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research-article2015
FAIXXX10.1177/1071100715586182Foot & Ankle InternationalHunt et al
Article
Surgical Treatment of Insertional Achilles Tendinopathy With or Without Flexor Hallucis Longus Tendon Transfer: A Prospective, Randomized Study
Foot & Ankle International® 2015, Vol. 36(9) 998–1005 © The Author(s) 2015 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1071100715586182 fai.sagepub.com
Kenneth J. Hunt, MD1, Bruce E. Cohen, MD2, W. Hodges Davis, MD2, Robert B. Anderson, MD2, and Carroll P. Jones, MD2
Abstract Background: Chronic insertional Achilles tendinopathy is a common pathology that can be difficult to manage. Some experts have advocated augmentation with the flexor hallucis longus (FHL) tendon in patients over age 50 and those with more severe tendon disease. We hypothesized that FHL augmentation would be associated with superior clinical outcome scores and greater ankle plantar flexion strength compared with Achilles debridement alone. Methods: Consecutive patients older than 50 years who had failed nonoperative treatment for chronic insertional Achilles tendinopathy were randomly assigned to Achilles decompression and debridement alone (control group) or Achilles decompression and debridement augmented with FHL transfer (FHL group). Outcome measures included American Orthopaedic Foot & Ankle Society (AOFAS) ankle/hindfoot score, visual analog scale (VAS) for pain, ankle and hallux plantar flexion strength, and a patient satisfaction survey. A total of 39 enrolled patients had a minimum 1-year follow-up, 18 in the control group and 21 in the FHL transfer group. The average patient age was 60.5 years. Results: AOFAS and VAS scores improved in both groups at 6 months and 1 year with no difference between groups. There was greater ankle plantar flexion strength in the FHL group at 6 months and at 1 year compared with the control group (P < .05). There was no difference between the 2 groups in hallux plantar flexion strength preoperatively and at 1 year after surgery. Some 87% of patients were satisfied with the outcome of their procedure. There was no significant increase in wound complications in the FHL group (P < .05). Conclusion: We found no differences in pain, functional outcome (as measured by the AOFAS ankle/hindfoot scale), and patient satisfaction when comparing patients treated with Achilles debridement alone versus FHL augmentation for chronic Achilles tendinopathy. Ankle plantar flexion strength appeared to be improved with FHL transfer, with no loss of hallux plantar flexion strength. Although FHL transfer was a safe adjunct to tendon debridement and partial ostectomy for insertional Achilles tendinopathy in older patients with little compromise in function, it may not be necessary for primary cases. Level of Evidence: Level 1, prospective randomized trial. Keywords: tendon disorders, outcome studies Chronic insertional Achilles tendinopathy is a common pathology with a multifactorial cause. Although it has been described as an overuse phenomenon, predisposing factors include anatomic and biomechanical abnormalities, errors in athletic training, and improper shoe wear.1,3,16 Nonoperative management, usually consisting of activity and shoe wear modification, nonsteroidal anti-inflammatory medications, stretching, and physical therapy, is effective in the majority of cases.5,13 For patients in whom conservative management fails to alleviate symptoms, a number of operative techniques have been described. Debridement of the degenerative Achilles
tendon with calcaneal ostectomy has been shown to be effective in reducing pain and improving function in patients younger than 50 years with moderate tendon involvement.13,21 However, results have been less reliable in 1
Department of Orthopaedic Surgery, Stanford University, Redwood City, CA, USA 2 OrthoCarolina Foot and Ankle Institute, Charlotte, NC, USA Corresponding Author: Carroll P. Jones, MD, OrthoCarolina Foot and Ankle Institute, 2001 Vail Ave, Suite 200B, Charlotte, NC 28207, USA. Email: [email protected]
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Hunt et al Table 1. Patient Demographics. Control Group a
Age, y Weight, lba Body mass indexa Affected side, left/right, n Preoperative AOFAS scorea Smoker, % Diabetes mellitus, % Wound healing issues, % Gastrocnemius recession, %
60.1 ± 7 201.8 ± 31 31.7 ± 4.8 10/8 56 ± 13 0.0 11.1 22.2 44.4
FHL Group 60.8 ± 6.9 215.1 ± 35 35.9 ± 6 10/11 61 ± 9 9.5 14.3 38.1 33.3
P Value >.05 >.05 >.05 >.05 >.05 >.05 >.05 >.05 >.05
Abbreviation: AOFAS, American Orthopaedic Foot & Ankle Society. a Values expressed as mean ± SD.
patients over age 50.13,21 Potential problems associated with debridement alone may include persistent pain and functional limitations. This may be due to the reduction in blood flow and healing potential of the Achilles tendon that occurs with increasing age, a more advanced degree of tendinopathy, or less capacity for full rehabilitation. For these reasons, the addition of a flexor hallucis longus (FHL) tendon transfer to augment the repair has been advocated for patients with more severe tendinosis, in patients older than 50, and in patients with a high body mass index (BMI).4,6,18 The theoretical benefits of FHL augmentation include mechanical support to protect the reattached Achilles tendon in the event of inadvertent early loading, and the addition of a muscle with significant volume and strength.10 Good results have been described in case series of older patients treated with FHL augmentation.4,6,18,22 However, the benefits of FHL augmentation have not been demonstrated in a prospective, randomized controlled clinical trial. The purpose of this study was to determine whether Achilles tendon debridement, decompression, and partial calcaneal ostectomy, augmented with FHL tendon transfer, would result in improved clinical outcomes and ankle plantar flexion strength compared with debridement and decompression alone in patients over 50 years of age with chronic insertional Achilles tendinosis. In a prospective, randomized trial, we hypothesized that FHL augmentation would be associated with superior clinical outcome scores and greater ankle plantar flexion strength compared with Achilles debridement alone.
