Effect of different positions of splinting on flexor tendon relaxation: a cadaver study

Abstract

We performed a cadaver study to evaluate how six different static heat-moulded splints affect flexor tendon relaxation. Each splint positioned the wrist and metacarpophalangeal (MCP) joints in different positions. We evaluated the tendon relaxation in 12 fresh adult cadaver forearms by measuring the flexor tendon displacement between two solid markers for each splint. The wrist position ranged from 30° flexion to 45° extension and the MCP joints from 30° to 60° flexion. For each splint, tendon relaxation was achieved relative to the neutral reference position. Tendon relaxation was greatest when the MCP joints were positioned in 60° flexion. We also noted the persistence of tendon relaxation when the wrist was positioned in extension (30° or 45°) as long as MCP joint flexion was maintained (30° or 60°). We conclude that the wrist extension with the MCP joints flexion may optimize tendon relaxation during immobilization after flexor tendon repairs.

Keywords

Flexor tendon rehabilitation splint tendon relaxation

Introduction

Multistrand repair techniques have significantly improved the quality and strength of flexor tendon repairs in the hand (Cao et al., 2005; Dona et al., 2004, Sandow and McMahon, 2011; Savage and Risitano, 1989). However, postoperative rehabilitation protocols and immobilization positions are numerous. Rehabilitation protocols should be customized to the severity of injury, repair quality and patient characteristics (Peck, 2012). Early active motion of primary flexor tendon repair is used when the patient complies with the protocol (Cullen et al., 1989; Elliot, 2002; Rigó et al., 2017, Sandow and McMahon, 2011; Tang, 2007, 2018a). Savage (1988) suggested that 45° of wrist extension is the best position to reduce the forces required during the work of digital flexion when using an early active mobilization protocol. Peck et al. (2014) reported a short dorsal splint to allow maximal wrist flexion and up to 45° of wrist extension with a block to 30° of metacarpophalangeal (MCP) joint extension. In this study, we evaluated how six different static heat-moulded splints impacted tendon relaxation using cadaveric hands.

Methods

Design of splints

We analysed and compared six different static heat-moulded splints that placed the wrist and MCP joints in six different positions. The interphalangeal (IP) joints were always straight. The first splint immobilized the wrist at 0° and the MCP at 60° flexion (0°/−60° splint). This splint was considered the reference splint in our current clinical practice. Five other splints were made to immobilize the wrist at 30° flexion and MCP at 60° flexion (−30°/−60° splint), the wrist at 30° extension and the MCP at 60° flexion (+30°/−60° splint), the wrist at 30° extension and MCP at 45° flexion (+30°/−45° splint), the wrist at 30° extension and the MCP at 30° flexion (+30°/−30° splint), and the wrist at 45° extension and MCP at 30° flexion (+45°/−30° splint) (Figure 1). Designing and measurement of angles (goniometer, Prestige® Medical, Jasper, GA, USA) for each splint was performed by an independent examiner (AT) with more than 10 years of clinical experience in physical and rehabilitation medicine.

Figure 1.

Design of the different static heat-moulded splints positioning the wrist and MCP joints in different positions. (a) The wrist could be positioned at 30° flexion, 0°, 30° extension or 45° extension. (b) MCP joints could be positioned at 30° or 45° or 60° flexion.

