| BackgroundThe Achilles tendon is the most injured tendon in the lower extremity. The incidence of Achilles tendon ruptures reportedly occurs in up to 18 of 100,000 people, most often in athletic men in their 30s and 40s. A rupture may also be associated with systemic disorders (inflammatory conditions, auto immune disorders, exposure to fluoroquinolone antibiotics, and systemicsteroids) and local disorders injectable steroids, collagen abnormalities, and repetitive microtrauma to the tendon 1. Achilles tendinopathy, in particular Achilles tendinosis, results in degeneration within the tendon, which may be a predisposing factorin rupture. Acute Achilles tendon ruptures may be missed or misdiagnosed up to 27% of the time or the patient may not seek immediate medical care because they are still able to ambulate and the pain is tolerable. Neglected Achilles tendon (AT) rupture is generally defined as a rupture with a delay of more than 4 weeks prior to diagnosis or treatment, which will lead to Achilles tendon defect. Although pain and swelling are not common, the proximal calf muscle retraction make weak function for plantar flexion to produce poorer functional result. Limping and inability to do heel life were occurred and may have difficulty with walking uphill or climbing stairs or gait disturbance eventually. Numerous surgical procedures have been described for the reconstruction of Achilles tendon defect. Surgical repair of neglected Achilles tendon defect presents the challenge of restoring the function of the Achilles tendon complex while repairing the large defect. There is controversial about an Achilles tendon defect.Compared to acute AT ruptures, there is a strong consensus for surgical reconstruction with neglected AT rupture. Currently, there is no golden rule for the neglected AT rupture, operative treatment selection for chronic Achilles tendon disease is based on the size of tendon rupture. Smaller gaps (< 2 cm) can often be repaired with an end-to-end technique. Intermediate degenerations (2-6 cm in size) might better be treated by V-Y myotendinous flap. Various surgical techniques have been described for large defect (>6 cm in size)of neglected AT rupture including local tissue augmentation, free flaps or trurndown flaps, local tendon transfers (peroneus brevis; flexor digitorum longus and flexor hallucis longus tendon), free tissue transfers (gracilis and allografts), and synthetic grafts or combination thereof, especially local tendon was widespread used. The FHL is an ideal tendon to use and well suited for tendon transfer to augment neglected AT repairs.In 1991,Hansen et al first described flexor hallucis longus (FHL) tendon transfer for the AT, which was single incision technique to harvest FHL. Wapner et al reported the FHL tendon transfer technique for reconstruction of chronic AT rupture with dual incision, which locates the FHL tendon through a medial incision over the mid-foot, has been noted to be effective and safe. The benefit of this technique will get longer FHL to repair the large defect of AT. Since its introduction more than 20 years, the transfer of the FHL has been found widespread use in treating chronic and irreparable AT disease. It provides good to excellent clinical outcomes while improving pain and plantar flexion strength. In summary, FHL transfer for AT has some advantages a s follows:(1)The FHL tendon offers stronger plantarflexion and the axis of contraction is more in line with the Achilles than the FDL and peroneus brevis tendons. The FHL tendon fires in-phase with the Achilles tendon and maintains normal muscle balance around the ankle. (2) Autologous material has no rejection, avoiding the rejection of allograft and synthetic materials. (3)The benefit of this technique is not only mechanical support but also the advantage that its muscle belly covers the tendon defect and provides additional blood supply to the healing, thereby reducing re-rupture and deep infection incidences.Flexor hallucis longus transfer alone also have some disadvantages. After FHL transfer for the treatment of chronic Achilles tendinopathy, a loss of active plantar flexion of the big toe can be observed. During walking, the pressures and forces under the big toe are reduced and load is transferred to the lateral metatarsal heads with a resulting asymmetry in gait measured with pedobarography. So some scholars think the FHL transfer with other methods for repairing AT defect, which reduce the incidence of these complications. Den Hartog et al reported repair At defect with FHL combined with turndown flap. Lee KB et al reported about three patients with an AT rupture neglected, who were treated by interposed scar tissue repair combined with FHL tendon transfer. Elias et al reconstructed with V-Y lengthening and FHL tendon transfer for large defect (>8cm)of Achilles tendon rupture. TayD et al reported 2 turndown tendon flaps with FHL transfer for chronic Achilles Tendon rupture. Mulier et al compared the FHL transfer combine with turndown flap or without, which may be preferable over the turn down flap procedure alone.These scholars reported with goo clinical result, but Cybex strength testing revealed deficits in plantarflexion peak torque comparing to the normal side.In order to solve the above problems, this topic will focus on increasing plantar flexion strength, reducing complications and other issues. This research will include into two parts:basic research and clinical research.