Retrograde intramedullary headless compression screws for treatment of extra-articular thumb metacarpal base fractures

Abstract

The purpose of the study was to evaluate clinical and radiological outcomes of extra-articular fractures involving the base of the thumb metacarpal treated with fixation using a retrograde intramedullary cannulated headless screw. A review of prospectively collected data was conducted on a consecutive series of 13 patients, treated with headless screw fixation for acute displaced fractures. All workers resumed full duties, while non-workers returned to unlimited leisure activities within a mean of 42 days. At 3 months follow-up, all range of motion measurements in the treated and untreated thumb were similar. Mean visual analogue pain score was 0.8 at rest and 1.4 during exercise and mean Quick Disabilities of the Arm, Shoulder, and Hand score was 5. All patients achieved radiographic union by 8 weeks. We conclude that the intramedullary headless screw fixation is safe and reliable for base of thumb metacarpal fractures, allowing for early postoperative motion and good functional recovery.

Level of evidence: IV

Keywords

Cannulated headless screws thumb metacarpal thumb metacarpal fracture minimally invasive fixation

Introduction

Fractures of the base of the thumb metacarpal account for 4% of hand fractures and can be further divided into extra-articular and intra-articular injuries (Stanton et al., 2007). Extra-articular fractures involving the base of the thumb metacarpal are commonly localized at the proximal metaphyseal-diaphyseal junction.

Primary aims in the treatment of extra-articular fractures of the base of the thumb metacarpal are restoring the initial length of the thumb and preserving the opening of the first web space (Liverneaux et al., 2015). Stable fractures and those angulated lesser than 30° can be managed conservatively by closed reduction and a wet plaster thumb spica. For unstable, shortened or angulated fractures, operative techniques include locking plates (Diaconu et al., 2011), open screw fixation (Leclère et al., 2012), percutaneous K-wire fixation (Greeven et al., 2012; Surzur et al., 1994) and tension band wiring (Safoury and Atteya, 2014). Each technique has advantages and complications and there is no consensus regarding the optimal treatment modality (Diaconu et al., 2011; Liverneaux et al., 2015).

To reduce the main complications of the classical surgical techniques for metacarpal fractures (re-displacement, collapse, soft tissue complications including superficial infection or tendon irritation) (Stahl and Schwartz, 2001; Zhang et al., 2016), some authors have fixed unstable extra-articular fractures of the finger phalanges and metacarpals using a single retrograde intramedullary cannulated headless screw with highly successful results (Boulton et al., 2010; Del Piñal et al., 2015; Eisenberg et al., 2019). The aim of the current study is to describe the technique of retrograde intramedullary cannulated headless screw fixation for extra-articular fractures involving the base of the thumb metacarpal and report our clinical and radiographic outcomes.

Methods

Patients

The current study was approved by our institutional research ethics committee and informed consent was obtained from all patients. Clinical and radiographic data was collected prospectively on 13 consecutive patients diagnosed and treated surgically for unilateral displaced extra-articular fractures involving the base of the thumb metacarpal with retrograde intramedullary cannulated headless screw fixation between January 2015 and December 2018. This series includes all eligible patients, without exclusions or loss to follow-up. There were 12 men and one woman, mean age 29 years (range 18–51). Eight fractures were work-related injuries, while five were sports injuries. Seven were transverse and six were short oblique. Twelve patients were right-handed, and the dominant hand was injured in 11 of 13. All fractures were closed. There were no associated neurovascular injuries.

Operative technique

Operative treatment was performed in all cases by a level 4 highly experienced surgeon (S.B-O.) (Tang and Giddins, 2016) within a single academic hand surgery practice using the same technique. This method of fixation is similar to the ‘axial strutting’ procedure described previously for extra-articular fractures of the base of the proximal phalanx (Del Piñal et al., 2015).

