Etiology

Seminal observational studies have formed the basis of much what has been taught globally about Kienböck’s disease in the last 50 years. More recently, a basic science model of Kienböck’s disease has challenged traditional dogma and furthered our understanding of disease etiology. It is likely that a “perfect storm” of biologic and mechanical risk factors are required for disease onset and progression. ^, Recent work on dynamic imaging and fracture mapping of Kienböck’s disease wrists suggest that the morphology of lunate fractures and the pathogenesis of lunate collapse are not random and are likely to be affected by the vector of forces in the “at-risk” patient in the “at-risk” wrist with the “at-risk” lunate.

Osseous

The macro- and microanatomy of the lunate are important, as are its relationship to the neighboring carpal bones and distal radius. The morphology of the lunate has been described by Viegas. Viegas-Type 1 lunates predominate in Kienböck’s disease but not in the general population. They have a single articular facet for the capitate, are smaller, and tend to sit on the ulnar aspect of the lunate facet. Type 2 lunates are larger and have a separate facet for the hamate. Zapico described three lunate types and postulated that the “trapezoidal”-type 1 lunate was at high risk, due to the shape of the bone and trabecular angulation p redisposing it to osseous failure and development of Kienböck’s disease.

Micro-CT studies of the lunate demonstrate ( Fig. 12.1 ) that the proximal subchondral bone plate of the lunate is only a single trabecular layer thick. Proximal subchondral bone plate fractures are significantly more common than distal fractures, may be multiple, and often precede collapse of the bone.

Microanatomy of the lunate. 3D micro-CT scan of the lunate demonstrating the thin proximal single layer of subchondral bone plate, which was measured to be 0.1 mm thick. Arrows: There are spanning trabeculae principally on the radial aspect.

(Copyright Dr Gregory Bain.)

Ulnar variance is usually negative in patients with Kienböck’s disease. Load is focused on the radial edge of the lunate, leaving an exposed unloaded edge and a significant stress riser. The relationship between radial inclination and Kienböck’s disease, however, is contentious.

Vascular

Lee and Gelberman have described the complex arterial patterns within the lunate, and it has been postulated that a single arterial flow may predispose to Kienböck’s disease. We propose that the venous system within the bone may be more important. Crock demonstrated that the subarticular venous plexus in the lunate is positioned near the susceptible proximal subchondral bone plate of the lunate ( Fig. 12.2 ). When the lunate is subjected to high stresses and repetitive loading, hyperemia occurs, and intraosseous pressures can exceed systolic blood pressure. At this stage, the process is still reversible, but with repetitive insult and loading, an intraosseous compartment syndrome can occur ( Fig. 12.3 ). Venous occlusion due to compression in the subarticular venous plexus leads to interstitial edema and swelling within the marrow fat. The fat cells lyse and are phagocytosed to form foam cells, which tamponades capillaries and sinusoids. Stasis and intravascular thrombosis further accentuate ischemia, leading to cellular necrosis, fracture, and fragmentation.

Subarticular venous plexus. (A) A composite image of subarticular venous plexus and 3D micro-CT of the subchondral bone plate. The small box on the left of the image depicts the area demonstrated in the magnified views shown in (B), where the venule within the subarticular plexus is seen in profile. The subarticular venous plexus is directly adjacent, making it particularly at risk, even with a stress fracture. The calcified zone of the articular cartilage and subchondral bone plate are well seen. 3D, Three-dimensional; AC, articular cartilage; CT, computed tomography; SBP, subchondral bone plate.

Compartment syndrome of bone. Diagrammatic representation of the normal vascularization of the lunate (superior half) with the normal fat cells and venous drainage. With ischemia (inferior half), there is interstitial edema and the marrow fat cells become swollen. This leads to tamponade of the sinusoids, thus decreasing the venous outflow. This further increases the intraosseous pressure, reducing arterial inflow and producing necrosis.

(Copyright Dr Gregory Bain.)