Methods After institutional review board approval, we initiated our prospective, randomized study protocol. All patients older than 50 years who had failed appropriate nonoperative treatment for chronic insertional Achilles tendinopathy were invited to participate. Nonoperative treatment included
boot immobilization and a period of relative rest, an Achilles sleeve device, shoe wear modification, and nonsteroidal anti-inflammatory medications over at least a 6-month period. Patients meeting the inclusion criteria were randomly assigned using the sealed envelope method to Achilles debridement and ostectomy alone (control group) or Achilles debridement and ostectomy augmented with FHL transfer (FHL group). Exclusion criteria included previous ipsilateral Achilles surgery, previous Achilles tendon rupture, active wound or infection on the ipsilateral leg, and lack of an FHL tendon suitable for transfer. A clinic research coordinator selected and opened the sealed envelope assigning the patient group. This was securely communicated to 1 of the 4 operating surgeons participating in the study. Patients were blinded to their treatment group. Patients followed a standard postoperative protocol, including formal physiotherapy. Outcome measures collected in the clinic included American Orthopaedic Foot & Ankle Society (AOFAS) ankle/hindfoot score, visual analog scale (VAS) for pain, ankle and hallux plantar flexion strength (measured with MicroFET2 isokinetic dynamometer; Hoggan Health Industries, West Jordan, UT), and a patient satisfaction survey. Patients were evaluated postoperatively in clinic by an independent, blinded examiner at 3 months, 6 months, and 1 year. All operative complications were recorded. A total of 49 patients were enrolled in the study between May 2009 and June 2011. Five patients withdrew from the study before undergoing surgery, and 5 patients were not available for the 1-year follow-up, leaving 39 patients with complete data at a minimum 1-year follow-up. There were 18 patients in the control group and 21 in the FHL transfer group. The average patient age was 60.5 ± 7 years (range, 50.2-75.7 years). There were 25 females and 14 males. Average body weight was 208 ± 33.5 pounds (range, 129270 pounds). There was no difference between groups in terms of smokers, diabetes, and BMI. Patient demographics are listed in Table 1.
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Surgical Technique A single incision technique was used for all cases. The location of the skin incision was at the discretion of the attending surgeon. The surgeon’s preferred skin incision (medial, lateral, or central) was used along with a centralsplitting of the Achilles tendon, debridement of the tendon insertion, and resection of a Haglund lesion if present. All areas of tendinosis were debrided and typically included between 25% and 60% of the tendon’s diameter, leaving only intact, healthy tendon fibers. For patients randomized to the FHL transfer group, all 4 surgeons used the same technique. The deep posterior compartment fascia was incised to expose the FHL tendon. The FHL tendon was identified and tenotomized at the FHL tunnel along the medial calcaneus and then transferred to the calcaneus as described previously for patients in the FHL group.4 A cannulated drill was used to create a drill hole in the calcaneus, and an appropriately sized interference screw was used to secure the FHL tendon into the calcaneus. The ankle was held in neutral dorsiflexion, and moderate tension was placed on the FHL as it was secured in the tunnel with the screw. The FHL tendon was then tenodesed to the Achilles during the Achilles repair. For all patients, the Achilles was reattached with lateral and medial suture anchors (just distal to the interference screw in the FHL patients). Layered closure was performed, including the paratenon, subcutaneous tissue, and skin. The deep compartment fascia was not closed primarily. If a gastrocnemius equinus was found to be present, a gastrocnemius lengthening was performed through a separate incision at the musculotendinous junction. The postoperative protocol was the same for all patients and included non-weight-bearing in a splint for 2 weeks followed by non-weight-bearing in a short-leg cast for 2 to 3 weeks. Patients were then fit with a tall CAM walker boot with 2 adjustable lifts and began weight bearing as tolerated. The lifts were peeled layer by layer every 2 to 3 days until no lift remained. At 6 to 8 weeks postoperatively, patients transitioned out of the boot and initiated a standardized physical therapy Achilles repair protocol. Activities were advanced as tolerated by the patient, with avoidance of impact exercise until 3 months postoperatively.
Postoperative Follow-up Evaluation Patients were evaluated clinically by an independent examiner at the following intervals: preoperatively, 3 months, 6 months, and 1 year postoperatively. All postoperative complications were recorded at 3 months and 1 year. Patients were scored on a 2-item satisfaction scale (Appendix 1). All patients underwent testing of ankle plantar flexion strength
Figure 1. Clinical photograph demonstrating hallux plantar flexion testing with the MicroFET2.
and hallux plantar flexion strength on both the operative and nonoperative limbs using a MicroFET2 isokinetic dynamometer. Ankle plantar flexion strength was tested by placing the heel on the ground with the patient seated and the knee extended. The patients were asked to plantar flex the foot with as much force as possible. Patients were monitored to ensure that they did not use body weight during plantar flexion, isolating the gastroc-soleus complex. Hallux plantar flexion strength was measured in a similar fashion, with the heel resting on the ground with the knee bent. The patients were asked to plantar flex the hallux only and were monitored to ensure that the ankle remained in neutral and that body weight was not shifted (Figure 1). For each analysis, a total of 5 tests were performed. The highest and lowest numbers were discarded, and an average of the 3 remaining values was used.
Statistical Analysis A sample size estimate was calculated using nQuery Advisor software (version 7.0). Standard descriptive statistics were calculated. Between-group paired comparisons were made using an independent t test for normally distributed data and a Mann-Whitney test for nonnormally
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Figure 2. Bar chart illustrating American Orthopaedic Foot & Ankle Society (AOFAS) ankle/hindfoot scores in each group at all preoperative and postoperative time points. There was a significant difference between each postoperative time point and the preoperative value, with no difference between groups at any time point. FHL, flexor hallucis longus. Table 2. Clinical Outcomesa. Control Group AOFAS score Preoperative 56.7 ± 12.6 3 months 78.4 ± 11.8 6 months 85.9 ± 11.3 1 year 91.5 ± 13 VAS score Preoperative 68 ± 19.8 3 months 34.3 ± 23.5 6 months 25.8 ± 25 1 year 14.6 ± 18.6 Ankle plantar flexion strength, lb Preoperative 11.8 ± 7.2 3 months 13.5 ± 8.1 6 months 12.2 ± 5.8 1 year 13.5 ± 6.6 Hallux plantar flexion strength, lb Preoperative 13.7 ± 6.5 3 months 15 ± 6.4 6 months 14.9 ± 5.4 1 year 16.6 ± 6.5
FHL Group 61.4 ± 9.93 79.7 ± 13 91 ± 11.3 92.3 ± 15.2 64 ± 21.3 28.4 ± 22.8 21.2 ± 28.2 10 ± 18 16.1 ± 8.3 16.7 ± 7.7 18.1 ± 9.1 20.3 ± 10.8 18.2 ± 10.2 13.6 ± 6 16.3 ± 6.9 18.3 ± 7.1
Abbreviations: AOFAS, American Orthopaedic Foot & Ankle Society; FHL, flexor hallucis longus; VAS, visual analog scale. a Values expressed as mean ± SD.
distributed data. Normality was determined using a Kolmogorov-Smirnov test. All statistical tests were performed at an a priori significance level of .05.