Minimally invasive retrograde intramedullary cannulated headless screw fixation was performed through a 0.5 to 1 cm (mean 6 mm; range 4–7 mm) transverse (11 cases) or longitudinal (two cases) skin incision (Figure 1). The incision was measured at the end of the surgery with a surgical caliper. Access to the metacarpal head was longitudinal between the extensor pollicis longus (EPL) and extensor pollicis brevis (EPB). The EPB tendon was retracted in a radial direction, while the EPL tendon was retracted in an ulnar direction, followed by a limited dorsal arthrotomy. Initially, fracture reduction was improved manually through extension and abduction of the distal fragment. The proximal phalanx of the thumb was maximally flexed to expose the head of the metacarpal. Under fluoroscopic guidance, a 1.3 mm guidewire was inserted along the longitudinal axis of the metacarpal medullary canal, as dorsal as possible, up to the distal edge of the fracture. At that point, reduction of the fracture was fine-tuned by extending the guidewire like a joystick (Figure 2). After the fracture was reduced, the surgeon temporally stabilized it by passing the guidewire through the trapeziometacarpal joint. Once the guidewire’s position was confirmed by fluoroscopy, the subchondral bone of the metacarpal head was countersunk with the cannulated countersink. The appropriate screw length was calculated based on preoperative imaging. A cannulated headless screw, slightly shorter than the total length of the metacarpal, was then inserted until its leading tip abutted the subchondral plate at the base of the thumb metacarpal. At this point, the screw inside the medullary canal is acting as an internal strut and supporting the base of the bone (Figures 1 and 2). For all the fractures in our series, 4.0-mm-diameter screws were used (FootMotion cannulated headless screw, Newclip Technics, Haute Goulaine, France). The maximum available length for the 4.0-mm screws is 50 mm, which is longer than the average length of a metacarpal (roughly 4.8 cm). At the end of the operation, the surgeon ensured that the trailing threads were completely buried below the surface of the cartilage. Over insertion of the implant was avoided. Frequent fluoroscopic checks prevented both these complications.

After surgery, a soft-bandage was used for the first week, during which each patient performed active range of motion (ROM) and passively assisted exercises and used their hand for daily activities. After 3 to 4 weeks (mean 24 days; range 19–29), unrestricted activities were permitted.

Assessments

At follow-up, an independent examiner evaluated all patients clinically. Catalogued assessments included objective and subjective clinical findings, radiological data, intraoperative and postoperative complications, secondary procedures and the need for revision, which we defined as removal of the screw for any reason. All the assessments were performed at 3 months follow-up on the affected and contralateral sides, except postoperative complications, such as arthrosis or chondrolysis on plain radiographs, which were assessed until the latest follow-up.

Movement of the thumb in opposition (0–10) and retropulsion (0–3) was assessed using the Kapandji classification system (Kapandji, 1986). Thumb radial abduction, thumb palmar abduction and measurements of thumb metacarpophalangeal (MCP) and interphalangeal (IP) active flexion and extension were recorded to the nearest 5° using a handheld goniometer. Grip, key pinch and tip pinch strength were recorded, in kilograms, using standard dynamometers (Jamar Dynamometer, Preston, MI, USA). All the objective assessments were performed at 3 months follow-up on the affected and contralateral sides. To compare the pinch and grip strength between the injured and non-injured hand, a minimal clinically important difference was defined as a difference of 20%, relative to the contralateral side, adjusted for hand dominance, as suggested by Crosby et al. (1994).

At the 3-month follow-up, patient-rated outcomes were assessed using the Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) score, and a 10-point visual analogue pain scale (VAS).

All patients had pre- and postoperative sagittal and coronal radiographs of the thumb. Serial postoperative radiographs were taken until the fracture had healed, and at the last visit. The degree of angulation and length of the metacarpal were measured (Centricity PACS; GE Systems, Bucks, UK). Comparisons were performed between the pre- and postoperative radiographs of the injured metacarpal and between the injured and contralateral, non-injured metacarpal. Radiographs were also taken until the latest follow-up to assess migration or subsidence of the screws and the development of narrowing, arthrosis or chondrolysis at the MCP and trapeziometacarpal joints. All patients underwent preoperative computed tomography (CT), and postoperative CT at 3 months follow-up, using a standard reformatting protocol to document union (union was defined as >50% of cross-sectional trabeculation). Articular surface measurements on multi-slice CT studies were performed (Del Piñal et al., 2015; Ten Berg et al., 2013) to estimate the impact of the screw on the cartilaginous surface of the head of the thumb metacarpal. Three-dimensional reconstruction and articular surface measurements (in square millimeters) were performed using OsiriX software (Pixmeo SARL, Bernex, Switzerland). Subsequently, the percentage of the joint area of the head of the thumb metacarpal occupied by the 4.0-mm-diameter screw was calculated. An independent radiologist read all images.