Putting it all together

The “at-risk” lunate is small and trapezoidal with a single distal point load from the capitate and a single proximal point load from the lunate fossa. There may be a single arterial blood supply. The patient has an “at-risk wrist”—there is no proximal or distal load-share with the ulna and hamate, respectively. The “at-risk” patient is likely to be male and in manual work. Repetitive occupational loading of the wrist exposes the vulnerable lunate to considerable stress rises between the capitate, creating a shear force. The proximal edge pivots on the ulnar edge of the radius, which acts as a cantilever with lunate translation restricted by the attachments of the volar radiolunate ligaments. Repetitive point-loading causes the capitate to act as a nutcracker on the lunate. Thus the perfect storm is created for increased intraosseous pressure, compartment syndrome of bone, stress fracture, and osseous collapse of the lunate and wrist.

The three phenotypes of Kienböck’s disease

Kienböck’s disease occurs in a spectrum of patients and is not a disease exclusive to the “middle-aged male manual worker.” MacLean et al have recently performed a review following the natural radiographic progression of the disease after nonoperative management and have identified three specific patient phenotypes.

• 1.
  

  The young “Teenbock” patient, with disease usually self-limiting.

  
  
• 2.
  

  The typical “middle-aged male manual worker,” with negative ulnar variance.

  
  
• 3.
  

  The “older female” patient, often with positive ulnar variance.

The rate of progression of disease varies significantly. Radiographic progression is higher in older patients (60 years and over). Female patients tend toward having a higher rate of radiographic progression compared to male patients. The reason for these differences remains unclear. Age-related osteoporosis leads to changes in the trabecular microarchitecture within the lunate and reduced ability to withstand load. This may increase susceptibility to stress fracture and fragmentation. Impaction of the ulnar head that occurs with positive ulnar variance will increase impaction on the ulnar edge of the lunate, which may in some cases predispose to osseous collapse in the “at-risk” lunate.

The dynamic aspect of Kienböck’s disease

Study of Kienböck’s disease on 4D CT imaging has furthered our understanding of the dynamic aspects of the disease—both symptoms and pathogenesis. What is clear is that disease progression and pain are not purely a result of degeneration, proximal row instability, and carpal collapse. ^,

Carpal instability may be internal (within the lunate), intrinsic (within the proximal row), or extrinsic (between the radius and carpus). Instability can be static or dynamic ( Figs. 12.4 and 12.5 ). Failure of ligamentous restraints can occur through attenuation, rupture, or avulsion.

Intrinsic and extrinsic carpal instability in Kienböck’s disease. Left: Intrinsic instability is a dissociative instability due to failure of the intra-osseous ligaments of the proximal carpal row. It is not a ligament tear, but is an avulsion fracture of the scapholunate (or lunotriquetral) ligament attachment, which radiologically is similar to scapholunate instability. So it is an “apparent” scapholunate instability, or scapholunate instability “equivalent” injury. Right: Extrinsic instability is a non-dissociative instability, due to failure of the extrinsic radiocarpal ligaments, leading to ulnar translocation (arrow), of the proximal carpal row. It is often due to collapse of the lunate or avulsion fractures of the volar long radiolunate ligament and/or dorsal radiocarpal ligament .

Dynamic lunate internal instability. With wrist motion, there is independent movement of the dorsal and volar horns of the lunate, due to the loading of the capitate (arrows). In this case the dorsal lunate fragment remains attached to the scapholunate ligament, and the dorsal fragment attached to the lunotriquetal ligament.

Ulnar translocation.

Ulnar translocation occurred in all advanced cases in our published series. Three mechanisms may be responsible.

Other pathologies also exist: (1) attenuation of extrinsic ligaments due to synovitis—found in all patients on arthroscopy, (2) pseudolaxity of the extrinsic ligaments after central column collapse, and (3) direct avulsion of the long and short radiolunate ligaments with a volar horn fragment.

Osseous impingement can occur in Kienböck’s disease. Pain from Kienböck’s disease is generally considered diffuse throughout the wrist. We have identified a cohort of patients, however, with pain and mechanical symptoms on specific movements, localized to the ulnar or volar aspects of the wrist.

Volar radiolunate impingement can occur in patients with a coronal fracture or radiolunate ligament avulsion fragment ( Fig. 12.6 ). On dynamic 2D-sagittal sequences, the fragment is seen to impact the volar rim of the lunate facet with wrist flexion and can be a cause of persistent pain before or after treatment.

Two mechanisms for volar radiolunate impingement. (A) Proximal subchondral bone plate collapse, leading to loss of joint congruity. With flexion the volar lunate hinges on the lunate facet (horizontal arrow), creating a “kissing lesion”, geode of the volar radius. (B) Short radiolunate ligament avulsion fracture (vertical arrow), abuts the lunate fossa on flexion.

