Single Buried Intramedullary K-Wire Fixation in Nonthumb Metacarpal Shaft Fractures with Immediate Postoperative Mobilization without Any Immobilization

Objective This study aims to evaluate the outcomes of single intramedullary K-wire fixation in nonthumb, metacarpal shaft fractures with immediate postoperative hand mobilization without any immobilization. Method This is a retrospective case series conducted from January 2019 to December 2022. We included patients with closed, simple transverse, or short oblique metacarpal shaft fracture treated with single, 1.4 mm, intramedullary K-wire fixation. Gentle postoperative range of motion exercise was encouraged in every patient without any hand, finger, or wrist motion restriction material. Clinical outcomes were evaluated with total active flexion; grip strength; disability of arm, shoulder, and hand (DASH) score; and the American Society for Surgery of the Hand Total Active Flexion (ASSH TAF) score. Results This study included 34 patients, 25 males and 9 females with a mean age of 33.14 years (ranging 18–59). A total of 43 metacarpal shafts were treated. The mean DASH score at two and 6 weeks postoperative was 41.5 (ranging 19.16–60.34) and 9.58 (ranging 0.83–23.27). The mean final DASH score at last follow-up was 3.48 (ranging 0–8.33). Mean TAF at 2 weeks postoperative, 6 weeks postoperative, and at final follow-up was 203.8 (ranging 185–240), 238.2 (ranging 220–270), and 259.25 (ranging 240–270) degrees, respectively. The mean grip strength of the injured hand was 66.14 and 86.1% of the uninjured hand at 6 weeks and 3 months postoperative. There was no nonunion, malrotation, or infection. In conclusion, single intramedullary K-wire fixation gives excellent outcomes in the treatment of single or multiple, simple, metacarpal shaft fractures without the need of postoperative immobilization.


Introduction
Fracture of the metacarpal and phalanges are the most common fractures of the upper extremity [1,2].Te estimated incidence of metacarpal fracture is 13.6 per 100,000 person/ year [3].Although hand fractures can be successfully treated by nonoperative treatment, several complications (e.g., malunion and stifness due to prolonged immobilization) are common in this treatment method [1,4].Open reduction and internal fxation with plate and screw could provide excellent fracture reduction and stability; this operative treatment method has a higher risk of soft-tissue damage, adhesion, or infection [1,[5][6][7][8].Hence, minimal invasive operative treatments have gained popularity as they promote bone healing with minimal soft-tissue dissection and limited fracture immobilization duration [1,4,6,7,9,10].
Tere is still no consensus on the postoperative management of metacarpal fracture.Te rehabilitation protocol varies and depends on the preference and experience of each institute.Several authors have lessened the immobilization material and promoted early mobilization after K-wire fxation [14,15,[18][19][20][23][24][25][26][27][28].Moreover, recent evidence revealed that early mobilization of fngers after the injury causes signifcant consequences in only a few patients who underwent nonoperative treatment [29][30][31][32].Tese studies raise the question of the necessity of postoperative hand immobility.
Terefore, our objective was to evaluate outcomes along with the complications of immediate postoperative hand mobilization in metacarpal shaft fracture patients who underwent single buried antegrade IM K-wire fxation without postoperative immobilization.We hypothesized that immediate postoperative hand mobilization can be initiated after single IM K-wire fxation in metacarpal shaft fracture and the fracture unite without serious complications.

Study Population.
We conducted a retrospective case series of patients diagnosed with metacarpal shaft fracture to evaluate the outcome of single, buried, antegrade IM Kwire fxation within 2 weeks of the initial injury.Te study was conducted between January 2019 and December 2022.Te inclusion criteria were as follows: (1) closed simple transverse or short oblique metacarpal shaft fractures and (2) unacceptable deformities [13,18] that could not be treated by nonoperative treatment or patients who could not withstand conservative treatment with a slab or cast immobilization.We included patients with either single or multiple metacarpal shaft fractures.We excluded patients with comminuted, spiral, and long oblique metacarpal shaft fracture which were not appropriate for IM Kwire fxation [1,5].Patients with concomitant injury that would preclude early hand mobilization (i.e., severe head injury) were also excluded from this study.Te Institutional Review Board approved our study protocol (num 027/65).

