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Early mobilization vs delayed mobilisation following the use of a volar locking plate with non-vascularized bone graft in scaphoid non-union. A multicentred randomised controlled-trial
∗Corresponding author: Cameron Muirhead. drcgmuirhead@gmail.com
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Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
This randomized clinical trial investigated the potential for early mobilization of the wrist following open reduction and internal fixation (ORIF) with a scaphoid specific volar locking plate and non-vascularized bone graft for scaphoid non-union.
16 patients with scaphoid non-union underwent internal fixation with a scaphoid-specific volar locking plate and iliac crest bone graft and were randomized to one of two treatment arms (A) The control were immobilized in a below elbow cast for 6 weeks (n = 9) and (B) The experimental arm were mobilized early with a removable wrist splint (n = 7). Outcomes were measured preoperatively, and at 3 months post operatively. These included the primary outcome of union, and secondary outcomes of grip strength and patient reported outcomes of disabilities of arm shoulder and hand (DASH) and patient reported wrist evaluation (PRWE). Discrete variables were analyzed using the chi squared test while continuous variables used the students t-test.
The experimental (early mobilization) group developed metalware complications resulting in the early termination of the study. No significant difference in the demographic characteristics of age, gender, time to surgery, smoking status and handedness was found between groups. A significant difference was found in BMI, with significantly higher proportion of obese patients (p = 0.05) in the experimental group. There was no significant difference in the primary outcome measure of the rate of union between groups. The secondary outcomes of grip strength, Dash and PRWE also showed no significant difference between the immobilized and mobilized groups.
We recommend immobilization following scaphoid non-union ORIF using a volar locking plate due to high complication rates in our cohort with early mobilization.
Type of study/level of evidence: Therapeutic 2.
Trial registration.
Australian New Zealand Clinical Trials Registry (ACTRN12614001050640). Date of registration, 02/10/2014.
Keywords
Early mobilization
Non-vascularized bone graft
Open reduction and internal fixation
Scaphoid Non-union
Volar plate
1 Introduction
The scaphoid bone is the most commonly fractured carpal bone, accounting for 70% of all carpal fractures. Most fractures of the scaphoid heal without surgical intervention, however there is a reported non-union rate of 5–20%.1 Factors increasing the likelihood of non-union include delayed diagnosis or presentation, proximal or displaced fractures and general patient factors such as diabetes and smoking.2,3
Scaphoid fractures most commonly occur in young men aged 15–40 years.4 This population are often involved with professions and/or sports with high physical demands. Prolonged immobilization and rehabilitation is therefore problematic for this population with severe social, recreational and economic impacts. This can lead to non-compliance and compromised surgical outcomes.5 The principle of early mobilization has long been accepted as best practice for fractures fixed with stable constructs avoiding joint stiffness and contractures.6 An intervention that allows for high union rates while enabling early return to activities is therefore appealing.
The scaphoid bone is unique in that 80% of the surface of the bone is covered by articular cartilage.7 This results in limited entry points for the bloods supply to the bone. Due to this limitation, the scaphoid is reliant upon retrograde blood flow that largely enters the bone on the dorsal surface. Fractures which disrupt this flow may place the bone at risk of avascular necrosis and non-union. The unique anatomy of the scaphoid as described also limits the potential surgical options. Until recently, screw fixation has been the gold standard for scaphoid fixation. The most common type of screw uses a variable pitch screw,8–11 which offers good compression across the fracture site but low rotational stability and as such requires prolonged immobilization postoperatively.8–13 This treatment yields high rates of union but requires prolonged physical therapy and rehabilitation to return to normal function.9,11 To overcome this problem, some surgeons prefer two-screw fixation to single screw fixation.14
With the recent advances in implant design, scaphoid specific locking plates with an anatomical contour and low profile have been produced. In vitro studies have shown improved resistance to rotational forces, and a similar load to failure when compared to a single screw fixation.8 A recent cadaveric study demonstrated the biomechanical advantage of both double screw fixation and plate fixation compared with a single screw used for fixation.15 We have previously demonstrated no statistical difference in union rates for screw or plate fixation using iliac crest bone graft16 in the non-union setting, as assessed on postoperative CT. This result provides the potential for a method of fixation that could yield equivalent rates of union while allowing for an earlier mobilization of the wrist and therefore reduced morbidity, social and economic impacts.