Results Clinical Outcomes AOFAS ankle/hindfoot scores improved in both groups at 6 months and 1 year with no difference between groups (Figure 2, Table 2). Activity-related VAS scores improved significantly in both groups, with no difference between groups at 6 months and 1 year (Figure 3, Table 2).
Plantar Flexion Strength There was greater ankle plantar flexion strength in the FHL group at 6 months and 1 year compared with the control group (Figure 4, Table 2) (P < .05). There was not a significant difference in the number of patients who underwent gastrocnemius lengthening in the control group (n = 8) compared with the FHL group (n = 7). There was no difference between the 2 groups in hallux plantar flexion strength preoperatively and at 1 year (Figure 5, Table 2) (P = .43), and no patients complained of functional difficulties or weakness in their great toe.
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Figure 3. Bar chart illustrating visual analog scale (VAS) scores for activity-related pain in each group at all preoperative and postoperative time points. There was a significant difference between each postoperative time point and the preoperative value, with no difference between groups at any time point. FHL, flexor hallucis longus.
Figure 4. Bar chart illustrating ankle plantar flexion strength (pounds) at each data collection time point. There was significantly more improvement at 1 year in the FHL group compared with the control group. FHL, flexor hallucis longus.
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Figure 5. Bar chart illustrating hallux plantar flexion strength (pounds) at each data collection time point. There was no significant difference between groups at any time point. FHL, flexor hallucis longus.
Patient Satisfaction
Discussion
At 1 year, 34 of 39 patients (87.2%) were satisfied with the outcome of their procedure, again with no difference between groups (18/21 satisfied in FHL group, 16/18 in control group).
Flexor hallucis longus transfer has been well described as an augmentation for repair of chronic Achilles tendon ruptures and reruptures.7,18,22 The FHL has been shown to have significantly greater muscle volume and greater strength than the flexor digitorum longus (FDL) and peroneal tendons, which have also been used in the treatment of chronic Achilles conditions.10 While many authors recommend augmentation with the FHL for insertional Achilles tendinopathy, very few reports are isolated to older patient groups, and there are no published prospective randomized series.4,6,8,20 Wapner et al20 described results of FHL transfer for insertional Achilles tendinopathy in 17 patients (age range, 25-71 years) with high satisfaction and return to function. Den Hartog4 reported on 26 patients, including 18 patients 50 years of age or older, and found a higher magnitude of improvement in patients older than 50. In fact, AOFAS scores improved to levels in the over-50 group that were equivalent to levels in patients younger than 50.4 This is in contrast to previous articles by McGarvey et al13 and Watson et al,21 who reported worse outcomes in patients over 50 who underwent partial calcanectomy and Achilles debridement alone. Our data demonstrate, in patients 50 years of
Complications There were no neurologic complications and no deep vein thromboses. No patients required additional surgical procedures. While there were no major complications, we identified 12 minor complications in 39 cases (31%), all related to the surgical wound. These included minor superficial wound dehiscence (6 patients), skin blistering or cellulitis (2 patients), delayed wound healing (2 patients), and peri-incisional maceration (2 patients). All wounds healed without additional surgical intervention. There was no significant difference in the rate of wound complications comparing the FHL group with controls (8/12 vs 4/12, respectively, P = .236). There was also no significant difference in wound complications based on location of surgical incision (2/8 medial incisions, 2/9 lateral, 8/22 central midline).
1004 age and older, no difference in clinical outcome scores and patient satisfaction comparing those treated with Achilles debridement and ostectomy alone versus debridement and ostectomy with FHL augmentation. This is similar to a series published by Nunley et al14 of 19 patients treated with Achilles debridement and exostectomy without FHL transfer and a long-term 96% satisfaction rate. However, we did find greater ankle plantar flexion strength in the FHL augmentation group and no difference in hallux plantar flexion strength between groups at 1 year. Minor wound complication rates were relatively high, particularly in the FHL transfer group, although all wound problems healed without need for additional surgical intervention and there were no nerve injuries. It is possible that the additional dissection and bulk of the FHL muscle belly contributed to the increased wound complication risk. FHL transfer did not appear to result in hallux plantar flexion weakness compared with controls. Elias et al6 reported on 40 patients (mean age 57 years; range, 39-76 years) undergoing Achilles debridement and FHL transfer for insertional Achilles tendinopathy. The investigators found improved VAS and AOFAS scores with no loss of ankle plantar flexion strength. Schon et al18 reported significant improvement in physical function and pain intensity in a group of 46 inactive, older, overweight patients (mean age 54 ± 10 years and BMI 34 ± 6). This closely approximates the demographics of our groups. To our knowledge, the present study is the first Level I study comparing FHL transfer to debridement alone in patients over 50. Our results suggest that ankle plantar flexion strength improves more rapidly, and with a greater overall magnitude at 1 year, when FHL augmentation is incorporated into Achilles debridement and decompression alone. Pain relief, functional scores, and satisfaction were no different between groups with our selected metrics. It is possible that superior clinical outcome metrics with better precision (ie, VISA-A, FAAM, PROMIS instruments) may have better differentiated differences in function between the groups, but the strength difference appears clear-cut.
Hallux Plantar Flexion Strength The concerning potential morbidity of FHL transfer is loss of great toe plantar flexion strength, which could in theory affect balance, endurance, and gait. We found similar hallux plantar flexion strength in patients having undergone FHL transfer compared with controls, and no patients reported functional difficulties with the great toe at 1 year. This finding is similar to those reported in previous studies.18,22 It is likely that the strength necessary for daily function is accommodated for by the flexor hallucis brevis or distal connections between the FHL and FDL tendons. It is important to note that the patients in our study were
Foot & Ankle International 36(9) 50 years of age and older and were, on average, obese. It is possible that younger, more active, athletic individuals would develop symptomatic hallux weakness after FHL transfer, and we rarely perform FHL transfers in this population.
Role of the Surgical Incision A variety of surgical approaches and techniques have been described for patients undergoing treatment for insertional Achilles tendon disorders. These include a lateral longitudinal incision,13,19 a medial J-shaped incision,12,17 and a 2-incision approach with medial and lateral incisions.2 McGarvey et al,13 Johnson et al,11 and Nunley et al14 described the central tendon splitting approach to debride the Achilles tendon without a tendon augmentation. Wapner et al19,20 described harvesting the FHL tendon through a double-incision approach. We harvested and transferred the FHL tendon through a single incision in all patients. We found no difference in clinical outcome based on incision location. Nunley et al14 also reported excellent long-term results with a single midline incision and only 1 superficial wound problem.