(1) basic research:it can be divided into two parts:â‘ the maximum length of FHL and intersection between FHL with FDL were observed in the cadaver lower limb specimens.â‘¡Biomechanical study:Neglected AT rupture treated with FHL transfer with two turndown gastrocnemius fascia flap and reinforced with plantaris tendon through dual incision in fresh lower limb. Through the biomechanical test, the maximum tensile strength of tendon will be tested in the BOSE machine in different surgical techniques.The effect of different surgical methods will be confirmed by the biomechanical test. (2) Clinical study:We used the new technique to repair large defect of AT, which was confirmed in MRI and Isokinetic testing, objective data evaluate the surgical effect after follow up. This study will provide a scientific theoretical basis for the development of new surgical techniques for AT defect, and provide scientific guidance for the treatment ofAT defect from the anatomical and biomechanical aspects.Since Hansen and Wapner reported that FHL has been the first choice for repairing chronic AT rupture, many scholars published a modification of the technique. Martin et al reported complete Achilles tendon excision with FHL transfer reduced pain in 95.5% patients, and 86.4% patients were satisfied with the result. Endoscopic assisted flexor hallucis tendon transfer in the management of chronic rupture of AT was reported by Lui TH. Amlang M et al reported another new approach which is direct plantar for FHL tendon harvest using of a double-incision. It will avoid the damage of medial plantar nerve. Tashjian et al completed a study on 14 fresh-frozen cadavers to evaluate the length of the FHL tendon with both a single-and double-incision techniques. The authors found that with a single incision procedure, the average tendon graft length was 5.16 cm, whereas it was 8.09 cm with the double incision, less than 10-12cm by Wapner reported. Panchbhavi has described a minimally invasive at the base of big toe approach for FHL harvest demonstrating more tendon length than the double incision technique by Wapner and Tashjian reported.The anatomical relationship between the FDL and FHL in the "knot of Henry" still is a subject of controversy. The literature is inconsistent regarding the need for tenodesis of the remaining FHL to the FDL. The three identified patterns have been described with sixteen embalmed non-paired cadaveric feet by O’SULLIVAN. Type I showed tendinous fibres directed from FHL to FDL. Type II showed tendinous fibres directed from FDL to FHL. Type III showed tendinous fibres directed from FDL to FHL and an additional tendinous slip directed from FHL to FDL. The other three different configurations were found by Bernard G. In type 1, a tendinous slip branched from the FHL to the FDL. In type 2, a slip branched from the FHLto the FDL and another from the FDL to FHL.In type 3, no attachment was present. Mulier et al found cross-attachments directed from the FHL to the FDL in 14 of 24 specimens (58%), cross-attachments in both directions in seven of 24 specimens (29%), and no cross-attachments in three of 24 specimens (13%). These studies had a very limited number of cases and were limited to Caucasian population. There have been no such anatomic studies in the Asian population to be date. The anatomical relationship in the "knot of Henry" and tendon length available for harvest with double-incision may show variations in a different ethnic or racial. The results of Mulier’s reports confirm the occurrence of nerve injury during FHL tendon harvest. Injuries were observed ina large percentage of foot specimens (33%,8/24 eight feet).The large percentage of foot specimens with nerve lesionsleads us to question why the resulting clinical symptomshave not been previously described and seem to have gone unnoticed. One explanation may be a long period of casting after the operation may prohibit discovery of the symptoms.Although the FHL was mostly to used with good results in chronic Achilles tendinopathy, there are still have weakness of big toe, plantar flexion of AT, rerupture of AT. Although several publications discuss the transfer of the FHL tendon combing with turndown flap, to our knowledge there was no reported on FHL tendon combing with turndown flap reinforced with plantaris tendon for AT rupture. Cohn et al have done with comparative studies on the biomechanical properties of the FHL and the traditional FHL with the absorbable screw fixation. The maximum load of the later is greater than that of the former. Rahm et al treated chronic irreparable AT ruptures with large FHL transfers. Both techniques for FHL transfer to AT, intratendinous and transosseous, provided good to excellent clinical and functional outcome in the treatment of irreparable AT disease. Gebauer et al reported cadaveric humanAT was tested depending on either the suture technique, the suture material (PDS thread or PDS-cord). The findings identify the AT suture with a PDS-cord according to Bunnell’s technique as a mechanically strong method, Ilhami et al compared the ruptured rabbit Achilles tendons reinforced with intratendinous and peritendinous plantaris grafts. They think intratendinous more better for repairing AT. These studies suggest that the plantar tendon provides a better strength for the AT rupture.To sum up, FHL transfer repairing chronic AT rupture need to solve the following problems. (1)The purpose of the study was to quantify the length of tendon graft with different incisions.