Most patients reported their overall satisfaction as excellent (n = 49, 49.5%) or good (n = 29, 29.3%), but ten patients were dissatisfied, reporting poor (n = 8, 8.1%) or very poor (n = 2, 2.0%) results. Only 63 patients (63%) were pain-free at follow-up: in eight patients (8.1%), the MOXFQ score worsened. There was no statistically significant difference in outcome between surgery on single or multiple sites. However, the MOXFQ scores were significantly worse after revision surgery (p = 0.004).
Conclusions The patient-reported outcomes after resection of a symptomatic Morton’s neuroma are acceptable but may not be as good as earlier studies suggest. Surgery at several sites can be undertaken safely but caution should be exercised when considering revision surgery.
Cite this article: Bone Joint J 2016;98-B:1376–81.
Morton’s neuroma is a benign fibrous enlarge- ment of the tissue surrounding a common plantar digital nerve, most frequently in the second and third intermetatarsal spaces.1-3
The condition is characterised by pain and burning in the interdigital webspace, which is exacerbated by periods of walking, standing and wearing constrictive footwear.2,4-7 Ten- derness, even on light touch, can adversely affect activities of daily living. A palpable mass can often be felt in the intermetatarsal space. Axial compression may be accompa- nied by a demonstrable painful click known as Mulder’s sign.2,8
The aetiology of this condition is still uncer- tain. It is thought that a traumatic entrapment neuropathy causes an inflammatory process which results in local symptoms. It has been suggested that the digital nerve is subjected to repetitive compression between the deep trans-
verse ligament, the intermetatarsal bursa and plantar soft tissues.9-11 Histologically, the digi- tal nerve adopts the characteristic features of fibrosis of the soft tissues, endoneurial fibrosis of the nerve and demyelination.12
Ultrasound and MRI can be used to aid diagnosis and exclude other causes of metatar- salgia. However, the incidence of asympto- matic Morton’s neuroma on imaging is relatively high with some studies quoting rates of up to 54%.13,14 Consequently, the clinical history and examination remain the most sen- sitive and specific methods of correctly diag- nosing a neuroma.13,14
Morton’s neuroma can be managed conserv- atively with modification of footwear, orthoses or injections of local anaesthetic and steroid. However, due to the low response rate to these methods of treatment, excision of the interdig- ital nerve is often recommended.2,15,16
OUTCOMES FOLLOWING EXCISION OF MORTON’S INTERDIGITAL NEUROMA 1377
VOL. 98-B, No. 10, OCTOBER 2016
Despite the frequency with which this surgery is under- taken, there is little information regarding surgical out- comes. Furthermore, where validated patient-reported outcomes and satisfaction scores have been described, many of the patient cohorts are small and the data collected retrospectively.1,17
This is the first prospective study to report the pre- and post-operative patient-reported outcomes and satisfaction scores after excision of a Morton’s neuroma in a large cohort of patients.
Patients and Methods Between May 2006 and April 2013, 108 consecutive patients who were to undergo excision of a suspected Mor- ton’s neuroma were invited to take part in the study. One patient died four months following surgery and eight were lost to follow-up. The remaining 99 patients (111 feet) were included in the study. There were 78 women and 21 men with a mean age at the time of surgery of 56 years (22 to 78).
Conservative treatment was undertaken pre- operatively in 75 patients (75.8%): five (7%) of these received steroid injections, 14 (19%) tried orthotics alone and 56 (75%) used both steroids and orthotics. The mean interval between presentation and surgery was 25 months (3 to 91).
All operations were undertaken by one of four specialist foot and ankle consultant surgeons (SB, JM, HS and G. Keenan) at two centres in the United Kingdom; The Royal Infirmary of Edinburgh and St John’s Hospital Livingston. With the patient under general anaesthetic and a tourniquet
applied, a dorsal approach to the neuroma was used in each case.
In total, 137 neuromas were excised from 111 feet belonging to 99 patients: 39 patients underwent excision of a neuroma from the second webspace in isolation, 46 from the third web space and 26 patients underwent simultane- ous excision from both the second and third web spaces on the ipsilateral side during the same surgical sitting. A total of 12 patients had operations on both feet. The left foot was involved in 45 patients and the right foot in 66. Of the 99 patients, 24 were for surgery of a single webspace due to recurrence.