Complications While our patients had no nerve complications and no deep vein thromboses, there was a relatively high rate of minor wound complications. The complication rates in the present study are slightly higher than rates reported in other studies.6,18,20 Wegrzyn et al22 did not report minor complications.
Limitations The study has some limitations. We included only a minimum of 12 months of follow-up. Schon et al18 noted small but continued improvement in a similar cohort between 12 and 24 months. Thus, we would not expect our results to deteriorate in the immediate short term for the FHL transfer group. Another limitation was our use of the AOFAS scale as a clinical outcome instrument. This is not a validated scale, and the AOFAS has recommended against its continued use.15 However, during the development of this trial and the IRB approval process, the AOFAS scale was the most widely used and accepted outcome measure in the foot and ankle literature (and remains so).9 We have incorporated validated, reliable scores into ongoing trials at our institution. Finally, 4 different surgeons contributed patients to this study, and different approaches were used that could have affected the outcomes. The numbers were not large enough to determine whether there was a difference between surgeons.
Hunt et al
Conclusions FHL tendon transfer combined with Achilles tendon debridement and partial calcaneal ostectomy may offer improved ankle plantar flexion strength for patients undergoing treatment for insertional Achilles tendinopathy. However, we did not find significant differences in pain relief and functional outcomes. It remains unclear whether differences would be noted with more powerful outcome instruments, such as the VISA-A or FAAM. We found no loss of hallux plantar flexion strength and a significant increase in ankle plantar flexion strength in these patients relative to controls. Based on these results, the routine use of FHL transfers as an adjunct to Achilles tendon debridement and partial ostectomy in older, sedentary patients may not be necessary. However, it was a safe procedure and may be better suited for revision cases. Longer follow-up and a standardized surgical incision may provide additional insight into the ideal surgical approach for this difficult problem.
Appendix 1 Two-Item Patient Satisfaction Survey Administered to All Patients at Final Follow-up Thank you for participating in this clinical study. All of the questions relate to the surgery that you had on your Achilles tendon.
1. Would you have the operation again? □ Yes □ No □ Unsure
2. Rate your satisfaction (check 1): □ Very Satisfied □ Satisfied □ Dissatisfied □ Very Dissatisfied
Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by the OrthoCarolina Research Institute (OCRI).
References 1. Clain MR, Baxter DE. Achilles tendinitis. Foot Ankle. 1992;13(8):482-487. 2. Clain MR, Baxter DE. Simultaneous calcaneocuboid and talonavicular fusion: long-term follow-up study. J Bone Joint Surg Br. 1994;76(1):133-136.
1005 3. Clancy WG Jr, Neidhart D, Brand RL. Achilles tendonitis in runners: a report of five cases. Am J Sports Med. 1976;4(2): 46-57. 4. Den Hartog BD. Flexor hallucis longus transfer for chronic Achilles tendinosis. Foot Ankle Int. 2003;24(3):233-237. 5. DeOrio MJ, Easley ME. Surgical strategies: insertional Achilles tendinopathy. Foot Ankle Int. 2008;29(5):542-550. 6. Elias I, Raikin SM, Besser MP, et al. Outcomes of chronic insertional Achilles tendinosis using FHL autograft through single incision. Foot Ankle Int. 2009;30(3):197-204. 7. Hahn F, Meyer P, Maiwald C, et al. Treatment of chronic Achilles tendinopathy and ruptures with flexor hallucis tendon transfer: clinical outcome and MRI findings. Foot Ankle Int. 2008;29(8):794-802. 8. Hansen S. Trauma to the heel cord. In: Jahss M, ed. Disorders of the Foot and Ankle. 2nd ed. Philadelphia, PA: WB Saunders; 1991:2355-2360. 9. Hunt KJ, Hurwit D. Use of patient related outcome measures in foot and ankle research. J Bone Joint Surg Am. 2013;95(16):e118. 10. Jeng CL, Thawait GK, Kwon JY, et al. Relative strengths of the calf muscles based on MRI volume measurements. Foot Ankle Int. 2012;33(5):394-399. 11. Johnson KW, Zalavras C, Thordarson DB. Surgical management of insertional calcific Achilles tendinosis with a central tendon splitting approach. Foot Ankle Int. 2006;27(4):245-250. 12. Martin RL, Manning CM, Carcia CR, et al. An outcome study of chronic Achilles tendinosis after excision of the Achilles tendon and flexor hallucis longus tendon transfer. Foot Ankle Int. 2005;26(9):691-697. 13. McGarvey WC, Palumbo RC, Baxter DE, et al. Insertional Achilles tendinosis: surgical treatment through a central tendon splitting approach. Foot Ankle Int. 2002;23(1):19-25. 14. Nunley JA, Ruskin G, Horst F. Long-term clinical outcomes following the central incision technique for insertional Achilles tendinopathy. Foot Ankle Int. 2011;23(9):850-855. 15. Pinsker E, Daniels TR. AOFAS position statement regarding the future of the AOFAS Clinical Rating Systems. Foot Ankle Int. 2011;32(9):841-842. 16. Schepsis AA, Jones H, Haas AL. Achilles tendon disorders in athletes. Am J Sports Med. 2002;30(2):287-305. 17. Schepsis AA, Leach RE. Surgical management of Achilles tendinitis. Am J Sports Med. 1987;15(4):308-315. 18. Schon LC, Shores JL, Faro FD, et al. Flexor hallucis longus tendon transfer in treatment of Achilles tendinosis. J Bone Joint Surg Am. 2013;95(1):54-60. 19. Wapner K, Hecht P. Repair of chronic Achilles tendon rupture with flexor hallucis longus tendon transfer. Op Tech Orthop. 1994;4:132-137. 20. Wapner KL, Pavlock GS, Hecht PJ, et al. Repair of chronic Achilles tendon rupture with flexor hallucis longus tendon transfer. Foot Ankle. 1993;14(8):443-449. 21. Watson AD, Anderson RB, Davis WH. Comparison of results of retrocalcaneal decompression for retrocalcaneal bursitis and insertional Achilles tendinosis with calcific spur. Foot Ankle Int. 2000;21(8):638-642. 22. Wegrzyn J, Luciani JF, Philippot R, et al. Chronic Achilles tendon rupture reconstruction using a modified flexor hallucis longus transfer. Int Orthop. 2010;34(8):1187-1192.