(2) The purpose of the study was to describe the anatomical variations of the connection between the FHL and FDL tendons in the knot of Henry in Asians specimens. At the same time, the purpose of the study was to describe the anatomical variations of the relationship between the FHL and plantar nerves in plantar area, introduce a thorough classification system, assess the risk of nerve injury from FHL harvest.(3) The goal of the present study was to investigate biomechanical difference outcomes of FHL transfer to the AT and to compare the transtendinous technique to the transosseous technique, assess the result of different surgical techniques.(4) Comparing the difference between 2different techniques,the clinical result was observed postoperative follow-up with MRI and isokinetic testing to assess difference of the 2 techniques.Objectives1.The purpose of the study was to describe the anatomical variations of the connection between the FHL and FDL tendons in the knot of Henry in Asians specimens, and quantify the length of tendon graft with different incisions. Therefore, we will determine which incision will be better to repair AT defect.2.The goal of the present study was to investigate biomechanical difference outcomes of FHL transfer to the AT and to compare the transtendinous technique to the transosseous technique, assess the result of different surgical techniques.3. The purpose of this study was to assess the clinical outcome of all patients who underwent the procedure. The clinical results were assessed with objective index such as AOFAS ankle and foot score, MRI and constant isokinetic testing and so on. Therefore which technique is a good option for repairing large gap defect of Achilles tendon will be confirmed.Methods:This research will include into two parts:basic research and clinical research. The circuit diagram is as follows:1. Applied anatomy of FHL and FDL in plantarForty-eight feet from 24 cadavers that had been embalmed with formalin were studied. The cadavers,15 female and seven male cadavers, red latex was injected manually under physiologic pressure with a syringe. The FHL and FDL were analyzed anatomically with respect to the individual cross-links in the planta pedis. The width, length and diameters of the FHL tendon, FDL tendons and the tendinous connections were measured using a caliper to the closest millimeter.1.1 Observe the intersection type between the FHL and FDL in the Henry’s knotSixty-four cadaver legs from 32 cadavers donated for anatomical and surgical training were dissected. There were 17 male and 15 female cadavers were fixed by immersion in formalin solution for at least 1 year. All subjects were Asians, and none showed signs of major previous surgery around the foot or ankle or relevant deformities. Skin, superficial fascia, and the plantar aponeurosis were removed. Then the musculus flexor digitorum brevis (FDB), musculus flexor hallucis brevis (FHB), the musculus abductor hallucis (ABH) and lumbrical muscles meticulously were removed. The adjacent neurovascular structures were retracted with deep bladed retractors. The width, length and diameters of the FHL tendon, FDL tendons and the tendinous connections were measured using a caliper to the closest millimeter.1.2 Quantify the length of FHL tendon graft with different incisions.The distance between the musculotendinous junction of FHL and the point at sustentaculum tali was measured in millimeters using a slide gauge, which represented harvesting the length of the FHL tendon through a single posterior-medial incision. Also, the distance between the musculotendinous junction of FHL and the level of the master knot of Henry was measured to represent the available FHL graft from double-incision technique. Additionally, the length from musculotendinous junction of FHL to first IP joint was measured to represent the available FHL graft with minimally invasive incision. Meanwhile, the relationship between the FHL and plantar nerves in plantar area was observed, assess the risk incidence of nerve injury from FHL harvest.2. Biomechanical testing of fresh specimensSix paired fresh cadaveric AT specimens(12 legs) were divided into group 1 (transtendinous technique and group 2 (transosseous technique) and performed with FHL transfer to AT. Achilles tendon were remove 5cm before 4cm AT insertion. In group 1, the FHL tendon was harvested through double incision technique,sutured to the stump of the Achilles tendon directly. In group 2, the FHL tendon was harvested proximal to the medial malleolus and rerouted through a calcaneal tunnel. The FHL tendon was then put into the prepared tendinous bed of the remnants of the Achilles tendon. The maximum peak load, the displacement of maximum load and stress were recoded with tensile failure testing on BOSE machine. Statistical analysis was performed to compare the differences between groups and determine