Proximal Interphalangeal Joint Congruity: A Biomechanical Study.

BACKGROUND: Surgical approaches to the proximal interphalangeal (PIP) joint often require disruption of soft tissue stabilizers. Additionally, PIP joint injuries frequently result in soft tissue disruption. This study evaluates the necessity of repairing soft tissue stabilizers by assessing their role in maintaining native joint congruity. METHODS: Eight specimens were used to evaluate congruity at 0° and 30° flexion when loaded with 2 N of valgus force. This was performed in the native joint and after sequential sectioning of the surrounding ligaments in order: volar plate (VP), radial collateral ligament (CL), and ulnar CL. The skin flap was sutured with the ligaments unrepaired and the load was reapplied. Radiographs were taken after each load and used to measure the joint line convergence angle (JLCA). RESULTS: Mean JLCA increased in both degrees of flexion after ligaments were sectioned but was only significantly different from the native joint after the VP was disrupted along with 1 CL. Joint congruity improved following repair of the skin flap in both degrees of flexion but was not significant. Joints were more congruent in 30° flexion for all subgroups, but none were significantly different compared to 0° flexion. CONCLUSIONS: Disruption of the VP is insufficient to significantly alter PIP joint congruity. While sectioning of both the VP and CLs resulted in a statistically significant change in joint congruity, mean JLCA demonstrated changes of minor clinical significance. The osseous anatomy of the phalanges imparts inherent stability that maintains a congruent joint despite loss of the soft tissue stabilizers.

Palpation of the lateral bands of the extensor apparatus of the fingers. Anatomy of a neglected clinical finding.

This study aimed to determine by ultrasonography, and cadaveric dissection, whether the firm cords felt by palpation at the sides of the proximal phalanx (PP), actively flexing, and extending the proximal interphalangeal (PIP) joint while keeping the metacarpophalangeal (MCP) joint extended are the lateral bands (LBs) of the extensor apparatus. If so, palpation of the LBs could help evaluate hand conditions that impact the digits' intrinsic muscles. To this end, the PP of the middle and ring fingers of the dominant hand of seven subjects were studied by palpation on both sides. Ultrasonography (US) was performed with a hockey-stick transducer placed on the ulnar side. Five cadaveric hands were dissected, exposing the dorsal extensor apparatus. On palpation, a firm cord was consistently felt at the PP's sides in all subjects. These cords moved widely forward on PIP flexion and backward with PIP extension. By US scanning, the cords corresponded to the LBs. However, the forward movement had only a median of 1.8 mm (range 0.7-3 mm) in the middle finger and a median of 1.1 mm (range 0.3-2.7 mm) in the ring finger compared with an estimated 5-10 mm upon palpation. Cadaveric dissection confirmed the forward movement of the LBs in PIP flexion. We concluded that the firm cords felt at the PP sides are the LBs of the extensor apparatus. We confirmed their movement with the active flexion/extension of the PIP joint. Comparing the wide palpatory and the meager US motion, a haptic illusion of motion may be present.

Extension Mechanism of the Proximal Interphalangeal Joint of the Human Phalanx: A Cadaveric Biomechanical Study.

Our purpose was to compare the contributions of these two systems to assess PIP joint extension in fresh cadaver models. Nine middle fingers of fresh cadavers were used. The PIP joint angle was measured while an extension load was applied on the extensor tendons. Specimens on which extension load was applied on the extrinsic extensors were classified as the extrinsic group, and those on which extension load was applied on the intrinsic extensors were classified as the intrinsic group. Linear regression analyses were performed to obtain regression equation and the extension load-PIP joint angle curve. The mean of slope of the curve was compared between the two groups using paired t-test. The same experiments were done for the metacarpophalangeal (MP) joint in 0° and 60° flexion to evaluate the effect of MP joint flexion on PIP joint extension. The mean slope of the extension load-PIP joint angle curve of the extrinsic group was significantly greater than that of the intrinsic group. With the MP joint in 0° flexion, the mean slope of the extrinsic and intrinsic groups was -0.148 and -0.117, respectively (greater absolute value means greater slope, p = 0.01). With the MP joint in 60° flexion, the mean slopes were -0.147 and -0.104, respectively (p = 0.015). The contribution of the intrinsic extensor for PIP joint extension shows decreasing trends with MP joint flexion. The extrinsic extensors have greater contribution for PIP joint extension compared with the intrinsic extensors.

