Introduction

Distal humeral hemiarthroplasty (DHH), although first described in 1947, has only recently emerged as a surgical option for a number of distal humeral disorders. This has resulted from an improved understanding of the anatomy and biomechanics of the elbow,²⁶ an increasing availability of anatomical prostheses and the recognition that DHH may provide advantages over current treatments for complex fractures of the distal humerus or pathology that destroys large segments of the distal humeral articular joint surface.

Early series reported the use of a small number of implants ²^–⁸ in a variety of pathologies, including trauma, inflammatory arthritis and tumour management. Prostheses were either custom made, non-anatomical (capitellocondylar, Kudo) or had anatomical components (Street). All these arthroplasties provided options other than open reduction and internal fixation (ORIF), interposition arthroplasty and total elbow arthroplasty (TEA)⁹^–¹¹ for the treatment of complex elbow pathology.

Aetiology

Trauma and its sequelae are the commonest cause of an unreconstructable distal humeral articular surface. Usually the patient is a middle-aged or elderly female, but occasionally a young patient may sustain this type of injury as the result of high-energy trauma. Rarely, tumour or avascular necrosis results in loss of the articular surface.

Indications

The indications for DHH are currently evolving in terms of what is appropriate and achievable, and will continue to evolve as longitudinal studies provide more clinical data. My initial experience with DHH involved younger patients with comminuted fractures of the distal humeral joint surface, sometimes combined with a column fracture, where adequate ORIF was not achievable and the attendant outcomes were unsatisfactory. In addition, with the increased use of TEA for the treatment of comminuted distal humeral fractures in the elderly patient,¹²^–¹⁴ ²⁷ it was apparent that some older patients placed too high a demand on these TEAs and DHH provided a number of advantages.

Current indications for DHH include:

1. acute trauma with involvement of specific columns of load bearing

2. salvage of failed ORIF

3. chronic malunion or non-union of the distal humeral intra-articular surface

4. avascular necrosis of the trochlea with collapse of the subchondral plate

5. tumour of the trochlea where adequate resection allows preservation of the bone columns, epicondyles and collateral ligaments.

In the early series of DHH, patients with rheumatoid arthritis reported stiff, painful joints. This, however, may not be typical of all cases and the technique may be of value in the younger patient with ‘burnt-out’ disease or the patient on ‘disease-modifying agents’ who has an eburnated but congruent joint. I have found pain relief in patients undergoing DHH for primary osteoarthritis to be unpredictable.

In terms of selecting whether ORIF, bone grafting, DHH, TEA or even radiocapitellar arthroplasty (RCA) is appropriate, this depends on the load-bearing columns involved, the age of the patient and the activity levels as outlined in the treatment algorithm (Fig. 18.1).

Figure 18.1 (A) The distal articular joint surface is divided into medial and lateral columns, the division between the two being the central trochlea. Depending on the articular segment that is lost, the various options are outlined in the algorithm above. (B) In the elderly, patient factors come into play.

Figure 1A courtesy William PLT. Pocket picture guides to the anatomy of the joints: elbow joints. Gower Medical Publishing.

Contraindications include infection, poor neurovascular status, insufficient bone columns to support an arthroplasty, loss of the collateral ligaments and associated epicondyles, and loss of the radial head and coronoid bony structures. Articular damage to the radial head or sigmoid fossa from trauma or inflammatory joint disease may lead to incomplete pain relief, less function and uncertain longevity of the implant. A non-anatomical sigmoid fossa as a result of developmental humeral insufficiency (e.g. fishtail deformity) results in poor congruency with a DHH.

Clinical Pearl 18.1

In an intra-articular fracture of the distal humerus with complete loss of the medial, lateral or both columns, DHH should be considered if an adequate ORIF cannot be achieved.

Summary Box 18.1 Indications and contraindications for DHH

Indications	Contraindications
Acute trauma	Infection
Salvage of failed ORIF	Poor neurovascular status
Chronic malunion/non-union	Insufficient bone columns
Avascular necrosis of the trochlea	Loss of collateral ligaments and epicondyles
Tumours of the trochlea	Loss of radial head/coronoid

Implants

Street and Stevens ⁶ designed a near-anatomical DHH spool in 1974. However, experience with TEA and the mechanism of humeral component loosening suggests that DHH implants should be stemmed and preferably have an anterior flange to resist joint reactive forces. There are currently two TEA systems (Fig. 18.2) available that allow a DHH (Sorbie-Questor elbow, Wright Medical Technologies; and the Latitude elbow system, Tornier) and another under development (Coonrad/Morrey DHH, Zimmer). These current prostheses have their strengths and weaknesses. Advances in the understanding of elbow anatomy and biomechanics¹⁵^–¹⁸ have helped determine the correct shape and sizing of joint surfaces, along with the landmarks for appropriate implantation ensuring good stability and function.

Figure 18.2 (A) The Sorbie-Questor humeral component is a monobloc construct with medial and lateral condyles which hug the medial and lateral bony columns. (B) The Latitude humeral component is shown with anatomical spool and anterior flange to prevent stem loosening.

The Sorbie-Questor ¹⁹ humeral component is a monobloc component with three sizes, which allows a best fit in 95% of all elbows. Its cupped condylar shape allows for impaction up into the supracondylar columns and humeral shaft, leaving adequate space for periarticular plates for column fixation. The stem, however, is relatively short and has no anterior flange to resist anteroposterior (AP) forces; thus condylar fixation is imperative to prevent implant loosening.

The Latitude system ²⁰ has three stem sizes (with an anterior flange) and six modular anatomical spools. Although reconstruction of the epicondyles is the preferred option, a central axis hole allows suture fixation of collateral ligament repair if required. Although both systems would theoretically allow conversion to a TEA, the practicality of this is still to be demonstrated. The use of an anterior flange in humeral implant design has been shown to give better long-term humeral stem fixation and may therefore result in improved outcome for the Latitude system. At present, however, it is too early to know if this will be borne out by the long-term results.