the superiority of different techniques.3. AT defect treated with Flexor Hallucis Longus transfer with two turndown gastrocnemius fascia flap and reinforced with plantaris tendonTen cases of chronic Achilles tendon rupture were assessed with AOFAS ankle and hindfoot score and MRI before this procedure. We completed data collection sets American Orthopaedic Foot and Ankle Society ankle-hindfoot scores, isokinetic evaluation, postoperative magnetic resonance imaging (MRI) at 1 year of follow-up. The differences between pre and post-operation were analysed.Results1. Intersection type between the FHL and FDL in the Henry’s knotThe only two configurations of the distal relationship of the FHL to the FDL were identified. Type I described an attachment branching from the FHL tendon proximally to the FDL tendon. Type II were attachments branching from the FHL tendon proximally to the FDL tendon and from the FDL tendon proximally to the FHL tendon. In no case was there an attachment from the FDL tendon to the FHL tendon alone or no cross-attachment type. Tension was applied to the FHL tendon manually to determine the subdivisions of the slips of the FHL tendon to the lesser. The three subdivisions were illustrated categorizing the connection to the lesser toes. There was a connection to second toe in 100%, an additional slip to the third toe in 60.9% and to the fourth toe in 7.8%. No patient showed a connection of the FHL to all lesser toes. Only two specimens had different configurations between the left and right foot. The variation in the split of the distal FDL tendon to the lesser toes was evaluated. The distal FDL tendon was classified into two types according to it’s distal insertions. Type I described 3 slips to the2nd,3 rd and 4th toes (56.7%,34/64), where the slip from the FHL always formed the most part of the 2nd toe. Type II was 4 attachments to the lesser toes(43.3%,30/64), where the slip from the FDL always formed the most part of the 2nd the toe.2. Quantify the length of FHL tendon graft with different incisions.The knot of Henry was indentified at 10.89 (range,13.04 to 9.22, SD=1.08) cm proximal to the IP joint and 2.21 (range,1.59 to 3.04, SD=0.34) cm under the navicular tuberosity. Length of FHL tendon graft was measured for all the specimens in single posterior-medial incision (group 1), double-incision (group 2) and minimally invasive incision (group 3). The average length of the FHL graft available from a single posterior-medial incision measured 5.08 cm (range,3.32 to 10.35, SD= 1.09). The average length of the FHL graft available from double-incision technique measured 6.72 cm (range,4.69 to 12.09, SD= 1.03). The average length of the FHL graft available from minimally invasive incision measured 17.49 cm (range,13.51 to 20.52, SD= 1.80). The One-Way ANOVA test comparing differences between all three groups revealed a statistically significant difference (p<.001). Furthermore, a post hoc power multiple comparisons using Bonferroni test was showed the statistically significant difference between any two of them (Table3). No statistical significance was found by gender or sides difference between these three Groups. At the same time, the distance between FHL and medial plantar nerve is 3.6±1.23mm (range 1.46-7.86mm), which indicate the probability of the medial plantar nerve injury was high risk after FHL transfer.3. AT defect treated with FHL transfer with two turndown gastrocnemius fascia flap and reinforced with plantaris tendonTen patients, eight men and two woman, underwent FHL transfer with two turndown gastrocnemius fascia flaps reinforced with plantaris tendon. The mean age was 35.5 years (range from 22to 55). The mean time of injury to surgical intervention was 5.3 months (range from 4 to 8). The length of the defect, which was estimated preoperatively, varied from 4cm and 10cm (mean rupture length 6.6 cm) on MR1. The mean tendon defect was 8.1cm (range from 7 to 11) after debridement, which was longer than the MRI measurement. Mean preoperative AOFAS score improved from 64.4 (range from 58 to 70) points to 94.3 (range from 88 to 100) points and VAS scores was statistically significant at the last follow-up (Table 1). Ankle range of motion was close to the noninvolved ankle with an average of 12°of dorsiflexion (range from 5 to 15°) and 40.5°of plantar flexion (range from 35 to 50°). Residual calf atrophy was a common finding. Calf girth deficit averaged 1.5 cm (range from 0.5 to 2.5 cm). All patients were able to do single-leg stance and maintain their balance (mean,32.5 seconds; range from 8 to 50 seconds). The reconstructed side showed little difference with the contralateral control side (mean,8.5 seconds; range from 5 to 30 seconds). Isokinetic testing at 30 deg/sec and 120 deg/sec revealed an average decrease of 24.5% and 34.5%, respectively, in the plantar flexion peak torque of the involved ankle compared with the non-involved ankle.4. Biomechanical study of ATSix paired fresh cadaveric AT specimens(12 legs) were divided into group 1 (transtendinous technique and group 2 (transosseous technique) and performed with FHL transfer to AT. Achilles tendon were remove 5cm before 4cm AT insertion. The FHL tendon was sutured to the stump of the Achilles tendon directly or in a transosseous position onto the