Radiographic analysis of pisotriquetral joint and pisiform motion

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.

Patient Satisfaction with Pisiform Excision for Pisotriquetral Instability or Arthritis: A Prospective Review

Background  Pisotriquetral pain and instability is an elusive cause of ulnar-sided wrist pain. Initial treatment of chronic pisotriquetral pathology should involve a trial of nonoperative therapy such as neutral wrist splint, anti-inflammatories, and intra-articular steroid injections. The mainstay of surgical management of pisotriquetral pain is pisiform excision. Purpose  This prospective study seeks to understand patient satisfaction after pisiform excision in patients with isolated pisotriquetral pathology. Patients and Methods  A consecutive series of nine cases of pisiform excision was performed by the senior surgeon. The primary outcome measure was determined a priori to be the Patient-Rated Wrist Evaluation (PRWE) score. Wrist range of motion, grip strength, and QuickDASH (shortened version of Disabilities of the Arm, Shoulder and Hand) scores were also collected preoperatively and at 3 and 12 months postoperatively as secondary outcome measures. Results  There was a very rapid improvement in the PRWE by 3 months, which was maintained at 12 months. The QuickDASH score was slower to improve, with a significant improvement by 12 months. There was no change in grip strength or wrist range of motion at any time point. Conclusion  Pisiform excision results in a very rapid improvement of symptoms and should be considered in cases of pisotriquetral instability or arthritis that fail conservative management. Level of Evidence  Level IV, case series.

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.

Our Disagreement on "Iceberg View" on the Ulnar Wrist and Clinical Implications

The diagnosis of ulnar-sided wrist symptoms concentrates on distal radioulnar joint and triquetral-hamate joint pathology. I consider this is only looking at the "tip of the iceberg" and ignoring other possible pathologies. In particular, this ignores the role of triquetrohamate and pisotriquetral pathologies. I outline our approaches to these pathologies noting the important ligamentous structures, the clinical presentations, the relevant investigations, and the surgical treatments and outcomes that I have found to be reliable. I would encourage hand surgeons to think more widely about ulnar-sided wrist symptoms, in particular triquetrohamate and pisotriquetral joint instabilities.

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.

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.

Joint Space Narrowing in Patients With Pisotriquetral Osteoarthritis

BACKGROUND

Patients with suspected pisotriquetral osteoarthritis may show joint space narrowing. However, the extent of joint space narrowing and its deviation from the joint space width (JSW) in normal anatomy is unknown. In this pathoanatomic study, we therefore compared the JSW in the pisotriquetral joint between osteoarthritic patient wrists and healthy wrists.

METHODS

We reviewed preoperative computed tomography (CT) scans of 8 wrists of patients with ulnar-sided wrist pain who underwent a pisiformectomy with confirmed pisotriquetral osteoarthritis at surgery. We also reviewed CT scans of 20 normal wrists from healthy volunteers serving as control group. Three-dimensional CT models of the pisiform and triquetrum were obtained from both affected and normal wrists, after which the minimum JSW was calculated in an automated fashion.

RESULTS

In the patient group, the median (interquartile range) of the minimum JSW was 0.1 mm (0.0-0.2), and in the control group, 0.8 mm (0.3-0.9) ( P = .007).

CONCLUSIONS

We showed that the pisotriquetral joint space in osteoarthritic patient wrists was significantly narrowed compared with healthy wrists. These results suggest that JSW evaluation has a potential diagnostic value in the work-up of patients with suspected pisotriquetral osteoarthritis. This is an interesting area for future clinical research, especially because no gold standard for diagnosing pisotriquetral osteoarthritis has been established yet.

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.

Fracture dislocation of the pisiform bone in children: a case report and review of the literature

Simultaneous fracture and dislocation of the pisiform is a rare condition, and only two cases have been reported in children. We retrospectively collected and reviewed clinical and radiographic data of a child with a type II Salter-Harris fracture of the distal radius, associated with fracture dislocation of the pisiform. In addition, we performed a systematic review of the literature available to date.

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.

Pisiform excision for pisotriquetral instability and arthritis

PURPOSE

To evaluate wrist strength and kinematics after pisiform excision and preservation of its soft tissue confluence for pisotriquetral instability and arthritis.

METHODS

We evaluated 12 patients, (14 wrists) subjectively and objectively an average of 7.5 years after pisiform excision. Three additional patients were interviewed by phone. Subjective evaluation included inquiry about pain and satisfaction with the treatment. Objective testing included measuring wrist flexion and extension range of motion, grip strength, and static and dynamic flexion and ulnar deviation strengths of the operative hand compared with the nonsurgical normal hand. Four patients had concomitant ulnar nerve decompression at the wrist.

RESULTS

All patients were satisfied with the outcome. Wrist flexion averaged 99% and wrist extension averaged 95% of the nonsurgical hand. Mean grip strength of the operative hand was 90% of the nonsurgical hand. Mean static flexion strength of the operative hand was 94% of the nonsurgical hand, whereas mean dynamic flexion strength was 113%. Mean static ulnar deviation strength of the operative hand was 87% of the nonsurgical hand. The mean dynamic ulnar deviation strength of the operative hand was 103% of the nonsurgical hand.

CONCLUSIONS

Soft tissue confluence-preserving pisiform excision relieved pain and retained wrist motion and static and dynamic strength. Associated ulnar nerve compression was a confounding factor that may have affected outcomes.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

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.

[Hypothenar eminence]

The hypothenar eminence is of great surgical interest yet its complex anatomy is yet to be fully discovered. This review focuses on: the osteoligamentous floor and topography of the Guyon's canal and the carpal ulnar neurovascular space. The canal under the Pisohamate ligament must be individualized. It corresponds to the zone 2 of Shea and McClain where the deep branch of the ulnar nerve is particularly vulnerable. Usually described as a hole, it is a real canal that circumvents the hamulus; the hypothenar muscles are extremely variable. The short abductor of the little finger may be harvested for opposition transfer but its absence penalizes abduction of the little finger if an independent flexor digiti minimi brevis inserts on the head of the fifth metacarpal; the termination of the ulnar nerve distribution to the hypothenar muscles and medio-ulnar anastomoses. The ulnar artery, its close relationship with the hook of the hamate and its variable course that may put it at risk during endoscopic carpal tunnel release. Finally, blood supply of fat pads and skin and their use as flaps to cover the palm and fingers.

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.

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.

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.

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.

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.