Abstract
Introduction:
Some authors have suggested that metacarpophalangeal joint (MCPJ) flexion is limited to 45° after finger amputation through the proximal phalanx. The aim of this study was to investigate if flexor digitorum superficialis (FDS) tenodesis improves MCPJ flexion.
Methods:
Patients who had had a FDS tenodesis between April 2022 and April 2023 were included in this study, and their outcomes were compared with patients who had received a conventional amputation between June 2018 and January 2023. All patients were invited to come to the hospital for follow-up to measure the MCPJ range of motion. Adverse events and pain were also assessed.
Results:
Twenty patients (25 fingers) without FDS tenodesis and 11 patients (13 fingers) with FDS tenodesis with a median follow-up of 21 (range 7–60) and 6 (range 2–12) months, respectively, were included in the study. Mean MCPJ flexion was 78° (SD 17, range 32–110) after conventional amputation and 86° (SD 8, range 70–95) after FDS tenodesis. Mean MCPJ extension was 6° (SD 9) in the conventional group and 7° (SD 6) in the FDS group. Adverse events were recorded in 20/25 fingers in the conventional group and 8/13 fingers in the FDS group. Pain was reported in 3/25 fingers after conventional amputation and 1/13 fingers after FDS tenodesis.
Conclusion:
The MCPJ flexion was almost normal after finger amputation through the proximal phalanx. While FDS tenodesis appeared to be safe, no advantage could be shown over conventional amputation. Owing to the lack of clinical benefit, we have abandoned the technique in our practice.
Level of evidence:
III
Keywords
Introduction
Digital amputation is a procedure that is commonly performed by hand surgeons. When amputation is performed proximal to the insertion of the flexor digitorum superficialis (FDS) tendon, both extrinsic flexor tendons are resected. Therefore, flexion of the metacarpophalangeal joint (MCPJ) is entirely dependent on the intrinsic muscles. It has been postulated that, as a result, active flexion at the MCPJ is limited to 45° (O’Shaughnessy and Kakar, 2017). Global hand function has been shown to be affected when flexion of the MCPJ is limited to 60° (Hayashi et al., 2014). O’Shaughnessy and Kakar (2017) therefore described the technique of FDS tenodesis, where the FDS tendon is preserved and fixed to the proximal phalanx with transosseus sutures. In their case series of eight patients with 12 amputations, the average range of motion at the MCPJ was 82°. Based on this study, FDS tenodesis for amputations through the proximal phalanx was recommended in Green’s Operative Hand Surgery (Kakar and Carlsen, 2022). We began using FDS tenodesis in our institution in April 2022.
The aims of this study were to assess the outcomes after conventional finger amputation at the level of the proximal phalanx and to compare them with those that included FDS tenodesis.
Methods
Ethical approval for this study was obtained from the state medical council of Saxony–Anhalt (ref. no. 62-22). Oral and written consent was obtained from all patients participating in this study. Patients who underwent FDS tenodesis were specifically consented for it as part of the preoperative surgical consent. The study was pre-registered with the German Clinical Trials Register and has the registration number DRKS00030324.
Data for patients who had undergone digital amputations with FDS tenodesis between April 2022 and April 2023 at the BG Hospital Bergmannstrost in Halle, Germany, were prospectively noted in the patients’ files at different follow-up moments in the hospital. Patients were followed up at 2 and 6 weeks and as needed thereafter. The patients were followed between August 2022 and September 2023.
Outcomes of patients with FDS tenodesis were compared with those of patients who underwent conventional amputations between June 2018 and January 2023. Data were retrospectively identified through our electronic medical record. Patients were contacted by telephone in reverse chronological order and asked to attend for clinical assessment. The assessment took place between December 2022 and November 2023.
Because the follow-up of patients with conventional amputation was longer than that of FDS tenodesis, all FDS tenodesis patients were invited for a second assessment after 2 years. Those who were unwilling or unable to attend were asked to provide photographs of their affected hand in full flexion and full extension. The second follow-up was performed between August 2024 and January 2025.