Results

While all the clinical assessments were made at 3 months after operation, patients were followed-up for a mean of 19 months (range 6–33) to exclude postoperative complications, such as arthrosis or chondrolysis on plain radiographs. All operations were performed within 7 days of the injury (average 4.2 days; range 2–7). The mean operative time was 18 minutes (range 15–26). Results for active ROM, strength and pain are summarized in Table 1.

Table 1.

Outcomes after 3 months compared with the contralateral hand.

Assessments	Fractured hands	Contralateral hands
Range of motion
Thumb opposition (0–10)^a	9 (8–10)	9 (8–10)
Thumb retropulsion (0–3)^a	3 (2-3)	3 (2–3)
Thumb radial abduction (°)	47 (40–50)	46 (40–50)
Thumb palmar abduction (°)	45 (40–50)	46 (40–50)
MCP flexion (°)	44 (30–70)	41 (30–70)
MCP extension (°)	12 (0–20)	5 (0–20)
IP flexion (°)	85 (80–90)	85 (80–90)
IP extension (°)	5 (0–10)	5 (0–10)
Strengths
Grip (Kg)	38 (31–50)	35 (28–50)
Key pinch (Kg)	9 (5–14)	10 (5–14)
Tip pinch (Kg)	6 (3–11)	6 (3–11)
Function
Quick-DASH scores	5 (0–10)	3 (0–7)
Pain
VAS rest (0–10)	1 (0–1)	0 (0–1)
VAS activity (0–10)	1 (0–3)	1 (0–2)

Data presented as mean (range).

Kapandji index.

IP: interphalangeal; MCP: metacarpophalangeal.

ROM and strength

All patients demonstrated full active MCP joint extension or hyperextension and full composite flexion at 3 months of follow-up. All the ROM measurements between the treated and untreated thumb were clinically similar. In the affected hand, mean grip, key pinch and tip pinch strength were 110%, 92% and 105% of the values in the unaffected hand, respectively, with no clinically important difference noted in any patient.

Pain and function

At the 3 month follow-up, no patient expressed a clinically important difference in the level of pain in their affected versus unaffected hand. There was no tenderness with compression of the thumb base or MCP joint in any patients. All employed patients resumed their full work duties, while unemployed individuals returned to unlimited leisure activities within a mean of 42 days (range 32–61) postoperatively.

Radiological measurements

Eight weeks after surgery, bone healing on plain radiographs was observed in all patients, with 92% (SD 7%; range 84%–99%) cross-sectional trabecular bridging on CT scan at 3 months follow-up. All exhibited medial and volar periosteal callous, suggesting secondary fracture healing. The mean angulation of the thumb metacarpal improved from 38° (SD 1.5°; range 36°–40°) preoperatively to 6° (SD 0.9°; range 5°–8°). Mean length improved from 41 mm (SD 2.1; 38–43 mm) preoperatively to 47 mm (SD 2.2; 44–49 mm) postoperatively. No intra-articular fracture extension was recognized on preoperative CT. Postoperative radiographs and CT imaging revealed no hardware migration or deterioration of metacarpal alignment. There was no evidence of arthrosis or chondrolysis on plain radiographs at latest follow-up. The mean surface area of the head of the thumb metacarpal was 223 mm² (SD 4.8 mm²; range 211–237 mm²), while the mean articular surface area used by the cannulated screws was 17% (SD 2%; range 15%–17%) for the 4.0-mm screw (Figure 3).

Complications

There were no intraoperative complications and it was not necessary to abandon the retrograde intramedullary cannulated headless screw technique during surgery in any cases. There were no postoperative complications and no secondary procedures or revisions were required at the latest follow-up.

