Pisiform kinematics in vivo

Atraumatic Isolated Dislocation of Pisiform With Ulnar Nerve Palsy

Isolated pisiform dislocation is an uncommon condition, with a limited number of cases reported in the literature. We present a unique case of a 15-year-old male who experienced an atraumatic isolated dislocation of the pisiform bone in his left wrist and presented with pain, deformity, and ulnar nerve palsy in his little and ring fingers. Radiographic investigations confirmed the diagnosis of isolated pisiform dislocation, and the patient successfully underwent an open reduction, stabilization of pisiform, and exploration of the ulnar nerve.

Carpal dislocations

Carpal dislocations result from sequential disruption of the complex relationship between the bones and ligaments of the wrist. Injuries to the carpus occur via predictable mechanisms, an understanding of which is critical to identify and treat these frequently missed patterns of injury and to avoid the sequela of chronic instability. Lunate dislocations are by far the most common, but isolated dislocation of other carpal bones can also occur. Open reduction and internal fixation still remains the gold standard for treatment regardless of the debate around the specific approaches. These high-energy injuries are associated with significant long-term morbidity even when identified promptly and appropriately treated. This review will focus on the evaluation and management of common forms of carpal dislocations.

The effect of ulnar variance on the pisotriquetral joint

BACKGROUND

Pisotriquetral joint (PTJ) disorders are an important cause of ulnar-sided wrist pain but are often underrecognized. Ulnar variance (UV) has been associated with several wrist pathologies.

PURPOSE

To determine the effect of UV on PTJ in patients with trauma.

MATERIAL AND METHODS

A total of 143 patients (77 men, 66 women; mean age=41.64 ± 18.07 years) were included. Patients with fractures, severe and high-energy trauma, arthritic conditions, avascular necrosis, congenital deformity, bone and soft-tissue tumors, suboptimal image quality, and incorrect joint position were excluded. UV and the amount of PTJ subluxation were evaluated using coronal and sagittal computed tomography images.

RESULTS

PTJ subluxation was divided into five grades. A statistically significant difference was found between the presence of PTJ subluxation and sex (P = 0.045). PTJ subluxation was more common in men (46.8%) than in women (30.3%). There was no significant difference between the presence of PTJ subluxation and age (P = 0.758). The patients were also divided into three groups as positive, neutral, and negative UV. A statistically significant relationship was found between the UV and presence of PTJ subluxation (P = 0.01). PTJ subluxation was significantly less in the neutral (none=51.1%, present=48.9%; P < 0.05) and negative (none=77.8%, present=22.2%; P < 0.05) groups.

CONCLUSION

PTJ subluxation was found to be less among the groups with neutral and negative UV in our study population. PTJ subluxation is more common in men while there is no relationship with age. UV and gender may be risk factors for PTJ subluxation by affecting force dynamics at the wrist joint.

Luxação distal isolada do pisiforme: Relato de caso

Isolated pisiform dislocation is a rare lesion with few cases described in the literature. This type of lesion is typically observed in young males and can be easily overlooked at first assessment. Isolated proximal dislocation is more common due to the action of the flexor carpi ulnaris (FCU) muscle.

We present the case of a 19-year-old male patient with isolated distal pisiform dislocation after wrist trauma. He underwent open reduction and internal fixation with Kirschner wires with excellent functional outcomes.

Although there is no consensual therapeutic method, closed reduction is a first-line treatment for acute presentations. Pisiform open reduction or excision may be performed alternatively or after a failed closed reduction.

Long-Term Results of Pisiformectomy in a Cohort of 57 Patients

Background  Excision of the pisiform is an infrequently used option for pisotriquetral joint dysfunction when nonoperative treatment is ineffective. This study reviews the patient-reported outcomes of patients treated with pisiformectomy, and furthermore focuses on the complications and the need for and time to revision procedure. Materials and Methods  Medical records of 57 patients were manually reviewed and assessed for complications, rate of unplanned reoperations, and type of reoperations. Thirty-seven patients (65%) completed patient-rated outcomes surveys at a median of 10 years after their procedure. Results  The complication rate was 13% ( n  = 7). Ulnar nerve symptoms were noted in three patients. No reoperations were performed after the pisiform excision. Out of the 16 patients who had preoperative symptoms of ulnar nerve compression at the wrist, 10 patients reported that their symptoms had completely resolved after the surgery. The median Quick Disability of Arm, Shoulder and Hand (QuickDASH) score after surgery was 4.5 (2.3-16), median score for pain 0 (interquartile range [IQR]: 0-2), and median score for overall satisfaction 10 (IQR: 8-10). Conclusions  Pisiformectomy is a surgery used sparingly in cases with refractory pain associated with arthrosis of the pisotriquetral joint or enthesopathy of the flexor carpi ulnaris/pisiform interface. When utilized in this fashion, patients report limited disability on patient-rated outcome measures, low pain scores, and high satisfaction at mid- to late follow-up.

