The ‘Cruciform Test’: A diagnostic tool to detect pectoralis major rupture

Introduction

Pectoralis major (PM) muscle rupture is a rare but severe injury that can benefit from prompt diagnosis and appropriate surgical management. As a result, it is crucial to establish the presence of a tear at the earliest opportunity and gather sufficient diagnostic information to decide whether or not operative repair is indicated. However, it remains the case that there is no single, reliable, established test for PM rupture. An index has been devised ¹ in an attempt to quantify the presence and structural significance of PM tears, but it is relatively complex and not widely used. The incidence of this injury has steadily risen in recent years, possibly due to greater participation in contact and collision sport, weightlifting and the use of anabolic-androgenic steroids.^2–6 We describe a new clinical test for detection of PM rupture, and review our experience of using this test to assess both amateur and professional athletes in a clinical setting.

The injury tends to occur while lifting heavy weights (classically during ‘bench press’, especially more than 100 kg) or during contact sports and other high-risk activities including rugby, American football, and martial arts.^7–10 Typical patients therefore include athletes, weight-lifters and military personnel^11,12 and there exists a need for a simple test that can be applied as part of a pitch-side assessment (or during subsequent examination in clinic). In the majority of cases, it is the deep (sternal) head of the muscle that is injured.^1,3,4,7

Diagnosis is generally made through a combination of history taking, physical examination and specific imaging. PM rupture usually occurs when lifting particularly heavy weights in resistance training or from sudden, eccentric strain on the muscle with the arm abducted and externally rotated.^7–9,13 Patients often describe a classical tearing sensation or “pop” felt in the shoulder area, followed by shoulder pain and weakness. On clinical examination, there may be bruising along the anterolateral chest wall or upper arm (as seen in Figure 2), as well as loss of the anterior axillary fold and bunching of the pectoralis major over the anterior thorax. This is caused by retraction of the muscle belly medially and may lead to a drop in nipple height relative to the unaffected side. This bunching can be clearly seen on the patient's right side in Figure 3, while the intact pectoralis major on the left side can be seen to maintain its tension across the anterior axilla. In the same patient loss of the anterior axillary fold can be observed (Figure 2) relative to the uninjured side (Figure 1). The muscle defect and loss of contour of the axilla can be accentuated by resisted adduction of the shoulder, during which the patient may experience weakness or pain in the event of PM tear, and this is often used to aid diagnosis. Unfortunately, these signs are sometimes inconsistent and can be difficult to detect.

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Figure 1.

Normal left shoulder.

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Figure 2.

Right shoulder of same patient showing loss of PM tendon contour and bruising.

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Figure 3.

Asymmetry of muscle bulk with bunching of muscle belly on right indicating complete PM rupture.

We have found the Cruciform Test to be a valuable addition to our existing assessment as it demonstrates loss of function consistent with a PM tear, as well as being useful in the assessment of the integrity of the PM following surgical repair. Furthermore, the simplicity of this test allows it to be used immediately in a ‘pitch-side’ setting to inform decisions on management.

The Cruciform Test

The diagnosis of a PM tear depends on a careful history and physical examination; the ‘Cruciform Test’ should not replace these, but instead be used to complement a thorough assessment. The patient is first asked to lie supine with arms abducted to 90 degrees and elbows extended. In this position, the contour of the anterior axilla can be compared with the injured side, which will often demonstrate a thin falciform skin fold, due to traction on the clavicular head insertion onto the deep brachial fascia. Maintaining elbow extension and shoulder abduction, the patient is then asked to raise each arm in adduction toward the midline, as shown in Figure 4. Inability to lift the arm due to either pain or weakness indicates a positive test result, which supports the diagnosis of PM rupture, and visible retraction of the PM muscle belly or loss of the anterior axillary contour suggests complete rupture.

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Figure 4.

Cruciform test positive on the right (inability to lift the right arm with shoulder abducted and elbow extended).

In the example shown, the patient was able to perform this action without difficulty on the uninjured left side but was unable to lift the arm on the right side (the diagnosis of complete PM rupture was confirmed at surgery). The test can be repeated at follow-up after surgical repair and can demonstrate successful restoration of the muscle function.

Case series

We reviewed a series of PM injuries presenting since 2015 and managed by operative repair.

14 patients had a Cruciform Test performed and documented pre-operatively. This was positive in all cases and there were no patients in which the test was falsely positive. 8 patients out of the 14 (57%) were found to have a complete avulsion from the humerus, 5 (36%) had tears of the musculotendinous junction, and one patient had a combined avulsion from the humerus with a tear of the musculotendinous junction. There was no relationship between the test outcome and whether the tear was partial or complete.

In each case the repair was carried out via a deltopectoral approach, using a minimum of two unicortical titanium buttons (Arthrex Inc., Sheffield UK) placed at the lateral lip of the bicipital groove. Tears of the musculotendinous junction were managed by apposition of muscle to tendon using non-absorbable tapes deployed in a Kessler-type pattern.

5 patients were formally tested with the Cruciform Test at post-operative follow-up. All had previously had positive test results due to PM avulsion from the humerus but were now found to have negative tests and were able to lift the arm without difficulty. Of 9 patients with a documented description of the axillary contour, 6 (67%) had no remaining visible deformity post-operatively.

These consistent results in a relatively small series of patients suggest that the Cruciform Test may have potential as a clinical indicator of PM rupture. It may also have value as a confirmatory test for successful repair. The sample size reflects the rarity of this injury and limits any conclusions about the sensitivity and specificity of this test. A prospective, multi-centre trial is needed to critically evaluate the Cruciform Test on a larger scale.

Discussion

PM rupture is a severe injury and can be a challenging diagnosis to make. Prompt surgical management is essential to achieve a good outcome and facilitates a predictable return to activity. In order to give the greatest possible chance of success, priority must be placed on establishing the diagnosis early and facilitating surgical planning. There exists a need for a test that specifically identifies this injury and can also be used in both a clinical and a pitch-side environment. The Cruciform test is a simple yet valuable addition to existing diagnostic methods, as it illustrates the functional deficit associated with PM rupture.