length, calf muscle volume, and muscle fatty degeneration after surgery for acute Achilles tendon rupture. ... flexion strength deficits after surgical repair of Achilles tendon rupture. ... New magnetic resonance imaging (MRI) and ultrasound.
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T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
Tendon Length, Calf Muscle Atrophy, and Strength Deficit After Acute Achilles Tendon Rupture Long-Term Follow-up of Patients in a Previous Study Juuso Heikkinen, MD, Iikka Lantto, MD, PhD, Juuso Piilonen, MS, Tapio Flinkkil¨a, MD, PhD, Pasi Ohtonen, MSc, Pertti Siira, PT, Vesa Laine, MSc, Jaakko Niinim¨aki, MD, PhD, Prof, Ari Pajala, MD, PhD, and Juhana Leppilahti, MD, PhD, Prof Investigation performed at the Division of Orthopaedic and Trauma Surgery, Department of Surgery, Oulu University Hospital, Medical Research Center, University of Oulu, Oulu, Finland
Background: In this prospective study, we used magnetic resonance imaging (MRI) to assess long-term Achilles tendon length, calf muscle volume, and muscle fatty degeneration after surgery for acute Achilles tendon rupture. Methods: From 1998 to 2001, 60 patients at our center underwent surgery for acute Achilles tendon rupture followed by early functional postoperative rehabilitation. Fifty-five patients were reexamined after a minimum duration of followup of 13 years (mean, 14 years), and 52 of them were included in the present study. Outcome measures included Achilles tendon length, calf muscle volume, and fatty degeneration measured with MRI of both the affected and the uninjured leg. The isokinetic plantar flexion strength of both calves was measured and was correlated with the structural findings. Results: The Achilles tendon was, on average, 12 mm (95% confidence interval [CI] = 8.6 to 15.6 mm; p < 0.001) longer (6% longer) in the affected leg than in the uninjured leg. The mean volumes of the soleus and medial and lateral gastrocnemius muscles were 63 cm3 (13%; p < 0.001), 30 cm3 (13%; p < 0.001), and 16 cm3 (11%; p < 0.001) lower in the affected leg than in the uninjured leg, whereas the mean volume of the flexor hallucis longus (FHL) was 5 cm3 (5%; p = 0.002) greater in the affected leg, indicating FHL compensatory hypertrophy. The median plantar flexion strength for the whole range of motion ranged from 12% to 18% less than that on the uninjured side. Finally, the side-to-side difference in Achilles tendon length correlated substantially with the strength deficit (r = 0.51, p < 0.001) and with medial gastrocnemius (r = 0.46, p = 0.001) and soleus (r = 0.42, p = 0.002) muscle atrophy. Conclusions: Increased Achilles tendon length is associated with smaller calf muscle volumes and persistent plantar flexion strength deficits after surgical repair of Achilles tendon rupture. Strength deficits and muscle volume deficits are partly compensated for by FHL hypertrophy, but 11% to 13% deficits in soleus and gastrocnemius muscle volumes and 12% to 18% deficits in plantar flexion strength persist even after long-term follow-up. Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.
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espite surgical repair of acute Achilles tendon rupture, calf muscle isokinetic strength does not usually return to completely normal, instead showing an 8% to 20% deficit compared with that of the uninjured leg after mid-term to long-term follow-up1-5. Earlier studies have shown that the triceps surae muscle undergoes volume atrophy and fatty degeneration1,5,6. Increased Achilles tendon length, or elongation, during rehabilitation has been proposed as a possible explanation for these structural changes and for the strength deficit after Achilles tendon rupture5,7,8.
Previous investigators assessed elongation of the Achilles tendon after rupture by using metallic radiographic markers that had been placed on both sides of the tendon ends during surgery8,9. They reported that the Achilles tendon elongates during the first 3 months postinjury, leading to up to 8 mm of elongation at 1 year. However, reported correlations of tendon elongation with plantar flexion strength have been controversial. Pajala et al. found substantial correlation between Achilles tendon elongation and ankle plantar flexion peak torque8, whereas Kangas et al. found no correlation between elongation
Disclosure: This study was funded by the University of Oulu Graduate School, UniOGS. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/E334).