Identifying the homology of the short human pisiform and its lost ossification center

Background

The pisiform and calcaneus are paralogous bones of the wrist and ankle and are the only carpal and tarsal, respectively, to develop from two ossification centers with an associated growth plate in mammals. Human pisiforms and calcanei have undergone drastic evolutionary changes since our last common ancestor with chimpanzees and bonobos. The human pisiform is truncated and has lost an ossification center with the associated growth plate, while the human calcaneus has expanded and retained two ossification centers and a growth plate. Mammalian pisiforms represent a wide range of morphologies but extremely short pisiforms are rare and ossification center loss is even rarer. This raises the question of whether the sole human pisiform ossification center is homologous to the primary center or the secondary center of other species. We performed an ontogenetic study of pisiform and calcaneus ossification patterns and timing in macaques, apes, and humans (n = 907) from museum skeletal collections to address this question.

Results

Human pisiforms ossify irregularly and lack characteristic features of other primates while they develop. Pisiform primary and secondary center ossification timing typically matches that of the calcaneus of non-human primates, while the human pisiform corresponds with calcaneal secondary center ossification. Finally, human pisiforms ossify at the same dental stages as pisiform and calcaneal secondary centers in other hominoids.

Conclusions

These data indicate that the human pisiform is homologous to the pisiform epiphysis of other species, and that humans have lost a primary ossification center and associated growth plate while retaining ossification timing of the secondary center. This represents an exceptional evolutionary event and demonstrates a profound developmental change in the human wrist that is unusual not only among primates, but among mammals.

Locked Traumatic Pisiform Dislocation: A Case Report

CASE

A 32-year-old man presented to the emergency department with several carpal bone fractures and a locked distal pisiform dislocation after trauma. Treatment consisted of open surgical and reduction, osteosynthesis with a single Kirschner wire, and ligament repair. The patient's functional outcome was excellent, and his Mayo wrist score was 90 at 36 months after injury.

CONCLUSIONS

Pisiform dislocations may be difficult to diagnose because anteroposterior and lateral radiographs may not be sufficient to visualize the injury. A 30° semisupinated wrist x-ray and computed tomography can be helpful. A satisfactory clinical result may be achieved if distal pisiform dislocations are detected early and managed surgically with open reduction and ligament repair.

Sesamoids in tetrapods: the origin of new skeletal morphologies

Along with supernumerary bones, sesamoids, defined as any organized intratendinous/intraligamentous structure, including those composed of fibrocartilage, adjacent to an articulation or joint, have been frequently considered as enigmatic structures associated with the joints of the skeletal system of vertebrates. This review allows us to propose a dynamic model to account for part of skeletal phenotypic diversity: during evolution, sesamoids can become displaced, attaching to and detaching from the long bone epiphyses and diaphysis. Epiphyses, apophyses and detached sesamoids are able to transform into each other, contributing to the phenotypic variability of the tetrapod skeleton. This dynamic model is a new paradigm to delineate the contribution of sesamoids to skeletal diversity. Herein, we first present a historical approach to the study of sesamoids, discussing the genetic versus epigenetic theories of their genesis and growth. Second, we construct a dynamic model. Third, we present a summary of literature on sesamoids of the main groups of tetrapods, including veterinary and human clinical contributions, which are the best-studied aspects of sesamoids in recent decades. Finally, we discuss the identity of certain structures that have been labelled as sesamoids despite insufficient formal testing of homology. We also propose a new definition to help the identification of sesamoids in general. This review is particularly timely, given the recent increasing interest and research activity into the developmental biology and mechanics of sesamoids. With this updated and integrative discussion, we hope to pave the way to improve the understanding of sesamoid biology and evolution.

Isolated acute pisiform dislocation presenting atypically as wrist sprain in the emergency department

The pisiform is a sesamoid bone with in flexor carpi ulnaris tendon. Isolated dislocation of the pisiform bone is not common. It is usually missed and diagnosed as a soft tissue injury or a sprain of the wrist by the emergency physicians. We present an unusual and unique case of a young man involved in a rugby tackle and who himself presented to the emergency department with a painful wrist. The diagnosis of a dislocated pisiform was initially missed; however it was later successfully treated with an open reduction leading to a satisfactory outcome.Early diagnosis and reduction is imperative to avoid prolonged morbidity and loss of earnings. A high index of suspicion is needed in young patients with wrist trauma displaying ulnar sided wrist pain.

Does pisiform subluxation affect the postoperative outcomes in a cohort of patients with distal radius fractures?

Background

In this study, we retrospectively surveyed the presence or absence of pisiform subluxation in surgically treated distal radius fractures (DRF) cases. In addition, we investigated whether or not the postoperative short-term treatment outcome differs due to the presence of pisiform subluxation.

Materials and methods

The subjects were 134 DRF patients treated with volar locking plate fixation (53 males and 81 females, mean age: 64 years old). The pisotriquetral joint was observed on a preoperative CT to investigate the presence or absence of pisiform subluxation according to the criteria reported by Vasilas. 134 patients divided into subluxation group and non-subluxation group, and the clinical outcomes were compared between these groups.

Results

Pisiform subluxation was noted in 23.1% (31 patients, 15 males and 16 females, mean age 61 years). No significant difference was noted in patient background in both groups. The postoperative pronation angle in the non-subluxation group was significantly greater than that in the subluxation group, but there was no significant difference in any other parameter (the range of motion of the wrist, grip strengths, VAS, Q-DASH scores, and Mayo score) between these 2 groups. However it concomitantly occurred in 23.1% of DRF cases in our series, there was no significant difference in the postoperative treatment outcome between these 2 groups.

Conclusions

Therapeutic intervention of pisiform subluxation is unnecessary during treatment of DRF, since pisiform subluxation does not affect the postoperative clinical outcomes of distal radius fractures.