Discussion

The results of our study suggest that retrograde intramedullary cannulated headless screw fixation, previously popularized for fractures of the finger phalanges and metacarpals (Del Piñal et al., 2015; Ruchelsman et al., 2014), is effective for fixation of extra-articular fractures of the base of the thumb metacarpal. The technique has been recommended for treating transverse and short oblique diaphyseal or metaphyseal fractures involving the metacarpals (distal or subcapital) and metaphyseal fractures of the phalanges (proximal or base). Minimally invasive retrograde fixation of fractures involving phalanges and metacarpals with cannulated headless screw was found to be reliable and associated with excellent functional results (Boulton et al., 2010; Del Piñal et al., 2015; Ruchelsman et al., 2014).

The technique can be described as ‘axial strutting’ because the screw acts as a girder inside the phalanx. Our technique is an adaptation of the method for thumb metacarpal neck fractures. In the thumb metacarpal, extra-articular fractures most commonly occur at the proximal metaphyseal–diaphyseal junction (Karl et al., 2015) with a similar pattern to finger proximal phalangeal fractures.

Fixation of bone via a minimally invasive approach has several advantages, one of which is not stripping the periosteum, which allows for minimal devascularization while providing enough stability to permit early ROM (Beck et al., 2019; Boulton et al., 2010). It may also minimize the need for hardware removal or additional surgery. It is not a new concept, having been employed previously for fractures of other bones, including the femur, humerus and tibia, for which intramedullary nailing is commonly used for diaphyseal and metaphyseal–diaphyseal fractures (Veillete and Steinmann, 2008).

The optimal management for extra-articular fractures of the base of the thumb metacarpal is not well established (Diaconu et al., 2011; Liverneaux et al., 2015), with the selection of technique largely governed by fracture characteristics and surgeon preference. Taking into account our experiences, and despite several articles documenting excellent results for this type of fracture with various other fixation methods (Henry, 2008; Meals and Meals, 2013), we believe that minimally invasive retrograde intramedullary cannulated headless screw fixation is a hybrid solution that offers the mechanical advantages of formal open reduction internal fixation (Del Piñal et al., 2015), yet fewer complications than other alternatives (Beck et al., 2019; Jann et al., 2018; Nucci et al., 2018).

However, retrograde intramedullary screw fixation is contraindicated in the presence of an active infection, in skeletally immature patients, and in fractures with intra-articular extension of the fracture (Del Piñal et al., 2015; Ruchelsman et al., 2014). As for most periarticular fractures (Dukas and Wolf, 2015), we recommend performing a preoperative CT in all patients to enhance preoperative planning and avoid fractures with intra-articular extension.

Although, in all our patients, the leading threads of the cannulated headless screw extended distal to the fracture line, because of the fracture pattern, we think that it is not necessary to use screws with shorter leading threads. Healing of the bone is secondary to the internal strutting of the screw not through the compression of the fracture.

One potential disadvantage of the retrograde intramedullary cannulated headless screw technique might be the risk of developing arthritic changes in the MCP joint, as a result of penetration of the screw through the cartilage. In several other studies (Beck et al., 2019), when the surface involved measured under 20% of the total surface area of the capsular cartilage, no short or midterm changes were noticed using intramedullary devices. In our series, the mean involvement was just 17%, and we too saw no articular changes at the latest follow-up. Nevertheless, long-term arthritic changes cannot be ruled out.

This study has the inherent limitations. The technique in our study was not compared with other treatment techniques. We also had only 13 patients in our sample. The length of follow-up was too short to assess potential longer-term complications, including the development of osteoarthritis. Nonetheless, we believe that retrograde intramedullary cannulated headless screw fixation is an attractive alternative to formal open reduction internal fixation and percutaneous K-wire techniques for treatment of extra-articular fractures of the thumb metacarpal.

Footnotes

Confidentiality

The authors declare that patient confidentiality was maintained throughout the duration of this study and afterwards.

Declaration of conflicting interests

The authors declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical approval

This study was approved by our institutional research ethics committee.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Informed consent

Informed consent was obtained from all included patients.

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