Outcomes of Percutaneous Achilles Repair Compared With Endoscopic Flexor Hallucis Longus Tendon Transfer to Treat Achilles Tendon Ruptures

Abstract

Background:

Both percutaneous and endoscopically assisted methods are reported to produce good results in the surgical management of acute Achilles tendon ruptures. The aim of this retrospective study was to compare between a percutaneous method and a recently described isolated endoscopically assisted flexor hallucis longus (FHL) transfer method as surgical means of management in patients with acute Achilles tendon ruptures.

Methods:

One hundred seventeen patients were included in the current study and divided into 2 groups: 59 patients who underwent percutaneous Achilles repair (PAR Group) and 58 patients who underwent isolated endoscopic FHL transfer (FHL Group) were compared. Patients were clinically evaluated using American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score, Achilles tendon Total Rupture Score (ATRS), and Achilles tendon resting angle (ATRA) measures. In addition, ankle plantarflexion power, FHL dynamometry, Tegner activity levels, and return to previous levels of activity were also documented for all patients.

Results:

Nine months after surgery, patients in the FHL transfer group were more likely to be able to return to normal activities (91% vs 73%, P < .01). Thirty months after surgical treatment, we found no difference in ATRS, AOFAS, ATRA, ankle plantarflexion strength, or Tegner activity scores between study groups. Overall complications were reported in 6 patients in the FHL group (10.3%) and in 8 patients in the PAR group (13.6%). No major neurovascular or skin complications were encountered.

Conclusion:

The current study demonstrated satisfactory and comparable results and complications when comparing isolated endoscopic FHL tendon transfer or percutaneous Achilles tendon repairs in the surgical management of acute Achilles tendon ruptures.

Level of Evidence:

Level III, retrospective controlled trial.

Keywords

Achilles tendon acute Achilles rupture endoscope FHL tendon tendon transfer tendoscopy percutaneous repair Achilles surgery

Introduction

Acute Achilles tendon rupture (AATR) is a common injury occurring largely in active middle-aged males.^20,25,34,57 There is still controversy when deciding on the optimal methods of treatment for Achilles tendon ruptures and even more so when discussing surgical options.^{18,21,24,32,34,36,45,46,51,56,57} The surgical possibilities have classically included open, percutaneous, or endoscopically assisted repairs of the tendon.^{14,15,18,21,24,32,34,36,38,45,46,51,56,70} The term “percutaneous repairs” has been used to describe any surgical procedure ranging from the truly percutaneous approaches, as that originally described by Ma and Griffith in 1977,⁴⁰ to those techniques that utilize Kirschner wires, endoscopic assistance, or minimally invasive techniques using specialized instrumentation kits.^{10,27,28,31,64} The percutaneous technique used in this study has been reported to be successful in the treatment of such injuries.^{11,12,16,28,43}

Endoscopic methods of management have also been described.^{10,17,19,26,39,55,59,60} Recently, an endoscopic method using isolated flexor hallucis longus (FHL) tendon transfer has been described and has also been associated with similarly good results both in less active individuals and in high professional athletes.^1,3 These studies were based on the reported success of the same technique albeit for chronic Achilles ruptures^4,22,30,62 or for management of Achilles tendinopathies.^13,65,66

The aim of this study was to compare the clinical and functional results of isolated endoscopic FHL transfer vs a percutaneous Achilles repair in the management of a series of patients with acute Achilles tendon ruptures and documenting these results at a minimum follow-up period of 30 months.

The study null hypothesis was that outcomes with these surgical approaches would be clinically and functionally comparable.

Methods

Patients signed an informed consent after appropriate institutional review board approval was attained. All included cases had their surgical procedure performed between January 2016 and December 2018. The inclusion criteria for this retrospective study were the traumatic occurrence of a unilateral midsubstance Achilles tendon rupture within a maximum of 10 days before the initial presentation in patients aged ≥18 years, with no history of a previous ipsilateral Achilles tendon injury. Patients with previous Achilles tendon surgeries, or those previously diagnosed with either insertional or noninsertional Achilles tendinopathies, were not included in the present study. Moreover, patients presenting with either distal avulsions of the Achilles tendon or musculotendinous ruptures were likewise excluded from the current study.

