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To review retrospectively the outcome of retrograde intramedullary absorbable pin fixation for intra-articular fractures of the metacarpal head.
Methods
Nine patients with intra-articular fractures of the metacarpal head were treated surgically with 1.5-mm-diameter unsintered hydroxyapatite particles and a poly-l-lactide pin. There were 2 women and 7 men, mean age 28.9 years. Patients were observed for a mean of 13.1 months after surgery. The metacarpophalangeal joint was exposed through a dorsal skin incision. After reduction of the fracture, 2 unsintered hydroxyapatite particles and poly-l-lactide pins were inserted from the articular surface of the distal bone fragment into the medullary canal of the metacarpal. A volar aluminum orthosis was applied in the intrinsic plus position for a mean of 1.8 weeks (range, 0–4 weeks), and range of motion exercises were started after the orthosis was removed.
Results
Anatomical reduction and bony union were achieved in all patients. Mean period required to achieve bone union was 4.6 weeks. No patients experienced pain after healing; all resumed normal activities at the time of follow-up, when mean flexion and extension of the metacarpophalangeal joint were 82.8° and –2.2°, respectively. There were no malunions or osteoarthritic changes, no breakage of the pin, aseptic inflammation, or avascular necrosis of the metacarpal head, and no foreign body reactions.
Conclusions
We performed a retrograde intramedullary absorbable pin fixation for intra-articular fracture of the metacarpal head. Using this method, damage to the articular cartilage and surrounding soft tissue was minimized, range of motion exercise could be started early after surgery, and hardware removal surgery was not necessary.
There are few reports of metacarpal head fractures and a consensus on treatment has not been obtained. Because closed reduction is often impossible, a common practice is to perform open reduction internal fixation.
Metacarpal head fractures are intra-articular and the distal bone fragment is often small. The bone fragment is surrounded by soft tissues such as the joint capsule, collateral ligaments, tendons, and skin. The surgery involves a degree of damage to the soft tissue. Also, because the distal bone fragment is covered with cartilage, partial damage to the cartilage may occur, depending on the fixation method employed. Although K-wire,
A new technique for closed management of displaced intra-articular fractures of metacarpal and phalangeal head delayed on presentation: report of eight cases.
have been used as fixation materials, each has associated morbidity.
To avoid potential problems, we performed a retrograde intramedullary absorbable pin fixation from the articular surface into the medullary canal of the metacarpal. We used Super-Fixsorb 30 threaded pins (Johnson & Johnson, Tokyo, Japan; and Teijin Medical Technologies, Osaka, Japan). This is an absorbable 1.5-mm-diameter threaded pin made from unsintered hydroxyapatite particles and poly-l-lactide (PLLA) (u-HA/PLLA). We considered this method to minimize such complications and effectively fix bone fragments. In this article, we describe surgical methods and clinical outcomes.
Materials and Methods
Nine consecutive patients with intra-articular fractures of the metacarpal head who underwent surgical treatment with 1.5-mm-diameter u-HA/PLLA pins between July, 2013 and December, 2017 were evaluated retrospectively. Patients included 2 women and 7 men, mean age 28.9 years (range, 13–70 years). The right hand was treated in 5 patients, and left in 4. Affected fingers included 1 index, 1 middle, 3 ring, and 4 little fingers. Three patients had 2-part fracture, 5 had 3-part fractures, and one patient had a 5-part fracture. Patients 2 and 3 had 2-part fractures with no collateral ligament attached to the distal bone fragment. Patients 1 and 6 through 9 had 3-part fractures, with the radial collateral ligament attached to one of the distal bone fragments and the ulnar collateral ligament attached to the other. Patient 4 had a 5-part fracture, with the radial collateral ligament attached to one of the distal bone fragments, the ulnar collateral ligament attached to the other, and the collateral ligaments unattached to the remaining 2 bone fragments. Patients were observed for a mean of 13.1 months (range, 12.3–14.4 months) after surgery without loss of follow-up.