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Pisiform subluxation occurred in 23.1% of distal radius fracture cases, suggesting that it is not a rare pathology.

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Therapeutic intervention of pisiform subluxation may be unnecessary during treatment of distal radius fracture.

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The therapeutic intervention of pisotriquetral joint disorders should be considered when they develop.

Pisiform malalignment associated with distal radius fractures

BACKGROUND

The association of scaphoid or other carpal bone fractures with distal radius fractures is frequently reported, whereas few studies have described pisiform malalignment associated with distal radius fractures. The purpose of this study was to investigate the frequency and characteristics of pisiform malalignment associated with distal radius fractures.

METHODS

We performed a retrospective study by reviewing the data of 152 consecutive patients with a mean age of 63 years who were treated surgically for distal radius fractures during a five-year period. We evaluated the pisotriquetral joint via preoperative sagittal computed tomography (CT) and assessed pisiform malalignment. Pisiform malalignment was defined as follows: (1) wide type, joint space ≥4.0 mm; (2) non-parallel type, loss of parallelism of the joint surface of ≥20°; or (3) overriding type, proximal or distal overriding of the pisotriquetral joint ≥2.0 mm. We investigated the relationship between pisiform malalignment and the patterns of distal radius fractures. Pisiform malalignment was assessed using postoperative CT to determine whether it had been reduced.

RESULTS

Pisiform malalignment was observed in 48 cases involving 44 patients with a mean age of 58 (17-81) years. The patients included 16, 17, and 15 cases of the wide type, non-parallel type, and overriding type, respectively. Distal radius fractures with dorsal displacement exhibited pisiform malalignment significantly more frequently than those with volar displacement. No significant difference was noted between intra- and extra-articular fractures or between patients with and without distal ulnar fractures. Among the 22 pisiform malalignment cases assessed via postoperative CT, 15 cases were reduced, and 7 cases remained malaligned. The non-parallel type exhibited the lowest reduction rate among the 3 types.

CONCLUSIONS

Among distal radius fractures, 29% were complicated by pisiform malalignment. Distal radius fractures with dorsal displacement exhibited a significantly increased frequency of pisiform malalignment compared to those with volar displacement.

Treatment of Pisotriquetral Arthritis by Pyrocarbon Interposition Arthroplasty

Purpose  Pisiformectomy is the baseline treatment for pisotriquetral arthritis when medical treatment fails to address the problem. This operation may lead to loss of mobility and strength in the wrist. This study reports the short-term outcomes of a new technique for treating pisotriquetral arthritis using a pisotriquetral interposition arthroplasty with a pyrocarbon implant. Patients and Methods  We performed a clinical and radiographic study on a series of eight patients who received this treatment at a mean follow-up of 2.8 years. We also studied the mobility of the implant and did assessed articular instability using dynamic radiology and fluoroscopy. Results  We observed one proximal dislocation of the implant in one hand which was reoperated to reposition the implant and strengthen the capsule. All patients were satisfied or very satisfied with their operation and had an average functional recovery period of 1.6 months. At the last follow-up, the Mayo Wrist Score (MWS), Quick Disability of Arm Shoulder and Hand (QDASH), and Patient-Rated Wrist Evaluation (PRWE) scores were 89, 18, and 20, respectively. Postoperatively, there was a 22% improvement in the grip strength of the wrists as well as improved mobility, mainly as regards the radioulnar deviation (47% improvement) and the Visual Analogue Scale (VAS) pain scores decreased from 8 preoperatively to 2 at the latest follow-up. The functional radiologic and fluoroscopic study reported good adaptive mobility of the implant in all the patients, without any indication of pisotriquetral joint instability. Conclusion  The short-term results of pisotriquetral arthroplasty using the Pyrocardan implant are encouraging. This new surgical solution appears to be a valid alternative to pisiformectomy or pisotriquetral arthrodesis. Long-term studies are required to confirm these preliminary findings.

Management of Pisotriquetral Instability

Pisotriquetral instability is an often-overlooked condition that can lead to ulnar-sided wrist pain and dysfunction. Various case series and biomechanical studies have been published regarding the diagnosis and treatment of this condition. We review current methods for examining, diagnosing, and treating pisotriquetral instability.

Assessment of pisotriquetral misalignment with magnetic resonance imaging: Is it associated with trauma?

OBJECTIVE

Our objective was to determine whether there is an association between pisotriquetral (PT) malalignment and acute distal radius fracture by using magnetic resonance imaging (MRI).

METHODS

We evaluated 138 patients who underwent 3-T MRI of the wrists. Group A comprised 85 patients with acute distal radius fracture, and group B comprised 53 patients without trauma. PT interval and angle and pisiform excursion were measured on oblique axial and sagittal multiplanar reformats. The presence of abnormalities in the flexor carpi ulnaris tendon (FCU), pisometacarpal ligament (PML), and pisohamate ligament (PHL) were evaluated.

RESULTS

PT interval was wider in group A on both the axial and sagittal planes (P < 0.001). Axial PT angle opened more radially in group A (P < 0.001), and the absolute value of the sagittal PT angle in group A was wider than that in group B (P = 0.006). Abnormalities in FCU, PML, and PHL were more frequently observed in group A (P < 0.001). On multiple linear regression, distal radius fracture remained significant after adjusting for the patient's age and PT osteoarthritis.