calcaneus before it was woven into the remaining Achilles tendon. Calcaneal osteotomy was performed before the AT insertion, ant then the retention of calcaneal and Achilles tendon were fixed using a clamp for biomechanical testing. The results suggest that the 2 groups had no significant difference in the tensile force.Conclusions1.Comparing western scholars reports having 4 types, the only two configurations of the distal relationship of the FHL to the FDL were identified. Typeâ… described an attachment branching from the FHL tendon proximally to the FDL tendon. Typeâ…¡ were attachments branching from the FHL tendon proximally to the FDL tendon and from the FDL tendon proximally to the FHL tendon. The type â… accounted for more than 90%, which shows the distal FHL should be tenodesis with FDL in order to reserve the hallux plantar flexion strength. In over 96% of the feet, a proximal to distal connection from the FHL to the FDL was found, which might contribute to the residual function of the lesser toes after FDL transfer.2.The difference between the lengths obtained from these three techniques was significant. The benefits of minimally invasive incision is suit to repair large defect of AT, which will sacrifice the flexion strength of big toe. While using the FHL transfer for Achilles tendonopathy with a single incision approach may be applicable, which also will sacrifice the flexion strength of big toe. We think the double incision technique is the best way to obtain the maximum length of FHL for AT defect. In addition it allows the tenodesis for the distal part of FHL to the FDL and maintains active flexion of the big toe and then to avoid a possible cock-up deformity.3. The distance of FHL and FDL with the medial plantar nerve is relatively close, so the probability of medial plantar nerve injury is high risk after FHL or FDL transfer. But the resulting clinical symptoms have not been previously described and seem to have gone unnoticed. One explanation may be a long period of casting after the operation may prohibit discovery of the symptoms. The association with the operation and its possible nerve injuries may then not be made. These results show that extensive dissection and large exposure of neurovascular bundle,the FHL and FDL tendons are required.4. Biomechanical studies divided into group 1 (transtendinous technique) and group 2 (transosseous technique) comparing the strength of the Achillon repair with FHL transfer. There was no significant difference in the tensile force between this 2 groups. This provides biomechanical evidence to support the transtendinous technique to repair large AT defect. This technique suggest a significantly longer graft than transosseous technique.5. Transfer of the FHL to treat neglected AT rupture associated with two turndown flaps and plantaris tendon yielded good clinical and functional outcomes with a high satisfaction and relatively low complication rate. Patients in this study had excellent pain relief and were satisfied with their results after surgery. The described technique is advantageous in that it is simple to perform. The technique described here has been found to be reliable for repairing the large gap defect of AT. Our subjective and objective data indicate that the reconstructive technique using flexor hallucis longus transfer with two turndown gastrocnemius fascia flaps and plantaris tendon is a good option for repairing large gap defect of Achilles tendon.The innovative point of the study1.The anatomical relationship of the tendons and their cross-links has been previously reported in foreign countries. But the anatomical relationship between the FDL and FHL in the "knot of Henry" still is a subject of controversy. In addition, the length FHL available for harvest through a single or double incision technique remains controversial. These studies had a very limited number of cases and were limited to Caucasian population. The purpose of the study was to describe the anatomical variations of the connection between the FHL and FDL tendons in the knot of Henry in Asians specimens, introduce a thorough classification system, analyze the position of the interconnections relative to the surgical relevant bony landmarks, and quantify the length of tendon graft with different incisions. This provides anatomical basis for repairing large area of Achilles tendon defect.2. This is the first time to simulate the FHL transfer to repair Achilles tendon defect and biomechanical study in the fresh lower limb specimens. The maximum tensile force of tendon in different techniques were tested through biomechanical test. The effect and difference of different techniques were compared with the biomechanical study.3. Foreign scholars have reported FHL transfer with turndown gastrocnemius fascia flaps or combined with V-Y tendon advancement for AT defect.But to our knowledge there was no reported on FHL tendon combing with other two techniques for AT rupture. Base on the biomechanical research, We designed new techniques AT defect treated with FHL transfer with two turndown gastrocnemius fascia flap and reinforced with plantaris tendon. The differences of the biomechanical study and clinical resul were evaluated with objective data. |
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