The calcar screw in angular stable plate fixation of proximal humeral fractures - a case study
© Osterhoff et al; licensee BioMed Central Ltd. 2011
Received: 1 September 2010
Accepted: 24 September 2011
Published: 24 September 2011
With new minimally-invasive approaches for angular stable plate fixation of proximal humeral fractures, the need for the placement of oblique inferomedial screws ('calcar screw') has increasingly been discussed. The purpose of this study was to investigate the influence of calcar screws on secondary loss of reduction and on the occurrence of complications.
Patients with a proximal humeral fracture who underwent angular stable plate fixation between 01/2007 and 07/2009 were included. On AP views of the shoulder, the difference in height between humeral head and the proximal end of the plate were determined postoperatively and at follow-up. Additionally, the occurrence of complications was documented. Patients with calcar screws were assigned to group C+, patients without to group C-.
Follow-up was possible in 60 patients (C+ 6.7 ± 5.6 M/C- 5.0 ± 2.8 M). Humeral head necrosis occurred in 6 (C+, 15.4%) and 3 (C-, 14.3%) cases. Cut-out of the proximal screws was observed in 3 (C+, 7.7%) and 1 (C-, 4.8%) cases. In each group, 1 patient showed delayed union. Implant failure or lesions of the axillary nerve were not observed. In 44 patients, true AP and Neer views were available to measure the head-plate distance. There was a significant loss of reduction in group C- (2.56 ± 2.65 mm) compared to C+ (0.77 ± 1.44 mm; p = 0.01).
The placement of calcar screws in the angular stable plate fixation of proximal humeral fractures is associated with less secondary loss of reduction by providing inferomedial support. An increased risk for complications could not be shown.
KeywordsProximal humerus fracture locked screw locking plate
Patients with minimally displaced or stable fractures of the proximal humerus are treated conservatively in the majority of cases . In contrast, patients with fractures fulfilling the criteria of instability, referred to as displaced or unstable fractures, benefit from surgical intervention which mostly renders reliable results, both, clinically and radiographically [2, 3]. However, surgery of displaced proximal humeral fractures is technically demanding. A wide array of surgical options has been described and controversially discussed [4–10].
The introduction of locking plate systems represents a milestone in fracture treatment with the advantage of improved osseous anchorage and higher resistance to failure by combining axial and angular stability [11, 12]. These plates are suitable for pathologic and osteoporotic fractures. Additionally, locking plates do not depend on friction or compression between plate and bone to stabilize the fracture and therefore do not compromise periosteal blood supply [13, 14].
Therefore, orthopaedic surgeons cannot be sure if they either increase the risks of complications or potentially miss a better long term fracture reduction implicating a better treatment outcome.
Thus, the purpose of this study was to investigate if the presence of calcar screws can reduce secondary loss of reduction and if it has influence on the occurrence of possible complications-especially cut-out and axillary nerve lesions.
All patients with a proximal humeral fracture who underwent angular stable plate fixation (PHILOS, Synthes, Oberdorf, Switzerland) in our hospital between 01/2007 and 07/2009 were included in the present study. All data was collected according to the terms of reference specified by the local ethics committee.
Criteria for exclusion were: age younger than 18 years, previous ipsilateral fractures of the humerus and bony metastases. The indication for surgery was set when posttraumatic radiographs showed evidence of displacement of > 1 cm or an angulation > 45° according to Neer's criteria for displaced fractures . Fracture morphology was classified in two-, three- and four-part fractures on posttraumatic true AP and Neer radiographs. Surgery was performed either via a deltopectoral approach or in minimally-invasive technique via short delta-split approach combined with skin incisions for the distal screws, depending on the surgeons' choice.
All patients underwent a standardized postoperative treatment schedule characterized by early passive motion under physiotherapeutic surveillance.
Patients with one or two calcar screws were assigned to group C+, patients without a calcar screw to group C-. The surgical reports of all patients were checked for the approach that was used. Complications were evaluated based on follow-up radiographs (AP and Neer) and a retrospective chart review of the patients' medical records. The incidence of humeral head necrosis, delayed union, implant failure or neurological deficits was documented. Cut-out was defined as penetration of the proximal screws (humeral head screws) into the joint cavity in the absence of humeral head necrosis. Humeral head necrosis was determined by a collapse of the humeral head with an unrounding of the articular surface.
Statistical analysis of nominal data was done using 2-sided Fisher's Exact Tests, and metric data was processed using the Mann-Whitney Test with SPSS for windows 17.0 (SPSS, Chicago, Illinois, USA). Differences were considered significant for values of p < 0.05. A post-hoc power analysis for comparing loss of reduction was calculated using PS Power and Sample Size Calculations 3.0 (alpha error: 0.05) .