CONCLUSIONS

Acute distal radius fracture can affect normal alignment of the PT joint, resulting in associated injuries to the primary PT joint stabilizers.

KEY POINTS

• Acute distal radius fracture is associated with malalignment of PT joints. • Acute distal radius fracture is associated with abnormalities of PT stabilizers. • PT joint alignment can be evaluated with MRI with 3D sequences. • Wrist MRI is useful for evaluating primary PT stabilizer injuries.

Triquetral fracture with associated pisiform subluxation

We herein present a case of right triquetral fracture with associated pisiform and flexor carpi ulnaris subluxation in a 29-year-old man. Initial radiography showed a right triquetral fracture. Computed tomography and magnetic resonance imaging demonstrated a triquetral fracture with a subluxated pisiform. Open reduction and lag screw fixation of the right triquetrum was performed, with good subsequent recovery of function. Although triquetral fracture with subluxation of the pisotriquetral joint is uncommon, attending clinicians should bear in mind the possibility of such an injury when managing traumatic ulnar-sided wrist pain.

The pisiform growth plate is lost in humans and supports a role for Hox in growth plate formation

The human pisiform is a small, nodular, although functionally significant, bone of the wrist. In most other mammals, including apes and Australopithecus afarensis, pisiforms are elongate. An underappreciated fact is that the typical mammalian pisiform forms from two ossification centers. We hypothesize that: (i) the presence of a secondary ossification center in mammalian pisiforms indicates the existence of a growth plate; and (ii) human pisiform reduction results from growth plate loss. To address these hypotheses, we surveyed African ape pisiform ossification and confirmed the presence of a late-forming secondary ossification center in chimpanzees and gorillas. Identification of the initial ossification center occurs substantially earlier in apes relative to humans, raising questions concerning the homology of the human pisiform and the two mammalian ossification centers. Second, we conducted histological and immunohistochemical analyses of pisiform ossification in mice. We confirm the presence of two ossification centers separated by organized columnar and hypertrophic chondrocyte zones. Flattened chondrocytes were highly mitotic, indicating the presence of a growth plate. Hox genes have been proposed to play a fundamental role in growth plate patterning. The existence of a pisiform growth plate presents an interesting test case for the association between Hox expression and growth plate formation, and could explain the severe effects on the pisiform observed in Hoxa11 and Hoxd11 knockout mice. Consistent with this hypothesis, we show that Hoxd11 is expressed adjacent to the pisiform in late-stage embryonic mouse limbs supporting a role for Hox genes in growth plate specification. This raises questions concerning the mechanisms regulating Hox expression in the developing carpus.

[Is there pisotriquetral instability after carpal tunnel release? Retrospective study of 55 cases]

The aim of this study was to determine if pisotriquetral instability is present after neurolysis of the median nerve in the wrist. Fifty-five patients who underwent carpal tunnel release between December 2005 and March 2009 were included in this retrospective study. The surgical procedure consisted of cutting the transverse carpal ligament under local anesthesia through an anterior approach. Instability was evaluated clinically and radiologically by measuring the pisometacarpal angle. The mean patient age was 61years and the mean follow-up 42months. Only 9% of patients complained of pain on the ulnar side of wrist. The pisometacarpal angle in all the operated wrists was the same as in the non-operated wrists. Our findings suggest there is no pisotriquetral instability after median nerve neurolysis.

The pisotriquetral joint: osteoarthritis and enthesopathy

Pisotriquetral (PT) osteoarthritis (OA) and enthesopathy of the flexor carpi ulnaris (FCU) are pathologies of the hypothenar eminence which both often remain undiagnosed, but can cause ulnar wrist pain. This study determined the prevalence of these pathologies in an older donor population. Twenty wrists were obtained from 10 cadavers with an age ranging from 65 to 94 years. Radiographs were taken of all wrists with the hand in pisotriquetral view and were assessed for osteoarthritic changes of the PT joint and signs of enthesopathy of the FCU. Ten wrists were grossly dissected and the other ten wrists were sagitally sectioned at a thickness of 10 μm. The wrists were analyzed for type and grade of osteoarthritis and signs of enthesopathy. On radiology, 2 out of 20 wrists showed no signs of osteoarthritis, 5 wrists showed severe changes. One wrist showed signs of enthesopathy. On macroscopy, 9 out of 10 wrists showed osteoartritic changes; 5 of these were severely osteoarthritic. On microscopy, all wrists showed some degree of osteoarthritis of which five showed severe changes. Signs of enthesopathy were seen in seven wrists. Pisotriquetral osteoarthritis has a high prevalence in the older donor population and may therefore be a cause of ulnar sided wrist pain. It should therefore always be considered in the differential diagnosis of ulnar sided wrist pain. By performing clinical examination with these pathologies in mind, diagnosis could be a lot faster. Furthermore, based on our results, radiographs seem to be not accurate in diagnosing osteoarthritis of the PT joint and enthesopathy of the FCU.

Anatomical study of the pisotriquetral joint ligaments using ultrasonography

OBJECTIVE

The aim of this study was to demonstrate that ultrasonography may allow a precise assessment of the primary stabilizers of pisotriquetral joint (pisohamate, pisometacarpal, and ulnar pisotriquetral ligaments).