Study protocol

We carried out a cadaver study using 12 fresh adult elbows, forearms and hands provided by the anatomy laboratory of our medical school. The specimens included six right upper limbs and six left. The limbs were disarticulated at the shoulder and prepared in a manner similar to that described by Pollock et al. (2010). None had any pre-existing lesions of the hand, fingers or wrist. All wrists were prepared by two senior surgeons (LA and RD, Level 4, specialist – highly experienced, Tang and Giddins, 2016) using the same protocol, which consisted of longitudinal incisions along the entire volar aspect of the forearm and wrist to locate the flexor tendons (flexor digitorum superficialis [FDS] and flexor digitorum profundus [FDP]). First, a 0.45-kg weight was applied in the forearm axis to the muscle bodies of the flexor tendon unit to simulate physiological tension. Next, we placed two markers. The first was fixed above the medial epicondyle (fixed marker) and the second, 20 cm distally (movable marker). The resting position of the hand and wrist before application of each splint was standardized, with the wrist, MCP and IP at 0° (neutral reference position). We used a Fiberwire™ 2-0 (Arthrex®) suture to whip stitch all the flexor tendons (FDP and FDS); this served as the second marker (Figure 2). The limb was then positioned horizontally on a specially designed workstation to stabilize it. Each splint was tested on each upper limb.

Figure 2.

Photographs of the study protocol. (a) Incisions along the entire volar aspect of the forearm and wrist to locate the flexor tendons. The two markers: fixed marker above the medial epicondyle and movable marker at 20 cm distally (movable marker). (b) A 0.45 kg weight was applied in the forearm axis to the muscle bodies of the flexor tendon unit to simulate physiological tension (arrow).

Tendon excursion measurement

To evaluate tendon excursion, an independent examiner calculated the displacement, in millimetres, of the second marker induced by the position of each splint. Proximal displacement (toward the medial epicondyle) was rated positively and considered a relaxation effect; a distal displacement (toward the hand) was rated negatively and considered a tension effect (Figure 3).

Figure 3.

An example of the neutral reference position (a) and tendon relaxation with the 0°/−60° splint (b) and the +30°/−60° splint (c).

Statistical analysis

The recorded data were summarized using mean values and ranges. The mean values obtained were compared using paired Student’s t-test. p < 0.05 was considered statistically significant.

Results

Tendon displacement induced by different splints are presented in Table 1. The greatest tendon relaxation was achieved when the MCP joints were in 60° flexion. The 0°/−60° and −30°/−60° splints achieved more tendon relaxation (11 mm and 19 mm, respectively). The tendon relaxation persisted even when the wrist was positioned in extension (+30° or +45°) as long as the MCP joints were in flexion.

Table 1.

Tendon relaxation (mean and range) for the different type of splints (n = 12) compared to the reference 0°/−60° splint.

Splint (wrist°/MCP°)	0°/−60° (reference)	−30°/−60°	+30°/−60°	+30°/−45°	+30°/−30°	+45°/−30°
Tendon relaxation (mm)	11.2 (8–18)	18.8 (11–25)	8.8 (5–15)	6.8 (4–12)	4.2 (2–9)	3.0 (1–9)
Comparison with reference splint (p-value)	N/A	0.07	0.024	0.009	0.001	0.0001

+: extension; −: flexion.

When we compared the results between the 0°/−60° splint (reference splint) and the other splints (Table 1), there was no significant difference in tendon relaxation with the −30°/−60° splint (p = 0.07). However, we found a significant difference in tendon relaxation with all the other splints positioning the wrist in extension (+30° and +45°) (p < 0.05). The smallest difference was observed with the +30°/−60° splint (p = 0.024).

Discussion

Our measurements indicate that the greatest tendon relaxation may be induced as of 30° MCP flexion and is independent of wrist position, whether in flexion (30°), neutral (0°) or in extension (30° and 45°). However, tendon relaxation seemed most effective when the MCP joints were positioned in 60° flexion. We did not find a significant difference between our reference splint (0°/−60°, current clinical practice) and the splint with a slightly flexed wrist (−30°/−60°). Furthermore, comparison of our reference splint with the other splints showed the least tendon relaxation with the +30°/−60° splint.

Leiber et al. (1996, 1999) and Zhao et al. (2002) suggested the forces exerted on flexor tendons are dependent on wrist position and there is increased passive tendon excursion during wrist tenodesis. Savage (1988) examined the influence of wrist position on the forces required to move the IP joints and concluded that 45° of wrist extension is the optimal position to minimize the work of digital flexion when using an active mobilization protocol. However, this position is uncomfortable when wearing a splint for 6 weeks continuously. We consider the position in 30° wrist extension could be an alternative.