The Importance of Restoring Anatomy of the Proximal Interphalangeal Joint in Dorsal Fracture Dislocations.

The proximal interphalangeal joint (PIPJ) is a complex anatomical structure. In managing fracture dislocations about the PIPJ, the aim is to restore a congruent joint that allows for smooth gliding motion. Detailed knowledge of the anatomy and biomechanics of the PIPJ is necessary in managing these injuries with predictable success. The breadth of techniques previously described in the treatment of such injuries is testament to the difficulties faced in achieving optimal clinical and radiological outcomes. In this article we detail the anatomy and biomechanics of the PIPJ and summarize current literature and principles for the treatment of dorsal fracture dislocations.

Finite element modal analysis and harmonic response analysis of human arm grasping model.

Based on CT scan, the finite element models of human arm were constructed. Modal analysis of the arm was performed, and the natural vibration characteristics were evaluated. The dynamic simulation of the vibration transmission process was carried out when grasping the handle, and the vibration response and transmission characteristics were investigated. Resonance was likely to occur in the ranges of 5-10 Hz and 35-40 Hz, which caused fatigue damage to the arm. Vibrations in the ranges should be avoided having direct contact with the handle. The analysis results were found to be consistent with those of modal analysis.

The Pathogenesis and Treatment of the Stiff Finger.

"Stiff finger," defined as a finger with decreased range of motion in one or more joints, is commonly found after hand injury and is classified into flexion or extension deformities. Pathogenesis is due to dysfunction in one or more of the following anatomic components: (1) osseous and articular; (2) capsuloligamentous; (3) musculotendinous units; (4) soft tissue and fascia. Evaluation and treatment are based on accurate identification and correction of pathologic structures. The mainstay of treatment is directed hand therapy with exercises and splinting to mobilize stiff joints. Operative interventions are offered after gains from therapy have been exhausted.

Redefining Zone II: Anatomy of the Flexor Digitorum Superficialis Insertion.

BACKGROUND: Flexor zone II is defined as the region spanning the proximal aspect of the A1 pulley to the insertion of the flexor digitorum superficialis (FDS) tendon. Descriptions of the FDS insertion are inconsistent in the literature, but zones of injury are frequently determined with reference to superficial landmarks. The purpose of this study was to describe the footprint of the FDS insertion and define its relationship to the proximal interphalangeal (PIP) skin crease. METHODS: The FDS insertion on the index, middle, ring, and small fingers was dissected in 6 matched pairs of fresh-frozen cadaveric hands. A Kirschner wire was used to mark the level of the PIP skin crease on bone before measurements of the FDS footprint and its position relative to the PIP skin crease were made using digital calipers. RESULTS: The radial and ulnar FDS slips inserted a mean distance of 3.22 mm from the distal aspect of the PIP skin crease and varied by digit. The mean distal extent of the FDS insertion was 8.29 mm. The mean length of the insertion of each FDS slip was 5.15 mm and the mean width was 1.9 mm. CONCLUSIONS: The radial and ulnar FDS slips insert on average 3.22 mm distal to the PIP skin crease and vary by digit. Knowledge of the FDS insertion is clinically relevant when differentiating between flexor zone I and zone II injuries, planning surgical approaches to the finger, and in guiding patient expectations for surgery given the variability in outcome based on zone of injury.

Anatomical Basis for Arthroscopy of the Proximal Interphalangeal Joints.