We included patients in our study who were at least 18 years old and had had an amputation through the proximal interphalangeal joint or the proximal phalanx of one or more fingers excluding the thumb. No restrictions were placed on the length of the remaining proximal phalanx. However, we rarely perform amputations through the proximal phalanx if the remainder of the proximal phalanx is shorter than 1–2 cm, as the stump will ‘disappear’ within the palm. Only patients with a minimum follow-up period of 6 months at the first and/or second follow-up were included in the study. Patients with active infection at the time of amputation were excluded.
Surgical procedure
Amputations were performed as emergency or planned surgeries. The surgeries were performed under general, regional or local anaesthesia.
The FDS tenodeses were done by SL and MG with a surgical experience of level 2 according to Tang and Giddins (2016). The technique first described by O’Shaughnessy and Kakar (2017) was employed. The surgical steps are shown in Figure 1. Briefly, the FDS tendon was preserved, and the flexor digitorum profundus tendon was resected far proximally under full traction on the tendon. Two bone tunnels were drilled into the proximal phalanx using a 1.0 mm K-wire, entering the bone at the resection margin and exiting through the dorsal cortex. The FDS tendon was attached to the proximal phalanx using two 4–0 non-resorbable suture loops (FiberWire, Arthrex, Munich, Germany), which were anchored on either side of the tendon using a Tsuge technique, passed through the bone tunnels and knotted, ensuring high resting tension of the tendon. The tendon was affixed with broad contact to the resection margin of the bone. The distal end of the tendon was further secured to the dorsal periosteum, taking care not to catch the extensor tendon. A tenodesis test with wrist flexion and extension was used to confirm sufficient tensioning of the FDS tenodesis (Figure 1(f) and (g)). The extensor tendon was resected proximal to the exit of the bone tunnels. The neurovascular bundles and soft tissues were managed as in conventional amputation.
Surgical technique for flexor digitorum superficialis (FDS) tenodesis for amputation after a severe crush trauma of the index finger (a and b). (c) The FDS tendon is secured with a looped suture on either side. (d) The sutures are passed through bone tunnels in the proximal phalanx drilled from the cut end of the bone through the dorsal cortex with 1 mm K-wires. (e) The FDS tendon is secured to the distal end of the proximal phalanx. (f and g) Intraoperative tenodesis confirms sufficient tensioning of the tendon.
In the conventional amputation group, both extrinsic flexor tendons were resected as far proximally as possible. The conventional amputations were performed by different surgeons working in the department. Their surgical experience level according to Tang and Giddins (2016) was 1 in six patients, 2 in 10 patients and 3 in four patients.
Postoperatively, patients with FDS tenodesis were immobilized in a dorsal intrinsic-plus splint, leaving the interphalangeal joints of the other fingers free to move. If other injuries did not require further postoperative immobilization, the splint was removed after 2 weeks, and patients were advised to start range-of-motion exercises. Gradual strengthening was allowed after 6 weeks. In the conventional amputation group, range-of-motion exercises were encouraged immediately with strengthening exercises starting once the wounds had healed. Both groups were encouraged to start amputation stump desensitization from the first postoperative day.
Data collection
The principal outcome variables were flexion and extension at the MCPJ, pain, and the occurrence of adverse events.
Range of motion at the MCPJ of amputated and contralateral uninjured fingers was measured using a finger goniometer. A finger goniometer was also used to measure range of motion on the photographs provided by some patients in the FDS tenodesis group at the second follow-up. Metacarpophalangeal joint extension was measured from neutral joint position with positive numbers indicating hyperextension and negative numbers extension deficit. Clinical examination was done by KR after initial training and supervision by SL.
It was noted if patients had pain and our own medical records were searched for any adverse events. In addition, patients were asked whether they had experienced postoperative problems of any kind and were then specifically asked about the occurrence of delayed wound healing, infection or revision surgery. Any other reported symptoms were classified post-hoc.
