Rationale and Basic Science

Pain in the ulnar aspect of the wrist is a common symptom in the field of hand surgery. This presenting complaint has a large number of possible etiologies, however, and the treatment for any given etiology is largely dependent on the diagnosis. Although treatment options for isolated tears of the triangular fibrocartilage complex (TFCC) or the lunotriquetral (LT) ligament have been studied for many years, there is very little research on outcomes for patients with arthritic change of the proximal pole of the hamate. This is surprising, given that the proximal hamate is one of the most frequent sites of arthrosis in the wrist.^1,2

In 1990, two unrelated anatomical studies closely characterized the lunate articular anatomy.^1,3 These descriptions referred to the distal joint morphology of the lunate in the midcarpal joint and two types were described (Figure 25.1). A type I lunate is one in which the distal lunate articulation makes contact with only the capitate. It was observed in approximately 30% of specimens. A type II lunate is one with an obvious distal lunate medial facet that articulates with the proximal pole of the hamate in addition to the regular facet that articulates with the capitate. The size of this medial facet ranges between 1 and 6 mm in width. This type II variant was observed in up to 70% of specimens. A type I lunate has no contact with the proximal pole of the hamate regardless of wrist position, whereas a type II lunate has a variable amount of contact between the hamate and medial lunate facet—primarily when the wrist is in an ulnarly deviated position.

FIGURE 25.1 Lunate morphology. (A) Type I lunate: no contact between proximal hamate and medial lunate. (B) Type II lunate: contact between proximal hamate and medial facet of lunate.

Cadaver studies have revealed that cartilage erosion of the proximal pole of the hamate is the most common arthrotic condition within the wrist.^1,2 An increasing rate of degeneration is noted with increased age. When proximal hamate arthrosis is present, it is noted almost exclusively in specimens with type II lunates. This appears to be directly related to the increased midcarpal motion observed in patients with type II lunates during radioulnar hand movements, and is presumed to be a result of overloading of the proximal hamate over the long term.^4,5 Patients with symptomatic proximal hamate arthrosis typically complain of ulnar-sided wrist pain, especially with gripping. This appears to correlate with radiographic studies that clearly show increasing contact areas between the hamate and lunate with ulnar deviation. The larger the medial facet of the lunate the more likely arthrosis is to develop. The cartilage degeneration is most evident dorsally on the hamate, and matching degeneration on the medial facet of the lunate is observed up to 50% of the time.

Clinical and cadaveric studies have also demonstrated a strong association between arthrosis at the proximal hamate and tears in the lunotriquetral interosseous ligament (LTIL). Complete or partial disruption of the LTIL has been documented almost 90% of the time when arthrosis of the proximal hamate is identified. Because of this strong association, we have proposed the term HALT (hamate arthrosis lunotriquetral ligament tear) wrist to describe this common clinical condition. There has been little crossover of this anatomical and biomechanical data to the clinical arena, however. The role a torn LTIL may play in the development of hamate arthrosis has not been delineated. A prospective longitudinal study would be required to delineate whether LT instability predisposes wrists with type II lunates to increased or earlier degeneration of the proximal hamate.

Published clinical studies examining the treatment regimens for hamate arthrosis are limited. Thurston and Stanley reported on four patients with arthrosis of the proximal pole of the hamate who were treated by proximal hamate excision. All of the patients were reported to have done well after surgery.⁶ Harley et al. reviewed a much larger series of patients who were treated by arthroscopic excision of the proximal hamate and found favorable results in the majority of patients.⁷ A biomechanical arm of this latter study evaluated the unloading effect of proximal hamate resection. Cadaver wrists with type II lunates were mounted on a custom vice and testing stand.

Pressure-sensitive film was inserted into the ulnar half of the midcarpal joint to measure the joint pressures in the hamatolunate and hamatotriquetral articulations with the wrist loaded in 25 degrees of ulnar deviation. The proximal pole of the hamate was then excised and the joint loading was repeated. These studies revealed that on average resecting 2.4 mm of the proximal pole of the hamate fully unloads the hamatolunate articulation. This amount of bony resection was not observed to alter the load across the triquetrohamate articulation. This biomechanical data supports our clinical observation that an arthroscopic resection of the proximal pole of the hamate for the treatment of arthrosis is a sound surgical procedure.

Indications

The typical patient with a HALT wrist presents with a long history of increasing ulnar-sided wrist pain. The patient frequently presents after an acute exacerbation from a lifting or twisting injury, or in some cases a fall on the affected wrist. The pain typically worsens over time and has the typical arthritic qualities: pain with activities, reduced motion, post-activity ache, and variable response to anti-inflammatory medicines or splinting.

On the physical examination the patient will typically have diffuse nonlocalizing ulnar-sided wrist tenderness. In that the spectrum of pathological findings seen in patients with a HALT wrist encompasses LTIL tears, ulnocarpal and midcarpal synovitis, and chondromalacia of the proximal hamate, it is not surprising that these patients frequently do not specifically localize their pain to the hamate. In most cases, the LT “shuck” test and deep palpation of the hamate elicit a withdrawal reflex. However, most patients have little or no radial-sided tenderness. TFCC tears are noted frequently in patients with proximal hamate arthrosis. Ulnar-sided wrist pain attributable to these tears can further diminish the specificity of the physical exam.

Plain radiographic studies of the affected wrist should be compared to the opposite asymptomatic wrist. Cystic change within the proximal hamate, or a sharp and sclerotic proximal hamate margin, can aid in the identification of this condition preoperatively. However, in most instances plain radiographic studies are noncontributory (Figure 25.2). Furthermore, it is important to realize that plain radiographs are not always diagnostic of a type II lunate morphology.⁸ MRI scans of the wrist that demonstrate edema within the proximal hamate are suggestive of this condition. Likewise, a wrist CT-arthrogram study that outlines a thinned proximal hamate cartilage surface and/or reveals a sclerotic subchondral ridge can also assist in making the diagnosis preoperatively. Unfortunately, neither of these two expensive diagnostic modalities consistently identifies this condition.

FIGURE 25.2 (A) PA wrist radiograph of patient with proximal hamate arthrosis but no obvious changes on X-ray. (B) Same patient, for whom CTarthrogram reveals cyst in proximal hamate, loss of cartilage signal (absent black rim), and LTIL tear (contrast flow through LTarticulation).