BACKGROUND: Arthroscopy is a widely used minimally invasive technique. Nevertheless, no report describes the arthroscopic anatomy of the proximal interphalangeal (PIP) joint for portal creation. To facilitate arthroscopy, this study elucidated the anatomy of the lateral bands of the extensor mechanism and collateral ligaments of PIP joints. METHODS: A total of 39 fingers from the right hands of 10 cadavers (4 males, 6 females) were evaluated in this study. We defined the extension line from the proximal interphalangeal volar crease as the C-line. We also defined an imaginary line along the distal edge of the proximal phalanx, which is parallel to the C-line, as the J-line. The distance between J-line and C-line was measured. On the C-line and J-line, we measured the following: from the dorsal skin to the lateral edge of the lateral band (LB), the dorsal edge of the collateral ligament (CL) and from the lateral band and the collateral ligament (D), the width of the finger (W). The finger half-width (M) was measured on the J-line. Comparison between the digits and comparison between radial and ulnar distance were measured and statistical analysis was performed. RESULTS: All PIP joint spaces were distal from the C-line, except for one ring finger. The average distances between the J-line and C-line were 1.8-3.2 mm. On the C-line, only 11 cases (14.1%) showed an interval between the lateral bands and the collateral ligaments, but, on the J-line 72, cases (92.3%) had such an interval. The interval was located 1.6-2.9 mm in a dorsal direction from the midlateral on the J-line. CONCLUSIONS: Portal creation at the J-line is safer than at the C-line. This study revealed that safe portals for arthroscopy of the PIP joint are 2 mm dorsal to the midlateral line of the finger on the J-line.

Management of posttraumatic finger contractures in adults.

This lecture will focus on posttraumatic finger contractures affecting the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints in adults. The pathophysiology, main causes and essential rehabilitation methods that can be used before resorting to surgical treatment are described, along with the clinical examination. The goal is to define the surgical indications, even though the literature shows the functional outcomes are disappointing. While there is little to no change in a joint's angular amplitude, the functional range of motion can be improved. There is practically no functional improvement except in cases of MCP extension contracture. For the PIP joint, the aim is to shift the range of motion into the functional range. Surgical approaches, surgical techniques and rehabilitation protocols are described in detail.

Ultrasonography could be used to predict extended insertion of the EPB tendon noninvasively.

INTRODUCTION: An abnormal distal insertion of the extensor pollicis brevis (EPB) tendon into the thumb interphalangeal joint (IP) has been observed in refractory cases of de Quervain's disease. This is associated with the extensor being wider at the midpoint of the proximal phalanx; however, there is no method to noninvasively measure this. This study evaluated the accuracy of measuring the extensor width using ultrasonography, to establish a noninvasive method for predicting an EPB extending the IP insertion. MATERIALS AND METHODS: Of 23 arms from 12 fresh frozen cadavers, the extensor tendon width at the midpoint of the proximal phalanx was measured using ultrasonography and directly at dissection. The association between these values was evaluated using correlation analysis. A cut-off value of extensor tendon width was obtained using receiver operating characteristic analysis. RESULTS: A strong correlation was observed between the ultrasonography and the measured values. The EPB tendons were normal in 13 arms (57%) and extended in 10 (43%), with a significant difference between these groups in the mean width of the extensor tendon (6.8 ± 1.1 vs. 8.4 ± 1.0 mm). A cut-off extensor tendon width of 8.0 mm yielded an EPB extending the IP. CONCLUSION: An EPB extending the IP tendon can be predicted by measuring the extensor tendon width at the midpoint of the proximal phalanx using ultrasonography. The cut-off tendon width value of ≥ 8.0 mm may be useful for assessments prior to surgery and for conservative care.

Minimally Invasive Proximal Interphalangeal Joint Arthrodesis Using Headless Screw: Surgical Technique.

