a Departamento de Ortopedia, Santa Casa de São Paulo, São Paulo, SP, Brasil
b Serviço de Ortopedia e Traumatologia, Hospital Israelita Albert Einstein, Universidade Federal de São Paulo (Unifesp), São Paulo, SP,Brasil
c Instituto de Ortopedia, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (USP), São Paulo, SP, Brasil
d Escola Paulista de Medicina, Universidade Federal de São Paulo (Unifesp), São Paulo, SP, Brasil
Introduction
After observing that the cubital nerve was compressed atthe elbow, in a fibro-osseous space defined by a ligamentbetween the medial epicondyle and the olecranon, Feindeland Stratford1used the term "cubital tunnel syndrome" forthe first time. One year earlier, Osborne2had described sim-ple decompression of the nerve by means of sectioning thissame ligament. However, the first published papers date from1878, the year in which Panas3described the condition andMarchand4described a procedure for releasing and stretch-ing the cubital nerve. The condition of "toxic neuritis of thecubital nerve" was also described by Buzzard5in 1922 and,two decades later, Learmonth6also described techniques forsubmuscular and intramuscular decompression and transpo-sition.
Compression of the cubital nerve is a common conditionand may occur at several levels. Compression at the elbow isthe commonest form of cubital compression7-9and is the sec-ond commonest compression neuropathy of the upper limbs.
The diagnosis is based on symptoms, signs, orthopedictests and electrophysiological studies.
Many cases of cubital tunnel syndrome can be treated con-servatively without surgery. Nevertheless, some cases requiresurgical treatment with a view to avoiding persistence of thesymptoms and progression of the neurological deterioration.The surgical treatment should be guided by the following prin-ciples: (1) release of all the possible compression sites; (2)preservation of the vascularization of the cubital nerve at theelbow; and (3) early mobilization of the elbow.
The commonest surgical options include simple decom-pression, medial epicondylectomy, subcutaneous anteriortransposition, intramuscular anterior transposition and sub-muscular anterior transposition.
The elbow is a dynamic joint. Over the course of the day,it flexes and extends to place the hand in functional pos-itions. Through this mobility, changes to the shape and spaceof the cubital tunnel take place. When the elbow is flexed, thetunnel becomes flatter10and the arcuate ligament becomestensioned,11which leads to reduction of the space availablefor the nerve11,12and increased pressure inside the tunnel.
Feindel and Stratford1and Osborne2advocated that sec-tioning the fibrotic band that forms the ceiling of thistunnel would be sufficient for relieving the pressure and consequently relieving the symptoms in the majority of thecases.
Under natural conditions, the nerve is also subject to trac-tion and excursion during the normal movement of the elbow.
Anterior transposition has the aim of transferring the nerveto a point anterior to the axis of mobilization of the elbow.This diminishes the tension and also eliminates the pressureon the cubital tunnel.
There is no consensus in the literature regarding thebest surgical treatment for cubital tunnel syndrome. Anteriortransposition is perhaps the procedure most often effected.14Nonetheless, other authors have defended the notion thatsimple decompression is just as effective as transpositionand presents a similar success rate and lower complicationrate.15-17
The present study had the aim of expanding the infor-mation available on comparisons of results between twotechniques that are widely used for treating cubital tunnelsyndrome: in situ decompression and subcutaneous anteriortransposition.
Material and methods
The records of all patients who were treated surgically atour institution between January 2004 and December 2011were reviewed. The inclusion criterion was taken to be adiagnosis of idiopathic cubital tunnel syndrome based onphysical examination and electromyographic analysis. Casesof proximal compression of the nerve, angular deformitiesof the elbow and systemic diseases associated with non-compressive neuropathy were excluded.
In this manner, 97 cases were obtained, corresponding to96 patients (56 men and 40 women), with a mean age of 51.91years (range: 15-84). The right side was involved in 51 patientsand the left side in 46 (Table 1).
All the patients were classified on a scale of four grades,in accordance with the modified McGowan classificationsystem.18Thus, patients with subjective symptoms and with-out objective findings were classified as grade I; those withgood intrinsic strength without atrophy of the intrinsic mus-cles were classified as IIA; those presenting atrophy of theintrinsic muscles were classified as IIB; and those with markedsensory disturbance in association with marked atrophy of theintrinsic muscles were classified as III.
Thus, 14.4% (14) of the patients were in grade I, 27 (27.8%)in IIa, 26 (26.8%) in IIb and 30 (30.9%) in III (Table 2).