J Bone Joint Surg Am. 2017;99:1509-15
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http://dx.doi.org/10.2106/JBJS.16.01491
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and a strength deficit9. In addition, we previously found that the Achilles tendon elongates up to 3 mm from 1 to 14 years after repair but total elongation measured on radiographs did not correlate with any isokinetic strength parameters or with clinical results at the time of long-term follow-up4. New magnetic resonance imaging (MRI) and ultrasound techniques allow researchers to compare Achilles tendon length between affected and uninjured sides, and they are therefore considered more accurate than techniques using metallic markers5,7,10,11. However, the results from studies using these new methods have not been consistent. Using ultrasound, Silbernagel et al. showed that the side-to-side difference in Achilles tendon length, measured from the calcaneal insertion to the muscle-tendon junction of the medial head of the gastrocnemius, correlated substantially with heel-rise height deficits 1 year postoperatively 7. Using MRI in a retrospective study with a 91month follow-up after treatment of Achilles tendon rupture, Rosso et al. found that the Achilles tendon in the affected leg was on average 1.8 cm longer than that on the unaffected side, but they did not assess correlation with isokinetic calf muscle strength5. They also found a 17% lower triceps surae muscle volume, which correlated with peak torque deficit5,12. We are not aware of any prospective long-term MRI studies of Achilles tendon length, calf muscle volume, fatty degeneration, and ankle plantar flexion strength. The objective of the present study was to use MRI to measure Achilles tendon length, calf muscle volume, and muscle fatty degeneration after surgery for acute Achilles tendon rupture. We also assessed whether these structural findings were associated with the calf muscle strength deficits in the affected leg at the time of long-term follow-up. Materials and Methods Study Design his study was conducted as a part of a long-term follow-up study of patients in a previously published randomized controlled trial comparing augmented and nonaugmented surgical repair of Achilles tendon ruptures4. The original study was registered at ClinicalTrials.gov (NCT02018224). The local research ethics committee approved the original trial protocol and the reexamination of the patients. All patients received oral and written information about the trial and provided informed consent to participate. The inclusion criteria were a complete acute Achilles tendon rupture and an age of 18 to 65 years. The exclusion criteria were a delay of ‡1 week between the rupture and treatment, local corticosteroid injection(s) around the Achilles tendon within 6 months before the rupture, a previous Achilles tendon rupture on the contralateral side, an open Achilles tendon rupture, skin problems over the Achilles tendon area, residence outside the country, and diabetes mellitus. Between October 1998 and January 2001, 83 patients were screened for trial eligibility at our university teaching hospital. Twenty-one patients were excluded, and 2 eligible patients declined to participate. The remaining 60 patients were randomized into augmented and nonaugmented repair groups.
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T E N D O N L E N G T H , C A L F M U S C L E A T R O P H Y, AF T E R AC U T E AC H I L L E S T E N D O N RU P T U R E
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STRENGTH DEFICIT
The short-term (1-year) and long-term (14-year) clinical results of this study were published previously4,8. We combined the augmented and nonaugmented groups to investigate structural changes of the muscles and the Achilles tendon length after surgical repair of Achilles tendon rupture4,8. Patients A total of 57 patients from the original study8 were contacted between December 2013 and March 2014, and 55 of them were included in the long-term cohort4. Of these 55 patients (48 male and 7 female; mean age and standard deviation [SD], 38 ± 8 years), 28 had nonaugmented and 27 had augmented surgical repair. Two patients were excluded from the present analysis because they had Achilles tendon rupture on the contralateral side during the follow-up period, and another patient was excluded because of MRI artifact in the analyses of muscle volume and fatty degeneration. The participants underwent MRI and isokinetic plantar flexion strength measurement of both legs after an average of 14 ± 0.5 years, and a minimum of 13 years, of follow-up. Operative Techniques One surgeon performed all operations. For the nonaugmented repairs, the tendon was operated on using the Krackow technique with 2 polydioxanone-0 absorbable sutures (PDS; Ethicon) and smaller 2-0 polyglactin appositional sutures (Vicryl; Ethicon)13. The augmented procedure started with