Alex Lluch

Etiology of Kienböck disease.

The etiology of Kienböck disease is still unknown and, consequently, the ideal treatment is in doubt. Many different hypotheses have been suggested. There are reasons to believe that there are mechanical, vascular, and metabolic factors predisposing to the disease, and probably some factors triggering the development of the process. Among mechanical factors, the short ulna has been thought to be the most relevant. However, presently there are insufficient data to support a significant association between negative ulnar variance and Kienböck disease. With regard to vascular factors, anatomical studies have shown consistent dorsal and palmar arteries entering the bone, and thus, the most likely site for vascular impairment may be at the subchondral level. Many triggering factors have been proposed during the past years, but until this is truly clarified, finding the real cause of Kienböck disease will continue to be a real challenge.

The role of proprioception and neuromuscular stability in carpal instabilities

Carpal stability has traditionally been defined as dependent on the articular congruity of joint surfaces, the static stability maintained by intact ligaments, and the dynamic stability caused by muscle contractions resulting in a compression of joint surfaces. In the past decade, a fourth factor in carpal stability has been proposed, involving the neuromuscular and proprioceptive control of joints. The proprioception of the wrist originates from afferent signals elicited by sensory end organs (mechanoreceptors) in ligaments and joint capsules that elicit spinal reflexes for immediate joint stability, as well as higher order neuromuscular influx to the cerebellum and sensorimotor cortices for planning and executing joint control. The aim of this review is to provide an understanding of the role of proprioception and neuromuscular control in carpal instabilities by delineating the sensory innervation and the neuromuscular control of the carpus, as well as descriptions of clinical applications of proprioception in carpal instabilities.

Role of muscles in the stabilization of ligament-deficient wrists

This article reviews the results of a series of cadaver investigations aimed at clarifying the role of muscles in the stabilization of ligament-deficient wrists. According to these studies, isometric contraction of some forearm muscles induces midcarpal (MC) supination (ie, the abductor pollicis longus, extensor carpi radialis longus, and flexor carpi ulnaris), whereas other muscles induce MC pronation (ie, the extensor carpi ulnaris). Because MC supination implies tightening of the volar scaphoid-distal row ligaments, the MC supination muscles are likely to prevent scaphoid collapse of wrists with scapholunate ligament insufficiency. MC pronator muscles, by contrast, would be beneficial in stabilizing wrists with ulnar-sided ligament deficiencies owing to their ability to tighten the triquetrum-distal row ligaments. Should these laboratory findings be validated by additional clinical research, proprioceptive reeducation of selected muscles could become an important tool for the treatment of dynamic carpal instabilities.

The effect of individual isometric muscle loading on the alignment of the base of the thumb metacarpal: a cadaveric study

Stability of the thumb carpometacarpal joint relies upon equilibrium between its ligaments, muscular support and joint congruity. We wanted to identify the muscles important in preventing or increasing dorsoradial subluxation of this joint. In ten cadaveric hands, a Fastrak® motion tracking device was used to assess the effects of individual isometric muscle loading on the base of the thumb metacarpal relative to the radius and to the base of the middle finger metacarpal. We found that the first dorsal interosseous muscle caused the least dorsoradial translation and highest distal migration of the base of the first metacarpal, whereas abductor pollicis longus was the primary destabilizer, increasing dorsoradial misalignment. The findings show different impacts of these muscles on joint alignment and stability, which suggests that treatment should be targeted to enhance the action of the primary stabilizing muscle, the first dorsal interosseous muscle.

Bizarre Parosteal Osteochondromatous Proliferation (Nora's Lesion) of the Hand: A Report of Two Atypical Cases

Bizarre parosteal osteochondromatous proliferation (BPOP), also called Noras lesion, is an unusual, benign, bony lesion frequently found in the hand. Originally, two of the key radiological features used to describe such lesions were: (1) a lack of corticomedullar continuity and (2) an origin from the periosteal aspect of an intact cortex. The authors present 2 unique cases of histologically proven BPOP in which the integrity of the cortex was affected. In the first case there was medullary continuity, and in the second case there was saucerization of the underlying cortical bone. The authors support that simple X-ray evaluation is insufficient to diagnose BPOP in atypical cases. Careful axial CT scanning or MRI may prove helpful. Taking into account these new notions, histopathology gains greater importance as a diagnostic tool for this particular group of entities.

Transverse loaded pronosupination test

A new test to evaluate the ability of the distal radioulnar joint to sustain transverse loads while the forearm rotates from pronation to supination is described. Both arms were tested in 100 normal volunteers. The average weight-bearing capability of the normal unsupported forearm was 5.07 kg, equating to a force of 49.8 N. The test may be useful in the assessment of pathological conditions involving weakness of the forearm rotator muscles, with or without joint incongruity, as well as being an indirect way to assess the load-bearing capacity of radioulnar implants.

