Cosmetic calf reduction: from basic research to clinical practice
即將於2012年出版的美國整形書籍: 抽脂與蘿蔔腿整形, 邀請蔡豐州醫師撰寫專文
Feng-Chou Tsai, M.D., Ph.D.
Chief, Division of Plastic Surgery, Department of Surgery, Taipei Medical University Hospital, Taipei Medical University
Several kinds of destructive surgery not intended for disease treatment were developed: refractive surgery for nearsightedness, bariatric surgery and calf reduction. These operations sacrificed parts of healthy human structures to meet unique non-disease demands with the intent of achieving a balance between the residual function and treatment goals. The above principles have long been utilized for conventional reconstruction including grafts and flaps.1-2 The author (F.C.T.) introduced the multidisciplinary principles (bio-chemistry, -mathematics, clinical experience, etc.) to not only explore various phenomena of interest but also to develop novel and powerful techniques.
Leg beauty has been a significant concern especially in Asian females with a short stature and a chubby, muscular leg shape.3 In Western and Eastern culture, the ideal contour of the calf has been defined as relatively long and slender on the medial upper third then gradually tapering towards the ankle (Figure 1). Several methods of leg sculpture have been developed to target specific compositions: muscle (temporary or non-specific: botulinum toxin (BoNT) injection, radiofrequency; permanent or specific: total or subtotal muscle resection and selective neurectomy), fat (liposuction) and vein (varicose vein surgery) as shown in Table 1.4-10 These techniques drawn on clinical experience from reconstructive surgery showing that sacrifice of the gastrocnemius and soleus muscles have little consequences. Here neurectomy and myomectomy directly resects the nerve and muscle respectively, while BoNT denervates muscle by temporarily inhibiting the release of acetylcholine at the neuromuscular junction (NMJ).11 Both BoNT and neurectomy are classified as denervation. The advantage of muscle resection is that it deals directly with the oversized muscle deformity. Myomectomy does its shortcomings including multiple and often large incisions, long recovery times, bloody operative dissection, uneven contour, painful postoperative period and technical challenges intra-operatively. All of these reasons make myomectomy procedures less than ideal for the cosmetic patients seeking a simple solution.
The ideal cosmetic operation should be simple, easily reproducible, quick and produce a good outcome. The author (F.C.T) has been investigating denervation muscle atrophy, bio-mathematical models and their clinical implications over a long period of time in more than one thousand cases. The advantages of combined procedures such as selective neurectomy and liposuction are short operative and recovery time, even and symmetrical atrophy, and inconspicuous scarring. In this scenario, the techniques and related information are described and highlighted. General muscle atrophy was also considered for arbitrary applications and the results pertaining to this issue provided.
Multidisciplinary information (Anatomy, biochemistry and mathematics)
Skeletal muscle comprise more than 40% of the human body and play a major role in body physiology and contours. Triceps surae (from Latin caput and sura. “three-headed calf muscle”), composed of the medial, lateral gastrocnemius and soleus muscles, is responsible for plantar flexion and ankle stabilization.11
The anatomy and plastic departments at the Taipei Medical University Hospital disclosed the following novel findings from cadavers and more than 1000 clinical cases: First, the nerve to the soleus muscle has two branches: medial and lateral. Second, nerve diameter correlated with muscle bulk in a way similar to the principles of electric theory. Third, the shape of the male medial gastrocnemius muscle was found to be similar to the soleus muscle in terms of its bulky and tendinous appearance. Fourth, the more bulging the muscle is (especially where maximal calf circumference (M.C.C.) > 40 cm), the deeper the nerve attached the underneath of the muscle is as well. Figure 2 indicates the relationship between the different components of calves.
Since Gutmann established the foundation of muscle research in the 1950s many advances have been made in this field.12 Transmission electron microscopy (TEM) showed that neurectomy induced irreversible progressive alterations of myofibrils involving the staggering and disorientation of z-discs with sarcomere disarray and interfiber widening.13
AIF (apoptosis-inducing factor)-mediated caspase-independent apoptosis (cell death) appeared to result in permanent denervated muscle atrophy after neurectomy. By way contrast, no significant changes in apoptosis or survival signaling are seen in the reversible muscle atrophy that occurs after BoNT injection. Apoptosis resulted in the elimination of individual myonuclei (myonuclear apoptosis) and the related portion of sarcoplasm without demise of the entire fiber. In other words, denervation may reduce the size of myofibers without completely destroying the multi-nucleated fibers, enabling muscle weight recovery in a manner similar to a balloon being deflated or inflated.