METHODS AND MATERIALS

This study was initially undertaken in eight cadavers. Metal markers were placed in the ligaments using ultrasonographic guidance, followed by the dissection of the wrists. High-resolution ultrasonography was then performed in 15 volunteers (30 wrists) for the analysis of the presence, appearance, and thickness of the ligaments.

RESULTS

At dissection, the metal markers were located in the ligaments or immediately adjacent to them, confirming that they were correctly depicted using ultrasonography. The three ligaments could also be identified in each volunteer. The optimal positioning of the probe and the dynamic maneuvers of the wrist allowing the strain of these ligaments could be defined. No significant changes in the appearance and thickness of the ligaments could be observed.

CONCLUSIONS

The three ligaments stabilizing the pisotriquetral joint can be identified using ultrasonography. Further studies are now required to know whether this knowledge may be useful in the assessment of pain involving the ulnar part of the wrist.

Latent pisotriquetral arthrosis unmasked following carpal tunnel release

The causes of persistent wrist pain following carpal tunnel release include scar tenderness and pillar pain. The goal of this study was to evaluate latent pisotriquetral arthrosis as a source of ulnar-sided wrist pain following open carpal tunnel release. Seven hundred consecutive carpal tunnel releases were reviewed, looking for postoperative presentation of pisotriquetral arthrosis, as well as management and outcome. Fourteen patients with long-standing postoperative pain at the base of the hypothenar eminence had clinical and radiographic signs of pisotriquetral degenerative arthrosis, which conceivably had existed preoperatively and been unmasked thereafter. In 6 patients with persistent symptoms despite conservative measures, excision of pisiform was curative. Altered isometric stresses over the pisotriquetral articulation as a result of releasing the transverse ligament, which constitutes a major radial static stabilizer of this joint, seems to cause articular maltracking, and consequently aggravates a preexisting asymptomatic pisotriquetral arthrosis. Long-standing discomfort is characteristically associated with loss of grip strength and dexterity. Pisotriquetral dysfunction and arthrosis should always be considered in the differential diagnosis of persistent wrist pain following either open or endoscopic carpal tunnel release that does not respond to nonoperative measures. Clinical scrutiny, adequate clinical inspection, and radiographic evaluation readily establish the diagnosis. Conservative treatment includes immobilization, nonsteroidal anti-inflammatory drugs, and intra-articular injection of corticosteroids under fluoroscopic control. The corticosteroid injection combined with a local anesthetic also serves as a diagnostic test. Excision of the pisiform is indicated where conservative treatment has failed.

An immunohistochemical study of the extracellular matrix of entheses associated with the human pisiform bone

The immunohistochemical labelling patterns of the extracellular matrix at the insertion of the flexor carpi ulnaris tendon and the entheses at both ends of the pisometacarpal and pisohamate ligaments were compared in order to relate the molecular composition of the attachment sites to their mechanical environment. Tissue was obtained from elderly dissecting room cadavers and labelled with a panel of monoclonal antibodies directed against collagens, glycosaminoglycans, proteoglycans and matrix proteins. All entheses were fibrocartilaginous and labelled positively for molecules typically associated with articular cartilage (type II collagen, chondroitin 6 sulphate, aggrecan and link protein). Labelling for type II collagen was most conspicuous at the attachment of the flexor carpi ulnaris tendon. In the ligaments, type II collagen labelling was always greater at the pisiform end. Matrilin 1 was universally present at all five entheses examined and fibromodulin labelling was most intense around the tidemark. Fibromodulin may thus be involved in anchorage and/or the control of mineralization at the hard-soft tissue interface of entheses. The greater prominence of fibrocartilage at the pisiform enthesis of the flexor carpi ulnaris tendon than at any ligament attachment may relate to the marked change in the tendon insertional angle that occurs with wrist movements. We also suggest that the more fibrocartilaginous character of the proximal compared with the distal ends of the ligaments relates to the fact that the pisiform is anchored in position and is thus at the centre of rotation of any movement of ligaments attached to it.

Pisotriquetral dysfunction following limited and total wrist arthrodesis

PURPOSE

We report a series of pisotriquetral arthritis cases following wrist and intercarpal arthrodesis, offer an anatomic and biomechanical rationale, and introduce intraoperative considerations to avoid this potential complication.

METHODS

Nine patients with pisotriquetral arthritis requiring pisiform excision following wrist and intercarpal arthrodesis were retrospectively evaluated at 2 institutions. Five paired cadaver wrists were tested for alterations in pressure and kinematics of the pisotriquetral joint following four-corner and total wrist fusions.

RESULTS

Nine patients were successfully treated with pisiform excision for pisotriquetral arthritis following wrist and intercarpal fusions. Biomechanical cadaver testing demonstrated profound alterations in pisotriquetral kinematics and pressure changes in measured degrees of wrist position following wrist and intercarpal fusions.

CONCLUSIONS

Patients undergoing four-corner and/or wrist arthrodesis should be assessed for pisotriquetral discomfort before surgery, including a physical examination and a 30 degrees supinated radiograph to look for degenerative changes. Attempts should be made intraoperatively to ensure that the proximal row is not fused in an extended position. After surgery, if discomfort develops and conservative treatment fails, then pisiform excision can successfully alleviate the pain.

