1 Introduction

Extensor tendon injuries, predominantly extensor pollicis longus (EPL), secondary to distal radius fractures have been reported occasionally since the first ever description by Duplay in 1876. The incidence of this complication has been variably represented between 0.07% and 17% of distal radius fractures which includes those which are conservatively managed and those underwent internal fixation.^1–3 However, the incidence appears to be slightly higher with surgical treatment than the conservative treatment⁴ leaving aside the possibility of underreporting. The dorsal plating system that evolved primarily, quickly was realized to be notorious for causing extensor tendon irritation, attrition and even ruptures which led to the advent of the currently popular volar locking plates. These were designed with the claim of avoiding the aforementioned complication, but the recent literatures report otherwise. Here, the culprit being the over projecting screw tip dorsally or off shooting of the drill while operating. Nevertheless, the ruptures have been also reported with conservatively managed distal radius fractures, especially the un-displaced ones wherein the extensor retinaculum remains intact (Fig. 1). Hematoma, bone displacement and callus formation further narrow the confined space in the compartment and predisposes the tendon to ischemia and attrition.⁵

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Fig. 1 EPL rupture in a patient with undisplaced distal radius fracture treated conservatively.

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From our hospital database, we identified patients who presented with rupture of EPL or other extensor tendons secondary to distal radius fractures (and implants in the distal radius) and retrospectively analyzed the factors leading to the tendon rupture. Based on our analysis, we herein suggest preventive measures to minimize the incidence of such ruptures and elaborate the reconstructive options available for treating them.

2 Materials and Methods

21 patients who underwent treatment for extensor tendon rupture following distal radius fractures in the period of 2014–2022 were retrospectively analyzed. Table 1 details the patient demography and the surgical details. There were 11males and 10 females which included four pediatric patients. Two of these 21 patients had been managed conservatively, one for the extra-articular distal radius fracture and the other with wrist pain following fall on outstretched hand (radiograph not showing any fracture) whereas rest 19 had undergone surgery for the radius fracture. The average age of the patients was 38 years (range 7–70 years). The dominant hand was affected in eight patients. The time interval between the fracture fixation and tendon rupture, the time interval between tendon rupture and presentation, the extensor tendons injured and the position of the impinging screws or bony spur in relation to the extensor compartments, necessity for implant removal and modality of tendon reconstruction were studied in these patients.

2.1

2.1 Surgical technique

All the patients were operated with brachial plexus block under tourniquet control. The ruptured extensor tendon is approached through a longitudinal incision over the dorsum of distal third of the forearm where the proximal cut end was identified. The distal cut end was often not seen in the forearm incision and it was identified with a separate longitudinal incision over the medial border of the first metacarpal. There was always a gap at the rupture site and direct approximation was never possible (Fig. 2). The adjacent extensor tendons-the Extensor Indicis Proprius (EIP) and the Extensor Digitorum Communis (EDC) slip to index and middle fingers were always inspected for a concomitant injury. In two of our 21 cases there was concomitant injury to the extensor tendons of the index finger. The underlying cause for the rupture is then addressed-irregular bone surfaces are flattened; prominent screws are removed in recent fractures or the total implant is removed when the fracture has united. The implants are removed through a separate volar incision as and when required. The choice between the tendon grafting to bridge the gap between the ruptured ends and tendon transfer to the EPL was based on three factors:-Patients who presented more than 2 months from their rupture were straight considered for tendon transfer as in such delayed presentations the proximal cut end of EPL would have undergone adaptive shortening and may not function well after repair. In such cases, our preference is to use the EIP to EPL transfer. In cases with early presentation, the gaps were bridged with tendon graft (often with palmaris longus).-If the proximal cut end had a good tendon tissue, it was considered for grafting whereas if the rupture was very close to the musculotendinous junction where strong repair would not be possible, we opted for tendon transfer.-If there was concomitant injury to the extensor tendon of the index finger, tendon transfer of the EIP would not be possible, therefore, we opted for tendon grafting, if the above factors favored it, else we opted for Flexor Digitorum Superficialis (FDS) transfer to EPL.

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Fig. 2 An intra-operative picture showing the gap between the ruptured ends after trimming of the frayed tissue in a case which presented within a week. End to end was never possible in our series. The gap could be bridged by a tendon graft (as in this case) or one could resort to tendon transfer.