research-article2015
FAIXXX10.1177/1071100715586182Foot & Ankle InternationalHunt et al
Article
Surgical Treatment of Insertional Achilles Tendinopathy With or Without Flexor Hallucis Longus Tendon Transfer: A Prospective, Randomized Study
Foot & Ankle International® 2015, Vol. 36(9) 998–1005 © The Author(s) 2015 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1071100715586182 fai.sagepub.com
Kenneth J. Hunt, MD1, Bruce E. Cohen, MD2, W. Hodges Davis, MD2, Robert B. Anderson, MD2, and Carroll P. Jones, MD2
Abstract Background: Chronic insertional Achilles tendinopathy is a common pathology that can be difficult to manage. Some experts have advocated augmentation with the flexor hallucis longus (FHL) tendon in patients over age 50 and those with more severe tendon disease. We hypothesized that FHL augmentation would be associated with superior clinical outcome scores and greater ankle plantar flexion strength compared with Achilles debridement alone. Methods: Consecutive patients older than 50 years who had failed nonoperative treatment for chronic insertional Achilles tendinopathy were randomly assigned to Achilles decompression and debridement alone (control group) or Achilles decompression and debridement augmented with FHL transfer (FHL group). Outcome measures included American Orthopaedic Foot & Ankle Society (AOFAS) ankle/hindfoot score, visual analog scale (VAS) for pain, ankle and hallux plantar flexion strength, and a patient satisfaction survey. A total of 39 enrolled patients had a minimum 1-year follow-up, 18 in the control group and 21 in the FHL transfer group. The average patient age was 60.5 years. Results: AOFAS and VAS scores improved in both groups at 6 months and 1 year with no difference between groups. There was greater ankle plantar flexion strength in the FHL group at 6 months and at 1 year compared with the control group (P < .05). There was no difference between the 2 groups in hallux plantar flexion strength preoperatively and at 1 year after surgery. Some 87% of patients were satisfied with the outcome of their procedure. There was no significant increase in wound complications in the FHL group (P < .05). Conclusion: We found no differences in pain, functional outcome (as measured by the AOFAS ankle/hindfoot scale), and patient satisfaction when comparing patients treated with Achilles debridement alone versus FHL augmentation for chronic Achilles tendinopathy. Ankle plantar flexion strength appeared to be improved with FHL transfer, with no loss of hallux plantar flexion strength. Although FHL transfer was a safe adjunct to tendon debridement and partial ostectomy for insertional Achilles tendinopathy in older patients with little compromise in function, it may not be necessary for primary cases. Level of Evidence: Level 1, prospective randomized trial. Keywords: tendon disorders, outcome studies Chronic insertional Achilles tendinopathy is a common pathology with a multifactorial cause. Although it has been described as an overuse phenomenon, predisposing factors include anatomic and biomechanical abnormalities, errors in athletic training, and improper shoe wear.1,3,16 Nonoperative management, usually consisting of activity and shoe wear modification, nonsteroidal anti-inflammatory medications, stretching, and physical therapy, is effective in the majority of cases.5,13 For patients in whom conservative management fails to alleviate symptoms, a number of operative techniques have been described. Debridement of the degenerative Achilles
tendon with calcaneal ostectomy has been shown to be effective in reducing pain and improving function in patients younger than 50 years with moderate tendon involvement.13,21 However, results have been less reliable in 1
Department of Orthopaedic Surgery, Stanford University, Redwood City, CA, USA 2 OrthoCarolina Foot and Ankle Institute, Charlotte, NC, USA Corresponding Author: Carroll P. Jones, MD, OrthoCarolina Foot and Ankle Institute, 2001 Vail Ave, Suite 200B, Charlotte, NC 28207, USA. Email: [email protected]
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Hunt et al Table 1. Patient Demographics. Control Group a
Age, y Weight, lba Body mass indexa Affected side, left/right, n Preoperative AOFAS scorea Smoker, % Diabetes mellitus, % Wound healing issues, % Gastrocnemius recession, %
60.1 ± 7 201.8 ± 31 31.7 ± 4.8 10/8 56 ± 13 0.0 11.1 22.2 44.4
FHL Group 60.8 ± 6.9 215.1 ± 35 35.9 ± 6 10/11 61 ± 9 9.5 14.3 38.1 33.3
P Value >.05 >.05 >.05 >.05 >.05 >.05 >.05 >.05 >.05
Abbreviation: AOFAS, American Orthopaedic Foot & Ankle Society. a Values expressed as mean ± SD.
patients over age 50.13,21 Potential problems associated with debridement alone may include persistent pain and functional limitations. This may be due to the reduction in blood flow and healing potential of the Achilles tendon that occurs with increasing age, a more advanced degree of tendinopathy, or less capacity for full rehabilitation. For these reasons, the addition of a flexor hallucis longus (FHL) tendon transfer to augment the repair has been advocated for patients with more severe tendinosis, in patients older than 50, and in patients with a high body mass index (BMI).4,6,18 The theoretical benefits of FHL augmentation include mechanical support to protect the reattached Achilles tendon in the event of inadvertent early loading, and the addition of a muscle with significant volume and strength.10 Good results have been described in case series of older patients treated with FHL augmentation.4,6,18,22 However, the benefits of FHL augmentation have not been demonstrated in a prospective, randomized controlled clinical trial. The purpose of this study was to determine whether Achilles tendon debridement, decompression, and partial calcaneal ostectomy, augmented with FHL tendon transfer, would result in improved clinical outcomes and ankle plantar flexion strength compared with debridement and decompression alone in patients over 50 years of age with chronic insertional Achilles tendinosis. In a prospective, randomized trial, we hypothesized that FHL augmentation would be associated with superior clinical outcome scores and greater ankle plantar flexion strength compared with Achilles debridement alone.