Ulnar styloid-triquetral impingement can be identified in patients with advanced stages of the disease, particularly in the setting of decreased carpal height and ulnar translocation ( Fig. 12.7 ). These patients often have ulnar-sided wrist pain. Motion-preserving procedures designed to improve carpal height led to disimpaction of the ulnar side of the wrist.

Coronal CT image showing ulnotriquetral impingement. This is a treatable cause of ulnar-sided wrist pain in Kienböck’s disease.

Natural history (Sanjeev Kakar)

Kienböck’s disease is characterized by disruption of the vascular supply to the lunate. If left untreated, it may result in fragmentation with progressive collapse of the lunate and possible wrist arthritis. Typically affecting males aged 20 to 40 years old with central wrist pain and swelling, risk factors include mechanical factors such as negative ulnar variance, radial inclination, lunate morphology, variances in lunate blood supply, and systemic conditions such as diabetes and systemic lupus erythematosus.

In determining treatment for patients with Kienböck’s disease, it is important to delineate the natural history of the condition and risk factors for progression. van Leewen and colleagues retrospectively screened more than 50,000 patients over an 11-year period and found 0.1% (n = 51) of cases with incidental findings and 0.17% (n = 87) with symptomatic Kienböck’s disease. The patients within the former category tended to be older (mean age 54 years), and 18% had Lichtman stages III and IV, raising awareness that AVN of the lunate can exist without symptoms. In determining possible risk factors for progression of lunate collapse, the same group of authors noted that increasing negative ulnar variance (adjusted odds ratio 1.5 [per mm]; P < 0.05) and increasing age (adjusted odds ratio 1.03; P < 0.05) were associated with greater lunate collapse.

Beckenbaugh et al reported on 46 patients with Kienböck’s disease over a 2- to 27-year period. At the time of diagnosis, 72% had a history of wrist injury and 67% of patients had evidence of lunate fracture or fragmentation. In 10 patients treated nonoperatively, 1 had no pain and 9 had mild wrist pain during follow-up. All had some degree of wrist swelling. Grip strength tended to be approximately one-third weaker compared to the unaffected wrist, and average wrist extension was 46 degrees, flexion 43 degrees, 27 degrees radial deviation, and 33 degrees ulnar deviation. None of the patients changed their occupation, which included six who were heavy laborers. Radiographs showed progression over time but were not associated with worsening clinical symptoms. Compared to their initial presentation, two patients stated that their wrists were better, five were unchanged, and three noted that their wrists were worse over time. The authors concluded that “patients were relieved of pain and had functional wrists whether they were treated or not and regardless of the type of surgical treatment.”

DeGeorge and colleagues reported on the functional and radiographic outcomes of patients with Kienböck’s disease managed nonoperatively. Twenty-five patients were included at a mean age at diagnosis of 43 years (range 12–73 years) with an average length of clinical follow-up of 3.9 years (range 1.1–12 years) and radiographic follow-up of 5.2 years (1.2–15.2). Results demonstrated that there was no significant change in motion with an improvement in pain, grip strength, and Mayo Wrist Scores over time. As with the findings reported by Beckenbaugh et al, patients’ radiographs continued to progress over time, especially if they were smokers. Similar results have been reported by others regarding a reduction of pain over time, and the authors did not find a benefit of immobilization compared to no treatment at initial presentation regarding patients’ symptoms.

Amalgamated classification system and precision treatment algorithm (David M. Lichtman, William Pientka, and Gregory Bain)

The first known Kienböck’s disease classification system was introduced by Professor Stahl of Malmo, Sweden, in 1946. He described five progressive stages of lunate collapse based on hard-to-distinguish roentgenographic findings. No mention of carpal instability or wrist degeneration was made. Consequently, staging was not recorded in most articles of that era.

In April 1977, in a study of the timing of silicone replacement arthroplasty for Kienböck’s disease, Lichtman identified four distinct stages to distinguish early versus late radiographic changes. This classification included stage IV representing late carpal degenerative findings. Subsequently, the osseous classification was modified to include findings of carpal instability (stage IIIB) and lunate fracture and disintegration (stage IIIC). The system eventually found widespread acceptance because it was now possible to compare results of treatment at various stages of chronicity. It also led to a useful treatment algorithm ( Table 12.1 ).

