Ulnar impaction syndrome

2018 Billy Vunipola holds his wrist after sustaining an injury Action Images via Reuters/Andrew Boyers

Ulnar impaction syndrome (UIS – sometimes called ulnocarpal abutment) is a condition in which the ulna of the forearm is too long relative to the radius, resulting in excessive loading on the ulnar side of the wrist. In most cases, this condition is congenital and present from birth, but sometimes ulnar impaction syndrome can be secondary to shortening of the radius after a fracture. Regardless of the origin, however, most patients only become symptomatic in later life, when accumulated and degenerative wear and tear takes its toll on the ligaments and cartilage, causing ulnar-sided wrist pain. For athletes whose sports involve loading of the upper limbs, this can be a particular problem.

Wrist stability

To fully appreciate how ulnar impaction can result in ulnar-sided wrist pain, it helps to understand the structure and role of the triangular fibrocartilage complex (TFCC) and loading across the ulnocarpal joint (see figure 1). Ulnar-sided wrist stability is enhanced via the TFCC, an arrangement o f ligaments and fibrocartilage originating from the sigmoid notch on ulnar border of the radius and inserting into the base of the ulnar styloid and fovea of the ulnar head.

Studies have shown that there is a direct relationship between increasing ulnar length (relative to radius length) and increased force transmission across the TFCC. In a neutral wrist, the ulnacarpal joint takes around 18% of the total load applied to the wrist (with the radiocarpal joint taking the other 82% or so). However, a positive variance of 2mm will increase the ulnocarpal load to approximately 40%, while an increased dorsal tilt due to previous injury of the radius can further increase the ulnar load to 65% of total load transferred^(1,2). In addition, thinning of the articular disc (which is common with increased ulnar length) also increases the risk of TFCC wear and perforation⁽³⁾.

While it’s most commonly associated with congenital or acquired positive ulnar variance, UIS can also occur in ulnar neutral or even negative ulnar variance wrists^(4,5). Athletes performing power and/or gripping tasks associated with axial loading and rotation are particularly at risk of ulnar impaction syndrome because of the ‘dynamic ulnar variance’ that occurs during tasks requiring maximal grip and pronation⁽⁶⁾. More generally, athletic events that place repetitive compression and rotation demands on the upper limbs increase the risk of ulnar impaction via traumatic development.

Although symptoms of UIS rarely present in younger athletes, the risk for these symptoms in later life may be increased by events during these formative years. One reason for this is that distal radius fractures are the most frequently occurring fracture in children under the age of sixteen. Research shows that when significant radial shortening (5mm or more) occurs as a result of such fractures, there’s a greatly increased risk of long-term functional impairment⁽⁷⁾. Moreover, even in the absence of distal radius fractures, we know that submitting an immature wrist to prolonged compression and repetitive micro-trauma has can lead to a premature arrest of radial growth plate and subsequent ulnar overgrowth, which of course greatly increases the risk of UIS in later years^(8,9).

Symptoms of ulnar impaction syndrome

The development of UIS leads to the progressive degeneration and increased abutment of the distal ulna or TFCC against the ulnar carpus. Although any athlete can suffer from this condition, gymnasts, boxers, racquet and stick sport athletes are particularly at risk, with symptoms of pain particularly occurring during wrist rotation. It’s important to understand, however, that the development of this condition is not always linear; the load-bearing demand placed on the TFCC means that there’s an increased susceptibility towards an acute traumatic injury, as well as the secondary degenerative concerns implicated with ulnar impaction⁽¹⁰⁾.

Common symptoms of ulnar impaction syndrome include the following:

• Pain (especially during rotation), aggravated with activity and (generally) relieved with rest;
• Painful clicking or locking during pronation and supination;
• Occasional edema;
• Decreased wrist range of motion;
• Decreased forearm rotation;
• Tenderness to palpation dorsally, just distal to the ulnar head and just volar to the ulnar styloid process;
• All of the above tend to be aggravated by forceful grip, forearm pronation, and ulnar deviation.

What tends to distinguish chronic ulnar impaction syndrome from an acute TFCC injury (which may itself be made more likely by ulnar impaction) is the insidious, progressive nature of the pain, which gradually limits range of motion, grip strength, and performance. In 1981, Palmer and Werner introduced (a now widely used) classification system to help clinicians determine whether a TFCC injury is primarily progressive and degenerative or acute in nature (or indeed both). This is shown in Box 1.

Figure 1: Diagrammatic representation of the ulnocarpal joint and triangular fibrocartilage complex (TFCC)

Diagnosis

When attempting to make a diagnosis of UIS, a comprehensive wrist examination is needed, together with a detailed patient history (for example, has the patient suffered a radius fracture in the past?). Unfortunately, however, there’s no single clinical test that can fully diagnose UIS, not least because many tests performed in the clinic are inconclusive as to whether TFCC-related pain is acute or degenerative in nature (see Box 1). For this reason, diagnostic imaging (such as MRI) should be performed to support the findings from the clinical exam. Having said this, the clinician can gain valuable supporting evidence from a thorough examination that includes the following:

On palpation, is there:

• Tenderness dorsally just distal to ulnar head?
• Tenderness just volar to the ulnar styloid process?
• Positive ulnar variance, while static or dynamic?