Methods After institutional review board approval, we initiated our prospective, randomized study protocol. All patients older than 50 years who had failed appropriate nonoperative treatment for chronic insertional Achilles tendinopathy were invited to participate. Nonoperative treatment included
boot immobilization and a period of relative rest, an Achilles sleeve device, shoe wear modification, and nonsteroidal anti-inflammatory medications over at least a 6-month period. Patients meeting the inclusion criteria were randomly assigned using the sealed envelope method to Achilles debridement and ostectomy alone (control group) or Achilles debridement and ostectomy augmented with FHL transfer (FHL group). Exclusion criteria included previous ipsilateral Achilles surgery, previous Achilles tendon rupture, active wound or infection on the ipsilateral leg, and lack of an FHL tendon suitable for transfer. A clinic research coordinator selected and opened the sealed envelope assigning the patient group. This was securely communicated to 1 of the 4 operating surgeons participating in the study. Patients were blinded to their treatment group. Patients followed a standard postoperative protocol, including formal physiotherapy. Outcome measures collected in the clinic included American Orthopaedic Foot & Ankle Society (AOFAS) ankle/hindfoot score, visual analog scale (VAS) for pain, ankle and hallux plantar flexion strength (measured with MicroFET2 isokinetic dynamometer; Hoggan Health Industries, West Jordan, UT), and a patient satisfaction survey. Patients were evaluated postoperatively in clinic by an independent, blinded examiner at 3 months, 6 months, and 1 year. All operative complications were recorded. A total of 49 patients were enrolled in the study between May 2009 and June 2011. Five patients withdrew from the study before undergoing surgery, and 5 patients were not available for the 1-year follow-up, leaving 39 patients with complete data at a minimum 1-year follow-up. There were 18 patients in the control group and 21 in the FHL transfer group. The average patient age was 60.5 ± 7 years (range, 50.2-75.7 years). There were 25 females and 14 males. Average body weight was 208 ± 33.5 pounds (range, 129270 pounds). There was no difference between groups in terms of smokers, diabetes, and BMI. Patient demographics are listed in Table 1.
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Surgical Technique A single incision technique was used for all cases. The location of the skin incision was at the discretion of the attending surgeon. The surgeon’s preferred skin incision (medial, lateral, or central) was used along with a centralsplitting of the Achilles tendon, debridement of the tendon insertion, and resection of a Haglund lesion if present. All areas of tendinosis were debrided and typically included between 25% and 60% of the tendon’s diameter, leaving only intact, healthy tendon fibers. For patients randomized to the FHL transfer group, all 4 surgeons used the same technique. The deep posterior compartment fascia was incised to expose the FHL tendon. The FHL tendon was identified and tenotomized at the FHL tunnel along the medial calcaneus and then transferred to the calcaneus as described previously for patients in the FHL group.4 A cannulated drill was used to create a drill hole in the calcaneus, and an appropriately sized interference screw was used to secure the FHL tendon into the calcaneus. The ankle was held in neutral dorsiflexion, and moderate tension was placed on the FHL as it was secured in the tunnel with the screw. The FHL tendon was then tenodesed to the Achilles during the Achilles repair. For all patients, the Achilles was reattached with lateral and medial suture anchors (just distal to the interference screw in the FHL patients). Layered closure was performed, including the paratenon, subcutaneous tissue, and skin. The deep compartment fascia was not closed primarily. If a gastrocnemius equinus was found to be present, a gastrocnemius lengthening was performed through a separate incision at the musculotendinous junction. The postoperative protocol was the same for all patients and included non-weight-bearing in a splint for 2 weeks followed by non-weight-bearing in a short-leg cast for 2 to 3 weeks. Patients were then fit with a tall CAM walker boot with 2 adjustable lifts and began weight bearing as tolerated. The lifts were peeled layer by layer every 2 to 3 days until no lift remained. At 6 to 8 weeks postoperatively, patients transitioned out of the boot and initiated a standardized physical therapy Achilles repair protocol. Activities were advanced as tolerated by the patient, with avoidance of impact exercise until 3 months postoperatively.
Postoperative Follow-up Evaluation Patients were evaluated clinically by an independent examiner at the following intervals: preoperatively, 3 months, 6 months, and 1 year postoperatively. All postoperative complications were recorded at 3 months and 1 year. Patients were scored on a 2-item satisfaction scale (Appendix 1). All patients underwent testing of ankle plantar flexion strength
Figure 1. Clinical photograph demonstrating hallux plantar flexion testing with the MicroFET2.
and hallux plantar flexion strength on both the operative and nonoperative limbs using a MicroFET2 isokinetic dynamometer. Ankle plantar flexion strength was tested by placing the heel on the ground with the patient seated and the knee extended. The patients were asked to plantar flex the foot with as much force as possible. Patients were monitored to ensure that they did not use body weight during plantar flexion, isolating the gastroc-soleus complex. Hallux plantar flexion strength was measured in a similar fashion, with the heel resting on the ground with the knee bent. The patients were asked to plantar flex the hallux only and were monitored to ensure that the ankle remained in neutral and that body weight was not shifted (Figure 1). For each analysis, a total of 5 tests were performed. The highest and lowest numbers were discarded, and an average of the 3 remaining values was used.
Statistical Analysis A sample size estimate was calculated using nQuery Advisor software (version 7.0). Standard descriptive statistics were calculated. Between-group paired comparisons were made using an independent t test for normally distributed data and a Mann-Whitney test for nonnormally
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Figure 2. Bar chart illustrating American Orthopaedic Foot & Ankle Society (AOFAS) ankle/hindfoot scores in each group at all preoperative and postoperative time points. There was a significant difference between each postoperative time point and the preoperative value, with no difference between groups at any time point. FHL, flexor hallucis longus. Table 2. Clinical Outcomesa. Control Group AOFAS score Preoperative 56.7 ± 12.6 3 months 78.4 ± 11.8 6 months 85.9 ± 11.3 1 year 91.5 ± 13 VAS score Preoperative 68 ± 19.8 3 months 34.3 ± 23.5 6 months 25.8 ± 25 1 year 14.6 ± 18.6 Ankle plantar flexion strength, lb Preoperative 11.8 ± 7.2 3 months 13.5 ± 8.1 6 months 12.2 ± 5.8 1 year 13.5 ± 6.6 Hallux plantar flexion strength, lb Preoperative 13.7 ± 6.5 3 months 15 ± 6.4 6 months 14.9 ± 5.4 1 year 16.6 ± 6.5
FHL Group 61.4 ± 9.93 79.7 ± 13 91 ± 11.3 92.3 ± 15.2 64 ± 21.3 28.4 ± 22.8 21.2 ± 28.2 10 ± 18 16.1 ± 8.3 16.7 ± 7.7 18.1 ± 9.1 20.3 ± 10.8 18.2 ± 10.2 13.6 ± 6 16.3 ± 6.9 18.3 ± 7.1
Abbreviations: AOFAS, American Orthopaedic Foot & Ankle Society; FHL, flexor hallucis longus; VAS, visual analog scale. a Values expressed as mean ± SD.
distributed data. Normality was determined using a Kolmogorov-Smirnov test. All statistical tests were performed at an a priori significance level of .05.
