Ulnar stress reaction in an axillary crutch user

Abstract

Ulnar stress fractures have been reported in athletes performing repetitive, high-impact activities, such as baseball pitchers and gymnasts. Crutch-assisted walking also results in cyclical forearm loading. We report the first case of ulnar stress reaction due to axillary crutch use. A 23-year-old right-handed woman experienced right forearm pain and imaging confirmed a right ulnar stress injury. The patient was also found to have mild hypercortisolism, low bone mass and vitamin D deficiency. Crutches were discontinued and physical therapy to normalise weight bearing through the left leg was prescribed. The patient’s right forearm symptoms resolved and she was started on oral vitamin D supplementation. Axillary crutch use may result in ulnar stress injury, particularly in vulnerable populations. The addition of an upper extremity injury to someone with impaired mobility may compound disability. As such, clinicians should be aware of the clinical presentation of ulnar stress fractures in the long-term axillary crutch user.

Background

Upper extremity stress fractures are rare, comprising only 3% of all injuries to American high school athletes.¹ These injuries arise from either repetitive high-impact loading at tendinous insertions on bone or from direct axial weight bearing.² Stress fractures of the ulnar diaphysis due to repetitive muscular loading at tendinous attachment sites have been reported in volleyball players, tennis players, softball pitchers and golfers. Yoga, cheerleading and gymnastics have been implicated in ulnar diaphyseal injuries due to repetitive axial loading.³ Crutch-assisted gait likely results in both repetitive musculotendinous loading and impact loading of the forearm. Forearm crutches, which are used more commonly in Europe, distribute these loads through the forearms and wrists.⁴ There have been four reported cases of ulnar stress injuries in forearm crutch users.^5–8 In contrast, axillary crutches, which are used more commonly in Canada and the USA, are thought to distribute these loads through the shoulder muscles and wrist joints.⁹ We present the first case of an ulnar diaphyseal stress reaction in a patient using axillary crutches. The addition of an upper extremity injury to someone who already has lower extremity impairment may compound disability and impair quality of life. We review risk factors for bone stress injury and review why a high index of suspicion for crutch-related ulnar stress injuries is necessary.

Case presentation

A 23-year-old right-handed Caucasian woman suffered a slip and fall on ice, resulting in an undisplaced S3 fracture, mild T7 compression fracture and undisplaced left radial head fracture. At the time, she was on no medications or supplements. Her previous medical history was significant for bilateral developmental dysplasia of the hip that resolved with non-operative treatment in infancy. At age 12, she had suffered a right distal radius fracture due to a fall onto an outstretched hand that was managed with casting. She did not smoke or drink alcohol. After the fall, all fractures were managed non-operatively. After 4 weeks of bed rest due to the sacral fracture, the patient began using bilateral axillary crutches due to left buttock pain.

The patient was referred to Physical Medicine and Rehabilitation for management of widespread chronic pain following the accident. When seen for initial consultation at 17 months postfall, the patient had gained 40 pounds and was taking amitriptyline 125 mg p.o./day. She reported occasionally experiencing right proximal medial forearm discomfort that had started about 12 months postfall. However, her mid-back and left greater trochanter were more painful than the forearm. Family history was significant for primary hyperparathyroidism in the patient’s mother and cervical cancer in the paternal grandmother. There was no family history of osteoporosis. On examination, the patient was tender over the right proximal forearm flexors and proximal medial ulna, with no overlying warmth or erythema. There was no elbow effusion or radial head tenderness. In standing without crutches, the patient disproportionately bore weight through the right lower extremity in order to protect her painful left leg. When ambulating with bilateral crutches, she had an asymmetric gait with left-sided antalgia. Her axillary crutches were found to be 3.5 cm too long bilaterally.¹⁰ The remainder of her examination resulted in the following diagnoses: left trochanteric pain syndrome, left iliotibial band dysfunction, chronic myofascial thoracic paraspinal-based pain and right ulnar diaphyseal stress injury.

Investigations

At 10 months postfall, the patient had undergone a technetium-99 whole body bone scan with bone flow and blood pool imaging and single-photon emission CT (SPECT)/CT of the thoracic spine due to persistent mid-thoracic pain. Mild activity was noted at T7 on the delayed planar and SPECT/CT images. The lumbar spine, sacroiliac and hip joints were normal. However, increased activity in the right proximal ulna was incidentally noted (figure 1A). Radiographs of the right forearm at that time were normal. A repeated bone scan performed 16 months postfall due to ongoing back pain showed no abnormalities in the thoracic or lumbar spine. However, there was even greater activity noted in the right ulnar diaphysis compared with the previous study (figure 1B). Repeated right forearm radiographs showed new periosteal thickening in the proximal ulnar shaft corresponding to the area of increased uptake on the bone scan, in keeping with stress reaction (figure 2).

Figure 1.

(A) Technetium-99 whole body bone scan performed at 10 months postfall demonstrated increased uptake in the right proximal ulnar diaphysis (arrow) consistent with bone stress reaction. (B) A repeated scan done 16 months postfall showed even more uptake (arrow) in the same region.