(n = 21)
(n = 60)
List of patients that required revision surgery
1st - 2nd
l o r w/cut-out
l o r w/cut-out
l o r w/cut-out
l o r w/cut-out
Complications and Reoperations due to complications
(n = 39)
(n = 21)
(n = 60)
In those patients that were stabilized using a short delta split approach, loss of reduction was significantly higher (2.33 ± 1.99 mm) when compared with those stabilized using a deltopectoral approach (1.08 ± 1.93 mm; p = 0.23). Due to the small number of patients with a minimally-invasive delta split approach (n = 12), however, post-hoc analysis revealed a power of only 0.44 for this statement.
With new minimally-invasive approaches for the angular stable plate osteosynthesis, the need for calcar screws has been discussed increasingly. In order not to harm the axillary nerve some surgeons tend to avoid placement of calcar screws, especially when done percutaneously in minimal-invasive plating. In the present study it was shown that a loss of reduction over time could be prevented by the placement of one or two screws running tangentially to the medial curvature of the humeral surgical neck, commonly referred to calcar screws. It has been suggested that the placement of calcar screws in minimally-invasive approaches increases the risk for lesions to the axillary nerve . In our study, the insertion of calcar screws did not increase the risk of adverse events like damage to the axillary nerve, cut-out, delayed union. Humeral head necrosis occurred similarly in both groups-as far as this conclusion can be drawn with a follow-up of 6 months. Since the rate of humeral head necrosis after locking plates is increasing over time , a follow-up of 6 months is too short to draw definitive conclusions about humeral head necrosis. For the evaluation of varus malalignment and consecutive cut-out, however, this time period seems sufficient as the bone-plate-interface plate osteosynthesis of proximal humeral fractures usually fails during the first three, four weeks postoperatively .
Loss of fracture reduction was linked to the presence or absence of medial support in locking-plate fixation of proximal humeral fractures by Gardner et al. [29, 38]. Yet, this study did not distinguish between anatomic cortical reduction, head-shaft-impaction or an inferomedial screw (analogous to the calcar screw in the present study). In the clinical setup or during surgery, however, it might be difficult to properly evaluate the first two named entities. Moreover, in some cases cortex-to-cortex reduction can result in varus fixation with the clinical problems associated with varus malunions .
Even though our findings concerning the measurements of loss of reduction were statistically significant, one has to consider statistical effects associated with the relatively small number of patients. Radiographic loss of reduction indicates humeral varus mal-union, thus resulting in a shorter lever arm of the rotator cuff [39, 40] and subacromial impingement due to a reduced acromio-humeral distance [40, 41].
The method of measuring the head-plate distance has been described previously , but highly depends on a similar humeral rotation on the true AP radiographs. In our institution the latter one is usually defined by rotating the patient 40° towards the affected side, hands lying on the abdomen [42, 43]. Due to pain, in some patients it was not possible to rotate the arm accordingly. This implies a considerable variance of humeral rotation and is the main reason urging us to exclude 14 patients from the evaluation of loss of reduction.
We did not take into account bone quality or differences of fracture morphology between the two groups. The complexity of fractures influences the incidence of sustaining nonimplant-related complications , and humeral head necrosis is associated with more complex fractures  as this is suggested by our data as well (no 2 part fractures were followed by osteonecrosis). In our study, the occurrence of complications (cut-out, axillary nerve lesion, delayed union) and the rate of humeral head necrosis did not differ significantly among the two groups, however.
On the other hand, age and complexity of fractures was higher in group C+, suggesting lower complication rates in the presence of calcar screws.
It is known that the surgical approach to the glenohumeral joint influences the functional but not the radiological outcome . The effect of the surgical approach in the present study is not clear. Seemingly, patients with a short delta-split had higher radiographic loss of reduction. A possible explanation would that the minimally-invasive procedure hardened reduction. However, power of these results is insufficient due to the small number of patients with a delta-split approach. Undoubtedly, no axillary nerve lesions were observed in our study population. Yet, in almost all patients with a delta-split (11/12) the surgeon refrained from placing a calcar screw. Thus, a final statement concerning the influence of the approach on loss of reduction and other complications can not be made.
The placement of calcar screws in the angular stable plate fixation of proximal humeral fractures is associated with less secondary loss of reduction by providing inferomedial support. An increased risk for cut-out, delayed union or axillary nerve lesion could not be shown. Future studies should consider the importance of medial calcar support.
Ethics committee approval
All data was collected according to the terms of reference specified by the local ethics committee http://www.kek.zh.ch/internet/gesundheitsdirektion/kek/de/home.html.
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