Inclusion in the current study was for patients who required operative repair for an Achilles tendon midsubstance rupture. There were 2 surgical groups; a group of patients who underwent percutaneous repair of the sustained Achilles ruptures (PAR group) and the other group had an endoscopy-assisted isolated FHL tendon transfer performed as a means of management of the sustained Achilles ruptures (FHL group). At our institutions, and within the time frame of this study, when surgically treating patients with midsubstance AATR, the standard of care was the use of percutaneous Achilles tendon repair techniques. This current retrospective study compared our results with that treatment to other simultaneous cohorts that had endoscopic use of FHL transfer for AATR during that same period that has been previously reported.^1,3 All patients who required operative repair for sustained midsubstance rupture of their Achilles tendon were included in the current study. Patients were informed regarding the merits and disadvantages of both techniques and independently selected their preferred surgical procedure.

The study protocol included clinical assessment by the Achilles tendon Total Rupture Score, American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score, and Tegner activity level scores done both preoperatively and postoperatively. Additionally, all included patients were also evaluated at the end of the follow-up period at a mean of 42.82 (SD 9.04; range, 30-64) months after surgery. Magnetic resonance imaging (MRI) was performed preoperatively, at 1 week postoperatively (to document the tunnel position in the FHL group) and likewise performed for all included patients at a minimum of 1.5 years after surgery. Ankle plantarflexion and great toe flexion strengths were assessed using the MicroFET2 isokinetic digital dynamometer (Hoggan Health Industries, West Jordan, UT).^1,3,29 Hallux proximal interphalangeal plantarflexion power assessment was measured as described previously.^1,3,29 Additional evaluations were made for both the involved and the normal sides at 2.5 years postoperatively to provide comparative data.

Achilles tendon elongation was assessed using the Achilles tendon resting angle (ATRA).^1,3,6 Assessments were performed during the intraoperative repair and during subsequent follow-up evaluations.⁶⁹

The primary outcome measure was the clinical evaluation by the Achilles tendon Total Rupture Score, AOFAS ankle-hindfoot score, and Tegner activity scores and to document any changes in that activity level. Secondary outcome measures were assessment of hallux, ankle plantarflexion power, and Achilles tendon lengthening.

Overall, 120 patients (112 males and 8 females) were initially included in both groups. Three patients were lost during the follow-up period, so the study group ultimately comprised 117 patients (110 males and 7 females). In the FHL group, there were 58 patients (55 males and 3 females) with an average age of 36.67 (range, 25-59). In the PAR group, there were 59 patients (55 males and 4 females) with an average age of 35.83 (range, 18-55). Twenty-two of the included 58 patients in the FHL group were professional athletes compared with 23 of the included 59 patients in the PAR group (37.9% and 39% respectively). Additionally, 55.2% and 54.2% of patients were graded with Tegner activity levels of 7 or more in the FHL and PAR groups, respectively. There were no statistically significant differences between both groups regarding age, sex, number of athletes, or Tegner activity levels in both study groups. Pertinent patient data are presented in Table 1.

Table 1.

Relevant Patient Data for the Included Patients in Both Study Groups.

	FHL Transfer Cases		PAR Cases		P value
	Mean	SD	Mean	SD	P value
Age	36.67	8.10	35.83	8.38	0.582
Follow-up period, mo	42.98	9.04	42.66	9.05	0.848
Specific data	Count	Percentage	Count	Percentage
Gender
Female	3	5.2	4	6.8	>.999
Male	55	94.8	55	93.2	>.999
Professional athletes
Yes	22	37.9	23	39.0	0.907
No	36	62.1	36	61.0	0.907
Tegner level 7 or more
Yes	32	55.2	32	54.2	0.919
No	26	44.8	27	45.8	0.919
Tegner level 5 or more
Yes	43	74.1	42	71.2	0.720
No	15	25.9	17	28.8

Abbreviations: FHL, flexor hallucis longus; PAR, percutaneous Achilles repair.

Statistical Analysis

Statistical data were coded and entered using the Statistical Package for the Social Sciences (SPSS) version 26 (IBM Corp, Armonk, NY). Data were summarized using mean and SD for quantitative variables and frequencies (number of cases) and relative frequencies (percentages) for categorical variables. Comparisons between groups were done using unpaired t test. Comparison between 2 sides within same patient was done using paired t test.⁸ For comparing categorical data, χ² test was performed. Exact test was used instead when the expected frequency was less than 5.⁹ P values less than .05 were considered statistically significant.