Carpal kinematics after proximal row carpectomy

PURPOSE

Proximal row carpectomy (PRC) is a clinically useful motion-sparing procedure for the treatment of certain degenerative conditions of the wrist. Clinical outcome studies after PRC have shown that wrist flexion-extension averages approximately 60% of that of the contralateral wrist. The purpose of this study was to determine how the kinematics of the wrist are altered after PRC.

METHODS

Eight fresh-frozen cadaver forearms were scanned with computed tomography before and after PRC. Forearms were scanned in 5 different wrist positions (neutral, extension, flexion, radial deviations, and ulnar deviation). Wrists were positioned dynamically and then held statically in a custom fixture through forces applied to the 4 wrist flexor/extensor tendon groups. Three-dimensional computer models of the radius, lunate, and capitate were generated from the computed tomographic images, and the kinematics of the capitate and lunate were calculated relative to the neutral position. For the intact wrist, the motion of the capitate was calculated relative to both the lunate (midcarpal motion) and the radius (overall wrist motion) and the motion of the lunate was calculated relative to the radius (radiocarpal motion). After PRC, only the movement of the capitate relative to the radius was calculated, which represents radiocapitate and overall wrist motion. All motions were plotted in 3 dimensions for purposes of qualitative visualization.

RESULTS

After PRC, the capitate articulated with the lunate fossa of the radius for all positions in all samples. Overall wrist motion decreased 28%, 30%, 40%, and 12% in flexion, extension, radial deviation, and ulnar deviation, respectively. Motion at the radiocarpal joint after PRC, however, was greater compared with motion at the radiocarpal and midcarpal joints of the intact wrist during flexion and extension. This was not the case in radial deviation because of impingement of the trapezoid on the radial styloid. In radial and ulnar deviation, motion of the capitate head changed from predominantly rotational in the intact wrist (midcarpal joint) to a combination of rotation and translation after PRC (radiocarpal joint).

CONCLUSIONS

Removal of the proximal carpal row decreased normal wrist flexion and extension. Although ulnar deviation was preserved, radial deviation was limited by impingement of the trapezoid on the radial styloid. Radiocapitate range of motion after PRC was greater than capitolunate range of motion in the intact wrists. Compared with previously published requirements, wrist range of motion observed after PRC was sufficient for activities of daily living.

Kinematics of the midcarpal and radiocarpal joint in flexion and extension: an in vitro study

PURPOSE

To apply carpal kinematic analysis using noninvasive medical imaging to investigate the midcarpal and radiocarpal contributions to wrist flexion and extension in a quasidynamic in vitro model.

METHODS

Eight fresh-frozen cadaver wrists were scanned with computed tomography in neutral, full flexion, and full extension. Body-mass-based local coordinate systems were used to track motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion parameters and Euler angles were calculated for flexion and extension.

RESULTS

Minimal out-of-plane carpal motion was noted with the exception of small amounts of ulnar deviation and supination in flexion. Overall wrist flexion was 68 degrees +/- 12 degrees and extension was 50 degrees +/- 12 degrees. In flexion, 75% of wrist motion occurred at the radioscaphoid joint, and 50% occurred at the radiolunate joint. In extension, 92% of wrist motion occurred at the radioscaphoid joint, and 52% occurred at the radiolunate joint. Midcarpal flexion/extension between the capitate and scaphoid was 0 degrees +/- 5 degrees in extension and 10 degrees +/- 13 degrees in flexion. Midcarpal flexion/extension between the capitate and lunate was larger, with 15 degrees +/- 11 degrees in extension and 22 degrees +/- 19 degrees in flexion.

CONCLUSIONS

The capitate and scaphoid tend to move together. This results in greater flexion/extension for the scaphoid than the lunate at the radiocarpal joint. The lunate has greater midcarpal motion between it and the capitate than the scaphoid does with the capitate. The engagement between the scaphoid and capitate is particularly evident during wrist extension. Out-of-plane motion was primarily ulnar deviation at the radiocarpal joint during flexion. These results are clinically useful in understanding the consequences of isolated fusions in the treatment of wrist instability.

Pathologic Conditions of the Hypothenar Eminence: Evaluation with Multidetector CT and MR Imaging

Pain, weakness, and sensory loss occur frequently in the hypothenar eminence. However, clinical examination is difficult and nonspecific, and the prescribed imaging technique may be inadequate, or images may be misinterpreted. Different imaging modalities have various degrees of usefulness for the diagnosis of painful pathologic conditions of the hypothenar eminence. Radiography, multidetector computed tomography (CT), multidetector CT arthrography, and magnetic resonance (MR) imaging of the wrist are useful for surveying the anatomy of the hypothenar eminence, the Guyon canal, and the ulnar nerve and artery and for determining the cause of pain or other symptoms. A fracture of the pisiform bone or the hook of the hamate bone, osteoarthritis or osteochondromatosis of the pisotriquetral joint, Guyon canal syndrome, hypothenar hammer syndrome, tendinopathy of the flexor carpi ulnaris, an anomalous muscle, a ganglion cyst, or a tumor may be responsible for ulnar neuropathy. Specific radiographic views, such as the semisupinated oblique view and the lateral view with the hand radially deviated and the thumb abducted, often provide a sufficient basis for the diagnosis of acute fracture of the hook of the hamate or the pisiform bone. Multidetector CT angiography is an efficient method for diagnosing hypothenar hammer syndrome, and multidetector CT arthrography is well suited for evaluation of the pisotriquetral joint. MR imaging is the modality of choice for depiction of the ulnar nerve.