Results Clinical Outcomes AOFAS ankle/hindfoot scores improved in both groups at 6 months and 1 year with no difference between groups (Figure 2, Table 2). Activity-related VAS scores improved significantly in both groups, with no difference between groups at 6 months and 1 year (Figure 3, Table 2).
Plantar Flexion Strength There was greater ankle plantar flexion strength in the FHL group at 6 months and 1 year compared with the control group (Figure 4, Table 2) (P < .05). There was not a significant difference in the number of patients who underwent gastrocnemius lengthening in the control group (n = 8) compared with the FHL group (n = 7). There was no difference between the 2 groups in hallux plantar flexion strength preoperatively and at 1 year (Figure 5, Table 2) (P = .43), and no patients complained of functional difficulties or weakness in their great toe.
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Figure 3. Bar chart illustrating visual analog scale (VAS) scores for activity-related pain in each group at all preoperative and postoperative time points. There was a significant difference between each postoperative time point and the preoperative value, with no difference between groups at any time point. FHL, flexor hallucis longus.
Figure 4. Bar chart illustrating ankle plantar flexion strength (pounds) at each data collection time point. There was significantly more improvement at 1 year in the FHL group compared with the control group. FHL, flexor hallucis longus.
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Figure 5. Bar chart illustrating hallux plantar flexion strength (pounds) at each data collection time point. There was no significant difference between groups at any time point. FHL, flexor hallucis longus.
Patient Satisfaction
Discussion
At 1 year, 34 of 39 patients (87.2%) were satisfied with the outcome of their procedure, again with no difference between groups (18/21 satisfied in FHL group, 16/18 in control group).
Flexor hallucis longus transfer has been well described as an augmentation for repair of chronic Achilles tendon ruptures and reruptures.7,18,22 The FHL has been shown to have significantly greater muscle volume and greater strength than the flexor digitorum longus (FDL) and peroneal tendons, which have also been used in the treatment of chronic Achilles conditions.10 While many authors recommend augmentation with the FHL for insertional Achilles tendinopathy, very few reports are isolated to older patient groups, and there are no published prospective randomized series.4,6,8,20 Wapner et al20 described results of FHL transfer for insertional Achilles tendinopathy in 17 patients (age range, 25-71 years) with high satisfaction and return to function. Den Hartog4 reported on 26 patients, including 18 patients 50 years of age or older, and found a higher magnitude of improvement in patients older than 50. In fact, AOFAS scores improved to levels in the over-50 group that were equivalent to levels in patients younger than 50.4 This is in contrast to previous articles by McGarvey et al13 and Watson et al,21 who reported worse outcomes in patients over 50 who underwent partial calcanectomy and Achilles debridement alone. Our data demonstrate, in patients 50 years of
Complications There were no neurologic complications and no deep vein thromboses. No patients required additional surgical procedures. While there were no major complications, we identified 12 minor complications in 39 cases (31%), all related to the surgical wound. These included minor superficial wound dehiscence (6 patients), skin blistering or cellulitis (2 patients), delayed wound healing (2 patients), and peri-incisional maceration (2 patients). All wounds healed without additional surgical intervention. There was no significant difference in the rate of wound complications comparing the FHL group with controls (8/12 vs 4/12, respectively, P = .236). There was also no significant difference in wound complications based on location of surgical incision (2/8 medial incisions, 2/9 lateral, 8/22 central midline).
1004 age and older, no difference in clinical outcome scores and patient satisfaction comparing those treated with Achilles debridement and ostectomy alone versus debridement and ostectomy with FHL augmentation. This is similar to a series published by Nunley et al14 of 19 patients treated with Achilles debridement and exostectomy without FHL transfer and a long-term 96% satisfaction rate. However, we did find greater ankle plantar flexion strength in the FHL augmentation group and no difference in hallux plantar flexion strength between groups at 1 year. Minor wound complication rates were relatively high, particularly in the FHL transfer group, although all wound problems healed without need for additional surgical intervention and there were no nerve injuries. It is possible that the additional dissection and bulk of the FHL muscle belly contributed to the increased wound complication risk. FHL transfer did not appear to result in hallux plantar flexion weakness compared with controls. Elias et al6 reported on 40 patients (mean age 57 years; range, 39-76 years) undergoing Achilles debridement and FHL transfer for insertional Achilles tendinopathy. The investigators found improved VAS and AOFAS scores with no loss of ankle plantar flexion strength. Schon et al18 reported significant improvement in physical function and pain intensity in a group of 46 inactive, older, overweight patients (mean age 54 ± 10 years and BMI 34 ± 6). This closely approximates the demographics of our groups. To our knowledge, the present study is the first Level I study comparing FHL transfer to debridement alone in patients over 50. Our results suggest that ankle plantar flexion strength improves more rapidly, and with a greater overall magnitude at 1 year, when FHL augmentation is incorporated into Achilles debridement and decompression alone. Pain relief, functional scores, and satisfaction were no different between groups with our selected metrics. It is possible that superior clinical outcome metrics with better precision (ie, VISA-A, FAAM, PROMIS instruments) may have better differentiated differences in function between the groups, but the strength difference appears clear-cut.
Hallux Plantar Flexion Strength The concerning potential morbidity of FHL transfer is loss of great toe plantar flexion strength, which could in theory affect balance, endurance, and gait. We found similar hallux plantar flexion strength in patients having undergone FHL transfer compared with controls, and no patients reported functional difficulties with the great toe at 1 year. This finding is similar to those reported in previous studies.18,22 It is likely that the strength necessary for daily function is accommodated for by the flexor hallucis brevis or distal connections between the FHL and FDL tendons. It is important to note that the patients in our study were
Foot & Ankle International 36(9) 50 years of age and older and were, on average, obese. It is possible that younger, more active, athletic individuals would develop symptomatic hallux weakness after FHL transfer, and we rarely perform FHL transfers in this population.