Surgical Technique

Both surgical procedures have been well documented previously in literature, and the reader is referred to the descriptive publications for more detailed surgical descriptions.^1,3,12,28 Both surgical techniques were carried out by a single surgeon at 2 separate institutions. All procedures were performed under epidural anesthesia and with the patients in a prone position.

The PARS (Arthrex, Inc, Naples, FL) technique was performed as described previously in the treatment of such injuries.^{11,12,16,28,43} Also, the endoscopy-assisted isolated FHL transfer technique was performed as described recently.^1,3 In both groups, the surgical wounds were closed with 3/0 Ethilon. As a postoperative prophylaxis against deep venous thrombosis, all patients in both groups were prescribed 10 mg rivaroxaban for 3 weeks postoperative.

A plantarflexed below-knee cast was applied for the PAR group,¹⁶ whereas a neutral ankle one was applied for the FHL group.^1,3,4,22 This cast was kept for 2 weeks during which the patient was advised nonweightbearing for 1 week and partial weightbearing during the second week.³ After that period and for both groups, the patients were then progressed to full weightbearing inside a below-knee walker shoe, between the third or fourth week. The only other difference was that the PAR group of patients had a 3-cm heel rise insert in their walking boots, which was gradually reduced by 1 cm at the end of every week sequentially. During this initial weightbearing period, active range of motion of the involved ankle was allowed in plantarflexion, but dorsiflexion was prohibited for those initial 3 weeks. All patients then started a functional accelerated rehabilitation program.^1,3,5

Results

The mean follow-up duration for all the included patients in both groups was 42.8 (±9.045; range, 30-64) months. AOFAS ankle-hindfoot scores taken at 30 months postoperatively were 97.14 (±4.22) and 97.19 (±4.2) for the FHL and PAR group, respectively. The Achilles tendon Total Rupture Scores documented at 30 months postoperatively were 96.98 (±3.02) for the FHL group and 97.68 (±2.87) for the PAR group. The Tegner activity levels were also documented preoperatively and postoperatively. The difference in Tegner activity levels were 0.09 (±0.34) and 0.14 (±0.43) for the FHL group and the PAR group, respectively. All the previous results showed no statistically significant differences between both study groups (Table 2). Additionally, ankle plantarflexion power, differences in ankle plantarflexion between operated and nonoperated sides, ATRA, and relative ATRA measurements likewise showed no statistically significant differences between the 2 study groups. Hallux proximal interphalangeal joint flexion power was clinically measured exclusively in all patients of the FHL transfer group (as the FHL tendon was not transferred in the PAR group), and the results between the operated and normal side were not different (P = .61) (Table 2).

Table 2.

Results of Different Clinical Parameters and the Tegner Activity Levels Measured for Both Study Groups, and Their Clinical Significance.

	FHL Transfer Cases		PAR Cases		P Value
	Mean	SD	Mean	SD	P Value
Ankle plantarflexion normal side	19.13	2.20	19.28	2.14	.706
Plantarflexion SD normal side	6.85	1.01	6.86	1.01	.990
Ankle plantarflexion 30 mo postop.	19.00	2.56	19.00	2.47	.991
Plantarflexion SD 30 mo postop.	6.80	1.42	6.82	1.39	.938
Difference in ankle plantarflexion (normal – operated)	0.13	1.22	0.29	1.17	.480
ATRA at 30 mo, normal	42.55	8.52	42.47	8.12	.960
ATRA at 30 mo, operated	41.97	8.35	41.85	8.05	.938
Relative ATRA at 30 mo	−0.22	2.43	−0.19	2.41	.933
ATRS at 30 mo postop.	96.98	3.02	97.68	2.87	.204
AOFAS ankle-hindfoot score at 30 mo postop.	97.14	4.22	97.19	4.20	.950
Tegner activity level preop.	6.69	2.41	6.56	2.49	.774
Tegner activity level postop.	6.60	2.39	6.42	2.49	.691
Difference in Tegner activity level (preop – postop)	0.09	0.34	0.14	0.43	.495

Abbreviations: AOFAS, American Orthopaedic Foot & Ankle Society; ATRA, Achilles tendon resting angle; ATRS, Achilles tendon Total Rupture Score; FHL, flexor hallucis longus; PAR, percutaneous Achilles repair; preop, preoperative; postop, postoperative.

