# Upper Limb Orthotics/Rupture of the Finger Flexor Annular Pulley A2

Abstract here...

## Case Study Description

A healthy 28 year old woman experiences a ‘pop’ sound in the ring finger of her right hand on a rock climbing adventure. She is a highly experienced climber who reports no previous serious finger injuries. She ceases climbing immediately and seeks treatment on the same day. An MRI shows that she has a complete rupture of the finger flexor annular pulley A2. The treating doctor classifies the injury as Grade 3, and refers her to an orthotist for a thermoplastic splint. The patient aims to be able to return to rock climbing in time for a competition in two months.

## Written information
### Rupture of the Finger Flexor Annular Pulley

The phalanges of the hand are capable of many precision and strength grips. For rock climbers the ability to use the hands to grip small ledges and nooks is essential and can require them to adopt unusual grip positions. One of the most common injuries for rock climbers is a rupture or tear to one or more of the annular pulleys of the fingers (V. Schöffl, Hochholzer, Winkelmann, & Strecker, 2003). Repair of these injuries can be either surgical or conservative and depends upon what pulley is damaged and the degree of damage. Little evidence is available regarding the recommended orthotic management for this condition; however the epidemiological data, role of the annular pulleys in finger flexion and mechanism of injury are well documented.

### Epidemiology

The occurrence of injuries to the annular pulleys of the fingers was first documented in the 1980’s and the first substantial piece of research was published in the early 90’s, in accordance with an increase in the popularity of the rock climbing sport (V. Schöffl et al., 2003). A prospective study over four years from 1998 in Germany found that 40% of rock climbers with upper limb injuries had damaged their fingers, and half of these were ruptures or strains to the annular pulleys, making annular pulley injuries the most common upper limb grievance for rock climbers (V. Schöffl et al., 2003). A retrospective study of South African rock climbers in 1994 showed similar figures, with 44.3% of all rock climbing injuries -including trunk and lower extremities -being isolated to the hand (Holtzhausen & Noakes, 1996). A more recent study of rock climbers in the United Kingdom found 35% of upper limb injuries were to the fingers (Jones, Asghar, & Llewellyn, 2008), suggesting that the epidemiology of rock climbing injuries is similar in various geographical locations. Studies on the occurrence of pulley injuries in non-climbers have found their subjects in bowlers, professional baseball pitchers and people lifting heavy objects (Lourie, Hamby, Raasch, Chandler, & Porter, 2011; Patel, Schucany, Toye, & Ortinau, 2012; V. Schöffl et al., 2003).

### Role of Annular Pulleys in Finger Flexion

The individual phalanges of the hand have the capability of flexing at three joints: the metacarpal-phalangeal, the proximal inter-phalangeal (PIP) and the distal inter-phalangeal (DIP). A number of muscles are involved in this process, but in order to prevent them from bowstringing a digital flexor sheath is needed. It is comprised of two constituents- a membranous component and a pulley component, of which the pulley component is relevant to the rock climbing injury being investigated. The pulleys are composed of fibrous tissues which wrap around the flexor tendons, with the membranous component of the sheath being visible between the pulleys (Doyle, 2001). There are five annular pulleys and three cruciform pulleys, numbered from proximal to distal. The annular pulley A2 is positioned between the metacarpal-phalangeal joint and the PIP joint. The role of the annular pulleys is to prevent bowstringing and allow for force transferral (Schoffl, Einwag, Strecker, & Schoffl, 2006).
* Approximation of the Five Annular Pulleys and Three Cruciate Pulleys of the Fingers. Based upon the research by Doyle (2001). Image: Rebecca Kelly 2014.

### Mechanism of Injury

The mechanism of injury has been well investigated in rock climbers. The crimp grip is one of two common grips used by rock climbers, usually when contact between the fingers and a small ledge or rock needs to be at its closest (Marco, Sharkey, Smith, & Zissimos, 1998). The grip involves the DIP joint being hyper-extended and the PIP joint being flexed to 90-100° (Crowley, 2012; Marco et al., 1998). It allows for the maximum amount of power to be generated by flexor digitorum profundus (FDP) and for maximum force transferral over the A4 and A2 pulleys (Crowley, 2012; Holtzhausen & Noakes, 1996). There is some disagreement regarding the maximum possible load upon an A2 before pulley rupture occurs when using the crimp grip. It has been calculated at 375N (Tang, 1994) to an estimation as high as 450N based upon a case study (Bollen, 1990). A more recent study suggested a figure of 400N, but conceded that the maximum force could be higher in experienced rock climbers (Schweizer, 2001).
An annular pulley injury typically occurs when a climber is in the crimp position and experiences a sudden loss of footing (Bollen, 1990) or when performing a difficult move (V. Schöffl et al., 2003). Eccentrically loading the annular pulleys is also associated with a higher rate of injury (I. Schöffl et al., 2009). This is due to the friction created between the FDP tendon and the pulley. However, the friction also increases the holding ability of the flexor muscles, so it can be an advantage to the climbers (I. Schöffl et al., 2009).
* Saggital plane view of the crimp grip commonly used in rock climbing. Image: Rebecca Kelly 2014.
* Superior view of the crimp grip. Image: Rebecca Kelly 2014.
* Coronal plane view of the crimp grip. Image: Rebecca Kelly 2014.