Of the 99 patients undergoing excision of a Morton’s neu- roma, 12 underwent concurrent surgery to the foot. These procedures included cheilectomy (n = 1), first ray osteotomy (n = 3), Weil’s osteotomy (n = 3), proximal interphalangeal joint fusion (n = 3), Lapidus fusion (n = 1) and BioPro hemi- arthroplasty (Port Huron, Michigan) (n = 1).
All patients were examined and outcome measures including the Manchester-Oxford Foot Questionnaire (MOXFQ),18 the Short-Form 12 (SF-12)19 were recorded three months pre- and six months post-operatively. The MOXFQ is a validated scoring system with three main domains which grade pain, walking/standing and social interaction during the previous four weeks. There are 16 items with five responses scored from 0 to 4, where 0 is the best score attainable. The total raw scores out of 64 can be subsequently converted to a metric scale 0 to 100, where 0 is the best score possible and represents an excellent outcome.
To what extent do you agree with the following statement? Tick one box for each question where:
1 = Strongly agree, 2 = Agree, 3 = No opinion, 4 = Disagree, 5 = Strongly disagree
Question 1 2 3 4 5
(2) I no longer have pain in the area operated
(3) My ability to undertake daily tasks is now improved
(4) I am able to participate in sports/ heavy work
(5) The surgery has met my expectations
(7) I would recommend this surgery to a friend
(1) I am satisfied with the outcome of my foot surgery
(6) I would have the surgery again if needed
Fig. 1
Supplementary patient satisfaction survey.
1378 V. BUCKNALL, D. RUTHERFORD, D. MACDONALD, H. SHALABY, J. MCKINLEY, S. J. BREUSCH
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The SF-12 is a generic age-dependent measure of health which incorporates both physical (PCS) and mental (MCS) components. There are 12 questions. The scores derived from the responses are converted into a metric scale and compared with a national norm with a mean score of 50.0 and a standard deviation of 10.0. Scores in the region of 24.0 for PCS and 19.1 for MCS represent poor health, whereas a PCS of 56.6 and an MCS of 60.8 represent good health.
Seven supplementary questions involving a five-point Likert scale where ‘1’ represents an excellent outcome and ‘5’ a poor outcome were also used to assess satisfaction (Fig. 1). Statistical analysis. This was undertaken using Microsoft Excel (Microsoft, Redmond, Washington) and IBM SPSS statistical software (SPSS, IBM Inc., Armonk, New York). Non-parametric tests were used where data were not nor- mally distributed. Changes in scores before and after
surgery were analysed using the paired t-test and factors affecting outcome were analysed using Pearson’s chi- squared. A p-value < 0.05 was used to define statistical sig- nificance.
Results Histological results for eight of the 137 neuromas excised were not available. Of the remaining 129 specimens, 100 (78%) had the characteristic histological changes of Mor- ton’s neuroma. However, there was no statistically signifi- cant correlation between outcome and the confirmatory histological findings (p = 0.24, 0.097 and 0.152 for MOXFQ, PCS and MCS, respectively).
Statistically significant differences were found between the mean pre- and post-operative MOXFQ and physical component of the SF-12 scores (p < 0.001) (Table I). The MOXFQ score worsened post-operatively in eight patients (8%) by a mean 11.75 points (2 to 34). Of these patients, five (5%) also had worse SF-12 scores with a mean reduc- tion of 10.30 in the PCS (9.18 to 12.53) and 15.62 points in the MCS (4.55 to 24.24).
Using Pearson’s chi-squared test, no statistically signifi- cant differences in outcome scores were found when com- paring multiple site with single site surgery (Table II), Similarly, no statistically significant differences were found when comparing excision of neuroma from the second webspace compared with the third or in the subgroup of 12 patients who underwent additional simultaneous ipsilateral surgery to the foot. However, revision surgery after previ- ous excision of a Morton’s neuroma gave a poorer mean MOXFQ score (p = 0.003) (Table II).
Satisfaction was reported by most patients as excellent (n = 49) or good (n = 29): 11 patients were indifferent and ten patients were dissatisfied with poor (n = 8) or very poor (n = 2) results (Fig. 2, Table III). Of those patients who reported dissatisfaction, nine (90%) had histological con- firmation of a Morton’s neuroma.