Figure 2.

(A) Anteroposterior and (B) cross-table lateral radiographs of the right forearm at 16 months postfall demonstrated ulnar diaphyseal periosteal thickening (arrows) corresponding to the area of increased bone scan activity. This periosteal reaction had not been present on forearm radiographs (not shown) obtained at 10 months postfall.

Given the patient’s history of multiple fractures prior to the ulnar stress injury, a workup for metabolic, endocrine and nutritional conditions was performed (table 1). The patient was found to have mild hypercortisolism, low serum vitamin D level and low bone mineral density.

Table 1.

Investigations for secondary causes of bone insufficiency

Test	Value	Abnormal?	Normal value
Serum
Alkaline phosphatase	57 U/L	N
Beta C-terminal telopeptide	185 ng/L	N
Calcium	2.38 mmol/L	N
Parathyroid hormone	24 ng/L	N
AM cortisol	824 nmol/L	High	170–500 nmol/L
Dehydroepiandrosterone sulfate	8.9 umol/L	N
Prolactin	16 ug/L	N
Testosterone	1.5 nmol/L	N
Thyroid stimulating hormone	2.03 mIU/L	N
25-hydroxy-vitamin D	57 nmol/L	Low	80–200 nmol/L
Urine
24 hours cortisol	135.6 nmol/day	N
Bone densitometry	Z-score (BMD)
Lumbar spine	−1.3 (1.021 g/cm2)	N
Left femoral neck	−2.1 (0.749 g/cm2)	Low	Z-score <−2.0
Left femur total	−2.6 (0.681 g/cm2)	Low	Z-score <−2.0

Abnormal values are indicated by bold and italicization.

AM, morning; BMD, bone mineral density; N, normal.

Differential diagnosis

A young woman presenting with insidious onset forearm pain after prolonged crutch use may have medial or lateral epicondylopathy, proximal radioulnar joint injury, wrist or finger flexor tendinopathy or bone stress reaction of the radius or ulna. We were most suspicious for bone pathology given the number of fractures the patient had endured at such a young age, particularly from a fall from standing. Underlying medical conditions such as hypercortisolism,¹¹ osteoporosis,¹² nutritional deficiencies and altered menstruation¹³ make bone more vulnerable to mechanical stress. Although rare, an unexplained stress fracture in a young person can also be seen in malignancy.¹⁴ This was felt to be less likely given the absence of fever, chills, weight loss or night pain as well as the very gradual onset of pain in association with crutch use. Although the patient may have sustained trauma to the ulnar diaphysis with her initial fall, this was felt to be unlikely as her forearm radiographs at 10 months postfall were normal. Traumatic ulnar diaphyseal fractures also typically result from a direct blow to the ulna, such as from being hit by a bat or nightstick, which was not the mechanism of injury in our patient’s case.¹⁵ Finally, the location of the periosteal reaction, at the proximal anterior ulna, where the flexor digitorum profundus originates, also suggests that repeated tendinous stress on the bone resulted in the injury seen.⁵

Treatment

We advised the patient to stop using axillary crutches and recommended using hiking poles only if absolutely needed to normalise gait symmetry and minimise ulnar loading. A physiotherapy prescription to address the left trochanteric pain syndrome and improve gait and balance was provided. We referred the patient to a dietician and recommended increasing her dietary calcium intake to 1200 mg/day.¹⁶ Endocrinology was consulted and the patient was started on ergocalciferol 50 000 international units/day for 8 weeks, followed by lifelong cholecalciferol 800 international units/day.

Outcome and follow-up

When seen in follow-up, 2 months later, the patient had abandoned all walking aids and had a more symmetric gait. Her right forearm pain and tenderness had resolved. Endocrinology recommended repeating the bone mineral density in 3 years. By 9 months, the patient’s greater trochanteric pain syndrome and iliotibial band dysfunction had resolved, and her thoracic pain had improved.

Discussion

There have been three reported cases of ulnar stress fracture (one bilateral and two unilateral)^6–8 and one case of unilateral ulnar stress reaction⁵ related to forearm crutch use. A single case of unilateral ulnar stress fracture in a cane user has also been reported.¹⁷ This is the first reported case of an ulnar stress reaction in an axillary crutch user.

Normally, the axillary crutch handle experiences 44% body weight forces during swing-through gait.¹⁸ This high-impact loading likely caused our patient’s stress injury. Axial loading of the wrist typically results in higher loads borne by the proximal than the distal ulna,¹⁹ which may explain why the proximal ulna is more vulnerable to stress fracture with crutch use. Our patient’s disproportionate weight bearing to protect her painful left lower extremity likely also resulted in increased weight bearing through the right wrist, further increasing the load through the right ulna. Suarez et al⁷ similarly hypothesised that an asymmetric weight-bearing pattern caused a left ulnar stress fracture in an 11-year-old forearm crutch user trying to offload the right knee. Requejo et al⁴ also found that higher forces were experienced in the upper extremity that was contralateral to the weaker lower extremity in a bilateral forearm crutch user with a T12 incomplete spinal cord injury. Further studies investigating the influence of asymmetric lower extremity weight bearing on upper extremity forces in crutch users are needed.

