Outcome improved in most cases
Intra-articular fractures need to be corrected precisely with respect to the original joint anatomy, which otherwise is associated with pain and an inferior functional outcome [
13]. Detailed quantification of the preoperative joint situation and the use of 3D patient-specific guides have shown to be helpful in various situations such as treatment of malunited fractures and complex situations in various joints [
5,
6,
14‐
18]. When involving the articular surface, residual intra-articular deformity is not well tolerated [
19,
20] and accurate reconstruction of joint congruency is of upmost importance. Since studies using PSI for intraarticular correction of postoperative malformation are lacking, comparison and discussion of results is not possible. However, as with every patient-specific technology, it is most important to reference the guidance on the patient’s anatomy. However, in small bones such as phalanx this is not as simple. Previous studies have demonstrated the feasibility of executing this technique with excellent precision, without compromising accuracy [
4]. A correction of a malunion of 1.4 mm on average was corrected to a malunion of 0.4 mm, which corresponds very closely to the results of our study. Compared to freehand techniques, PSI has the advantage of good reproducibility and accurate osseous quantification of the correction, which has only been done in one previous case with an intra-articular malunion of finger joints.
Surgery at the phalanges are more challenging and prone to complications when compared to the MCs. In MCs it often leads to correction osteotomies, not in the malunited area, but rather in the more proximal, less demanding MC region [
21]. This technique can be applied for rotational deformities, not addressing intra-articular problems. It is also challenging to address 3D plane deformity with a single cut osteotomy with no patient-specific guidance, which in this case is required [
22]. In addition to intra-articular correction, this technique allows the off-cut to be planned, quantified and removed in a guide-controlled manner. This is particularly important in cases where a Bennett’s fragment is present.
It is interesting to note that extra-articular approaches to intra-articular problems were described early on in order to prevent invasive intra-articular approaches. Similar concepts were described already with external Kirschner-wire fixation of the phalanx, aiming to unload force from the fracture zone of the interphalangeal joints [
23]. Although this technique does not open the joint capsule, it has an indirect effect on the intra-articular situation via ligamentotaxis. Besides the technical feasibility, an improved postoperative functionality of the affected fingers could be achieved. The observed deficits in the proximal interphalangeal joint (PIP) extension are within a range that is clinically well tolerated and thus usually do not require further therapy as described previously [
24]. In a posttraumatic intra-articular malunited situation, a technique was described by Harness et al. that addresses this situation without capsular penetration [
25]. He describes an extra-articular wedge osteotomy with correction of joint alignment and demonstrated an improvement of total digit motion from 154° to 204°. However, it is clear that those techniques do not address the intra-articular malformation, which can then lead to its own complications as described above. Therefore, the authors of this study share the belief the intra-articular situation must be corrected in order to achieve the best result for the patient [
26].
Teoh et al. demonstrated in six patients with phalangeal unicondylar malunions a technique, which he corrected with an intra-articular osteotomy [
27]. He was able to demonstrate good alignment of the initially deformed joint-line, yet did not quantify the osseous correction and solely used conventional x-rays. His primary goal was to realign the joint-line. He reported an increase in total range of the interphalangeal joint motion from 112° to 155°, yet two of six patients developed a new extension deficit of 10°. Pinal et al. demonstrated the correction of intra-articular malunion via a shot gun approach and extensive reconstruction of the joint in a case series of eleven patients [
28]. Despite pain reduction and DASH score improvement, the function worsened in five patients, explained by the authors with the patients’ malcompliance. Yang et al. performed corrective osteotomies of 16 PIP joints using an extensive volar or dorsal approach with following screw- and plate fixation. They reported pain-relief in 14 cases and an increase in ROM from 30.3° to 68.4°, but no PROMs were collected [
29]. In a small case series of intra-articular corrective osteotomies for symptomatic Bennett fracture malunions Van Royen et al. were able to decrease the pain from a VAS from 88 to 7 with an increase of grip- and pinch strength [
3]. Our results contribute to the previously sparse literature on operative intra-articular correction of malunions. As in previous studies, functionality was improved, and for the first time, osseous correction was precisely quantified. We agree with the authors of many studies that intra-articular malunion must be addressed, but as here presented with the advantages of an extra-articular approach. In our opinion, this novel technique ranks among the current possibilities and advantage of PSI and should be considered when approaching such pathologies.
One limitation of PSI are the associated costs and time needed for surgical planning and production of the surgical guides [
4]. In the case of malunions which do not need to be scheduled urgently, we think the benefits of a precise 3D PSI planning and surgical execution outweigh the costs and delay caused by the planning and production of the guides. Furthermore, the present study represents a small case series that needs to be confirmed by broader application and larger cohorts. Short follow-up time does not allow conclusion about osteoarthritis in the long-term. However, all patients reported excellent patient-reported outcome measures after medium-term follow-up of a minimum of three years. In case of present radiologic signs for osteoarthritis it appears that, it has no significant impact on the functional outcome at mid-term follow-up. Another limitation may be the operation by a single surgeon. For better comparability and the uniform intraoperative approach, this may be an advantage for this feasibility study, but needs to be reproducible in a larger scale including more surgeons. Furthermore, the retrospective assessment of the patients function preoperatively represents a certain bias and important limitation concerning the functional outcome. Nevertheless, even though it is not objectifiable retrospectively, all patients reported on clear improvement compared to their situation prior to the corrective osteotomy. Concerning the pre- and postoperative clinical examination results presented in Table
2. has to be mentioned, that certain information are missing limiting the expressive power. However, in our opinion, there is still enough data to be able to give a statement on the improvement the patient have undergone. For the same reason, we decided to include the patient for whom PSI correction of malformation was performed without 3D-planned guides. Technically, it still represents a corrective osteotomy of an intraarticular step. Inclusion of this case might diminish the expressiveness of 3D-planned PSI, but clinically the patient gives us further information on the outcome of an intraarticular correction. This case, due to a very small fragment size which needed correction, may also demonstrate the boundaries of PSI surgery in the phalanges at the current stage. The personal experience showed, that a fragment needs to be at least 4x5x6mm to use PSI guides. Additionally, surface structure is of importance, since edgy surfaces, where fragments can fit into are easier to address. Further scientific investigations are needed to be able to draw conclusions concerning this special problem.