06 June 2023: Articles
Optimizing Treatment for Combined Midshaft Clavicle Fracture and Acromioclavicular Joint Injury: A Case Study Highlighting the Efficacy of Knowles Pin Fixation
Unusual or unexpected effect of treatmentYu-Jen Shih12BDEF, Hui-Chin Chang 3CDF, Chih-Lung Wu 24ABDEF*
Am J Case Rep 2023; 24:e939325
BACKGROUND: An ipsilateral fracture of the midshaft clavicle with dislocation of the acromioclavicular joint (ACJ) is a rare combination injury and almost always occurs following high-energy trauma. Currently, there is no optimal surgical approach for this kind of rare injury. We present a 60-year-old man with a traumatic combined linear midshaft clavicle fracture and ACJ injury simultaneously treated with Knowles pin fixation.
CASE REPORT: A 60-year-old male patient presented a linear midshaft clavicle fracture in the emergency room (ER) due to a road traffic accident. A linear fracture progressed to a displaced fracture at followup in the outpatient orthopedic department 3 days later. After open reduction with Knowles pin fixation for displaced clavicle fracture, postoperative followup radiographs revealed unexpected ipsilateral type V ACJ dislocation according to Rockwood classification. The next day, a closed reduction with percutaneous Knowles pin fixation was performed for ACJ dislocation. At the 1-year followup, radiographic and clinical results demonstrated complete union of the clavicle fracture and anatomic reduction of the ACJ with painless and full range of motion.
CONCLUSIONS: This report highlights that even a linear midshaft clavicle fracture can be combined with ipsilateral ACJ dislocation if the traumatic injury was caused by a high-energy road traffic accident. Therefore, an intraoperative stress view of the injured shoulder is recommended to recheck the stability of the ACJ after the clavicle fracture fixation to prevent a missed ACJ injury. In our case, an excellent outcome was achieved by using Knowles pin fixation simultaneously to treat the dual shoulder injury.
Keywords: Acromioclavicular Joint, Clavicle, Cost Savings, Fracture Fixation, Internal
Clavicular fractures are common, and constitute 2.6% to 5% of all fractures . The Allman classification system divides clavicle fractures into thirds according to anatomic regions. Group I fractures occur on the middle third of the clavicle, Group II fractures on the lateral third, and group III on the medial third. Midshaft fractures account for approximately 75% to 80% of all clavicle fractures . Midshaft clavicle fractures are common traumatic injuries caused by a direct impact on the shoulder girdle. There are 2 patterns of injury mechanism: a fall to the lateral aspect of the shoulder (85%) and direct impact to the clavicle (15%). Displaced midshaft clavicle fractures with nonoperative treatment have higher rates of nonunion and a greater risk of long-term sequelae. Most surgeons prefer open reduction with plate fixation due to rigid fixation, but closed reduction with intramedullary fixation uses smaller incisions and can also sufficiently restore the anatomy .
The acromioclavicular joint (ACJ) is one of the most common sites of shoulder girdle injury, accounting for 4–12% of all such injuries. The disruptions can be attributed to 2 mechanisms. In the first mechanism, a direct blow in the vertical direction damages the ACJ and ruptures the acromioclavicular (AC) and coracoclavicular (CC) ligaments. On the other hand, a fall on an extended and outstretched arm could cause the humeral head to be driven inferiorly into the acromion . For a better prognosis, the Rockwood classification of ACJ injury has been proposed. In type I injury, the AC and CC ligaments are intact. In type II injuries, the AC ligament is completely torn and radiographs may show the ACJ widened in the transverse plane with a slight elevation of the lateral end of the clavicle. Type III injuries involve complete disruption of both the AC and the CC ligaments. The clavicle is unstable in both the horizontal and the vertical plane, and stress-view radiographs are abnormal, with a CC interval widened up to 100%. In type IV injuries, the distal clavicle is displaced posteriorly into the trapezius and may tent the posterior skin. Type V is a more severe form of type III injury with disruption of trapezial and deltoid fascia, manifested by a 100–300% increase in the CC distance. Type VI is a complete dislocation with inferior displacement of the distal clavicle into a subacromial or subcoracoid position . Conservative treatments are highly recommended for type I and II dislocations. As for type III dislocation, there has been much debate over the optimal management. For type IV–VI dislocations, surgical interventions serve as an advantageous option . Among all published surgical techniques, 44% of surgeons prefer hook plate fixation for ACJ dislocation .