2 Methods/design
This study was a multicenter randomized control trial. Ethics approval to conduct the study was obtained from the relevant institutional ethics committees. It was designed as a Non-inferiority study powered to detect a 20% difference in the primary outcome of union. Patients over 18 years of age with non-united scaphoid fractures were identified and approached to participate in the trial. The only exclusion criteria were patients who had previously failed internal fixation for this injury (n = 2). Sixteen participants were recruited across the two Health Networks over a period of 2 years from 27 of April 2015 to the 27 of February 2017. The study was terminated early due to preliminary analysis of the results showing a trend towards unacceptable metalware complications in the experimental group.
All patients attended a pre-operative assessment where collection of demographic information and preoperative measurements of Grip strength and Patient reported outcomes (PROMs) was conducted. At this consultation the senior author reviewed the plain radiographs for non-union which was classified as any scaphoid fracture which was not united following a period of greater than three months from the original injury. Each patient provided written informed consent prior to participation in the trial.
2.1 Surgical technique and randomization
All participants underwent open reduction and internal fixation (ORIF) by a single surgeon using an anatomically contoured scaphoid specific locking plate (Aptus 1.5 Scaphoid Plate, Medartis® AG, Austrasse, Basel, Switzerland) with non-vascularized bone graft (iliac crest) by a volar approach as previously described.16 Once the procedure was complete participants were randomly allocated to one of two groups by computer-generated block randomization utilizing the online platform Sealed envelope™️. Group A was the control arm while Group B was the experimental arm. Participants in Group A were immobilized in a below elbow back slab postoperatively for two weeks, followed by a fiberglass thumb spica cast for 4 weeks. Participants in Group B were not immobilized postoperatively, instead being placed in a bulky dressing for two weeks and fitted with a removable wrist splint without thumb spica, which they wore for comfort only for the next 4 weeks. No specific physiotherapy regime was allocated to the mobilization group during the 4 weeks of splint application, instead they were informed to wear the splint for comfort and to come out of the splint to range the wrist gently in the sagittal plane as tolerated. All Participants received standard post-operative management with a wound review at two weeks, a further review with X-ray at six weeks and a review at three months with a CT to assess the primary outcome of union, as per the surgeon's standard care. Secondary outcome measures were collected at six weeks and three months.
2.2 Outcomes
The primary outcome measure of union was assessed using a CT scan. Percentage union was calculated using the method described by Singh et al.17 Union was defined as crossing bony trabeculae with greater than 50% volumetric bony bridging. This was quantified by assessing percentage union at three points (Lateral, central and Medial) along the fracture line on sagittal CT reconstructed slices (1 mm sections at 1 mm intervals.
Percentage union = (sum of total length of united scaphoid (mm)/sum of total length of fracture (mm)) X 100%.
Union was defined as percentage union >50% and non-union as <50%. If a participant was deemed to be not united, they had a repeat CT at 6 months for further assessment. The CT scans were assessed by one of two consultant radiologists who were blinded to the allocation of the participants.
The secondary outcome measures included Participant reported outcome measures (PROMs) and Grip strength. Two commonly utilized and validated PROMs were selected, the ‘Disabilities of Arm, Shoulder and Hand’ (DASH) and the ‘Patient reported wrist evaluation’ (PRWE). Grip strength was measured using Jaymo digital dynamometer and the average of three readings was utilized for comparison. Participant demographic details collected included age, gender, BMI, smoking status and presences of diabetes were collected and compared as was the side of the injury, when the injury occurred and the Participant's hand dominance.
2.3 Statistical analysis
As a non-inferiority study, it was deemed that a clinically significant difference in the primary outcome of union would be 20%, a previously reported union rate of 80–90% for screw fixation with bone graft and immobilization3,18 was selected for comparison. A sample size of 28 in each arm was calculated for a total sample size of 56. This calculation was made with an alpha value of 0.5 and a beta value of 0.80 according to a power calculation for a binary outcome non-inferiority trial. This number could not be achieved due to early termination of the trial following an interim analysis of results. At the time of termination 16 participants had been recruited.
Continuous data such as DASH score, age and BMI were analyzed using the students T-test and reported in terms of the mean and 95% confidence interval. Dichotomous data such as union, gender, diabetes and smoking will be compared using the Chi-squared test. Intention to treat analysis was utilized for one patient who was lost to follow up. Where data was available it was included in the data analysis.