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3 Results

EPL was found to be the most commonly ruptured tendon, seen in all our patients except one where EIP was the only tendon found to be ruptured. Two patients had concomitant rupture of EIP and EDC tendon to index finger along with EPL. One patient had associated rupture of the EIP tendon with attrition of the EDC slip. The time interval between the fracture fixation and tendon rupture averaged at 32.5 months (range: immediate post-operative period to 17 years) [Table 1]. Among the 19 patients who underwent internal fixation, four pediatric patients were operated with intramedullary nail and one adult patient was operated with K- wires. All the other patients were treated with volar locking or dynamic compression plate (LCP/DCP) [Table 1]. Complete rupture of the EPL tendon was noted in 20 patients and it was found impaled at the fracture site in one patient. In eight of these cases, the distal and medial most screw of the volar locking plate was found to be the prominent and impinging on the extensor tendons. The distal most shaft screw of DCP was found to be protruding beyond the dorsal cortex in one patient. All these patients, except one underwent implant removal (18 at the time of tendon reconstruction and two were removed earlier before presentation to us). End to end repair of the ruptured tendons was never possible even in patients who presented earlier. 10 patients underwent reconstruction of the EPL tendon with inter-tendinous bridge grafting utilizing the native stump (Palmaris longus- 8 and Extensor carpi radialis longus split graft- 2). One patient underwent inter-tendinous grafting between Palmaris longus and EPL. All the other patients underwent transfer of either EI (8), FDS of ring finger (1) or Palmaris longus to EPL (1). 15 patients were available for follow-up at six months. Thumb extension was restored in all these patients; EPL function was noted by the patient's ability to lift the thumb off the table when the palm is placed flat on it. We observed that full thumb extension was achieved with both the techniques-tendon grafting or tendon transfer (Fig. 3&4). However, the typical ‘normal’ hyperextension of the thumb IP joint was consistently restored by tendon grafting of the original cut EPL tendon. All the patients achieved a Kapandji score of nine and none demonstrated any donor deficit (see Fig. 4).

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Fig. 3 A&B) Preoperative and C&D) Six months Post-operative outcomes in a patient treated with EIP-EPL transfer.

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Fig. 4 A&B) Preoperative and C&D) 12 months Post-operative outcomes in a patient treated with Palmaris longus intertendinous bridge grafting for EPL rupture.

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4 Discussion

EPL ruptures secondary to distal radius fractures is an uncommon but well-known complication. Various reasons have been proposed, some related to the peculiar anatomy of the EPL and others related to the roughness of the bone created by the fracture and by attrition from the implants in its vicinity. Attrition from the implant or roughness of the bone is easily understandable however, its rupture in cases of undisplaced radius fractures points to peculiar hemodynamic and mechanical factors as previously highlighted by Enkvist (1979) and Helal (1982).^7,8 The extensor retinaculum remains undisturbed in undisplaced distal radius fractures. The evolving fracture hematoma and callous formation subsequently narrow down the third extensor compartment at the Lister's tubercle and could strangulate the EPL. Hirasawa (1990) described a watershed area at the Lister's tubercle.⁹ He found the EPL to be devoid of mesotenon for a length of 5mm where the visceral tendon is poorly vascularised but the synovial tendon sheath was richly vascularised. It indicates that the tendon receives its nourishment at this watershed area primarily through the diffusion of the synovial fluid. The narrowed down compartment compromises both the circulation and the diffusion of synovial fluid and accompanied by the ongoing tendon irritation, devitalises the tendon eventually leading to its rupture. Recent literature mentions about prophylactic release of the third compartment (EPL) in cases with the possibility of a fracture or periosteal rupture involving the EPL floor ulnar to the Lister's tubercle at the time of distal radius fracture fixation.¹⁰ In our series, only two of the 21 patients had EPL ruptures secondary to an undisplaced fractures whereas remaining 19 had implants in the distal radius.

The reported incidence of extensor tendon injury after volar plating ranges between 4.4% and 8.6%.^1–4 Direct damage due to inadvertent drilling and prominent screw protruding beyond the dorsal cortex have been attributed to the rupture of extensor tendons. Numerous reports of screw impingement related EPL ruptures broke into the literature since it was first described by Wong in 1989¹¹ Few studies have listed down the high risk holes with the commonly used plating system and suggest the practice of careful drilling (avoiding overshooting the dorsal cortex), use of unicortical screws and even avoidance of screw in these holes.^12–14 In our study, the central distal most screw of the transverse stem of the volar locking plate was found to be most commonly impinging on the extensor tendons (EPL) similar to the findings of the study by Perry et al.¹²

Ruptures are commonest for the EPL because the dorsal penetration of the screw tip in this region is often masked on the radiograph by the Lister's tubercle (Fig. 5). However, the adjacent extensor tendon also can be injured by the prominent screw. In our series, in two cases the dorsally prominent screw had caused attrition of the index finger extensors in the fourth compartment. Extensor tendon injuries other than EPL have been reported by very few studies.^15,16 Concomitant EDC and EIP injuries are even rare but could have a serious implication in deciding for tendon transfer.^6,17

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Fig. 5 Schematic representation of the axial section of distal radius showing the screw penetration into the third extensor compartment (red arrow) medial to the Lister's tubercle (LT). The surgeon should be aware that the Lister's tubercle might mask the penetrance in a lateral radiograph.

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In our series there are two children who had EPL rupture because of the attrition caused by the end of the intramedullary nail put for the radius. (Suppl. 1). Although the complication appears to be imminent owing to the insertion sites of these nails, but the related literature seems to be very sparse^18,19; lending the surgeons unguarded about this major complication which is easily preventable. We recommend, visualizing the EPL and preferably opening up the third compartment and rerouting the EPL in the subcutaneous plane while inserting the nail and routine removal once the fracture is united.