Isolated midshaft clavicle shaft fractures and ACJ dislocation are very common injuries, but midshaft clavicle fracture with ipsilateral ACJ dislocation is rare in shoulder girdle injuries. This kind of rare injury almost always occurs in high-energy trauma such as road traffic accidents or a fall from a horse, according to previous case reports [8,9]. Various treatments have been proposed in the literature, including conservative treatment  or precontoured plate fixation [9,11–14] for midshaft clavicle fracture; and wire [15,16], screw [10,17], hook plate [14,18–20], graft , tightrope [12,21], or endo-button  for unstable ACJ dislocation. However, there is currently no optimal surgical approach for this kind of rare injury. We report the case of a 60-year-old man with a traumatic combined linear midshaft clavicle fracture and ACJ injury, simultaneously treated with Knowles pin fixation.
A 60-year-old male patient suffered pain in the left shoulder due to a road traffic accident. He was unable to use his shoulder and reported local tenderness in the middle of the clavicle, but there was no neurovascular injury on physical examination in the emergency room (ER). Radiographs of the injured shoulder revealed a linear clavicle fracture (Figure 1). Conservative treatment with figure-of-eight bandage fixation and arm sling was recommended. Three days later, he visited our outpatient orthopedic department for progressively worsening shoulder pain. The followup radiograph showed that the linear midshaft clavicle fracture had converted into an inverted V-pattern displaced fracture (Figure 2). After discussing the risks and benefits of operative treatment for midshaft clavicle fracture, he decided to undergo surgical treatment due to intolerable pain. Under general anesthesia induction, the surgery was performed with the patient in the supine position. A skin incision was made over the clavicle fracture. The fracture site was identified by blunt dissection. The intramedullary canal of the proximal and distal fractured fragments was pre-drilled with a 3-mm Kirschner wire. Then, the Kirschner wire was penetrated through the posterolateral cortex of the distal fragment to make an entrance. A suction tip following the pre-drilled canal passed through the prepared entrance out of the skin. A Knowles pin (Zimmer 3.9 mm) was inserted from the posterolateral entrance of the clavicle by using a 2 mm suction tip as a guide tool. After fracture reduction, the Knowles pin was advanced into the proximal fragment to achieve fixation. Although the postoperative radiograph showed anatomic reduction of the clavicle fracture, we unexpectedly discovered an ipsilateral type V ACJ dislocation according to the Rockwood classification (Figure 3). For the treatment of ACJ dislocation, a closed reduction with percutaneous Knowles pin fixation was carried out the next day. With the aid of a C-arm image intensifier, the Knowles pin entry point was prepared at the lateral midportion of the acromion with a 2-cm longitudinal skin incision. A Kirchner wire was forcibly pushed downward to make a closed reduction (Figure 4A). The Knowles pin was then inserted from the entry point crossing the AC joint into the distal clavicle to achieve cortical anchoring over the posterior aspect of the distal clavicle (Figure 4B, 4C). The affected arm was held in suspension with an arm sling for 4 weeks after surgery. Active motion exercises started as tolerated by the patient in the fifth week. He could move his shoulder with almost full range of motion of the injured shoulder at the 2-month followup visit. Four months later, the fixation implants were removed under local anesthesia by outpatient surgery (Figure 5). After implant removal, the followup radiography showed that the clavicle fracture was fully healed and the ACJ dislocation was maintained in good reduction (Figure 6). At 1-year followup, the functional assessment score was the same between the injured and contralateral shoulders in the Constant-Murley Shoulder Score (96/96).