Pisotriquetral arthrodesis as an alternative to excision for pisotriquetral instability in high-demand patients: a case report in a gymnast

A gymanast developed ulnar wrist pain caused by pisotriquetral instability. Pisotriquetral arthrodesis resulted in pain relief and sufficient functional return to allow her to return to gymnastics. Pisotriquetral arthrodesis is a feasible alternative to pisiform excision worth consideration in high-demand patients with symptomatic pisotriquetral instability or arthrosis.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic, Level V.

Pisiform ligament complex syndrome and pisotriquetral arthrosis

PLC syndrome is a spectrum that encompasses PLC instability and ends with PTA. Early recognition and treatment of PLC instability may disrupt its progression to PTA. The pisiform tracking test is a provocative maneuver that aids in diagnosing PLC syndrome. Pisiformectomy with preservation of the soft tissue confluence remains the treatment of choice for severe PLC syndrome that does not respond to nonoperative treatment.

Kinematics of the midcarpal and radiocarpal joints in radioulnar deviation: an in vitro study

PURPOSE

Carpal kinematics have been studied widely yet remain difficult to understand fully. The noninvasive measurement of carpal kinematics through medical imaging has become popular. Studies have shown that with radial deviation the scaphoid and lunate flex whereas the capitate moves radiodorsally relative to the lunate. This study investigated the midcarpal and radiocarpal contributions to radial and ulnar deviation of the wrist. This was accomplished through noninvasive characterization of the scaphoid, lunate, and capitate using 3-dimensional medical imaging of the wrist in radial and ulnar deviation.

METHODS

Eight fresh-frozen and thawed cadaveric wrists were used in an experimental set-up that positioned the wrist through spring-scale actuation of the 4 wrist flexor and extensor tendon groups. The wrists were scanned by computed tomography in neutral and full radial and ulnar deviation. Body mass-based local coordinate systems were used to track the motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion and Euler angles were calculated from neutral to radial and ulnar deviation for the capitate relative to the radius, lunate, and scaphoid and for the lunate and scaphoid relative to the radius.

RESULTS

The capitate, scaphoid, and lunate moved in a characteristic manner relative to the radius and to one another. Radial and ulnar deviation occurred primarily in the midcarpal joint. Midcarpal motion accounted for 60% of radial deviation and 86% of ulnar deviation. In radial deviation the proximal row flexed and the capitate extended; the converse was true in ulnar deviation.

CONCLUSIONS

Radioulnar deviation (in-plane motion) occurred mostly through the midcarpal joint, with a lesser contribution from the radiocarpal joint. The results of our study agree with previous investigations that found the scaphoid and lunate flex in radial deviation (out-of-plane motion) relative to the radius whereas the capitate extends (out-of-plane motion) relative to the scaphoid/lunate (with the converse occurring in ulnar deviation). Our study shows how these out-of-plane motions combine to produce in-plane wrist radioulnar deviation. The use of 3-dimensional visualization greatly aids in the understanding of these motions. The results of our study may be useful clinically in understanding the consequences of isolated midcarpal fusions in the treatment of wrist instability.

The pisotriquetral joint: anatomic, biomechanical, and radiographic analysis

PURPOSE

To examine anatomically and radiographically the ligaments stabilizing the pisotriquetral (PT) joint and to determine the contribution of each ligament to the stability of this joint.

METHODS

Twelve cadaver arms were used. The study had 3 components: (1) anatomic dissection of the PT joint ligaments and patterns of degenerative changes, (2) biomechanical sequential sectioning of the supporting ligaments, and (3) radiographic assessment of PT joint motion in several planes both before and after ligament sectioning.

RESULTS

The ligaments that attached to the pisiform were the pisometacarpal (PM), pisohamate (PH), radial PT, ulnar PT, and transverse carpal ligament. The PH ligament was shorter, wider, and thicker than the PM ligament. The transverse carpal ligament attachment in the pisiform was insubstantial. In 10 limbs degenerative changes were present, most of them peripheral. Biomechanical testing showed that the primary stabilizers of the PT joint were the PM, PH, and ulnar PT ligaments and that these were responsible for resisting proximal, ulnar, and radial forces, respectively. The PH distance increased along with the pisiform sagittal motion during wrist flexion on oblique x-rays after transection of the PM and ulnar PT ligaments. Concomitantly this distance decreased on the anteroposterior x-rays during radial deviation. The PH distance increased along with the pisiform frontal motion after transection of the PH and radial PT ligaments.

CONCLUSIONS

The pisiform ligament complex has primary and secondary stabilizers to the PT joint. The primary stabilizers are the PH, PM, and ulnar PT ligaments. The transverse carpal and radial PT ligaments are secondary stabilizers. Injuries of the primary stabilizers of the PT joint may lead to instability that predisposes to degenerative joint disease.