In recent years, however, it has become evident that the system has not kept up with the flow of information about Kienböck’s disease. For instance, it does not consider the natural history of Kienböck’s disease in children and the elderly. It also does not consider the viability of the lunate articular cartilage and bone.

Kienböck’s disease in children was described by Ferlic and Irisarri early in the 21st century. According to these authors, children under the age of 15 have an excellent prognosis with nonoperative treatment. Between the ages of 15 and 20, the prognosis is still good, but some may require treatment as an adult if unresponsive to conservative measures. In physiologically aged people, the prognosis is also good. A study by Tanaguchi et al indicates that people over 70 respond favorably to splinting and antiinflammatory medication. Kienböck’s disease in the elderly resembles an autoimmune or inflammatory arthritis and may coexist with osteoporosis. Tanaguchi et al recommends a workup for these conditions along with nonoperative treatment.

Further experience and availability of contrasted magnetic resonance imaging protocols and diagnostic arthroscopy has led to the development of two other important classification systems. One is based on the vascularity and presumed viability of the bone within the lunate ( Table 12.2 ) and the other on the condition of the cartilage around the lunate and within the carpus ( Table 12.3 ). Bain’s initial classification was based on arthroscopic findings of the central column. Later publications have been on an “articular-based approach,” which respects the functional status of the articular cartilage, including assessment via MRI, CT, or direct inspection. Both classification systems add further guidance and nuance to the treatment selection for most patients.

At present, highly individualized treatment methods are being introduced in many areas of medicine. It is therefore timely to acknowledge the advances described above by introducing an amalgamated classification system ( Table 12.4 ) and a “precise” treatment algorithm for Kienböck’s disease ( Table 12.5 ). It is anticipated that the new algorithm will add further nuance to each patient’s treatment selection. However, it is important to remain cognizant the original classification systems because they are the building blocks of the new algorithm and can be used individually when certain information or skills are not available to the treating physician.

The treatment algorithm generated from the new classification is divided into three groups: A: For the age of the patient, B: For whether the adult disease is limited to the lunate bone and cartilage, and C: For the status of the carpus. For all patients in group A, the initial treatment is nonoperative. Patients between 16 and 20 who do not respond to conservative treatment can be treated as adults, preferably with minimally invasive techniques. In elderly patients, a workup for inflammatory joint disease and osteoporosis is indicated. Arthroscopic synovectomy can be considered if pain and swelling persist. In rare instances, a wrist fusion might be indicated.

For adults whose disease is limited to the lunate (group B), the Bain and Schmitt categories are most relevant. In group B1, the lunate bone and cartilage are intact, and a standard unloading procedure is indicated. A local vascularized bone graft can be added for poor lunate vascularization (Schmitt C). In group B2, the salvageability of the lunate is compromised by either a destroyed proximal lunate or a coronal fracture. A free vascularized pedicle (usually from the medial femoral trochlea) is added to reconstruct the proximal lunate. If a coronal fracture is viable (Schmitt A, B), a compression screw is added to assist healing. In group B3, the fractured lunate is either comminuted or has no viable blood supply (Schmitt C). A PRC or limited wrist fusion is usually indicated in this situation.

In the C group, the remainder of the carpus is affected. C1 is analogous to Lichtman stage IIIB and a wrist-stabilizing procedure is preferred, usually a SC fusion. C2 includes wrists with cartilage damage to the radiocarpal joint. Most will respond favorably to a PRC. In group 3C, the radiolunate damage is excessive, and there may be extensive degenerative changes throughout the carpus. A total wrist arthrodesis or arthroplasty is the preferred surgical option. These concepts have slowly evolved over time.

Roles of imaging

We need to direct our imaging to best understand the pathoanatomy of the disease to be able to use the Amalgamated Classification System.