Patients were placed in the supine position under general anesthesia. A longitudinal 1.5-cm skin incision was made dorsally over the metacarpophalangeal (MCP) joint. The central band and joint capsule were longitudinally split at the center and the MCP joint was exposed. The fracture was reduced with the MCP joint passively flexed. Two 1.6-mm (0.062-in) K-wires were inserted from the articular surface of the distal bone fragment into the medullary canal of the metacarpal (Fig. 1A, B). These K-wires were used as temporary fixation of bone fragments and a predrilling tool for the u-HA/PLLA pin. If the distal bone fragment was comminuted into 2 fragments, one K-wire was inserted for each bone fragment. If the distal bone fragment was comminuted into 3 or more fragments, 2 K-wires were inserted into the 2 main bone fragments. The K-wires were inserted as deeply as possible into the metacarpal. When the metacarpal intramedullary canal was narrow, the first K-wire was inserted into the proximal end of the metacarpal and the other was inserted as deeply as possible. By measuring the length of the K-wire outside the metacarpal, the length of the inserted part of the K-wire was determined. The u-HA/PLLA pins were cut with a pin cutter at the measured length. The first K-wire was removed and the u-HA/PLLA pin was inserted instead of the K-wire (Fig. 1C). Using a plunger, the u-HA/PLLA pin was inserted slightly deeper than the articular surface so that the pin did not protrude from the articular surface. In the same way, the other K-wire was also removed and the u-HA/PLLA pin was inserted (Fig. 1D). When necessary, artificial bone substitute (OSferion 60, Olympus Terumo Biomaterials, Tokyo, Japan), a metal screw, or both were used. A volar aluminum orthosis was applied in the intrinsic plus position for a mean of 1.8 weeks (range, 0–4 weeks) and range of motion (ROM) exercises were started after the orthosis was removed. In the early cases, an orthosis was placed for 3 weeks after the operation (Table 1, patients 1–4); however, if fixation stability was confirmed, ROM exercises were started the day after surgery in more recent cases (patients 7–9). In patients with collateral ligaments attached to the bone fragment, buddy taping with the adjacent finger was performed for 4 weeks after the operation to prevent migration caused by radial or ulnar deviation of the MCP joint.
Figure 1Schematic of the operative technique: anteroposterior view of the 3-part metacarpal head fracture. Two 1.6-mm K-wires (asterisks) were inserted from the articular surface. A The first K-wire was inserted as deeply as possible to the proximal end of the metacarpal. B The second K-wire was inserted as deeply as possible. C The first K-wire was removed and the first u-HA/PLLA pin (dagger) was inserted instead of the K-wire. D In the same way, the second u-HA/PLLA pin was inserted.
We evaluated the period required to achieve bone union, the degree of pain, ROM of the MCP joint at follow-up, and postoperative complications. Bone union was defined as continuity of the trabeculae pattern on a plain radiograph.
We obtained informed consent from each patient and obtained appropriate institutional review board approval before case review.
Results
Bone union was achieved in all patients. Anatomical reduction was achieved in all except patients 4. In that patient, complete anatomical reduction was not achieved but satisfactory alignment of the metacarpal and congruency of the articular surface were achieved. The mean period required to achieve bone union was 4.6 weeks (range, 4.0–7.4 weeks). All patients reported no pain at latest follow-up and all had resumed normal activities. Mean flexion and extension of the MCP joint were 82.8° (range, 60° to 95°) and –2.2° (range, –20° to 0°), respectively, follow-up. In patient 1, the distal bone fragment was divided into dorsal and volar parts, so an additional K-wire was inserted in the dorsovolar direction. In patient 4, because of severely comminuted fractures, the ulnar bone fragment was fixed with the cortical screw and artificial bone substitute was employed to prevent shortening. In patient 5, a considerable MCP joint contracture remained because of noncompliance with therapy. There were no malunions, osteoarthritic changes, aseptic inflammation, avascular necrosis (AVN) of the metacarpal head, or foreign body reactions.
Table 1 lists general information for the 9 patients; a typical case is shown in Figures 2 and 3.
Figure 2A 20-year-old woman with a 2-part metacarpal head fracture (patient 3). Preoperative A radiograph and B, C computed tomography scans, D immediate postoperative radiograph, and E radiograph at 12.4 months after operation. Intraoperative photographs: F the metacarpal head was located completely on the dorsal side of the shaft; G the fracture was reduced and 2 K-wires were inserted from the articular surface; H the K-wire was removed and the u-HA/PLLA pin (arrow) was inserted instead of the K-wire; I good reduction and alignment were obtained.
Figure 3A 37-year-old man with 5-part metacarpal head fracture (patient 4). Preoperative A radiograph and B computed tomography scans, C immediate postoperative radiograph, and D radiograph at 13.7 months after operation. There was a large fracture void, so an artificial bone substitute was used. Two u-HA/PLLA pins were inserted and the large extra-articular bone fragment was fixed with a small cortical screw. Although the screw protruded slightly, it was not removed because there was no problem due to it. Despite the marked comminution of the metacarpal head, no avascular necrosis was observed.
there are few reports of metacarpal head fracture.
Different types of fixation methods for metacarpal head fractures have been reported, but none have gained consensus. By using K-wires, small bone fragments can be fixed; damage to the articular surface is small.