Our patient also reported a 40-pound weight gain after her fall, which may have increased mechanical bone loading and thus risk of stress injury. Obesity was identified as a risk factor in a 60-year-old woman who suffered an ulnar stress fracture after 15 months of forearm crutch use.⁶ A cross-sectional study of 53 walking aid users also found increased incidence of device-related injury in obese individuals.²⁰ Obesity has been linked to reduced osteoblast differentiation, which may increase the vulnerability of bone to injury.²¹ As such, heightened suspicion of stress fracture may be warranted in the obese axillary crutch user who presents with upper extremity pain, particularly as stress fractures in other populations are often initially missed.³

Hand dominance may also have played a role, as our patient was right-handed and suffered a right-sided stress fracture. Handedness was not reported in four of the five walking aid-related ulnar stress injuries in the literature. However, a left-handed woman suffered a left ulna stress fracture with bilateral forearm crutch use,⁶ which may support this theory. The influence of hand dominance in differential loading when using bilateral crutches has not been reported and would also be an important avenue for future research.

Finally, excessive tensile stresses through tendinous attachments to bone may have contributed to our patient’s stress fracture. Amin et al⁵ proposed that a 21-year-old female forearm crutch user suffered a right ulnar diaphyseal stress fracture due to excessive firing of the flexor digitorum profundus, a secondary stabiliser of the wrist when the fingers are clenched such as when they are around a crutch handle. Abductor pollicis longus, flexor carpi ulnaris and flexor digitorum profundus originate at the proximal ulnar diaphysis. Based on the location of our patient’s fracture, overfiring of all three of these muscles may have contributed. Wrist motion and forearm muscle electromyographic activity during axillary crutch-assisted gait have not been reported. These would be important areas of future study in order to better understand the biomechanical consequences of axillary crutch-assisted gait on the forearm and wrist. In addition, in many sports, factors such as fatigue, poor technique and muscle imbalance contribute to stress fractures.²² As such, clinicians might consider instructing patients who will be using axillary crutches to strengthen the scapular stabilisers and stretch the wrist and finger flexors in order to minimise muscular loading through the forearm.

Treatment of stress fractures generally involves several weeks of relative rest from aggravating activities depending on clinical and imaging severity.² For the ulnar stress injuries in other walking aid users, treatment included instructing two of the users to stop using forearm crutches.^{5 7} The fractures were casted in two of the four cases.^{7 8} In a third osteopenic patient with a displaced fracture, surgical fixation was used.¹⁷ Based on our patient’s imaging and physical examination, casting and operative management were not indicated.

This is the sixth reported ulnar stress injury associated with walking aid use and the first reported case of ulnar stress injury in an axillary crutch user. The case illustrates that high index of suspicion of upper extremity stress fracture in walking aid users is necessary among physicians, surgeons and therapists, as early intervention may prevent progression from stress reaction to stress fracture. Obesity, asymmetric crutch use, improper reliance on forearm muscles instead of scapular stabilisers during the gait cycle and metabolic bone factors may contribute to increased risk of ulnar stress injury in the axillary crutch user. Clinicians should be aware of these risk factors and ensure patients are properly trained on crutch-assisted gait in order to minimise the risk of secondary crutch-related upper extremity injury.

Patient’s perspective.

You are ‘a unique case’, a common phrase I came to know all too well; a minor fall led to various bone fractures changing my life forever. After months of therapy and minimal improvement, I had the opportunity to see various specialists including orthopaedic surgeons and sports medicine doctors who ultimately pointed me in the direction of a physiatrist. On the initial visit, my physiatrist immediately requested lab testing to investigate possible underlining issues. The lab results discovered that I have a vitamin deficiency and high cortisol levels. On this discovery, my physiatrist requested I see an endocrinologist and the osteoporosis clinic due to the possible link to numerous bone fractures. As a result, the osteoporosis and the endocrinologist physicians were able to send me for a bone scan and further testing, diagnosing me with osteopenia and vitamin deficiencies. With the help of these physicians, I have received a bone diagnosis, my vitamin levels are now being monitored, I have been referred to a dietitian to work around my dietary needs, and further investigation of my high cortisol and vitamin deficiencies will all contribute to answers that have been left unanswered with the hopes of improving my overall bone health and solving my ‘unique case’.

Learning points.

• Prolonged axillary crutch use may result in proximal ulnar stress fracture.

• Underlying medical conditions such as hypercortisolism and low vitamin D may increase the risk of stress fracture.

• Stress fracture risk may also be increased by mechanical factors such as asymmetric weight bearing, obesity and poorly fit crutches.

• Clinicians should consider stress fracture in the differential diagnosis of a walking aid user with upper extremity pain.