Comparative Study Between Intramedullary K Wires Versus Mini-plates and Screws in Fixation of Metacarpal Shaft Fractures in Adults

INTRODUCTION

Metacarpal bone fractures are one of the commonest orthopedic injuries,¹represent about 10% of all fractures,² and the most frequent hand fractures reaching up to 40%.³ The metacarpals are miniature long bones that are slightly arched in the longituidinal axis and concave at the volar surface. The weakest point is just behind the head.^{4, 5}

Metacarpal fractures may be complicated by deformity from neglection of treatment, stiffness from overtreatment, and both deformity and stiffness from mal-treatment.⁶

The goals of treatment include early diagnosis, anatomical reduction correcting the rotational and deformities, preservation of soft tissue, preservation of the longitudinal and transverse arches, and maintaining length of the metacarpus because shortening of more than 3 mm will lead to an imbalance between the extrinsic and intrinsic hand muscles.⁷

Operative fixation of hand fractures has gained increasing popularity ⁸ due to better materials, implant designs, instrumentation,⁹ a better

understanding of the biomechanics of internal fixation, availability of subspecialists in hand surgery, ease of anesthesia and improvement of hand physiotherapy methods.¹⁰

Over the last 25 years, treatment of metacarpal fractures have greatly expanded.⁸ It can be treated by closed reduction and splinting ¹¹ which have the disadvantage of difficulty to preserve joint mobility to avoid stiffness,¹² Kirschner wires fixation, intraosseous wiring, and screw fixation with or without plating having the advantage of early active motion but carry the disadvantage of wide surgical exposure and soft tissue injury.¹¹

The  purpose of  this comparative study   was to assess Q.DASH score, TAF score, hand grip and union time to determine which fixation method (mini plates or K wires) provides a better functional and radiological outcome for the treatment of metacarpal shaft fractures. Where K wire fixation is a common technique that has the advantages of the subcutaneous nature of hand bones, small size, and their limited loading potential for the stress placed on hardware,¹³ While mini-plates produce an anatomical reduction with  good stabilization that is rigid enough to allow rapid mobilization, but rupture of extensor tendons, stripping of periosteum with affection of nutrition, difficult technique, loosening and distraction of the implant and infection are common problems with mini-plates.⁸

Rehabilitation is the most important aspect of treatment. Early motion after fixation of hand fractures is particularly important because tendon gliding and joint mobility are crucial to a well functioning hand.¹⁴

PATIENTS AND METHODS

All patients included in this prospective comparative randomized study were managed and followed up at Al-Azhar University Hospital. All patients were selected from the orthopedic outpatient clinic of Al-Azhar University Hospitals, Cairo, Egypt. The protocol was discussed and approved for clinical study by the Ethical Research Committee of Al-Azhar University and written informed consent was obtained. All patients were evaluated over the period from January 2019 to February 2020. All patients were followed up for 6 months.

Thirty (n=30) patients with  fracture of shaft metacarpal bone were dividedinto 2 groups: group A (n=15) were managed by closed reduction and percutaneous fixation by antegrade intramedullary K-wires, and group B (n=15)  were managed by ORIF by mini-plates and screws.

The inclusion criteria comprised adult patients (≥18 years old) with recent closed fractures of shaft of any medial four metacarpal bones ( Transverse, oblique, and spiral fractures) with angulation of more than 30^o or with a shorting of more than 2 mm or rotational deformity and we excluded pathological fractures, contaminated compound fractures, fractures with bone loss, thumb metacarpal fractures, stable undisplaced fractures, old fractures and fractures with Intra-articular extension.

Clinical assessment was based on the hisrory taking in the form of the patient's name, age, gender, hand dominance, medical diseases, special habits of medical importance, time and mechanism of trauma and complaints of the patients (Pain. Swelling. Limited range of movement. Paraesthesia ). The patient was fully examined systematically for any other associated injuries and locally for checking the initial deformity (angulation, rotational malformation), the rest of the hand skeleton, skin condition, the intensity of the edema and neurovascular examination. Below elbow extended slab was done for all patients.  Elevation of the limb with analgesics, anti-edematous measures were recommended until the operation.

Radiographic evaluation: Anteroposterior view, Lateral view, and Oblique view.

Surgical technique:

      The operations were done under brachial anesthesia or general anesthesia and the position of the patients was supine with affected limb on side table. Prophylactic intravenous antibiotic was given preoperatively.

Fixation by Mini-plates (Figure 1,2):

After inflation of the pneumonic tourniquet and sterilization, a direct skin incision is made at the ulnar border of the 5^th  MCB and the radial border of the 2^nd MCB.  A longitudinal incision is made between the 3^rd and 4^th  metacarpal rays for exposure of 3^rd and 4^th MCB fractures. Then dissection of subcutaneous tissue with identification and preservation of superficial nerves and veins. Then retraction of extensor tendons. The periosteum over the fracture is elevated. Then fixation of the fracture by mini-plates and screws which placed on either the dorsal or the lateral surface of the metacarpal bone.  Tourniquet is deflated with proper hemostasis and then skin closure. Then below elbow extended slab is applied dorsally and finger motion exercises were encouraged. Sutures are removed within 14-16 days.