2.4 Clinical comparison
Each secondary outcome was also assessed for variation between groups using a previously reported minimal clinically important difference (MCID). The pre-operative measurements were taken as a baseline and compared to the three-month measurements, if the difference was greater than or lesser than the baseline by the suggested MCID it was counted as a either a clinically important increase or decrease.
3 Results
3.1 Participant demographic data
Of the 16 participants recruited 7 were allocated to Group A (control) and 9 were allocated to Group B (experimental). Demographic data are shown in Table 1. The groups were no different, except for a difference in BMI that was found to be significant.
| Group A - Immobilized | Group B - Mobilized | p Value | |
| Age (years) | 21 ± 14.9 | 33 ± 29.1 | 0.3 |
| Smoking status (%) | 22.2 | 62.5 | 0.43 |
| BMI | 22.3 ± 2.97 | 29.1 ± 7.3 | 0.049∗ |
| Time to operation | 23.5 ± 18 | 56.4 ± 114.2 | 0.33 |
3.2 Primary outcome
No statistically significant difference in the rates of union was found between the Group A (immobilized) and Group B (early mobilized) at either the three- or six-month reviews. At three months the union rate in group A (control) was 71% and 44% in Group B (experimental). At six-month review union rates were 86% and 67% respectively. This was not statistically significant (Table 2).
3.3 Secondary outcomes
Secondary outcomes were assessed for statistically significant difference and compared to previously reported minimal clinically important difference (MCID). These are displayed in Table 3.
| Group A | Group B | p Value | |
| Grip Strength | |||
| Pre-op | 38 ± 11.2 | 34.5 ± 20.9 | 0.32 |
| 3 Months | 32.4 ± 12.7 | 31.1 ± 14 | 0.46 |
| DASH | |||
| Pre-op | 33.4 ± 18.7 | 44.9 ± 22.2 | 0.02∗ |
| 3 Months | 20.5 ± 24.9 | 25.6 ± 15.7 | 0.49 |
| PRWE | |||
| Pre-op | 61 ± 18.6 | 35 ± 14.9 | 0.78 |
| 3 Months | 51.9 ± 16.2 | 33 ± 17.8 | 0.86 |
3.4 Grip strength
Both groups showed an overall decrease in grip strength from the preoperative measures to the three-month review. This was a significant decrease for Group A (immobilized) with a mean reduction of 4.5 kgs (p = 0.05), but not for Group B (mobilized) which decreased by 1.56 kgs. The reduction in grip strength of group A was found to decrease by the MCID (5–6.5 kgs)19 in 37.5% of participants. Group B also showed a reduction in grip strength reaching a MCID in 42.8% of participants. No significant difference was identified in grip strength between groups either preoperatively or postoperatively.
3.5 Disability of shoulder and hand (DASH)
Preoperative DASH scores were significantly different between groups with Group A (Immobilized) scoring less than Group B (mobilized) by 15 points (p = 0.05).
There was no significant difference between groups at 3 months. There was also no significant difference found between the pre-operative and post-operative scores within Group A (immobilized). Although not statistically significant, 72% of the immobilization group improved by more than the MCID (10 points).20 Group B in contrast improved between the preoperative and postoperative period by an average of 17.86 points and this was found to be significant (p = 0.002).
3.6 Patient reported wrist evaluation (PRWE)
No significant difference was found between groups at either the pre or postoperative reviews. However, both groups showed a significant decrease in PRWE score between their pre-operative and 3-month reviews. MCID (15 points).20
4 Discussion/conclusion
This prospective, randomized controlled trial sought to investigate if early mobilization following ORIF and ICBG of Scaphoid non-union would lead to equivalent rates of union as the current practice of immobilization.
The rates of union were not significantly different between the 2 groups based on CT. However, due to the early termination of the study as a result of unacceptable metalware failure in the treatment arm, recruitment of a population of only 16 participants cannot accurately prove non-inferiority.
This study utilized the protocol outlined by Singh et al., 2005,17 to assess and define union. In biomechanical studies Guss, M. et al.21 showed a 50% intact scaphoid following ORIF with a single screw had a similar load to failure and significantly higher stiffness than the intact scaphoid. While Mandaleson A.8 found that both two screw fixation and plate fixation demonstrated significantly greater stability, stiffness and energy absorption that a single screw. Taking these together 50% cross bridging is a commonly utilized definition of union and biomechanically is a safe point at which to allow patients to return to unrestricted activities.