Operative Technique.
Surgery was performed under wrist block which allows for intraoperative active hand motion to ensure proper fracture reduction and fxation.Te patient was placed in the supine position with the pronated and extended arm on a hand table.Te tourniquet was infated to control the bleeding.Te procedure was performed under fuoroscopic guidance.
A 1 cm skin incision was made, starting from the base of the afected metacarpal and continued proximally.Subcutaneous vessels and tendons were retracted and protected using a Senn retractor while exposing the metacarpal base.Te dorsal cutaneous branch of ulnar nerve (DCBUN) should be identifed and protected when operating on the fourth or ffth metacarpal.Te 2.0 mm K-wire was inserted into a universal T-handle chuck.Tis K-wire was used as an awl to create an entry hole at the cancellous bone of the metacarpal base, just distal to the carpometacarpal joint.Tis entry hole should always be in line with the central axis of the operated metacarpal.
Typically, a 1.4 mm K-wire is chosen.Before bending, the pointy tip of the K-wire is cut to prevent any potential injury to the surgeon.Te blunt end of the K-wire will be introduced into the medullary canal to avoid metacarpal head perforation.Once the metacarpal fracture is reduced, the K-wire is placed in position with the assistance of an image intensifer.Te distal tip of the K-wire is positioned at the subchondral bone of the distal metacarpal metaphysis.Te length of the implant is determined by measuring the length from the tip of the K-wire to the entry point.At the entry point, the K-wire is bent up about 45 degrees and its proximal end is twisted into a loop.Each patient's soft tissue thickness will determine the position of the loop.Tis loop should be located in the subcutaneous tissue when the implant was properly introduced into the metacarpal (Figure 1).
Te implant was introduced into the medullary canal through the previously made entry point.Any malrotation must be corrected before passing the K-wire through the fracture site.Te K-wire was pushed to engage frmly into the subchondral bone.Intraoperative active hand motion under the image intensifer was always performed to evaluate any displacement from early hand motion.Te implant was buried under the skin and the skin was closed using a nonabsorbable suture.

Postoperative Protocol.
Immediate mobilization of the wrist and all fngers was initiated after surgery without any motion restriction instrument.During the frst two weeks, with no specifc rehabilitation protocol from the surgeon or hand therapist, only gentle fexion and extension of all metacarpophalangeal and interphalangeal joints were allowed.Te patients were permitted to resume performing light daily activities, that is, the patients can use their hand in their daily activities only as pain allows.Te patients were encouraged to do gentle progressive hand and fnger motions to eventually achieve full range of motion (ROM).Forceful hand clenching or pinching was strictly prohibited.
Te suture material was removed 2 weeks after the operation.Carefree contact with water in daily activities was allowed after the removal of the suture material.All patients were advised that no pain or discomfort should be felt in the injured site during the activities.If any discomfort is felt, the patient should discontinue that activity and rest the operated hand.

Advances in Orthopedics
Finger malrotation was assessed clinically by observing fnger scissoring at full fnger fexion and extension [30].We observed the ROM and malrotation, evaluated the grip strength and DASH score, and obtained a repeat plain radiograph of the hand at 2 and 6-8 weeks then 3 months after the operation.We defned radiographic bone healing as a present of bony coalition at the fracture site [33].If clinical signs of bone union and radiographic bone healing were observed, the K-wire was removed.Te average time for implant removal was approximately 6 weeks.We removed the K-wire under local anesthesia in an out-patient department.Grip strength and total active fexion (TAF) of the operated hand were compared to the uninjured hand.When multiple metacarpals were broken, data of the fnger with worse TAF were recorded.
Functional outcomes were assessed at 2 weeks, 6 weeks, and 3 months postoperative by using the American Society for Surgery of the Hand (ASSH) TAF score [34], disability of arm shoulder and hand (DASH) score [35] and TAF compared to the uninjured hand (%TAF).ASSH TAF was determined to be excellent (>220 o TAF), good (120-80 o TAF), or poor (<80 o TAF).

Statistical Analysis.
All statistical analyses were performed using STATA 16 (StataCorp LLC, College Station, TX, USA).Data distribution was evaluated with the Shapiro-Wilk test.Continuous data with normal distribution were demonstrated using mean ± standard deviation (SD) and median with interquartile range (IQR) for non-normal distribution.Categorical data were presented with count and percentage.Inferential statistics were determined using paired t-test, Wilcoxon signed rank test, and Fisher's exact test according to data characteristics.Te level of statistical signifcance was set at p < 0.05.