Table I. Changes in pre- and post-operative MOXFQ and SF-12 scores
Pre-operative MOXFQ
Post-operative MOXFQ
Pre-operative PCS SF-12
Post-operative PCS SF-12
Pre-operative MCS SF-12
Post-operative MCS SF-12
Mean 59.71 39.53 35.84 42.12 47.14 48.55 Range 13.00 to 64.00 0.00 to 63.00 19.20 to 55.59 21.34 to 56.4 20.61 to 64.49 23.79 to 64.77 Mean difference -20.19 6.28 1.41 SD 18.28 10.66 10.85 p-value 0.00081* 0.00092* 0.200
* Statistically significant MOXFQ, Manchester-Oxford Foot Questionnaire; PCS, physical component summary; MCS, mental component summary; SF-12, short form-12; SD, standard deviation
Table II. The effect of surgical parameters on the outcome following excision of an interdigital neuroma
p-value MOXFQ p-value PCS SF-12 p-value MCS SF-12
Multiple site surgery 0.142 0.094 1.000 Second vs third webspace 0.510 0.278 0.116 Revision surgery 0.003* 0.625 0.614
MOXFQ, Manchester-Oxford Foot Questionnaire; PCS, physical component summary; SF-12, short form-12
0
5
10
15
20
25
30
35
40
45
50
%
Fig. 2
Bar chart showing percentage patient satisfaction following excision of Morton’s neuroma.
OUTCOMES FOLLOWING EXCISION OF MORTON’S INTERDIGITAL NEUROMA 1379
VOL. 98-B, No. 10, OCTOBER 2016
Only 63 patients were pain-free at six months follow-up (Fig. 3, Table III). Of the 21 patients who reported ongoing dis- comfort, five (24%) avoided long-distance walking and pro- longed periods of standing, four (19.0%) described shooting pains and three (14%) had night pain using the MOXFQ tool.
Overall, 25 patients (25.3%) reported no improvement in their ability to undertake activities of daily living and 26 patients (26.3%) were unable to participate in heavy work. However, 83 patients (83.8%) said they would undergo the surgery again and 82 (82.8%) would recommend the sur- gery to a friend (Table III).
There were post-operative complications in ten patients (10%): these included tenderness along the scar (n = 4); neu- ropathic pain (n = 3); superficial wound infection (n = 2) and splaying of the toes (n = 1): none underwent further surgery. In all, seven patients underwent revision surgery for the re- excision of a neuroma after a mean 26 months (9 to 52): five of the seven were a re-revision.
Discussion This is the largest known study to assess the pre- and post- operative patient reported outcomes of Morton’s neuroma prospectively using validated scoring tools. Other studies have attempted to quantify outcome, but these have been retrospec- tive in design, involved few patients or have relied on the find- ings of clinical examination to quantify improvement.1,19
We found that statistically significant benefit can be expected from the excision of a Morton’s neuroma. The MOXFQ and the physical component of the SF-12 both showed significant improvements post-operatively. How- ever, this is the first study to highlight that mental improve- ment may trail physical recovery, as the mental component of the SF-12 did not achieve statistical significance.
In this study, there was a predilection for Morton’s neu- roma to affect the interdigital nerve of the third web space. This has previously been reported.1,19,20 It has been sug- gested that this is due to greater mobility between the third and fourth metatarsals, causing local injury to the third interdigital nerve which, being formed by the branches of the medial and lateral plantar nerves, is larger and therefore more susceptible to such injury.20 However, contrary to the findings of Womack et al,21 we found no statistically signif- icant difference when comparing the outcome of excision of neuroma from the second and third webspaces.10
We also found that the outcome of resecting Morton’s neuromas from adjacent web spaces can be expected to be as good as that of resecting a single neuroma. This is con- sistent with the findings of Benedetti, Baxter and Davis.22
However, it is contrary to the findings of others.23 Further- more, concomitant ipsilateral forefoot surgery undertaken at the time of excision of a neuroma does not statistically worsen the outcome. The presence of concurrent foot pathology in this study accords with the findings of Mor- ris,6 who suggests that the mechanics of the foot are rele- vant in the development of Morton’s neuroma. Diez and Mas24 have also suggested that Morton’s neuroma can be associated with other forefoot pathology in up to 80% of patients. In our study, 12 patients underwent ipsilateral forefoot procedures at the same time as excision of a Mor- ton’s neuroma – their outcome was not statistically worse. This is consistent with findings reported by Kasparek and Schneider.10
Table III. Number of patients responding to each supplementary satisfaction question using a 5-point Likert scale
Number of patients responses
Question 1 2 3 4 5 (1) I am satisfied with the outcome of my foot surgery 49 29 11 8 2 (2) I no longer have pain in the area operated 34 29 15 11 10 (3) My ability to undertake daily tasks is now improved 29 34 11 13 12 (4) I am able to participate in sports/ heavy work 26 29 18 11 15 (5) The surgery has met my expectations 42 22 6 19 10 (6) I would have the surgery again if needed 62 21 6 6 4 (7) I would recommend this surgery to a friend 59 23 7 4 6
1, strongly agree; 2, agree; 3, no opinion; 4, disagree; 5, strongly disagree
Disagree 11%
Pie chart showing patient agreement to relief of pain post-operatively.