We also recorded sex, age (at the time of surgery), hand dominance, associated injuries, the affected finger, length of follow-up, the reason for the amputation and the length of the proximal phalanx on postoperative radiographs. Postoperative posteroanterior (PA) and lateral radiographs of the affected finger(s) were taken as part of the standard postoperative protocol. The length of the proximal phalanx was measured from the base of the proximal phalanx to its most distal aspect on the PA radiograph. No postoperative radiographs were available for three patients with three amputated fingers (one in the FDS group and two in the conventional group).
Statistical analysis
Variables are reported as frequencies for categorical data and mean (standard deviation) for normally distributed continuous data. Normality was assessed using histograms and quantile–quantile plots.
The finger was the unit of analysis. Since several patients had multiple affected fingers, a restricted analysis was performed, where only one finger was used in patients with multiple amputated fingers. In these cases, the most radial finger was selected.
O’Shaughnessy and Kakar (2017) reported an average flexion–extension arc of 82° with a range of 45–95° in 12 digits. Assuming normal distribution and using the d2 constant for sample size 12, the standard deviation was estimated to be 15°. As flexion less than 60° will be clinically relevant, a power calculation was performed to detect a 20° difference between the groups. Nine patients are required in each group to detect a 20° difference with a power of 80% at a 0.05 significance level.
Since no data were available on expected range of motion after conventional amputation, it seemed reasonable to aim for 20 patients in the conventional group to get a better estimate of the spread of the data. At the time 20 patients had been recruited and assessed in the conventional amputation group; 12 patients had received FDS tenodesis. Preliminary analysis of the conventional amputation group showed similar MCPJ flexion with both techniques. Therefore, no more patients were included in the FDS tenodesis group.
Results
Study population
Fourteen FDS tenodesis procedures were performed on 12 patients. In two of these patients who underwent amputations of two fingers, FDS tenodesis was performed on one finger and conventional amputation on the other. The reasons for performing conventional amputations in these patients was a hypoplastic FDS tendon of the small finger in one case and traumatic loss of the FDS tendon of the index finger in the second case. Both patients are included in the FDS tenodesis group. The fingers with conventional amputation were excluded from the analysis.
One patient in the FDS tenodesis group required surgical revision owing to wound dehiscence before the first follow-up appointment. In the revision procedure, the bone required further shortening and conventional amputation was performed. This patient was included in the FDS group for baseline data, pain and adverse events but was excluded from range of motion analysis. Another FDS patient with one finger was excluded because the minimum follow-up of 6 months was not reached at the first follow-up and the patient declined participation at the second follow-up. A flow chart of patient inclusion and follow-up is shown in Figure 2 and baseline data of both groups are shown in Table 1.
Flow chart of patient recruitment. The numbers in brackets show the number of affected fingers.*Of the eleven patients included with flexor digitorum superficialis (FDS) tenodesis, one was converted to conventional amputation owing to wound infection requiring revision and shortening. This patient is included for baseline, pain and adverse event data only.
Baseline data of patients with conventional amputation and flexor digitorum superficialis (FDS) tenodesis.
For analysis of the injured finger and the relative length of the proximal phalanx stump, the unit of analysis is the individual finger. bData on the postoperatively remaining length of the proximal phalanx were missing in three patients with three fingers (one with FDS tenodesis and two with conventional amputation). IQR, Interquartile range.
Outcomes
The principal outcomes are shown in Table 2. Mean MCPJ flexion after conventional amputation was 78° (SD 17°). For comparison, mean MCPJ flexion of the uninjured finger contralateral to the injured finger in this group was 89° (SD 4°). The nominal loss of flexion after proximal phalangeal amputation was therefore 11°. After FDS tenodesis, mean MCPJ flexion was 86° (SD 8°). At the second follow-up time point in the FDS tenodesis group, there was no change in any of the outcome parameters. The restricted analyses, where only one finger per patient was included, showed similar results and excluded relevant effects owing to clustering or nesting. The number of adverse events was similar in the two groups.
Range of motion (ROM) of the metacarpophalangeal joint (MCPJ) and complications after amputation through the proximal phalanx in patients without and with flexor digitorum superficialis (FDS) tenodesis.
Restricted analysis of one finger per patient. bAt second follow-up, nine patients (11 fingers).