In situ neurolysis of the cubital nerve was performed in64 cases, while subcutaneous anterior transposition was per-formed in 33 cases. Among the patients who underwentneurolysis, 12.5% were in grade I, 29.7% in IIA, 28.1% in IIBand 29.7% in III. Among those who underwent anterior trans-position, 18.2% were in grade I, 24.2% in IIA, 24.2% in IIB andthe remaining 33.3% in III (Table 3). No statistically significantdifferences in the patients' preoperative stage according tosurgery group were observed (p = 0.817).
The postoperative evaluation was stratified in accordancewith the system of Wilson and Knout,19in which an excellentresult corresponded to minimal sensory and motor alter-ations, without tension at the incision site; good signifiedmoderate sensory and motor alterations; satisfactory signifiedimproved, but with persistent alterations; and poor signifiedno improvement or even worsening of the state.
In the descriptive analysis, the continuous variableswere represented by the mean and standard deviation.
The categorical variables were represented by the abso-lute frequency (n) and the relative frequency (%). Withthe aim of selecting appropriate statistical tests, theKolmogorov-Smirnov test was used to ascertain whether thestudy variables followed normal distribution. To comparemeans, Student's t test for independent samples was used.The chi-square test or Fisher's exact test (when applicable)were used to analyze associations between pairs of categoricalvariables.
The four grades of the modified McGowan scale wereregrouped into two levels: grade I with IIA; and grade IIB withIII. The postoperative evaluation using the Wilson and Knoutsystem was reclassified into two groups: excellent and satis-factory, good and poor. The statistical tests were conductedbilaterally with a significance level of 5%. The statistical anal-ysis on the data was performed using the IBM SPSS Statistics20.0 software.
Results
From the modified Wilson and Knout classification, out of the97 operations performed, 48 (49.5%) produced an excellentresult, 18 (18.6%) good, 17 (17.5%) satisfactory and 14 (14.4%)poor. A new surgical intervention was only necessary in rela-tion to two patients (Table 1).
No differences relating to sex were observed with regard tothe surgical technique. The mean age was 52 (14.9) years. Thepatients who underwent transposition surgery were two yearsolder than those who underwent neurolysis (53.3 versus 51.2).
Comparison between the results from the two surgicaltechniques showed that there were no statistically sig-nificant differences, with similar values for the rates ofexcellent results (48.4% for neurolysis versus 51.5% for anterior
transposition) and good results (18.8% versus 18.28%).Regarding the results that were only satisfactory or poor, therates were 32.8% for neurolysis and 30.3% for subcutaneoustransposition (Table 4).
In the analysis stratified according to the initial grade forthe two techniques (Tables 5 and 6), it was seen that 41 patientswere in grades I and IIa, of whom 27 underwent neurolysisand 14, transposition. Among the patients who underwentneurolysis, 55.6% achieved an excellent result and 44.4% agood, satisfactory or poor result. An excellent result was alsoachieved by 64.3% of the 14 patients who underwent transpo-sition. Among the patients initially classified in grades IIB orIII, 37 underwent neurolysis and 19 transposition, and excel-lent results were attained by 43.2% and 42.1%, respectively,while the results were good, satisfactory or poor in 56.8% and57.9%, respectively.
Only two patients had the need for further surgical inter-vention. Both of these had undergone simple decompression(Table 2).
Discussion
Several surgical techniques have been put forward fortreating compression of the cubital nerve in the elbow.
Medial epicondylectomy is rarely performed.20,21Subcuta-neous anterior transposition and simple decompression arethe procedures most used. In our study, only patients whounderwent operations using these two techniques wereincluded, given that by a large majority, these are the tech-niques most performed in our department.
In analyzing the results, it seems that there was no pre-ponderance of one technique over the other. Independent ofthe technique, the rate of excellent results among the patientsreached 48.5%. When compared according to technique, therates of excellent results were close: 48.4% for neurolysisand 51.5% for transposition. Satisfactory or poor results wereobtained by 32.8% and 30.3%, respectively, which reinforcedthe similarity (Fig. 1). This analysis also showed that therewas a tendency for patients with higher grades at the timeof the surgery (IIB and III) to have lower rates of excellentresults (43.2% and 42.1%), although no statistically significantdifferent was observed in this regard (neurolysis p = 0.957; andtransposition p = 0.559). This tendency was shown to be inde-pendent of the technique and confirms what has been widelydisseminated in the literature, i.e. that the chances of allevi-ating the pain and recovering sensitivity and motor strengthare inversely related to the initial grade of neuropathy.