With regard to the MCP joint, we found tendon relaxation induced by the position at 30° flexion. According to Wehbé and Hunter (1985), 30° MCP flexion makes it easier to initialize flexion with the FDP tendons and to achieve differential sliding between the flexor tendons. Positioning the MCP joints in excessive flexion would bias active motion in favour of the proximal IP joints. Confining active motion to the proximal IP joint only would encourage adhesions between flexor tendons and patients would attempt distal IP joint flexion only at the end of its range (Peck et al., 2014). Active motion should be initiated from the distal IP joint; this is facilitated in most patients by positioning the wrist joint in 10° to 30°extension and the MCP joints in 30° flexion (Bigorre et al., 2018). In addition, wrist extension significantly increases the excursion of the FDP and FDS tendons relative to the neutral position or the flexion position (Amadio et al., 2005).

In our study, we analysed tendon relaxation on non-sutured tendons and this study remains an anatomical investigation. We therefore could not assess tendon healing or repair rupture in the different wrist and MCP positions. This was a cadaver study, which cannot include assessment of other factors, such as the patient’s co-morbidities, injury mechanism, associated injuries, size of suture used, impingement with pulleys, oedema, haematoma, joint stiffness, size of dressing and patient compliance. All these factors play a role in tendon relaxation and excursion after tendon repair clinically. Tendon displacement may suggest tendon relaxation, but we concede that it is not equal to tension reduction in tendon in vivo.

In recent publications, authors consider wrist position not important and the MCP joint is usually in a functional position (Giesen et al., 2018; Lalonde 2018; Moriya et al., 2017; Pan et al., 2017; Reissner et al., 2018; Tang, 2018a, 2018b). There were no or few repair ruptures associated with these positions (Giesen et al., 2018; Pan et al., 2017). It is also considered that after pulley-venting and strong surgical repair, exact position of splinting the wrist is no longer a major concern and out of splint active motion is practised (Tang 2018b). However, our current cadaveric study provides information that the +30°/−60° and +30°/−30° splints can be most favourable for tendon relaxation, an anatomical finding that may provide surgeons with information of tension on tendons at different wrist and hand positions.

Footnotes

Acknowledgements

The authors thank Dr. Joanne Archambault for English language editing assistance

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Ethical approval

The participants had given informed consent for the use of their bodies for medical research.

References

Amadio

. Friction of the gliding surface. Implications for tendon surgery and rehabilitation. J Hand Ther. 2005, 18: 112–9.

Bigorre

Delaquaize

Degez

Celerier

. Primary flexor tendons repair in zone 2: Current trends with GEMMSOR survey results. Hand Surg Rehabil. 2018, 37: 281–8.

Cao

Tang

. Biomechanical evaluation of a four- strand modification of the Tang method of tendon repair. J Hand Surg Br. 2005, 30: 374–8.

Cullen

Tolhurst

Lang

Page

. Flexor tendon repair in zone 2 followed by controlled active mobilisation. J Hand Surg Br. 1989, 14: 392–5.

Dona

Gianoutsos

Walsh

. Optimizing biomechanical performance of the 4-strand cruciate flexor tendon repair. J Hand Surg Am. 2004, 29: 571–80.

Elliot

. Primary flexor tendon repair—operative repair, pulley management and rehabilitation. J Hand Surg Br. 2002, 27: 507–13.

Giesen

Reissner

Besmens

Politikou

Calcagni

. Flexor tendon repair in the hand with the M-Tang technique (without peripheral sutures), pulley division, and early active motion. J Hand Surg Eur. 2018, 43: 474–9.

Lalonde

. Conceptual origins, current practice, and views of wide awake hand surgery. J Hand Surg Eur. 2017, 42: 886–95.