Figure 3 shows the postoperative results of the two patients who received FDS tenodesis of one finger and conventional amputation of the other. Range of motion was similar in both fingers of each patient, which is representative of the entire study population. The photographs that were used to assess flexion of the MCPJ of the four patients in the FDS tenodesis group who opted for remote assessment at the second follow-up are shown in Supplemental Figure 1.
(1) Full finger extension and (2) flexion of the two patients who underwent flexor digitorum superficialis (FDS) tenodesis in one finger and conventional amputation of another finger. Patient A is shown 28 months postoperatively and patient B 18 months postoperatively. Patient A had FDS tenodesis of the middle finger and conventional amputation of the small finger owing to a hypoplastic FDS tendon of the small finger. Patient B had FDS tenodesis of the middle finger and conventional amputation of the index finger owing to traumatic loss of the FDS tendon of the index finger.
The MCPJ flexion data are plotted against follow-up time in Figure 4. There was no apparent association between length of follow-up and MCPJ flexion. The early and late follow-up time points in the FDS group show no pattern regarding change of MCPJ flexion with longer follow-up time. MCPJ flexion ⩽60° was observed in three fingers of two patients in the conventional group and in one finger after FDS tenodesis at the second follow-up. All four fingers were painful, whereas pain was only reported in one of the other 37 fingers with MCPJ flexion greater than 60°. The patient with FDS tenodesis had limited flexion at the second follow-up, but not the first. At 7 months follow-up, this patient had no pain (0 on a numerical rating scale (NRS) between 0 and 10) and MCPJ flexion of 80°. After 24 months, pain was NRS 3 at rest and 6–7 with activity, and MCPJ flexion was 54°.
Scatter plot showing metacarpophalangeal joint flexion of 20 patients with 25 fingers after conventional amputation and ten patients with 12 fingers after flexor digitorum superficialis (FDS) tenodesis against follow-up time stratified by surgical group. Early and late assessments of the same finger are connected with dotted lines. A horizontal dotted line was added at 60° flexion.
Discussion
The central finding of the current study is that MCPJ range of motion was almost normal after amputation at the level of the proximal phalanx, even though all extrinsic flexors were lost.
Our findings are inconsistent with those of previous publications. According to Moran and Berger (2003), amputation through the PIP joint leaves all remaining stump flexion to the control of the intrinsic muscles, which allows for flexion to approximately 45°. Moran and Berger (2003) refer to a book chapter (Duparc et al., 1979). Duparc et al. (1979) divide amputation levels into zone II, which includes the head of the proximal phalanx and zone III proximal to the head of the proximal phalanx. They recommend leaving the amputated finger as long as possible in zone II. In zone III, the authors prefer transmetacarpal amputations in most cases, claiming better dexterity with transmetacarpal amputation. This is expert opinion as no data are referenced to support this claim. No mention is made of poor MCPJ motion after proximal phalangeal amputation. In fact, the chapter contains a picture of a hand after proximal phalangeal amputation of a ring finger with almost 90° of MCPJ flexion of the ring finger stump. We were unable to find publications with any data on MCPJ flexion after conventional proximal phalangeal amputation.
The mean MCPJ flexion after FDS tenodesis in our study was 86° after a median follow-up of 6 months, which remained unchanged after 28 months’ follow-up. This is similar to the 82° reported in eight patients with 12 amputated fingers assessed after 15 months by O’Shaughnessy and Kakar (2017).