Return to the same level of activity was also recorded and documented at the end of the follow-up. In the FHL group, 54 patients (93.1%) were able to return to their preinjury levels of activity, whereas in the PAR group, 53 (89.8%) were able to return to their preinjury levels (Figures 1 and 2). Those that did not return to their exact preinjury levels were also documented for their current Tegner activity levels (Table 3). Further analysis of the return to activity data at earlier time durations established that cases of FHL transfer were more likely to return to normal activities by 9 months than the PAR group patients (91% vs 73%, P = .009) (Table 3).

Table 3.

Return to Same Level of Activity Evaluated at 6, 9, and 30 Months Postoperatively for the 2 Study Groups.^a

	FHL Transfer Cases		PAR Cases		P Value
	Count	%	Count	%	P Value
Return to same level of activity at 6 mo follow-up
Yes	45	77.6	36	61.0	.052
No	13	22.4	23	39.0	.052
Return to same level of activity at 9 mo follow-up
Yes	53	91.4	43	72.9	.009
No	5	8.6	16	27.1	.009
Return to same level of activity at 30 mo follow-up
Yes	54	93.1	53	89.8	.743
No	4	6.9	6	10.2	.743
At end of follow-up, patient transferred to:
Tennis/jogging 5 times a week	1	1.7	0	0.0
Sedentary work	0	0.0	1	1.7
Recreational sports/jogging 2 times a week	0	0.0	1	1.7
Recreational soccer	0	0.0	1	1.7
Recreational football	1	1.7	0	0.0
Lower-level football division	1	1.7	2	3.4
Light labor	1	1.7	1	1.7
Same-level activity	54	93.1	53	89.8	.743

Abbreviations: FHL, flexor hallucis longus; PAR, percutaneous Achilles repair.

A higher rate of return to normal activity was observed for patients in the FHL group, especially at 9 months postoperatively. The difference in return to activity for patients in both study groups at the end of the follow-up period is also documented.

Postoperative MRI was performed for all included patients at a minimum of 18-month follow-up and showed a homogenous continuous signal for 45 patients (77.6%) and heterogenous signal intensity in 13 patients (22.4%) in the FHL group, and a homogenous continuous signal for 44 patients (74.5%) and heterogenous signal intensity in 15 patients (25.5%) in the PAR group (Figures 3 and 4). Achilles tendon MRI integrity was assessed and defined according to Goutallier et al.²³

Surgical complications were documented (Table 4). In the FHL group, complications were recorded in 6 patients (10.34%). Major complications occurred in 2 patients (3.44%). These were a case of deep venous thrombosis, and a case of Achilles tendon rerupture at 2.5 months postoperation. The retear was visualized by MRI to be at the site of the previous Achilles tendon rupture, albeit in the presence of an intact previously transferred FHL tendon (Figure 5). This patient was initially restricted to weightbearing in a below-knee walker brace for 3 weeks with 3-cm heel rise inserts, which were gradually reduced by 1 cm at the end of every week sequentially, then proceeded with the same accelerated physiotherapy protocol although by restarting once more from the beginning of that regimen. Four other patients had minor complications (lasting less than a month postoperatively) and were the following: portal pain (2 patients), and superficial infection (2 cases).

Table 4.

Complications Encountered in the FHL and PAR Groups in the Current Study.

	FHL Transfer Cases		PAR Cases		P Value
	Count	%	Count	%	P Value
Total complications
Yes	6	10.3	8	13.6	.592
No	52	89.7	51	86.4	.592
Superficial infection
Yes	2	3.4	3	5.1	>.999
No	56	96.6	56	94.9	>.999
Sural nerve injury
Yes	0	0.0	2	3.4	.496
No	58	100.0	57	96.6	.496
Achilles rerupture
Yes	1	1.7	1	1.7	>.999
No	57	98.3	58	98.3	>.999
Portal pain
Yes	2	3.4	0	0.0	0.244
No	56	96.6	59	100.0	0.244
Deep venous thrombosis
Yes	1	1.7	2	3.4	1
No	57	98.3	57	96.6

Abbreviations: FHL, flexor hallucis longus; PAR, percutaneous Achilles repair.