Mathematics or Biophysics
Our studies disclosed the symmetry and pattern of process between skeletal muscle growth (expanding state) and atrophy (contracting or dissipative state) as shown in Figure 3a. This so-called “time-reversal symmetry” implies that there are the keys that manipulate the different biological states. The reversible course of BoNT is an obvious example of both the expanding (recovery) and contracting (atrophic) states (Figure 3b).
The expression pattern of muscle, especially the integrins and myofiber surface complexities, are biphasic (initial increase later decay) and coherent. In fact, other tissues and even cancers also express a similar molecular Levy distribution pattern.14,15 Selective neurectomy in cosmetic calf reduction also provides a good human model to observe the changes in muscle atrophic states. The above anatomical and biochemical findings may be of use to those seeking ways of prolonging the effects of BoNT or minimizing the negative sequelae of nerve injuries in the future.
1. Subjective calf hypertrophy or obvious muscle bulge
2. maximal calf circumference larger than 34 cm
3. male to female transsexuals
4. calf asymmetry
1. spinal cord injuries
2. congenital limb disorders
3. joint diseases
4. psychological disorders
The patients were measured in the standing position. The midline of the popliteal fossa in the popliteal crease was marked. The following parameters including the M.C.C. with and without toe-standing, calf length, and the gastrocnemius muscle excursion should be recorded. The frontal, back and lateral views with or without toe standing should be documented in the pre-operative and post-operative follow-up.
The procedure was performed under general anesthesia with the patient in the prone position. No muscle relaxants were given because they make accurate intra-operative identification of motor nerves impossible. Although local anesthesia is possible, care should be taken with pain and irritability during the operation. A 1 cm incision was made starting at the midpoint of the popliteal fossa extending medially.
The steps of the selective neurectomy are described below and shown in the supplementary video files. After dissecting the subcutaneous plane, the first structure encountered is the short saphenous vein. The vein is preserved and retracted medially. The specially designed small self-retractor is used to expose the small operative field. The deep fascia is then cut and blunt dissection performed subfascially to locate the motor nerves. We use the fish hook to retract the medial gastrocnemius muscle reduce the number of assistants required. Between the medial and lateral points three small nerves can usually be identified: 1) the nerve to the medial gastrocnemius; 2) the nerve to the lateral gastrocnemius; and 3) the nerve to the soleus muscle (Figure 2). These nerves are isolated and their innervations confirmed with a nerve stimulator (the VARI_STIM III surgical nerve locator; Medtronic Xomed, Inc., Jacksonville, Fla.). Stimulation of the nerve must clearly trigger the contraction of the targeted muscle for a positive identification to be made. Sensory nerves that do not produce muscle contractions must be preserved. Once a positive identification is made, a 1 cm segment neurectomy of all nerve to the triceps surae is performed to prevent spontaneous re-innervation of the muscle due to the close proximity of the cut ends. The operation time of neurectomy is about 20 minutes.
Liposuction was performed by the smaller and long cannula. Smaller and long cannula prevents skin irregularities and sucks out the adipose tissues around the Achilles tendon to recreate the natural hollow. The wound is then closed in layers and the stitches removed after 2 weeks.
Mobilization is encouraged immediately after the procedure and patients are required to wear compressive stockings on their lower limbs for at least 3 months. As the strong tension on the neurectomy wound often induced conspicuous hypertrophic and hyperpigmented scarring, the patient is not encouraged to actively exercise for at least one month and wound taping after removal of the stitches should be longer than two months. To help the patient achieve a normal look to their walkafter the operation, the wearing of high-heel shoes as a “crutch” during the recovery period are suggested.
Predicted results for the doctors or explanation to the patients receiving BoNT and neurectomy are as follows:
1. Time course and muscle weight reduction (Figure 3b): Neurectomy induced rapid loss of denervated skeletal muscle in the first 2 months of denervation then approached 11% of the skeletal muscle mass after 6 months. By comparison, BoNT induced a V-shape recovery curve of muscle weight with a trough seen at one month after each injection. The muscle weight ratio of the BoNT group achieved incomplete recovery to 90% after one year but never recovered in the selective neurectomy group. There were some lasting changes in the BoNT group despite the fact that muscle recovery is generally thought to occur with regard to NMJ stabilization, remodeling, and myogenesis after BoNT injection.