1380 V. BUCKNALL, D. RUTHERFORD, D. MACDONALD, H. SHALABY, J. MCKINLEY, S. J. BREUSCH
THE BONE & JOINT JOURNAL
The rate of failure after revision surgery ranges from 14% to 21%. The most common causes of recurrent symp- toms are inadequate resection, friction, pressure or forma- tion of a terminal neuroma.23,25,26 We found statistically worse outcomes in those who underwent revision surgery: five of seven patients who had further surgery did so for re- revision. Some studies have recommended methods of reducing this incidence, including implanting the stump of the nerve into muscle.23
The satisfaction scores described in this study are in line with those reported by Friscia et al27 who found that in the long term (mean 5.9 years, 2.8 to 13), of the 313 patients studied, 45.2% of patients were completely satisfied and 33.8% were satisfied. Kasparek and Schneider10 also found similar results. However, Akermark, Saartok and Zuber28
reported much higher scores where 86% of the 55 patient cohort expressed excellent or good results following sur- gery with a mean follow-up of 29 months.
Excision of a Morton’s neuroma is not always success- ful. In this study, only 63 patients (64%) were pain-free at follow-up and eight (8%) were worse. Other studies have also reported persistent pain in the affected foot after exci- sion of a Morton’s neuroma.23 The presence of unrecog- nised pathology may, however, account for the persistent pain.
In this study, 100 out of 129 specimens (78%) had histo- logical evidence of neuroma. These findings are similar to those of Pace, Scammell and Dhar2 and Vachon, Lemay and Bouchard,29 who reported that up to a third of operation specimens were histologically normal. Histological confir- mation of the diagnosis has little bearing on patient- reported outcome measures as nine patients (90%) in this study who were reported to be dissatisfied post-operatively had a Morton’s neuroma confirmed on histological exami- nation. This would suggest that outcomes are not solely dependent on complete excision.
The patients in this study were reviewed at six months post-operatively. This is a limitation of the study as a longer period of follow-up may have revealed changing results with time. However, many of the outcomes shown in this study are comparable to those reported in current literature where longer periods of follow-up have been used. Further- more, this is the largest study to record and compare pre- and post-operative outcomes using standardised validation tools, thus making this study highly important in our mod- ern understanding of surgical resection of Morton’s neuroma.
In conclusion, patient-reported outcomes after resection of a symptomatic Morton’s neuroma are acceptable, but may not be as favourable as earlier studies have suggested. Excision of neuromas from several sites give comparable results, but caution should be exercised when considering revision surgery, which has been shown to be a poor prog- nostic indicator.
Surgical excision of a Morton’s neuroma does not improve the mental component of SF-12.
Take home message: Revision surgery for Morton’s neuroma should be undertaken
with caution as less favourable outcomes in this cohort are
demonstrated.
Author contributions: V. Bucknall: Data collection, Drafting, writing and editing the paper. D. Rutherford: Data collection, Data analysis, Editing the paper. D. MacDonald: Editing the paper, Data collection. H. Shalaby: Performed surgery, Editing the paper. J. McKinley: Performed surgery, Editing the paper. S. J. Breusch: Study concept, Performed surgery, Editing the paper.
The authors would like to acknowledge G. Keenan who carried out some of the surgery included in the study.
No benefits in any form have been received or will be received from a commer- cial party related directly or indirectly to the subject of this article.
This article was primary edited by A. C. Ross and first proof edited by J. Scott.
References 1. Pastides P, El-Sallakh S, Charalambides C. Morton’s neuroma: A clinical versus
radiological diagnosis. Foot Ankle Surg 2012;18:22–24. 2. Pace A, Scammell B,…
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