Using this definition both arms of this study showed a decreased union rate compared to other recently published studies utilizing iliac crest bone graft and volar plate fixation with 87% reported by Esteban-Feliu,I.,22 93% by Ghoneim, A23 and 100% Leixnering, M.24 The rates of union achieved in the study were however in keeping with previously reported rates of union for several other studies3,11,25,26 with Group A achieving 71% union at three months and Group B achieving 44%. This shows the rate of union reported in the literature to be highly variable. This likely relates to the lack of a universal definition for scaphoid union.
The difference seen during our investigation could be partially explained by the stringent reporting protocol this study utilized to diagnose union as well as the assessment of the primary outcome at 12 weeks (3 months). Our study required greater than 50% volumetric bridging at three distinct points on CT for union to be reported. It is likely that this would lead to a greater percentage of scans showing delayed union as this volume of healing will take more time. Janjowski, J.27 showed the average time to union, defined as cortical union of the grafted portion on computed tomographic scan, was 14 weeks. While Leixnering, M24 found union to take place between two to seven months with an average of 4.4 months. Our study also found that union rates increased over time as the six-month reviews conducted with both Group A and B showing an increase in union during this time reaching 71.4% and 66.7% respectively.
The secondary measures aimed to assess if early mobilization provided any benefit over immobilization in regard to grip strength and patient satisfaction. No benefit in Grip strength was found with early mobilization, as both groups decreased from pre-operative measures to three-month review with no significant difference between groups. The Immobilized group with an average decrease of 4.5 kgs was significantly decreased from pre-operative to three months review (p value = 0.05). This result supports previous literature in this area that has shown immobilization to cause stiffness and disuse atrophy.3,11,13 The results for Group B (Mobilized) also decreased on average but to a lesser extent (1.56 kgs) and not significantly. This decrease in group B occurred in the patients with the highest pre-operative scores and those with a grip strength below 21 kgs all showed improvement at the three-month review. This is likely related to these patients suffering greater pre-operative pain and therefore re-gaining comparatively greater function once this resolved. These reductions in grip strength were clinically important with 42.85% of each group decreasing by more than 6.5 kgs (MCID 5–6.5 kgs).19 This result highlights the morbidity associated with this injury and its post-operative course. With almost 50% of patients failing to return to pre-operative function by the three-month review.
The trial was terminated early following interim analysis and evidence of an unexpectedly high rate of delayed union and/or metal ware failure in Group B - the mobilized cohort. At the time of this analysis it was identified that two participants had broken plates or screws and ongoing non-union. Participants in this study who suffered prosthesis complications underwent scaphoidectomy and four corner fusion as definitive management of this issue.
Similar problems with prosthesis failure were reported by Esteban-Feliu, I22 who found that 4 of 15 participants experienced complications following volar plating at three year follow up. Likewise, Mehling, I26 describes plate and screw breakage in one patient of the 15, this number may have been higher however this paper showed a 66.7% plate removal for mechanical block or perceived interference.
These failures were reviewed by the lead investigators and excessive load bearing and prolonged time to surgery were identified as the likely causative factors. Participant 1 had returned to weightlifting following his two-week wound review and was routinely bench pressing in excess of 100 kgs during his three-month recovery period. He was identified as having non-union at 3 months at six months the CT scan showed union. However, he re-presented with wrist pain at 9months with re-fracture of his scaphoid and metalware failure (plate breakage and screw back-out) following a new wrist injury (Fig. 1). Participant 2 suffered no repeated injury but had failed to unite at both three month and six-month reviews and was found to have screw backout. He was identified as having a time from injury to surgical fixation of greater than 30 years.
These two cases represented a 28.5% failure rate in the experimental arm, and it was deemed unsafe to continue the trial.
5 Conclusion
In a cohort of 16 patients this study showed that early mobilisation may lead to increased rates of complications and therefore as a result of this study, we recommend immobilization following scaphoid ORIF with Iliac crest bone graft and a volar locking plate. No significantly different in the rates of union were observed. Grip strength following ORIF was decreased in both groups and had not returned to pre-operative levels by 3 months for either group. The mobilized cohort showed significantly improved PROM scores from the pre-operative and three-month reviews however these were not significantly different to the immobilized cohort.
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