In the PAR group, the total number of complications was recorded in 8 patients (13.6%). Major complications occurred in the 5 patients (8.47%). These were 2 cases of deep venous thrombosis, 2 cases of sural nerve injury (both resolved spontaneously within 4 months postoperatively), and 1 Achilles tendon rerupture at 5 months postoperative. This patient was treated conservatively by functional weightbearing immobilization in a below-knee walker brace for a month and instructed to restart the accelerated functional physiotherapy protocol once more from the onset. Three further cases of superficial infection were graded as minor complications (lasting less than a month postoperatively).

Discussion

In this retrospective study, we found that both techniques to repair an acute Achilles tendon overall performed well and equally. The only major difference was noted at 9 months after surgery with a higher rate of return to normal activities in the FHL group than in the PAR group (91% vs 73%, P = .009). Ultimately, both the FHL group and the PAR group showed an equally high rate of return to preinjury activity (93.1% and 89.8%, respectively). This was an important finding considering 54.7% of the included cases were originally of Tegner activity level 7 or higher. Additionally, the patient population demographics was representative of both athletic and nonathletic populations, and this obtained result also seemed to compare well with other similar studies.^{14,15,33,34,38,48,50,51,68}

Zellers et al⁶⁹ demonstrated that the relative ATRA is an adequate guide for tendon elongation and is consequently indicative of tendon mechanical properties and heel-rise test performance. Also, Carmont and colleagues⁶ have stated that the ATRA itself may be used as a measure of Achilles tendon length during intraoperative repair and rehabilitation. In the current study, we found that the relative ATRA was equivalent to the normal uninjured side at 30 months postoperatively (P = .93).

The optimum method to manage the acute Achilles rupture remains debatable.^24,34,50,67 Recent meta-analyses have concluded that if surgical management is being considered, minimally invasive surgical methods of management can be recommended for AATR.^21,45,56 Surgical and functional outcomes of the percutaneous methods of management have been satisfactory for AATR.^{11,12,14,21,24,28,36,38,43,45,54,56,67} Authors have cited reduced risk of superficial wound infection, greater patient satisfaction,⁴² reduced risks of postoperative complications, and significantly higher subjective good or excellent outcomes as some advantages.²⁴ These results have also been found to be similar when using the instrumentation device system we used in the current study for percutaneous repairs of midsubstance AATR.^11,12,16,28

Endoscopic assistance in surgical management of Acute Achilles tendon ruptures has been investigated by several groups.^{10,17,19,26,39,55,59,60} Recently the endoscopic approach we used herein was described as a method of management of acute ruptures of Achilles tendon.^1,3 This method used the more familiar posterior ankle endoscopic approach,⁶¹ combined with FHL tendon transfer that is commonly used with success for chronic ruptures of the Achilles tendon,^{4,22,30,41,47,62,65} as well as a method for the management of chronic Achilles tendinopathies.^65,66 The rationale for the use of the FHL tendon transfer reported by all of these authors was the strong muscle tendon segment available, the biological advantage of placing a muscle bulk near to the pathologic area, the vicinity of the tendon itself, and its being an “in-phase” muscle biomechanically that acts in synchronicity with the Achilles tendon during the gait cycle.^62,65

Harvesting and transfer of the FHL tendon has been classically associated with a loss of push-off strength.^41,47,52,65 This deficit has been associated with the use of more “distal methods” to harvest the FHL tendon.^63,65 This appears to be reduced with single-incision techniques, and those authors cite an absence of clinical evidence of patient-reported complications related to the harvesting of the FHL tendon in their cases.^{13,37,49,62,63,66}