A new technique for closed management of displaced intra-articular fractures of metacarpal and phalangeal head delayed on presentation: report of eight cases.
However, depending on the placement of the K-wire, ROM exercise may not be possible early after surgery. In addition, long-term penetration of the K-wire into soft tissues such as the skin, joint capsule, and collateral ligament is common and may cause joint contractures. The K-wire needs to be removed as soon as possible once bone union is obtained. Headless compression screws (HCS) can achieve stronger fixation than K-wires.
Because the HCS can be inserted from the articular surface and completely buried in the bone, this type of screw does not protrude from the articular surface and is commonly used in intra-articular fractures.
Because of the pitch difference between the proximal and distal threads, compression can be applied to the fracture site. The HCS is completely implanted into the bone and cannot be removed. The articular surface area of the metacarpal head is small, so choosing the smallest possible screw is desirable, as is minimizing damage to the articular surface. del Piñal et al
used 3.0- and 4.0-mm cannulated HCS (proximal diameter is 4.0 and 5.2 mm, respectively) for metacarpal head fractures. The pitfall is that a large defect of the articular surface may occur in the small metacarpal head. Plate fixation provides rigid stability
and is especially useful for unstable fractures involving comminution of the metacarpal neck. However, a disadvantage is that the plate is bulky and interferes with surrounding soft tissues, such as extensor tendon and collateral ligament. This may cause extensor tendon rupture or joint contracture and often requires subsequent removal.
As described earlier, each reported treatment has associated morbidity. We performed retrograde intramedullary fixation by inserting a u-HA/PLLA pin from the articular surface to minimize damage to the articular cartilage and surrounding soft tissue. The u-HA/PLLA pin is 1.5 mm in diameter and is thinner than any screw, so damage to the articular cartilage can be minimized. Even if the distal bone fragment is comminuted, one u-HA/PLLA pin can be inserted per bone fragment. Because the u-HA/PLLA pin is completely inserted in the metacarpal, there is no influence on surrounding soft tissue such as the joint capsule or collateral ligament. The surface of the pin is threaded so that pin backout is unlikely to occur. Fixation stability of the u-HA/PLLA pin is stronger than that of the K-wire but weaker than that of the screw. In all cases, passive flexion and extension were performed during surgery after internal fixation, but migration of bone fragments was not observed and fixation stability was good.
The u-HA/PLLA pin is made from 30% unsintered hydroxyapatite particles and 70% PLLA. Absorbable implants such as screws, pins, and plates made of u-HA/PLLA are in clinical use for orthopedic, oral, and plastic surgery.
Surgical treatment of facial fracture by using unsintered hydroxyapatite particles/poly l-lactide composite device (OSTEOTRANS MX(®)): a clinical study on 17 cases.
The complete process of bioresorption and bone replacement using devices made of forged composites of raw hydroxyapatite particles/poly l-lactide (F-u-HA/PLLA).
Sintered hydroxyapatite fabricated by applying heat has high strength but is difficult to absorb in vivo because of its dense structure. Because hydroxyapatite of this pin is unsintered, the pin is absorbed in vivo and does not require subsequent removal. Unsintered hydroxyapatite has low strength, which is increased by combining it with PLLA. Shikinami and Okuno
reported that the bending strength of u-HA/PLLA decreased with rectilinear profiling and the bending strength of greater than 200 MPa was maintained even after 24 weeks. The period of bone union for metacarpal head fracture is reported to be 6 to 10 weeks.
reported that foreign body reaction was elicited by PLLA and polyglycolic acid, and the incidence was 0.2% and 5.3%, respectively. In general, foreign body reactions caused by PLLA are unlikely, but careful attention should be paid when using PLLA. Our study identified no cases of foreign body reactions.
Using this method, damage to the articular cartilage and surrounding soft tissue was minimized, ROM exercise could be started early after surgery, and removal surgery was not necessary. Although we observed no complications owing to the use of u-HA/PLLA in this series, accurate assessment of complications was difficult because of the small number of patients. Further studies are needed to evaluate the complications.
Acknowledgments
We would like to acknowledge the professional manuscript services of Springer Nature Author Services.
A new technique for closed management of displaced intra-articular fractures of metacarpal and phalangeal head delayed on presentation: report of eight cases.
Surgical treatment of facial fracture by using unsintered hydroxyapatite particles/poly l-lactide composite device (OSTEOTRANS MX(®)): a clinical study on 17 cases.
The complete process of bioresorption and bone replacement using devices made of forged composites of raw hydroxyapatite particles/poly l-lactide (F-u-HA/PLLA).
Declaration of interests: No benefits in any form have been received or will be received by the authors related directly or indirectly to the subject of this article.
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