The treatment proposed for the management of extensor tendon ruptures falls into three groups: primary repair, tendon transfer and an intercalary/intertendinous grafting. In some earlier descriptions, primary repair has been mentioned^20,21; but as these injuries are attritional ruptures with loss of tendon substance, direct repair was never possible in our patients. We found even with patients presenting early, primary repair was not feasible because the tendon had attrition over a longer segment rendering the tendon tissue unsuitable for repair. Tendon transfer remains the popular choice for management of these ruptures with EIP as the commonest donor.²² The tendon is endorsed with appropriate direction and excursion as of the EPL and availability in the field of surgery, it becomes the numero uno. However, one should make sure that the ED slip of the index is not injured before one commit to EIP transfer by exploring and inspecting this tendon lest the index finger extension would be totally lost.⁶

Grafting for the defect in the EPL tendon is another option. However, the need for taking a graft from the volar side, two repair sites and concern about the contracted and retracted proximal cut end of EPL often prompts surgeons to use these options less often and opt for EIP tendon transfer. We have used tendon grafting across the cut ends in 10 of our 21 patients and observed good results in all of them. Interestingly, the typical hyperextension of the thumb IP joint could be achieved better in the cases with tendon grafting. Furthermore, use of the native muscle assures a rapid return of function. Having seen good results with grafting, we offer this procedure to patients who present early after rupture (within 2 months), have the proximal muscle tendon mass reparable with good excursion and who have concomitant injury to other finger extensors. Though, Magnell (1988) found that the muscle contractures were reversible for upto five months²³ we often resort to EIP tendon transfers in patients presenting after 2 months from the rupture because in chronic ruptures the muscle probably starts having adaptive shortening and contracture much before the final rupture happens and given that the EIP transfer works equally well.

EPL rupture related to the distal radius fracture does cause a lot of concern to the surgeon and the patient however, with either of the technique of reconstruction, the patient satisfaction was immense as the function improves dramatically once the thumb is drawn out of the palm.

5 Recommendations

Based on the various studies and our observations on the distal radius fractures related EPL ruptures, we recommend the following measures to avoid this complication:1.The surgeon must be careful while drilling and avoid passing beyond the dorsal cortex.2.Various studies demonstrate the existence of ‘high risk holes’ in a volar locking plate, the fourth hole from the radial side in AO Synthes LCP, for example. The surgeon must exercise caution while using screws in these holes and can use unicortical screws or avoid screws in these holes. Screws of shorter length can be used as it has been studied that only 75% of the measured screw length would provide similar construct stiffness as bicortical fication.²⁴ When using bicortical screws, the surgeon must ensure that the screw tips are flush with the dorsal cortex.3.Intraoperative fluoroscopy can be helpful in determining the screw length. The dihedral shape of the distal radius and the Lister's tubercle obscure the screw length in a proper lateral radiograph. Multiple oblique (30° supination/pronation) views might be required. The skyline or dorsal horizon view may help to identify prominent screw tips dorsally, particularly adjacent to the Lister's tubercle.²⁵ If still there is a concern, one must not hesitate to use intra-operative ultrasound, which has been shown to be a reliable method to detect screw penetration after volar plate fixation.²⁶4.Whenever the surgeon encounters a fracture pattern where he/she expects an EPL attrition (undisplaced fractures, displaced fractures with dorsal metaphyseal bone spur, fractures involving the EPL floor medial to the Lister's tubercle), prophylactic measures should be implemented. These include proper splinting of the distal radius fracture that allows flexion of the metacarpophalangeal and interphalangeal joints of the thumb facilitating EPL motion which is found to promote the synovial diffusion, decompression of the third extensor compartment by needle aspiration in acute situations and hematoma evacuation and proper reduction of dorsal roof fragments in patients undergoing surgery.^27,28 Freeing the tendon from the third compartment and leaving it subcutaneously is most preventive for its rupture and does not affect the thumb function.5.The ruptures were mostly associated with a period in which patient had prodromal symptoms like mild pain or grating and had tenderness over the Lister's tubercle. Ultrasonogram is a valuable tool in diagnosing the condition accurately in the prodromal stages. Presence of such clinical features and radiological evidence, should be considered as critical and merit intervention in the form of implant removal, third extensor compartment release, decompression and let the EPL out of the extensor retinaculum in the subcutaneous plane.

Funding

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

Ethical approval

Institutional research ethical committee approval was obtained for the study.

Informed consent declaration

Written informed consent was obtained from all subjects before the study. There is no information (names, initials, hospital identification numbers or photographs) in the submitted manuscript that can be used to identify patients.

CRediT authorship contribution statement

Praveen Bhardwaj: Conceptualization, Methodology, Writing – review & editing. Vigneswaran Varadharajan: Data curation, Writing – original draft. Darshan Jain: Visualization, Resources, Investigation. S Raja Sabapathy: Conceptualization, Supervision.