Results
Tis study included 34 patients, 25 males and 9 females with a mean age of 33.52 years (ranging 18-59).Tere were 9 patients with multiple metacarpal fracture.A total of 43 metacarpal shafts were treated.Demographic data of the patients are shown in Table 1.
Te mean overall clinical follow-up period was 97.08 days (ranging 40-154).Healing was obtained in all patients.A sign of radiographic bone union was observed at a mean of 47.3 days (range 37-56).No infection was observed.
Among 34 patients, three patients satisfed with the treatment result and declined further appointment after Kwire extraction.Four patients were lost after implant removal.All 7 patients with short follow-up showed sign of bone union and achieved excellent ASSH TAF score (Figure 2).
Scissoring of fnger during full fngers' fexion had never been observed throughout the treatment course.Tere was no infection, stifness, tendon irritation, or metacarpal head perforation observed.Five patients with ffth metacarpal fracture reported minimal postoperative paresthesia on the dorso-ulnar side of the injured hand.All patients' symptoms resolved within 3 months after surgery.One patient with ffth metacarpal shaft fracture had a dorsal callus bump at the fracture site.

Discussion
IM K-wire fxation in metacarpal fracture is a well-known treatment.Tere are many described techniques and postoperative protocols for this procedure.Abulsoud et al. were the frst to report a study that describes and investigates the outcomes of fxation of metacarpal shaft fractures using a single, 1.8-2.0mm, buried K-wire [18].In our technique, due to a smaller body confguration of the Asian population, it is difcult to insert a 1.8 mm K-wire into the metacarpal medullary canal.Tus, we have chosen to use the 1.4 mm Kwire instead.A bigger or smaller diameter of the K-wire can be chosen based on the diameter of the medullary canal [28].Nonetheless, by performing intraoperative active hand motion under an image intensifer and based on the fndings of our study, we found that single 1.4 mm K-wire can also maintain fracture stability throughout the treatment course, even in a ffth metacarpal where the medullary canal diameter is wider than the others.However, it is of utmost importance to note that the tip of the implant must frmly engage with the subchondral bone to achieve stability and only gentle postoperative hand movement that cause no hand discomfort can be allowed until bone union.
According to Abulsoud et al., their study population was limited only to patients with single metacarpal shaft fractures [18].Various studies also reported outcomes of single IM K-wire fxation in metacarpal neck fractures, further supporting the concept of single IM K-wire fxation [18][19][20][21][22]. Nonetheless, every study on a single IM K-wire applied postoperative immobilization.Based on our fndings, immediate postoperative gentle hand motion can be initiated, without the need of postoperative immobilization in patients with simple metacarpal shaft fracture.Our results support the idea of single IM K-wire fxation in metacarpal shaft fracture.Furthermore, we observed that single IM K-wire fxation is also adequate in stabilizing multiple metacarpal shaft fractures (Figure 3).
From our fndings and previous reported literature, immediate gentle postoperative ROM of the metacarpophalangeal joint (MPJ) and interphalangeal joint (IPJ) does not afect fracture healing or patient's hand function [28].Immediate mobilization provides several advantages, including a rapid return to daily activities, fast recovery of hand ROM, and fewer complications and discomfort from prolonged immobilization [18,23,24,27,28,30].Our operative technique and protocol of immediate mobilization are slightly diferent from what was described earlier by Rocchi et al. [28].We apply a single K-wire in every metacarpal fracture.Te operation is always carried out under local anesthesia to evaluate intraoperative active hand motion.Consequently, it can be ensured that every fracture achieves stability during active hand mobilization (Figure 4).In addition, the implant is buried under the skin.By doing so, every patient reported that they can comfortably return to daily activity such as bathing and self-care after the operation.
We prefer to curl the proximal end of the K-wire into a loop and bury them under the skin to prevent tendon and soft-tissue irritation or a possibility of pin tract infection.In previously reported techniques of buried IM K-wire, the proximal end of the K-wire was frankly cut.With such a straight cut, there have been reports of tendon rupture, skin irritation, pain, and stifness [12,22,36].Even the surgeon cut the K-wire at the periosteum level to reduce the overlying soft-tissue irritation, late K-wire migration, or pain and stifness from soft-tissue irritation can occur [14,26,36].Moreover, the K-wire that was cut too close to the bone is difcult to remove [25,36,37].Our patients never report pain or stifness from the buried implant.Observing from our treatment results, we believe that our technique could reduce soft-tissue complications such as skin or tendon irritation.In addition, the twisted proximal end of the K-wire can be easily identifed and removed.
In our protocol, an adequate intensity of postoperative mobilization must be tailored according to the patient's tolerability.Te patient is advised to limit the afected hand activity if there is any pain at the fracture site.As a result, the patient's rehabilitation intensity increased inversely to pain.Subsequently, the patients will gradually regain their normal ROM along with the fracture healing.
Complications of single IM K-wire fxation in metacarpal shaft fractures include stifness, nonunion, and metacarpal head perforation [18].Tough we did not observe these complications in our population, we did notice other complications.In patients with ffth metacarpal shaft fractures, DCBUN irritation can be observed.our patient, hyposthesia also recovered within 3 months after surgery as stated by She et al. [22].Tere can be a dorsal callus formation at the fracture site which may limit full fnger extension.Nonetheless, this complication was observed in only one of our patients, who had full fnger fexion and excellent return of function at 6 weeks postoperative.Te patient declined further appointment, thus we were unable to  Advances in Orthopedics observe a long-term result of this complication (Figure 5).
From the previously reported literature, we supposed that extension lag would resolve within one year after surgery [31].
To the best of our knowledge, we are the frst to report outcomes of metacarpal shaft fracture fxation using single buried K-wire, with immediate postoperative hand motion without any immobilization.However, there are some   6 Advances in Orthopedics drawbacks to this study and the surgical protocol.Firstly, the follow-up time was relatively short.We attempted to follow our patient for up to one year, but every patient declined further appointments when the function of their operated hand was comparable to their contralateral hand.Secondly, there is also a faw in exposing surgeons, personnel, and the patient to radiation during the operation.After bone union, the patient requires a second operation to remove the implant.Lastly, this is a retrospective case series without comparison with other techniques.Terefore, a larger prospective comparative study with a longer follow-up period is needed to further investigate these outcomes.