Midshaft clavicle fracture combined with ipsilateral ACJ dislocation is a rare injury in the literature. However, Ottomeyer et al  reported that ipsilateral clavicle fracture and ACJ injury is much more common than traditionally believed, with an overall incidence of 6.8% in 383 patients with clavicle fracture. As stated above, this means that some cases of clavicle fracture associated with ipsilateral ACJ injury may have been misdiagnosed. The reason is that the distal clavicle may not be strongly pulled upward by the sternocleidomastoid muscle when a midshaft clavicle fracture is present. So, most reported cases initially presented with a displaced midshaft fracture combined with high-grade ACJ dislocation. The other cases with ACJ injury were misdiagnosed, just as our patient’s ACJ dislocation was neglected before open-reduction internal fixation (ORIF) of the clavicle. In our case, we ignored the ACJ injury because the radiograph revealed a linear midshaft clavicle fracture without obvious ACJ space widening or elevation of the lateral end of the clavicle, in the ER. However, tracing the initial shoulder radiograph of our patient, it appeared that the radiograph revealed a little widening in the ACJ space at that time. The extent and nature of bone injury can be determined by the traumatic energy of an accident. Therefore, an accurate evaluation of shoulder injury in a high-energy road traffic accident should require an axillary view radiograph or a computed tomography scan to examine the ACJ, if an ACJ injury is suspected. Furthermore, the grade of ACJ injury may be underestimated prior to fixation of the clavicle fracture in this dual injury, as presented in our case. We recommend an intraoperative stress shoulder view to recheck the stability of the AC joint after clavicle fracture fixation to prevent missing the presence of an ACJ injury.
Although the treatment algorithms for isolated clavicle fracture and ACJ dislocation are quite clear, there is no protocol for midshaft clavicle fracture combined with ipsilateral ACJ dislocation, due to the rarity of cases in the literature. However, most surgeons who have published case reports believe that an optimal treatment result depends on achieving clavicle fracture union and restoring ACJ stability. Historically, midshaft clavicle fractures were treated nonoperatively; however, recent data suggest an increased risk of nonunion or symptomatic mal-union for conservatively treated comminuted displaced fractures . Open reduction with plate fixation can obtain rigid fixation conducive to fracture healing. This method is now a criterion standard treatment for midshaft clavicle fractures. Almost all authors of previous case reports used a locking plate to stabilize the clavicle fracture. However, surgical intervention through intramedullary fixation with Knowles pin has shown a result comparable to that from plate fixation, as reported in our previous study  and in a report by Lee et al . Although Knowles pin fixation is less stable than locking plate fixation for clavicle fracture, plating increases both the operative time and the surgical wound length, which are both related to the patient’s suffering. In addition, the cost of the precontoured locking plate is 40 times more expensive in comparison with the Knowles pin, in Taiwan (NT$ 40 000 vs NT$ 1 000, respectively). Based on the above reasons, we decided to use ORIF with Knowles pin to treat the clavicle fracture for this patient.
On the basis of case reports, most authors use a hook plate to treat this combined ACJ dislocation, as half of orthopedic surgeons prefer hook plate fixation for isolated ACJ dislocation. The hook plate is placed on top of the clavicle end with locking screws and a trans-articular hook is placed below the acromion, which provides sufficient reduction of the lateral clavicle. A previous study stated that vertical and horizontal reduction can be achieved after hook plate fixation . Despite the positive result, various complications such as wound infection, shoulder impingement, AC joint osteoarthritis, acromial erosion, and even clavicle fracture have been reported [28,29]. Most complications caused by the hook plate can be attributed to the implant design. As the device serves the function of providing stability, it could also induce a stress riser on the medial side of the plate resulting in clavicle fracture and over-correction of the ACJ related to poor hook angle leading to the erosion of the acromion.