Proximal interphalangeal (PIP) joint arthritis causes debilitating hand pain and instability leading to significant functional impairment. Arthrodesis remains the gold standard for treatment of PIP arthritis. We present a minimally invasive PIP arthrodesis that provides rigid fixation with a headless compression screw. Seven patients who presented to the senior author with PIP joint arthritis underwent PIP arthrodesis by minimally invasive technique. A 1 cm transverse incision is made over the PIP joint, incising skin, central band, and articular capsule. PIP joint is flexed to expose the articular surface. Articular surfaces are prepared with a fine tipped rongeur, exposing subchondral bone until flat surfaces are obtained. Under fluoroscopy a guide wire for cannulated headless screw (3.0, 2.4, or 2.0 mm) is inserted in an antegrade manner. It progresses from the center of the proximal phalangeal articular surface until it exits through the dorsal cortex and the distal end lies within the subchondral bone. This is the most critical step of the procedure because the guide wire angle determines the degree of flexion of the fusion. A 5 mmincision is made over the guide wire and the wire is advanced through the center of the medullary canal of the middle phalanx. The wire is then overdrilled, length is measured, and a headless compression screws is inserted. Reevaluate alignment after insertion of the screws because malrotation may be induced by torque during compression. Six consecutive patients underwent the procedure by the senior author. All patients healed the arthrodesis without complications and hardware removal was not needed. Minimally invasive PIP joint arthrodesis is a safe and viable procedure. Critical portions of the procedure include placing the wire at the angle of the desired angle of fusion and avoiding malrotation during screw insertion.

Anatomy and Biomechanics of the Finger Proximal Interphalangeal Joint.

A complete understanding of the normal anatomy and biomechanics of the proximal interphalangeal joint is critical when treating pathology of the joint as well as in the design of new reconstructive treatments. The osseous anatomy dictates the principles of motion at the proximal interphalangeal joint. Subsequently, the joint is stabilized throughout its motion by the surrounding proximal collateral ligament, accessory collateral ligament, and volar plate. The goal of this article is to review the normal anatomy and biomechanics of the proximal interphalangeal joint and its associated structures, most importantly the proper collateral ligament, accessory collateral ligament, and volar plate.

Management of Proximal Interphalangeal Joint Fracture Dislocations.

Fracture dislocations of the proximal interphalangeal (PIP) joint of the finger are often caused by axial load applied to a flexed joint. The most common injury pattern is a dorsal fracture dislocation with a volar lip fracture of the middle phalanx. Damage to the soft-tissue stabilizers of the PIP joint contributes to the deformity seen with these fracture patterns. Unfortunately, these injuries are commonly written off and left untreated. A late-presenting PIP joint fracture dislocation has a poor chance of regaining normal range of motion. The provider must be suspicious of these injuries. Treatment options and algorithm are reviewed.

Treatment of Proximal Interphalangeal Joint Contracture.

Proximal interphalangeal joint (PIPJ) flexion contracture is a challenging and often frustrating problem. Treatment of PIPJ contracture begins with conservative measures. With good compliance and prolonged use, favorable results can be achieved using these modalities. For contractures that fail to respond to conservative treatment, surgical intervention can be considered. The affected structures that can be released during surgery include the accessory collateral ligaments, volar plate, checkrein ligaments, retinacular ligaments, and the flexor and extensor tendons. A stepwise approach to release is typically favored in which active motion is tested after each release to determine the need for subsequent releases.

Complications of Proximal Interphalangeal Joint Injuries: Prevention and Treatment.

Proximal interphalangeal joint injuries are one of the most common injuries of the hand. The severity of injury can vary from a minor sprain to a complex intra-articular fracture. Because of the complex anatomy of the joint, complications may occur even after an appropriate treatment. This article provides a comprehensive review on existing techniques to manage complications and imparts practical points to help prevent further complications after proximal interphalangeal joint injury.

[The size and proportion of the interphalangeal finger joints: an anatomic study]. / Die Gelenkfläche und Größenverhältnisse der Fingergelenke: Eine anatomische Studie.

Background This study aimed to evaluate the size of the joint surfaces of the proximal and distal interphalangeal finger joints. Material and Methods 117 proximal and distal interphalangeal joints of 30 formalin-fixed hands of body donors were included in this study. The size of the articular surface was determined for each joint. Results The mean size of the proximal joint surface of the distal interphalangeal joint is 56.1 mm2; the distal joint surface averages 30.9 mm2 (ratio: 1.8:1). The size of the proximal articular surface of the proximal interphalangeal joint is 92.5 mm2. The size of the distal articular surface averages 52.4 mm2 (ratio 1.7:1). Conclusions This is the first study to describe the articular surface area of the proximal and distal interphalangeal joints of the hand.