Hayashi et al. (2014) sought to understand at what range of MCPJ flexion hand function becomes impaired. While they studied global hand function in normal hands and when flexion of all MCPJs was limited, it seems reasonable to assume that flexion ⩽60° will reduce the usefulness of a finger stump. In our study population four fingers in three patients had MCPJ flexion of ⩽60°. Pain was reported in all four fingers, whereas only one patient with normal range of motion reported pain. It therefore seems plausible that pain may be a contributing factor to flexion deficit after proximal phalangeal amputations. In one of the four fingers normal flexion was measured at an earlier time point, when the patient reported no pain. The finger was reported to be painful at the second follow-up and MCPJ flexion had deteriorated. This patient had had FDS tenodesis, which showed that FDS tenodesis was unable to prevent the deterioration in flexion. An ultrasound assessment of the same patient confirmed that the FDS tendon was still attached to the proximal phalanx at the second follow-up. The postoperative course of another patient who underwent FDS tenodesis of the ring and little finger showed the opposite development and this lends further support to the above hypothesis. This patient had a painful neuroma of the ring finger (NRS 10) at 7 weeks. Metacarpophalangeal joint flexion of the ring and little finger was 50 and 40° respectively. After successful treatment of the neuroma (ring and little finger NRS 2 and 0, respectively), MCPJ flexion improved to 90° for both fingers at follow-up after 42 weeks. There was also no difference between the two groups for both MCPJ extension and adverse events. This suggests that FDS tenodesis is a safe technique.
The median follow-up period was 15 months longer in the conventional group. Therefore, patients in the FDS group were invited for a second follow-up assessment. While not all patients attended, MCPJ range of motion could be assessed in almost all patients. The data we collected suggest that the results remain stable between 6 and 28 months follow-up.
Limitations of this study are the small sample size and its retrospective nature. Our initial power calculation indicates that the sample was large enough to be confident that the difference in MCPJ flexion between conventional amputation and FDS tenodesis is not in excess of 20°. The nominal difference in flexion between conventional amputation and FDS tenodesis was 8° in our study. Our study was not powered to detect a difference of this magnitude. A sample size of 46 patients in each group would be necessary to detect a 10° difference between the groups. It remains to be shown whether a 10° difference is clinically relevant. The shortest proximal phalanx stump in our study was 22 mm, and 85% of the included fingers had a stump of at least 30 mm. It is possible that MCPJ flexion will decrease as the length of the remaining proximal phalanx decreases and the extensor expansion, into which the intrinsic muscles insert, becomes shorter. However, a stump shorter than 2 cm is unlikely to participate meaningfully in grip. Another limitation is that four of the nine patients who were assessed at second follow-up were only assessed on photographs rather than in an in-person clinical assessment. This may have affected the accuracy of the measurements of MCPJ range of motion in these patients. Although the safety profile of FDS tenodesis and conventional amputation were similar, FDS tenodesis was performed in 14 fingers only. Rare adverse events or late adverse effects could have eluded detection in this small cohort. This study did not address the clinical phenomenon of poor MCPJ motion after amputation through the proximal phalanx seen at times in clinical practice, because it was only observed in four out of 37 fingers. Future studies might explore factors that may play a role in the development of poor MCPJ motion after proximal phalangeal amputations.
While FDS tenodesis appeared to be safe, it does not seem to confer a clinically relevant advantage. Therefore, we no longer use this technique.
Supplemental Material
sj-tif-1-jhs-10.1177_17531934261444260 – Supplemental material for Finger flexion after amputation through the proximal phalanx with and without flexor digitorum superficialis tenodesis
Supplemental material, sj-tif-1-jhs-10.1177_17531934261444260 for Finger flexion after amputation through the proximal phalanx with and without flexor digitorum superficialis tenodesis by Sebastian Leuschner, Kathleen Rätzer, Kemal Irga, Michael Geßner and Frank Siemers in Journal of Hand Surgery (European Volume)
Footnotes
Acknowledgements
The authors thank Carolin Gräbsch for providing logistical and administrative support for this study. We would like to express our appreciation to Helga Poppe and Kerstin Salm for their assistance in the assessment of grip strength and clinical photography. Furthermore, the authors gratefully acknowledge the valuable editorial input of Professor Nadine Hollevoet, whose constructive comments and thoughtful revisions substantially improved this manuscript.
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.
Funding
The authors received no financial support for the research, authorship and/or publication of this article.
Ethical approval
Ethical approval for this cohort study was obtained from the ethics committee of the state medical council (Ärztekammer Sachsen-Anhalt, ref. no. 62-22).
Informed consent
Oral and written informed consent was obtained from all subjects before the study.
Study registration
DRKS00030324.
Supplemental material
Supplemental material for this article is available online.
References
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