2. M.C.C.: The average M.C.C. goal is around 32 cm. The more obvious muscle bulge the more reduction can be expected. At present, the record for M.C.C reduction is around 6cm. The exact M.C.C. reduction can be predicted preoperatively. Only reduction range (1.5 to 6 cm) is informed.
3. Additive effects of BoNT: Muscle weight reduction by BoNT did not depend only on the dose. Additive effects were also obtained through repeated injections. The muscle weight ratio after a single full-dose BoNT injection recovered incompletely to 90% of original weight after 58 weeks. The muscle weight ratio with repeated full- and half-dose BoNT injections decreased to 75% and 85% respectively 6 months after the first injection, to 60% after the second injection and to 75% at one year. In short, higher frequency and doses of BoNT-A injections increased and prolonged the effect of muscle atrophy.
4. Functional recovery: Serial functional assessments showed that patients receiving full-dose BoNT exhibited maximal functional deficit at around 1 week of denervation before soon returning to normal values. The neurectomy group exhibited immediate and significant reductions in motor function between one to two months, then showed little improvement. At 6 months there was a residual functional deficit (20%). Neurectomy not only results in irreversible muscle mass reduction, but also induces a lasting functional deficit, as previously shown in the author's 2008 study.
Our clinical studies showed that electromyographic recruitment of the muscle (20 cases) ranged from –3 to –4, signifying near total denervation. Gait analysis and clinical observations also revealed that gait approached that of normal levels after 6 months over the knees and ankles.
5. Specific goals of denervation—muscle volume reduction (eg, calf or masseter muscle hypertrophy) and iatrogenic functional loss (eg. dynamic wrinkles): Our previous study revealed that denervation first results in loss of motor function followed by muscle mass reduction. For clinical purposes, ideally only the motor function or the muscle volume should be targeted. To create iatrogenic motor function loss (i.e., for wrinkle relief), denervation should focus as completely as possible on the muscle that performs a specific function; on the other hand, denervation should target a specifically-innervated muscle as little as possible, in order to reduce muscle mass with minimal functional deficit. In short, the degree of the motor function deficit depends on the extent and number of denervated muscles.
There are several types of patients that may produce a poor result or dissatisfaction:
1. Swollen calves. It may indicate that calf hypertrophy not only results from muscle or fat hypertrophy but also poor venous return. There are so far no surgical methods for managing leg edema.
2. M.C.C. > 40 cm or < 29 cm. The patient with extreme calf hypertrophy always combined total muscle hypertrophy including the toe muscles and a thick tibial bone. Furthermore, it is difficult to achieve the ideal M.C.C. from this level even when a 6 cm reduction achieved. On the other hand, for a smaller M.C.C. the improvement was too small to be considered reasonable.
Cases of calf reduction (selective neurectomy and liposuction) are provided. Figure 5a, b, c and d shows the pre- and post-operative pictures respectively.
a. Management of complications:
Most common sequels were numbness of lateral ankle. Spontaneous recovery can be expected but vitamin B complex and massage accelerated the course. The worst complications were damage of the nerve to toe muscles. If the loss of any toe extension or flexion was found postoperatively, the re-exploration and microsurgical anastomosis should be performed as soon as possible because small muscles are less tolerant of long-term nerve injury.
b. Issues for revision
If a missed nerve during dissection led to a poor result or compensatory hypertrophy, a secondary procedure was suggested. The same incision was performed to explore the previous surgical neurectomy scar. Often the glistening neuroma was easily seen. The dissection should however be via the healthy surgical plane as for other secondary procedures. In other words, we should initially explore all nerve to toe muscles, avoid damage to these nerves, then separate and cut all the nerves above to triceps surae.
The irregularities after liposuction can be smoothened by the smallest cannula if it is run delicately over the whole area. Fluid infiltration should be set to a higher amount than a routine liposuction procedure.
Conclusion box of Pearls for success
All nerves to the triceps surae (gastrocnemius and soleus muscle) should be completely resected in 1 cm lengths at least while the saphenous sensory nerve and nerve to the toe muscles are kept intact. The territory of liposuction should be as extensive as possible even around the ankle by the smallest cannula. The incision wound should be given high priority due to the potential of conspicuous hypertrophic and hyperpigmented scar. High-heel shoes are strongly recommended during the recovery or rehabilitation period to serve as the “crutch”.