Smooth or threaded pins had been used in the past for the treatment of ACJ dislocation and reliably provided good long-term function outcome in older reports. In a study by Wang et al , open reduction with extra-articular Knowles pin fixation and ligament repair was used for type V ACJ dislocation, and achieved great results. In our case, we modified the technique using a closed reduction with percutaneous pinning under the guidance of a C-arm fluoroscope. Since several authors have reported serious complications due to broken pin migration to vital organs [31,32], the use of smooth pins to treat ACJ dislocation was abandoned recently. However, a 3.9-mm diameter Knowles pin stabilizing the ACJ dislocation is more difficult to break compared with the less-than-2.5-mm diameter pins used in previous studies.
Compared with the clavicle hook plate, percutaneous Knowles pin fixation can be performed without exposure of the injured site. ORIF with plating for clavicle fracture and ACJ dislocation could cause extensive damage to normal soft tissue leading to possible wound complications. In addition, most patients need an additional surgery to remove the implants afterward. Additionally, there are some other advantages of Knowles pin fixation, including a small surgical wound, less soft tissue dissection, no palpable hardware, and easy application with a short operating time. Furthermore, the Knowles pin could be easily removed under local anesthesia by outpatient surgery.
With the rapid progress of arthroscopy, it is possible to obtain a stable reduction in ACJ with arthroscopic-assisted ACJ dislocation repair by using either a single or double tightrope suspensory loop device, a single or double endobutton, or a synthetic ligament with an absorbable polydioxansulfate sling to restore the coracoclavicular anatomic relationships . This new technique has been accepted and popular in recent years. However, the modern technique is more difficult to apply compared with percutaneous Knowles pinning and may require a long learning curve to skillfully operate.
This report highlights that even a linear midshaft clavicle fracture can be combined with a hidden ipsilateral ACJ injury in a high-energy road traffic accident. Therefore, an intraoperative stress shoulder view is recommended to recheck the stability of the AC joint after ORIF of the clavicle to prevent missing an ACJ injury. A displaced midshaft clavicle fracture can be treated with plate or intramedullary fixation, and surgical treatment of ACJ dislocation can be performed with various techniques in the literature. However, there is no protocol for midshaft clavicle fracture combined with ipsilateral ACJ dislocation due to the rarity of cases in the literature. Our method is relatively easy to perform, has less scarring, and is cost-effective. In our case, an excellent outcome was achieved after using Knowles pin fixation, at 1-year followup.
FiguresFigure 1.. Plain anteroposterior radiography of the shoulder revealing a linear midshaft clavicle fracture without obvious widening of the acromioclavicular joint space or elevation of the lateral end of the clavicle. Image was taken in the emergency department. Figure 2.. The followup radiograph taken in the outpatient department 3 days after the emergency department visit revealed an inverted V-pattern displaced midshaft clavicle fracture. Figure 3.. The immediate postoperative shoulder radiograph revealed a significant displacement of the acromioclavicular joint (ACJ) after open reduction and internal fixation with a Knowles pin for clavicle fracture. Type V ACJ dislocation was diagnosed according to the Rockwood classification. Figure 4.. (A) With the aid of a C-arm image intensifier, a closed reduction was made by using a Kirschner wire to push the clavicle into the anatomical position. (B) The Knowles pin from the acromion tip that crossed the acromioclavicular joint (ACJ) to the distal clavicle achieved cortical anchoring over the posterior aspect of the distal clavicle. The ACJ space was maintained by the lag screw technique when using the Knowles pin fixation method. (C) Postoperative radiograph showing a good reduction in ACJ dislocation treated with closed reduction with percutaneous Knowles pin fixation. Figure 5.. The 2 Knowles pins were removed under local anesthesia in outpatient surgery. The surgical wound is small when a Knowles pin is used. Figure 6.. After implant removal, chest radiograph showed that the clavicle fracture was fully healed and the acromioclavicular joint dislocation was maintained with good reduction at 1-year followup.
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