The notable study on cadavers by Gelberman et al.22demonstrated that intraneural pressure increases more thandoes extraneural pressure when flexion is greater than 90?.Gelberman therefore concluded that traction contributestoward nerve compression and took the view that the increasein intraneural pressure could not be due solely to extraneuralcompression. Despite this work, controversy continues to sur-round the evidence for nerve distress due to traction, ratherthan distress due to compression.9,11,22-27Cubital tunnel syn-drome is not the only case of compressive neuropathy in theupper limb. In most other neuropathies, a compressive fac-tor seems to be implicated. It is also known that nerves arecapable of stretching and growing at a velocity of 1 mm/day.This raises the question of what might explain why the nor-mal functioning of the elbow would require greater excursionof the nerve and why the organism is incapable of respon-ding to and accommodating this need? Iba et al.28brought upthe issue of the clinical validity of the pressure values foundby Gelberman et al.22when they found in vivo intraneural pressure values that were high all the time, even in extension,and which were around four times higher in flexion.
More recent studies,29also conducted on cadavers, havedemonstrated that elongation of the nerve occurs especially inthe segment proximal to the epicondyle and between 30?and90?and then the length remains constant until 135?. However,at around 135?, the area and sagittal curvature of the tunneldecrease and force the nerve into a flattened shape. Thesefindings suggest that the compression is greatest at 135?.
Based on the findings of Gelberman et al.,22many ortho-pedists abandoned the surgical technique initially describedby Osborne and started to perform anterior transpositions.However, over the last few years, several studies have demon-strated not only that simple decompression may be just aseffective as anterior transposition, but also that the lattermay be associated with a greater number of complications.One of the factors may be the possibility that blood vascu-larization might be disturbed during the transposition.30-32Ogata et al.33demonstrated in an experimental study thatthis transposition is associated with decreased regional bloodflow for at least three days after the surgery. In a randomizedprospective study on 44 patients, Biggs and Curtis16concludedthat there were no differences in the results between sim-ple neurolysis and anterior transposition and recommendedthe former because of the lower number of complications. Inanother randomized prospective study on 152 patients, Bar-tels et al.15compared subcutaneous anterior transpositionand simple decompression and also concluded that simpledecompression had equal efficacy but with a lower compli-cation rate (23 versus 7, among a total of 30), which wouldalso be associated with lower cost. In another randomizedstudy on 70 patients and 48 months of follow-ups, Gervasioet al.17also did not find any statistically significant differencesbetween simple decompression and submuscular transposi-tion. In a fourth prospective study with a follow-up of 63.1months, Keiner et al.34concluded that the two techniques ledto similar results and that simple decompression should bepreferred because it was less invasive. Nabhan et al.35alsoprospectively compared simple decompression and subcuta-neous anterior transposition and reported that there were nodifferences in the results and therefore also recommendedsimple decompression as the preferred treatment because itis a simpler procedure. Furthermore, two meta-analyses con-ducted by Macadam et al.36and Zlowodzki et al.37did not findany statistically significant differences between the varioustechniques.
Our study seems to be concordant with most of the recentlypublished papers on surgical treatment of this pathologicalcondition. Despite the need for reintervention in the casesof two patients who were initially treated by means of sim-ple decompression, most of the patients treated using thistechnique achieved the same result as those who underwentsubcutaneous transposition, independent of the initial grade.The absence of complications in our study, in comparison withthe others cited, can be explained by the fact that in someof these other studies, anterior transposition that sometimeswas intra or submuscular was used as the comparison. This isgenerally associated with a higher complication rate.
From the analysis on the literature, it also seems thatmedial epicondylectomy has an increasingly limited role. Muermans et al.38analyzed their results from 60 epi-condylectomy procedures performed on 51 patients and foundexcellent results in 75% of them. However, 21 of these 51patients reported pain in the medial epicondyle after theoperation. This was similar to the result obtained by Efs-tathopoulos et al.,39in which 45% of the patients operatedcontinued to present pain six months afterwards.
Conclusion
This study was limited by its retrospective nature and by thesmall number of patients in some of the subgroups analyzed.The postoperative results did not present any correlationwith the surgical technique used, given that independent ofthe technique, most of the patients achieved an excellentresult. This reinforces the idea that simple decompressionenables results similar to those from subcutaneous anteriortransposition. Therefore, with due regard for the greater tech-nical simplicity of simple decompression, we would reservetransposition only for cases of nerves with a potential forsubluxation, post-traumatic stiffness, valgus instability, lateparalysis of the cubital nerve or failure of simple decompres-sion.
Conflicts of interest
The authors declare no conflicts of interest.
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