Anatomic study of the first extensor compartment and the relationship between the extensor tendon width and its distal insertion.

INTRODUCTION: The extensor pollicis brevis (EPB) tendon normally inserts into the base of the proximal phalanx of the thumb. However, a distal insertion of the EPB tendon into the thumb interphalangeal joint has been reported in refractory cases of de Quervain's disease. We hypothesized that the EPB tendon is wider beyond the thumb metacarpophalangeal joint in patients with extended EPB. This study aimed to evaluate the relationship between the extensor tendon width and the point of distal insertion of the EPB tendon. MATERIALS AND METHODS: In 45 hands from 18 male and 27 female adult cadavers, the first extensor compartment was dissected and the existence of the intertendinous septum was assessed. The extensor tendon width was measured at the midpoint of the proximal phalanx, and relationships between extended EPB tendon, existence rate of the intertendinous septum, sex, and extensor tendon width were examined. RESULTS: Of 45 cases, intertendinous septum and extended EPB tendon were observed in 37 (82.2%) and 23 (51.1%), respectively. There was no significant difference between the existence rates of both these factors and sex. The mean extensor tendon width in the extended EPB group was significantly greater than in the normal EPB group. The cut-off value of extensor tendon width in the extended EPB group was 7.12 mm. CONCLUSIONS: The extensor tendon width was wider in the extended EPB group than in the normal EPB group, suggesting that the differences in the EPB tendon width can be used to identify various anatomical variations in extended EPB.

Assessing Finger Joint Biomechanics by Applying Equal Force to Flexor Tendons In Vitro Using a Novel Simultaneous Approach.

BACKGROUND: The flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) are critical for finger flexion. Although research has recently focused on these tendons' coactivity, their contributions in different tasks remain unclear. This study created a novel simultaneous approach to investigate the coactivity between the tendons and to clarify their contributions in different tasks. METHODS: Ten human cadaveric hands were mounted on our custom frame with the FDS and FDP of the third finger looped through a mechanical pulley connected to a force transducer. Joint range of motion, tendon excursion and loading force were recorded during individual joint motion and free joint movement from rest to maximal flexion. Each flexor tendon's moment arm was then calculated. RESULTS: In individual motions, we found that the FDP contributed more than the FDS in proximal interphalangeal (PIP) joint motion, with an overall slope of 1.34 and all FDP-to-FDS excursion (P/S) ratios greater than 1.0 with force increase. However, the FDP contributed less than the FDS in metacarpophalangeal (MCP) joint motion, with an overall slope of 0.95 and P/S ratios smaller than 1.0 throughout the whole motion except between 1.9% and 13.1% force. In free joint movement, the FDP played a greater role than the FDS, with an overall ratio of 1.37 and all P/S ratios greater than 1.0. CONCLUSIONS: The new findings include differences in finger performance and excursion amounts between the FDS and FDP throughout flexion. Such findings may provide the basis for new hand models and treatments.

Jam Injuries of the Finger: Diagnosis and Management of Injuries to the Interphalangeal Joints Across Multiple Sports and Levels of Experience.

CONTEXT: Jam injuries of the finger are frequently encountered in general orthopaedic and sports medicine practice. The finger joints in particular are very susceptible to traumatic injury, but in the absence of severe deformity, digital trauma is often downplayed in the hopes of a more rapid return to game play. EVIDENCE ACQUISITION: Articles published from 1966 to 2015 were reviewed to capture historical and current views on the presentation, diagnosis, and treatment of jam injuries in athletes. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 5. RESULTS: Although jam injuries are frequently grouped together, they represent a host of injuries that can be challenging to differentiate. A thorough knowledge of finger joint anatomy and injury mechanism is critical to perform an appropriate examination, establish an accurate diagnosis, and identify a treatment plan for each patient. CONCLUSION: Every member of the athletic care team must be aware of the spectrum of digital injuries, including the basic signs present on examination, which may indicate the need for more formal workup. Additionally, preventing injury through athlete education is paramount to athletic care.