### Grading System for Annular pulley Injuries

The diagnosis of annular pulley injuries is recommended to be carried out using an MRI or CT scan, or possibly an ultrasound (Kubiak, Klugman, & Bosco, 2006) though some research argues that ultrasonography is also highly reliable (Klauser et al., 2002). Once the injured pulley has been identified it can be classified based on its severity into four categories (V. Schöffl et al., 2003). The type of injury- strain or rupture- and its pulley number allow it to be defined as grade 1-4. For instance, a complete rupture of A2 is classified as Grade 3, but a partial rupture of A2 is Grade 2 (V. Schöffl et al., 2003).
| Grade | 1 | 2 | 3 | 4 |
| Injury Description | Pulley strain | Complete Rupture A4 or Partial A2, A3 | Complete Rupture A2, A3 | Multiple ruptures, or single rupture with damage to lumbricalis muscle or tendon |
| Recommended Treatment | Conservative | Conservative | Conservative | Surgery |
Table: Grading System and Treatment Options. Table adapted from Schloff et al (2003).

### Recommended Treatment

Often at the onset of injury, an audible ‘pop’ is heard, notifying the climber that something is wrong with their finger (Holtzhausen & Noakes, 1996; Kubiak et al., 2006; V. Schöffl et al., 2003). It is recommended that they cease climbing immediately and seek treatment from a health professional, commonly a doctor or physiotherapist (Jones et al., 2008). A pulley injury that is not severe enough to be categorized as Grade 4 and operated upon is therefore best treated by conservative methods.
The use of anti-inflammatory drugs, immobilisation and elevation is recommended for acute injuries (V. Schöffl et al., 2003). After the removal of the immediate immobilization device, functional therapy should begin. When climbing, taping is recommended for the next 3-6 months as it can take this long for strength to return to normal in the pulley (V. Schöffl et al., 2003; Schoffl et al., 2006). A H type configuration of taping is the most effective as it decreases the tendon-bone distance (I. Schöffl, Einwag, Strecker, Hennig, & Schöffl, 2007).

### Orthotic treatment options

Conservative management of annular pulley ruptures is recommended for grades 1-3, with buddy taping for 0-10 days for grades 1 and 2, and a soft cast ring or palmar thermoplastic splint for 14 days for grade 3 (V. Schöffl et al., 2003). The splint should be removed after 10-14 days so as to avoid the possibility of a flexion contracture developing. There is little evidence regarding the efficacy of various splint designs for the immobilization of the digit and it appears that the design of the thermoplastic splint is at the discretion of the treating health professional. The splint does need to completely immobilize the joint, and biomechanical research has suggested that a three or four-point force system is effective. The hand is best positioned with slight flexion of the metacarpal-phalangeal and PIP joints (Holtzhausen & Noakes, 1996).
The use of finger rings to prevent flexion/ extension is an alternative to the thermoplastic splint. Commonly found as pre-fabricated devices, the metal structure applies a three point force system to the finger that can be manipulated by the clinician using pliers. A metal ring specifically for A2 pulley injuries has been designed and is sold commercially. It works to prevent bowstringing of the flexor tendon and is also available in a hinged version for swollen or large PIP joints (SIRIS Ring Splints, 2014). This device would be useful when clinical bowstringing is an issue, but it does not immobilise the pulley for repair. No pre-fabricated device exists specifically to immobilise the A2 pulley, however a design similar to that used for PIP joint injuries would be sufficient, as it prevents flexion (Trulife, 2014, p. 26).
* A Force Analysis of a Metal Finger Ring Orthosis for Preventing Flexion. L-R: Posterior Coronal, Saggital and Anterior Coronal. Design and Image: Rebecca Kelly 2014.

### Comparison of orthotic treatment options

There have been no clinical studies published that compare the effectiveness of finger rings to thermoplastic splints for the immobilisation of the finger. Provided that the device achieves the orthotic aim of immobilisation, it would be suitable for a patient. The ring design has the added bonus of great cosmesis, however it is assumed that most doctors/physiotherapists or orthotists do not keep a prefabricated pulley ring or flexion prevention ring in stock and so would have to order one in for their patient. This of course would take delivery time and as the aim is to immobilise the joint immediately, a custom-made thermoplastic splint may be a faster and easier solution. Aside from this argument of convenience, there is no other supporting information for choosing one device over the other.
There is however, a large body of research that has determined when surgery is a better option than conservative management of these injuries. Surgical treatment is recommended for grade 4 annular pulley injuries where there is involvement of two or more pulleys or damage to the lumbricalis muscle or ligament (V. Schöffl et al., 2003). Surgical reconstruction for all open pulley injuries was recommended for a time but research on the strength of surgically repaired versus conservatively managed injuries suggested no long term differences, except for grade 4 injuries (Schoffl et al., 2006). There is no current evidence on the outcomes for operative vs. non-operative measures (Kubiak et al., 2006), however one study on outcome measures found that five patients with grade four injuries who were treated conservatively regained full strength in their finger (Schoffl et al., 2006), suggesting that operative methods for grade four injuries are not always necessary. It is concluded that pulley injuries of grades 1-3 should be managed conservatively, unless there is a persistent strength deficit, and grade 4 injuries should be evaluated for surgical reconstruction (Schoffl et al., 2006).
* Summary of Evidence for Justification of Prescription for Case Study
* Orthosis should immobolise the soft tissue over the annular pulley
* Finger should be in slight flexion
* Worn for 10-14 days
* Only surgically fixed if there is a persistent strength deficit

### Overview

Although injuries to the annular pulleys of the fingers are isolated to a very specific population, the impact of this injury upon a patient’s ability to undertake the sport they enjoy is detrimental to their wellbeing. Research into the epidemiology, role of the pulleys, mechanisms of injury, proposed grading systems and surgical methods for repair have provided useful information for climbers and clinicians. However, the absence of information on the efficacy of orthotic splints for immobilisation highlights a lack of evidence in the non-surgical treatment stream. A common splint design should be readily available for health professionals to access if they need to immobilise an annular pulley injury.