Osteoporosis and BMD of the Proximal Humerus

Fig. 12.1

Anatomic reduction of osteopenic dislocated Neer type 4 impacted varus fracture of the proximal humerus with precontoured low profile fixed-angle locking plate and rotator cuff suture fixation

Delayed healing, non-union or simply implant cut out of the osteopenic bone (Fig. 12.2) mostly result due to prevention of dynamic bone contact caused by too rigid implants [11]. The high initial stiffness of rather rigid implants such as intramedullary nails and conventional plates leads to an early loosening and failure of the implant-bone interface under biomechanical cyclic loading [8]. In contrast implants with low stiffness and flexible characteristics such as the newer precontoured locking plates with suture augmentation (Fig. 12.1) minimize the peak stresses at the bone-implant interface [9]. This rather dynamic fixation construct makes them favorable especially for osteoporotic bone fractures in the elderly population [8]. However despite the experimentally shown strong evidence of local osteoporosis on fracture fixation implant anchorage in clinical studies this impact could not be directly reproduced yet. Lack of missing complication definitions, correct osteoporosis assessment and unclear inclusion criteria are thought to be responsible for this. Prospective studies directly examining the correlation between local BMD and the fixation failure risk are needed [5].

Fig. 12.2

Non-union with cranial screw cut out (indicated by arrows) of the osteopenic bone 9 months after anatomic proximal humerus fracture reduction

In order to manage surgical difficulties and avoid intra- and postoperative complications associated with osteoporosis sufficient preoperative assessment of the local bone quality is of utmost importance. This facilitates decision-making in the surgical treatment of patients sustaining proximal humerus fractures leading to better results.

Diagnostical Workup

The cornerstones of the preoperative fragility fracture workup are strictly based on a clinical setting where the time-span between initial radiological diagnosis of a proximal humerus fracture and its surgical treatment should be kept as short as possible in terms of morbidity and outcome [10].

Trauma Mechanism

A history of low-energy trauma, especially in the elderly population is highly suspicious for an underlying osteoporotic fracture genesis.

Evaluation of Osteoporosis Risks

Beside age and gender, in the medical history individual risk factors as diseases or medications, alcohol usage or smoking contributing to a low BMD should be questioned. As osteoporosis itself has no symptoms, one should focus on consequences of osteoporosis like an increased risk of fragility fractures. The skeletal history should include fractures and their healing in the past. Also chronic pain may be attributed to chronic fragility fractures.

In the physical examination signs of fragility fractures like a vertebral collapse, possibly presenting with sudden back pain or radicular pain, hump or loss of height as well as deformities of the extremities or an impaired mobility could serve as a warning signal. As osteoporosis is a recognized complication in specific diseases and disorders also external signs of these co-morbidities such as malnutrition, endocrine disorders like Cushing’s syndrome or hypogonadal states should be assessed.

Blood evaluation should be performed routinely for serum electrolytes, calcium, total protein, albumin, kidney and liver parameters and thyroid-stimulating hormone. For detection of potentially underlying causes of a low BMD in patients with a suspicious history it may be tailored enlarged with additional parameters such as phosphorus, magnesium, intact parathyroid hormone, 25-hydroxy vitamin D, serum testosterone and complete blood count. However in a clinical setting these additional parameters should not be routinely assessed.

Dual-energy X-ray absorptiometry (DXA) for quantitative assessment of BMD plays no role in a preoperative setting. Nevertheless DXA is considered the gold standard for osteoporosis diagnosis and should be employed postoperatively for further diagnosis and therapy.

Conventional Radiography

For preoperative assessment of osteoporotic changes in the proximal humerus plain radiography can be helpful. Prediction of local BMD via radiographs provides the most technically uncomplicated and cost-effective process for clinicians [10]. Thereby in anteroposterior radiographs the cortical thickness of the proximal humeral diaphysis may serve as a reliable predictor of local bone quality at the level of humeral head, surgical neck, greater and lesser tuberosity [14]. In general patients over 70 years show significantly lower cortical thickness and local BMD than those under 70 years [14]. However for decision making regarding operative and non-operative treatment (spiral) computed tomography imaging (CT) is more valuable [10].

Computed Tomography (CT)

Spiral CT is an established diagnostic tool for assessing local BMD in the spine. As CT scans display the preoperative imaging of choice in complex and/or low BMD proximal humeral fracture repairs they could be easily used at the same time for preoperative determination of local humeral BMD [10]. By calculating the average Hounsfield unit values in standardized regions of the proximal humerus and linear calibration equation to calculate from the obtained Hounsfield units to BMD, assessment of cancellous BMD of the proximal humerus is by principle possible with high intraobserver and interobserver reliability (intraclass correlation coefficient >0.9) [7]. In a clinical investigation with this method low local BMD has been shown to correlate with fracture fixation failure [6]. However it still remains to be determined whether CT based local BMD assessment can be easily reproduced and efficiently applied by clinicians in daily routine [10].

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