Histological assessment of the triangular fibrocartilage complex

The morphological structure of the seven components of triangular fibrocartilage complexes of 11 cadaver wrists of elderly people was assessed microscopically, after staining with Hematoxylin-Eosin and Elastica van Gieson. The articular disc consisted of tight interlaced fibrocartilage without blood vessels except in its ulnar part. Volar and dorsal radioulnar ligaments showed densely parallel collagen bundles. The subsheath of the extensor carpi ulnaris muscle, the ulnotriquetral and ulnolunate ligament showed mainly mixed tight and loose parallel tissue. The ulnolunate ligament contained tighter parallel collagen bundles and clearly less elastic fibres than the ulnotriquetral ligament. The ulnocarpal meniscoid had an irregular morphological composition and loose connective tissue predominated. The structure of the articular disc indicates a buffering function. The tight structure of radioulnar and ulnolunate ligaments reflects a central stabilizing role, whereas the ulnotriquetral ligament and ulnocarpal meniscoid have less stabilizing functions.

New surgical approach to advanced Kienböck disease: lunate replacement with pedicled vascularized scaphoid graft and radioscaphoidal partial arthrodesis.

Reconstructive procedures such as proximal row carpectomy or partial arthrodesis have been commonly proposed for advanced Kienböck disease (Lichtmann IIIB to IV). The purpose of this study is to evaluate an alternative surgical technique to advanced Kienböck disease: lunate excision and replacement with pedicled vascularized scaphoid graft and partial radioscaphoidal arthrodesis. The main advantage of the proposed intervention is to preserve mobility while not jeopardizing prime clinical outcomes such as pain. By replacing the devitalized lunate we aim at maintaining midcarpal range of motion, and preventing disease progression with carpal collapse and osteoarthritis of the wrist. Between 2002 and 2008, 13 patients of mean age 41 years (range, 25 to 57 y) were operated using this technique. The surgical act included 3 key steps. First, we excised the lunate, then, filled the generated gap with the rotated scaphoid, using it as a pedicled vascularized autograft. Finally, we performed a partial radioscaphoid arthrodesis. At the final follow-up, none of the intervened patients had pain at rest, and 6 patients could perform nonrestricted daily activities. The average postoperative range of motion in flexion/extension was 70 degrees (range, 55 to 90 degrees), 44% (range, 38% to 54%) of what could be achieved by the contralateral arm, and only 16% (range, 14% to 19%) or 25 degrees (range, 18 to 30 degrees) less than the preoperative range of motion of the same wrist. Grip strength improved by more than 30% (range, 24% to 36%). At an average follow-up of 4 years after surgery, 12 of 13 patients had no radiographic evidence of osteoarthritis or collapse of subchondral bone at the level of the new scaphocapitate joint. At follow-up evaluation, the average DASH score was 14 points (range, 6 to 20). The patients experienced a significant improvement in their functional abilities, achieving good results compared with the conventional techniques. The absence of carpal collapse and good functional results are encouraging.

A Possible Mechanism of Direct Injury to the EPL Tendon at Lister’s Tubercle During Falls with the Wrist Fully Extended

We present three cases of pathology of the extensor pollicis longus tendon at the level of Lister’s tubercle after falls with the wrist fully extended. A small anatomical study demonstrates the possibility of the base of the third metacarpal impacting this area in hyperextension. This mechanism of injury to the tendon may explain the clinical findings.

How to Avoid Ulnar Nerve Injury When Setting the 6U Wrist Arthroscopy Portal.

The dorsal sensory branch of the ulnar nerve (DSBUN) is at risk in setting the 6U wrist arthroscopy portal. Although surgeons know the risk and are careful when they set the 6U portal, DSBUN injuries still occur. The purpose of the present anatomical study was to evaluate the possibility that DSBUN undergoes dynamic anatomical variations in its location during wrist arthroscopy. The goal of the study was to clarify (1) whether the nerve-to-portal (NTP) distance changes with flexion/extension wrist and/or hand/forearm rotation, and (2) whether there is any particular combination of flexion-extension/hand-forearm rotation where the NTP distance is maximal. Six fresh cadaver arms were suspended in a traction tower with forearm rotation locked, the skin and subcutaneous tissue around the ulnar head was removed, and the NTP distance measured in three predetermined loading/positional conditions. Of all options, the one that consistently showed the longest and safest NTP distance involved wrist flexion and radiocarpal supination when forearm rotation is limited. In conclusion, when an arthroscopic traction device restricts the forearm rotation, the 6U portal should not be set under traction with the hand passively pronated. Failure to observe this precaution can result in serious neuropathic pain.