Role of the Surgical Incision A variety of surgical approaches and techniques have been described for patients undergoing treatment for insertional Achilles tendon disorders. These include a lateral longitudinal incision,13,19 a medial J-shaped incision,12,17 and a 2-incision approach with medial and lateral incisions.2 McGarvey et al,13 Johnson et al,11 and Nunley et al14 described the central tendon splitting approach to debride the Achilles tendon without a tendon augmentation. Wapner et al19,20 described harvesting the FHL tendon through a double-incision approach. We harvested and transferred the FHL tendon through a single incision in all patients. We found no difference in clinical outcome based on incision location. Nunley et al14 also reported excellent long-term results with a single midline incision and only 1 superficial wound problem.
Complications While our patients had no nerve complications and no deep vein thromboses, there was a relatively high rate of minor wound complications. The complication rates in the present study are slightly higher than rates reported in other studies.6,18,20 Wegrzyn et al22 did not report minor complications.
Limitations The study has some limitations. We included only a minimum of 12 months of follow-up. Schon et al18 noted small but continued improvement in a similar cohort between 12 and 24 months. Thus, we would not expect our results to deteriorate in the immediate short term for the FHL transfer group. Another limitation was our use of the AOFAS scale as a clinical outcome instrument. This is not a validated scale, and the AOFAS has recommended against its continued use.15 However, during the development of this trial and the IRB approval process, the AOFAS scale was the most widely used and accepted outcome measure in the foot and ankle literature (and remains so).9 We have incorporated validated, reliable scores into ongoing trials at our institution. Finally, 4 different surgeons contributed patients to this study, and different approaches were used that could have affected the outcomes. The numbers were not large enough to determine whether there was a difference between surgeons.
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Conclusions FHL tendon transfer combined with Achilles tendon debridement and partial calcaneal ostectomy may offer improved ankle plantar flexion strength for patients undergoing treatment for insertional Achilles tendinopathy. However, we did not find significant differences in pain relief and functional outcomes. It remains unclear whether differences would be noted with more powerful outcome instruments, such as the VISA-A or FAAM. We found no loss of hallux plantar flexion strength and a significant increase in ankle plantar flexion strength in these patients relative to controls. Based on these results, the routine use of FHL transfers as an adjunct to Achilles tendon debridement and partial ostectomy in older, sedentary patients may not be necessary. However, it was a safe procedure and may be better suited for revision cases. Longer follow-up and a standardized surgical incision may provide additional insight into the ideal surgical approach for this difficult problem.
Appendix 1 Two-Item Patient Satisfaction Survey Administered to All Patients at Final Follow-up Thank you for participating in this clinical study. All of the questions relate to the surgery that you had on your Achilles tendon.
1. Would you have the operation again? □ Yes □ No □ Unsure
2. Rate your satisfaction (check 1): □ Very Satisfied □ Satisfied □ Dissatisfied □ Very Dissatisfied
Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by the OrthoCarolina Research Institute (OCRI).
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1005 3. Clancy WG Jr, Neidhart D, Brand RL. Achilles tendonitis in runners: a report of five cases. Am J Sports Med. 1976;4(2): 46-57. 4. Den Hartog BD. Flexor hallucis longus transfer for chronic Achilles tendinosis. Foot Ankle Int. 2003;24(3):233-237. 5. DeOrio MJ, Easley ME. Surgical strategies: insertional Achilles tendinopathy. Foot Ankle Int. 2008;29(5):542-550. 6. Elias I, Raikin SM, Besser MP, et al. Outcomes of chronic insertional Achilles tendinosis using FHL autograft through single incision. Foot Ankle Int. 2009;30(3):197-204. 7. Hahn F, Meyer P, Maiwald C, et al. Treatment of chronic Achilles tendinopathy and ruptures with flexor hallucis tendon transfer: clinical outcome and MRI findings. Foot Ankle Int. 2008;29(8):794-802. 8. Hansen S. Trauma to the heel cord. In: Jahss M, ed. Disorders of the Foot and Ankle. 2nd ed. Philadelphia, PA: WB Saunders; 1991:2355-2360. 9. Hunt KJ, Hurwit D. Use of patient related outcome measures in foot and ankle research. J Bone Joint Surg Am. 2013;95(16):e118. 10. Jeng CL, Thawait GK, Kwon JY, et al. Relative strengths of the calf muscles based on MRI volume measurements. Foot Ankle Int. 2012;33(5):394-399. 11. Johnson KW, Zalavras C, Thordarson DB. Surgical management of insertional calcific Achilles tendinosis with a central tendon splitting approach. Foot Ankle Int. 2006;27(4):245-250. 12. Martin RL, Manning CM, Carcia CR, et al. An outcome study of chronic Achilles tendinosis after excision of the Achilles tendon and flexor hallucis longus tendon transfer. Foot Ankle Int. 2005;26(9):691-697. 13. McGarvey WC, Palumbo RC, Baxter DE, et al. Insertional Achilles tendinosis: surgical treatment through a central tendon splitting approach. Foot Ankle Int. 2002;23(1):19-25. 14. Nunley JA, Ruskin G, Horst F. Long-term clinical outcomes following the central incision technique for insertional Achilles tendinopathy. Foot Ankle Int. 2011;23(9):850-855. 15. Pinsker E, Daniels TR. AOFAS position statement regarding the future of the AOFAS Clinical Rating Systems. Foot Ankle Int. 2011;32(9):841-842. 16. Schepsis AA, Jones H, Haas AL. Achilles tendon disorders in athletes. Am J Sports Med. 2002;30(2):287-305. 17. Schepsis AA, Leach RE. Surgical management of Achilles tendinitis. Am J Sports Med. 1987;15(4):308-315. 18. Schon LC, Shores JL, Faro FD, et al. Flexor hallucis longus tendon transfer in treatment of Achilles tendinosis. J Bone Joint Surg Am. 2013;95(1):54-60. 19. Wapner K, Hecht P. Repair of chronic Achilles tendon rupture with flexor hallucis longus tendon transfer. Op Tech Orthop. 1994;4:132-137. 20. Wapner KL, Pavlock GS, Hecht PJ, et al. Repair of chronic Achilles tendon rupture with flexor hallucis longus tendon transfer. Foot Ankle. 1993;14(8):443-449. 21. Watson AD, Anderson RB, Davis WH. Comparison of results of retrocalcaneal decompression for retrocalcaneal bursitis and insertional Achilles tendinosis with calcific spur. Foot Ankle Int. 2000;21(8):638-642. 22. Wegrzyn J, Luciani JF, Philippot R, et al. Chronic Achilles tendon rupture reconstruction using a modified flexor hallucis longus transfer. Int Orthop. 2010;34(8):1187-1192.