Leiber

Amiel

Kaufman

Whitney

Gelberman

. Relationship between joint motion and flexor tendon force in the canine forelimb. J Hand Surg Am. 1996, 21: 957–62.

10.

Leiber

Silva

Amiel

Gelberman

. Wrist and digital joint motion produce unique flexor tendon force and excursion in the canine, forelimb. J Biomech. 1999, 32: 175–81.

11.

Lister

Kleinert

Kutz

Atasoy

. Primary flexor tendon repair followed by immediate controlled mobilization. J Hand Surg Am. 1977, 2: 441–51.

12.

Moriya

Yoshizu

Tsubokawa

Narisawa

Matsuzawa

Maki

. Outcomes of flexor tendon repairs in zone 2 subzones with early active mobilization. J Hand Surg Eur. 2017, 42: 896–902.

13.

Pan

Qin

Zhou

Chen

. Robust thumb flexor tendon repairs with a six-strand M-Tang method, pulley venting, and early active motion. J Hand Surg Eur. 2017, 42: 909–14.

14.

Reissner

Zechmann-Mueller

Klein

Calcagni

Giesen

. Sonographic study of repair, gapping and tendon bowstringing after primary flexor digitorum profundus repair in zone 2. J Hand Surg Eur. 2018, 43: 480–6.

15.

Rigó

Haugstvedt

Røkkum

. The effect of adding active flexion to modified Kleinert regime on outcomes for zone 1 to 3 flexor tendon repairs. A prospective randomized trial. J Hand Surg Eur. 2017, 42: 920–9.

16.

Peck

. Customizing flexor rehabilitation based on zone or type of injury. In: Tang

Amadio

Guimberteau

Chang

. (eds) Tendon surgery of the hand, Philadelphia: Elsevier Saunders, 2012; 415–26.

17.

Peck

Roe

Duff

McGrouther

Lees

. The Manchester short splint: a change to splinting practice in the rehabilitation of zone II flexor tendon repairs. Hand Ther. 2014, 19: 47–53.

18.

Pollock

Sieg

Baechler

Scher

Zimmerman

Dubin

. Radiographic evaluation of the modified Brunelli technique versus the Blatt capsulodesis for scapholunate dissociation in a cadaver model. J Hand Surg Am. 2010, 35: 1589–98.

19.

Sandow

McMahon

. Active mobilisation following single cross grasp four-strand flexor tenorrhaphy (Adelaide repair). J Hand Surg Eur. 2011, 36: 467–75.

20.

Savage

. The influence of wrist position on the minimum force required for active movement of the interphalangeal joints. J Hand Surg Br. 1988, 13: 262–8.

21.

Savage

Risitano

. Flexor tendon repair using a “six strand” method of repair and early active mobilisation. J Hand Surg Br. 1989, 14: 396–9.

22.

Tang

. Indications, methods, postoperative motion and outcome evaluation of primary flexor tendon repairs in Zone 2. J Hand Surg Eur. 2007, 32: 118–29.

23.

Tang

. Recent evolutions in flexor tendon repairs and rehabilitation. J Hand Surg Eur. 2018a, 43: 469–73.

24.

Tang

. New developments are improving flexor tendon repair. Plast Reconstr Surg. 2018b, 141: 1427–37.

25.

Tang

Giddins

. Why and how to report surgeons’ levels of expertise. J Hand Surg Eur. 2016, 41: 365–6.

26.

Wehbé

Hunter

. Flexor tendon gliding in the hand. Part I. In vivo excursions. J Hand Surg Am. 1985, 10: 570–4.

27.

Zhao

Amadio

Berglund

Zobitz

. A new testing device for measuring gliding resistance and work of flexion in a digit. J Biomech. 2003, 36: 295–9.

28.

Zhao

Amadio

Momose

Couvreur

Zobitz

. Effect of synergistic wrist motion on adhesion formation after repair of partial flexor digitorum profundus tendon lacerations in a canine model in vivo. J Bone Joint Surg Am. 2002, 84: 78–84.