Figure 1 :
Figure1: Te steps in the K-wire prebending:(a)  how to measure the length of the implant, (b) using the blunt end of the K-wire as an implant tip, the tip was bent up about fve degrees and the proximal part of the K-wire was bent up about 45 degrees, (c) the loop was made by twisting the wire around the plier, (d) the plier is used to further compress the loop diameter, (e) cut and remove the remaining K-wire, (f ) the cut proximal K-wire end was twisted to align with the implant, thus preventing the present of any sharp edge that could irritate the soft tissue, and (g) the fnal shape of the implant.

Figure 2 :
Figure 2: A 19-year-old male, with fracture of the fourth and ffth metacarpal shafts: (a) preoperative radiographs, (b) 2 weeks postoperative range of motion, (c) at 6 weeks after the operation, the patient's radiographs showed a sign of bone union.He regained excellent ASSH TAF score.His TAF of his left ring fnger was 265 degrees (normal: 270).His grip strength was 71.15% of the contralateral hand.His DASH score was 14.16.He had lost to follow-up after implant removal.

Figure 4 :
Figure 4: A 23-year-old female with fracture of the fourth metacarpal shaft of her left hand: (a) preoperative radiographs, (b) postoperative radiographs and clinical pictures of her hand motion at 2 weeks, (c) the patient regained full ROM at 6 weeks after the operation, and (d) uneventful bone healing and excellent functional outcomes were observed at 5 months.Her grip strength was 86.48% and the DASH score was zero.She denied further appointment.

Figure 3 :
Figure 3: A 23-year-old male with fracture of the fourth and ffth metacarpal shafts: (a) pre and postoperative radiographs of his right hand, (b) clinical pictures of the patient's hand ROM at 6 weeks postoperative, (c) clinical pictures of his ROM at 3 months after surgery.Te radiograph showed bone union.He regained full ROM.His DASH score was 5 and his grip strength was 77.46% compared to his left hand.
PO: postoperative; DASH: disability of arm shoulder and hand; TAF: total active fexion.