With the currently described technique, the FHL tendon is transected endoscopically at the posterior subtalar joint, which is anatomically more proximal than the knot of Henry. Recent anatomical studies have shown that if the tendon is transected at the knot of Henry, loss of hallux push-off strength will be more than if that transection is performed at a more proximal zone.⁷⁰ Additionally, it was found that the interconnections of the chiasma plantare were able to replace the functions of the FHL or flexor digitorum longus after transfer.⁷⁰ In their anatomical study, the authors could not conclude the exact functional deficit that might result despite this compensatory effect of the chiasma plantare and stated that there was a need for more clinical studies and patient outcome reports.⁷⁰

In the current study, while comparing both groups and because FHL transfer was not used in the PAR group, FHL dynamometry was not used as a comparative variable between the 2 study groups. However, FHL plantarflexion power was clinically measured in all patients of the FHL group, and the results between the operated and the nonoperated sides were found to be statistically insignificant (P = .61). There is a wide variability and a general lack of consensus in the exact methodology for measurements of strength following Achilles tendon rupture and likewise so for the measurements of functional deficits or ankle and hallux flexion powers. This has been recently demonstrated by a literature review, which stated that 78 of the 100 examined articles used a dynamometer to measure those strength variables. These authors called for a more uniform and validated method of quantification of strength measurements after acute Achilles tendon ruptures.² On the other hand, several studies have shown the reliability and validity of the measurement of ankle flexion power and hallux power by handheld dynamometry instrumentation.^{7,35,44,53,58} In the current study, measurements of hallux proximal interphalangeal joint plantarflexion power were measured by methods similar to those used in previous studies and comparable to the technique used by a recent randomized control study on surgical treatments of chronic insertional tendinopathy with or without the use of FHL transfers.²⁹

Notably, immobilization for the 2 initial weeks within the 2 groups was different. Our intention was to provide the best possible environment for healing and to regain the normal range of ankle motion without adversely affecting outcomes. In the PAR group and following the standard of care and the recommended position of postoperative immobilization and management for these patients, the immediate postoperative position was in maximum plantarflexion.^16,28 The PAR repair is advised to be made in maximum plantarflexion and due to the presence of only the sutures that were used for repair of the tears; the original technique description and consequently postoperative protocol has commonly started from a position of plantarflexion and worked its way toward dorsiflexion gradually to “protect” this repair from undue early tension on the suture sites.^12,16,28 In distinction with the FHL tendon transfer, we intraoperatively set equinus based on the contralateral resting ATRA, so the position is rarely that of extreme plantarflexion. Both rehabilitation programs advance these patients to neutral position over time, with the PAR group requiring more time.

The limitations of the present study are that it is a retrospective study albeit a comparative one performed during the same time interval, and some confounders may exist that we have not recognized as there was no randomization in the choice of either procedures. Additionally, the patients were predominantly male. Although this does correspond with reported gender differences of this tendon rupture, generalizability of the results may have limitations. Despite these limitations, and to our knowledge the current study is the first describing the use of both these techniques in a comparative method and with adequate outcome measures and with relatively reasonable follow-up periods of a minimum of 30 months.

In conclusion, the current study demonstrated adequate and nearly equivalent results when using both the FHL tendon transfer and the percutaneous approach we used to surgically treat acute Achilles tendon ruptures. Recorded complications were minimal in both study groups. Significant discrepancies of hallux push-off, ankle plantarflexion, or Achilles tendon lengthening were not found. There was a significant tendency toward an earlier return to preinjury levels of activity in the FHL group especially at 9 months postoperative.

Supplemental Material

sj-pdf-1-fai-10.1177_10711007221096674 – Supplemental material for Outcomes of Percutaneous Achilles Repair Compared With Endoscopic Flexor Hallucis Longus Tendon Transfer to Treat Achilles Tendon Ruptures

Supplemental material, sj-pdf-1-fai-10.1177_10711007221096674 for Outcomes of Percutaneous Achilles Repair Compared With Endoscopic Flexor Hallucis Longus Tendon Transfer to Treat Achilles Tendon Ruptures by Nasef Mohamed N. Abdelatif and Jorge Pablo Batista in Foot & Ankle International

Footnotes

Declaration of Conflicting Interests

The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Nasef Mohamed N. Abdelatif, MD, PhD, reports payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events: consultant and instructor for Arthrex GmbH. Personal fees from Arthrex GmbH, outside the submitted work. ICMJE forms for all authors are available online.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Nasef Mohamed N. Abdelatif, MD, PhD,

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