end-to-end repair that was identical to the nonaugmented procedure. The repair was then augmented with a 10-mm-wide central gastrocnemius aponeurosis flap that was turned down over the suture line and stitched to the Achilles tendon with 2-0 Vicryl14. The ankle was gently placed in a neutral position, and routine skin closure was performed after the repair. Postoperatively, a temporary below-the-knee rigid plaster splint was applied with the ankle in a neutral position in all cases. Postoperative Management Postoperative treatment was identical for all patients. On the first postoperative day, all patients received a Soft Cast individual below-the-knee dorsal brace (3M) that allowed active free plantar flexion of the ankle but restricted dorsiflexion to neutral; this was worn for 3 weeks8. The patients were allowed 20 kg of weight-bearing for 3 weeks, half weight-bearing for 3 to 6 weeks, and full weight-bearing thereafter. The patients were instructed to perform exercises according to a standard rehabilitation program8. Outcome Measures Outcome measures included Achilles tendon length, calf muscle volume, and fatty degeneration of the muscle in both the affected and the uninjured leg. The isokinetic plantar flexion strengths of the calf muscles were measured on both sides. MRI was performed on the same day as, but before, the isokinetic strength tests. The first author measured tendon length and the degree of fatty degeneration, the third author measured muscle volumes, and 2 physiotherapists measured calf muscle strength. All
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T E N D O N L E N G T H , C A L F M U S C L E A T R O P H Y, AF T E R AC U T E AC H I L L E S T E N D O N RU P T U R E
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Fig. 1
Axial T1-weighted MRIs of both calves acquired 14 years after surgery for an Achilles tendon rupture. The cross-sectional area was measured on a clinical workstation by manually drawing the region of interest around a muscle or muscle compartment. DF = deep flexors, FHL = flexor hallucis longus, S = soleus, GM = gastrocnemius medialis, GL = gastrocnemius lateralis.
assessments were performed independently without knowledge of the results of the other measurements. MRI MRI was performed on the affected and uninjured legs at the same time, with the uninjured leg serving as a normal matched control. The MRI was carried out with a 1.5-T imaging system (MAGNETOM Aera; Siemens Healthcare). The imaging sequences included T1-weighted turbo spin echo (TSE) sagittal images (a slice thickness of 4 mm, with a 0.8-mm interslice gap) and axial images (a slice thickness of 4 mm, with a 1.6-mm interslice gap). The T1-weighted sagittal images covered both calves from the proximal part of the tibia to the distal part of the calcaneus, and the T1-weighted axial images covered both calves from the distal femoral condyles to the distal part of the calcaneus. Patients were scanned in the supine position, and their ankles were supported in the plantigrade position (the ankle at a 90 angle and the knee at a 0 angle). Achilles Tendon Length The Achilles tendon length was measured in both the uninjured and the affected leg with MRI as the distance from the most distal part of the medial head of the gastrocnemius to the most distal end of the Achilles tendon11. The most distal end of the
Achilles tendon was defined by the axial plane intersecting the most cranial aspect of the calcaneal tuberosity. The difference in tendon length was calculated by subtracting the length in the uninjured leg from that in the affected leg. The relative difference in tendon length was calculated as ([affected – uninjured]/affected) · 100 to assess its correlation with isokinetic deficits. Calf Muscle Volume The outline of each muscle was identified on axial MRIs, and the cross-sectional area of the muscle or muscle compartment was measured on every third axial slice from the femoral epicondyles to the distal part of the calcaneus (Fig. 1)15. The muscle volume was calculated using the formula for frustums of cones: h/3 · (A1 1 O[A1 · A2] 1 A2), where h is the height of the cylinder (e.g., three 4-mm slices 1 1.6-mm interslice gaps = 16.8 mm), and A1 and A2 are the cross-sectional areas at the 2 ends of the cylinder. This method is a modification of the method described by Rosso et al., who calculated volumes using a formula for regular cylinders rather than frustums of cones5. The final muscle volume was the sum of all cylinders measured in that muscle. Muscle volumes were calculated (in cubic centimeters) for each compartment, including the soleus, the medial and lateral gastrocnemius muscles, the flexor hallucis longus (FHL),
TABLE I Calf Muscle Volume at a Mean of 14 Years After Surgery for Achilles Tendon Rupture Mean Volume (SD) (cm3) Affected Leg
Uninjured Leg
Difference Mean (SD)* (cm3)
%†
P Value
Soleus
429.1 (92.8)
492.1 (94.6)
63.0 (61.0)
12.8
