Introduction

Lesions of the distal radioulnar joint (DRUJ) demand close attention since instability of the latter may impair the forearm function significantly [1–3]. Triangular fibrocartilage complex tears (TFCC) which cause instability of the DRUJ happen frequently without concomitant fractures [4]. Stabilising structures of the DRUJ are mainly the interosseous membrane, the TFCC, the bony joint geometry, the DRUJ capsule and the extensor carpi ulnaris tendon [5–10]. The distal radioulnar ligaments are considered as crucial in order to preserve stability of the DRUJ [1, 2, 11–16]. The capsule becomes a decisive stabilising tissue if the TFCC is insufficient [12, 14].

Up to now several reconstructive surgical techniques for the treatment of DRUJ instability have been published [17–28]. The majority of these reconstructions require wide dissections in comparison to the capsular imbrication of the DRUJ which may rise the postoperative complication rate [23, 29]. Gofton et al. [30] examined four different reconstructive techniques. A capsule suture technique and three different transosseous ligament reconstructions using tendon grafts were evaluated with regard to the DRUJ biomechanics in a cadaver model [17, 18, 25, 30].

The capsular imbrication of the DRUJ proved to be reliable and sufficient in the short term [31]. This surgical technique is reasonably simple and does not compromise osseous structures. Furthermore, this procedure does not jeopardize other reconstructive techniques and may be combined with additional interventions [29].

Therefore, the aim of this study was to examine patients with capsular imbrication after a midterm follow-up period.

We hypothesized that patients after capsular imbrication are characterized by good subjective and functional outcome measurements after this postoperative interval.

Materials and methods

The study design was approved by the institutional ethics committee. All patients gave their written consent to participate in the study. We performed a retrospective analysis of 11 patients (2 females and 9 males) who were treated by capsular imbrication for posttraumatic dorsal DRUJ instability. Patients’ mean age was 35.9 years (range 21–50 years of age; median 35 years of age). Inclusion criterium was minimum follow-up of 36 months (range 46–114 months; mean 72.2 months; median 66 months). Exclusion criteria were ulnar positive variance (>2 mm), rheumatoid arthritis, arthritis of the DRUJ, cervical spine operations and any systemic neural or connective tissue disease.

To ensure consistency the same resident who was not part of the surgical team conducted data collection throughout the entire study.

Preoperative symptoms prior to surgery persisted on average 3.8 months (range 1.3–6 months). The most frequent cause of instability was a fall on the outstreched arm (n 7). Three patients could not recall a definite trauma in the past. One patient suffered from ulnar-sided pain and loss of power without a specific trauma. Demographic data and distribution of injured hand dominance are illustrated in Table 1. Subjective preoperative clinical symptoms are outlined in Table 2. Evaluation of the DRUJ instability was performed using the anterior-posterior stress test and push-off test respectively [17, 29, 32, 33]. The severity of instability was graded using the anterior-posterior stress test [32] (Tables 3, 4). Dorsal instability of the DRUJ grade II to III were considered for capsular imbrication.

Table 1 Demographic data
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Table 2 Subjective preoperative clinical symptoms and subjective postoperative evaluation of pain, instability, function and satisfaction
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Table 3 Objective outcome measurements
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Table 4 Anterior-posterior stress test: grading of the DRUJ instability
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The follow-up evaluation included clinical examination and questionnaire testing. We assessed functional and subjective parameters. We used a manual goniometer to measure range of motion (ROM). ROM of the operated wrist was compared to ROM of the contralateral wrist (Table 5). We measured grip strength using a calibrated Jamar dynamometer at position 2 (Sammons Preston Pattersol Medical Products, Inc., Bolingbrook, IL). These measurements were done in a standardized manner for both hands. The patients were positioned according to the recommendations of the American Society of Hand Therapists [34]. Each hand was measured 3 times and the mean values were calculated (Tables 3, 6).

Table 5 Range of motion
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Table 6 Grip strength
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The patient’s opinion regarding preoperative pain, prior subjective instability, range of motion and grip strength were assessed retrospectively and the postoperative outcome was acknowledged with: “excellent”, “better”, “unchanged” or “worse” (Table 2).

Radiological examination of the wrist was performed preoperatively, as well (Table 1).

Surgical technique of capsular imbrication

The fifth extensor compartment was opened and the extensor digiti minimi tendon was retracted radially. The dorsal joint capsule was exposed and divided longitudinally. Sufficient tissue on the lateral border of the capsule ought to be left to ensure a solid suture technique. Two sutures were applied using FiberWire number 2 (AR-7200; Arthrex, Naples, Florida) to overlap the capsule (Figs. 1, 2). Afterwards the elbow was flexed and the forearm elevated, and after reducing the ulnar head, the capsule was imbricated with the forearm in supination. The sutures were tightened, which resulted in a capsular imbrication. This stabilized the ulna in its physiological position. To tighten the imbrication, we used an additional running suture with a 4-0 absorbable material. Each patient received a long-arm cast with the forearm in supination for 4 weeks. Then a Bowers splint was applied for 4 weeks in order to limit forearm rotation [29, 31].

Fig. 1
figure 1

The ulnar-sided capsule is addressed first using Fiber Wire number 2 (with friendly permission of Springer Science and Business Media)

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Fig. 2
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Two U-shaped sutures are applied properly before reduction and tightening (with friendly permission of Springer Science and Business Media)

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Statistical methods

All variables were analysed descriptively by tabulation of the measures of the empirical distributions. According to the level of the variables, means and standard deviations or absolute and relative frequencies were reported, respectively.