Figure 1: skin incision and exposure of 5^th MCB fracture 

Fig. 1: show plate fixation of 5^th MCB fracture andskin closure

Fixation by Percutaneous K-wires (Figure 3,4): 

Skin incision about 1 cm is done over the base of each metacarpal under direct fluoroscopic image then the base of the fractured metacarpal bone is perforated by drilling in a nonarticular area directed to medullary canal. Prepared K-wire is introduced antegrade in the proximalfragment using a T handle. At the fracture site, the reduction done by Jahss maneuver.¹⁵ Then K-wire is  inserted in the distal fragment, then rotated 180 degrees to keep the bent distal end of the wiredirected volarly to maintain reduction, correct volar angulation, and achieve three-point fixation. The thickness of the K wire is ranged from 1.6 to 2.0 mm. One or Two K wires are used which gave more rotational and angular stability. The proximal part of the wire is bent and keep out to be removed later on. The wound was closed withstitches.

Figure 3: skin incision andpenetration of base of 3^rd MCB by drill under the image

Figure 4: insertion of K wire using T handle

Postoperatively, a below elbow extended slab in the intrinsic-plus position was applied for all the patients and encouraged to start active and passive exercises for fingers within the splint. Five weeks postoperative or when there were radiological signs of bone healing, the wires were removed and patients were advised to do wrist and finger motion exercises without a splint.  

Statistical analysis:

Data were analyzed by the Statistical Program for Social Science (SPSS) version 24.  Expression of quantitative data was as mean± standard deviation (SD). Qualitative data were expressed as frequency and percentage and The following tests were done:

Independent-samples t-test of significance used when comparing two means, Mann–Whitney U test used when comparing two means (for abnormally distributed data), Chi-square test was used when comparing non-parametric data and probability (P-value): P-value < 0.05 was considered significant and P-value > 0.05 was considered insignificant.

The sample size was calculated using the following formula:

N = (Z / Δ)² X P (100 – P)

Z: a percentile of slandered normal distribution determined by 95% confidence level = 1.96.

Δ: the width of the confidence interval = 12

P: the prevalence of disease = 10% of all fractures

N = (1.96/12)² X 10 (100 - 10) = 24 patients

Patients were randomized in blocks of three to receive either K wire fixation or mini-plate fixation. Randomization, data entry, storage, and processing were performed using a web-based electronic data capture (EDC) system.

Figure 5: Male patient 20 yrs old with RT 5^th MCB fracture. Images show preoperative facture, k-wire fixation, after healing and range of motion.

Figure 6: Male patient 24 years old with RT 4^th  MCB fracture. Images show preoperative facture, k-wire fixation, after healing and range of motion.

RESULTS

Fifteenpatients were managed K wire, and 15 were managed by mini-plate. All patients had a fracture of a single metacarpal bone. Non-patients involved in the study were diabetic, hypertensive nor having other debilitating diseases. Summary of the demographic data is detailed in Table 1 and assessment was done according to Q. DASH score, TAF score, grip strength (Figures 5 and 6).

Results as regards Quick DASH Score, TAF score, and handgrip

The grip strength measured at third months after fixation using a manual dynamometer and compared to the normal hand. It ranged from 70-95% in group A and 70-98 %. The grip strength was nearly equal in both groups(P=0.713). The TAF score of studied patients ranged from 200 - 260 with no significant difference between the two groups except 1 patient in group B with his score of about 170. There was no statistical significant difference between studied groups as regard hand grip %, quick DASH score & TAM score (P-value: 0.74).

Results as regards union time

Although all fractures eventually healed (except one case in the miniplate group), the plate fixation group had a longer time for radiological union (8 – 12 weeks) when compared with the Kirschner wires group (4 – 8 weeks).   There was a statistically significant difference (p-value < 0.05) between studied groups as regard union time (P-value: 0.001).

Result as regards operative time

Percutaneous K. wire fixation under fluoroscopic imaging (despite its radiological hazards) had a shorter operative duration than with ORIF by mini-plates with highly statistically significant difference (p-value < 0.001) between studied groups.

Results as regards complication

There was no statistically significant difference between studied groups as regard complications.

Final Results

It was found that after 6 months of follow up, group A showed 93 % satisfactory results, while group B showed 85 % satisfactory results with a total result of 90% satisfaction for all cases with no statistically significant difference (p-value > 0.05) between studied groups as regard total result.

Table (1): summary of demographic data

Table (2): Comparison between studied groups as regard Quick DASH score, TAF, and handgrip

Table (3): comparison between studied groups as regard union time.

Table (4): comparison between studied groups as regard operative time.

Table (5): comparison between studied groups as regard complications.

Table (6 ): comparison between studied groups as regard total result