Do range of motion tests show:

• Painful passive ulnar deviation and forceful pronation?
• Decreased flexion, extension, radial & ulnar deviation?

Does a strength measurement reveal:

• Decreased grip strength compared to the unaffected wrist when using dynamometer?

* L-T = lunotriquetral ligament

Is the Gripping Rotary Impaction Test (GRIT) positive? (see box 2)

The ulnocarpal stress test described in Box 2 was originally introduced by Nakamura and his colleagues⁽¹³⁾. In the authors’ original study, 33 of 45 patients (73%) with positive ulnocarpal stress test results demonstrated positive ulnar variance of 1mm or more on the affected wrist. In the 33 patients who had a positive ulnar variance, 19 (58%) were confirmed as suffering from class II TFCC lesions resulting from ulnocarpal impaction. The majority of these patients suffered a spontaneous onset of pain, and were diagnosed with class IIB lesions involving TFCC wear with lunate and/or ulnar chondromalacia (see box 1). More generally , a detailed history of spontaneous ulnar sided wrist pain combined with provocative testing should prompt the astute clinician to seek further evaluation using imaging.

Is an ulnocarpal stress test positive?

Treatment options

When treating athletes with UIS, earlier is better; studies show that early diagnosis and intervention may significantly reduce the risk of long-term disability and injury progression^(14,15). Conservative treatment should be attempted before surgery and can include immobilisation or limiting aggravating movements such as pronation, gripping and ulnar deviation for 6-12 weeks. Following immobilisation/ restriction, other conservative treatment options include, non-steroidal antiinflammatories (NSAIDs) and corticosteroid injections.

However, while conservative treatments such as anti-inflammatories combined with immobilisation or restricting range of movement may be reasonably effective for the general population, they are often insufficient for athletes because they don’t address the fundamental biomechanical factors that predispose the athlete to UIS. Therefore, when conservative management fails to produce a significant improvement, evidence suggests that surgery is indicated^(16,17).

When surgery is required, many athletes opt to postpone surgery until the close of the season, allowing recovery from surgery to take place during the off-season. In terms of surgical options, this is best determined by the surgeon after thorough radiologic screening. These options may include:

• Ulnar shortening osteotomy – the ulna is shortened by 2-3mm of shaft and fixated with a tubular or standard compression plate. This option is indicated when there is ulnar wrist pain worsened by rotation and ulnar deviation, a positive ulnocarpal stress test, and positive ulnar variance with or without cystic changes.
• Arthroscopic wafer procedure – this procedure uses arthroscopy to debride the central triangular fibrocartilage complex tear, along with debridement of the distal pole of the ulna causing the impaction. The debridement of the ulna is performed to the degree at which the patient is ulnar neutral or slightly ulnar negative. The benefit of this procedure is that open surgery is not required, and recovery is faster. However, if the ulnar variance is greater than +4mm, this option is not suitable.

Following surgery, athletes can expect to undergo at least 3-4 months or recovery/ rehab. Depending on the surgical procedure and individual response, this period will typically consist of:

• Weeks 1 and 2 – control pain and swelling using ice/anti-inflammatory medication. Wearing a sugar-tong splint or long-arm cast to protect the surgical site while maintaining as much range of movement (ROM) in unaffected joints.
• Weeks 3 to 6 – Protect surgical site and continue to maintain ROM in unaffected joints. Switch to a removable elbowhinged splint or wrist cock-up brace. Try to increase elbow & wrist ROM. Attend to scar management.
• Weeks 7 and 8 – Switch to removable splint worn at night. Progress to full ROM exercise for elbow & wrist and introduce isometric elbow flexion/extension and supination/pronation.
• Weeks 9 onwards – continue with stretching and mobilisation. Introduce low-load resistance exercises to develop strength.

Athletes should expect a return to full activity around 3-4 months after an arthroscopic wafer procedure, and around six months after an ulnar shortening osteotomy.

Summary

Although ulnar impaction syndrome is often congenital in its aetiology, advancing years and athletic activity can combine to produce progressively more debilitating symptoms in athletes. For the clinician, early diagnosis is desirable but not always straightforward; even if range of movement tests strongly suggest UIS, imaging will be required to determine whether TFCC-related pain is acute or degenerative in nature, which in turn affects treatment options. Unless the UIS i s mild or the athlete i s able to significantly modify his/her activity, it may be that conservative treatment is ineffective and surgery is required. The surgical options will vary according to the individual but in many cases, the longerterm outcomes are favourable despite the requirement for extended recovery and rehab after surgery.

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