We evaluated possible differences between groups using the Chi-square test in case of categorical variables or Wilcoxon U test in case of continuous variables. Possible differences between patients were evaluated by 1-sample t tests. For all tests, a p value of 0.05 or less.

was considered statistically significant.

Results

Range of motion

No significant difference was detected after surgery regarding range of motion in comparison to the contralateral side (Table 5).

Grip strength

No significant difference was detected after surgery regarding grip strength in comparison to the contralateral side (Table 6).

Modified Mayo Wrist Score (MMWS)

The MMWS was 91.8 for the study population (range 75–100; SD 9.0) (Table 3).

Disabilities of Arm, Shoulder and Hand questionnaire (DASH)

The DASH score of the study population was 6.7 (range 0–22.5; SD 7.2) (Table 3).

Pain

Reduction of pain was regarded as “excellent” by eight patients (72.7 %). Two patients (18.2 %) felt “better” postoperatively and one patient (9.1 %) regarded the postoperative situation as “unchanged” (Table 2).

Subjective instability

Reduction of instability was regarded as “excellent” by two patients (18.2 %). One patient (9.1 %) felt “better” postoperatively and eight patients (72.7 %) regarded the postoperative situation as “unchanged” (Table 2). Six of the latter eight patients did not recognize any instability at all preoperatively whereas two patients considered instability of minor concern (Table 2).

Instability testing (Table 3)

Patient’s evaluation

Overall opinion are illustrated in Table 2.

Complications

One (9.1 %) delayed wound healing was observed. Four patients (36.4 %) suffered from postoperative painful sensation during palpation of the DRUJ.

Discussion

Several surgical techniques are published for the treatment of posttraumatic DRUJ instability [17–27]. Petersen and Adams evaluated different procedures in an ex vivo model [35]. The techniques of Eliason [27], Fulkerson-Watson [18], Boyes-Bunnell [36], Hui-Linscheid [20] and Breen-Jupiter [19] were examined regarding their static biomechanical stability and were compared to the physiological articulation. Neither procedure was able to reach the physiological level of stability. Adams and Berger described a surgical procedure using tendon grafts and transosseous fixation between radius and ulna [17]. Fourteen patients were treated by this procedure and were evaluated after mean follow-up of 2,2 years. Wong et al. [23] published a similar suture technique to the one we used. The authors facilitated anchors in order to fix the capsule at the sigmoid notch. Six patients were evaluated after a mean 16 months.

Gofton et al. [30] examined a capsule suture technique and three different transosseous ligament reconstructions using tendon grafts with regard to the DRUJ biomechanics in a cadaver model [17, 18, 25, 30]. The reconstruction of the capsule using the suture technique proved to restore the kinematics of the DRUJ significantly. Moreover, Watanabe et al. [37] could prove that on the one hand the capsule provides significant stability to the DRUJ and that on the other hand capsular imbrication restores stability after compromising DRUJ lesions especially in pronation and supination.

Eleven patients were treated by capsular imbrication because of posttraumatic dorsal instability of the DRUJ. The mean MMWS was 91.8 which is excellent [38, 39]. The surgical technique did not limit range of motion and did not reduce grip strength significantly in comparison to the contralateral side. Grip strength was 96.7 % of the healthy hand which is excellent in comparison to the results published by Adams and Berger [17] who measured 85 % and Wong et al. [23] who reported 80 % [40].

The DASH score was 6.7 overall which is comparative to age-matched healthy individuals [41, 42] and were comparable to the subjective outcome measurements published by Adams and Wong [17, 23]. Postoperative pain levels, subjective function and overall opinion highlighted the above-mentioned good outcome measurements.

DRUJ instability was diagnosed for all 11 patients whereas six patients did not recognize DRUJ instability as such and two patients considered instability of minor concern. Therefore, the clinical appearance of instability is not unequivocal at all [43]. Patients will not regularly identify DRUJ instability as such.

The ulnar-sided wrist pain which exacerbates in pronation and supination is the most frequent symptom [44]. Subluxation of the radius or piano key sign happen rarely [45]. Further symptoms are limited range of motion, diminished strength and subluxation of the extensor carpi ulnaris tendon [19, 20, 46–48]. Simulating the trauma mechanism may often reproduce typical symptoms [3].

A standardised diagnostic algorithm is mandatory to guarantee reliability in order to identify DRUJ instability [3, 49]. Ulna fovea sign, anterior-posterior stress test and press test proved to be efficient [3, 32, 33, 50]. The anterior-posterior stress test and the push off test as a modified press test were used as diagnostic tools for this study. The extent of translation between ulna and radius seems to be decisive for diagnosing DRUJ instability [51].

Moreover, complications were comparable to the studies of Adams and Wong [17, 23].

We applied very strict inclusion and exclusion criteria and very carefully selected our patients to generate the findings as meaningful as possible. Furthermore, the outcome measurements were based on a reasonable follow-up interval. In addition, only 1 examiner who did not belong to the surgical team was commissioned to conducting the examination of our patients, which thus reduced potential variability between different examiners.

The study’s weaknesses are its retrospective design and the lack of a control group. Another weakness is that we conducted the study entirely at our clinic, so that patients were mostly from the same region of the country.

All in all, the ulnar-sided wrist pain is the most reported symptom in case of DRUJ instability. Therefore, the former ought to be examined thoroughly and diligently in order to initiate adequate treatment based on the correct diagnosis.

Capsular imbrication proved to be reliable and sufficient in order to treat posttraumatic DRUJ instability. It is reasonably simple and does not jeopardize other reconstructive techniques. Moreover, combination with additional procedures is feasible.