Plain radiographs are used as the routine initial investigation in all patients. In symptomatic patients, CT scans are used to define the extent of the lunate fracture/fragmentation/collapse. This includes fine-slice axial scans with 2D and 3D reformations. There is considerable variability in the site and extent of the fracture configuration. Fractures can be in the coronal plane, sagittal plane, or involve the proximal and/or distal subchondral bone plate. ^,

Fractures that involve the ligamentous attachments will create a dynamic carpal instability. ^, Examples include scapholunate equivalent instability and volar cortex avulsion creating ulnar translocation. Comminution of the proximal or distal subchondral bone plate leads to a loss of support and creates a “nonfunctional” articular surface. The dynamic 4D CT scan provides valuable information on the dynamic instability in Kienböck’s disease. ^,

MRI is not usually required for Kienböck’s disease, but it will provide information on the articular cartilage. MRI with IV gadolinium will determine lunate perfusion and is recommended before performing a vascularized graft. ^,

Arthroscopy will enable visualization and palpation of the articular changes to determine which articular surfaces are functional. ^, If an experienced arthroscopist is not available, an MRI will give some insight into the articular changes.

Strategies

We therefore need to direct our imaging to best understand the pathoanatomy to be able to use the Amalgamated Classification System. We use plain x-rays and CT scans on all symptomatic patients. The 2D and 3D CT scans best define the osseous fragmentation and collapse. The 4D CT dynamic scan is the best assessment of the dynamic aspects, including instability and impingement. ^, An MRI with IV gadolinium is recommended when considering a vascularized graft. ^, For patients for whom surgery is required, we include arthroscopy to define the articular changes and grade the extent and distribution of the articular changes. ^, If an experienced arthroscopist is not available, an MRI will give some insight into the articular changes.

Two interesting observations are that the natural history of Kienböck’s disease and distal radius forage has been shown to be safe and has improved clinical outcomes. ^, Forage involves opening the distal radial cortex and curetting the metaphyseal bone. It is thought that it stimulates a “vascular storm,” a regional hyperemia, and it is for this reason that it helps the pain. Its simplicity is appealing, but one cannot help but think the “vascular storm” increases the regional arterial preload, and therefore indirectly increases the lunate venous drainage, which creates the positive clinical effect. There are a number of philosophical consequences of these observations.

• 1.
  

  The addition of targeted simple mechanical or articular surgical treatments, in correctly selected patients, are likely to provide even better outcomes.

  
  
• 2.
  

  For procedures in which the lunate vascularity may be a concern, radial forage is an alternative option.

  
  
• 3.
  

  Complex reconstructive surgery is likely to be a significant overtreatment.

As a consequence of these important points, we developed the concept of a multimodal approach to Kienböck’s disease. The concept is to identify minimally invasive options that tilt the outcome in the patient’s favor, but with minimal risk and morbidity. Examples include arthroscopic procedures and minimally invasive osteotomies. Also, if there are procedures where greater vascularization is required, then indirect revascularization with radial forage is an option.

It is now a common principle to provide a multimodal approach to medical conditions such as cancer, rheumatoid arthritis, and TB.

In summary, we use the “Precise Treatment Algorithm” to direct the fundaments of the surgical decision-making, and we use the multimodal minimally invasive concepts to fine-tune the management plan.

Single-cut, single-screw capitate shortening osteotomy

Our preference now is to perform the osteotomies as a single-cut, single-screw shortening osteotomy ( Fig. 12.9A–D ). It is best done in the following order to maintain the alignment of the osteotomy during the procedure. ^,

• 1.
  

  The screw position is predrilled first, so that there is less chance of loss of alignment of the osteotomy. This is done with a guidewire introduced with fluoroscopic guidance. A canulated drill is then advanced over the wire. The drill and wire are removed.

  
  
• 2.
  

  An extraarticular osteotomy is performed at the metaphysis, with a fine narrow saw blade or side cutting reamer. Only one pass of the blade is used, with care taken to preserve the periosteum. This maintains stability and optimizes healing. The osteotomy needs to be oriented so that it is naturally stable. The Kirschner (K) wire is reinserted, and a compression screw advanced over the wire.

  
  
• 3.
  

  Postoperatively, a splint and avoidance of heavy activities is all that is required, as the periosteum and soft tissue envelope have not been violated. The patient can return to most activities at 6 weeks and to sports at 3 months if radiographs confirm union.

  
  
• 4.
  

  For the capitate osteotomy, we remove the dorsal lip of the third metacarpal to create the correct line to advance the wire. The wire is passed parallel to the dorsal cortex of the capitate, into the middle of the head of the capitate. It is not advanced through the proximal capitate subchondral bone plate, as this would compromise the articulation.

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