Dysfunction of the pisotriquetral joint: degenerative arthritis treated by excision of the pisiform

From 1995 to 2000, 21 patients (14 women and 7 men) with a mean age of 42 were treated with excision of the pisiform for a dysfunction of the pisotriquetral joint. Follow-up ranged from 6 to 36 months (average: 30 months). The diagnoses included degenerative arthritis of the pisotriquetral joint (15 patients), degenerative arthritis associated with a ganglion (3 patients), and calcifications caused by flexor carpi ulnaris tendinopathy (3 patients). All patients had pain secondary to direct pressure on the pisiform. Side-to-side passive motion of the pisiform occasionally led to pain and crepitus. Degenerative arthritis and calcifications in the pisotriquetral joint were confirmed by a wrist radiograph (lateral view in 30 degrees supination). In five patients, local injection with anesthetic temporarily resolved the symptoms. Excision of the pisiform resulted in complete relief of pain without functional deficit.

Development and Validation of a Computed Tomography-Based Methodology to Measure Carpal Kinematics

Motion of the wrist bones is complicated and difficult to measure. Noninvasive measurement of carpal kinematics using medical images has become popular. This technique is difficult and most investigators employ custom software. The objective of this paper is to describe a validated methodology for measuring carpal kinematics from computed tomography (CT) scans using commercial software. Four cadaveric wrists were CT imaged in neutral, full flexion, and full extension. A registration block was attached to the distal radius and used to align the data sets from each position. From the CT data, triangulated surface models of the radius, lunate, and capitate bones were generated using commercial software. The surface models from each wrist position were read into engineering design software that was used to calculate the centroid (position) and principal mass moments of inertia (orientation) of (1) the capitate and lunate relative to the fixed radius and (2) the capitate relative to the lunate. These data were used to calculate the helical axis kinematics for the motions from neutral to extension and neutral to flexion. The kinematics were plotted in three dimensions using a data visualization software package. The accuracy of the method was quantified in a separate set of experiments in which an isolated capitate bone was subjected to two different known rotation/translation motions for ten trials each. For comparison to in vivo techniques, the error in distal radius surface matching was determined using the block technique as a gold standard. The motion that the lunate and capitate underwent was half that of the overall wrist flexion-extension range of motion. Individually, the capitate relative to the lunate and the lunate relative to the radius generally flexed or extended about 30 deg, while the entire wrist (capitate relative to radius) typically flexed or extended about 60 deg. Helical axis translations were small, ranging from 0.6 mm to 1.8 mm across all motions. The accuracy of the method was found to be within 1.4 mm and 0.5 deg (95% confidence intervals). The mean error in distal radius surface matching was 2.4 mm and 1.2 deg compared to the use of a registration block. Carpal kinematics measured using the described methodology were accurate, reproducible, and similar to findings of previous investigators. The use of commercially available software should broaden the access of researchers interested in measuring carpal kinematics using medical imaging.

Pisotriquetral instability causing an unusual flexor tendon rupture

We present a case of a closed rupture of the flexor digitorum profundus tendon of the small finger. It is our hypothesis that because of pisotriquetral instability as a result of a lesion of the pisotriquetral ligaments the flexor digitorum profundus tendon was entrapped repeatedly between the pisiform and triquetrum. This resulted in an attritional lesion of the tendon. The pisotriquetral joint showed no bone abnormalities.

In vivo analysis of carpal kinematics and comparative review of the literature

PURPOSE

Techniques have been developed very recently with which it is possible to quantify accurately in vivo 3-dimensional (3-D) carpal kinematics. The aim of this study was to evaluate the feasibility of our novel 3-D registration technique by comparing our data with data found in the literature.

METHOD

The right wrists of 11 healthy volunteers were imaged by spiral computed tomography (CT) during radial-ulnar deviation and 5 of those wrists were imaged also during flexion-extension motion. With a matching technique relative translations and rotations of the carpal bones were traced. We compared our in vivo results with data presented in the literature.

RESULTS

We found our in vivo data largely to concur with in vitro data presented in the literature. In vivo studies revealed only larger out-of-plane motions within the proximal carpal row than described in most in vitro studies. In vivo studies also showed larger interindividual variations.

CONCLUSIONS

A single functional model of carpal kinematics could not be determined. We expect that in vivo 3-D CT studies on carpal kinematics, especially when applied to dynamic wrist motion, will have future diagnostic applications and provide information on long-term results of surgical interventions.

Radiographic analysis of pisotriquetral joint and pisiform motion

We evaluated 45 wrists of normal volunteers fluoroscopically (15) and radiographically (30) to determine the optimal radiographic technique for profiling the pisotriquetral (PT) joint and to assess the pisiform motion. Real-time fluoroscopy showed that 4 views are necessary for optimal PT joint and pisiform visualization: wrist neutral/30 degrees forearm supination, wrist extension/30 degrees forearm supination, and active plus passive wrist flexion/45 degrees forearm supination with thumb abduction. Excursion percentage of the PT articular surface apposition on video imaging occurred 10% proximally in neutral, 20% distally in extension, and 40% proximally in flexion. Radiography showed pisiform excursion distally (2.5 mm) in extension and proximally with active (3 mm) and passive (2 mm) flexion. Pisotriquetral angle opened proximally (15 degrees ) in extension and distally with active (10 degrees ) and passive (5 degrees ) flexion. Pisotriquetral space averaged 1.5 mm in neutral, 1 mm in extension, 3.5 mm in active, and 3 mm in passive flexion. Pisohamate distance averaged 7.5 mm in neutral, increased to 8 mm in extension, and decreased to 2 mm with active and 0 mm with passive flexion. These views and parameters are useful for evaluating patients with PT joint injury and disease.