Introduction

Neuropathic pain is a common and often severe problem for individuals with spinal cord injury (SCI) [1, 2]. It is characterized by burning, sore, tingling, or uncomfortable pain sensations related to the SCI. Between 40 and 73% of the individuals with SCI experience neuropathic pain [3,4,5]. The pain influences many aspects of the person’s life and also can affect quality of life [1]. Reconstruction of hand function in tetraplegia has the potential to improve independence and to facilitate a more active lifestyle [6,7,8] as well as positively affect psychological aspects and quality of life [9,10,11]. Being physically active seems to decrease pain [12]. Hand function also has been rated as the most desired function to restore in persons with tetraplegia [13,14,15].

Historically, surgeons and physicians have been cautious (or even have declined) to offer reconstructive hand surgery to individuals with neuropathic pain [16]. By declining to offer this surgery, maximal hand function is not available for these persons. The center where the study is performed has extensive experience of performing reconstructive hand surgery on individuals with tetraplegia, independent of whether or not they experience pain in their hands.

The aim of this study is to evaluate the results from reconstructive surgery to restore hand function in individuals with preoperative neuropathic pain following an SCI.

Methods

Data were retrospectively collected from medical records on all patients with tetraplegia who underwent reconstruction of grip function at the center between January 2012 and May 2015. They all underwent early active rehabilitation including active training of transferred tendons within 24 h and an overall active approach was used to maintain general fitness and independence [17]. All patients with 6 month follow ups were included in the study.

The following demographic data were collected; age, gender, time after injury, wheelchair dependence, motor level from the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) [18] and the International Classification for Surgery of the Hand in Tetraplegia (ICSHT) [19]. The study group was divided into the two groups; patients with neuropathic pain and those with no pain. The definition of neuropathic pain was based on information by a neurorehabilitation physician on the referral SCI unit or a direct question to the patient if they were diagnosed with neuropathic pain from their responsible SCI unit. Patients rated their mean preoperative pain in the arm/hand during the last 7 days, on a visual analog scale (VAS). Patients who rated any degree of pain (>0) not related to a known musculoskeletal cause were classified into the “Pain” group (PG). Patients without any pain in the arm/hand were categorized into the “No pain” group (NPG).

Grip strength, grip ability, and activity outcome at 6 months post-surgery compared with preoperative status were analysed. Length of stay and compliance to postoperative rehabilitation were also recorded.

The outcome measures were:

– Grip and pinch strength: Jamar grip strength (kg) and key pinch strength (kg). The maximum score from three attempts was recorded.

– Grip ability: Grasp and release test (GRT) [20]. This test was developed to evaluate grip ability in tetraplegia after grip improvement intervention. The GRT includes six items and measures the number of successful grasps and releases in 30 s for each item.

– Activity and participation change: In order to evaluate patients’ activity and participation performance, the Canadian Occupational Performance Measure (COPM) was used [21]. Prior to surgery, patients depicted their prioritized activity limitations due to their restricted hand function during a semi-structured interview. A maximum of five activity limitations was then selected. These selected activities were rated on the following two scales; current performance of the activity and satisfaction with that performance, on a scale of 1–10 (1 = not able to perform the activity/not satisfied at all and 10 = able to perform that activity extremely well/extremely satisfied). The ratings of selected activities were performed preoperatively and 6 months postoperatively. The COPM has been recommended as an evaluation tool for research in upper limb surgery in tetraplegia and has proven to be a sensitive measurement tool for this intervention [6, 22].

– Complications: Extended length of hospital stay and lack of compliance to participate in the postoperative rehabilitation were identified from medical records.

Statistics

Data are presented as means, ranges, and standard deviations (SD). For significant test of ordinal data, the Wilcoxon signed-rank test was used and for parametric variables, the T-test was used.

Results

During the period from October 2011 to November 2015, 43 patients with tetraplegia underwent tendon transfers to restore grip function. Of these, 37 attended a 6-month follow-up and thereby were included in the study (86%). All surgeries were unilateral. The combinations of tendon transfers performed are shown in Table 1. Surgery was performed on 17 patients with preoperative neuropathic pain, representing 46% of the study population. Most were men (65%), the mean age at surgery was 43 years, time after injury ranged from 1 to 42 years with a mean of 6 years. All had triceps function prior to grip reconstruction, and 13 (30%) were reconstructed.

Table 1 Demographics
Full size table

There were no significant differences between the PG and NPG regarding age, time after injury, or level of injury. There were more women in the NPG, 45%, compared with 23.5% in the PG. Patients in the NPG had lower ISNCSCI motor levels and higher ICSHT scores. All individuals who had incomplete SCI and were able to walk were in the NPG. Because this group had a lower degree of impairment, it included more patients who had both active finger and thumb flexors reconstructed. By comparison, reconstructions of wrist extension with passive key pinch were more common in the PG (Table 1).

Outcome at 6 months

There were no significant differences in outcomes between the groups. Patients with preoperative pain in the hand improved in both hand function and use of the hand in daily life to the same, or a slightly greater extent, as those without pain. The outcome measures evaluated included physical functions such as grip strength, basic activities with grasp test (GRT) and hand function ratings. It also included activity and participation with performance as well as satisfaction with their prioritized activities (COPM).

