Hemiarthroplasty for Proximal Humeral Fractures: How Important Are the Tuberosities?

Danny P. Goel, M.D., MSc, FRCSC
Division of Arthroscopic, Reconstructive Surgery and Joint Preservation
UBC Department of Orthopaedic Surgery, Faculty of Medicine
Burnaby, BC

Jeffrey M. Pike, M.D., MPH, FRCSC
Division of Distal Extremities
UBC Department of Orthopaedic Surgery, Faculty of Medicine
Vancouver, BC

Introduction

Proximal humerus fractures account for six percent of orthopaedic injuries and are third among all fractures1. As the population ages, and remains active, it is likely that an increased incidence of these fractures will require management. Although the majority of these fractures are successfully treated nonoperatively, those requiring surgery will continually provide a therapeutic challenge to the orthopaedic surgeon1.

 

Dr. Charles S. Neer in his original article "concluded that the preferable method for three-part fractures was open reduction and that for four-part fractures was prosthetic replacement. Using these indications, the typical result was satisfactory but imperfect and many months were required for maximum recovery"2,3. As implant technology has evolved so too have the indications for hemiarthroplasty following proximal humerus fractures.

Indications / Outcomes for Hemiarthroplasty

Hemiarthroplasty can be considered in the setting of head-splitting fractures, poor bone quality precluding osteosynthesis and 3- or 4-part fractures in older individuals. Unfortunately, the literature does not guide the surgeon on optimal management of these fractures. This is in part due to the poor inter- and intra-observer reliability of classification systems4,5, lack of consensus surrounding the primary blood supply to the proximal humerus6-9, and documented inconsistent management amongst fellowship-trained shoulder and trauma surgeons10. Furthermore, literature citing comparable outcomes following both operative and nonoperative care for 3- and 4-part proximal humerus fractures11 are difficult to interpret in the setting of those suggesting superior results following reverse arthroplasty12-16. Although certain fracture patterns may appear to be well served with a hemiarthroplasty, the precise indications should be considered on a case-by-case basis as an unsuccessful hemiarthroplasty can result in significant complications, patient morbidity, complex revision and health care costs17-19.

Etiology of Failed Hemiarthoplasty

Poor outcome following hemiarthroplasty for proximal humerus fractures has been outlined by Boileau. In his series, 15% of patients described an excellent outcome, 24% good, 33% fair, and 33% poor. Suboptimal results were observed in females over the age of 75 with either malpositioned components (non-anatomic head height or excessive retroversion) or tuberosities20. Tuberosity malposition was noted in a high percentage of these patients and can occur both in the horizontal and vertical plane20. A prosthesis positioned too high with increased retroversion and an inferior greater tuberosity position was referred to as the "unhappy triad20". This combination was noted to have the worst outcomes and was associated with proximal humeral migration.

The direct correlation of outcomes following hemiarthroplasty and tuberosity position and osteosynthesis has been previously described21, 22. External rotation in a prosthesis with malpositioned tuberosities requires an eightfold increase in torque when compared to an anatomically reconstructed 4-part fracture23. As expected, a malpositioned prosthesis is directly correlated with malpositioned tuberosities (Figure 1).

goel1
Figure 1: Consequences of excessive prosthetic version in fractures. (A) The prosthesis is cemented with excessive retroversion. (B) Osteosynthesis is possible with the arm in external rotation. (C) This leads to suture pull out as the arm is rotated to neutral. (D) posterior migration of the greater tuberosity is noted when the arm is placed in internal rotation (arm in sling at end of procedure). Figure courtesy of Dr. Pascal Boileau.

 

Authors' Recommendations

A functional shoulder history and physical examination may alter surgical decision-making when evaluating patient candidacy for intervention. Patient demands and goals, and the expected bone quality intraoperatively are important considerations. Computed tomography is useful to identify fragment size and location, specifically in the case of comminuted fractures. Patients are placed in the semi-beach chair position with intraoperative imaging available to assist in the height of the prosthesis and tuberosities relative to the humeral head. In an attempt to address the risk factors described by Boileau, several key points are highlighted in an attempt to avoid malposition.

Version:
An intraoperative (Figure 2) anatomical landmark (metaversion) similar to the medial calcar of the hip has recently been described. If intact, this landmark is useful to position the prosthesis within two degress of the patients' native version24. If absent, reestablishing anatomical retroversion remains an extremely difficult task, as normal version can be anywhere between 10 - 55o 25. In this situation, an arbitrary retroversion between 20o - 30o has been recommended26.

goel2
Figure 2: The metaphyseal version method of determining humeral head version may be used in 3- and 4-part proximal humerus fractures undergoing hemiarthroplasty. (A) The medial calcar/metaphyseal segment must be intact. (B) The version of the metaphyseal segment, termed metaversion, is determined by axially viewing the orientation of the proximal humerus metaphysis. (C) The metaphysis projects medially, and the apex of the projection is referenced to the forearm to determine the meteversion, which is highly predictive of humeral head version. (D) The implant is then inserted with its version aligned to the metaversion to recreate anatomic humeral head version. (E) A one-year follow-up anteroposterior radiograph demonstrates reconstruction of the proximal humerus with tuberosity healing.

 

Prosthetic Height:
An intact medial metaphysis adjacent to the anatomic neck serves as the landmark upon which the prosthetic head rests to establish an anatomic head height. This effectively restores the "gothic arch" of the shoulder as previously described28. However, if medial calcar comminution is present, the distance between the most superior aspect of the humeral head and upper margin of the intact pectoralis can be used to guide the height of the prosthesis27. This distance, based on cadaveric studies, has been identified as 5.6 cm +/- 0.5cm (Figure 3).

goel3
Figure 3: Technique used to calculate distance between pectoralis muscle and superior aspect of humeral head. (Figure courtesy of Dr. J.P. Warner)

 

Tuberosity Position:
The greater tuberosity is located approximately 7-8 mm (range 2-20mm) inferior to the superior aspect of the humeral head29, 30 Tuberosity positioning can also be confirmed with intraoperative fluoroscopy after provisional fixation to the trial implant.

Tuberosity Security:
Tuberosity fixation has been previously described with both horizontal and vertical fixation31. Cerclage wiring provides further biomechanical stability as described by Frankle32. Large caliber, high-tensile-strength suture may decrease suture failure rates. Overcompression of the greater tuberosity should be avoided to maintain its lateral offset relative to the humeral head. This is facilitated by bone grafting deep to the tuberosities, which is typically obtained from the  humeral head. Bone graft substitute may also be helpful.

Postoperative Rehabilitation:
In an effort to avoid the poor outcomes noted after tuberosity failure, the rehabilitation protocol aims to protect against failure of tuberosity fixation. The protocol allows gentle short-arc passive motion with otherwise full-time sling immobilization for the first four to six weeks. This is followed by gentle passive full-arc ROM, with active-assisted motion progressing to active motion at six to eight weeks postoperatively. Strengthening is often initiated beyond 12 weeks.

Conclusion

The healing of anatomically aligned tuberosities is critically important for a successful hemiarthroplasty and coincide with an appropriately positioned humeral implant. Careful consideration for humeral implant height and version, the position and security of the tuberosities, and individualized rehabilitation protocol can optimize patient outcomes.

References
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