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,^12–1427 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:

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.

Implants

Street and Stevens⁶ 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 biomechanics^15–18 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-Questor¹⁹ 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 system²⁰ 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.

Presentation, investigation and treatment options

The prerequisites for implanting a DHH include (1) the ability to reconstruct both humeral bone columns, (2) an intact or stable reconstruction of the radial head and coronoid, and (3) an intact or reparable medial collateral ligament (MCL) and lateral collateral ligament LCL).

The majority of patients for whom a DHH is appropriate are elderly and have sustained their fracture following a fall from standing height. They present with a painful swollen elbow, any movement of which exacerbates the pain. Clinical examination must include a careful neurovascular assessment, together with an examination of the elbow for bruising, grazes and open wounds. A smaller proportion of patients present some time after the acute fracture either because an attempt has been made to treat the fracture conservatively and a non-union or malunion has occurred or because they have undergone ORIF that has failed.

Preoperative imaging should include good AP and lateral radiographs of the elbow. In addition, since it is often unclear whether a fracture is reconstructable or will require a DHH, a CT scan should also be considered to help clarify the situation. If reconstruction is not achievable, an X-ray of the contralateral elbow will help with accurate templating (Fig. 18.3). Sizing is based on the direct correlation between the AP dimensions of the normal articular surface and the radii of the capitellum and trochlea. In addition, in the AP view, the longitudinal axis of the radial neck should align with the centre of the capitellum, while at the same time the prosthetic trochlea should align accurately with the trochlea or sigmoid fossa.

Figure 18.3 The AP X-ray is templated to ensure the correct anatomical component is selected. This can be in relation to the coronoid and radial head. The axis of the radial neck should align with the centre of the capitellum at the same time the prosthesis is congruent with the sigmoid fossa.