Change in grip strength and grip ability

There was an improvement in grip strength for the PG from 0.3 preop to 5.2 kg post-surgery. The corresponding strengths for the NPG were 0.3 and 4.9 kg, respectively. The pinch strength 6 months postoperatively was 2.1 kg in the PG and 1.6 kg in the NPG. Grip ability, as measured by the GRT, improved more in the NPG with an improvement of 74.1 compared with 48.6 in the PG (Table 2). The differences between the groups were not statistically significant. Rated current hand function on the VAS increased by 3.7 in the PG and 3.5 in the NPG.

Table 2 Treatment outcomes
Full size table

Change in performance and satisfaction with prioritized activities

Both groups experienced improvements in their prioritized activities, according to the COPM. Persons without pain rated their performance slightly higher than those with pain, both preoperatively and at follow-up. The ratings of improvement between preoperative and 6 months postoperative were, however, similar in both groups. Persons with pain improved their performance with their prioritized activities with 3.1 scale steps (from 2.0 preop to 5.1 postop). The corresponding scores in the NPG were 3.0 steps (from 2.4 preop to 5.4 postop).

Satisfaction with performance was slightly higher than rated performance with 3.6 scale steps improvement in both groups.

Change in rated pain

In the PG, 12 of 17 (70%) rated their pain again at 6 months follow-up. The pain intensity in the group decreased from 3.2 (range 0.7–7.8) preoperatively to 1.5 (range 0–6.0) postoperatively. Seven individuals with preoperative pain rated no pain 6 months after surgery.

Compliance to the rehabilitation plan

No extra visits or changes from the planned rehabilitation concept were required in any of the patients. As planned, they were discharged 3 days postsurgery (except one patient related to postoperative bleeding who required an extra day) and returned for 5 days’ intensive in-clinic rehabilitation 3 weeks after surgery.

Discussion

This study demonstrated no differences in function or activity outcomes related to pre-existing neuropathic pain in the hand. There were no differences in either grip strength or activity improvements between the groups. According to this small study, pre-existing pain does not seem to influence outcome after reconstructive hand surgery in tetraplegia, nor did patients with pre-existing pain require extra resources in post-surgery treatment in terms of length of stay and compliance to the rehabilitation routine protocol.

There was a tendency for individuals in the NPG to have less impairment, as evidenced by a higher ICSHT, a lower ISNCSCI motor level and more partially ambulatory persons. For those with less impairment and more residual function, a greater extent of a full reconstruction was achieved, including both finger and thumb flexors, compared with the PG. Notwithstanding, the PG had similar overall results to the less impaired NPG.

In the studied group, 46% had pre-existing neuropathic pain. With respect to various definitions of neuropathic pain, the prevalence is still similar to studies on neuropathic pain in the overall population with SCI [3,4,5]. This might indicate that people with neuropathic pain seem to be willing to undergo surgery to a similar extent as those without pain but further studies needs to confirm this indication. In addition, they were able to participate in post-operative rehabilitation according to standard routines to the same extent as those without pain. Since both outcome and postoperative compliance are the same and independent of pre-existing pain, the decision to undergo grip reconstructive surgery should be made on the basis of patients’ needs and desires rather than factors such as preoperative pain.

The current study indicates that pre-existing pain can decrease or even disappear after grip reconstruction. This observational result requires further study to confirm the findings and to understand the mechanisms behind it. Previous studies have shown that being active can decrease pain [12]. After a grip reconstruction, individuals improve their performance in daily activities and also have the potential to increase the feeling of manageability and social participation [6, 9]. It is also known that participation and social interaction are correlated to quality of life in individuals with SCI [23,24,25]. These factors can account for the tendency toward decreased pain after surgery.

The follow-up interval in this study is 6 months postoperatively. It is known from previous studies in tendon transfers that most improvements occur during the first 6 months, even if some additional improvements are to be expected between 6 and 12 months [6]. A long-term follow-up is needed to ascertain whether surgery has the potential to reduce pain and if the activity improvements will increase further over time.

Limitations and further studies

The current study comprises a small number of participants. The results from this study, therefore, should be regarded as an indicator of the extent to which neuropathic pain can have an impact on outcome of grip reconstruction in tetraplegia. Further studies are needed to confirm this result. Neuropathic pain is vaguely defined in this study. There are no obvious musculoskeletal reasons for the pain but individuals with other types of pain might be hidden in the PG. The indication that pain might decrease after grip reconstruction needs to be investigated further. Moreover, the study was performed in a specialized center, and the findings may not be directly transferable to other settings.

Conclusion

Individuals with tetraplegia and neuropathic pain in the arm/hand improve after grip reconstructions in a similar way to those without pain. There were no significant differences between the two groups in grip strength, grip function, or in improvements in performance, nor satisfaction of prioritized activities. There also were indications that the pain decreased after surgery. The results from this study, thereby, suggest that the decision to perform tendon transfer to restore grip function in tetraplegia should be based on patients’ needs and desires, and pre-existing neuropathic pain in the hand does not seem to be a factor that should influence the decision.