Estudio morfológico y biométrico de los vínculos de los tendones de los músculos flexores superficial y profundo de los dedos de la mano humana / Anatomic and biometric study of the vincula of the tendons of flexor digitorum superficialis and profundus muscles of the human hand

Los vínculos son estructuras especializadas inherentes a los tendones flexores de los dedos, y tienen gran importancia en la nutrición de los mismos, además de facilitar la flexión de los dedos después de una transección distal del tendón (es), permitiendo que éste (os) actuen indirectamente a través de las articulaciones interfalángicas. El presente estudio tuvo como objetivo revisar aspectos morfofuncionales de los vínculos largos y cortos de los músculos flexores de los dedos de la mano. El trabajo fue realizado en 60 manos de cadáveres formolizados de individuos adultos, brasileños, con una edad promedio de 53,1±17,8 años. Los vínculos cortos fueron encontrados en 100 % de los casos, tanto en los músculos flexores superficiales de los dedos como en los profundos, siempre en número de uno en cada tendón y su localización siempre estuvo en la extremidad del tendón, antes de la inserción de éste en la articulación interfalángica proximal. Los vínculos largos presentaron gran variación morfológica, con una presencia promedio de 61,3 % en los tendones del músculo flexor superficial y de 77,9 % en el músculo flexor profundo. El número de vínculos por tendón varió aún más, no siendo posible identificar un patrón independientemente del músculo. En relación a la localización de los vínculos largos, en los tendones del músculo flexor superficial de los dedos, están insertos en la vaina fibrosa de la falange proximal, con un trayecto oblicuo y próximo a la articulación interfalángica proximal; los vínculos de los tendones del músculo flexor profundo estaban localizados en su mayoría (86,7 %) entre los tendones a nivel de la articulación interfalángica proximal, presentando un trayecto rectilíneo entre esos dos tendones, mientras que en 13,3 % estuvieron localizados muy próximos a la abertura del tendón del músculo flexor superficial para el paso del tendón del músculo flexor profundo. Los vínculos son estructuras escenciales en la mantención de la nutrición y de los movimientos de los dedos aún en presencia de lesiones, por lo tanto, es importante tener una comprensión clara de ellos para una correcta evaluación clínica pensando en la reparación, reconstrucción y rehabilitación de las disfunciones de la mano.

The vincula are specialized structures inherent in the flexor tendons of the fingers, and are of great importance in their nutrition. In addition they facilitate flexion of the fingers following a distal transection of this tendon, allowing it to operate indirectly across the interphalangeal joints. The aim of the present study was to describe anatomic and biometric aspects of the long and short vincula of the flexor muscles of the fingers. The work was carried out in hands of 60 adult Brazilian corpses, of both sexes, with an average age between 17.8±53.1 years. The short vincula were found in 100 % of cases of flexor digitorum superficialis tendons and flexor digitorum profundus muscles, and only one in each tendon, with its location always at the extremity of the tendon, prior to insertion in the proximal interphalangeal joint. The long vincula presented great morphological variation, with an average presence of 61.3 % in tendons of the flexor digitorum superficialis and 77.9 % in the flexor digitorum profundus muscle. Furthermore, the number of vincula per tendon changed, and it was not possible to identify a pattern independently of the muscle. With respect to the location of the long vincula, in the flexor superficial tendons they are inserted in the fibrous sheath of the proximal phalanx, with an oblique course and next to the proximal interphalangeal joint. The vincula of the tendons of the flexor digitorum profundus were located (86.7 %) between both tendons to level of the proximal interphalangeal joint, presenting a rectilinear course between these two tendons, whereas in 13.3 % they were located very close to the opening of the flexor superficialis muscle tendon for passage of the flexor digitorum profundus muscle tendon. The vincula are essential structures in nutrition and finger motion even when injuries are present. It is therefore, important to have a clear understanding of these structures forproper clinical evaluation in the repair, reconstruction and rehabilitation of hand dysfunctions.